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Soil Suitability/Nitrate Loading Study Irerracon Vacant Commercial Property■ Stockton, California December 7, 2018 ■ Terracon Project No. NAI 87056 Soil Name/ Depth USDA Unified Soil Clay Permeability Soil Salinity Septic tank reaction (m Map (in) Texture Classification M (in/hour) m) cabsorption Symbol (pH) cm) fields 0-22 clay CL 40-60 0.06-0.2 6.6-8.4 <2 ----- _............. ..._._._._—.__.........__.........------------- .............. ._ --- clay loam, 0.06-0.2 22-34 clay, silty CL 35-60 7.9-9.0 <2 Severe; Jacktone clay cemented clay/ -- -- an, 34-37 indurated --- --- --- --- --- P 180 —--------—--------------------....---.....-------...-----------------------------___.._..._._...-- ---- -------------- percolates 37-46 loam, clay CL-ML 20-30 0.2-0.6 7.9-9.0 <2 slowly loam ------------ -----—----___.......—-------------------------- ------ 46-60 cemented --- --- --- --- --- `Selected USDA physical and chemical properties 2.1.2 Mass Transport Soil Properties The longer effluent remains near the surface, the more treatment is enhanced due to natural processes within the soil. Stockton clay soils are located on the northwestern portion of the parcel and consist of somewhat poorly drained soils with 0 to 2 percent slopes. Parent material consists of alluvium derived from mixed rock sources. Jacktone clay soils are located on the southeastern portion of the site and consist of somewhat poorly drained soils with 0 to 2 percent slopes. Parent material consists of alluvium derived from mixed rock sources. The USDA Soil Survey of San Joaquin County indicated the main limitations for both soil types on sites with septic leach fields is the slow permeability which can be overcome by increasing the size of the leachfield, backfilling the trench with sandy material, and/or ripping the hardpan. 2.2 Groundwater Analysis 2.2.1 Regional Groundwater A discussion of regional groundwater, including depth to groundwater and flow gradient is included in Section 1.4.1. No significant seasonal trends were evident from the sources consulted. 2.2.2 Potential Ground Water Contamination Issues A discussion of issues related to potential groundwater contamination is included in Section 1.4.2. 2.2.3 Current and Future On-Site Ground Water Uses One nonoperational domestic groundwater well is located near the southeastern corner of the site. The proposed future use of the well is not currently known. Based on the identified groundwater contamination and soil and groundwater remediation conducted on the site, the EHD should be consulted prior to future groundwater use. In addition, if the domestic well will remain Responsive ■ Resourceful ■ Reliable 16