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• •i Former Countryside Market,Stockton,California Feasibility Study and Interim Remedial Action Plan May 20,2013 system equipment components, installation, and construction. The drawings will be used for permitting and system/equipment procurement. The treatment system equipment is proposed in general terms in the conceptual approach detailed herein; however, much of the equipment is standard for this application and will only require modification in size/capacity to enable effective remediation. If feasible and technically justified by the testing data (Section 5.0), the wells installed to assess the viability of sparging at the Site (i.e., AS-1 &AS -2)will be brought online prior to the installation of the full- scale system. Efforts will be made to install and permit the test system t allow for this possibility and enable active groundwater remediation to commence as soon as possible ssuming it is cost effective to utilize temporary power versus a portable generator for the testing equipment among other factors). In this case, the encroachment permitting, installation and tie-in of all the off-site sparge wells would subsequently be conducted as a separate phase of work. If field conditions require significant deviations from this plan, the CRW CB will be notified prior to changing the scope of work outlined above. 7.2.1 Sparge Wells AS wells will be aligned in a grid-like fashion across areas of elevated concentrations of groundwater and spaced approximately 20 feet on center. The actual well spacing will be based on the results of the feasibility test and the calculated ROI. Figure 5 shows the proposed AS well layout, based on an estimated 20 foot well spacing grid pattern. The AS wells will likely be drill ad, constructed, installed and screened in the same manner as test wells AS-1 and AS-2 (see Section 5.1 for specifications/ procedures, including proposed soil sampling/analysis and waste storage, profiling and disposal). 7.2.2 Observation Wells As shown on Figure 8, a total of four observation wells (two on-Site and two off-site) will be installed to help assess the effectiveness of the treatment system and to further delineate the petroleum hydrocarbon plume. The on-Site observation well locations are proposed in the former UST area and in the northeastern portion of the Site, respectively. The off-site observation wells are proposed to be situated approximately 20 feet north of the northernmost strip of AS wells in-line with existing monitoring wells MW-E and MW-7. These strategic well locations will help to confirm ongoing sparge system performance along this critical downgradient portion of the plume. The observation wells will likely be drilled, construc ed, installed and screened in the same manner as test well OBS-1 (see Section 5.1 for specifications/p ocedures, including proposed soil sampling/analysis and waste storage, profiling and disposal). 7.3 Sparge System Operations and Maintenance Start up and operations and maintenance (O&M) of the sparge system wi I be performed in accordance with this TRAP. During system start up, short-term testing of the AS wells (a few hours duration) will be Feasiulay S"aN Feaziblity Stutly a MP_Te#Finaltl 7-4 The Source Group,Inc.