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Farmington Murphy Property N%/ Page 2 Our Project Number: E07213A December 24, 2007 The Hantzsche and Fennemore approach is "...a conservative (worst case) first approximation of ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and precipitation. This (the equation and approach) is for estimation of long-term effect (i.e., over years) on ground-water quality, and is not intended for prediction of seasonal changes" (Hantzsche and Finnemore, 1992). The method takes into account the development area, soil denitrifaction factor, rainfall volume, rainfall nitrate concentration, waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations used for the analysis are shown on Plates 1 and 2. The units of nitrate used in the mass balance equation are nitrate-N, whose maximum drinking water contaminant level is 10 mg/L. The specific property use is undetermined at this time; therefore, our office will perform at scenario which represents the maximum allowable quantity and concentration of total nitrogen from the site. When the exact project is determined, a nitrate loading update study could be performed to determine weather ground water will be impacted from the project. 1.0 CHEMICAL AND PHYSICAL PROPERTIES OF SOIL 1.1 Chemical and Physical Soil Properties For a discussion of on-site soil properties, refer to Section 5 of the SSS completed by Dillon & Murphy. 1.2 Mass Transport Soil Properties The percolation tests have revealed that the soils are permeable to the maximum depth of exploration of 42-inches. These soils will allow moderate infiltration of water through the surface soils. The longer the effluent remains near the surface, the more treatment occurs due to natural processes within the soil. The San Joaquin County Soil Survey indicates clayey soils exist to a depth of 60 inches. A San Joaquin County ground water investigation report with maps prepared by the California Department of Water Resources was checked for the sand thickness. These maps indicate that no mappable sand exists in the vicinity of Jack Tone Road and Highway 4 to a maximum depth of 50 feet (DWR, 1967). Finer grain soils tend to slow the downward movement of percolating effluent from a septic system disposal field when compared to sandy soils. Due to the lack of sandy soils below the site, the potential impact to deep ground water is reduced when compared to other sites with thicker sections of sandy soil. 2.0 GROUND WATER ANALYSIS 2.1 Regional Ground Water Regional ground water information, including depth to ground water and directional ground water gradient, is discussed in Section 4.1 of the SSS completed by Dillon & Murphy. ,.44 902 Industrial Way•Lodi,CA 95240•209.367.3701 •Fax 209.369.4228 ©2007 Neil O.Anderson&Associates.Inc