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UEC Document No.: R3579901 February 8, 1999 3.2 Known &/or Suspected Nitrate Sources In general, a primary source of nitrate groundwater contamination tends to be from dairy farms and other farming operations where large quantities of livestock reside. No such farming operations exist on or adjacent to the subject site. Additionally, certain food processing plants have the capacity to discharge waters which contain relatively high levels of nitrogen which is eventually transformed into nitrates. Vidor Foods, existing to the east of the subject site and east of State Highway Route 99, may be a source of elevated nitrates; Victor foods appears to be down gradient of the subject site and could therefore be expected to have minimal impact on the groundwater beneath the subject site. However, groundwater gradients have a tendency to fluctuate, especially in agricultural areas; as a result, the impact of the Victor Foods site upon the subject site groundwater can not be reliably established without the collection of groundwater samples. It is not recommended that this analysis be performed as part of this Lot Line Adjustment process. The maintenance of the vineyard existing to the north of the drainage ditch has not resulted in highly r elevated levels of Nitrogen /Nitrates in the soil at a depth of 5 feet below grade. More specifically, the Nitrate/Nitrogen levels in the soil are reported as being 1.7 ppm (see FGL Analytical Report in Appendix E). 3.3 Groundwater Impact Analysis The groundwater impact analysis presented below has been developed by Hantzche and Finnemore to aide engineers and septic system designers /planners in assessing the long term potential impact that domestic sanitary systems may have on groundwater with respect to nitrate contamination. The simplified prediction of nitrate impacts of on-site sewage disposal systems over a defined geographical area is made by constructing a mass balance, considering only inputs from waste water and recharge of rainfall and losses due to denitrification in the soil column and the upper portion of the aquifer. The most favorable soil conditions for denitrification are (a) the abundance of organic carbon sutrate, (b) high soil moisture content, and (c) high soil pH.' Denitrification losses range from 1 to 75%, 25% being the most typical. The assumptions applied in the following analysis are believed to accurately represent existing subject site conditions. Essentially, the nitrate concentration reaching the upper portion Hantzche and Finnemore, "Predicting Ground-Water Nitrate-Nitrogen Impacts", Ground Water journal, Volume 30, Number 4; July-August 1992 5