SITE INFORMATION AND CORRESPONDENCE_FILE 1

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PUBLIC HEALTH SERVICES P.4 tl1N SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH DIVISION Ernest M. Fujimoto , M.D . , M.P.H., Acting Health Officer -_ 304 E.Weber Ave. , 3rd Floor • P. O. Box 388 • Stockton, CA 9521`0388 . P �'� p4LiFOR A` 209/468-3420 � f KLYE CHRISTIE \\�J ARCO PRODUCTS COMPANY Ord, E � � 1995 2155 SOUTH BASCOM AVE STE 202 CAMPBELL CA 95008 RE: ARCO Station #548 SITE CODE: 1121 1612 Hammer Lane, Stockton CA 95207 San Joaquin County, Public Health Services Environmental Health Division (PHS/EHD) has completed review of the 'Interim Soil Remediation Plan and Well Installation Workplan Associated with the Removal and Replacement of the Underground Storage Tanks and Product Delivery Lines " dated October 5, 1995 . PHS/EHD has the following comments for your consideration . Monitoring Well Destruction and Monitoring and Vapor Extraction Well Installation The work plan proposed to destroy MW1 and possibly MW2 and to replace MW1 with MW7 and to replace MW2 with MWS should it be necessary. The work plan also proposed to install an additional vapor extraction well, VW5 . The necessity to destroy and replace the monitoring wells is to accommodate the installation of new underground storage tanks. The monitoring well (s) will be destroyed by overdrilling using a 12 " hollow stem auger. Enclosed is a copy of permit #7717 for the destruction of monitoring well (s) . The work plan included a proposal for the installation of monitoring well (s) to replace well (s) to be destroyed along with the installation of an additional vapor extraction well to remediate shallow soil contamination . Enclosed is a copy of permit #7718 for the installation of monitoring well (s) and a vapor extraction well . Please note that the site map included did not indicate the location of the proposed vapor extraction well . Prior to initiating field activities, please provide a site map indicating the proposed location of the additional vapor extraction well . Soil samples should be collected during the installation of wells to adequately characterize the subsurface distribution of contaminants. Please contact PHS/EHD following the proposed field activities to discuss which soil samples will undergo laboratory analysis. Also note that PHS/EHD should be notified 48 hours in advance of any field activity. Tank Removal and Over-excavation As per our meeting of August 8, 1995 a tank removal permit application must be submitted prior to the removal of underground storage tanks. The work plan submitted included soil sampling during tank removal and possible over-excavation. The proposal included two samples per gasoline tank which is acceptable since the tanks are all less than 10,000 gallons each . One soil sample will be collected from beneath the waste oil tank which is less than 1000 gallons. Soil samples will be collected from beneath each dispenser and every 20 feet of product piping which is to be removed . Total metals should be analyzed using EPA Method 6010 and total lead by EPA Method 7420. Should total metal levels exceed water quality standards, the Waste Extraction Test shall be performed. The work plan failed to propose the dimension of the possible over-excavation . PHS/EHD agrees that over- excavation of soil contamination is an effective remedial option, particularly at the time of tank removal . Based on a telephone conversation with an EMCON representative on October 23, 1995, PHS/EHD understands that the maximum depth would be to 22 feet and that the reason for the excavation would be to obtain relatively undisturbed soil samples. PHS/EHD recommends that soil samples be obtained by soil borings rather than by excavation . Furthermore, PHS/EHD questions the cost effectiveness of over-excavation for the purpose of soil sample collection . A Division of San Joaquin County Health Care Services