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• 04 March 1996 <br /> ' AGE-NC Project No 95-0144 <br /> Page 16 of 18 <br /> ' utility pump-and-treat <br /> till ofsY stems is in preventing migration of contaminated ground water <br /> 7 2 5 COST <br /> Ground water extraction is usually a very costly method of ground water treatment Costs for <br /> installation of a"pump and treat" system is typically $20,000 00 to $30,000 00, including installation <br /> of one large-diameter extraction well However, once extracted, the contaminated water has to be <br /> treated or disposed Treatment is highly dependant upon the concentrations of dissolved <br /> hydrocarbons in the ground water For the Chase Chevrolet - Madison site, the cost per gallon could <br /> be as great as $2 00, based upon the extraction/treatment of approximately 100,000 gallons of <br /> ' contaminated ground water Costs for the entire treatment project would likely be between <br /> $100,000 00 and $300,000 00 <br /> ' 7 3 IN-SITU BIORENIEDIATION/BIOENHANCEMENT <br /> 73 1 BASIC PRINCIPLES <br /> Bioremediation involves the introduction of hydrocarbon-degrading microbes and/or nutrients to <br /> ' enhance naturally-occurring bacteria, through wells into the ground water The microbes degrade <br /> hydrocarbons and spread laterally (and vertically) by migration and reproduction <br /> ' Hydrocaibon-degrading microbes are able to metabolize hydrocarbons Typically, the light-end <br /> hydrocarbons are degraded more rapidly, and heavier hydrocarbon compound are degraded more <br /> ' slowly <br /> ' 7 3 2 NUTRIENT REQUIREMENTS AND TOXICITY <br /> The microbes require certain essential nutrients that are sometimes available in ground water If <br /> ' supplemental nutrients are required, which consist of nitrogen and phosphorus as ammonium <br /> phosphate in liquid phase, the quantity is usually very low However, a Waste Discharge Permit is <br /> requii ed by the CVRWQCB for the infection of nutrients into ground water <br /> ' Typically, microbes utilized in bioremediation are aerobic and usually require additional oxygen to <br /> r <br /> supplement dissolved oxygen concentrations in ground water Generally, several air spargi ng or in- <br /> '` well aeration sources are sufficient to provide the necessary oxygen However, in some cases the <br /> addition of hydrogen peroxide may be necessary <br /> , t <br />