SR0084171_SSNL - Laserfiche WebLink

Home Browse Search

Soil Suitability/ Nitrate Loading Study Eagle's Nest Motorcycle School Stockton, California July 27, 2021 Terracon Project No. NA217040 Table 6. Summary of Percolation Test. 1rerracon, Test No. Percolation Test Percolation Rate Test Duration Comments Date Tested Depth feet min/in hours see note P4 Unsatisfactory 07-07-2021 25 31.25 4 Percolation Rate P5 Satisfactory 16 25 4 07-07-2021 Percolation Rate P6 3.5 0.0 --- Unsatisfactory 07-07-2021 Percolation Rate Note: A sanstactory percolation rate is tiU minutes per inch or less Tor shallow leach lines and 3U minutes per inch or less for septic pits per San Joaquin County Onsite Wastewater Treatment Systems Standards (EHD 42-014), January 2017. 1.6.7 Discussion of Percolation Test Results Based on the percolation tests results, percolation test boring P5 at 16 feet bgs achieved a passing percolation rate of 30 minutes per inch or less for seepage pits. Boring P4 at 25 feet bgs demonstrated a percolation rate of 31.25 minutes per inch which is slightly slower that the EHD required 30 minutes per inch for seepage pits. The shallow percolation test P6 at 3.5 feet bgs failed to demonstrate a satisfactory percolation rate of 60 minutes per inch for shallow leach lines. Based on the percolation tests results, the site appears suitable for deep seepage pits. 1.6.8 Discussion of Septic System Sizing In general, septic system construction should follow the San Joaquin County On -Site Wastewater Disposal Standards (OWTS) where applicable. 2.0 NITRATE LOADING STUDY Because of concern regarding nitrate leaching into groundwater from septic systems, a nitrate loading analysis is required by the EHD for the proposed development to determine the potential concentration of percolating effluent and rain fall over the long term. Where percolating effluent leaches into the ground, groundwater quality may be impacted to some degree should the effluent reach groundwater. 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 groundwater nitrate impacts on an area - wide basis. Hantzsche and Finnemore found that over a long period of time, water quality in the upper saturated groundwater 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, Responsive ■ Resourceful ■ Reliable 12