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N CLEARWA`I'ER c F 'LP 13P highly impacted zones. Additional details about chemical oxidants and injection are supplied in j; Attachment 2. ISCO was not considered in the 2002 CAP as an option because of regulatory policies of the Central Valley Regional Water Quality Control Board (CVRWQCB), which limited subsurface chemical injection at that time. A permit will be required for underground injection of chemical oxidants into the saturated zone. Clearwater and the Responsible Party (Floyd Barnes) would apply to become an "enrollee" under General Permit # R5-2008-0149, issued by the CVRWQCB. As such, a copy of this report is being sent to the CVRWQCB for their information. The terms of this general permit and the notice-of-intent-to-comply information are included in Attachment 3. To gain a more effective radius of influence, a temporary dewatering system will be used both to create a hydraulic control and to dewater the saturated soil interval within the injection zones. Using groundwater extraction for hydraulic control, a system of temporary extraction points will be installed and connected to a liquid ring pump to dewater upgradient and downgradient of the source area. The details and location of the temporary dewatering system and injection points, will be the focus of a future remediation action plan (RAP), which is recommended to be created after approval of this CAP by S7CPHS-EHD. Based on the Site Conceptual Model, across the site, the treatment zone is generally located between 20 and 25 feet below ground surface (bgs), with several locations reporting olfactory detections to 34 feet bgs from the 1997 and 2000 soil investigation and well installation events, respectively (see figures in Attachment 4). Table 3 provides well construction data for all wells at the site. The dewatering system would be placed both upgradient and downgradient of the injection points, at a point within the effective hydraulic radius to maximize extraction of groundwater impacted with hydrocarbons desorbed via ISCO activity. In reference to the Site Conceptual Model (SCM) of 2009, there are likely to be two major zones at the site of sorbed- phase impacts (although the lack of data points between these two areas may mean that they are one large area). Area A includes the area around the former underground storage tank (UST), i and Area B includes the area between wells IW-6 and IW-12, with AS-1 being at the western jedge of Area B . These areas may be horizontally contiguous, but data gaps between them preclude this conclusion. Chemical oxidation injection points would need to be located in both zones, with a dewatering system across both areas. The need for soil samples for Bench Testing and the need for data between MW-4 and MW4 dictate a soil sampling event using direct push technology (DPE) equipment in this middle area. OVERVIEW OF ISCO TECHNOLOGY 1r4-Situ Chemical Oxidation (ISCO) relies on the capacity of oxidants to chemically destroy hydrocarbon bonds and release hydrocarbons that are electrostatically bound to colloidal surfaces of"clay and silt. Chemical oxidants work by producing free radicals, such as the hydroxyl radical, which oxidize hydrocarbons by breaking the chemical bonds of the target compounds. Floyd Flames 4 Updated CAP ZB178 Update to CAP March 2010