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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2008-0148 -4- LAWRENCE LIVERMORE NATIONAL SECURITY, LLC AND THE U.S. DEPARTMENT OF ENERGY FOR LAWRENCE LIVERMORE NATIONAL LABORATORY SITE 300 SAN JOAQUIN AND ALAMEDA COUNTIES systems, and results of an analysis of threat to groundwater from septic systems and percolation pits discharges based on the designated level methodology. The Discharger conducted the designated level methodology analysis to evaluate the potential threat to beneficial uses of groundwater from constituents in mechanical equipment and cooling tower discharges. The Discharger applied an attenuation factor for all constituents likely to be discharged to percolation pits and septic systems, except trihalomethanes. The Regional Water Board has since determined that because salts (as represented by measured specific conductance values, and sulfate, total dissolved solids, sodium, chloride, and nitrate concentrations) do not fully attenuate as they move through the soils, the Discharger will need to re- evaluate the potential for discharges of these salts to degrade groundwater. Monitoring and Reporting Program (MRP) No. R5-2008-0148, included with this Order, requires the Discharger to conduct additional monitoring of wastewater effluent for salts and metals in cooling tower and mechanical equipment effluent. 14.This Order also requires the Discharger to conduct studies and modeling to determine appropriate attenuation factors for salts and re-evaluate whether the discharges of salts and metals are degrading or have the potential to degrade groundwater. If the studies or modeling identify any discharges with the potential to degrade groundwater, the Regional Water Board will require that the Discharger monitor the groundwater near those discharges, which may require the installation of new monitoring wells. If groundwater degradation is confirmed, the Regional Water Board will require the Discharger to evaluate and conduct source control, and if beneficial uses of groundwater have been degraded, to prepare a feasibility study proposing groundwater remediation. PREVIOUS ANALYSIS OF GROUNDWATER IMPACTS 15.Site 300 conducts extensive monitoring of groundwater in connection with the CERCLA project. Some of the septic systems are within areas undergoing remedial investigation or areas where cleanup remedies have been selected and are being implemented. 16.CERCLA-conducted monitoring near septic systems at Buildings 812, 834, 850, and 899 have shown concentrations of nitrate above the maximum contaminant level (MCL). The septic systems at these four locations are within 30 feet of groundwater. In each of these areas nitrate is also a constituent of concern in the CERCLA investigation but, according to studies conducted by LLNL staff, the groundwater nitrate concentrations cannot be completely explained by CERLCA-related releases.