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5400-5606 Pacific Avenue -2 - 4 October 2004
<br /> Stockton, San Joaquum County
<br /> • camtamnmant distribution in deeper aquifer zones Also,there appears to be some recent plume movement
<br /> in shallow groundwater to the north and east of 5606 Pacific Avenue
<br /> e 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 contammants,reporting the
<br /> cbemical reactions in molar concentrations
<br /> 1 If metals of concern(Cre',etc)are not detected,or general mmerals (SO4,etc) are not present at
<br /> levels favorable for adverse reactions in saturated soil,then submit a Pilot Study Workplan with the
<br /> GE Report Note that all Pilot Study analytical detection limits 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 monitor groundwater during the Pilot Study for the know petroleum hydrocarbon
<br /> contaminants and general parameters(dissolved oxygen,pH,specific conductance,temperature)
<br /> 2 If metals of concern(Cro%etc.)are detected, or minerals of concern(SO4,efe)are detected at
<br /> potentially harmful levels,then include a Workplan for a Bench Scale Test(BST)with the GE report
<br /> The BST should show which contarmnant(s)are produced and whether the produced contaminants)
<br /> will persist after termination of oxygen injection,using the graphed slope of the declizimg
<br /> contammant(s) concentrations versus time to calculate a decay rate(tune to revert to non-detect) If a
<br /> contammant(s)is produced and persistent,provide that information in the BST report for my
<br /> evaluation If contammant(s)produced are not persistent,provide Workplan for the Pilot Study with
<br /> 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
<br /> evidence
<br /> o By 15 December 2004,begin the Pilot Study During the Pilot Study phase, groundwater sampling and
<br /> analyses will be conducted, at a minimum,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 proposed
<br /> decay rates,if applicable If a BST is not required prior to the Pilot Study,then, at a mimmum,analyze
<br /> at least once before and 1 hour after startup of ozone injection
<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 /> the effectiveness of ozone injection
<br /> You may call me at(916)464-4615 for questions or additional information
<br /> iI Ai&
<br /> AMES L BARTON,R G
<br /> Engineering Geologist
<br /> cc_ Mr Mark O-ens, LIST Cleanup Fund, SWR[-'B,Sacramento
<br /> Mr Mike Infurna, San Joaquin County Environmental Health Division, Stockton
<br /> Ms Jill Tracy,Esq,UNOCAL, Brea
<br /> Mr Ben Hennmgburg,ENSR International, Sacramento
<br /> -MT-Gary-Hall, GHH Environmental, Auburn
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