ARCHIVED REPORTS_COMBINED ANNUAL AND SECOND-HALF 2012 GROUNDWATER MONITORING REPORT 01-31-2013

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WASTE DISCHARGE REQUIREMENTS ORDER R5-2012-0105 11 DIAMOND PET FOOD PROCESSORS OF RIPON, LLC AND RIPON COGENERATION, LLC DIAMOND PET FOOD RIPON FACILITY SAN JOAQUIN COUNTY does not allow degradation beyond that which may already exist. This Order includes a performance-based effluent limitation of 800 mg1L for TDS as an annual average, which is subject to review and revision depending on the outcome of the Dischargers' salinity reduction efforts. To address the sources of salinity discharged to the wastewater treatment system and the LAAs, this Order requires the Discharger to submit a Salinity and Nutrient Evaluation and Minimization Plan. Although the WOPS (background groundwater quality) of 713 mglL for TDS was established for this site, the current (pre-Diamond) groundwater TDS concentrations exceed this limit and shallow groundwater quality at the site exhibits high spatial variability. Therefore, it is not appropriate to set a numerical TDS limitation for groundwater. The Groundwater Limitations of this Order prohibit any statistically significant TDS increase in the groundwater monitoring wells and require the Dischargers to evaluate groundwater TDS annually using intra-well statistical analysis methods. b. For nutrients such as nitrate, the potential for unreasonable degradation depends not only on the quality of the treated effluent, but the ability of the vadose zone below the effluent storage/disposal ponds to provide an environment conducive to nitrification and denitrification to convert the effluent nitrogen to nitrate and the nitrate to nitrogen gas before it reaches the water table. The predicted untreated wastewater has a nitrate nitrogen concentration of 11 mg/L, which is greater than the MCL of 10 mglL for nitrate nitrogen. Although the nitrate concentrations of treated wastewater are expected to be reduced after treatment, there is some threat that the discharge could cause a violation of the MCL for nitrate. It is therefore appropriate to adopt a total nitrogen numerical limitation of 10 mg/L for effluent, to protect the municipal and domestic use of groundwater. The estimated loading rate of 256 lb/ac/year for total nitrogen for the untreated wastewater is significant, but the RWD did not include an estimate of the nitrogen reduction that could be achieved in the treatment system. Therefore, this Order requires the Dischargers to submit and implement a Salinity and Nutrient Evaluation and Minimization Plan within one year of adoption of the WDRs. 50. This Order establishes effluent and groundwater limitations that will not unreasonably threaten present and anticipated beneficial uses or result in groundwater quality that exceeds water quality objectives set forth in the Basin Plan. Current groundwater monitoring data indicate that groundwater has been degraded by previous discharges at the site, and that the discharge as proposed does not pose a threat of further degradation. The requirements of this Order do not allow any further degradation to occur. 51. The Dischargers currently provide treatment and control of the discharge that incorporates: a. Solids collection system to remove solids from the raw wastewater; and b. A lined aeration stabilization basin. Although some treatment and control has been implemented at the facility, the Dischargers may need to propose and implement additional treatment or control in order to ensure compliance with the Basin Plan.