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U \I KLEINFELDER L 8. SEPTIC/LEACH FIELD REQUIREMENTS As stated previously, the restroom facilities of the proposed office will connect to the existing septic/leach field system that is connected to the barn. Based on the permit information, this system consists of a 1,200-gallon septic tank and three 80-foot leach lines for a total leach line r. length of 240 feet. The following calculations are based on SJCEHD requirements for commercial septic tanks. L We understand that after construction of the proposed office that the toilet and sink in the bam will be used infrequently. Although five employees will work in the office, to account for usage in the barn the following calculations include one additional employee, for a total of six employees. 1.5 Average Daily flow = 180 gallons per day(based on 6 employees multiplied by 30 15 L gallons per person per day.) L Leach Line Soil Factor = 0.2 (based on the native sand encountered during our investigation) Base Tank Capacity = 1,200 gallons s ce U Length of Leach Line = 276 feet (calculated by(1,200+ 180) x 0.2) (cJ 9. CONCLUSIONS L The results of our percolation tests indicate that a suitable soil percolation stratum exists at the percolation test location at the depth tested of about 3.1 feet below existing site grade. A suitable soil condition for tests 3 to 3'/2 feet in depth is defined as a stratum capable of L percolating water at a rate of 60 min/inch or faster. 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 facility, and that there is no need for an engineered system to be installed at the site. As previously discussed, we calculate 9.1 mg/l of nitrate-nitrogen (N) in groundwater resulting from the proposed leach fields, a result that is below the state drinking water standard of 10 mg/l. Based on this level of nitrate-nitrogen, we anticipate that the impact on surrounding wells will be low. The San Joaquin River is the nearest water body to the site and is located approximately 1 mile west of the property. Due to the distance to the San Joaquin River, we anticipate that the impact to surface water will be low. Based on SJCEHD requirements, the existing septic tank is of sufficient size for the propose commercial use. However, in order to connect the office to the bam's existin se tic systemLa new leach line measuring at least 40 feet in length would need to be added. L, 52251.00]/ST05RI92 Q4tX.i��^"' v� eb 17,2005 ©2005 Kleinfelder,Inc. ` , Page 7 of 8 f/Q,"rtt+' �avt