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i f k k L E I N F E L D E R groundwater, based on previous testing by our firm the value of nitrate as N compared to NO3 is usually about 25 percent or less. In other words, if 10 mgll is expected for NO3, the initial or background level of nitrate as N might be expected to be on the order of 2.5 mg/1 or less. When this value is combined with the 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 470 acre site should not cause a rise of nitrate levels above State standards. Furthermore, the Hantzsche equation has several limitations when applied to this project. The equation does not take into account the large depth to groundwater or the 70 to .95 feet of interlayered of silts and clays underlying that site. Both factors can contribute significantly to denitrification of the waste water. Using Designated Level Methodology (DLM) in accordance with the California Regional Water Quality Control Board criteria (equation 4 on page 43, October 1986), assuming an environmental attenuation factor (EAF) of 100, the nitrate concentration of nitrified leach field effluent (N,N) would need to be 1,000 mgll or' greater to effectively increase the nitrate N of the groundwater above 10 mg/l. As we have indicated, the typical nitrate concentration of nitrified leach field effluent ranges from 35 to 45 mg/l; The EAF 1 represents an average disposal situation like a landfill in the alluvium of the Central Valley with a significant depth (i.e., 15 to 50 feet) of soil containing appreciable and continuous clay or silty- clay strata between the base of the landfill and groundwater. LIMITATIONS The conclusions of this report are based on the information provided regarding the existing and proposed development and on the site conditions. It was assumed that the�percolatiori test result M is representative of the subsurface conditions in the general area. This completes the scope of work requested. Our work was performed in general accordance with the standard of care that exists in San Joaquin County. No other guarantee or warranty, expressed or implied is made. Respectfully submitted, pFESSlQN KLEINF ER, IG(I�-�F16 c� s e w No. 2283 m 410 f G� v a 1 �0r' S nior gi eer OF C:, GH :lr Att chment N 0 V 27 2006 GRAM L , sv, i rE�J�I jON CO. STOCKTON 20-1108-31.G02/2000R 1099 November 21,2000 ©2000 Kleinfelder,Inc. Page 4 of 4 - G