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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2008-0148 -8- LAWRENCE LIVERMORE NATIONAL SECURITY, LLC AND THE U.S. DEPARTMENT OF ENERGY FOR LAWRENCE LIVERMORE NATIONAL LABORATORY SITE 300 SAN JOAQUIN AND ALAMEDA COUNTIES 31 . In March 1997, the Discharger submitted a 100-year Storm Event Study for the Site 300 Sanitary Sewer Ponds (1997 Study) evaluating the capacity of the system to contain the 100-year precipitation event. The 1997 Study evaluated the maximum flow into the sewage evaporation and percolation ponds, the 100-year precipitation, infiltration and exfiltration, and percolation and concluded that the sewage ponds can hold the maximum discharge and the influx from a 100-year storm event. 32.To augment the 1997 Study, in 2005 the Discharger submitted a water balance evaluation to account for the evaporation from the system. The 2005 evaluation concluded that the evaporation potential is greater than the amount of water entering the sewage evaporation pond; approximately 75% of the flow into the sewage evaporation pond is lost to evaporation annually. During the winter months of December through March, the evaporation decreases and flows to the percolation pond may occur 33.The Order preceding Order No. 96-248 did not have freeboard requirements. For 10 years prior to issuance of Order No. 96-248, the Discharger operated the sewage evaporation pond with one foot of freeboard without incident of structural problems or wave action washing over the berm. Since depth to groundwater varies between zero and 10 feet below the base of the sewage ponds, overflow to the percolation pond has the potential to degrade groundwater. 34.This Order requires the Discharger to maintain adequate freeboard in the sewage evaporation pond to prevent over-topping or erosion of the pond embankment which may threaten the integrity of the pond. The Discharger will maintain the minimum freeboard determined as adequate to reduce or eliminate the overflow frequency to the percolation pond during winter months. Removable boards control flow into the spillway to the percolation pond and maintain freeboard depth. 35.This Order requires the Discharger to monitor quarterly the wastewater entering the sewage evaporation pond for specific conductance (SC), pH and biochemical oxygen demand (BOD) and the wastewater in the sewage evaporation pond for pH, SC, dissolved oxygen (DO), (BOD), total and fecal coliform and metals. Any discharge from the sewage evaporation pond to the sewage percolation pond is sampled and analyzed for DO, BOD, SC, total and fecal coliform, pH and metals. The Discharger also monitors groundwater downgradient and upgradient of the sewage ponds semi- annually for pH, SC, fecal and total coliform, chloride, nitrate, sulfate, sodium, total dissolved solids (TDS), metals and groundwater elevation. Sewage pond and groundwater sampling locations are shown on Attachment 8, a part