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CLEARWATER ' G R O L P [ \ C • E rr r r ra rune rr I a!Serr ices Groundwater monitoring was conducted in accordance with the schedule proposed in Clearwater's Groundwater and Remediation System Operation Monitoring Report-First Quarter 1999 dated April 5, 1999 Wells were purged prior to collection of groundwater samples Clearwater gauging and well purging data sheets are included in Appendix B 2.2 Groundwater Monitoring Results Results of second quarter 1999 groundwater monitoring and sampling are summarized below Depth to groundwater Ranged from 16 39(MW-3)to 17 82(MW-7) feet below top of casing 0 Flow direction/gradient Northeasterly at 0 0018 ft/ft i a SPH-wells/thickness No SPH present TPHg concentrations <50 pg/L (DW) to 1,500 pg/L(MW-1) o Benzene concentrations <0 5 pg/L (DW and MW-1)to 2 3 pg/L(MW-2) C MTBE concentrations <0 5 pg/L (DW)to 162 pg[L (MW-1) The general groundwater flow direction and gradient for this quarter (Figure 3) were similar to conditions previously observed at the site The extent of dtssolved-phase gasoline contamination remains well delineated by the existing monitoring well network (Figure 4) It is noteworthy that contaminant concentrations this quarter are approximately an order of magnitude lower than those for the first quarter 1999 and approximately two orders of magnitude lower than those detected for the fourth quarter 1998 This reduction in contaminant concentrations is likely the direct result of ongoing active remediation at the site since the beginning of October 1998 These trends are shown graphically for plume well MW-1 and MW-2 on Figures 5A and 5B,respectively If these trends continue, it is likely the SVE/AS system can be shut-down before winter 1999 Sample results indicate that the domestic well continues to be free of detectable gasoline hydrocarbon concentrations The domestic well will continued to monitored on a quarterly schedule Groundwater monitoring data and analytical results are presented in Table 2, and laboratory analytical reports are attached in Appendix C 3 0 SOIL VAPOR EXTRACTION AND AIR SPARGE SYSTEM The SVI /AS system design includes seven wells plumbed for vapor extraction (VW-I to VW-4, MW-1, MW-2, and RW-1), and two wells plumbed for air sparging (SW-1 and SW-2)(Figure 2) The remediation system was constructed to mid 1998 in accordance with Clearwater's Problem Assessment Report, Feasibility Study, and Remedial Action Plan D-107 2Q99 GW&Sys Mon Report 2 July 21. 1999