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The second NO3-N loading factor originating from the almond orchard is the organic matter and -� Estimated Nitrogen Release (ENR). The organic matter concentration is issued in percent- as a percent of soil weight. Percent by weight is equal to 10,000 ppm. As noted, the organic matter percentages are relatively equal throughout the soil profile. At 12 ft, the organic matter percentage is 0.4%, which is equal to 4,000 ppm, with an ENR of 38 lbs/ac. As referenced above, the 7 inches of soil tested for NO3-N concentration at the 12-ft depth was 3 ppm. On average, for each 7 inches of soil depth analyzed for NO3-N concentration, the resultant ppm can be multiplied by 2 to obtain pounds of NO3-N/ac. This is because one acre of soil, 7 inches deep weighs approximately 2 million pounds. Consequently;the 3 ppm NO3-N determined at the 12-ft depth has 6 lbs NO3-N within this 7-inch depth throughout this one acre. Therefore, the NO3-N release originating from the organic matter and estimated by the ENR can be calculated backwards to determine NO3-N in terms of a concentration in ppm: 38 lbs/ac ENR-2 = 19 ppm NO3-N estimated nitrogen release for this 7-inch depth sample, over this one acre. Therefore, we have 4,000 ppm organic matter liberating 19 ppm NO3-N. However, the actual amount of nitrogen released is highly dependent upon climate, particularly rainfall, soil aeration, pH, and C:N ratio. Since decomposition is taking place deep within the soil profile and may be impeded,the calculated ENR concentration of 19 ppm will be reduced 75%: 19 ppm x (1 - .75) = 5 ppm NO3-N. This concentration of 5 ppm NO3-N can then be - added to the existing soil NO3-N concentration of 3 ppm = 8 ppm NO3-N. Since there was no chemical analysis performed on the soils during the growing season, nitrate- nitrogen loading can be theoretically quantified for this time period: Assume 20% le c forr everry5 b.s_a£_nitry en g�zU led= 50 lbs/ac NO3-N - 20% = 10 lbs/ac NO3-N leaches past the root zone after every fertilization. Conversion of this "amount" into a "concentration" yields 10 lbs/ac_ 2 = 5 ppm NO3-N leaching into the groundwater. To determine the time for the nitrate- nitrogen to leach 6 ft(from 6 ft to 12 ft) past the root zone: Hydraulic conductivity below the hardpan layer= 0.5 cm/hr. 6 ft x'12 in./ft= 72 in. x 2.54 cm./in. = 183 cm_ 0.5 cm/hr= 366 hrs or 15 days. The total, estimated amount (in terms of weight) of NO3-N leaching from fertilizer applications over the growing season= 10 lbs NO3-N/ac/application x 4 applications/yr= 40 lbs/ac x 4.5 ac= 180 lbs NO3-N leaches into groundwater after each growing season. This amount can be compared with the theoretical amount (in terms of weight) originating from the two proposed SFRs: 8 people (4 people per house) x 113 gals/person/day= 904 gals/day x 3.79 L/gal = 3,426 L/day x 32 mg N/L/day = 109 grams N/day x 365 days/yr =40 kg N/yr x 2.2 lb/kg = 88 lbs NO3-N/yr leaches into groundwater each year from septic effluent. These two amounts (180 lbs NO3-N and 88 lbs NO3-N) are worst-case scenarios. No reductions have been provided for, through denitrification, etc. 10 Va&y AB Research