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ASSISTED BY: December 27, 2019 Kaleb Ledford Staff Geologist Soil Suitability Nitrate Loading Study Manteca Unified School District 5700 East Nile Ave., Manteca, CA Page 10 near vicinity and agricultural use in the general region. Due to these factors and assumptions described, the shallow aquifer beneath the Site is already impaired. 2.4.2 Methods Proposed to Mitigate Known or Future Impact to Soil and Groundwater from Nitrate, and/or any Other Constituent of Concern, at and/or Around the Project Site The Site is located within historical and current rural housing and agricultural farmlands. Activities related to these practices and the use of existing septic systems are considered potential influences on soil suitability and nitrate loading results. Historical shallow groundwater elevation may further contribute to past and future nitrate concentrations. Typical mitigation measures to minimize potential building up nitrate in the shallow aquifer may include advanced treatment options to reduce effluent nitrate-N concentrations to below 10 mg/L and/or a designed groundwater offset that creates a separation of at least five feet between the bottom of the leach trench(es) and the static groundwater level. 3.0 CONCLUSIONS AND RECOMMENDATIONS Although the result of this nitrate loading report and calculation indicates that mitigation measures may be warranted in areas of unimpacted groundwater, existing impairment of the shallow aquifer suggests that mitigation may not be warranted. 3.1 REPORT CERTIFICATION Our professional services were performed, our findings obtained, and our conclusions proposed in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties either expressed or implied. Test findings and statements of professional opinion do not constitute a guarantee or warranty, expressed or implied. The professional findings contained in this nitrate loading study are strictly based on the information provided regarding the proposed project, other consultant's reports and conclusions, surficial geologic conditions encountered across the site by others. Furthermore, the analysis, conclusions and recommendations contained in this report are based on the site conditions as they existed at the time, we performed our study. Respectfully submitted, CONDOR EARTH ENVIRONMENTAL PROFESSIONAL: John P. Lane, CA PG No. 6795 Environmental Services Manager X: \Project\ 7000_prj \ 7862 MUSD Nile Garden Elementary \ 7862B - Soil Suit-Nitrate Loading \ Reports \ FR_20191219_Nile Garden_Soil Suit- Nitrate.docx CONDOR