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REVISED CLEANUP AND ABATEMENT ORDER NO. 5-01-703 • <br /> CITY OF RIVERBANK WASTEWATER TREATMENT PLANT -5 <br /> STANISLAUS COUNTY <br /> long as the Sun Garden-Gangi discharge complies with the BOD and flow limits contained in <br /> its industrial discharge permit. <br /> b. An assessment of necessary treatment plant improvements with a cost estimate. The <br /> evaluation studied two scenarios: projected population growth of 14,000 with no increase in <br /> flow from the cannery, and projected population growth of 14,000 with a 16.7% increase in <br /> flow from the cannery. The report concluded that about 12 acres of additional percolation <br /> ponds would be required in either scenario with one to three additional 75-hp aerators <br /> depending on cannery growth. The projection concluded that this expansion would be <br /> needed no sooner than 2013. <br /> c. A water balance for the existing treatment and disposal system. The water balance <br /> confirmed the excess storage and disposal capacity, provided that percolation rates are at <br /> least 1.4 inches per day. To accomplish this, it was assumed that each percolation pond <br /> would be out of service three months each year for drying and discing. <br /> d. A preliminary assessment of pond berm condition prepared by a geotechnical engineer. The <br /> report concluded that the western berm that contains the Summer 2 and Summer 3 <br /> percolation ponds is constructed of relatively loose, sandy soil, which is vulnerable to failure <br /> due to burrowing animals and piping. The exterior and interior slopes of the berm are <br /> oversteepened. The northern berm, which contains the Summer Aeration Cell and the <br /> Summer 1 treatment/percolation pond, is apparently constructed of finer-grained material, <br /> but also had many burrows. The engineer's preliminary recommendations were to <br /> permanently repair the western berm, including correcting the oversteepened exterior slope <br /> and lining the interior slope or other similar measures to prevent piping. The engineer <br /> recommend that both the western and northern berms be evaluated further based on a <br /> subsurface investigation. <br /> 22. On 5 March 2001, the Discharger's consultant reported freeboard violations in all of the ponds due <br /> to reduced percolation rates. The Discharger proposed to construct an emergency percolation <br /> pond on one of two neighboring sites previously identified as possible future expansion sites. The <br /> purpose of the emergency percolation pond was to provide immediate relief of freeboard problems <br /> and allow the existing ponds to be dried out, repaired, and disced prior to the next rainy season. <br /> 23. On 21 March 2001, staff met with the Discharger at the facility to inspect conditions and discuss <br /> emergency measures. The Discharger stated that the following emergency measures had already <br /> been implemented to reduce pond water levels and the risk of catastrophic berm failure: <br /> a. The Discharger asked RBAAP to cease their discharge; <br /> b. The Discharger excavated small, deeper holes in the bottom of Winter Ponds 1 through 4 to <br /> enhance percolation; <br /> c. The Discharger entered into negotiations with a neighboring landowner for use of a vacant <br /> field west of the Summer 2 pond for emergency effluent storage; <br /> d. The Discharger implemented a program of inspecting the western berm every two hours <br /> round the clock with emergency leak repairs; <br /> e. The Discharger considered the need to revoke the Sun Garden-Gangi discharge permit for at <br /> least one year; and <br />