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Additional-Off-Site Assessment"}Work Plan <br /> RIPON FARM SERVICE <br /> F 932 East Prontage:Road- South Highway 959, Ripuon;,California F <br /> x 1.0.' 'INTR01)VCTION _ <br /> •;�M - ,.;,R � •� " :a - <br /> At the request of kipon Farm Service(RFS),Advanced GeoEn Vironri ental,.Inc (AGE)has prepared <br /> this Additional Off-Site Assessment Work Plan for additional groundwater investigation at 93'2 East '_-- <br /> _ Frontage Road - South Highway 99, Ripon; California(the site) <br /> t , _ , <br /> y: <br /> The-scope-of work includes the-advancement.ofthre'e'soil borings to delineate".the lateral extent of <br /> hydrocarbon-impacted (1,2-Zchlor6ethane: I,2=DCA)ground water ,If additional soil;borings are . <br /> - required; ,AGE will.;confirm boring. and/or. well 'locations,-,dnd construction details •with :r <br /> ,T <br /> representatives of the Sari Joaquin County Environmental Health Department(EHD)prior to drilling. r <br /> - ' The location of the site is illustrated on.Figure 1':A plan of the site;and the proposed,boring locations:_ ; <br /> are depicted on.Figure-2.: <br /> This work pl4nds prepar.6d in:accordarice with the EHD letter dated 31 July 2006 A endix A and^ <br /> Central Valley Regional Water'Quality Control Board(CVRWQCB)1,,&idelines for the investigation ` <br /> + ofunderground storage tank:(UST) -sites: t y <br /> 0.- <br /> `. REMEDIATION.PROGRESS E s, <br /> {-- S r - •Y- - g - <br /> r. - -' "r '• r _ may. _ S� <br /> L -� I�•' Zi <br /> Between December 2000 and December 2003, a.soil=vapor extraction.(SVE)-unit was operational <br /> _ at°tlie site,while an air-sparge {IAS) system was'installed'at.the.site iii August 200:1; Operation oft _ ;4 <br /> the S VE unit at the ceased in January.2004 and soil-vapor samples call"ected from the monitoring <br /> r s events during the fourth quarter of 2003,were absent of detectable hydrocarbons,therefore SVE was. <br /> not.restarted-. 4s a result-of the remediation; dissolved hydrocarbon;concentrations declined below.: <br /> detection limits in most of the-wells'and remain below the highest coricentrations detected at the°site. <br /> However;AGE began analyzing the ground,water for fuel a#ddrtives,m:October 200 1,.well after 4 <br /> .•air-_airbegan operation..The lead scavenger 1,2-DCA was detected m samples from well MW-4 w: 5 <br /> as high as•300 micrograms per liter(4g11)in June 2002 and has declined in-concentration.to <br /> -DCA wad :also detected I'n'samples from.well.-MW=211, :riortlih of.the forn3er UST area, at..' <br /> ' concentration-as high as 44:pg/l in June.2002;though it is currently non-detect.1,2-DCA was also 7. <br /> detected in samples=from.Wells MW=9 and MW-10;west of the former UST-area,at concentrations: '• <br /> y _. - r r. � <br /> as high as 78 µg/l and 73 pg/l,in--_May72005. Dissolved 1,2 DCA.concentrations at the site-have <br /> remained stable and generally declining;-however,the-concentrations are still above the DHS'"s <br /> f Maximum Contaminant Level(MCL)of0.5 µg/l in drinking water'and are undefined-west afwells <br /> - r1v1W=9 and MW-10. F - r <br /> The hydrocarbon impact to soil has been mitigated. Site background information, rncludtng details = _ _ <br /> J <br /> of;previous site assessment work is presented in Appendix B <br /> ' - <br /> 9. _A" ne4GeoEnvironmental,Inc.,} <br /> g' "- 1 <br />