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SPECIFIC SOURCE CONSIDERATIONS 1.) The scientific literature has determined fluid runoff from silage pits and other types of feed storage areas are potential contributors to nitrate groundwater contamination. However, the feed storage areas for the subject facility are concrete lined and the runoff is minimal. Runoff should II be monitored throughout the year accounting for volume of feed and impact from the weather to ensure runoff is managed properly. Potential nitrate impact from this source can be considered inconsequential. la .y 2.) As referenced in the Soil Suitability Study, the number of septic systems connected with the area of the dairy facility (515 acres) can be considered low density. Data from various sources such as independent investigators, the U.S. EPA, and the Regional Water Quality Control Board estimate nitrogen loading from domestic sewage from 12 grams N per person per day (g N/capita/day) to a high of 90 g N/capita/day. Hantzche and Finnemore (1992) correlated septic tank effluent concentrations multiplied by water discharge to the septic tank. They formulated a water discharge of 50 gal/capita/day with an effluent concentration of 30-50 mg N/L. This translates to 9.5 g N/capita/day, using 50 mg N/L. It is our opinion that 17 g N/capita/day as issued by the EPA to be most accurate. r Consequently, if 25 people (high approximate)were on the dairy facility 365 days per year, loading would calculate to 425 g N/day (using 17 g N/capita/day), or 155 kg N per year. Two important variables must be factored into this equation: The first being loss of N by ammonia volatilization which occurs within the septic tank. The second are N losses attributed to denitrification. Sandy et al. (1987) estimated N losses in the septic tank to be between 20 and 35 percent. Twenty-eight percent will be used in our calculations. Regarding denitrification, Ramlit(1982) and Finnemore (1992) both estimate N losses by denitrification to be 0 to 25 percent. With the indigenous clay soils, denitrification will be promoted, so losses of 20 percent are reasonable. Therefore, a total nitrogen loading adjustment from on-site sewage is predicted to be: 155 kg N - 48%= 81 kg N per year or 178 pounds of N per year, over 515 acres. 3.) The freestall corrals contribute very little nitrogen to the underlying soil due to the concrete- lined flush system which transports wastes from these corrals. Since these corrals are covered, there is virtually no hydraulic head from rainfall or other sources that could drive the nitrate molecules continually deeper into the soil. 5