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Nitrate LoadingStudy 1rarracon Rowe Propertyya Lodi, CA November 6, 2017 ■ Terracon Project No. NA177059 Based on the nitrate loading balance calculation (Table 4), nitrate levels for the reported current site use is 7.2 mg/L-N for two people who will reportedly be using the existing residence which is below the maximum contaminant level (MCL)of 10.0 mg/L-N. The current land use and proposed future use is anticipated to be 11.0 mg/L-N slightly above the MCL, with the addition of the two occupants in the proposed residence. Table 4 additionally indicates the potential nitrate levels for the existing three bedroom residence (x 2 people per bedroom) and proposed two bedroom residence (x 2 people per bedroom) are 13.5 mg/L-N and 16.7 mg/L-N respectively, which are above the MCL of 10.0 mg/L-N. 3.5.3 Impact of Nitrate Loading to Nearby Water Sources Based on a review of the USGS, Lodi (1976) and Waterloo (1978), California Quandrangles topographic map (Appendix A), the site is located at an elevation between 50 and 55 feet above mean sea level with a topographic gradient toward the west-southwesterly direction. The nearest surface water source to the site is the Pixley Slough located approximately 2,000+ feet south of the site. As the subject property is relatively flat, we do not foresee percolating effluent affecting the surface water resources. 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 reported existing residential use and proposed development (11.0 mg/L-N) on the parcel may cause a buildup of nitrates in the aquifer above the MCL of 10 mg/L-N. In considering the potential (2 persons per bedroom) as required by EHD, the existing three bedroom residence and proposed future two bedroom residence have the potential to cause a slight buildup of nitrates above the MCL (13.5 mg/L-N and 16.7 mg/L-N). 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 three bedroom residence (13.5 mg/L-N) and proposed future two bedroom residence (16.7 mg/L-N) have the potential to cause an increase in nitrates above the MCL when an average two person occupancy is calculated per bedroom. Responsive ■ Resourceful ■ Reliable 9