SU0002193 SSNL - Laserfiche WebLink

Home Browse Search

F COLATION TEST RESULTS s were conducted on September 13, 1999 under U.S.E.P.A. and San Joaquin7and al Health guidelines. Since the soil at the perc test depth of 45 inches is san six inches of water seeped away after one-half hour, the test was conducted over a one-hour period. The depth at which the perc test was done represents effluent percolation which normally takes place at the bottom of a leachline trench. As illustrated on the attached FIELD PERCOLATION TESTING REPORT, the perc rate increased as a greater hydraulic head was placed on the water in the perc test boring. In general however, the perc rate slowed over the test period, signifying the soil was becoming increasingly saturated. The perc test results indicate rapid percolation of approximately 9.3 min/in at the shallow test depth. D. GROUNDWATER INFORMATION Groundwater elevation determinations are delineated on maps published by the San Joaquin County Flood Control District. The Lines of Equal Elevation map denotes the elevation at 0 feet mean sea level. As illustrated on the attached USGS map,the ground elevation is approximately 15 feet above mean sea level. Therefore,the static water table depth should be approximately 15 feet below grade. However,the capillary fringe was encountered at 22 feet, indicating the water table depth to be around 25 feet below existing grade. The groundwater under the subject property is being influenced by the Highway 120 Bypass, Interstate 5 and the Union Pacific Railroad tracks. This influence on the groundwater by these structures can be quantified, however,this is beyond the scope of this investigation. As with all groundwater tables,there are fluctuations in elevation. The critical issue with regards to the groundwater elevation under the subject property is that there is sufficient distance between the bottom of the leachline trench(or sump) and the highest anticipated depth to groundwater. This distance is sufficient for wastewater treatment to occur. The groundwater directional flow appears to be toward the northwest. As the groundwater is measured closer to the Delta, the greater the influence in elevation and directional flow. The directional flow cannot be accurately established because of the referenced influences. To determine the extent of past nitrate impact to the underlying drinking water aquifers, a water sample was taken from the well that serves the Cunha Trucking (braying) Company. This well water contains a nitrate concentration of 3 ppm and a chloride concentration of 28 ppm. Both of these indicators are very low concentrations and indicates a background nitrate impact to the respective aquifer(s). A well log was not available for this well. Chloride was measured to determine septic influence which may have originated from upgradient residential structures and confined animal facilities. Chloride travels especially well in the groundwater environment and is one of the primary indicators of septic and/or animal waste impact. 3 Va!!ey Ag Research