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INFORMATION SHEET ORDER NO. R5-2008-0148 LAWRENCE LIVERMORE NATIONAL SECURITY, LLC AND THE U.S. DEPARTMENT OF ENERGY FOR LAWRENCE LIVERMORE NATIONAL LABORATORY SITE 300 SAN JOAQUIN AND ALAMEDA COUNTIES Depth to groundwater varies across the site. Depth to groundwater below the sewage ponds ranges from 10 feet below to even with the base of the sewage ponds. Below the percolation pits groundwater is 30 to 130 feet below ground surface (bgs). Only the percolation pit at Building 812 overlies groundwater shallower than 65 feet bgs. Below the septic systems depth to groundwater ranges from less than 30 feet to 240 bgs. Sewage Evaporation and Percolation Ponds A lined sewage evaporation pond located on the southeast boundary of the site in the General Services Area receives sanitary and mechanical equipment wastewater. The evaporation pond discharges to a percolation pond during periods of heavy rainfall. The Discharger estimates that between 3.4 and 5.1 inches of rain over the rainy season is required to produce discharge to the percolation pond when operated with two feet of freeboard. Because depth to groundwater ranges between zero and 10 feet below the sewage ponds, discharge to the percolation pond has the potential to contaminate groundwater. This Order removes the freeboard requirement for the sewage evaporation pond to allow the Discharger to better manage the evaporation pond to reduce the frequency of discharge into the percolation pond. Prior to discharging under WDR Order No. 96-248, the Discharger operated under WDR Order No. 85-188, which had no freeboard requirements. Prior to 1995, the Discharger maintained a one-foot freeboard without incidence of structural damage or wave action washing over the berm. When operated with one foot of freeboard, there was no discharge to the percolation pond. The Discharger designed the sewage evaporation and percolation ponds to hold the maximum potential discharge plus influx from a 100-year storm event. This Order requires monitoring of the sewage ponds and groundwater as follows: • The influent to the sewage ponds must be monitored semi-annually for specific conductance (SC), pH, and biochemical oxygen demand (BOD). • The wastewater in the sewage pond must be monitored serni-annually for SC, pH, and dissolved oxygen and observed monthly for freeboard, color, odor, and levee condition. • If the sewage evaporation pond discharges to the percolation pond, the discharge shall be sampled for BOD, SC, total and fecal coliform, and pH. • The groundwater upgradient, crossgradient and downgradient of the sewage ponds must be monitored for SC, pH, nitrate, chloride, sulfate, sodium, total dissolved solids (TDS), total and fecal coliform, and ground water elevation.