SR0056541 SSNL - Laserfiche WebLink

Home Browse Search

E. SURFACE WATER INFORMATION Lr � Storm water management on the land-side of the levee is not too much of a concern since there is a ditch directly on the east side of the subject property that can manage runoff from the schoolhouse building and soil surface. Since the groundwater directional flow is predominately west-east based on water body orientation, Water in this ditch percolating into the top aquifer mixing layer may create a dilution effect on the crossgradient percolating septic system effluent. Groundwater dilution effects can only be truly r discerned with groundwater monitoring and modeling. According to a scientific paper authored by Shaw and Turyk (1994), reduction of nitrate concentrations in groundwater can occur primarily through dispersion, dilution, or by percolating rainwater recharge. Climatic Data: Rainfall versus Evapotranspiration NLS§3.2. 'It is generally and scientifically accepted that when precipitation exceeds evapotrans- piration (Eto); deep percolation of surface rainwater may occur. Evapotranspiration refers to water` evaporation that takes place both at the soil surface and transpiration by plants, and is defined as Water. loss from a large field of 4-to-7 inch tail, cool-season grass that is not water stressed. The following Table illustrates rainfall and evapotranspiration for the Stockton area, which was the closest data to the project site. Precipitation data was obtained from the Soil Survey of San Joaquin County. The conservative "2 years in 10" data was used and not the "average rainfall' data. Evapotranspiration data was obtained from the California Irrigation Management Information System (CIMIS): TABLE 5 FF PRECIPIT ' �4 ATION A1 �;Ety DATA,FOR STOCKTON CA,� .2 Years in 10 will have more Eto Average Potential Deep precipitation than: (in/mo) Percolation(in/mo) (in/mo) (in/day) January 4.42 1.24 0.04 3.18 February 3.20 1.96 0.07 1.24 March 3.43 3.41 0.11 -- April 1.92 5.10 0.17 May 0.50 6.82 0.22 -- June 0.25 7.80 0.26 -- July 0.23 8.06 0.26 -- August 0.40 7.13 0.23 -- September 0.76 5.40 0.18 -- 7 Chesney Consulting