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17-103978RECEIVED COMMUNITY DEVELOPMENT DEPARTMENT 1 2017 33325 8`h Avenue South A A� ] Federal Way, WA 98003 Cirr OF `��` = { Old( pF FEdWAY 253-835-2607; Fax 253-835-2609 Federal 1ll�ay Cd1�Mv F F p�>rOPM�NT w°w\v.citvoffederahvay.com SHORELINE SUBSTANTIAL DEVELOPMENT PERMIT File # EXEMPTION APPLICATION 1-7-10,*5g1jg_Qo-Sff TO BE COMPLETED BY APPLICANT Project Name: Shah-Ananth Retainin Walls Project Address: _30016 and 30020 20th Place SW, Federal Way WA 98023 Applicant Viral Shah and Aparna Mailing Address: 1911 SW campus Drive #861., Federal Way WA 98023 253-347-6903 Phone Number: Email: viraipaiidit@grnaii.com 1-7 -10-�q?0 to-S F Description of Project: Protect the structures permitted under 15-106525-00-SF and 15-106521- 00-SF by a combination of grading of the slope behind the structures, installation of drainage and retaining walls. These walls are more than 50 feet landward from the OHWM as shown on the survey. Meets the criteria for exemption under which section of * WAC 173-27-040:_(2)(g) *Washington Administrative Code online: apps.leg.wa.gov 0. Applicant's Signature T I� 0 Date Bulletin # 143 — March 25, 2013 1 of 2 k:\Handouts\Shoreline Exemption TO BE COMPLETED BY STAFF 1) The proposed development is consistent with Section C21 L of WAC 173-27-040 and is therefore exempt from the Substantial Development Permit Process. ®® Yes ❑ No (explanatory narrative attached) _ artt 6(,lcL—:�4 a S,' r 2) Proposal requires: Yes No ❑ Clf Shoreline Variance ❑ Shoreline Conditional Use ❑ Review, Approval or Permit by other State or Federal Agency 3) Proposal complies with applicable provisions of the City's Shoreline Master Program. dYes ❑ No Condition(s) attached: d Yes ❑ No 4) In accordance with FWRC Section 15.05.130, this application is hereby: dApproved ❑ Denied 2 ector, Community Development Department Date Distution: riM Applicant ❑ Owner d File ❑ Outside Agency Bulletin #143 — March 25.2013 2 of 2 k:\Handouts\Shoreline Exemption CITY OF+ Federal Way Conditions of Shoreline Exemption Approval Federal Way Revised Code (FWRQ 15.05.130 `Shoreline Exemption' Shah-Ananth Retaining Wall, File #17-103978-00-SH The Planning Division has reviewed the shoreline substantial development permit exemption based on the exemption provision from WAC 173-27-040(2)(g), relevant code sections of FWRC Chapter 15.05 Shoreline Management, materials submitted August 17, 2017, and subsequent resubmittals received August 24, 2017, August 28, 2017 and September 18, 2017. PROPOSAL The applicants, Viral Shah and Aparna Ananth, own residential property at 30016 and 30020 SW Campus Drive along the Puget Sound shoreline. Existing retaining walls on a steep slope are located behind their home, within 200 feet of the shoreline ordinary high water mark. The walls are four feet tall, constructed to provide grade separation for a shoreline access path. There is no record of the city issuing the required Shoreline Exemption approval for the walls. A wall design analysis prepared by GeoResources, dated August 25, 2017, recommends flattening the slope above the lowest existing wall to improve stability in regard to bearing, sliding and overturning. In order to achieve the recommended slope, a new keystone retaining wall is needed below the existing path and upper wall. Gravel backfill for drains will be installed behind the new wall and a collector PVC pipe will route groundwater or seepage to an approved discharge point. The subgrade will be compacted to a firm and unyielding condition prior to wall installation. A building permit application (file #17-103970-00-SF) was submitted on August 17, 2017 for the new wall. GeoResources also prepared a geotechnical engineering report, dated September 12, 2017, to assess the existing walls and the stability of the slope in question. The subsurface conditions were evaluated via hand auger holes. GeoResources confirms the site meets FWRC technical definition of a landslide hazard area due to the slope's steepness greater than 15 percent. However, the slope should be considered "man-made" due to regrading for the construction of the existing walls, and the existing walls and drainage improvements adequately mitigate against surficial failure. No setbacks or buffers are recommended in relation to the proposed wall. CODE ANALYSIS ■ Shoreline Management The subject property is designated `Shoreline Residential' in the city's Shoreline Management Plan (SMP) overlay. Areas within 200 feet of the Puget Sound marine shoreline, including the Shoreline Residential designation area, are regulated under the state's Shoreline Management Act, which is administered locally via the city's SMP. The project is exempt from Shoreline Substantial Development permit provisions pursuant to WAC 173-27-040(2)(g), construction on shorelands by an owner of a single-family residence and those structures and developments that are normal appurtenances. ■ Critical Areas The subject property is also located within a Geologically Hazardous Area (GHA), erosion, steep slope, and landslide hazard area. Any actions proposed on the subject hillside are subject to shoreline standards and critical areas standards pursuant to FWRC 15.10.160, and may be approved by the director only if no reasonable alternative exists and if the proposal will not lead to or create any increased slide, seismic, or erosion hazard. Based on the aforementioned geotechnical engineering report from GeoResources, the project conforms to FWRC Chapter 15.10, Critical Areas. The City hereby approves the Shoreline Exemption Permit for the existing and proposed walls as conditioned below: CONDITIONS OF APPROVAL - SHORELINE EXEMPTION 1. GeoResources must be on site during construction of the new wall to monitor slope stability conditions and confirm construction activities do not adversely affect site stability. 2. A letter, prepared by GeoResources, verifying construction of the new wall is in compliance with recommendations of the geotechnical report, dated September 12, 2017, and wall design analysis, dated August 25, 2017, must be submitted to the City no later than 30 days after the wall has been finalled. 3. An as -built survey of the new retaining wall is required to be submitted to the City after the wall is constructed. This will provide baseline data for monitoring any long-term movement of the wall. 4. In the event that any ground -disturbing activities or other project activities related to this development uncovers protected cultural material (e.g., bones, shell, antler, horn, or stone tools) an Inadvertent Archaeological and Historic Resources Discovery Plan must be implemented. Prepared by: Dave Van De Weghe, Senior Planner Date: September 20, 2017 - - GEORESOURCES earth science & geotechnical engineering 5007 Pacific Hwy E., Suite 16 1 fife, WA 98424 1 253.896.1011 1 www.georesources.rocks Dr. Viral Shah Dr. Aparna Ananth 30020 - 20th Place SW Federal Way, WA (253) 347-8207 RESUBMITTED SEP 18 2011 G[TY OF FEDERAL WAY COMMUNITY DEVELOPMENT September 12, 2017 Geotechnical Engineering Report Addendum No. 2: Critical Areas 30020 - 20th Place SW Federal Way, WA Doc ID: Shah.20thPlaceSW.ARG2 This letter is an addendum to our previously prepared Limited Geotechnical Engineering Report dated March 11, 2016 for the proposed ADU and gazebo, and to supplement our recent site plan and engineering calculations for the unpermitted retaining walls. As part of permit review process and because of the height and steepness of slopes on and within the site vicinity, the City of Federal Way is requiring an assessment to address the potential steep slope or landslide hazards for the slope between the existing residence and the ADU and gazebo. In addition to our previous report, a Geotechnical Engineering Report was also prepared for the proposed shoreline improvements by Associated Earth Sciences dated June 10, 2003. We were not involved in the permitting of the newly constructed ADU and gazebo but provided deep foundation design recommendations in our May 11, 2016 report. Our understanding of the project is based on our discussions with you, our review of the available maps and geotechnical data, our review of the plans provided by you, our multiple site visits, our experience in the area and our understanding of the City of Federal Way development requirements. The site is currently developed with a single-family residence, attached garage. An ADU and gazebo is currently under construction. As stated in our previous wall design report, the slope failure occurred during construction of the gazebo and ADI in the areas where vegetation and old stairs/path had been removed. SITE CONDITIONS Surface Conditions As stated in our original report, the subject parcel is located at 30020-20th Place SW in the Federal Way area of King County, Washington. The site is generally rectangular in shape, measures approximately 1,400 to 1,800 feet deep (north to south), by 80 to 100 feet wide (east to west), and encompasses about 3.94 acres. The northern portion of the site is currently developed with an existing residence located in the northern portion of the site, south of the proposed location of the three additional structures, while the southern portion of the site is undeveloped. There is an Sha h.20th PlaceSKARG2 September 12, 2017 page 12 existing concrete bulkhead that extends across the northern properly boundary. The parcel is bounded by Puget Sound to the north and existing large -lot residential development to the south, east, and west. The site generally slopes down from south to north towards the Puget Sound. The undeveloped southern portion of the site slopes down at an inclination of approximately 13 to 25 percent. The northern, developed portion of the site flattens out to inclinations of about 9 to 12 percent to the north of the existing residence. The site then steepens to slopes of approximately 60 to 75 percent before flattening out onto a level building pad where the gazebo and ADU is being constructed. The slope between the residence and gazebo appears to have been graded as part of the original construction activities on the site. When comparing the slope on the site to the adjacent parcels, the native slopes to the east are considerably taller and steeper. There are several new retaining walls that provide grade separation for a path that extends down to the new gazebo and ADU. The building pad extends north to the existing bulkhead. This steep slope has a vertical height of approximately 20 feet. Beyond the bulkhead, the site gently slopes down to the Puget Sound. The existing site configuration with King County topographic contours are shown on the attached Site and Exploration Plan, Figure 2. Before construction began, the slope between the residence and the proposed ADU and gazebo was moderately vegetated with vine maples and blackberry bushes. As construction began, access paths were made that removed part of the vegetation and old stairs and paths. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey for King County maps the soils in the site area as Coastal Beaches (Cb) along the northern most portion of the site, and as Alderwood Gravelly Sandy Loam (AgB) across the majority of the site. Alderwood soils are derived from glacial drift or glacial outwash over dense marine deposits, form on slopes of 0 to 8 percent, have a "slight" erosion hazard when exposed, and are included in hydrologic soils group C. A copy of the NRCS Soil Conservation Survey map for the site vicinity is attached as Figure 3. Site Geology The Geologic Map of the Poverty Bay 7.5-Minute Quadrangle, Washington, by Derek Booth, Howard Waldron, and Kathy Troost (2003) maps the site as being underlain by mass -wastage deposits (Qmw). Then native, undisturbed soils mapped east of the mass wasting deposit is identified as glacial deposits of pre -Olympia age (Qpogc). These deposits are typically characterized as pre-Vashon glacial till or outwash sand and gravel. Given the size and shape of this deposit, it appears to be typical of mass wasting deposit, is appears to be pre -historic deposit associated with the retreat of the most recent Vashon continental ice mass, and likely occurred 12,000 to 15,000 years ago, likely where the younger Vashon deposits failed into the sound after the retreated ice age, exposing the deeper, older sediments. An excerpt of the above referenced map is included as Figure 4. The Washington State Department of Ecology (DOE) Coastal Atlas maps the site as "stable" and "intermediate" with "unstable" areas to the northeast of the site. The project site is mapped as being "stable," while the area to the south of the proposed structures and north of the existing residence is mapped as "intermediate." These designations are likely based on slope inclinations. A copy of the Coastal Zone Atlas is included as Figure 5. GEORESO RCES Shah.20thPlaceSKARG2 September 12, 2017 page 13 Subsurface Conditions Subsurface explorations by Associated Earth Sciences and GeoResources were performed on the area where the gazebo and ADU are being constructed at along the top of the slope. On January 14, 2016 we explored subsurface conditions at the site by advancing the excavation of three hand auger samples. The hand auger holes were located in the field by our representative by pacing from existing site features such as building corners and existing rockeries. The locations of these holes are and are indicated on the attached Site Plan and Exploration plan, Figure 2. Our hand auger holes encountered subsurface conditions that somewhat confirmed the mapped stratigraphy. The stratigraphy across the site, as observed in our hand auger holes, consisted of 4 inches to a foot of topsoil overlying 6-inches to 2.5 feet of gravelly sand with organics and debris that we interpret to be beach fill material in all hand auger holes. In hand auger holes HA-1 and HA-2, the fill material was 6-inches to 1 foot thick and was underlain by 2.5 to 3 feet of medium to very dense sand that we interpret to be glacial till. Hand auger HA-3 encountered approximately 6 inches of topsoil overlying beach fill material to the full depth explored. Groundwater and minimal caving were observed in hand auger holes HA-1 and HA-2 at 2 to 2.5 feet. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure 6. The hand auger logs are included as Figure 7. Slight groundwater seepage was noted in the two upper hand augers at the time of digging in January 2015. At the time of the failures, shallow seepage was also noted on the face of the slope. The seepage in both the hand augers and failures appeared indicative of a shallow, seasonal - perched groundwater. Perched groundwater develops when the vertical infiltration of groundwater through the shallow, more permeable soils is slowed by a deeper, less permeable soil such as the older glacial till. GEOLOGIC HAZARDS The City of Federal Way Critical Areas Ordinance for Geologically Hazardous Areas (Chapters 15 and 19 within the shoreline area and outside of the shoreline area, respectively) states "geologically hazardous areas shall mean areas that, because of their susceptibility to erosion, landsliding, seismic or other geological events, are not suited to sitting commercial, residential or industrial development consistent with public health or safety concerns." Landslide Hazard Areas per Federal Way Revised Code The Federal Way City Code 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. c. Areas potentially unstable as a result of rapid stream incision, stream bank erosion, and undercutting by wave action. GEORESOURCES Shah.20thPlaceSW.ARG2 September 12, 2017 page 14 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" From the above listed indicators we offer the following comments. The slopes on the site are steeper than 15 percent but have no adverse geologic or soil contacts. Some evidence of seepage was observed in our initial hand augers, during our November 4, 2016 site visit, as well as some surficial erosion where excavation cuts were made on the slope. The recently installed French drain at the top of the slope, along with wall drains on the slope, will intercept, collect and convey water to a suitable discharge place. No evidence of recent or Holocene epoch movement is shown on the published geologic map, nor was any evidence of recent landslide activity noted during our site visit. No surface water was observed to be flowing on the site. No area of alluvial fans was noted or was observed on or within the vicinity of the subject site. The Alderwood soils mapped on the lower steeper portion of the site are listed as having a slight erosion hazard when exposed by the USDA Soil Conservation Service. No areas of Uos or Urs were mapped in the site vicinity. Based on our observations and literature review, the lower portion of the site meets the technical definition of a landslide hazard area because the slope inclination. However, in our opinion and based on a review of published geologic literature, the slope appears to have been regraded and should be considered a man-made slope. As indicated in our July 21, 2017, the unpermitted walls stabilize the recent surPicial failures. Since the site slopes are man-made and since the failures have been mitigated by the walls and drainage improvements, no buffers or setbacks should be required. Erosion Hazards The site soils are mapped as Cb and AgB, which have a slight erosion hazards when exposed, respectively. Conventional construction BMP's should be installed prior to beginning construction and soil not worked for more 7 days during wet weather conditions should be covered with plastic sheeting or mulch. Temporary erosion control should consist of a silt fence along the downslope side and side slopes of the active construction area. Provided standard BMP's are installed prior to beginning construction, the potential for erosion or sediment leaving the site should be minimal. Seismic Hazards per Federal Way Revised Code The City of Federal Way Municipal Code 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." Characterization of soil profile type is required to determine the site class definition. Based on the inferred range of likely Standard Penetration Test (SPT) values encountered by observing onsite excavations, it is our opinion that the project site can be classified as a Site Class C. s GEORESOURCES Sha h.20th PlaceSW.ARG2 September 12, 2017 page 15 LIMITATIONS We have prepared this addendum report for the Shahs for use in evaluating a portion of this project. This addendum report should be used in conjunction with the previously prepared Limited Geotechnical Engineering Report, which provides recommendations for temporary cut slopes, structural fill, subgrade preparation, and erosion control. The analyses, conclusions, and recommendations contained in this report are based on site conditions and subsurface explorations as they were observed in specific locations only. If the actual conditions differ from those assumed for the site are observed or appear to be present during construction, we should be advised at once so that we can review these conditions and reconsider our recommendations, where necessary. If there is a substantial lapse of time between submission of our report and the start of work at the site, or if conditions have changed because of natural forces or construction operations at or near the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations. This report may be made available to regulatory agencies or others, but this report and conclusions should not be construed as a warranty of subsurface conditions. Subsurface conditions can vary over short distances and can change with time. The scope of our services did not include environmental assessment or evaluation regarding the presence or absence of wetlands or hazardous or toxic materials in the soil, surface water, groundwater, or air at the subject site other than those activities described in this report. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time this report was prepared. No warranty, express or implied, should be understood. GEORESOURCE-5 Shah.20thPlaceSW.ARG2 September 12, 2017 page 16 We trust this supplemental information will be sufficient for your needs, and look forward to your favorable consideration so that the project may proceed Respectfully submitted, GeoResources, LLC Keith S. Schembs, LEG Principal KSS:DCB/kss Doc ID: Shah.20thPlaceSW.ARG2 Attachments: Figure 1: Site Location Map Figure 2: Site and Exploration Plan Figure 3: NRCS SCS Soil Survey Figure 4: USGS Geology Map Figure 5: DOE Coastal Atlas Map Figure 6: Unified Soil Classification System Figure 7: Hand Auger Excavation Logs 111.. L`' 4 14A01 zz Dana C. Biggerstaff, PE Senior Geotechnical Engineer GEORF.SOLIRCE-S� ound L'i k. ) i �I ti IV4 31 th i17t1 Federal WaNT Approximate Site Location EOREsou RCE 'a, -Val j'. jQ14 V�i wrot ,Ib ( �q !I i fe A& P 5 31 2tb St sl rn 1:4tr, st Site Location Map 30020 20th Place SW Federal Way, WA 98023 Doc ID: Shah.20thplSW.F I Sept2017 7.1 Not to Scale I Figure I C 0 c 0 Approximate Site Locations & GEORESOURCES clyff 0. 13"-, c pocv' C;"Poteti 4','t, ca? 31r� tit'iCdGs :f n9 %LC 9 sacb a 4w91's 14 2r "i � 4ae 06 9W14 ! J AVG 141t aura �au�wxstsira► "U'C" GRAM OCATJ Not to Scale Site and Exploration Plan 30020 201h Place SW Federal Way, WA 98023 Doc ID: Shah.20'hPISW.F I Sept 2017 1 Figure 2 Approximate Site Locations (map created from the USDA Natural Resource Conservation Service Web Soil Survey) Soil Soil Name Type Parent Material Slopes Erosion Hazard Hydrologic Soils Group Glacial drift and/or glacial AgB Alderwood Gravelly outwash over dense 0-8 Slight C Sandy Loam laciomarine deposits Cb j Coastal Beaches N/A 1-5 None N/A GEORESOURCES 52.9>>cfi'caxgE.6ste`5P,F6a a,a9Ad1�tt?}}}'qes;awn;aatiz:.v:a♦ixxs Not to Scale NRCS SCS Soils Map 30020 20' Place SW Federal Way, WA 98023 Doc ID: Shah.20"'PISW.F Sept 2017 1 Figure 3 QrnCIP�.:. 1�' v � r f % Q �r a 1 46 - 4 ) yyl I Approximate Site Locations Excerpts from the Geologic Map of the Poverty Bay 7.5-Minute Quadrangle, Washington, by Derek B. Booth, Howard H. Waldron, and Kathy G. Troost (2003) Qmw Mass -wastage deposits (Holocene) GEORESOURCES USGS Geology Map 30020 20th Place SW Federal Way, WA 98023 Not to Scale Doc ID: Shah.20"'PISW.F Sept 2017 Figure 4 Approximate Site Locations (map created from the DOE Coastal Atlas hftps://fortress.wa.gov/ecy/coastalatias/tools/Map.aspx) Drift cells c, Dvve-rc;elwe zc�rle Left n.-� righ N'o appre.-ci"-:ibl. GEORESOURCES S'Icype stability �) DOE Coastal Atlas 30020 201h Place SW Federal Way, WA 98023 Not to Scale Doc ID: Shah.20thplSW.F I Sept 2017 Figure 5 SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP SYMBOL GROUP NAME GRAVEL CLEAN GW WELL -GRADED GRAVEL, FINE TO COARSE GRAVEL GRAVEL COARSE GP POORLY -GRADED GRAVEL GRAINED More than 50% SOILS Of Coarse Fraction Retained on No. 4 Sieve GRAVEL WITH FINES , GM SILTY GRAVEL GC i CLAYEY GRAVEL More than 50% SAND CLEAN SAND I SW III WELL -GRADED SAND, FINE TO COARSE SAND Retained on No. 200 Sieve SP POORLY -GRADED SAND More than 50% Of Coarse Fraction SAND SM SILTY SAND Passes WITH FINES No. 4 Sieve Sc CLAYEY SAND SILT AND CLAY INORGANIC ML SILT CL CLAY FINE GRAINED SOILS Liquid Limit Less than 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT More than 50% Passes CH CLAY OF HIGH PLASTICITY, FAT CLAY No. 200 Sieve Liquid Limit 50 or more ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT 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 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 30020 20th Place SW Federal Way, WA 98023 Doc ID: Shah.20thplSW.F I Sept 2017 I Figure 6 Hand Auger HA-1 Location: Top of Slope, Center of Property Depth (feet) Soil Type Soil Description 0 - 0.3 Topsoil 0.3 - 1.0 SM Brown SAND with silt, some gravel, and organics (loose, moist) 1.0 - 2.0 SM Brown SAND with silt, some gravel (medium dense, moist) 2.0 - 3.0 SM Brown silty SAND with gravel (loose, wet) 3.0 - 4.0 SM Light brown/ tan silty SAND with gravel (very dense, wet, till) Minimal caving observed. Groundwater seepage observed at approximately 2 feet below ground surface. Hand Auger HA-2 Location: Midslope near existing stairs Depth (feet) Soil Type Soil Description 0 - 1.0 Heavy brush, roots, topsoil 1.0 - 2.0 SM Brown silty SAND with trace gravel and organics (medium dense, moist) 2.0 - 2.5 SM Tan/grey SAND with silt and mottling (medium dense, moist to wet, weathered till) 2.5 - 3.5 SM Grey silty SAND with mottling and gravel (very dense, wet, till) Minimal caving observed. Groundwater seepage observed at approximately 2.5 feet below ground surface. Hand Auger HA-3 Location: Bottom of Slope, eastern portion of property Depth (feet) Soil Type Soil Description 0 - 0.5 Topsoil, organics 0.5 - 3.0 SM Brown gravelly sand with silt, organics, and debris (medium dense, moist, fill) Minimal caving observed. No groundwater seepage observed. Logged by: DIRT Excavated on: January 14, 2015 Hand Auger Excavation Logs 30020 20' Place SW r E 0 R E S O U R C Federal Way, WA 98023 e .4 Ad,-�d;J ![; YT� is Doc ID: Shah.20"'PISWY Sept 2017 Figure 7 Site Plan and Cross Sections (Geollesources, 2017) ?40'0' pgq`�EtO 1p. E r y r t % � pfCq ALL EXISTING UTILITIES SHOWN ON PLANS ARE TO BE VERIFIED HORIZONTALLY AND VERTICALLY PRIOR TO r ANY CONSTRUCTION. ALL EXISTING FEATURES 7 o INCLUDING BURIED UTILITIES ARE SHOWN AS INDICATED ON RECORD MAPS AND SURVEY FURNISHED BY OTHERS. WE ASSUME NO LIABILITY FORTHE ACCURACY OFTHOSE RECORDS AND Know what's below. SURVEY, FOR THE FINAL LOCATION OF EXISTING Call before dig. UTILITIES IN AREAS CRITICAL TO CONSTRUCTION OU Y 9 CONTACTTHE UTILITY OWNER/AGENCY. �90 `Ih 9aF6 , ,� NQ On O°°prF�oh°,'� S o\ Oa�asr8e P�4oy \o EXISTING CONDITIONS GRAPHIC SCALE w taFEET � 1 inch = eO TL '010�0 '��O • � U � � 89'3 ' V.25.38 -q l51S ��Y u o 4 S F9� N ((4 [y qp "- •9 F o 07 w S t/ 4 Cm cE� gcc� ey9�,s�r�q o 20 . IS, 'ap Tb•F�� o� o � ��0°s❑T 0 otr'�f 'r"aH� e A G SHEET PRE: SITE PLAN SHEET NO.I OF NEW DRAINAGE PIPE 3� PREVIOUSLY EXISTING OUTFALL ,-- PREVIOUSLY EXISTING DRAINAGE PIPE PREVIOUSLY EXISTING DRAINAGE PIPE Y , 1 1 .• - r EXISTING KEYSTON ETAINiNG WALL.BACKSLOPE 6 BE GRADED AT 2H:1V. 5 ETAIL 1 ON SHEET 3 PROPOSED KEYSTONE AFT NiNG WALL. MAX 32 INCHES TOTAL HEIGHT. 12" MIN EMBEDMENT AND LEVEL BACKSLOPE. SEE SHEET 3 FOR DETAILS. h ALL EXISTING UTILITIES SHOWN ON PLANS ARE TO BE VERIFIED HORIZONTALLY AND VERTICALLY PRIOR TO ANY CONSTRUCTION. ALL EXISTING FEATURES 1 c INCLUDING BURIED UTILITIES ARE SHOWN AS INDICATED ON RECORD MAPS AND SURVEY / FURNISHED BY OTHERS. WE ASSUME NO LIABILITY FOR THE ACCURACY OF THOSE RECORDS AND Know what's below. SURVEY, FOR THE FINAL LOCATION OF EXISTING Call UTILITIES IN AREAS CRITICAL TO CONSTRUCTION before OU dig. Y 9 CONTACT THE UTILITY OWNER/AGENCY. 1 ` � r� II ��1 • e� ,� " T S ly A � fe N N O "*11�� GRAPHIC SCALE av a +a x ( IN FEET') I Inch a 20 fL i J Q U Z I U W C Y W a3 �c A m Ax o a � 3 w U Z W N 0 I N C y r m\ N a 0 o ` � a a u o ¢ o o rn Z O LLI (n z U Z __j V) oa-<LU � � I Ili < 0:� N CDQ _ 3 N Q N J O = O Q to O [�, `1 LLJ 0 W LL- 91EFT 11TLE SITE PLAN 'SHEET NOZ 0 F 3 NOTE: GEORESOURCES PERSONNEL SHOULD BE PRESENT ONSITE DURING THE CONSTRUCTION OF THE PROPOSED WALL BELOW THE EXISTING PATH TO CONFIRM THAT THE ASSUMED SOIL CONDITIONS ARE PRESENT. ALL EXISTING UTILITIES SHOWN ON PLANS ARE TO BE VERIFIED HORIZONTALLY AND VERTICALLY PRIOR TO ANY CONSTRUCTION. ALL EXISTING FEATURES INCLUDING BURIED UTILITIES ARE SHOWN AS Q n INDICATED ON RECORD MAPS AND SURVEY FURNISHED BY OTHERS. WE ASSUME NO LIABILITY FOR THE ACCURACY OF THOSE RECORDS AND Know what's b@IOW. Call before you dig. SURVEY, FOR THE FINAL LOCATION OF EXISTING UTILITIES IN AREAS CRITICAL TO CONSTRUCTION CONTACT THE UTILITY OWNER/AGENCY. 6° WALL BATTER FROM VERTICAL 12" MIN V 6" MINIMUM THICKNESS 4A7ELY 2 FEET WIDE ET DEEP MAX SLOPE CRUSHTED DRAINAGE ROCK IN UNITS AND BEHIND WALL CONCRETE BLOCK UNIT EXPOSED WALL HEIGHT (PER SECTION NOTES) SECTION NOTES) I d (MIN) BENCH - (214:1V MAX SLOPE FOR PROPOSED WALL) TYPICAL CUT WALL DETAIL srue : xrs id Z O I— W (n Z U ZJ(n2 W W Q 0 a) U I � oN> 0 Q � _ 01 N Q N J O = O Q U� O ry W 0 W II SHEET TTLE: SITE SECTION 'SHEET N� OF 3 GEORESOURCES r earth science & geotechnical engineering 5007 Pacific Hwy E., Suite 16 1 fife, WA 98424 1 253.896.1011 1 www.georesources.rocks Dr. Viral Shah Dr. Aparna Ananth 30020 - 201h Place SW Federal Way, WA (253) 347-8207 August 25, 2017 AUG 2 8 2017 OI'TY OF FEDERALWAY COMMUMTY DNELORMEE 17 Retaining Wall Design Gravity Block Wall 30020 - 20th Place SW Federal Way, WA Doc ID: Shah.20thPlaceSW.RW We are pleased to provide wall design calculations for the concrete block wall located at the above referenced parcel. Our understanding of the project is based on our conversations with you, our November 2016 site visit, and our experience in the area. We understand that the purpose of the wall is to provide grade separation for the shoreline access path. The wall is constructed using CornerStone modular block. We understand that the wall was constructed in front of a native glacial till cut. The wall location is shown on the previously prepared site plan. Gravity Retaining Wall The existing block wall was constructed as a gravity retaining wall, where the mass of the wall material is capable of supporting the earth and gravitational forces acting on the wall. The blocks used for the wall were the CornerStone Flat Face 200 block by Mutual Materials. According to information obtained from the manufacturers' website and manuals, the blocks measure 18 inches wide by 8 inches tall by 22 inches deep and weigh 130 pounds each, Our design calculations account for a block wall in front of cut that will have a maximum total height of 4 feet (6 rows of blocks) with a maximum backslope of 2H:1V (Horizontal:Vertical). It was assumed that the slope below the proposed retaining wall will be flat, and the slope above the wall will be a 2H:1V final slope. The wall has a minimum of 6 inches of embedment. Our gravity wall calculations are included as Appendix A. Recommendations We understand that the existing block walls are 4 feet in total height with a 11-1:1V slope above them. The current configuration does not satisfy the standard factors of safety for overturning and sliding because the slope above the wall is about 1H:1V. Our calculations indicate that if the slope is cut back to 2H:1V or flatter, the wall is stable with regard to bearing, sliding, and overturning. In order to obtain a 2H:1V slope above the existing lower wall, a new wall will need to be constructed below the existing path that is located below the existing upper wall. The proposed wall will be 5 blocks tall and should be embedded a minimum of 12 inches. The subgrade below the proposed retaining wall should be compacted to a firm and unyielding condition prior to the placement of the block wall. Any fill material placed below the Shah.20thPISW.RW August 25, 2017 Page 12 proposed retaining wall, and all material placed as backfill, should be placed and compacted to 95 percent of the maximum dry density (MDD), as established in accordance with ASTM D:1577. The wall should be founded on native soils that are in a firm and unyielding condition or on properly placed and compacted structural fill. Drainage material consisting of WSDOT gravel backfill for drains (WSDOT spec 9-03.12(4)) should be installed behind the walls at least 12-inches from the back of the walls. A collector pipe consisting of perforated or slotted PVC pipe should be installed at the base of the wall and at the back of the reinforce earth fill zone. The pipes should collect any groundwater or seepage and route it to an approved discharge point. Since subsurface conditions were not observed along the wall alignment prior to design, GeoResources or the project engineer of record should verify bearing conditions to assure adequate bearing capacity, and verify the assumed conditions to be accurate, observe the drain placement, and provide intermittent observations and field density testing of the backfill material during the wall construction. This Retaining Wall Design Letter was prepared under direct supervision. It is our opinion that the information provided herein and the preparation of this Letter is in accordance with the applicable standards. We trust this is sufficient for your current needs. Should you have any questions, or require additional information, please contact us at your earliest convenience. Respectfully submitted, GeoResources, LLC Kyle Billingsley, EIT Staff Engineer in Training ■ i.. W 01 I BF .. Dana C. Biggerstaff, PE Senior Geotechnical Engineer KSS:DCB/keb DoclD: Shah.20thPISW.RW.doc Attachments: Wall Design Calculations Site Plan Principal GEORESOURCES Project: TerryJensen.Shah Feature: Gravity Retaining Wall Subject: Retaining Wall Design Calculation No. GC-001 Revision No. Rev. 01 Job No. TerryJensen.Shah Gravity Retaining Wall Calculations Soil Properties Block Properties Block Height: h:=8 in Unit Weight: y:=125 ��' Block Width: w:=18 in .ft'3 Block Depth: d:=22 in Ib Effective Friction Angle: 0':= 38 ° Block Weight: ybtn,ks'=130 t ft Soil/Block Base Friction: µ:=0.45 (From NAVFAC DM7.2) Wall Properties Slope Angle Above Wall: Wall Batter: Wall/Soil interface Friction Angle: Total Wall Height: Embedment Depth: Exposed Height: Equivalent Fluid Pressures lb Gam:=35 ft2 0:=32 ° (2H:1V) a:=(-6) ° Ow 24 ° Ht:=R•h=4 ft He:=0.5 ft H:=Ht—He=3.5 ft Rows of Blocks: R:=6 Note: Equivalent flud pressure based on cut being made into native glacially consolidated soils with a 2H:1V backslope Project: TerryJensen. Shah Feature: Gravity Retaining Wall Subject: Retaining Wall Design Retaining Wall Calcs: Calculate Wall Weights Wtotal := Ht - d --tblocks' 1 f t = 953.3 1b Check Bearing Capacity: Allowable Bearing Pressure = qA:=2000 lb ft Net Bearing Pressure Factor of Safety Check Overturning: Calculation No. GC-001 Revision No. Rev. 01 Job No. TerryJensen.Shah ' Wta� q —520 ft d•1 t qA > 2.0 OK FSbearing := q, = 3.8 Available Resisting Moment = MA:=Wtotal • 2 = 873.9 lb • ft Overturning Moment : F1:= 1 . Ht2 • Gac = 280 lb 2 H MA:=F1.3t =373.3 lb• ft Factor of Safety = FS... rturning := MA = 2.3 > 1.5 .,. OK A 1 WEq rp I Check Sliding Resistance: Project: TerryJensen.Shah Feature: Gravity Retaining Wall Subject: Retaining Wall Design Calculation No. GC-001 Revision No. Rev. 01 Job No. TerryJensen.Shah Sliding Force = F'R:=Fi=280 lb Resistance to Sliding from friction = FR:=Wtoto1•µ=429 lb (neglecting passive pressure) Factor of Safety - FSslidi,,9:= R =1.5 1.5> 1.5 .'. OK FIR Passive Pressure was neglected for sliding, which is a conservative assumption for this case Ph. 253-896-1011 Fx. 253-896-2633 Terry Jensen Construction Corp PO Box 1237 Seahurst, WA 98062 Attn: Mr. Terry Jensen (425) 557-9500 jensenco@comcast.net GeoResources, LLC 5007 Pacific Hwy. E, Suite 16 Fife, Washington 98424 Marchl_�1 i IMITTE® AUG 2 4 2017 CITY OF FEDERAL WAY CO MMUN[TY DEVELOpME:NT Limited Geotechnical Engineering Report Proposed Residential Additions 30020 — 20th Place SW Federal Way, WA PN: 012103-9113, -9114 Job: TerryJensenConst.ShahRes.GR INTRODUCTION This limited geotechnical report presents the results of our subsurface explorations for the proposed addition of a gazebo and outbuildings to the existing residence located at 30020 20th Place SW in the Federal Way area of King County, Washington. The general location of the site is shown on the attached Site Vicinity Map, Figure 1. Our understanding of the project is based on our discussions with you, our January 14, 2016 site visit, and our experience in the area. We understand that you propose to construct a gabezo and new outbuildings in the northern portion of your property in the same location as a previously existing builders were located. The proposed structures are shown on the Proposed Site Plan, Figure 2a. We understand that these additions will consist of two single - story wood framed buildings, and one two-story, wood framed ADU. Due to the proximity of the proposed additional buildings to an existing concrete bulkhead and shoreline, we anticipate the additions will need to be supported on small diameter pin piles or helical anchors. SCOPE The purpose of our services was to evaluate the surface and subsurface conditions at the site as a basis for developing and providing geotechnical recommendations and design criteria for the proposed residential addition. Specifically, our scope of services for the project included the following: 1. Visiting the site and conducting a geologic reconnaissance to assess the site's soil, groundwater, and slope conditions; 2. Exploring the subsurface conditions across the proposed building site by excavating three hand augers at selected locations across the site; 3. Addressing the current building code; and 4. Providing recommendations and design criteria for conventional foundation and floor slab support, including allowable bearing capacity, subgrade modulus, lateral resistance values and estimates of settlement, as well as drainage recommendations for the proposed structures. TerryJensenConst. ShahRes. GR. doc March 11, 2016 Page 2 SITE CONDITIONS Surface Conditions The subject parcel is located at 30020 20t�' Place SW in the Federal Way area of King County, Washington. The site consists of two tax parcels. The site is generally rectangular in shape, measures approximately 1,400 to 1,800 feet deep (north to south), by 80 to 100 feet wide (east to west), and encompasses about 3.94 acres. The northern portion of the site is currently developed with an existing residence located in the northern portion of the site, south of the proposed location of the three additional structures, while the southern portion of the site is undeveloped. There is an existing concrete bulkhead that extends across the northern property boundary. A concrete path provides access from the residence to the lower bulkhead and proposed building areas. The site is bounded by Puget Sound to the north and existing large -lot residential development to the south, east, and west. The site generally slopes down from south to north towards the Puget Sound. The undeveloped southern portion of the site slopes down at an inclination of approximately 13 to 25 percent. The northern, developed portion of the site flattens out to inclinations of about 9 to 12 percent to the north of the existing residence. The site then steepens to slopes of approximately 60 to 75 percent before flattening out to a bench along the existing concrete bulkhead. This steep slope are has a vertical slope of approximately 20 feet. Beyond the bulkhead, the site gently slopes down to the Puget Sound. Total topographic relief across the site is on the order of 245 feet. The existing site configuration with King County topographic contours are shown on the attached Site and Exploration Plan, Figure 2b. Vegetation across the site consists of coniferous and deciduous trees with a moderately dense understory of native shrubs in the southern portion of the site. The northern portion of the site around the existing residence consists of typical residential landscaping. The steep slope north of the existing residence is moderately vegetated with vine maples and blackberry bushes. The northern portion of the site where the proposed structures are to be constructed is vegetated with sparse grasses. No evidence of surface water or seepage was observed on the site or the slope below the site at the time of our site visit. No evidence of erosion, soil movement, landslide activity or deep-seated slope instability was observed at the site or the adjacent areas at the time of our site visit. Site Soils The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey for King County maps the soils in the site area as Coastal Beaches (Cb) along the northern most portion of the site, and as Alderwood Gravelly Sandy Loam (AgB) across the majority of the site. Alderwood soils are derived from glacial drift or glacial outwash over dense marine deposits, form on slopes of 0 to 8 percent, have a "slight" erosion hazard when exposed, and are included in hydrologic soils group C. A copy of the NRCS Soil Conservation Survey map for the site vicinity is attached as Figure 3. Wa observed no evidence of surficial erosion at the site during our reconnaissance. Site Geology The Geologic Map of the Poverty Bay 7.5-Minute Quadrangle, Washington, by Derek Booth, Howard Waldron, and Kathy Troost (2003) maps the site as being underlain by mass - wastage deposits (Qmw). Given the size and shape of this deposit, it appears to be typical of landslides associated with the retreat of the most recent Vashon continental ice mass, and likely occurred 12,000 to 15,000 years ago. An excerpt of the above referenced map is included as Figure 4. TerryJensenConst. Shah Res. GR.doc March 11, 2016 Page 3 The Washington State Department of Ecology (DOE) Coastal Atlas maps the site as "stable" and "intermediate" with "unstable" areas to the northeast of the site. The project site is mapped as being "stable," while the area to the south of the proposed structures and north of the existing residence is mapped as "intermediate." These designations are likely based on slope inclinations. A copy of the Coastal Zone Atlas is included as Figure 5. Subsurface Explorations On January 14, 2016 we explored subsurface conditions at the site by advancing the excavation of three hand auger samples. The hand auger holes were located in the field by our representative by pacing from existing site features such as building corners and existing rockeries. The locations of these holes are and are indicated on the attached Site Plan and Exploration plan, Figure 2. A field representative from our office performed the excavations, maintained logs of the subsurface conditions encountered in each hang auger, obtained representative soil samples, and observed pertinent site features. Representative soil samples obtained from the explorations were placed in sealed plastic bags and taken to our laboratory for further examination, as deemed appropriate. Subsurface Conditions Our hand auger holes encountered subsurface conditions that somewhat confirmed the mapped stratigraphy. The stratigraphy across the site, as observed in our hand auger holes, consisted of 4 inches to a foot of topsoil overlying 6-inches to 2.5 feet of gravelly sand with organics and debris that we interpret to be beach fill material in all hand auger holes. In hand auger holes HA-1 and HA-2, the fill material was 6-inches to 1 foot thick and was underlain by 2.5 to 3 feet of medium to very dense sand that we interpret to be glacial till. Hand auger hole HA-3 encountered approximately 6 inches of topsoil overlying beach fill material to the full depth explored. Groundwater and minimal caving were observed in hand auger holes HA-1 and HA-2 at 2 to 2.5 feet. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure 7. The hand auger logs are included as Figure 8. Groundwater Conditions Groundwater was encountered in hand auger holes HA-1 and HA-2 at 2 to 2.5 feet. Mottling was observed in hand auger HA-2 at 2 to 3.5 feet. We expect that perched groundwater conditions, and the resulting above optimum soil moisture, will vary seasonally. To some extent, these conditions will change with changes in site utilization, precipitation and other factors. The highest shallow or perched ground water and soil moisture conditions typically occur during the late winter and spring. The lowest soil moisture and perched ground water conditions typically occur during September/October, prior to normal seasonal wet weather conditions. CONCLUSIONS Based on our data review, site observations, subsurface explorations, and engineering analysis, it is our opinion that the proposed structures are feasible from a geotechnical standpoint. Based on the results of our subsurface exploration program, data review, and our experience in the area, it is our opinion that the proposed structures can be constructed in the planned location provided the foundation support is extended through the shallow soils and below the base of the adjacent bulkhead. We have provided geotechnical recommendations for conventional spread footings, needle pile, and helical anchor type foundations below. TerryJensenConst. Shah Res. GR.doc March 11, 2016 Page 4 Provided the recommendations contained herein are included in the plans, the proposed development should have minimal impacts to the site and adjacent properties. Helical Anchors Helical piers (such as the proprietary systems offered by AB Chance and Atlas Systems) typically consist of one or more plates constructed in the shape of a helix and attached to a shaft. Helix plates range from 6 to 14 inches in diameter and extension shafts vary from 1.5 to 4 inches in diameter. Helical piers are typically fabricated from a high strength, alloy material. Helical piers are screwed into the ground with a rotary -type torque motor until the refusal criterion is met. Refusal is typically defined as achieving a specific torque that corresponds to a specific compressive capacity. The lateral capacity of the battered piling may be taken as the horizontal vector of the axial pile capacity. The Chance anchor system is a proprietary system which utilizes helical anchors affixed to a square steel shaft. The capacity of the anchor in uplift (tension) is related to the torsional resistance encountered as the anchor is installed. Torque monitoring of individual anchors is completed as the anchors are installed using a shear pin that shears once the design load (torque) is achieved. The number and size of helix plates required to achieve to design loads should be determined by the specialty subcontractor. Needle Piling Needle piling consist of small diameter Schedule-40 galvanized or Schedule 80 steel pipe that are driven into the underlying soils.to refusal. The steel pipe diameters range from 2 3/8" to 6-inches. Individual pipe segments typically range from about 5 to 21 feet long and are successively joined with external friction couplers, threaded couplings, or butt welds as pile driving progresses. For the proposed structures, we recommend that 2-inch needle piling be utilized since access will likely be limited, preventing the use of larger, machine -mounted hammers. The 2- inch needle piles should be driven into the subgrade by means of a 140 pound pneumatic or hydraulic hammer. We recommend that, for 2--inch diameter needle piles, each pile be driven to a point of refusal defined as less than 1 inch of penetration during 1 minute of sustained driving. Actual capacities and refusal criteria should be verified by the contractor, and verified by a geotechnical professional. We anticipate that the needle piles will meet refusal in the underlying dense glacial till or at least 2 feet below the nearest adjacent bulkhead, whichever is deepest. 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. A test pile could be installed to evaluate refusal depths more accurately. 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-degree 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. In our opinion, a properly installed 2-inch-diameter needle piling driven to refusal (as defined above) will provide the following allowable axial capacities. These capacities assume a minimum pile spacing (center to center) of six pipe diameters. Furthermore, the stated uplift capacity would be applicable only to needle piles that are installed with tension -resisting couplings. The allowable pile capacities are provided below. TerryJensenConst.ShahRes.GR.doc March 11, 2016 Page 5 Design Parameter Allowable Value 2-inch-diameter Static Compressive Capacity 4,000 pounds Transient Compressive Capacity 5,300 pounds Alternatively, if access for a small bobcat size machine is feasible, it may be more economic to utilize fewer, but larger diameter piling. A properly installed 3-inch diameter or 4- inch diameter needle pile driven to refusal (as defined by the contractor) will provide the following allowable axial capacities. These capacities assume a minimum pile spacing (center to center) of six pipe diameters. Furthermore, 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 Allowable Value 3-inch-diameter 12,000 pounds 16,000 pounds 4-inch-diameter 20,000 pounds 26,000 pounds It should be noted that the 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. Load testing of 5 percent of the piles is required for 3 and 4-inchp diameter pin piles, with a minimum of 1 test. Load testing should be performed per ASTM D1143, quick load test method to 2 times the allowable compressive load. We recommend that we be called at the start of the pile installation to verify appropriate depths and spacing. We do not need to witness all of the piling, but do want to verify conditions are as expected and that the wall/piling are being installed as recommended. If you have questions please call us. Structural Fill All material placed as fill associated with mass grading, as utility trench backfill, under building areas, or under roadways should be placed as structural fill. Structural fill should be placed in horizontal lifts of appropriate thickness to allow adequate and uniform compaction of each lift. Fill should be compacted to at least 95 percent of MDD (maximum dry density as determined in accordance with ASTM D-1557), within 2 percent of the optimum moisture content for compaction. The appropriate lift thickness will depend on the fill characteristics and compaction equipment used. We recommend that the appropriate lift thickness be evaluated by our field representative during construction. We recommend that our representative be present during site grading activities to observe the work and perform field density tests. The suitability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines (material passing US No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult to achieve. During wet weather, we recommend use of well -graded sand and gravel with less than 5 percent (by weight) passing the US No. 200 sieve based on that fraction passing the 3/4-inch sieve, such as Gravel Backfill for Walls (WSDOT 9-03.12(2)). If prolonged dry weather prevails during the earthwork and TerryJensenConst. Shah Res. G R.doc March 11, 2016 Page 6 foundation installation phase of construction, higher fines content (up to 10 to 12 percent) may be acceptable. Material placed for structural fill should be free of debris, organic matter, trash and cobbles greater than 6-inches in diameter. The moisture content of the fill material should be adjusted as necessary for proper compaction. Foundation Support Based on the subsurface soil conditions encountered across the site, we recommend that spread footings for the proposed buildings be founded on the stiff 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 re -compacted, 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 16 inches for 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 1,500 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 0.35 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). Passive resistance from soil should be ignored in the upper 1-foot. A factor of safety of 1.5 has been applied to these values. We estimate that settlements of footings designed and constructed as recommended will be less than 1 inch total, for the anticipated load conditions, with differential settlements between comparably loaded footings of/z inch or less over a distance of 50 feet. 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. Seismic Hazards 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 "C" in accordance with Table 1613.5.2 in the 2012 IBC (International Building Code) documents. 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. Site Drainage All ground surfaces, pavements and sidewalks at the site should be sloped away from structures. 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, similar to the existing drainage system. The roof drain should not be connected to the footing drain. TerryJensenConst. Shah Res. GR. doc March 11, 2016 Page 7 LIMITATIONS We have prepared this report for Mr. Terry Jensen and other members of the design team for use in evaluating a portion of this project. 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 conditions 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 monitoring, 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 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 any 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. TerryJensenConst.ShahRes. GR.doc March 11, 2016 Page 8 We have appreciated working for you on this project. Please do not hesitate to call at your earliest convenience if you have any questions or comments. Respectfully submitted, GeoResources, LLC TV x44 Keith S. Schembs, L.E.G. Principal KSS:DCB:kss Doc ID: TerryJensenConst.ShahRes.GR Attachments: Figure 1: Site Location Map Figure 2a: Proposed Site Plan Figure 2b: Site and Exploration Plan Figure 3: BRCS SC5 Soil Survey Figure 4: USGS Geology Map Figure 5: DOE Coastal AtIaS Map Figure 6: Unified Soil Classification System Figure 7: Hand Auger Excavation Logs -I a It 4 {7 Dana C. Biggerstaff, P.E. Senior Geotechnical Engineer y Ci i O U -RN a �+ a T a p' } F � i s, d r a.' 320th Ar1t z �ri�: _ a2��z• L 4!1•g .r:•'a r7E ioR¢ M d G C? Ss,r 31 th �� Si'r 3± 2 t h SN' 32Oth �t r, Q 4 m ��1361n 5:u k �= St pus Federal Way" f I. ram. 7 s 312th St L� i 4 e �1"ni;• r S.3 ., p s a 3: �►Fr ct N '� Ya fA rLrr� L'� e Approximate Site Location (map created from Pierce County GIS http://matterhorn3.co.pierce.wa.us/publicgis/) GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Site Location Map Proposed Residential Development 30020 20th Place SW Federal Way, WA 98023 Job: TerryJensenCon.ShahRes.F January 2016 Not to Scale I W-A—E• T Logged by: DRT tr- Ir - Partial Site Plan I.�� ., Approximate Site Locations (site plan created by Roger H. Newell, Architect) GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Not to Scale Excavated on: January 14. 2016 Proposed Plan Proposed Residential Development 30020 20th Place SW Federal Way, WA 98023 Job: TerryJensenCon.ShahRes.F January 2016 Figure 2a r 3 -- i3dL ir30010 H 25 ft 2�4 96 '4 i 0 6 F f . 1 Approximate Site Locations (map created from http://matterhorn3.co.pierce.wa.us/publicgis/) AV--k1K T S 9 bv: DRT GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Not to Scale Excavated on: January 14, 2016 Site and Exploration Plan Proposed Residential Development 30020 20t' Place SW Federal Way, WA 98023 Job: TerryJensenCon.ShahRes.F January 2016 Figure 2b Approximate Site Locations (map created from the USDA Natural Resource Conservation Service Web Soil Survey) Soil Soil Name Parent Material Slopes Erosion Hazard Hydrologic Soils Group Type Glacial drift and/or glacial AgB Alderwood Gravelly outwash over dense 0-8 Slight C Sandy Loam ` Coastal Beaches laciomarine deposits N/A 1-5 None N/A Cb GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 NRCS SCS Soils Map Proposed Residential Development 30020 20th Place SW Federal Way, WA 98023 Not to Scale Job: TerryJensenCon.ShahRes.F January2016 1 Figure 3 Approximate Site Locations Excerpts from the Geologic Map of the Poverty Bay 7.5-Minute Quadrangle, Washington, by Derek B. Booth, Howard H. Waldron, and Kathy G. Troost (2003) EQQ M—W Mass -wastage deposits (Holocene) 1 GeoResources, LLC 5007 Pacific Highway East, Suite Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Not to Scale USGS Geology Map Proposed Residential Development 30020 20'h Place SW Federal Way, WA 98023 ob: TerryJensenCon.ShahRes.F January 2016 Figure 4 Approximate Site Locations (map created from the DOE Coastal Atlas https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) Drift cells 0 %—.e- Divergence zoine �► Left to right �� o appreciable drift Right to I -eft Undefined 9 GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Slope stability 0 v Stable rQ Intermediate ilod€fled ;a Unstable I Unstable (old slide) Unstable (recent slide) Not to Scale DOE Coastal Atlas Proposed Residential Development 30020 20th Place SW Federal Way, WA 98023 Job: TerryJensenCon.ShahRes.F January 2016 1 Figure 5 SOIL CLASSIFICATION SYSTEM MAJOR DIVISIONS GROUP SYMBOL, GROUP NAME GRAVEL CLEAN GW WELL -GRADED GRAVEL, FINE TO COARSE GRAVEL GRAVEL COARSE GP POORLY -GRADED GRAVEL GRAINED More than 50% SOILS Of Coarse Fraction Retained on No. 4 Sieve GRAVEL WITH FINES GM SILTY GRAVEL GC I CLAYEY GRAVEL More than 50% SAND CLEAN SAND SW WELL -GRADED SAND, FINE TO COARSE SAND Retained on No. 200 Sieve SP POORLY -GRADED SAND More than 50% Of Coarse Fraction SAND SM SILTY SAND Passes WITH FINES No. 4 Sieve SC CLAYEY SAND SILT AND CLAY INORGANIC ML SILT CL CLAY FINE GRAINED ORGANIC OL ORGANIC SILT, ORGANIC CLAY SOILS Liquid Limit Less than 50 SILT AND CLAY INORGANIC MH SILT OF HIGH PLASTICITY, ELASTIC SILT More than 50% Passes CH CLAY OF HIGH PLASTICITY, FAT CLAY No. 200 Sieve Liquid Limit 50 or more ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT 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 Residential Development 30020 20th Place SW Federal Way, WA 98023 DocID: AJCHomes.75thAveE.F I January 2016 1 Figure 6 Hand Auger HA-1 Location: Top of Slope, Center of Property Depth feet Soil Type Soil Description 0 - 0.3 Topsoil 0.3 - 1.0 SM Brown SAND with silt, some gravel, and organics (loose, 1.0 - 2.0 SM Brown SAND with silt, some gravel (medium dense, mois 2.0 - 3.0 SM Brown silty SAND with gravel (loose, wet) 3.0 - 4.0 SM Light brown/ tan silty SAND with gravel (very dense, wet Minimal caving observed. Groundwater seepage observed at approximately 2 feet below ground surface. Hand Auger HA-2 Location: Midslope near existing stairs Depth (feet) Soil Type Soil Description 0 - 1.0 Heavy brush, roots, topsoil 1.0 - 2.0 SM Brown silty SAND with trace gravel and organics (medium dense, moist) 2.0 2.5 SM Tan/grey SAND with silt and mottling (medium dense, moist to wet, weathered till) 2.5 - 3.5 SM Grey silty SAND with mottling and gravel (very dense, wet, till) Minimal caving observed. Groundwater seepage observed at approximately 2.5 feet below ground surface. Hand Auger HA-3 Location: Bottom of Slope, eastern portion of property Depth feet Soil Type Soil DesCri tion 0 - 0.5 Topsoil, organics 0.5 - 3.0 SM Brown gravelly sand with silt, organics, and debris (medium dense, moist, fill) Minimal caving observed. No groundwater seepage observed. Logged by: DRT GeoResources, LLC 5007 Pacific Highway East, Suite 16 Fife, Washington 98424 Phone: 253-896-1011 Fax: 253-896-2633 Excavated on: January 14, 2015 Hand Auger Excavation Logs Proposed Residential Development 30020 20th Place SW Federal Way, WA 98023 DocID: TerryiensenCon.ShahRes. F March 2016 Figure 7 17 LN WL qpt -r I-t Ito M: MLM IL � � v- �L s • � 4 � � i .ire +\ \ r r a _ �~+� •i ~ -fir. y LI f [ v i�: 9 • ice= x' : -.� . ram. .: 11 - -: • i�OW is _ k_�, � � _ _ • ,.� - - �` �. `'�-. •'t • r r• f 5 , ��-� y � • '7, ; �;. • 2 ' ��. . rs%�..1� � �:\' � Y'-` '� 'r'.'•. j _ • � � i 1,'jy�'•: �`"-, � � L� . %r's..r� ��, is -_ r�w' d:, y _ 1 �'�� -'.\� •, r �,. 1 +, .i.�j Al - ''�� rr.Y 7 .n ti _ 'r_\ 51\�-•`ill''`-�•s'{ ,,.yam:• a ,f�S ��Ii _ �_s- 1t L\Y\, T� 1� 'l 1 �• r' j i 1 . - 0 Doc Hansen From: Doc Hansen Sent: Monday, November 05, 2018 11:49 AM To: 'Dana Biggerstaff' Subject: RE: permit 17-103978-00-SH Dana; I knew you were a man as soon as I sent the email. Sorry. I will have to discuss this with my director and get back -to you. I don't want Dr. Ananth to tear down the wall. Doc Robert "Doc" Hansen Planning Manager "rrr o, _. Federal Way Community Development Department 33325 8th Avenue South Federal Way, WA 98003-6325 Phone:253/835-2643 www.cityoffederaiway-com From: Dana Biggerstaff [mailto:Dana B@georesources.us] Sent: Monday, November 05, 2018 10:16 AM To: Doc Hansen Cc: Keith Schembs; Cole Elliott; 'Viralpandit@gmail.com'; Brian Davis; Natalie Kamieniecki Subject: RE: permit 17-103978-00-SH Mr. Hansen, First of all I'm a guy, so I would appreciate it if you don't call me Ms. Secondly, I understand what you are asking for and I am telling you that based on the times we were on site, the wording we used is as strong as we can make it. If there wasn't enough inspection there is nothing we can do about that. We were not called to go out there. You need to decide whether or not you are going to approve it based on what has been provided, or not. If you want to meet to discuss it we can do that, but I will not stamp something that says "the wall is built" a certain way. Thanks, Dana Biggerstaff, P.E. (WA) / Senior Geotechnical Engineer -= G EO RESO U FACES earth science & geotechnical engineering 5007 Pacific Hwy E„ Suite 16 1 Fife, WA 98424 1 25M96.101 t 1 www,georesources,rocks wwwaLoresources.mc3cs dWiLb rr=gearesourc oLus, ABe green - think before you print From: Doc Hansen <Robert.Hansen@cityoffederalway.com> Sent: Friday, November 2, 2018 8:22 AM To: Dana Biggerstaff<DanaB@georesources.us> Cc: Keith Schembs <KeithS@georesources.us>; Cole Elliott <Cole.Elliott@cityoffederalway.com>; 'Viralpandit@gmail.com' <Viralpandit@gmail.com>; Brian Davis <Brian.Davis@cityoffederalway.com>; Natalie Kamieniecki <Natalie. Kam ieniecki@cityoffederalway.com> Subject: RE: permit 17-103978-00-SH Ms. Biggerstaff; The timing of your email is appropriate because I was preparing an email to Keith regarding the report provided us. Meetings prevented me from finishing this before now. Dr. Ananth has been in touch with me often about this issue, and has been very patient throughout this ordeal, a problem that they inherited and did not create. I understand your perspective regarding the issue presented. However, there are a few things that must be addressed before this is completely closed out. We have to request that there is verification that things were completed correctly on this project that are not addressed by statements within your "Final Letter" dated October 18, 2018. Our response to this letter is based upon several issues. On September 20, 2017, the wall was approved given certain conditions. These conditions were sent to you. One of those conditions was, • GeoResources must be on site during construction of the new wall to monitor slope stability conditions and confirm construction activities do not adversely affect site stability. Another was: • A letter, prepared by GeoResources, verifVing construction of the new wall is in compliance with recommendations of the geotechnical report, dated September 12, 2017, and wall design analysis, dated August 25, 2017, must be submitted to the City no later than 30 days after the wall has been finalled (sic). The letter provided on October 10 indicates that the City did not specifically require that the original walls be taken down. This is true. In fact, providing conditions to be met during the re -construction of the wall outlined within the September 20th letter were intended to provide remedy so that your clients would not be required to remove the walls. One of those conditions was to be on site during construction of the new wall in order to verify that construction of the wall would not affect the soil stability. There was no indication that we could allow you to "assume that the rest" went per plan. Our intent was to have someone on site to verify that the wall was built per plan and approval. The City is not "vague" in inspection requirements as you indicate in your November 1 email, because we are not expert in knowing when or under what conditions inspection should occur. That would fall upon the experts expected to "monitor" the conditions as construction proceeded. We did not expect that your company would be there every day, however, we did anticipate that there would be inspection before, during and after construction in order to meet the intent of the condition. We have only one record at one point on one day during the monitoring period. That is not acceptable unless you can verify that the wall is constructed so that soil stability is not threatened. As stated before, our intention here is to find a solution to this problem that verifies that the wall was constructed appropriately without taking down and reconstructing the wall. If what was provided "is typically ... done and is the standard of practice in the area," then we will have to change that practice. We are subject to the obligation that conditions are adequately met. I would suggest at this time that we find some solution that accomplishes two things. Find some method of verifying the bearing conditions, backfill soil composition or compaction either through sample drilling at several points or other means that provides information that allows you to make statement that the walls were constructed appropriately. Have some means to conclude that more than one point observed during one visit so that you can provide with more confidence as geotechnical engineers that "construction and site grading" is completed in accordance with approved plans, and not just "were likely completed" as stated within your letter. 1- ) I am more than willing to sit down with you and our team to discuss this matter in order to find a solution for Dr. Ananth. Thanks. Robert "Doc" Hansen Planning Manager 4 Federal Way Community Development Department 33325 8ch Avenue South Federal Way, WA 98003-6325 Phone:253/835-2643 www.citvoffederalway.com From: Dana Biggerstaff[mailto:DanaElfteoresources_.us] Sent: Thursday, November 01, 2018 10:58 AM To: Doc Hansen Cc: Keith Schembs Subject: FW: permit 17-103978-00-SH Mr. Hansen, The conditions observed in the field are documented in our field reports and the wall design is a separate document that the owner can provide to you. These items should have already been submitted to the City. If not we can provide them at the owners request. What you are asking for with regards to the total work completed, we cannot provide. We can only document what we saw and assume that the rest went per plan. We were not called out there much and the City was vague in their inspection requirements so there is no way we can say that the wall was built absolutely correctly. We can say it looks like it was, based on observations, and that is typically what is done and is the standard of practice in the area. If the wall needs to be "certified" then full time inspection should have been requested. Believe it or not I'm not trying to be difficult. As an engineer I have to protect life and property. Saying that the wall was built correctly in exact accordance with the design would give it a level of certainty that is inappropriate for the observation requested and potentially dangerous. The owner has to know what their risks are or I am not doing my job. We cannot provide any stronger language than what was provided in our last letter. For jurisdictions in this area and per the IBC, periodic inspection is allowed and the final letter(s) we have prepared are typical. Let me know if you have any questions, Dana Biggerstaff, P.E. (WA) / Senior Geotechnical Engineer 000 - - GEORESOURCES earth science & geotechnical engineering 5007 Pacific Hwy F., Suite 16 1 Fife, WA 98424 1 253.896.1011 9 www.georesources,rocks wMvwgcorrsaurccs.rncks danahla georesoumes.us `a ` Be green - think before you print From: Keith Schembs Sent: Thursday, November 1, 2018 10:17 AM To: Dana Biggerstaff <DanaB@eeoresources,us> Subject: FW: permit 17-103978-00-SH O k, Doc still didn't like revised version. Can you email, call, or talk to him. Thanks Keith From: Doc Hansen [rnai[to:Robert. Hansen cit offederalwa .com] Sent: Tuesday, October 9, 2018 2:10 PM To: Keith Schembs <KeithS eoresources.us> Subject: RE: permit 17-103978-00-SH Keith; I just talked to your client Dr. Shah, asking for my approval of this issue. I had not the chance to get back to you regarding your email to me on Friday, but I spoke to Dr. Shah about the things that are going to have to be done. We will need a more substantial report. Specifically: • Provide the initial design report referenced within your letter. It would be most beneficial to your client and our review to include the summary and basics of the initial report within this final report. • There should be some notes regarding your "several observations" indicated within the letter. When were those visits and what exactly was found at those visits? i.e. what were your evaluations? • Provide a map within this report that indicates the points at which you made recorded observation. • Why you were unable to verify subgrade? While the taking of the wall is not necessary, couldn't trace of subgrade be measured above or below the wall at near distance without interfering with the wall? If not, why not? There should be some method of measuring subgrade. • What did you specifically observe on May I" and the impact on the construction of the walls at the points you mentioned previously? • There will have to be some documentation of specific professional examination in order to provide the final conclusion within your next to final sentence. We cannot make the assumption that "the construction we observed is representative of the total work completed..." We need you to provide us with the construction of the total work completed to conclude that the wall you observed is representative of the entire wall. It appears that a number of things will have to be done before we can close this out. There should definitely be provided some report that shows the above items for us to be able to accept the conclusion. While this is most likely going to result in more cost to Dr. Shah, it is for his and our protection to have this done. I think Dr. Shah is going to ask you to call me regarding this. Robert "Doc" Hansen Planning Manager Federal Way Community Development Department 33325 8th Avenue South Federal Way, WA 98003-6325 Phone: 253/835-2643 www.citvoffederalway.com From: Keith Schembs [mailto:KeithS(&Qeoresources.us] Sent: Friday, September 14, 2018 7:53 AM To: Doc Hansen Subject: permit 17-103978-00-SH Doc, Trying to close out the above referenced permit. I think you are familiar with this site, it is for Viral and Arpna Shah. This is for a site where several walls were built without permits. To make the walls conform to conventional design standards, several of the walls were shortened and the slopes and drainage were reconfigured. The walls were never taken apart and reconstructed, so we can't "certify" or "verify" the original construction, but as we state, provided what we were able to see and verify is representative of the original work, then the walls do meet the approved plans. The inspector thought we were a little soft on the language and understands that we weren't there for all of the work, but couldn't really provide any more comment as what he wanted us to say. Can you call at you convenience so we can discuss the wording and maybe what can be changed so that the inspector can final? Thanks, Keith S. Schembs, LEG Principal GeoResources, LLC 5007 Pacific Hwy E., Ste. 16 Fife, WA 98424 Office: 253.896.1011 Mobile: 253.444.8921 www.geo reso u rces. rocks GEORESOURCES earth & geotechotr_al engenccnng MA Be green - think before you print. 41k CITY Federala. Way April 26, 2019 Mr. Viral Shah and Ms. Apama Ananth 30020 20`" Place SW Federal Way, WA Department of Communit� Development 33325 8 Avenue South Federal Way, WA 98003 253-835-2601 — Fax: 253-835-2609 www.0yo FFed era Ewa v.com RE: Resubmittal of Final Engineering Report, Updated Report from Bruce MacVeigh, P.E., File #17- 103978 Dear Mr. Shah and Ms. Ananth; Thank you for the report dated April 16, 2018 by Bruce S. MacVeigh, Civil Engineer from Tukwila, the third submittal for finalizing the constructed wall leading to the water accessary dwelling unit. The April 16, 2019 report submitted is the same report submitted on November 14, 2018 with the addition of pictures and review of the dismantled section verifying the November report. While I would have preferred documentation of "observations of the work" done "at each stage," his dismantling the wall and confirming his observations with his professional engineering stamp concluding that the work completed "should provide a long maintenance -free" use, is accepted and this file "closed." If the walkway is an issue regarding maintenance in the future, Mr. MacVeigh's stamp is verification that the walkway was constructed correctly. Thank you again for the report and action. Sincerely, —ZLf— � I Robert "Doc" Hansen Planning Manager CC. Bruce S. MacVeigh, P.E.; 14245 59t' Ave S.; Tukwila, WA 98168 Cole Elliot, Development Services Manager, City of Federal Way (via email) i Bruce S. MacVeigh, P.E. Civil Engineer/Small Site Geotechnical 14245 59th Ave. S. Tukwila, WA 98168 Cell Ph: 206-571-879'PESUBMI17ED November 14, 2018/Update April 16, 2019 APR 19 2019 Cityof Federal WCfiY OF FEDERAL WAY Way CaMMUNf Y DEVELOPMENT Attn: Dave Van-De-Weghe, Senior Planner �~ I �'lctn_.e Subject: DOCUMENTATION OF SITE RETAINING WALL CONSTRUCTION 30020 20th Place S.W., Federal Way, WA 98023 Shah-Ananth Retaining Wall, Federal Way File No.: 17-103978-00-SH Dear Mr. Van eghe: This letter is an update of the construction report prepared by this office dated November 14, 2018. Since the previous report, and at the City's request, a sample wall section was dismantled (at a random chosen location, about one-half way down the slope) and observations were performed. Specifically observed, and verifying the initial report, were the following: 1. Rear wall gravel. 2. Gravel base material under wall. 3. PVC footing drain pipe with filter fabric. The result is that it is verified the wall was well constructed, and complies with approved plans and specifications. No remedial measures are required. Attached are additional photographs taken of the dismantled wall section, showing the rear gravel, gravel base, and the footing drain pipe. The following information, from the initial version of this report, is provided as a more detailed record of the wall construction: The following information is provided as documentation for the construction of the block retaining walls at the above address. The walls were constructed as part of the concrete access walkway down the hillside to the new site ADU building. Several aspects of the wall construction will be addressed. In summary, the wall was well constructed using proper materials and procedures, and no alterations or corrections are noted at this time. Walkway Excavation - The excavation was into the existing slope which has a natural slope of typically 1:3. The walkway cut was entirely into existing soil and no significant fill areas were needed under the walkway area. Encountered soils were a very silty rocky loam, with a trace of clay. Soils appeared reasonably uniform in all areas. Removed materials were removed from the work site. While the soils would not contribute significant groundwater flows, the surface could receive surface flows from land areas above. Footing Drain - As constructed, the footing drain was installed below the footing directly behind the rear wall line. The footing drain consisted of a fabric wrapped perforated 4" line, bedded in a filter fabric wrapped gravel bedding. The location and installation were correct. See photos. Wall Base Gravel - The base directly under the wall was required to be level and dense. The base consisted of a bedding of imported 5/8" minus crushed rock, typically 3" to 6" compacted (more or less as needed to level the base), placed on cleared undisturbed and proof compacted native soil. The crushed rock base was leveled true and heavily compacted with a mechanical "jumper' compactor. Based on the observed true horizontal lines of the place wall blocks, very good care was taken to level the base surface true. Rear Wall Drainage - The cut soil face behind the wall was undisturbed. Behind the placed wall blocks was placed washed drain rock, with the same rock used to fill the voids in the blocks (allowing block -to -block interlocking). In most areas a layer of filter fabric was placed behind the blocks with the drain rock placement. While the filter fabric is a good improvement, its use is not critical to long-term safety of the wall since the wall itself is porous, the wall blocks being dry -stacked. Walkway Installation - The finished concrete walkway is 6.5' to 7' wide, per the intended design. It was installed with a thickness of 5-6" deep, with a grid of #4 bars in both directions with 12-16" spacing. Note that the surface was "V" shaped to prevent side runoff from the walkway pavement going onto the adjacent hill slope. Observations - Observations of the work were done periodically during construction and the above information verified at each stage. Summary: The observations made during the installation of the above wall and walkway verify proper adherence to the approved design and specifications. No areas were observed requiring changes or alterations. The wall and walkway should provide a long and maintenance -free service life for the new ADU building use. Thank you for your assistance. Sincerely ours, Bruce S. MacWigh, P.E. Civil Engineer - #18657 viralshahretwallfinal/18 100 INITIAL EXCAVATION INTO NATIVE SOIL FOOTING DRAIN AND BASE BLOCK PLACEMENT (FABRIC AND ROCK NOT AROUND PIPE END YET) biw i WALKWAY READY FOR CONCRETE WITH REBAR IN PLACE p J „fir._;; . DISMANTLED SECTION T,zww--- DISMANTLED SECTION .A :.Y • �- . BASE GRAVEL, PIPE AND FILTER FABRIC CLOSE UP SHOWING CLEARED AWAY FILTER FABRIC AND PIPE Photo - May 1, 2018 Original, unpermitted upper wall, pathway, and new lower wall. Firm native soils under crushed surfacing GEORESOURCES Car Llt SCienCe & geuLe0111iCal r--tlgllleet mg st,,? Pacific 4xy E., Su le t4 Fife. nA 96114 1 2S3.m w i I wwe jearesources rods Site Photographs 30020 — 201h Place SW Federal Way, WA Permit Number: 17-103978-00-SH Doc ID: Shah.20thPlaceSW.FL.Photos I October 2018 1 Photo 1 Photo - May 1, 2018 New wall, below path, 2 blocks embedment meets or exceeds recommended 1 foot of embedment. Firm native soils visible in pathway in under blocks GEORESOURCES eartl-I science & georechnicai engineering, S:d7 ?au( c Ll wy E„ Suile i6 I Fife, A•4 994,14 12!-9:i 1011 I ■ww Searemurces rocks Site Photographs 30020 - 20th Place SW Federal Way, WA Permit Number: 17-103978-00-SH Doc ID: PortofGrapeview.GrapeviewLoopRd.F I September 2018 1 Photo 2 Photo - May 1, 2018 Original unpermitted lower walls, firm native soils visible in pathway in under blocks, slope above wall regraded and flattened. GEORESOURCES earth science & geotechnicai engineering Sr v7 Iacifie 9vvj E.. Saile !0 1 Fife. WA 99424 1 2S2.91s 101I I ■VW jeareSDUrrei.061 Site Photographs 30020 - 20th Place SW Federal Way, WA Permit Number: 17-103978-00-SH - T — Photo by owner - undated Installation of cutoff drain across top of slope above walls GEORESOURCES earth science & geotechnical engineering W7 Pacific Hay E., Suite HI Fife. W4 09424 1 2S3.11M.10I I I P.w bearesourrn.rocks Site Photographs 30020 - 20th Place SW Federal Way, WA Permit Number: 17-103978-00-SH Doc ID: Shah.20thPlaceSW.FL.Photos October 2018 Photo 4 Photo by owner - undated Drain rock behind wall during initial construction GEORESOURCES earth science & geotechnical engineering 5[47 Pacific H%Rj E., Suile !L I Fife. WA M424 1253.134.1011 I wimdeoresources rocks Site Photographs 30020 - 20th Place SW Federal Way, WA Permit Number: 17-103978-00-SH Doc ID: PortofGrapeview.GrapeviewLoopRd.F I September 2018 1 Photo 5 1 ft f Photo by owner - undated Construction of upper wall with drain pipe behind wall. GEORESOURCES earth science & geotechnicai engineering Sc47 -Yacific Hey E., iuile !G 1 fife. OVA 9U24 1 2SSIM.101I I now gearesrarras.roclrs Site Photographs 30020 — 20th Place SW Federal Way, WA Permit Number: 17-103978-00-SH Bruce S. MacVeigh, P.E. Civil Engineer/Small Site Geotechnical 14245 59th Ave. S. Tukwila, WA 98168 Cell Ph: 206-571-8794 November 14, 2018 City of Federal Way Attn: Dave Van De Weghe, Senior Planner Subject: DOCUMENTATION OF SITE RETAINING WALL CONSTRUCTION 30020 20th Place S.W., Federal Way, WA 98023 Shah-Ananth Retaining Wall, Federal Way File No.: 17-103978-00-SH Dear Mr. Van De Weghe: The following information is provided as documentation for the construction of the block retaining walls at the above address. The walls were constructed as part of the concrete access walkway down the hillside to the new site ADU building. Several aspects of the wall construction will be addressed. In summary, the wall was well constructed using proper materials and procedures, and no alterations or corrections are noted at this time. Walkway Excavation - The excavation was into the existing slope which has a natural slope of typically 1:3. The walkway cut was entirely into existing soil and no significant fill areas were needed under the walkway area. Encountered soils were a very silty rocky loam, with a trace of clay. Soils appeared reasonably uniform in all areas. Removed materials were removed from the work site. While the soils would not contribute significant groundwater flows, the surface could receive surface flows from land areas above. Footing Drain - As constructed, the footing drain was installed below the footing directly behind the rear wall line. The footing drain consisted of a fabric wrapped perforated 4" line, bedded in a filter fabric wrapped gravel bedding. The location and installation were correct. See photos. Wall Base Gravel - The base directly under the wall was required to be level and dense. The base consisted of a bedding of imported 5/8" minus crushed rock, typically 3" to 6" compacted (more or less as needed to level the base), placed on cleared undisturbed and proof compacted native soil. The crushed rock base was leveled true and heavily compacted with a mechanical "jumper" compactor. Based on the observed true horizontal lines of the place wall blocks, very good care was taken to level the base surface true. Rear Wall Drainage - The cut soil face behind the wall was undisturbed. Behind the placed wall blocks was placed washed drain rock, with the same rock used to fill the voids in the blocks (allowing block -to -block interlocking). In most areas a layer of filter fabric was placed behind the blocks with the drain rock placement. While the filter fabric is a good improvement, its use is not critical to long-term safety of the wall since the wall itself is porous, the wall blocks being dry -stacked. Walkway Installation - The finished concrete walkway is 6.5' to 7' wide, per the intended design. It was installed with a thickness of 5-6" deep, with a grid of #4 bars in both directions with 12-16" spacing. Note that the surface was "V" shaped to prevent side runoff from the walkway pavement going onto the adjacent hill slope. Observations - Observations of the work were done periodically during construction and the above information verified at each stage. Summary: The observations made during the installation of the above wall and walkway verify proper adherence to the approved design and specifications. No areas were observed requiring changes or alterations. The wall and walkway should provide a long and maintenance -free service life for the new ADU building use. Thank you for your assistance. Sincerely yours, DRAFT Bruce S. MacVeigh, P.E. Civil Engineer - #18657 viralshahretwalldoc/18 100 INITIAL EXCAVATION INTO NATIVE SOIL FOOTING DRAIN AND BASE BLOCK PLACEMENT (FABRIC AND ROCK NOT AROUND PIPE END YET) 7�1 WALKWAY READY FOR CONCRETE WITH REBAR IN PLACE Know what's below. Call before you dig. ALL EXISTING UTILITIES SHOWN ON PLANS ARE TO BE VERIFIED HORIZONTALLY AND VERTICALLY PRIOR TO ANY CONSTRUCTION. ALL EXISTING FEATURES INCLUDING BURIED UTILITIES ARE SHOWN AS INDICATED ON RECORD MAPS AND SURVEY FURNISHED BY OTHERS. WE ASSUME NO LIABILITY FOR THE ACCURACY OF THOSE RECORDS AND SURVEY, FOR THE FINAL LOCATION OF EXISTING UTILITIES IN AREAS CRITICAL TO CONSTRUCTION CONTACT THE UTILITY OWNER/AGENCY. 11� Cp T o�A7oy o� s� 7� jJ9000 0, � 9 73.9 Vcy OTT F 3Q�F 0 \ f /2,60 O 6 , O 9 Tom` T0� O � 009 F.oy Q o�� CO/� \v i J O \o �p�.� C14 \ 00 QQ SFo 0 Cn o 0 071 Iv O N 0� �S 0 (-A Fqs� EXISTING CONDITIONS 0 �3g,13„E c,, N 89, ,25.38 -9 o � O �j/°(�5/O \ \ iIP0� w 0 0 s s 000 0 00, .K GRAPHIC SCALE 60 0 30 0 ( IN FEET ) 1 inch = 60 ft. ,°6 �S os(, j , v U �O o, h ) (JI I I AUG 2 8 201? 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Call before you dig. 0 I rn L LO w CD j< U Z I U • W ' "' 0 W • � (� m , M a °- w o L W N � oo o N s 00 w a w U Z w 0 in _ Q to Y 0' Q a- m W o� I 3 > I I U c) �_ O N °' p 41 a 6 m z O �(-D on<0-) w0> N Q O _ N —1 O O Q cn on, �w 0 w w w 0 Of SHEET TITLE: SITE PLAN SHEET NO 2OF3 rvTr�rrnl� I rNlA/rn 1/rVC`T/lnlC nCTATBITBI!^ %A/AI 1 —AT.—.— � CVTC-rTAI!` I lr%nCn 1/CVCT/I AIC nCTATAITAI/" %A/AI 1 _._. ___ f-1 rrn CC i%D ATM IN 201 N OTE GEORESOURCES PERSONNEL SHOULD BE PRESENT ONSITE DURING THE CONSTRUCTION OF THE PROPOSED WALL BELOW THE EXISTING PATH TO CONFIRM THAT THE ASSUMED SOIL CONDITIONS ARE PRESENT. Know what's below. Call before you dig. ALL EXISTING UTILITIES SHOWN ON PLANS ARE TO BE VERIFIED HORIZONTALLY AND VERTICALLY PRIOR TO ANY CONSTRUCTION. ALL EXISTING FEATURES INCLUDING BURIED UTILITIES ARE SHOWN AS INDICATED ON RECORD MAPS AND SURVEY FURNISHED BY OTHERS. WE ASSUME NO LIABILITY FOR THE ACCURACY OF THOSE RECORDS AND SURVEY, FOR THE FINAL LOCATION OF EXISTING UTILITIES IN AREAS CRITICAL TO CONSTRUCTION CONTACT THE UTILITY OWNER/AGENCY. V1. vLL I 11111vvr1%1 LE 6° WALL BATTER FROM VERTICAL 12" MIN V 0 6" MINIMUM THICKNESS TYPICAL CUT WALL DETAIL CRUSHED DRAINAGE ROCK IN UNITS AND BEHIND WALL CONCRETE BLOCK UNIT 4' (MIN) BENCH - (2H:1 V MAX SLOPE - FOR PROPOSED WALL) SCALE: NTS EXPOSED WALL HEIGHT (PER SECTION NOTES) SECTION NOTES) O_ I cfl rn M LO J Q w oX 0 Z I 0 • W 4 LLJ 0 W N • (� o V m �rn Q Q o n 3 o CL w L Lcl- Of W �i W � M-M N � &5 00 o N 00 w Gi i < W U Z W 2 V)Lij = Q = cn V U) rn U C Q a- m W Y 5 I D U 3 > cif I I U N U o O N rn \ Ln C3 6 v) z O E- CD wv)z zJ(=� LLJ Q o=3:0) U LLJ O Q = � N O = N --] O O Q (� O 0 W LL I:I.; 1— U W 0 a SHEET TITLE: SITE SECTION SHEET N OF 3