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California f egional Water Qualitecontrol Board , Central Valley Region; Steven T. Butler, Actin Chair Winston H. Hickox � g Gray Davis Secreta or Environmental Sacramento Main Office Governor Protection Internet Address: littp://www.swrcb.ca.gov/-rwgcb5 3443 Routier Road, Suite A, Sacramento, California 95827-3003 Phone (916) 255-3000 • FAX (916) 255-3015 11 February 1999 Mr. Werner Sicvol BP Oil Company 200 Public Square 7-I Cleveland, Ohio 44114-2375 REVIEW OF SEVERAL DOCUMENTS, BP OIL/APPLIED AEROSPACE, STOCKTON, SAN JOAQUIN COUNTY I have reviewed fire reports prepared by Parsons Engineering Science, Inc.'s (PES): Additional Hydropunch Groundwater Sampling, Amendment to the Remedial Action Work Plan, Short Term Pumping Test, Simulation of Proposed Groundwater Extraction System, and the 1998 fourth quarter monitoring report for the BP Oil/Applied Aerospace facility in Stockton. I have no comment on the first two documents. hlv only comment on the third document is that the report should include the raw data so that the results can be verified. My comments on the remaining two documents are presented below. Simulation of Proposed Groundwater Extraction System The ground -,eater extraction and treatment system (GWETS) does not capture the leading edge of the main plume which extends beyond monitoring wells (MWs) 5, 6, and occasionally 8 in the downgradient direction. Also, there is a more dilute plume to the northwest of the facility which is not being captured by the GWETS. PES should explain how the GWETS will be modified to capture the plume northwest of the facility and the leading edge of the main plume, particularly at MW -5R whose concentrations are increasing. 2. PES has done a good job of establishing the requisite drawdowns in designated wells to establish capture of the bulk of the contamination. However, changing water levels due to seasonal changes or pumping in the area will likely affect these requisite drawdowns. Also, since the hydraulic conductivities for the groundwater regimes in GW -2 and GW -3 are based on the pumping test from GW -1 and literature values, the actual hydraulic conductivities for these groundwater regimes and the resultant capture zones may be different from those predicted by the model. PES should explain how the requisite drawdowns will be affected by these conditions and more importantly, how they will be established under changing groundwater conditions. California Environmental Protection Agency 4n1 Recycled Paper