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Home My WebLink AboutLog012 Section 6 . . . ~B , Myers Biodynamics i...c. _ geotechnical engineering. geological sciences. 'coastal processes , I~ A~ f~~r2~5 ~ ~.II 'I '. '~'''''''''-''.._--.. I i ,..."',.__.., ____, ,,_J ~ ,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 Bremerton, w' ashington 98312-2234 Prepared by: Myers Biodynamics, Inc. Rolling Bay Mercantile Building 11254 Sunrise Drive Bainbridge Island, Washington 98110 June 16, 2005 Project No. 041136A-5 R(HLlNG 11<\ Y 131 'ILDING . 1125,) SUNRISE DRIVE BAINBRII)GE ISL;\ND. WASHINGTON l)XIIO . l-z..., , '~::~f,::.,~:~'~:~[.... 20h,X')2,60!J .. . . Table, of Contents Section Page No. 1.0 INTRODUCTION ......... ........ ............. .......;.... ......... ......... :..... ................. ........1 2.0 SITE DESCRIPTION.. ......... ...........; ........................ ........... ..... .......... .:............1 2.1 U~l~d Area. ................ .......:........ ..... .......... ........................ ......... ...... ...........2 . 2.2 Beckett Point.. ........ ....... ......... .............. ...... ......... ..... ........ .............. .............2 3.0 PROJECT DESCRIPTION ............ ............ .......... ..................... ........... ...~........2 4.0 INFORMATION REVIEW ........................................................:.....................3 ' 5.0 . GEOLOGIC SETTING..... ......... ...... ................. ....... .... ......... .......... ..... .............4 5.1 Soil............................... ............... ..:................ .,....... ................ ..... ,................4.' 5.2 Groundwater........... ..:....... ...........:...... ......... ....... ..... ........................ ............4 6.0 SEISMI C CONSIDERATIONS............... ....... ....:.... ..... ...................... ...... .......5 7'.0 SITE RECONNAISSANCE.......... ........ .......... .............. ............................ .......5 7 .1 Topography... ........... .......... ....................... ........... .................. .......~.... ........6 7 .2 Vegetation.. ..... ............. ...... ...:................... ....................... ....... .......... ...........6 7.3 Drainage........................................ ..... ...................... .......... ..........................7 7.4 Soil Exposures and Groundwater Evidence.................................................. 7 8.0 GENERALIZED SUBSURFACE CONDITIONS..........................................8 8.1 Soi1... ................... ...........:..................... ........................ ...............................8 8.1.1 Upland Area ........ ............ ....... ....... .... .......... .... .......... ............... ........8 8.1.2 Beckett Point.... .............. ........................... .,.....:...............................8 8.2 Groundwater..:.......... ..,........................................................ ...;.............. .....9 9.0 GEOLOGICALLY HAZARDOUS AND FREQUENTL Y FLOODEp AREAS.......;.................:...............................:..l 0 ! GHA Assessment Beckett Point Wastelfater Treatment system . jefJerson County. Washington Project No. 041/ 36A-5 June ]6. 2005 , Myers Biodynamics. Inc. - i - fl- , _~'-_.~-"-.-?:l? . \ . ' I 9.1 Landslide Hazard Assessment .....,.....................,.......................................11 9.1.1 Qmllifative SlQpe Evaluation ......................~.......;...........................11 9.1.2 Quantitative Slope Evaluation..............................:......................... 12 ,. , 9.2 Seismic Impacts to, Slope Stability.....,............................................:....I....12 , . 9.3 Erosion Hazard.......... ..... .............. .......:..... ...... ..................~.... ........ .... ........13 9.4 Liquefaction. Seismic Hazard ............................. .................... ....... ..............13 9.5 Frequent Flooding Hazard.. ........ ...... ........... ...... ........... .............. ................13 , . 10.0 GEOTECHNICAL RECOM~ENDA TIONS .............................................14 10.1 Excavation and Temporary Shoring .......................................;.:..............14 10.1.1 Upland Area ...................... ..................... ......... ...'.... ...,'... ............... .14 10.1.2 'Beckett 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. ............. ................ ...:...... ............................... ........ ................. ..... i 7 FIGURES: Figure 1 - Geologically Hazardous Areas Site Plan' Figure 2 - Site and Exploration Plan Figure 3 - Generalized Subsurface Cross-Section A-A' Figure 4 - Generalized Subsurface Cross-Se<;:tion B-B' APPENDICES: Appendix A - Field Exploration Program . GHA' Assessment Beckett Point Wastewater Treatment system Jeffer~on County. Washingtoh - ii - Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. ..... .._"~_t~....."..,,..._~.- 33K.. .. . , , . ru Ie (CfN' ~ \lr~T~~I\ lJ .. .- I !. i 'U1J JUN 't 0 IUUJ \I! TRANSMITTAL Date: To:' From: Subject: Jime 16, 2005 Mr. James Hasslinger, P.E. Mr. M~chael Moren, P.E. Parametrix, Inc. 5700 Kitsap Way, Ste. 202 Bremerton, WA 98312-2234 '!_.-/j~ I Jane Myers, P.E., L.E.G. 2/I/L ! Myers Biodynamics, Inc.' :,.... / ' Geologically Hazardou" Areas Assessment - Seckett Point Enclosed please find two bound copies and one un-bound reproducible copy of the' Geologically Hazardous Areas Assessment prepared for Beckett Point. Please contact our office if you have any questions. ,END Myers Biodynamics Inc. Rolling Bay Mercantile Building .' 11254 Sunrise Orive . Bainbridge Island, WA 98110 206.842.6073 . Fax 206.842.3797 . myersbiodynamics@bainbridge.net . . . 1:0 Introduction , . This report presents our Geologically Hazardous Areas (GHA)assessment and recommendations fora proposed sewerage system, and large on-site wastewater treatment area supporting the Beclcett 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 No.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 the site and to provide recommendations for . hazard mitigation of the proposed wastewater treatment and cpnveyance 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. ~ortions of the previous report are presented herein fQr reference. 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 on 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 to 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 general location and configuration of the project site are shown on the Vicinity Map and Geologically Hazardous Areas Site Plan, Figure 1. ' 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 delinea~e 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. GHA Assessment Beckett Poin! Wastewater Treatment System Jefferson County. Washington / of /7 . Project No. 04//36A -5 , June /6, 2005 Myers Biodynamics, . .J.~ ...". .,......hM.. 5...3[,,,,.. . . . 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 grades within the upland forested area are gentle to moderate with average" slopes ranging from 1 0 to 30 percent with locally 'steeper zones of approximately 40 percent. Several hundred feef northwest and southwest of the proposed treatment area, grades increase J;1ear the steep coastal slopes. Grades OIl the steep coastal slopes average 100 percent above View Point Lane and 10 to 110 percent above'The Point. The upland area includes a residential development area on more moderate grades where Beckett Point Road descends the slope. Grades around existing residences average 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 hy seasonal changes in the coastal process long-sh<;>re sediment drift direction, that forms triangular shaped deposits, The Point comprise~ 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 in 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 of the steep' coastal slope. Several buildings are located at the terminus of the road. These buildings are apparently associated with an historic water supply system that collectyd water from a'spring at the toe of the slope. Further discussion of the spring and existing site conditions are , I presented below in$ection 8.0 Site Reconnaissance. ' ' 3.0 Project Description The proposed community wastewater treatment system will collect wastewater from individual residence~ 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 comer 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 wastewater collection system and pump stations is shown on the Site and Exploration Plan, Figure 2. GHA Assessment , Beckell Point Wastewater Treatment System Jefferson County, Washington Project No. 0411 36A-5 June 16, 2005 Myers Biodynamics, Inc. 2 of 17 Tlk~~C3"'~~--A ,lQ,,,,,-,,,,,,, ", e' U'.. ",.-0"",,;,,0, . . . The cUrrent wastewater treatnient (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 grading will b~ required for the treatment system construction. W eund~rstand that the proposed community wastewater treatment system is being designed- in accordance with the Washington State Department of Health i'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 residential lots, which generally do not conform to current Health Department s4mdaids: The new system will also account for buildout of some of the remaining undeveloped lots for a total on 02 residential hook-ups. 4.0 Information Review ~ Reference information for the area waS reviewed as a part of our work and included soil and geologic mapping, water supply information,. and water well logs. The general reference information is presented below. A summary of soil and groundwater information obtained from the information review is summarized in Section 4.0 Geologic Setting. ~ Geology and' Groundwater Resources'ofEastem 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.1 of Jefferson County, by Economic and Engineering Services, Inc. and Pacific Groundwater 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 Wastewater Treatment Area, by Myers Biodynamics, Inc. (MBI), May 10,2005. GHA Assessment , Beckell Point Wastewater Treatment System Jefferson County, Washington Project No. 04II36A-5 June 16, 2005 Myers Biodynamics, Inc. 3 of 17 . . . 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 subsurface explorations are presented in Sections 7..0 and 8.0. 5.1 Soil Geologic mapping generally indicates the local area northeast of the project site is capped by glacial till. Gllicial till is composed of a mixture of gravel, sand, silt, and clay that was deposjted and overridden by the tnost 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 slop~ above The Point. Glacial advance out;wash soils are generally composed of sandor 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 horizon due to the weight of glacial ice. . Southeast of The Point, mapping also shows interglacial deposits below the advance outwash that can include sand and gravel, silt, or clay soils, which are also in a very dense or hard condition below the surface soil horizon. The Point is mapped as recent, post' glacial deposits including loose sand and gravel beach deposits along' the shoreline and soft organic soils associated with the lagoon located on the interior of The Point. USDA Soil Survey reference mapping indicates the proposed treatment area is Cassolary Sandy Loam, 15 to 30 percent (CfD) and The 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 Slide" identified i,?mediately north and east of The Point and local community1 The upland area and The Point are described as "Stable" with respect to slope stability. 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.W ells were identified north, northeast, and southeast ofthe project site. Well logs show a likely cap of glacial till underlain by sand or sand and gravel with clay layers at depth. Static water levels in the well logs were typically more than 170 feet below the grade at thewell locations. The Jefferson County PUD No. I was also contacted for additional information regarding water supply wells in the IQcal area. No current water wells or associated well logs were identified on the project site. All potable water is reportedly provided by the PUD No. 1 system that obtains its water from the Ql!ilcene River located more than 15 miles south of the project site. GHA Assessment Beckett Point Wastewater Treatment System Jefferson County, Washington Project No. 04JJ36A-5 June J 6, 2005 Myers Biodynamics, Inc, 4 of /7 , Jy"...,.~.. <{, ,,3!r,. . The lack of local water wells precludes a determination of site specific groundwater gradient or flow direction. However, revie~'ofbackground information shows 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 selsmically active western Washington region. For seismic design under the 2003 International Building Code (IDC), a.site class is sel~cted ' based on the' average soil properties in the upper 100 feet. U:sing information obtained from site subsurface explorations, reference information, and 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"). 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 ~ percent probability of exceedance in 50 years (475 and 2,475 return intervals) were obtained for the local area using the USGS National SeismiC Hazards website and latitude and longitude coordinates. The peak ground acceleration is approximately 0.3g and 0.5g for the 10 percent and 2 percent probability of exceedance in 50 years criteria, respectively. As noted above, loose saturated sand soils located near existing grade on The Point are susceptible to liquefaction during earthquake strong ground motion. A more detailed discussion of the potential for site soil liquefaction is presented in Section 9.0 Ge6logically Hazardous Areas Evaluation. 7.0 Site Reconnaissance Site conditions were evaluated by conc.lucting a reconnaissance of the property and local area at various'dates from October 2004 through April 2005. Site and local conditions including topography, vegetation, surface drainage, and soil exposures and groundwater evidence are presented below. Subsurface conditions were also investigated by conducting test pit explorations in the proposed treatment area and by hollow stem auger boring explorations in the proposeq 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. GHA Assessment Beckell Point Wastewater Treatment System Jefferson County, Washington, Project No. 04JJ36A-5 June J 6, 2005 Myers Biodynamics, Inc. 5 (If 17 ", , '1,t::'H'" '" '.',,,,,,,<,,,o>,,,;,"<-w, '''',' ,.,.,......"."..,~....,' . . . 7 .1 Topography Topography in the upland area generally slopes down to the 'north and northwest as shown on Figures I and 2. In the extreme northeast corner of the site (treatment area) elevations drop from a maxiplUffi 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 downtothe northwest, west, and south'Yest towards the steep coastal slope. North of The Point, View Ppint 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 des~ends to the lagoon and existing structures located at the terminus of Beckett Point Road. East of Th~ 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 slope is less steep at times above The Point and lagoon with grades of70 to 100 percent (31 to 45 degrees). . At the terminus of Beckett Point Road the toe of the slope was apparently excavated for a cul-de-sac creating a locally' steeper segment 20 to 30 feet above the road elevation with grades of 100 to 119 percent (45 to 50 degrees). I ' I On Beckett Point, grades are generally level along Beckett Point Road and View Point Lane. Historic grading and fill placement likely occurred for road construction. Grades are several feet lower in the interior of The Point where delineated wetlands (by others) and the lagoon are present. During high tide events the wetland area is inundated bys~face water. It is reported that during extreme high tide events and stqrm surge, portions of The Point are flooded including portions of Beckett Point Road. 7.2 Vegetation The upland area on the northeast corrier of the site including the treatment area is densely forested/with an established canopy of deciduous and conifer trees including Douglas fir, Western red cedar, western hemlock, red alder and big leaf maple. The understory vegetation is moderately dense, comprised of shrubs and herbaceous groundcover including sword fern, salal, and Oregon grape. Beyond the treatment area the forested condition continues down 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 historically graded) for residential homes and Beckett Point Road. Some,established trees and understory vegetation remain within the residential areas. On the slope above 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 Project No. 041136A-5 June 16, 2005 Myer$ Biodynamics, Inc. 6 of 1'7 .~ . . . 7.3 Drainage " Topography within the proposed wastewater treatment area oh the northwest comer 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 course& 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 and northwest of the site. Elsewhere, surface gradients direct surface water flow down tile steep coastal slope northwest, west, anp sOiuthwest of the treatment area. Observ~tion of the local area indicates no evidence of significant surface water runoff or erosion on the steep coastal slope. This includes a utility trench alignment reportedly excavat~d 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 gull eying 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 groundwater 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 co'astal slope. A local" gravel pit" off of Beckett Point Road and west of the treatment area (see Figure 2) contains significant soil exposures. A steep cut slope is present on the east and 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 of groundwater seepage was noted Oil the steep coastal 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. GHA Assessment Becket! Point Wastewater Treatm,ent System Jefferson County. Washington Project No. 041136A-5 June 16. 2005 Myers Biodynamic~~ ~ of 17 l~ '.'''',.<.'.;"..,..:..., JL.$, .. . . 8.0 Generalized Subsurface Conditions Subsurface boring explorations for this report were conducted along the alignment of the proposed wastewater collection an<ilconveyanc~ system to evaluate the geologic hazards and provide recommendations for hazard mitigation ~d treatment system design and construction. In addition, test pit explorations and laboratory testing were previously conducted in the proposed wastewater treatinent( drainfield) area to investigate suitability and hydraulic design parameters for the proposed drainfield area. A description of the subsmrace 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 alignment of the proposed wastewater collection and conveyance system. On the upland portion of the site above The Point, boring B-1 and B~2 were advanced in the area of proposed ,pump stations to provide information for pump station excavation, shoring, and to als~ 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 upland 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 arid B-2 were advanced to depths of approximately 69 and 61 feet below existing grade, respectively, I;\S shown on Figures A-I and 1\.-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 underlying the steep coastal slope. Generalized subsurface conditiop.s observed in the eleven test pit explorations in the proposed wastewater treatment area also indicated subsurface conditions consistent with the geologic mapping and reconnaissance of the area. Soils were composed of glacial advanced outwash consisting of gravelly slightly silty sand, fine sand, 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 surficial layer of fill generally up to 3 feet thick. Below the fill, beach deposits composed of loose to medium dense gravelly sand to fine sand were generally encountered. Variations in GHA Assessment Beckell Point Wastewater Treatment System Jefferson County, Washington Project No. 04JJ36A-5 , June 16, 2005 Myers Biodynamics, Inc. 8 of J7 -j3=-- 3ft , t .' - ",. . . . subsurfacesoil conditions in each of the borings reflect their location on The Point and depositional characteristics of each area. Boring B-3. was .advanced near the base of the steep coastal slope on View Point Drive and showed minor fill underlain bymediUl11 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 underlying the steep coastal slope that have been eroded to form a i1beach 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 , fee~ of fill, the soil was generally composed ofloose to medium dense gravelly sand to sandy gravel. Boring B-5 advanced adjacent to the lagoon area showed 3 feet of fill over medium stiff organic silt likely associated with lagoon deposits (prior to filling). Below the organic silt, loose to medium dense gravelly sand was genera~ly 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 Qf 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 foot depth, ,respectively. The interbeds of sandy silt and silt showed 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 conducted 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 belo", in Table 1. Monitoring indicates that the granular soils comprising Beckett Point are tidally influenced. ' GHA Assessment Beckell Point Wastewater Treatment System Jefferson County, Washington Project No. 041136~-5 June 16, 2005 Myers Biodynamics. Inc. 9 oj /7 . ....,."tJ-,., d ""..~.._ 13 ,'J[[ . . . TABLE 1 Shallow Monitoring Well Observations Beckett Point, Jefferson County Monitoring Well No.1 , MW-l Depth below Date and Time of grade to Reading Tide Condition2 groundwater3 3/25/05 11 :00 am Rising Tid~ 72" , 4/20/05 5:30 pm Fallins 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 Fal1ing 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" 4/25/054:20 pm Rising Tide Dry -at 66" Location View Pclint Lane MW-3 Beckett Point Road near tip of Point MW-5, Beckett Point Road cul-de-sac Notes: 1. Monitoring well number based on original installation by others. 2.. Tidal information based on NOAA published tidal informatiol) for Port Townsend, WA: 3/25/05 2.7 ft low at 10:00 am; 4/20/055.8 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 tbe 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 depositscomposed ofloose sand and gravel and orgari:ic soils 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 ha~ards on the steep coastal slope and increased landslide hazards during a seismic event (seismic hazard). The presence oftelatively 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 tsunamis (Frequently Flooded Hazard). The following sections present our evaluation of the project site geologic and frequently flooded hazard areas. ' GHA Assessment Beckett Point Wastewater Treatment System Jefferson County, Washington Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. 10 of 17 ." _._..l_._;f-,. '_.,'___' " -' .''''--' ,3_.~','.-.-~_,_. {in -- . . . 9.1 Landslide Hazard Assessment Landslide hazards for the site were assessed using both qualitative and quantitative " assessment' of slope stability. In addition, two scenarios for potential landslide hazard impacts 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 landslid~ hazard/slope stability risk associated with construction of the sewerage system pipe a~ignment up the steep.slope. \ I 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 instabiHty, in out opinion. This is supported by Coastal Zone Atlas mapping of~e steep coastal slope as "unstable". Risk factors for future slope stabilityllandsliding 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 ~nstability 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 generaIly 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 in the shallow surface soil horizon can .increase the risk oflandsliding. 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 will have a negligible adverse aff~ct / on slope stability. This opinion is due to: 1) the primarily granular nature of the 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; and 5) the lack of evidence of significant perched groundwater in the soil explorations advanced in the upland area. In addition, wastewater treatment systems for residence,S currently on the GHA Assessment BeckeJ/ Point Wastewater Treatment System Jefferson County. Washington Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. 1I of 17 _12::..._,.....".,_.,.,,\7(' ,~,= .,...'30 . . '. coastal slope will have their wastewater input tel the slope moved over 500 feet east to the 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 ~lope Evaluation. Quantitative slope stability analyses were conducted to model existing site slope conditions ~d provide a method for assessing potential impacts to slope stability from the proposed treatment system. Slope stability - analyses were conQ.ucted 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 (actor of safety of . 1.0 indicates marginally stable conditions where the driving force and resisting force. are . eqilaL 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 construction. 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 t6 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 faetor of safety is reduced by approximately 5 percent with a static factor of safety still above 1.0. These 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 static conditions, the effects of seismic strong ground motion would tend to reduce slope stability and increase the risk of seismically induced landslide activity. Pseudostatic analyses of the steep coastal slope indicate a risk of lands Ii ding during a large seismic event. However, along the pipe alignment, slope grades ate more moderate and a factor of safety of greater than 1.0 was determined for the moderate grades along the pipe alignment under pseudostatic conditions. While nothing can be done to prevent seismic activity and increased risk to existing slopes, GHA Assessment Beckell Point Wastewater Treatment System Jefferson County, Washington , Project No. 041136A-5 JUlie 16, 2005 Myers Biodynamics. Inc. 12 of 17 l;" l.6.~..':.'...'.';':-':j~.."" . . :. measures can be taken to help reduce slope stability, risk to the system including adequate compaction of backfill mat~rial, vegetation management, and stormwater control. See' Section 10.0 Geotechnicl,ll Recommendations. 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 t4e area of the proposed pipe alignment and on the steep coastal slope. Where covered by existing vegetation, the erosion hazard appears to be low ~ased 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 minor erosion of the slope face soils above the ,cul-de'-sac at the end of Beckett PointRoad where soils were apparently cut for the cul-de-sac and unprotected from erosion. In our opinion, the implementation of conventional erosion c<;>ntrol 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 ppre water pressure which can result ~n 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.3gand 0.5g (recurrence intervals of 475 and 2,475 years, respectively) there is ~risk o(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 including 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 sO,ils following the earthquake. Also, empty or partially empty buried vessels in liquefied soil can become buoyant and "pop-up" during a seismic event. Recommendations to mitigate risk from site soil liquefaction for the proposed wastewater treatment facilities on The Point are presented 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 ly,ingportions of The Point including portions of Beckett Point Road. In addition, flooding can occur as a result of large seismic events and resulting tsunamis. Design of the proposed wastewater collection and conveyance system on The Point should include measures to avoid adverse impacts as the result of surface water/system flooding. These include "pop-up" risk to buried structures during 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 GHA Assessment Beckett Point Wastewater Treatment System Jefferson County, Washington, Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. 13 of 17 l)/ .1,1."".", . . . , . should be avoided by appropriate system design details. See Section 10.0 Geotechnical Recommimdaiiops. 10.0 GEOTECHNICAL RECOMMENDATIONS , . Geotechnical recommendations for the projec! site to help mitigate risk from geologically hazardous and frequently flooded areas are presented below and include recommendations for excavation and temporary shoring, structural fill, uplift resistance, drainage and vegetation management. ' 10.1 Excavation and Temporary Shoring The proposed wastewater treatment collection and conveyance systems will require maximuin excavatiO,ns of 8 to 10 feet at pump 'stations and relatively shallowtrench excavations for the sewerage pipe alignment aroUnd The Point. Recommendations for the upland area pump stations and The Point pipe alignmenUrre presented below. 10.1.1 Upland Area. Excavation within upland areas will likely encounter loose to medium dense soils in the upper 31to 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 toa maximum 3/4 to 1 horizontal to 1 vertical (3/4 to IH:IV) 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 recoffil;11end an equivalent fluid unit weight of35 pcffor soil in the upper 5 feetofthe excavation and 25 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 encountered below the fill in areas near the lagoon. Groundwater will be present at depth and will likely depend on the tidal elevations during excavation. Groundwater was generally observed at depths of 3-112 to 6 feet below grade during the drilling and ~onitoring w~ll 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 particular.ly below groundwater levels. Where shoring is provided, we recommend' the upper unsaturated soil zone be designed for an equivalent fluid unit weight pf 35 pcf. Below the groundwater elevation, a unit weight based on the combined soil and hydrostatic loading of 80 pcf is recommended. 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 _ of 1-1/2 H: 1 V. Where groundwater is encountered, flatter open cuts or shoring would likely be required. GHA Assessment Becke/l Point Wastewater Treatment System Jefferson County. Washington Project No. 04/ /36A-5 . June /6. 2005 Myers Biodynamics, Inc. /4 of 17 G~ 1<R-c()~- (}-- ii:-:"..-~" . . . 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 and 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 granular nature of the site soils, we anticipate that the majority of soils will be suitable for re-use as structural fill. In some locations on The Point, organic silt or clay . .' soils are present. These organic silt or clay soils are not suitable for re-use as structural fill. If construction and fill placement are to occur during wet weather conditions or on wet , subgrade soil surfaces, we recommend stru.ctural fill material be utilized that is suitable for wet weather construction. A suitable material is "Gravel Borrow" as presented in Section 9- 03.14 of the Washington State Department QfTransportation (WSDOT) Standard Specifications (or Road, Bridge, and Municipal Construction (Standard Specifications). However, the gradation should be modified so that a maximum 5 percent by 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. Ea,ch lift should be compacted to a firm, non-yielding condition and t6 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. TABLE 2 Recommended Structural Fill Compaction Beckett Point, Jefferson County / Fill Location Required Minimum Relative Compaction 1 Under Roadways: Upper 2 feet Greater than 2 foot depth Landscap.e Areas The Point Upland 95 percent 90 percent 90 percent2 85 percent 1 Expressed as a percentage ofthe 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. GHA Assessment Beckett Point Wastewater Treatment System Jefferson County, Washington , Project No. 041136A-5 June /6, 2005 Myers Biodynamics, Inc. /5 of I7 ..._ ^,~2:::____ f 'jr :.'<',.. :'.'-,', i: :i'~:~"",,:':, ,:" '0: '''3~::.:''._'''", . '. I. 10.3 Uplift R~sistance Buried structures on The Point will likely be located partially below the tidally influenced groundwater fevels, 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 a total soil unit weight of 120 pcf and a submerged unit weight of 58 pcf for granular soil backfill above buried structures. This assumes backfill is placed and compacted as structUral fill. . 10.4 Drainage Control of site surface water is ~n 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 locatiort(s) at the base of the steep coastal slope. This includes new access roads and other impervious surfaces in the treatment system 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 discharge pipe. 10.5 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 soils 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 revegetated as soon as possible following construction. GHA Assessment Beckell Point Wastewater Treatment System Jefferson County, Washington \ Project No. 041136A-5 June 16, 2005 Myers Biodynamics, Inc. ?6 of 17 l'Y ....~.~=.~,:'!~'.F~~." . 11.0 Closure I This report was prepared for the exclusive use of Parametrix, Inc. and the project design team for specific application to the geologically hazardou~ and frequently flooded areas associated witlithe Proposed Beckett Point Community Wastewater Treatment System in Jefferson County. The data and report conclusions and interpretations sqould 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 conclusions 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 retained to review our report if: I) there is a substantial lapse of time between submission of this report and the start of construction; 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 . :ecommendations considering the time lapse and/or changed conditions. We appreciate the opportunity to provide ypu with geotechnical engineering services. Please cont~ct our office at your convenience should you have any questions or require additional servIces. ~incerely Yours, MYERS BIODYNAMICS, INC. JNM:esw :.. GHA Assessment Beckett Point Wastewater Treatment System Jefferson Counly. Washington 17 of 17 Project No. 041136A-5 June 16. 2005 Myers Biodynamics. Inc. l'Y "'?J'('U'_'M'"";~.. e:":- ....."...,... ......~ ..', . . ( APPENDIX A . . ._,...,.l~ Jd...' . '1--- . '" cJlf' . ........... "S'"-~":''''.',''i,.",~~~_,......." , I : 1~" l' ::. ~ ~ A ~,~ "t) ~ 's: e Cl.. " ~ ~ ~ ~lC) .s~ &~ ~~ ~"l;) <l>~ ~.g ~8 "0':: ~~ 2~ c:~ <IS itS - ~ f Iii b z \ , , , \ , ().\ ~~\ ~\' ()o\ \ " ~. Q) - .... CIS G> ~.S! s~ CIS C'l E II 'x .c o u ... C 0. .- c...... oct c.. <( :s . ~ z (3 :> ~ ;.. ~ 'J .~ S ~~ . . 2 w a: :> " Ii: ~ en <3: LU a: <3: en ::) o c a:Z <(<3: N..J <(0. ::tILl ~!::: ..Jen <( o - " o ..J o LU " o l() (\J I- Z w ~E (f)(1) (f)... W0 ~~ <(... C (f)C.s <(~g>> W ... .- a:ca.t: (1)0 <(F ca (f)1...~ ::J(1)>\ 0...... ~C ~(1)g <((;)(.) 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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' explorations are presented on the logs attac,hed to this Appeiidix. The explorations were located in the field ,by tGlping or pacing relative to existing physical site features. The ~pproximate 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 J?1ethod used. . . A licensed geotechnical engineer/engineering geologist from Myers Biodynamics was I 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 Ptactice 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 the results of laboratory testing. Boring Explorations Borings B-1 through B-:-5 were drilled with a trailer-mounted, DeepRock X24 hollow:.. stem auger drill rig on March 24 and 25,2005 to depths of approximately. 69.1,60.5, 20.0, 19.0 and 19.0 feet; respectively. Boring logs B-1 through B-5 are presented as 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 2-112 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 freCly 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. GHA Assessment . Beckett Point Wastewater Treatment System Appendix A Jefferson County, Washington Project No.041136A June 16, 2005 Myers Biodynamics. 1nc. ..JO:. Jey to Soil Exploration Logs _ample 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 Fine-Grained Soil Density SPT* Soil Consistency 1;~~~\~~f:~:;;1i;Kjf::~::1;~!lii~~~&:i@!;;~&i"i:1~;J~~:~~:{::f;i: ; ,'. , Medium Dense 10-30 Medium Stiff .~:~~:~se: ":::~~~9:,:!r:ij:Y j~;'ffIj'~;i~G"':; . .;":: -.: ::.;:~_;:;::::: ::~~:_:::;:;::;:: :~~:-:;:: ::>:'; :::';~::::/~ ::,~ <.:~:~_::-:\;'::~: ::,~:\~8i((-:;::!:;_::~,:i::X:':~>::\~:: :;:.:;\;: :/,:-;~;: :,:':l#~.ntft.~; .f/:,::; :': ;):--:~:~: ;'; :~::: :::<- ., .Standard Penetration Test measured in blows per foot SPT* 0-2 :~~1i{( 4-8 , ";j;<:," ,E!.7;J;~: 15-30 >$Q'" Estimated Percentage 0-5% ""$~'1~'Xlr'" 12-30% Minor Constituents Trace. ~lig1Jit!k.,.(~(ltf1"g~ii?JJt"f!t~;) Clayey; Silty; Sandy; Gravelly Y~'fY{r-?i,!f~:-?~Q~J1I~tl;tiJi:.,"" .Not identified as a Minor Constituent Moisture Some perceptible moisture, probably below optimum ~Xt Much perceptible moisture, probably above optimum Laboratory Test Symbols GS Grain Size classification . Pocket Penetrometer (compressive strength in TSF) 'T:Q:l1f$,~~,i~~11'flett1'$,tf.(f.ngifrl'nJ)$ff}< ...... . ....... Consolidation . ......i7t'~t~l~j;{fJ~iQg~~~liqijt~q.t)h~t~iati#/:<................... Triaxial Consolidated Undrained .' "<'.T:~~l!l,,/f$.~~'&~lii;t~t~(i'jJ)rnio~di""'" UfI~?flfin.~.~ 9?mpression m~i~~~$fj~~r,/" . Permeability . ..............C,~Ii!prniijjf?(jjl#tin~t{ati() Nfoisture, pe,nsity Curve PP TV CN TV#' TeU rCD;.. au D.S, K CBR MD l~ . J. 4." "'<'" '5Q"- iOO~...,." Unified Soil Classification System 'O~ ~.! .c:'" ~~ i~ ~~ Vie: "'.l! ~-:: -g~ .~.!! r~ ~.~ "'~ 0" uE .... '0,"", Q) ""Q).~ ~ e>'" c:~~ J!l.!Il.!!l ""<:'" e~'l' 013 . ~~~ k31~ ~~~ gu.;: ~ .<: ~l <3Zl 1:>.!!l t::t: ;::.s ~~ 5- :=:; ... ,<I) ~~ .,e ts.':'~ -g:~ ~ .,-.c: ~~~ &i.~ .... Highly Organic Soils ~~.~ 'iQt\:lUJ ~~~ ~.!:e'~ ~<:'l' e.Sl . o13~ ~e! ,~CIl lI)":::' "tj~t: <:.,., <i'!8s !!! '0 .~ ....'" Oic .c:c <:<\1 s~ eCll 0:::' ~<: '. ., ~-s 0'" fIl.!!l -g~ .5 .. ~~ d,.2! .5 ~ 1..:., EO ~ !!!g f:!....w <!)o<l) <:~~ a!<:=. (3 '" ~:!! !!!u: d~ ~ ~g as....(i)' CIlO<l) ~~~ c3~ S 1;", ~.~ <:LL <i'! Observation Well Symbols Bentonite seal Ground Water Level: date of reading ATD: At Time of Drilling 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 3.0" dia. Thin Wall Tube Sampler 8f7192 ~ .' ". .. ATD~ ::.:. .:: :: .:: 8-1 8-2 8-3 P = Sampler pushed .No sample recovery Test Pit Symbols ~M> Myers Biodynamics Inc. Romng Bay Mercantile Building' 11254 Sunrise Drive BaInbridge Island, Washington 98110 TEL: 2061842.6073 FAX: 2061842-3797 eORING LOG B-1 This log applies only to boring location etthe time of driJJlng. Subsurface conditions may differ at other loCations and may eJso change over time. This log is a simplified interpretation of the actual conditions. Beckett Point z (J) 0 ~ t; Ii: z ~ UJO 0 (J) ~ Jefferson County, Washington ex: I- UJ ~ UJ > ::)z I- .z ...J ex: I-UJ ex: I- > a.. 3: UJ...J (J)I- UJ a.. UJ :: 0 (J)...J -z :c UJ ...J <( ...J DESCRIPTION mUJ 00 b c UJ (J) m 03: ::0 Fill - disturbed soil from gravel pit operations -- -- -- 19 - - S-1 41 23 5 204 -- -- I--- 14 -- 20 S-2 22 10 199 -- -- -- 31 -- S-3 33 50/3' 15 194 -- -- -- -- ] 18 S-4 50/6" 20 189 -- -- . -- -- 27 S-5 38 ~~ .n 39 - - - - - - - - - - -- ,.... Very Gravelly Fine to Coarse SAND; very dense, gray brown, moist to vel}' moist, trace slit rough drilling abundant gravel less gravel based on drilling action Slightly Gravelly Fine to Coarse SAND; dense, gray brown, moist to very moist Vel}' Gravelly Fine to Coarse SAND; very dense, gray brown, moist Gravelly to Very Gravelly Fine to Coarse SAND; very dense, gray brown, moist, trace silt in bottom of sampler ,1J-"d....__ 30,. ,38':0' Gravelly Fine to Coarse SAND; very dense, gray brown, moist DATE DRILLED Myers Biodynamics inc. BUS: 206 842-6073 Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 FAX: 206 842-3797 eORING LOG B-1 cont. This log applies only to boring location at the time of drlJling. Subsurface conditions may differ at other locations and may aJso change over time. This log Is a simplified interpretation of /he actuaJ conditions. Beckett Point Z C/) 0 -;R. l- t: Z ~ WO C/) 0 C/) !e Jefferson County, Washington a: I- W ~ W > ::JZ I- ::C -I C/) a: I-W a: I- > Q. s: W-I C/)I- W Q. W :E 0 C/)-I -z J: W -I c:( -I DESCRIPTION I mW 00 l- e W C/) m oS: :EO 0 -- -- -- 50/6' --S-6 30 179 -- -- -- -- S-7 50/6" 35 174 -- -- -- -- S-8 34 50/6" 40 169 -- -- -- -- 15 a S-9 28 45 164 b 37 -- 16 S-10 27 41 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 ., ..JJ:~ ....~"._ 3L.."..."'~",,,. SILT to Vel}' Fine SAND; vel}' dense, gray brown, moist, granularnon-plastic grading to Fine SAND;vel}' dense, gray brown, moist, no soil staining, faint parlings DATE DRILLED Myers BiDdynamics Inc. BUS: 206 842-6073 Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 FAX: 206 842-3797 ~ORING LOG B-1cont. t: ~ :i ~ I- > 0. W W ..J C W en W ..J 0. :: <( en 24 - - S-l 19 28 55 154 -- -- -- 38 -- -12 50/4" 60 149 -- -- -- -13 01 -- 1/2' 65 144 -- -- -- S-l 29 -- 50/1' 70 139 -- -- This log appHes onJy /0 boring Jocstion at the time of driJJing. Subsurface conditions may differ at other loCations and may also change over time. ThJs log is a simpHfled Jnterpre/at/on of the actuaJ conditions. io en 3: o ..J a:a Beckett Point Jefferson County, Washington DESCRIPTION --------- Fine SAND; dense, gray brown, slightly moist, trace coarse sand, slightly gravelly at top of sample Slightly Gravelly Fine to Medium SAND; vel)l dense, gray brown, slighlty moist, trace coarse sand Very Gravelly Fine to Coarse SAND; vel)l dense, gray brown, slightly moist, trace silt rough drilling - increased gravel Vel}' Gravelly Fine to Coarse SAND; very dense, gray brown, slightly moist Bottom of boring at 69. 1 foot depth It?l 3~.',>3f Z o ~ > 0: W...I en..J a:aW 03: en ';/l. t; WO VI 0:1- W ::::lz I- I-w 0: !!l!z ~ 00 1-0 ::0 Myers Biodynamics inc. . 2 842-6073 Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 842-3797 DATE DRILLED ~ORING LOG B-2 This log applies only to boring 1oCa/ion at the tJme of drllJing. Subsurface condltfons may differ at other locations and may also change over time. This log Js a simpJified interpretation of the actuaJ condnions. . z (/) Beckett Point 0 ~ In z ~ UJO Ii: 0 (/) ~ Jefferson County, Washington a: I- UJ ~ UJ > ::)z I- ~ ..J a: I-UJ a: ~ > Q. == UJ..J (/)1- UJ UJ :5 0 (/)..J -z J: UJ ..J ~ ..J DESCRIPTION mUJ 00 l- e UJ (/) m o=: :50 0 Grasses / trace Topsoil over - - - - - - ,.- - - - 6 S-1 7 SIi9hfrv Gravelo/, Fine to Medium SAND; medium dense, yellow brown to red brown, 5 69 8 slighty moist, race coarse sand, trace organics (1/4- Inch root) - - - - - - - - Slightly Gravelly Fine to Medium SAND; dense, gray brown, slightly moist, trace 10 S-2 17 coarse sand . 10 64 20 - - - - - - - - 17 Slightly Gravelly Fine to Coarse SAND; vety dense, gray brown, slightly moist S-3 40 15 59 33 - - rough drilling, increased gravel content - - - - - - J ~0/5" Slightly Gravelly Silty to Vety Silty SAND to Sandy SILT, vety dense*, gray brown, 5-4 moist 20 54 *Sampler bouncing on pravel - - rough drilling at 2 foo - depth .J~ - - 31' 33 ," ',0',,;,' ,.hr., ',"'" - - - - 117 ~---------- S-5 Vety Fine SAND to SILT; vety dense, gray brown, slightly moist, faint partings, ^~ ,^ 29 granular non-plastic --~v DATE DRILLED Myers Biodynamics inc. Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 - 797 eaORING LOG B-2 cont. t: z = 0 en ia :f !ci UJ ...J I- ~ D. 3: D. ~ 0 UJ ...I <( ...J C UJ en m ,0 .... 8-5 J 49 -- -- -- 16 a 27 3044 S-6 b 28 -- -- ~- . ~- 25 a S-7 38 35 39 b 47 -- -- -- -- a 19 S-8 27 40 34 b 37 -- -- -- -- 17 8-9 28 45 29 29 -- -- . -- -- 1~~16 -'_ 8-1 34 ~- This Jog appRes only /0 boring location at the time of dri"/ng. Subsurface ccndI/ions may differ at other Iocat/oils and may aJso change over lime. ThJs Jog Is a simplified interpretation of the ac/uat conditions. Beckett Point Jefferson County, Washington DESCRIPTION Vel)' Fine SAND tq SILT; vel}' dense, gray brown, slightly moist, faint partings, granular non-plastic Vel}' Fine S~ND to Siltv Fine SAND; vel}' 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 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 Vel)' Fine SAND to SILT; hard, gray brown. slightly moist, granular non-plastic, fine sand partings, trace iron staining in sand parting SILT; hard, gray brown, slightly moist, massive f------------- Fine SAND; vel}' dense, light gray, slightly moist l?-: 3tf .:3K...... Fine SAND; vel}' dense, light gray to gray brown, slightly moist grades to silt in a 2-inch zone at 50 foot depth z o !ci > 0: UJ...J en...J mUJ 03: en ~ t; UJO UJ 0:1- I- ::>>ffi 0: 1-1- UJ ~z :J: 00 01- ~o DATE DRILLED 2405 74:t AGURE SH OF A-2 2 3 PROJECT N'b41136A-5 Myers Biodynamics inc. Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 thORING LOG B-2 cant. . Beckett Point z (/) 0 ~ ~ t: z !:i WO 0 (/) to . Jefferson County, Washington a: I- W !:i W en > ::)z I- :i ..J a: I-W a: I- > 0- 3: W..J (/)1- W 0- w ::a 0 (/)..J -z J: W ..J <( ..J DESCRIPTION IX!W 00 I- q W (/) IX! 03: ::au 0 vV <::.. s-15 J 50 Slightly Gravegr Fine SAND; vel}' dense, light gray, slightly moist, trace medium to coarse san - - - - ~ - - .- - - 21 S-11 33 Fine SAND; vel}' dense, Ii!f!:t gray to gral brown, sightly moist 55 19 1-inch Silty Fine SAND to ine Sandy S T moist zone at approximately 40 50-foot depth - - - - - - - - 21 18-12 40 Fine SAND; vel}' dense, light gray, slightly moist 60 14 50 - - Bottom of boring at 60.5 foot depth - - - - - - 65 9 - - - - - - - - 70 4 - - - - - - jc~ - - 3$,.. .'. This log appJies only to boring location at the time of driJJing. Subsurface conditions may differ at other loCations and may also change over time. This log is a sJmplifled interpretation of the actual ccndJ/ions. DATE DRILLED SH OF 3 3 PRO.JECT N'041136A-5 Myers Biodynamics Inc. Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 .ORING LOG B-3 This log appJles only /0 boring Jocatlon at the time of driRing. Subsurface conditions may differ at other locations and may aJso change over time. This log is a simplified Interpretation of the actuaJ conditions. Beckett Point z en 0 ~ t; t: z ~ WO 0 en (g Jefferson County, Washington a:~ w ~ w en > ~ :i' ..J a: :::::Iw a: ~ > a. 3: W..J t;~ W w :!l 0 en..J -z :t: w ..J c:( ..J DESCRIPTION IIIW 00 ~ c w en III 03: :!lU 0 Gravel surfacing over -- Fill?: Sandy Coarse Gravel and cobbles in cuttings ~- - - - - - - - -- Myers Biodynamics inc. -- 10 ~- S-l 15 16 -- 5 1 5 S-2 10 -- 9 -- 10 -- S-3 9 6 -- 10 -4 24 -- S-4 16 21 -- -- 13 S-5 20 36 -- 15 -9 8 S-6 23 -- 30 -- 12 -- 23 S-7 36 -- 20 -14 ]21 S-8 50/6' . 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) ATD ~ Gravelly Fine to Coarse SAND; medium dense, gray brown, wet ----------- 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 Gravelly SAND; very dense, gray brown, wet Bottom of boring at 20 foot depth ..' . Ld- 31)"'..., .,'77 , '" ". 3~~. DATE DRILLED Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 6.:t eBORING LOG 8-4 This log appJies onJy to boring Jocstion at the time of driJJing, Subsurface conditJons may differ at other locations and may also change over lime. ThJs log Js a simplified Jnterpreta/ion of the ac/uaJ conditions. Beckett Point z tJ) 0 '#. t; z ~ Ii: 0 tJ) ~ Jefferson County, Washington WI- W ~ W > D:z l- X ..J D: ::)w D: S: :> a. 3: W..J 1-1- W W :E 0 tJ)..J ~z :J: W ..J 0( ..J DESCRIPTION COW 00 b c W tJ) co 03: :EO Trace grasses over -- Fill?: Slightly Gravelly Fine SAND cuttings with occasional cobbles -- - - - - - - - -- -- 4 -;-- S-l 16 17 -- 5 1 8 S-2 12 -- 8 -- 4 -- S-3 3 5 -- 10 -4 5 -- S-4 5 9 -- -- 11 S-5 7 8 -- 15 -9 10 S-6 12 -- 11 -- 12 -- 12 S-7 14 -- 20 -14 -- -- .-- -- 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? - .- Vel}' 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 Medium to Coarse Sandy GRA VEL; medium dense, gray brown, wet gravel Slightly Gravelly Fine SAND; medium dense, gray brown, vel}' moist to wet rough drilling occasional gravel Gravelly Fine to Coarse SAND; medium dense, gray brown, wet occasional gravel no recovel}' except gravel piece in bottom of sampler Bottom of boring at 19 foot depth I~ 31 3f DATE DRILLED Myers Biodynamics inc. Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 FIGURE SH OF A-4 1 1 6.:t PROJECT NC041136A-5 .ORING LOG 8-5 This log appJies onJy to boring location at the tJme of drilling. Subsurface conditions may differ at other loCations and may aJso change ovet time. This leg is a simplified interpretation of the actual conditions. . - Beckett Point z en 0 ~ t; Ii: z = ~ WO W 0 en ~ Jefferson County, Washington a: I- I- ~ W :> :::lZ ::i ..J a: I-W a: h: :> Do 3: W..J en I- W ILl :E 0 en..J -z :J: W ..J <C ..J DESCRIPTION mW 00 b c ILl en m 03: :EO Grasses I trace topsoil over - - - - a 2 FILL: Gravelly Silty SAND; loose, brown, vel}' moist - - S-l 3 Organic SILT; medium stiff, dark brown, vel}' moist - - b 4 - - 5 1 ATD ~ 4 groundwater at 5.5 foot depth (9:35 am) - - S-2 4 Gravelly Slightly Silty SAND; loose, brown, wet 4 - - 6 Gravelly Fine to Coarse SAND; medium dense, gray, wet - - 5-3 7 8 - - add drilling mud 10 -4 6 S-4 10 Gravelly Fine to Coarse SAND; medium dense, gray, wet, gravel in bottom of sampler - - 9 - - - - 10 S-5 15 Gravelly Fine to Coarse SAND; dense, gray brown, wet, trace silt, trace shell 16 fragments - - rough drilling 15 -9 10 5-6 15 Gravelly Fine to Coarse SAND; medium dense, gray brown, wet, trace silt, - - 12 trace to few fine shell fragments - - rough drilling 18 - - 12 Gravelly SAND; dense, gray, wet S-7 26 - - Bottom of boring at 19 foot depth 20 -14 - - - - - - (r - - :]t" $- DATE DRILLED FIGURE SH OF A-5 1 1 PROJECT NO 6.:t 041136A-5 Myers Biodynamics Inc. Rolling Bay Mercantile Bldg. 11254 Sunrise Drive ELEVATION (FT) Bainbridge Island, WA 98110 . 7 7