ARCHIVED REPORTS XR0006550 - Laserfiche WebLink

Home Browse Search

CLEARWATER E- 1101,m,nt 05,rrrr,s • 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 third quarter 1999 groundwater monitoring and sampling are summarized below Depth to groundwater Ranged from 13 19 (MW-3)to 14 83 (MW-7)feet below top of casing Flow direction/gradient Southwesterly at 0 0008 ft/ft U SPH-wells/thickness No SPH present TPHg concentrations <50 pg/L (DW)to 1,900 pg/L (MW-1) o Benzene concentrations <0 5 pg/L(DW)to 23 pg/L (MW-1) MTBE concentrations <0 5 pg/L(DW)to 77 pg/L (MW-2) The southwesterly groundwater flow direction observed this quarter are inconsistent with the northeasterly direction typically observed beneath the site (Figure 3) However, it is noteworthy that a southwesterly flow has historically been Observed beneath the site during this time of the year Additionally the groundwater levels are approximately two to three Leet over the previous quarter, which is also typical of this time of year for the site increases in groundwater levels combined with a change in flow direction during the late summer are interpreted to be the result of local irrigation practices The extent of dissolved-phase gasoline contamination remains well delineated by the existing monitoring well network (Figure 4) It is noteworthy that contaminant concentrations this quarter continue to remain much lower than pre- remediation levels 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 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 SVE/AS system design includes seven wells plumbed for vapor extraction (VW-1 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 D-107 3Q99 GW &Sys Mon Report 2 September 29 1999