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Soil Suitability Nitrate Loading Study Manteca Unified School District 5700 East Nile Ave.,Manteca,CA Page 4 Condor on April 19, 2019. Historical permits available for the Site suggests groundwater has been as shallow as 5 feet bgs in 2004. Department of Water Resources (DWR's) GeoTracker website was additionally reviewed for potential groundwater information. A closed Leaking Underground Storage Tank (LUST) clean-up site, RB Case Number 391052 is located at 5151 Almondwood Drive, approximately 2,000 feet southwest of the site. According to the Fourth Quarter 2005 Groundwater Monitoring Report,dated December 16,2005 depth to groundwater, measured from eleven groundwater monitoring wells onsite, had a groundwater depth of approximately 5 to 7.5 feet bgs. The flow direction was reported to generally flow northwest at an average of 0.0009 feet per foot based on these monitoring wells. The direction of groundwater flow is confirmed in the Fall 2015 Groundwater Report published by the San Joaquin County Flood Control and Water Conservation District. 1.4.2 Existing and/or Potential Groundwater Contamination Issues in the General Location The presence of nitrates is not uncommon in shallow groundwater aquifers in the San Joaquin County region. Nitrate in groundwater occurs as a result of the application of fertilizers, livestock waste, and untreated septic tank waste.The Site is located within rural housing and agricultural farmlands and activities related to these practices and the use of existing septic systems should be considered potential contamination sources. In addition, elevated concentrations of nitrate (as NO3), arsenic, and 1,2,3- trichloropropane(TCP)have been detected in on-site water supply well(s). 1.4.3 Location,Type and Construction of Well and Well Sample(s) Two water supply wells are located on-site that are used for irrigation only due to contamination issues.No well construction details are readily available for the older well, identified as 3901169-001 (Global ID W0603901169). The newer well, known as Main Well #2 3901169-008, (Global ID W0603901169), was completed to a depth of approximately 290 feet, with a 200-foot sanitary seal. A copy of the well log for Main Well#2 is included in Appendix E. 1.4.4 Constituents Being Tested for in the Water Sample MUSD tests drinking water quality from the on-site water supply well on a regular basis for many constituents as required by state and federal regulations. According to the 2018 Consumer Confidence Report dated March 3, 2019, Main Well #2 testing confirmed the presence of coliform bacteria, lead, copper, nitrate as nitrogen (nitrate-N), arsenic and TCP. The older well contained nitrate (as NO3) at a concentration of 59.5 milligrams per liter(mg/L)in June 2002,which exceeds the drinking water Maximum Contaminant Level (MCL)of 45 mg/L. Main Well#2 has consistently contained elevated levels of arsenic and TCP. Arsenic in the well has ranged from 15 micrograms per liter(gg/L)to 39.1 µg/L, which exceed the MCL of 10 µg/L for arsenic,and TCP has been detected as high as 0.072 µg/L,which exceeds the MCL for TCP of 0.005 ttg/L. In response, safe drinking water is being provided to the school using bulk storage tanks to deliver the drinking water. Copies of readily available testing results pertaining to the wells (DWR's GAMA database)are included in Appendix E. 1.4.5 Sample Collection and Handling Methodology No groundwater samples were directly collected as part of this report. Available groundwater analytical results from Main Well#2 were downloaded from DWR's GAMA database. 1.4.6 Chain of Custody Documentation No chain of custody documentation is provided in standard consumer confidence reports. rs �i� CONDOR