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lierracon Soil Suitability / Nitrate Loading Study Morada Produce — Ag Processing Building e Stockton, California May 14, 2021 & Terracon Project No. NA217014 Septic System No. Building ID Number Hours of Operation per day Number of Employees per day Employee Effluent Number Visitors / Truckers per day Visitor Effluent Maximum Septic Tank Usage Employee GPO + Visitor GPO Average Number of Days per Year Long Term ADF (GPO) (Sep-Oct) Total Existing ADF (Septic Systems 1, 2, 3) 12,148 4 Proposed Ag Processing Building - Southeast Restrooms 9 (Jul-Aug) 40 585 4 12 597 60 98 12 (August) 40 780 3 9 789 30 65 Total Existing ADF + Proposed ADF (Septic Systems 1, 2, 3, 4) 12,311 ADF = Employee Effluent GDP + Visitor Effluent GPD x Average # days per year / 365 days per year Refer to Section 1.3.7 for additional information regarding maximum septic tank usage. The long term average daily wastewater flow for each septic system is listed as follows: Septic System No. 1 - Northwest Restroom = 152 gpd Septic System No. 2 — South Restrooms = 11,377 gpd Septic System No. 3 — Northeast Restrooms = 619 gpd Septic System No. 4 — Proposed Ag Processing Building = 163 gpd It should be noted, five months of the year (April to June and August to September) the facility ADF may exceed 10,000-gallons per day. The remainder of the year, ADF is below 1,462 gpd for the three existing systems plus the proposed system. The average total nitrogen concentration of domestic wastewater is normally considered to be 20 to 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. For the purposes of the nitrate loading estimate, it is estimated that the average concentration for total nitrogen in wastewater for the project is approximately 85 mg/L-N seven months per year during a standard season and 75 mg/L-N five months per year during the peak season. 2.3.4.2 Denitrification Estimate Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates are estimated to denitrify at a lower rate, about 10 to 15 percent. Responsive • Resourceful • Reliable 17