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Stantec Work Plan for Vapor ProbeDestruction, Well Destruction;and Well Installation ARCO Service Station No.2186 October 14,2008 be set within the annulus of the auger.Jhe annulac-space between the:inner diameter of the auger and the outerdiameter of the conductor casing will be filled with neat cement and/or grout via tremae 4 pipe from total depth to`12-inches from the surface. ;The grout will be given.at least -116' rt toxo cure, after which, a drill rig equipped with an eight-inch:diameter, continuous flight, hollow-stem f auger will be used to advance MW71 D from 65 ft bgs to 85 ft bgs down the inside of the conductor _ _ casing. . _� �. .,.:. .. s � �-w._ During advancement, soil samples will be collected at-five-foot intervals using a--steel-.-split-spoon sampler driven approximately 24:inches using a 140-Ib hammer that is dropped 30'inches.-Ari attending geologist will log cuttings and sample in accordance with American Society for Testing and Materials (ASTM) D-2488 —.Standard Practice for.Description and'Identification�of Soils Manual l- Manual Procedure) under the direction'of a State of"California 'Professi a['Geologist or Professional Engineer. Soil cores will-be screened in the_field for the presence of volatile organic compounds using aphoto-ionization detector (PID). Alf down=hole drilling equipment will'be decontaminated with high pressure steam following the acompletion of each soil boring.Down-hole. sampling equipment will..be__dec_o_ntaminated betweensamples using an Alconox detergent solution` and a tap water rinse. The wells will be constr -' ch diameter,flush-threaded, schedule 40 poly vinyl chloride. (PVC)well casing with.,20 ft of 0.020-in6fi:factory-sl6tted well screen set at deptlis`of 35 to 55-ft bgs (MW-1 R and MW-31R)ans(MW-,1 D). A sand filter pack will be placed in'the annular space surrounding`the entire screened interval,-arid will extend approximately,one-to_two ft above the screen.interval. -A two to three-foot thick bentonite annular seal will be+placed'aljoVe the,-filter pack and will be hydrat4e he remainder of the annulars pace will be filled with neat cement and/or grout from the top of the}bentonite seal to within 12.inches of the surface:" The well will.be secured'' v with a locking well cap, and completed with a watertight traffic-rated_well box installed at grade: - 2.5 Soil Sample Analysis Soil samples selected for chemical analyses will be contained in two-inch-diameter by six-inch-long brass or stainless steel sleeves,which will then be sealed on each end with Teflon tape and plastic end caps. The soil samples selected for chemical analyses will be based on visual observations -and PID measurements. The selected samples will be placed on ice in,an insulated cooler until relinquished, under documented chain-of-custody control, to a California certified analytical laboratory. Selected soil samples will be analyzed for.GRO by Environmental Protection Agency (EPA) Method 8015B(M)and benzene, toluene,-.ethylbenzene;xylenes, MTBE, di-isopropyl ether, ethyl tert-butyl ether,tert-amyl.methyl ether,-tert-butyl..alcohol; ethanol;, 1,2-dichloroethane,}and 1,2-dibromoethane by EPA Method 8260B.-_ `" T . .. 2.6 Well Development Following well installation,the groundwater monitoring well seals will be allowed to cure for at least 48-hours,prior,to development. Development (to clean the filter pack and stabilize the aquifer materials around the slotted.well casings)will be accomplisIHed by rigorously surging the—.well over the length of the screen interval:with-a vented surge:block .followed fbyr.bailing.to,remove accumulated sedimentaand by purging approximately ten casing volumes of water.. Final.purging will be performed'with either a submersible:puTp_o_r bailer, during 0fiich'time,.pH, temperature, and conductivity will be me tired at reg lar intervals: Development will be considered co:mplete.when - . .. 2186 Work Plan for Vapor Probe Destruction,Well Destruction, and Well Installation,doc 4 r