SR0087834_NITRATE LOADING STUDY ADDENDUM

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On February 23, 2024,percolation testing commenced. Almost 6" of standing water was observed in the test borings after the 24-hr soak period. Consequently, EHD Perc Test Procedure#2 was conducted. Testing was done over a.four-hour period. l A summary of the perc test results with corresponding application rates in gallons of effluent accepted per square foot of soil per day, are illustrated below in Table 1: TABLE 1 PERCOLATION TEST RESULTS WITH CORRESPONDING . APPLICATION RATES IN GALLONS/FT'-/ DAY 24 INCH PERC TEST 125.0 min/inch / 0.10 gallons/ft'/day 36 INCH PERC TEST 0 min/inch / 0.0 gallons/ftZ/day Soil chemistry and textural analyses are important parameters in assessing nitrate loading from any project. A soil sample was obtained from the 2-ft perc test depth,which will be the approximate depth of the filter bed soil-effluent interface when installed. Table 2 below illustrates the soil characteristics of the soil sample retrieved from the disposal area soil: TABLE 2 SOIL TEXTURE CLASSIFICATION AND ANALYTICAL TEST RESULTS SAMPLE I.D.DEPTII SOIL TEXTL!RE SOIL_NITRATE- pll CLASSIFICATION NITROGEN CATION EXCHANGE CAPACITY AND SAND SILT AND CONTENT ORGANIC MATTER% CLAY PERCENTAGES DISPOSAL AREA Clay 4.29 ppm NO;N 7.6 34.1 meq/100g 2.3% 24"-26" DEPTH 11% 40% 49% DISPOSAL AREA Silty Clay Loam 3.1;ppm NO,-N 7.9 32.2 meq/100g 2.0% 38"-42" DEPTH 14% 53% 34% NITRATE LOADING STUDY ADDENDUM i Referenced parameters used in the Nitrate Loading Study conducted by LOGE have been changed: The denitrification factor has been increased to 50% from 35%,based on the high clay content soils referenced in Table 2. This high clay content creates anaerobic micro-sites preventing nitrification and promoting denitrification of nitrified ammonium. The Net Rainfall Recharge (NRR)has been increased to 8.82 inches/yr from 3.39 inches/yr based upon a Water 1 Balance Analysis by Norm Hantzsche for the Stockton area. This document is found in Appendix E. The lab results reveal chemist from the soil sample obtained from the disposal area soils r1' p p 1 reveals a low nitrate-nitrogen concentration of 4.3 ppm and 3.2 ppm, indicating a 27%reduction in only one ft distance. Page -2- Chesney Engineering, Inc.