SITE INFORMATION AND CORRESPONDENCE

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URS ' Ms. Kathy Amaru Page 3 of 6 Regional Water Quality Control Board—Central Valley Region May 8,2011 On April 4 and May 2, 2011,URS conducted baseline groundwater monitoring which included: Measuring groundwater levels in six on-site monitoring wells and calculating the hydraulic gradient ' at the site. • Purging and collecting groundwater samples from the scheduled on-site monitoring wells (Mw-2- BP,MW-5-BP,MW-6-BP, MW-7-BP,MW-24-BP, and MW-25-BP). Monitoring well sampling data sheets are included as Attachment A. • Submitting groundwater samples to a California-certified laboratory for analysis of organic ' compounds by United States Environmental Protection Agency(EPA)Method SW8260B, anions, metals, hexavalent chromium,total organic compounds(TOC), and alkalinity. For a comprehensive list of analytes,please refer to the laboratory analytical report provided as Attachment B. Approximately three well volumes were purged from each well before sampling. Purging was performed by using dedicated, single-use, high-density polyethylene bailers. As each well was purged, ' temperature,pH,specific conductivity, and total dissolved solids were monitored periodically to verify that groundwater entering the well was indicative of aquifer conditions. After the purge volume was reached and when the above parameters indicated that the water in each well was representative of the aquifer, a water sample was collected from the well. Each sample was collected by lowering a new, pre- cleaned, dedicated bailer slowly to the water line and allowing it to fill while causing minimal agitation to the water column. Groundwater samples were carefully transferred to pre-cleaned, laboratory- provided sample containers. Once collected, the sample containers were labeled with the time and date ' of collection,project and sample identification codes, sampler's initials,type of analysis to be performed,and preservative method. The samples were then sealed in plastic bags and stored in an ice-filled chest at approximately 4 degrees Celsius until delivery to the laboratory. Each groundwater sample was delivered to the laboratory within the designated holding time and was accompanied by the appropriate chain-of-custody documentation. The groundwater samples were submitted to Curtis & Tompkins Laboratories in Berkeley, California. PILOT TEST ACTIVITIES ' For the pilot test activities,30 injection point locations were installed from south of monitoring well MW-6-BP, located in the former burn pit,to south of MW-5-BP. At each injection location, approximately 165 gallons of EOS diluted solution(at a 10:1 ratio of potable water to EOS)was injected into the subsurface from approximately seven to 23 feet bgs. The injection location borings were destroyed using bentonite slurry. 1 H:\Wpm=\RESD\DVI-Burn Pit@0110W.BP.IQMRI I Re cft,doc