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I k" KLEINEELDER I P-20 2.7 83.3 P-21 18.9 250 P-22 3.3 62.5 P-23 2.0 No percolation P-24 19.1 No percolation P-25 2.8 250 P-26 2.5 250 P-27 2.7 41.7 P-28 2.7 50 P-29 9.7 41.7 P-30 9.0 No percolation P-31 18.4 No percolation P-32 1.5 250 P-33 5.8 No percolation P-34 22.7 62.5 P-35 2.6 250 P-36 14.2 250 NITRATE LOADING CALCULATIONS Per-San Joaquin County Public Health Services (SJCPHS) Department Environmental Health Division (PHS/EHD) requirements, the following summarizes our nitrate loading calculations for the proposed leach fields. The drinking water standard for nitrate is 45 milligrams per liter (NO3) and 10 mg/l as Nitrogen (N) in groundwater. In our evaluation of nitrate loading, we have used the Hantzsche mass balance equation (source: Predicting Ground-Water Nitrate-Nitrogen Impacts, Hantzsche and Finnemore (1992)), which is presented below with an explanation for each factor and the value used in our study. Since there is currently no deed restriction limiting the number of homes on each lot to one, we have calculated the average nitrate (Nc) in groundwater based on both one and two homes per lot as required by Mr. Huggins with SJCPHS. The selection of other parameters was based on previous studies by our firm, as well as a report dated March 19, 1997 prepared by the Questa Engineering Corporation and authored by Mr. Hantzsche. Mr. Hantzsche prepared his report for a subdivision that had similar fine-grained silts and clays to those encountered at the subject site. Fore these reasons, we have chosen to use the same values considered appropriate by Mr. Hantzsche for his report, with the exception of an increased value for percent denitrification (D) that has been modified based on recent local testing. i 20-4476-01.602/201181242 Page 4 of 6 ©2001 Kleinfelder, Inc. October 11,2001