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• page 2, 205 N. Center Street interim remediation method at a similar site with success, or has other information to support this remedial alternative, please submit it for PHSIEHD review. In addition, there is concern that tertiary butyl alcohol (TBA), which has a California State Department of Health Services (DHS) action level of 12 parts per billion (ppb) in water, is the predominant breakdown product of MtBE. Remediation systems that propose only to breakdown MtBE without removing it from the subsurface environment should be avoided until further information about its eventual environmental fate is available. PHSIEHD recommends that if ARCO wishes to pursue interim remediation at this site they consider a system or method that will work to prevent further plume migration as well as remediate the site. PHSIEHD has received three Quarterly Groundwater Monitoring Reports for this site. The first monitoring event took place on February 16, 1999, following the development of the newly installed wells. According to the report, the wells were developed by surging over the length of the screen interval and by purging ten casing volumes of water. The two subsequent events took place on June 1, 1999 and September 24, 1999. At these events, grab water samples were collected from the first encountered water. The wells were not purged tr move the of groundwater sampling at well casing. PHSIEHD has not approved the use of the no-purge metthis site. Both the California State Water Resources Control Board, as referenced in the Leaking Underground Fuel Tank(LOFT) Field Manuel, and the United States Environmental Protection Agency (EPA) recommend that monitoring wells are purged until a minimum of three well volumes are removed, or until measured parameters of pH, temperature and conductivity of the discharged water stabilize to +1-10% over two successive well volumes. In order to evaluate if the same analytical results are obtained from samples using the no-purge method and the purge method, ARCO may want to collect a water sample prior to purging and then after purging from each well, have the samples analyzed and compare the results. If ARCO can show through several sampling events that the same results are obtained, PHSIEHD will allow the no-purge sample collection method at this site. Please proceed with securing encroachment permits from the City of Stockton for the off-site wells and submittal of a well permit application and required $89.00 fee to PHSIEHD for each parcel of land on which borings or wells are proposed. Please notify PHSIEHD at least two working days in advance of all scheduled field activity. If you have any questions or comments please call Lori Duncan at(209)468-0337. Donna Heran, RENS, Director Environmental Health Division U�u a " Margaret Lagorio, REHS Lori Duncan, Senior REHS Supervisor, Unit IV LOP/Site Mitigation Unit IV cc: Marty Hartzell, CVRWQCB Rusty Benkosky, SECOR Kitty Walker, City of Stockton Redevelopment Agency Bill Brown, Daley & Heft