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Nitrate Loading Study Irerracon Guillermo Ramirez Property ;w Ripon, California April 29, 2019 i: Terracon Project No. NA197019 4.0 DISCUSSION OF NITRATE LOADING RESULTS RELATIVE TO PROPOSED METHOD OF WASTEWATER DISPOSAL 4.1 Total Nitrate Impact Based on the method and assumptions described, the result of the nitrate loading balance indicates that the proposed residential use on the site may cause a buildup of nitrates (20.0 mg/L- N) in the aquifer above the MCL of 10 mg/L-N. 4.2 Methods of Mitigation Mitigation may consist of the utilization of an advanced water treatment product such as those available by Orenco, which are specifically designed to lower nitrates at point of discharge. Other mitigation options include the use of a carbon source such wood chips. Based on the proposed usage, mitigation may be required by the EHD. 5.0 CONCLUSIONS AND RECOMMENDATIONS The proposed residential use has the potential to cause a buildup of nitrates (20.0 mg/L-N)above the MCL of 10 mg/L-N when an average double occupancy is calculated per bedroom. A groundwater well is not located on the site; therefore, a groundwater sample was not collected. Elevated nitrate levels (up to 70.4 mg/L-N) were reported in off-site groundwater wells located approximately one mile north and east of the site. Depth to groundwater is anticipated between 45 and 68 feet bgs. Agricultural land use on the site and vicinity is anticipated to be the highest contributor of nitrates in groundwater. If the EHD requires mitigation for the project, an advanced water treatment product or carbon source may be considered mitigation options. 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