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Nitrate Loading Study 1 rerr�con Landavazo Property Tracy, CA December 15, 2017 < Terracon Project No. NA177067 term effect (i.e., over years)on groundwater quality, and is not intended for prediction of seasonal changes" (Hantzsche and Finnemore, 1992). The method takes into account the development area, soil denitrification factor, rainfall volume, rainfall nitrate concentration, waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations used for the analysis are shown in Appendix B. The units of nitrate used in the mass balance equation are nitrate-N, whose maximum drinking water contaminant level (MCL) is 10 mg/L. 1.0 CHEMICAL AND PHYSICAL SOIL PROPERTIES 1.1 Chemical and Physical Soil Properties Terracon reviewed the United States Department of Agriculture (USDA) Natural Resources Conversation Service (NRCS) Web Soil Survey (https://websoilsurvey.sc.egov.usda.gov), for information regarding soil properties. Based on information obtained from the website, onsite soils consist of Stomar clay loam which consist of well drained soils with 0 to 2 percent slopes. Parent materials consist of alluvium derived from sedimentary rock. Typical soil profiles consist of 0 to 17 inches fine clay loam, 17 to 47 inches clay, and 47 to 60 inches clay loam. 1.2 Mass Transport Soil Properties Based on a review of the USDA Soil Survey of San Joaquin County California (Issued 1992), Stomar clay loam soils, have slow permeability, and high shrink swell potential. Water in-take in irrigated areas is anticipated at 0.5 inches per hour. The slow permeability is a limitation and can be mitigated by increasing the leachfield size, backfilling trenches with sand, and/or increasing the length of the leach lines. The longer the effluent remains near the surface, the more treatment is enhanced due to natural processes within the soil. Based on the Stomar clay soils anticipated near the surface, the potential for effluent to remain near the surface is likely. 2.0 GROUNDWATER ANALYSIS 2.1 Regional Groundwater Regional groundwater information was obtained from a variety of sources. According to the California Department of Water Resources Water Data Library, between 1958 and 1991, groundwater measured between 7.2 feet and 19 feet below ground surface(bgs)at a groundwater well located approximately 1,000 feet north of the site. Based on a review of the Groundwater Information Center Interactive Map, (https://gis.water.ca.gov) Fall 2013, Fall 2014, and Fall 2016 groundwater depth and elevation maps, groundwater depth lies between approximately 90 and 140 feet bgs. Spring groundwater data for the site was not available on the groundwater information center website. Based on a review of the San Joaquin County Flood Control and Water Conservation District Groundwater Report, in Fall 2016 depth to groundwater near the site Responsive■ Resourceful ■ Reliable 3