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Soil Suitability /Nitrate Loading Study 1rerracon Eagle's Nest Motorcycle School Stockton, California July 27, 2021 ,_ Terracon Project No. NA217040 Depth to groundwater was reported between 41.5 to 61.5 feet bgs in two former onsite monitoring wells. Groundwater flow direction was reported to the south-southwest. No groundwater samples were collected. The site is anticipated to be connected to Cal Water supply. The expected onsite maximum septic tank usage for the proposed motorcycle school is approximately 55 gallons of effluent per day. The result of the nitrate loading balance indicates that proposed development may increase nitrate levels up to 3.1 mg/L-N which is below the MCL; therefore, mitigation measures appear unwarranted. The client should be aware of two former groundwater monitoring wells associated with the off- site upgradient Canteen Corporation (1500 North Shaw Road) which were abandoned via grout backfill. Additionally, a historic industrial waste pond formerly located on the southern portion of the site was associated with the northern adjoining US Chemical and Beaver Chemical Co. facility (1448 North Shaw Road). Approximately 2,500 yards of contaminated soil was removed and replaced with clean fill dirt. The State Regional Water Quality Control Board granted the former on-site pond regulatory closure status in December 1994. In summary, the parcel appears suitable for the proposed 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. Kesponsive ■ Resourceful ■ Reliable 17