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WASTE DISCHARGE REQUIR _ENTS ORDER NO. 5-01-055 -4- TRI VALLEY GROWERS PLANT NO. 4 STOCKTON, SAN JOAQUIN COUNTY 21. Based on soil borings drilled at the site, shallow soils consist of sand, silt, and clay mixtures interbedded to a depth of at least 80 feet. The San Joaquin County Soil Survey describes surface soils as the Jacktone Clay. Permeability is slow (0.06-0.2 inch per hour) and a hardpan generally exists at a depth of 20 to 40 inches. 22. Groundwater exists at approximately 55 feet below the ground surface. 23. Groundwater monitoring has been performed at the site on a quarterly basis since July 1990. Average concentrations for selected constituents are presented below: Well FDS (mg/1) TDS (mg/1) EC (µmhos/cm) Nitrate (mWI) TKN m 1 MW-1 805 965 1,442 7.1 2.5 MW-2 716 901 1,333 36.4 8.7 MW-3 534 673 1,000 40.3 10.1 MW-4 624 850 1,209 37.7 9.8 MW-5 439 624 864 28.4 7.6 TKN denotes Total Kjeldahl Nitrogen 24. Based on staff's review of groundwater monitoring data, there are an insufficient number of wells to determine if the discharge has degraded groundwater quality beneath the site. In addition, Well MW-5 is located in the area that will be sold. This Order requires installation of upgradient and downgradient monitoring wells. 25. The Discharger has performed annual monitoring of shallow soil pH, electrical conductance, nitrate, and total nitrogen since 1995. The data collected in the monitoring programs are summarized below. Constituent concentrations were averaged for the three available sampling depths. The data indicates that nitrogen compounds may be leaching to depths below crop root zones. Sample EC NO3 NO3 as N TKN Total N Depth pH (µmhos/cm) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Surface 6.5 1008.1 75.0 8.1 582.5 588.5 2 ft depth 7.4 788.7 10.7 4.4 340.0 332.9 6 ft. depth 7.8 1127.5 20.5 4.5 217.6 205.3 26. Board staff inspected the facility on 19 July 2000 and found that crops were not being grown on the land application areas. 27. Odor complaints were received by the Board in September 1995 and have been a recurring problem at the site. Future generation of odors are a concern due to the growth of residential housing in formerly agricultural areas surrounding Stockton. 28. Water softening (ion exchange) is used to treat boiler water. Regeneration brine is discharged to the process water treatment and disposal system. This Order requires wastewater with high concentrations of total dissolved solids to be separated and disposed of separately.