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I I Mr. Marty Hartzell Project 803026 September 80 2000 Page 5 ear the dowagradied edge of the plume at the approximate location shown on Figure 2. Well MW-8 will be installed within a distance of approximately DO feet from well MWfi and screened in a deeper water-bearing zone approximately too feet below the screemed interval in well MW-6. The well is projected to be dotted to a total depth of approximately 85 feet below ground surface (age). A steel conductor rasing will he installed across the upper water-baring zone to -reduce (be potential for comes contamination. Well installation procedures are presented in Appendix A. EVALUATION OF FREE-PHASE PRODUCT RECOVERY AND THICKNESS IN THE SOURCE ZONE Table t summarizes blstorlcal groundwater elevations, product thickness, Product volumes recovered, and concentrations of TPH& BTEX and MTBH in groundwater samples collected from wells MW-I through MW-], end GWX-L In 1"3 sort 1994, free product was measured in wells MW-1. MW-2, and MW-3 at a thickness ranging from 0.03 to 2.22 f Approximately 7, 13, and 2 gallons of free product was bailed from wells MW-1, MW-2, and MW-3, respectively, daring 1993 and the beginning of t994. Historical monitoring records show that approximaely 22 gallons of product has beenbailedfinmwellsMW-lthrough MW-3. Freeproductlenneverberomeasuredin wells MW-4 through MW-7 and GWX-L Groundwater monitoring data was not available for the period from May 1994 through March 1997. Beginning in April 19W, groundwater elevation data indicates that groundwater levels rose and have submerged the screened mtery ll in wells MW-t Omugb MW-3. Free Product in these wells carmem be measured (ifpresem) because the water levels haverben above the top oflhe well scmens. Well GWX-1 located man the f er UST's is screened across the current water table Gam 15 to 60 f bgs. The absence of fine product in this well and in wells MWA through MW-T suggests that vary limited quantities (if any) of product remains beneath the site. IT's espeience shows that soil vapor eenaction and air sparging should be an effective mechanism for removing residual Gee-phase product. TECHNICAL PLAN FOR AN AIR SPARGE TEST PRIOR TO FULL-SCALE IMPLEMENTATION IT proposes m conduct a pilot air sparge test to obtain design parameters prim to Ul- sandebriplemostationofereaspargesyeems. Upromeesto inject ambiwlairwith five poorest (by volume) beliun him three an sparge wells (AS-1, AS-2, and AS-3). The /IlO1Wa1>Aul ryox�mwiaope.mtsa.Arw�u+vmmamam.maoxx l