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15-101159FILE CITY OF . Federal Way April 9, 2015 Carl Jonasson 4346 SW 307, Street Federal Way, WA 98023-2127 Re: File #15-101159-00-PC, PREAPPLICATION CONFERENCE SUMMARY Dumas Bay West Bulkhead, **No Site Address", Federal Way Dear Mr. Jonasson, CITY HALL 33325 8th Avenue South Federal Way, WA 98003-6325 (253) 835-7000 www. cityoffederalway. com Jim Ferrell, Mayor Thank you for participating in the preapplication conference with the City of Federal Way's Development Review Committee (DRC) held March 26, 2015. We hope that the information discussed at that meeting was helpful in understanding the general requirements for your project as submitted. This letter summarizes comments given to you at the meeting by the members of the DRC. The members who reviewed your project and provided commments include staff from the City's Planning and Building Divisions and Public Works Department, and representatives from Lakehaven Utility District and South King Fire and Rescue. Some sections of the Federal Way Revised Code (FWRC) and relevant information handouts are enclosed with this letter. Please be advised, this letter does not represent all applicable codes. In preparing your formal application, please refer to the complete F`JVRC and other relevant codes for all additional requirements that may apply to your project. The key contact for your project is Becky Chapin, 253-835-2641, becky.chapin@cityoffederalway.com, for specific technical questions about your project; please contact the appropriate DRC representative as listed below. Otherwise, any general questions about the preapplication and permitting process can be referred to your key contact. PROJECT DESCRIPTION Proposed shoreline stabilization and emergency repair along six marine shoreline properties in order to protect against recent landslide activity. MAJOR ISSUES Outlined below is a summary of the major issues of your project based on the plans and information submitted for preapplication review. These issues can change due to modifications and revisions in the plans. These major issues only represent comments that the DRC consider most significant to your project and do not include the majority of the comments provided. The major issues section is only provided as a means to highlight critical requirements or issues. Please be sure to read the entire department comments made in the next section of this letter. Mr. Jonasson Page 2 April 9, 2015 * Planning Division Shoreline bulkheads are not considered an outright permitted use on the Puget Sound shoreline. A bulkhead may be permitted only if it complies with all applicable shoreline regulations and Shoreline Master Program policies, including but not limited to evaluation of non-structural shoreline protection alternatives. DEPARTMENT COMMENTS Outlined below are the comments made by the representatives of each department present at the preapplication conference. Each section should be read thoroughly. If you have questions, please contact the representative listed for that section. COMMUNITY DEVELOPMENT — PLANNING DIVISION Becky Chapin, 253-835-2641, becks.chapin(a)cityoffederalway.com 1. Zoning, Comprehensive Plan, and Shoreline Designations— The subject properties' comprehensive plan designations are all low density residential and zoned Suburban Estates (SE). The properties are designated Urban Conservancy in the city Shoreline Master Program (SMP) overlay. 2. Summary of Applicable Regulations — The proposed area of work is approximately 615 linear feet located along the Puget Sound shoreline, encompassing six high bluff properties. The following regulations apply to any work proposed on these properties as discussed further in this letter: tL Shoreline — This property is designated `Urban Conservancy' in the city's SMP overlay. Areas within 200 feet of the marine shoreline, including the Urban. Conservancy designation area, are regulated under the state's Shoreline Management Act, which is administered locally via the city's SMP. Depending on the scope of the work, the project may be exempt from Shoreline Substantial Development permit provisions as set forth in Washington Administrative Code 173-2 7- 040(2)(c). A written response on how the project meets the exemption (see section 3 below) will be required along with the Shoreline Exemption permit application. If the scope of work does not meet this exemption, a Shoreline Substantial Development pen -nit is required. Additionally, a Shoreline Conditional Use is required and a Shoreline Variance may be required as discussed below. Relevant subsections of the SMP include the following: + Shoreline modifications — Bulkheads are considered a form of hard armoring shoreline stabilization and are regulated under FWRC 15.05.050(1). • Critical Areas — According to the City's.critical areas map, the property contains geologically hazardous areas with soils that meet the definition of erosion hazard, landslide hazard, seismic hazard as well as steep slopes hazard areas. All work on or within 25 feet of these areas and within the shoreline is regulated under FWRC 15.10.160. • Flood Hazard — The updated Puget Sound Coastal Flood Map shows portions of the shoreline property flagged as within a 100-year high velocity flood hazard area. Work in 15-101159-00-PC Doc LD.:68683 Mr. Jonasson Page 3 April 9, 2015 these areas is therefore regulated under FWRC 15.15.060 and require a FEMA habitat assessment review. ■ Cultural Resources — Due to shoreline artifact discovery, a site inspection and evaluation by a professional archaeologist may be required prior to issuance of any permits as provided in FWRC 15.05.040(6). B Environmental Review — Work on lands covered by water is generally subject to environmental review under the State Environmental Policy Act (SEPA). 3. Shoreline Regulations — As noted above, areas within 200 feet of the marine shoreline are regulated tn under the state's Shoreline Management Act. This .will impact proposed bulkhead work and steep slope stabilization, as follows: a. Proposed Bulkhead Work: Pursuant to Washington Administrative Code (WAC) 173-27- 040(2)(c), the construction of a normal protective bulkhead common to a single-family residence is exempt from the shoreline substantial development permit requirements; provided the bulkhead is installed at or near, and parallel to the ordinary high water mark for the sole purpose of protecting an existing single-family residence from loss or damage by erosion. In addition, FWRC 15.05050 Shoreline Modifications contains bulkhead regulations as a shoreline stabilization component. Hard armoring is subject to a shoreline conditional use permit in the urban conservancy environment. Shoreline stabilization is not considered an outright permitted use on the eity's shoreline. In order for shoreline stabilization to be permitted, the city must find that relevant decisional criteria contained in FWRC 15.05.050(1)(a-b) are met. The following highlights primary applicable regulations, but does not necessarily identify all requirements. ■ , The applicant shall provide a geotechnical report, prepared by a qualified professional, that estimates the rate of erosion and evaluates alternative solutions; and the urgency associated with the specific situation; In the case of proposed hard armoring stabilization solutions (e.g., bulkheads and riprap), erosion from waves or currents presents a clear and imminent (damage within three years) threat to a legally established primary structure, one or more substantial accessory structures, water -dependent development, ecological restorationTtoxic clean-up remediation projects, or public improvements; • The maximum height of the proposed bulkhead or other stabilization structure is no more than one foot above the elevation of mean higher high water on tidal' waters, measured from grade on the waterward side of the bulkhead or structure. "Note: A shoreline variance is required if the height exceeds this requirement All shoreline proposals must also comply with the general development standards of FWRC 15-05.040 and can only be approved if specific criteria of FWRC 15..05.040 (1) - (8) are met. The formal application must demonstrate that any proposed improvement meets all applicable criteria. The Washington State Department of Ecology must also review and approve a Conditional Use Permit or Shoreline Variance before any work can commence. 15-101159-00-PC Doc LD.:68683 Mr. Jonasson Page 4 April 9, 2015 b. Slope Stabilisation: According to critical areas maps, the hillside between the homes and the beach contains slopes in excess of 60 percent. It is generally covered in second growth trees and vegetation which has become unstable from a recent landslide_ Any actions proposed to repair the da;naged hillside are subject to shoreline standards and critical areas standards pursuant to FWRC 15.10.160. Any work that is on or within 25 feet of a defined geologically hazardous area including erosion hazard, landslide hazard, seismic hazard, and steep. slope hazard areas may be only if no reasonable alternative exists and if the proposal will not lead approved by the director to or create any increased slide, seismic, or erosion hazard. In order to review the repair request, a professionally prepared soils report that describes how the proposed actions will impact each of the following on the subject property and on nearby properties most be submitted for review: o Slope stability, landslide hazard, and sloughing; o Seismic hazards; o Groundwater; o Seeps, springs, and other surface waters; and o - Existing vegetation. The report should also include recommended methods for mitigating identified impacts and a description of how these mitigating measures may impact adjacent properties. The geotechnical report review will be subject to land use review and environmental review and can be included with other reviews for the subject property. Please note that peer review will be required as provided under FWRC 15.10.090 Basis for Determination. Your proposal will be forwarded to the City"s geotechnical engineering consulting firm for fee evaluation. The applicant must pre -pay the Geotechnical Consultant review fee, which will be held in an account maintained by the City. Any fees not used by the consultant will be returned to the applicant. Flood Hazard Areas —The draft Federal Emergency Management Agency (FEMA) Puget Sound Coastal Flood Map shows portions of your property with elevations of 16 feet and lower flagged as a 100-year Special Flood Hazard Area, velocity hazard, as provided in FWRC chapter 15.15 Flood Damage:Protection. It appears the proposed bulkhead will be below this elevation. Pursuant to new mandates from FEMA, a habitat assessment which identifies the impacts (and potential mitigation) of the project is required. The habitat assessment will be evaluated in conjunction with shoreline exemption review. d. Cultural Resources.— The city is aware of archaeological sites f;hat have been located in and along this slioreline...With authority granted by FWRC 15.05.046(6), the department will require, as a condition to the shoreline permits, a site inspection and evaluation by a professional archeologist prior to issuance.of any permits. The evaluation shall include recommendations for monitoring of potentially disruptive activities, data recovery, and/or mitigation measures if warranted. The archeologist report should be submitted as a component of the shoreline permit request package. Note that the City would consider waiving this report if Department of Archaeology and Historic Preservation (DAHP) indicates that such a report. is not necessary in this case. If artifacts are found, work must stop immediately and the city, state DAHP, Muckleshoot Indian Tribe, and Puyallup Indian Tribe must be notified. Please contact Gretchen Kaehler with the Washington State DAHP for information at 360-586-3088 regarding additional permits and requirements. Doc LD :68683 15-101159-00-PC Mr. Jonasson Page 5 April 9, 2015 4. Sate Environmental Policy Act (SEPA) — Work done on lands covered by water is not exempt from SEPA review. The proposed shoreline stabilization is not an exempt action. An environmental checklist for the nonexempt work must be submitted and reviewed prior to tine city issuing an environmental decision. All property owners and residents within 300 feet of the subject property are notified by the city of that decision. (Refer to the enclosed public notice mailing handout). The notification includes a 14-day comment and 14-day appeal period. Environmental review must be concluded before the land use approval can be issued, or a public hearing scheduled. 5. Emergency Exemption — Due to the recent slide activities several properties/homes are in potential danger of failing and it has been brought to the city's attention that emergency action is being proposed. There are several provisions in the FWRC, WAC, and SEPA rules that allow for emergency action to take place. Below is an outline of those provisions and submittal requirements. ® Any proposed emergency action will require a geotechnical report, prepared by a qualified professional, to identify property in imminent danger and proposed mitigation work to stabilize the failing slope. Please note: Third -party review will be required before any emergency work may begin. Your proposal will be forwarded to the City's geotechnicaI engineering consulting firm for fee evaluation. The applicant must pre -pay the Geotechnical Consultant review fee, which will be held in an account maintained by the City. Any fees not used by the consultant will. be returned to the applicant. Per WAC 173-27-040(2)(d), emergency construction necessary to protect property from dama by tile ge e elements does not require a substantial development permit. An "emergency" is an unanticipated and irnminent threat to public health, safety, or the enviroru-nent which requires immediate action within a time too short to allow full compliance with this chapter. Emergency construction does not include development of n previously existed. ew permanent Protective structures where none Where new protective structures are deemed by the administrator to be the appropriate means to address the emergency situation, upon abatement of the emergency situation the new structure shall be removed or any pennit which would have been required, absent an emergency, as addressed above, must be obtained. All emergency construction shall be consistent with the Policies of chapter 90.58 RCW and the local master program. As a general matter, flooding or other seasonal events that can be anticipated and may occur but that are not imminent are not an emergency. ■ Per FWRC 15.10 `Critical Areas,' emergencies that, in the. opinion of the shoreline administrator, threaten the public health, safety, and welfare, where impacts to critical areas and their buffers are mitigated to the extent feasible following the emergency actions are not subject to the provisions Of the critical areas chapter. ■ Pursuant to WAC 197-11-980, Emergency actions that must be undertaken immediately or within a time too short to allow full compliance with SEPA rules, to avoid an imminent threat to public health or safety, to prevent an imminent danger to public or private property, or to prevent an imminent threat of serious environmental degradation, shall be exempt. 15-101159-00-PC Doc LDA8683 Mr. Jonasson Page 6 Apri19, 2015 6. Public Notice — The Process IV and SEPA applications are subject to public notice of application, notice of the environmental determination, and a notice of public hearing for the Process IV. Depending on the scope of the proposal, the appropriate number of sets of stamped, addressed envelopes for property owners within 300 feet of the subject site must be submitted with the land use application. For our records, provide separarcellists ma sh owing the 300 foot radius from hants within e subjecfeet t the subject site and provide a corresponding p p site. Refer to the enclosed mailing notice handout for City notice services. 7. Fees —The formal application must be prepared in accordance with the City,s Development Requirements checklist (enclosed) and must be accompanied by the appropriate fees. Below is the fee chart based on the 2015 fee schedule. � eacmultiple �� anal �,��e5 �� required for �� cost. SEPAame L the highest fee is charged at full cost fees shall be charged at the full rate shown. Land Use Public Automation Total Permit Required Fees Notice Fee Fee Shoreline Conditional Use $5,857.50 $290.00 $20.00 $6, 167.50 SEPA $800.50 $145.00 $20.00 $965.50 Fees charged at 25%: Shoreline Variance $969.25 N/A $20.00 $989.25 Shoreline Exemption $21.37 N/A $20.00 $41.37 Shoreline Substantial $611.62 N/A $20.00 $631.62 T)n_valonment Permit As fees change annually, please contact Development Specialist staff for the current application fees and other review fees identified in this letter. Development Specialists can be reached at 253-835- 2607. or provals 8. Other Agency Review and PermitsSeveral t erolceoss is agencies may have permits independent of other agency permits The City is required for the proposal. The City p p not responsible for determination of other applicable permits; however, you should contact the fallowing agencies regarding permit requirements: Washington State Department of Fiff En ineers. and iBeife (Larry Fisher, 425-649-7042) for Hydraulic Permit approval, and CIS Army Corps advised that other agency permit and mitigation requirements vary from the City regulations and requirements, and will require coordination by your project manager. PUBLIC WORKS — DEVELOPMENT SERVICES DIVISION Ann Xiower. 253-835-2732 ann.dow y citvoffederalway.com If materials will be hauled to or from the site via public streets, FWRC 8.40.010 imposes route restrictions on all vehicles over 30,000 pounds. A haul route should be provided for staff review and approval. Pollutants may not be transported into the public right-of-way, onto neighboring property, or into Puget Sound. Best Management Practices, as specified in the King County Surface Water Design Manual, shall Doc LD.:68683 15-101159-00-PC Mr. Jonasson Page 7 April 9, 2015 be used to control pollution from storm water, and to comply with the standards in FWRC Title 16, Surface Water Management. COMMUNITY DEVELOPMENT — BUILDING DIVISION Scott Sproul. 253-835-2G33 scott.s rout citvoffederal'vvaY.corn .International Building Code (IBC), 2012 Washington State Amendments WAC 51-50 International Mechanical Code (IMC), 2012 Washington State Amendments WAC 51-52 Uniform Plumbing Code (UPC), 2012 Washington State Amendments WAC 51-56 & WAC 51-57 Inte)-natiORal Fire Code (]FC), 2012 Washington State Amendments WAC 51 -54 National Electric Code (NEC), 2012 Accessibility'Code, ICC/ANSI A117.1 - 2009 International Residential Code, 2012 Washington State Amendments WAC 51-51 Washington State Energy Code, 2012 WAC 5 1 -11 Building Criteria Wind/Seismic: Basic wind speed 85 Mph, Exposure, 25# Snow load, Seismic Zone D-1. A complete building permit application and commercial checklist. (Additional copies of application and checklists maybe obtained on our web site at www.ci offederalwa .com.) Submit _2_ sets of drawings and specifications. Specifications shad include: 2 Soils report, and 2 Structural calculations. Note: A Washington State Registered architects, stamp is required for i — additions/alterations (new or existing) of 4,000 gross floor area or greater unless specifically Iisted as an "exempt" structure per the Revised Code of Washington (RCW). Energy code compliance worksheets are required to be completed and included with your permit application. A wet stamp and signature is required on all sheets of plans and on the cover page of any calculations submitted. Federal Way reviews plans on a first in, first out basis; however, there are some small projects with inconsequential review requirements that may be reviewed out of order. 15-101159-00-PC Doc I.D.:68653 Mr. Jonasson Page 8 April 9, 2015 Review Tinning The first comment letter can be expected within 3 weeks of submittal date. Re -check of plans will occur in one to three weeks after re -submittal. Revised or resubmitted plans shall be provided in the same format, size, and amount as the originally submitted plans. Revised/resubmitted drawings shall indicate by means of clouding or written response, what changes have been made from the original drawings. Plans for all involved departments will be forwarded from the Department of Community Development. Other Permits & inspections Separate permits may be required for electrical, mechanical, plumbing, fire suppression systems, and signs. Applicants may apply for separate pernlits at any time prior to commencement of construction. A third party review will be required as part of the building permit application. This is an additional cost to the applicant. Fees are either per hour rate or based on .a percentage of the permit fee. When required, special inspections shall be performed by WABO approved agencies or by agencies approved by the building official prior to permit issuance- Construction must be approved by all reviewing departments prior to final building division inspection. All concerned depa<<fnents (Planning, Public Works, Electrical, & Fire) must sign off before the Building Department can final the structure for occupancy. Building final must be approved prior to the issuance of a Certificate of Occupancy. All construction projects may be required to have a pre -construction conference. If a pre -con meeting is required, the general or representative, all subs, the architect or representative, the engineer or representative, electrical contractor and any other interested party, should attend this meeting. Meetings will occur at the Building Department and will be scheduled by the inspector of record for the project. Site -Specific Requirements 1803.6 Reporting. Where geotechni cal investigations are required, a written report a the investigations shall be sut)mitted to the building official by the owner or authorized gent at the time of permit application. This geotechnical report shall include, but need not be limited to, the following information: o A plot showing the location of the soil investigations o A complete record of the soil borin; and penetration test logs and soil samples. o A record of the soil profile. n Elevation of the water table, if encountered. o Recommendations for foundation type and design criteria, including but not limited to: bearing capacity of natural or compacted soil; provisions to mitigate the effects of expansive soils; mitigation of the effects of liquefaction, differential settlement and varying soil strength; and the effects of adjacent loads. o Expected total and differential settlement. o Deep foundation information in accordance with Section 1803.5.5. o Special design and construction provisions for foundations of structures founded on expansive soils, as necessary. o Compacted fill material properties and testing in accordance with Section 1803.5.8. o Controlled low -strength material properties and testing in accordance with Section 18,03.5.9. Doc I D.:68683 15-101159-00-PC Mr. Jonasson Page 9 April 9, 2015 705.1.1 Special cases. Special inspections. shall be required for proposed work that is, in the Opinion of the building official, unusual in its nature, such as, but not limited to, the following examples: 1. Construction materials and systems that are alternatives to materials and systems prescribed by this code.2. Unusual design applications of materials described in this code. 3. Materials. and systems required to be installed in accordance with additional manufacturer's instructions that prescribe requirements not contained in this code or in standards referenced by this code. 1704.2.1 Special inspector qualifications- The special inspector shall provide written documentation to the building official demonstrating his or her competence and relevant experience or training. Experience or training shall be considered relevant when the documented experience or training is related in complexity to the same type of special inspection activities for projects of similar complexity and material qualities. These qualifications are in addition to qualifications specified in other sections of this code. • 704.2.3 Statement of special inspections. The applicant shall submit a statement of special inspections in accordance with Section 107.1 as a condition for permit issuance. This statement shall be in accordance with Section 1704.3. • 1704.2.4 Report requirement. Special inspectors shall keep records of inspections. The special inspector shall furnish inspection reports to the building official, and to the registered design Professional in responsible charge. Reports shall indicate that work inspected was or was not completed in conformance: to approved construction documents. Discrepancies shall be brought to the immediate attention of the contractor for Correction. if the}, are not corrected, the discrepancies shall be brought to the attention of the building official and to the registered design professional- in responsible charge prior to the completion of that phase of the work. A final report documenting required special inspections and correction of any discrepancies noted in the inspections shall be submitted at a point in time agreed upon prior to the start of work by the applicant and the building official. The information provided is based on limited plans and information. The comments provided are not intended to be a complete plan review and further comments are possible at time of building permit plan review. The information provided is based on limited plans and information. The comments provided are not intended to be a complete plan review and further comments are possible at time of building permit plan review. CLOSING This letter reflects the information provided at the preapplication meeting and is intended to assist you in preparing plans and materials for formal application. We hope you found the comments useful to your project. We have made every effort to identify major issues to eliminate surprises during the City's review of the formal application. The completion of the preapplication process in the content of this letter does not vest any future project application. Comments in this letter are only valid for one year as per FVVRC 19.40.070 (4). .15-101 159-00-PC Doc I-D.:68683 Mr. Jonasson Page 10 April 9, 2015 As you know, this is a preliminary review only and does not take the place of the full review that will follow submission of a formal application. Comments provided in this letter are based on preapplication materials submitted. ted for thisfluence and modify Modifications and revisions to .the project as prey outlned aba et In addition to tl�ispplication maytpreapplicat an letter, information regarding development requirerments relevant codes carefully. Requirements that are found in please examine the complete FWRC and other the codes that are not addressed in this letter are still required for your project. if you have questions about an individual comment, please contact the appropriate department representative noted above. Any general questions can be directed towards the key project contact, Becky Chapin 253-835-2641. We look forward to working with you. Sincerely, Becky 4 r' � Chapin Associate Planner enc: Master Land Use Application Shoreline Exemption Permit Application Shoreline Substantial Development Conditional Use, and/or Variance submittal Requirements SEPA Checklist c: Ann Dower, Senior Engineering Plans Reviewer Scott Sproul, Assistant Building Official Doc LD.:68683 15-101159-00-PC CITY OF FEDERAL WAY DEVELOPMENT REVIEW COMMITTEE (DRC) Preapplication Conference Sign -In Sheet Dumas Bay West Bulkhead 15-101159-00-PC, March 12, 2015 NAME J SAn-C, �r-1 l �a�sh n !rilrilP/'�'uf WITH PHONE PLC rho (CEP f Zs3 �3�' 2G�1>� ��.� 172ve \c�i r�enb Sera�� ZS S Z�o� /f>w ev,-&T Ir�C. L;za-- 26?.©37;W c11V_ . /lSc.i (SSt,N a'Sv1-4A s Ui�%� 2 I� w/� G�: cL3 -- r Av, coAje, r ft 77. 25 953- - 93v® CD �wiC�l�1. �r`v�st��1 zs 3- 2L6 x 112103-908 1V 3062 30626 432 •r- ti .,112'103-9007 30 6 '. • 1: i+ �� µ' - 4346 3 �.lf - 32G Ix *K 4316 E1� Sir•.,, �.� ^' { • A A - 4343 1121037fail 4• r� t FILE CITY OF L Federal Way March 13, 2015 Carl Jonasson' 4346 SW 3071h Street Federal Way, WA 98023 RE: File #15-101159-00-PC; PREAPPLICATION CONFERENCE SCHEDULED Dumas Bay West Bulkhead Project, Federal Way Dear Mr. Jonasson: CITY HALL 33325 8th Avenue South Federal Way, WA 98003-6325 (253) 835-7000 www. cityoffederalway. cam Jim Ferrell, Mayor The Community Development Department is in receipt of your preapplication conference request. The application has been routed to members of the Development Review Committee and a meeting with the project applicant has been scheduled as follows: 9:00 a.m. — Thursday, March 26, 2015 Hylebos Conference Room Federal Way City Hall, 2nd Floor 33325 8th Avenue South Federal Way, WA 98003 We look forward to meeting with you. Please coordinate directly with anyone else you would like to attend the meeting as this will be the only notice sent by the department. If you have any questions regarding the meeting, please contact me at becky.chapin@cityoffederalway.com, or 253-835-2641. Sincerely, Be"Chapi Associate Planner Doc ID 68254 CITY OF FEDERAL WAY DEPARTMENT OF COMMUNITY DEVELOPMENT DEVELOPMENT REVIEW COMMITTEE TRANSMITTAL DATE: March 12, 2015 TO: Ann Dower, Development Services Rick Perez, Traffic Scott Sproul, Assistant Building Official Brian Asbury, Lakehaven Utility District Chris Ingham, South King Fire & Rescue FROM: Becky Chapin FOR DRCMTG. ON. March 19, 2015 - Internal . March 26, 2015, 9:OOAM - with applicant **I routed materials to all DRC members, but if you have no concerns and will not attend the meeting let me know. ** —Thanks! FILE NUMBER(s): 15-101159-00-PC RELATED FILE NOS: None PROJECT NAME: Dumas Bay West PROJECTADDRESS: 4346 SW 307d' St to 3625 43`d Ave SW ZONING DISTRICT: SE PROJECT DESCRIPTION: Construction of a bulkhead for landslide protection between six property owners. LAND USE PERMITS: PROJECT CONTACT: MATERIALS SUBMITTED: Preapplication Conference Carl Jonasson 4346 SW 307rh St Federal Way, WA 98023 • Master Land Use Application • Dumas Bay West HOA non-profit certification • Aerial photo of properties • Site photos • Gabion Wall details • Site Plan 4ik CITY OF �Icvjv Federal Way : a� MASTER LAND USE "PLICATIGN DEPARTMENT OF COMMUNITY DEVELOPMENT SERVICES 33325 8`h Avenue South federal Way, WA 98003-025 253-835-2607; Fax 253-835-2609 www.cityoffederalway.com of �E015zw Application No(s) ' l d `l J —' IDS Date March I0 ,20I5 IF Project Name Dumas Bay West Slide Repair. Property Address/Location 4346 SW 3076 St to 30625 43rd Ave SW Parcel Number(s) _1121039030, 071, 031, 059, 093, 088 Project Description Construct a bulkhead from the western property line of 4346 SW 307* St at the toe of the landslide to the eastern terminus of the slide at the eastern property line of 3625 43rd Ave SW at the toe of the landslide PLEASE PRINT Type of Permit Required Applicant Annexation Binding Site Plan Name: Dumas Bay West Homeowners (DBWH) Boundary Line Adjustment Address:PMB 148, 1000 Town Center, Ste 180 Comp Plan/Rezone City/State:Tacoma, WA _r Land Surface Modification Zip:98422 Lot Line Elimination Phone:25-3--988-8-873- X Preapplication Conference Fax: Process I (Director's Approval} Email:Thomas.donovan@igilaw.com Process II (Site Plan Review) Signature: Process III (Project Approval) - Process IV (Hearing Examiner's Decision) Process V (Quasi -Judicial Rezone) Process VI Agent (if different than Applicant) SEPA w/P-roject SEPA Only Name: Carl F. Jonasson, Director, DBWH Shoreline: Conditional Use Address:4346 SW 307a' St Shoreline: Substantial Development City/State: Federal Way Shoreline: Variance Zip:98023 f Short Subdivision Phone: 206-963-1718 Subdivision Fax: Variance: Commercial Email: earl jonasson comcast.net Variance: Residential Signature: r p Required Information Owner See attached list of homeowners SE Zoning Designation Name: Address: Comprehensive Plan Designation City/State: NIA Value of Existing Improvements Zip: Phone: $742,000 Value of Proposed Improvements Fax: International Building Code (IBC): Email: Signature: U Occupancy Type I and 11 Construction Type Bulletin #003 — January 1, 2015 Page 1 of 1 k:\Handouts\N4aster Land Use Application 'LEGEND NOTES TO U- Tnm riyp k Nt aM al MmriMrtnp Ina Waon]I Fbaa Icdumrcr Pr.pra4,, II ogee rdl [aecaaH10f adrl,h'f aF near atm}eG I. ttado'CE. pareGWuf0 NOm heel *.Mx ew v! shod iM eeatmrfnmy r NP•eAwy ahauld 6. eenAM4 b, passible updated or addftbnal flood hazard Informalbn. To obtain mare detailed blormalbn In areas where Base Flood El... fina (BFEs) .noRk dPeaw.ya h.a. am dekrmv»d. uvula axe aWW.gtd n eam.N fir Flood P'.Nol 414 Flppeawy Dau alt4'ae 6umnsaryar 0alAmMd F Nbrn. bek. CMdsIwE IN. I,=Ymsne. Iftw (FLSI R.pod pall araerr" 'a M FIRM, UMm Wtt11 lot .x.t9 Pal;" .1e•Ms on Its FAM ..pease u s Md sdgl.aA.I rkratlam. Il r. OF" an: I kmkd Is, &.4 k.haanoc mbp pup -se any.nd should not be used as the sold courca of Mad elevatlon Information. Aocordingy, flood elwftn deb pmtemed In the FIS Rapm1 Ovauld be uAAArd In can)uno9on with the FIRM for pulpea.a of Pondmclbn alea'eI Aaadplan m ssaOMrarb Coastal Base Flood Elevaltans shown on this map apply any landward of Off Nvlh Ameppn VeIrIW Datum yr 19l0 R7AY0 00). Uaefs cf AhIf FIRM .1wuM be are Ihot o,*1 Ibnd mWillnprle an afro prodded h Iht SwMaerr at SI.r/aler Eleratbristtlk nine Fiend A- yUMr Report forµ Iu1WCl4ru Eldvalrab .hbwn In Its Summary of Stll"O Elarwbtn bids should be uMC far onnstruclbn on&v ffoodplaba masage u,1 PUtP+es Wien T.y are higher tru, the elevations shown on this FIRM. tda 40.a o11he Tpadwaya w.I. ep Iocr a1 M. aeelban ale w%.IpoLmd ""on M otolkrm TN eneM.t•.-N tpeead- h ..x wftd..roda wen bgpld to icgtwANM of tAn 4.1 FMM hawoode Pxepras, n9E1Way waaf andids. p.GrrX M aoaOay Mb H. proVod An IN Flood baWsru &MV AONd I for this )urlcdic0on. Certain amas rwt In Dp.cb1 Fineday. Nm Atv.s may m pMN o br Mad mntrol structures. ReferbSadpn2A lFiwd PlPletlbn Measure! of asl Fgpd lnaumnce Study Report for mformaeon on Mod oonbol slructuras for this Jurisdiction. The pm)eldfon used In the peaper.W- of IM m.p was UrAdriet I'd-o arcs Mercator (UTM) i0ne 1O The NNl aplpc dalum was NAD 83, GRS 1980 aphera W. Differences In do_. aph,.Oid• YaFdw• or UTM hones used In the Pud.lian of FIRM. gr .dpbtrl kAad . maj result In slight poshbnal MIN— In reap %.I— acre. Judadt]ree Wn shMNM These differences do not .%,ache x,tcuraey.NM FIRM. Fbod ekwllsons on I" aaapsra trRlnee44 IN. tWN Amerran'Nnn7m r Datuof 19eA The. Aoad rW.O -a be meac.x.d to *udure rwd OrMad.lcv.W.A. r Wqr fed 0 IN .me verLII aeedwr Fd Mbrmalbn [rga.ekep twee On between the National Geodetic VeNwl Datum of 1029 and me North Amedoen ,A DMMn of 1900. YMd the WW.1 Gavdetb Survey non4le at klolRww.s.o,A r mNW the ANTipnpl G>edAfe Survey at the 1pttpanng add..: NGS Inblmatbn Servi na NOAA, NINGS12 National G.W.U. Survey SSMC 'Ifsa 2 1315 EaduNed Highway SINer Spring. Maryland 209103252 (301)713-3242 Tic oNshd ,tch"Non, de INIpOfrA an{'Pt fn.neN nbrmMen for bench marks sheave tin "may, pla.. codas gee NktflWgrr SeMett ararreh ft .1" dud Ceod.Y Survey.! lbuTt 7M-3142. w volt IN wobult at EeJp'Pw•n1s.r nsMladn. Reae May werndfion .hewn on this FIRM wet drrHoa Nam mud k wmcra R." crap eke.r4tt [aeen.F In d'gt'a! Wfasi 07 ov couny M. VA C.M. WS00T, I'd Phan O..My 016. Tlil ertarmapan vas eampieddst9lry of 1:12=le 2a,000 during the ffme period of 1994-2012. Th. profile ".Mo. deplrid-tnis Map Npte .N IN Npdnule me0flwp W-1 n melmoch da !ad patios H Inn FIS rrp4R, Aa a F.adl of MW MO bpOQPapeie data, ne perod. Wa.Ods.. ST ., In Io" ladY mwbIbptd45t ra r101 APm IN.'NaNl cent, lne dappearculEATMthe SFHA. Tide map rd Mae P v wta14d .rd up4ddole abeam chtdaal eenrigunliena pun #_ dram an env pr i*ua FIRM let the ydadCbNL Re lbaeplak. sad Mudwwy. INI , rtv, uanalrentl korp IN III— FtgM vuY nave ba.n a3)Iltbd Is 1» """ M 1nae' n.w Mttem cheraaal onfqur l,om. As . fats Iltr Mod PteNes a+d Flo.0-F Dauf rallea nI nI w.YNF M dre POW Iuuble. 61vof Report tea voulm slltnit.l4n eydeaarre GMj roar a.yd m nn atrcnchpal EjnM . that dlTtr hem v41M h fhoNn vn ink map. Gmpwak Imps aNpeel en mi ma;are based on fhe Gstbab asabbl. of IN cl,a Mne v1 p,6IoeW,. BePluar I do It, .mrcp' Wft yr drannrAMMna may h.Y e eacwaad altar thit m.y won pltrl.had, m P, uddq .heals Petltarl .ppsup"I. community officials to verify turned! carpomb long locations- Md. nor to IN 'tarty p._._. Map 1nakA Ede an pwnew mac el pr ...IV OW-60 The tayetd a[ hoes piMk; ee.l+raW W m.p repa.Rary .ddMLwti end . IdunO of Sammpngn tabb Wn4:1h's1 Hebenal Meet ls$yratp Freylam Glee nr [IleN eemmWs%y .. RrF.a.Ierry of Nis p.nMs v^ wMtt seen wtnmwWr• Is located. P. rlfbrmMrll an rvF4tl4 pfvRKiA asaaetaled WIT uric FIRM YiX nee M.0 rw uke C-1c, ixcl -bode .T Tdm'AmA fs-ArAUW padlrts nuI Ir"If. ptvYWUM, issued GEOn.T IMp the, A MOO En,sr:r SWsay yt a _LW dgCal w IN..I N6a Top,Meta of Tau Irca4ads con TI4 -&,M fie obtained dlmciy from the MSC webslte, F you Ica. 4aeelivna atrm% this msp. Iww 10 oIG1 p,a4ueEp, pr the dtAOenal Floes: Inurarwa PmprsM in gnMe( pYex tea vy F{AU Map Ine, r Ion .Xch.rrge (FIA a! 1�TTiEMA.MAP lt.0T7.y30'.TG771 n riot the FEMA Yrebsb el lw'Awv.kma veol9anne rdMm ZONE AE s39—E "I"" s39�"'E e_`nnl=EL tat � 122'30'CW I SW 255nrtNI y[SSSTaN q%N rr .. .. fe{pFAIT A ST ZONE VE 5410°o"E MI. 15) s42-E s43ew"'E MIILS NMA OY50I w _ ��OOCti rra ZONE VE s44°°r'E'L1m e45°°o"E e46ppenE ION_ .L EI ._. 122' 22'30' 14722'30' 1 - 25 y J (SL 13J ZONE AE I"UNt Yf } OE.W ...... ays T� (EL14 1 b.Y /2, / ZONEx 29 ION VI: sNxEiiar0. 4 s w Tban r.' Ia I' .. ... :Et •" 20NE% � LONE VE F}ti(:t [IT•ti I'1 g w E1 1 1}tif'IlNFI IkA l F.11 IFt I•',lti •SI30 .. p rn .YEay+ LO ff 11" sari 1 .. .. ;I F..S. u45"'N + �+ z arrmi'IH aT rhfrr a '. 4wsseN st 1 I' IONEAE 32T 4 ZwNEat :1__{dL 14) yyy grsT •Z"IA Nt lE 36 r+ . a..... � 34 2' . . . ONE AF ZONE %a T. RI N, - 6 5 i_1H -lt1kE:VE >aJ SL PSa: tl[r.5st[,Itiaa•:frl.:nly FArtE.r:.:•iOAlx Fi.Y••.cr,l;a.t (I5k11. 2? MOT " I[:1"1,% iNEr•, R4 jCGE2 LR�:iNO�YgVTybld[!.•'V[ff[T!I,AnhlGi]EdS TbOM ;e1NE �• ,�'rC d�f' uallGF,I. A:a1� sp `r,LNi6NIP 7"tOPFI• RAlff.i'•1 E'A`"•. AM IIIW 1 :uf:£'JE n'NE VE s43^^e^N f- £I - IW paTrN.Or� . - : OrcE VE ';AvtiIft1W- I,/111.a! I �`df t I :. , ZONE VE srr»lHal•` 1'lifh 7 il"INII �•, IAE ICE EE ' �31 f --ZONE1EVE 72` GI :ONE 'JE"�N Ey @ `ti. (EL 201 ."UNE VE / cl. l'sa -ZONE AE 1i� TS) r0 N L A lr IOtE FE . •'.:.OI�E •lE �c� I"Ora a kitir; f:I if XxI ! • LC=IF Lf ZO!rE VE: :E. a- 1..NIV:I IHI'l)R.I IF Tp .1H F..1ti Fy .Y,y,H �•grNrN BA' ANGIM 61 5 ]u0 1 F' •��.. � Px aonl 1• Pr � �,�11m Fx slomcT r ` WQ P'r i "41—N ".. -w } + II tiR lL + yv rlaM" � } vt R eAaaec+lilwfw " :} 40 - ', - pERCEcaw:lr...~ _. 'A' +p unnTltlm 11 W]16eIrA CITY OF FEDERAL WAY ZONE X 530322 '4000PvN - �. + + V �. 23 sa39fso"N -� r y k + + n35p0OnN -I i T + + + + + + 4P 15 00 1M. es-DD' SPECIAL FLOOD MaMD A" (S 1II SUIl M M'CATWN Sy THE L%uttWd O} W-E PWOO ;1lr.d..IrhaNa A.P111tt,earrptq,aM A -.W r-.spitkTN bee one raa , n. near tl k-9 arrka-..r.rW . car e.n r.w. TA. swew rMa1 t%.w ana h nra arbinTlo IMsa•n aT v. Ir rrr-•I.wenaW. sass NSI-MI..�WSH nu.•w Eats A A[. AIL at4 M +v, p W w, 1vr..a. Flwl li.nln r g--rywt%n eYvelbn al tle 1% anwel darce rb.L lONEA Na Bau shod FJnadans de2md.ed, ZONEPE ode Rood Be:aPoos tlde�mnM. ZONEPH Rao4 da40. a1Im3feNlwuaaY seas of poMMN; .sse shod BaVNMs Wemrroe LONEPO Paod Mse44 l k]t 4dusepf .lpaMMlpr.g f.nPM, ar..aae deptle rm•+a IR ar4n d aa.dtlfrroa./. •eaea-a r.. xn.r,amd. IOYO as iberell4ee WlarO Aw.a latnea, lraeseM so 14._ safe.. +�waf • Iw4 rc..s n..._ n.-..ww•«sr «assess, sees Ae rdwuo vur H rain II>ea rx'nl rn•+a n [dq wrr.e pa a.vtM. s-+.rw frw Iaa p"t .•-+ta rw•. w p-.x dad ]]N4 Aft ,w ron-.Nnaa l.++fa•+awlrwnNxvyahW mllpep P'.lrtsa!an,rn N•dstamLs•ti•" r Ipsa fad fk.mr nsae...ed IpapY Coasml Aaod mne xih rtlodry MsnN (wove actlon); no 0ase stood Bwdbm denmdned. VE Uastel flood mne wN, vtlatlN'kmM(vawe acibn)i _RbodE dsso xm ea C] FLOODWAY AREAS W ZONE AE �.awa..<p qua sstxwrdsseaet Awdw be �irsaW saYdwlya,aa.ae M «hod Not. OTHER FLOOD AREAS —EX As.•i ca epaawwalrAMG ll.ra. arissd IN nn,alrH.r.ffvA--N erae 4r.iba a t law N -.AAn sqd war Is, ad 1 wwN av4, aN.rt-N+>.aaaH In. awe I%.howl ta.•ctfA.L OTHER AREAS Mel Mas de2mNMNbe ouOlde the0lM.mwl tl�n¢Poodphln. ZONED AmasNwfikM1 Pood lands am unhkmke4, but possbk. ® COASTAL BARRIER RESOURCES SYSTEM (®RS) AREAS OTHERWISE PROTECTED AREAS (OPAS) C0a5 ,uddo DPAs ns-.*iota iwehp or adtazmt m S,-lRued WmM Arco. alb Aww1 cetu rbAwe 1 saaw axes. -col o-es.+b./as,n r-.w .�- Foo "', boon&ry Tree D hounGry ............. C.RS aM OPA bounmry �--e-aearreutlnr Stv!'Mrys4rwaN Arta Ann fM ba-dah LJ' n.�e.twi"`a.rd..i -e.� Ndmemr.w Romtb.tam, —513— E}t,atun a<aM win; dwetlen bidet• IELOeTI wwltwv lt+cw.rA-,.an xvtm nG-rr+. as.+rts,nn rear NMd.mW b Nu North AmNcd YI-a norm d Mat q q Cms sdtbn a,e 23 Toms rc rS OYM', 9]'D!'1S ^ee'uH ��' A 0e North AmuLan Dahmof »nfnmunwaeem Iemaptc+s - N 100Unehf unMwsnl T nsvex Mdmbr pM WAPA, mne Is DXEE10 x adch msd ls: dpbnbn in Notes as lode sedkn o/ Mh_14 perNl M1E PAer14 W,P RF305'TCR10 Rtl' b .1 RepOpbrlm Eaton Map nda` &Tc —R4TEO-II—DE FiDW INSIIR4NCERATEMAp SepmmberM food EH♦�f1.E FJ.rU0�Or 05vegtln T011K A.rtOl lea MeatY•mp� a� bodFk-vm�p7erY wialrwu• rty rcperanra gaaena4w w.srr mlbrkror lerrA rpm rry.eYa-a bides oa.enpdoaa a� ka+.'�40aar0 Laraw ry.arary W raweTpasr eel . rmwreaw fevnry. tIN t r. Cm mwfy alm.rmrlyd. bpaw n ar apr+L.,waa bwi I.pen W P. r••wvr. Tohbmbea Nee rw.�Or..rWaM w N6axway —d W u eaulmoe gad or W tle N.wN FM4 ay.ree Fwala. d akaWaORR MAP SCALE 1'=2000' Im o 0 Was r0p0 [s1 Y0 refs des sob PANEL 1225G FIRM FLOOD INSURANCE RATE MAP KING COUNTY, WASHINGTON AND INCORPORATED AREAS PANEL 1225 OF 1700 (SEE MAP INDEX FOR FIRM PANEL LAYOUT) ":.s G= "'!_ wsv Oo nma %1L 9Ir q� uNrr 9ooie sas a PRELIMINARY FEBRUARY 1, 2013 Ib1bs M Vwf: Th. Mep Numb.r shown labw µOPo tre used when pl4 lry maa alo.rc; " co,oluaNy Nlant. ono. Ir6eva shod M u on irs,uj ea T. au*cE Wm W, 0Qar+ MAP NUMBER 53033CI225G 1�t_-VP ;] MAP REVISED Fead��rarl EEmmergenq hLnagemenfAgenry Becky Chapin From: Carl Jonasson <carljonasson@comcast.net> Sent: Wednesday, March 18, 2015 9:15 AM To: Becky Chapin Subject: RE: Jonasson's 1st & 2nd Preferences.pdf Hi Becky, I viewed 15.05.050(4) a week or two ago and dropped the idea then. The only way I could see a possibility was under an emergency situation. If the lower work cannot be considered an emergency situation, then there would be no chance for groins or breakwaters. Even under an emergency I'm not sure that anyone would allow them, as long as the bulkhead is built. I don't think that groins or breakwaters alone would be sufficient to protect the toes of our banks, so there may be little reason to pursue those ideas further, unless Ecology and WDFW viewed them as beneficial to habitat. In listening to Isaac in our driveway the other day, I may have misunderstood his statements, thinking that under an emergency, and tentative buy -in by the regulatory agencies, permit could be issued for groins. Later during the formal permit application, we would still have to prove their need to the agencies. Obviously we would not want to have to remove them later. Could we discuss this briefly during the Pre -Application conference when Ecology is present, without compromising the rest of the meeting? If it is an entirely separate issue and would harm the conference, then we can discuss it later. Carl Jonasson From: Becky Chapin rmailto:Becky.Chapin ❑acityoffederalway.m. ] Sent: Wednesday, March 18, 2015 8:26 AM To: 'Carl Jonasson' Subject: RE: Jonasson's 1st & 2nd Preferences.pdf Hi Carl, After viewing the proposal for breakwaters and groins, I checked with Federal Way Revised Code (FWRC) Chapter 15.05 — Shoreline Management, to see what code allows. Unfortunately, neither of the options would be a feasible solution. I've included FWRC below. FWRC 15.05.050(4): (4) Breakwaters, jetties and groins. (a) Floating breakwaters are permitted in the shoreline residential and urban conservancy environments, with a conditional use permit, when the following conditions apply: (i) Floating breakwaters may be allowed if necessary to protect a public boat launch, when no other alternative with less impact to the environment is feasible. (ii) When permitted, development of floating breakwaters shall include mitigation measures consistent with this chapter as to ensure no net loss of ecological function. (iii) Nonfloating breakwaters are prohibited. (b) Jetties are prohibited within all shoreline environments in the city. (c) Groins are prohibited in all shoreline environments in the city. We can discuss this further at the meeting, but will move forward with comments for just the bulkhead proposal. Becky Chapin Associate Planner City of Federal Way 33325 8th Avenue South Federal Way, WA 98003-6325 Phone:253-835-2641 Beck .Cha in cit offederalwa .cam From: Carl Jonasson rrfailto:ca . on sson comcast.net Sent: Tuesday, March 17, 2015 5:40 PM To: Becky Chapin Subject: Jonasson's 1st & 2nd Preferences.pdf Becky, Attached are my preferences. They might be considered as additive alternates, if Ecology would consider them as beneficial to habitat development. Another thought for Dave is would either the groins or breakwaters serve to reduce littoral drift to Dumas Bay, which is apparently building up with sand and helping to contribute to the summertime rotting sea lettuce problem? It seems that the Bay could stand to lose some of its buildup. Carl Jonasson Becky Chapin Subject: Emergency Exemptions - Dumas Bay West Location: Steel Lake Room Start: Fri 5/1/2015 2:30 PM End: Fri 5/1/2015 3:00 PM Recurrence: (none) Meeting Status: Meeting organizer Organizer: Becky Chapin Required Attendees: Isaac Conlen; Scott Sproul; Mark Orthmann Resources: Steel Lake Room Meeting to discuss emergency permit exemptions for a proposed retaining wall in an area that recently had a landslide event and potential to fail again. Discuss legal implications for requiring permits vs. not requiring permit as it relates to the emergency/imminent threat status. Related emergency code sections: WAC 173-27-040 (Shoreline Exemption) (d) Emergency construction necessary to protect property from damage by the elements. An "emergency" is an unanticipated and imminent threat to public health, safety, or the environment which requires immediate action within a time too short to allow full compliance with this chapter. Emergency construction does not include development of new permanent protective structures where none previously existed. Where new protective structures are deemed by the administrator to be the appropriate means to address the emergency situation, upon abatement of the emergency situation the new structure shall be removed or any permit which would have been required, absent an emergency, pursuant to chapter 90.58 RCW, these regulations, or the local master program, obtained. All emergency construction shall be consistent with the policies of chapter 90.58 RCW and the local master program. As a general matter, flooding or other seasonal events that can be anticipated and may occur but that are not imminent are not an emergency; WAC 197-11-800 (SEPA, Emergencies) Actions that must be undertaken immediately or within a time too short to allow full compliance with this chapter, to avoid an imminent threat to public health or safety, to prevent an imminent danger to public or private property, or to prevent an imminent threat of serious environmental degradation, shall be exempt. Agencies may specify these emergency actions in their procedures. FWRC 15.10.110 (Certain activities not subject to critical area standards) The following activities are not subject to the provisions of this chapter: (a) Emergencies that, in the opinion of the shoreline administrator, threaten the public health, safety, and welfare, where impacts to critical areas and their buffers are mitigated to the extent feasible following the emergency actions; Building Code [A] 105.2.1 Emergency repairs. Where equipment replacements and repairs must be performed in an emergency situation, the permit application shall be submitted within the next working business day to the building official. ° Jonasson'S z-"Preference G bion Wall ,_-y Brea1 a ters in lieu Of Groins ., puge[ scland �onas won e• e e♦ e e Reagan Ansa i ''•••........,. .-. - ],Pill Slide Area y 7 i>✓ wn "0"4 tk ��- K r I a� L - -_ ' 14 1 _fonasson's .s' Preference G bion Wall Littoral Drift P/L MLLW ? Slide Debris � ■ Pc� r 5 ❑ �i �iti Y 1D n ass,c -) ri i 74.88' �fC A11SdT1 go i go' Slide Area IT — Borelll 1721 Imminent f Danger Threatened - -,� Threatened tlift, ■ Spalding 120� 110� Imminent Danger 4"" P/G Groin 130' j . Imminent Danger AiM IrMA. A- ■ . •�• • � _ *` � II'.y�` � l 1 Jr 1l 1 "�� I' � _.. _, , ;ems` '�i"' _ - �• ��' _ � �.• I f �. 1 .i �- •, �' ;.•' rya . 3 Y i r .{.r�7 ` -r: #_ r tea.. •p.. � r �4i• � tb: _ i�ri 1• ` J_`< _Sri i-'�� -Tens1 n crae .Y YA nkle Y _+ Mm + w OC • j~ - ( � .:,� � � '� ..1►-fir. ' Y 'i- - �•. 1 _ "� � � ;rat" a • } ` �S � � ■ • � • .,� • r i . � i �- WATER AT TIME OF PHOTOGRAPH`S C + I —0.02 its CD L Proposed location of 256 cy of spoils from augured 24" Q + diameter piles. Fill averages 3.6 feet in depth. Area can be reduced if necessary, requiring a deeper depth of spoil Hv162 _ placement. The spoils will be generated from the auguring of .72 piles on the Jonasson, Reagan and Ansari properties. --- 1 ❑ - - _ ----------------------- 5: {jI r m slide- __ a - _ _ _ eF7� 7•F?7T r7- s x_ _ _ - _ - --- - - - _ - -- - - - - - - - - -= tiff?�= r_:---•___ _ --- - ---- -- -- - -- - -- - - - __ •'� - �- - - - _ - - --•_- _ - l•;ter �_ - - - �� __ _ � '_ __ - -- _ _ eft-. .• -..- _• - _ _ {�� _ _ _ - _ - - _ _ ;tF••e_-+ 2� �• _�-��2__••= - _ �e� � it _ - _ _ - - r - - - _ _ _ - .�a - wr a� -- - _ _--.-c.e'e F - ~S _ 3, - g_ r ig' - - i3 - - L - ' - a- _ - • £e - - yy _ Gx - - a•Irr- � �s-• e y v. 143.2 v• : I 147-e 19 29 4 24-6 � ® r `� o Dune. o ,d _4- �149-5 129.7 Cl � ® $m 124.6 110. • SWP Conn Deck R S D.& Deck Deck eeiwm 0ek ,.5 u 124.7 116.6 104 a 0 BLDG. e�Dc. BLDG. elnc. 10 0 7a4-7 Ca c. e 1 0 - If 01.9 I 1 Bur— lf BLDG. j 159 13..16j I OCALF V.40' OE81CNM ! K II a"WR sx 9MO M am AF,mm SKET / OF 2 Fj -9 IRA U a-1 t_4 ON O ^ O 00 00 M ON oo O 00 M C% Q C � iMP1 f� O M +� 1f1,®, �p .M.O ^Ln � 00 � � M � CU u tn It-00 w u O NUN y N .ti rn W � Q U I AJ i U ^ va f N V� to •> N n �J N n V C� M r�n M O fl C'r to O'er(�Nr) "� o C u � c Ocu cu u P-4 rG I flu (U o� �.� - = • "" v� fil .off -4 15 �Q O .O O r-1 .;-4 v 7A 0 fu bn ro CI.4 O O i .4 T ram^ WVJ W INA a „ L m m a S N C � c a a 10 `a CL c ro O s Q 9 a It Ali 4000ox i.:- .•., rrr 'iF�IL• rr!de. "IWOAII w J 4Ago l•� r rr id F op : r. Idj ► +b 1} , rl fw Aa r Sri ' r. `+�'0'JII t M+i r� }{'Q i r Ji �!al {74lit�i, !t�.I;.i 7fif•'� f i Iu Mlj or �, r�� f � Idl ►• s7� 20 , dif ti SIF !1 , .0 Im ilM, IIA1;tF fffr.fth. 04i0-awt to V f) : 7 6I►-: ' w pit .#tr Hr�t►, 4 - ri Ito: till 07 M kl; V� wlf bn lz ;J m I e A;dip r. i'54ri A,, r i�iku �u.Fll r i 0i . ij 1 T*� •5twill 11 71jo iA1S r � R+ r Dumas Bay West Homeowners Plan View in zoo9 fVV.0 STATES OF ISO; •'�sTArFQ� a _ of Al ,p II'S -7 AN if AIr►mi I (vitl Secretaryy_.' of State I, KIM WYMAN, Secretary of State of the State of Washington and custodian of its seal, hereby issue this CERTIFICATE OF INCORPORATION to DUMAS BAY WEST HOMEOWNERS a/an WA Non -Profit Corporation. Charter documents are effective on the date indicated below. .i .R..iR. Ri!!� itWar ■r..i iRw.. ■!ri .Rew wRiw.. .rrrfi De� 10 i TUN: ■.. Date: 2/16/2015 UBI Number: 603-477-196 Given under my hand and the Seal of the State of Washington at Olympia, the State Capital /14';� */t*— Kim Wyman, Secretary of State Date Issued: 2/17/2015 RECEIVED AUG 07 Z015 CITY OF FEDERAL WAY CDS July 16, 2015 File No. 15-046 Dumas Bay West Homeowners c/o Mr. Carl Jonasson 4346 SW 307'h Street Federal Way, WA 98023 fbnGEO C 6 R P G R A T E 0 Geotechnical & Earthquake Engineering Consultants Subject: Geotechnical, Engineering Study Dumas Bay West Coastal Bluff Stability Evaluation — 6 Properties: 4316, 4326, 4338, 4342, 4346 SW 3071h Street & 30625 43rd Ave. SW Federal Way, Washington Dear Mr. Jonasson, The enclosed report contains the results of our gotechnical field reconnaissance and explorations, along with conclusions and preliminary recommendations regarding the steep slopes present on the subject six residential properties. This study was undertaken at the authorization of the Dumas Bay West Homeowners (DBWH) to address and evaluate the stability of the coastal bluff that lies to the north and below the residences of the DBWH. The enclosed report provides the basis for the analysis and conclusions regarding site geology, hydrogeology and slope stability of the six parcels. Other reports or memoranda may supplement this report with recommendations for specific actions that may be employed to improve or stabilize the coastal bluffs on individual parcels of the DBWH. Please do not hesitate to call with any questions. Sincerely, obert E imerling, P.E., L.E.G. Principal Geotechnical Engineer Enclosure: Geotechnical Engineering Study 3213 Eastlake ':venue East Suite B Seattle, WA 98102-7127 Tel (206)262-0370 Fax (206) 262-0374 e GEOTEOHNIOAL ENGINEERING STUDY Dumas Bay West Coastal Bluff Stability Evaluation Federal Way, Washing—W-11 Prepared for: Dumas Bay West Homeowners f-l&,( 1 N C 0 R P PROJECT NO.15-046 July 2015 Geoteehnical & Earthquake Engineering Consultants Dumas Bav West July 16, 2015 TABLE OF CONTENTS 1.0 INTRODUCTION................................................................................................................... I 2.0 SITE DESCRIPTION............................................................................................................. 2 2.1 LOCATION AND LAND USES.................................................................................................. 2 2.2 SURFACE CONDITIONS........................................................................................................... Y. 2.3 SURFACE WATER MANAGEMENT.......................................................................................... 3 2.4 HISTORICAL AND RECENT MASS WASTING ....................... ............ :....................................... 6 3.0 SUBSURFACE EXPLORATIONS..................................................................................... it 4.0 SUBSURFACE CONDITIONS........................................................................................... 11 4.1 SITE GEOLOGY.................................................................................................................... 11 4.2 SOILS................................................................................................................................... 12 4.3 GROUNDWATER................................................................................................................... 13 5.0 SEISMIC CONSIDERATIONS..........................................................................................13 5.1 DESIGN CRITERIA............................................................................... ,................................. 13 6.0 SLOPE STABILITY.............................................................................................................14 6.1 STABILITY ANALYSES......................................................................................................... 14 6.2 DISCUSSION OF RESULTS..................................................................................................... 15 6.3 STABILITY RISKS................................................................................................................. 15 6.4 SURFACE WATER CONSIDERATIONS.................................................................................... 16 7.0 CONCEPTUAL STABILIZATION OPTIONS................................................................17 8.0 ADDITIONAL SERVICES.................................................................................................17 9.0 LIMITATIONS.....................................................................................................................18 10.0 REFERENCES.................................................................................................................... 20 LIST OF TABLES TABLE Page No. Table 1 Summary of Groundwater Measurements....................................................................... 13 Table 2 Seismic Design Parameters per 2012 TBC....................................................................... 13 Table 3 Summary of Slope Stability Analyses and Results.......................................................... 15 15-046 DBWH Geotechnical Study.docx i PanGEO, Inc. Dumas Bay West July 16, 2015 LIST OF FIGURES Figure 1 Vicinity Map Figure 2 Site and Exploration Plan Figure 3 Static Globai Stability Analysis, Section 'A' Figure 4 Static Global Stability Analysis, Section 'A' Figure 5 Static Global Stability Analysis, Section 'A' Figure 6 Static Global Stability Analysis, Section 'B' Figure 7 Static Global Stability Analysis, Section 'C' LIST OF APPENDICES APPENDIX A FIELD EXPLORATIONS APPENDIX B LABORATORY TESTING —Existing Condition — Existing Condition at Setback — Back -analysis of Section 'B' Slide — Post -slide Condition — Existing Condition 15-046 DBWH Geotechnical Study.docx ii PanGEO, Inc. Dumas Bay West July 16, 2015 GEOTECHNICAL ENGINEERING STUTDIV Du-mAs BAY WEST COASTAL BLUFF STABILITY EVALuxmN — 6 PROPERTIES: 4316, 4326, 4338, 4342, 4346 SW 307TR STREET & 30625 43RD AvE. SW FEDERAL WAY, WASHINGTON 1,0 INTRODUCTION This report presents the geotechnical exploration, analyses, conclusions and recommendations regarding the coastal bluff located along the north side of each of the six properties included within the Dumas Bay West Homeowners (DBWH) association. The scope of our work included: • Reviewing existing geologic data to gain an understanding of the site conditions, • Performing a site reconnaissance which specifically included noting and documenting the existing stormwater management practices employed on each property, • Conducting a subsurface exploration program consisting of two borings both of which were converted to groundwater observation wells. • Performing slope stability analyses of the coastal bluffs at representative locations, and • Preparing the conclusions and recommendations presented in this report. Our work was performed in accordance with our proposal to DBWH, which was authorized on February 27, 2015. For reference purposes in describing various site features, the following nomenclature has been adopted for the six properties of the DBWH for use in this report (west to east): • Parcel 1: 4346 SW 3071h Street • Parcel 2: 4342 SW 307th Street • Parcel 3: 4338 SW 307`h Street • Parcel 4: 4326 SW 307th Street ■ Parcel 5: 4316 SW 307th Street • Parcel 6: 30625 43rd Avenue SW The location of the DBWH properties is shown on Figure 1, Vicinity Map and the parcel number convention cited above is shown on Figure 2, Site and Exploration Plan. 15-046 DBWH Geotechnical Study.docx 1 PanGEO, Inc. Dumas Bay West July 15, 2015 2.0 SITE DESCRIPTION 2.1 LOCATION AND LAND USES The DBWH properties are all located with street frontage along SW 307`� Street in the Dumas Bay area of the City of Federal Way, Washington. Southwest 307`h Street is a private street that is not part of the City right of way, which ends at the intersection of SW 307'h Street and 43rd Avenue SW at the eastern end of the six DBWH properties. The row of six adjacent DBWH residential properties are bound to the north by Puget Sound, the east and south by other residential properties, and on the west by property owned by the Archbishop Brunett Retreat at the Palisades (Archdiocese of Seattle). 2.2 SURFACE CONDITIONS Surface conditions were observed during site reconnaissance performed by PanGEO personnel on February 15 and March 24, 2015. The overall topographic relief at the site is approximately 150 feet, ranging from the inter -tidal zone at the base of the coastal bluff to the maximum elevation of 150 feet on the westernmost of the DBWH properties. The DBWH properties occupy an east -west trending ridge with the crest at the approximate location of the primary residential buildings on each parcel. From this ridge, the coastal bluffs slope steeply, at gradients exceeding 100 percent, to the north and the beach below. The slopes to the south of the ridge are less steep, varying in slope, and averaging approximately 20 percent extending down to a pond at approximately El. +55 feet. The ridge itself loses elevation from west to east, with a fall of approximately 55 feet from approximately El. +150 feet at Parcel 1 to approximately El. +95 feet at Parcel 5. Further east, the ridge continues to descend down to sea level at the western fringe of Dumas Bay. To the west of the DBWH properties the topography continues to rise gently to moderately an additional 20 to 30 feet onto the Archbishop Brunett parcel. Vegetation consists of mature, tended landscaping on the upland portions of all six DBWH properties. Below the crest of the coastal bluff, vegetation ranges from mature coniferous and deciduous trees with brush and shrub understory to fully denuded slopes within the areas where mass wasting has occurred (discussed further, below). A portion of the slope below Parcel 3 extending east to include Parcel 4 and a portion of Parcel 5 has experienced recent cutting of the vegetative cover on the slope. The cutting has left stumps approximately 2 to 4 feet above the ground surface. An area of recent instability is visible from the beach mid -slope and along the Parcel 3/4 boundary. The slope comprising the coastal bluff from the ridge where the residential structures are sited to the toe of the slope at the beach of Puget Sound was visually observed during the site reconnaissance. This slope differs from other tall coastal bluffs that exist around Puget Sound in 15-046 DBWH Geotechnical Study.docx 2 PanGEO, Inc. Dumas Bay West July 15, 2015 several respects. First, the slope is remarkably dry. No evidence of seeps or springs that would contribute to slope instability was noted during the reconnaissance. Second, the slope is less steep as compared to other coastal bluffs around Puget Sound that are comprised of glacially overridden soils. According to the site survey that provides the basis for the topography shown in Figure 2, Site and Exploration Plan, the undisturbed portions of the bluff are approximately at a slope of 100%. Where mass wasting has occurred (discussed further, below), the slopes are flatter, ranging between about 70% and 90%. Locally, notably on Parcel 1, the coastal bluff slope is steeper than 100%, to near vertical, just above the toe of the slope at approximately mean higher high water level. Third, the soils observed in the slope are outwash sands, with some silt layers, capped with a relatively thin glacial till layer at the top of the bluff. No evidence was observed of the overconsolidated clay (locally termed "Lawton Clay", "Seattle Clay" and "glaciolacustrine deposits") that is notorious as a major contributor to landslides around Puget Sound. 2.3 SURFACE WATER MANAGEMENT During the site reconnaissance made on March 24, 2015 the collection and disposition of surface water was visually observed on each of the six parcels. Due to the topography of the ridge upon which the DBWfi parcels sit, all surface runoff to the south of the primary residential structures is ultimately routed in a southerly direction and not toward the coastal bluff. The observations are generally organized to discuss surface drainage in the following order: • Surface drainage on the north (rear) side of the primary residence, • Disposition of primary residence roof gutter downspouts, • Garage pad surface runoff, ■ Secondary structure roof downspouts (if any), • Driveway runoff, • Other surface runoff or miscellaneous drainage items noted on the south (front) side of the residence, and • Underground collection system discharge (if any or known). Observations at each parcel are discussed below. Parcel 1 — On the north (rear) side of the residence surface water collects in a topographic depression below the deck structure between the house and the crest of the coastal bluff. The glacial till cap (discussed in more detail below under Geology and Subsurface Conditions) is for all practical purposes impermeable and therefore water ponds in the depression. Both the depression caused by a slight topographic ridge right at the crest of the coastal bluff 15-046 DBIVH Geotechnical Study.docx 3 PanGEO, Inc. 1 Dumas Bay West July 16, 2015 (hereafter referred to as the "lip") and ponding-on top of the glacial till is a condition that repeats on other parcels as discussed separately, below. When the water level in the depression on this parcel reaches a nuisance level, the homeowner operates a small sump pump to route and discharge the water to the catch basin system on the south (front) side of the residence. All roof gutter downspouts on the primary residential structure are collected in tight lines and routed together into the underground storm drainage system. The garage pad on the south side of the residence is concrete flatwork and directs surface runoff to either a strip drain immediately in front of the garage doors or to a catch basin at the south center edge of the pad. Roof gutter downspouts on the detached garage or shed building discharge to the driveway and collects with the surface runoff from the garage pad. Further surface water that collects on the concrete driveway is contained by edge gutters until it directs the runoff to a strip drain at the driveway entrance (gate) to the parcel. The discharge of the strip drain is uncertain, but at this point the surface drainage is well below the topographic high on the parcel and well away from the coastal bluff.. A water feature operates south of the garage pad and flows in a southerly direction to its collection/pump pond. Overflow during heavy precipitation is directed to a cobble/gravel strip drain feature along the eastern property line, which also intercepts other surface runoff from the landscaped areas. This collection area may join the discharge from the underground storm drain system, or infiltrate, or combine with the strip drain at the end of SW 307"' Street. All drainage collected by tight lines and catch basins appear to converge to the low point of the catch basin at the south center edge of the garage pad. The discharge from this point is uncertain, but according to the resident, the system has never clogged or backed up. Parcel 2 — Due to the mass wasting that has recently occurred on the north side of this parcel, the "lip", if there was one, is no longer present and surface runoff is free to flow to the north and over the crest of the coastal bluff. Catch basins are also present closer to the residence that collect surface water into the underground piping system. All roof gutter downspouts on the primary residence are collected into tight line underground piping. There are no secondary structures on this parcel. The garage pad on the south side of the residence is constructed of permeable asphalt and was constructed relatively recently in accordance with modern site development requirements for impermeable surface areas. 15-046 DBNATH Geotechnical Study.docx 4 PanGEO, Inc. Dumas Bay West July 16, 2015 The driveway is concrete and directs surface runoff to the south and the roadside ditch of SW 307t" Street. Landscape walls have been constructed south of the garage and garage pad and one of these walls was observed with a weep hole that was discharging water onto the paved surface of SW 3070' Street. According to the resident of Parcel 2, all drainage collected in tight lilies is routed to an infiltration gallery located south of the garage. The resident also reports that the infiltration gallery has never overflowed. Parcel 3 — This parcel also exhibits the "lip" at the crest of the coastal bluff that prevents surface water on the north (rear) side of the residence from flowing to the north and a topographic depression similar to that observed on Parcel 1 collects and ponds surface water within a rock garden style landscape feature. No catch basins or other means of collecting this ponded water were noted, although the topography indicates that if the depression overflows, the flow is to the south via the east side of the residence. All roof gutter downspouts on the primary residence are collected into tight line underground piping. There are no secondary structures on this parcel. The garage pad on the south side of the residence is constructed of modular pavers and is therefore considered pervious. A catch basin collects surface runoff at the low point located at the center of the east side of the pad. The driveway is asphalt and drains surface water to the roadside ditch along the north side of SW 307`" Street. A manhole cover labeled "Drain" is located about midway down the driveway. This appears to be the collection point for the underground tight line drainage, but the outfall is not known. Two pipes outfall to the roadside ditch at the southeast corner of the property. Neither of the pipes was discharging water at the time of the visual reconnaissance, despite rainfall occurring the previous night. Parcel 4 — Observations of this parcel were limited to what could be seen from the boundaries of the parcel and from the beach below the bluff. The north (rear) of the residence has a combination of concrete flatwork, deck and lawn. The deck is over -hanging the edge of the bluff by several feet and is therefore acting in cantilever. The concrete flatwork extends beneath a deck that overhangs the coastal bluff. These landscape elements appear to allow surface runoff to now to the north and over the crest of the bluff. The "lip" either never existed on this parcel, or was removed during landscaping and deck construction activities. All roof gutter downspouts on the primary residence appeared to be collected into tight line underground piping. The south side of the residence has numerous landscape walls and a partially underground garage structure. Some of the associated walls are moderately tall and the wall drainage (if 15-046 DBWH Geotechnical Study.doex 5 PanGEO, Inc. Dumas Bay West July 1 b, 2015 any) is unknown. However, due to the decrease in topographic elevation from the primary residence to the south, all surface drainage and runoff is also directed to the south. Parcel 5 — Similar to Parcels 1 and 3, this parcel also exhibits the "lip" at the crest of the coastal bluff that prevents surface water on the north (rear) side of the residence from flowing to the north. The ridge at the bluff is more prominent on this parcel and directs all surface runorT to the south. A water feature (not active at the time of reconnaissance) flows from the north to the south in the landscape area between the residence and the bluff (rear of house). If the water feature overflows during precipitation, the overflow would collect in a depression beneath the deck attached to the rear of the residence. According to the owner, there is a catch basin present near the deck that is hidden in the surfacing of a "dry stream" and that surface water collected there is discharged to the roadside ditch along SW 307th Street. All roof gutter downspouts on the primary residence are collected into tight line underground piping with the exception of the southwest corner of the residence which drains directly to the ground surface via a "chain drain." Although the water that reaches the ground surface at this location is not positively directed away from the structure, the topographic relief ensures that all gutter drainage that reaches this location eventually becomes surface runoff flowing to the south. There are no secondary structures on this parcel. The unpaved driveway, together with the rest of the parcel south of the residential structure. sheds runoff to the south where it is collected into the roadside ditch along SW 307`h Street. Parcel 6 — Due to the mass wasting that has occurred on the north side of this parcel, the "lip", if there was one, is no longer present to prevent surface drainage from flowing over the crest of the coastal bluff. However, the area between the residence and the bluff is relatively level and may drain slightly to the south where there are several catch basins that collect surface water into the underground piping system. All roof gutter downspouts on the primary residence are collected into tight line underground piping with the exception of one downspout which discharges onto concrete flatwork where flow is then directed into one of the aforementioned catch basins. There are no secondary structures on this parcel. The garage pad and driveway on the south side of the residence is constructed of a combination of concrete flatwork and asphalt and drains via surface flow to the south and east towards the roadside drainage ditches of SW 3071h Street and 43rd Avenue SW. 2.4 HISTORICAL AND RECENT MASS WASTING The term "mass wasting" includes landslides, surficial sloughs, debris flows and other occurrences where earth materials, with or without the presence of water, move downhill under the force of gravity. The coastal bluffs north of the residences comprising DBWH are typical of 15-046 DBWH Geotechnical Study.doex 6 PanGEO, Inc. Dumas Bay West July 16, 2615 steep slope areas around the Puget Sound region that have experienced mass wasting in the past, both historically and pre -historically. There are two notable areas of mass wasting in the slopes north of the DBWH properties. These are generally located north of and below the residences on Parcel 2 and Parcel 6, although there are some mass wasting impacts that extend laterally onto parcels adjacent to Parcels 2 and 6. Parcel 2 — The recent slope movements below Parcel 2 occurred on January 18, 2015 sometime between mid -day and early evening. The landslide developed on a relatively deep surface as compared to most mass wasting that occurs on coastal bluffs around the Puget Sound. Since the topography of the slope before the slide occurred is not well defined (i.e., by survey, LIDAR or other means) the exact depth of material that was mobilized during the slide is not known for certain. However, based on the volume of material deposited at the beach level and comparisons with neighboring slopes that did not slide, the depth of the failure surface is estimated to be on the order of 20 feet (measured normally into the slope face). A comparison of the cross sections shown on Figure 3 (Section `A', Parcel 1) and Figure 6 (Section `B', Parcel 2) corroborates this conclusion. These movements coincided with a pair of anomalously high tides at approximately 12 noon and 10 pm (see Plate 1). Both of these tides crested nearly a foot above the predicted tide elevation and almost a foot above the mean higher high water (M14HW) elevation of +11.84 feet. At the same time, a storm with sustained northerly to northeasterly winds of approximately 10 knots and gusts to 20 to 30 knots (see Plate 2) produced heavy surf that, when combined with the unusually high tides, created a highly erosive condition at the toe of the coastal bluff. Plate 3 provides the relationships between various vertical datums in use around the Tacoma regions of southern Puget Sound. Note that the vertical datum used as the basis for Figure 2, Site and Exploration Plan is NAVD88, which differs from the tidal datum used in Plate 1. According to the survey that forms the basis for Figure 2, the toe of the coastal bluff is at El. +9 feet. Accounting for the difference between the datums, the tides on January 18, 2015 were at least one foot above the toe of the bluf. Wave action and height above the tide level created a highly erosive condition on the soils exposed at the toe of the bluff. Under these conditions beach erosion is also likely. Also of note is the cumulative rainfall in the days prior to the landslide (see Plate 4). The rainfall amounts were at threshold levels for landslide risk in the Puget Sound region according to research by the U.S. Geological Survey (see Plate 5). The top of the recent slide (head scarp) is over -steepened to near vertical and has several tension cracks behind the main head scarp that may break back or spall off over time. 15-046 DBVM Geotechnical Study.dom 7 PanGEO, Inc. Dumas Bay West July 16, 2015 -- NOAAINOSIC04" 06eerved We1er L *Vah e! 9448484, Teeetne WA F►otn 2018101M7 00-00 OUTt3o 201WIM8 2&69 OW 1 5.0 i 5.A 12.5 12.5 10.0 01 — — — — -- Me 7.5 7.5 5.0 5.0 r 2.5 Saturday, Jan 17 2015, 12:30 GMT 2, 5 Predictions: 10.396ft. Verified: 10.577ft. 0.0 0,0 j NORAINDSICante[ fof pylrllWnsk 0CSa0N9ra9nk hoducls and SeniCEi DD:00 06:00 12:0D 18:00 MOD 06:00 12:00 18:00 1117 1117 1/17 1/17 1/18 1/18 ilia 1/18 i — Predictions — Verified — Preliminary I _r Plate 1: Tide Levels on January 18, 2015 (source: h!W://www.noaa.aoil �e rrtrl. a* eaaa, Tream. e>eTw1► tYaN >�, ea+n v o0:60 ®.T,o mea,M a »1{a larr 'r s.NNmv,l.n 17,14:546Mr W11ds0.55kn. from NE (401 1 S� "" 7f Gusting to 1.1 kn. 04:00 08:00 12:00 16:00 20:00 18.j- 04:00 0800 12:00 16:00 20:00 • Winds — Gusts '. N0M/NOi/CM NN0yvaUwWOm ra0 nod—„asmne.: Plate 2: Wind Gusts on January 18, 2015 (source: http:llwww.noaa.gov/) 15-046 DBWH Geotechnical Study.docx 8 PanGEO, Inc. Dumas Bay West July 16, 2015 TACOMA PUBLIC WORKS VERTICAL DATUMS FIXED DA T UM NGS ELEV 17.454 (1973) -- 1920 NGS BENCH MARK CITY OF TACOMA ELEV 17.45 NGS (NGV029) k C17Y OF TACOMA DATUM 0.00 A DATUM 0.009 � CORPS OF ENGINEERS do PORT OF TACOMA DATUM 0.00— 'OLD CITY DATUM" 0.00 — (PRIOR TO JULY 1, 1"0) TIDAL DATUM EPOCH 1960-1978 (VARIES ON A 19 YEAR CYCLE) n hl1i H>✓.' n� vie —r^ MEAN TIDE LEVEL W 8 i !m MtAN LOW WATER 1O1 i.BE FEET MLLW MLLW (TIDAL DATUM 0.00) MHHW: MEAN HIGHER HIGH WATER MLLW: MEAN LOWER LOW WATER Revised February 20D4 using Coto from Dove Maroon, PLS U S Army Corps of Engineers, Scottie District Tacoma Public Works South Puget Sound Region 90 — Tacoma Chief Surveyor phone: 253-591-5772 Plate 3: Tacoma Vertical Datums 15,046 DBWH Geotechnical Studv-doex 9 PanGEO, Inc. Dumas Bay West July 16, 2015 U.S_ Department of Commerce Record of Climatological Observations National Oceanlc & Atmospheric Administration These data are quality controlled and may not be National Environmental Satellite, Data, and Information Service identical to the original observations. Elev.- 136 ft. Lac 47.346' N Lon: 122.322' W Generated on 04/2812015 Station: FEDERAL WAY 2.5 NNE, WA US GHCND:US1 WAKG0088 Temperature (iF) Precipitolioo fsoe "J 24 hrs. ending at O 24 Hour Amounts ending At Obs P r at observation at observationtime Time e time b I Y M s I e o D e m a n a y r Rain, F Snow, ice F Ste' ice Pe m r h Max. Min, a melted snow, etc. I a pallets, hall I a hall, ice on a t (in) 9 (in) 9 ground r i (in) y o n 2015 1 1 0.00 0.0 2015 1 2 -0.00 0.0 2015 1 3 0•00 2015 1 4 0.15 2015 1 5 0•66 2015 1 6 2015 1 7 1 0.07 2015 1 a T 2015 1 9 0.00 0.0 .2015 1 10 0.1a 2015 1 11 2015 1 12 2015 1 13 0.00 0.0 2015 1 14 0.00 0.0 2015 1 15 0.00 0.0 2015 1 16 0.42 2015 1 17 0.01 2015 1 18 1 11.25 Plate 4: Rainfall Data for Federal Way prior to Jan. 18, 2015 landslide (image croped; source: h ://www.ncdc.noaa. ovn to w 06 Z ' 2 95 H 14 Landslides likely U w a. 3 w Z Cumulative Precipitation Threshold J 2 P34.".67Pi6 Landslides c0i 1 - unlikely a0 ~ 0 1 2 3 4 5 6 7 8 9 10 li 1315, 15-DAY CUMULATIVE PRECIPITATION BEFORE P3, INCHES Plate 5: Cumulative 3-day and previous 15-day rainfall threshold [for landslides] (Chleborad, et al., 2006) 15-046 DBWH Geotechnicat Study.docx 10 PanGEO, Inc. Dumas Bay West July 16, 2015 Parcels 314 — An area of recent instability is visible from the beach mid -slope between Parcels 3 and 4. This sloughing may or may not be related to the removal of vegetation. Parcel 6 — This area has been a location of instability over a number of years. A variety of surface stabilization treatments have been put in place that have been moderately, but not completely, successful in arresting mass wasting processes on the slope. Currently, portions of the slope are covered with lute matting, while other portions remain exposed and un-vegetated leaving them vulnerable to erosion and mass wasting. 3.0 SUBSURFACE EXPLORATIONS Field explorations completed for this study included two borings, both of which were completed as standpipe observation wells. The first boring, designated B-1, was located at the east end of the row of parcels comprising DBWH, near the southeast corner of Parcel 6, and was drilled to a total depth of 101 feet. The second boring, designated B-2, was located on Parcel 2, along the eastern side of the property, and was drilled to a total depth of 140.5 feet. The borings were drilled using a truck -mounted, mud rotary drill supplied by Holocene Drilling of Graham, Washington. Boring R-1 was begun on March 24, 2015, with well completion on March 25, 2015. Boring B-2 was drilled on March 26 and 27, 2015, with well completion on March 30, 2015. Standard Penetration Tests (SPT) samples were taken at intervals of between 5 and 10 feet, as needed to characterize the geologic materials encountered during drilling. The locations of these borings are shown on Figure 2, Site and Exploration Plan. An engineering geologist or engineer from PanGEO was present throughout the field exploration program to observe the drilling, log the materials encountered in the borings, and obtain representative samples from the explorations for laboratory testing. The soils were described in the field in general accordance with ASTM D2488, Standard Practice for Description and Identification of Soils (Visual -Manual Procedure) following the guidelines of the Unified Soil Classification System, as shown on Figure A-1 of Appendix A. Summary logs from the borings are presented in Appendix A as Figures A-2 and A_-3. More detailed information about the field exploration program is presented in Appendix A. The results of the laboratory tests are presented in Appendix B. 4.0 SUBSURFACE CONDITIONS 4.1 SITE GEOLOGY According to draft mapping by Troost and Booth (Open File Report, in press), the entire ridge that comprises the six parcels of the DBWH is advance outwash (Qva) deposits with a small cap of glacial till (Qvt) present on top of the ridge. However, older mapping by Luzier (1969) shows 15-046 DBWH Geotechnical Study.docx 11 PanGEO, Inc. Dumas Bay West July 16, 2015 the glacial till (Qvt) cap to be much more extensive. Based on our own observations and the materials encountered in the test borings drilled for this study, the mapping by Luzier (1969) appears most representative of the conditions on the six parcels. The glacial till cap is present all along the topographic ridge of DBWH parcels, with the advance outwash deposits exposed in the steep coastal slopes below the bluff. Beach deposits (Qb) are noted in both maps as present along the base of the bluff, consistent with our site observations, but these soils are not a major factor in the analysis and conclusions of this study. Luzier (1969) describes the glacial till and advance outwash materials as follows: Glacial Till Qvt) — "Compact mixture of gravel and occasional boulders in a gray clayey, silty sand matrix. Includes sand and gravel lenses within and on top of till. Thickness generally 10 to more than 50 feet." Advance Outwash (Ova) — "Pebble -cobble gravel... may include very fine sand and laminated silt. Thickness generally less than 100 feet, but may exceed 300 feet in bluffs adjacent to Puget Sound." 4.2 SOILS In general, the soil conditions encountered in the site explorations are consistent with the mapped surface geologic units. The soils encountered in the site borings have been generalized and graphically depicted in two subsurface profiles that were chosen for slope stability analyses (cross sections) and are included as Figures 3 through 7. The soil units identified in both profiles are described below: Unit 1 Fill — Fill was encountered only in boring B-2 at the ground surface where the boring was advanced through planter backfill in a landscape area adjacent to the Parcel 2 driveway. This fill was encountered down to a depth of 5 feet where undisturbed native soils were encountered. Unit 2 Glacial_ Till (Q)Lt) — The uppermost native (in situ) soils encountered in both borings was dense silty sand with gravel that was moist and massive. This material was encountered to depths of 7% and 35 feet in borings B-1 and B-2, respectively. Unit 3 Advance Outwasli va — Below the Unit 2 glacial rill soils, both borings encountered medium dense to very dense silty sand with occasional interlayers of silt that were moist and layered to massive. These soils were encountered to the maximum depths penetrated in both borings. 15-046 DBWH Geotechnical Study.docx 12 PanGEO, Inc. Dumas Bay West July 16, 2015 4.3 GROUNDWATER Measurements of groundwater elevations collected to date are presented in Table 1, Table 1 Summary of Groundwater Measurements Well Date of Reading I B-1 I B-2 Depth (ft) (1) Elev. (ft) (2) Depth (ft) (1) Elev. (^ft) (2) April 1, 2015 74 +21 101 T`FV Notes: 1. Measurements taken from the top of the monument. 2. Monument elevations of 95 feet and 141 feet for B-1 and B-2, respectively (site survey by DeGross Aerial Mapping, Inc., April 27, 2015) 5.0 SEISMIC CONSIDERATIONS 5.1 DESIGN CRITERIA The seismic evaluation of structures should be accomplished in accordance with the 2012 International Building Code (IBC). The IBC seismic design parameters are in part based on the site soil conditions and site classifications. Based on 2012 IBC and the publication ASCE 7-02, it is our opinion that Site Class C is appropriate for the project site based on borings B-1. and 13-2. The Table 2 below provides seismic design parameters for the site that are in conformance with the 2012 edition of the International Building Code (IBC), which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps: Table 2 Seismic Design Parameters per 2012 IBC Spectral Spectral Site Design Spectral Control Site Acceleration Acceleration at Coefficients Response Periods Class at 0.2 sec. (g) 1.0 sec. (g) Parameters (sec.) Fa F,, SDs SDI To Ts Ss S1 C 1.322 0.509 1.00 1.30 0.881 0.441 0.10 0.50 15-046 DBWH Geotechnicat Study.doex 13 PanGEO, Inc. Dumas Bay West July 16, 2015 6.0 SLOPE STABILITY 6.1 STABILITY ANALYSES Global slope stability analyses were conducted to evaluate the stability of the coastal bluff and shoreline slope to determine if the slopes had adequate factors of safety for the site conditions or if stabilization would be required to reduce risk to the residences of DBWH. Based on the topography of the site as shown on Figure 2, Site and Exploration Plan, three sections were selected for analysis and are denoted 'A', 'B' and 'C' on Figure 2. The first section (Section 'A') is located across the long axis of Parcel 1 and was selected on the basis of being the tallest overall slope in an un-failed condition along the DBWH properties. Figure 3 depicts the cross section. geometry and subsurface conditions based on boring B-2. Figure 3 shows the critical failure surface and factor of safety at this location. A second analysis was performed with the search limit fixed at the setback location of the residential structure on Parcel 1 and is shown on Figure 4. Section 'A' was also selected for back -analysis of soil shear strength at the time of the recent mass wasting on the adjacent parcel represented by Section 'B'. A nominal amount of beach erosion and bluff undercutting: was included based on tidal and surf conditions on the day of failure as described above. This geometry is shown on Figure 5. This analysis validates the soil shear strength used in all other analyses as well as confirming the impact on stability of toe undercutting and beach erosion. The second section (Section 'B') is located across the long axis of Parcel 2 where the most recent mass wasting occurred. This section also closely corresponds to the location of test boring B-2. Figure 6 depicts the cross section geometry and subsurface conditions based on boring B-2 and the computed post -failure factor of safety for the critical failure surface. The third section (Section 'C') is located through the axis of the previous mass wasting that has occurred below Parcel 6 and was selected on the basis of previous mass wasting and also proximity to test boring B- 1. Figure 7 depicts the cross section geometry and subsurface conditions based on boring B-1 and the computed factor of safety for the critical failure surface at this location. All analyses were completed using the computer program SLIDE v.6, by RocScience. In general, both circular and non -circular failure surfaces were checked for each analysis performed. However, non -circular surfaces generally yielded slightly lower factors of safety, even when approximating circular surfaces, so these are the results that are reported. 15-046 DBIAW Geotechnical Study.docx 14 PanGEO, Inc. Dumas Bay West J..,_l.y . , � '1015 ui 6.2 DISCUSSION of RESULTS Table 3 summarizes the factors of safety computed from the slope stability analyses described above. Generally speaking, slope stability factors of safety should be above about 1.25 to 1.3 for permanent slopes that do not directly support a critical structure. Table 3 Summary of Slope Stability Analyses and Results Location F Condition Factor of Safety Section `A' (Figure 3) Existing condition for Parcel 1 1.12 Section `A' (Figure 4) Failure surface at setback of existing structure on Parcel 1 1.24 Section `A' (Figure 5) Back -analysis of incipient failure condition on Parcel 2 0.99 [ Section `B' (Figure 6) Post -failure on Parcel 2 1.50 Section `C' (Figure 7) Existing condition for Parcel 6 1.48 The near -unity factor of safety calculated for the back -analysis conducted at Section `A' (Figure 5) provides a validation of the soil shear strength parameters used in the other analyses as well as supporting the conclusion that significant beach erosion and undercutting occurred during the abnormally high tides and heavy surf that coincided on the day of the failure at Parcel 2 (discussed further above under section 2.4 Historical and Recent Mass Wasting). The higher factors of safety reported in Table 3 are associated with slopes that have seen previous movement and are therefore generally less steep than adjacent slopes which have not experienced recent movement. An exception is the near vertical head scarp on Parcel 2 which continues to exhibit tension cracks behind the head scarp that indicate the locally over -steepened condition is still at risk of breaking back further. While greater than unity, the computed factors of safety for slopes that have not experienced recent failure are marginal relative to commonly accepted design values. 6.3 STABILITY RISKS The relative risks of slope instability identified during this evaluation are discussed on a parcel - by -parcel basis below in this section. It should be noted that all construction near or adjacent to earthen slopes presents some risk of instability and that where "lovv risk" is identified, it should not be considered to mean "no risk". Parcel 1 — As indicated in Figures 3 and 4, the computed factors of safety for the slopes below this parcel are marginally acceptable. Since this parcel has the tallest overall slope between the building site area and the beach, combined with a relatively steep slope angle, the relative risk of 15-046 DBIVH Geotechnical Study.doex 15 PanGEO, Inc. Dumas Bay West July 16, 2615 potential future instability is considered highest for this parcel relative to the other parcels that are subjects of this evaluation. Parcel 2 — The recent mass wasting below this parcel has resulted in a slope configuration that is overall in a more stable condition than it was prior to failure, as can be seen from the relatively high factor of safety computed as shown on Figure 6. However, the over -steepened condition at the top of the slide area (head scarp) remains vulnerable to additional movements as the soil between the head scarp and tension cracks behind the head scarp lose strength and seek a more stable configuration by moving downhill. Over time, unless this condition is improved, the remaining setback between the top of slope and the residential structure could be lessened to the point that the structure is in imminent danger and would require emergent measures to protect the structure. Continued erosion of the slide mass that is now resting on the beach will also tend to reduce the overall global factor of safety as the buttressing effect of this material is removed. Parcel 3 — Due to the setback distance between the crest of the bluff and the residential structure on this parcel, the risk to the structure from a large scale movement similar to the recent movement on adjacent Parcel 2 is considered moderate. However, this parcel has two factors that increase the relative risk. The first is the proximity to the failed area below Parcel 2 and the potential for the mass wasting to propagate eastward and affect Parcel 3. The second factor is the denudation that has recently occurred on adjacent Parcel 4 that also extends partially onto Parcel 3. As the root masses die off, the stabilizing effect will diminish and increase the potential for slope movements. Parcel 4 — The denudation of stabilizing vegetation has occurred over most of the extents of the coastal bluff slopes below this parcel. The potential for slope movements will likely increase as the stabilizing effect provided by the root masses diminishes. Setback risks are similar to Parcel 3 and considered low to moderate for the primary residential structure, although the deck that overhangs the coastal bluff is at risk of losing stability at virtually any time. Parcel 5 — This parcel has the largest setback distance between the crest of the bluff and the residential structure of all the parcels that are the subject of this evaluation. The risk of mass wasting affecting the residence is considered low. Parcel 6 — Although the setback distance from the bluff to the residential structure is relatively large on this parcel, the evidence of relatively recent slope movements indicates that mass wasting is more active in this area, which increases the risk relative to the adjacent parcel(s). The risk of additional slope movements that could impact landscape areas is considered relatively high, while risk to the residential structure itself remains relatively low. 6.4 SURFACE WATER CONSIDERATIONS A discussion of the existing surface water management on each of the six parcels that are the subject of this report is provided in section 2.3, above. Based on the observations reported in 15-046 DBWH Geotechnical Study.docx 16 PanGEO, Inc. Dumas Bay West July 16, 2015 section 2.3, it is generally concluded that surface water management practice is good on all of the properties and that poor control of surface water runoff is not a significant contributing factor to the mass wasting processes discussed and analyzed herein. Additionally, the groundwater level below the existing ground surface is sufficiently deep that infiltration and groundwater mounding are not considered significant as related to mass wasting occurrences on the coastal bluff slopes. No specific deficiencies in surface water management practices were noted, and therefore no recommendations for improvement to surface water management practices are deemed necessary. 7.0 CONCEPTUAL STABILIZATION OPTIONS Several options are available that would improve the stability of the coastal bluff. These options generally fall into categories of: a) work solely along the base of the bluff, b) work solely along the crest of the bluff, and c) work that extends from the crest of the bluff down the slope face to at or below the high water level. Measures that could be put in place along the base of the bluff include bulkheads and similar structures that would reduce the erosion and undercutting of the slope by wave and tide action. To be effective, such erosion protection structures would need to be continuous along the entire slope below the six DBWH parcels and should be embedded a sufficient distance below the mean higher high water elevation to prevent undercutting by wave and tide action or beach erosion. In order to safely construct this type of structure at the base of a steep slope, work should only proceed in small slot cuts that will not trigger slope movement. Structures could be constructed along the crest of the bluff that would protect the residential structures from future slope movements. It is considered feasible that a wall -type structure could be built that would stabilize the ground behind the wall and protect the residential structure(s) even if slope movement occurs below the wall. Stability of the slope could also be improved by surficial and/or shallow surface treatments that extend from the crest to the base of the slope. This type of slope stabilization would employ passive elements such as soil nails combined with surface stabilization and erosion protection in the form of mats or meshes attached to the heads of the passive elements. A major drawback to this approach is that it requires denudation of the existing vegetation over the entire slope face in order to put the surface treatment in place. Another risk for this option is that wave and tide action could still potentially undercut and destabilize the toe of the treatment. 8.0 ADDITIONAL SERVICES This evaluation of coastal bluff stability is intended to form the basis for recommendations that could improve the stability of the slopes on the subject residential parcels. To facilitate construction permitting, geotechnical engineering recommendations for stabilization measures 15-046 DBWH Geotechnica] Study.docx 17 PanGEO, Inc. Dumas Bay West July 16, 2615 will be provided as supplements to this report according to the risks identified on each parcel and the desires of the individual property owners. Specifically, we anticipate that the following additional geotechnical engineering services may be needed, • Parcel -specific reports or technical memoranda that provide design recommendations unique to the parcel • Construction support services for geotechnical improvertnents : Other consultation as may be required during construction 9.0 LIMITATIONS We have prepared this report for use by the Dumas Bay West Homeowners. Recommendations contained in this report are based on a site reconnaissance, a subsurface exploration program, review of pertinent subsurface information, and our understanding of the goals and aims of the Homeowners. The study was performed using a mutually agreed -upon scope of work. Variations in soil conditions may exist between the locations of our explorations and the actual conditions underlying the site. The nature and extent of soil variations may not be evident until construction occurs. If any soil conditions are encountered at the site that are different from those described in this report, we should be notified immediately to review the applicability of our recommendations. Additionally, we should also be notified to review the applicability of our recommendations if there are any changes in the project scope. The scope of our work does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors' methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Additionally, the scope of our work specifically excludes the assessment of environmental characteristics, particularly those involving hazardous substances or wetlands. PanGEO does not employ mold consultants nor are our recommendations to be interpreted as being preventative of mold development. A mold specialist should be consulted for all mold -related issues. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on -site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. It is the client's responsibility to see that all parties to this project, including the designer, contractor, subcontractors, etc., are made aware of this report in its entirety. The use of 15-046 DBwH Geotechnical Study.docx 18 PanGEO, Inc. Dumas Bay West July 16, 2015 information contained in this report for bidding purposes should be done at the contractor's option and risk. Any party other than the client who wishes to use this report shall notify PanGEO of such intended use and for permission to copy this report. Based on the intended use of the report, PanGEO may require that additional work be performed and that an updated report be reissued. Noncompliance with any of these requirements will release PanGEO from any liability resulting from the use this report. Within the limitation of scope, schedule and budget, PanGEO engages in the practice of geotechnical engineering and endeavors to perform its services in accordance with generally accepted professional principles and practices at the time the Report or its contents were prepared. No warranty, express or implied, is made. We appreciate the opportunity to be of service to the Dumas Bay West Homeowners. Please feel free to contact our office with any questions you have regarding our study, this report, or any geotechnical engineering related issues pertaining to the site. Robert E. Kimmerling, P.E., L.E.G. Principal Geotechnical Engineer Stephen H. Evans, L.E.G. Senior Engineering Geologist 15-046 DBWH Geotechnical Study.docx 19 PanGEO, Inc. Dumas Bay West July 16, 2015 10.0 REFERENCES AASHTO, 2012. LRFD Bridge Design Specifications, 6`' edition, American Association of State Highway and Transportation Officials Chleborad, A.F., Baum, R.L., and Godt, J.W., 2006. Rainfall thresholds for forecasting landslides in the Seattle, Washington, area—Exceedance and probability: U.S. Geological Survey Open -File Report 2006-1064. Luzier, J.E., 1969, Geology & Groundwater Resources of SW King Co., WA, Water -Supply Bulletin No. 28 International Building Code (IBC), 2012, International building code: Country Club Hills, Ill., International Code Council, Inc., 690 p. Troost, K. G. and Booth, D. B., in press, Geologic Map of the Tacoma North 7.5' Quadrangle, King and Pierce Counties, WA, USGS -Open File Report Washington State Department of Transportation (WSDOT), 2014, Standard Specifications for Road, Bridge, and Municipal Construction M 41-10: Washington State Department of Transportation. Washington State Department of Ecology, 2012, Stormwater Management Manual for Western Washington: Report prepared by the WSDOE, August 15-046 DBWH Geotechnical Study.docx 20 PanGEO, Inc. EIGUR.ES -�1 5242 Study Area $and I Tarp SO p• L 8unty Perk �. •t• } - u41 Sand `ssades�:' p TI ..j Q •..� '£ E R K "40 ' H Ir Approximate Scale 112 mile FbnGE(D Dumas Bay West VICINITY MAP SW 307t" Street r w C O R P D a w r H 0 Federal Way, Washington Project No. Fini:re `.' f 5-046 i ou" BYr NTW CHECBEO BY, RER om 4/29/2015 Z:�Artl �) T fV o0 L m N m L0. m c z .. : j v 1 m m m 0 j IZ C m o Illy m m N y n� ^ m m o � Q 5CD a w 0 FL B� Er Q A 0 n y T a CD mo 3 su s C W En 7 N m � m � N C, j N O � " m m 1 a Z o X O 0 N Z r D 2 P+olac h\ 15-046 2 V. and EXAlorOu0 Pla-4-9 •+. �• . ..,,ram_ '�:r S � a- �A e a 9 Ln . O a 4 z 0 w ft--�— : ; A 59 ova 150 a a 3 m �. O c � � m r1 2. ii w to uj to m 0 c 0 c Q � � A Lrl O O C gyp?�p N N O Q N � S a) m In c IUD m Uf c N m N C11 Of' O 7 N O 7 ai = O 250 4k. N O a O CO) D rt m G) x o Q too vNr 710 Q 7 c D m N N ID to 6 -5i] 59 as ' y-V CD L7 IIjIaaaaa0--ItT-I Fin - b 4 o O fD a ID m cn 4N s S ca Qo �f N 3 C O Q O O i fD N � O CD N y O Q _ D1 (n r W fA r � 7 � _rt O N H w 0 N � 0 0 D a m ` 0 a f N iD a El o ,-1 I.� � Ln Ln � m N � � m 7 '� 3 0 0 S s o c a Q S 0 CD 7 N N N � � t On Ln IA C G C N N 6�1 N N m O O = � C � K fu 'C m � a § § ■ § ■ ■ ■ ■ � ■ ■ | R ® � � � g ® c �& 0 § § m 2 ƒ E 0 _ = § 2 2 0 2 � / \ ri � �m E o —: q » t 7 7 § $ ■ / / / R. ; ; m § 2 , , k \ \ 2 -50 _ 0 50 100 - `, 150 Poo o- 9 O - �J O- Q d O y KC SOD - y rtKLn 3ID CT - O 0 N O O �o A J A� ice} Q En X. J � 00 rr S o L p1 W I ■ a � � 7 n r�r � � O Z w � S Q C 7 Q' \ lWl1 lWi1 .� 10 V S M M S S N o � O C O S � o• m A a� N N N OC N S C (�D N ro C W C W C n ro n ro n ro 0 0 = c � m 3 M � ro APPENDIX A FIELD EXPLORATIONS Dumas Bay West July 16, 2015 APPENDIX A: FIELD EXPLORATIONS This appendix presents factual and interpretive results of our exploratory drilling program. The descriptions of the materials encountered in the subsurface explorations are based on the samples extracted from the borings. The sample descriptions are augmented by observation of the drilling action and drill cuttings brought to the surface during field operations. The paragraphs below describe the field operations and sampling procedures used during the geotechnical field explorations. FIELD EXPLORATIONS The subsurface exploration program consisted of drilling two test borings for the purpose of identifying the subsurface materials, stratigraphy and groundwater conditions along the coastal bluff beneath the residential properties along SW 307u1 Street in Federal Way, WA. The two borings (13-1 and B-2) were drilled by Holocene Drilling of Puyallup, Washington, using a truck mounted drill. The borings were advanced using a mud rotary drill string. Both borings were completed as stand -pipe groundwater observation wells. Boring B-1 was located on the easternmost property of the Dumas Bay West homeowners, in the driveway area on Parcel 6, 30625 43rd Avenue SW. Boring B-1 was begun on March 24, 2015 and was advanced to a total depth of 101 feet below the ground surface on March 25, 2015. The boring was completed as a 2-inch diameter stand -pipe groundwater observation well with a screened interval from 80 to 100 feet below the ground surface and a sand pack from 60 to 100 feet below the ground surface. Boring B-2 was located toward the west end of the Dumas Bay West homeowners, in a planter area on Parcel 2, 4342 SW 307th Street. Boring B-2 was begun on March 26, 2015 and was advanced to a total depth of 140.5 feet on March 27, 2015. On March 30, boring B-2 was completed as a 2-inch diameter stand -pipe groundwater observation well with a screened interval from 110 to 140 feet below the ground surface and a sand pack from 90 to 140 feet below the ground surface. Standard Penetration Tests (SPT) samples were taken in both borings at intervals of between 5 and 10 feet, as needed to complete the borings and characterize the sediments. The locations of these borings are shown on Figure 2, Site and Exploration Plan. A representative of PanGEO logged the test borings and collected from samples from the borings at selected intervals. The locations of the borings were noted using identifiable site features and are shown approximately on Figure 2, Site and Exploration Plan. 15-046 DBVdH Geotechnical Study.docx A-1 PanGEO, Inc. Dumas Bav West July 16, 2015 .SAMPLING METHODS Standard penetration tests (SPT) were taken at 5- and 10-foot intervals, starting at 10 feet below the ground surface after clearing the upper 10 feet with a vactor truck. A SPT test consists of advancing a 2 inch outside diameter (OD), steel, split spoon sampler 18 inches into the undisturbed soil below the deepest soil penetrated by the drill bit by striking it with a 140 pound hammer dropped 30 inches. During a SPT sample, the number of blows to drive the sampler each 6 inches over an 18-inch interval was recorded and indicated on the boring log. The number of blows to drive the sampler the final 12 inches is termed the SPT resistance, or N-value, and is used to evaluate the strength and consistency/ relative density of the soil. The hammer used to perform SPT sampling was an automatic trip -release mechanism, which generally delivers a higher energy than a "standard" hammer equipped with a rope and cathead mechanism. The efficiency of the hammer mechanism is considered when evaluating the liquefaction potential of a soil. The SPT N-values reported on the borehole logs are field values, and are therefore not corrected for hammer efficiency, overburden stress or rod lengths. Soils samples were identified and described in general accordance with the guidelines shown on Figure A-1. Summary boring logs are included as Figures A-2 and A-3. The stratigraphic contacts shown on the summary logs and subsurface profiles (Figures 3 through 7, main text) represent the approximate boundaries between soil types; actual stratigraphic contacts encountered at other locations in the field may differ from the contact elevations shown on the logs, and may be gradual rather than abrupt. The soil and groundwater conditions depicted are only for the specific date and locations reported, and therefore, are not necessarily representative of other locations and times. 15-046 DBWH Geotechnical Study.docx A-2 PanGEO, Inc. RELATIVE, ASITY 1 CONSISTENCY SAND / GRAVEL SILT / CLAY SPT Approx. Relative SPT Approx. Undrained Shear Dens N-values : Density (%) Consistent y N-values Strength (psq Very Loose <4 <15 Very Soft <2 <250 Loose 4 to 10 15.35 Soft 2 to 4 250.500 Mod. Dense = 10 to 30 35 - 65 Med. Stiff 4 to 8 500 -1000 Dense 30 to 50 ? 65 - 85 = Stiff 8 to 15 1000 - 2000 Very Dense = >50 = 85.100 : Very Stiff 15 to 30 2000.4000 Hard >30 >4000 I wlown Sn11 CI A.q.mFir-A nnN SYSTEM MAJOR DIVISIONS GROUP DESCRIPTIONS GW: Weil -graded GRAVEL Gravel GRAVEL (<5% fines) e ....................................................... GP - Poorly -}traded GRAVEL 50% or more of the coarse fraction retained on the #4 sieve. Use dual symbols (eg. (' GM : Silty GRAVEL GP-GM)for 5%to12%fines. ° GRAVEL (>12/ofines) ..... :............................... .............. GC : Clayey GRAVEL ........................................................ ..........................._............................. .. SW: Well -graded SAND Sand SAND (<5%fines) .................................... SP Poorly -graded SAND 50% or more of the coarse S M . fraction passing the #4 sieve. Use dual symbols (ag. WWI SAND (>12%fines) : SM : Silty SAND . ..................I.................................. fors%to12°%fines. SC Clayey SAND.. ..................... ............................... ... ..... .. .. .......................... MLSILT. Liquid Umtt <50 .................................................. CL Lean CLAY Silt and Clay — _ OL Organic 5LT or CLAY .. , ............................................... ...... . 50%or more passing f1200 slave MH : Elastic SILT Uquid Limit> 5o .......................................... CH : Fat CLAY ............................................. :.. OrganicOH SILT or CLAY ..................................................... ...............................................I.........._.......... Highly Organic Soils PT =PEAT Notes: 1. Soil exploration I s contain material descriptions based an visual observation and laid tests using a system modified from the Uni orm Soil Classification System JUSCS). Where necessary laboratory tests have been conducted (as noted in the "Other Tests' column), um descriptions may include a classification. Please refer to the discussions in the report text for a more complete description of the subsurface conditions. 2, The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs, Other symbols may be used where field observations indicated mixed sal constituents or dual oonstituent materials. DESCRIPTIONS OF SOIL STRUCTURES Layered: Units of material distinguished by color and/or composition from material units above and below Laminated: Layers of soil typically 0.05 to 1 mm thick, max 1 cm Lens: Layer of soil that pinches out laterally Intedayered: Alternating layers of differing soil material Pocket: Erratic, discontinuous deposit of limited extent Homogeneous: Soil with uniform color and composition throughout Fissured: Breaks along defined planes Slickensided: Fracture planes that are polished or glossy Blocky: Angular soil lumps that resist breakdown Disrupted Soil that is broken and nixed Scattered: Less than one per foot Numerous: More than one per foot BCN: Angle bekwcen budding plane and a plane normal to c--re axis COMPONENT DEFINITIONS COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE Boulder. > 12 inches Sand Cobbles: 3 to 12 inches Coarse Sand: #4 to #10 sieve (4.5 to 2.0 mm) Gravel Medium Sand: #10 to #40 sieve (2.0 to 0.42 min) Coarse Gravel: 3 to 3/4 inches Fine Sand; #40 to #200 sieve (0.42 to 0.074 man) Fine Gravel: 3/4 inches to #4 sieve Silt 0.074 to 0,002 mm Clay <0.002 mm rJmGE9 Terms and Symbols for I N C 0 R P 0 R A T@ 0 Boring and Test Pit Logs TEST SYMBOLS for In 6Itu and Laboratory Tests listed i n "Other Tests" column. ATT Afterberg Limit Test Cone Compaction Tests Con Consolidation DD Dry Density DS Direct shear %F Fines Content GS Grain Size Perm Permeability PP Pocket Penetrometer R R-value SG Specific Gravity TV Torvane TXC Triaxial Compression UCC Unconfined Compression SYMBOLS Samplelin Situ test types and intervals OD Split Spoon, SPT ®2-inch (140-lb. hammer, 30" drop) OD Spilt Spoon e3.25-inch (300-lb hammer, 3(r drop) Non-standard penetration test (see boring log for details) Thin wall (Shelby) tube Grab Rock core ® Vane Shear MONITORING WELL SZ Groundwater Level at time of drilling (ATD) 1 Static Groundwater Levei Cement / Concrete Seal Bentonite grout) seal Silica sand backfiill Slotted tip Slough Bottom of Boring MOISTURE CONTENT Dry Dusty, dry to the touch Moist Damp but no visible water Wet Visible free water Figure A-1 Protect: Dumas Bay Landslide Assessment Surface Elevation: 95.0ft ! Job Number: 15-W Top of Casing Elev.: 95.0ft I Location: SHIN 307th Street, Federal Way, WA Drilling Method. Mull Rotai, Coordinates: Northing: , Easting: Sampling Method: SPT N-Value Ak z CLc k PL Moisture ILL aCL y MATERIAL DESCRIPTION I 0 ® ROD Recovery 0 50 100 0 Dense, brown, silty, fine to medium SAND with gravel; moist, non -plastic, massive. (Till). 5 Dense, brown, poorly graded, fine to medium SAND with silt (SP-SM): moist, gravel beds, homogenous, laminated to massive. (Advanced Outwash). 10 9 S-1 21 GS 23 15 S-2 35 50/5 Gravelly drilling, very dense. 20 27 Very dense, brown to gray, fine SAND with silt, moist, S-3 48 39 non plastic. laminated to massive. Very dense, brown gray, sandy, fine GRAVEL: very moist, trace silt, rounded, blocky gravel, slightly weathered. 25 S-4 34 D (Outwash). 50/6 0(30, a �i6 30 18 Q D Losing drilling fluid into formation. Grading to fine to coarse S-5 33 41 a O° GRAVEL with sand, massive. aD ° Oo Drilling mud color becomes gray. o D 35 Gravelly drilling stops at 36 feet. _ _ _ Hard, brown, silty swb (SM): moist, slightly plastic fines, slow dilatancy, gray fine silt interlaminae, dips to 15°, homogeneous, laminated. (Outwash Beds). Completion Depth: 101.Oft Remarks: Groundwater measured 4/1/15. Date Borehole Started: 3/24/15 Date Borehole Completed: 3/25/15 Logged By: S. Evans Drilling Company: Holocene Drilling FbnGFj@ LOG OF TEST BORING B-1 INC0R/OR A T 5 0 FigureA-2 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Ot 3 Project: Dumas Bay Landslide Assessment Surface Elevation: 95.0ft Job Number: 15-046 Top of Casing Elev.: 95.Oft Location: SW 307th Street, Federal way, »vA Drilling Method: Mud Rotary Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A o Z w a N o PL Moisture LL c 0) Q .0 E MATERIAL DESCRIPTION i�� p a 0 _ - ® ROD Recovery 0 5o 100 Hard, brown, silty SAND (SM): moist, slightly plastic fines, . 40 16 slow dilatancy, gray fine silt intedaminae, dips to 1511, S-6 17 GS homogeneous, laminated. (Outwash Beds). fCondnued) 23 45 50 Dense Gravel, very moist. (Outwash). r r r _ — — 15 S-7 X19 p 20 ° ❑e C]D Fine gravel cuttings, 50 to 55 feet. 55 o D - 0 Some fine gravel. _ _ _ _ _ Dense to very dense, brown, silty, fine SAND (SM): very moist, non -plastic fines, laminated with dips to 5', clayey silt 60 16 and gravelly interbeds. (Outwash). S-8 X 19 22 65 Gravel bed 65-66 feet. Some gravel 66 to 70 feet. 70 S-9 X 15 16 Clayey SILT bed. 23 75 Completion Depth: 101,Oft Remarks: Groundwater measured 4/1/15. Date Borehole Started: 3/24/15 Date Borehole Completed: 3/25115 Logged By: S. Evans Drilling Company: Holocene Drilling FbnG]FB LOG OF TEST BORING B-1 I N C O N P O K A T E O Figure A-Z The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 2 Of 3 Proiect: Dumas Bay Landslide Assessment I Surface Elevation: 95.0ft Job Number: 15-046 ? Top of Casing Elev.: 95.0ft Location: SW307th Street, Federal Way WA[)rilling Method.M�'.d Rotary Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A z p PL Moisture LL 00)) a �, ~ MATERIAL DESCRIPTION t -� 0 ! M a cEa o - ® ROD Recovery �.. u1 m O 0 50 100 Dense to very dense, brown, silty, fine SAND (SM): very moist, non -plastic fines, laminated with dips to 50, clayey silt 80 25 and gravelly interbeds. (Outwash). (Continued) S-10 34 GS Siiry, fine SAND, moist, non -plastic, laminated, _ 36 sub -horizontal laminae. Gravelly bed 83 to 86 feet. 85 Very dense, brown SILT with fine sand: very moist, non plastic, rapid dilatancy, homogenous, laminated with 90 36 rusty laminae, dips 3 to 100. (Outwash). S-11 50/5 95 1{30 S-12 30 50/6 Bottom of Boring. 105 it0 115 Completion Depth: 101.Oft Remarks: Groundwater measured 4/1115, Date Borehole Started: 3124115 Date Borehole Completed: 3125/15 Logged By: S. Evans Drilling Company: Holocene Drilling PmGFO LOG OF TEST BORING B-1 I III C O a P D R A T E Q Figure A-2 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 3 OT j Project: Dumas Bay Landslide Assessment Surface Elevation: 141.Oft Job Number: 15-046 ; Top of Casing Elev.: 141.Oft Location: SW 307th Street, Federal way, WA ! Drillin method- Mud Rotary- i Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A O z m o PL Moisture LL °' F` MATERIAL DESCRIPTION 2 �� a m®RQO Recovery O 50 100 0 Planter Backfill, mixed sand, gravel, silt and organics. (Fill). 5 Dense, brown, silty, fine SAND (SM); moist,siightly plastic, some gravel, massive with occasional fine rusty mottles. (Till). 10 11 S-1 13 GS 18 15 20 11 Light brown, fine sandy SILT, some gravel, massive. S-2 17 17 Some gravelly drilling at 22 feet. 25 - 30 is • Grading to silty, fine to medium SAND with fine, rounded , S-3 16 18 gravel, moist, massive. Gravelly drilling 31 to 35 feet. 35 Medium dense, brown, silty, fine SAND: moist with very moist interbeds, non -plastic, finer/coarser beds, laminated. (Outwash). Completion Depth: 140.5ft Remarks: Groundwater measured 4/1/15. Date Borehole Started: 3126115 Date Borehole Completed: 3130/15 Logged By: S. Evans Drilling Company: Holocene Drilling PmG]FB LOG OF TEST BORING B-2 I C 0 R P 0 R A T 0 D FigureA-3 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet i OT 4 Project: Dumas Bay Landslide Assessment Surface Elevation: 141.Oft Job Number: 15-046 Top of Casing Elev.: 141.Oft Location: SW 307th Street, Federal Way, WA If Drilling Method: Mud Rotary Coordinates: Northing: , Easting: 1 Sampling Method: SPT N-Value A z a to N 0 PL Moisture LL { Q E IN E MATERIAL DESCRIPTIONcc QM 0 O ® ROD Recovery sfo 0 50 100 Medium dense, brown, sflty, fine SAND: moist with very 40 12 moist interbeds, non -plastic, finer/coarser beds, laminated. S-4 s (Outwash). (Continued) 12 45 Dense, brown, silty, flne to medium SAND (SM): very moist, silty interbeds and laminae, occasional rusty bands, laminated, dips to 5°. (Outwash). 50 13 S-5 X 16 18 - 55 60 S-6 22 33 GS Very dense, brown, fine to medium SAND, very moist, 40 massive, with pockets of slit Trace gravel at 62 feet. Losing drilling fluid 62 to 65 feet. 65 70 19 .f Brown, fine to medium SAND, very moist to wet, massive. S-7 22 28 75 Very dense, brown gray, silty, fine SAND: very moist, r non -plastic, homogeneous, massive. (Outwash). Completion Depth: 140.5ft Remarks: Groundwater measured 4/1/15. Date Borehole Started: 3/26/15 f Date Borehole Completed: 3/30/15 jl Logged By: S. Evans Drilling Company: Holocene Drilling RnGEO LOG OF TEST BORING B-2 ! A C U R V b R A T E L Figure A-3 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet L OT 4 Proiect: Dumas Bay Landslide Assessment Surface Elevation: 141.Oft Job Number: 15-046 Top of Casing Elev.: 141.Oft Location: S?n1307th Street, Feder -a! Way, IMF [irillinVAA-.ho- t�A„d }?nF�r� Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A c z m � c � o PL Moisture LL c d L. a � N ~ MATERIAL DESCRIPTION i o0 m ® ROD Recovery o 0 50 100 Very dense, brown gray, silty, fine SAND: very moist, non -plastic, homogeneous, massive. (Outwash). 80 26 (Continued) S-8 38 48 85 90 27 Brown gray, fine SAND with non -plastic silt, laminated, dips S-9 X 34 35 0 to 50. t 95 ----------------------------------- Very dense, gray to brown SILT (ML). very moist with wet layers, non -plastic to slightly plastic, rapid dilatancy in some layers, laminated, some rusty weathering. (Outwash). •100- 13 S-10 26 GS 33 105 Very dense, fight brown gray, fine SAND with silt: very moist, non -plastic, homogeneous, laminated. (Outwash). _ 110 S-11 35 50/6 115 -------------------------- -- Completion Depth: 140.5ft Remarks: Groundwater measured 4/1116. Date Borehole Started: 3/26115 Date Borehole Completed: 3/30115 Logged By: S. Evans Drilling Company: Holocene Drilling FbnGE@) LOG OF TEST BORING B-2 INcosro0ATeo FigureA-3 The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 3 Ot 4 Protect: Dumas Bay Landslide Assessment Surface Elevation: 141.0ft Job Number: 15-046 Top of Casing Elev.: 141.0ft Location: SW 307th Street, Federal Way, WA Drilling Method; Mud Rotary Coordinates: Northing: , Easting: Sampling Method: SPT N-Value A Z CL to N o PL Moisture LL m w a ; I� E MATERIAL DESCRIPTION I CL N 0 L O Rt2D Recovery 0 50 100 Very dense, light brown gray, fine sandy SILT (ML)- very moist, non -plastic fines, iaminated with occasional rusty laminae. (Outwash). (Continued) 120 27 S-12 35 GS 44 125 130 S-13 50/4 J. dusty brown, fine sandy SILT, very moist to wet, non -plastic, .' i X. rapid dilatancy, one rounded pocket of low plastic, gray, clayey silt. 135 140 S-14 5016 Fine sandy SILT, homogeneous, massive, non -plastic. ' Bottom of Boring. 145 950 155 Completion Depth: 140,5ft Remarks: Groundwater measured 411/15. Date Borehole Started: 3/26115 Date Borehole Completed: 3/30/15 Logged By: S. Evans Drilling Company: Holocene Drilling PmGE@ LOG OF TEST BORING B-2 N C Q R. 0 R A T E D FigureA-3 The stratification lines represent approximate boundaries. The transition may be gradual. zjneet 4 OT 4 APPENDIX B LABORATORY TESTING Dumas Bay West July 16, 2015 LABORATORY TESTING This appendix contains descriptions of the procedures and results .of physical (geotechnical) laboratory testing conducted on soil samples recovered during the field exploration program. The selected samples were tested to determine basic physical index properties of the soils for purposes of classifying the material types encountered and to measure or correlate parameters used in the geotechnical design. The laboratory tests were performed in general accordance with the following ASTM Standard Test Methods: D2216 — Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock D422 — Standard Test Method for Particle -Size Analysis of Soils D 1140 — Standard Test Method for Percentage of Material Finer than #200 Sieve Moisture contents and percent finer than #200 Sieve (where determined) are shown on the summary boring logs. The results of particle -size analyses (grain size distribution) are presented on Figure B-1. 15-046 DBWH Geotechnical Study.docx B-1 PanGEO, Inc. U.S. SIEVE OPENING IN in.. -S I U.S. SIEVE NUMBERS i HrUR0METER 6 4 3 2 1.5 1 3 4 1/2 3 6 810 1416 30 40 50 60 100 140 200 90 80 70 60 w m z 50 U- w 40 a 30 20 10 0 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MILLIMETERS COBBLES �.GRAVEL SAND SILT OR CLAY fine coarse medium fine Specimen Identification Classification LL PL PI Cc Cu * 13-1 @ 10.0 ft. Poorly graded SAND with silt (SP•SM) 1.62 3.95 m B-1 @ 40.0 ft. silty SAND (SM) ♦ B•1 @ 80.0 ft. silty SAND (SM) * 2 B-@ 10.0 ft. silty SAND (SM) O B-2 @ 60.0 ft. silty SAND (SM) Specimen Identification D100 D60 D30 D10 %Gravel %Sand %Silt °/,Clay • 8.1 10.0 9.5 0.304 0.194 0.077 0.1 90.2 9.7 m B-1 40.0 0.075 ! 0.0 0.0 46.9 .♦ B-1 80.0 9.5 0.214 0.089 0.0 74.3 25.6 * B-2 10.0 19 0.18 4.8 54.1 41.1 O B•2 60.0 4.75 0.183 0.093 0.0 76.2 23.8 GRAIN SIZE DISTRIBUTION PanGEG) Project: Dumas Bay West Figure I N C o N P 0 N A T E o Job Number: 15-046 B-1Phone: 206.262.0370 Location: SW 307th Street, Federal Way, WA i N� I PanGEE) C D A P C A A T G A Geotechnical & Earthquake Engineering Consultants July 17, 2015 Project No. 15-117 Mr. & Mrs. Carl Jonasson LDT' 4346 SW 307" Street Federal Way, Washington 98023 Subject: Geotechnical Engineering Recommendations 4346 SW 307`h Street Federal Way, Washington Dear Mr. & Mrs. Jonasson, PanGEO, Inc. (PanGEO) prepared this letter report presenting our geotechnical engineering design recommendations for a slope stabilization wall to be constructed at the crest of the bluff on the north side of the subject residential property. The purpose of this wall is to provide long-term protection from mass wasting and slope retrogression at the crest of the coastal bluff that is experiencing sloughs and landslides to the north and below the subject residence. This letter report is supplemental to the geotechnical engineering study report that was prepared by PanGEO titled Dumas Bay West Coastal Bluff Stability Evaluation, and dated July 16, 2015, to address the overall geotechnical condition of the coastal bluff that runs along the northern (rear) portion of all the Dumas Bay West Homeowners (DBWH) properties. Please refer to that report for a discussion of the geologic, groundwater and geotechnical conditions of the DBWH properties, including the subject parcel. A discussion is provided in the coastal bluff stability report (PanGEO, July 16, 2015) regarding the field explorations, laboratory testing program, geotechnical slope stability analyses and conclusions regarding the stability of the coastal bluff that flanks the northern side of the DBWH properties. Retaining Wall Purpose and Design Recommendations The concept of the retaining wall recommended herein is to provide a structural system at the crest of the coastal bluff that can be retrofitted in the future according to the volume of mass wasting (sloughing or landsliding) that occurs below the wall in response two continued coastal erosion processes. Upon the completion of the initial construction, there will be little or no exposed face of wall. Slope movements below the wall may then 3213 Eastlake Avenue E. Suite B Seattle, WA 98' 102 (206) 262-0370 FAX ("206) 262-0374 Pau 2 Project No. 15-117 July 17, 2015 be allowed to occur until a pre -determined height of the wall is exposed that requires retrofitting to increase the lateral resistance of the system. Up to this pre -determined height, lagging or facing elements will need to be installed to prevent caving of retained soil from between the vertical elements. The system may be comprised of conventional soldier piles that can function in pure cantilever up to a pre -determined limiting height according to the structural moment resistance of the system. If slope movements expose a portion of the soldier piles, conventional lagging should be provided. If slope movements continue to expose the wall such that the pre -determined limiting height is reached or exceeded, additional lateral restraint should be provided for the wail system in the form of permanent ground anchors (tiebacks). A second and possibly third pre -determined height of exposed wall should also be identified when additional row(s) of tiebacks are required. The pre- determined heights and retrofit action required should be identified on the structural drawings for the wall. The system may also be comprised of micropiles with vertical elements at the location where a wall face would be constructed in the future, but also tied -back with a battered micro -pile connected by a grade beam to add lateral resistance to the system and provide for a taller exposed height before addition of tiebacks for additional lateral resistance is required. Limiting heights and retrofit requirements should be shown on the structural drawings similar to the soldier pile option described above. Figure 1 (attached) provides lateral earth pressures that may be used for structural design of either of the systems described above with a single point of lateral restraint, or for pure cantilever of a soldier pile system. Figure 2 (also attached) provides lateral earth pressures that may be used for structural design of the retrofit options for multiple rows or lateral restraint elements (tiebacks). The minimum embedment length for the vertical elements (soldier piles) should be 60 feet. Global Stability No new backfill or loading above the slope will be required on the subject parcel. The vertical elements (soldier piles) are being installed as a precautionary measure in anticipation of possible future slope movements similar to the recent landsliding on the adjacent parcel to the east. Figure 3 presents the results of global stability analysis with the inclusion of the retaining structure as a soldier pile and the incremental increase in loading due to the new backfill. The stabilization provided by the soldier pile increases 15-117 DBW Parcel 1 Wall Design Recommendations.docx PanGEO, Inc. Paae 3 Project No. 15-117 July 17, 2015 the overall global stability to 1.24 from 1.12 as compared to the existing condition (Figure 3 from PanGEG, July 16, 2015). Tiebacks Tiebacks will not be required as part of the initial installation of wall elements on the subject parcel. The following reconunendations are provided for future addition of tiebacks should slope movements expose sufficient height of wail to require increased lateral restraint for structural stability. The manner in which the tieback anchors carry load will depend on the type of anchor selected, the method of installation, and the soil conditions surrounding the anchor. Accordingly, we recommend use of a performance specification requiring the contractor to install anchors capable of satisfactorily achieving the design structural loads, with a pullout resistance factor of safety of 2.0. For planning purposes, however, the anchors may be sized for an allowable skin friction value of 2.5 kips per lineal foot of anchor bond length, assuming that small diameter (about 6 inches) pressure -grouted tiebacks will be used. Post -grouting may also be needed in order to achieve the design capacity. We recommend that the allowable tieback loads be limited to about 90 kips per anchor. The tiebacks for this project should be installed by experienced personnel. Temporary casing may be required to prevent excessive ground loss. In addition, the use of compressed air to flush the drill cuttings must be properly controlled; the use of excessive amount of compressed air while drilling tiebacks could lead to reduction of soil strength and ground movements. The actual capacity of the anchors should be checked with 200% verification tests. At least one 200% test should be performed prior to installing production anchors. All production anchors should be proof tested to 150% of the design load. The anchor installations should be conducted in accordance with the latest edition of the Post Tensioning Institute (PTI) "Recommendations for Prestressed Rock and Soil Anchors". Elements of the testing are as follows: Verification Tests 20 % Tests • Prior to installing production anchors, perform a minimum of one test each on each anchor type, installation method and soil type with the tested anchors constructed to the same dimensions as proposed production anchors. • Test locations to be determined in conjunction with, and approved by, the geotechnical engineer. 15-117 DBW Parcel 1 Wall Design RecommendationsAocx PanGEO, Inc. Paine 4 Project No. 15-117 July 17, 2015 a Test anchors, which will be loaded to 200% of the design load, may require additional prestressing steel (steel load not to exceed 80% of the ultimate tensile strength) or reinforcing of the reaction soldier pile. ■ Load test anchors to 200% load in 25% design load increments, holding each incremental load for at least 5 minutes and recording deflection of the anchor head at various times within each hold to the nearest 0.01 inch. • At the 200% load, the holding period shall be at least 60 minutes. ■ A successful test shall provide a measured creep rate of 0.04 inches or less at the 200% load between 1 and 10 minutes, and 0.08 inches or less between 6 and 60 minutes, and all time increments shall have a creep rate that is linear or decreasing with time. The applied load must remain constant during all holding periods (i.e. no more than 5° � variation from the specified load). Verification tested anchors not meeting the acceptance criteria will require a redesign by the contractor to achieve the acceptance criteria. Proof Tests 050% load tests on all production anchors • Load test all production anchors to 150% of the design load in 25% design load increments, holding each incremental load until a stable deflection is achieved (record deflection of the anchor head at various times within each hold to the nearest 0.01 inch). • At the 150% load, the holding period shall be at least 10 minutes • A successful test shall provide a measured creep rate of 0.04 inches or less at the 150% load between 1 and 10 minutes with a creep rate that is linear or decreasing with time. The applied load must remain constant during the holding period (i.e., no more than 5% variation from the 150° o load). Anchors failing this proof testing creep acceptance criteria may be held an additional 50 minutes for creep measurement. Acceptable performance would equate to a creep of 0.08 inches or less between 5 and 50 minutes with a linear or decreasing creep rate. In the tieback construction, a bond breaker shall be constructed in the no load zone when the installation procedures use single stage grouting. As discussed above, the structural design of the retaining wall should include pre- determined height(s) of exposed wail that would require installation of additional tiebacks if slope movements below the wail result in exposure of wall face. Installation of tiebacks in the future should be accomplished as soon as possible after observation that exposed wall heights have exceeded the pre -determined limits and should follow the installation and testing criteria recommended above. 15-117 DBW Parcel 1 Wall Design Recommendations.doex PanGEO, Inc. Page 5 Project No. 15-117 July 17, 2015 Baseline Survey and Monitoring Since installation of vertical elements (soldier piles) on the subject parcel will not result in grade changes or new wall backfill, ground movements are not expected. However, existing structures or improvements to be saved that are near the construction zone should have baseline physical 'location data established prior to beginning work. Asa minimum, optical survey points (points known, or PK's) should be established at the corners and midpoint of the residential structure. The selection of monitoring points should be made with concurrence of the geotechnical engineer. The monitoring program should include measurement of changes in both the horizontal and vertical directions. The monitoring should be performed at least weekly while active wall construction is underway. The monitoring should be by a licensed surveyor, and the results be promptly submitted to the geotechnical engineer for review. The results of the monitoring will allow the design team to confirm design parameters, and for the contractor to make adjustments to means and methods of construction, if necessary. Construction Considerations The following should be taken into consideration during the design and construction of the retaining structure described herein: 1. Based on the groundwater level measurements taken in the borings drilled for the DBWH (PanGEO, July 16, 2015), groundwater is not expected to be encountered during construction of vertical elements (soldier piles) or for tiebacks. 2. Care should be taken during construction to not unnecessarily place live load surcharges close to the crest of the bluff as this could result in local instability. 3. Upon completion, grades between the retaining structure and the residential structure should be returned to similar conditions as before construction such that surface water runoff is not directed over the wall and onto the steep slopes below the coastal bluff 4. We recommend that the following should be incorporated into the project plans and specifications: The geotechnical engineer shall verify the suitability of all soldier ,pile holes before concrete placement; • Temporary casing should be used if caving occurs as determined by the geotechnical engineer; 15-117 DBW Parcel 1 Wall Design Recommendations.docx PanGEO, inc. Page 6 ,1 Project No. 15-117 July 17, 2015 ■ Tremie methods shall be used for concrete placement in all holes having 3 or more inches of accumulated water; and • All soldier pile holes shall be drilled and filled with concrete on the same day. If you have any questions, or require additional information, please contact our offices at (206) 262-0370. Sincerely, Robert E. Kimmerling, P.E. Principal Engineer Attachments: Figure 1 — Wall Design Parameters, Cantilever Wall / Single Tieback Figure 2 — Wall Design Parameters, Multiple Tiebacks Figure 3 — Static Global Stability Analysis, Section `C' - with Soldier Pile and Backfill 15-117 DBW Parcel 1 Wall Design Recommendations.docx PanGEO, Inc. 0 A w i i i i i I i Surface I Surcharge = q 6 X Micro -pile or �4 Soldier Pile Wall Existing Grade 0.5X 600 No -Load Zolve 2Bq 0.4(1 - X/H) q Bottom of Exposed Wall Height 6H (psf) Surcharge 27 Pc ' H14 0 - — Pressure (Level Backslope) 5' min Seismic Pressure 1 Increment 1:1 (max.) Z 67 pcf 1 Active Pressure Passive Pressure i Notes: 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present. Minimum pile embedment shall be 60 feet below Existing Grade (crest of bluff). 2. A factor of safety of 1.5 has been applied to the recommended passive earth pressure value. Increase allowable passive pressure by 1/3 for resistance to tranisient loads, including seismic earth pressure_ 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the j base of the excavation, and over one pile diameter below the base of the wall face. f 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussions. Dumas Bay West WALL DESIGN PARAMETERS 1—bnGEO Jonasson Parcel CANTILEVER WALL / SINGLE TIEBACK W C O„ P O .. T e o 4346 SW 307th Street Federal Way, Washington Project No. 15-117 Figure No. 1 Surface Surcharge = q 2Bq 6H (psf) Seismic Pressure Increment 0.5X do B" —►-- X 7 I ! T ! Existing Grade No -Load 60° Zone 0.4(1 - x/H) q Surcharge Pressure 27H psf - 27 pcf (Level Backslope) 1 Micro -pile or Soldier Pile Wall H Bottom of Exposed Wall Height HA or 5' min 1:1 (max.) Z 67 pcf 1 Lt Active Pressure Passive Pressure Notes: 1- Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present, Minimum pile embedment shall be 60 feet below crest of bluff. 2. A factor of safety of 1.5 is included in the recommended allowable passive earth pressure value, Increase allowable passive pressure by 1/3 for resistance to tranisient loads, including seismic earth pressure_ 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussion and recommendations. FtnGE& C O R r O 4 A T W a Dumas Bay West Jonasson Parcel 4346 SW 307th Street Federal Way, Washington WALL DESIGN PARAMETERS MULTIPLE TIEBACKS 0. 15-117 Irigure No. 2 100 ISO b SR S v of 3 �D N C W A,C � EL d �� Va;;R o. ` p1 : O 7 y o �* OZ i 0 oI o• w N i_ V � LTI � f a °a � a a m N tl1 cu A n o t a m of ro - = O Z m i �GE N C O R P O R A T i 0 Geotechnical & Earthquake Engineering Consultants July 17, 2015 Project No. 15-116 Mr. & Mrs. Tom Donovan 30625 43rd Avenue SW Federal Way, Washington 98023 Subject: Geotechnical Engineering Recommendations 30625 43rd Avenue SW Federal Way, Washington Dear Mr. & Mrs. Donovan, PanGEO, Inc. (PanGEO) prepared this letter report presenting our geotechnical engineering design recommendations for a slope stabilization wall to be constructed at the crest of the bluff on the north side of the subject residential property. The purpose of this wall is to provide long-term protection from mass wasting and slope retrogression at the crest of the coastal bluff that is experiencing sloughs and landslides to the north and below the subject residence. This letter report is supplemental to the geotechnical engineering study report that was prepared by PanGEO titled Dumas Bay West Coastal Bluff Stability Evaluation, and dated July 16, 2015, to address the overall geotechnical condition of the coastal bluff that runs along the northern (rear) portion of all the Dumas Bay West Homeowners (DBWH) properties. Please refer to that report for a discussion of the geologic, groundwater and geotechnical conditions of the DBWH properties, including the subject parcel. A discussion is provided in the coastal bluff stability report (PanGEO, July 16, 2015) regarding the field explorations, laboratory testing program, geotechnical slope stability analyses and conclusions regarding the stability of the coastal bluff that flanks the northern side of the DBWH properties. Retaining Wall Purpose and Design Recommendations The concept of the retaining wall recommended herein is to provide a structural system at the crest of the coastal bluff that can be retrofitted in the future according to the volume of mass wasting (sloughing or landsliding) that occurs below the wall in response to 3213 Eastlake Avenue E. Suite B Seattle, WA 95102 (206) 262-0370 FAX (206) 262-0374 Page 2 Project No. 15-116 July 17, 2015 continued coastal erosion processes. Upon the completion of the initial construction, there will be little or no exposed face of wall. Slope movements below the wall may then be allowed to occur until a pre -determined height of the wall is exposed that requires retrofitting to increase the lateral resistance of the system. Up to this pre -determined height, lagging or facing elements will need to be installed to prevent caving of retained soil from between the vertical elements. The system may be comprised of conventional soldier piles that can function in pure cantilever up to a pre -determined limiting height according to the structural moment resistance of the system. If slope movements expose a portion of the soldier piles, conventional lagging should be provided. If slope movements continue to expose the wall such that the pre -determined limiting height is reached or exceeded, additional lateral restraint should be provided for the wall system in the form of permanent ground anchors (tiebacks). A second and possibly third pre -determined height of exposed wall should also be identified when additional row(s) of tiebacks are required. The pre- determined heights and retrofit action required should be identified on the structural drawings for the wall. The system may also be comprised of micropiles with vertical elements at the location where a wall face would be constructed in the future, but also tied -back with a battered micro -pile connected by a grade beam to add lateral resistance to the system and provide for a taller exposed height before addition of tiebacks for additional lateral resistance is required. Limiting heights and retrofit requirements should be shown on the structural drawings similar to the soldier pile option described above. Figure 1 (attached) provides lateral earth pressures that may be used for structural design of either of the systems described above with a single point of lateral restraint, or for pure cantilever of a soldier pile system. Figure 2 (also attached) provides lateral earth pressures that may be used for structural design of the retrofit options for multiple rows or lateral restraint elements (tiebacks). The minimum embedment length for the vertical elements (soldier piles) should be 50 feet. Global Stability A small portion of the retaining structure may retain up to 6 feet of new backfill in the vicinity of the existing deck. Figure 3 presents the results of global stability analysis with the inclusion of the retaining structure as a soldier pile and the incremental increase in loading due to the new backfill. The stabilization provided by the soldier pile increases 15-116 DBW Parcel 6 Wall Design Recommendations.doex PanGEO, Inc. Page 3 Project No. 15-116 July 17, 2015 the overall global stability to 1.58 from 1.48 as compared to the existing condition (Figure 7 from PanGEO, July 16, 2015), Tiebacks The manner- in which the tieback anchors carry load will depend on the type of anchor selected, the method of installation, and the soil conditions surrounding the anchor. Accordingly, we recommend use of a performance specification requiring the contractor to install anchors capable of satisfactorily achieving the design structural loads, with a pullout resistance factor of safety of 2.0. For planning purposes, however, the anchors may be sized for an allowable skin friction value of 2.5 kips per lineal foot of anchor bond length, assuming that small diameter (about 6 inches) pressure -grouted tiebacks will be used. Post -grouting may also be needed in order to achieve the design capacity. We recommend that the allowable tieback loads be limited to about 90 kips per anchor. The tiebacks for this project should be installed by experienced personnel. Temporary casing may be required to prevent excessive ground loss. In addition, the use of compressed air to flush the drill cuttings must be properly controlled; the use of excessive amount of compressed air while drilling tiebacks could lead to reduction of soil strength and ground movements. The actual capacity of the anchors should be checked with 200% verification tests. At least one 200% test should be performed prior to installing production anchors. All production anchors should be proof tested to 150% of the design load. The anchor installations should be conducted in accordance with the latest edition of the Post Tensioning Institute (PTI) "Recommendations for Prestressed Rock and Soil Anchors". Elements of the testing are as follows: Verification Tests (200% Tests Prior to installing production anchors, perform a minimum of one test each on each anchor type, installation method and soil type with the tested anchors constructed to the same dimensions as proposed production anchors. • Test locations to be determined in conjunction with, and approved by, the geotechnical engineer. • Test anchors, which will be loaded to 200% of the design load, may require additional prestressing steel (steel load not to exceed 80% of the ultimate tensile strength) or reinforcing of the reaction soldier pile. 15-116 DBW Parcel 6 Wall Design Recomroendations.docx PanGEO, Inc. Page 4 Project No. 15-116 July 17, 2015 s road test anchors to 200% load in 25% design load increments, holding each incremental load for at least 5 minutes and recording deflection of the anchor head at various times within each hold to the nearest 0.01 inch. At the 200% load, the holding period shall be at least 60 minutes. • A successful test shall provide a measured creep rate of 0.04 inches or less at the 200% load between 1 and 10 minutes, and 0.08 inches or less between 6 and 60 minutes, and all time increments shall have a creep rate that is linear or decreasing with time. The applied load must remain constant during all holding periods (i.e. no more than 5% variation from the specified load). Verification tested anchors not meeting the acceptance criteria will require a redesign by the contractor to achieve the acceptance criteria. Proof Tests ,150% load tests on all production anchor • Load test all production anchors to I50% of the design load in 25% design load increments, holding each incremental load until a stable deflection is achieved (record deflection of the anchor head at various times within each hold to the nearest 0.01 inch). • At the 150% load, the holding period shall be at least 10 minutes • A successful test shall provide a measured creep rate of 0.04 inches or less at the 150% load between 1 and 10 minutes with a creep rate that is linear or decreasing with time. The applied load must remain constant during the holding period (i.e., no more than 5% variation from the 150% load). Anchors failing this proof testing creep acceptance criteria may be held an additional 50 minutes for creep measurement. Acceptable performance would equate to a creep of 0.08 inches or less between 5 and 50 minutes with a linear or decreasing creep rate. In the tieback construction, a bond breaker shall be constructed in the no load zone when the installation procedures use single stage grouting. As discussed above, the structural design of the retaining wall should include pre- determined height(s) of exposed wall that would require installation of additional tiebacks if slope movements below the wall result in exposure of wall face. Installation of tiebacks in the fixture should be accomplished as soon as possible after observation that exposed wall heights have exceeded the pre -determined limits and should follow the installation and testing criteria recommended above. 15-116 DBW Parcel 6 Wall Design Recommendations.docx PanGEO, Inc. Page 5 `� Project No. 15-116 July 17, 2015 Baseline Survey and Monitoring Ground movements are expected to be relatively small as a result of wall construction activities since most of the construction will not result in an initial exposed wall face. However, existing structures or improvements to be saved that are near the construction zone should have baseline physical location data established prior to beginning work. /AS a minimum, optical survey points (points known, or PK's) should be established at the corners of existing features to remain. The selection of monitoring points should be made with concurrence of the geotechnical engineer. The monitoring program should include measurement of changes in both the horizontal and vertical directions. The monitoring should be performed at least weekly while active wall construction is underway. The monitoring should be by a licensed surveyor, and the results be promptly submitted to the geotechnical engineer for review. The results of the monitoring will allow the design team to confirm design parameters, and for the contractor to make adjustments to means and methods of construction, if necessary. Construction Considerations The following should be taken into consideration during the design and construction of the retaining structure described herein: 1. Based on the groundwater level measurements taken in the borings drilled for the DBWH (PanGEO, July 16, 2015), groundwater is not expected to be encountered during construction of vertical elements (soldier piles) or for tiebacks (if needed). 2. Care should be taken during construction to not unnecessarily place live load surcharges close to the crest of the bluff as this could result in local instability. 3. Upon completion, grades between the retaining structure and the residential structure should be returned to similar conditions as before construction such that surface water runoff is not directed over the wall and onto the steep slopes below the coastal bluff. 4. We recommend that the following should be incorporated into the project plans and specifications: ■ The geotechnical engineer shall verify the suitability of all soldier pile and tieback holes before concrete or grout placement; + Temporary casing should be used if caving occurs as determined by the geotechnical engineer; 15-116 D13W Parcel 6 Wall Design Recommendations. docx PanGEO, Inc. Page 6 Project No. 15-116 July 17, 2015 0 Tremie methods shall be used for concrete or grout placement in all holes having 3 or more inches of accumulated water; and ■ All soldier pile holes shall be drilled and filled with concrete on the same day. • The geotechnical engineer shall witness and validate verification and proof testing of tiebacks and confirm that test results meet acceptance criteria. If you have any questions, or require additional information, please contact our offices at (206) 262-0370. Sincerely, Robert E. Kimmerling, P.E. Principal Engineer Attachments: Figure 1— Wall Design Parameters, Cantilever Wall / Single Tieback Figure 2 — Wall Design Parameters, Multiple Tiebacks Figure 3 — Static Global Stability Analysis, Section `C' - with Soldier Pile and Backfill 15-116 DBW Parcel 6 Wall Design Recommendations.docx PanGEO, Inc. i f Surface Surcharge = q Bo _ X Micro -pile or Soldier Pile Wall Existing Grade 0.5X 600 No -Load ZoKe 2Bq H 0.4(1 - x/H) q Bottom of Exposed Wall Height 6H (psf) Surcharge 27 pcf I U4 or Pressure (Level Backslope) 5' min Seismic Pressure 1 Increment 1:t (max.) Z 67 pcf 1 1 Active Pressure Passive Pressure i f Notes: II 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location If present. Minimum pile embedment shall be 50 feet below Existing Grade (crest of bluff). 2. A factor of safety of 1.5 has been applied to the recommended passive earth pressure value. Increase allowable passive pressure by 113 for resistance to tranisient loads, including seismic earth pressure_ 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussions. RanDumas Bay West WALL DESIGN PARAMETERS GE& Donovan Parcel CANTILEVER WALL /SINGLE TIEBACK ■ o R. o. T E o 30625 43rd Avenue SW Federal Way, Washington 'Project No. 15-116 Figure No. 1 1 I I Surface Surcharge = q 8X Micro -pile or Soldier Pile Wall I FREE Existing Grade \ No -Load 0.5X Zone 600 26q IF i 18H H 0.4(1 - x/H) q Bottom of Exposed Wall Height 6H (psf) Surcharge _� r Pressure 27H psf o 5 H�4 4 Seismic 27 pcf Pressure (Level Backslope) Inrmn 1 � 1:1 (max.) Z 67 pcf Active Pressure Passive Pressure f Notes: ` 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present. Minimum pile embedment shall be 50 feet below crest of bluff. 2. A factor of safety of 1.5 is included in the recommended allowable passive earth pressure value. Increase allowable passive pressure by 1/3 for resistance to tranisient loads, including seismic earth pressure_ 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussion and recommendations. RanGFO Dumas Bay West WALL DESIGN PARAMETERS Donovan Parcel MULTIPLE TIEBACKS CC A o G A A s K 0 30625 43rd Avenue SW Federal Way, Washington :Project No. 15-116 Figure No. 2 0. O N O W FtA a 3 W o' °< a » M ^ d r- Z d (D Lh f Vf I Is I E2. n Li r N r V1 r W ui W " 0 0 0 h A h h ' c c c c tr Q t G O O O N � O O N O O N ? a 1 1 1 1 1 C C C C11 C N N' N nD ej m tth m O O O O = C N h Ol 61 =3 N ? y A 1 PmGEE) C O R O Earthquake T r 0 l otechnical & Earthquake Engineering Consultants July 17, 2015 Project No. 15-115 Drs. Shaista Quddusi and Dr. Irfan Ansari 4338 SW 307"' Street Federal Way, Washington 98023 Subject: Geotechnical Engineering Recommendations 4338 SW 307t" Street Federal Way, Washington Dear Drs. Quddusi and Ansari, PanGEO, Inc. (PanGEO) prepared this letter report presenting our geotechnical engineering design recommendations for a slope stabilization wall to be constructed at the crest of the bluff on the north side of the subject residential property. The purpose of this wall is to provide long-term protection from mass wasting and slope retrogression at the crest of the coastal bluff that is experiencing sloughs and landslides to the north and below the subject residence. This letter report is supplemental to the geotechnical engineering study report that was prepared by PanGEO titled Dumas Bay West Coastal Bluff Stability Evaluation, and dated July 16, 2015, to address the overall geotechnical condition of the coastal bluff that runs along the northern (rear) portion of all the Dumas Bay West Homeowners (DBWH) properties. Please refer to that report for a discussion of the geologic, groundwater and geotechnical conditions of the DBWH properties, including the subject parcel. A discussion is provided in the coastal bluff stability report (PanGEO, July 16, 2015) regarding the field explorations, laboratory testing program, geotechnical slope stability; analyses and conclusions regarding the stability of the coastal bluff that flanks the northern side of the DBWH properties. Retaining Wall Purpose and Design Recommendations The concept of the retaining wall recommended herein is to provide a structural system at the crest of the coastal bluff that can be retrofitted in the future according to the volume of mass wasting (sloughing or landsliding) that occurs below the wall in response to continued coastal erosion processes. Upon the completion of the initial construction, there will be little or no exposed face of wall. Slope movements below the wall Tray then 13 Eastlake Avenue F. Suite B Seattle, WA 9S 102 (206) 262-03 70 FAX (2ii16j 262- 374 Page G Project No. 15-115 July 17, 2015 be allowed to occur until a pre -determined height of the wall is exposed that requires retrofitting to increase the lateral resistance of the system. Up to this pre -determined height, lagging or facing elements will need to be installed to prevent caving of retained soil from between the vertical elements. The system may be comprised of conventional soldier piles that can function in pure cantilever up to a pre -determined limiting height according to the structural moment resistance of the system. If slope movements expose a portion of the soldier piles, conventional lagging should be provided. If slope movements continue to expose the wall such that the pre -determined limiting height is reached or exceeded, additional lateral restraint should be provided for the wall system in the form of permanent ground anchors (tiebacks). A second and possibly third pre -determined height of exposed wall should also be identified when additional row(s) of tiebacks are required. The pre- determined heights and retrofit action required should be identified on the structural drawings for the wall. The system may also be comprised of micropiles with vertical elements at the location where a wall face would be constructed in the future, but also tied -back with a battered micro -pile connected by a grade beam to add lateral resistance to the system and provide for a taller exposed height before addition of tiebacks for additional lateral resistance is required. Limiting heights and retrofit requirements should be shown on the structural drawings similar to the soldier pile option described above. Figure 1 (attached) provides lateral earth pressures that may be used for structural design of either of the systems described above with a single point of lateral restraint, or for pure cantilever of a soldier pile system. Figure 2 (also attached) provides lateral earth pressures that may be used for structural design of the retrofit options for multiple rows or lateral restraint elements (tiebacks). The minimum embedment length for the vertical elements (soldier piles) should be 50 feet. Global Stability No new backfill or loading above the slope will be required on the subject parcel. The vertical elements (soldier piles) are being installed as a precautionary measure in anticipation of possible future slope movements similar to the recent landsliding on the adjacent parcel to the west. As no new fill or loading is proposed, the global stability will be improved over the existing condition by inclusion of the vertical elements (soldier piles). 15-115 DBW Parcel 3 Wall Design Recommendations.docx PanGEO, Inc. Page 3 Project No. 15-115 July 17, 2015 Tiebacks Tiebacks will not be required as part of the initial installation of wall elements on the subject parcel. The following recommendations are provided for future addition of tiebacks should slope movements expose sufficient height of wall to require increased lateral restraint for structural stability. The manner in which the tieback anchors carry load will depend on the type of anchor selected, the method of installation, and the soil conditions surrounding the anchor. Accordingly, we recommend use of a performance specification requiring the contractor to install anchors capable of satisfactorily achieving the design structural loads, with a pullout resistance factor of safety of 2.0. For planning purposes, however, the anchors may be sized for an allowable skin friction value of 2.5 kips per lineal foot of anchor bond length, assuming that small diameter (about 6 inches) pressure -grouted tiebacks will be used, Post -grouting may also be needed in order to achieve the design capacity. We recommend that the allowable tieback loads be limited to about 90 kips per anchor. The tiebacks for this project should be installed by experienced personnel. Temporary casing may be required to prevent excessive ground loss. In addition, the use of compressed air to flush the drill cuttings must be properly controlled; the use of excessive amount of compressed air while drilling tiebacks could lead to reduction of soil strength and ground movements. The actual capacity of the anchors should be checked with 200% verification tests. At least one 200% test should be performed prior to installing production anchors. All production anchors should be proof tested to 150% of the design load. The anchor installations should be conducted in accordance with the latest edition of the Post Tensioning Institute (PTI) "Recommendations for Prestressed Rock and Soil Anchors". Elements of the testing are as follows: Verification Tests 200°/o Tests) • Prior to installing production anchors, perform a minimum of one test each on each anchor type, installation method and soil type with the tested anchors constructed to the same dimensions as proposed production anchors. • Test locations to be determined in conjunction with, and approved by, the geotechnical engineer. • Test anchors, which will be loaded to 200% of the design load, may require additional prestressing steel (steel load not to exceed 80% of the ultimate tensile strength) or reinforcing of the reaction soldier pile. 15-115 DBW Parcel 3 Wall Design Recommendations.doex PanGEO, Inc. Page 4 Project No. 15-115 July 17, 2015 • road test anchors to 200% load in 25% design load increments, holding each incremental load for at least 5 minutes and recording deflection of the anchor head at various times within each hold to the nearest 0.01 inch. At the 200% load, the holding period shall be at least 60 minutes. A successful test shall provide a measured creep rate of 0.04 inches or less at the 200% load between 1 and 10 minutes, and 0.08 inches or less between 6 and 60 minutes, and all time increments shall have a creep rate that is linear or decreasing with time. The applied load must remain constant during all holding periods (i.e. no more than 5% variation from the specified load). Verification tested anchors not meeting the acceptance criteria will require a redesign by the contractor to achieve the acceptance criteria. Proof Tests (150% load tests on all production anchors} • Load test all production anchors to 150% of the design load in 25% design load increments, holding each incremental load until a stable deflection is achieved (record deflection of the anchor head at various times within each hold to the nearest O.Olinch). • At the 150% load, the holding period shall be at least 10 minutes + A successful test shall provide a measured creep rate of 0.04 inches or less at the 150% load between 1 and 10 minutes with a creep rate that is linear or decreasing with time. The applied load must remain constant during the holding period (i.e., no more than 5% variation from the 150% load). Anchors failing this proof testing creep acceptance criteria may be held an additional 50 minutes for creep measurement. Acceptable performance would equate to a creep of 0.08 inches or less between 5 and 50 minutes with a linear or decreasing creep rate. In the tieback construction, a bond breaker shall be constructed in the no load zone when the installation procedures use single stage grouting. As discussed above, the structural design of the retaining wall should include pre- determined height(s) of exposed wall that would require installation of additional tiebacks if slope movements below the wall result in exposure of wall face. Installation of tiebacks in the future should be accomplished as soon as possible after observation that exposed wall heights have exceeded the pre -determined limits and should follow the installation and testing criteria reconunended above. 15-115 DBW Parcel 3 Wall Design Reeommendations.doex PanGEO, Inc. Page 5 Project No. 15-115 July 17, 2015 Baseline Survey and Monitoring Since installation of vertical elements (soldier piles) on the subject parcel will not result in grade changes or new wall backfill, ground movements are not expected. However, existing structures or improvements to be saved that are near the construction zone should have baseline physical location data established prior to beginning work. As a minimum, optical survey points (points known, or PK's) should be established at the corners and midpoint of the residential structure. The selection of monitoring points should be made with concurrence of the geotechnical engineer. The monitoring program should include measurement of changes in both the horizontal and vertical directions. The monitoring should be performed at least weekly while active wall construction is underway. The monitoring should be by a licensed surveyor, and the results be promptly submitted to the geotechnical engineer for review. The results of the monitoring will allow the design team to confirm design parameters, and for the contractor to make adjustments to means and methods of construction, if necessary. Construction Considerations The following should be taken into consideration during the design and construction of the retaining structure described 'herein: 1. Based on the groundwater level measurements taken in the borings drilled for the DBWH (PanGEO, July 16, 2015), groundwater is not expected to be encountered during construction of vertical elements (soldier piles) or for tiebacks. 2. Care should be taken during construction to not unnecessarily place live load surcharges close to the crest of the bluff as this could result in local instability. 3. Upon completion, grades between the retaining structure and the residential structure should be returned to similar conditions as before construction such that surface water runoff is not directed over the wall and onto the steep slopes below the coastal bluff. 4. We recommend that the following should be incorporated into the project plans and specifications: • The geotechnical engineer shall verify the suitability of all soldier piie holes before concrete placement; Temporary casing should be used if caving occurs as determined by the geotechnical engineer; 15-115 DBW Parcel 3 Wall Design Recommendations.doex PanGEO, Inc. Page 6 Project No. 15-115 July 17, 2015 Tremie methods shall be used for concrete placement in all holes having 3 or more inches of accumulated water; and • All soldier pile holes shall be drilled and filled with concrete on the same day. If you have any questions, or require additional information, please contact our offices at (206) 262-0370. Sincerely, Robert E. Kimmerling, P.E. Principal Engineer Attachments: Figure 1 — Wall Design Parameters, Cantilever Wall / Single Tieback Figure 2 — Wall Design Parameters, Multiple Tiebacks 15-115 DBW Parcel 3 Wall Design Recommendations.docx PanGEO, Inc. w LO 0 m E IL to Surface Surcharge = q 14 BQ X Micro -pile or Soldier Pile Wall Existing Grade r' r r 0.5X 600 No -Load Zone 2Bq 9 0.4(1 - x/H) q _ Bottom of Exposed Wall Height 6H (psf) Surcharge 27 pcf H14 o Pressure (Level Backslope) 5, min Seismic Pressure 1 Increment 1:1 (max.) �67 pcf Active Pressure Passive Pressure H Z Notes: 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present. Minimum pile embedment shall be 50 feet below Existing Grade (crest of bluff). 2. A factor of safety of 1.5 has been applied to the recommended passive earth pressure value. Increase allowable passive pressure by 1/3 for resistance to tranisient loads, including seismic earth pressure_ 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for legging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussions. F�nGE& [ O R r O R A T 6 a Dumas Bay West Ansaris Parcel 4338 SW 307th Street Federal Way, Washington WALL DESIGN PARAMETERS CANTILEVER WALL / SINGLE TIEBACK 15-115 (Figure No Surface Surcharge = q 2Bq 6H (psf) Seismic Pressure Increment E° — X Micro -pile or Soldier Pile Wall I Exisfing Grade No -Load 0.5X 600 Zone /f 18H 0.4(1 - x/H) q Surcharge r- _ Pressure 27H psf 5' rr 27 pcf (Level Backslope) Active Pressure Bottom of Exposed Wall Passive Pressure Notes: 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present, Minimum pile embedment shall be 50 feet below crest of bluff. 2. A factor of safety of 1.5 is included in the recommended allowable passive earth pressure value. Increase allowable passive pressure by 1/3 for resistance to tranisient loads, including seismic earth pressure_ 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussion and recommendations. LnG� I N C O R r O R A T E O Dumas Bay West Ansaris Parcel 4338 SW 307th Street Federal Way, Washington WALL DESIGN PARAMETERS MULTIPLE TIEBACKS 15-116 (Figure No. 2 H Z r Y Y y y •� - 4 cv�� f, r ik r d: • ,y � ! T s 1 •_ �7•'•'1z:Sl•Syy = 'r._ _. a ^i •� �-. ";_ � � . .i .R lr r 7 7 K ic� U ■ CD % & \ 0 0 k � 0 �� 5 k / \ 0 2 { 0 \ 2 % \ -I ■ � ®200 ,9 / $�® �, \ ~-C CD w _ o u > a \ 00 n $ _ \ ® � o / � ■ �� k �\ o » � , y « ■ et ai o ¢ \ Ln \ \ ¥ 1121 0 % . J � ] t \ \ a �E w o Q @ 7 1121 @ D CL 112 4.5 ti Je w k 0 12 > . 2 e ' / 2 h / > Qat& 3 o $ ® t , 2 PaAnGEO p N V O A A T 8 Q Geotechnical & Earthquake Engineering Consultants July 17, 2015 Project No. 15-098 Mr. & Mrs. Kirk Ream 4342 SW 307th Stl-eet y Federal Way, Washington 98023 Subject: Geotechnical Engineering Recommendations 4342 SW 307"' Street+ Z Federal Way, Washington Dear Mr. & Mrs. Reagan, PanGEO, Inc. (PanGEO) prepared this letter report presenting our geotechnical engineering design recomnvndations for a slope stabilization wall to be constructed at the crest of the bluff on the north side of the subject residential property. The purpose of this- wall is to provide long -tern protection from mass wasting and slope retrogression at the crest of the coastal bluff that is experiencing sloughs and landslides to the north and below the subject residence. This letter report is supplemental to the geotechnical engineering study report that was prepared by PanGEO titled Dumas Bay West Coastal Bluff Stability Evaluation, and dated Jury 16, 2015, to address the overall geotec'nnicai condition of the coastal bhiff that runs along the northern (rear) portion of all the Dumas Bay West Homeowners (DBWH) properties. Please refer to that report for a discussion of the geologic, groundwater and geotechnical conditions of the DBWH properties, including the subject parcel. A discussion is provided in the coastal bhiff stability report (PanGEO, July 16, 2015) regarding the field explorations, laboratory testing program, geotechnical slope stability analyses and conclusions regarding the stability of the coastal bluff that flanks the northern side of the DBWH properties. Retaining Wall Purpose and Design Recommendations The concept of the retaining wall recorr ner.ded herein is to provide a structural system at the crest of the coastal bluff that can be retrofitted lit the future according to the vohime of mass wasting (sloughing or landsliding) that occurs below the wall in response to continued coastal erosion processes. Upon the completion of the initial construction, there will be segrnents of the wall with little or no exposed face of wall, while in the area 321 —asttalce Avenue E. sun-: B Seattle. WA 93102 (206, 262-0370 FAX (206) 262-0374 Page 2 Project No. 15-098 July 17, 2015 of recent landsliding, some new wall and backfill will be built to maintain a straight wall alignment and improve the stability of the crest of the bhiff in this area. Slope movements below the wall may then be allowed to occur until a pre -determined height of the wall is exposed that requires retrofitting to increase the lateral resistance of the system Up to this pre -determined height, lagging or facing elements will need to be installed to prevent caving of retained soil from between the vertical elements. The system may be comprised of conventional soldier piles *at can f action m pure cantilever up to a pre -determined limiting height according to the structural moment resistance of the system. If slope movements expose a portion of the soldier piles, conventional lagging should be provided. if slope movements continue to expose the wall such that the pre -determined limiting height is reached or exceeded, additional lateral restraint should be provided for the wall system in the form of permanent ground anchors (tiebacks). A second and possibly third pre-detemmned height of exposed wall should also be identified when additional row(s) of tiebacks are required. The pre- determined heights and retrofit action required should be identified on the structural drawings for the wall The system may also be comprised of micropiles with vertical elements at the location where a wall face would be constructed in the firture, but also tied -back with a battered micro -pile connected by a grade beam to add lateral resistance to the system and provide for a taller exposed height before addition of tiebacks for additional lateral resistance is required. Limiting heights and retrofit requirements should be shown on the structural drawings similar to the soldier pile option described above. Figure 1 (attached) provides lateral earth pressures that may be used for structural design of either of the systems described above with a single point of lateral restraint, or for pure cantilever of a soldier pile system. Figure 2 (also attached) provides lateral earth pressures that may be used for structural design of the retrofit options for multiple rows or lateral restraint elements (tiebacks). The minimum embedment length for the vertical elements (soldier piles) should be 60 feet. Global Stability About one-third of the retaining structure will retain up to 10 feet of new backfill in the vicinity of the head scarp of the recent landslide area. Figure 3 presents the results of global stability analysis with the inclusion of the retaining structure as a soldier pile and the incremental increase in loading due to the new backfill. The stabilization provided by 15.098 DBWPan el 2 Wall Desigi Recommendations.docm PanGEO, Inc. Page Project No. 15-098 July 17, 2015 the soldier pile increases the overall global stability to 1.56 from 1.50 as compared to the existing post -slide condition (Figure 6 from PanGEO,. July 16, 2015). Tiebacks The manner in which the tieback anchors carry load will depend on the type of anchor selected, the method of installation, and the soil conditions surrounding the anchor. Accordingly, we recommend use of a performance specification requh-iiig the contractor to install anchors capable of satisfactorily achieving the design structural loads, with a pullout resistance factor of safety of 2.0. For planning purposes, however, the anchors may be sized for an allowable skin friction value of 2.5 kips per lineal foot of anchor bond length, assuming that small diameter (about 6 inches) pressure -grouted tiebacks will be used. Post -grouting may also be needed in order to achieve the design capacity. We recommend that the allowable tieback loads be limited to about 90 kips per anchor. The tiebacks for this project should be installed by experienced personnel Temporary casing may be required to prevent excessive ground loss. In addition, the use of compressed air to flush the drill cuttings must be properly controlled; the use of excessive amount of compressed air while drilling tiebacks could lead to reduction of soil strength and ground movements. The actual capacity of the anchors should be checked with 200% verification tests. At least one 200% test should be performed prior to installing production anchors. All production anchors should be proof tested to 150% of the design load. The anchor installations should be conducted in accordance with the latest edition of the Post Tensioning Institute (PTl) "Recommendations for Prestressed Rock and Soil Anchors". Elements of the testing areas follows: Verification Tests (200% Tests + Prior to installing production anchors, perform a minimum of one test each on each anchor type, installation method and soil type with the tested anchors constructed to the same dimensions as proposed production anchors. Test locations to be deters-nincd in conjunction with, and approved by, the geotechnical engineer. • Test anchors, which will be loaded to 200% of the design load, may require additional prestressing steel (steel load not to exceed 80% of the ultimate tensile strength) or reinforcing of the reaction soldier pile. 15-098 DBWParcel 2 Wall Desip Recommendations.doex PanGEO, inc. Page 4 Project No. 15-098 July 17, 2015 Load test anchors to 200% load in 25% design load increments, holding each incremental load for at least 5 minutes and recording defection of the anchor head at various times within each hold to the nearest O.Olinch. ■ At the 200% load, the holding period shall be at least 60 minutes. • r4 successful test shall provide a measured creep rate of 0.04 inches or less at the 200% load between 1 and 10 minutes, and 0.08 inches or less between 6 and 60 minutes, and all time, increments shall have a creep rate that is linear or decreasing with time. The applied load mast remain constant during all holding periods (ie. no more than 5% variation from the specified load). Verification tested anchors not meting the acceptance criteria will require a redesign by the contractor to achieve the acceptance criteria. Proof Tests (150% load tests on an production anchors) • Load test all production anchors to 150% of the design load in 25% design load increments, holding each incremental load until a stable deflection is achieved (record deflection of the anchor head at various tinges within each hold to the nearest 0.01 inch). s At the 150% load, the holding period shall be at least 10 rnirMes * A successful test shall provide a measured creep rate of 0.04 inches or less at the 150% load between 1 and 10 minutes with a creep rate that is linear or decreasing with time. The applied load must remain constant during the holding period (ie., no more than 5% variation from the 150% load). Anchors failing this proof testing creep acceptance criteria may be held an additional 50 minutes for creep measurement. Acceptable performance would equate to a creep of 0.08 inches or less between 5 and 50 minutes with a linear or decreasing creep rate. In the tieback construction, a bond breaker shall be constructed in the no load zone when the installation procedures use single stage grouting. As discussed above, the structural design of the retaining wall should include pre- determined height(s) of exposed wall that would require installation of additional tiebacks if slope movements below the wall result in exposure of wall face. Installation of tiebacks in the fixture should be accomplished as soon as possible after observation that exposed wall heights have exceeded the pre -determined limits and should follow the installation and testing criteria reconuaaended above. 15-098 D13WParcel2 WallDesigp Recommendations.dom PanGEO, inc. Page 5 Project No. 15-098 July 17, 2015 Baseline Survey and Monitoring Ground movements are expected to be relatively small as a result of wall construction activities since most of the construction will not result in an initial exposed wall face. However, existing structures or improvements to be saved that are near the construction zone should have baseline physical location data established prior to beginning work. As a minimum, optical survey points (points known, or PK's) should be established at the corners and midpoint of the residential structure and at 10-foot o$sets to the north of the PK's on the residence itself The selection of monitoring points should be made with concurrence of the geotechnical engineer. The monitoring program should include measurement of changes in both the horizontal and vertical directions. The monitoring should be performed at Least twice weekly, wl'le active wall construction is underway, and should be increased to daily monitoring if movement is detected at the locations offset from the residence. The monitoring should be by a licensed surveyor, and the results be promptly submitted to the geoteckwal engineer for review. The results of the monitoring will allow the design team to conform design parameters, and for the contractor to make adjustments to means and methods of construction, if necessary. Construction Considerations The following should be taken into consideration during the design and construction of the retaining structure described herein: 1. Based on the groundwater level measurements taken in the borings drilled for the DBWH (PanGEO, July 16, 2015), groundwater is not expected to be encountered during construction of vertical elements (soldier piles) or for tiebacks. 2. Care should be taken during construction to not unnecessarily place live load surcharges close to the crest of the bluff as this could result in local instability. 3. Upon completion, grades between the retaining structure and the residential strucuze should be returned to similar conditions as before construction such that surface water runoff is not directed over the wall and onto the steep slopes below the coastal WE 4. We recommend that the following should be iincorpor"atcd into the project plans and specifications: The geotechnical engineer shall verify the suitability of all soldier pile and tieback holes before concrete or grout placement; 15.098 DBWPaTeel 2 Wall Desi@i Remmmendations.docx PanGEO. Inc. Page 6 Project No. 15-098 July 17, 2015 • Temporary casing should be used if caving occurs as determined by the geotechnical engineer; • Tremie methods shall be used for concrete or grout placement in all holes having 3 or more inches of accumulated water; and • All soldier pile holes shall be drilled and filled with concrete on the same day. • The geotechnical engineer shall witness and validate verification and proof testing of tiebacks and confirm that test results meet acceptance criteria. If you have any questions, or require additional information, please contact our offices at (206) 262-0370. Sincerely, Robert E. Kimmerling, P.E. Principal Engineer Attachments: Figure 1 — Wall Design Parameters, Cantilever Wall / Single Tieback Figure 2 — Wall Design Parameters, Multiple Tiebacks Figure 3 — Static Global Stability Analysis, Section `C' - with Soldier Pile and Backfill 15-098 DBW Parcel 2 Wall Design Recommendations.docx PanGEO, Inc. w 0 m E 2 W 9 0 t2 i i Surface Surcharge = q Bo �_ X Micro -pile or Soldier Pile Wall Existing Grade 0.5X , 60° No-I_o Zn e 2Bq l H a Y� ^ 0.4(1 - x/H) q Bottom of Exposed Wall Height 6H (psf) Surcharge 27 pc or 1114 Pressure (Level Backslope) 5 4 or Seismic in Pressure 1 Increment 1:1 (max.) Z 67 pcff J Active Pressure Passive Pressure Notes: 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present. Minimum pile embedment shall be 60 feet below Existing Grade (crest of bluff). 2. A factor of safety of 1.5 has been applied to the recommended passive earth pressure value. Increase allowable passive pressure by 1/3 for resistance to tranisient loads, including seismic earth pressure_ 3, Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussions. lbn G Dumas Bay West WALL DESIGN PARAMETERS Reagan Parcel CANTILEVER WALL/ SINGLE TIEBACK E& 4342 SW 307th Street I n e o r r o K w r e o Federal Way, Washington Project No. 15-09t3 Figure No. Y LU 0 a m a 3 E E a w 9 V Surface Surcharge = q 6H (psf) Seismic Pressure Increment 0.5X 2Bq 0.4(1 - x!H) q Surcharge Pressure B4 — . Micro -pile or Soldier Pile Wall 27 pcf (Level Backslope) r Bottom of Exposed Watt Height =� 1 1 (max.) Z ��7 pcf Active Pressure Passive Pressure Notes: 1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present. Minimum pile embedment shall be 60 feet below crest of bluff. 2. A factor of safety of 1.5 is included in the recommended allowable passive earth pressure value. Increase allowable passive pressure by 113 for resistance to tranisient loads, including seismic earth pressure. 3. Seismic earth pressure is the incremental value; combine with static active earth pressure. 4. Active, seismic and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the wall face. 5. Passive pressure should be applied to three times the diameter of the vertical elements. 6. Use uniform earth pressure of 150 psf and 200 psf for lagging design with vertical elements spaced at less than or equal to 6 feet and between 6 and 8 feet, respectively. 7. Refer to report text for additional discussion and recommendations. f-bnGE& C 0 w A 0 0 A T i 0 Dumas Bay West Reagan Parcel 4342 SW 307th Street Federal Way, Washington WALL DESIGN PARAMETERS MULTIPLE TIEBACKS 15-098 (Figure No. 2 v c CL CD 1w IA d o K W � vre- ' S S to 7 7 y C'1 w 200 CL W Pr n _ n M M fo = O c 3 si Z Access to properl`� s from The Palisades property, via their 7 stages. path in red. RECEIVED AUG 07 2015 The gravel path is approximately 6 feet wide, to be repaired when the walls are complete. The blue portion CITY OF FEDERAL WAY diverting from the 7 stages path running east over ivy and downed branches need not be repaired, as long as major CDS live timber is not damaged or cut. A path has been flagged. Path to properties from 7 stages path requires no clearing. Trees are avoided, except for occasional limbing up of branches for equipment clearance. Ivy City of Federal Way standard ground cover will re-establish soon after silt fence contract completion Best Management Practices to be Employed Construction activity will be staged to minimize exposed areas. Stabilized construction entrance at Palisades entrance. Sweep and remove any sediments tracked onto pavement. Staging area will be used for sediment retention, if needed. Dust is to be controlled on the construction sites. All disturbed areas will be re -vegetated. Silt fences will be removed from site upon completion. r rP Staging, offload & reload area, when drv. Access to Jonasson, Reagan Excess spoils deposition, 27' x 49' i n Max width available between houses = 6'. 4' " chain link and tubular steel fence and some plants would have to be removed and replaced. ,Curb ramp Alternate paths 0 Erosion Control, Grading, Access, G1 Dumas Bay West Homeowners Jonasson, Reagan, & Ansari properties Staging Job # Scale See Above_ Designed _CJ Date JONASSON CONSULTANTS LLC 4346 SW 307th St, Federal Way, WA 98023 206-963-1718 C+"7 410 Ilk -.. 30625 43rd Ave SVVF" i r •.jI' r r FfStaging,offload y ;I& reload area ESL { I -A . I • ■ Upon completion of construction ILI acti�rity, all disturbed areas mill be ' ree�egetated writh plantings and 'ractices to be Employed grass, similar to that existing prior be staged to minimize exposed areas. to ConStruCtion. entrance off of 43rd Ave. sediments tracked onto pavement. d for sediment retention, if needed. )n the construction sites. ►e re -vegetated. ,ed from site upon completion. IyI .. • I cell ..ii I.. .n earth Goo, 1 'I 11 M 1) `1 v011vI I vvi ILI %J11 u%niI Iy, I Iy Scale See Above IWTJONA55ON UUN5UL 1 F � Dumas Bay West Homeowners Designed _CJ 4346 SW 307th St, Federal Way, WA