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Region 5,No Further Action `,/ 5 <br /> 10 October 1996 <br /> DRAFT DRAFT' DRAFT DRAFT' DRAFT DRA>~i' DRAFT DRAFT <br /> �. GROUND WATER CASES <br /> Central Valley aquifers are unique because they constitute the State's largest aquifer <br /> with about 75%;of the available water storage in California. Additionally, much of <br /> the Central Valley's surface waters are exported for use in Southern California and <br /> the San Francisco Bay area, leaving ground waters to provide the majority of Central <br /> Valley municipal and domestic use. Considering California's historic growth and <br /> growth projections, it is apparent that water demands already exceed the surface water <br /> supplies. <br /> Ground water cases are those where petroleum hydrocarbons have reached the <br /> ground water or capillary fringe, and include the pollutants in the vadose zone. <br /> Water found in tank pits during "tank pulls" may result from local storm events and, <br /> so, must be sampled, analyzed and pumped out. If water seeps into the pit after <br /> pumping, it is ground water. <br /> CRITERIA FOR LOW RISK GROUND WATER DESIGNATION <br /> All the following criteria must be met: <br /> .. 1. Contaminants remaining in the vadose zone must not reverse or threaten to <br /> reverse the mass reduction rate of ground water pollutants discussed in#4 <br /> below. <br /> Aquifer water levels may rise in response to rainfall events and, thereby, <br /> be impacted by the hydrocarbon contaminants remaining in the <br /> vadose zone. Information must be supplied to show that this will <br /> not reverse the mass reduction rate. <br /> 2. Separate phase product has been removed to the extent practicable. <br /> See Title 23, CCR, Section 2655, Article 5 of the Underground Storage <br /> Tank Regulations which requires removal of "free product to the <br /> maximum extent practicable" to minimize "the spread of <br /> contamination into previously uncontaminated zones." <br /> 3. No existing water supply wells, deeper aquifers,surface waters or other receptors <br /> are threatened by pollutants remaining in the aquifer. <br /> Water supply wells include municipal, local service or private wells, <br /> r agricultural and industrial wells. Central Valley aquifers generally <br /> are not segregated into discrete units, but are subject to vertical and <br /> horizontal migration of water and any pollutants carried by or in <br /> .. the water, often by local pumping. Other receptors include <br /> basements, buildings, subsurface utilities, wildlife, etc. <br /> V <br /> V <br />