SITE INFORMATION AND CORRESPONDENCE

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Mr. Kirk Williams • - 2 - • 25 April 2008 The most mobile constituent, 1,2,3-trichloropropane, has moved off-site into the second and third water-bearing zones. North Pond In response to Regional Water Board's request for further information regarding the northern evaporation pond, Western Farm Service provides a discussion of the history in the Annual Report. In 1994 and 1995, four soil sample borings were taken from beneath the pond. Two borings produced composite samples between 0 and 3 feet and between 3 and 6 feet bgs, and two of the borings extended to depths of 70 feet bgs producing discrete samples at various depths. In 1996, the pond was excavated about 1.5 feet, lined, filled, and capped with a low-permeability engineered surface. The soil sampling data show that in 1995, of 14 soil samples analyzed for 1,2-dichloro- propane, six contained more than 50 ug/kg. The site-specific cleanup goal for 1,2-DCP in soil is 0.5 ug/kg, as communicated in a 24 January 2004 letter transmitting Designated Levels for Soil Constituents, and not the general cleanup goal of 700 ug/kg stated in the Annual Report. The 1995 soil sample data also contained concentrations of Total Kjeldahl Nitrogen (TKN) ranging from 500 to 1,000 mg/kg between 10 feet and 70 feet bgs, with the higher concentrations at the deeper intervals. In fertilizer handling facilities, TKN typically is predominately ammonium. Both 1,2-DCP and ammonium are present in groundwater at high concentrations downgradient of the north pond. GeoSyntec shows that historically, the groundwater surface elevation has ranged from 32 feet to 76 feet bgs, which is beneath the highest 1,2-DCP concentrations, and concludes that since the concentrations of constituents are decreasing in downgradient monitoring wells, that the north pond is not an on-going impact to groundwater quality. The slow decline in constituents in downgradient wells indicate that constituents are still present beneath the pond and leads Regional Water Board staff to conclude that remediating the pond will accelerate the rate that groundwater cleanup occurs. South Pond The south pond contains a different mix of constituents than the north pond, and soil sampling conducted in 1994 and 1995 show that ammonium was present at high concentrations (1,000 mg/kg or greater) at three feet, six feet, and 11 feet bgs. The concentration of TKN dropped to 400 mg/kg at 16 feet bgs. The south pond did not contain appreciable amounts of pesticides, herbicides, or volatile compounds. To date, nitrate and ammonium have not been observed in groundwater about 300 feet downgradient of the south pond (MW-5) at concentrations much greater than background concentrations. The proximate monitoring well however, MW-4, was destroyed in 1996. Since the profile of nitrogen concentrations is similar in both ponds, Western Farm Service should also include some soil samples and grab groundwater samples beneath the south pond to assess whether this is or will be a source of nitrogen to groundwater. Pond Summary The questions of whether these capped ponds are on-going sources of groundwater pollution can be resolved with new data. Western Farm Service needs to obtain current soil data from beneath the north and south ponds, without compromising the cap and liner, to identify if soil remediation is warranted. If the soil was remediated, or was determined to not be contributing