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REVIEWED PLN BLD2022-0462+Geotechnical_Report+5.6.2022_2.46.01_PM+2853668GEOTECH CONSULTANTS, INC. R & P Investments Co., LLC c/o CDA Architects, Incorporated , P.O. Box 55429 Seattle, Washington 98155 Attention: Seth Hale 13256 Northeast 20th Street, Suite 16 Bellevue, Washington 98005 (425) 747-5618 FAX (425) 747-8561 August 20, 2001 ti 01248 RECEIVED ' Reviewed by 5/6/2022 City of Edmonds ; 1 pOF DEVEL '�"•"""F--ai�lanning Division ' CITY EL OEPMONDS J' PMENT 1 _ ' SERVICES DEPARTMENT RECEtVEU Subject: Transmittal Letter — Geotechnical Engineering Study �► 2 j 2o4i Proposed Edmonds Terrace Multi -Family Project 236XX — 84th Avenue West J .6k Edmonds, Washington Dear Mr. Hale: We are pleased to present this geotechnical engineering report for the multi -family development to be constructed at 236XX — 84th Avenue West in Edmonds, Washington. The scope of our work consisted of exploring site surface and subsurface conditions, and then developing this report to provide recommendations for general earthwork and design criteria for foundations, retaining walls, and pavements. This work was authorized by your acceptance of our proposal, P-5561, dated July 20, 2001. The attached report contains a discussion of the study and our recommendations. Please contact us if there are any questions regarding this report, or for further assistance during the design and construction phases of this project. SES/JHS: esm Respectfully submitted, GEOTECH CONSULTANTS, INC. J2 ames H. Strange, Jr. Senior Geotechnical Engineer RECEIVED AUG 2 8 2001 �UIILDiNG DEPT. An GEOTECH CONSULTANTS, INC. GEOTECHNICAL ENGINEERING STUDY Proposed Edmonds Terrace Multi -Family Project 236XX — 84th Avenue West Edmonds, Washington This report presents the findings and recommendations of our geotechnical engineering study for the site of the proposed Edmonds Terrace multi -family development to be located at 236XX — 84th Avenue West in Edmonds, Washington. We were provided with site plans and a topographic map. CDA Architects along with D. R. Strong developed these plans, which were provided on July 19, 2001. Based on these plans and conversations with CDA, we anticipate that the development will consist of four multi -family residential buildings, with parking and drive access from the surrounding streets. The proposed multi -unit buildings will be two stories over a partially submerged basement. The two eastern buildings will have a footprint approximately 3,560 square feet, while the two western buildings will have a footprint approximately 4,380 square feet. Building setbacks from the property lines are shown to be at least 10 feet. The remainder of the lot will be used for parking and drive access. All of the buildings are proposed to be slab -on -grade construction with finished floor slabs from elevation 994.00 to 995.75 feet. The parking areas and driveways are proposed to be at, or near, the elevation of the existing grade. Excavation for the proposed structures is anticipated to be less than 5 feet below the existing grades. SITE CONDITIONS SURFACE The Vicinity Map, Plate 1, illustrates the general location of the site. The site is approximately 78,239 square feet in size and is bordered to the north by 236th Street Southwest and to the west by 84th Avenue West. The subject site is generally rectangular in shape with an access easement on the order of 20 feet wide extending south approximately 300 feet. The extension reaches from the southeastern side of the property to give access from 238th Street southwest. Residential property abuts the site to the south with commercial property to the east. Currently, the site is cleared of all vegetation and buildings. The site formerly was developed with two single-family residences with detached garages and several smaller buildings. The residences were burned down by the Edmonds Fire Department during training exercises. One residential footprint is currently marked by a 2-foot depression in surface elevation. The foundation appears to have been removed. Standing water was noted in the depression with some ash and burn evidence on the surface. The foundation of the other northern house was not observed. The existing residence at 23703 — 84th Avenue West appears to be part of the subject property. Based on the development drawings provided, it appears that this existing house will remain and a parking strip will be constructed to the east of the proposed residence. The majority of the site has been graded relatively level. The topography of the site slopes gently to the south with a total elevation change of approximately 6 feet across the entire site. A mound of soil has been placed on the southeastern corner of the property. This mound is approximately 5 feet above the existing grade and appears to consist of recently placed fill soils. GEOTECH CONSULTANTS, INC. J N 01248 R&P Investment Co., LLC. c% CDA Architects Page 2 August 20, 2001 SUBSURFACE The subsurface conditions were explored by excavating eight test pain Wapproximate locations as based on the proposed shown on the Site Exploration Plan, Plate 2. Our exploration prog p construction, anticipated subsurface conditions and those encountered during exploration, and the scope of work outlined in our proposal. excavated on July 31, 2001 with a rubber -tired backhoe. A geotechnical The test pits were exca logged the test pits, and obtained engineer from our staff observed the excavation ab'ceam les of selected subsurface soil were representative samples of the soil encountered. est Pit Logs are attached to this report as Plates 3 collected from the backhoe bucket. The 9 through 6. Soil Conditions The test pits encountered 2 to 5 feet of loose topsoil and fill soils below the generally level portion of the site. Test Pit 5 encountered 8 feet of fill soil, however, its surface he lotion ion was approximately 5 feet higher in elevation than the rest of the sand Underlying dense with soils, we observed weathered, silty sand that became a �oav elfy ry dense approximately 4 to depth. This soil becomes glacially consolidated and soils are referred to in this report as glacial 8 feet below the existing grade. These dens till. The till was observed to the maximum depth explored of 12 feet below grade. Groundwater Conditions Perched ground P water seepage was observed at a depth of 4.5 to 7.0 feet. The test pits . were left open for only a short time period. Therefore, the seepage levels on the logs represent the location of transient water seepage and may not indicate the static groundwater level. It should be noted that groundwater levels vary seasonally with rainfall and layers then ithin f the till We anticipate that groundwater could be found in more permeable soil lay and between the near -surface weathered soil and the underlying denser glacial till. The final logs represent our interpretations of the field logs. The stratification lines on the logs repre sent the approximate boundaries between soil types at the exploration locations. T b actual transition between soil types may be gradual, and subsurface conditions can vary between explorati on locations. The logs provide specific subsurface information only at the locations tested. The relative densities and moisture descriptions indicated on the test pit logs are interpretive descriptions based on the conditions observed during excavation. The compaction of backfil I was not in the scope of our services. Loose soil will therefore be found In the area of the test pits. If this presents a problem, the backfill will need to be removed and replaced with structural fill during construction. GEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c/o CDA Architects JN 01248 August 20, 2001 Page 3 CONCLUSIONS AND RECOMMENDATIONS GENERAL THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE CONTAINED IN THE REMAINDER OF THiS REPORT. ANY PARTY RELYING ON THIS REPORT SHOULD READ THE ENTIRE DOCUMENT. The test pits conducted for this study generally encountered from 2 to 5 feet of loose topsoil and fill soils overlying native, medium -dense, silty sand. This soil becomes gravelly and glacially consolidated glacial till approximately 4 to 8 feet below the existing grade. Based on this, the proposed multi -family residential buildings can be constructed on conventional foundations bearing directly on the medium -dense to dense, native soils, or atop of structural fill placed above this competent soil Test Pit 5 was located in the southeastern corner of the site in the location of the suspected fill mound. The elevation of the top of the test pit was approximately 5 feet above the surrounding grade. The test pit encountered approximately 8 feet of loose fill soils over weathered silty sand. The glacial till was observed approximately 10 feet below grade. The fill soil will need to be removed in the building and areas for the construction of the project. The parking and driveways can be constructed on the medium -dense weathered soils underlying the topsoil and fill soils or atop granular fill placed above the medium -dense, native soils. The fill soils observed were loose with a relatively high amount of organic content. Placing the parking and driveways on top of the fill soil could result in significant settlement of the pavement. if not overly wet at the time of placement, the native soils excavated during the grading for the foundations of the buildings could be reused as parking and driveway sub -base. These soils will need to be relatively dry during placement and compacted as described in the Pavement Areas section of this report. A significant geotechnical consideration for development of this site is the overly moist to wet condition of the silty soils. Based on our observations, and the results of our laboratory tests, the moisture contents of the upper on -site soils are significantly above the optimum moisture content necessary for the required structural fill compaction. These fine-grained, silty soils are sensitive to moisture, which makes them impossible to adequately compact when they have moisture contents even 2 to 3 percent above their optimum moisture content. The reuse of these soils as structural fill to level the site will only be successful during hot, dry weather. Aeration of each loose lift of soil will be required to dry it before the lift is compacted. Alternatively, the soil could be chemically dried by adding lime, kiln dust, or cement, provided this is allowed by responsible building department. Regardless of the method of drying, the earthwork process will be slowed dramatically. The earthwork contractor must be prepared to rework areas that do not achieve proper compaction due to high moisture content. Utility trench backfill in structural areas, such as pavements, must also be dried before it can be adequately compacted. improper compaction of backfill in utility trenches and around control structures is a common reason for pavement distress and failures. Imported granular fill will be needed wherever it is not possible to dry the on -site soils sufficiently before compaction. We anticipate excavations for the foundations will be approximately 4 to 5 feet below the existing grade. The only other excavations we anticipate will be for utility trenches and detention vaults. GEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c% CDA Architects JN 01248 August 20, 2001 Page 5 Depending on the final site grades, overexcavation may be required below the footings to expose competent, native soil. Unless lean concrete is used to fill an overexcavated hole, the overexcavation must be at least as wide at the bottom as the sum of the depth of the overexcavation and the footing width. For example, an overexcavation extending 2 feet below the bottom of a 2-foot-wide footing must be at least 4 feet wide at the base of the excavation. If lean concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing. The following allowable bearing pressures are appropriate for footings constructed according to the above recommendations: Placed directly on competent, 5,000 psf dense to very dense glacial till. Supported on weathered silty 2,500 psf sand or on structural fill placed above competent, native soil Where: (1) psf Is pounds per square foot A one-third increase in these design bearing pressures may be used when considering short-term wind or seismic loads. For the above design criteria, it is anticipated that the total post -construction settlement of footings founded on competent, native soil, or on structural fill up to 5 feet in thickness, will be about'/2 inch, with differential settlements on the order of %-inch in a distance of 50 feet along a continuous footing with a uniform load. Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level structural fill. We recommend using the following ultimate values for the foundation's resistance to lateral loading: VALUE7F PARAMETER ULTIMATE Coefficient of Friction 0.50 Passive Earth Pressure 350 pcf Where: (i) pcf is pounds per cubic foot, and (ii) passive earth pressure is computed using the equivalent fluid density. We recommend maintaining a safety factor of at least 1.5 for the foundation's resistance to lateral loading, when using the above ultimate values. PERMANENT FOUNDATION AND RETAINING WALLS Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures imposed by the soil they retain. The following recommended parameters are for walls that restrain level backfill: GEOTECH CONSULTANTS, INC RAP Investment Co., LLC. c% CDA Architects August 20, 2001 J N 01248 Page 6 PARAMETER Active Earth Pressure * 35 pcf Passive Earth Pressure 350 pcf Coefficient of Friction 0.50 Soil Unit Weight 130 pcf Where: (i) pcf is pounds per cubic foot, and (ii) active and passive earth pressures are computed using the equivalent fluid pressures. * For a restrained wall that cannot deflect at least 0.002 times its height, a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above active equivalent fluid pressure. The values given above are to be used to design permanent foundation and retaining walls only. The passive pressure given is appropriate for the depth of level structural fill placed in front of a retaining or foundation wall only. The values for friction and passive resistance are ultimate values and do not include a safety factor. We recommend a safety factor of at least 1.5 for overturning and sliding, when using the above values to design the walls. Restrained wall soil parameters should be utilized for a distance of 1.5 times the wall height from corners or bends in the walls. This is intended to reduce the amount of cracking that can occur where a wall is restrained by a corner. The design values given above do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent foundations will be exerted on the walls. If these conditions exist, those pressures should be added to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The wall design criteria assume that the backfill will be well -compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should be accomplished with hand -operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. Retaining Wall Backfill and Waterproofing Backfill placed behind retaining or foundation walls should be coarse, free -draining structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. If the native silty sand is used as backfill, a minimum 12-inch width of free -draining gravel and a drainage composite similar to Miradrain 6000 should be placed against the backfilled retaining walls. The drainage composites should be hydraulically connected to the foundation drain system. Free -draining backfill or gravel should be used for the entire width of the backfill where GEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c% CDA Architects August 20, 2001 JN 01248 Page 7 seepage is encountered. For increased protection, drainage composites could be placed along cut slope faces, and the walls backfilled entirely with free -draining soil The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfill. The section entitled GENERAL EARTHWORK AND STRUCTURAL FILL contains recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls. The above recommendations are not intended to waterproof the below -grade walls. The performance of subsurface drainage systems will degrade over time. Therefore, waterproofing should be provided where moist conditions or some seepage through the walls are not acceptable in the future. This typically includes limiting cold joints and wall penetrations, and using bentonite panels or membranes on the outside of the walls. Applying a thin coat of asphalt emulsion is not considered waterproofing, but will only help to prevent moisture, generated from water vapor or capillary action, from seeping through the concrete. With any project, adequate ventilation of basement and crawl space areas is important to prevent a build up of water vapor that may be transmitted through concrete walls from the surrounding soil. SLABS -ON -GRADE The building floors may be constructed as slabs -on -grade atop the native, medium -dense, silty sand, the dense to very dense glacial till, or on structural fill placed above competent native soils. The subgrade soil must be in a firm, non -yielding condition at the time of slab construction or underslab fill placement. Any soft areas encountered should be excavated and replaced with select, imported structural fill All slabs -on -grade where moisture transmission through the slab is of concern should be underlain by a capillary break or drainage layer consisting of a minimum 4-inch thickness of coarse, free - draining structural fill with a gradation similar to that discussed in PERMANENT FOUNDATION AND RETAINING WALLS. As noted by the American Concrete institute (ACI) in Section 3.2.3 of the Guides for Concrete Floor and Slab Structures, proper moisture protection is desirable immediately below any on -grade slab that will be covered by tile, wood, carpet, impermeable floor coverings, or any moisture -sensitive equipment or products. ACi also notes that vapor retarders, such as 6-mil visqueen, are typically used. A vapor retarder is defined as a material with a permeance of less than 0.3 US perms per square foot (psf) per hour, as determined by ASTM E 96. It is possible that concrete admixtures may meet this specification, although the manufacturers of the admixtures should be consulted. However, if no potential for vapor passage through the slab is desired, a vapor barrier should be used. A vapor barrier, as defined by ACI, is a product with a water transmission rate of 0.00 perms per square foot per hour when tested in accordance with ASTM E 96. Reinforced membranes having sealed overlaps can meet this requirement. Additionally, ACI (Section 4.1.5) recommends that a minimum of 4 inches of compactible granular fill, such as crushed rock, should be placed over the vapor retarder or barrier for protection. Sand is not recommended by ACI for use as the protection layer. GEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c% CDA Architects JN 01248 August 20, 2001 Page 8 Isolation joints should be provided where the slabs intersect columns and walls. Control and expansion joints should also be used to control cracking from expansion and contraction. Saw cuts or preformed strip joints used to control shrinkage cracking should extend through the upper one- fourth of the slab. The spacing of control or expansion joints depends on the slab shape and the amount of steel placed in it. Reducing the water -to -cement ratio of the concrete and curing the concrete, by preventing the evaporation of free water until cement hydration occurs, will also reduce shrinkage cracking. We recommend proof -rolling slab areas with a heavy truck or a large piece of construction equipment prior to slab construction. Any soft areas encountered during proof -rolling should be excavated and replaced with select, imported structural fill ROCKERIES We anticipate that rockeries may be used in the site development. A rockery, is not intended to function as an engineered structure to resist lateral earth pressures, as a retaining wall would do. The primary function of a rockery is to cover the exposed, excavated surface and thereby retard the erosion process. We recommend limiting rockeries to a height of 8 feet and placing them against only dense, competent, native soil. The construction of rockeries is, to a large extent, an art not entirely controllable by engineering methods and standards. it is imperative that rockeries, if used, are constructed with care and in a proper manner by an experienced contractor with proven ability in rockery construction. The rockeries should be constructed with hard, sound, durable rock in accordance with accepted local practice. Soft rock, or rock with a significant number of fractures or inclusions, should not be used, in order to limit the amount of maintenance and repair needed over time. Provisions for maintenance, such as access to the rockery, should be considered in the design. In general, we recommend that rockeries have a minimum dimension of one-third the height of the slope cut above them. Tiered rockeries are not recommended, unless there is sufficient space to construct upper tiers that do not exert lateral pressure on the lower tiers. The base of a tiered rockery's upper wall should be set back from the rear of the lower rocks an amount equal to the height of the lower tiers. EXCAVATIONS AND SLOPES Excavation slopes should not exceed the limits specified in local, state, and national government safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be made near property boundaries, or existing utilities and structures. Based upon Washington Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as Type B. Therefore, temporary cut slopes greater than 4 feet in height cannot be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. The very dense glacial till soils could be excavated more steeply, but based on proposed excavation depths, these soils will not be encountered in the anticipated cut slopes. The above -recommended temporary slope inclination is based on what has been successful at other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet weather. The cut slopes GEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c/o CDA Architects JN 01248 August 20, 2001 Page 9 should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that loose soil can cave suddenly and without warning. Excavation, foundation, and utility contractors should be made especially aware of this potential danger. All permanent cuts into native soil should be inclined no steeper than 2:1 (H:V). DRAINAGE CONSIDERATIONS Foundation drains should be installed at the base of all footings where the slab or floor is below the outside grade. Drains should also be placed at the base of all earth -retaining walls. These drains should be surrounded by at least 6 inches of 1-inch-minus, washed rock and then wrapped in non- woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a crawl space, and it should be sloped for drainage. All roof and surface water drains must be kept separate from the foundation drain system. A typical drain detail is attached to this report as Plate 7. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. Drainage inside the building's footprint should also be provided where an excavation encounters significant seepage. In general, an outlet drain is recommended for all crawl spaces to prevent a build up of any water that may bypass the footing drains. We can provide recommendations for interior drains, should they become necessary, during excavation and foundation construction. Groundwater was observed during our field work. If seepage is encountered in an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to the buildings should slope away at least 2 percent, except where the area is paved. Surface drains should be provided where necessary to prevent ponding of water behind foundation or retaining walls. _ PAVEMENT AREAS The pavement section may be supported on competent, native soil or on structural fill placed above competent native soils. Because the site soils are silty and moisture sensitive, we recommend that the pavement subgrade be in a stable, non -yielding condition at the time of paving. Additional granular structural fill or geotextile fabric may be needed to stabilize soft, wet, or unstable areas. To evaluate pavement subgrade strength, we recommend that a ,proof -roll be completed with a loaded dump truck immediately before paving. In most instances where unstable subgrade conditions are encountered, an additional 12 inches of granular structural fill will stabilize the subgrade, except for very soft areas where additional fill could be required. The subgrade should be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to grade. Recommendations for the compaction of structural fill beneath pavements are given in the section entitled GENERAL EARTHWORK AND STRUCTURAL FILL. The performance of site pavements is directly related to the strength and stability of the underlying subgrade. OEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c/o J N 01248 CDA Architects Page 10 August 20, 2001 The pavement for lightly loaded traffic and parking areas should consist of 2 inches of asphalt concrete (AC) over 4 inches of crushed rock base (CRB) or 3 inches of asphalt -treated base (ATB). We recommend providing heavily loaded areas with 3 inches of AC over 6 inches of CRB or 4 inches of ATB. Heavily loaded areas are typically main driveways, dumpster sites, or areas with truck traffic. Water from planter areas and other sources should not be allowed to infiltrate into the pavement subgrade. The pavement section recommendations and guidelines presented in this report are based on our experience in the area and on what has been successful in similar situations. We can provide recommendations based on expected traffic loads and California Bearing Ration (CBR) value tests, if requested. As with any pavements, some maintenance and repair of limited areas can be expected as the pavement ages. To provide for a design without the need for any repair would be uneconomical. GENERAL EARTHWORK AND STRUCTURAL FILL All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. It is important that existing foundations be removed before site development. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building, behind permanent retaining or foundation walls, or in other areas where the underlying soil needs to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process. As discussed in the GENERAL section, the reuse of the on -site soils as structural fill will be challenging in dry weather and not possible in the wet season. This is due to the soils' silty nature and sensitivity to moisture. The allowable thickness of the fill lift will depend on the material type selected, the compaction equipment used, and the number of passes made to compact the lift. The loose lift thickness should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not sufficiently compacted, it can be recompacted before another lift is placed. This eliminates the need to remove the fill to achieve the required compaction. The following table presents recommended relative compactions for structural fill: Beneath footings, slabs 95% or walkways Filled slopes and behind 90% retaining walls 95% for upper 12 inches of Beneath pavements subgrade; 90% below that level 11 Where: Minimum Relative Compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D 1567-91 (Modified Proctor). GEOTECH CONSULTANTS, INC. R&P investment Co., LLC. c% CDA Architects August 20, 2001 JN 01248 Page 11 Use of On -Site if The GENERAL section should be reviewed for considerations related to the reuse of on -site soils. If grading radin activities take place during wet weather, or when the silty, on -site soil is wet, site preparation costs may be higher because of delays due to rain and the potential need to import granular fill. The on -site soil is generally silty and therefore moisture sensitive. Grading operations will be difficult during wet weather, or when the moisture content of this soil exceeds the optimum moisture content. Moisture -sensitive soil may also be susceptible to excessive softening and "pumping" from construction equipment, or even foot traffic, when the moisture content is greater than the optimum moisture content. It may be beneficial to protect subgrades with a layer of imported sand or crushed rock to limit disturbance from traffic. Structural fill that will be placed in wet weather should consist of a coarse, granular soil with a silt or clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve should be measured from that portion of soil passing the three -quarter -inch sieve. LIMITATIONS The analyses, conclusions, and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil and groundwater conditions encountered in the test pits are representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated soil conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking soil samples in test pits. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require making additional expenditures to attain a properly constructed project. It is recommended that the owner consider providing a contingency fund to accommodate such potential extra costs and risks. This is a standard recommendation for all projects. This report has been prepared for the exclusive use of R&P Investment Co., LLC, CDA Architects, and their representatives, for specific application to this project and site. Our recommendations and conclusions are based on observed site materials, and engineering analyses. Our conclusions and recommendations are professional opinions derived in accordance with current standards of practice within the scope of our services and within budget and time constraints. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. ADDITIONAL SERVICES GEOTECH CONSULTANTS, INC. R&P Investment Co., LLC. c% JN 01248 CDA Architects Page 12 August 20, 2001 that subsurface conditions are consistent with those indicated by our exploration, to evaluate whether earthwork and foundation construction activities comply with the general intent of the recommendations presented in this report, and to provide suggestions for design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. However, our work would not include the supervision or direction of the actual work of the contractor and its employees or agents. Also, job and site safety, and dimensional measurements, will be the responsibility of the contractor. The scope of our work did not include an environmental assessment, but we can provide this service, if requested. The following plates are attached to complete this report: Plate 1 Vicinity Map Plate 2 Site Exploration Plan Plates 3 - 6 Test Pit Logs Plate 7 Typical Footing Drain We appreciate the opportunity to be of service on this project. If you have any questions, or if we may be of further service, please do not hesitate to contact us. Respectfully submitted, GEOTECH CONSULTANTS, INC. Scott Stevens Geotechnical Engineer LsTo�; ST'� o was�� n n z R ° ��`� o .� IST SIGNAL�C� EXPIRES 01-31- a Z James H. Strange, Jr. P.E. Senior Geotechnical Engineer SES/JHS: esm GEOTECH CONSULTANTS, INC. —SMSET M 5TON bN"E"ROW'AiER K,1MG,PARK 24 MARINA > (n ALDQ Cn rfr > WILbUFE 104 a: SANCTUARY H M -7 A�* DR IEDWARDS MIP"V 21dTH ST IDWARDS = SIN 21 p:'A — — ::_, I.- 4PL 8 z Op 5 LLA OLA z E 418 U p .3 -KUL5�4 11 --A ET —4 aZ R SEE CS I FRIAR TUCK LN PA 2 ALAN-A-DALE PL S D 3 LITTLE JOHN CT f MwoHAVEN STP N01 2M S w PT e 238 SI c!— WELLS TSw 3: 23: 23 Vvy PL PL Sw I Lf T Sw > < > EA TOTEMPOLE L11 Cr L D T W MERRY LN) r --V?f GEOTECH CONSULTANTS,, UNC. VICINITY MAP 236xx - 84th Avenue West Edmonds, Washington Job NO. - ©a te: ae.Aug 'SeNRolte Plate. 2001 1 to Scale I 236TH STREET SOUTHWEST 1000' BLDG C t 1 998v\ .� BLDG D 996' N , -"TP-1 EXISTING BUILDING ( 238TH STREET SOUTHWEST 994' GEOTECH CONSULTAN-TS, INC. LEGEND APPROXIMATE TEST PIT LOCATIONS SITE EXPLORATION PLAN 236xx - 84th Avenue West Edmonds, Washington Jab No: pate: Scale: plate.. 01248 Aug 2001 Not to Scale 2 TEST PIT I 9�� �a�° �`� Description Brown organic FILL, loose 10 10 Brownish gray silty SAND, fine grained, moist, loose -becomes gray silty SAND w/trace gravel, fine to medium -grained, moist, medium- SM dense becomes glacially consolidated, dense glacial till Test Pit was terminated at 9 feet on July 31, 2001. * Groundwater seepage was observed at 7 feet during excavation. * No caving was observed during excavation. TEST PIT 2 4VN e faro �� Description Top I Black organic topsoil, moist, loose Brownish gray silty SAND, fine-grained, moist, loose Gray silty SAND with gravel, fine to medium -grained -becomes dense (glacial till) , moist, medium -dense * Test Pit was terminated at 10 feet on July 30, 2001. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. GEOTECH CONSULTANTS, INC. TEST PIT LOG 236XX - 84th Avenue West Edmonds, Washington Job No: Date: Logged by: Plate: 1 01248 1 July 2001 sEs 3 TEST PIT 3 wo���a��ti� c 5 10 15`— 5 iLl 15 Des criptio n Brownish gray silty SAND, fine-grained, moist, loose -becomes gray silty SAND wlgravel, fine to medium -grained, medium -dense * Test Pit was terminated at 5 feet on July 31, 2001. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. o Topi lopso TEST PIT 4 Description Brownish gray silty SAND, fine-grained, moist, loose gM with trace gravel, medium -dense -becomes fine to medium -grained, wet becomes gray gravelly silty SAND, dense (glacial till) * Test Pit was terminated at 9 feet on July 31, 2001. * No groundwater seepage was observed at 5 feet during excavation. * No caving was observed during excavation. GEOTECH CONSULTANTS, INC. TEST PIT LOG - 235XX - 84th Avenue West Edmonds, Washington Job No: Date: Logged by: Plate: 01248 July 2001 SES 4 TEST PIT 5 1m0��a �ti� G� 'Q�' 0 ,�a -�p Description Brown/ black organic silty SAND/ sandy silt FILL, moist, loose old tree found A Brownish gray, silty SAND, fine-grained, moist, medium -dense 10 SM -becomes gray, gravelly, silty, sandy, fine -to medium -grained, moist, dense (glacial till) 1 Test Pit was terminated at 12 feet on July 31, 2001. 15 No groundwater seepage was observed during excavation. * No caving was observed during excavation. TEST PIT 6 Description FILL Black w/ concrete FILL. Brownish gray, silty SAND, fine-grained, moist, loose. 5 SM -becomes gray, gravelly, silty, sandy, fine -to medium -grained, moist, dense (glacial till) SAND, dense, very moist 10 * Test Pit was terminated at 8 feet on July 31, 2001. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. * STRONG petroleum odor from V to 8. 15 AMNON * Discoloration in soil from 5' to 8'. GEOTECH CONSULTANTS, INC. TEST PIT LOG 236XX - 84th Avenue West Edmonds, Washington Job No: pate: Logged by: 1 Plate: 01248 July 2001 1 SES 5 TEST PIT 7 o�'N G� FILL FiLLI concrete rubble Description 5 Brownish gray, silty SAND, fine-grained, moist, loose becomes fine -to medium -grained; with trace gravel, medium -dense sM is -becomes glacially consolidated, dense (glacial till) 10' * Test Pit was terminated at 10 feet on July 31, 2001. L I * No groundwater seepage was observed during excavation. 15 * No caving was observed during excavation. CP (sp, �5 opsoul i opsoi TEST PIT 8 Description Brownish gray, silty SAND, fine-grained, moist, loose SM j -becomes fine -to medium -grained with trace gravel, medium -dense '. -becomes glacially consolidated (glacial till) 5 10 * Test Pit was terminated at 6 feet on July 31, 2001. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 15 GEOTECH CONSULTANTS, INC. TEST PIT LOG 236XX - 84th Avenue West Edmonds, Washington Job No: Date: Logged by: Plate: 01248 July 2001 SES 6 Slope backfill away from foundation. Provide surface drains where necessary. Backfill (See text for requirements) Nonwoven Geotextile Filter Fabric �- a- o- o- a-- IN v01Y QOc eOvQv0v o� oc? 00 00 OOO^ O - ^ Gn O J O O t, - 7- O- O - 6" min. I �_ o Tightline Roof Drain (Do not connect to footing drain) Vapor Retarder or Barrier -�-, .ca.�'. p- •a.�'. p� .a . �- .a . p- .Q . p- .Q . p- .Q . p- .Q •�o..Q.Oou��'O.'� �0•0Op00 � 00 9 Gi o o•. a •''. o '0'. n �, "o'. 0 •o'. 4.00 o e•a.00 _ o �.Op"�'� p • 4.00" = o. ° 'e1.0� . o. ° Q.OG O p , . O . •p . O • 'O . ' O •6 . ' O '0 . • O 4" Perforated Hard PVC Pipe (Invert at least 6 inches below slab or crawl space. Slope to drain to appropriate outfall. Place holes downward.) Free -Draining Gravel (if appropriate) NOTES; (1) In crawl spaces, provide an outlet drain to prevent buildup of water that bypasses the perimeter footing drains. (2) Refer to report text for additional drainage and waterproofing considerations. GEOTECH CONSULTANTS. INC. FOOTING DRAIN DETAIL 236xx - 84th Avenue West Edmonds, Washington Job No. Date. I scale: Plate. 01248 1 Aug 2001 1 Not to Scale 7