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Nitrate Loading Study Irerracon Martinez Property■ Manteca, California March 2, 2018 ■ Terracon Project No. NA187004 4.0 DISCUSSION OF NITRATE LOADING RESULTS RELATIVE TO PROPOSED METHOD OF WASTEWATER DISPOSAL 4.9 Total Nitrate Impact Based on the method and assumptions described, the result of the nitrate loading balance indicates that the existing residential use is above the MCL of 10 mg/L-N. Additionally, the proposed residential use is anticipated to cause additional buildup of nitrates in the aquifer. 4.2 Methods of Mitigation Based on the proposed usage, mitigation may be required by the County. Mitigation may consist of the utilization of an advanced water treatment product such as those available by Orenco and others, which are specifically designed to lower nitrates at point of discharge. 5.0 CONCLUSIONS AND RECOMMENDATIONS Based on the nitrate loading results, the existing and proposed residential use has the potential to cause an increase in nitrates above the MCL when an average two person occupancy is calculated per bedroom. If the EHD requires site mitigation for the project, an engineered packaged septic system (such as those available by Orenco and others) specifically designed to lower nitrates at point of discharge may be used. 6.0 LIMITATIONS As indicated, our study takes into account the subject property only with the sewage load applied over the property site area. The study does not take into account surrounding properties and/or lands. The method utilized for the nitrate loading analysis is based on a simple mass balance formula, discussed in a published article by Hantzsche and Finnemore (1992), which provides a convenient and simplified method to estimate long-term groundwater nitrate impacts on an area- wide basis. A more detailed analysis was not requested nor intended. 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. Responsive ■ Resourceful ■ Reliable 9