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Nitrate Loading Study Irerracon � Valencia Property ■ Ripon, California September 6, 2018 ■ Terracon Project No. NA187044 NITRATE LOADING STUDY VALENCIA PROPERTY (APN 245-070-81) CARROLTON ROAD AND ALLEN ROAD RIPON, SAN JOAQUIN COUNTY, CALIFORNIA OUR PROJECT NUMBER: NA187044 Our office was contacted by Mr. Bryan Valencia, site owner, to conduct a Nitrate Loading Study (NLS) for the property at Carrolton Road and Allen Road, Ripon, San Joaquin County, California. The formatting of this report has been designed to follow, to the greatest degree possible, San Joaquin County Environmental Health Department (EHD) Nitrate Loading Study Requirements Checklist, dated July 14, 2003. The site is located on an approximately 1.5-acre parcel currently improved with an orchard. Based on information received from Mr. Valencia, we understand the site is proposed to be developed with an approximately 3,900-square foot(SF)four bedroom three bathroom residence. We further understand future site expansions will include an approximately 4,800 SF shop building and a detached pool house (size not reported) with restroom and additional septic system. For the purpose of this study, the pool house shall be calculated as an additional bedroom. Terracon did not receive a site plan prior to the issuance of this report. Because of concern regarding nitrate leaching into groundwater from septic systems, a nitrate loading analysis is required by the EHD for the proposed development to determine the potential concentration of percolating effluent and rain fall over the long term. Where percolating effluent leaches into the ground, groundwater quality may be impacted to some degree should the effluent reach groundwater. 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. Hantzsche and Finnemore found that over a long period of time, water quality in the upper saturated groundwater zone closely approximates the quality of percolating recharge waters. They believe that their method is a good planning tool and provides useful information to planners and local officials but with some real limitations. In their article published in Ground Water, Hantzsche and Finnemore mention that "...the equation ignores dispersion, lateral flow, and mixing with groundwater flow from up-gradient areas. These processes would generally contribute to additional reduction of nitrate-nitrogen concentrations in groundwater to the extent that the nitrate-nitrogen concentration of groundwater flow from up-gradient areas is lower." Responsive ■ Resourceful ■ Reliable 2