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Home My WebLink AboutLog031 'MB Myers Biodynamics inc. - geotechnical engineering. geological sciences. coastal processes GEOLOGICALLYHAZARDOUS AREA ASSESSMENT AND RECOMMENDATIONS Beckett Point Wastewater Treatment System Jefferson County, Washington Prepared for: Mr. James Hasslinger, P.E. Mr. Michael Moren, P.E. Parametrix, Inc. 5700 Kitsap Way, Suite 202 Bremenon, Washington 98312-2234 - I 31 ( 30 ROLLING BAY BUILDING . 11254 SUNRISE DRIVE BAINBRIDGE ISLAND, WASHINGTON 98110 . 206,842,6073 Prepared by: Myers Biodynamics, Inc. Rolling Bay Mercantile Building 11254 Sunrise Drive Bainbridge Island, Washington 98110 June 16, 2005 Project No. 041136A-5 , Table of Contents Section Page No. 1. 0 INTRODUCTION ................'....... ..l.. ... ...... ..... ....... .................~. ...... .... ....... .... ..1 . 2.0 SITE DESCRIPTION................. ........... ....................... .......:......... ............... ....1 2.1 Upland Area. ...... .......... .................... ........... ......... ..;'...'....... .... ... ...................2 2.2 Beckett Point...............................................................................................2 3.0, PROJECT DESCRIPTION.......... ..... ....... .......... ........... ................. ...................2 4.0 rNFORMA TI ON REVIEW. ........... .~.. ........ .................. .................... .... ........ .....3 5.0 GEOLOGIC SETTING ....................................................................................4 , 5.1 Soil. ........ ...... ........ .... ............... ....... ...... ........... ....... ...... ................ ....... ...... ....4 5 .2 Groundwater ............................................................................................... 4 6.0 SEISMI C CONSIDERATIONS........ ...... .......... ......... ...... ......... ..... ..............,....5 7.0 SITE RECONNAlsSANCE... .................,... ............ ....................... ........ .... ......5 7 .1 Topography............. .;........................ .............. .(.... .......... ..... .................. .....6 , 7 .2 Vegetation............ ................ .... ............ ................... ............... '" ......... ..... ......6. 7.3 ,Drainage......................................... .'.............................................................. 7 7.4 Soil Expos~esand Gr~undwater Evidence.................:.............................~.. 7 8.0 GENERALIZED SUBSURFACE CONDITIONS .....................:....................8 . .. ~ ~- 8.1 Soil........... .'.................... ....... ............... ......... ......... ............ .......... ....... .........8 8.1.1 Upland Area .......; ....................... ...... .~.... ..... ...... ...... .............. ...........8 8.1.2 Beckett Point ............... ........... ....... ..... ......... ..... .............. .............. ....8 8.2 'GroUndwater.. ......... ........... ....... .............. ... .................... ..... ......... ..... ..........9 9.0 GEOLOGICALLY HAZARDOUS AND FREQUENTL Y FLOODED AREAS........'.................................................... 1 0 GHA Assessment Beckett Point Wastewater Treatment. system Jefferson County, Washington . 31 2.. Project 1VQ 041136A,5 \ June 16, 2005 Myers Biodynamics; Inc. -i- 3f.o 9.1 Landslide Hazard Assessment ........................................:.................:.......: 11 9.1.1 Qualitative Slope Evaluation ........................................................,.11 9.1.2 Quantitative Slope Evaluation........................................................ 12 9.2 Seismic Impacts to Slope Stability............................................................ 12 I . , " 9.3 Erosion Hazard............. ...... ............... ............ .... ..... ..... .... ..... ......... ...... .......13 , 9.4 Liquefaction S(fismic ,Hazard .....;................:...............:..............",...............13 9.5 Frequent Flooding Hazard..........:.............. ............. .... .....:.... .~.... ....... .... .,...13 10.0 GEOTECHNICAL RECOMMENDA nONS ......................................"....14 10.1 Excavation and Temporary ~horing ........................................................14 10.1.1 Upland' Area.................. ............ ......... ..... ....... ....... ............. ...... ....14 I 1 0.1.2 Becke~ Point/Sewerage Alignment ..:..........................................14 10.2 Structural Fill...... ...... ....... .................... .......... ......................... .................15 . 10.3 Uplift Resisitance. ................................ ................... ..................:.... .........16 10.4 Drainage:........................... .................... .................. ..........,............ ..........16 1 0.5 Vegetation Management.......................................................................... 16 11.0 CLOSURE.. ............ ..... ....... ............ ... .... .... .... .......... ..... .... ...... .... ...... ......... ....17 ; Figure 1 - Geologically Hazardoll$ Areas Site Plan Figure 2 - Site. and Exploration Plan . , Figure3 - Generalized Subsurface Cross-Section A-A' Figure 4 - Generalized Subsurface Cross-Section B-B' FIGURES: APPENDICES: Appendix~ A - Field Exploration Program 3( 3 .t 3h GllA Assessment Beckett Point Wastewater Treatment system Jefferson County, Washington -ii- Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. 1.0 Introduction ; DEPT. Of COivir/PJ(,;tT"/ OEVE OPViEN-r ~----_.----- This report presents our Geologically Hazardous Areas (GHA) asseSsment and recommendations for a proposed sewerage system and large on-site wastewater treatment area supporting the,Beckett Point Community in Jefferson County, Washington. This work was conducted in general accordance with our sub-consultant agreement executed October 22, 2004 and Contract Amendment N~. 1 dated March 4, 2004. The scope of our work included review of previous site information, slope reconnaissance, subsurface explorations,' laboratory testing, analyses, and preparation of this report. The purpose of our work was to evaluate the geologic hazards associated with ttIe site and to provide recommendations for hazard mitigation of the proposed wastewater treatment and conveyance system. A previous report was prepared for the project to address soil infiltration rates and perform a water and . nitrate balance of the proposed wastewater treatment (drainfield) area. The previous work was summarized in a report "Geotechnical Report, Beckett Point Community Wastewater Treatment Area, Jefferson County, Washington" prepared by our firm and dated May 10, 2005. Portions of the previous report are presented herein fpr reference. r 2.0 Site Description . . The project site is located in the Beckett Point area of Jefferson County located southwest of Port Townsend, Washington. The project area currently includes, undeveloped upland forested areas <m the northeast side of the site, moderate to steep coastal slopes, and the cuspate forelands that incorporate the sand spit/lagoon features defining Beckett Point. The site is generally bounded on the north by Hill Crest Avenue and Beckett Point Road. Adjacent property borders the east side of the site and coastal slopes descend tQ Beckett Point, which is bordered by Discovery Bay. Beckett Point road descends the coastal slope and provides access around The Point. A spur road, View Point Lane, provides access to residences at the toe of the steep coastal slope north of The Point. The generalIocation .and configuration ~fthe project site are shown on the Vicinity Map and Geologically Hazardous Areas Site Plan, Figure I. The project site is composed of two principle geomorphic features: the upland area on the northeast side of the site and Beckett Point (The Point). These two distinct areas generally delineate the geologically hazardous zones of the site. The upland area includes moderate to steep slope areas that reflect landslide, seismic, and erosion hazard areas identified by Jefferson County. Beckett Point generally meets the criteria of a seismic hazard area due to loose or soft soils and liquefaction/settlement risks associated with seismic.events. The Point also meets the criteria of a frequently flooded area, as shown on Figure 1. ,3( L.j 3' C:, '" GHA Assessment Beckett Point Wastewater Treatment System Jeffirson Cpunty, Washington 1 of 17 ProjectNo.041136A-5 ~ Ju~e 16, 2005 Myers Biodynamics,.Inc. 2.1 Upland Area The upland area includes approximately 30 acres of undeveloped, forested land on the northeast comer of the site. Within approximately 5 acres of this area, at the extreme northeast comer of the property, the proposed wastewater treatment drainfield area is planned as described below in Section 3.0 Project Description and as generally shown on Figure 1. Topographic' grad~s within the upland forested area are gentle to moderate with average slopes ranging from 10 to 30 percent with locally steeper zones of approximately 40 percent. Several hundred feet northwest and southwest of the proposed treatment area,' grades increase near the ste.ep coastal slopes. Grades on the steep coastal slopes average 100 percent above View Point Lane an~ 70 tq 110 percent above The Point. The upland area includes a residential development area on more moderate grades where Bec~ett Point Road descends the slope. Grades around existing residences ayerage 20 to 30 percent with locally level to ' more steeply. sloped areas, created by grading for residential construction. A more detailed description of the upland area is presented below in Section 7.0 Site Reconnaissance. 2.2 Beckett Point Beckett Point is a cuspate foreland shore feature likely created by seasonal changes in the \ . coastal process long-shore sediment drift direction that forms triangular shaped deposits. The Point comprises approximately 40 acres of beach/lagoon deposits and fill associated with Beckett Point Road and residential development around the perimeter of The Point. Residences are generally constructed between the road alignment and.the beach. On the interior side of the roadway, garages and other out buildings associated with the residences are present, apparently built on fill. The interior of The Point is lower it]. elevation and consists of a periodically inundated lagoon/marsh as shown on Figure 1. Beckett Point Road terminates at the east end of The Point in a cul-de-sac constructed at the base ofthe steep coastal slope. Several buildings are located at the terminl.ls of the road. These buildings are apparently associated with an historic water supply system that collected water from a spring at the. toe of the slope. Further discussion of the spring and existing site conditions are presented below in section 8.0 Site Reconnaissance. 3.0 Project Description' The proposed community wastewater treatment system will collect wastewater from. individual residences' in a sewerage system placed along Beckett Point Road and View Point Lane. Collected wastewater will be pumped up the coastal slope by two pump stations along existing access roads to the treatment area on the northeast corner of the site. We understand that temporary excavations for the proposed pump stations, will range from 8 to 10 feet below existing grade. Temporary shoring may be used for the pump station excavations to limit the aerial extent of the required cut. The approximate alignment of the proposed ~astewater collection system and pump stations is shown on the Site and Exploration Plan, Figure 2. GHA Assessment Beckett Point Wastewater TreatmentSystem Jefferson County, Washington 2 of 1 7 Project No. 0411 36A-5 June 16, 2005 Myers Biodynamics, lnc. 31 5 36 The cllrrent wastewater treatment (drainfield) area layout will cover approximately 5 acres of the total 30-acre forested area northeast of The Point. Existing forest within the 5 acre area will be' cleared. We understand only'minor gr.ading will be required,for the treatment system construction. We understand that the proposed community wastewater treatment system is-being designed in accordance with the Washington State Department of Health "Design Standards for Large On-site Sewage Systems with Design Flows of Greater than 3,500 Gallons Per Day". The proposed system will 'replace existing individual systems located on the residentiaf lots, !": .." ,0.,. which generally do not conform to current Health Department standards. The new systen).L". . will also account for buildout of some of the remaining undeveloped lots for a total of 102, " r- residential hook-ups. j '. ' ; I i 4.0 Information Review i i \ I Reference information for the area was reviewed as a part of our work and included soil a~4 {I geologic mapping, water supply information, ,and water well logs. The general reference! ,.,:Ii::.::: information is presented below. A summary of soil and groundwater information obtaine<l:' Li' _c"., from the information review is summarized in Section 4.0 Geologic Setting. lL:::..'-- _~,o< ~ Geology and Groundwater Resources of Eastern Jefferson County, Washington, Water Supply Bulletin No. 54, April 1981. ~ State of Washington Department of Ecology Coastal Zone Atlas, Volume 11, Jefferson County, July 1978. ~ Washington State ,Department of Ecology Well Logs website. ~ U.S. Department of Agriculture Soil Conservation Service, Soil Survey of Jefferson County Area, Washington, 1975. , ~ Eastern Jefferson County Groundwater Characterization Study, prepared for Public Utility District No. t of Jefferson County, by Economic and Engineering Services, Inc. and Pacific Grouridw&ter Group, May 1994. ~ Stage 1 Technical Assessment as of February 2000, Water Resource Inventory Area 17, by Parametrix, Inc., Pacific Groundwater Group, Inc., Montgomery Water Group, ~Inc., and Caldwell and Associates, Inc., October 2000. ~ USGS National Seismic Hazards Mapping Project website. http://eqhazmaps.usgs.gov/, Hazard by Lat/Lon, 2002. ~ Geotechnical Report, Beckett Point Community WasJewater Treatment Area, by / Myers Biodynamics, Inc. (MBI), May 10, 2005. ' GHA Assessment _ Beckett Point 'Wastewater Treatment System Jeffirson County, WashingtOn 3 of 17 Project No. 041 1 36A~5 June J 6, 2005- Myers Biodynamics. Inc. 3{ o 36 5.0 Geologic Setting . . A general summary of the site and local area soil and groundwater conditions is presented below. The summary is based on the information review presented above. The results of site specific observations and subsuiface explorations are presented in Sections 7.0 and ~.O. . 5.1 Soil Geologic mapping generally indicates the local area northeast of the project site is capped by glacial till. Glacial till is composed of a mixture of gravel, sand,' silt, and clay that was deposited and overridden by the most recent glacial advance that covered the area. ,Glacial advance outwash is mapped below the glacial till across much of the project site and along the steep coastal slope above The Point. Glacial.advance outwash soils are generally composed of sand or sand and gravel that have been deposited by melt waters of the advancing glacier and subsequently overridden by the glacial ice. Both the outwash and, '..' glacial till soils are generally ,in a very dense or hard condition below the surface soil hori2'fil due to the weight of glacial ice. Southeast of The ,Point, mapping also shows interglaciali, " ". . deposits below the advance outwash that can include sand and gravel, silt~ or clay soils,i, which are also in a very dense or hard.condition below the surface soil horizon. The Point lsJ;;li\ mapped as recent, post glacial deposits including loose sand and gravel beach deposits alon~:)) i\ the shoreline and ~oft organic soils associated with the lagoon located on the interior of The\ (;~~,'r Point. tl~l \ USDA Soil Survey reference mapping indicates the proposed tr~atment area is Cassolary L.-..- Sandy Loam, 15 to 30 percent (CID) andThe Point is tidal marsh (Td) ,and Coastal Beaches (Co). Coastal zone atlas mapping shows the steep. coastal slope in the Beckett, Point Community as "Unstable" with areas of "Unstable Old Slide" and "Unstable Recent Sliqe" ide!ltified immediately north and east of The Point and local c~mmunity. The upland area' and The Point are described as "Stable" with respect to slope stability. . C) UJ o .~ 0- W o .,.,..,".'""..."...,~, ,.....-.- 5.2 Groundwater Water well logs were obtained from the Washington State Department of Ecology (DOE) website and reviewed to help evaluate the subsurface conditions within the local area. Wells I were identified north, northeast, and southeast ofthe project site. Well logs show a likely cap of glacial till underlain by sand or sand and grav~l with clay layers at depth. Static water levels in the well logs were typically more than 170 feet below the grade at the well locations. I . The Jefferson County PUD No. 1 was also contacted for additional information regarding water supply wells in the local area. No current water wells or associated well logs were identified on the project site. All potable water is reportedly provided by thePUD No. 1 system that obtains its waterfrom the Quilcene River located more than 15 miles south ofthe project site. 3( 7 3/:;' GHA Assessment I Beckett Point Wastewater Treatment System Jefftrson County, Washington 4 of 17 . Project No. 041136A-5 JUlJe 16, 2005 Myers Biodynamics, Inc. The lack of local water wells precludes a determinatiori of site specific groundwater gradient or flow direction. However, review ofbackgroudd information show,S an estimated groundwater flow direction generally following local topography, flowing northwest, west and southwest from the upland'area towards the shoreline. 6.0 Seismic Considerations The Beckett Point project site is located in the s~ismically active western Washington region. . ,Forseismlc design under the 2003 International Building Code (lBe), a site class is selected based on the average soil properties in the upper 100 feet. ,Using i.nformation obtained from site subsurface explorations, reference information, t!.11d well logs in the area, a site class "E" is recommended for The Point (except that susceptibility to liquefaction classifies the site as , an "F"). I A site class of "C" is recommended for the upland area including the steep coastal slopes. - Peak ground accelerations based on a 10 percent and 2 percent probability of exceedance in 50 years (475 and 2,475 return intervals) were obtained for the local area using the USGS ,H National Seismic Hazards website and latitude and longitude coordinates. The peak ground, acceleration is approximately O.3g and 0.5g for the 10 percent and 2 percentproba~ility of\ exceedance in 50 years criteria, respectively. r--.. . C"~ u..... ("J As noted above, loose saturated sand soils located near existing grade on The Point are susceptible to ~iquefaction during earthquake strong ground, motion~ A more detailed, discussion of the potential for site. soil liquefaction is presented in Section 9.0 Geologically! Hazardous Areas Evaluation. I C) LU a 7.0 Site Reconnaissance , . ' Site conditions were evaluated by conducting a reconnaissance of the property and local are~ at various dates from October 2004 through April 2005.', Site and local conditions including topography, vegetation, surface drainage, and soil exposures an~ groundwater evidence are presented below. Subsurface conditions \yere also investigated by conducting test pit explorations in the proposed treatment area and by hollow stem auger boring explorations in the proposed pump station: areas and around the perimeter of Beckett Point. Exploration ~ locations are shown On Figure 2. A description of the subsurface conditions observed in the explorations is presented in Section 8.0 Generalized Subsurface Conditions. J 31 g, 3" GHA Assessment Beckett Point Wastewater Treatment System Jeffirson County, Washington 5 of 17 Pr~jectlVo, 04II36A-5 June /6, 2005 Myers Biodynamics. Inc. \ ' c' 7.1 Topography Topog~aphy in the upland area generally slopes down to the north and northwest as shown on Figures 1 and 2. In the extreme northeast corner of the site (treatment area} elevations drop from a .maximum of approximately 380 feet on the southwest side of the site to approximately 290 feet on the north side of the site. Average site grades range from 10 to 25 percent with locally steeper areas of 30 to 40 percent. The site topography includes areas of localized draws that likely reflect prehistoric drainage routes. The locally steeper areas of the site are generally associated with the draw side slopes. Beyond the proposed treatment area, grades in the upland area slope down to the northwest, west, and southwest towards the steep coastal slope. North of The Point, View Point Drive and associated residences are located between the toe of the slope and a concrete bulkhead west of the road along the shoreline. On the northwest side, of The Point, the steep coastal slope descends to the lagoon and existing structures located at the terminus of Beckett Point Road~. East of The Point, the steep slope descends to the Discovery Bay Shoreline. Coastal slope grades average 100 percent (45 degrees) above View Point Lane and associated residences. The coastal slopy is less steep at times above The Point and lagoon with grades of 70 to 100 percent (31 to 45 degrees). At the terminus of Beckett Point Road the toe of the sl.ope was apparently excavated for a cul-de.,.sac creating a locally. steeper segment 20 to,30 feet above the road elevat!on with grades of 100 to 119 percent (45 to 50 degrees). On Beckett Point, grades are generally level along Beckett Pqint Road,and View Point Lan~. ~. Historic grading and fill placement likely occurred for road construction. Grades are' sevenH feet lower in the interior of The Point where delineated wetlands (by others) and the lagoo~ are present. During high tide events the wetland area is inundated by surface water. It is reported that during extreme high tide events and storm surge, portions of The Point are flooded including portions of Beckett Point Road. 7.2 Vegetation The upland area on the northe,ast comer of the site including the trlfatmeht area is densely forested with an established canopy of deciduous and conifer trees including Douglas fir, Western red cedar, we;;tern hemlock, red alder and big leaf maple. The understory vegetation is moderately dense, comprised of shrubs and herbac-eous groundcover including sword fern, salal, and Oregon grape. ' Beyond the treatment area the forested-condition continues dQwn to the steep coastal slope. ~ The steep slope above View Crest Lane is also well vegetated with established trees and understory vegetation dominated by .Douglas fir and madrona. Above The Point, portions of the more moderate slopes have been cleared (and histori~ally graded) for residential homes and Beckett Point Road. Some established trees and understory vegetation remain within the residential areas. On the slope ah9ve the lagoon and the Beckett Point Road cul-de.,.sac vegetation is primarily grasses with occasional small trees. Vegetation on The Point is dominated by grasses and herbaceous groundcover. GHA Assessment Beckett Point Wastewater Treatment System Jefferson County. Washington 6 of 17 \ Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. 3/ 1 3~ . ' 7.3 Drainage , Topography within the proposed wastewater treatment area on the northwest corner of the site would generally direct any surface water flow north and northwest towards Beckett Point Road and Hillcrest Avenue. No evidence of significant surface water runoff, erosion, or' active drainage courses was observed in the proposed wastewater treatment area. It appears the current site conditions including soil and vegetative cover allow for infiltration and evapo-transpiration of incident precipitation on the site. Grades in the local area surrounding the wastewater treatment area generally direct surface ' water runoff into the Beckett Point Road drainage ditch north arid northwest of the site. Elsewhere, surface gradients diFect surface water flow down the st~ep coastal slope northwest, west, and southwest of the treatment area. Observation of the local area indicates no evidence of significant surface water runoffor erosion onth~,steep coastal slope. This includes a utility trench alignment reportedly excavated and backfilled down the steep coastal slope. It appears surface water directed towards the steep slope infiltrates and/or is of insufficient quantity and rate to create rilling or gulleying on the slope or within the Beckett Point,Road drainage ditch. , 7.4 Soil Exposures and Groundwater Evidence / , Due to vegetative cover in the propOsed wastewater treatment area, no significant soil exposures were observed on the site. However, minor soil exposures were present along' a primitive road system around the proposed drainfield area indicating primarily granular (sand and gravel) soils. No groun4water seepage or evidence of seasonal daylighting groundwater was observed in the treatment area on the northwest side of the site. Soil exposures were observed at various locations along Beckett Point Road and on the steep coastal slope. A'local "gravel pit" off of Beckett Point Road and west of the treatment area (see Figure 2}contains sig~ificant soil exposures. A steep cut slope is present on the eastand southeast side of the pit with near vertical exposures of interbedded gravelly sand, fine sand, and fine sandy silt. No evidence of groundwater seepage or soil staining/mottling that would indicate seasonal perched groundwater was observed on the gravel pit cut slopes. Soil exposures were limited on the steep coastal slope due to vegetative cover. However, at the terminus of Beckett Point Road a cul-de-sac was constructed by apparently cutting .into the toe of the slope. 'Along the cul-de-sac exposures of interbedded fine sand, siltY fine sand and gravelly sand were observed. No groundwater or evidence ofgr6undwater seepage was noted 011 the steep cpastal slope except at one location. At the terminus of Beckett Point Road, vegetation surrounding the historic "spring house" indicates very moist to wet soil conditions. . . 3( ,to 3t:, GHA -Assessment Beckett Point Wastewater Treatment System Jefferson County, Washington J of 17 Project No. 041136A-5 June i 6, 2005 Myers Biodynamics, inc. 8.0 Generalized Subsurface Conditions Subsurface boring explorations for this report were conducted along the alignment of the proposed wastewater collection and conveyance system to evaluate the geologic hazards and provide recommendations for hazard mitigation and treatment system design and' construction. In addition, test pit explorations and laboratory testing Were previously conducted in the proposed wastewater treatment (drainfield) area to investigate suitability- and hydraulic design parameters for the proposed drainfield 'area. A description of the subsurface soil and groundwater conditions observed in the explorations are presented below in Sections 8.1 and 8.2. 8.1 Soil Boring explorations, B-1 through B-5 were performed along the.-aligI1n1ent of the proposed wastewater collection and convey,ance system. On the upland portioit of the site above The Point, boring B-1 and B-2 were advanced in the area ofprQposed pump station~ to provide information. for pump station excavation, shoring, and to also provide subsurface information on the conditions underlying the steep coastal slope. Borings B-3 through B-5 were conducted on The Point along Beckett Point Road and View Point Lane to evaluate conditions along the proposed sewerage system alignment. As part of previous work, eleven test pits were excavated in the l,lpland portion. of the site in the proposed wastewater treatment area. 8.1.1 Upland Area. Subsurface conditions within the upland portion of the site were investigated by borings B-1 and B-2 and the previous test pit excavations, Borings B-1 and B-2 were advanced to depths of approximately 69 and 61 feet below existing grade, respectively, as shown on Figures A-I and A-2 in Appendix A. The borings showed primarily very dense gravelly sand to fine sand soils with occasional interbeds of hard sandy silt and silt. The "conditions are consistent with the site reconnaissance' observations and geologic mapping of the area'denoting glacial advance outwash deposits tinderJying the steep coastal slope. Generalized subsurface conditions observed in the eleven test pit explorations in the ' proposed wastewater treatment area also indicated subsurface condit~ons consistent with the geologic mapping and reconnaissance of the area. Soils were composed of glacial advanced outwash consisting of gravelly slightly silty,sand,fine sancl,and gravelly sand. , Detailed information on soil conditions in the treatment area.and logs of the test pits are presented in our previous report "Geotechnical Report, Beckett Point Community Wastewater Treatment Area, Jefferson County, Washington" dated May 10,2005. - 8.1.2 Beckett Point. Borings B-3 through B-5 were performed on Beckett Point along View Point Road and Beckett Point Road. All three borings showed a surficiallayetof fill generally up to 3 feet thick. Below the fill, beach qeposits composed. of loose to medium dense gravelly sand to fine sand were generally encountered. Variations in GHA Assessment I . Beckett Point Wastewater Treatment Sys,tem . Jeffirson County, Washington 8 of 1 7 ProjectJVo.04ll36A.5 June l6, 2005 Myers Biodynamics, lnc. '3( (( 3b subsUrface soil conditions in each of the borings reflect their location on The Point and depositional characteristics' of each area. Boring B-3 ~as advanced near the .base of the steep coastal slope on View Point Drive and showed minor fill underlain by medium dense slightly gravelly to gravelly sand to a depth of about 10 feet below grade. Below the medium dense soils, the gravelly sand and sand became dense to very dense, likely associated with the dense soils underlyinR the steep coastal slope that have been eroded to fonn a "beach terrace" at the base of the bluff. Boring B-4 was advanced near the tip of The Point and showed relatively loose soils associated with beach deposits that form the end of The Point. Below approximately 2 feet offill, the soil was generally composed of loose to medium dense gravelly sand to sandygravel. Boring B-5 [idvancedadJacent to the lagoon area showed 3 feet offill over medium stiff organic silt likely associated with lagoon deposits (prior to :Qlling). Below the organic silt, loose to medium dense gravelly sand was generally encountered in the . boring with dense conditions and occasional shell fragments at depth. , 8.2 Groundwater ' No groundwater was encountered in the boring or test pit explorations conducted in the upland portion of the site. Explorations in the treatment area generally extended to depths of 7 to 10 feet below grade. Boring explorations on the coastal slope"at the proposed pump stations, B-1 and B-2, also encounter no groundwater to depths of approximately 69 to 61 footdepth,respectively. The interbed~ of sandy silt and silt shOlwed no perched groundwater (wet soil conditions) or evidence of perched groundwater (soil mottling and/or heavy staining). Within two samples minor isolated iron staining was observed in thin sand laminae but did not, in our opinion, reflect significant seasonal perch groundwater conditions. , ) 'Groundwater was present in the boring explorations B-3 through B-5 c~nducted on Beckett Point. Groundwater was generally encountered at 5 to 7 feet below existing site grade as . shown on the boring logs. Groundwater levels likely vary based on precipitation, tide, and other on-site and off-site factors. To provide additional information on the site groundwater conditions, monitoring of existing shallow monitoring wells (installed by others) was , conducted on the site. The results of groundwater monitoring are presented below in Table 1. Monitoring indicates that the granular soils comprising Beckett Point are tidally influenced. , 31 I?, 3" GHA Assessment Beckett Point Wastewater Treatment System Jefferson County. Washington 9 of 17 . Project No. 041136A-5 , June 16,2005 Myers Biodynamics. Inc. ../ TABLE 1 Shallow Monitoring Well Observations Beckett Point, Jefferson County Monitorinp; Well No. MW-l Depth below Date and Time of grade to Reading Tide Condition2 groundwater3 3/25/05 11 :00 am Rising Tide 72" 4/20/05 5 :30 pm Falling Tide 74.5" 4/25/05 4:00 pm Rising Tide 78" 3/25/05 10:35 am Rising Tide 45" 4/20/05 5:40 pm Falling Tide 48" 4/25/054:10 pm Rising Tide 51" 3/25/05 10:20 am Rising Tide Dry at 66" 4/20/055:50 pm Falling Tide Dry at 66" 4/25/05 4:20 pm Rising Tide Dry at 66" Location View Point Lane MW-3 Beckett Point Road near tip of Point MW-5 Beckett Point Road cul-de-sac Notes: 1. Mon~toring well number based on original installation by others. 2. Tidal information based on NOAA published tidal information for Port Townsend, W A: 3/25/05 2.7 ft low at 10:00 am; 4/20/05 5.8 ft high at 2:40 pm; 4/25/55 -1.5 ft low at 11 :26 am. 3. Dry designation indicates no groundwater observed in the monitoring well to the depth in inches shown. 9.0 Geologically Hazardous And Frequently Flooded Areas Site explorations and subsurface characterization indicate very dense, primarily granular soils underlie the upland portion of the site including the steep coastal slopes~ Fill, beach and lagoon deposits composed of loose sand and gravel and organic ~oils comprise The Point with denser granular soils at depth. The soils on The Point are tidally influenced and periodically saturated. Portions of the project site are designated as potential geologically hazardous areas; These include erosion and landslide hazards on the steep coastal slope and increased landslide hazards during a seismic event (seismic hazard). The presence of relatively loose, saturated granular soils underlying The Point indicate the potential for liquefaction during earthquake strong ground motion. In addition, the relatively level, low elevation topography of The Point indicates a potential for flooding during storm surge, extreme high tide events, and 10 of /7 "- '\ \ Project No. 04i /36A-5 June /6, 2005 Myers Biodynamics, ii/c. GHA Assessment Beckett Point Wastewater Treatment System Jefferson County, Washirrgton 31 l3 3~ 9.1 Landslide Hazard Assessment i I tsunamis (Frequently Flooded Hazard). The following sections present our evaluation of the project site geologic and frequently flooded hazard areas. Landslide hazards for the site were assessed using both qualitative and quantitative assessment of slope stability.' In addition, two scenarios for potential landslide hazard impa~ts from the'proposed wastewater treatment system were assessed and included potential adverse impact to the slope from increased groundwater infiltration at the proposed wastewater treatment infiltration area and landslide hazard/slope'stability risk associated with construction of the sewerage system pipe alignment up the steep slope. . 9.1.1 Qualitative Slope Evaluation. No evidence of recent landslide activity was . observed on the steep coastal slope. However, the steep slope grade does indicate a moderate risk of futUre instability, in oUr opinion. This is supported by Coastal Zone Atlas m~pping of the steep coastal slope as "unstable". Risk factors for future slope stability/landsliding include, but are not limited to, heavy precipitation, uncontrolled stormwater runoff, infiltration of stormwater or wastewater, seismic events, clearing ,vegetation, loading the top of a slope or cutting at the toe. Evidence. of potential instability includes the vegetation on the steep slope above View Point Lane. The vegetation shows indications of "soil creep",< the slow downslope movement of shallow slope face soils due to gravity. . Trees have rounded trunks that have apparently responded over time to the shallow slope face soil movement. The somewhat steeper slope angle above View Point Road Lane compared to the slope above the lagoon area is likely a factor contributing to soil creep and a somewhat greater risk of instability. Soil creep may also be occurring elsewhere on the steep coastal slope, however, evidence was limited where vegetation is dominated by grasses. Along the proposed pipe alignment for the wastewater collection system, site grades are less steep. The pipe alignment will generally follow the-existing road and driveways connecting the residences above The Point. In these/areas, vegetation is generally upright and shows no evidence of landslide activity or soil creep. Also in this area, the relative risk of future landsliding is low in our opinion due to the more moderate slope angle. Groundwater that daylights as seepage on a steep coastal slope or accumulates as perched groundwater ip the shallow surface soil horizon can increase the risk of landsliding, The proposed treatment system will result in an annual increase' in groundwater input to the local system of less than 6 inches based on prior analyses of the wastewater treatment area (MBI May 2005). Due to the relatively minor estimated increase to the groundwater regime, it is our opinion that the input to the system wilJ have a negligible adverse affect on slope stability. This opinion is due to: 1) the primarily granular nature ofthe soils underlying the upland and steep slope area; 2) the soil's relatively high infiltration rate; 3) the distance of the treatment area from the slope; 4) the apparent lack of continuous silt/clay layers to' transmit groundwater horizontally to the slope face; and5) the lack of GHA Assessment Beckett Point Wastewater TreatmentSystem , Jefferson County, Washington ' 11 ~f 17 ProjectlVo.04J/36A-5 June.i6, 2005 Myers Biodynamics, inc. '31 1,.3 G f" ...<:0, //. ./,....:~ . \ evidence of significant perched groundwater in the soil explorations advanced ir{i~ " upland area. In addition, wastewater treatment systems for residences currently on'the ' \ \ coastal slope will have their wastewater input to th~ slope moved over 500 feet eastlp,~~~\ proposed treatment area. In order to better quantify the risk to the'slope, we also\':",:;:;:\ performed slope stability analyses to evaluate the potential influence of increased \\':::'~~;;~'\ groundwater on slope stability. \\>>:;~\ 9.1.2 Ouantitative Slope Evaluation. Quantitative slope stability analyses were conducted to model existing site slope conditions and provide a method for assessing potential impacts to slope'stability from the proposed. treatment system. Slope sta~ility analyses were conducted for the steep coastal slope using representative cross sections and soil parameters based ,on published correlations and experience. Analyses were performed to determine the "factor of safety" for the existing slope conditions, The factor of safety (FS) is generally defined as. the resisting soil strength divided by the soil . mass/driving force along a potential failure surface and soil mass. A factor of safety of 1.0 indicates marginally stable conditions where the driving force and resisting force are equal. A factor of safety of less than 1.0 indicates a failure condition and resulting movement/displacement along the failure surface. Factors of safety of 1.25 or more are typically used as design standards for new constructio~. Factors of safety between 1.0 and 1.25 are generally considered "marginally stable". Stability analyses were performed using infinite slope methods to assess the steep coastal slope above View Point Lane and above The Point. Analyses were also conducted for the slope along the proposed pipe alignment. Analyses indicated a marginally stable slope (under existing conditions) for shallow failure surfaces on the steep slope above View Point Lane and The Point where average grades range from 70 to 100 percent (35 to 45 degrees). The potential impact of shallow perched groundwater on the slope face was also assessed. Where shallow Perched groundwater is assumed on the slope face, the slope stability factor of safety is reduced by approximately 5 percent with a static factor of safety still above 1.0. Jhese analyses aSsumed potential perched groundwater ' conditions of approximately 6 inches within a 3 foot thick theoretical failure zone. On the more moderate grades for the proposed pipe alignment, stability analyses for the slope indicate a factor of safety of greater than 3.0. This factor of safety indicates-an acceptable slope stability condition for construction of the proposed pipe alignment. This increased factor of safety compared to the, other steep coastal slope areas is due to the more moderate slope angles of20 to 30 percent (11 to 17 degrees). 9.2 Seismic Impacts to Slope Stability Based on the marginally stable condition of the steep coastal slope under stati,c conditions, the effects of seismic strong ground motion would tend to reduce slope stability and increase the fisk of seismically induced landslide activity. Pseudostatic analyses of the steep coastal slope indicate a risk of landsliding during a large seismic event. However, along the pipe alignment, slope grades are more moderate and a factor of safety of greater than 1.0 was GHA Assessment Beckett Point Wastewater Treatment System Jeffirson County: Washington Project No. 04ii36A-5 June i 6, 2005 Myers Biodynamics, inc. 12 of 17 3/ ',. ' 15 J~ . \ ',' f"........~'- determined ~or the moderate grades along the pipe alignment under rseudostatic conditWIls.>"'>. While nothing can be done to prevent seismic activity and increased risk to existing sl~eesr, ,I';' measures can be taken to help reduce slope stability risk to the system .including ade5Itla~ei', " .... <~: compaction gfbackfill material,. vegetation management, and stormwater control. See"" Section 10.0 GeotechnicalRecommend(1tions. ' 9.3 Erosion Hazard The site soils are composed of primarily sand and gravel. These soils can be susceptible to erosion on the steep slope grades in the area of the proposed pipe alignment and on the steep coastal slope. Where, covered by existing vegetation, the erosion hazard appears to be low based on the lack of significant erosion on the site. However, where vegetation is removed and soils are exposed by excavation, erosion potential is increased. This is confIrmed by l!1inor erosion of the slope face soils above the cul":de-~c at the end of Beckett Point Road where sQils were apparently cut for the cul-de-sac and unprotected from erosion. ' In our j opinion, the implementation of conventiomil erosion control techniques and best management practices (BMP's) during construction will mitigate the erosion hazard risk on the property. 9.4 Liquefaction, Seismic Hazard Under the effects of earthquake strong ground motion, relatively loose saturated granular soils experience an increase in soil pore water pressure which can result in a loss of soil strength and a "liquefied" condition. Using boring information, the site soils were evaluated to determine the potential for liquefaction. Based on peak ground accelerations ofO.3g and .o.5g (recurrence intervals of 475 and 2,475 years, respectively) there is a risk of site soil liquefaction of loose saturated sand soils on The Point. Based on the very dense condition of the soils underlying the steep coastal slope there appears to be no liquefaction potential for the upland portion of the site includingl steep coastal slope soils: Impacts from liquefaction include potentially .large total and differential settlement across The Point due to dissipation of increased pore water pressure in the sand soils following the . earthquake, Also, empty or partially empty buried vessels in liquefied soil can become buoyant arid "pop-up" during a seismic event. Recommendations to mitigate, risk from site soil liquefaction for the proposed wastewater treatment facilities on The Point are1p!esented in Section 10.0 Geotechnical Recommendations. 9.5 Frequent Flooding Hazard . Due to the relatively low elevation of The Point, extreme high tide events and storm sUrges have reportedly resulted in flooding on the lower lying portions of The Point including portions of Beckett Point Road. ,In addition, Hooding can occur as a~esult oflarge seismic events and resulting tsunamis. Design of the proposed wastewater collection and conveyance system on The Point should include measures' to avoid adverse il11-pacts as the result of surface water/system flooding. These include "pop-up" fisk to buried structures during 3( If> 31:> GHA Assessment' Beckett Point Wastewater Treatment System Jefferson County, Washington 13 of 17 Projei:t No. 04i i 36A-5 . June i 6, 2005 Myers Biodynamics, Inc. periods of elevated tides and flooding where groundwater and hydrostatic pressures are increased. In addition, the potential for infiltration of surface (flood) waters in the system should l:>e avoided ,by appropriate system design details. See Section 10.0 Geotechnical Recommendations. 10.0, GEOTECHNICAL RECOMMENDATIONS Geotechnical recommendations for the project site to help mitigate risk from geologically,,, hazardou~ and frequently flooded areas are pre~ented below and include recommendations C i;.;; fO,r exc~vation and temporary shoring, structural fill, uplift'resistance, drainage and .. "'.-. '.--'- -- ,],',', vegetatIon management. ' " Z 7 2005 ' , 10.1 Excavation and Temporary Shoring J E :~. F F 'i,Sc]f~~';~'i':~iTr~"f\:;T,~;' . The proposed wastewater treatment collection and conveyance systems will require maximum excavations of 8 to 1 0 feet at pump stations and relatively shallow trench excavations for the sewerage pipe alignment around The Point. Reco!!linendations for the upland area pump stations and The Point pipe alignment are presented below. GE\/[LOpi\ ; 10.1.1 Upland Area. Excavation within upland areas will likely encounter loose to medium dense soils in the upper 3, to 5 feet underlain by dense sand and gravel. Excavation can likely be performed using conventional equipment. For open cuts, the site soils would generally be considered Type A to B soils and can be cut to a maximum 3/4 to 1 horizontalto Ivertical (3/4 to IH: 1 V) based on the Safety Standards for Construction Work, Chapter 296-135 WAC. If open cuts are' not possible due to space limitations temporary shoring could be used. Shoring should be designed to support the granular site soils. We recommend an equivalent fluid unit weight of35 pcffor soil in the upper 5 feet of the excavation and25 pcf in the dense sand and gravel soils typically at depths greater than 5 feet. 10.1.2 Beckett Point! Sewerage Alignment: Excavation within the soils on The Point will likely encounter loose fill and loose granular beach deposits (sand and gravel). Soft organic soils may also be encc;>untered below the ,fill in areas near the lagoon. ' Groundwater will be present at depth and will likely depend on the tidal t(levations durihg excavation. Groundwater was generally observed at depths of 3-112 to 6 feet below gnide . during the drilling and monitoring well observations presented in this report. Due to the loose nature of the site soils and groundwater, excavations will be subject to caving and sloughing unless shored particularly below groundwater levels. Where shoring is provided, we recommend the upper unsaturated soil zone be designed for an equivalent fluid unit weight of 35 pcf. Below the groundwater elevation, a unit weight based on the combined soil and hydrostatic loading of 80 pcf is re~ommended. Above the groundwater level, open cuts could be used. Based on the WAC safety standards, the loose sand and gravel soils would be considered Type C soils with a maximum open cut GHA Assessment Beckett Point Wastewater 'Treatment System Jeffirson County, Washington 14 of 17 ProjectlVo.04ii36A-5 June i 6, 2005 Myers Biodynamics, Inc. 3( ( 17 3b of 1-112 H: 1 V. Where groundwater is encountered, flatter open cuts or shoring would likely be required. 10.2 Structural Fill To help reduce buoyancy forces during periods of elevated groundwater, seismic events and flooding, we recommend that fill placed around the proposed improvements including pump station apd trench backfill (above pipe bedding)be placed as structural fill. ' Structural fill should consist of a well~graded, granular material free of,organic debris or other deleterious material. Structural fill should be at a moisture content to allow-for proper compaction. Due to the primarily gr~ular nature of the site soils, we anticipate that the majority of soils will be suitable for re-us~ as structural fill. In some locations on The Point, organic silt or clay , soils are present. These organic silt or clay soils ~e not suitable for re-use as. structural fill. If construction and fill}?lacement are to occur during 'wet weather conditions or on wet subgrade soil surfaces, we recommend structural fill material be utilized that is ,suitable for wet weather construction, Asuitable material is "Gravel Borrow" as presented, in Section 9- 03.14' of the Washington State Department of Transportation (WSDOT) Standard ~pecifications for Road, Bridge, and Municipal ConstruCtion (Standard Specifications). , However, the gradation should be modified so that a ,maximum 5.percentby weight of the material passes the U.S. No. 200 sieve as based on the minus 3/4-inch fraction. Structural fill should generally be placed in lifts not exceeding 10 to 12 inches in loose thickness. Each lift should be compacted to a firm, non-yielding condition and to the minimum relative densities presented below in Table 3. Where hand or other lightweight compaction equipment is used, we recommend maximum lift thicknesses of 6 to 8:-inches. Fin Loeation Required Minimum' Relative Compaction 1 TABLE 2 Recommended Structural Fill Compaction Beckett Point, Jefferson County Under Roadways: Upper 2, feet Greater than 2 foot depth Landscape Areas The Point Upland 95 percent 90 percent 90 percene 85 percent I Expressed as a percentage of the maximum dry density as determined by ASTM D-1557 (Modified Proctor). , 2 Recommended for backfill above potentially buoyant structures where minimum soil unit weight of 120 pcfrequired for uplift resistance. 3( tsr 3~ GHA Assessment Beckett Point Wastewater Treatment System Jefferson COU!'l(y, Washington T5 of 17 Project No, 041l36A-5 June 16, 2005 Myers Biodynamics, Inc. 10.3 Uplift Resistance Buried structures on The Point will likely be located partially below the tidally influenced groundwater levels, subject to flooding, and/or within liquefiable soils, These structures should be designed to resist hydrostatic uplift forces. Uplift forces can be resisted by increasing the weight of the structure such as additional concrete mass incorporated Into a pump station, holding tank, and/or thrust blocks. Additionally, soil backfill above buried structUres provides some resistance to uplift. We recommend using it total soil unit weight of 120 pcf and a submerged unit weight of 58 pcf for gtanull;lf soil backfill above buried structures. This assumes backfill is pl~ced and compacted' as structural fill. . lOA Drainage Control of site surface water is an important risk mitigation factor for both erosion and landslide hazards. We recommend that the proposed site improvements include a drainage system to capture and direct surface water runoff to suitable discharge location(s) at the base of the steep coastal slope. This includes new access roads and other impervious surfaces in .\ the treatment syst~m area on the upland portion of the site. Collected water should be routed down the slope via the existing Beckett Point Road swale, assuming adequate capacity is available, or via a separate drainage discharg~, pipe. ' 1 0.5 Vegetation Management The presence of established vegetation on the upland portion of the site and steep coastal slope helps reduce the risk of slope instability and erosion. Vegetation removes water from the shallow slope soils, helps to reinforce the shallow sOlis via live vegetative root systems, and intercepts incident precipitation. We recommend that vegetation be maintained on all , portions of the site, except where required for the treatment system installation. This will help maintain the current site slope condition and help avoid adverse impacts to the steep coastal slope. Where construction activity requires clearing and/or disturbs existing vegetation, the areas should be immediately protected from erosion and revegetatedas soon as possible following construction. 3( 11 3b GHA Assessment ' . Beckett Point Wastewater Treatment System Jefferson County, Washington i 6 of i 7 Project No. 04i i 36A-5 June i6, 2005 Myers Biodynamics, Inc. 11.0 Closure This report was prepared for the exclusive use of Parametrix, Inc. and the project design team for specific application to the geologically hazardous and frequently flooded areas associated with the Proposed Beckett Point Community Wastewater Treatment System in Jefferson County. The data and report conclusions and interpretations should not be construed as a warranty of subsurface conditions. ' , ~ Within the limitations of scope, schedule, and budget this report was prepared ,in accordance with generally accepted geotechnical engineering principles and practices in the area at the time this report was prepared. No other warranty, whether expressed or implied, is made. The condusions and recommendations presented herein 'are based on our understanding of the project as described in this report and on-site conditions observed at the time of our explorations. If project plans change from those described in this report, we should be contacted and 'retained to review the changed conditions. We should also be contacted and retaiIied to review our report' if: 1) there is a substantial lapse of time between submission of this report, and the start of con~truction; 2) conditions have changed due to natural causes or construction operations at the site; or 3) conditions appear different from those described in our report. The purpose of the review is to determine the applicability of the conclusions and recommendations considering the time lapse and/or changed conditions. " Sincerely Yours, MYERS BIODYNAMICS, INe. 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(]) -10 <!) .... (J) :-0 .l!! E .l!! ~:;:: ~ '0 1ii e. I:: . ~ 50 .s; ~~ ... ~ ... I>Jl e ~ 'O:i' LO LO I 0 <( 0 to N C') Q) ,.. c .; :s 20 "") I -- N\. ~ (j Z llJ ~ ii: ~ w U if- a:0? ::>rIl (/)Z rIlO ::)- (/)1- c~ W(I) NI -(I) ....I(/) <0 a: a: w(.) z w G o LO I- Z W :EE en <1> en +-A wen en>- en en c: <2: +-A 0 t:+-A en <1> 0) <( E.5 W+-A.c o:~en <(F~ en Q; "' :J..... >' o rat: O::::::J 0:<1>0 <((;)0 N~ c: <(:> 0 J: +-A en c:~ >:.- <1> :.J 0.0 :t: ...I <1> <!::::"J g~ Go 0<1> ...1m o W " LO C\I o u .~ cQ -j III ... U ~~~ e ~il ra fi~ III c I~~ ~ fi!i ~ .. rf.. II!: = u~ ~ ( APPENDIX A :_'o'--~ .,_._...........~.,,"..~__s_. .~.."._.,...._., ~.,.........-~",'_.._ '_~."'.~_........,...._."............-o>.__.._-.,.,;_...... 11,'-'"":,. F,,',,: "., r. ~,,; I .... k . ,~-l.~, ~.il \~l I \ r~<,!~"' Ll hI DEe 2 7 2005 ~ ~~~"\\:i '; I : 'I It I "h I' IJ ' I ! t to" j " i"'" 1 I ~~-_-..........~-_.. JEFFH\SON COUNTY . ; OEPT OfCPyiti.\lJhlTY DEVELOPiV,P~ ( L.._.__~ ',f"""\;,,,-.,, L...., ~ rn.::f\1 , 31~_",_ 2-5 (,,? 3b .:~-,..:_.~-""~" ,""_.,",,-,,,.;.,,:.:.:,y~z< 'AppendiX A Field Exploration Program Subsurface conditions for the project site were explored by advancing 5 borings, B-1 through B-5, at the approximate locations shown on the Site and Exploration Plan, Figure 2, Subsurface conditions observed in the' exploiationsare presented on the logs atta~hed to this Appeiidix. /' The explorations were located in the field .by tc;lping or pacing relative to existing physical site features. The approximate ground surface elevations presented on the logs wen;: interpolated from topographic mapping provided by Parametrix; Inc: The location and elevation of the explorations should be considered, accurate to the degree , implied by the l!lethod used, ' A licensed geotechnical engineer/engineering geologist from Myers Biodynamics was' present throughout the field work to observe the explorations; obtain soil samples, , and to prepare field logs of the explorations. Soils were classified in general accordance with ASTM D-2488 "Standard Practice for Description and Identification , of Soils (Visual-Manual Procedure)" and the Key to Soil Exploration Logs presented 'in this Appendix. A legend for the logs describing symbols and abbreviations is also shown on the Key. The exploration logs presented in this Appendix represent our interpretations of the contents of the field logs and fhe results of laboratory testing, Boring Explorations Borings B-1 through B-:-S were drilled with a trailer-mounted, DeepRock X24 ho1l9W"' stem auger drill rig on March 24 and 25, 2005 to depths of approximately, 69.1, 6Q;5, 20,0, 19.0 and 19.0 feet, respectively. Boring logs B-1 through B-5 are presented ~"',. Figures A-I through A~5 in this Appendix,' Sampling was performed through the!' hollow':stem of the auger using Standard Penetration Test methods, Standard Penetration Tests (SPT) were taken at 2-1/2 and 5 foot sample interv?-ls with a split-spoon sampler driven into the soil a distance of 18 inches with a 140 pound hammer freely falling from a height of 30 inches. Blows for each 6 inches of p~netration are shown on the boring logs. The number of blows required to drive the samples the last 12 inches is termed the Standard.Penetration Resistance (N value). Generally, where blow counts of 50 or more are reached for 6 inches or less of penetration, the test is terminated and the number of blows for the observed penetration are recorde4. The N value provides a qualitative measUre of the relative density of the cohesionless, granular soils or the stiffness of cohesive, fine-grained soils. Representative portions of the split-spoon samples were placed in p~astic jars, sealed, and transported to our office fo~ further evaluation and selective labpratory testing. 31 2.eo 36, GHA Assessment . Beckett Point Wastewater Treatment System Appendix A Jefferson County, Washington Project No. 041136A-5 June I6, 2005 Myers Biodynamics, Inc. Key to Soil Exploration Logs Sample Descriptions consist of the following: Minor constituents, major constituents; density or consistency, color, moisture, and additional comments including trace constituents. Soil classification is based on visual field soil sample observations and laboratory results on selected samples, where indicated on the logs. Soil classification is based on grain size, plastic- ity, color, density!consistency, and moisture. Visual- manual methods of ASTM D2488 were used as an identification guide. Soil Density and Consistency Soil density/consistency in borings is related to the Standard Penetration Test (SPT) as shown below. Soil density/consistency estimates in test pits are based on visual observation and presented parenthetically on the soil logs. Coarse-Grained Soil Density Ye..ryL,o,?St!! ", g:QQ~j~W~m'!l\fu@:@:",,,, '" Medium Dense Fine-Grained Soil Consistency ';!.~ii~~!~~~i;!1i':m;:", '" Medium Stiff SPT* 0-2 '2~14\j;~i,! 4-8 SPT* 0-4 ~~;:'1:f1;'}FS>< to-3D Minor Constituents Trace * $JrglitlY($J!t9;}$~n?!YA@.tg/~<..""."',< ' ' Clayey,SiJt}l,t3~nd}l, ", 0ravelly V.l?fi(($!!ty/'$?Q(:f.0'~t.~M>.'..",.,..,,',..., ... .,.,' *Not identified as a Minor Constituent Estimated Percentage 0-5% . . , . -...~.... ...,- ,. ,',. .',";6}1-g'f!fV> ' 12-30% Moisture p{g;,r .,...',.,.'.,.:L;fit(~:ti:iiiqR~(C~pt!j:)I~m6f~tl.!rf1, ~~Z:ly Some perceptible moisture, probably below optimum ;;;~t Much perceptible moisture, probably above optimum Laboratory Test Symbols Size classification P()cket Penetrometer (compressive strength in TSF) ":<,+.,:Jt9,Wiiij~i.(~fi~flfii~t~~rj'grfj"4ti:P$,Flf?.".:",,."...,.)...'1'....,',.;;,.').)'. Consolidation '.."...,.....fff~i~j0QmQ9~$~fjg~t~Cft:!6&raifi~&i!.'...'..,.,..,.')...,.',..',","...."",'" , TriaXiaiconsoiidated UndraineddH'" ..,""ti(fgr~l,.~~~$tiJlC/~,f~C/./flifi!o~ai).,., ..,'......,. Unconfined Compression .'tfiJri!i,~t?$ti~:gt'C<.'.'., · Permeability .""..'.....,..Q~~lt?l1't1f?tf}e'f!rif1f#.F.atid. PP 1!.V:.".< CN CPt4lfJ.' TeU 'ifliJOL au os.... K QE1.fi Unified Soil Classification System 'O~ 1a .~ .c:'" c::g ,lgC>l ~~ c ::E~ U;C:: :::0'" ~~ '0 III .~ r lll- ~.~ d>~ l!!., "'- c'" uE: .... C...., ~Q)N ~ e>Vi c:S3! ~ ~~.~ ~~: ::E~<: ~.,~ -~.... ~taC: e 8J! (!l - iil ,c:: 1/)'" "'-s .!!!'" 0'" 'Co!!! t:~ ~,s; ~:;:; CI)'5 <:r :::J ... ,Q) ~ca "'~ G Oliil -g~ ~ ",-.c: '0- 1/)'_ ""'" <ii.>!' .... Highly Organic Soils ~~.~ cacav, .c:E;1ll c::1/):' ~ .!2 ~~ -c::.". ~.Q . ~~~ l~U) I/)lll:::l 1j~t:: ~~tU CI)"S ., ....:. o .~ ....1/) liio .c:o c::<Il ~ci -<: ~(J) C:::l ::Ec:: .. '" ~~ (J).!!! '0.. III E S'" ~.l!! %'] Sa; 1.I.;'ci; E: .l(! ~g ~ '-~ (!l c., ~~~ .,<;:, U tJ) ~.~ :'1.1.; !!!.c: (!l~ {lc c::c:: (\1 .....(i) (J)C., ~~~ <3::;::' S '~ I/) ~.~ c::lJ: '" (J) pt Peat, muck and other highly organic soils Observation Well Symbols Bentonite seal p 3.0" dia. Thin Wall Tube Sampler 8f7192 ~ ATD ~ ::~ ':. .:: ":. .:: ':. 8-1 8-2 8-3 Ground Water Level: date of reading ATD: At Time Sand pack and well screen or hydrotip Boring Symbols 7 2.0" dia. Split Spoon 24 Sampler (SPT) 27 3 50 5014" 3.25" dia. Split Barrel Ring Sampler P = Sampler pushed "No sample recovery Test Pit Symbols 3fo Myers Biodynamics inc. Drive BORING LOG B-1 This log applies only to boring location at the time of drilling. Subsurface conditions may differ at other locations and may also change ovar time, This log is a simplified interpretation of the actual conditions, Beckett Point z Cf) 0 ~ l- t: z ~ WO 00 0 00 Co Jefferson County, Washington 0:1- W ~ W en > ;:)z I- :i' ..J a: I-W a: I- > 0- ~ W..J 001- UJ 0- W :E 0 C1J..J -z :J: W ..J <( ..J DESCRIPTION caW 00 l- e W 00 ca o~ :Eo 0 Fill - disturbed soil from gravel pit operations -- -- 19 -- 8-1 41 23 5 204 8-2 14 20 22 10 199 -- 31 -- 8-3 33 50/3' 15 194 -- -- -- -- 18 8-4 50/6" 20 189 -- -- -- -- 27 8-5 38 39 Myers --------- Very Gravelly Fine to Coarse SAND; very dense, gray brown, moist to very moist, trace srlt rough drilling abundant gravel less gravel based on drilling action Slightly Gravelly Fine to Coarse SAND; dense, gray brown, moist to very moist Very Gravelly Fine to Coarse SAND; very dense, gray brown, Gravelly to Very Gravelly Fine to Coarse SAND; very dense, gray brown, moist, trace silt in bottom of sampler ~, Z$ 3(P Gravelly Fine to Coarse SAND; very dense, gray brown, moist DATE DRILLED Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) dORING LOG B-1cont. This log applies only to boring location at.the time of drilling. Subsurface conditions may differ at other locations and may also change over time, This log is a simplified Interpretation of the actual conditions. Beckett Point z en 0 ~ l- t: ~ WO en CJ) iD Jefferson County, Washington 0:1- w W W > ::IZ I- ..J 0: I-W 0: a. ~ W..J (1)1- W :E 0 I CJ) jjj -z J: <C ..J DESCRIPTION ~3: 00 I- CJ) !Xl :EO 0 -- -- -- 50/6' -- 8-6 30 179 -- -- -- -- 8-7 50/6" 35 174 -- -- -- -- 8-8 34 50/6" 40 169 -- -- -- -- is a 8-9 28 45 164 b 37 16 8-10 27 41 Myers Vel}' Gravelly Fine to Coarse SAND; vel}' dense, gray, moist to vel}' moist Gravelly Fine to Coarse SAND; vel}' dense, gray, vel}' moist Gravelly Fine to Coarse SAND; vel}' dense, gray, vel}' moist, trace silt Fine SAND; vel}' dense, gray brown, slightly moist, no soil staining, no perched groundwater evidence Vel}' Fine SAND to SILT; hard, gray brown, moist, granular non-plastic 31 ~CJ ~ SILT to Vel}' Fine SAND; vel}' dense, gray brown, moist, granular non-plastic grading to Fine SAND;vel}' dense, gray brown, moist, no soil staining, faint pat1ings DATE DRILLED Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) SH 2 OF 3 41136A-5 BORING LOG B-1cont. This log applies only to boring location at the time of driJiing. Subsuriaes conditions may differ at other locations and may also change over lime. This log is a simplified interpretation of the actual condflions. Beckett Point z en 0 ~ ti ti: z ~ UJO UJ 0 en io Jefferson County, Washington a: I- I- ~ UJ en > ::>z :i ..J a: I-UJ a: I- > Cl. s: UJ..J C/)I- UJ Cl. UJ :\; 0 C/)..J -z J: UJ ..J <t ..J DESCRIPTION IIlUJ 00 l- e UJ en III oS: :\;0 0 24 -- 8-1 19 28 55 154 -- -- -- 38 -- -12 50/4" 60 149 -- -- -- -13 01 -- 1/2' 65 144 -- -- -- 8-1 29 -- 50/1' 70 139 -- -- -- -- Myers Fine SAND; dense, gray brown, slightly moist, trace coarse sand, slightly gravelly at top of sample Slightly Gravelly Fine to Medium SAND; vel}' dense, gray brown, slighlty moist, trace coarse sand Vel}' Gravelly Fine to Coarse SAND; vel}' dense, gray brown, slightly trace silt rough drif/ing - increased gravel Vel}' Gravelly Fine to Coarse SAND; vel}' dense, gray brown, slightly moist Bottom of boring at 69. 1 foot depth 31 30 3fo SH OF 3 3 DATE DRILLED AGURE /24/05 Rolling Bay Mercantile Bldg, 11254 Sunrise Drive ELEVATION (Fl) dORING LOG B-2 This IDg applies only to boring location at the time of drilling. Subsurface conditions may differ st other locations and may aiso change over time, This log is e simplified interpretation of the actual cond#ions. Beckett Point 2: CJ) 0 ~ l- t: z ~ UJO CJ) 0 CJ) to Jefferson County, Washington 0:1- W ~ W en > ;:)2: I- :t' -J 0: I-W a: I- > Q. ~ UJ-J (/)1- W Q. W :E 0 (/)-J -2: :I: W -J <t -J DESCRIPTION [OW 00 I- 0 W CJ) [0 o~ :EO 0 Grasses / trace Topsoil over -- -- Slightly Gravelly Fine to Medium SAND; medium dense, yellow brown to red brown, slightfy moist, trace coarse sand, trace organics (1/4- Inch root) Slightly Gravelly Fine to Medium SAND; dense, gray brown, slightly moist, trace coarse sand Slightly Gravelly Fine to Coarse SAND; very dense, gray brown, slightly moist rough drilling, increased gravel content 8-4 6 Slightly Gravelly Silty to Very Silty SAND to Sandy SILT, very dense"',gfa.Ybr6wn~ 50/5" moist *Sampler bouncing on gravel rough drilling at 20 foot - depth 31 31 3" 8-5 17 29 Very Fine SAND to SILT; very dense, gray brown, slightly moist, faint partings, granular non-plastic DATE DRILLED Myers Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) BORING LOG B-2 cont. This log applies only to bOring location at tha time of drilling. SUbsurface conditions may differ at other locations and may also change over time. This log Is a simplified interpretation of the actual conditions. Beckett Point z en 0 ~ l- t: z ~ WO en 0 en Co Jefferson County, Washington "t- W ~ ILl W > ::IZ t- ~ ...I " I-W " b: > Do 3: W...I ent- W W :E 0 (/)...1 -z :I: W ..J < ...I DESCRIPTION roW 00 t- o W en m 03: :EO 0 8-5 49 Very Fine SAND tq SILT; vel}' dense, gray brown, slightly moist, faint partings, granular non-plastiC -- 30 44 a 8-6 b 35 39 a $-7 b a S-8 40 34 b 17 8-9 28 29 Myers 16 27 28 Very Fine S~ND to Siltv Ane SAND; very dense, light gray to gray brown, slightly mOIst to mOIst grades (0 Fine Sandy SILT to SILT; hard, gray brown, moist, one sand parting with iron staining grades to Fine sand at bottom of sampler 25 38 47 2 inches SILT to Silty Fine SAND at top of sampler, faint partings Fine SAND; very dense, gray brown to light gray, slightly moist, trace medium to coarse sand 19 27 37 Very Fine SAND to SILT; hard, gray brown, sfi~htly moist, granufar non-pfastic, fine sand partings, trace iron staining in sand partmg SILT; hard, gray brown, slightly moist, massive --------- Fine SAND; very dense, light gray, slightly moist 3{ Fine SAND; very dense. light gray to gray brown. slightly moist ~~es to ~k a 2-inch zone at 50 foot depth DATE DRIlLED AGURE SH OF A-2 2 3 PROJECT NC041136A-5 Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION(FT) DORING LOG B-2 cant. Ii: z 0 en to ~ ~ W en ...I I- > D. ;: D. W :::: 0 W ...I <( ...I C W en m 50 -10 -- -- 55 19 60 14 65 9 70 4 -11 21 -12 40 50 Myers This log applies only to boring location at the time of drilling, Subsurface conditions may differ at other Jaeations and may also changa over tima, This Jag is a simplifiad interpretation of the actual condflions. Beckett Point Jefferson County, Washington Z en o ~ ~ 6 WO en .... 0::1- W :> ::JZ I- 0:: I-W 0:: W...I enl- W (/)...1 -z :I: mW 00 I- 0;: :ao 0 DESCRIPTION Slightly Gravelly Fine SAND; vel)l dense, light gray, slightly moist, trace medium to coarse sand ' 21 33 40 Fine SAND; vel)l dense, liQjJt gray to gray brown, sightly moist 1-inch Silty Fine SAND to Fine Sandy SfL T moist zone at approximately 50-foot depth Fine SAND; vel)l dense, light gray, slightly moist Bottom of boring at 60.5 foot depth DATE DRILLED Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) 31 33 3b 30RING LOG B-3 t: Z 0 CJ) ~ ~ w :i ...J I- > a. :: a. UJ :E 0 UJ ...J < ...J a UJ CJ) m -- -- 10 8-1 15 16 -- 5 5 8-2 10 -- 9 -- 10 -- 8-3 9 6 -- 10 -4 24 -- 8-4 16 21 -- -- 13 8-5 20 36 -- 15 -9 8 8-6 23 -- 30 -- 12 8-7 23 36 -- 20 -14 8-8 Myers This log applies only to boring location at the time of driJIing, Subsurface conditions may differ at other locations and may also change over time, This log is a simplified interpretation of the actual conditions, Beckett Point Jefferson County, Washington DESCRIPTION Gravel surfacing over Fill?: Sandy Coarse Gravel and cobbles in cuttings --------- Slightly Gravelly Fine to Medium SAND; medium dense, gray brown, moist, trace coarse sand Gravelly Fine to Coarse SAND; medium dense, gray brown, wet groundwater at 6.5 foot depth (3:25 pm) Gravelly Fine to Coarse SAND; medium dense, gray brown, wet ATD ~ Gravelly Fine to Coarse SAND; dense, gray brown, wet --------- Fine SAND; very dense, gray brown, wet 1 foot heave - blow counts may not be representative SAND; very dense, gray brown, wet, trace gravel 2 1/2 foot heave' - blow counts may not be representative add drilling mud Gravelly SAND; very dense, gray brown, wet 21 50/6' Gravelly SAND; very dense, gray brown, wet Bottom of boring at 20 foot depth Rolling Bay Mercantile Bldg. 11254 Sunrise Drive :z CJ) o ~ l- t; WO CJ) ...... a:.... w > :::JZ l- e: ....W a: ~::i ~~ w mW 00 ~ 0:: :EO 0 31 3'-( 30 DATE DRILLED 3 24 05 6:t ELEVATION (FT) AGURE SH OF 1 1 PROJECT N~41136A-5 BORING LOG 8-4 t 5 :r: ~ I- > 0.. W UJ ...J o W 5 10 -4 5 _ _ 8-4 5 9 __ 11 8-5 7 8 15 -9 en W ...J 0.. :2: q: en 4 8-1 16 17 8-2 8-3 8-6 8-7 Myers This log applies only to boring location at tha time of driliing. Subsurface cond11ions may differ at other locations and may also change over time. This log Is a simpnfied interpretation of the actual conditions. (0 en :s: o ...J ca Beckett Point Jefferson County, Washington DESCRIPTION z (/) o ~ l- E; WO en ,..., a:1- W > ;:,Z I- a: I-W a: ~j ~~ W caW 00 i!: 03: :2:0 0 Trace grasses over Fill?: Slightly Gravelly Fine SAND cuttings with occasional cobbles Slighly Gravelly Fine SAND; dense, brown to light gray, slightly moist, trace organics, gravel piece in bottom of sampler - blow count not representative rough drilling gravel, cobbles? 8 12 8 Ve/)' Gravelly Fine to Coarse SAND; medium dense, gray brown, wet groundwater at 6.5 foot depth (8: 18 am) ATD ~ add drilling mud Slightly Gravelly SAND grading to Sandy GRA VEL; loose, gray brown, wet, gravel to 1- 1 1/2- inch diameter 4 3 5 Medium to Coarse Sandy GRA VEL; medium dense, gray brown, wet gravel Slightly Gravelly Fine SAND; medium dense, gray brown, very moist to wet rough drilling occasional gravel 10 12 11 Gravelly Fine to Coarse SAND; medium dense, gray brown, wet occasional gravel 12 12 14 no recove/}' except gravel piece in bottom of sampler Bottom of boring at 19 foot depth! \ 3/ 35 3to DATE DRILLED Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (Fi) 30RING LOG 8-5 This log applies only to baring locatJon at the time of drilling, Subsurface conditions may differ at ather locations and may also change over time, This lag is a simplified interpretation of the actual conditions. Beckett Point z (/J 0 ';.!!. l- t: z ti WO (/J 0 en to Jefferson County, Washington 0:1- w ~ W en > ::::>z I- :i ..J 0: I-W 0: I- > Q. :s: W..J (/JI- W Q. W :E 0 (/J..J -z :I: W ..J <( ..J DESCRIPTION lOW 00 l- e W en 10 03: :EU 0 Grasses I trace topsoil over -- " 3~ 30 DATE DRILLED Myers Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT)