SR0082465_SSNL - Laserfiche WebLink

Home Browse Search

7It is known that perched water table conditions do occur in this locale whereby the water table can be shallower than what has been recorded on the Groundwater Maps. No capillary fringe, or phreatic groundwater was observed in the 10 ft deep backhoe test pit. NLS§2.2,3.1, SSS§2.1, 4.2. Properties to the north, south, east and west are currently in agricultural production and rural residential. Considering this area has been farmed for decades, there is a significant potential for nitrate contamination to the underlying groundwater from nitrogen fertilizer applications and residual organic matter decomposition. NLS§2.3, SSS§4.3,4.4, 4.5,4.6. There are no wells on the property. A new public well is in the permitting process through EHD and the State of California. Calculation of the Alkalinity Requirements for Nitrification The nitrate-nitrogen loading calculations are contingent upon the environmental factors required for nitrification to occur. These conditions include soil pore-space oxygen content, soil temperature,pH, electrical conductivity, organic matter, cation exchange capacity, and alkalinity. Alkalinity in wastewater effluent is derived from the water source, in addition to the introduction of wastes and soil alkalinity. Nitrification consumes approximately 7.1 mg of alkalinity for every mg of ammonia-nitrogen(NH4 N) oxidized. Nitrification of the Total Kjeldahl Nitrogen(TKN) concentration of 144 mg/L, as determined below,would require: 144 mg/L NH4-N x 7.1 mg CaCO3 = 1,022 mg/L alkalinity. The alkalinity in well water is unknown but probably around 150 mg/L. The alkalinity determined from the septic tank effluent sample was 863 mg/L. 150 + 863 = 1,013 mg/L alkalinity. Therefore,there may be sufficient alkalinity for nitrification of the effluent ammonium fraction to occur. E. SURFACE WATER INFORMATION AND CALCULATIONS NLS§3.2. As referenced, the school grounds encompass two complete APN Parcels that will formulate the area portion of the Nitrate Loading Study,and totals 18.06 acres. The school facility consists of the portable classrooms, concrete hardscape areas and asphalt paved areas. This area totals 5.5 acres and is considered impervious. The remaining area is specified as the ball fields, decomposed granite (DG)walkways,and undeveloped/landscape areas. These areas can be considered pervious and totals 12.6 acres. The following Table illustrates the precipitation and evapotranspiration data for the Tracy area. The area delineation data above, correlated with this rainfall and Eto data will be used to develop estimated annual rainfall recharge. Page -5- Chesney Consultin,