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May 25, 2004 ` NCA Project Number: E04061A Page 14 Lot Test No., Percolation Percolation Rate Test Comment Number Date Tested Test Depth (minutes/inch) Duration (see notes) (ft) 63 PT 63-1 shallow, 3.4' 62.5 4 hr Failed 4/29/04 63 PT 63-1 shallow, 4' 8.1 4 hr Satisfactory percolation 4/]3/04 rate Notes: A satisfactory percolation rate for a"shallow"test is less than or equal to 60 minutes per inch. A satisfactory percolation rate for a"deep"test is less than or equal to 30 minutes per inch. •Estimated. r 6.5 Discussion of Percolation Tests Soils on each lot have demonstrated a satisfactory percolation rate in accordance with the requirements of the San Joaquin County EHD. The soils of the Site appear to be suitable for a septic system utilizing shallow leach lines and seepage pits. 6.6 Required Size of Septic System The EHD Sewage Standards should be followed to size the septic system. 7.0 NITRATE LOADING ANALYSIS Because of the concern regarding nitrate leaching into ground water from septic systems, a nitrate loading analysis was required by the San Joaquin County Public Health Services, Environmental Health Division for the proposed facility to measure the potential concentration of percolating effluent and rain fall over the long term. Where percolating effluent leaches into the ground, ground water quality may be impacted to some degree should the effluent reach ground water. The method utilized for the nitrate loading analysis is based on a simple mass balance formula, discussed in a published article by Hantzsche and Finnemore(1992)which provides a convenient and simplified method to estimate long-term ground-water nitrate impacts on an area-wide basis. Hantzsche and Finnemore found that over a long period of time, water quality in the upper saturated ground-water zone closely approximates the quality of percolating recharge waters. They believe that their method is a good planning tool and provides useful information to planners and local officials but with some real limitations. In their article published in Ground Water,Hantzsche and Finnemore mention that "...the equation ignores dispersion, lateral flow, and mixing with ground water flow from up-gradient areas. These processes would generally contribute to additional reduction of nitrate-nitrogen concentrations in ground water to the extent that the nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower." r.