SITE INFORMATION AND CORRESPONDENCE

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{ � r VNWW SWRCB Workshop Hearing November 3 1.999 Mr. Chairman, Members of the Board My name is Laurie Cotulla, I am with the San Joaquin County Public Health Services Environmental Health Division which is the Local Oversight Program agency for the case before you. I am not sure if you have a copy of our August 12`h letter to Mr. Anton regarding this proposed action. If not, I have copies for your perusal. My comments today will specifically address several of the assertions made in the staff report. • The staff report repeatedly asserts that the groundwater in the vicinity of the site is generally of inferior quality and not viewed by local purveyors as a source of drinking water, that municipal wells in the area are generally constructed with annular seals with depths of 150 to 200 feet, and the "shallow" groundwater at this site is not hydraulically connected to the deeper aquifer. • There are 4 municipal wells within 3,000 ft of this site. None of these wells have annular seals deeper than 96 ft and in fact the California Water Service well #4-02 which is less than 2,000 ft from the site is only sealed to 72 ft. All of these municipal wells are constructed with gravel packs that extend the entire depth of the well, allowing unrestricted vertical movement of groundwater below the annular seal. Three of the four are currently active and are capable of sustained pumping rates of 450 to 900 gallons per minute. • The first well construction ordinance for San Joaquin County was enacted in 1971 and required a minimum annular seal depth for domestic water wells of 50 ft. In 1992, that standard was revised to 100 ft. The majority of municipal wells in the vicinity of this site were constructed prior to 1971 and as the chart for City of Stockton wells indicates, most wells have shallower rather than deeper annular seals and are gravel packed. + In addition, we would like to see the data mentioned that indicates that the groundwater monitored on this site is confined and not hydraulically connected to the lower aquifer. In speaking with the Office of Drinking Water field branch engineer in Stockton, he was amazed that anyone would make a statement that there is no hydraulic connection between the water bearing zones in this area. + The only way to ensure complete removal of lingering, residual, detectable concentrations of petroleum constituents in the site groundwater would be to excavate thousands of cubic yards of soil. If complete removal of detectable traces of petroleum constituents becomes the standard for UST corrective actions, the statewide implications would be enormous. • First of all, we do not consider 130,000 ppb TPHg and 9,700 ppb benzene in groundwater at 50 to 60 ft below ground surface to be trace amounts. • Secondly, this site has already been shown to be amenable to soil vapor extraction so why is excavation the only corrective action mentioned.