Laserfiche WebLink
Soil Suitability / Nitrate Loading Study <br />Ernst Property ■Tracy,CA <br />February 21, 2019 revised April 9, 2019 ■ Terracon Project No.NA197000 <br />Responsive ■Resourceful ■Reliable 16 <br />2.3.6 Impact of Nitrate Loading to Nearby Water Sources <br />Since the subject property building area is relatively flat, we do not foresee percolating effluent <br />affecting any surface water resources. <br />2.4 Discussion of Nitrate Loading Results <br />2.4.1 Total Nitrate Impact <br />Based on the method and assumptions described, the result of the nitrate loading balance (38.3 <br />mg/L N) indicates that the development on the parcel may cause a buildup of nitrates in the aquifer <br />above the MCL of 10 mg/L-N. <br />2.4.2 Methods of Mitigation <br />Mitigation may consist of the utilization of an advanced water treatment product such as those <br />available by Orenco, which are specifically designed to lower nitrates at point of discharge. Other <br />mitigation options include the use of a carbon source such wood chips. Based on the proposed <br />usage, mitigation may be required by the EHD. <br />3.0 CONCLUSIONS AND RECOMMENDATIONS <br />In summary, a satisfactory percolation rate of 35.71 minutes per inch was obtained at 3.0 feet <br />bgs. The parcel appears suitable for the use of a standard septic system utilizing shallow leach <br />lines designed for the intended usage. Final septic system construction should follow the San <br />Joaquin County On-Site Wastewater Disposal Standards where applicable. <br />Based on the nitrate loading results, nitrate levels for the current five bedroom residence (20.2 <br />mg/L-N) exceeds the MCL of 10 mg/L-N for nitrate in drinking water when an average two person <br />occupancy is calculated per bedroom. The construction of the proposed three bedroom mobile <br />home (18.1 mg/L-N) is anticipitated to further increase nitrate levels to 38.3 mg/L-N, also above <br />allowable limits for groundwater. <br />The site drinking water is provided by the County Service Area #35; therefore, a groundwater <br />sample was not collected. Elevated levels of Nitrate as N and DBCP were not identified above <br />MCLs in the County water supply. <br />If the EHD requires mitigation for the project, an advanced water treatment product or carbon <br />source may be considered mitigation options.