SITE INFORMATION AND CORRESPONDENCE

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Federal Facility Agreement: A document that specifies required actions at a federal facility (such as LLNL Site 300)as agreed upon by various agencies(e.g.,DOE,DTSC,EPA,RWQCB). Ground water extraction: The process of removing ground water from the subsurface, usually accomplished by pumping ground water. Can be used for removal of dissolved contaminants (such as TCE), lowering of the water table, and/or ground water migration control. MCLs: Maximum contaminant level(s). A drinking water standard. Monitor well: A well used for the purpose of ground water and/or soil vapor sample collection and water level measurements. Parts per billion(ppb): A unit of measure for the concentration of a substance in the surrounding medium. For example, one million liters of water containing one gram of TCE has a TCE con- centration of one ppb. This can be compared to 1 penny in$10,000,000 or 1 inch in 16,000 miles. Parts per billion (ppb /v): Parts per billion on a volume-to-volume basis. Plume: A relatively well-defined area of contamination found in ground water, surface water, soil vapor, soil, sediments, or bedrock. Present-worth cost: Present-worth analysis is a method of evaluating total costs (i.e.,the cost of each remedial alternative)for projects that vary in duration by discounting all costs to a common base year (1995) to adjust for the time value of money. The present-worth cost represents the amount of money,which if invested in the initial year(1995)of the remedial action and dispersed over the life of the project (i.e., 60 years), would be sufficient to cover all associated costs. The discount rate is based on the anticipated difference in investment return(i.e.,net interest income) and inflation. The present-worth cost of the Preferred Remedial Alternative (3b) is $19.75 mil- lion,assuming a discount rate of 3.5% (i.e.,6.5%interest and 3.0%inflation). However,govern- ment project funding is more likely to occur incrementally(i.e.,annually)as the project proceeds rather than as a lump sum investment at the beginning of the project. Under this scenario, the equivalent non-present-worth project cost for Alternative 3b is $35.29 million (1995 dollars). Regional aquifer: The primary water-supply aquifer underlying Site 300 and nearby areas. See also aquifer. Soil vapor: Vapor in the pore spaces of the unsaturated zone. The vapor can consist of air,water, VOCs, or other compounds. Soil vapor extraction: A means of removing soil vapor usually accomplished by applying a vacuum to one or more wells or buried horizontal slotted pipes. Typically used for remediation of soil/rock above the water table or in a dewatered zone. Trichloroethylene (TCE): A commonly used industrial solvent. A liquid at room temperature, TCE is heavier than water and therefore,in high concentrations,can sink through a water-bearing zone. TCE is a suspected human carcinogen. VOCs: Volatile organic compound(s). A group of organic compounds characterized by their tendency to evaporate easily at room temperature. Some familiar substances containing VOCs are solvents,gasoline,paint thinners,and nail polish remover. TCE,DCE,PCE,and TCA are all VOCs. This work was performed under the auspices of the U.S. Department of Enegy by Lawrence Livermore National Laboratory under Contract W-7405-ENG-48. 18