SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

CLEANUP AND ABATEMENT C&R NO. 5-01-703 • -5 - CITY 5 - CITY OF RIVERBANK WASTEWATER TREATMENT PLANT STANISLAUS COUNTY 21. On 6 November 2000, the Discharger submitted a technical report that included the following: a. A review of existing conditions and system capacity for the wastewater treatment plant. The report concluded that there was sufficient excess treatment capacity to serve 2,400 additional residences and sufficient excess disposal capacity to serve an additional 3,600 residences as long as the Sun Garden-Gangi discharge complies with the BOD and flow limits contained in its industrial discharge permit. b. An assessment of necessary treatment plant improvements with a cost estimate. The evaluation studied two scenarios: projected population growth of 14,000 with no increase in flow from the cannery, and projected population growth of 14,000 with a 16.7% increase in flow from the cannery. The report concluded that about 12 acres of additional percolation ponds would be required in either scenario with one to three additional 75-hp aerators depending on cannery growth. The projection concluded that this expansion would be needed no sooner than 2013. c. A water balance for the existing treatment and disposal system. The water balance confirmed the excess storage and disposal capacity,provided that percolation rates are at least 1.4 inches per day. To accomplish this, it was assumed that each percolation pond would be out of service three months each year for drying and discing. d. A preliminary assessment of pond berm condition prepared by a geotechnical engineer. The report concluded that the western berm that contains the Summer 2 and Summer 3 percolation ponds is constructed of relatively loose, sandy soil, which is vulnerable to failure due to burrowing animals and piping. The exterior and interior slopes of the berm are oversteepened. The northern berm,which contains the Summer Aeration Cell and the Summer 1 treatment/percolation pond, is apparently constructed of finer-grained material, but also had many burrows. The engineer's preliminaryrecomrnendations wei a to permanently repair the western berm, including correcting the oversteepened exterior slope and lining the interior slope or other similar measures to prevent piping. The engineer recommend that both the western and northern berms be evaluated further based on a subsurface investigation. 22. On 5 March 2001, the Discharger's consultant reported freeboard violations in all of the ponds due to reduced percolation rates. The Discharger proposed to construct an emergency percolation pond on one of two neighboring sites previously identified as possible future expansion sites. The purpose of the emergency percolation pond is to provide immediate relief of freeboard problems and allow the existing ponds to be dried out, repaired, and disced prior to the next rainy season. 23. On 21 March 2001, staff met with the Discharger at the facility to inspect conditions and discuss emergency measures. The Discharger stated that the following emergency measures have already been implemented to reduce pond water levels and the risk of catastrophic berm failure: a. The Discharger asked RBAAP to cease their discharge; b. The Discharger has excavated small, deeper holes in the bottom of Winter Ponds 1 through 4 to enhance percolation;