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02 June 2015 AGE Project No. 14-3154 Page 2 of 6 and free-product removal is unlikely to achieve closure levels. Based upon available data and AGE's past experience at similar sites, we have determined that dual phase extraction (DPE) is a viable option to mitigate petroleum-impacted soil below the water table and shallow free-product on the groundwater surface at the subject property. SCOPE OF WORK In response to the Condor-prepared, Site Groundwater Investigation Work Plan and CVRWQCB letter dated 16 March 2015, AGE has the following comments, revisions, and additions to the scope of work for the plan. The scope of work includes advancement of numerous (up to approximately 14) soil probe borings for the collection of soil and groundwater samples to evaluate the presence, type, and extent of hydrocarbon-impacted soil and groundwater between 15 and 30 feet below surface grade (bsg) in the area of the free-phase petroleum and down-gradient of the impacted area; borings are proposed up to 350 feet down-gradient of the most impacted area. Additionally, the scope of work includes installation of two additional remediation wells within the free-phase petroleum-impacted area. The Wells should be constructed consistent with the current on-site remediation wells (i.e. 4-inch PVC with 10 feet of screen and #3 sand). Reinstallation is not recommended for wells RW-1 to RW-4 as proposed in the original Condor-prepared work plan; AGE believes this unnecessary for remediation. AGE provides the following comments on the scope of work in the order presented in the above-referenced CVRWQCB letter: 1. The deep soil zone is presumed to be greater than 30 feet bsg and not anticipated to be greater than 40 feet bsg. Three soil borings will be sampled by continuous core sample methods or equivalent to determine stratigraphy for soil and deep groundwater sampling. The static water table over the period of time in which the diesel release and transport has been observed has been near the current water level of 15 feet bsg. Deep groundwater samples will be conducted during the soil sampling. As prepared in the workplan, each boring will have a shallow and deep grab groundwater sample collected. 2. Two sumps are located on the north edge of the building interior. However, those sumps are typically dry or do not produce groundwater which is recoverable. 3. The approximate range of historical groundwater flow is northeast to east. Seven of the soil boring are proposed north or northeast and east of the release area and should be presumed to be down-gradient. 4. Samples will be analyzed for petroleum based on field observations, organic vapor measurements (PID) and need to fill data gap within the current soil sample set. The goal of the soil sampling is the collected of clean soil samples Advanced GeoEnvironmenlal,Inc.