SITE INFORMATION AND CORRESPONDENCE

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WASTE DISCHARGE REQUIREMENTS SIMPSON INVESTMENT COMPANY AND SIMPSON PAPER COMPANY RIPON MILL SAN JOAQUIN COUNTY 4. Regeneration brine from the cogeneration plant water softeners and the mill effluent are collected in a sump and discharged into a circular primary clarifier. The clarifier effluent is discharged into two aeration stabilization basins (ASB) in series (see Attachment B which is hereby made part of this Order). The first ASB No. 1 is a 14- foot deep lined basin converted from an abandoned sludge pit. The second ASB No. 2 is an unlined 5-foot deep basin. Effluent from ASB No. 2 is disposed of on-site to percolation fields and orchards through a system of pumps and irrigation pipelines. The original No. 1 and No. 3 effluent ponds (renamed as Dry Ponds No. 1 and No. 2) have been removed from the wastewater treatment system and are used only to contain excess wastewater in the event of a system upset or a 100-year storm event. Similarly, two other "dry ponds", known as Dry Pond No. 3 and No. 4, can be used for overflow situations. Clarifier sludge is discharged to an on-site sludge pond. 5. The Discharger also operates an electric cogeneration plant. Water supplied to the cogeneration plant is treated by a reverse osmosis (RO) filtration unit. The 4-stage RO process removes 95 percent of the dissolved solids from the water; the purified water is used to make steam. The steam can then be recycled without contaminants clogging the system and damaging the generator turbine blades. The RO effluent goes directly to ASB No. 2. 6. The Discharger, in an effort to abate odors emanating from its ponds, has converted the inactive sludge pond (see Attachment B) to an aeration basin for secondary treatment of mill effluent. Inert dewatered sludge from the inactive sludge pond has been placed on 50 acres and disced into the top eight inches of soil as a soil amendment. 7. The discharge has resulted in elevated levels of total dissolved solids (TDS) beneath the disposal areas. Wastes discharged to percolation areas in the past had TDS levels as high as 2500 mg/1. 8. Regional Board staff determined that past waste discharges were classified as "designated wastes" under Title 23, California Code of Regulations, Division 3, Chapter 15. 9. Subsequent to the Regional Board's determination that the waste was designated, the Discharger has completed or proposed three projects in order to reduce effluent total dissolved solids (TDS): a. The Discharger has reduced the alum consumption by making changes in the manufacturing chemistry. This change has reduced the effluent TDS to 1400 mg/1.