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HomeMy WebLinkAbout03393 - Technical Information Report - Geotechnical . • ������ � 13Z�6 Northeast ZOth Street, Suite I 6 Bellevue,N�'ashington 9800� CONSULTANTS, INC_ ca2s>�a�-s6is FAX(425)747-8561 November 10, 2006 JN 06366 LDK Construction, Inc. PO Box 2764 Renton, Washington 98056 Attention: Larry Kupferer via facsimile (425) 255-6416 Subject: Transmittal Letter— Geotechnical Engineering Study Proposed Residential Short Plat 1824 Camas Avenue Northeast Renton, Washington Dear Mr. Kupferer: We are pleased to present this geotechnical engineering report for the proposed residential short plat to be constructed in Renton. The scope of our services consisted of exploring site surface and subsurFace conditions, and then developing this report to provide recommendations for general earthwork, design criteria for foundations and retaining walls, and infiltration considerations. This work was authorized by your acceptance of our proposal, P-7166, dated September 29, 2006. 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. Respectfully submitted, GEOTECH CONSULTANTS, INC. ��'/�— i�• /�%/� Marc R. McGinnis, P.E. Principal cc: Schweikl � Associate4 , ,� ��� � � ��.: , � .�..��:1 '�;1�-� :i GEOTECH CONSULTANTS, INC. GEOTECHNICAL ENGINEERING STUDY Proposed Residential Short Plat 1824 Camas Avenue Northeast Renton, Washington This report presents the findings and recommendations of our geotechnical engineering study for the site of the proposed short plat to be located in Renton. We were provided with a preliminary site plan and a topographic map. Schweikl 8� Associates, PLLC developed these plans. We understand that the development will consist of dividing the property into four lots, regrading the southern portion of the site and building three new single- family residences. From the plan, the new construction would require relatively small cuts and fills, on the order of 1 to 2 feet. The existing house to the north (#1824), adjacent to Camas Avenue Northeast is to remain. We also understand that you propose to develop several infiltration trenches to disperse of stormwater on-site. If the scope of the project changes from what we have described above, we should be provided with revised plans in order to determine if modifications to the recommendations and conclusions of this report are warranted. SITE CONDIT/ONS SURFACE The Vicinity Map, Plate 1, illustrates the general location of the site. The property is located near the southem extent of Camas Avenue Northeast in Renton. The site is irregularly shaped, with approximately 50 feet of frontage along the Camas Avenue cul-de-sac. The property site widens out to the south and covers nearly 27,500 square feet. The northern end of the site is relatively flat, then a moderate slope begins to rise up to the south and southeast beyond the existing house and detached garage. The house is one-story, and the existing garage has been set into the slope. The southern slope remains landscaped but mostly undeveloped, except for a small shed in the southwest corner of the site. A short gravel dnveway connects Camas Avenue Northeast to a small concrete pad in front of the garage. There are also several small rockeries on the site. The site is surrounded on all sides by single family residences, except for the portion in the north that connects to Camas Avenue Northeast. There is a large rockery east of the site that ranges in height from 12 feet tall in the north end of the property down to 2 feet at the south end. The grade on the site is lower than the property to the east. We observed no signs/of slope instability on, or adjacent to, the subject property. SUBSURFACE The subsurface conditions were explored by excavating test pits at the approximate locations shown on the Site Exploration Plan, Pfate 2. Our exploration program was based on the proposed construction, anticipated subsurface conditions and those encountered during exploration, and the scope of work outlined in our proposal. GEOTECH CONSUITANTS, INC. LDK Construction J N 06366 November 10, 2006 Page 2 The test pits were excavated on October 3, 2006 with a rubber-tired backhoe provided by LDK Construction. A geotechnical engineer from our staff observed the excavation process, logged the test pits, and obtained representative samples of the soil encountered. "Grab" samples of selected subsurface soil were collected from the backhoe bucket. The Test Pit Logs are attached to this report as Plates 3 through 5. Soil Conditions We excavated five test pits at various locations around the property. In the test pits we encountered loose slightly silty sands overlying medium-dense sand with occasional gravels. The depth to the medium-dense sands varied across the site, from 2.5 to 4.5 feet, and became dense with depth. The excavation depth was limited to a maximum of 6 feet by the small size of the backhoe. Caving conditions were encountered in the upper, loose, soils. No obstructions were re�ealed by our explorations. However, debris, buried utilities, and old foundation and slab elements are commonly encountered on sites that have had previous development. Groundwater Condifions No groundwater seepage was observed during excavation. The test pits were left open for only a short time period and it was only possible to reach a depth of 6 feet. It should be noted that groundwater levels vary seasonally with rainfall and other factors. The stratification lines on the logs represent the approximate boundaries between soil types at the exploration locations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration 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 obsenred during excavation. The compaction of backfill 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. CONCLUSIONS AND RECOMMENDATIONS GENERAL THlS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FlNDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE CONTAINED 111! THE REMAINDER OF TNlS REPORT. ANY PARTY RELYING ON rHlS REPORT SHOULD READ THE ENTIRE DOCUMENT. The test pits conducted for this study encountered loose slightly silty sand overlying medium-dense sand that became dense with depth. It is our professional opinion that the proposed single family residences can bear on the medium-dense to dense sand underlying the loose, slightly silty sands. GEOTECH CONSULTANTS. INC. LDK Construction JN 06366 November 10, 2006 Page 3 It will be important that any soils loosened by the teeth of the backhoe bucket be removed from foundation subgrades before concrete is poured. Excavation must not undermine adjacent existing structures, such as the rockery to the east. In general, temporary cuts should not extend below a 2:1 (Horizontal:Vertical) zone sloping from footings, walls or rockeries, unless shoring is provided. We also conducted infiltration tests in Test Pits 1 and 2 by the method outlined in King County's Surface Water Design Manual (SWDM). Each test was conducted at 5.5 to 6 feet, near the bottom depth of the proposed infiltration facilities. After a period of soaking's; three trials were performed in each of the two test pits. From the data obtained from the infiltration tests and what we understand about the planned facilities' geometry, we recommend a design infiltration rate of no more than 11 inches per hour. Under the King County SWDM, a geometry correction would need to be applied to this value once the preliminary system geometry has been determined. The performance of any subsurface infiltration system will degrade over time, due to clogging of the ' surrounding soil with silt and debris carried in by the runoff. The effective life of an infiltration system can be prolonged by frequent cleaning of gutters and surface drains. Storm detention/retention facilities and other utilities are often installed below, or near, structures. I The walls of storm vaults must be designed as either cantilever or restrained retaining walls, as appropriate. Wall pressures for the expected soil conditions are presented in the permanent foundation and retaining walls section of this report. It is important that the portion of the structure above the permanent detained water level be backfilled with free-draining soil, as recommended for retaining walls. Should drainage not be provided, the walls must be designed for hydrostatic forces acting on the outside of the structure. The backfill for all underground structures must be compacted in lifts according to the criteria in the pervious section of this report. Trenches for underground structures and utilities should not cross a line extending downwards from a new or existing footing at an inclination of (1:1) (Horizontal:Vertical), or a line extending downwards from a property line at an inclination of 1:1 (H:�. We should be consulted if these excavation zones will be exceeded for installation of storm facilities or other utilities. The erosion control measures needed during the site development wifl depend heavily on the weather conditions that are encountered. We anticipate that a silt fence will be needed around the downslope sides of any cleared areas. Rocked construction access roads should be extended into the site to reduce the amount of soil or mud carried off the property by trucks and equipment. Wherever possible, these roads should follow the alignment of planned pavements, and trucks should not be allowed to drive off of the rock-covered areas. Existing catch basins in, and immediately downslope of, the planned work areas should be protected with pre-manufactured silt socks. Cut slopes and soil stockpiles should be covered with plastic during wet weather. Following rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable conditions, including, but not limited to, moisture problems with flooring systems, excessively moist air within occupied a�eas, and the growth of molds, fungi, and other biological organisms that may be harmful to the health of the occupants. The designer or architect must consider the potential GEOTECH CONSULTANTS, INC. LDK Construction J N 06366 November 10, 2006 Page 4 vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or mechanical, to prevent a build up of excessive water vapor within the planned structure. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report, in its entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. SElSMIC CONSIDERATIONS 'I In accordance with Table 1615.1.1 of the 2003 International Building Code (IBC), the site soil pro- file within 100 feet of the ground surface is best represented by Soil Profile Type C (Very Dense Soil. The site soils are not susceptible to seismic liquefaction because of their dense nature and the absence of near-surface groundwater. � CONVENTlONAL FOUNDATJONS The proposed structures can be supported on conventional continuous and spread footings bearing on undisturbed, native sand, or on structural fill placed above this competent native soil. See the section entitled General Earthwark and Structural Fill for recommendations regarding the placement and compaction of structural fill beneath structures. Adequate compaction of structural fill should be verified with frequent density testing during fill placement. Prior to placing structural fill beneath foundations, the excavation should be observed by the geotechnical engineer to document that adequate beanng soils have been exposed. We recommend that continuous and individual spread footings have minimum widths of 16 and 24 inches, respectively. Exterior footings should also be bottomed at least 18 inches below the lowest adjacent finish ground surface for protection against frost and erosion. The local building codes should be reviewed to determine if different footing widths or embedment depths are required. Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. 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. An allowable bearing pressure of 2,500 pounds per square foot (psfl is appropriate for footings supported on competent native soil. A one-third increase in this design bearing pressure 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 one inch, with differential settlements on the order of half an inch in a distance of 50 feet along a continuous footing with a uniform load. GEOTECH CONSULTANTS, INC. LDK Constructron J N 06366 November 10, 2006 Page 5 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: I, � � � o � Ij Coefficient of Friction 0.50 Passive Earth Pressure 300 pcf Where: (i)pcf is pounds per cubic foot,and (ii) passive earth pressure is computed using the equivalent fluid density. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. 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 le�el backfill: � . � Active Earth Pressure " 35 pcf Passive Earth Pressure 300 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 unifortn 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. GEOTECH CONSULTANTS, INC. LDK Constructron J N 06366 November 10, 2006 Page 6 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 sfopes, 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. The surcharge due to tra�c loads behind a wall can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid density. 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. Retaininq Wall Backfil!and Waterproofina 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 sand is used as backfill, 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 seepage is encountered. For increased protection, drainage composites should be placed along cut slope faces, and the walls should be backfilled entirely with free-draining soil �I The purpose of these backfill requirements is to ensure that the design critena 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 i impermeable soil or topsoil, or the surface should be pa�ed. 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 FiII contains recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls. The above recommendations are not intended to waterproof below-grade walls, or to prevent the formation of mold, mildew or fungi in intenor spaces. Over time, the performance of s�rbsurFace drainage systems can degrade, subsurface groundwater flow patterns can change, and utilities can break or develop leaks. Therefore, waterproofing should be provided where future seepage through the walls is not acceptable. This typically includes limiting cold-joints and wall penetrations, and using bentonite panels or membranes on the outside of the walls. There are a variety of different waterproofing materials and systems, which should be installed by an experienced contractor familiar with the anticipated construction and subsurface conditions. Applying a thin coat of asphalt emulsion to the outside face of a wall is not considered waterproofing, and will only help to reduce moisture generated from water vapor or capillary action from seeping through the concrete. As with any project, adequate ventilation of basement and crawl space areas is important to GEOTECH CONSULTANTS, INC. LDK Construction J N 06366 I November 10, 2006 Page 7 important to prevent a build up of water vapor that is commonly transmitted through concrete walls from the surrounding soil, even when seepage is not present. This is appropriate even when waterproofing is applied to the outside of foundation and retaining walls. We recommend that you contact a specialty consultant if detailed recommendations or specifications related to waterproofing design, or minimizing the potential for infestations of mold and mildew are desired. The General, Slabs-On-Grade, and Drainage Considerations sections should be reviewed for additional recommendations related to the control of groundwater and excess water vapor for the anticipated construction. SLABS-ON-GRADE The building floors can be constructed as slabs-on-grade atop the native sand, or on structural fill. 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. Even where the exposed soils appear dry, water vapor will tend to naturally migrate upward through the soil to the new constructed space above it. All interior slabs-on-grade must be underlain by a capillary break or drainage layer consisting of a minimum 4-inch thickness of gravel or crushed rock that has a fines content (percent passing the No. 200 sieve) of less than 3 percent and a sand content (percent passing the No. 4 sieve) of no more than 10 percent. As noted by the American Concrete Institute (ACI) in 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 plastic sheeting, are typically used. A vapor retarder is defined as a material with a permeance of less than 0.3 US perms per square foot (psfl 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. Where plastic sheeting is used under slabs, joints should overlap by at least 6 inches and be sealed with adhesive tape. The sheeting should extend to the foundation walls for maximum vapor protection. If no potential for vapor passage through the slab is desired, a vapor barrier should be used. A vapor bamer, 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. ROCKERIES We anticipate that rookeries 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 an exposed height of 8 feet and placing them against only dense, competent, native soil. The lower 12 inches of any rockery must be embedded below the finish grade that will exist at the face of the rockery. Rockeries that are taller than 8 feet, or that are placed in front of loose soil or in areas of compacted fill will require additional engineering. Special design will also be required for rockeries that would support surcharges from vehicles or other load-bearing elements. GEOTECH CONSULTANTS, INC. LDK Construction JN 06366 November 10, 2006 Page 8 The construction of rockeries is, to a large extent, an art not entirely controllabie 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 and standards. In general, the lowest two rows of rocks should have a minimum depth (as measured perpendicular to the rockery's face) of 1/3 of the rockery's height. 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. 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. The upper soils are loose and prone to caving, vertical cuts in this sand may not maintain stability for long periods of time. 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 A. Therefore, temporary cut slopes greater than 4 feet in height should not be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. The above-recommended temporary slope inclination is based on the conditions exposed in our explorations, and on what has been successful at other sites with similar soil conditions. It is possible that variations in soil and groundwater conditions will require modifications to the inclination at which temporary slopes can stand. 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. It is also important that surface water be directed away from temporary slope cuts. The cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that sand can cave suddenly and without warning. Excavation, foundation, and utility contractors should be made especially aware of this potential danger. These recommendations may need to be modified if the area near the potential cuts has been disturbed in the past by utility installation, or if settlement-sensitive utilities are located nearby. All permanent cuts into native soil should be inclined no steeper than 2:1 (H:�. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficial layer of soil. � DRAINAGF CONSIDERATIONS Foundation drains should be used where (1) crawl spaces or basements will be below a structure, (2) a slab is below the outside grade, or (3) the outside grade does not slope downward from a building. 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 GEOTECH CONSULTANTS, INC. � LDK Construction J N 06366 November 10, 2006 Page 9 crawl space, and it should be sloped for drainage. All roof and su►face water drains must be kept separate from the foundation drain system. A typical drain detail is attached to this report as Plate 6. 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 (1) a crawl space will slope or be lower than the surrounding ground surface, (2) an excavation encounters significant seepage, or (3) an excavation for a building will be close to the expected high groundwater elevations. We can provide recommendations for interior drains, should they become necessary, during excavation and foundation construction. As a minimum, a vapor retarder, as defined in the S/abs-On-Grade section, should be provided in any crawl space area to limit the transmission of water vapor from the underlying soils. Also, an outlet drain is recommended for all crawl spaces to prevent a build up of any water that may bypass the footing drains. No 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 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. Additionally, a drainage swale should be provided upslope of the buildings to intercept surface run-off and direct it into the storm drains. Water from roof, storm water, and foundation drains should not be discharged onto slopes; it should be tightlined to a suitable outfall located away from any slopes. GFNERAL EARTHWORK AND STRUCTURAL F1LL All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. 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 mafsture 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. 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: GEOTECH CONSULTANTS, INC. LDK Consfruction J N 06366 November 10, 2006 Page 10 � � � � � � � � Beneath footings, slabs 95% or walkwa s Filled slopes and behind 90% retainin walls 95% for upper 12 inches of Beneath pavements subgrade; 90% below that level Where: Minimum Relative Compaction is the ratio,expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accorda�ce with ASTM Test Designation D 1557-91 (Modified Proctor). 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. L/MITAT/ONS The 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 i subsurface conditions encountered during construction are significantly different from those observed in our explorations, we shoutd 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 �ocations. 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 LDK Construction, and its representatives, for specific application to this project and site. Our recommendations and conclusions are based on observed site materials, and selective laboratory testing and engineering analyses. Our concfusions 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. Our services also do not include assessing or minimizing the potential for biological hazards, such as mold, bacteria, mildew and fungi in either the existing or proposed site development. GEOTECH CONSULTANTS, INC. � LDK Construction J N 06366 November 10, 2006 Page 11 ADDITIONAL SERV/CES In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide geotechnical consultation, testing, and observation services during construction. This is to confirm 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. During the construction phase, we will provide geotechnical observation and testing services when requested by you or your representatives. Please be aware that we can only document site work we actually observe. It is still the responsibility of your contractor or on-site construction team to verify that our recommendations are being followed, whether we are present at the site or not. The following plates are attached to complete this report: Plate 1 Vicinity Map Plate 2 Site Plan Plates 3 - 5 Test Pit Logs �', Plate 6 Typical Footing Drain Detail I i i , � � ' GEOTECH CONSULTANTS, INC. � LDK Construction J N 06366 November 10, 2006 Page 12 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. Zack J. Munstermann Geotechnical Engineer � �° ���'� � �� ��:���`�� � �� �,`°�� '� �,/,��.� �� � y ��,:�y� �4C �'t.`• �t,"" ..� � R;� ;-� T ��� ��,D :t/%fd''w �f;�. _ � r��`�y ��`���� ,�� �� j,o � � � �. � f .tY..l� � 1��� ����� ;��� �� �ta� Marc R. McGinnis, P.E. Principal ZJM/MRM: jyb GEOTECH CONSULTANTS, INC. � • � � _ i( Au�„t^i�( ��'�_.mj, � �m �/�F x o��00 311S ..'��� NE ABERD�EN � ... . f�� _:�Nmryi ,x ..` N srt�,�auiuw��y-�.��~ N��si,�rirtrr�- Sx, N Z GY -11�' � ----..-i �� .�^T"'"i�� � .y�� z I� �" _ � ._I �c,uus_ I�PL NE g�N� ��� o�� @ -a F���.�,��a�J,tS ��T-Nic�i '^ � �� 1� �F 9 m I � c� xE- < 1 , ^a � i i'^ Im ..I ii3rx��v ; DA7T0 �� I `� �AVNE`a uw5 u x 5.AL NE_ '^ICAMA$ V f.i NE ��G�}/ ( � M,� �o �� �� � '� V.�.� _" AV NE ....— � �YiUYAY P iNFY[� rION[�r IUA=7;0a�_—"—__ -.-. 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O c� N19r'�'' � .,AV._;f � � m q J' .__...SE_ i o N �- . .� --. NB� .. `"�c,`�, M n�i � I0y �'� . � � _ .��Im: -�I� � ��n i �� - � YAs`�—Q- ��1. � �.o� a � ti � � CW �P�SF�� N v � . � i�, � �' a�d� � � =.�� `��C�� ��; �/ L�, �'` ; ' � ; .: '� �'." '.,.. '•� '',•. � � � �', TP 1 ��; ; � ; o ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ___----"" Existing House � _----'' � ;�-- � � � � � � � � � � � ; � ; � TP3 � TP2 � � � � � ; � ; ; � � � � � � � � � � ; � � � � � � � � � � � � � � � ; � ` � TP 4 TP 5 � � , , � � � � Property Line � � � � — Approximate test pit location SITE PLAN � GEOTECH 1824 Camas Ave NE � CONSULTANTS,nvc. Renton, WA � ,--� � Job No: ate: ate: 06366 Nov2006 No Scale 2 • l {� oj\ �����o,����,����<� � TEST P IT 1 o�~��' a�� 5� • � G �S �S Description I Crushed gravel over ` " Brown, slightly silty SAND, medium-to fine-grained, organics, moist, SP medium-dense � 5 * Test Pit was terminated at 6 feet on October 3, 2006. * No groundwater seepage was observed during excavation. * Caving was observed from 0 to 2.5 feet 10 during excavation. 15 �� �,je ��`� TEST PIT 2 '� w'�� o��w��� a�'�ti� �5 ��� �G°� `��a�° �}5 Description !' Grass over Brown, slightly silty SAND with organics, medium-to fine-grained, moist, :: SP ; loose - becomes medium-dense, no silt, no organics � - becomes gray, dense at bottom of hole * Test Pit was terminated at 5.5 feet on October 3, 2006. * No groundwater seepage was observed during excavation. " No caving was observed during excavation. 10 15 TEST PIT LOGS � GEOTECH 1824 Camas Avenue NE corrsuLT.arrrs,nvc. Renton, Washington � �,��� Job No: Date: Logged by: Plate: 06366 Nov.2006 ZJM 3 t�' °I� �� ti�` �� TEST PiT 3 ti��o~�fi�,�,�a�'roti� 5 G � ��� G° ��' �;5 Description ' Grass over Brown, slightly silty SAND, organics, medium- to fine-grained, moist, loose SP - no silt, no organics, becomes gray, medium-dense 5 * Test Pit was terminated at 4 feet on October 3, 2006. '` No groundwater seepage was observed during excavation. * Caving was observed in the upper 2 feet during excavation. 10 15 �,� ��,<�,����� TEST PIT 4 �,r' o`���,���a�',��,� GS 9�� ��° �a �}5 Description , Brown, slightly silty SAND with organics, medium- to fine-grained, moist, ; gp . loose �: - no organics, no silt, becomes medium-dense, gray 5 * Test Pit was terminated at 4 feet on October 3, 2006. " No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 � 15 ' TEST PIT LOGS � � GEOTECH 1824 Camas Avenue NE corrsvLT�,rrrs,nvc. Renton, Washington Job No: Date: Logged by: Plate: 06366 Nov. 2006 ZJM 3 �� . �,�<���'�t TEST PIT 5 ' w���,o���,��'�a'`roti� ��a ��� G° �S°' �5 Description Brown, slightly silty SAND with organics, medium- to fine-grained, moist, Sp loose '�: - becomes light gray, medium-dense, no silt, no organics - becomes gray 5 * Test Pit was terminated at 5 feet on October 3, 2006. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. 10 15 � � i , TEST PIT LOGS � � GEOTECH 1824 Camas Avenue NE corrsuLT�rrrs,nvc. Renton, Washington � Job No: Date: Logged by: Plate: 06366 Nov.2006 ZJM 3 Slope backfill away from foundation. Provide surFace drains where necessary. Tightline Roof Drain (Do not connect to footing drain) Backfill �a (See text for � requirements) e O � � � Nonwoven Geotextile � � Filter Fabric o Washed Rock � Possible Slab (7/8" min. size) .�- - .a.• - G�:c�• o�°���. c-• o•. o-•�•.. � •o.�. �.��� a- o.�a��• �.• a 0 o G � ' '�oo 00°•�oe„�o�•o�u a�?�•000 :.,o.o� oo°�coa v'�o . o,:� '� o .C... o'o o.� o o a:� ° � °,:� °�� o:c l7 ° . . . . .�Qap °'. op� �'•�.o�o�O•�.op� �••o.op� �"•a.o� . O�G,�O � o ab''�.o .•o' .o .•o. •b .y''�.'o .•o'S.o 0 0 0 • . 4" min °o 0 00 0�- � ° ° _ � Vapor Retarder/Barrier and Capillary Break/Drainage Layer 4" Perforated Hard PVC Pipe (Refer to Report text) (Invert at least 6 inches below slab or crawl space. Slope to drain to appropriate outfall. Place holes downward.) 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, waterproofing, and slab considerations. � FOOTING DRAIN DETAIL � � GEOTECH 1824 Camas Ave NE CONSULTAN'1'S,nvc. Renton, WA � o Date: ca e: P/ate: ��� 06366 Nov.2006 Not to Scale 6