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u KLEINFELDER D = Fraction of nitrate-nitrogen loss due to dentrification of leach field effluent = 0.20 (Per Hantzsche and Finnemore (1992), 0.10 to 0.35 is typical). The .. 0.20 value was selected given that groundwater in the project area is relatively deep and the subsurface soils are interbedded with silt and some clay strata that would inhibit or slow infiltration of effluent to the groundwater. R = Average recharge rate of rainfall = 12.4 inches per year (representing 80 percent of the average annual rainfall of approximately 15.5 inches. The remaining 20 percent of rainfall is assumed to drain off-site into natural or manmade drainages or be lost to evapotranspiration.) Nb = Background nitrate nitrogen concentration of rainfall recharge at the water table = 0.5 mg/I (per Technical Memorandum, Hydrologic and Soil Investigation for the Chico Urban Area, page 6, Dames and Moore, April 1996) Our calculation that includes both the proposed temple and the existing home is as follows: Nc = 1.69(70)(1-0.20) + (12.4)(0.5) = 7.2 mg/I as N (1.69 + 12.4) Given the above factors, we estimate that the facility would require an average ` waste/sewage flow over 11 ,000 gal./week in order to exceed the state drinking water standard for nitrogen (N) of 10 mg/I in groundwater. 10. CONCLUSIONS The results of our percolation tests indicate that a suitable soil percolation stratum exists at the percolation test location at the SJCEHD approved depths tested of about 31/4, 41/2and 15 feet below existing site grade. A suitable soil condition is defined as a stratum capable of percolating water at a rate of 60 min/inch or faster at shallow depths and 30 min/inch for deep tests. Based on these results, it is our professional opinion that a conventional septic tank/leach trench sewage disposal system designed per SJCEHD criteria should adequately serve the proposed temple and that there is no need for an engineered system to be installed at the site. As previously mentioned, the concentration of DBCP found in the groundwater was above the drinking standard. Even though the estimated waste/septic flow and nitrate concentration of the leach field effluent value used in our calculations are probably conservative, we estimate that the potential nitrate-nitrogen (N) concentration in groundwater resulting from both the 59149.G011ST05R1062 December 15,2005 Copyright 2005 Kleinfelder, Inc. Page 6 of 7 r