SITE INFORMATION AND CORRESPONDENCE

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URS Ms.Kathy Amaru Page 3 of 9 Regional Water Quality Control Board—Central Valley Region April 30,2014 GROUNDWATER MONITORING ACTIVITIES On February 18, 2014, prior to purging and using an electronic water level meter, URS measured the depth-to-groundwater and total depth of each well,to an accuracy of 0.01 foot bgs,to a known surveyed point at each well location. These measurements were used to calculate the purge volume and ground- water elevation for each well. ' URS conducted groundwater monitoring,which included: • Measuring groundwater levels in on-site monitoring wells and calculating the hydraulic gradient at the site. • Purging and collecting groundwater samples from the scheduled on-site monitoring wells. Appendix A includes monitoring well sampling data sheets for this sampling event. • Submitting groundwater samples to a California-certified laboratory for analysis of organic compounds by United States Environmental Protection Agency Method SW8260B,anions, dissolved metals,hexavalent chromium(Cr[VU),total organic compounds(TOC), and alkalinity. Appendix B provides the laboratory analytical report,which includes a ' comprehensive list of analytes. Approximately three well volumes were purged from each well, with a downhole electric pump before ' collecting a groundwater sample. As each well was purged, temperature, pH, specific conductivity, dissolved oxygen (DO), oxidation reduction potential (ORP), and ferrous iron (Fe'+) were monitored periodically to verify that groundwater entering the well was representative of aquifer conditions prior to sampling. After the purge volume was reached and when the above parameters had stabilized, a groundwater sample was collected from the well. Groundwater samples were carefully transferred to pre-preserved, laboratory-provided sample containers. Once collected, the sample containers were labeled with the collection date and time,project and sample identification codes, sampler's initials,type of analysis to be performed,and preservative method(if any). The samples were sealed in plastic bags and stored in an ice-filled chest at approximately 4 degrees ' Celsius for delivery to the laboratory.All groundwater samples were delivered to the laboratory within the designated holding time and were accompanied by the appropriate chain-of-custody documentation. The groundwater samples were submitted to Curtis&Tompkins Laboratories in Berkeley,California, ' for analysis. GROUNDWATER MONITORING RESULTS The groundwater flow direction and gradient are highly variable at the site. The general direction of groundwater flow beneath the site for this sampling event is to the southwest, with a gradient of 0.002 feet per foot. Table 1 and Figure 3 summarize groundwater flow direction and gradient data. Table 2 summarizes the groundwater elevation data. Table 3 summarizes analytical and field results related to the vegetable oil injection activities. Appendix C provides time-series plots for select wells and plots of ' relevant field parameters. ' HAWPoc CDCROeuel Vocatiom Witution(Bum Pit)0VI-BP-IQMR14 Pe n.&c