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Site Investigation Work Plan-Second Revision Raymond Investment Corporation Former Helena Chemical Facility Page 4 Hydrologic surface flow in this area is generally toward the east. Site specific surface flow directions are shown on Figures 2A and 2B. Hydrologic subsurface flow, groundwater, in the area is generally toward the east in this area,away from the San Joaquin River. 2.4 ENVIRONMENTAL AND/OR HUMAN IMPACT The previous investigations were discussed above in Section 2.2 and the historic analytical data is included in Appendix B Tables A through D. Contaminants of concern (COCs) were hydrocarbons related to the removed underground storage tanks; nitrate, ammonia and TKN related to the removed above ground tanks;and metals, or OCPs OPPs related primarily to materials storage and handling. Among these investigations that have been completed over the past 30 years only the nitrate impact to groundwater, documented again in 2013, appears to have exceeded the California Drinking Water Maximum Concentration Limit (MCL) of 10 milligrams per liter. The presence of endosulfan in a soil disposal characterization sample was the only known detection of OCPs or OPPs. Other Site clean-up activities have indicated that oil, sulfur and metals (cadmium, chromium, and lead) were removed. The CVRWQCB directive dated April 1, 2014 indicated that the COCs to be investigated were pesticides petroleum hydrocarbons, and metals. Additionally the CVRWQCB has directed that fumigant pesticides should also be included. The CVRWQCB indicated that Triazine should be included within the OPP analysis. The BC laboratory chemist indicated that Triazine is a chemical family name and that Atrizine and Simazine were the compounds that are analyzed. The purpose of this investigation is to provide the CVRWQCB information to confirm the presence and extent of fertilizer impacted soils and groundwater and provide a more through confirmation that other COCs are unlikely to be present.These results should allow the CRWQCB to focus future investigations or cleanup efforts on a narrower group of COCs. Soil and groundwater samples will be collected from locations laterally farther away from the location of the former above ground storage tanks in order to define the extent of fertilizer impacts.Locations that are considered more likely to have been impacted by pesticides or metals will also be analyzed by the laboratory for those additional COCs. 3.0 DATA QUALITY OBJECTIVES Condor compared the detection limits and analyte list from three laboratories to published site assessment criteria. The site assessment criteria for groundwater were United States Environmental Protection Agency(US EPA) MCLS for drinking water and California Environmental Protection Agency(CA EPA) MCLS for drinking water updated July 1, 2014; Office of Environmental Health Hazard Assessment (OEHHA) Public Health Goals (PHGs) as of February 2015; OEHHA Notification Levels for Drinking Water; State Water Resources Control Board(SWRCB)Historic Drinking Water Action Levels(ALs)for Chemicals with MCLS; SWRCB Drinking Water Notification Levels (NLs) and Response Levels (RLs): An Overview; SWRCB Archived Advisory Levels For Drinking Water; and California Regional Water Quality Control Board (CRWQCB) Water Quality-Based Assessment Thresholds (WQBATs). The CVRWQCB letter dated September 10, 2015 clarified the WQBATs for groundwater were to be applied and that the"lowest commercially available and achievable reporting limits"should be used. Condor began the process of selecting a laboratory by contacting Jane Jensen of the State of California Water Quality Control Board Environmental Laboratory Accreditation Program(ELAP).Jensen provided a list of laboratories the were accredited to perform analysis of 1,2,3-trichloropropane (123-TCP) using Environmental Protection Agency Method 524.2 modified by the California State Laboratory (SRLB) to attain the acceptable low level detections designated as SRL 524M-TCP. Condor also obtained the list of ELAP accredited laboratories for hazardous waste. The lists were queried and laboratories eliminated using an iterative process. First, laboratories that were non-commercial were stricken from the list, n +.1� CONDOR