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Terracon Consultants Inc. 902 Industrial Way Lodi, CA 95240-3106 <br />P 209-367-3701 F 209-333-8303 terracon.com <br />February 27, 2020 <br />Ms. Cynthia Acosta <br />Acosta Construction <br />PO Box 947 <br />Woodbridge, CA 95220 <br />Re:Soil Suitability / Nitrate Loading Study - Addendum <br />Whitlow Property, APN: 063-040-23 <br />11065 N. Alpine Road <br />Stockton, San Joaquin County, California <br />Terracon Project No. NA197078 <br />Dear Ms. Acosta, <br />This letter is in response to the San Joaquin Environmental Health Department (EHD) letter for <br />the Soil Suitability /Nitrate Loading Study (SSNLS), 11065 Alpine Road, Stockton, CA APN 063- <br />043-23, SR0081473 dated February 13, 2020 and Memorandum dated February 12, 2020 <br />prepared by Questa Engineering Corp. (Questa). Per the request of the EHD, Questa performed <br />a third party review of Terracon’s SSNLS dated November 20, 2019 for the subject property. The <br />Questa Memorandum recommended Terracon reduce the site wastewater flow based on long <br />term average discharge of wastewater. Questa additionally recommended Terracon adjust <br />rainfall recharge calculations based on reduced evapotranspiration rates for residential <br />landscapes. <br />Based on a February 27, 2020 telephone conversation with Ms. Kasey Foley of the EHD, Terracon <br />revised the long term average discharge of waste water for the nitrate loading calculation from <br />560 gallons per day to 250 gallons per day for a 4 bedroom residence. Ms. Foley recommended <br />100 gallons for the first bedroom and 50 gallons for each additional bedroom. Per the <br />recommendation of Questa, Terracon adjusted the estimate of net rainfall recharge from 4.49 <br />inches per year to 6.80 inches per year. The following table presents a summary of the nitrate <br />loading calculation for the site based on the reduced long term average discharge and increased <br />rainfall recharge. <br />Summary of Nitrate Mass Balance Equation - Revised. <br />Land Use <br />Result <br />(Nc)* <br />(mg/L-N) <br />Acres <br />(A) <br />Average <br />Daily Flow <br />(Q) (gpd) <br />Effluent <br />Concentration <br />(Nw) <br />(mg/L-N) <br />Leachfield <br />Denitrification <br />(d) <br />Net Rainfall <br />Recharge <br />(R) (in/year) <br />Residence 8.0 1.50 250 45 35%6.80 <br />Nitrate as N Total 8.0 <br />* Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N.