SITE INFORMATION AND CORRESPONDENCE

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MONITORING AND REPORTINOROGRAM NO. R5-2008-0819 • - 2 - PIONEER 2 -PIONEER AMERICAS LLC TRACY, SAN JOAQUIN COUNTY supply wells are located on the Site. The four domestic water supply wells are located approximately 40 to 100 feet north of the Site. Required laboratory analyses, and monitoring and sampling frequencies for the 15 monitoring wells, three industrial supply wells, four domestic supply wells, and any wells installed or added subsequent to the issuance of this MRP, shall conform to the requirements presented in Table 1 and the schedule presented in Table 2. Sample collection and analysis shall follow standard U.S. EPA protocol. Volumes of groundwater extracted from each of the three production wells shall be recorded. monthly. Pioneer has established a conceptual site model that includes three subsurface groundwater monitoring horizons: The Upper, Middle, and Lower Horizons. Monitoring wells MW-1 through MW-9, MW-11, and MW-13 are screened within the Upper Horizon over the interval between approximately 10 and 33 feet below ground surface (bgs). Monitoring wells MW-10, MW-12, and MW-14 are screened within the Middle Horizon over the interval between approximately 42 and 58 feet bgs. Monitoring wells MW-15, AP-2, LM151 B, and LM177B are screened within the Lower Horizon below approximately 70 feet bgs. Pioneer has observed that the groundwater gradient beneath the Site within the Upper and Middle Horizons has been toward the northeast. Pioneer has not observed the gradient within the Lower Horizon because, until recently, it has only monitored one well within this horizon. However, DLA has shown at their Tracy distribution depot, that historically the natural gradient beneath the area was diverted from northeast to north in the Lower Horizon by pumping of several agricultural wells located approximately 3,000 to 7,000 feet northwest of the Pioneer Site. DLA subsequently purchased the agricultural parcel that the wells were located on and decommissioned the wells. Table 1 Required Laboratory Analytical Methods and Practical Quantitation Limits USEPA Laboratory Analytical Maximum Values for Practical Constituent Method Quantitation Limits (milligrams per liter) Volatile Organic 8021 or 8260B 0.0005 Compounds Chloride 300 10 Sodium 6010 10 c Total Organic Carbon 415.1 20 ' Total Dissolved Solids 160.1 20 ._ o Nitrate & nitrite 300 0.1 v Sulfate 300 0.2 Sulfite 377.1 6 Total Iron 6010A 0.02 Ferrous Iron Direct Field Measurement 0.1 Total Alkalinity 310.1 5 1 Each analyte concentration between the Method Detection Limit and the Practical Quantitation Limit (PQL) shall be flagged, estimated, and reported.