SITE INFORMATION AND CORRESPONDENCE

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• Public Works - 3 - 27 July 2016 1810 Hazelton Avenue Stockton, San Joaquin County of groundwater impact northeast of MW-2, which has recently contained benzene and MTBE at concentrations of 6,100 ug/L and 37,000 ug/L, respectively. On 19 May 2016, Ms. Condon of the Central Valley Water Board, spoke via phone with Mr. Bill Cook of Condor and discussed the fact that lateral and vertical delineation of petroleum pollution in groundwater in the down-gradient direction was still needed, and that Sam Joaquin County will need to perform additional assessment and install additional wells subsequent to Central Valley Water Board review of a submitted NOI. In the Work Plan due 30 September 2016, please provide a proposal for the collection of an adequate number of groundwater samples to delineate the horizontal and vertical extent of impacts from the unauthorized release of petroleum hydrocarbons from the Public Works property. 7. In a phone call to Ms. Cori Condon of the Central Valley Water Board on 19 May 2016, Mr. Nuel Henderson of the San Joaquin County Environmental Health Department informed her that while he was onsite with Condor overseeing the installation of the ozone sparge wells, and that they had encountered a wet sand with significant diesel hydrocarbon odors at 2 feet below the ground surface (bgs). Shallow soil sampling should be conducted on Site to determine the extent of petroleum impacts in soil in the upper 10 feet of the soil column. Soil samples were collected from 5 and 10 feet bgs in hand auger borings HA-1 and HA-2, as detailed in the Site Assessment Report dated 11 May 1999. These borings were located between the southern dispenser island and UST#2, and contained total petroleum hydrocarbons as diesel as high as 4,500 mg/kg. However, these borings are 17 years old, and no samples were collected as shallow as 2 feet bgs where hydrocarbon odor was recently observed. As such, assessment of current shallow soil hydrocarbon impact is needed. It should be noted that shallow soil assessment is required as part of the Low Threat Closure Policy, and will aid in closure eligibility assessment of the Site in the future. In the Work Plan due 30 September 2016, please provide a proposal to collect an adequate number of soil samples from the surface to 10 feet bgs to characterize the extent of hydrocarbon impact to shallow soil. Sampling locations should be based on odor and PID readings observed during ozone injection well installation. Additionally, by 30 September 2016, please submit a Well Installation Report which details the installation of the eight (8) ozone injection wells and provides any collected soil or groundwater data, and all applicable installation permits. 8. Recently submitted Site map figures do not depict the location of the two existing Site USTs and product piping. As such, please include the location, size, and fuel type of each of the existing USTs and associated product piping on Site map figures included in the Work Plan due 30 September 2016. In summary, Central Valley Water Board staff request the following: • By 30 September 2016, please submit a Well Installation Report which includes: c A summary of the installation of the eight (8) ozone injection wells, including well construction details, any collected soil or groundwater data, and all applicable installation permits.