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�.. k'9 KLEINFELDER High Estimate Nc = 0.3(1.75)(45)(1 —0.1)+1.0(3) = 21.3 +3.0 = 6.9 mg/1 as N 0.3(1.75)+3 0.52 + 3 Average Nc = 6.21 mg/I as N One of the factors that is required by the SJCPHS is to determine the existing value of nitrate in the groundwater below the site. A groundwater sample was obtained for the existing on-site well using "clean" methods. At least 5 gallons of water was first bailed from the well prior to obtaining our sample. The water sample was submitted to GeoAnalytical Laboratories, Inc. using chain-of-custody procedures to evaluate nitrate as N in accordance with EPA Test Method 300. Results of the test showed a non-detectable nitrate as N concentration. A copy of our test results and chain of custody are attached. When this value is combined with our low and high nitrate-nitrogen (N) in groundwater calculated above, the total nitrate-nitrogen is well below the state drinking water MCL standard. Accordingly, we conclude that placement of the new septic system on the site should not cause a rise of nitrate levels above State standards. The results of a DBCP test performed that was used for nitrate testing indicated a non-detectable concentration of DBCP. The results of the DBCP test is also attached. DRAINAGE BASIN There are many factors that influence storm water disposal. Clear water was used in our tests, whereas oil residue, silt, organic matter and other deleterious material will likely be included in the actual storm water. Variations in soil conditions within the basin will also likely affect percolation characteristics. For use in design, a factor of safety on the order of 1.5 to 2 should be applied to the percolation rates estimated. The above percolation values apply to drainage trenches or drywells installed in the basins and possibly to the sides of the basins. Depending on the depth of the basins, the design percolation rates for the basin sides should be further reviewed. Over time, very little percolation should be assumed through the basin bottoms due to silting and organic build-up unless a vigorous program is followed to maintain the basins by frequent cleaning and discing to reduce silt build-up. Subsurface drain trenches and/or drywells should be equipped with filtered intakes. Our representative should be allowed to observe the soils exposed during construction of the basins and subsurface trenches or drywells in order to confirm that the design rates used are appropriate for the actual soils encountered. 20-4630-O1.G01/201 IR986 Page 4 of 5 Copyright 2001 Kleinfelder,Inc. August 16,2001