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A.Taehert 6 Son Inc.Mobile Equipment Shop 103 N.'E'St.Stockton,CA. Remedial Action Pian March. 1994 y� 224 Air Sample Analysis and Projected Hydrocarbon Removal Rates One air sample was collected after three hours of maximum flow had elapsed. This time was considered sufficient to allow for stabilization. Two, one-liter samples contained in Tedlar bags were collected for analysis and were submitted under chain-of-custody to Sparger Technology. The sample was analyzed for TPH gasoline and BTEX by modified 8015/8020 methodology. Conversion of the analytical results of TPH gas in ug/ml to parts-per-million volume (ppmv) indicates a concentration of TPH of approximately 13,000 ppmv. Air sample laboratory analytical results are included in Appendix E. Based upon the pilot test parameters of 13,000 ppmv, an SVE system generating 36 CFM may be expected to remove (initially) up to 136 pounds/day of TPH as gasoline and lessor quantities of BTEX. Calculations of system TPH and BTEX removal are included in Appendix D. 3.0 Remedial Action Plan An SVE system is proposed for soil and groundwater remediation. We recommend that the system consist, as proposed in the February 8, 1994 work plan, of SVE/monitoring well MW-14, 2-inch diameter plastic vapor connecting-conveyance piping and a blower - treatment system compatible with design criteria. 3_i System Requirements This system design is predicated upon existing information and the March 16, 1994 pilot test results. These test results generated the requirements for a system generating a minimum of 35 CFM at the blower, and at least -0.25 WC on wells within the radius of influence. These wells include MW-9, MW-3, MWA 0 and MWA 1. This radius generally exceeds the known limit of elevated petroleum hydrocarbon contamination in soil, and the current extent of hydrocarbon impact in groundwater. Note that a radius of influence from well MWA 4 extending to and including well MW-9 includes known historical groundwater contamination. As discussed above, elevated concentrations of gasoline constituents (exceeding 100 ppm) are limited to the area adjacent to MW-13 and MW-14. Based upon the pilot test the area adjacent to wells MW-13 and MW-14 is subject to much higher vacuums than those measured in peripheral wells, and hydrocarbon removal may be expected to occur rapidly (Figure 6). Based upon the pilot test, this flow rate and radius of influence requires a vacuum of 98- 100 WC. Air from the subsurface, or "formation" produced by advection of the system contained approximately 13,000 ppmv, and only 3% oxygen. The low oxygen content of the airstream, while it may indicate microbial breakdown of petroleum hydrocarbons, also warrants the dilution or attenuation of inlet system air to allow combust ionloxidation. 6