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Soil Suitability&Nitrate Loading Study Page 5 Munoz Property,Escalon, CA Project No. 605.1 ! June 18, 2009 4.0 GROUNDWATER RESOURCES 4.1 Depth and Flow of Groundwater According to the maps ai d in the San Joaquin County Flood Control and Water Conservation D' trio rep rt entitled "Spring 2003 Groundwater Report", i (Appe ix B) the depth to first g oundwater in this area lies at a depth of about 5 feet below ground 1 vel (+ Ft above MSL) and along most of the river frontag , flows toward the thwest. Locally, the map may not reflect this due o a ck of data points or to local influence such as groundwater pumping. onal variation in the depth to water in the area is typically in the range of several feet, and the direction of flow fluctuates, but will generally return to a southwesterly flow direction., obliquely towards the river. �-~ The neared open water in the area is the Stanislaus River, which lies about 300 J feet to the southeast, but in the down gradient direction (southwest), the distance to the river is over 1/2 mile. 4.2 Known and Potential Groundwater Contamination; There are many possible sources of groundwater contamination including f leaking storage tanks, surface releases of hazardous materials, over-use of agricultural chemicals, leakage from dairy lagoons, and septic sewage seepage. A detailed investigation of potential groundwater contamination was beyond the f scope of this investigation however, the State Water Board's "GeoTracker" website http://geotracker.swreb.ca.aov/ was searched to help identify possible sources of nearby groundwater contamination. No such sites were identified i within one mile of the site. Other maps, however, indicate that the Escalon ksewage treatment plant lies only about 0.1 miles (500 feet) southwest of the property (see Fig. 6 in Appendix B), and this could represent a source of nitrates to the groundwater. No nearby dairy lagoons or other common potential sources of contamination were noted in the air photo. r k ' Agricultural chemicals from off-site sources and nitrate from waste disposal must be considered as possible sources of groundwater contamination at this site. The waste treatment plant is in the generally down-gradient position, and is unlikely to have affected the site. In the up-gradient direction, there are several residential septic systems (estimated at about 5 or 6) within 1/ mile in the generally up gradient direction. These systems are not believed likely to + contribute more that a trace of additional nitrates to the subject site. This l assessment is based partially on the dispersion that occurs as septic tank p i effluent mixes and flows with the groundwater. 2937 Veneman Ave.,#B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto, CA 95356 Fax: (209)569-0295