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HomeMy WebLinkAboutRS_Geotech Report_191031_v1.pdf16"FIRCATCH BASINRIM 400.1312" CONC SW 397.30 IESANITARY SEWER MANHOLEWF A5WF A7WF A8WF AA8WF AA6----LSWF AA7----WATER MANHOLE30" Fir18" MAPLE30" FIRWF A6SANITARY SEWERMANHOLERIM 400.4312" CONC NE 388.08 IE8" PVC S 388.91 IE12" CONC SW 388.08 IESANITARY SEWERMANHOLERIM 400.7112" CONC NE 388.80IE12" CONC SW 388.61IESBSIGNAL BOXTVN63°57'27"E1423.14' (M)1423.21' (ST)595.07' (C)595.10' (ST)30'UP UP91053124678111213141516UTILITYELEV.MECH.FIRESPRINKLERCOMMERCIAL1075 SQ.FT.+/- 398 FFCOMMERCIAL825 SQ.FT.+/- 398 FFMAIL30' COMMERCIAL DEPTH REQ'DBIKEBIKEBIKEBIKEBIKEBIKEBIKEBIKERESIDENTIAL LOBBY +/- 395' FFELEV.PERVIOUS SURFACE PARKING STALLS ROOF DRAIN CONNECTION UNDERGROUND DETENTION COMMERCIAL SEWER SERVICE ROOF DRAIN CONNECTION UNDERGROUND DETENTION UNDERGROUND DETENTION RESIDENTIAL SEWER SERVICE FLOOR DRAIN / PRE-TREATMENT REQUIRED IN GARAGE? FDC HYDRANT PIVPPP-SS-TTTTSUNSET HIGHLANDS MIXED USESUNSET HIGHLANDS MIXED USECivil Engineers Structural Engineers Landscape Architects Community Planners Land Surveyors Neighbors T A C O M A 2215 North 30th Street, Suite 300 Tacoma, WA 98403 253.383.2422TEL 253.383.2572FAX www.ahbl.comWEB S E A T T L E S P O K A N E T R I-C I T I E S Checked for Compliance to City Standards Q:\2019\2190210\10_CIV\CAD\2190210-SH-UTIL-COMP.dwgNGRAPHIC SCALE 0 10 20 1" = 10 FEET 5 PERVIOUS SURFACE PARKING STALLS COMPOSITE UTILITY PLAN PERVIOUS CONCRETE DETENTION SYSTEM DETENTION SYSTEM POTENTIAL BIORETENTION POND POTENTIAL BIORETENTION POND 40.0 ft STORM OUTFALL LOCATION BUFFER RESTORATION ALONG STORM FF 399.0 FF 399.0 FF 396.50 FG 400.5 FG 400.5 TO BE EVALUATED TO BE EVALUATED FG 396.0 FG 396.0FG 399.0 EXIST ING ROAD GRADE 400 .5+ / - ANTICIPATED 3:1 GRADING DAYLIGHT IN WETLAND BUFFER. APPROXIMATE LIMITS OF RESTORATION TO BE EVALUATED UPUPR O W IN C R E A S E6' - 6 "S E T B A C K15' - 0 "MI N20' - 0 "MIN20' - 0"PARKING SIZE:RENTON MUNICIPAL CODE:TITLE IV - CHAPTER 4 -4-4-080-D8ADA PARKINGA117.1-2009502-503RISER ROOMELEV.COMMERCIAL1105 SQ FT+/- 398 FFCOMMERCIAL820 SQ FT+/- 398 FFUTILITYELEVACCESSBIKESTORAGEFF 395.5 FF 399.0 FF 399.0 South Sound Geotechnical Consulting February 12, 2018 ADF Properties, LLC 15007 Woodinville Redmond Road, Suite A Woodinville, WA 98072 Attention: Mr. Dale Fonk Subject: Geotechnical Engineering Report Sunset Highlands Mixed Use Development 4409 NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 Mr. Fonk, South Sound Geotechnical Consulting (SSGC) has completed a geotechnical assessment for the planned mixed use development at the above address. Our services have been completed in general conformance with our proposal P17092 (dated November 27 2017) and authorized per signature of our services agreement. Our scope of services included completion of five test pits and two infiltration tests, laboratory testing, engineering analyses, and preparation of this report. PROJECT INFORMATION Mixed use development is planned on property at 4409 NE Sunset Boulevard in Renton, Washington. The property is on the south side of the street and encompasses approximately 0.8 acres. We understand two multi-family buildings are planned with two separate retail spaces. Residential buildings will be three-story structures, with retail buildings anticipated to be one- to two-story structures. Buildings will be supported on conventional spread footing foundations with concrete slab-on-grade floors. Porous pavements are being considered to facilitate stormwater control. SITE CONDITIONS The property is currently vacant and covered with principally grass and weeds. It slopes gently down to the south (from street grade of Sunset Boulevard) with overall elevations change on the order of 5 (+/-) feet. A wetland borders the southern property boundary. SUBSURFACE CONDITIONS Subsurface conditions were characterized by completing five (5) test pits on the site on January 24, 2018. Test pits were advanced to final depths between about 5 and 6 feet below existing ground surface. Approximate locations of the explorations are shown on Figure 1, Exploration Plan. Logs of the test pits are provided in Appendix A. A summary description of observed subgrade conditions is provided below. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 2 Soil Conditions Surface topsoil and/or fill was observed in all test pits and ranged in depth from about 1 to 1.5 feet at the test pit locations. We understand the site was previously developed as a single-family residence, and therefore thicker fill sections may locally be present in other areas. Native soil below the topsoil/fill was fine-medium sand with silt, to silty sand. These soils were in a loose to medium dense condition and extended to depths between 2.5 to 4 feet in the test pits. These soils are interpreted to represent alluvium outwash or reworked sandy glacial till. Below these soils was silty sand with gravel in a medium dense to dense condition that extended to the bottom of the test pits. This soil is considered sandy glacial till. Groundwater Conditions Seepage was observed in all of the test pits at depths between about 2.5 to 3.5 feet. The dense glacial till below the upper sand is considered impermeable to vertical groundwater flow and can cause perched groundwater conditions during the wetter seasons of the year. Groundwater levels will fluctuate due to seasonal precipitation variations and on- and off-site drainage patterns. Geologic Setting Soils within the project area have been classified by the NRCS in the Soil Survey of King County Area, Washington. Surface soils on the site are mapped as Ragnar -Indianola Association. This soil is described as fine sandy loam and loamy fine sand that formed on glacial terraces near streams. Glacial till (Alderwood and Everett soils) are mapped nearby the property. Upper sand soils observed in the test pit appear to confirm the mapped soil type, with dense glacial till below. GEOTECHNICAL DESIGN CONSIDERATIONS The development is considered feasible based on observed soil conditions in the test pits. Properly prepared native soils can be used for support of conventional spread footing foundations, floor slabs, and pavements. Infiltration to assist in stormwater control will be difficult at this site. The dense glacial till at fairly shallow depth will create a barrier to vertical groundwater flow as observed by shallow seepage in test pits. Some infiltration potential is present in the looser upper sands, but the limited thickness of these layers will most likely only support porous pavements or shallow dispersion type infiltration facilities. Recommendations presented in the following sections should be considered general and may require modifications when earthwork and grading occur. They are based upon the subsurface conditions observed in the test pits and the assumption that finish site grades will be similar to existing grades. It should be noted that subsurface conditions across the site may vary from those depicted on the exploration logs and can change with time. Therefore, proper site preparation will depend upon the Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 3 weather and soil conditions encountered at the time of construction. We recommend SSGC review final plans and further assess subgrade conditions at the time of construction, as warranted. General Site Preparation Site grading and earthwork should include procedures to control surface water runoff. Grading the site without adequate drainage control measures may negatively impact site soils, resulting in increased export of impacted soil and import of fill materials, thereby potentially increasing the cost of the earthwork and subgrade preparation phases of the project. Site grading should include removal (stripping) of topsoil and any fill encountered, or very loose or soft soils in building and pavement areas. Subgrades should consist of firm, undisturbed native soils following stripping. General Subgrade Preparation Subgrades in building footprints and pavement areas should consist of firm, undisturbed native soil. We recommend exposed subgrades in building and conventional pavement areas are proofrolled using a large roller, loaded dump truck, or other mechanical equipment to assess subgrade conditions following stripping. Proofrolling efforts should result in the upper 1 foot of subgrade soils in building and conventional pavement areas achieving a compaction level of at least 95 percent of the maximum dry density (MDD) per the ASTM D1557 test method. Wet, loose, or soft subgrades that cannot achieve this compaction level should be removed (over-excavated) and replaced with structural fill. The depth of over-excavation should be based on soil conditions at the time of construction. A representative of SSGC should be present to assess subgrade conditions during proofrolling. Subgrade preparation guidelines for porous (pervious) pavements typically recommend limiting or eliminating compaction of subgrade so densification and reduction of infiltration capacity will not occur. Subgrades in porous (pervious) pavement areas should not be proofrolled following stripping. Probing of porous pavement subgrades should be completed to identify soft or loose areas that should be remediated. Grading and Drainage Positive drainage should be provided during construction and maintained throughout the life of the development. Allowing surface water into cut or fill areas, utility trenches and building footprints should be prevented. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 4 Structural Fill Materials The suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil when it is placed. Soils with higher fines content (soil fraction passing the U.S. No. 200 sieve) will become sensitive with higher moisture content. It is often difficult to achieve adequate compaction if soil moisture is outside of optimum ranges for soils that contain more than about 5 percent fines. Site Soils: Topsoil or organic rich soils are not considered suitable as structural fill. Native soils observed could be suitable for use as structural fill provided they can be moisture conditioned to within optimal ranges. Some of the native soils have considerable fine (silt) content and therefore will be moisture sensitive and difficult to use as structural fill. Optimum moisture is considered within about +/- 2 percent of the moisture content required to achieve the maximum density per the ASTM D-1557 test method. If moisture content is higher or lower than optimum, soils would need to be dried or wetted prior to placement as structural fill. Import Fill Materials: We recommend import structural fill placed during dry weather consist of material which meets the specifications for Gravel Borrow as described in Section 9-03.14(1) of the 2016 Washington State Department of Transportation (WSDOT) Specifications for Road, Bridge, and Municipal Construction (Publication M 41-10). Gravel Borrow should be protected from disturbance if exposed to wet conditions after placement. During wet weather, or for backfill on wet subgrades, import soil suitable for compaction in wetter conditions should be provided. Imported fill for use in wet conditions should 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 2016 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. Structural fill placement and compaction is weather-dependent. Delays due to inclement weather are common, even when using select granular fill. We recommend site grading and earthwork be scheduled for the drier months of the year. Structural fill should not consist of frozen material. Structural Fill Placement We recommend structural fill is placed in lifts not exceeding about 10 inches in loose measure. It may be necessary to adjust lift thickness based on site and fill conditions during placement and compaction. Finer grained soil used as structural fill and/or lighter weight compaction equipment may require significantly thinner lifts to attain required compaction levels. Granular soil with lower fines contents could potentially be placed in thicker lifts if they can be adequately compacted. Structural fill should be compacted to attain the recommended levels presented in Table 1, Compaction Criteria. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 5 Table 1. Compaction Criteria Fill Application Compaction Criteria* Footing areas 95 % Upper 2 feet in pavement areas, slabs and sidewalks, and utility trenches 95 % Below 2 feet in pavement areas, slabs and sidewalks, and utility trenches 92 % Utility trenches or general fill in non-paved or -building areas 90 % *Per the ASTM D 1557 test method. Trench backfill within about 2 feet of utility lines should not be over-compacted to reduce the risk of damage to the line. In some instances the top of the utility line may be within 2 feet of the surface. Backfill in these circumstances should be compacted to a firm and unyielding condition. We recommend fill procedures include maintaining grades that promote drainage and do not allow ponding of water within the fill area. The contractor should protect compacted fill subgrades from disturbance 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 we t soil can be removed. We recommend consideration is given to protecting haul routes and other high traffic areas with free-draining granular fill material (i.e. sand and gravel containing less than 5 percent fines) or quarry spalls to reduce the potential for disturbance to the subgrade during inclement weather. Earthwork Procedures Conventional earthmoving equipment should be suitable for earthwork at this site. Earthwork may be difficult during periods of wet weather or if elevated soil moisture is present. Excavated site soils may not be suitable as structural fill depending on the soil moisture content and weather conditions at the time of earthwork. If soils are stockpiled and wet weather is anticipated, the stockpile should be protected with securely anchored plastic sheeting. If stockpiled soils become wet and unusable, it will become necessary to import clean, granular soils to complete wet weather site work. Wet or disturbed subgrade soils should be over-excavated to expose firm, non-yielding, non-organic soils and backfilled with compacted structural fill. We recommend the earthwork portion of this project be completed during extended periods of dry weather. If earthwork is completed during the wet season (typically October through May) it may be necessary to take extra measures to protect subgrade soils. If earthwork takes place during freezing conditions, we recommend the exposed subgrade is allowed to thaw and re-compacted prior to placing subsequent lifts of structural fill. Alternatively, the frozen soil can be removed to unfrozen soil and replaced with structural fill. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 6 The contractor is responsible for designing and constructing stable, temporary excavations (including utility trenches) as required to maintain stability of excavation sides and bottoms. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. Temporary excavation cuts should be sloped at inclinations of 1.5H:1V (Horizontal:Vertical) or flatter, unless the contractor can demonstrate the safety of steeper cut slopes. Permanent cut and fill slopes should be inclined at 2H:1V, or flatter. A qualified geotechnical engineer and materials testing firm should be retained during the construction phase of the project to observe earthwork operations and to perform necessary tests and observations during subgrade preparation, placement and compaction of structural fill, and backfilling of excavations. Foundations Foundations can be placed on native subgrade soils or on a zone of structural fill above prepared subgrades as described in this report. The following recommendations are for conventional spread footing foundations: Bearing Capacity (net allowable): 2,500 pounds per square foot (psf) for footings supported on firm native soils or structural fill over native subgrades prepared as described in this report. Footing Width (Minimum): 18 inches (Strip) 24 inches (Column) Embedment Depth (Minimum): 18 inches (Exterior) 12 inches (Interior) Settlement: Total: < 1 inch Differential: < 1/2 inch (over 30 feet) Allowable Lateral Passive Resistance: 325 psf/ft* (below 12 inches) Allowable Coefficient of Friction: 0.35* *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 forces. Lateral resistance to footings should be ignored in the upper 12-inches from exterior finish grade unless restricted. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 7 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 foundation level become excessively dry, disturbed, saturated, or frozen, the affected soil should be removed prior to placing concrete. We recommend SSGC observe all foundation subgrades prior to placement of concrete. Foundation Drainage Ground surface adjacent foundations should be sloped away to facilitate drainage. We recommend footing drains are installed around perimeter footings. Footing drains should include a minimum 4- inch diameter perforated rigid plastic or metal drain line installed along the exterior base of the footing. The perforated drain lines should be connected to a tight line pipe that discharges to an approved storm drain receptor. The drain line should be surrounded by a zone of clean, free-draining granular material having less than 5 percent passing the No. 200 sieve or meeting the requirements of section 9-03.12(2) “Gravel Backfill for Walls” in the 2016 WSDOT Standard Specifications for Road, Bridge, and Municipal Construction manual (M41-10). The free-draining aggregate zone should be at least 12 inches wide and wrapped in filter fabric. The granular fill should extend to within 6 inches of final grade where it should be capped with compacted fill containing sufficient fines to reduce infiltration of surface water into the footing drains. Alternately, the ground surface can be paved with asphalt or concrete. Cleanouts are recommended for maintenance of the drain system. On-Grade Floor Slabs On-grade floor slabs should be placed on native soils or structural fill prepared as described in this report. We recommend a modulus subgrade reaction of 225 pounds per square inch per inch (psi/in) for native soil or compacted granular structural fill over properly prepared native soil. We recommend a capillary break is provided between the prepared subgrade and bottom of slab. Capillary break material should be a minimum of 4 inches thick and consist of compacted clean, free- draining, well graded course sand and gravel. The capillary break material should contain less than 5 percent fines, based on that soil fraction passing the U.S. No. 4 sieve. Alternatively, a clean angular gravel such as No. 7 aggregate per Section 9-03.1(4) C of the 2016 WSDOT (M41-10) manual could be used for this purpose. We recommend positive separations and/or isolation joints are provided between slabs and foundations, and columns or utility lines to allow independent movement where needed. Backfill in interior trenches beneath slabs should be compacted in accordance with recommendations presented in this report. A vapor retarder should be considered beneath concrete slabs that will be covered with moisture sensitive or impervious coverings (such as tile, wood, etc.), or when the slab will support equipment or stored Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 8 materials sensitive to moisture. We recommend the slab designer refer to ACI 302 and/or ACI 360 for procedures and limitations regarding the use and placement of vapor retarders. Seismic Considerations Seismic parameters and values in Table 2 are recommended based on the 2015 International Building Code (IBC). Table 2. Seismic Parameters PARAMETER VALUE 2015 International Building Code (IBC) Site Classification1 D Ss Spectral Acceleration for a Short Period 1.408 S1 Spectral Acceleration for a 1-Second Period 0.530g Fa Site Coefficient for a Short Period 1.00 Fv Site Coefficient for a 1-Second Period 1.5 1 Note: In general accordance with 2015 International Building Code, Section 1613.3.1 for risk categories I,II,III. IBC Site Class is based on characteristics of the upper 100 feet of the subsurface profile. Ss, S1, Fa, and Fv values based on the USGS US Seismic Design Maps website using referenced site latitude and longitude. 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. The King County “Liquefaction Susceptibility” Map (Map 11-5, dated May 2010) depicts the site in an area with very low to low liquefaction potential. Native soils at fairly shallow depth consist of dense to very dense glacial till. The risk of liquefaction at this site is considered low for the design level earthquake. Infiltration Characteristics We understand stormwater control will be provided by infiltration facilities, if feasible. Assessment of infiltration was completed per the 2016 King County Surface Water Design Manual (and 2014 DOE Stormwater Management Manual for Western Washington. Two small-scale Pilot Infiltration Tests (PIT) were attempted on the site. However, shallow seepage into the PIT-1 test hole prevented accurate measurements. Seepage was not observed in the PIT-2 test site. Results of the infiltration test is provided in Table 3. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 9 Table 3. Infiltration Rates Test Site and Depth (ft) Soil Type Field Infiltration Rate (in/hr) Corrected Infiltration Rate (in/hr) Correction Factors* (Fg/Ft/Fp) PIT-1, 2 ft Alluvium N/A N/A (0.7/0.5/0.8) PIT-2, 2 ft Alluvium 1.5 0.42 (0.7/0.5/0.8) *Correction Factors from the 2016 King County Surface Design Manual. Calculated and corrected infiltration rates are considered appropriate for the upper soil tested. Gradation tests completed on samples from two of the test pits suggests the upper sand soils are similar across the site and would provide similar infiltration rates. We recommend a preliminary long-term design rate of 0.4 inches per hour (in/hr) is used for design of infiltration facilities located in soils above dense unweathered till. Other correction factors should be applied to the above recommended long-term rate, as required for the type of infiltration system selected. It should be noted that infiltrated water will migrate down to the denser till and then flow laterally downslope towards the wetland (to the south). Shallow perched groundwater was observed in all of the test pits. Infiltration facilities such as trenches or ponds are not considered feasible on this site. Bioswales, pervious pavements, or other shallow dispersion systems could be considered in the upper sand soils, if allowed by the City. Cation Exchange Capacity (CEC) and organic content test were completed on a sample from the base of the PIT-2 site. Test results are summarized in the table below. Table 4. CEC and Organic Content Results Test Location, Sample Number, and Depth CEC Results (milliequivalents) CEC Required* (milliequivalents) Organic Content Results (%) Organic Content Required* (%) PIT-2, S-1, 2 ft 12.1 ≥ 5 4.11 ≥1.0 *Per the 2016 DOE Stormwater Management Manual for Western Washington Organic content and CEC test results satisfy King County and DOE requirements. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 10 Conventional Pavement Sections Subgrades for conventional pavement areas should be prepared as described in the “Subgrade Preparation” section of this report. Subgrades below pavement sections should be graded or crowned to promote drainage and not allow for ponding of water beneath the section. If drainage is not provided and ponding occurs, the subgrade soils could become saturated, lose strength, and result in premature distress to the pavement. In addition, the pavement surfacing should also be graded to promote drainage and reduce the potential for ponding of water on the pavement surface. Minimum recommended pavement sections for conventional pavements are presented in Table 5. Pavement sections in public right-of-ways should conform to City of Edgewood requirements for the road designation. Table 5. Preliminary Pavement Sections Traffic Area Minimum Recommended Pavement Section Thickness (inches) Asphalt Concrete Surface1 Portland Cement Concrete2 Aggregate Base Course3,4 Subbase Aggregate5 Access Drive 3 - 6 12 Parking 2 - 4 12 1 1/2 –inch nominal aggregate hot-mix asphalt (HMA) per WSDOT 9-03.8(1) 2 A 28 day minimum compressive strength of 4,000 psi and an allowable flexural strength of at least 250 psi 3 Crushed Surfacing Base Course per WSDOT 9-03.9(3) 4Although not required for structural support under concrete pavements, a minimum four-inch thick base course layer is recommended to help reduce potentials for slab curl, shrinkage cracking, and subgrade “pumping” through joints 5 Native granular soils compacted to 95% of the ASTM D1557 test method, or Gravel Borrow per WSDOT 9-03.14(1) or Crushed Surfacing Base Course WSDOT 9-03.9(3) Conventional Pavement Maintenance The performance and lifespan of pavements can be significantly impacted by future maintenance. The above pavement sections represent minimum recommended thicknesses and, as such, periodic maintenance should be completed. Proper maintenance will slow the rate of pavement deterioration, and will improve pavement performance and life. Preventative maintenance consists of both localized maintenance (crack and joint sealing and patching) and global maintenance (surface sealing). Added maintenance measures should be anticipated over the lifetime of the pavement section if any existing fill or topsoil is left in-place beneath pavement sections. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 11 Porous Pavements Porous (pervious) asphalt pavements could be considered to facilitate stormwater control provided subgrades consist of the upper sand (alluvium) soil. We recommend pervious pavements are only considered in light duty traffic areas. Porous pavements are not recommended in heavy duty traffic areas, or areas directly underlain by dense glacial till. Infiltration characteristics of site soils are discussed in the “Infiltration Characteristics” section of this report. Porous pavement sections typically use a storage bed of free–draining imported granular material under the surface pavement. The thickness of the storage layer should be sized for the amount of stormwater to be stored and infiltration characteristics of the soil, and can range from about 6 inches to over 18 inches. Storage bed material should conform to the gradation criteria presented in Section 9- 03.9(2) “Permeable Ballast” of the WSDOT Specifications for Road, Bridge, and Municipal Construction (Publication M 41-10). A thin (approximately 2-inch) choker course layer of material meeting criteria of Section 9-03.12(4) of the WSDOT manual should be placed above and below the storage bed material. A geotextile separation fabric could be used in lieu of the lower choker course material. Gradations of the storage bed and choker course layers are presented in Table 6. Table 6. Storage Bed and Choker Course Materials US Standard Sieve Size Total Percent Passing Sieve Storage Bed WSDOT 9-03.9(2) Choker Course WSDOT 9-03.12(4) 2 ½” 99-100 2” 65-100 1 ½” 1” 100 3/4” 40-80 80-100 3/8” 0-40 #4 5 0-4 #200 0-1.5 0-2 We recommend the pervious asphalt layer have a thickness of at least 3-inches. Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 12 The lower choker course layer and initial lift of storage bed material should be compacted with non-vibratory rollers to limit densification of subgrade soils. The upper storage bed and the choker course layer should be compacted to a firm and unyielding condition achieving a compaction level of approximately 92 percent of the maximum dry density per the ASTM D-1557 test method. Porous Pavement Maintenance The performance and lifespan of porous pavements is highly dependent on maintenance. Maintenance of porous pavements will be necessary to retain the drainage characteristics of the asphalt. Regular cleaning of the surface will be required for the porous pavement. Typically, this is completed using vacuum equipment to remove fine sediment and vegetation that will collect on the asphalt surface. It is not practical at this time to estimate the amount of cleaning required for this site as it will be dependent on the amount of vehicle traffic, surrounding vegetation, and cleanliness of adjacent road surfaces leading into the site. However, at least annual cleaning of the surface via vacuuming should be completed with more frequent cleaning if excessive dirt or vegetation is observed collecting on the pavement surface during particular times of the year. Regular sweeping of the asphalt surface could help in maintaining a cleaner surface. Porous pavements typically have slightly coarser average aggregate size (fewer fines) to achi eve the porosity of the asphalt. As such, they have the tendency to ravel and not wear as well as conventional asphalt sections, particularly in high traffic areas and in areas where repetitive short radius turns occur. Regular maintenance will improve the lifespan of the porous pavement section. REPORT CONDITIONS This report has been prepared for the exclusive use of ADF Properties and their agents 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 i mplied, are intended or made. The analysis and recommendations presented in this report are based on observed soil conditions and test results at the indicated locations, and from other geologic information discussed. This report does not reflect variations that may occur 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. This report was prepared for the planned type of development of the site as discussed herein. It is not valid for third party entities or alternate types of development on the site without the express written consent of SSGC. If development plans change we should be notified to review those changes and modify our recommendations as necessary. N South Sound Geotechnical Consulting P.O. Box 39500 Lakewood, WA 98496 (253) 973-0515 Figure 1 – Exploration Plan Sunset Highlands Mixed-Use Renton, WA SSGC Project #18003 Approximate Test Pit Location PIT - 1 TP - 1 PIT-1 PIT - 1 Approximate Infiltration Test Location Scale: NTS Base map from drawing “Profile Exhibit”, by AHBL, Inc) TP-2 Legend TP-4 TP-1 TP-3 TP-1 TP-1 TP-1 PIT-2 TP-5 TP-1 Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 A-1 Appendix A Field Exploration Procedures and Test Pit Logs Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 Field Exploration Procedures8 Our field exploration for this project included five test pits and one infiltration test completed on January 24, 2018. The approximate locations of the explorations are shown on Figure 1, Exploration Plan. The exploration locations were determined by pacing from site features. Ground surface elevations referenced on the logs were inferred from Google Satellite imagery. Test pit locations and elevations should be considered accurate only to the degree implied by the means and methods used. A private excavation company subcontracted to SSGC dug the test pits. Soil samples were collected and stored in moisture tight containers for further assessment and laboratory testing. Explorations were backfilled with excavated soils and tamped when completed. Please note that backfill in the explorations will likely settle with time. Backfill material located in building areas should be re-excavated and recompacted, or replaced with structural fill. The following logs indicate the observed lithology of soils and other materials observed in the explorations at the time of excavation. Where a soil contact was observed to be gradational, our log indicates the average contact depth. Our logs also indicate the approximate depth to groundwater (where observed at the time of excavation), along with sample numbers and approximate sample depths. Soil descriptions on the logs are based on the Unified Soil Classification System. Project: Sunset Apartments SSGC Job # 18003 TEST PIT LOGS PAGE 1 OF 2 Location: Auburn, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting TP-1 TO TP-5 Logged by: THR Test Pit TP-1 Depth (feet) Material Description 0 – 1 1 – 3.5 3.5 - 5.5 Fill/Topsoil: Silt, sand, and gravel over about 3 inches of topsoil. SAND with some silt: Loose to medium dense, moist to wet, reddish brown. (Sample S-1 @ 2 feet) Silty SAND with gravel: Medium dense to dense, moist, gray. (Sandy Glacial Till) Test pit completed at approximately 5.5 feet on 1/24/18. Seepage observed at about 3.5 feet at time of excavation. Approximate surface elevation: 398 feet Test Pit TP-2 Depth (feet) Material Description 0 – 1 1 – 4 4 - 6 Topsoil: Silty sand with organics: Loose, moist, dark brown. SAND with some silt: Loose to medium dense, moist to wet, reddish brown. SAND with silt and gravel: Medium dense to dense, moist, gray. (Sandy Glacial Till) Test pit completed at approximately 6 feet on 1/24/18. Seepage observed at about 3.5 feet at time of excavation. Approximate surface elevation: 396 feet Test Pit TP-3 Depth (feet) Material Description 0 – 1.5 1.5 – 2.5 2.5 - 5 Fill: Silt, sand, and gravel with some organics: Loose, moist, dark brown. SAND with some silt: Loose to medium dense, moist to wet, reddish brown. SAND with silt and gravel: Medium dense to dense, moist, gray. (Sandy Glacial Till) Test pit completed at approximately 5 feet on 1/24/18. Seepage observed at about 2.5 feet at time of excavation. Approximate surface elevation: 396 feet Project: Sunset Apartments SSGC Job # 18003 TEST PIT LOGS PAGE 2 OF 2 Location: Auburn, WA TEST PIT LOGS FIGURE A-1 South Sound Geotechnical Consulting TP-1 TO TP-5 Logged by: THR Test Pit TP-4 Depth (feet) Material Description 0 – 1.5 1.5 – 3.5 3.5 - 6 Fill: Silt, sand, and gravel with some organics: Loose, moist, dark brown. Silty SAND with some gravel and occasional cobble: Medium dense, moist, grayish brown. SAND with silt and gravel: Medium dense to dense, moist, gray. (Sandy Glacial Till) Test pit completed at approximately 6 feet on 1/24/18. Seepage observed at about 3 feet at time of excavation. Approximate surface elevation: 397 feet Test Pit TP-5 Depth (feet) Material Description 0 – 1 1 – 2.5 2.5 - 5 Fill: Silt, sand, and gravel with some organics: Loose, moist, dark brown. Silty SAND with some gravel and occasional cobble: Medium dense, moist, grayish brown. SAND with silt and gravel: Medium dense to dense, moist, gray. (Sandy Glacial Till) Test pit completed at approximately 5 feet on 1/24/18. Seepage observed at about 2.5 feet at time of excavation. Approximate surface elevation: 398 feet Geotechnical Engineering Report SSGC South Lawrence Avenue Self Storage South Lawrence Avenue at South 19th Street Tacoma, Washington SSGC Project No. 17051 July 18, 2017 B-1 Appendix B Laboratory Testing and Results Geotechnical Engineering Report SSGC Sunset Highlands Mixed-Use Development NE Sunset Boulevard Renton, Washington SSGC Project No. 18003 February 12, 2018 B-1 Laboratory Testing Select soil samples were tested for organic content and cation exchange capacity (CEC) by Northwest Agricultural Consultants of Kennewick, Washington. Gradation tests were completed by Construction Testing Laboratories (CTL) of Puyallup, Washington. Results of the laboratory testing are included in this appendix. Report shall not be reproduced except in full without the written approval of the Laboratory. Report pertains only to the material tested.Tested By: B. Rowden Checked By: C. Pedersen Particle Size Distribution Report ASTM C-117,C136 PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 3.8 5.1 49.8 31.1 10.26 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO) Material Description Atterberg Limits Classification Remarks Source of Sample: TP-5 Sample Number: 18-098 Date: Client: Project: Project No:Figure Grab Sample, S-1 Sampled at 2'3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100 #200 100.0 99.5 98.4 96.2 92.2 84.6 61.0 24.0 13.9 10.2 Report: #02 Sampled by: Client South Sound Geotechnical Sunset Apartments (JO #18003) 7073 PL=LL=PI= USCS=AASHTO= *(no specification provided) 01-31-18 Construction Testing Laboratories 400 Valley Ave. NE, Suite #102 Puyallup WA, 98372 Tel. (253) 383-8778 Report shall not be reproduced except in full without the written approval of the Laboratory. Report pertains only to the material tested.Tested By: B. Rowden Checked By: C. Pedersen Particle Size Distribution Report ASTM C-117,C136 PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 0.6 2.6 47.8 39.5 9.56 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200SIEVE PERCENT SPEC.*PASS? SIZE FINER PERCENT (X=NO) Material Description Atterberg Limits Classification Remarks Source of Sample: TP-1 Sample Number: 18-097 Date: Client: Project: Project No:Figure Grab Sample, S-1 Sampled at 2'3/8" #4 #8 #16 #30 #50 #100 #200 100.0 99.4 97.6 91.6 70.8 28.0 13.0 9.5 Report: #01 Sampled by: Client South Sound Geotechnical Sunset Apartments (JO #18003) 7073 PL=LL=PI= USCS=AASHTO= *(no specification provided) 01-31-18 Construction Testing Laboratories 400 Valley Ave. NE, Suite #102 Puyallup WA, 98372 Tel. (253) 383-8778 2545 W Falls Avenue Kennewick, WA 99336 509.783.7450 www.nwag.com lab@nwag.com Sample ID Organic Matter Cation Exchange Capacity IT-2, S-1 4.11% 12.1 meq/100g Method ASTM D2974 EPA 9081 South Sound Geotechnical Consulting PO Box 39500 Lakewood, WA 98496 Report: 43567-1 Date: February 5, 2018 Project No: 18003 Project Name: Sunset Highlands UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels Less than 5% finesC Cu  4 and 1  Cc  3E GW Well-graded gravelF Cu  4 and/or 1  Cc  3E GP Poorly graded gravelF Gravels with Fines More than 12% finesC Fines classify as ML or MH GM Silty gravelF,G, H Fines classify as CL or CH GC Clayey gravelF,G,H Sands 50% or more of coarse fraction passes No. 4 sieve Clean Sands Less than 5% finesD Cu  6 and 1  Cc  3E SW Well-graded sandI Cu  6 and/or 1  Cc  3E SP Poorly graded sandI Sands with Fines More than 12% finesD Fines classify as ML or MH SM Silty sandG,H,I Fines Classify as CL or CH SC Clayey sandG,H,I Fine-Grained Soils 50% or more passes the No. 200 sieve Silts and Clays Liquid limit less than 50 inorganic PI  7 and plots on or above “A” lineJ CL Lean clayK,L,M PI  4 or plots below “A” lineJ ML SiltK,L,M organic Liquid limit - oven dried  0.75 OL Organic clayK,L,M,N Liquid limit - not dried Organic siltK,L,M,O Silts and Clays Liquid limit 50 or more inorganic PI plots on or above “A” line CH Fat clayK,L,M PI plots below “A” line MH Elastic SiltK,L,M organic Liquid limit - oven dried  0.75 OH Organic clayK,L,M,P Liquid limit - not dried Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW -GM well-graded gravel with silt, GW -GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW -SM well-graded sand with silt, SW -SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 6010 2 30 DxD )(D F If soil contains  15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains  15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains  30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains  30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI  4 and plots on or above “A” line. O PI  4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line.