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INTRODUCTION AND BACKGROUND INFORMATION Chesney Consulting has been retained by Mr. Danny Costa to design an onsite wastewater treatment system (OWTS) to serve a new agricultural office building he is in the process of developing. Mr. Mel Loureiro, owner of Progressive Designs in Manteca, has designed the building and provided improvement details for this report. The Site Plan and Floor Plan produced by Progressive Designs are attached and found in Appendix B. All OWTS in San Joaquin County must comply with requirements promulgated by the San Joaquin County Environmental Health Department (EHD). Since this project must operate on a well and onsite disposal system, Mr. Costa and Mr. Loureiro wanted assurance that the OWTS for this project will comply with all EHD requirements including the Soil Suitability and Nitrate Loading Studies conducted under EHD guidelines.. Additionally, the filter bed and seepage pit OWTS to be installed have been economically designed, and provide a long lifespan in correlation with a high degree of environmental protection by promoting effluent management by a filter bed effluent disposal structure. Since the exact location and dimensions (i.e., rectangle or square) of the filter bed and seepage pit structures to be installed is unknown as of the date of this report, OWTS design plans cannot be formulated at this time. This report provides the OWTS calculations, discussion of construction details, setback issues, and the 100% replacement area, location and construction details. SOIL SUITABILITY STUDY The subject property details are referenced on the Title Page with the Parcel vicinity illustrated on the Parcel Viewer Map and aerial photo. Mr. Costa operates a fresh cut sweet corn processing facility on the property, which also includes an office trailer building, a residential modular home and the future administrative building. The entire region has been in agricultural production for the last several decades. Consequently, nitrate impact has occurred in the underlying groundwater from agricultural nitrogen inputs and not due to OWTS in this locale since septic tank usage is sparse in this locale. Only one EBD permit for repair/additions was located within the one-half mile study area due to the low number of OWTS. The permit is found in Appendix F. There are three separate OWTS on the subject property. One serves the fresh cut sweet corn facility, the second serves the current office trailer building and the third serves the modular home at the north end of the property. The 1999 groundwater maps, which can be considered the highest depth to groundwater, show the water table at 50 ft b.g.s. The Fall 2018 Depth to groundwater map shows the depth to the water table to be 70 ft; a 20 ft decline in 19 years due to drought conditions and over pumping. The Groundwater Surface Elevation maps show the groundwater flow to be in a northeasterly direction. A water sample was retrieved from the sample port on the well illustrated on the aerial photo site plan. Analysis for nitrate-nitrogen, the agrichemical Dibromochloropropane (DBCP) and total alkalinity was conducted, with the results found Appendix H. Test results reveal a nitrate nitrogen concentration of 7.62 ppm. The DBCP concentration was determined to be 0.0550 ug/L, a 73% decrease from the MCL of 0.2 p,g/L. Page -1- Chesney Consulting