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during the test. Wells MW -1, MW -2, MW -3, and SVE-1 B were used as observation/monitoring points. The injection rate was initially set at approximately 2.5 cubic feet per minute (cfm) at a pressure of 50 pounds per square inch (psi). Throughout the 96 -hour event, the flow rate varied between 1.6 to 2.5 cfm and the injection pressure ranged from 25 to 50 psi. Based on the performance of the 96 -hour air sparge test, RDM estimates a conservative radius of influence of 30 feet. Results of the air sparge pilot testing is summarized in RDM's Semiannual Groundwater Monitoring Report — Third Quarter 2014 & Remediation Pilot Testing Results Report, dated November 9, 2014. Between April 15 and April 29, 2015, RDM supervised the installation of off-site, downgradient monitoring wells MW -5, MW -5B, and MW -6B, and the advancement of soil borings RDM-3 through RDM-5 in the suspected former waste oil UST areas. In addition, RDM supervised the destruction of the on-site abandoned well on April 14, 2015. Results of the investigation are presented in RDM's, Report Summarizing Installation of Monitoring Wells MW -5, MW -58 and MW -68; Additional Soil Assessment of Suspected Former Waste Oil UST Areas; and, Destruction of On -Site Abandoned Well, dated July 1, 2015. On October 6, 2015, RDM submitted its Site Conceptual Model, Low Threat Closure Policy Evaluation, and Corrective Action Plan. The corrective action plan (CAP) proposed limited on-site remediation (soil vapor extraction and air sparging) in the northeast corner of the property to reduce secondary source concentrations. It was approved by the CVRWQCB on November 4, 2015. The SWRCB, in its Review Summary Report — Additional Preliminary Review- November 2016 (RSR), dated December 1, 2016, determined "the currently approved Corrective Action Plan did not need to be implemented, and if implemented, the Responsible Party may not be reimbursed". Instead, the SWRCB staff "recommended that the CVRWQCB direct the Responsible Party to obtain a limited number of groundwater samples in the downgradient direction to verify plume lengths to Water Quality Objectives." The SWRCB also stated in the RSR that "pending favorable results of the off-site downgradient groundwater sampling (confirmation that plume lengths are less than 1,000 feet), State Water Board staff recommend that Regional Water Board staff initiate closure of the Site". On February 16, 2017, the CVRWQCB issued a directive requiring two additional groundwater monitoring events to evaluate trends of MTBE and 1,2 DCA in off-site, downgradient monitoring well MW -5 and stated that if MW -5 concentrations continue to rise then additional plume delineation downgradient of MW -5 may be required. To expedite the evaluation of groundwater trends, the CVRWQCB requested sampling for two consecutive quarters in the first and second quarters 2017; however, due to OSCF grant budget approval delays, the groundwater monitoring had to be delayed until third and fourth quarters 2017. The directive also required continued semi-annual groundwater sampling in the first and third quarters until a determination of no further action required is made by the CVRWQCB.