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54GO-5606 Pacific Avenue y. -2 - y 4'October 2004
<br /> Stockton, San Joaquin County W
<br /> contammmt distribution in deeper aquifer zones Also,there appears to be some recent plume movement
<br /> m shallow groundwater to the north and east of 5606 Pacific Avenue
<br /> • By 15 November 2004, submit a`geochemical evaluation (GE)'report signed by a geochemist,which
<br /> compares the results of the soil and groundwater analyses, and thoroughly discusses the expected worst-
<br /> case scenario reactions,i e.,-100% conversion of constituents of concern into contannnants,reporting the
<br /> -cbenucal reactions mn nolar concentrations
<br /> 1 If metals of concern(Cry, etc)are not detected, or general minerals(SO.i etc.)are not present at
<br /> levels favorable for adverse reactions m,satumted soil,then submit a Pilot Study,Workplan wi4 the
<br /> GE Report Note that all'Pilot Study analy#ical detection lunits must be sufficiently low to test'the"
<br /> theories proposed in the GE Report and provide comparisons to Water Quality Objectives You will
<br /> continue to morutor groundwater during the Pilot Study for the know petroleum hydrocarbon
<br /> contaminants and general parameters(dissolved oxygen,pH, specific conductance, temperature) i
<br /> 2 If metals of concern(Cir", etc)aredetected, or minerals of concern(SO4,efc)are detected at
<br /> f
<br /> potentially harmful levels,'then mclude a Workplan for a Bench Scale Test(BST)with the GE report.
<br /> The BST should show which contaminants)are produced and whether the produced contammant(s)
<br /> will persist after termination of oxygen injection, using the graphed slope of the declining
<br /> contaminant(s) concentrations versus time to calculate a decay rate(time to revert to non-detect) If a
<br /> -r contaim:nant(s)is produced and persistent,provide that mforniatioa is the BST report for my-
<br /> evaluation If contammant(s)produced are not persistent,provide Workplan for the Pilot Study with
<br /> 4 _the BST Report containing modifications to the.Pilot Study monitoring program, specifically,the ,
<br /> frequency of analyses needed to confirm contaminant decay rates as calculated from BST analytical-- `- • I
<br /> evidence
<br /> .
<br /> Thi 14 Yl"amhov WMA I%pm-+hM Pilnt Ctniiy llimncv tl%F-Pilnf gt»riy pharra�rnmrlwatier eslmniino nnei
<br /> _ analyses will be conducted, at a mmmiuiu,immediately before startup of the ozone injection system, and
<br /> at intervals of one and 2 hours afterwards,in order to validate all contaminant(s)analyses and proposedT
<br /> decay_rates,if applicable -If_a_BSTAs not required pnor_to_the P_ilot_St dy,_thon, at a minimum,analyze
<br /> at least once before and 1 hour after startup of ozone mjection n
<br /> • Install automated data loggers in selected monitoring well(s)to record changes in dissolved oxygen,pH,
<br /> specific conductance, and temperature during the Pilot Study The test data will be helpful to determine
<br /> zv. ---'the effectiveness-of ozone mjectiori`
<br /> You may call me at(916) 464-4615 for questions or additional information I
<br /> AMES L BARTON,R G
<br /> Engineering Geologist
<br />- cc Mr Mark Owens UST Cleanup_Fund, SWRCB Sacramento
<br /> - Mr Mike Infuina, San Joaquin County Environmental Health Division,Stockton -
<br /> Ms Jill Tracy, Esq.,UNOCAL, Brea
<br /> Mr Ben Henningburg, ENSR International, Sacramento
<br /> Mr Gary Hall, GHH Environmental, Auburn
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