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C"1 <br /> File No. 20-2921-01 <br /> KLEINFELDER <br /> March 25, 1992 <br /> ITEM C-5: <br /> "Other information as required by the San Joaquin Local Health <br /> District to determine the cumulative effect of the existing and the <br /> proposed development on ground water contamination. " <br /> San Joaquin County Environmental Health has expressed concern <br /> regarding the additional nitrate loading to the upper aquifer <br /> beneath the site area. The maximum allowable nitrate <br /> concentration in drinking water, according to State <br /> standards, is 45 mg/1. With suspected elevated nitrate <br /> concentrations in the groundwater beneath the site area, <br /> there is concern that the groundwater has a limited capacity <br /> for additional nitrate loading from septic systems. <br /> The following evaluation regarding nitrate loading has been <br /> prepared using information obtained from the following <br /> reports: <br /> 1. "Staff Report - Chico Urban Area, Butte County, " <br /> Principal Author, Ronald Dykstra, California <br /> Regional Water Quality Control Board (CRWQCB) , <br /> Central Valley Region <br /> 2 . "On-Site Wastewater Treatment, " Proceedings of the <br /> Fourth National Symposium on Individual and Small <br /> Community Sewage Systems, 12-10-11, 1984, New <br /> Orleans, Louisiana, American Society of Agricultural <br /> Engineers <br /> 3 . "Review Committee Report on Evaluation of Sources of <br /> Nitrate in Groundwater of the Chico Urban Area, <br /> Butte County, September 26, 1989 <br /> 4 . A Review of the Nitrate Problems in the Groundwater <br /> of the Santa Ana region and Their Relationship to <br /> High Density Developments on Septic Tank-Subsurface <br /> Disposal Systems, CRWQCB, Santa Ana region, <br /> September 8 , 1989 <br /> According to our review of the above references and our <br /> discussions with Mr. Dykstra, the "Hantzche" mass balance <br /> equation is one means of estimating nitrate concentrations in <br /> groundwater. In the CRWQCB report on nitrate concentrations <br /> in the Chico area, this formula was found to be sensitive to <br /> flow figures, home occupancy levels, and denitrification <br /> rates. The "Hantzche" equation is presented below with an <br /> explanation for each factor. <br /> Copyright 1992 Kleinfelder, Inc. Page 4 of 9 <br /> l <br />