SITE INFORMATION AND CORRESPONDENCE_FILE 2

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San Joaquin County DIRECTOR Donna Heran,REHS °W Environmental Health Depnartment M ASSISTANT DIRECTOR � 600 East Main Street Laurie Cotulla,REHS I� Stockton, California 95202-3029 PROGRAM COORDINATORS 1 ItSYY� Carl Borgman,REHS J. Mike Huggins,REHS, RDI Website: www.sjgov.org/ehd Margaret Lagorio,REHS �i oR phone: (209) 468-3420 Robert McClellon, REHS Fax: (209) 464-0138 .teff Carruesco,REHS, RDI Kasey Foley,REHS STEPHANIE FURGAL TICT Z 'I CHEVRON ENVIRONMENTAL MANAGEMENT COMPANY 6001 BOLLINGER CANYON RD ROOM K2050 SAN RAMON CA 94583 RE: Former Unocal #0187 437 E. Miner Street Stockton, CA A meeting was held at the offices of San Joaquin County Environmental Health Department (EHD) on August 13, 2007, to discuss the above referenced site. Attending the meeting were you representing Chevron, Kent Baugh and George Forsythe representing ENSR Corporation, and Margaret Lagorio and Nuel Henderson representing the EHD. On October 9, 2007, ENSR sent"Meeting Notes" by electronic mail to the EHD. The EHD provides the following summary of the meeting and other comments. Chevron/ENSR proposed destruction of wells in "high-traffic areas"that they consider to be unsafe to sample due to traffic hazards. All the wells discussed are in City of Stockton right-of- ways (in the sidewalk or on the edge of the street next to the sidewalk). The EHD discussed potential measures that could be taken to mitigate hazards concerns such as traffic control or having two personnel at the well site so one can sample and the other can watch for their safety, or if justified by site data, reducing monitoring frequency of"riskier" wells. The EHD also noted that sampling wells at operating gas stations also has traffic hazards due to vehicles entering and leaving the station, backing up etc., but contaminated sites must still be investigated. The EHD emphasized that the extent of the contamination must be demonstrated by monitoring wells where the groundwater samples collected have no detection of the contaminants of concern. The EHD pointed out that since it is difficult to obtain permission for placement of monitoring wells on off-site private property; monitoring wells are commonly placed in public right-of-ways. The position that a well is unsafe to sample simply because it is located in a sidewalk or on the edge of a street next to the sidewalk is not acceptable to EHD. Objective criteria for establishing that the risk is unacceptably high should be presented that demonstrates the location of the well to be unsafe for sampling (i.e. City of Stockton statistics on traffic accidents at the location or a casualty risk model). The EHD also mentioned that some of these wells might be used for definition of the groundwater plume at Chevron's 242 N. Sutter Street, Stockton site. The EHD discussed this subject with the Central Valley Regional Water Quality Control Board (CVRWQCB) prior to the meeting and the CVRWQCB stated that if the well could be relocated to private property, then the existing well could be destroyed. The CVRWQCB emphasized that prior to site closure all wells had to be sampled so unless a well had been replaced it should not be destroyed until closure of the site had been agreed upon. Chevron/ENSR suggested that there was a problem with monitoring wells U-16 or U-17. The EHD has reviewed the groundwater sampling data sheets for these wells. It appears that in May 2006 the sampler encountered an obstruction in well U-17 at about 90 feet. Since that time the sampling data sheets for U-17 note an obstruction at 96 feet to 102 feet. According to the