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Soil Suitability /Nitrate Loading Study Irerracon ALL STAR HEAVY HAUL & TOWING INCORPORATED Tracy, California July 1, 2022 Terracon Project No. NA217024 Groundwater was not encountered in our soil profile / percolation test boring (131). Terracon recommends groundwater elevation be verified at various locations across the site. Two groundwater samples collected from the existing house (GW -1) were reported below laboratory reporting limits for nitrate as N and DBCP. The total maximum daily flow rate for Phase I - Septic System 1 is 16.875 gpd. Based on the nitrate loading balance, nitrate levels for the proposed development are anticipated to increase nitrate levels up to 1.7 mg/L-N which is below the MCL of 10 mg/L-N. The result of the nitrate loading balance indicates that the future development is not anticipated to increase nitrate levels above the MCL; therefore, nitrate mitigation appears unwarranted. In summary, the parcel appears suitable for the proposed development; however, based on the rapid percolation rates, shallow depth to groundwater encountered during field activities, and the EHD required 8 -foot separation between the bottom of the dispersal field and groundwater, Terracon recommends an engineered septic system for the development. The septic system design should accommodate peak flows and follow the San Joaquin County OWTS standards where applicable. 4.0 LIMITATIONS As indicated, our study takes into account the subject property only with the sewage load applied over the property site area. The study does not take into account surrounding properties and/or lands. 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. A more detailed analysis was not requested nor intended. Our professional services were performed, our findings obtained, and our conclusions proposed in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties either expressed or implied. Test findings and statements of professional opinion do not constitute a guarantee or warranty, expressed or implied. Responsive ■ Resourceful ■ Reliable 19