ARCHIVED REPORTS_XR0002498 - Laserfiche WebLink

Home Browse Search

Second Quarter 1993 Groundwater Monitoring Report Tri-Valley Growers, Thornton, Cahfomia Page 2 Groundwater samples were collected from monitoring wells MW 1 and MW6 on June 28, 1993 after stabilization of pH, electrical conductivity (EC) and temperature The monitoring wells were purged using an above-ground centrifugal pump with dedicated tubing. Well purge logs are included in Attachment 1 Samples were analyzed for benzene, toluene, ethylbenzene, xylenes (BTEX), and total petroleum hydrocarbons as gasoline (TPHG), by EPA methods 8020 and modified 8015, respectively Analy1ical Results No dissolved gasoline hydrocarbon constituents were reported at or above detection limits in monitoring wells MW 1 and MW6 Influent and effluent samples from the pumping well (MW4) were collected for analysis of BTEX and TPHG on June 28, 1993 Analytical results indicate a decrease In TPHG in the influent sample collected during this sampling round, BTEX concentrations generally rema>ned unchanged The samples collected from carbon filter 1 (TVGT EFF1C) and carbon filter 2 (TVGT EFF2C) did not contain any detectable analytes during this sampling round. Influent BTEX and TPHG concentrations over time are plotted on Figures 4 and 5 • Laboratory analyses were performed by Sequoia Analytical Laboratory (FLAP No 1210) The analytical results are summarized in Table 2, the laboratory reports and chain-of-custody documentation are presented in Attachment 2 Remediation System Performance Overall, analytical results support the effectiveness of the system Historical sampling results show fluctuating influent hydrocarbon concentrations which may be attributed to fluctuating water table elevations However, for the most part, laboratory results indicate that influent TPHG and BTEX concentrations have been significantly reduced since system start-up Based upon an average flow rate of 2 liters/minute and an average influent gasoline hydrocarbon concentration of 3,000 µgl f, at is estimated that approximately 547,200 gallons of groundwater have been treated and approximately 2.0 gallons of gasoline hydrocarbons have been removed since remediation system start up in May 1991 RESNA personnel will continue with the quarterly monitoring program which will include reports detailing system performance We will continue to monitor system performance and adjust pumping rates as necessary If permission is granted, the neighboring domestic well will be sampled next quarter in order to evaluate pumping effects of the domestic well on the QRTERLYI2QMR1993 FNL