SITE INFORMATION AND CORRESPONDENCE

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Fernando's Place - 2 - 29 September 2016' 1201 South Center Street Stockton, San Joaquin County Boring CPT-15 (2007), the farthest sampling location to the east (approximately 430 feet), contained benzene concentrations of 69 ug/L in HU1 Upper, 27 ug/L in HU1, 650 ug/L in HU3, and 500 ug/L in HUS. Boring CPT-13 (2007), approximately 40 feet north of the Site, contained benzene concentrations of 71 ug/L in HU1 Upper, 11 ug/L in HU1 Lower, 22 ug/L in HU2, and 25 ug/L at 184 feet bgs (between HU4 and HU5). Depth discrete groundwater sampling in boring CPT-4 (2001), located approximately 60 feet southwest of the Site across French Camp Road, indicated the presence of benzene above the WQO as deep as HU3 (68 ug/L), and a maximum benzene concentration of 7,300 ug/L in HU1 Upper. These data indicate that additional lateral and vertical delineation is needed to the north, northeast, east, and southeast of the Site. By 30 November 2016, please submit a Work Plan which includes a proposal for the collection of a sufficient number of groundwater samples to adequately delineate groundwater pollution to the WQOs laterally and vertically to the north, northeast, east, and southeast of the Site. 2. The Central Valley Water Board permits and regulates the injection of oxidizers into the subsurface such as ozone or in-situ chemical oxidants (ICSO) like peroxide under Order No. R5-2015-0012, Waste Discharge Requirements General Order for In-Situ Groundwater Remediation and Discharge of Treated Groundwater to Land(General Order). It appears that prior to the ozone injection pilot test that was conducted at the Site between 11 November 2013 and 2 October 2014, a Notice of Intent (NO]) application for permit under the General Order was not submitted to the Central Valley Water Board, nor was a Notice of Applicability (NOA) issued by the Central Valley Water Board. Any further injection of oxidants at the Site must be permitted by the Central Valley Water Board. In the 4Q15 Report, AGE recommends a continuation of the ozone injection pilot test as well as an ISCO pilot test using hydrogen peroxide. Based on data presented in the Pilot Test Report, it does not appear that ozone injection has been effective at reducing groundwater contamination at the Site. Shallow screened (36-40 feet bgs) ozone wells OZ-4 through OZ-8 were located on the southeast corner of the property near groundwater monitoring wells MW-1 and MW-5, and intermediate screened (66-70 feet bgs) ozone wells OZ-1 through OZ-3 were located in the northeast corner near groundwater monitoring wells MW-3 and MW-4. While decreases in total petroleum hydrocarbons as gasoline (TPHg) and benzene concentrations were observed in shallow monitoring well MW-5A over the course of the pilot test, the application of ozone does not appear to have accelerated the decreasing trend in this well that began several years prior to the implementation of ozone. Also, concentrations in MW-1 fluctuated over the course of the pilot test, and cannot be described as decreasing when compared to the historical pattern of the monitoring data. Additionally, both MW-1 and MW-5A demonstrated significant increases in TPHg and benzene concentrations subsequent to the completion of the pilot test, which for some constituents were much higher than concentrations before ozone was implemented. In the Pilot Test Report, reductions in TPHg and benzene concentrations in wells MW-3A and MW-313 were used as evidence of effectiveness for the intermediate depth