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S E C 0 R _ Work Plan for Soil Vapor Survey August 9, 2007 ARCO Service Station No. 2186 Page 5 of 8 If necessary, an access agreement will be secured from the current property owner prior to �� starting any field work. �,I Soil Vapor Probe Installation f A I • rlfi In order to evaluate the vapor-.intrusion°pathway,SECOR.,.proposes,to .installahree.permanent., a" soil vapor:sampling points (VP-1.,through VP-3) at the approximate locations shown on Figure 2. The vapor probes will be installed using 3-inch diameter hand auger. borings to a-depth_of approximately six feet.bgs. The contractor will`=coAect-.vapor samples_from-approximately 5'/2 feet below ground surface(bgs). Tygon® tubing will,be placed into each open boring with the tubing bottom at approximately_5% feet bgs.uA-6-incFilong-section_ of.9-inch-diameter, machine, slotted PVC (or.stainless`steel)rwill-extend from approximately.51/4 to 534#eetrbgs.�A filter pack co�sisting`of .#3 Monterey .Sand ,(or -the equivalent) will be placed in the annular space surrounding the entire screened"interval from:5'to-6 feet°bgs.., The sand pack;will`be covered with 1 foot of dry granular bentonite followed by hydrated�bentonite 1,foot-bgs'Each p be will then- be completed with cement and/or grout..from.•the top'of the-seal to_the.ground.surface� I f+ The tubing will be capped with a gas-tight cap (such as Swag elok®,cap) at�.the ground surface to prevent the potential for barometric pressure`fluctuations.to induce vapor transportbetween the subsurface and atmosphere. The excess length-of Tygon® tubing with the Swagelok® type valve will be-coiled up'ihi ide the well box. The probe will be secured in a watertight traffic-rated well box installed at grade. Atypical&aporprob.e.detail.-is included as Figure Soil Vapor Sample Collection Soil vapor sampling-1willrbe rperformed.,after,minirnUrn rtime.duration of one week, to allow the neat cement grout to cure, and to allow-the subsurface-vapor"concentrationsy.disturk�ec during installation,activities to.equilibrate. Vapor sampling willnot be scheduled until after a minimum of-five.consecutive precipitatiori-free days. If there are any landscaped areas-nea_ the'vapor� probes, the landscape irrigation will be turned off for five days prior to sampling. The sampling apparatus-fdrTO15-anal`sis will consisFof two-six liter-Summa-canisters-(one for vapor sample collection and:one for system purging}connected"via amanifold-f6 a vacuum gauge,,a 1/2-hour (100 to 200 ml/minute) flow regulator and a filter.-The sampling apparatus will be assembled-and'a leak check will be'performed_prior_to mobilization to the field. The leak check will be performed'by cl6sing the=system ai the down-hole side of the filter d-opening the valve`on:.the.purge Summa canister. -:If the negative vacuum pressureof 30 inches of.mercury (inft is.,maintained over a .fifteen,.minute period, the apparatus passes the leak crieck.-Once the sampling apparatus is"assembled in the field, Tygon® tubing ikill."be:attached to-thxe down- hole side_of the filter d connected to the Swagelok® type valve on'the soil vapor_sampling} probe T.he�apparatus will be_teak checked..again: Once�the apparatus`passes the..field.leak check, the system will;�be `purged of three system volumes-The purge time will be calculated by 4-6dding wthesvolume -of-the lerigtli�of=Tygon® .tubing-between the soil vapor probe and the Swagelok® type valve, the volume of the length of tubing between the Swagelok®.type.valve and the sampling apparatus, and the-volume 'of the_sampling--apparatus (minus-the:Summa canisters). This volume will be divided-by-the-flow-rate.of.200_ml/minute to derive the purge time.- After imer After the system purge, the soil vapor will be collected by closing the valve on thepurge-Summa' canister and opening the valve-onrthe-7samplirigT Summa canister. The sampling start time will be recorded-on,a,fieId-data-sheet wlsopropyI alcohol-(IPA)"ortheequivalent�will be used,as-a . 2186 SVI 8-07.doc SECOR International Incorporated