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Nitrate Loading Study Page 7 Proposed Warehouse 26550 South Banta Road Tracy, California Awl 15, 2014 CTE Job No. 20-2463G 5.0 NITRATE LOADING RESULTS & PROPOSED METHOD OF DISPOSAL 5.1 Nitrate Impact from Proposed Proiect The conservatively estimated nitrate loading (9.6 mg/1) impact on groundwater is below the State of California drinking water standard of 10 mg/L for nitrogen (N). In addition, the low percolation rate (480 min/inch) determined to exist (see Soil Suitability Study under separate cover) at the site may slow introduction of nitrate from the septic system to groundwater. The impact of the proposed septic system is believed to be relatively small in comparison to the potential nitrate- nitrogen introduced through agricultural practices in the vicinity. However, there are wells that are located adjacent to, and/or down gradient from the site which could be impacted by the proposed septic system. 5.2 Methods to Miti¢ate Impacts to Soil and Groundwater As indicated in our Soil Suitability Study (previously provided), the low percolation rate of the underlying soil will require an engineered design system to mitigate the slow percolation rate established. Such engineered system could also incorporate other controls such as a filtration system to reduce nitrate-nitrogen concentrations. 6.0 CONCLUSIONS AND RECOMMENDATIONS The calculated average concentration of nitrate-nitrogen loading in recharge groundwater is below, although, near the State of California's drinking water standard for nitrate-nitrogen in ground water. Therefore, the design engineer should consider incorporating engineered controls that reduce the amount of nitrate-nitrogen introduced to groundwater by the septic system. Additionally, the design is expected to consider system details that will mitigate the slow percolation/infiltration rate established at the site. The engineered system suitable for a septic/leach trench sewage disposal should be designed and constructed in accordance with SJEHD criteria. Able soil condition for septic percolation tests is defined by SJEHD as a stratum capable of percolating water at a rate of 60 minutes per inch (min/inch) at a depth of up to 3.5 feet below existing,site grade or 30 min/inch for deeper tests. CTE's percolation results for this project were 480 min/inch at a depth of up to 3.5 feet. As stated above, CTE estimates that the potential nitrate- nitrogen (N) concentration in groundwater resulting from the new leach field should be below the state standard of 10 mg/L. 7.0 LIMITATIONS The field evaluation, laboratory testing, and analysis presented in this report have been conducted according to current practice and the standard of care exercised by reputable consultants performing similar tasks in this area. No other warranty, expressed or implied, is made regarding the conclusions, recommendations and opinions expressed in this report. Variations may exist and conditions not observed or described in this report may be encountered during construction.