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14-103866 (2)T South Sound Geotechnical Consultin UREIC WORKS July 3, 2014 Mr. Paul Sandhu 11813 SE 290`�' Place Auburn, WA 98092 Subject: Geotechnical Engineering Report Red Lion Pool Facility South 347" Street Federal Way, Washington SSGC Project No. 14042 Dear Mr. Sandhu: PERMIT #: 14-103866-00-MF ADDRESS: 168pI bui ding addition th Street PROJECT: Po RED LION INN DATE: 7/31 /14 JUL 31 Z014 CITY OF FEDERAL WAY CDS South Sound Geotechnical Consulting (SSGC) has completed our geotechnical evaluation for the planned pool facility at your motel on South 347`h Street in Federal Way, Washington. Our services have been completed in general conformance with our proposal (P14027), dated June 4, 2014. The purpose of our services was to assess subgrade soils for foundations for the pool facility. Our scope of services included excavating two (2) test pits at the site, engineering analyses, and preparation of this report. PROJECT INFORMATION A new covered pool is planned on the east side of the existing motel in an asphalt paved parking lot. We understand that the bottom of the pool will be on the order of about 5 feet below current lot grades. The pool cover structure is anticipated to be steel or wood framed and supported on conventional spread footings. Building loads are assumed to be light. SITE CONDITIONS Asphalt pavement currently covers the planned pool footprint. The site is fairly level with overall grade changes estimated at less than one foot. A block retaining wall on the order of a few feet tall is above the curb on the east side of the lot and separates the parking lot from a sloped gravel lot to the east. Overall topography in the area gently slopes from higher ground (east) down to the west. A concrete retaining wall on the order of 10 (+/-) feet tall separates the eastern side of the motel (court yard area) from the planned pool site. SUBSURFACE CONDITIONS Subsurface conditions were assessed by excavating two (2) tests pits on June 27, 2014. Approximate test pit locations are shown on Figure 1, Site Plan. Test pits were advanced to depths ranging from about 6 to 7.5 feet below existing surface grades. A summary description of observed subgrade soils is provided below, with complete logs of the explorations provided in Appendix A. Please note that subsurface conditions can vary across the site from those observed at the exploration locations. P.O. Box 39500, Lakewood, WA 98496 (253) 973-0515 Geotechnical Engineering Report SSGC Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 Soil Conditions Asphalt pavement was about 2 inches thick at the test pit locations. An approximate 6 inch thick layer of sand and gravel fill (base course) was observed below the asphalt. Fill consisting of silty sand with gravel was observed below the base course. This fill was in a medium dense condition and extended to depths between about 2 feet (TP-2) and 4.5 feet (TP-1). Some cobbles and a boulder were encountered in the fill. Below the fill was native silty sand with gravel. It was in a medium dense condition and continued to the bottom of the test pits. Groundwater Conditions Groundwater was not observed in the test pits at the time of excavation. It should be anticipated that perched groundwater can develop in the fill and upper native soils during the wet seasons of the year and due to on- or off- site development factors. Groundwater is not expected to adversely impact construction of the pool facility. Geologic Conditions General geologic conditions of the project area are shown on the "Geologic Map of the Poverty Bay 7.5 Quadrangle, King and Pierce Counties, Washington" by the United States Geologic Survey (USGS) (dated 2004). Surface soils are mapped as Qvt (Quaternary Vashon Till). This unit is described as "Compact diamict containing subrounded to well-rounded clasts in massive, silt- or sand -rich matrix. Glacially transported and deposited." Native soil in the test pits appears to conform to the mapped (glacial till) soil type. GEOTECHNICAL DESIGN CONSIDERATIONS The principal geotechnical issue relative to conventional spread footing support for the pool facility is the presence of fill. Fill extended to depths ranging from about 2 to 4.5 feet in the test pits, but could be deeper in other locations. In addition, although the fill observed was in a medium dense condition and appeared to have had some compaction applied during placement, the condition of all fill in the planned pool building footprint is unknown. New building or pool elements supported on inadequately compacted fill could be subject to excessive settlement. Native fine glacial till or properly placed and compacted fill over firm native soils should provide suitable support for the planned pool facility. The concrete retaining wall along the west side of the parking lot (planned pool site) that separates the parking lot from the lower court yard area of the motel is about 10 feet high. The pool or cover building could impart additional lateral earth pressures on this wall if placed too close (within active pressure wedge). We recommend that a structural engineer evaluate the wall if planned improvements are placed laterally closer than the height of the wall. Recommendations presented in this report are based upon the subsurface conditions observed in the test pits and our current understanding of project plans. Our recommendations assume that finish pool building foundation grades will be similar to existing grades. It should be noted that subsurface conditions across the site may vary from those observed in our test pits and can change with time. Geotechnical Engineering Report SSGC Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 Therefore, proper site preparation will depend upon the weather and soil conditions encountered at the time of construction. We recommend that SSGC review final plans and assess subgrade conditions for foundations at the time of construction. Site Preparation Preparation for site grading and earthwork should include procedures intended to drain ponded water and control surface water runoff. Grading the site without adequate drainage control measures may negatively impact the amount of site soil available for use, increase the amount of export soil and import fill materials, and potentially increasing the cost of the earthwork and subgrade preparation phases of the project. Erosion control measures such as silt fencing, straw bales/waddles, or other measures approved by the regulating building department should be placed prior to earthwork activities. We recommend that the asphalt and existing fill (or native soils) are removed (stripped) down to footing subgrades for the cover structure. The base of the pool should be on native firm glacial till. Subgrade Preparation Exposed subgrades following stripping should consist of medium dense fill or native till. Footing and pool subgrades should be proofrolled (compacted) with a heavy vibratory compactor, loaded dump truck, or hoe pack. Proofrolling efforts should result in the surface attaining a firm and unyielding condition and a compaction level of at least 95 percent of the maximum dry density per the ASTM D1557 test method. Subgrades that are soft or deflect (pump) during proofrolling, or cannot be compacted to the recommended density, should be over -excavated by at least one foot and replaced with new compacted structural fill. Temporary and Permanent Cut or Fill Slopes The contractor is responsible for constructing and maintaining stable temporary excavations. Excavations should be sloped or shored following local and federal regulations. On a preliminary basis, we estimate that temporary cut slopes having a maximum inclination of 1H:1V (Horizontal:Vertical) will be required at this site. Permanent cut or fill slopes should have a maximum inclination of 2H:1 V. Structural Fill Materials The suitability of soil for use as structural fill depends primarily on the gradation and moisture content of the soil when it is placed. As the amount of fines (soil fraction passing the U.S. No. 200 sieve) increases, soils can become increasingly sensitive to small changes in moisture content. It can become difficult to impossible to achieve adequate compaction if soil moisture is outside of optimum condition for soils that contain more than about 5 percent fines. Geotechnical Engineering Report Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 SSGC Site Soils: The fill observed in the test pits consisted of silty sand with gravel having variable cobbles and boulders. This material is similar to native soils in the area, and both have fines contents that can make them moisture sensitive. Existing fill and native soils are considered suitable as structural fill provided they can be moisture conditioned to near optimum moisture contents. In general, optimum moisture is within about +/- 2 percent of the moisture content required to achieve the maximum density per the ASTM D-1557 test method. If natural moisture contents are higher than optimum, soils would need to be dried prior to placement as structural fill. It is our opinion that the fill and native soils will be difficult to use as structural fill during wetter weather, or if they have moisture contents above 2 percent of optimum. Import Fill Materials: We recommend that import structural fill placed during extended dry weather periods consist of material which meets the specifications for Gravel Borrow as described in Section 9-03.14(1) of the 2010 Washington State Department of Transportation (WSDOT) Specifications for Road, Bridge, and Municipal Construction (Publication M 41-10). Gravel Borrow should be placed in horizontal lifts not exceeding 10 inches in loose thickness. Each lift must be conditioned to the proper moisture content and uniformly compacted to a firm, unyielding condition using mechanical equipment. Gravel Borrow fill must be protected from disturbance if exposed to wet conditions after placement. Imported fill for use in wet conditions should generally conform to specifications for Select Borrow as described in Section 9-03.14(2), or Crushed Surfacing per Section 9-03.9(3) of the 2010 WSDOT M-41 manual, with the modification that a maximum of 5 percent by weight shall pass the U.S. No. 200 sieve for these soil types. It should be noted that the placement of structural fill is often weather -dependent. Delays due to inclement weather are common, even when using select granular fill. We recommend that site grading and earthwork be scheduled for the drier months of the year, if possible. Structural Fill Placement We recommend that all structural fill is placed in lifts not exceeding 10 inches in loose measure. Structural fill beneath structures (buildings and the pool) should be compacted to a minimum of 95 percent of the maximum dry density per the ASTM D-1557 test method. Backfll against pool sides should be compacted to a maximum of 92 percent. Utility trench backfill should be compacted to at least 92 percent of the referenced test method. Trench backfill within about 2 feet of the utility line should not be over -compacted to reduce the risk of damage to the line. Fill should be compacted to at least 90 percent of the maximum dry density in utility trenches that are outside of foundation or pavement areas, or in non-structural (e.g. landscape) areas. We recommend that all fill procedures include maintaining grades that promote drainage and do not allow for ponding within the fill area. The contractor should protect compacted fill subgrades from disturbance 4 Geotechnical Engineering Report Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 SSGC during wet weather. In the event of rain during structural fill placement, the exposed fill surface should be allowed to dry prior to placement of additional fill. Alternatively, the wet soil can be removed. Structural fill should not consist of frozen material. Spread Footing Foundations Conventional spread footing foundations can be placed on existing native glacial till subgrades or on structural fill that have been prepared as described in the above sections of this report. The following recommendations have been prepared for conventional spread footing foundations. Bearing Capacity {net allowable) 2,000 pounds per square foot (psf) for footings supported on firm native soils; 1,500 psf on existing or new structural fill prepared as described in this report. Footing Dimensions Minimum): Column: 24 inches Embedment Depth (Frost Protection): Exterior Footings: 18 inches Settlement: Total: < 2 inches Differential: < 1.5 inches (between columns) Allowable Lateral Passive Resistance: 300 psf/ftl (below 12 inches) Allowable Coefficient of Friction: 0.35' (native till or granular structural fill) These values include a factor of safety of approximately 1.5 The net allowable bearing pressures presented above may be increased by one-third to resist transient, dynamic loads such as wind or seismic. Foundation Construction Considerations All foundation subgrades should be free of water and loose soil prior to placing concrete, and should be prepared as recommended in this report. Concrete should be placed soon after excavating and compaction to reduce disturbance to bearing soils. Should soils at bearing level become excessively dry, disturbed, saturated, or frozen, the affected soil should be removed prior to placing concrete. We recommend that SSGC observed all foundation subgrades prior to placement of concrete. Geotechnical Engineering Report S S GC Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 Seismic Considerations The following seismic parameters and values are recommended based on the 2012 International Building Code (IBC). PARAMETER 2012 International Building Code (IBC) Site Classification Site Latitude Site Longitude VALUE D N 47.29000 W 123.31090 S, Spectral Acceleration for a Short Period 1.280g�N1 Si Spectral Acceleration for a 1-Second Period 0.492g Fa Site Coefficient for a Short Period 1.00 F, Site Coefficient for a 1-Second Period 1.508 ' Note: In general accordance with 2012 International Building Code, Section 1613.3.2 for risk categories I,HJH. IBC Site Class is based on the specified characteristics of the upper 100 feet of the subsurface profile. S.,, S1, F. and F, values based on the USGS US Seismic Design Maps website using referenced site latitude and longitude. The 2012 IBC requires a site soil profile determination extending to a depth of 100 feet for seismic site classification. Test pits completed on the site do not satisfy the required 100 foot soil profile. The recommended seismic site class considers that a stiff soil profile continues below the maximum depth of the test pits and is based on the referenced maps in this report and other geol9gir, information in the area. Liquefaction Soil liquefaction is a condition where loose, typically granular soils located below the groundwater surface lose strength during ground shaking, and is often associated with earthquakes. Native soils on the site consist of firm glacial till. The risk of liquefaction at this site is considered low for the design level earthquake. Lateral Earth Pressures We anticipate that the buried pool will be constructed of concrete and understand it will be a maximum of about 5 feet deep. Soils on the sides (walls) of the pool will impart lateral earth pressures against the walls. We recommend that an at -rest equivalent fluid density pressure of 50 psf is used in design of pool walls. This pressure should be applied as a triangular distribution starting at the top of the wall. It assumes level backfill behind the wall and that drainage is provided to prevent the buildup of hydrostatic pressures. Surcharge loads (such as vehicles, sloped ground, etc) should be accounted for as necessary. 6 Geotechnical Engineering Report Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 REPORT CONDITIONS This report has been prepared for the exclusive use of Mr. Paul SandhU for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices in the area. No warranties, either express or implied, are intended or made. Site safety and earthwork construction procedures are the responsibility of others. In the event that changes in the design or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless SSGC reviews the changes and either verifies or modifies the conclusions of this report in writing. The analysis and recommendations presented in this report are based on observed soil conditions in the test pits at the indicated locations and from other information discussed. This report does not reflect variations that may occur between explorations, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include any environmental or biological assessment of the site including identification or prevention of pollutants, hazardous materials, or conditions. Other studies should be completed if the owner is concerned about the potential for contamination or pollution. We appreciate the opportunity to work with you on this project. Please contact us if additional information is required or we can be of further assistance. Respectfully, South Sound Geotechnical Consulting Timothy H. Roberts, P.E., R.G. Member/Geotechnical Engineer Attachments: Figure 1, Site Plan Appendix A — Site Exploration Procedures and Test Pit Logs Unified Soil Classification System cc: Kaul Design Associates, LLC — Mr. Brad Kaul 7 Legend TV 1 6M Approximate Test Pit Location Scale: NTS Soua Soawd Geotechnical Consulting P.O. Box 39500 Lakewood, WA 98496 (253) 973-0515 Base map from Google Maps Figure 1— Site Plan Red Lion Pool Facility Federal Way, WA SSGC Project #14042 Geotechnical Engineering Report Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 Appendix A Field Exploration Procedures and Test Pit Logs SSGC Geotechnical Engineering Report SSGC Red Lion Pool Facility Federal Way, Washington SSGC Project No. 14042 July 3, 2014 Field Exploration Procedures Our field exploration for this project included two (2) test pits completed on June 27, 2014. The approximate exploration locations are shown on the Site Plan (Figure 1). The exploration locations were determined by pacing from existing site features. Ground surface elevations referenced on the logs were inferred from USGS 7.5 minute quadrangle maps. Exploration locations and elevations should be considered accurate only to the degree implied by the means and methods used. A private excavating contractor subcontracted to SSGC excavated the explorations. Soil samples were collected and stored in moisture tight containers for further identification or laboratory testing. Explorations were backfilled with excavated soils and tamped when completed. Please note that backfill in the explorations will likely settle with time. Should test pits be discovered in building or pavement areas, the backfilled material should be re -excavated and recompacted, or replaced with structural fill. Test pit logs indicate the lithology of subgrade materials observed in the explorations at the time of excavation. The logs indicate • an average (or interpreted) contact depth where soil contacts appeared gradational. Approximate groundwater depth (where observed at the time of excavation), sample numbers, and sample depths are also shown on the logs. Soil descriptions on the logs are based on the Unified Soil Classification System. 9 Pra'ect: Red Lion Pool Facili I SSGC Job # 14042 1 TEST PIT LOGS PAGE 1 OF 1 Location: South 347` Street, Federal Way, WA I Approximate Elevation: Refer to logs Test Pit TP-1 Depth (feet) Material Description p — 4.5 Fill: 2 inches asphalt over 6 inches base course gravel over Silty SAND with gravel, variable clay and cobbles/boulder: Medium dense, moist, brown/gray. (Sample S-1 @ 2 to 3 feet) 4.5 — 7.5 Silty SAND with gravel: Medium dense, moist, gray. Grades dense at about 6 feet. (Sample S-2 @ 5 to 6 feet) Test pit completed at approximately 7.5 feet on 6/27/14. No groundwater observed at time of excavation. No caving observed at time of excavation. Approximate surface elevation: 315 feet Test Pit TP-2 Depth (feet) Material Description 0-2 Fill: 2 inches asphalt over 6 inches base course gravel over Silty SAND with gravel, variable cobbles: Medium dense, moist, brown/gray. 2-3 Silty SAND with gravel: Medium dense, moist, buff. 3-6 Silty SAND with gravel: Medium dense, moist, gray/brown. Test pit completed at approximately 6 feet on 6/27/14. No groundwater observed at time of excavation. No caving observed at time of excavation. Approximate surface elevation: 315 feet TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting TP-1 TO TP-2 Logged by: THR UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests" Coarse Grained Soils: More than 50% retained on No. 200 sieve Fine -Grained Soils: 50% or more passes the No. 200 sieve Gravels: Clean Gravels: More than 50% of coarse Less than 5% fines c fraction retained on No 4 Gravels with Fines: sieve More than 12% fines c Clean Sands: Sands: Less than 5% fines° 500/6 or more of coarse fraction passes No. 4 sieve Sands with Fines: More than 12% fines Silts and Clays: Liquid limit less than 50 Silts and Clays: Li uid limit 50 or more Inorganic: Organic: Inorganic: Cu>-4and 1<_Cc53E Cu < 4 and/or I > Cc > 3 E Fines classify as ML or MH Fines classify as CL or CH Cuz6and l<Cc<3r: Cu<6and/or I>Cc>3E Fines classify as ML or MH Fines classify as CL or CH PI > 7 and plots on or above "A" PI < 4 or plots below "A" line i Liquid limit - oven dried < 0.75 Liquid limit - not dried PI plots on or above "A" line PI plots below "A" line Liquid limit - oven dried Soil Classification Group Symbol Group NameE GW Well -graded gravelF GP Poorly graded gravel r GM Silty gravelr-o�1 GC Clayey gravelr'.au SW Well -graded sand' SP Poorly graded sand' SM Silty sand""' SC CL Clayey sand❑,r>i Lean clay cn1 ML Siltx,LM OL Organic clay Organic silt ❑ CH Fat clay1,LA MH Elastic Slltr''L.M Organicclay Kil q Organic: <0.75 OH Liquid limit - not dried Organic silto^M•Q Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat Based on the material passing the 3-in. (75-mm) sieve H If fines are organic, add `with organic fines" to group name. a If field sample contained cobbles or boulders, or both, add `with cobbles or i If soil contains >— 15% gravel, add "with gravel' to group name. boulders, or both" to group name. i If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. c Gravels with 5 to 12% fines require dual symbols: GW-GM well -graded gravel x If soil contains 15 to 29% plus No. 200, add "with sand" or "with gravel," with silt, GW-GC well -graded gravel with clay, GP -GM poorly graded gravel whichever is predominant. with silt, GP -GC poorly graded gravel with clay. L If soil contains >_ 30% plus No. 200 predominantly sand, add "sandy" to group Sands with 5 to 12% fines require dual symbols: SW-SM well -graded sand with name. silt, SW -SC well -graded sand with clay, SP-SM poorly graded sand with silt, SP- M If soil contains >— 30% plus No. 200, predominantly gravel, add "gravelly" to SC poorly graded sand with clay group name. ( D )2 N Pl z 4 and plots on or above "A" line. e Cu = D6olDio Cc = 30 ° PI < 4 or plots below "A" line. D10 x D80 a PI plots on or above "A" line. F If soil contains ? I S% sand, add `with sand" to group name. Q PI plots below "A" line. o If fines classify as CL-ML, use dual symbol GC -GM, or SC-SM. 60 I For classification of fine-grained soils and fine-grained fraction ; 50 of coarse -grained soils Equation of "A" - line d Horizontal at PI=4 to LL=25.5. X 40 - then PI=0.73 (LL-20) Q f- - - - - - t p Equation of "U" - line �.' G�o z Vertical at LL=16 to PI=7, 30 - then PI=0.9 (LL-8)— f' V U ' ' o Qt0------- --1� _—[j�► - ------ MH or OH a I 10 7 --- L 4-- MLorOL 0 0 10 16 20 30 40 50 60 70 LIQUID LIMIT (LL) 80 90 100 110