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Revised Work Plan for Additional Site Investigation Raymond Investment Corporation Former Helena Chemical Facility February 27,2018 Page 2 metamorphosed sedimentary and volcanic rocks of Paleozoic and Mesozoic age (150 to 300 million years old) and plutonic rocks (chiefly granitic types) of Mesozoic age (80 to 150 million years old). Surface soils are identified as Yellowlark gravelly loam with Class C hydrologic group by the United States Department of Agriculture, Natural Resource Conservation Service (NRCS). The NRCS describes Group C soils as having a slow infiltration rate when thoroughly wet, that consist chiefly of soils having a layer that impedes the downward movement of water, and that have a slow rate of water transmission. Groundwater in the region generally flows toward the east. The site-specific groundwater flow direction, based upon the surveyed monitoring well casing elevations and measured depth to groundwater, has varied and has been measured toward the west-northwest, south, and southeast. Shallow groundwater at a site located across Charter Way to the south generally flows toward the east. 3.0 PROJECT BACKGROUND The facility has historically been occupied by various tenants for commercial and light industrial uses, including a beverage distribution facility, agricultural supplies (chemicals, fertilizers, and pesticides) storage and distribution facility, tractor repair facility, battery sales/recycling facility, and various contractor storage facilities. Liquid fertilizers were reported to have been stored in three above-ground storage tanks (ASTs) formerly located in the northwest corner of the Site. San Joaquin County Environmental Health Department (EHD) file records documented several incidents of improper storage and handling of hazardous chemicals, spills, and the presence of stained soil at the Site. Site investigations conducted in 2001 and 2002 found elevated levels of Total Kjeldahl Nitrogen (TKN), ammonia, and nitrate in soil samples. A subsurface investigation conducted in 2013 also showed that soil and groundwater contained TKN, ammonia, and nitrate. EHD subsequently placed the Site on their local "Contaminated Site List" and referred the case to the Central Valley Water Board for further review and evaluation. On September 17, 2001, Geomatrix Consultants, Inc. collected five surface samples at the former bulk tank farm area, and analyzed them for the presence of organochlorine pesticides, organophosphate pesticides, and various metals. Organophosphate and organochlorine pesticides and heavy metals were interpreted to be within published background ranges. TKN and Ammonia as Nitrogen (Ammonia-N) were detected at elevated concentrations. In April 2002, Kleinfelder Inc. collected soil samples in the area of the removed ASTs. Soil sample analytical results indicated that soil contained Nitrate-N concentrations as high as 1,600 milligrams per kilogram (mg/kg), TKN concentrations as high as 7,700 mg/kg, and Ammonia-N concentrations as high as 2,200 mg/kg. TKN was also detected at concentrations as high as 1,000 mg/kg in a boring intended as a background sample (BG), which was located approximately 200 feet southeast of the former ASTs. Groundwater samples collected near the former ASTs locations by Kleinfelder contained TKN up to 0.441 milligrams per liter (mg/L); ammonia up to 0.34 mg/L; and Nitrate-N up to 219 mg/L. In 2006, another release incident was reported involving the spill of sulfur and lime to soil near the north boundary of the Site. Various drums, sacks, and boxes had been compromised, and various materials were reportedly released to the soil. EHD subsequently issued a Notice to Abate to the owner of the property. The spilled materials were removed from the Site, and impacted soil was reportedly over-excavated. However, EHD contained no records of soil confirmation sampling. C4 CONDOR