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I. INTRODUCTION Chesney Consulting has been retained by Mr. Walter Azevedo of AG-CON Equipment Company to complete the requirements of the San Joaquin County Environmental Health Department(EHD) for the proposed installation of an office with a restroom and associated septic system at the subject property, located at 700 Mossdale Road in Lathrop, California. The business site is unique in that it is atop a man-made embankment, which is adjacent to the west of the Brown lake,which is also man-made. The Environmental Health Department has been at the forefront of nitrate impact investigations and the prevention or mitigation of environmental contamination from various sources of nitrate, particularly septic systems. EHD requires these investigations and corresponding septic system design criteria under Community Development Title 9-1105.2 (d) for projects in unsewered areas, in areas currently impacted with nitrate, or for projects that may potentially impact the underlying groundwater with nitrate. i The Environmental Health Department's main concerns regarding this project are 1.) The current environmental condition of the soil and groundwater under the proposed wastewater disposal area and the influence by the embankment the business is atop of, 2.)Natural mitigation measures through septic system design to alleviate future nitrate impact to the underlying groundwater, 3.) Assurance that sufficient wastewater disposal area exists to accommodate the average daily flow from the proposed septic system, 4.) Assurance that there is sufficient 100%replacement area that will remain designated as such, in the event of system failure, or a need to "rest" the primary ` disposal area, and 5.) Assurance that the primary disposal field and 100% replacement area comply l with the 200 foot rule, as stated in the S.J.C. Sewage Standards Section 8.1, Page 15, in which a sewage disposal area must be at least 200 feet from a lake or reservoir. As of this point in time,the Brown man-made lake is more than 290 feetawayfrom the Umposed effluent disposal area. In f addition, the Sewage Standards stipulate that the disposal area must be at least 10 feet from the / beginning of the downward slope (sometimes referred to as the heell, which has been incorporated into the design of the disposal area. A. SUMMARY OF FINDINGS The findings of our study reveal there has been no nitrate impact to the top groundwater(water table) under the proposed wastewater disposal area, no nitrate impact to the Brown lake and no nitrate impact to the underlying aquifers from the domestic well that serves the Brown Sand Company office. Therefore, septic system design criteria to alleviate and try to prevent future nitrate impact originating from the proposed septic system must be implemented. A non- pressurized filter bed system utilizing Infiltrator Chambers® has been designed to dispose of a projected 150 gallons er da d) o-f wastewater effluent. The chamber system will take Advanta e of_the_clay soils that were sed to construct the embankment which will mitigate nitrate impact_and promote evapotranspiration. Pae -2- Chesney Consulting