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HomeMy WebLinkAbout821173001 Geotech AssessmentGeo Engin ee r s Report Geotechnical EngineeringSer¥ices ' ProPosed_ Cre~kSide' II Residential Development Port Ludlow';~ Washington . ---January 15, ~1997 For - : Pope Resources ,L File No. 2378-040:T03/011597 eo Engineers Pope Resources P.O. Box 1780 Poulsbo, Washington 98370 January 15, 1996 Consulting Engineers and Geoscientists Offices in Washington, Oregon, and Alaska Attention: Mr. Jon Rose We are pleased to submit six copies of our "Report, Geotechnical Engineering Services, Proposed Creekside II Residential Development, Port Ludlow, Washington for Pope Resources." We appreciate the opportunity to be of service to Pope Resources. Please contact us if you have questions regarding this project or if we can provide additional services. Yours very truly, GeoEngineers, Inc. Gary W. Henderson Principal GHS:GWH:vc Document ID: 2378040R.R File No. 2378-040-T03 cc: ESM, Inc. 34004-9th Avenue South, Building A Federal Way, Washington 98003 Attn: Mr. John Chadwell GeoEngineers, Inc. 1101 Fawcett Ave., Suite 200 Tacoma, \VA 98402 Telephone (206) 3834940 Fax (206) 3834923 CONTENTS Pa.qe No. INTRODUCTION .................................................. 1 SCOPE OF SERVICES .............................................. 1 SITE CONDITIONS ................................................ 2 SURFACE CONDITIONS 2 SUBSURFACE EXPLORATIONS 2 SUBSURFACE CONDITIONS 2 CONCLUSIONS AND RECOMMENDATIONS ............................... 4 GENERAL LANDSLIDE HAZARD SETBACKS EROSION HAZARD EROSION CONTROL SEISMIC VULNERABILITY EARTHWORK General Clearing and Site Preparation Subgrade Preparation Structural Fill Suitability of On-Site Materials for Fill Fill Placement on Slopes Fill Slopes Fill Drainage Fill Settlement Cut Slopes FOUNDATION SUPPORT Shallow Spread Footings FLOOR SLAB SUPPORT RETAINING SYSTEMS Cantilevered Concrete Gravity Walls Rockeries Other Retaining Options DRAINAGE PAVEMENT DESIGN AND SUBGRADE PREPARATION EROSION AND SEDIMENTATION CONTROL 4 5 6 6 7 7 7 7 8 8 9 9 9 10 10 10 11 11 12 12 12 13 13 14 14 15 LIMITATIONS ................................................... 1 5 G e'o E n g i n e e r s i File No. 2378-O40-T03/011597 CONTENTS (continued) FIGURES Vicinity Map Site Plan Foundation Detail Soil Classification System Logs of Test Pits Logs of Hand-Auger Borings Figure No. 1 2.,,3 4 5 6...14 15...16 -APPENDICES Pa,qe No. Appendix A - Geologically Hazardous Areas Section of the Jefferson County Critical Areas Ordinance A-1 Appendix B - Pavement Design Calculations B-1 G e o E n g i n e e r s ii File No. 2378-040-T03/01~597 REPORT GEOTECHNICAL ENGINEERING SERVICES PROPOSED CREEKSIDE II RESIDENTIAL DEVELOPMENT PORT LUDLOW, WASHINGTON FOR POPE RESOURCES INTRODUCTION This report summarizes the results of prior geotectmical engineering studies GeoEngineers has performed for 'ihe Creekside II Residential Development in Port Ludlow, Washington. Specifically, we have previously presented reports for portions of the development dated November 20, 1992, March 16, 1995 and October 17, 1996. The Creekside II development is located in Section 17 of Township 28 North, Range 1 East, Willamette Meridian. The site is shown relative to surrounding features in the Vicinity Map, Figure 1. There have been several revisions to the development plans during the course of and subsequent to our studies. The currently planned layout of the development is shown in the attached Site Plan, Figures 2 and 3. SCOPE OF SERVICES The purpose of our services for this study is to compile the results of our prior studies in a single report presenting our findings, conclusions and recommendations for the Creekside II development. Specific scope of services are presented in the referenced reports describing our prior studies. In general, our scope of services included the following: 1. Excavate a series of backhoe test pits at the site to explore subsurface soil and ground water conditions. 2. Evaluate pertinent physical and engineering characteristics of the soils at the site. 3. Provide recommendations for site preparation and earthwork including stripping requirements, hillside grading, evaluation of on-site soils for use as fill and import fill, and compaction criteria. 4. Provide recommendations for building setbacks in steep slope areas in accordance with Jefferson County Critical Areas Ordinance No. 05-0509-94. 5. Provide recommendations for foundation and slab support of the proposed structures including allowable bearing values and estimates of settlement. 6. Provide geotechnical parameters for standard cantilevered-concrete retaining walls and/or rockery walls, if necessary. 7. Provide recommendations for site drainage, as appropriate. 8. Provide recommendations for pavement design including subgrade preparation. 9. Prepare a report containing our findings along with our conclusions and recommendations. G e o E n g i n e e r s 1 File No. 23784)40-T03/011597 SITE CONDITIONS SURFACE CONDITIONS The subdivision will be located west and south of the Creekside Village I site (now called Timberton Village) approximately as shown on the Site Plans, Figures 2 and 3. The site has been previously harvested for timber and is currently vegetated with grasses, brush,.some small alder, occasional large douglas fir and small replanted fir. Elevations generally range from about 175 to 270 feet above MSL (mean sea level). The site generally comprises four prominent ridge areas with moderate to steep side slopes and separated by a gently to moderately sloping upland area. In the southeas~t portion of the site a northwest to southeast trending ridge (southeast ridge) is flanked by moderate to steep slopes to the northeast and moderate to gentle slopes to the southwest. The ridge in the northwest portion of the site (north ridge) has a general north to south trend and is flanked by moderate to steep slopes to the east, moderate slopes to the west, and the moderate to gently sloping upland area to the south. The upland area is flanked by moderately to steeply sloping ridges to the south and west (south ridge and southwest ridge). Weathered basalt bedrock outcrops at several locations along the ridges and on the upper portions of knolls in the south portion of the upland area. Ridge side slopes range up to about 55 percent with occasional steeper areas. The lower portion of the side slopes generally range from 30 to 40 percent. A small creek flows in a swale and an area of standing water was observed in the south portion of the upland area. Small creeks flow in ravines comprising the lower portion of the steep slope east of the north ridge. Slopes along the ravines range up to about 40 percent. Some of the trees along the steep slope are butt bowed indicating slope movement may have occurred in this area. Ground water seepage was observed near the toe of the slope at the southeast end of the north ridge. SUBSURFACE EXPLORATIONS Subsurface conditions at the site were explored on September 15, 1992 and February 22 and 23, 1995 by excavating 25 test pits and advancing 4 hand auger borings at the approximate locations shown on the Site Plan. The test pits were excavated to depths ranging from 2~/5 to 12~A feet below the ground surface using a John Deere 310C rubber-tired backhoe. The location of the test pits and hand auger borings were established in the field by taping or pacing from existing features, and should be considered approximate. A representative from our firm continuously monitored the excavations and kept a detailed log of the soil, rock and ground water conditions encountered. Soils were visually classified in general accordance with the system described on Figure 5. The logs of our explorations are attached as Figures 6 through 16. SUBSURFACE CONDITIONS The results of our 1992 explorations indicate that most of the north ridge area and the northwest portion of the upland area are underlain by basalt bedrock at depths ranging from 0.5 G e o E n g i n e e r s 2 File No. 2378-040-T03/011597 to 9.5 feet below the ground surface. Materials overlying the bedrock are generally residual soil and/or recessional glacial outwash deposits. The residual soil materials consist of soft to stiff sandy silt with gravel. Where residential soils are present at the surface, the upper 0.5 to 1 foot contains organic matter and is in a soft to medium stiff condition. It is likely that the surficial soils were disturbed during clearing activities. In test pits 2 through 5 of our 1992 study, where these materials overlie the basalt bedrock, the soil 1 to 2 feet above the bedrock consists of silt with weathered basalt or weathered basalt with silt. In test pits 1, 6 and 9 of our 1992 study, we observed residual soils overlying outwash deposits which consist of dense sand and/or sand and gravel mixtures. Basalt bedrock was encountered below the outwash in these test pits at depths of 9.5, 6.5 and 7.0 feet, respectively. Outwash deposits were encountered at the surface in test pits 7 and 8 of our 1992 study. In test pit 7, the outwash is underlain by clayey silt at 9 feet. In test pit 8, the outwash is underlain by very dense glacial till at 5.5 feet below the ground surface. While bedrock was not encountered in these excavations, it is likely that the basalt also underlies both of these areas at relatively shallow depths. Our observations indicate that the residual and outwash materials are generally thinnest on top of the north ridge and thicker on the side slopes. We observed surface outcrops of basalt bedrock at the higher elevations of the. north ridge and upland areas. In test pits 2, 3, 6 and 9 of our 1992 study, the upper 1 to 2 feet of the basalt is fractured and broken. Subsurface conditions encountered in our 1995 explorations in the southeast ridge and upland areas indicate that most of this portion of the site is underlain by basalt bedrock at depths ranging from 3 to 9 feet below the ground surface. Joint spacing in the basalt is typically on the order of 6 to 10 inches in the upper few feet with joint spacing increasing with depth. Joints in the upper few feet of the basalt are filled with reddish brown silt, below the upper few feet of the basalt the joints are tight. Material overlying the bedrock generally consists of reddish brown silt grading to silty gravel with depth. This material is the residual soil resulting from the decomposition of the basalt. Silty sand with gravel in a dense to very dense condition (glacial till) was encountered overlying the bedrock in test pits 11, 15, and 16 of our 1995 study. This portion of the site is overlain with forest duff disturbed during logging of the site. Subsurface conditions encountered in our explorations in the southeast part of the upland area (1995 test pits TP-1 through TP-6) indicate that this portion of the site is underlain blt basalt bedrock. The bedrock surface appears to dip towards the north. Weathered basalt is exposed at the ground surface in the south portion of the upland area, and was encountered in test pits 1 thrbugh 3 at depths ranging from 6 to 7~/i feet.- In test pits 4 through 6 of our 1995 study, fine sand and silty sand in a medium dense to dense condition (glacial outwash) was encountered, extending to the depths explored (11 to 12 feet). Based on bedrock outcrops we observed, it is our opinion that the bedrock surface dips to the north and underlies these outwash deposits-at depth. G e o E n g i n e e r s 3 File No. 2378-040-T03/011597 Ground water seepage was observed in test pit 2 of our 1995 study within the residual basalt at depths of 4 and 7 feet. We also observed ground water seepage in test pits 9, 11, 14, 15, and 16 of our 1995 study at depths ranging from 3~/5 to 11 feet. Ground water seepage was encountered in fractured basalt in test pit 2 of our 1992 study at 4.5 feet below the ground surface. We expect that seasonally perched ground water conditions are likely to exist in the fractured zone~ in other areas of the site during wet weather conditions and/or during the winter season. CONCLUSIONS AND RECOMMENDATIONS GENERAL Based on our observations of surface and subsurface conditions, it is our opinion that the site is generally suitable for the proposed development. Specific grading plans for the site have not yet been developed, however, we have addressed general geotechnical considerations for the project as follows: Slopes at the site appear to be stable under existing conditions. General setback recommendations have been developed. Some of the on-site soils are moisture sensitive and grading will be more economical if- performed during dry weather conditions. · Grading may include fills on slopes. Ail fill should be properly keyed into the slopes and drained, as appropriate. ' The majority of the shallow basalt bedrock is highly fractured and we anticipate it can be excavated by ripping. Excavations and cuts into unweathered basalt'could require the use of hoe-rams or controlled blasting, and may generate large cobbles and boulders that are not suitable for structural fill. · Shallow foundations founded on native materials, bedrock or structural fill may be used for support of structures. · Where mixed subgrade materials (such as bedrock/native soil) occur at footing or floor grades, overexcavation and replacement with structural fill may be required or alternative footing designs should be considered. · Ground water may be seasonally perched immediately above bedrock or in fractured/weathered bedrock zones. Site development should include drainage facilities as appropriate to intercept ground water seepage. LANDSLIDE HAZARD A copy of the Geologically Hazardous Areas Section of the Jefferson County Critical Areas Ordinance is attached as Appendix A. Jefferson County defines landslide hazard areas as: · Areas of historic failures, including areas of unstable slopes and old and recent landslides. · Areas potentially unstable as a result of rapid stream incision, stream bank erosion, or undercutting by wave action. File No. 23784~40~T03/011597 · Areas described and mapped as having severe or very severe building limitations for dwellings without basements within the United States Department of Agriculture/Soil Conservation Service Soil Survey for Jefferson County. No evidence of landsliding or slope instability was observed on the site, except as noted below. However, we believe that surficial soils on the steeper slopes will be vulnerable to creep and/or sloughing if they are disturbed during construction, or if development of the top of the ridge increases or concentrates surface drainage or ground water seepage. Fills on or near slopes should be placed on properly proofrolled and compacted subgrade material, and should be keyed and drained as recommended below. Graded areas and fill slopes should be revegetated to reduce erosion potential. We recormnend that a surface water drainage system be developed for the subdivision to collect drainage from impermeable surfaces and yard areas, and direct it away from slope areas. Recommendations for fill construction, drainage and erosion protection are presented in greater detail in following sections of this report. We did not observe streams on or adjacent to the site which undercut site slopes except near the southeast end of the north ridge area. Some evidence of surficial soil movement or creep was observed on the steep slopes in this portion of the site. The site is located in an area mapped by the SCS (Soil Conservation Service) as having limitations to construction of dwellings with basements which range from slight to severe depending on the soil type and slope. Site soils are included in the Olete and Everett series in the Soil Survey of Jefferson County. The soil survey describes the limitations to dwellings with basements of the Olete soils as slight to moderate for slopes ranging from 0 to 30 percent. The soil survey describes the limitations to dwellings with basements of the Everett soils as slight for slopes ranging from 0 to 8 percent, as moderate for slopes ranging from 8 to 15 percent, and as severe for slopes greater than 15 percent. Portions of the site meet the Jefferson County criteria for landslide hazard areas due to the SCS classification. However, based on our site exploration and experience on similar sites it is our opinion that landslide hazards are not a limiting factor for this development provided the setbacks recommended below are maintained and our recommendations presented in other portions of this report are followed. The recommended setbacks are dependent on house locations and cannot be plotted on a plan until house locations are established. SETBACKS Ridge Areas: We recommend a minimum horizontal distance of 8 feet be maintained between the bottom outside edge of foundations and the face of slopes steeper than 30 percent, as illustrated in Figure 4. For slopes steeper than 50 percent, we recommend the foundation setback be 12 feet. Upland Areas: No landslide hazard areas were identified within this portion of the site. 9 G e o E n g i n e e r s 5 File No. 2378-040-T03/011597 If a lot straddles the approximate boundary between ridge and upland areas the ridge area setbacks should be applied. EROSION HAZARD Jefferson County defines erosion hazard areas as those areas that are classified as having severe or very severe erosion potential by the SCS. The site is located in an area mapped by the SCS as having erosion hazards which range from slight to moderate depending on slope. Site soils are included in the Olete and Everett series in the Soil Survey of Jefferson County. The soil survey describes the erosion hazard of the Olete soils as slight to moderate for slopes ranging from 0 to 30 percent. The soil survey describes the erosion hazard of the Everett soils as slight to moderate for slopes ranging from 0 to 30 percent and as moderate for slopes ranging from 30 to 50 percent. EROSION CONTROL It is our opinion that the potential erosion hazard of the site is not a limiting factor for the proposed development. The proposed development will be located primarily in the more gently sloping portions of the site. Temporary and permanent erosion control measures should be installed and maintained during construction or as soon as practical thereafter to limit the additional influx of water to exposed areas and protect potential receiving waters. Erosion control measures should include but not be limited to berms and swales with check dams to channel surface water runoff, ground cover/protection in exposed areas and silt fences. Removal of natural vegetation should be minimized and limited to the active construction areas, and reestablishment of vegetation should be undertaken as soon as possible. Graded areas should be shaped to avoid directing runoff onto cut or fill slopes, natural slopes or other erosion-sensitive areas. Temporary ground cover/protection such as jute matting, excelsior matting, wood chips or clear plastic sheeting should be used until permanent erosion protection is established. We recommend that graded or disturbed slopes be tracked in-place with the equipment running perpendicular to the slope contours so that the track grouser marks provide a texture to help resist erosion. Thereafter, all disturbed areas should be revegetated. We recommend that no loose fill be placed on the slopes and that no water be directed toward or discharged on the slope areas. However, on-site dispersal of stormwater from individual lots may be appropriate as discussed in the Drainage section. Long term erosion control will require that the vegetative cover on the slopes be maintained. Bare ground areas should be vegetated, as necessary. Erosion resistant plant species include: · Woody shrubs such as: oregon grape, service berry, and salal. · Grass mixtures including: rye~ fescue, bent, and clover. · Other deep rooted site tolerant vegetation. File No. 2378-040-T03/011597 SEISMIC VULNERABILITY In our opinion, the site does not contain seismic hazards areas as defined by Jefferson County criteria. The Puget Sound region is a seismically active area; all sites within this region can be expected to experience some damage in the event of a significant seismic event. Certain factors can result in increased probability or degree of damage at a particular site. We did not encounter conditions which in our opinion place this site at risk of unusual damage in the event of a significant seismic event. Specifically, potentially liquefiable soils, loose sands and silty sands below the water table, were not encountered on the site. EARTHWORK General We expect that the majority of the grading can be accomplished with conventional heavy earthmoving equipment. Heavy ripping should be expected for excavations in the basalt bedrock, especially where the bedrock is less weathered. Heavy ripping may necessitate using a Caterpillar D9L dozer with a single shank ripper, or comparable equipment. Blasting may also be required if unweathered, unfractured bedrock is encountered. Surficial soils at the site generally contain high amounts of silt, and are therefore sensitive to disturbance when they become excessively wet. Operation of heavy equipment at the site under wet conditions can be expected to result in considerable disturbance to the exposed subgrade soils. During wet weather construction, it will probably be necessary to provide temporary haul roads consisting of quarry spalls, crushed rock or pit run sand and gravel. We recommend that earthwork be undertaken during periods of dry weather, if feasible, to minimize grading costs. Clearing and Site Preparation The grading area should be cleared of all surface and subsurface debris including underbrush, tree stumps, roots and organic-laden soils. Portions of the project area have previously been cleared and we expect that only nominal stripping of vegetation will be required in these areas. However, our observations indicate that the upper 1/2 to 1 foot of soil has been previously disturbed. Stripping or recompaction of the soils to these depths may be required where previous site activities have softened surficial soils and/or mixed organic debris into the soil. If the clearing operations cause excessive disturbance, additional stripping depths may be necessary. Disturbance to a greater depth can also be expected if site preparation work is done during periods of wet weather. The organic laden strippings can be stockpiled and used later for landscaping purposes or be spread over disturbed areas following completion of grading. If spread out, the organic strippings should be in a layer less that .1 foot thick, and should not be placed on slopes. Materials which cannot be used for landscaping or protection of disturbed areas should be removed from the project site and wasted. File No. 2378-040-T03/011597 Subgrade Preparation Following stripping, the exposed subgrade should be evaluated prior to placing structural fill, pavement materials or constructing foundations. During dry weather, subgrade evaluation should consist of proofrolling with heavy rubber-tired construction equipment. During wet weather, subgrade evaluation should be accomplished using hand probing. Soft areas noted during proofrolling or probing should be overexcavated and replaced with structural fill as outlined below. We recommend that a GeoEngineers representative, or other qualified geotechnical engineer, be present during proofrolling and/or probing to evaluate exposed subgrade soils. Prior to placement of ~tructural fill, the exposed subgrade should be uniformly compacted to at least 90 percent of MDD (maximum dry density) determined in accordance with ASTM D-1557. Where foundations, slabs or pavement will be founded directly on native material, we recommend that the subgrade soil be compacted to at least 95 percent of MDD. Surficial materials over most of the site contain enough fines (material passing the No. 200 sieve) that compaction of subgrade will be difficult, if not impossible, to achieve during periods of wet weather. If grading takes place during the wet winter months, it will probably be necessary to overexcavate and replace native materials with compacted structural fill containing less than 5 percent fines. Beneath building and pavement areas, we recommend minimum overexcavation depths of 2 feet. Where underlying subgrades are excessively wet, it may be necessary to stabilize the subgrade with a layer of quarry spalls, clean gravel, or by placing a layer of geotextile fabric (such as Mirafi 500x) between the subgrade and structural fill. Structural Fill All fill in embankments and beneath structures or pavements should be placed as structural fill. Structural fill material should be free of debris, organic contaminants, and rock fragments larger than 6 inches. The workability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines (material passing the No. 200 sieve) increases, soil becomes increasingly more sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. If fill material is imported to the site for wet weather construction, we recommend that it be a sand and gravel mixture, such as high quality pit run, with less than 5 percent fines. All structural fill should be compacted in horizontal lifts to at least 90 percent of the MDD per ASTM D-1557. The uppermost 24 inches of subgrade soils below structures, slabs-on-grade and pavements should be compacted to at least 95 percent of the MDD. We recommend that the - fill prism supporting footings, defined by a plane extending down from the edges of the footing at 1 to 1 (horizontal to vertical) to native ground, be compacted to at least 95 percent of MDD. The lift size used during placement and compaction will depend on the moisture and gradation characteristics of the soil and the type of equipment being used. If necessary, the material should be moisture conditioned to near-optimum moisture content prior to compaction. G e o E n g i n e e r s 8 File No. 2378-040-T03/011597 During fill and backfill placement, sufficient testing of in-place density should be performed to verify that adequate compaction is being achieved. Suitability of On-Site Materials for Fill During dry weather construction, nonorganic on-site soil may be considered for use as structural fill provided it is at a suitable moisture content when placed and can be compacted as recommended. If the material is wet when excavated, it will be difficult or impossible to compact. The soil will require aeration and drying out prior to placement as structural fill. During wet weather construction, material with no more than about 5 percent fines should be workable. In general the site soils are not suitable for use as structural fill during wet weather construction. Fill Placement on Slopes Fill placed on slopes steeper than 5 to 1 (horizontal to vertical) should be benched into the slope face and include keyways and subdrains. Bench excavations should be level and extend into the slope face until a vertical step of about 3 feet is constructed. The excavated materials may be pushed out and compacted into the structural fill as it is brought up if adequate compaction can be achieved. Keyways should be located below fill embankment toe areas where new fills meet existing hillside slopes. Additional keyways may be necessary depending on the extent of the proposed fill and the quality of the soil and rock underlying the embankment. Keyways should be embedded at least 2 feet into stable material in the toe area. The width of the keyway will depend on several factors, such as the vertical height of the fill above the keyway and the size of the equipment used to construct the keyway. In general, keyways should be at least 10 feet wide or about 1 t/5 times the width of the equipment used for grading or compaction. Fill Slopes Permanent fill slopes should be constructed at inclinations of 2 to 1 (horizontal to vertical) or flatter, and should be blended into existing slopes with smooth transitions. To reduce postconstruction sloughing and ravelling,-we recommend that fill slopes be overbuilt where possible and subsequently cut back to expose well compacted fill. Retaining structures should be used where cut and fill slopes 2 to 1 or flatter cannot be achieved. To minimize erosion, newly constructed slopes should be hydroseeded as soon as practical. Until the vegetation is established, some sloughing and ravelling of the slopes should be expected. Erosion control measures such as temporary covering with clear plastic sheeting, straw mulch, revegetation fabric or jute matting should be used to protect these slopes until vegetation is established. We also recommend that graded areas above slopes be shaped to direct surface water away from the slope face. G e o E n g i n e e r s 9 File No. 2378-040-T03/011597 Fill Drainage Subdrains should be installed at the rear of each keyway and at other locations beneath fill embankments where ground water seepage is encountered during grading. The subdrains can be installed concurrently with fill placement, or in trenches excavated after filling, where the trench depth would not exceed about 4 feet. The drains should consist of a free-draining sand and gravel drainage material, placed in a trench about 2 feet wide, fully encapsulated within a suitable nonwoven, geotextile filter fabric, such as Mirafi 140N (or similar material). The drainage material should extend the full height of the rear keyway wall. Where subdrains are used to intercept ground water seepage at locations other than at keyways, the drainage material should be at least 3 feet high. A heavy-wall (SDR-35 or heavier) perforated pipe should be installed near the bottom of each subdrain and bedded in drainage material. Pipes should have minimum slopes of 1 percent and should drain to suitable collector and discharge points. All subdrain lines should include cleanout risers. We recommend that the cleanout risers be covered with tamper-proof locking caps. Discharge pipes should be covered with heavy galvanized wire mesh to prevent rodent access. When the grading plan has been completed, locations for subdrains can generally be predetermined by GeoEngineers prior to construction, based on our understanding of subsurface conditions. We recommend anticipating that additional subdrains will be required during grading to intercept ground water seeps that are encountered. A contingency for additional subdrains should be included in the project budget, Fill Settlement Postconstruction settlement of fill will depend on the type and compaction of the fill, the thickness of the fill, and subgrade conditions. We estimate that structural fills may experience settlement in the range of 1/2 to 1 inch for every 10 feet of new fill thickness. Because fill thickness may vary beneath each individual lot, settlement of the fill may occur differentially. Cut Slopes Permanent cut slopes in soils should be inclined at 2 to 1 (horizontal to vertical) or flatter, or should be retained with a properly designed retaining structure. Cut slopes should be hydroseeded shortly after completion of grading to prevent erosion. Temporary erosion protection may be necessary as discussed above for newly constructed fill slopes. For planning purposes, cuts in unweathered bedrock may be inclined at I to 1. Where the bedrock is fractured, weathered, jointed, or otherwise unstable, flatter cut inclinations or stabilization techniques may be required. It is likely that cuts in unweathered bedrock will require the use of heavy ripping equipment and/or controlled blasting. L~ G e o E n g i n e e r s 10 FileNo. 2378-040-T03/011597 FOUNDATION SUPPORT We recommend that residential structures be supported on conventional spread footings founded on medium dense to dense native soil, basalt bedrock, or structural fill, prepared as recommended in the "Earthwork" section of this report. Shallow spread footings designed and constructed as described below may be used where minimum setback distances can be achieved on moderate slopes. Shallow Spread Footings We recommend that all foqting elements be embedded a minimum of 18 inches below lowest adjacent finished grade. Where footings are placed on sloping ground, the horizontal distance from the bottom of the footing to the ground surface should not be less than 8 feet. We recommend a minimum width of 2 feet for isolated footings and.at least 16 inches for continuous wall footings. Deeper footing embedment may be required where minimum building setbacks cannot be achieved, and we recommend that design criteria for footings located on or near slopes be evaluated by a representative from our firm on a site-specific basis. Footings founded as described above can be designed using an allowable soil bearing pressure of 2,500 psf (pounds per square foot) for combined dead and long-term live loads, exclusive of the weight of the footing and any overlying backfill. This value may be increased by one-third for transient loads such as those induced by seismic events or wind loadings. Where a crawlspace is used, footing pads for floor support may be cast on the ground, providing that the ground is firm and level. These pads should be designed using an allowable bearing of 1,000 psf applied to dead and live loads. We estimate that postconstruction settlement of structures supported uniformly on basalt bedrock should be less than about 1/4 inch, with negligible differential settlement. Postconstruction settlement of structures supported on medium dense to dense native soil or on structural fill may range from about 1/2 to 1 inch. Maximum differential settlements of structures on native or fill soils should be less than 1/2 inch, measured along 25 feet of continuous wall footing or between adjacent comparably loaded isolated footings. We expect that settlements will occur essentially as the loads are applied. Structures constructed across mixed subgrade conditions could experience distress because of differential performance of the subgrade materials. This is a concern at the contact between cuts and fills, at contacts between dissimilar materials within CUTS, and especially where fills or native soils abut the basalt bedrock. Where contacts between dissimilar materials are exposed at pad or footing grade, we recommend that the subgrade beneath the structure be overexcavated at least 1 foot below design grade, and the overexcavation backfilled with structural fill compacted to at least 95 percent of the MDD. The limits of the overexcavation and structural fill placement should extend at least 1 foot outside of the building footprint or footing area. Alternatively, where dissimilar subgrade materials occur, it may be more economical to extend footings so that the entire foundation is supported on bedrock. G e o E n g i n e e r s 11 File No. 2378-040-T03/011597 Loose or disturbed subgrade soils in footing excavations may result in increased settlement. The native soils are susceptible to disturbance if allowed to become wet. If footings are constructed during wet weather, concrete should be placed as soon as possible after the footings are excavated. It also may be appropriate to place a lean concrete "mud mat" or a layer of crushed rock in footing excavation bottoms to protect the subgrades from disturbance. We recommend that all footing excavations be observed by a representative from our firm immediately prior to mud mat or crushed rock placement, or reinforcing steel and structural concrete placement to confirm that the bearing surface has been prepared in a manner consistent with our recommendations and that the subsurface conditions are as expected. FLOOR SLAB SUPPORT Floor slabs may be supported on-grade provided that the subgrade soils are prepared as previously recommended. Any areas disturbed by construction activities should be recompacted before proceeding with slab construction. We recommend that slabs-on-grade be constructed on a gravel layer to provide uniform support and to act as a capillary break. The gravel layer should consist of at least 4 inches of clean fine gravel, with negligible sand or silt, and preferably should be crushed material. A vapor barrier should be placed beneath the slab. In areas where ground water is near the surface, we recommend that underdrainage be provided to:collect and discharge ground water from below the slabs. This can be accomplished by thickening the gravel layer below the slabs to 6 inches, and installing a 4-inch;diameter perforated collector pipe in a shallow trench placed below the gravel layer. The collector pipe should be oriented along the center, long axis of the structure. The trench should measure about 1 foot wide by 1 foot deep and should be backfilled with clean gravel. The collector pipe should be sloped to drain and discharge into the storm water collection system to convey the water off site. This pipe should also incorporate a cleanout. RETAINING SYSTEMS Cantilevered Concrete Gravity Walls Portions of the building stem walls may serve as retaining walls, particularly if daylight basement construction is used. Other cantilevered concrete gravity walls may be used at the site for grade transitions. Retaining walls that are allowed to yield during backfilling should be designed for lateral pressures based on an equivalent fluid density of 35. pcf (pounds per cubic foot) if the ground surface behind the wall is level for a distance of two times the wall height. This value applies to fill behind the walls that is placed and compacted as recommended above, with the exception that fill within a distance equal to the wall height behind the wall should be compacted to a maximum of 92 percent of the MDD. Care must be' taken by the contractor to avoid overcompaction. Alternative design values can be presented for sloping backfills once the grading plans have been determined. ~_. G e o E n 'g i n e e r s 12 File No. 2378-040-T03/011597 The recommended equivalent fluid density assumes a free-draining condition behind the wall. This can be accomplished by placing a 12- to 18-inch-wide zone of sand and gravel containing less than 5 percent fines against the wall. The uppermost 1 foot should be backfilled with more silty soil to form a plug against surface water intrusion. A 4- or 6-inch-diameter, heavy-walled perforated drain pipe should be installed within the free-draining material at the base of the wall. The pipe should be laid with a minimum slope of one percent to a suitable discharge point. The pipe installation should include a cleanout riser with cover located at the upper end of the pipe run. The value for soil bearing presented for the foundation design is applicable to retaining wall design. Resistance to lateral loads will be developed both through friction on the base of the footing and passive resistance on the sides of the footing. Friction resistance between the concrete and native soils or compacted structural fill may be computed using a coefficient of friction of 0.35 applied to the vertical dead load forces. We recommend passive resistance be computed using an equivalent fluid density of 300 pcf applied over the embedment depth of the wall and footing. The above coefficient of friction and passive equivalent fluid density values include a factor of safety of about 1.5. We reCOmmend that we be provided the opportunity to review our recommendations if wall heights exceed about 8 feet or if retaining walls with sloping backfill will be constructed for this project. If free-standing retaining walls will be necessary in fill sections to accommodate grade transitions, we suggest that design alternatives that may include the use of geosynthetics be evaluated. Rockeries Rockeries may be planned in areas with grade transitions. Rockeries essentially serve as protection against erosion and minor sloughing along existing stable slopes and provide little "retaining" support. Rockeries are best suited for use along stable slopes cut in competent soils. When a rockery is constructed along the face of a fill embankment, adequate compaction of the fill behind the rockery is critical for long-term stability; the fill should be compacted to at least 95 percent of the MDD, and the fill height should be limited to about 4 feet. Any surcharge conditions above a rockery or seepage conditions within the fill embankment behind a rockery can lead to distress or failure of a rockery-faced slope. The potential need for maintenance of rockeries should be recognized. We recommend that rockeries be constructed in accordance with the most current edition of "The Association of Rockery Contractors Standard Rockery Construction Guidelines." For planning purposes, we recommend that all rockeries be limited to a maximum height of 8 feet. Other Retaining Options A variety of retaining systems may be used where the recommended maximum cut and fill slope inclinations will not accomplish the necessary grade transitions. Specific design criteria G e o E n g i n e e r s 13 File No. 23784)40-T03/011597 should be developed for each wall after its height and location are determined. Mechanically stabilized walls (fill embankments with geosynthetic reinforcement and facing materials), soldier pile walls, soil nailed walls and others may be cost effective depending upon the circumstances. DRAINAGE All ground surfaces, pavements and sidewalks should slope away from structures. Surface water runoff should be controlled by a system of curbs, berms, drainage swales, and/or catch basins, and conveyed off-site through a storm water collection system. Surface water should not be discharged into subdrains in fills and roadways. Roof drain water should not be discharged to footing drains. However, use of separate dispersal trenches on individual lots may be approi~riate for disposal of roof drainage and should be evaluated on a case by case basis. Footing, wall and underslab drainage systems may be needed depending on final design grades and localized ground water conditions. Footing drains with an invert elevation at the base of the footing are generally a good deterrent to prevent water collection in crawlspaces. The crawlspace should not be excavated deeper than the invert of the footing drains, or additional areal drains will need to be provided. Permanent drainage systems should be installed at the top and/or bottom of cut and fill slopes greater than 5 feet in height to intercept surface runoff and to prevent it from flowing in an uncontrolled manner across the slopes. Surface water should not be discharged over the undisturbed slopes outside the grading areas. PAVEMENT DESIGN AND SUBGRADE PREPARATION Roadway subgrades should be prepared as described previously for general earthwork. The upper 24 inches of roadway subgrade should have a density of at least 95 percent of the MDD. In areas where soft or disturbed soils are encountered, subgrade preparation should consist of overexcavating the unsuitable soils down to firm unyielding material, or about 2 feet maximum, whichever is less. If soft soils are present at 2 feet below design subgrade elevation, we recommend placing a woven geotextile fabric such as Mirafi 500X (or similar material approved by the geotechnical engineer) on the subgrade and covering the geotextile with at least 12 inches of gravel or rock spalls. Our recommended pavement section is for the proposed arterial roads and cul-de-sacs within the development. We anticipate that these roads will be subjected to primarily automobile traffic with occasional trucks. The recommended pavement section is 2 inches of Class B asphalt concrete underlain by a 2-inch layer of crushed top course material. The top course is underlain by 6 inches of gravel base compacted to 95 percent of the maximum dry density as determined by ASTM D-1557. Calculations supporting the proposed pavement section are included in Appendix B. G e o E n g i n e e r s 14 File No. 2378-040-T03/011597 EROSION AND SEDIMENTATION CONTROL Temporary erosion protection should be used and maintained during construction to protect slope surfaces, adjacent areas and receiving waters. Erosion control measures should include proper channeling of surface water runoff, and liberal use of straw bales or geotextile filters, as appropriate. Grading should be accomplished to avoid concentration of runoff onto fill areas, cut or fill slopes, natural slopes or other erosion-sensitive areas. We recommend that disturbance to slopes outside the immediate work areas be minimized. Removal of vegetation and forest duff should be limited. Some sloughing and ravelling of cut slopes and natural slopes that are disturbed should be expected. Graded areas should be shaped to divert water away from slope areas. Surface runoff should be prevented from flowing into excavations by using berms, drainage ditches, swales or other appropriate methods. As temporary erosion protection, we recommend the use of straw, jute matting, visqueen sheeting or other forms of ground cover on all areas disturbed by the construction. Permanent erosion protection should be provided by reestablishing vegetation. Slope surfaces should be restored so that surface runoff does not become channeled. We recommend that graded or disturbed slopes be tracked in place with the equipment running perpendicular to the slope contours so that the track grouser marks provide a texture to help resist erosion. Thereafter, all disturbed areas should be hydroseeded. LIMITATIONS We have prepared this report for use by Pope Resources and members of the project team involved in the Creekside Village Division II residential development. The data and report should be provided to prospective contractors for bidding or estimating purposes; but our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions. Our scope 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. The project was in the design development stage at the time this report was prepared. We expect that further consultation regarding specific design elements will be necessary. If there are any changes in the grades, location, configuration or type of construction planned, the conclusions and recommendations presented in this report might not be fully applicable. If such changes are made, we should be given the opportunity to review our conclusions and recommendations and to provide written modification or verification, as appropriate. When the design is finalized, we recommend that we be given the opportunity to review those portions of the specifications and drawings that relate to geotechnical considerations to see that our recommendations have been interpreted and implemented as intended. G e o E n g i n e e r s 15 File No.~378-040-T03/011597 There are possible variations in subsurface conditions between the locations of the explorations and also with time. Some contingency for unanticipated conditions should be included in the project budget and schedule. We recommend that sufficient monitoring, testing and consultation be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations; to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated; and to evaluate whether or not earthwork and foundation installation activities comply with the contract plans and specifications. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time the report was prepared. No other conditions, express or implied, should be understood. We appreciate the opportunity of working with you on this project. If you have any questions or need further assistance, please call. [ [xP,aEs t0/23/qT GHS:GWH:vc Document ID: 2378040R.R ,i Yours very truly, GeoEngineers, Inc. Garry H. Squires Senior Geotechnical Engineer Gary W. Henderson Principal Attachments Six copies submitted 16 File No. 2378-040-T03/011597 GeoEngineers 12 t 7 8 -- -~ PORT LL[DLOV~ 24I ~i~81TE~App~o~o~ Locetion) VICINITY MAP NOT TO SCALE 0 ~eference: Drowin~ provided by ~SM, Inc., doted.glO'f95 job number 52g-0~ -950-002. n ~&t~ VI CIN ITY M AP ~ Geo m*~ Engineers GHS:SPS 2378040C.DWG (VIEW 257804005:121196 TRAc T 'C' ill x r~ z 0 z -0 GHS:SPS <. O. Frl 2378040B.DWG 237804-003:121196 cm z · -o:;o "qO 0 © ~> 0 ~o~~o ©~ O~ O~ ~ Z-- Z-- X Z 0 Z -0 ~ /~ Foundation ~,x~~~x'~'¢~____ Minimum Setback Dense Native Soil or Properly Compacted Structural Fill DRAWING NOT TO SCALE NOTES: 1 Setback shall be at least 8' for slopes greater than 30%. . 2. Setback shall be at least 12' for slopes greater than 50%. ~_~ o FOUNDATION DETAIL lneers . FIGURE 4 :2 SOIL CLASSIFICATION SYSTEM GROUP MAJOR DIVISIONS SYMBOL GROUP NAME GRAVEL CLEAN GW WELL-GRADED GRAVEL. FINE TO COARSE GRAVEL COARSE GRAVEL GP POORLY-GRADED GRAVEL GRAINED SOILS More Than 50% of Coarse Fraction GRAVEL GM SILTY GRAVEL Retained - WITH FINES Ge CLAYEY GRAVEL on No. 4 Siove -More Than 50% SAND CLEAN SAND SW WELL-GRADED SAND, FiNE TO COARSE SANG Retained on No. 200 Sieve SP POORLY-GRADED SAND More Than 50% of Coarse Fraction SAND SM SILTY SAND WITH FINES .- Passes SC CLAYEY SANG No. 4 Siove FINE SILT AND CLAY ML SILT GRAINED INORGANIC CL CLAY SOILS Liquid Limit ORGANIC Ok ORGANIC SILT, ORGANIC CLAY Less Than 5;0 SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT More Than 50% INORGANIC Passes CH CLAY OF IqlGH PLASTICITY. ~:AT CLAY No. 200 Sieve Liquid Limit ORGANIC OH ORGANIC CLAY. ORGANIC SILT $0 or Moro HIGHLY ORGANIC SOILS PT I~AT NOTES: SOIL MOISTURE MODIFIERS: 1. F]eld classification is based on visual examination of soil Dry - Absence of moisture, dusty, dry to the touch in general accordance with ASTM D2488-90. Moist - Damp, but no visible water 2. Soil classification using laboratory tests is based on ASTM D2487-90. ' Wet- Visible free water or saturated, usually soil is obtained from below water table 3. Oescriptions of soil density or consistency are based on interpretation of blow count data, visual appearance of soils, and/or test data. SOIL CLASSIFICATION SYSTEM Geo Engineers LOG OF TEST PIT DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0 - 0.5 0.5 - 6.0 ML 6.0 - 11.0 SM 11.0 Basalt DESCRIPTION TEST PIT 1 Sod mat Reddish brown silt with gravel, sand and occasional cobbles (medium stiff, moist) Dark reddish brown silty sand with gravel and cobbles (dense, wet) Basalt bedrock Test pit completed at a depth of 11.0 feet on 02/22/95 Ground water seepage observed at depths of 3.0 and 6.0 feet Moderate caving observed below a depth of 6.0 feet 0.0 - 0.4 0.4 - 2.5 SM 2.5 - 7.5 SP 7.5 - 11.5 SM TEST PIT 2 Sod mat Reddish brown silty sand with gravel and cobble sized blocks of fractured basalt (medium dense, mois0 Yellowish brown f'me to medium sand with a trace of silt (medium dense, wet) Dark reddish brown silty sand with gravel (residual basalt) Test pit completed at a depth of 11.5 on 02/22/95 Ground water seepage observed at depths of 4.0 and 7.0 feet Caving observed between depths of 4.0 and 7.0 feet . 0.0 - 0.5 0.5 - 7.5 SP 7.5- 10.0 SM 10.0 Basalt TEST PIT 3 Forest duff Yellowish brown fine to medium sand (medium dense to dense, moist) Dark reddish brown silty sand and gravel (dense, moist) (residual rock) Basalt bedrock with cobble sized blocks of basalt Test pit completed at a depth of 10.0 feet due to refusal on 02/22/95 No ground water seepage observed Caving observed at a depth of 5.0 feet THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0. I FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE C- ONSIDERED ACCURATE TO 0.5 FOOT. Geo , ' Engineers LOG OF TEST PIT FIGURE 6 LOG OF TEST PIT DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0 - 0.3 0.3 - 2.5 SM 2.5 - 12.0 SP DESCRIPTION TEST PIT 4 Sod mat Reddish brown silty sand with gravel (dense, mois0 Light brown very fine to fine sand (dense, tools0 Grades to gray fine to medium sand Test pit completed at a depth of 12.0 feet on 02122/95 No ground water seepage observed No caving observed 0.0 - 2.5 SM 2.5 - 8.0 SM 8.0 - l !.0 SP TEST PIT 5 Reddish brown silty fine to medium sand (medium dense, moist) $~h4a to light gray silty very fine sand in thin layers (medium dense to dense, moist) Erratic basalt boulder encountered at a depth of 5.0 feet Gray fine to medium sand (dense, moist) Test pit completed at a depth of 11.0 feet on 02/22/95 No ground water seepage observed No caving observed 0.0- 1.5 SM 1.5 - 4.0 SP 4.0 - 7.0 ML 7.0 - 11.0 SP TEST PIT 6 Reddish brown silty sand Brown fine to medium sand (medium dense, moist) Gray fine silty sand (very stiff, moist) Erratic basalt boulder encountered at a depth of 7.0 feet Gray fine sand (dense, moist to we0 Test pit completed at a depth of 11.0 feet on 02/22/95 No ground water seepage observed No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo Engmeers LOG OF TEST PIT FIGURE 7 DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0 - 0.5 0.5 - 2.0 SM 2.0 - 3.0 Basalt LOG OF TEST PIT DESCRIPTION TEST PIT 7 Forest duff Reddish brown silty sand with gravel cobble sized blocks of basalt (dense, mois0 (residual rock) Highly fractured basalt Test pit completed at a depth of 3.0 feet due to refusal on 02/22/95 No ground water seepage observed No caving observed 0.0 - 2.5 SM 2.5 Basalt TEST PIT 8 Dark reddish brown silty sand with gravel to cobble sized blocks of basalt (dense mois0 (residual rock) Basalt Test pit completed at a depth of 2.5 due to refusal on 02/22/95 No ground water seepage observed No caving observed 0.0 - 0.7 0.7 - 2.0 SP 2.0 - 9.0 SM 9.0- 10.5 Basalt TEST PIT 9 Forest duff REddish brown silty sand with gravel and occasional cobbles and fractured blocks of basalt (medium dense, mois0 (residual rock) Orange silty coarse sand to gravel (medium dense to dense, moist) Highly fractured basalt Test pit completed at a depth of 10.5 feet due to refusal on 02/22/95 Moderate ground water seepage observed at a depth of 8.0 feet No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo ,' Engineers LOG OF TEST PIT FIGURE 8 LOG OF TEST PIT DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0 - 0.5 0.5 - 3.0 ML 3.0 - 5.5 SM 5.5 - 6.5 Basalt DESCRIPTION TEST PIT 10 Forest duff Dark brown silt with organic material (stiff, moist) Orange silty gravel (medium dense to dense, moist) Highly fractured basalt Test pit completed at a depth of 6.5 feet due to refusal on 02/22/95 No ground water seepage observed No caving observed 0.0 - 0.7 0.7 - 4.5 SM 4.5 - 11.0 SM 11.0" Basalt TEST PIT 11 Sod mat Dark reddish gray brown gravelly silt with occasional cobble-sized chunks of fractured rock (very stiff to hard, moist) Gray silty sand with gravel (dense, moist to we0 Fractured basalt with tight joints Test pit completed at a depth of 11.0 feet due to refusal on 02/22/95 Ground water seepage observed at a depth of 11.0 feet No caving observed 0.0- 1.0 SM 1.0 - 5.0 Basalt TEST PIT 12 Reddish brown silty sand (medium dense, moist) Fractured basalt with tight joints Test pit completed at a depth of 5.0 feet due to refusal on 02/22/95 No ground water seepage observed No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo ' Engineers LOG OF TEST PIT FIGURE 9 DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0- 1.5 SM 1.5 - 4.5 Basalt LOG OF TEST PIT DESCRIPTION TEST PIT 13 Orangish brown silty sand with gravel Basalt rock Test pit completed at a depth of 4.5 feet due to refusal on 02/22/95 No ground water seepage observed No caving observed 0.0 - 3.0 SM 3.0 - 8.0 Basalt TEST PIT 14 Orangish brown silty sod with gravel (medium dense, moist) (residual soil) Fractured rock Test pit completed at a depth of 8.0 feet on 02/22/95 Rapid ground water seepage observed at a depth of 5.0 feet No caving observed 0.0 - 0.8 0.8 -4.5 SM 4.5 - 6.5 SM 6.5 - 7.5 SP 7.5 - 8.5 Basalt TEST PIT 15 Forest duff Reddish brown silty sand with gravel cobbles and occasional blocks of fractured basalt Gray silty sand with gravel (dense, nmis0 (glacial till) Gray sand (dense, tools0 Reddish brown highly fractured basalt rock Test pit completed at a depth of 8.5 due to refusal on 02/22/95 Ground water seepage observed at a depth of 8.5 feet No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0. I FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo .,Engmeers I LOG OF TEST PIT FIGURE 10 DEPTH BELOW GROUND SURFACE {FEET) 0.0 - 0.8 0.8 - 3.5 3.5 - 7.5 7.5 - 8.5 SOIL GROUP CLASSIFICATION SYMBOL SM SM LOG OF TEST PiT DESCRIPTION TEST PIT 16 Forest duff Reddish brown silty sand with gravel cobbles and occasional blocks of fractured basalt (medium dense to dense, moist) Gray silty sand with gravel (dense, mois0 (till) Dark gray rock weathered to a granular material Test pit completed at a depth of 8.5 feet due to refusal on 02/22/95 Slight ground water seepage observed at depths of 3.5 and 7.5 feet No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo , Engineers TEST PITS FROM REPORT DATED NOVEMBER 20, 1992 DEPTH BELOW GROUND SURFACE {FEET) 0.0- 1.0 1.0- 8.0 8.0- 9.5 9.5+ 0.0- 1.0 1.0- 2.5 2.5- 4.8 4.8+ 0.0- 0.5 0.5- 2.5 2.5+ LOG OF TEST PIT SOIL GROUP CLASSIFICATION SYMBOL DESCRIPTION ML SP SP ML ML ML TEST PIT 1 Brown sandy silt with gravel (medium stiff, mois0 (fill) Yellowish-brown fine to medium sand with a trace of silt and occasional fine gravel (dense, mois0 Yellowish-brown fine to medium sand with silt and weathered basalt (dense, wet) Basalt bedrock Test pit completed with practical refusal at 9.5 feet on 09/15/92 No ground water seepage observed TEST PIT 2 Brown sandy silt with gravel (medium stiff, moist) Brown silt with weathered basalt (stiff, moist) Fractured basalt with silt (dense, mois0 Basalt bedrock Test pit completed with practical refusal at 4.8 feet on 09/15/92 Ground water seepage observed at approximately 4.5 feet TEST PIT 3 Brown sandy silt with gravel (soft, moist) Fractured basalt with some silt (dense, tools0 Basalt bedrock Test pit completed with practical refusal at 2.5 feet on 09/15/92 No ground seepage observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo , ' Engineers I LOG OF TEST PIT FIGURE 1 2 DEPTH BELOW GROUND SURFACE (FEET) 0.0- 0.5 0.5- 4.0 4.0- 5.0 4.0+ 0.0- 1.0 1.0- 3.0 3.0+ 0.0- 0.3 0.3- 5.5 5.5- 6.5 6.5- 7.5 7.5+ LOG OF TEST PIT SOIL GROUP CLASSIFICATION SYMBOL DESCRIPTION ML ML ML TEST PIT 4 Dark brown silt with sand and organic matter (soft, moist) Brown silt with sand and a trace of gravel (stiff, moist) Brown silt with weathered basalt Basalt bedrock Test pit completed with practical refusal at 5.0 feet on 09/15/92 No ground water seepage observed ML TEST PIT 5 Brown sandy silt with gravel and organic matter (medium stiff, moist) Fractured basalt with sandy silt (dense, mois0 Basalt bedrock Test pit completed with practical refusal at 3.0 feet on 09/15/92 No ground water seepage observed ML ML SP TEST PIT 6 Dark brown sandy silt with organic matter (soft, moist) Brown sandy silt with weathered basalt (stiff, moist) Yellowish-brown fine to medium sand with fractured basalt Fractured basalt with silt Basalt bedrock Test pit completed with practical refusal at 7.5 feet on 09/15/92 No ground water seepage observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo Englneers LOG OF TEST PIT FIGURE 13' LOG OF TEST PIT DEPTH BELOW GROUND SURFACE (FEET) 0.0- 0.3 0.3- 9.0 9.0- 10.0 0.0- 0.5 0.5- 5.5 5.5- 6.0 0.0- 2.0 2.0- 5.0 5.0- 7.0 7.0- 9.0 9.0+ SOIL GROUP CLASSIFICATION SYMBOL SP SP ML SP GP SM SM GP ML DESCRIPTION TEST PIT 7 Dark brown sand with organic matter (medium dense, moist) Light brown fine to medium sand with a trace of silt and a trace of fine gravel (medium dense to dense, moist) Gray clayey silt with brown mottles (stiff to very stiff, moist) T~'pit completed at 10.0 feet on 09/15/92 No ground water seepage observed TEST PIT 8 Dark brown sand with grovel and organic matter (meidum dense, moist) Brown sandy gravel with silt (dense, moist) Grayish-brown silty sand with gravel (very dense, mois0 (glacial till) Test pit completed at 6.0 feet on 09/15/92 No ground water seepage observed Disturbed sample obtained at 5.5 feet TEST PIT 9 Brown silty sand with clearing debris (soft, moist) Brown sandy gravel with silt (dense, moist) Silt with weathered basalt (dense, moist) Fractured basalt Basalt bedrock Test pit completed with practical refusal at 9.0 feet on 09/15/92 No ground water seepage observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. Geo ,; Engineers LOG OF TEST PIT FIGURE 14' AP-PENDIX A . Lb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 SECTION 9: GEOLOGICALLY HAZARDOUS AREAS Subsections: 9.10 9.20 9.30 9.40 9.50 9.60 Introduction Purpose Classification/Designation Applicability and Waivers Protection Standards Conditions 9.10 Introduction 15 Geologically hazardous areas in Jefferson County are characterized by 16 slope, soil type, geologic material, and groundwater that may combine 17 to create problems with slope stability, erosion, and water quality 18 during and after construction or during natural events such as 19 earthquakes or severe rainstorms. The following regulations will 20 guide development in these critical areas. 21 22 23 9.20 Purpose 24 25 To maintain the natural integrity of geologically hazardous areas and 26 their buffers in order to protect adjacent lands from the impacts of 27 landslides, mudslides, subsidence, excessive erosion, and to safeguard 28 the public from these threats to life and property. The purpose of 29 this ordinance section is, however, subordinate to the overall purpose 30 of this ordinance as stated in §1.201. 31 32 33 9.30 Classification/Desiqnation 34 35 9.301 Classification: For the purposes of this ordinance, 36 geologically hazardous areas shall be classified based upon a 37 combination of erosion, landslide and seismic hazard. 38 39 40 41 42 1. 43 44 45 46 47 48 49 50 2. 51 52 9.302 Desiqnation: The following erosion, landslide and seismic hazard areas shall be subject to the standards of this section: Erosion hazard areas: a. Areas containing soils or soil complexes described and mapped within the United States Department of Agriculture/Soil Conservation Service Soil Survey for Jefferson County as having a severe or very severe erosion hazard potential: Landslide hazard areas: Areas potentially subject to mass movement due to a combination of geologic, topographic and hydrologic factors including: 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 a. Areas of historic failures or potentially unstable slopes, such as: areas described and mapped as having severe or very severe building limitations for dwellings without basements within the United States Department of Agriculture/Soil Conservation Service Soil Survey for Jefferson County; (ii) areas described and mapped as recent or old landslides or slopes of unstable materials within the Washington State Department of Ecology Coastal Zone Atlas of Jefferson County; and (iii) areas described and mapped as areas of poor natural stability, former landslides and recent landslides by the Washington State Department of Natural Resources, Division of Geology and Earth Resources; Areas potentially unstable as a result of rapid stream incision, stream bank erosion, or undercutting by wave action; and c. Areas with any indications of earth movement, such as: (i) rockslides; (ii) earthflows; (iii) mudflows; and (iv) landslides. Seismic hazard areas: Areas subject to severe risk of damage as a result of earthquake induced ground shaking, slope failure, settlement, soil liquefaction, or surface faulting. These areas are identified by the presence of: poorly drained soils with greater than fifty percent (50%) silt and very little coarse material; loose sand or gravel, peat, artificial fill and landslide materials; or soil units with high organic content. 9.303 Sources Used for Identification: Sources used to identify 40 geologically hazardous areas include, but are not limited to: 41 42 1. 43 44 45 2. 46 47 3. 48 49 50 4. 51 52 United States Department of Agriculture/Soil Conservation Service, Soil Survey for Jefferson County. Washington State Department of Ecology, Coastal Zone Atlas. Washington State Department of Natural Resources, S!op~ Stability and GeoloGic Maps of Eastern Jefferson Count~. Washington State Department of Natural Resources, Geographic Information System: Soil Survey. 42 1 2 3 4 5 6 7 9,502 8 9 1. 10 11 12 13 14 15 16 17 18 19 2. 20 21 22 23 24 3. 25 26 27 29 30 31 4. 32 33 34 35 9. 503 36 37 1. 38 39 40 41 42 43 44 L~. 45 46 47 48 49 50 51 -- 52 9.50 protectio~ Standards ~,501 General:~ A triggering application for a project on a parcel of real property containing a designated geologically hazardous area or its buffer shall adhere to the requirements set forth below. Drainage and Erosion Control: An applicant submitting a triggering application shall also submit, and have approved, a drainage and erosion control plan, as specified in section 11 of this ordinance, when the triggerin~ application involves either of the following: a. The alteration of a geologically hazardous area or its buffer; or b. The creation of a new parcel within a known geologically hazardous area. Drainage and erosion control plans required under this section shall discuss, evaluate and recommend methods to minimize sedimentation of adjacent properties during and after construction. Surface drainage shall not be directed across the face of a marine bluff, landslide hazard or ravine. If drainage must be discharged from a bluff to adjacent waters, it shall be collected above the face of the bluff and directed to the water by tight line drain and provided with an energy dissipating device at the shoreline. In addition to any erosion control methods specified in the drainage and erosion control plan, the Administrator may require hydroseeding of exposed or disturbed areas. Clearinq and Gradinq: The following provisions regarding clearing shall apply: a. Clearing within geologically hazardous areas shall be allowed only from April 1 to November 1, unless the applicant demonstrates that such activities would not result in impacts contrary to the protection requirements herein. b. Only that clearing necessary to install temporary sedimentation and erosion control measures shall occur prior to clearing for roadways or utilities; c. Clearing limits for roads, septic, water and stormwater utilities, and temporary erosion control facilities shall be marked in the field and approved by the Department prior to any alteration of existing native vegetation; 44 1 5. 2 3 4 5 6. 6 7 Washington State Department of Natural Resources, Geologic Maps of Eastern Jefferson County, Compressibility of Earth M~erials i~ Eastern Jefferson County. United States Department of the Interior, USGS Quad Maps. 8 9.304 Geoloqic Hazard Area Maps: The maps prepared by the County 9 using the identification sources listed in subsection 8.303 have been 10 produced for informational purposes only and are not regulatory devices forming an integral part of this ordinance. 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 9.40 Applicability and Waivers 9.401 Applicability: 1. Critical area review shall be required for any triggering application for a project on a parcel of real property containing a designated erosion or landslide hazard area, unless waived under subsection 9.402, below. Critical area review shall be required where a triggering application is made for construction of any publicly owned facility in a designated seismic hazard area. 9.402 Waivers: The provisions of this section shall not apply when the applicant demonstrates either one of the following, to the satisfaction of the Administrator: Ail building sites and project related improvements (including any clearing or grading activity) will be located outside of any designated geologic hazard area or its buffer. There is adequate geologic information available for the project area to determine the impacts of the proposed development and appropriate mitigating measures, if any; and the proposal would not cause adverse geological impacts on or off the project site. 9.403 Waiver Conditions: In order to secure compliance with subsection 9.402, above, the Administrator may require conditions of approval which ensure that no portion of the proposed development will encroach upon a designated geologic hazard area or its buffer. Conditions of approval may include, but are not limited to: optional conservation easements; the graphic portrayal of building envelopes and related improvements on the face of final short or long plats and 50 binding site plans; drainage and erosion control plans; and notices to 51 title. 52 43 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 d. Clearing for roads and utilities shall-remain within construction limits which must be marked in the field prior to commencement of site work; and e. The authorized clearing for roads and utilities shall be the minimum necessary to accomplish project specific engineering designs and shall remain within approved rights-of-way. The following provisions regarding grading shall apply: a. An applicant submitting a triggering application shall also submit, and have approved, a grading plan, as specified in section 11 of this ordinance, when the triggering application involves either of the following: (i) The alteration of a geologically hazardous area or its buffer; or (ii) The creation of a new parcel Within a known geologically hazardous area; b. Excavation, grading and earthwork construction regulated under this section shall only be allowed from April 1 to November 1, unless the applicant demonstrates that such activities would not result in impacts contrary to the protection requirements herein. 27 9.504 Veqetation Retention: The following provisions regarding 28 vegetation retention shall apply: 29 30 1. During clearing for roadways and utilities, all trees and 31 understory lying outside of approved construction limits 32 shall be retained: Provided that understory damaged during 33 approved clearing operations may be pruned (see also, 34 subsection 9.503(1) (c), above). 35 36 2. Damage to vegetation retained during initial clearing 37 activities shall be minimized by directional felling of 38 trees to avoid critical areas and vegetation to be retained. 39 40 3. Retained trees, understory and stumps may subsequently be 41 cleared only if such clearing is necessary to complete the 42 proposal involved in the triggering application. 43 44 9.505 Buffer Markinq: The location of the outer extent of landslide 45 hazard area buffers shall be marked in the field as follows: 46 47 48 49 50 51 52 A permanent physical separation along the boundary of the landslide hazard area shall be installed and permanently maintained. Such separation may consist of logs, a tree or hedge row, fencing, or other prominent physical marking approved by the Administrator. 45 1 2. 2 3 4 5 6 7 8 3. 9 10 11 4. 12 13 14 15 16 17 9,506 18 19 20 1. 21 22 23 24 2. 25 26 27 28 29 30 3. 31 32 33 34 4. 35 36 37 38 5. 39 40 41 6. 42 43 44 45 46 47 Buffer perimeters shall be marked with temporary signs at an interval of one per parcel or every one hundred (100) feet, whichever is less. Signs shall remain in place prior to and during approved construction activities. The signs shall contain the following statement: "Landslide Hazard Area & Buffer - Do Not Remove or Alter Existing Native Vegetation." A notice to title shall be recorded with the Auditor in a form approved by the Prosecuting Attorney. In the case of short plat, long plat and binding site plan approvals under the Jefferson County Subdivision Ordinance, No. 4-0526-92, as amended, the applicant shall include on the face of any such instrument the boundary of the landslide hazard area and its buffer. Buffers - Standard Requirements: The following landslide hazard area buffer provisions shall apply: Buffer areas shall be required to provide sufficient separation between the landslide hazard area and the adjacent proposed project. The appropriate width of the landslide hazard area buffer shall be determined by either: application of the standard buffer width set forth below; or, an individual or firm meeting the criteria of subsection 11.702, below. Buffers shall remain naturally vegetated. Where buffer disturbance has occurred during construction, replanting with native vegetation shall be required. Buffers shall be retained in their natural condition, however, minor pruning of vegetation to enhance views may be permitted by the Administrator on a case by case basis. Ail buffers shall .be measured perpendicularly from the top, toe or edge of the landslide hazard area boundary. A standard buffer of thirty (30) feet shall be established from the top, toe and all edges of landslide hazard areas. 9.507 Reducinq Buffer Widths: The Administrator may reduce the standard landslide hazard area buffer width specified in subsection 9.506.6, above, when the project applicant demonstrates, to the satisfaction of the Administrator, that the reduced buffer will 48 adequately protect the proposed project and the landslide hazard area. 49 Under no circumstances shall the buffer width be reduced to less than 50 ten (10) feet. 51 52 46 1 9.508 Increasinq Buffer Widths: The Administrator may increase the 2 standard landslide hazard area buffer width specified in subsection 3 9.506.6, above,'°when a larger buffer is necessary to protect the 4 proposed project and the landslide hazard area. This determination 5 shall be made only when the Department, at its own expense, 6 demonstrates any one of the following through appropriate 7 documentation: 8 9 1. 10 11 2. 12 13 14 15 3. 16 17 18 19 1. 20 21 22 23 24 25 26 27 28 29 2. 30 31 32 33 34 35 36 37 38 39 4O 41 42 43 44 45 46 47 48 3. 49 50 51 52 The landslide hazard area is unstable and active. The adjacent land is susceptible to severe landslide or erosion, and erosion control measures will not effectively protect the proposed project or the landslide hazard area. The adjacent land has minimal vegetative cover. 9.509 Geotechnical Report: An applicant submitting a triggering application shall submit, and have approved, a geotechnical report, as specified in section 11 of this ordinance, when the triggering application involves any of the following: a. The alteration of a landslide hazard area or its buffer; b. The creation of a new parcel within a known landslide hazard area. c. The construction of a publicly owned facility in a designated seismic hazard area. Where a geotechnical report is required for a landslide hazard area, the triggering application shall not be approved unless the geotechnical report certifies all of the following: a. There is minimal landslide hazard as proven by a lack of evidence of landslide activity in the vicinity in the past; b. An analysis of slope stability indicates that the proposal will not be subject to risk of landslide, or the proposal or theilandslide hazard area can be modified so that hazards are eliminated; c. The proposal will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions; d. The proposal will not decrease slope stability on adjacent properties; and e. All newly created building sites will be stable under normal geologic conditions (if applicable). Where a geotechnical is required for a seismic hazard area, the triggering application shall not be approved unless the geotechnical report demonstrates that the proposed project will adequately protect the public safety. 47 1 2 3 4 5 6 7 8 9 10 11 12 13 Conditions 9,~0~ General:" In granting approval for a triggering application subject to the provisions of this section, the Administrator may require mitigating conditions that will, in the Administrator's Judgment, substantially secure the objectives of this section. 9,602 Basis for Conditions: Ail conditions of approval required pursuant to this section shall be based upon either the substantive requirements of this section or the recommendations of a qualified professional, contained within a special report required under this section. 48 LOG OF HAND AUGER BORING DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0 - 0.3 Duff 0.3- 1.0 SM 1.0 - 7.0 ML 7.0- 10.0 SP 0.0 - 0.3 Duff 0.3 - 0.5 SM 0.5 - 4.0 SP 4.0- 10.0 ML/SM 0.0 - 0.3 Duff 0.3 - 0.5 SM 0.5 - 3.0 SP 3.0 - 8.0 ML/SP DESCRIPTION BORING i Forest duff Reddish brown silty fine sand with occasional gravel (loose to medium dense, moist) Gray sandy silt (stiff, moist to wet) Gray fine sand with a trace of silt (medium dense, mois0 Hand auger boring completed at 10.0 feet on 2/22/95 No ground water seepage observed No caving observed BORING 2 Forest duff Reddish brown silty fine sand with occasional gravel (loose to medium dense, moist) Gray fine to medium sand (medium dense, moist) Gray sandy silt grading to silty fine sand (stiff/medium dense; moist) Hand auger boring completed at 10.0 feet on 2/23/95 No ground water seepage observed No caving observed BORING 3 Forest duff Reddish brown silty fine sand with occasional gravel (loose to medium dense, moist) Yellowish brown fine to medium sand (medium dense, moist) Gray sandy silt grading to silty fine sand (stiff/medium dense, mois0 Hand auger boring completed at 8.0 feet on 2/23/95 Refusal encountered at a depth of 8.0 feet No ground water seepage observed No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1-FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. c, ,m Engineers LOG OF TEST PIT FIGURE 15'. LOG OF HAND AUGER BORING DEPTH BELOW SOIL GROUP GROUND SURFACE CLASSIFICATION (FEET) SYMBOL 0.0 - 0.3 Duff 0.3 - 0.5 SM 0.5 - 4.0 SP 4.0- 10.0 ML/SP DESCRIPTION BORING- 4 Forest duff Reddish brown silty fine sand with occasional gravel (loose to medium dense, moist) Yellowish brown fine to medium sand (medium dense, moist) Gray sandy silt grading to silty fine sand (stiff/medium dense, moist) Hand auger boring completed at 10.0 feet on 2/23/95 No ground water seepage observed No caving observed THE DEPTHS ON THE TEST PIT LOGS, ALTHOUGH SHOWN TO 0.1 FOOT, ARE BASED ON AN AVERAGE OF MEASUREMENTS ACROSS THE TEST PIT AND SHOULD BE CONSIDERED ACCURATE TO 0.5 FOOT. ' Engineers LOG OF TEST PIT FIGURE 1 6 JOB BY DATE SHEET P o.¢.~ px~ ~-~ (,4ss,.,*,-./ c,gx = l :7.5 Ge() ~,'~ Engineers CHECKED BY PAVEMENT DESIGN .-CONSTANTS AADT % AADTT GROWTH RATE LANE FACTOR DESIGN EAL R% So PI APSt MIN. DEPTH AC MIN. TOTAL DEPTH AC l CSTC (,,, BALLAST BOULEVARD & ARTERIAL COMMERCIAL & INDUSTRIAL CO LLECTO R NEIGHBORHOOD C 0 LLECTO R LOCAL 15,000 8 5 0.5 4,000 15 $ 0.5 4,000 5 5 0.5 2,222,422 95 0.45 4.20 2.5 1.7 3.5" 12" ,, 1 ,I 11,205 90 0.45 4.20 2.4 1.8 3" 12" 370,406 85 0.45 4.20 2.3 1.9 .~" 4" 500 5 0.5 34,023 80 0.45 4.20 2.2 2.0 ~_" *STREET STRUCTURE REQUIRED IN LIEU OF DESIGN BASED ON FIELD VERIFIED "R" VALUE. ** 6" FOR INDUSTRIAL COLLECTOR, CITY OF' OLYMP£A__ PAVEMENT DESIGN PAVEMENT DESIGN - AASHTO METHOD SEE PREVIOUS PAGE FOR INPUT IN DOUBLE BOXES (~) SOIL TEST RESULTS MUST BE SUBMITTED STREET CLASSIFICATIOIx!:L--L~"~-/ ] WITH THIS WORKSHEET. INITIAL AADT'~ % OF AADTT:~.~ GROWTH RATE' ~ DESIGN LIFE: 20 YEARS RELIABILITY LEVEL (R%):~ STANDARD DEVIATION (So)' INITIAL SERVICEABILITY INDEX (Pi): 4-.2 TERMINAL SERVICEABILITY INDEX ,&PSI-- Pi- Pt = 4.2 -~___?,: SUBGRADE: Mr -- 1000 + (555 x R) RVALUE FROM SOILTEST= USING AASHTO DESIGN METHOD: SN =[_! ?- ], PROVIDE NOMOORAPH OR CALCULATIONS. SN =(A, DO +(A~D~) + (A3D~) + (A~D4) STRUCTURAL COEFFICIENT: CLASS B ASPHALT CONCRETE A1=0-4-2 ASPHALT TREATED BASE A2--0.54 CSTC OR CSBC A5--0'14 BALLAST A4.=O. - /,F& )~,7o .', IREVISED DA_____~ ~2/04/92 CITY OF OLYMPIA PAVEMENT DESIGN WORKSHEET i4-6B -10