ARCHIVED REPORTS XR0006544 - Laserfiche WebLink

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LEAkWXTER c R 0 u r • Environmental Servrcrs request and directed monitoring of the groundwater for two additional quarters to complete four continuous quarters of monitoring following active remediation Four quarters of verification monitoring were completed with the third quarter 2000 event Based on those results, Clearwater requested reconsideration of site closure The SJCPHS/EHD concurred with the closure recommendation and forwarded the case to the Central Valley Regional Water Quality Control Board (CVRWQCB) for concurrence on December 27, 2000 The CVRWQCB did not concur with the closure request and forwarded the project back to the SJCPHS/EHD for additional oversight, in a letter dated January 25, 2001 The primary concern of the CVRWQCB was that residual dissolved- phase MTBE concentrations in MW-2 were above primary Maximum Contaminant Levels (MCLS) and the trend at the very end of monitoring appeared to be unstable Based on these conditions, Clearwater resumed monitoring of groundwater at the project in February 2001 Groundwater Monitonng Methods On April 2, 2001, Clearwater attempted to monitor all project monitoring and remediation wells An electronic water level indicator was used to gauge depth to water accurate to within ±0 01-feet Wells ® RW-1 (silted in from soil vapor extraction), VW-1, VW-2, VW-3, and VW-4 were dry, and therefore removed from the sampling schedule tlus event All wells were also checked for the presence of Light Non-Aqueous Phase Liquid (LNAPL) gasoline product prior to purging No measurable thicknesses of LNAPL were observed in any of the wells Monitoring was performed in accordance with Clearwater's Field Protocols (attached) The wells with measurable water columns (MW-1 through MW-7, SW-1, SW-2, and Domestic Well) were purged until sampling parameters (e g temperature, pH and conductivity) stabilized, which occurred by approximately three wet casing volumes Groundwater monitoring and well purging information was recorded on Gauge Data/Purge Calculations and Purge Data sheets (attached) Following recovery of water levels to at least 80% of their static levels, groundwater samples were collected from the monitoring wells using dedicated polyethylene bailers Samples were transferred to laboratory supplied containers, labeled, documented on a chain-of-custody form, and placed on ice in a cooler for transport to the project laboratory Purging devices were decontaminated between wells in an Alconox® wash followed by double rinse in clean tap water to prevent cross-contamination Purge water and rinseate was stored on-site in labeled 55-gallons drums pending future removal and disposal All groundwater samples were analyzed by Kiff Analytical, a DHS-certified laboratory located in Davis, California Groundwater samples were analyzed for concentrations of TPHg, BTEX, and MTBE by EPA Method 8260B ZB107C GWMR 2Q01 3 April 9 2001