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HomeMy WebLinkAbout19-R-GEOT-2015-10-12-PanGEO________________________________________________ 3213 Eastlake Avenue E Ste. B Seattle, WA 98102 Tel: (206) 262-0370 Geotechnical & Earthquake Engineering Consultants October 12, 2015 PanGEO Project No. 07-107.200 Mr. Kent Khnor 26721 106th Avenue Kent, WA 98030 Subject: GEOTECHNICAL REPORT Proposed Boon-Phany Short Plat Chelan Avenue NE near NE 10th Street Renton, Washington Dear Mr. Khnor, As requested, PanGEO has completed a geotechnical engineering study for the proposed Boon- Phany short plat planned just north of the intersection of Chelan Avenue NE and NE 10th Street in Renton, Washington. This study was performed in accordance with our mutually agreed scope of work outlined in our proposal dated September 25, 2015. The proposal was subsequently approved by you on September 29, 2015. PanGEO previously completed a geotechnical report for the project site in 2007. Our current scope of work includes reviewing our previous report, conducting a site reconnaissance to confirm the site conditions remain unchanged, and updating the report. SITE AND PROJECT DESCRIPTION The project site is located on the east side of Chelan Avenue NE approximately 170 feet north of the intersection of Chelan Avenue NE and NE 10th Street in Renton, Washington (see Figure 1, Vicinity Map). Review of a preliminary site plan indicates that the vacant 1.32-acre, rectangular site extends approximately 200 feet in a north-south direction and approximately 285 feet in an east-west direction. The site is currently bound to the north by single-family houses and a grass lot, to the south by newly developed 2-story single family residences accessed by Chelan Place NE, to the east by Duvall Avenue NE, and to the west by Chelan Avenue NE which dead ends Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 2 near the northwest corner of the property. The Chelan Avenue NE right-of-way was being was being developed at the time of our field exploration in July, 2007. The northern-central portion of the site is currently occupied by a small shed that will be razed prior to redeveloping the site. The site is primarily vegetated with tall grass, miscellaneous trees and shrubs, and localized areas of blackberry brambles. Based on the topographic survey provided for our review (see Figure 2), much of the site is relatively level except for the approximately southwestern quarter of the site. In general, the southwestern quarter of the site descends to the southwest at gradients in the estimated range of 8 to 10 percent. Overall, there is an approximate elevation difference of 5 feet between the northeastern and southwestern site corners. Due to the relatively level site topography, we anticipate the new buildings will be constructed at or near existing grades. Cuts and fills in the southwestern quarter of the site may be on the order of 2 to 4 feet. As currently planned, the proposed development will create eight single-family residential lots, a stormwater drainage tract, and associated asphalt-paved access roads. We anticipate the buildings will be of lightly loaded wood frame construction with a combination of wood joist and slab-on-grade floors. An east-west trending stormwater drainage tract is planned along the approximately west half of the south property line. We understand that a detention vault may be utilized for stormwater/surfacewater management. Depending on the location and size of the vault, temporary excavations to reach construction elevations may extend off-site to the south and west. As such, it may be necessary to obtain temporary construction easements from the respective neighbor. SUBSURFACE EXPLORATIONS Five test pits (TP-1 to TP-5) were previously excavated on the subject property in 2007. The approximate test pit locations are indicated on Figure 2. A PanGEO geologist was present throughout the field exploration to observe the test pit excavation, to assist in sampling, and to prepare descriptive logs of the explorations. The test pits were excavated on July 23, 2007, using a Cat 330 tracked excavator owned and operated by Northwest Excavating of Mill Creek, WA. The test pits were excavated to depths ranging from 8 to 12 feet below the existing ground surface. The relative density and consistency of the underlying soil was estimated based on probing the walls of the excavation and the difficulty of completing the excavations. The soils Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 3 observed in the test pits were classified in the field, and a summary of the subsurface conditions is presented in Appendix A of this report. SITE GEOLOGY AND SUBSURFACE CONDITIONS Review of the geologic map of the Renton Quadrangle (Mullineaux, 1965) indicated the subject site and its vicinity are underlain by ground moraine deposits (Map Unit Qgt), also known as glacial till. Glacial till is a very dense heterogeneous mixture of silt, sand, and gravel laid down at the base of an advancing glacial ice sheet. Glacial till typically exhibits low compressibility and high strength characteristics. The test pits excavated at the site generally confirmed the mapped stratigraphy. Based on the results of our subsurface explorations, the site is underlain by a surficial layer of loose to medium dense weathered glacial till that extends up to approximately 2½ to 5 feet below existing site grades. The weathered glacial till typically consisted of light brown silty sand with gravel. The weathered till contained occasional cobbles and was generally dry to moist. Underlying the surficial layer of weathered glacial till we encountered dense glacial till, which consisted of silty sand with gravel, to the maximum exploration depth of about 12 feet. The glacial till was typically gray, moist, and contained sandy lenses and occasional cobbles. It should be noted that thin layers of loose existing fill with a varying organic content may be encountered at the site, as evidenced in Test Pit TP-5. Groundwater/seepage was not encountered in the test pits at the time of the excavations. However, iron oxide staining was typically observed near the contact with dense glacial till. The iron oxide stained zone is likely indicative of groundwater collecting above the low permeability glacial till. In addition, limited amounts of groundwater seepage are often present in sandy and gravelly zones of glacial till. It should be noted that groundwater elevations are likely to vary depending on the season, local subsurface conditions, and other factors. Groundwater levels are normally highest during the winter and early spring. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 4 SEISMIC DESIGN CONSIDERATIONS IBC Seismic Design Parameters The following provides seismic design parameters for the site that are in conformance with the 2012 International Building Code (IBC), which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years). Based on the subsurface conditions encountered at the test pits, it is our opinion that IBC Site Class C should be used used for seismic design. Table 1 – Summary Seismic Design Parameters per 2012 IBC Site Class Spectral Acceleration at 0.2 sec. (g) SS Spectral Acceleration at 1.0 sec. (g) S1 Site Coefficients Design Spectral Response Parameters Fa Fv SDS SD1 C 1.4 0.529 1.0 1.3 0.937 0.458 Liquefaction Assessment Soil liquefaction is a condition where saturated cohesionless soils undergo a substantial loss of strength due to the build-up of excess pore water pressures resulting from cyclic stress applications induced by earthquakes. Soils most susceptible to liquefaction are loose, uniformly graded sands and loose silts with little cohesion. Due to the presence of dense soils at shallow depths and based on the lack of a shallow groundwater table at the site, the susceptibility of the site to earthquake-induced soil liquefaction is considered to be negligible. Special design considerations associated with soil liquefaction are not necessary for this project. EARTHWORK CONSIDERATIONS Site Preparation Site preparation includes striping and clearing of topsoil and sod, surface vegetation, root balls, existing foundations, and any other deleterious materials within the proposed development area and excavating to the design subgrade. All stripped materials should be properly disposed off-site or be “wasted” on site in non-structural landscaping areas. Based on the thickness of topsoil and Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 5 sod observed at the test pit locations, we estimate stripping depths will be in the range of 4 to 9 inches. Soil disturbed during stripping and clearing activities should be compacted to a firm and unyielding condition. Following the removal of deleterious and unsuitable materials, the exposed subgrade within the development area, such as building foundation, slab, and pavement areas, should be proof-rolled with a fully-loaded dump truck or a smooth roller compactor. The proof-rolling operation should be observed by a representative of PanGEO. If loose or unstable subgrade soils are observed during the proof roll, the soil should be over-excavated and replaced with structural fill. Temporary and Permanent Slopes All temporary excavations should be performed in accordance with Part N of WAC (Washington Administrative Code) 296-155. The contractor is responsible for maintaining safe excavation slopes and/or shoring. Excavations more than 4 feet deep should be properly shored or sloped. For planning purposes, it is our opinion that temporary excavations may be sloped as steep as ¾H:1V (Horizontal:Vertical). The inclination of temporary slopes should be re-evaluated in the field during construction based on actual observed soil conditions. Permanent cut and fill slopes should be graded no steeper than 2H:1V and should promptly be planted with an appropriate species of vegetation. Fill slopes should be constructed using 8- to 12-inch thick lifts with each lift compacted to a dense and unyielding condition prior to placing a subsequent lift. Structural Fill and Compaction In the context of this report, structural fill is defined as non-organic compacted fill placed under buildings, roadways, slabs, pavements, or other load-bearing areas. It may be possible to reuse some of existing site soils for structural backfill during periods of dry weather, provided the soil can be properly moisture conditioned and adequately compacted. However, due to the moderate to high fines content of the on-site soils, the soils should be considered moisture sensitive and generally unsuitable for use during wet weather construction. Imported structural fill, if needed, should consist of well-graded granular soils such as Gravel Borrow (WSDOT 9-03.14(1)), or an approved equivalent. PanGEO should review import material intended for use as structural fill prior to placement. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 6 Structural fill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D 1557 (Modified Proctor). The procedure to achieve proper density of a compacted fill depends on the size and type of compacting equipment, the number of passes, thickness of the layer being compacted, and certain soil properties. When size of the excavation restricts the use of heavy equipment, smaller equipment can be used, but the soil must be placed in thin enough layers to achieve the required degree of compaction. Generally, inadequately compacted soils result from poor workmanship or soils placed at improper moisture content. Soils with a high percentage of silt or clay are particularly susceptible to becoming too wet, and coarse-grained materials easily become too dry for proper compaction. Silty or clayey soils with a moisture content too high for adequate compaction should be dried as necessary, or moisture conditioned by mixing with drier materials. Existing Test Pit Backfill It should be noted that the backfill in the test pits were backfilled with excavated soils and compacted with the excavator bucket. As such, the backfill is considered inadequate for supporting future load-bearing elements, including building foundation, pavements, slabs, underground vaults, buried pipes, etc. As such, where load-bearing elements are present, the existing backfill in the test pits should be removed and replaced with properly compacted structural fill. UTILITIES Trenching Utility trenches greater than 4 feet deep should be properly sloped. Temporary slope recommendations can be found on Page 4 of this report. Alternatively, conventional trench shoring systems such as trench boxes or steel sheets utilizing hydraulic bracing are considered feasible for this project. For shoring design purposes, the contractor may utilize an equivalent fluid weight of 35 pcf to represent the lateral earth pressures on the shoring. This pressure should be increased for backslopes above the shoring or to account for soil stockpiles and/or equipment traffic surcharges within a horizontal distance equal to the depth of the excavation. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 7 Pipe Bedding General recommendations relative to pipe bedding and backfill are presented below.  Pipe bedding material, placement, compaction, and shaping should be in accordance with the project specifications and the pipe manufacturer’s recommendations. As a minimum, the pipe bedding should meet the gradation requirements for Gravel Backfill for Pipe Zone Bedding, Section 9-03.12(3) of the 2014 WSDOT Standard Specifications;  Pipe bedding should be placed on relatively undisturbed native soils, or on compacted fill. If the native subgrades are disturbed, the disturbed material should be removed and replaced with compacted bedding material;  If the trench bottom encounters soft or unsuitable soils, it may be necessary to over- excavate the unsuitable material and backfill with pipe bedding material;  Pipe bedding should provide a firm, uniform cradle for the pipe. We recommend that a minimum 4-inch thickness of bedding material beneath the pipe be provided. Larger thicknesses may be necessary to prevent loosening and softening of the natural soils during pipe placement;  Prior to the placement of the pipe, the pipe bedding should be shaped to fit the lower part of the pipe exterior with reasonable closeness to provide continuous support along the pipe;  Pipe bedding material and/or backfill around the pipe should be placed in layers and tamped to obtain complete contact with the pipe. In areas where a trench box is used, the bedding material should be placed before the trench box is advanced. Trench Backfill In areas supporting pavements, trench backfill should be placed in 8- to 12-inch, loose lifts and compacted using mechanical equipment. If the trench backfill will consist of imported granular structural fill, the backfill should be compacted to at least 90 percent of its maximum dry density, as determined by test method ASTM D1557 (Modified Proctor). The upper 2 feet of backfill should be compacted to at least 95 percent of its laboratory determined maximum dry density. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 8 It is our opinion that the on-site till soils may be considered for use as trench backfill provided the soil can be compacted to the requirements of trench backfill. Because the on-site till soils are moisture sensitive, it may not be feasible to use the on-site soils as trench backfill in wet weather. Where used in structural areas, all trench backfill derived from the on-site soils should be compacted to 95 percent of its maximum dry density as determined by test method ASTM D1557 (Modified Proctor). We also recommend that trenches backfilled with the on-site fill be capped with at least 12 inches of imported granular structural fill. In non-structural areas where settlement of the trench backfill will not affect the use of the area, the trench backfill may be compacted to 85% of the materials maximum dry density. During placement of the initial lifts, the trench backfill should not be bulldozed into the trench or dropped directly on the pipe. Furthermore, heavy vibratory equipment should not be permitted to operate directly over the pipe until a minimum of 2 feet of backfill has been placed above the crown. Boulders and large sized cobbles should be removed from material to be used as trench backfill. PAVEMENT We anticipate that the future traffics in the development will be limited to light passenger-type vehicles. For lightly loaded pavement areas, we suggest a pavement section consisting of 2½- inches of hot-mix asphalt overlying a 4-inch thick layer of crushed surfacing top course (CSTC) or crushed surfacing base course (CSBC), overlying a properly compacted subgrade. The crushed rock base should be compacted to a minimum of 95 % of the materials maximum dry density determined in accordance with ASTM D1557 (Modified Proctor). Prior to placing the crushed rock, the pavement subgrade should be proof rolled using a fully loaded dump truck. The proof roll should be conducted under observation of a PanGEO representative. Any soft soils identified during the proof rolling should be removed and replaced with properly compacted structural fill. BUILDING FOUNDATIONS Based on the subsurface conditions encountered at the site, the new buildings may be supported on conventional spread and continuous footings bearing on competent native soils, or on properly compacted newly placed structural fill. Based on the results of our subsurface exploration, we anticipate competent native soils (glacial till) to be 2½ to 5 feet deep. Any loose soil should be Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 9 compacted to a dense condition. If loose soil cannot be adequately compacted, it should be overexcavated and replaced with a granular structural fill. On site soils should not be used as structural fill below the footings. Allowable Bearing Pressure We recommend that an allowable soil bearing pressure of 2,000 (psf) be used to size the footings. For allowable stress design, the recommended bearing pressure may be increased by one-third for transient loading, such as wind or seismic forces. Footing Embedment For frost heave considerations, exterior footings should be placed at a minimum depth of 18 inches below final exterior grade. Interior spread foundations should be placed at a minimum depth of 12 inches below the top of slab. Estimated Settlement Footings designed and constructed in accordance with the above should experience total settlement of less than one inch and differential settlement less than about ½ inch. Most of the anticipated settlement should occur during construction as dead loads are applied. Lateral Load Resistance Lateral loads on the structure may be resisted by passive earth pressure developed against the embedded near-vertical faces of the foundation system and by frictional resistance developed between the bottom of the foundation and the supporting subgrade soils. For footings bearing on competent native soil or on structural fill, a frictional coefficient of 0.5 may be used to evaluate sliding resistance developed between the concrete and the subgrade soil. Passive soil resistance may be calculated using an equivalent fluid weight of 300 pcf, assuming the footings are backfilled with structural fill. The above values include a factor of safety of 1.5. Unless covered by pavements or slabs, the passive resistance in the upper 12 inches of soil should be neglected. Footing Drain We recommend that a 4-inch diameter, schedule 40 PVC or SDR 35, perforated pipe embedded in pea gravel and wrapped in filter fabric be installed at the base of the perimeter footings to direct collected water to an appropriate outlet. Under no circumstances should roof downspout Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 10 drain lines be connected to the footing drain systems. Roof downspouts must be separately tightlined to an appropriate discharge. Cleanouts should be installed to allow for periodic maintenance of the footing drain and downspout tightline systems. Footing Excavation All footing subgrades should be in a dense, unyielding condition. The adequacy of the footing subgrade should be verified by PanGEO prior to placing forms or reinforcing steel. If the footing subgrade is still loose or yielding after re-compaction, it should be overexcavated down to competent native soil and replaced with structural fill or lean mix concrete. The overexcavation width should extend at least one-half the overexcavation depth beyond the edge of footing. FLOOR SLABS It is our opinion that conventional concrete slab-on-grade floors are appropriate for this site. Depending on the finished floor elevations, the floor slabs may be founded on the native soil compacted in-place to the requirements of structural fill or on newly placed structural fill. Interior concrete slab-on-grade floors should be underlain by a capillary break consisting of at least 4 inches of compacted ¾-inch, clean crushed rock (less than 3 percent fines). The capillary break material should also have no more than 10 percent passing the No. 4 sieve and less than 5 percent by weight of the material passing the U.S. Standard No. 100 sieve. The capillary break should be placed on a subgrade that has been compacted to a dense and unyielding condition. A 10-mil polyethylene vapor barrier should also be placed directly below the slab. RETAINING WALLS Based on our understanding of the current design concept and the lack of significant topographic relief at the site, we do not anticipate the need for retaining walls. However, depending on the final grading plan, short retaining walls may be needed to achieve the design grade. Given the competent foundation soils at the site, various wall types may be considered, including conventional cast-in-place concrete walls, gravity block walls such as Ultra Blocks or gabions, or mechanically stabilized earth (MSE) walls. Selection of wall types will largely depend on the desired aesthetics and cost considerations. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 11 In general, these walls should be designed to resist an active earth pressure of 35 pcf, and a uniform pressure of 7H pounds per square foot (psf) to account for the seismic loading condition, where H is the exposed wall height in feet. Lateral pressures from surface surcharges located within a distance equal to the exposed wall height should be estimated using a lateral pressure coefficient of 0.3 (i.e. the ratio of lateral pressure to vertical pressure). Where applicable, a lateral uniform pressure of 80 psf should be used to account for traffic surcharge. Proper drainage provisions such as weep holes or 4-inch perforated drain pipes should be incorporated into the design and construction of all retaining walls. For the design and construction of retaining wall foundations, the recommendations provided in the Building Foundations section of this report are applicable. INFILTRATION The site is underlain by glacial till at shallow depths. Glacial till is expected to exhibit very poor infiltration characteristics. In general, this soil unit is considered not appropriate for any significant stormwater infiltration. DETENTION VAULT DESIGN PARAMETERS Foundation We anticipate the bottom of the detention vault will be at least 5 feet below existing site grades. As such, dense glacial till is expected to be encountered at the vault foundation level. The detention vault should be supported on dense glacial till and/or granular structural fill. An allowable soil bearing capacity of 4,000 psf may be used for footings bearing on the dense to very dense glacial till and/or granular structural fill. If the vault foundation will straddle cross dense glacial till and granular structural fill, we recommend that the dense till be over-excavated 6 inches and replaced with crushed rock for a uniform support. The 6-inch crush rock should also be placed in the structural fill area. For allowable stress design, the recommended bearing pressure may be increased by one-third for transient loading, such as wind or seismic forces. Total footing settlement of less than one inch is anticipated with differential movement of less than ½ inch. Most of the anticipated settlement should occur during construction as dead loads are applied. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 12 If loose/soft soil is encountered at the vault foundation level, it should be overexcavated down to dense native till soil and replaced with granular structural fill and/or lean mix concrete. Vault foundation subgrade should be observed by a representative of PanGEO, prior to placing forms or rebar, to verify that conditions are as anticipated in this report. Lateral Earth Pressures Detention vault walls should be properly designed to resist the lateral earth pressures exerted by the soils behind the wall. The below grade portions of the walls with level backslopes should be designed for a static lateral earth pressure based upon an equivalent fluid weight of 50 pcf. A uniform lateral pressure of 7H psf should be added to reflect the increase loading for seismic conditions, where H corresponds to the buried depth of the wall. The recommended lateral pressures assume that the backfill behind the wall consists of adequately compacted free draining backfill and a footing drain. The portion of the wall located beneath the drainpipe, if any, should be designed to withstand a lateral pressure of 90 pcf to account for the potential accumulation of water behind the vault walls. Surcharge loads, where present, should also be included in the design of the vault walls. We recommend that a lateral load coefficient of 0.35 be used to compute the lateral pressure on the wall face resulting from surcharge loads located within a horizontal distance of one-half wall height. Lateral Resistance Lateral forces from seismic loading and unbalanced lateral earth pressures may be resisted by a combination of passive earth pressures and by friction acting on the base of the foundations. Passive resistance values may be determined using an equivalent fluid weight of 350 pcf. This value includes a factor of safety of 1.5, assuming the footing is poured against dense native soil or structural fill adjacent to the sides of footing has been compacted. A friction coefficient of 0.5 may be used to determine the frictional resistance at the base of the footings. These values include a factor safety of 1.5. Vault Backfill Vault backfill should consist of free draining granular soils such as Gravel Borrow (WSDOT 9- 03.14(1)). Vault backfill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 13 systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D 1557. Within 5 feet of the wall, the backfill should be compacted to 90 percent of the maximum dry density. Vault Drainage We recommend that a 4-inch diameter, schedule 40 PVC or SDR 35, perforated pipe embedded in pea gravel and wrapped in filter fabric be installed as low on the vault walls as possible to direct collected water to an appropriate outlet. Cleanouts should be installed to allow for periodic maintenance of the footing drain. SURFACE DRAINAGE AND EROSION CONSIDERATIONS Adequate drainage provisions are imperative and we recommend both short and long term drainage measures be incorporated into the project design and construction. Surface runoff can be controlled during construction by careful grading practices. Typically, this includes the construction of shallow, upgrade perimeter ditches or low earthen berms to collect runoff and prevent water from entering the excavation. All collected water should be directed under control to a positive and permanent discharge system. Permanent control of surface water should be incorporated in the final grading design. Adequate surface gradients and drainage systems should be incorporated into the design such that surface runoff is directed away from structures. Potential problems associated with erosion may also be reduced by establishing vegetation within disturbed areas immediately following grading operations. WET SEASON CONSTRUCTION General recommendations relative to earthwork performed in wet weather or in wet conditions are presented below. Because the site soils are considered moisture sensitive due to a relatively high fines content, grading may be difficult and likely more costly during periods of wet weather. If earthworks will be performed during wet weather conditions, we recommend that the following guidelines be incorporated:  Earthwork should be performed in small areas to minimize subgrade exposure to wet weather. Excavation or the removal of unsuitable soil should be followed promptly Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 14 by the placement and compaction of clean structural fill. The size and type of construction equipment used may have to be limited to reduce soil disturbance.  During wet weather, the allowable fines content of the structural fill should be reduced to no more than 5 percent by weight based on the portion passing ¾-inch sieve. The fines should be non-plastic.  The ground surface within the construction area should be graded to promote run-off of surface water and to prevent the ponding of water.  Geotextile silt fences should be strategically located to control erosion and the movement of soil.  Excavation slopes and soils stockpiled on site should also be covered with plastic sheets. Under no circumstances should water be allowed to pond immediately adjacent to paved areas or foundations. All pavement drainage should be directed into conduits which carry runoff away from the pavement into storm drain systems or other appropriate outlets. UNCERTAINTY AND LIMITATIONS We have prepared this report for use by Mr. Kent Khnor and their project team. Recommendations contained in this report are based on a site reconnaissance, a subsurface exploration program, review of pertinent subsurface information, and our understanding of the project. The study was performed using a mutually agreed-upon scope of work. Variations in soil conditions may exist between the locations of the explorations and the actual conditions underlying the site. The nature and extent of soil variations may not be evident until construction occurs. If any soil conditions are encountered at the site that are different from those described in this report, we should be notified immediately to review the applicability of our recommendations. Additionally, we should also be notified to review the applicability of our recommendations if there are any changes in the project scope. The scope of our work does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors’ methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 15 Additionally, the scope of our work specifically excludes the assessment of environmental characteristics, particularly those involving hazardous substances. We are not mold consultants nor are our recommendations to be interpreted as being preventative of mold development. A mold specialist should be consulted for all mold-related issues. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on-site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. It is the client’s responsibility to see that all parties to this project, including the designer, contractor, subcontractors, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the contractor’s option and risk. Any party other than the client who wishes to use this report shall notify PanGEO of such intended use and for permission to copy this report. Based on the intended use of the report, PanGEO may require that additional work be performed and that an updated report be reissued. Noncompliance with any of these requirements will release PanGEO from any liability resulting from the use this report. Within the limitation of scope, schedule and budget, PanGEO engages in the practice of geotechnical engineering and endeavors to perform its services in accordance with generally accepted professional principles and practices at the time the Report or its contents were prepared. No warranty, express or implied, is made. We appreciate the opportunity to be of service to you on this project. Please feel free to contact our office with any questions you have regarding our study, this report, or any geotechnical engineering related project issues. We appreciate the opportunity to be of service. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 16 Sincerely, Bryce C. Townsend, E.I.T. Siew L. Tan, P.E. Staff Geotechnical Engineer Principal Geotechnical Engineer Enclosures: Figure 1 Vicinity Map Figure 2 Site and Exploration Plan Appendix A Summary Test Pit Logs Figure A-1 Terms and Symbols for Boring and Test Pit Logs Logs of Test Pits TP-1 through TP-5 Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 17 REFERENCES International Building Code (IBC), 2012, International Code Council. Mullineaux, D. R., 1965, Geologic Map of The Renton Quadrangle, King County, Washington – Department of the Interior, U.S. Geologic Survey, scale 1:24,000. Washington State Department of Transportation/American Public Works Association, 2014, Standard Specifications for Road, Bridges, and Municipal Construction. 07-107.200 Boon-Phanny Short Plat Chelan Ave. NE near NE 10th St. Renton, Washington 1 VICINITY MAP Figure 1.grf 10/12/15 (9:48 ) Note: Base map obtained and modified from Google Maps. Not to Scale Figure No.Project No. Project Location Project No. Figure No.Boon-Phanny Short PlatChelan Ave. NE near NE 10th St. Renton, WashingtonSITE AND EXPLORATION PLAN07-107.200207-107 Boon-Phanny Short Plat Site Plan.grf 10/12/15 STSApprox. Test Pit Location(July, 2007)Legend:Approx. Scale1" = 50'Note:Preliminary site plan provided by client.Subject SiteTP-2TP-3TP-4TP-5TP-1432 4 33 4 34435436437 43 8437 438 ________________________________________________ 3213 Eastlake Avenue E Ste. B Seattle, WA 98102 Tel: (206) 262-0370 APPENDIX A SUMMARY TEST PIT LOGS MOISTURE CONTENT Layered: Laminated: Lens: Interlayered: Pocket: Homogeneous: Gravel Approx. RelativeDensity (%) Units of material distinguished by color and/orcomposition from material units above and below Layers of soil typically 0.05 to 1mm thick, max. 1 cm Layer of soil that pinches out laterally Alternating layers of differing soil material Erratic, discontinuous deposit of limited extent Soil with uniform color and composition throughout GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT <15 15 - 35 35 - 65 65 - 85 85 - 100 MONITORING WELL Highly Organic Soils Notes: GROUP DESCRIPTIONSMAJOR DIVISIONS UNIFIED SOIL CLASSIFICATION SYSTEM #4 to #10 sieve (4.5 to 2.0 mm) #10 to #40 sieve (2.0 to 0.42 mm) #40 to #200 sieve (0.42 to 0.074 mm) 0.074 to 0.002 mm <0.002 mm Liquid Limit < 50 Liquid Limit > 50 GRAVEL (<5% fines) GRAVEL (>12% fines) SAND (<5% fines) SAND (>12% fines) SILT / CLAY Terms and Symbols for Boring and Test Pit Logs Dusty, dry to the touch Damp but no visible water Visible free water 2-inch OD Split Spoon, SPT (140-lb. hammer, 30" drop) 3.25-inch OD Spilt Spoon (300-lb hammer, 30" drop) Non-standard penetration test (see boring log for details) Thin wall (Shelby) tube Grab Rock core Vane Shear Density Approx. Undrained ShearStrength (psf)California Bearing Ratio Compaction Tests Consolidation Dry Density Direct Shear Fines Content Grain Size Permeability Pocket Penetrometer R-value Specific Gravity Torvane Triaxial Compression Unconfined Compression <4 4 to 10 10 to 30 30 to 50 >50 SPTN-values Very Loose Loose Med. Dense Dense Very Dense Breaks along defined planes Fracture planes that are polished or glossy Angular soil lumps that resist breakdown Soil that is broken and mixed Less than one per foot More than one per foot Angle between bedding plane and a planenormal to core axis SPTN-values <2 2 to 4 4 to 8 8 to 15 15 to 30 >30 Sand Coarse Sand: Medium Sand: Fine Sand: Silt Clay Boulder: Cobbles: Gravel Coarse Gravel: Fine Gravel: CBR Comp Con DD DS %F GS Perm PP R SG TV TXC UCC Phone: 206.262.0370 Sand Very Soft Soft Med. Stiff Stiff Very Stiff Hard Bottom of Boring Well-graded GRAVEL Poorly-graded GRAVEL Silty GRAVEL Clayey GRAVEL Well-graded SAND Poorly-graded SAND Silty SAND Clayey SAND SILT Lean CLAY Organic SILT or CLAY Elastic SILT Fat CLAY Organic SILT or CLAY PEAT DESCRIPTIONS OF SOIL STRUCTURES 50% or more of the coarsefraction retained on the #4sieve. Use dual symbols (eg.GP-GM) for 5% to 12% fines. > 12 inches 3 to 12 inches 3 to 3/4 inches 3/4 inches to #4 sieve Figure A-1 50% or more of the coarsefraction passing the #4 sieve.Use dual symbols (eg. SP-SM)for 5% to 12% fines. for In Situ and Laboratory Testslisted in "Other Tests" column. <250 250 - 500 500 - 1000 1000 - 2000 2000 - 4000 >4000 Dry Moist Wet COMPONENT DEFINITIONS Fissured: Slickensided: Blocky: Disrupted: Scattered: Numerous: BCN: RELATIVE DENSITY / CONSISTENCY COMPONENT SIZE / SIEVE RANGE Groundwater Level at time of drilling (ATD)Static Groundwater Level Cement / Concrete Seal Bentonite grout / seal Silica sand backfill Slotted tip Slough 50%or more passing #200 sieve LOG KEY 07-041_EVERETT_AS.GPJ PANGEO.GDT 5/1/07SYMBOLS SAND / GRAVEL Consistency Silt and Clay Sample/In Situ test types and intervals 1. Soil exploration logs contain material descriptions based on visual observation and field tests using a systemmodified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have beenconducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to thediscussions in the report text for a more complete description of the subsurface conditions. 2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs.Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials. COMPONENT SIZE / SIEVE RANGE TEST SYMBOLS 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-1 Approximate ground surface elevation: 437 feet Ground Surface Conditions: Tall grass Depth (ft) Material Description 0 – 4 Loose to medium dense, dry to moist, rusty-brown, silty SAND with gravel, iron oxide staining (Weathered Glacial Till). 4 – 10 Dense, moist, gray, silty SAND with gravel and trace cobbles (Glacial Till). -occasional sandy lenses Test Pit terminated approximately 10 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-2 Approximate ground surface elevation: 437 feet Ground Surface Conditions: Tall grass Depth (ft) Material Description 0 – 5 Loose to medium dense, moist to wet, brown, silty SAND with some gravel (Weathered Glacial Till). 5 – 10 Dense, moist, gray, silty SAND with gravel, trace cobbles (Glacial Till). Test Pit terminated approximately 10 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-3 Approximate ground surface elevation: 438 feet Ground Surface Conditions: Blackberry brambles Depth (ft) Material Description 0 – 2½ Loose to medium dense, moist, rusty-brown, silty SAND with gravel (Weathered Glacial Till). -Iron oxide staining near contact. 2½ – 8 Dense, moist, gray, silty SAND with gravel, trace cobbles (Glacial Till). -Becomes very dense around 6 feet Test Pit terminated approximately 8 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-4 Approximate ground surface elevation: 438 feet Ground Surface Conditions: Tall grass Depth (ft) Material Description 0 – 4 Loose to medium dense, dry, light brown, silty SAND with gravel (Weathered Glacial Till). -Localized pockets of clean sand 4 – 10 Dense, moist, gray, silty SAND with gravel, contains cobbles (Glacial Till). -Increase in sand content and moisture content around 8 feet. Test Pit terminated approximately 10 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Date Test Pits Excavated: July 23, 2007 Test Pits Logged by: STS Test Pit TP-5 Approximate ground surface elevation: 433 feet Ground Surface Conditions: Blackberry brambles Depth (ft) Material Description 0 – 1.5 Loose, moist, dark brown, silty SAND with abundant organics (Topsoil & Fill). 1.5 – 4 Medium dense, moist, relatively clean sand and gravel, iron oxide staining (Outwash). 4 - 12 Dense, moist, gray, silty SAND with gravel, trace cobbles (Glacial Till). -contains occasional silt and relatively clean sand lenses Test Pit terminated approximately 12 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan.