SITE INFORMATION AND CORRESPONDENCE

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Skill sets from many disciplines a9equired for Consider Goals Ri'fltive to the "Site-Specific effective P&T system management: Conceptual Model" • policy and regulations A site-specific conceptual model is a combination of hydrogeology text and figures that describe the hydrogeologic • engineering system,the cause of the ground water impacts, and the • risk assessment fate and transport of the ground water contaminants. • contracting It is not a numerical model!The conceptual model should attempt to explain the items listed in Exhibit 1. Site managers may not have expertise in all of these disciplines,but this fact sheet can be used as a quick Exhibit 1 reference guide and checklist for site managers,to make sure that the key aspects of P&T system A Site-Specific Conceptual Model Should management have been adequately addressed. Identify/Explain the Following Items B. SYSTEM GOALS AND EXIT STRATEGY historical and continuing sources of ground water contamination,both above ground and below the ......••• surface Goals for P&T systems typically involve cleanup historical growth and/or retreat of the ground water and/or containment of impacted ground water as a plume means of protecting human health and the environment. It is recommended that goals,both short-term or long- ground water flow velocity(horizontal and vertical) term, and other parameters controlling contaminant fate and transport • are clearly stated and prioritized and include a potential human and ecological receptors time frame; anticipated results of remedial actions • are appropriate relative to the site-specific conceptual model; • include metrics for evaluating system If the conceptual model does not adequately identify performance; or explain all of these items,the data gaps should be addressed with a focused investigation. This does not • clearly indicate when some or all of the P&T imply a return to the"remedial investigation"phase. system can be discontinued; and The conceptual model should evolve over time, including during active remediation, as more • are revised over time as appropriate. information about the site becomes available. Each of these items is discussed below. The goals of the P&T system should be appropriate relative to the site-specific conceptual model; Clearly State and Prioritize Goals otherwise, they may not be achieved. For example,a P&T system will not likely restore ground water to The system goals should be unambiguous, and each cleanup levels in a reasonable time frame if there are goal should include the expected time frame for continuing sources of contamination, such as non- achievement, even if that time frame is subject to aqeuous phase liquid(NAPL) or soil contamination. uncertainty. When multiple goals are stated, they Example 1,on the following page,provides an excerpt should be prioritized. For instance, ground water from a conceptual model to demonstrate the type of cleanup may be a long-tens goal, but plume data and interpretation that should be included. The containment may be a short-term goal that is critical for example also highlights potential data gaps in the immediate protection of human health and the conceptual model and related considerations for the environment. In such a case, containment should be site-wide exit strategy. given the higher priority. 2