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February 27, 2020 Irerracon <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 RECEIVED <br /> Stockton, San Joaquin County, California <br /> Terracon Project No. NA197078 FEB 2 8 2020 <br /> ENVIRONMENTAL HEALTH <br /> Dear Ms. Acosta, DEPARTMENT <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 /> Effluent <br /> Result Acres Concentration Average Leachfield Net Rainfall <br /> Land Use (Nc)" A Daily Flow Nw Denitrification Recharge <br /> (mg/L-N) ( ) (Q)(gPd) (mg/L)N) (d) (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. <br /> Terracon Consultants Inc. 902 Industdal Way Lodi, CA 95240-3106 <br /> P 209-367-3701 F 209-333-8303 terracon.com <br /> i <br />