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17-10294341k CITY OF Federal Way RECEIVED JUN 16 2017 CITY OF FEDERALWAY C,0MMUNFTY DEVELOPMENT REQuEST FOR ADmiNiSTRATIVE DECISION FILE NUMBER 1-7 - 10 Z-9 1- --3. COMMUNITY DEVELOPMENT DEPARTMENT 33325 8 1h Avenue South Federal Way, WA 9800 253-835-2607; Fax 253-835-2609 www.citvoffederalway.com Date 6-16-17 — Applicant 12rmv) qleijt^,�g L-CF7- PRIMARY PHONE NAME 206-861-3728 Rolerl Britt- .5 & (n �jo s 1%,'6L K /I BUSINESS/ORGANIZATION ALTERNATE PHONE LL Management lic MAMIN G ADDRESS E-MAM 24913 104th ave se lawofficenow@gmail-com CITY STATE ZIP FAX kent wa 98030 Property Address/Locatio I Parcel: 7205310070 and Parcel: 1196003610 Description of Requ,st We working on parcel: 7205310070 and digging foundation out, due to the lot so small we looking for a stockpile for 2-3 weeks until foundation is poured, we found owner welling to let us stockpile on there property on percel: 1196003610 can you please take a look and see if you can help us with this temporary dirt. Thanks List/Describe Attachment For Staff Use 0 Code Interpretation/Clarification El Critical Areas Letter/Analysis/Peer Review 0 Request for Extension (Land Use/Plat Approval) D Revisions to Approved Permit 0 Tree Removal Zoning Compliance Letter No Fee No Fee (Actual Cost ifApplicable) Check Current Fee Schedule Check Current Fee Schedule No Fee Check Current Fee Schedule Bulletin #079 — January 4, 2016 Page I of I k:\Handouts\Request for Administrative Decision Map Map RS9.6 T SW 292ND ST ch < RS9.6 a I$ Hm In I (N RS9.6 t0apr RS9.6 BUENNA Z RS9.6 RS9.6 RS9.6 Ix Z RSq.d I Page 1 of 2 IK I Q;. R� S". RS9 6 S CE RS9.6". c) 29MH -PL R 4 Z 04 POIN Site Address Federal Way Zoning Boundary 13 City Limits SEPA Planned Action Area Boundary Subdivisions King County Zoning Boundary Federal Way Stream Classification Points La kes son Wetlands (1998 City Survey) Wellhead Protection Zones ,r.,6 Months [31 Year C35 Year r,7,,,'!, 1 o y e a r Landslide Hazard Areas 10 Erosion Hazard Area http://cfwgisweblaspnet—clientlESRIlWebADFIPrintTaskLayoutTemplatesldefault.htm 6/16/2017 Map Page 2 of 2 Streams Buildings Puget Sound Shoreline Designations - Federal Way Streets Shoreline Designations - King County 100 Year Floodplains Parcels ICI http://Cfwgisweblaspnet—clientlESRIlWebADFIPrintTaskLayoutTemplatesldefault.htm 6/16/2017 December 20, 2005 Mr. James D. Burbidge Ms. Jeanne A. Burbidge 2824 SW 300'h Place Federal Way, WA 98023-2325 Re: Inquiry #05-106162-00-AD; Request for Land Surface Modification Waiver Lot 4, Lakota Addition; Parcel Number 416660-0235-06 Dear Mr. and Ms. Burbidge: The following is in response to your December 2, 2005, letter. In the letter, you request a waiver from the city's land surface modification ("LSM") provisions to place approximately 100 cubic yards of fill dirt on the above referenced vacant lot. LSM is defined by the Federal Way City Code ("FWCC") as clearing or removal of vegetation and all grading, excavation and filling activities. Therefore, the proposed work you describe is classified as a LSM. LSM activity is regulated by FWCC Chapter 22, Article X111, Division 7. This article classifies two types of LSM activities. First, Section 22-1093 outlines 13 types of LSM activities that are permitted outright. Second, Section 22-1094 then provides a process for applicants to request LSM approval if not otherwise permitted outright by Section 22-1093. Beyond these types of activities, there is no other LSM exemption or waiver process provided by city code. - I have reviewed your proposal against the 13 LSM activities permitted outright under Section 22- 1093. Unfortunately, I do not see that the proposal matches up with any of the activities permitted outright under this section. I understand Kathy McClung spoke to you on December 19'h to clarify that the existing well isn't considered an active use to permit the proposed fill. Absent ability in city code to exempt or waive the LSM provisions that you have requested; your request can then only be considered under the process outlined in Section 22-1094. As you apparently already know, the process outlined under Section 22-1094 (requiring use process HI review) is both lengthy and costly in relation to the minimal nature of your proposal. It is likely that the cost and time involved in this process would far outweigh the value of the available fill material. It is also likely that a proposal of this nature would not meet the stipulated decisional criteria, which require extenuating circumstances to allow grading and filling in advance of a development proposal. File #05-106162-00-AD Doc. I.D. 34333 James D. Burbidge Jeame A. Burbidge Page 2 December 20, 2005 I am sorry I don't have better news for you. LSM provisions in city code are written to address more extreme cases of site grading. Unfortunately, there is no exemption or waiver of your type of minimal activity. Under these circumstances, you are essentially constrained to wait to fill and grade the property until a home is constructed. If you have any further questions about your proposal, please contact me in person at =jz.fewins@.ci�yoffederalway.com, or 253-835-2611. Sincerely, Greg Fewins Deputy Director of Community Development Services File #05-106162-00-AD Doc. I.D. 34333 Becky Chapin From: Becky Chapin Sent: Wednesday, December 24, 2014 12:01 PM To: 'Xiaoping Betsy Zhu (zhu@clangston.com)' Subject: Fill and Grade Proposal, City of Federal Way Hi Betsy, I wanted to follow-up with you regarding the fill and grade proposal. When you came to the counter last week, you proposed to use the excavated dirt from one of your projects to fill and develop a separate site. I believe the last thing we mentioned was with the large amount of dirt proposed, 13,000 cubic yards, you will need to do a preapplication conference to discuss any potential impacts/conflicts and code regulations. From what I can find in our records, there has been no project with this much fill. I cannot say whether this would be allowed or not; a preapplication conference will be necessary for any project. Are you still looking into potential development sites within the City, or have you decided to contract out to remove the soil? Hope you have a wonderful Holiday, Becky Chapin Associate Planner City of Federal Way 33325 8th Avenue South Federal Way, WA 98003-6325 Phone: 253-835-2641 Becky.Chapin(cDcityoffederalway.com Fx. 253-896-1011 Fx. 253-896-2633 Mr. Robert Britt c/o Advanced Building Consultants, Inc. 14422 SE 192 d Street Renton, WA 98058 Attn: Mr. Glenn Carter (206) 714-6246 FILE GeoResources, LLC 5007 Pacific Hwy. E., Ste. 16 Fife, Washington 98424-2462 P(ESUBMITTED October 27, 2015 FEB 2 2 2016 CITY OF FE0ERAL WAY CDS Geotechnical Consultation Single -Family Residence Redondo Highlands, #5, Lot 7 XXX SW 29,�h Street Federal Way, Washington PN: 7205310070 File: Britt. Lot7 Redondo. L We previously prepared a GeotechnicalReportf or the proposed residence for the project site near SW 297uStreet in Federal Way, Washington. We understand that the proposed foundation excavation for the west portion of the residence/garage will be approximately 9.5 feet deep. The proposed foundation elements for this portion of the structure will be setback from the existing roadway and utilities approximately 18 feet. 111a our opinion that provided the soils encountered are in a dense condition and no groundwater seepage is observed, there is sufficient room for the cut face to be adequately sloped per our previous report, and shoring will not be necessary. As with all excavation cut slopes, site safety is the responsibility of the contractor. If groundwater seepage or sloughing occurs, we should be contacted immediately. We have appreciated working for you on this project. Please do not hesitate to call at your earliest convenience if you have questions or comments. Respectf ully submitted, GeoResources, LLC Rrnrl P RinrtPrcztqff I P(-, BPB:DGB/bpb Doc 1D:Britt.8W297thSt.L Dana C. Biggerstaff, PE Senior Enc[44k� 0 50040 0 Fx. 253-896-1011 Fx. 253-896-2633 Mr. Robert Britt c/o Advanced Building Consultants, Inc. 14422 SE 192 nd Street Renton, WA 98058 Attn: Mr. Glenn Carter (206) 714-6246 GeoRe.sources, LLC 5007 Pacific Hwy. E., Ste. 16 Fife, Washington 98424-2462 November 25, 2014 Update - Geotechnical Report Single -Family Residence Redondo Highlands, #5, Lot 7 XXX SW 297 th Street Federal Way, Washington PN: 7205310070 File: Britt. Lot7Redondo.G Ru INTRODUCTION We previously prepared a Geotechnical Reportfor Stonegate Homes dated May 12, 2006 addressing the proposed residence on Lots 7 th roug h 10 in the Redondo H eig hts area located near SW 297"' Street in Federal Way, Washington. Our report included soil explorations on Lot 9 (B-2, TP-1, and TP2). Subsequently, you purchased Lot 7 and we have since completed additional explorations for your proposed site development. We have reviewed the proposed building plans and prepared a plan review letter. We understand that the City has requested that the original report be up0ated to reflect your ownership and proposed site development. This report is provided for that purpose. The onsite slope ranges from approximately 55 to 70 percent with about 60 feet of vertical relief. We understand the proposed residence will be constructed from the bottom up. This phasing approach will reduce the potential for erosion and help increase the stability of the site during construction. As previously indicated, because the upper 4 to 8 feet of soil material is old fill material, temporary shoring may be required to meet the L&I requirements for worker safety and maintain stability between the foundation excavation and the roadway above. On January 30 and 31, 2014, we monitored the excavation of three additional test pits in Lot 7. Exposed soils consisted of 4 to 8 feet of loose sandy gravel with assorted debris. These soils are related to uncontrolled fill material, likely from prior grading activity. Underlying the surficial soils, we observed medium dense to dense silty sand with gravel to gravelly sand with trace boulders and silt, representative of native outwash deposits. SITE CONDITIONS Surface Conditions The subject parcel is located at the east terminus of SW 297t' Street in Federal Way, Washington. The parcel is irregular in shape extending over the east portion of the lower steep slope. The site is currently undeveloped, but was previously used to place uncontrolled fill material during development of the surrounding area and the construction of 297th Street. The proposed new residence will include an upper driveway off 297th, and typical associated utilities. The site is bounded by existing Britt — Redondo Heights Lot 7 November 25, 2014 Page 2 single family residential development on the south and west, and by SW 297th Street to the west. Additional undeveloped lots are situated on the north. The site is located on the north margin and slope of the Redondo glacial upland area. The ground surface at the site and adjacent areas generally slopes down to the northeast at inclinations of 40 to 85 percent with locally steeper areas. West of the site, near the cul cle sac, the ground surface flattens to approximately 5 to 10 percent. The slope at the site is about 65 feet in height. A site plan with topography is included as Figure 2. Vegetation consists of invasive grass and brush with scattered trees along the north margin of the slope. No surface water or seepage was observed at the time of our site visits. The slope area appeared generally stable for the existing conditions at the time of our site visits. No evidence of erosion, soil movement, landslide activity or deep- seated slope instability was observed at the site or the adjacent areas. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey for King County maps the soils in the area of the site as Alderwood and Kitsap soils (AkF). These soils are typically derived from glacial till that form on slopes of 25 to 70 percent. These soils are listed as having a "moderate to very severe" erosion hazard, where exposed. However, as the site has been filled with uncontrolled silty sand material, we consider the erosion hazard the site to be very severe when the soils are exposed. A bopy of the SCS map for the site vicinity is attached as Figure 3. Site Geology The Geological Map of the Poverty Bay 7.5 minute Quadrangle, Washington by Booth, Waldron, and Troost (2003) indicates the site is underlain by pre -Olympia age glacial deposits (Qpog,). These older glacial soils typically consist of oxidized silt, sand and gravel that was deposited prior to the Vashon deposits. These soils are considered overconsolidated and exhibit high strength values and low compressibility characteristics where undisturbed. The near surface soils at the site have been disturbed by natural weathering processes that occurred since their deposition. An excerpt of the referenced map is included as Figure 4. As previously discussed, fill material was placed across the lots during the historic development of the area. The fill is thickest near the roadway and top of the slope, and decreases in depth towards to toe. Subsurface Explorations We previously completed both test pits and borings at and near the site, the adjacent lots. Copies of those explorations are included in Appenclix "A" as part of the previous geotechnical report. Additional test pits were complete on January 30, 2014 on Lot 7 to specifically address the depth and condition of the old fill material. The approximate locations of the previous and recent explorations are indicated on the attached Site Plan, Figure 2. A geologist from our office monitored the excavation of the test pits, created the soil logs of the subsurface conditions encountered, and obtained representative soil samples. The soil samples were placed in sealed plastic bags and taken to our laboratory for further examination and testing, as deemed appropriate. Subsurface Conditions The previous test pits (4) and borings (2) were completed for the short plat in 2006 (Appendix "A"). In general, the soil conditions encountered consisted of 4 to 15 feet of old Britt — Redondo Heights Lot 7 November 25, 2014 Page 3 fill material (silty sand with gravel and cobbles) interpreted to be till fill material. Belowthe fill material, medium dense to dense silty sand and sand were encountered in the borings to a depth of approximately 32 feet. Glacial till was encountered below the sandy material to the full depths explored, 40.5 feet and 41.0 feet. Similar fill depths were also encountered in the previous test pits. On January 30, 2014, we observed the excavation of three additional test pits in the lower portion of Lot 9. The soils encountered 4 to 7 feet of loose sandy gravel with assorted debris. These soils are related to uncontrolled fill material, likely from prior grading activity in the area. Underlying the surficial soils, we observed medium dense to dense silty sand with gravel to gravelly sand with trace boulders and silt, representative of native outwash deposits. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure 5. The test pit logs are included as Figure 6. Groundwater Conditions No groundwater seepage was observed in the explorations at the time of excavation, However, we expert that during periods of extended or heavy wet weather, perched groundwater conditions could develop in the old fill material, and at depth above the deeper till material. Appropriate drainage components for the proposed structure will address any potential drainage issues. Slope Stability A slope stability analyses was also conducted as part of the previous geotechnical report in 2006. That is discussed in detail in the attached report, Appendix "A". The analyses indicated an acceptable factor of safety for the developed sites, both under static and seismic conditions. GEOLOGIC HAZARDS The Federal Way City Code states "geologically hazardous areas shall mean areas that, because of their susceptibility to erosion, landsliding, seismic or other geological events, are not suited to siting commercial, residential or industrial development consistent with public health or safety concerns." Erosion Hazard Areas The City of Federal Way Code Chapter 19.150 defines erosion hazard areas as those areas having a "severe" or "very severe" erosion hazard due to natural agents such as wind, rain, splash, frost action or stream flow. Landslide Hazard Areas per City of Federal Way Chapter 19.150 The Federal Way City Code Chapter 19.150 defines landslide hazard areas as those areas potentially subject to episodic downslope movement of a mass of soil or rock including but not limited to the following areas: a. Any area with a combination of: 1. Slopes greater than 15 percent; 2. Permeable sediment overlying a relatively impermeable sediment or bedrock; 3. Springs or groundwater seeps. b. Any area which has shown movement during the Holocene epoch, from 10,000 years ago to the present, or which is underlain by mass wastage debris of that epoch. Britt — Redondo Heights Lot 7 November 25, 2014 Page 4 c. Areas potentially unstable as a result of rapid stream incision, stream bank erosion, and undercutting by wave action. d. Areas located in a canyon or on an active alluvial fan, presently or potentially subject to inundation by debris flows or catastrophic flooding. E). Areas that have a "severe" limitation for building site development because of slope conditions, according to the USDA SCS. f. Those areas mapped as Class U (Unstable), Uos (Unstable old slides), and Urs (unstable recent slides) by the Department. of Ecology. g. Slopes having a gradient steeper than 80 percent subject to rock fall during seismic shaking. Steep Slope Hazard The Federal Way City Code Chapter 19.150 defines steep slope hazard areas as "those areas with a slope of 40 percent or greater and with a vertical relief of 10 or more feet, a vertical rise of 10 feet or more for every 25 feet of horizontal distance. A slope is delineated by established its toe and top and measured by averaging the inclination over at least 10 feet of vertical relief." Seismic Hazards The City of Federal Way Municipal Code Chapter 19.150 defines seismic hazard areas as "those areas subject to severe risk of earthquake damage as a result of seismically induced ground shaking, slope failure, settlement or soil liquefaction, or surface faulting. These conditions occur in areas underlain by cohesionless soils of low density usually in association with a shallow groundwater table." CONCLUSIONS Based on our site observations and data review, subsurface explorations and our engineering analysis, it is our opinion that the proposed residential development on Lot 7 is feasible from a geotechnical standpoint. It is also our opinion that active landslide, erosion, or seismic hazards do not exist on the site. The old fill material is generally stable under the existing conditions, but should be reworked during the site development activities into an engineered and stable condition. The new structure may be supported on new conventional spread footings or floor slabs bearing on competent native soils or on structural fill placed above these native soils where the setback criteria is met and the old fill material is adequately mitigated. The fill and native soils at the site contain a relatively high percentage of fines (silt and clay -size particles), which makes them moisture sensitive. These soils will be difficult (to impossible if wet) to compact as structural fill in wet weather conditions. We understand that grading at the site will include cuts and fills associated with the foundation area for the proposed structure, d riveway/ga rage area and utilities. If grading activities take place during the winter season, the owner should be prepared to export unsuitable material and import free -draining granular material for use as structural fill and backfill. During wet weather conditions, perched water conditions may occur at the site. Stormwater infiltration is feasible in the lower portion of the site, and has been designed by others. We understand that several deep foundation contractors have looked at the project and determined that access is a challenge. Based on this, it was determined that hand operated or small track mounted equipment would be utilized for installation of the Britt — Redondo Heights Lot 7 November 25, 2014 Page 5 deepened foundation elements. Pertinent geotechnical recommendations and design criteria are included in below. Proper surface drainage and erosion control measures will reduce the risk for future erosion and slope instability at the site. Provided the recommendations contained herein are included in the project plans; the proposed development should have minimal impacts to the site and/or the adjacent properties. Erosion Hazard Areas The City of Federal Way municipal code Section 18-28 defines erosion hazard areas as those areas having a "severe" or "very severe" erosion hazard due to natural agents such as wind, rain, splash, frost action or stream flow. The USDA NRCS maps the eastern portion of the site soils as and Kitsap soils (AkF) which have a "severe" erosion hazard when exposed. This meets the technical criteria for a "severe" designation per the City ordinance. Based on the explorations completed at the site, the site surficial soils are fill material rather than native soils. But these soils also have the potential for severe erosion. Therefore, erosion control measures will be a critical element on this project site- We understand that spec�fic erosion mitigation for the project is included in the Erosion Control Plan prepar ed by others. Landslide Hazard Areas From the above listed indicators, we offer the following comments. Noevidence of active landslide activity was observed at the site at the time of our site visit. A slope steeper than 15 percent and 40 percent was observed on the property, but no seeps or springs were observed on the slopes and no adverse or intersecting contacts are mapped in the vicinity of the site. No other landslide hazard criteria were observed on the site at the time of our site visits. Based on our observations a * nd literature review, the site does mejet the technical criteria of the above landslide hazard indicators. it is our opinion however that the old fill material is marginally stable and the proposed development will improve the overall stability of the site and adjacent area. The construction of basement/retaining walls and drainage improvements will significantly improve the stability of the site. It is further our opinion that the developed site will not constitute an active landslide hazard area. Seismic Hazard The Federal Way City Code Chapter 19.150 defines seismic hazard areas as those areas subject to severe risk of earthquake damage as a result of seismically induced ground shaking, slope failure, settlement or soil liquefaction, or surface faulting. These conditions occur in areas underlain by cohesionless soils of low density usually in association with a shallow groundwater table. No groundwater was encountered at the site to depths of 41 feet. In addition, the previously completed stability analyses demonstrated factors of safety greater than 1.1 under seismic conditions. Based on our observation and the subsurface units mapped at the site, we interpret the structural site conditions to correspond to a seismic Site Class "D" in accordance with 2012 IBC (International Building Code) documents and ASCE 7- Chapter 20 Table 20.3- 1. This is based on the likely range of equivalent SPT (Standard Penetration Test) blow counts for the soil types observed in the site area. These conditions were assumed to be representative for the conditions based on our experience in the vicinity of the site. These soils are not prone to liquefaction and do not constitute a seismic hazard area. Britt — Redondo Heights Lot 7 November 25, 2014 Page 6 Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in pore water pressure. The increase in pore water pressure is induced by seismic vibrations. Liquefaction mainly affects geologically recent deposits of loose, fine-grained sands that are below the groundwater table. Based on the density and consolidated nature of the glacial soils observed on the site, it is our opinion that the risk for liquefaction to occur at this site during an earthquake is negligible. Provided the design criteria listed below are followed, the proposed structure will have no greater seismic risk damage than other appropriately designed structures in the Puget Sound area. Steep Slope Hazard The steep slope located at the site is approximately 65 feet in vertical height and meets the technical definition of a steep slope hazard area. A building setback from this slope is required by the International Building Code. Based on our subsurface evaluation, we have recommended a Structural Setback be utilized for the project. We understand that needle piling will be utilized to accomplish the Structural Setback where required, as well as extend foundation support through the old fill material. SETBACK CRITERIA The International Building Code requires a building setback from slopes that are steeper than 3H:1V (Horizontal: Vertical) or 33 percent unless evaluated and reduced, and/or a structural setback is provided, by a licensed geotechnical engineer. The setback distance is calculated based on the vertical height of the slope. The typical I BC setback from the top of the slope equals one third the height of the slope. Based on our site observations, and in accordance with IBC (international Building Code) Section 1805 guidelines, we recommend a setback distance of H/3 for slopes below the structure that are greater than 10 feet in height from the top of slopes greater than 33 percent. This equates to a prescriptive setback of 22 feet at this site. Where this setback distance cannot be met, the foundation elements of the structure should extend vertically, a Structural Setback (Figure 7), so that the setback is measured horizontally from the lower outside edge of the foundation element to the face of the slope. This structural setback is contingent on the foundation elements extending through the old fill material and into the dense to very dense native soils that underlie the site. We anticipate that portions of the foundation elements will not meet the IBC setback distance or will need to be extended through the old fill material. We understand that you have selected needle piling to accomplish the structural setback where required. In addition, temporary shoring may be required to maintain stable cut slopes above the building pad area, until the basement/garage fill walls are constructed. This is discussed in the "Construction Considerations" section of this report. Needle piling consist of small diameter Schedule-80 steel pipe that are driven into the underlying soils to refusal. Individual pipe segments typically range from about 8 to 21 feet long and are successively joined with external threaded couplings, internal slip couplings, or butt welds as pile driving progresses. Minimum embedment shall be 8 feet. We anticipate that the needle piles will meet refusal in the underlying stiff/very dense soils. However, because refusal depths are difficult to predict and because soil conditions could vary significantly across the site, the contractor should be prepared for variable pile lengths. Also, it may be necessary to modify pile layouts if rocks or other obstructions are encountered during pile -driving. Britt — Redondo Heights Lot 7 November 25, 2014 Page 7 When refusal has been achieved, the pin piles can be cut to a predetermined height or elevation. To provide a good bond between the piles and the pile cap, reinforcing bars with 90-clegree bends can be welded to the top of the pile or, alternatively, the top of the pile can be splayed apart. A structural engineer should be responsible for designing the reinforced steel and foundation elements. Allowable Value Design Parameter 2-inch diameter Static Compressive Capacity 0 pounds Transient Compressive Capacity 5,300 pounds We do not anticipate 2 inch piles will necessitate quick load testing. In areas where the lengths of the pin piles are exposed and not directly incorporated into the foundation grade beams, the area around the pin piles should be backfilled with a well draining material such as angular quarry spalls, or CDF (lean mix). If access for a small track driven machine is feasible, it may be more economic to utilize fewer, but larger diameter piling. A properly installed 3-inch-cliameter or 4-inch- diameter needle pile driven to refusal (as defined above) will typically provide the following allowable axial capacities. Actual capacities and refusal criteria should be verified by the contractor. Furthermo re, the stated uplift capacities would be applicable only to needle piles that are installed with tension -resisting couplings. Design Parameter Static Compressive Capacity Transient Compressive Capacity Transient Uplift Capacity Allowable Value 3-inch-diameter 12,000 pounds 16,000 pounds 8,000 pounds 4-inch-diameter 20,000 pounds 26,000 pounds 13,000 pounds It should be noted that the native and fill soil material in this area may include large soil particles (cobbles/boulders) or organic debris (roots). When encountered by piling, these can result in early refusal depths and an unacceptable pile. It will be necessary to move over and re -drive the piling or possibly increase the number of piling to achieve the required support of the wall. The contractor should be prepared for this condition. Based on our 2014 site observations, there has been no significant change in the site conditions since our 2006 explorations and site visit. Copies of our previous Geotechnical Report and Response to Comments Letter are attached for your reference. Construction Considerations All job site safety issues and precautions are the responsibility of the contractor providing services/work. The following cut/fill slope guidelines are provided for planning purposes only. Temporary cut slopes will likely be necessary during grading operations, foundation construction or utility installation. All excavations at the site associated with confined spaces, such as utility trenches and retaining walls, must be completed in accordance with local, state, or federal requirements. Based on current Washington Industrial Safety and Health Act (WISHA, WAC 296-155-66401) regulations, the shallow upper soils on the site would be classified as Type C soils. The very dense glacial till soils would be classified as Type A soils. Britt — Redondo Heights Lot 7 November 25, 2014 Page 8 According to WISHA, for temporary excavations of less than 20 feet in depth, the side slopes in Type A soils should be laid back at a slope inclination of 3/4H:1V (Horizontal: Vertical) and Type C soils should be laid back at a slope inclination of 11.5HAV or flatter from the toe to top of the slope. It should be recognized that slopes of this nature do ravel and require occasional maintenance. All exposed slope faces should be covered with a durable reinforced plastic membrane, jute matting, or other erosion control mats during construction to prevent slope raveling and rutting during periods of precipitation. These- guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away from the top of the slope and that significant seepage is not present on the slope face. Flatter cut slopes will be necessary where significant raveling or seepage occurs, or if construction materials will be stockpiled along the top of the slope. Where it is not feasible to slope the site soils back at these inclinations, a retaining or shoring structure will be required. Where retaining structures are greate� than 4-feet in height (bottom of footing to top of structure) or have slopes of greater than 15 percent above them, they should be engineered per Washington Administrative Code (WAC 51-16-080 item 5). Based on the height of the proposed cuts for the foundation wall, we expect shoring will be required. We can provide a variety of options for temporary shoring if the required cut slopes cannot be achieved. Typically this includes sheet piling, driven H-piling with batter boards, or soil nails. The most cost effective of these is the driven H-piling, which can then be used as the back form for the walls if appropriately designed. The void between the lagging wall and the cut slope are filled with drainage material, or a synthetic drainage membrain can be installed between the H-pile wall and the concrete. This information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that GeoResources assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project contractor. Foundation Support Based on the subsurface soil conditions encountered across the site, we recommend that beyond the recommended setback area, spread footings for the new residence be founded on dense native soils or on appropriately prepared structural fill that extends to suitable native soils. The soil at the base of the footing excavations should be disturbed as little as possible. All loose, soft or unsuitable material should be removed or recompacted, as appropriate. A representative from our firm should observe the foundation excavations to determine if suitable bearing surfaces have been prepared, particularly in the areas where the foundation will be situated on fill material. We recommend a minimum width of 24 inches for isolated footings and at least 12 inches for single story and 16 inches for two story continuous wall footings. All footing elements should be embedded at least 18 inches below grade for frost protection. Footings founded as described above can be designed using an allowable soil bearing capacity of 2,500 psf (pounds per square foot) for combined dead and long- term live loads. The weight of the footing and overlying backfill may be neglected. The allowable bearing value may be increased by one-third for transient loads such as those induced by seismic events or wind loads. Lateral loads may be resisted by friction on the base of footings and floor slabs and as passive pressure on the sides of footings. We recommend that an allowable coefficient of friction of 0.30 be used to calculate friction between the concrete and the underlying soil. Passive pressure may be determined using an allowable equivalent fluid Britt — Redondo Heights Lot 7 November 25, 2014 Page 9 density of 300 pcf (pounds per cubic foot). Passive resistance from soil should be ignored in the upper 1 foot, A factor of safely of 1.5 has been applied to these values. We estimate that settlements of footings designed and constructed as recommended will be less than I inch, for the anticipated load conditions, with differential settlements between comparably loaded footings of 1/2 inch or less. Most of the settlements should occur essentially as loads are being applied. However, disturbance of the foundation subgrade during construction could result in larger settlements than predicted. We recommend that all foundations be provided with footing drains. Subgrade/Basement Walls Based on existing topography of Lot 7, we expect that the now structure will include subgrade retaining walls. The lateral pressures acting on subgrade and retaining walls (such as basement walls) will depend upon the nature and density of the soil behind the wall. ft is also dependent upon the presence or absence of hydrostatic pressure, as well as any upgradient loads that influence the wall. If the walls are backfilled with granular well -drained soil, the design active pressure may be taken as 35 pcf (equivalent fluid density). Where the walls are restrained from moving, we recommend an at -rest equivalent earth pressure of 55 pcf be used for design. We assume a level backfill condition behind proposed basement or subgrade walls. Where a surcharge occurs above the wall, the pressures will increase. This includes structures, traffic or steep slopes. Based on the final design, this information can be provided at your request. Adequate drainage behind retaining structures is imperative. Positive drainage which controls the development of hydrostatic pressure can be accomplished by placing azone of coarse sand and gravel behind the walls. The granular drainage material should contain less than 5 percent fines. The drainage zone should extend horizontally at least 18 inches from the back of the wall. The drainage zone should also extend from the base of the wall to within I foot of the top of the wall. The drainage zone should be compacted to approximately 90 percent of the MDD. Over -compaction should be avoided as this can lead to excessive lateral pressures. Typical wall drainage and backfilling is shown on Figure 5. A minimum 4-inch diameter perforated or slotted PVC pipe should be placed in the drainage zone along the base and behind the wall to provide an outlet for accumulated water and direct accumulated water to an appropriate discharge location. We recommend that a nonwoven geotextile filter fabric be placed between the drainage material and the remaining wall backfill to reduce silt migration into the drainage zone. The infiltration of silt into the drainage zone can, with time, reduce the permeability of the granular material. The filter fabric should be placed such that it fully separates the drainage material and the backfill, and should be extended over the top of the drainage zone. Lateral loads may be resisted by friction on the base of footings and as passive pressure on the sides of footings and the buried portion of the wall, as described in the "Foundation Support" section. We recommend that an allowable coefficient of friction of 0.30 be used to calculate friction between the concrete and the underlying soil. Passive pressure may be determined using an allowable equivalent fluid density of 300 pcf (pounds per cubic foot). Factors of safety have been applied to these values. Retaining walls located on or near the toe of the slope that extends up behind the wall should be designed for a lateral pressure that includes the surcharge effects of the steep slope in proximity of the wall. For an irregular or composite slope, the equivalent Britt — Redondo Heights Lot 7 November 25, 2014 Page 10 slope angle may be determined by extending a line upwards from the toe of the wall at an angle of 1 to 1 (Horizontal to Vertical) to a point where the line intersects the ground surface. The surcharge effects may be modeled by increasing the equivalent fluid pressure for flat ground by the percentage given in the following table: TABLE 1 SLOPE INCLINATION: EbUIVALENT FLUD PRESSURE SLOPE ANGLE PERCENTINCREASE EQUIVALENT FLUID PRESSURE Horizontal 0% 35 pcf 3H:1V 25% 44 pcf 2HAV 50% 53 pcf 1H:1V 75% 61 pcf These pressures would apply for temporary cuts of 10 feet or less. Cuts of greater height would require shoring or alternative construction methods. Design parameters for temporary shoring can be provided at your request. Floor Slab Support Slab -on -grade floors, where constructed, should be supported on the medium dense native soils or on structural fill prepared as described above. Areas of old fill material should be evaluated during grading activity for suitability of structural support. Areas of significant organic debris should be removed. We recommend that floor slabs be directly underlain by a minimum 4-inch thick pea gravel or washed 5/8 inch crushed rock. This layer should be placed and compacted to an unyielding condition and should contain less than 2 percent fines. A synthetic vapor barrier is recommended to control moisture migration through the slabs. This is of particular importance where the foundation elements are underlain by the silty till sediments, or where moisture migration through the slab is an issue, such as where adhesives are used to anchor carpet or tile to the slab. A subgrade modulus of 400 kcf (kips per cubic foot) may be used for floor slab design. We estimate that settlement of the floor slabs designed and constructed as recommended, will be 1/2 inch or less over a span of 50 feet. Utilities We expect that underground utilities, such as sanitary sewer, storm, and water will consist of a series of pipes, vaults, manholes, and catch basins. The utility excavations should be performed in accordance with appropriate governmental guidelines. Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. We anticipate that the on -site, non -organic soils will be suitable for use as structural backfill. If import soil is used as utility trench backfill, it should consist of a material meeting the wet weather fill recommendations provided in the "Structural Fill" section of this report. We recommend that utility backfill soils be compacted according to the recommendations provided in the "Structural Fill" section of this report. Erosion Control Weathering, erosion and the resulting surficial sloughing and shallow land sliding are natural processes that affect steep slope areas. As noted, no evidence of surficial raveling or sloughing was observed at the site. To manage and reduce the potential for these natural processes, we recommend the following: Britt — Redondo Heights Lot 7 November 25, 2014 Page 11 No drainage of concentrated surface water or significant sheet flow onto or near the steep slope area. No fill should be placed on slopes greater than 25 percent unless placed as engineered and compacted fill. Grading should be limited to active construction areas to promote surface flows away from the top of slope to an appropriate discharge. Erosion protection measures will need to be in place prior to grading activity on the site. Erosion hazards can be mitigated by applying Best management Practices (BMP's) outlined in the Washington State Department of Ecology's (DOE) Stormwater Management Manual for Western Washington. We understand that an erosion control plan has been prepared by others for the project. Site Drainage All ground surfaces, pavements and sidewalks at the site should be sloped away from residences. The site should also be carefully graded to ensure positive drainage away from all structures and property lines. Surface water runoff from the roof area, driveways, perimeter footing drains, and wall drains, should be collected, tightlined, and conveyed to an appropriate discharge point. We recommend that footing drains are installed for the residence, and basement walls (if utilized) have a wall drain as describe above. The roof drain should not be connected to the footing drain. Stormwater Infiltration Based on our site observations, subsurface explorations and laboratory analysis; portions of the site have the abiNty to infiltrate the collected storm water runoff, provided the design is appropriate. We understand that a design has been prepared by others. Suspended solids could clog the underlying soil and reduce the infiltration rate for the pond. To reduce potential clogging of the infiltration system, the infiltration system should not be connected to the stormwater runoff system until after construction is complete and the site area is landscaped, paved or otherwise protected. Temporary systems may be utilized through construction. LIMITATIONS We have prepared this report for the Mr. Britt and members of the design team regarding the development of Lot 7. The data used in preparing this report and this report should be provided to prospective contractors for their bidding or estimating purposes only. Our report, conclusions and interpretations are based on data from others and limited site reconnaissance, and should not be construed as a warranty of the subsurface conditions. Variations in subsurface condit�ons are possible between the explorations and may also occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient monito(ing, testing and consultation should be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to Britt — Redondo Heights Lot 7 November 25, 2014 Page 12 evaluate whether earthwork and foundation installation activities comply with contract plans and specifications. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. If there are changes in the loads, grades, locations, configurations or type of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate. We have appreciated working for you on this project. Please do not hesitate to call at your earliest convenience if you have questions or comments. Respectfully submitted, GeoResources, LLC Brad P. Biggers&1f, LLEG Dana C. Biggerstaff, PE Principal Senior Engineer fy, 10 BRADLEY P. i&ERSTA-F-FI BPB:DCB.Ibpb Doc lD:Piec1khotin.SW297lhSl.RG Attachments: Figure 1: Vicinity Map Figure 2: Site Plan Figure 3: SCS Soil Survey Figure 4: USGS Geology Map Figure 5: Unified Soil Classilicaiion System Figure 6: New Test Pit Logs Figure 7: Structural Setback Appendix "A': 2006 GeolechniGal Report by GeoResources. LLC T LI Ile & i LI FA a, _a� T17-b --J L�__j To ST Approximate Site Location (Map created from King County iMap http http://www5.kingcounty.gov/iMAP� GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Site Vicinity Map Proposed Single Family Residence SW 297 th Street Federal Way, Washington Not to Scale Approximate Site Location (Map created from King County Nap http httpl//www5.kingcounty.gov/iMAPI) GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Site Topography Proposed Single Family Residence 15421115423 14" Ave NW Gig Harbor, Washington Not to Scale Approximate Site Location (An excerpt from the Geologic Map of the Poverty Bay 75-minute Quadrangle, Washington, Booth, D.B., Waldron, H.H., and Troost, K.G., 2003) r---j Opog- Glacial deposits of Pre-Olyrvia age r IV GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 USGS Geologic Map Proposed Single Family Residence 15421/15423 14" Ave NW Gig Harbor, Washington DocID: Britt. Lot7FIedondo.F Not to Scale December 2014 1 Figure 4 SETBACK FROM TO E OF SLOPE Standard Setback Slope > 30% & > i c F" Relief Setback Distance Daylight Basement Setback Slope > 30% & > 10 i� Rellei GeoResources, LLC 5007 Pacific Highway East, Suite 20 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Residential Structure Residential Structure 0 . -nent Figuref, Schematic Section Building Setback COARSE GRAINED SOILS More than 50% Retained on No. 200 Sieve FINE GRAINED SOILS SOIL CLASSIFICATION SYSTEM r-'Dn H D MAJOR DIVISIONS SYMBOL GROUPNAME I GRAVEL I CLEAN GW WELL -GRADED GRAVEL, FINE TO COARSE More than 50% Of Coarse Fraction Retained on No. 4 Sieve SAND More than 50% Of Coarse Fraction Passes No. 4 Sieve SILT AND CLAY Liquid Limit Less than 50 SILT AND CLAY More than 50% Passes No. 200 Sieve Liquid Limit 50 or more HIGHLY ORGANIC SOILS GRAVEL GRAVEL GP POORLY -GRADED GRAVEL GRAVEL GM SILTY GRAVEL WITH FINES - GC CLAYEY GRAVEL CLEAN SAND SW WELL -GRADED SAND, FINE TO COARSE SAND SID POORLY` -GRADED SAND SAND SM SILTY SAND WITH FINES INORGANIC SC ML CLAYEY SAND SILT CL CLAY ORGANIC OL ORGANIC SILT, ORGANIC CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT CLAY OF HIGH PLASTICITY, FAT CLAY CH ORGANIC OH PT ORGANIC CLAY, ORGANIC SILT PEAT NOTES: 1. Field classification is based on visual examination of soil in general accordance with ASTM D2488-90. 2. Soil classification using laboratory tests is based on ASTM D2487-90. 3. Description of soil density or consistency are based on interpretation of blow count data, visual appearance of soils, and or test data. GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 SOIL MOISTURE MODIFIERS: Dry- Absence of moisture, dry to the touch Moist- Damp, but no visible water Wet- Visible free water or saturated, usually soil is obtained from below water table Unified Soil Classification System Proposed Single Family Residence SW 297 1h Street Federal Way, Washington D: Britt. Lot7Redon do. F Dec TEST PIT LOGS BRITT RESIDENTIAL SITE LOT 7 SW 297 1h STREET FEDERAL WAY, WASHINGTON TEST PIT 1 — Location: toe of slope near gate (See Plan) Depth (ft.) Soil Twe Description 0.0 0.5 SM Sparse Grass and topsoil 0.5- 2.0 SM Brn silty SAND (med. Dense, moist)(Fill) 2.0 6.5 SM Dk. Brn/black silty gravelly SAND w/dimensional lumber(Fill) 6.5- 7.0 ML Gray/brn Mottled clayey SILT (hard, moist) 7.0-9.0 ML Grey SILT (hard, moist) (Lacustrine) Minor seepage and caving above 6.5 feet TEST PIT 2 - Location: 50-feet east of TP-1 toe of slope (see -Plan) Depth (ft.) Soil Type Description 0.0 - 3.0 SM Grey/brown silty gravelly SAND (loose dense, moist) (Till fill) 3.0 - 7.0 SM/GM Brn silty sandy Gravel to Gravelly SAND(loose, moist) (Fill) 7.0 -12.0 SM G ry w/ som e m ottling, silty SAN D (loose, m oist) (Fill) 12.0-15.0 SID Brn F-M SAND (medium dense, moist) Minor caving observed in clean sand Minor seepage at 8-feet and 15-feet observed TEST PIT 3 - Location: 60-feet east of TP-2 Toe of slope (see Plan) Depth (ft.) Soil Type Description 0.0 - 3.0 SM Grey/brown silty gravelly SAND (loose dense, moist) (Till fill) 3.0 - 8.0 SID Brn gravelly SAND wl trace gravel (loose, moist) (Fill) 8.0 - 12.0 SM Blue Grey silty gravelly SAND wl SILT (Loose, moist) (Fill) 12.0- 15.0 SM Grey/brown mottled silty gravelly SAND (loose dense, moist) w.Till) Terminated at approximately 15-feet below existing ground surface Caving observed Minor groundwater seepage observed Test Pi� Logs Stonegate, Homes 29 Street Page 2 of 2 TEST PIT 4 - Location: On skid road halfway up slope (see Plan) Depth (ft.) Soil Type Description 0.0 - 0.5 Topsoil/Forest Duff 0.5 - 4.0 SIM Grey/Brn silty gravelly SAND (loose to med. dense, moist) (Fill) 4.0 -5.0 SP Relic topsoil 5.0 -7.5 SP Brn gravelly SAND w/ trace silt (medium Dense, moist) Terminated at approximately 7Y2 feet below existing ground surface Significant caving observed in upper 4-feet No groundwater seepage observed on: December 1, 2005 Logged by: KWG -"Vd TEST PIT LOGS BRITT RESIDENTIAL SITE LOT 7 SW 297,1h STREET FEDERAL WAY, WASHINGTON TEST PIT 5 — Location: Toe of slope NW corner of Lot 7 (See Plan) Depth (ft.) Soil Tvoe Description 0.0 0.5 SM Sparse Grass and topsoil 0.5- 2.5 SM Bm silty SAND (med. Dense, moist)(Fill) 2.5 6.5 SM Dk. Brn/black silty gravelly SAND w/dimensional lumber(Fill) 6.5- 8.0 ML Gray/brn Mottled clayey SILT (hard, moist) 8.0- 9.5 ML Grey SILT (hard, moist) (Lacustrine) Minor seepage and caving above 6.0 feet TEST PIT 6 - Location: About 10 feet above toe of slope, center (see Plan) Depth (ft.) Soil Tyi2e Descrjp�on 0.0 - 2.0 SM Grey/brown silty gravelly SAND (loose dense, moist) (Till fill) 2.0 - 6.0 SM/GM Brn silty sandy Gravel to Gravelly SAND(loose, moist) (Fill) 6.0 -11.0 SM Gry wl some mottling, silty SAND (loose, moist) (Fill) 11.0-13.5 SID Brn F-M SAND (medium dense, moist) Minor caving observed in lower sand Minor seepage at 8-feet observed TEST PIT 7 - Location: 15 ft above toe of slope, SE corner (see Plan) Depth (ft.) Soil Type Description 0.0 - 3.0 SM Grey/brown silty gravelly SAND (loose dense, moist) (Till till) 3.0 - 7.0 SID Brn gravelly SAND w/ trace gravel (loose, moist) (Fill) 7.0 - 11.0 SM Blue Grey silty gravelly SAND wl SILT (Loose, moist) (Fill) 11.0- 14.0 SM Grey/brown mottled silty gravelly SAND (loose dense, moist) w.Till) Terminated at approximately 15-feet below existing ground surface Caving observed Minor groundwater seepage observed on: Jan 1014 Logged by: RH A B c D E IF 2 CONSTRUCTION ENTRANCE SEE �JCZ I`-- Lu Lu C'4 V) 2! MIN WOTH VARIES PER ARCH PLAN (157 MIN) L - - - - - (MIM) - - - -- _ 2%0 - 260 - 3 2 L la, 7111 F—, M::Y, T VFI. 2 ' ACP OVER FIRM UNEILDING G NATIVE SUBGRADE OR AS OTHERWISE EXISTING V INDICATED PER ARCHITECT 4 5 6 6' PVC 0 SL=O.OlFr/VT (MIN) (TYP) RETAINING WALL BY 6- PVC 0 SL=O-DIFT/FT OTHERS LINDER (MIN) (TYP) SEPARATE PERMIT. D x min IT 210 law EX'G DRAINAGE AND UTIUTY EASEMENT -01 OF —APPROXIMATE LOCA PIP� OUTFALL W--2KO A;FA,4LX4XC WTH. 12;! OLA '6,-8' QUARRY SPALL. A PPROXIMATE CONSTRUCTION/CLEARINS UMITS. NO CLEARING BEYOND PROPERTY LINES OR WITHIN SEPTIC DRAINFIO-D AREAS WITHOUT APPROVAL (rep) MTEHM" TANK: AMA-2.018 TANK TOP=220�5 TANK BOTTOM=214.5 MAIN (FE-2*.&t 1-72' DIA. TANKS @ 45' N N LF, SEE DETAIL 2/C3. RETAINING W U. BY APPROXIMATE LOCARON OF OTHERSIUNDER SILT FENCE. ACTUAL SEPARATE PERMIT. LOCATION TO BE DETERMINED IN FIELD AS CONSTRUCTION PROGRESSES SEE Z/C2 (T(P) GARAKE F111-1W.9 k k APPROXIMATE �-IMW-0 ROOF MANS 10 STOCKPILE LOCA 4m SIM MTEM W14' PW TION (TYP) OIL-MIM/FT (MIN) OR CPVC 0 SL-0.01flM (MIN) TRENCH DRAIN=252.80 N SLOPE TO DR�N I . x . (rtp) x % GRAPHIC SCALE 7N, E)(0 ORNPIAGE AND UTIUrY EASEMENI I -W AOL L F -jolmon--i W FM fL I inch - 10 DRIVEWAY SECTION SCALE : NTS 0 SITE STATISTICS LOT AREA - 10.00 SOFT OR 0 23 ACRES CLEARED/WORK AREA =10,083 SOFT FUTURE BUILDING AREA - 2.010 SOFT PROPOSED DRIVEWAY = 1,370 SOFT 7 Q) CL (5 Z�y C) LZ CL R L) 0 -j > 2s z 0 UJI LLJ L) Lu Lu W >: < cj (L X ry X LILI m x 0 uj LL- SmEr TITLE: CIVIL GRADING 8, DRAINAGE PLAN CALL 48 HOURS BEFORE YOU DIG C-1 '1-800-424-5555 SECTION 6 TOWNSHIP 21 RANGE 04 E WM.