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BLD20060233.pdf• CITY OF EDMONDS 121 5TH AVENUE NORTH - EDMONDS,WA 98020 PHONE: (425) 771-0220 - FAX: (425) 771-0221 *PERMIT MUST BE POSTED ON JOBSITE* STATUS: ISSUED ENG20060233 RIGHT OF WAYPERM IT (2-Multi-Fainfly) Pennit Number: ENG20060233 Expiration Date: 10/18/2007 Job Address: 23707 84TH AVE W, EDMONDS Location: PACIFIC HOMES DEVELOPMENT LLC PACIFIC HOMES DEVELOPMENT LLC 2400 NW 80TH ST 2400 NW 80TH ST SEATTLE, WA 98117 SEATTLE, WA 98177 INCOMPLETE 206-571-5978 LICENSE #: PACIFIHD97507 EXP: 12/20/2007 Widen 84th ave and pave, install c/g, s/w and utilites per approved civils ASSESSED VALUE: $0.00 PROPERTY AREA: 0 SIDEWALK (OXO) DURATION IN MONTHS 0 FEE $0 00 STREET DISRUPTION TRENCH CUT ( 0 X 0 ) PARKING: ( 0X0) DURATION IN MONTHS. 0 FEE: $0.00 YEAR OF OVERLAY: 0 FEE: $0.00 ALLEY: ( 0X0 1 DURATION IN MONTHS: 0 FEE: $0.00 INDEMNITY The Applicant has signed an application which states he/she holds the City of Edmonds harmless from injuries, damages or claims of any kind or description whatsoever, foreseen or unforeseen, that may be made against the City of Edmonds or any of its departments or employees, including but not limited to the defense of any legal proceedings including defense costs and attorney fees by reason ofgranting this permit. THE CO NTRACTO R IS RESPONSIBLE FO R WORKMANSHIP AND MATERIALS FOR A PERIOD O F O NE YEAR FOLLOWING THE FINAL INSPECTION AND ACCEPTANCE OF THE W ORK. • Traffic Control and public safety shall be in accordance with City regulations as required by the City Engineer. Every dagger must be trained as required by (WAC) 296-155-305 and must have certification verifying completion of the required training in their possesion. • Restoration is to be in accordance with City codes. All street -cut trench work shall be patched with asphalt or City approved material prior to the end of the workday -NO EXCEPTIONS. • Three sets of construction drawings of proposed work are required with the permit application. CALL DIAL -A-DIG (1-800424-5555) BEFOREANY EXCAVATION CALL FOR INSPECTION (425) 771-0220 EXT. 1326 24 HOUR NOTICEREQUIRED FOR ALL INSPECTION REQUESTS THIS APPLICATION IS NOTA PERMITUNTIL SIGNED BY THE CITY ENGINEEROR HIS/HER DEPUTY: AND FEES ARE PAID, AND RECEIPT IS ACKNOWLEDGED IN SPACE PROVIDED. RELEASED BY Printed: Thursday. J TE ❑ FILE COPY F� INSPECTOR COPY F—] APPLICANT COPY STATUS: ISSUED ENG20060233 • Restore ROW to City standards • Restore Landscape to like or better conditions. • Call for locates of underground utilities prior to any excavation. • Alert affected residents and/or businesses prior to work start. • Conform to approved working drawings and Tragic Control plan. • Public utilities maintain 5'separation fiomCity Utilities. • Verify clear bore crossings • Utility patch restoration to be in accordance with Edmonds Standard detail E2.3 • CDF is required for trench backfill. Refer to Edmonds Standard Detail E4.4 • Maintain erosion & sedimentation control. Keep street clean. • Construction hours are Monday -Friday Tan -bpm and Saturdays 10am-6pm No work on Sundays or Federal Holidays. • Call for required inspections as noted. INSPECT'ION'S • E Tra8ic Control • E-Curb/Gutter Form • GSidewalk Form • E -Driveway Form & Slope Ver. • E -Pavement Subgrade • E -Pavement Compaction Test Report • E -Pavement Striping • E -Engineering Final PARTIAL INSPECTION DATE: INITIAL: NOTES: PARTIAL INSPECTION DATE: INITIAL: NOTES: FINAL INSPECTION APPROVED DATE: INITIAL: GE4TECH CONSULTANT'S, INC_ 84th Avenue Edmonds, LLC 13215 — 8th Avenue Northwest Seattle, Washington 98177 Attention: Pat Archer Subject: Review of Plans Proposed Two Townhomes Buildings 23707 — 84th Avenue West Edmonds, Washington 13256 Northeast 20th Street, Suite 16 Bellevue, Washington 98005 (425) 747-5618 FAX(425)747-8561 July 24, 2006 JN 05481 Reference: "Geotechnical Engineering Study — Proposed Two Townhome Buildings", Geotech Consultants, Inc., December 22, 2005. Dear Mr. Archer- We rcher We previously prepared a Geotechnical Engineering Study for the above referenced project, dated December 22, 2005. As requested, we have. completed a general review of the geotechnical aspects of the plans for the two townhome buildings to be constructed in Edmonds. The plans we reviewed included a partial copy of the architectural and structural plans (Sheets 1, 2, 5, 6, 10, 10a, and 17). Ronald D. Johnson (Architect) prepared these plans, which are dated November 2005. Sheet 1 shows; that an allowable bearing pressure of 2,000 pounds per square foot (psf) was used in the design of the townhome foundations. In our study, we recommended an allowable bearing pressure of 3,000 psf. Thus, it is our opinion that the lower bearing capacity is acceptable, provided the footings still bear on the dense glacial till. We were only given the elevation views for Building 1 (Sheets 5 and 6). Based on discussions with Ryan Berry of Ronald D. Johnson (Architect), we understand that the proposed garage slab elevation for both buildings will be at elevation 448 feet. It appears that the necessary excavation for both buildings can be made safely within property limits. In our judgment, the plans that we reviewed conform to the recommendations in our geotechnical engineering report. Per conversations with you, we will be retained to perform geotechnical observation and testing services on this project as directed by the City of Edmonds. We acknowledge appointment as Special Inspector for this project, and by copy of this letter, request that we be kept informed of the progress of construction so we are able to make the necessary observations, as required by City of Edmonds, in a timely manner. CITY`y ESUB JUL 27 2006 BUILDING; DEPARTMENT Am CITY OF EDMONDS I' j 84th and Edmonds, LLC July 24, 2006 JN 05481 Page 2 We.trust that this letter meets your immediate needs for the proposed development. Please contact us if we can be:of further service. cc: Ronald D. Johnson (Architect) GDB/MRM: jybi Respectfully submitted, GEOTECH CONSULTANTS, INC. Gerry D. Bautista, Jr. Geotechnical Engineer s1ft 4 G VL- .Mei- . WAS cn 27 IS7'E4�'� NAL �/ZK f� EXPIRES Marc R. McGinnis, P.E. Principal GEOTECH CONSULTANTS, INC. EDM 06-09 OEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC 13215 — 8th Avenue Northwest Seattle, Washington 98177 Attention: Pat Archer Subject: Transmittal Letter — Geotechnical Engineering Study Proposed Two Townhome Buildings 23707 — 84th Avenue West Edmonds, Washington Dear Mr. Archer: 13256 Northeast 20th Street, Suite 16 Bellevue, Washington 98005 (425) 747-5618. FAX (425) 747-8561 December 22, 2005 JN 05481 We are pleased to present this geotechnical engineering report for the property at 23707 — 84th Avenue West in Edmonds. The scope of our services 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-6928, dated December 8, 2005. 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. GDB/MRM: esn Respectfully submitted, GEOTECH CONSULTANTS, INC. Gerry D. Bautista, Jr. Geotechnical Engineer GEOTECH CONSULTANTS, INC. RECEIvED VE8 - 7 2% .BUILDING DEPT. CITY COPY GEOTECHNICAL ENGINEERING STUDY Proposed Two Townhome Buildings 23707 — 84th Avenue West Edmonds, Washington This report presents the findings and recommendations of our geotechnical engineering study for the property at 23707 — 84th Avenue West in Edmonds. We were provided with a site plan showing the location of the existing residence and garage, and the proposed buildings. Ronald D. Johnson (Architect) prepared this plan, which is dated July 20, 2005. Based on this plan and conversations with Mr. Pat Archer, we understand that the existing .residence and garage will be demolished and be replaced .by two, 3 -unit townhouse buildings. This is similar to the recent development of the adjacent two southern parcels. Each building will have an approximate footprint of 28 feet by 58 feet, and each townhouse. unit will consist of two stories over an on -grade garage. The garage slab for each building will have a proposed elevation of 448 feet. The two buildings will be set back 10 feet from their nearest adjacent northern or southern property lines. Minimal excavation is anticipated to reach the planned excavation bottom for both buildings. A new driveway will enter the property from the center of the western property line and terminate near the east property line. A short retaining wall will be constructed at the driveway's eastern terminus. 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 CONDITIONS SURFACE The Vicinity Map, Plate 1, illustrates the general location of the site in Edmonds. The irregular- shaped, level property occupies approximately 100 feet of frontage along the eastern side of 84th Avenue West and is approximately 100 feet in depth at the northern property line, and 90 feet at the southern property line. A two-story, single-family residence (#23707) is situated at the center of the property. The residence contains a basement with an approximate floor elevation of 446 feet. We observed some vertical foundation cracking on the foundation of the residence. A detached garage is located at the northeast corner of the property. This garage has an approximate slab elevation of 450 feet. A concrete driveway enters the property from its northwest corner and serves the garage. This driveway is heavily cracked and shows signs of past settlement. The front and rear yards of the residence are covered with grass and some sporadic small trees and shrubs. A three-story townhouse building complex borders the property to the south. The northern building is set back approximately 10 feet from the southern property line of the subject property at its closest point, and has an approximate garage elevation of 447 feet, which is roughly the elevation of the adjacent street. As described above, we understand that the proposed townhomes will have a layout and configuration similar to this adjacent property. A fenced vacant lot covered with tall grass and sporadic trees borders the property to the north, and a . greenbelt/easement borders the property to the east. We previously performed a Geotechnical Engineering Study of the adjacent northern and eastern properties in 2001. Two GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 2 single-family residences were previously situated on the adjacent northern property but have since been destroyed and removed. SUBSURFACE The subsurface conditions were explored by excavating four test pits at the approximate locations shown on the Site Exploration Plan, Plate 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. The test pits were excavated on December 16, 2005 with a mini-trackhoe. 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 and 4. Soil Conditions The test pits generally encountered approximately 1.5 to 2 feet of topsoil directly underlying the surface, except for Test Pit 4 (excavated in front of the garage), which encountered approximately 6 inches of silty sand fill overlying this topsoil. Native, loose to medium - dense, silty sand was encountered below the topsoil. At a depth of 3 to 4 feet, the silty sand became very dense. The dense to very dense, native soils have been glacially compressed, and are locally referred to as glacial till. These soils were exposed to the maximum explored depth of the test pits. The test pits were excavated to depths of 4.5 to 5.5 feet below existing grade, until the native soils were difficult to excavate using the mini- trackhoe, or the mini-trackhoe encountered refusal conditions. No caving was observed in the test pits. As mentioned earlier, we performed a Geotechnical Engineering Study on the adjacent northern and eastern properties in 2001. The test pits we excavated in 2001 that are located adjacent to the subject property encountered 3 to 4 feet of loose fill overlying the native glacial till soils. The native soil conditions encountered in our previous study are consistent with the native soil conditions encountered for this study. Although not encountered in our test pits, boulders are often encountered scattered throughout glacial till soils. Groundwater Conditions No groundwater seepage was observed in the test pits. It should be noted that groundwater levels vary seasonally with rainfall and other factors. The test pits were excavated in late fall. It is relatively common that groundwater is found in more permeable soil layers, pockets within the till, and perched between the near -surface weathered soil and the underlying glacial till. This perched groundwater is often localized and typically forms following extended wet weather. 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 GEOTECH CONSULTANTS, INC. J f 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 3 on the test pit logs are interpretive descriptions based on the conditions observed 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 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 dense to very dense native silty sand soils within 3 to 4 feet of existing grade. It is our opinion that conventional footings can be used for building support bearing on these dense to very dense soils or on compacted structural fill placed over these soils. Overexcavation may be required to remove, loose, near -surface fill and native soils to expose the competent bearing soils. With the possibility of seepage and the moisture sensitivity of the silty sand, footing subgrades may need to be protected from disturbance by placing a mat of imported, granular fill. This prevents the subgrade soils from being softened under foot traffic during placement of foundation forms and reinforcing. We recommend that all existing topsoil and fill also be removed from beneath floor slabs. Where this does not occur, noticeable slab settlement relative to the foundations may occur. This recommendation is particularly important if "thickened slabs" will be used to support interior walls, shear walls, or columns in the buildings. The native. soils encountered in the test pits are typical for the vicinity, but they are fine-grained, making them moisture sensitive. These soils can be reused as structural fill or pavement fill only if they are 1) placed in dry weather, and 2) at, or near, the optimum moisture content. Reusability of the on-site, native sands and silty sands as structural fill will be weather- and time -dependent. These soils were generally at, or slightly above, their optimum moisture content at the time of our explorations. Overly most to wet soils will need to be dried by aeration during dry, sunny days, or by the addition of cement to kiln dust. Generally, this type of earthwork will require hot weather and grading over larger areas. In confined areas, such as utility trenches or behind retaining walls, the on-site soils will be difficult to impossible to reuse and obtain adequate compaction if they are wet. As a result of this, wet weather earthwork on till sites are typically more difficult and expensive than on sites that are underlain by cleaner sands. Prior to paving, we recommend that a proof -roll be performed with a fully -loaded dump truck or other heavy piece of construction machinery to identify any yielding subgrade areas that would need to be removed and replaced with imported, granular structural fill. If yielding areas are encountered, some overexcavation may be required to remove these loose, near -surface soils. Additional recommendations on pavements can be found in a subsequent section of this report. GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 4 Storm detention/retention facilities and other utilities are often installed below, or near, structures. 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 General Earthwork and Structural Fill 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). 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 will depend heavily on the weather conditions that are encountered. A rocked construction access road should be extended into the site to reduce the amount of soil or mud carried'off the property by trucks and equipment. Wherever possible, this road 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. As with any project, additional erosion control measures may be required depending on conditions encountered during construction. 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. SEISMIC CONSIDERATIONS The site class definition is illustrated on Table No. 1615.1.1 f the 2003 International Building Code (IBC). In accordance with Table 1615.1.1 of the 2003 IBP/he site soil profile 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. CONVENTIONAL FOUNDATIONS The proposed structures can be supported on conventional continuous and spread footings bearing on undisturbed, dense glacial till. We recommend that continuous and individual spread footings have minimum widths of 12 and 16 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 GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 5 prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand.. An allowable bearing pressure of 3,000 pounds per square foot (psf) is appropriate for footings supported on competent native soil or on properly compacted structural fill. 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 will be less than one inch. 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: PARAMETER VALUE Coefficient of Friction 0.45 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. 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 No significant retaining walls are expected for the development. However, 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: 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. GEOTECH CONSULTANTS, INC. 35 pcf PARAMETER Active Earth Pressure * Passive Earth Pressure 350 pcf Coefficient of Friction 0.45 Soil Unit Weight 140 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. GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 6 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., The surcharge due to traffic loads behind a wall can typically be accounted for by adding a uniform pressure equal to I 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. Retaining Wall Backfill and Waterproofin_g 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 till soils can be adequately compacted as wall backfill, a minimum 12 -inch width of free -draining sand and gravel should first be placed against the wall. For increased protection, drainage composites should be placed along cut slope faces, and the walls should be backfilled entirely with free -draining soil. The later section entitled Drainage Considerations should also be reviewed for recommendations related to subsurface drainage behind foundation and retaining walls. 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 below -grade walls, or to prevent the formation of mold, mildew or fungi in interior spaces. Over time, the performance of subsurface drainage systems can degrade, subsurface groundwater flow GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC December 22, 2005 JN 05481 Page 7 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 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. SLABS -ON -GRADE The building floors can be constructed as slabs -on -grade atop existing non-organic soils, 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 slabs -on -grade inside the buildings 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. This capillary break/drainage layer is not necessary if an underslab drainage system is installed. 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 (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. 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 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. In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well -graded compactible granular material, such as a 5/8 inch minus crushed rock pavement base, should be placed over the vapor retarder or barrier for protection of the retarder or barrier and as a "blotter" to aid in the curing of the concrete slab. Sand was not recommended by ACI for this purpose. However, the use of material over the vapor retarder is controversial as noted in current ACI literature because of the potential that the protection/blotter material can become wet between the time of its placement and the installation of the slab. If the material is wet prior to slab placement, GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 8 which is always possible in the Puget Sound area, it could cause vapor transmission to occur up through the slab in the future, essentially destroying the purpose of the vapor barrier/retarder. Therefore, if there is a potential that the protection/blotter material will become wet before the slab is installed, ACI now recommends that no protection/blotter material be used. However, ACI then recommends that, because there is a potential for slab cure due to,the loss of the blotter material, joint spacing ,in the slab be reduced, a low shrinkage concrete mixture be used, and 'other measures" (steel reinforcing, etc.) be used. ASTM E-1643-98 "Standard Practice for Installation of Water Vapor Retarders Used in .Contact with Earth or Granular Fill Under Concrete Slabs" generally agrees with the recent ACI literature. We recommend that the contractor, the project materials engineer, and the owner discuss these issues and review recent ACI literature and ASTM E-1643 for installation guidelines and- guidance on the use of the protection/blotter material. Our opinion is that with impervious surfaces that all means should be undertaken to reduce water vapor transmission. 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 A for the dense glacial till, and B for the near -surface soils. Therefore, temporary cut slopes greater than 4 feet in height should not be excavated at an inclination steeper than 0.75:1 or 1:1 (Horizontal:Vertical), respectively, extending continuously between the top and the bottom of a cut. Temporary cuts must not extend below a 1:1 (H:V) zone from footings without consideration by the geotechnical engineer. The above -recommended temporary slope inclinations are 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 loose soil 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:V). 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. GEOTECH CONSULTANTS, INC: 84th Avenue Edmonds, LLC December 22, 2005 DRAINAGE CONSIDERATIONS JN 05481 Page 9 We recommend that foundation drains be used at the base of all foundation and 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 5. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. No groundwater was observed during our field work. However, 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. PAVEMENT AREAS The pavement section may be supported on competent, native soil, or on structural fill compacted to a minimum 95 percent density based on Modified Proctor (ASTM Test Designation D-1557). Careful compaction of backfill over the around utilities is critical to prevent pavement settlement. 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. 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. 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. Increased maintenance and more frequent repairs should be expected if thinner pavement sections are used. 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. As with GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC JN 05481 December 22, 2005 Page 10 any pavements, some maintenance and repair of limited areas can be expected as the pavement ages. Cracks in the pavement should be sealed as soon as possible after they become.evident, in order to reduce the potential for degradation'of the subgrade from infiltration of surface water. For the same reason, it is also prudent to seal the surface of the pavement after it has been in use for several years. To provide for a design without the need for any maintenance or 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. 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: LOCATION OF FILL MINIMUM RELATIVE 11 PLACEMENT COMPACTION 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 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 1557-91 (Modified Proctor): The General section should be reviewed for considerations related to the reuse of on-site soils. 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. GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLC December 22, 2005 LIMITATIONS JN 05481 Page 11 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 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 84th Avenue Edmonds LLC, 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. 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. 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. ADDITIONAL SERVICES 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. GEOTECH CONSULTANTS, INC. 84th Avenue Edmonds, LLG December 22, 2005 The following plates are attached to complete this report: Plate 1 Vicinity Map Plate 2 Site Exploration Plan Plates 3 - 4 Test Pit Logs Plate 5 Typical Footing Drain Detail JN 05481 Page 12 We appreciate the opportunity to be ofservice on this project. If you have any questions, or if we may be of further service, please do not hesitate to contact us. GDB/MRM: esn Respectf6lly submitted, GEOTECH CONSULTANTS, INC. Gerry D. Bautista, Jr. Geotechnical Engineer Mc ) AS z,1 lN ikkL EXPIRES Marc R. McGinnis, P.E. Principal GEOTECH CONSULTANTS, INC. (Source: Thomas Brothers GEOTECH CONSULTANTS, INC. NORTH Street Guide and Directory) . VICINITY MAP 23707 - 84th Avenue West Edmonds, Washington Job No: Date: , ate: 05481 1 Dec. 2005 Not To Scale 1 `C Q 00 rmmmmm- a mm -N-8 mm -m- mommam a mm-mamm-mam 0 mm -mm 0 ON—V 0 0 ONNE 0 0 NOME a a NONE a 0 ' TP -4 ■ ■ ■ ■ .............. ■ 0 ■ TP -1 r■■Oman ■■mmI Legend Proposed Building +■•■■■ c Existing House/Garage . (Source: Site Plan; Ronald D. Johnson Architect, July, 20, 2005) GEOTECH CONSULTANTS, INC. NORTH Not To Scale SITE EXPLORATION PLAN 23707 - 84th Avenue West Edmonds, Washington Job No: Date:Plate: ' 4■■■■■■■■■■■■■ ■■.■■■■i ' • 05481 1 Dec.2005 1 1 2 ' TP -2 I ' I T 3 I I :mmmw a mammin a a mumms 0 NONE No NONE a a momm ME 1�mmm on � no NONE am NONE ME NONE 8 a women a NONE: Legend Proposed Building +■•■■■ c Existing House/Garage . (Source: Site Plan; Ronald D. Johnson Architect, July, 20, 2005) GEOTECH CONSULTANTS, INC. NORTH Not To Scale SITE EXPLORATION PLAN 23707 - 84th Avenue West Edmonds, Washington Job No: Date:Plate: 05481 1 Dec.2005 1 1 2 5 10 15 5 10 15 wr 0el40� %G G5 010 t 4�aro 45 opso TEST PIT 1 Description e to gray, silty SAND, fine- to medium -grained, moist, loose to medium -den becomes gray, with fine- to medium -grained sand lenses, medium -dense becomes very dense (Glacial Till) * Test Pit was terminated at 5 feet on December 16, 2005. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. Topsoil TEST PIT 2 Description .... Orange to gray, silty SAND, fine- to medium -grained, moist, loose to medium -der SM - becomes gray, with fine -.to medium -grained sand lenses, dense - becomes very dense (Glacial Till) * Test Pit was terminated at 4.5 feet on December -16, 2005. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. GEOTECH CONSULTANTS, INC. TEST PIT LOGS 23707 - 84th Avenue West Edmonds, Washington Job Date: Logged by: Plate: 05481 Dec. 2005 1 GDB 3 5 10 15 5 10 15 o��`t�aa�ti�' SG5 TEST PIT 3 opso Description rown, silty SAND, fine- to medium -grained, moist, loose becomes gray, with fine- to medium -grained sand lenses, medium -dense to den becomes very dense (Glacial Till) * Test Pit was terminated at 5.5 feet on December 16, 2005. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. TEST PIT 4 1, Silty SANU, con Topsoil Description Orange/brown, silty SAND, fine- to medium -grained, moist, loose gM ; - becomes orange/gray to gray, moist, medium -dense - becomes very dense (Glacial Till) * . Test Pit was terminated at 5.5 feet on December 16, 2005. * No groundwater seepage was observed during excavation. * No caving was observed during excavation. GEOTECH CONSULTANTS, INC. TEST PIT LOGS 23707 - 84th Avenue West Edmonds, Washington Job Date: Logged by. Plate: 05481 Dec. 2005 1 GDB 1 4 Slope backfill away from foundation. Provide surface drains where necessary. Tightline Roof Drain (Do not connect to footing drain) Backfill (See text for requirements) Nonwoven Geotextile K Filter Fabric TQ W Washed Rock Possible Slab (7/8 min. sizer 00 e -4 Fx``p A: .p .�1:'.p .f�.�.p .�1:�'.p .U.'Q'.p .A:�.p .U:�.p •�l 0 0 0 0 0 0 :$'t��, �.+s�� 0 0 n. ^^�vau3�a a -` �. �,�•Ch8'` .oW op°•000 op°•00'00°•000 00 op0/opo.OW W � `..) t.t •.+ �'. ,., 0: 0' _O— 0 0*0 0 ° °.� _ 0 ;:Q— p•° °:e - o° • o p a o° p o•°• Q p o.op op . �... ''S o �' O 0 00 00 0� }-/•ri1'(. '•,��,� •5+..tS�y S!RA . . •o o o . • b . R. 00000 .-F:i�N ci�f"iihzra?rb7r.f ,L:a?_icf�v tsrw�_..+� • 4" min. Vapor Retarder/Barrier and Capillary Break/Drainage Layer (Refer to Report text) 4" Perforated Hard PVC Pipe (Invert at least 6 inches below slab or crawl space. Slope to drain to appropriate outfall. Place holes downward.) NOTPES: (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. GEOTECH CONSULTANTS, INC. FOOTING DRAIN DETAIL 23707 - 84th Avenue West Edmonds, Washington Job Date: Scale: Plate: 05481 Dec. 2005 Not to Scale 5