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HomeMy WebLinkAboutEX_07_RS_Geotech_Report__210429_v1INNOVATIVE GEO-SERVICES, LLC ENGINEERING GEOLOGY SERVICES ENGGEOLOGIST.COM 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com HS Construction and Investments, LLC April 29, 2021 5140 S 172nd Lane Seatac, Washington 98188 Attn: Raman Sidhu Singh 6th ST Short Plat Geotechnical Evaluation Address: 615 Nile AV NE Renton, WA Parcel No. 1023059026 Site Visit 4/16/2021 INTRODUCTION It is the intent of this evaluation to describe the surface and subsurface conditions on the nearly 0.44-acre residential parcel (approx. 19,351 sf) located on the west side of Nile AV NE and north of NE 6th ST in Renton, WA. Development plans call for creating 1 new single family residential lot with access from NE 6th Street near the southeast corner of the new lot. The parent parcel is rectangular shaped and is approximately 200 ft long (E/W) and approximately 100 ft. (N/S) wide. The parent parcel will be divided into 2 residential lots which will be 0.24 to 0.20 acres in size with an existing residential structure on the parent lot. The property has a gentle 11% grade to the southwest. Topographically the parcel has 25 ft. of elevation change over 225 ft. The surface is covered with lawn grasses and some berry vines. No geologic or erosion hazards occur on the property as defined by the City of Renton, Chapter 4-3-050, Critical Areas Regulations. Development plans are to create 2 single-family home on the 0.44-acre property. The new homes will utilize a municipal water and sewer, and an on-site storm water control system. The new lot will be situated west of the existing home. This evaluation is for the exclusive use of HS Construction and Investments, LLC, their consultants and contractors for the intended purpose described. Site observations and exploration methods applied and described in this evaluation are standard practices for the industry. Sources of information cited are generally accepted resources when utilized in conjunction with field reconnaissance as confirmation. Opinions are based on use of these standardized practices to adequately characterize the local surficial geology and general conditions at the site. An Engineering Geologist from Innovative GEO-Services, LLC (IGS) visited the site on April 16th, 2021 to observe site conditions, explore near surface soil textures and conditions relating to the development of the residential lots which will be accessed from Nile AV NE to the eastern lot and from NE 6th ST. for the western lot. Preliminary site plans and topography were provided by AP Consulting Engineers, PLLC. Additional information was obtained from the King County GIS system. Exhibit 7 RECEIVED 01/04/2022 JDing PLANNING DIVISION DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 2 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com SITE AND PROJECT DESCRIPTION The residential parcel is a nearly rectangular shaped property with two distinct topographic areas. The eastern portion of land is level to gently sloping to the west while the western lot slopes to the southwest with gentle grades. The eastern parcel contains a single-family residential structure which is currently being remodeled. The western lot is undeveloped. Access to the property is from SE 270th ST near the northeast corner of the parcel. Development plans show the new home will be situated in the north third of the parcel where the surface is nearly level. The proposed development is surrounded by similar residential development and access. The surrounding homes are typically wood framed structures which utilize conventional foundation systems. SINGH 6TH STREET PLAT SITE PLAN EXPLORATION MAP Site Plan Provided by AP Consulting Engineers, PLLC (nts) IGS SOIL PITS (4/16/2021) SP 3 SP 4 EXISTING HOUSE 11% DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 3 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com SITE SOILS The Natural Resource Conservation Service (NRCS) describe the soils across the parcel as Alderwood gravelly sandy loam (AgC). NRCS SOIL MAPPING DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 4 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com NRCS SOIL CLASSIFICATION Alderwood AgC – Alderwood gravelly sandy loam, 6 – 15 percent slopes The Alderwood gravelly sandy loam is moderately well drained. It formed in glacial till on broad uplands. It is extensive in the Lake Tapps area. Predominant native vegetation is made up of hardwoods and conifers. The typical elevation of this soil series ranges from 200 to 800 feet. In a typical soil profile, a mat of undecomposed needles and wood fragments rests upon a 1 ½ inch thick very dark grayish brown gravelly sandy loam surface layer. The subsoil and the upper part of the substratum, to a depth of 38 inches, are dark yellowish brown, brown, and dark grayish brown gravelly sandy loam. The lower portion of the substratum, to a depth of more than 60 inches, is weakly cemented compact glacial till. A seasonal water table is perched above the very slowly permeable, weakly cemented and compact part of the substratum during periods of heavy rainfall. However, the perched water table is of short duration because the water flows laterally above this layer to seeps at the bottom of slopes. Very few roots penetrate this dense substratum. The available water capacity is low. Surface runoff is medium, and the erosion hazard is moderate. This rolling Alderwood soil is moderately well drained. It formed in glacial till on broad uplands. It is extensive in the Lake Tapps area. Vegetation is hardwoods and conifers. Elevation ranges from 200 to 800 feet. The mean annual precipitation is about 35 inches, mean annual air temperature is about 50 degrees F, and the frost- free season averages about 180 days. Individual soil areas average about 125 acres in size. Most slopes average about 8 percent. Granite boulders and stones are strewn across some slopes. Included with this soil in mapping are small areas of better drained Indianola loamy sand on the side slopes and poorer drained Norma sandy loam or Dupont muck in troughs. In addition, some areas of Alderwood gravelly sandy loam and Kapowsin gravelly loam, zero to six percent slopes, are included. In a typical soil profile, a mat of undecomposed needles and wood fragments rests upon a 1 ½ inch thick very dark grayish brown gravelly sandy loam surface layer. The subsoil and the upper part of the substratum, to a depth of 38 inches, are dark yellowish brown, brown, and dark grayish brown gravelly sandy loam. The lower parrot of the substratum, to a depth of more than 60 inches, is weakly cemented compact glacial till. Reaction is medium acid. The water table is perched above the very slowly permeable, weakly cemented and compact part of the substratum during periods of heavy rainfall. However, the perched water table is of short duration because the water flows laterally above this layer to seeps at the bottom of slopes. Very few roots penetrate this dense substratum. The available water capacity is low. Surface runoff is medium, and the erosion hazard is moderate. Because of its proximity to urban centers, this Alderwood soil is subject to urbanization pressure. The soil has an inherent ability to support a large load. Soil slope and the weakly cemented, compact substratum are its limiting features. In areas of moderate to high population density, onsite sewage disposal systems often fail or do not function properly during periods of rainfall in winter. Excavation for basements and utility lines is difficult to cover excavated soil material. DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 5 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com SITE GEOLOGY According to maps from the Washington Division of Geology and Earth Resources, this region of King County lies in the glacial lowland area of multiple glacial advance and recessional periods. The surface deposits are described as Proglacial stratified drift deposits of gravelly sands, fine sands described as ground moraine deposits. Moraines may form through a number of processes, depending on the characteristics of sediment, the dynamics on the ice, and the location on the glacier in which the moraine is formed. Moraine forming processes may be loosely divided into passive and active. Passive processes involve the placing of chaotic supraglacial sediments onto the landscape with limited reworking, typically forming hummocky moraines. These moraines are composed of supraglacial sediments from the ice surface. Active processes form or rework moraine sediment directly by the movement of ice, known as glacio-tectonism. These forms push moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment. Moraine may also form by the accumulation of sand and gravel deposits from glacial streams emanating from the ice margin. These fan deposits may coalesce to form a long moraine bank marking the ice margin. Several processes may combine to form and rework a single moraine, and most moraines record a continuum of processes. Ground moraines are till-covered areas with irregular topography and no ridges, often forming gently rolling hills or plains. They are accumulated at the base of the ice as lodgment till, but may also be deposited as the glacier retreats. In alpine glaciers, ground moraines are often found between the two lateral moraines. Ground moraines may be modified into drumlins by the overriding ice. Geologic Map of King County (Excerpt) Compiled by Booth, Troost & Wisher, March 2007 Qvt SINGH 6TH ST PLAT DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 6 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com City of Renton Critical Area Regulations 4-3-050B APPLICABILITY: 1. Lands to Which These Regulations Apply and Non-regulated Lands: The following critical areas are regulated by this Section. Multiple development standards may apply to a site feature based upon overlapping critical area(s) and/or critical area classifications: a. Flood hazard areas. b. Steep slopes (must have a minimum vertical rise of fifteen feet (15')), landslide hazards, erosion hazards, seismic hazards, and/or coal mine hazards or on sites within fifty feet (50') of steep slopes, landslide hazards, erosion hazards, seismic haz ards, and/or coal mine hazards classified under RMC 4-3-050G5a which are located on abutting or adjacent sites. c. Habitat Conservation Areas. d. Streams and Lakes. All applicable requirements of this Section apply to Class F, Np, and Ns water bodies, as defined in subsection G7 of this Section or on sites within one hundred feet (100') of Class F, Np, and Ns water bodies, except Type S water bodies, inventoried as “Shorelines of the State,” are not subject to this Section, and are regulated in RMC 4-3-090, Shoreline Master Program Regulations, and RMC 4-9-190, Shoreline Permits. e. Wellhead Protection Areas. f. Wetlands, Categories I, II, III, and IV or on sites within two hundred feet (200') of Category I, II, III, and IV wetlands. Wetlands created or restored as a part of a mitigation project are regulated wetlands. Regulated wetlands do not include those artificial wetlands intentionally created from no wetland sites, including, but not limited to, irrigation and drainage ditches, grass-lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990, that were unintentionally created as a result of the construction of a road, street, or h ighway. g. Sites Separated from Critical Areas, Nonregulated: As determined by the Administrator, these regulations may not apply to development proposed on sites that are separated from critical areas by pre-existing, intervening, and lawfully created structures, roads, or other substantial existing improvements. For the purposes of this Section, the intervening lots/parcels, roads, or other substantial improvements shall be found to: i. Separate the subject upland property from the critical area due to their height or width; and ii. Substantially prevent or impair delivery of most functions from the subject upland property to the critical area. Such determination and evidence shall be included in the application file. Public notification shall be given as follows: (a) For applications that are not subject to notices of application pursuant to Chapter 4 -8 RMC, notice of the buffer determination shall be given by posting the site and notifying parties of record, if any, in accordance with Chapter 4-8 RMC. (b) For applications that are subject to notices of application, the buffer determination or request for determination shall be included with notice of application. Upon determination, notification of parties of record, if any, shall be made. DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 7 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com Findings Based on our site observations, explorations and research it is our opinion there are no geologic hazards as defined by the City of Renton occur on or near the proposed development. The proposed new residential lots are proposed across gentle grades. The property is underlain by a massive deposit of glacial till. This glacial till dominates the regions and consists of a very dense, nearly impermeable compressed silty sand and gravel. The upland area and surface deposits are consistent with weathered glacial till. No steep slopes as defined by the City occur on or adjacent to the property. Our site observations and research found no indications of current or past morphology consistent with landslide activity. Site Preparation Preparation of the project site should involve erosion control, temporary drainage, clearing, stripping, cutting, filling, excavations, and subgrade compaction. Erosion Control: Before new construction begins, an appropriate erosion control system should be installed. This system should collect and filter all surface run off through either silt fencing or a series of properly placed and secured straw bales. We anticipate a system of berms and drainage ditches around construction areas will provide an adequate collection system. If silt fencing is selected as a filter, this fencing fabric should meet the requirements of WSDOT Standard Specification 9-33.2 Table 3. In addition, silt fencing should embed a minimum of 6 inches below existing grade. If straw baling is used as a filter, bales should be secured to the ground so that they will not shift under the weight of retained water. Regardless of the silt filter selected, an erosion control system requires occasional observation and maintenance. Specifically, holes in the filter and areas where the filter has shifted above ground surface should be replaced or repaired as soon as they are identified. Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or near-surface water within the construction zones before stripping begins. Because the selection of an appropriate drainage system will depend on the water quantity, season, weather conditions, construction sequence, and contractor's methods, final decisions regarding drainage systems are best made in the field at the time of construction. Based on our current understanding of the construction plans, surface, and subsurface conditions, we anticipate that curbs, berms, or ditches placed around the work areas will adequately intercept surface water runoff. Clearing and Stripping: After surface and near-surface water sources have been controlled, the construction areas should be cleared and stripped of all duff and topsoil. Also, it should be realized that if the stripping operation proceeds during wet weather, a generally greater stripping depth might be necessary to remove disturbed moisture-sensitive soils; therefore, stripping is best performed during a period of dry weather. Site Excavations: Based on our explorations, we expect site excavation will encounter dense to very dense gravelly sand with cobbles. Special teeth on excavators or rippers on bulldozers may be needed to rapidly excavate these soils. Excavations over 4 ft in depth may require side wall support. Dewatering: Explorations did not observe groundwater at elevations where earth work activity will occur, nor do we expect that groundwater will be present in excavations for the planned development. However, DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 8 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com if groundwater is encountered, we anticipate that an internal system of ditches, sump holes, and pumps will be adequate to temporarily dewater excavations. Temporary Cut Slopes: All temporary soil slopes associated with site cutting or excavations should be adequately inclined to prevent sloughing and collapse. Temporary cut slopes in loose gravelly sand should be no steeper than 1½H:1V and should conform to WISHA regulations Subgrade Compaction: Exposed subgrades for footings and floors should be compacted to a firm, unyielding state before new concrete or fill soils are placed. Any localized zones of looser granular soils observed within a subgrade should be compacted to a density commensurate with the surrounding soils. In contrast, any organic, soft, or pumping soils observed within a subgrade should be over excavated and replaced with a suitable structural fill material. Site Filling: Our conclusions regarding the reuse of on-site soils and our comments regarding wet-weather filling are presented subsequently. Regardless of soil type, all fills should be placed and compacted according to our recommendations presented in the Structural Fill section of this report. Specifically, building pad fill soil should be compacted to a uniform density of at least 95 percent (based on ASTM:D - 1557). On-Site Soils: We offer the following evaluation of these on-site soils in relation to potential use as structural fill: • Surficial Organic Soils: The duff and topsoil mantling some of the sites are not suitable for use as structural fill under any circumstances, due to their high organic content. Consequently, these materials can be used only for non-structural purposes, such as in landscaping areas. • Weathered and Unweather Glacial Till: The weathered and weathered glacial till layers are sensitive to moisture content variations. These soils can be reused during dry conditions but will become increasingly difficult to reuse as conditions become wetter. Permanent Slopes: Permanent cut slopes and fill slopes are not anticipated or shown on current designs. If permanent cut or fill slopes are incorporated, they should be adequately inclined to minimize long-term raveling, sloughing, and erosion. We generally recommend no permanent slopes be steeper than 2H:1V. For all soil types, the use of flatter slopes (such as 2½H:1V) would further reduce long-term erosion and facilitate revegetation. Spread Footings In our opinion, conventional spread footings will provide adequate support for the residential structures if the subgrades are properly prepared. Footing Depths and Widths: For frost and erosion protection, the bases of all exterior footings should bear at least 18 inches below adjacent outside grades, whereas the bases of interior footings need bear only 12 inches below the surrounding slab surface level. To reduce post-construction settlements, continuous (wall) and isolated (column) footings should be at least 18 and 24 inches wide, respectively. DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 9 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com Bearing Subgrades: Footings should bear on medium dense or denser, undisturbed native soils which have been stripped of surficial organic soils, or on properly compacted structural fill which bears on undisturbed native soils which have been stripped of surficial organic soils. In general, before footing concrete is placed, any localized zones of loose soils exposed across the footing subgrades should be compacted to a firm, unyielding condition, and any localized zones of soft, organic, or debris-laden soils should be over excavated and replaced with suitable structural fill. Care should be taken in identifying pockets of loose fill, placed during prior grading activities, which may be scattered across the site. Subgrade Observation: All footing subgrades should consist of firm, unyielding, native soils or structural fill materials compacted to a density of at least 95 percent (based on ASTM:D-1557). Footings should never be cast atop loose, soft, or frozen soil, slough, debris, existing uncontrolled fill, or surfaces covered by standing water. Bearing Pressures: For static loading, footings which bear on properly prepared subgrades can be designed for a maximum allowable soil bearing pressure of 2,000 pounds per square foot (psf). A one- third increase in allowable soil bearing capacity may be used for short-term loads created by seismic or wind related activities. Footing Settlements: Assuming structural fill soils are compacted to a medium dense or denser state, we estimate that total post-construction settlements of properly designed footings bearing on properly prepared subgrades will not exceed 1 inch. Differential settlements for comparably loaded elements may approach one-half of the actual total settlement over horizontal distances of approximately 50 feet. Footing Backfill: To provide erosion protection and lateral load resistance, it is recommended all footing excavations be backfilled on both sides of the footings and stem walls after the concrete has cured. Either imported structural fill or non-organic on-site soils can be used for this purpose, contingent on suitable moisture content at the time of placement. Regardless of soil type, all footing backfill soil should be compacted to a density of at least 90 percent (based on ASTM:D-1557). Lateral Resistance: Footings that have been properly backfilled as recommended above will resist lateral movements by means of passive earth pressure and base friction. We recommend using an allowable passive earth pressure of 300 pcf in the glacial till onsite, 250 pcf in the glacial outwash onsite, and 160 pcf for the silt onsite. We recommend an allowable base friction coefficient of 0.35 for glacial till and outwash, and 0.20 for silt. Slab-On-Grade Floors Soil-supported slab-on-grade floors can be used in the proposed structures if the subgrades are properly prepared. We offer the following comments and recommendations concerning slab-on-grade floors. Floor Subbase: Structural fill subbases do not appear to be needed under soil-supported slab-on-grade floors at the site. However, the final decision regarding the need for subbases should be based on actual subgrade conditions observed at the time of construction. If a subbase is needed, all subbase fills should be compacted to a density of at least 95 percent (based on ASTM:D-1557). Capillary Break and Vapor Barrier: To retard the upward wicking of groundwater beneath the floor slab, we recommend that a capillary break be placed over the subgrade. Ideally, this capillary break wo uld consist of a 4-inch-thick layer of pea gravel or other clean, uniform, well-rounded gravel, such as “Gravel DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 10 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com Backfill for Drains” per WSDOT Standard Specification 9-03.12(4), but clean angular gravel can be used if it adequately prevents capillary wicking. In addition, a layer of plastic sheeting (such as Crosstuff, Visqueen, or Moistop) should be placed over the capillary break to serve as a vapor barrier. During subsequent casting of the concrete slab, the contractor should exercise care to avoid puncturing this vapor barrier. Drainage Systems In our opinion, the proposed new structures should be provided with permanent drainage systems to reduce the risk of future moisture problems. We offer the following recommendations and comments for drainage design and construction purposes. Perimeter Drains: Site soil characteristics observed indicate the use of footing drains is optional. Footing drains if utilized are a perimeter drain system to collect seepage water. This drain should consist of a 4- inch-diameter perforated pipe within an envelope of pea gravel or washed rock, extending at least 6 inches on all sides of the pipe, and the gravel envelope should be wrapped with filter fabric to reduce the migration of fines from the surrounding soils. Ideally, the drain invert would be installed no more than 8 inches above the base of the perimeter footings. Subfloor Drains: Based on the groundwater conditions observed in our site explorations, we do not infer a need for subfloor drains. Discharge Considerations: If possible, all storm water drains should discharge to an approved infiltration system or other suitable location by gravity flow. Check valves should be installed along any drainpipes that discharge to a sewer system, to prevent sewage backflow into the drain system. Runoff Water: Roof-runoff and surface-runoff water should not discharge into the perimeter drain system. Instead, these sources should discharge into separate tight line pipes and be routed away from the building to a storm drain or other appropriate location. Grading and Capping: Final site grades should slope downward away from the buildings so that runoff water will flow by gravity to suitable collection points, rather than ponding near the building. Ideally, the area surrounding the building would be capped with concrete, asphalt, or low-permeability (silty) soils to minimize or preclude surface-water infiltration. Infiltration Rates: Soil characteristics and grain size observed in two soil pits excavated across the parcel found the native soil to be a fine sand and silt with some gravel (weathered Glacial Till) transitioning to a very dense gray glacial till. Raw infiltration rates in the upper 36 to 48 inches of soil can anticipate 10 in/hr. or less in the Alderwood soil based on the observed soil and grain size. We recommend storm water control plans use surface dispersion to the north side of the new home. Soil infiltration logs are attached to this report. Structural Fill The term "structural fill" refers to any placed under foundations, retaining walls, slab-on-grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and recommendations concerning structural fill are presented in the following paragraphs. DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 11 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com Materials: Typical structural fill materials include clean sand, gravel, pea gravel, washed rock, crushed rock, well-graded mixtures of sand and gravel (commonly called "gravel borrow" or "pit-run"), and miscellaneous mixtures of silt, sand, and gravel. Recycled asphalt, concrete, and glass, which are derived from pulverizing the parent materials, are also potentially useful as structural fill in certain applications. Soils used for structural fill should not contain any organic matter or debris, nor any individual particles greater than about 6 inches in diameter. Fill Placement: Clean sand, gravel, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be thoroughly compacted with a mechanical compactor. Compaction Criteria: Using the Modified Proctor test (ASTM:D-1557) as a standard, we recommend that structural fill used for various on-site applications be compacted to the following minimum densities: Fill Application Minimum Compaction Footing subgrade and bearing pad Foundation backfills Slab-on-grade floor subgrade and subbase 95 percent 90 percent 95 percent Subgrade Observation and Compaction Testing: Regardless of material or location, all structural fills should be placed over firm, unyielding subgrades prepared in accordance with the Site Preparation section of this report. The condition of all subgrades should be observed by geotechnical personnel before filling or construction begins. Also, fill soil compaction should be verified by means of in-place density tests performed during fill placement so that adequacy of soil compaction efforts may be evaluated as earthwork progresses. Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the "fines" content (that soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points above or below optimum. For fill placement during wet-weather site work, we recommend using "clean" fill, which refers to soils that have a fines content of 5 percent or less (by weight) based on the soil fraction passing the U.S. No. 4 Sieve. RECOMMENDED ADDITIONAL SERVICES Because the future performance and integrity of the structural elements will depend largely on proper site preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. Consequently, we recommend that IGS be retained to provide the following post-report services: • Review all construction plans and specifications to verify that our design criteria presented in this report have been properly integrated into the design. • Prepare a letter summarizing all review comments (if required by the City of Renton). DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 12 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com • Check all completed subgrades for footings and slab-on-grade floors before concrete is poured, to verify their bearing capacity; and • Prepare a post-construction letter summarizing all field observations, inspections, and test results (if required). CLOSURE The conclusions and recommendations presented in this report are based, in part, on the explorations that we performed for this study; therefore, if variations in the subgrade conditions are observed at a later time, we may need to modify this report to reflect those changes. Also, because the future performance and integrity of the project elements depend largely on proper initial site preparation, drainage, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. IGS is available to provide geotechnical monitoring of soils throughout construction. Innovative GEO-Services, LLC Rex Humphrey, L.E.G. Engineering Geologist 04/30/2021 DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 13 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com Soil Log Number: 3 Sheet 1 of 1 1. Site Address: 56XX NE 6th Street, Renton 2. Parcel Number: 102305170 3. Site Description: Glacial Terrace 4. List methods used to expose, sample, & test soils: Excavation of Test Pits and Field Examination 5. Number of test holes logged: 4 6. Saturated Percolation Rate: 10 in/hr. 7. Has fill material been placed over the proposed infiltration area? No 8. SCS Soil Series Alderwood 9. Hydrologic Soil Group C 10. Depth to seasonal high water: ➢ 4 ft. 11. Current water depth > 4 ft. 12. Depth to impermeable layer: >/= 4 ft. 13. Soil profile description: 1 – Dk Brown, Sandy Loam w/ gravel 2 - Lt Brown Sandy loam w/ gravel 3 – Glacial Till, gray, dry Horizon Depth Textural Class Mottling Induration 1 2 3 0 – 4 in. 4 - 36 in. 36 – 48 in IV IV IV - - Slight . I hereby state that I prepared this report and conducted or supervised the performance of related work. I state that I am qualified to do this work. I represent my work to be complete and accurate within the bounds of uncertainty inherent to the practice of soil science, and to be suitable for its intended use. Date: 04/29/2021 Registration No.: 1811 Stamp 4/29/2021 DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 Singh 6th Street Short Plat Geotechnical Evaluation April 29, 2021 Page 14 17903 82nd ST E, Bonney Lake, WA 98391 253 279-4205 c rex@enggeologist.com SOIL TEST PIT LOGS SOIL TEST PITS 1 THROUGH 4 DocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 494.5 493.0 492.0 491.5 CL- ML SP- SC SP- SM SP 0.5 2.0 3.0 3.5 (CL-ML) SOD TOPSOIL, ORGANIC, SANDY, SOME GRAVEL, DARK BROWN, DRY (SP-SC) SAND, GRAVELLY, BROWN, ROCKY, LOOSE TO MEDIUM DENSE, DRY (SP-SM) SAND, GRAVELLY, TAN, MEDIUM DENSE, DRY (SP) GLACIAL TILL, GRAY, SLIGHTLY MOTTLED, ROCKY, DRY Bottom of test pit at 3.5 feet. NOTES GROUND ELEVATION 495 ft msl LOGGED BY RBH EXCAVATION METHOD MiniExcavator TEST PIT SIZE 2' X 4' EXCAVATION CONTRACTOR Owner GROUND WATER LEVELS: CHECKED BY RBH DATE STARTED 4/16/21 COMPLETED 4/16/21 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---DEPTH(ft)0 1 2 3 SAMPLE TYPENUMBERPAGE 1 OF 1 SOIL PIT NUMBER TP 1 PROJECT NAME Singh 6th Street Short Plat PROJECT LOCATION 56XX NE 6th Street, Renton CLIENT Raman Sidhu PROJECT NUMBER 042113 GENERAL BH / TP / WELL - GINT STD US.GDT - 4/29/21 14:17 - F:\2021 PROJECTS\032112 SIDHU PLAT GEO\DATA\SIGNH 6TH STREET SHORT PLAT SOIL PITS.GPJINNOVATIVE GEO-SERVICES, LLC Engineering Geology and Septic Design 253 279-4205 rex@enggeologist.com U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 489.0 488.5 487.5 487.0 CL- ML SP- SC SP- SM SP 1.0 1.5 2.5 3.0 (CL-ML) SOD TOPSOIL, ORGANIC, SANDY, SOME GRAVEL, DARK BROWN, DRY (SP-SC) SAND, GRAVELLY, BROWN, ROCKY, LOOSE TO MEDIUM DENSE, DRY (SP-SM) SAND, GRAVELLY, TAN, MEDIUM DENSE, DRY (SP) GLACIAL TILL, GRAY, SLIGHTLY MOTTLED, ROCKY, DRY Bottom of test pit at 3.0 feet. NOTES GROUND ELEVATION 490 ft msl LOGGED BY RBH EXCAVATION METHOD MiniExcavator TEST PIT SIZE 2' X 4' EXCAVATION CONTRACTOR Owner GROUND WATER LEVELS: CHECKED BY RBH DATE STARTED 4/16/21 COMPLETED 4/16/21 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---DEPTH(ft)0 1 2 3 SAMPLE TYPENUMBERPAGE 1 OF 1 SOIL PIT NUMBER TP 2 PROJECT NAME Singh 6th Street Short Plat PROJECT LOCATION 56XX NE 6th Street, Renton CLIENT Raman Sidhu PROJECT NUMBER 042113 GENERAL BH / TP / WELL - GINT STD US.GDT - 4/29/21 14:17 - F:\2021 PROJECTS\032112 SIDHU PLAT GEO\DATA\SIGNH 6TH STREET SHORT PLAT SOIL PITS.GPJINNOVATIVE GEO-SERVICES, LLC Engineering Geology and Septic Design 253 279-4205 rex@enggeologist.com U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 484.5 483.0 482.5 482.0 CL- ML SP- SC SP- SM SP 0.5 2.0 2.5 3.0 (CL-ML) SOD TOPSOIL, ORGANIC, SANDY, SOME GRAVEL, DARK BROWN, DRY (SP-SC) SAND, GRAVELLY, BROWN, ROCKY, LOOSE TO MEDIUM DENSE, DRY (SP-SM) SAND, GRAVELLY, TAN, MEDIUM DENSE, DRY (SP) GLACIAL TILL, GRAY, SLIGHTLY MOTTLED, ROCKY, DRY Bottom of test pit at 3.0 feet. NOTES GROUND ELEVATION 485 ft msl LOGGED BY RBH EXCAVATION METHOD MiniExcavator TEST PIT SIZE 2' X 4' EXCAVATION CONTRACTOR Owner GROUND WATER LEVELS: CHECKED BY RBH DATE STARTED 4/16/21 COMPLETED 4/16/21 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---DEPTH(ft)0 1 2 3 SAMPLE TYPENUMBERPAGE 1 OF 1 SOIL PIT NUMBER TP 3 PROJECT NAME Singh 6th Street Short Plat PROJECT LOCATION 56XX NE 6th Street, Renton CLIENT Raman Sidhu PROJECT NUMBER 042113 GENERAL BH / TP / WELL - GINT STD US.GDT - 4/29/21 14:17 - F:\2021 PROJECTS\032112 SIDHU PLAT GEO\DATA\SIGNH 6TH STREET SHORT PLAT SOIL PITS.GPJINNOVATIVE GEO-SERVICES, LLC Engineering Geology and Septic Design 253 279-4205 rex@enggeologist.com U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390 484.5 482.5 482.0 481.5 CL- ML SP- SC SP- SM SP 0.5 2.5 3.0 3.5 (CL-ML) SOD TOPSOIL, ORGANIC, SANDY, SOME GRAVEL, DARK BROWN, DRY (SP-SC) SAND, GRAVELLY, BROWN, ROCKY, LOOSE TO MEDIUM DENSE, DRY (SP-SM) SAND, GRAVELLY, TAN, MEDIUM DENSE, DRY (SP) GLACIAL TILL, GRAY, SLIGHTLY MOTTLED, ROCKY, DRY Bottom of test pit at 4.0 feet. NOTES GROUND ELEVATION 485 ft msl LOGGED BY RBH EXCAVATION METHOD MiniExcavator TEST PIT SIZE 2' X 4' EXCAVATION CONTRACTOR Owner GROUND WATER LEVELS: CHECKED BY RBH DATE STARTED 4/16/21 COMPLETED 4/16/21 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION ---DEPTH(ft)0 1 2 3 4 SAMPLE TYPENUMBERPAGE 1 OF 1 SOIL PIT NUMBER TP 4 PROJECT NAME Singh 6th Street Short Plat PROJECT LOCATION 56XX NE 6th Street, Renton CLIENT Raman Sidhu PROJECT NUMBER 042113 GENERAL BH / TP / WELL - GINT STD US.GDT - 4/29/21 14:17 - F:\2021 PROJECTS\032112 SIDHU PLAT GEO\DATA\SIGNH 6TH STREET SHORT PLAT SOIL PITS.GPJINNOVATIVE GEO-SERVICES, LLC Engineering Geology and Septic Design 253 279-4205 rex@enggeologist.com U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOGDocuSign Envelope ID: 3B4D7BC6-B0BD-4F97-B0A2-27226522A390