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California RRional Water Quality Antrol Board vCentral Valley Region = Steven T.Butler,Chair Winston H. Hickos Gray Davis Secretary for Sacramento Main Office G= Governor Environmental Internet Address: hitp://v .sw b.ca.gov/— gcb5 Protection 3443 Routier Road,Suite A,Sacmmento,Califomia 95827-3003 Phone(916)255-3000•FAX(916)255-3015 - 18 October 2000 Mr. Randall Dodd, Public Works Director �? City of Riverbank cn 6707 Third Street Riverbank, CA 95367 NOTICE OF VIOLA TIONAND WATER CODE SECTION 13267 REQUEST FOR REPORTS, CITY OF RIVERBANK WASTEWATER TREATMENT PLANT, STANISLAUS COUNTY On 28 August 2000, City of Riverbank staff reported that a percolation pond containment berm at the City's wastewater treatment plant had failed the previous evening. The berm failure caused approximately 20 million gallons of treated but undisinfected wastewater to flow into neighboring private orchards. Some of the wastewater entered a slough known as the"Hall Drain"which discharges to the Stanislaus River approximately two miles northwest of the wastewater treatment plant. We understand that City staff discovered seepage from a rodent hole in the western berm of Summer Pond No. 2 on the evening of 27 August 2000 and were attempting to stop the seepage when a 25-foot section of the berm failed. City staff informed the affected private property owners and retained an agricultural consultant to provide recommendations for action to prevent damage to the orchards. Samples of ponded effluent and affected soil were also submitted for analyses. City staff were unable to return the spilled wastewater to the facility because of the quantity involved, the lack of available storage capacity, and relatively rapid percolation. Based on Board staff s 30 August 2000 inspection, most of the spilled effluent percolated into the ground within 48 hours of the spill and the water level in the drain had returned to its usual level. Because the Hall Drain is poorly maintained and has several blockages, it appears that only a small percentage of the spilled effluent was discharged to the Stanislaus River. Analytical results for samples of water obtained from the flooded orchard showed that concentrations of total coliform bacteria and fecal coliform bacteria were substantially less than those found in Summer Pond No. 1, whose effluent should be similar in character to the effluent accidentally released. The discharge is a violation of Waste Discharge Requirements (WDRs) Order No. 94-100. Specifically, Discharge Prohibition A.1 prohibits discharge of wastes to surface waters or surface watercourses. As you know, this is a serious violation. However, as discussed in the 5 October 2000 meeting with Board staff, we recognize that the City's response to the spill was timely and appropriate. California Environmental Protection Agency 0 Recycled Paper -