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HomeMy WebLinkAbout701325005 Geotech Assessment SOIL AND SLOPE SURVEY AND GEOTECHNICAL ENGINEERING STUDY PROPOSED TAYLOR RESIDENCE 384 McDONALD ROAD QUILCENE~ JEFFERSON COUNTY~ WASHINGTON PROJECT NO. 102-01036 MAY 30, 2001 Prepared for Zane and Pam Taylor 384 McDonald Road Quilcene, Washington 98376 Prepared by: KRAZAN & ASSOCIATES~ INC. GEOTECHNICAL ENGINEERING DIVISION 20714 STATE HIGHWAY 305 NE, SUITE 3C POULSBO, WASHINGTON 98370 (360) 598-2126 SITE DEVELOPMENT ENGINEERS & ASSOCIATES, INC ~ · GEOTECHNICAL ENGINEEP, ING · ENVIRONMENTAL ENGINEERING CONSTRUCTION TESTING & INSPECTION May 30, 2001 KA Project No. 102-01036 Zane and Pam Taylor 384 McDonald Road Quilcene, Washington 98376 Soil and Slope Survey and Geotechnical Engineering Report Proposed Taylor Residence, 384 McDonald Road Quilcene, Jefferson County, Washington Dear Mr. And Mrs. Taylor: In accordance with your request, we have completed a Geotechnical Engineering Investigation for the above-referenced site. The results of our investigation are presented in the attached report. If you have any questions or if we can be of further assistance, please do not hesitate to contact me at (253) 939-2500 or Shawn Williams at (360) 598-2126. Respectfully submitted, 7~IATES, INC. Allen L. Hart, CPG, RPG/CEG Senior Engineering Geologist With Eleven Offices Serving The Western United States 20714 State Highway 305 NE, Suite 3C · Poulsbo, Washington 98370 · (360) 598-2126 · Fax: (360) 598-2127 & ASSOCIATES, INC. GEOTECHNICAL ENGINEERING · ENVIRONMENTAL ENGINEERING CONSTRUCTION TESTING & INSPECTION May 30, 2001 KA Project #102-01036 Zane and Pam Taylor 384 McDonald Road Quilcene, Washington 98376 Report of Soil and Slope Survey and Geotechnical Engineering Study Proposed Taylor Residence 384 McDonald Road Quilcene, Jefferson County, Washington This report presents the results of a soil and slope survey and geotechnical engineering study directed at evaluating potential erosion and landslide hazards at the referenced site in accordance with the requirements of the Jefferson County Critical Areas Ordinance. The scope of the study was developed during our site visit on March 15, 2001, and outlined in our proposal to you dated April 2001. The services performed under the referenced proposal were in general compliance with requirements outlined in the Jefferson County Critical Areas Ordinance. As shown on the attached Location map, Figure 1, the site is located at the south end of the Bolton Peninsula, near the east end of McDonald Road in Jefferson County, and overlooks Dabob Bay to the south and east. Based on our discussions we understand that design plans for the residence are being developed at this time. However, conceptually it is understood that the residence is to be sited to the southwest of a mobile home presently on the property, at a location near the top of the south facing slopes with the south wall of the structure located in the vicinity of test pit 1. The residence will be a wood- framed structure with a basement daylighted into the slope. It is our understanding that the main floor will be at about the current site grade at test pit 1 or slightly higher. Vehicle access into the residence will follow the existing driveway. Based on our discussions, it is understood that no cleating of slope area below the building site is planned. It is further understood that no trees will be felled on the south facing slope, although some trees may be topped and/or limbed to enhance views. Previous development of the site has been limited in scope with the main features being the mobile home and septic drainfield shown on Figure 2. Overall, even though the portion of the property between Eleven Offices Serving The Western United States 20714 State Route 305 Suite 3C · Poulsbo, Washington 98370 · (360) 598-2126 · Fax: (360) 598-2127 102-01036 Tlylor.do~ KA No. 102-01036 May 30, 2001 Page No. 2 McDonald Road and the top of the slope shown on Figure 2 has been cleared there appears to have been minimal grading for site development. Under the current development plan, minimal grading of the site, beyond that required for construction, is anticipated. All areas of bare soil and disturbed vegetation will be landscaped such that no erosion hazards are created or will remain following development. Construction of the proposed residence and driveway improvements will not result in an increase of the potential landslide or erosion hazards of the site. SUBSURFACE EXPLORATION Site soils were explored and evaluated in the two test pits and a number of random excavations made on the slope below the building site and in natural outcrops both on the subject site and adjacent parcels. The observed natural exposures are located on the slopes to the east, west and south of the building site. The random excavations were made down slope in a general southerly direction from the building site and cover an elevation change of approximately 200 vertical feet. The approximate test pit locations are indicated on the attached Site Plan, Figure 2. Site soils were viewed in two test pits, various slope and road cut exposures in the area, and in random excavations made on the slope. Soil logs for the test pits are presented in Appendix A. Soils observed on the slopes are discussed in the following text. The soil strata shown on the logs were observed at spot locations. Actual subsoil conditions and thickness may vary between the test pit locations or as exposed in excavations or slope exposures. Elevations and distances referenced in this report were established using handheld instruments, i.e., tape measure, altimeter, and inclinometer, etc., and should be considered approximate. The base drawing for Figure 2 was prepared by Tillman Engineering, Inc. and is titled "Topographic Survey for Pamela Taylor, Quilcene, Washington", dated April 9, 2001. GEOLOGIC SETTING The site is located in the northwest portion of Puget lowlands, an elongate, north-south trending structural depression and topographic trough. The Puget lowlands have been filled several times by glacial ice, resulting in many topographic features, which are a result of glacial erosion and deposition and that caused by outwash streams. The site is in an area of glaciated bedrock and associated deposits. Site soils, topography and geology result primarily from the advance and retreat of the Vashon Stade (most recent glacial advance) of the Frazier Continental Glaciation. On a gross scale the typical soil sequence in the Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 3 area consists of mixed sands and gravels (Recessional Outwash) over glacial till which in turn overlies sands, gravels and silts (Advance Outwash and pre-glacial deposits) or bedrock. In the general vicinity of the site the glacial till caps much of the region and overlies both pre-glacial deposits and the local bedrock, which are identified on geologic maps as shale, siltstone, and mudstone. The site proper appears to be located on a flatter bench area sporadically cut and sculpted by drainages. In this area it appears that the till has been eroded and weathered to athin layer overlying pre-glacial sands and gravels. The glacial till in the area is comprised of materials picked up by the ice sheet as it moved, then were deposited at the base of the glacier and overridden and densified by some 1500 or more feet of ice. The pre-glacial materials are a mixture of sands and gravels deposited in association with glacial ice and/or outwash streams. Regional maps the area indicate that glacial till caps much of the area but in the site vicinity it is indicated that the area is underlain by pre-Vashon stratified sediments. Generally, the pre-glacial and glacial materials are found to be dense to very dense, however, it is not uncommon to find a layer or mantle of looser, weathered or disturbed material over the denser soils or bedrock. SURFACE CONDITIONS As previously described, the site has been previously cleared and to a minor extent developed for the existing residential development, but it does not look to have been significantly graded or otherwise modified. Topographically the proposed building site appears to be located on the south edge of a flatter bench extending to the north. To the south of the building site the ground slopes downward to Dabob Bay. Directly below the building site is a narrow ridge flanked to the east and west by shallow drainages, which converge about 200 feet vertically below the building site and terminate the ridge structure. To the north of the building site ground slopes are on the order of 10%. Through the building site to the top of the slope indicated on Figure 2 slopes steepen to the range of 22% to 25%. Below the indicated top of slope, slope grades typically range from about 46% to 78% with areas of steeper slope ranging from near 70% to 90%. The map "Relative Slope Stability In East-central Jefferson County, Washington" (OFR76-27, 1976, Washington State Department of Natural Resources, Division of Geology and Earth Resources) appears to identify the building site and areas northward as a Class 1 slope and the south facing slopes below the building site as Class 2 slopes. Slopes shown to be of class 3 stability are located to the west of the property and near the shoreline to the south. Class 1 slopes are considered stable while Class 2 slopes are considered "normally stable areas that may become unstable if modified by man". 'Class 3 slopes are considered to be "unstable areas". The Coastal Zone Atlas of Washington, Jefferson County volume, indicates a slope stability mapping similar to that shown on the OFR76-27 map. During our reconnaissance of the area it was observed that there are some indicators of past slope soil movement, Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 4 primarily a slight bowing of trees, soil slumps, and raveling. No indication of deep-seated or rotational landsliding was observed and the past soil movement appears to have occurred primarily as shallow face failures effecting only the topsoil and weathered zones on steeper slopes and near areas of outwatering. Based on our reconnaissance observations, it is our opinion that the slopes adjacent to the site generally reflect and match the slope stability mapping of the area. To the north of the top of the slope indicated on Figure 2 vegetation cover is primarily comprised of grass and weeds combining with berry vines and low-growing brush to near the top of the slope. Below the top of the slope ground cover is comprised of a medium to dense growth of ferns and low-growing shrubs and brush below a canopy of mixed evergreen and deciduous trees. The trees are openly spaced and evidence at least two harvests of the evergreens. The most recent harvest appears to have been selective taking trees on the order of 14 inches in diameter, based on recent looking stumps. Stumps from the older harvest range from about three to four feet in diameter and bear the notches of springboards used in felling. It is estimated that the trees taken at the earlier harvest may have ranged in age from order of 100 to 150 years in age. This age estimate is based on diameter vs. growth ring counts made on downed fir trees around Puget Sound and near Port Ludlow. A general reconnaissance of the property and adjacent areas was made to identify areas of ground water seepage. In the drainage down slope and east of the building site ground water seepage was observed approximately 130 feet below the building site, roughly elevation 340 to 360. Although no areas of outwatering were observed on or along the west side of the property a slight change in ground surface conditions occurs at about the elevation of the observed outwatering to the east and may indicate a proximity to ground water. During our reconnaissance of the general area no other zones of outwatering were located. However, it is possible that the nearly continuous vegetative cover may hide small or poorly defined areas of outwatering within the ordinance specified 1,000 feet of the site. SOIL PROFILE AND SUBSURFACE CONDITIONS The "Geologic Map Of East-central Jefferson County, Washington" (OFR76-26, 1976, Washington State Department of Natural Resources, Division Of Geology and Earth Resources) indicates that the site and adjacent areas are underlain by Vashon glacial till over Pre-Vashon stratified sediments On maps prepared by the Soil Conservation Service (SCS) it appears that the site lies on or very near the contact between two soil units. Based on the SCS mapping it appears that the upland portion of the property is underlain by Alderwood gravelly sandy loam, 0% to 15% slopes (soil type AIC) while the Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 5 slopes below the building area, and those to the east and west, are underlain by Quilcene silt loam, 30% to 50% slopes (soil type QuE). The SCS indicates that the AIC-type soils are typically located in areas of nearly level to rolling terrain on glacial terraces and derived from a glacial till parent material. The QuE- type soils are typically located on steeper upland areas where a 20 to 24 inch thickness of covering soil overlies a weathered shale bedrock. Based on the SCS description of the soils overlying the shale bedrock it appears that the covering layer may be derived from a mix of glacial till and weathered bedrock. As observed in the building area it appears that below a roughly two foot thick layer of silty sand with occasional gravel the soils become progressively more granular. The upper near surface soils appear to be a weathered sandy glacial till with the underlying soils appearing as gravelly sandy pre-glacial outwash materials. Although it is possible that bedrock may underlie the area as indicated by the SCS mapping, none was observed in exposures and water well logs from the general area do not indicate the presence of bedrock to depths approaching 300 feet. Based on the soils observed in the test pits, on the slopes, and exposed at various locations in the area, it is our opinion that the site soils are as a whole generally more consistent with those shown on the geologic map of the region. However, north of the slopes the surface soils appear similar to those indicated on the SCS and geologic maps. Differences between the mapped and observed soil conditions appear as a result of mapping scale, availability of exposures, and intended map usage. These differences are generally minor and not unexpected. CONCLUSIONS AND RECOMMENDATIONS GENERAL Based upon our site observations and review of pertinent materials, it is our opinion that the potential for ground movement in the area back of the site slopes is low. Similarly, we consider the potential for large scale landsliding on the south facing slopes on this property, in either the natural condition or resulting from the proposed development, to be low. The south facing slopes are mapped as Class 2 stability and the overall slope stability under the present conditions appears good away from the areas evidencing shallow ground movement. The present slope conditions should remain unchanged with the proposed development. Although the potential for larger scale landsliding on the south facing slopes appears low there is a potential of additional soil movement, similar to that which has occurred 'in the past on the steeper portions of the south facing slopes. However, the following setback recommendations considers this potential and as presently proposed no slope area below the top of slope shown on Figure 2 will be Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 6 disturbed for site development. Away from the slopes no evidence of erosion was observed and following proper construction and landscaping no erosion hazard will be developed. The Soil Conservation Service indicates a severe building site restriction for the AIC-type soils on slopes greater than 15% for structures without basements and a severe restriction in the QuE-type soils for structures without basements due to a high shrink-swell potential. Although the structure will be in an area meeting one or both of these criteria the residence is to have a basement area. Following our review of the Jefferson County critical areas ordinance, it is our opinion that portions of the subject property meet the requirements for definition as a landslide and erosion hazard area. Although it is our opinion that the property meets the requirements of the ordinance for definition as a critical area, it is also our opinion that the proposed building site can be safely and satisfactorily developed through geotechnical design and sound site planning. The following recommendations for site development are provided to address the concerns of the critical areas ordinance and should be incorporated into the site development plan. As previously noted, it is our opinion that overall the proposed development in and of itself will create a minimal risk of erosion or landslide damage, no disturbance of the slopes is expected, and the development will have little if any effect on adjacent properties. The site does not appear to meet the classification requirements to be designated as a seismic hazard area as defined in the Jefferson County ordinance. However, the property is located in seismic zone 3 as defined by the Uniform Building Code (UBC), as is much of western Washington. In the event of an earthquake of adequate magnitude and/or duration some soil movement on the slope is possible if other conditions are right, but the potential for soil movement on this property is no greater than that on the adjacent developed lots or for properties elsewhere with similar slope and soil conditions. Additionally, the slope core soils appear to be primarily dense glacial materials or bedrock which, where exposed to the west, is fractured but appears to be generally hard and sound. The recommendations contained in this report were developed considering the potential for slope failure, and that future structures are expected to be designed in accordance with current UBC seismic zone 3 requirements, or potentially more stringent future requirements. The SCS classifies the QuE-type soils to be of severe erosion hazard in the disturbed state while the AIC- type soils have only a slight to moderate erosion hazard. The QuE-type soils appear to be primarily located on the steeper site slopes, which we understand will not be disturbed. It is also our experience that the erosion hazard risk for disturbed areas can be mitigated through normal residential landscaping and re-vegetating of the disturbed areas. During construction and until fully landscaped the exposed site Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 7 soils will be subject to erosion. Erosion of the exposed soils will be most noticeable during periods of rainfall and may be controlled by the use of normal erosion control measures, i.e., silt fences, hay bales, mulching, control ditches or diversion trenching, and contour furrowing. By ordinance requirement a native vegetation buffer is required from the edge of all slopes that are geologically hazardous areas. It is our opinion that a vegetation buffer having a minimum width of 30 feet should be maintained parallel to the top of the south facing slopes below the building site. This setback is shown on Figure 2. In addition to the maintenance of buffer we recommend that all disturbed areas be replanted as soon as possible after construction is complete. It is our opinion that the vegetation buffer may be comprised of native vegetation and properly designed and installed landscaping. However, the portion of the buffer comprised of native vegetation should not be reduced to less than 10 feet in width along the indicated top of the slope. The following site preparation and foundation design recommendations are provided to aid in minimizing potential erosion and landslide damage risks and should be incorporated into site planning, design and construction. RECOMMENDATIONS Site Preparation and Grading Water Related Concerns: Only minor storm water related problems are anticipated if site grading and preparation are undertaken during the normally drier portions of' the year. If site work is undertaken during wet weather the near surface sands and silty soils may become over-saturated and temporarily unworkable. If' the site work is undertaken during wet weather the contractor should be fully prepared to deal with possible elevated water levels in addition to other soil and water problems normally encountered in these materials during wet weather work including the filtering of runoff, as needed, to prevent the siltation of down slope areas. It should be anticipated that silt fences and other erosion control devices could be used to control sediment transport off the site. Depending upon the final site grades and weather conditions it is possible that areas of perched water or seeps may develop in some areas. In that we are unable to predict where or when this might occur we recommend that any development of springs or seeps be treated as a construction/maintenance problem. The contractor should be prepared to deal with any water-related problems during cOnstruction. Water seepage can cause failure of the excavation walls and the contractor should be observant for possible cave-in or other hazardous conditions and provide shoring for all cuts and excavations in accordance with local, state, and federal regulations. Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 8 D~velopment Recommendations: Under all buildings, pavements and fill areas, it is recommended that all sod, organic soil, and debris is removed. Over most of the site it is anticipated that a stripping depth of 12 inches will be adequate. However, localized deeper stripping depths may be required to remove tree root balls. Stripped soils, contaminated with organics or debris, should be wasted off site or used in landscape areas. Stripped soils free of organics and debris may be used as structural fill subject to the following considerations. Following stripping of the site and prior to the placement of any fill, the exposed subgrade should be proof rolled to a firm, unyielding condition using suitability sized equipment. Compaction of the stripped subgrade should be continued until field density tests in soil areas show that a minimum compaction of 95% of the maximum dry density, as determined by ASTM method D-1557, has been achieved in the top 12 inches of subgrade beneath all building, driveway, and parking areas. In areas of bedrock exposure the architect, engineer, geologist or other qualified person should inspect the subgrade to confirm adequacy and absence of excessive amounts of disturbed/loose material. Any soft or weaving areas disclosed during proof rolling should be excavated and replaced with compacted structural fill. With the exception of driveway side slopes, it is recommended that permanent cut slopes not exceed 2H: 1V (50%). Fill slopes should not be steeper than 2H:IV (50%) for fill placed in accordance with the requirements of appendix chapter 33 of the Uniform Building Code (1997 edition) or 3 to 4H: 1V (33% to 25%) for uncontrolled fills of moderate quality material. In areas where steeper slopes are required, retaining structures should be provided. In areas where fills are to be made on slopes steeper than 5H: 1V the subgrade should be benched and prepared in accordance with UBC (1997) requirements prior to fill placement. Benches should be cut at a maximum vertical height of 24 inches. It should be anticipated that, if steeply cut, the more granular near surface soils may be subject to caving, and sloughing will occur as the soils are exposed to drying. All temporary cuts and excavations should be sloped or shored in accordance with local, state and federal requirements. Areas which are to be filled to bring the building or pavement grades up to the desired elevations should be filled with compacted granular material free from roots, trash or other deleterious'materials. During wet weather most of the on site soils are not expected to be suitable for use as fill. These soils are sufficiently fined grained, such that with the addition of small quantities of water they become overly saturated and are difficult or impossible to compact to the desired density. As a result, we recommend Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 9 that all site grading and preparation be undertaken and completed during dry weather. If grading in building or pavement areas is necessary during wet weather, we recommend that all excavated soil be removed from the site and that materials used as structural fill (fill placed on slopes or under buildings or pavements) consist of free draining sandy gravel with a maximum particle size of 3 inches and not more than 5.0% fines, material passing a U.S. No. 200 sieve. All imported fill material should conform to the above recommendation regardless of the weather. All structural fill should be placed in layers approximately 8 inches in loose thickness, conditioned to a moisture content suitable for compaction, and compacted to 95% of the maximum dry density as determined by ASTM D-1557. Field density tests should be made at a frequency adequate to assure that the required compaction is achieved. To preclude the possible build-up of ground water or storm runoff in the soils adjacent to the residence, it is recommended that a four inch diameter perforated, rigid pipe be placed, perforations down, around the outside of the building foundation at the footing subgrade elevation. All of the drainage system should be bedded in a drainage sand and gravel and designed to carry any accUmulated water away from the structure to an appropriate discharge area. Roof drainage should not be connected to the footing drains but may use the same outfall piping provided that the connection between the systems is located at least 10 feet down grade of the house and designed to prevent water from backing up into the footing drain. All runoff from roofs, driveways, patios and hard surfaced areas should be intercepted, collected and disposed of away from structures and site slopes, and discharged where the water will not effect down slope structures, slopes, walls or properties. Specific recommendations for and design of a storm water disposal system are beyond the scope of our services and should be prepared by other consultants fully familiar with design and discharge requirements. However, from a geotechnical perspective tight lining of the collected water to an infiltration system located on the flatter slopes to the east of the building site, near the present shed, would be an acceptable means of disposal. Buil0ing Siting For the siting of structures we recommend that the following top of slope setback and foundation embedments be maintained. From the indicated top of the south facing slope below the proposed building site shown on Figure 2 we recommend that a minimum top of slope setback of 30 feet be maintained. Additionally, all footings on gentle slopes (<15%) should bottom a minimum of 18 inches below the lowest adjacent exterior grade and 12 inches below the lowest interior grade. Footings on or within 10 feet of slopes steeper than 15% should be designed so that the bottom of the footing is a minimum of 36 Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 10 inches below the lowest adjacent exterior finished grade and a minimum of 60 inches back of the finished soil slope face. For foundations bearing on the medium dense to dense in sim soils a preliminary allowable soil bearing capacity of 1,800 psf may be used. Additional foundation design considerations should be in accordance with Uniform Building Code requirements, as modified by local codes and regulations, in effect at the time of construction, for structures within seismic zone 3 as defined by the Uniform Building Code (1997) or the UBC seismic zone in effect at the time of construction. It is recommended that all foundation excavations be inspected by Krazan & Associates, prior to placing concrete, to verify that the bearing surface has been properly cleaned, prepared and soil conditions are as anticipated. All foundation subgrade areas should be recompacted following excavation. Bearing surfaces should be firm and free of sloughed or water-softened soil. Preliminary Cast-In-Place Retaining and Subsurface Wall Recommendations The following earth pressures and preliminary design values are provided for cast-in-place retaining and subsurface walls up to ten feet in height. It is recommended that foundations for all retaining structures and subsurface walls be designed and constructed as previously described under the Foundation Design section of this report. Retaining and subsurface walls should be designed for an active equivalent fluid pressure of 35 pcf, if the top of the wall is allowed to deflect, assuming a horizontal ground surface behind the wall. If the top of the wall is restrained an equivalent fluid pressure of 50 pcf is recommended. Active or at rest pressures will need to be increased for sloping ground or surcharge loads behind the wall. Ultimate passive pressures for retaining structures, considering a horizontal ground surface, will be 150 pcf. Passive pressures will need to be reduced for a sloping ground condition in front of the wall. Additional resistance to sliding can be developed through base friction. A coefficient of friction between the footing and soil of 0.32 should be used. An appropriate safety factor should be applied to the above resistive values when calculating resistive values. The above-recommended pressures do not include the effects of hydrostatic pressure on the wall as they assume a drained condition exists. The maintenance of a dewatered/drained condition behind all retaining structures is required for the above values to be valid. The following drain system and backfill requirements are recommended. Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 11 A longitudinal subdrain with a minimum diameter of 4 inches should be constructed at the footing elevation behind the walls. This drain should be constructed of a 4-inch diameter perforated pipe laid perforations down, bedded in an eighteen-inch envelope of free-draining sand and gravel. This system should be sloped to drain and the water disposed of in the storm drainage system. Clean-outs should be provided at bends and convenient intervals, so that the drainage system can be maintained in a well- functioning condition. Flexible plastic piping (such as corrugated ADS-type piping) should not be used behind the wall. Roof and parking area drainage systems should not be connected to the wall subdrain system, but may utilize the same tight-line outfall well away from the wall. All wall backfill over the gravel envelope should consist of clean, free-draining, well-graded sand and gravel containing less than 2.0% fines (material passing an U.S. No. 200 sieve). This material should extend out from the rear wall face a minimum of eighteen inches. The free-draining backfill should be placed to the surface in paved areas or to within eighteen inches of the surface in non-paved areas. Backfill should be compacted as recommended above for fills. In non-paved areas, the final eighteen inches of backfill should consist of topsoil or native materials firmly tamped into place. Construction Considerations As a preliminary guideline for temporary cuts less than 10 feet in height we recommend temporary slopes be made no steeper than 1.5H: 1V for the loose to medium dense silty soils and 1H: 1V in the dense soils. For temporary cut slopes over 10 feet in height we recommend temporary slopes no steeper than 2H: 1V for the full height of the cut. Temporary slopes or excavations should be benched as required by safety regulations in effect at the time of construction. These temporary slope recommendations are for native soils and fill materials; flatter slopes may be required in wet weather or if soil conditions other than those previously described are encountered. The contractor should be aware that slope height, slope inclination, and excavation depths (including utility trench excavations) should in no case exceed those specified in local, state, or federal safety regulations; e.g., OSHA Health and Safety Standards for Excavations, 29 CFR Part 1926, or successor regulations. Such regulations are strictly enforced and, if not followed, the owner, the contractor, or the earthwork or utility subcontractors could be liable for substantial penalties. The contractor should be made responsible for the stability of all excavations and slopes during construction because he is continually on site and can observe the stability of the exposed soils. In addition, the contractor should be prepared to shore any unstable slope area and provide shoring as required by local, state, or federal laws or codes. In no case should excavated soils be placed on the slope or stockpiled within the defined buffer or slope setback areas along the steep slopes or within 20 feet of the top of any other existing or excavated slope, Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 12 rockery or retaining structure. Failure to comply with these guidelines may lead to destabilization of the slope. The site soils may be easily eroded by channelized water or sheet flow storm runoff. Therefore, it is recommended that all site preparation and excavation work be completed during the normally drier portion of the year. During periods of heavy rainfall, ditching should be used to divert water away from stripped areas and visqueen should be used to cover the slopes and soil stockpiles to aid in preventing excessive surface erosion. This covering also aids in preventing infiltration of water into the unprotected soils. Ail disturbed soil areas and slopes should be replanted with fast-growing, deep-rooted grass, shrubs and other ground cover as soon after final grading as possible. If the vegetation is not fully established prior to the on set of wet weather, the slopes should be covered with visqueen to aid in preventing excessive erosion and water infiltration. It should be anticipated that there could be a number of additional site development or construction problems, particularly, if the earthwork has not been completed and the site properly protected at the onset of wet weather. It is recommended that the architect, structural engineer or their representative make periodic inspections of all excavations and slopes to provide early recognition and recommendations. REPORT LIMITATIONS This report has been prepared for the exclusive use of Zane and Pam Taylor and their agents for use in planning of the referenced development. The conclusions and recommendations in this report are based on our interpretation of site conditions as they presently exist, anticipated future construction activities, and the expectation that the exploratory efforts adequately define the subsurface conditions throughout the building site. The soil conditions described in this report and the conclusions and recommendations contained in this report are provided for this specific site only and should not be expanded for use on adjacent properties without additional exploration and review of those sites by our firm. The data and report should be provided to prospective contractors for their bidding or estimating purposes, but the report conclusions and interpretations should not be construed as a warranty of the subsurface conditions. There are possible variations in subsurface conditions. In the event that the scope or location of the project should change or subsurface conditions different from those encountered during this study be observed or suspected, we should be advised. At that time a review of the changed conditions will be made, and alternative or remedial recommendations given as required. Krazan & Associates, Inc. Offices Serving The Western United States KA No. 102-01036 May 30, 2001 Page No. 13 NOTE: Although we have explored subsurface conditions as part of this study, we have not conducted analytical laboratory testing of samples obtained, nor have we evaluated the site for the potential presence of contaminated soil, and have not evaluated or addressed ground water conditions or concerns except as noted in this report. The evaluation of possible environmental or geo-environmental considerations is beyond the scope of this report. The owner and the contractor should make themselves aware of and become familiar with applicable local, state, and federal safety regulations, including current OSHA excavation and trench safety standards. Construction site safety generally is the sole responsibility of the contractor. The contractor shall also be solely responsible for the means, method, techniques, sequences, and operations of construction operations. The firm, Krazan & Associates, Inc., (including consultants and subcontractors) is providing the preceding information and recommendations solely as a service to Zane and Pam Taylor. Under no circumstances should the provision of this information or recommendations be construed to mean that the firm Krazan & Associate, Inc., (including consultants and subcontractors) is assuming responsibility for construction site safety or the contractor's activities; such responsibility is not implied and should not be inferred. Within the limitations of scope, schedule, and budget for this work, it is warranted that the work has been done in accordance with generally accepted practices followed in this area at the time this is report was made. No other warranty, expressed or implied is made. Should you have any questions or concerns which have not been addressed, or if we may be of additional assistance, please call me at (253) 939-2500 or Shawn Williams at (360) 598-2126. Sincerely, Allen L. Hart, CPG, RPG/CEG Senior Engineering Geologist Shawn E. Williams, Senior Environmental Geologist Krazan & Associates, Inc. Offices Serving The Western United States ';5 F. iJ ? Fisherman Portion of slope stability map "Relative Slope Stability in East-Central Jefferson County, Washington", OFR76-27, Washington State Department of Natural Resources, Division of Geology and Earth Resources, 1976 KRAZAN & ASSOCIATES, INC. 20714 State Highway 305 NE, Suite 3C Poulsbo, WA 98370 360-598-2126 FIGURE 1- Location & Stability Map Location: 384 McDonald Road, Quilcene, Jefferson County, Washington Job No.: 102-01036 Client: Zane and Pam Taylor Date: 5/30/01 U U Ul's Urs Uos ~SlTr rs fs Portion of slope stability map-Coastal Zone Atlas, Jefferson County volume. KRAZAN & ASSOCIATES, INC. 20714 State Hwy 305 NE, Suite 3C Poulsbo, WA 98370 360-598-2126 SLOPE STABILIT~ MAP Location: 384 McDonald Road, Quilcene, Jefferson County, Washington Job No.: 102-01036 Client: Zane and Pam Taylor Date: 5/30/01 FIGURE 3 Project: Talor Residence Client: Zane and Pam Taylor Location: Quilcene, WA Log of Test Pit 1 Depth to Groundwater: None observed Project No: 102-01036 Figure No.: A-1 Logged By: ALH SUBSURFACE PROFILE SAMPLE d Moisture Content z----. Remarks ~" Description ~ ~ (%)  E E >, ~o · 20 40 0 Ground Surface 0- .i.el. liiii~ SOD and TOPSOIL 1 -!, ::: Silty SAND (SM) 1 .~ii~'ii!i~ Loose, silty SAND with occasional gravel, brown, moist. ...-. ,~ ,~ ~' 2- . ~,, ~.,. . ~ ~ ,~ Gravelly SAND with silt (SP-SM) 3- · ~ .----, 3.. ~1· · Loose to medium dense becoming dense, gravelly SAND with 2 · ~,' ~~ silt, tan, moist. '"'" - 4 ~'-'. 4- · End of Test Pit . 5- Terminated at effective refusal 5-- · · 6- 6- 7-- 7-- 8.- 8.- 9- 9- 10- 10- 11- 11- 12'~ 12- . 13- 13- · · 14- 14- · · 15- 15- ,.~ Method: Hand excavation Contractor: Operator: Krazan and Associates 20714 State Hwy 305 NE, Suite 3C Poulsbo, WA, 98370 Excavation Date: 5/8/01 Sheet: I of 1 i Project: Taler Residence Project No: 102-01036 Client: Zane and Pam Taylor Figure No.: A-2 Location: Quilcene, WA Log of Test Pit 2 Logged By: ALH Depth to Groundwater: None observed SUBSURFACE PROFILE SAMPLE I d Moisture Content -5 Description ~z ~--- (%) Remarks ~ m · 20 40 Ground SuCace i · ~'~ ~ SOD and TOPSOIL O' . - ',~:: ::: Silty SAND (SM) 1- . ~ ':: ~ Loose, sil~ SAND with occasional gravel, brown, moist. . "~" 2- : &~ "'~ Gravelly SAND with silt (SP-SM) · ~,~ Loose to medium dense becoming dense, gravelly SAND with 4- - ~4~=~i silt, ~n, moist. . 6" End of Test Pit 6- . Terminated at effective refusal . 7- 7- 8- 8- 9- 9- 10- 10- 11- ' 11- 12- 12- 13- 13- 14- 14- 15- 15- Method: Hand excavation Contractor: Operator: Krazan and Associates 20714 State Hwy 305 NE, Suite 3C Poulsbo, WA, 98370 Excavation Date: 5/8/01 Sheet: 1 of 1 Particle Size Distribution Report ~ 50 i ~ ' · ~ , ,,i ~ ' I ' ' , ~' ~ , ~ , ..... ,' I .... ; ~ ~.,~ J 500 100 10 I 0.1 0.01 0.001 G~IN SIZE - mm SIEVE PERCENT SPEC.* PASS? ~ Soil Description SIZE FINER PERCENT (X=NO) I 3 in. 100.0 1.5 in. i I00.0 I in. 97.5 3/4 in. 91.9 Aflerber9 Limits 1/2 in. 85.0 PL= LL= PI= g4 62.8 ~8 52.1 Coefficients gl0 49.3 gl6 42.8 ! P85= 12.7 D60= 4.04 D50= 2.09 g40 32.5 ~ i D30= 0.359 D15= 0.183 D10= g60 22.9 Cu= Cc= g 100 11.1 Classification g200 10.3 USCS= ~SHTO= ~ : Remarks Tested b~ WVA (no specification provided) ,_ Sample No.: 011033 Source of Sample: Date: 5-19-01 Location: TP-I S-~ 36-42" Elev.IDepth: Client: Taylor K~N & ASSOCIATES, INC. Project: Taylor Project No: 102-01036 Plate SIEVE PERCENT SPEC.* PASS? SIZE FINER PERCENT (X=NO) 3 in. 100.0 1.5 in. I00.0 I in. 97.5 3/4 in. 91.9 1/2 in. 85.0 #4 62.8 #8 52.1 #10 49.3 #16 42,8 #40 32.5 #60 22.9 #100 11.1 #200 10.3