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Langston Is Market, 15615 Seventh Street, Lathrop, California I Work Plan-Phase II Lateral& Vertical Extent of January 10, 1996 Second Groundwater Aquifer, Revised Page. 5 34 Soil Sampling IAll soil sampling equipment will be thoroughly steam-clewedbefore and between sampling to I prevent cross contamination Relatively undisturbed soil samples will be taken at intervals of not more than 5 feet in. order to evaluate the subsurface materials, however, this sampling interval may be waived in saturated sands in which sample recovery is not possible The soil samples will be taken using a California Modified Split Spoon sampler with brass liners The sampler will be driven continuously by a wire lune hammer The laboratory samples will not have head space and will be immediately se--ea in their liners using aluminum foil or Teflon lined plastic caps The rernairma, sa.mpb will be removed from its liner to be used as an aide to the on-site geologist in lo&png the material at that depth Soil samples collected for analysis v�ill be analyzed using EPA. rriethod ('_O LOFT for � total petroleum hydrocarbons in the gasolzne range and EPA method 8020 -nr BTX&E � compounds The minimum detection hrris,a i.,ed for each analyte w ll be 0 005 mg/kg fcr BTX&E and 1 0 mg/Kg for gasolir_= Analyses wiil be conducted by Cahforiva Laboratory Services, a State-certified laboi atory in Rancho Cordova, California 35 Groundwater Sampling A travel link provided by me laboratorywill accompany the sample V1alE From the tune they are picked up from the lab to the tune they are deb,ered to the lab 'rh,s travel blank shotad be listed or. the Chain of Custody but poll be analyzed only ,f all ccntam thLe same contaminants All sampling equipment including the pump, bailer, and caoles, used by sampling personnel, will be disassembled, if appropriate, and steam-cleaned prior to coininencement of sampling These procedures will also be followed between each well, sampling point, and at the end of the sampling day De-ionized or organic-free water (also provided by the laboratory) will then be introduced into the pump or bailer as a final stage of cleaning This water will then be pumped or gently poured into sample vials to be used as pump or bailer blanks These blanks will be tested only if their corresponding samples are found to contain contaminants IImmediately prior to sampling, water levels and well depth measurements will be taken in all wells at the site Each well will be evacuated using a stainless steel bladder pump, which does not introduce air into the water column, or a Teflon bailer The pH, temperature, and electrical conductivity of the water will be monitored as the well is evacuated These parameters -will be noted on a field log Instruments calibrated to known standards will be used to monitor these parameters At least five well volumes will be evacuated from each well, and more, if necessary, until the above parameters have stabilized Wells that are de-watered before evacuation of five well volumes has been accomplished will be sampled upon eighty percent