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Soil Suitability/Nitrate Loading Study Irerracon Pickens Property ■ Tracy, California May 12, 2020 ■ Terracon Project No. NA207032 soil profile borings point to favorable conditions for shallow septic disposal. The presence of sandy soils at depths to 10 feet bgs allow for adequate seepage or percolation. Based on the percolation test results (5 minutes/inch), the soils within the proposed sewage disposal area appear suitable for a standard septic system. Septic system construction should follow the San Joaquin County Onsite Wastewater Treatment Systems Standards where applicable." Depth to groundwater is anticipated to be greater than 160 feet bgs. A domestic groundwater well is currently located on the site; therefore, groundwater samples were collected. Nitrate as N was reported at 14 milligrams per liter (mg/L) in groundwater sample GW-1 slightly above the MCL of 10 mg/L-N. Groundwater sample GW-2 reported below laboratory reporting limits of 0.010 micrograms per liter (ug/L) for DBCP. Based on the nitrate loading balance, nitrate levels for the existing residence is 11.6, above the MCL of 10.0 mg/L-N. The proposed second residence is anticipated to further increase nitrate as N levels to 15.9 mg/L-N, also above the MCL of 10.0 mg/L-N. 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. If the EHD requires mitigation for the project, an advanced water treatment product may be considered a mitigation option. 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 17