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i k4 KLEINFELDER� 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 t� 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 y follows: Nc = 1.69(70)(1.69 +0)12.41).4)(0.5) = 7.2 mg/I as N �.iS68 Given the above factors, we estimate that the facility would require an average 3l�) 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. j 10. CONCLUSIONS r_ 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 4'/z and 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 j depths and 30 min/inch for deep tests. Based on these results, it is our professional L opinion that a conventional septic tank/leach trench sewage disposal system designed /o• per SJCEHD criteria should adequately serve the proposed temple and that there is no 6- j need for an engineered system to be installed at the site. As previously mentioned, we note that a percolation test was not performed in the silty sand at a depth of 3'/2-feet as required by SJCEHD. Since lower permeable sandy silt was located within about 6-inches of the silty sand layer at the 3'/z-foot depth, it was our professional opinion and judgment that the silt layer would control the performance of a leach field system at the site. Therefore, we felt it was more relevant to perform the percolation test in the silt at the 41/2-foot depth. 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 existing and new leach fields should be below the state standard of 10 mg/I. The South Main Canal is the nearest water body to the site and is located approximately ( 0.4 miles west of the property. Due to the distance to the South Main Canal and the i 59149.G01/ST05R1062 August30,2005 Copyright 2005 Kleinfelder,Inc. Page 6 of 7