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H. SURFACE AND SUBSURFACE SOIL INFORMATION The subject property is currently planted in winter wheat; consequently, our subsurface exploration was somewhat restricted. Soil samples from the surface down to approximately 3.5 feet were taken from three locations around the subject site for analytical purposes. The Soil Analysis Report located in the Appendix illustrates several important parameters of the on-site native soils. For this study, the more important parameters include the organic matter fraction and the nitrogen (NO3-N) content, which are low within the top soil horizon. The pH is alkaline at 7.7 and the cation exchange capacity is extremely high, indicating a high clay content soil. A hydrometer test was performed on the upper soil horizon to quantify clay content. The American Society for Testing and Materials (ASTM) method D-422 is the test to determine clay content percentage in soil. Representative samples indicate the soil contains approximately 62% clay content, which can be considered exceptionally high. The subject site and surrounding study area have a varied agricultural history of irrigated and non- irrigated crop land, permanent crops, and dairies. There is low density housing, all with septic systems. High nitrate levels in groundwater may originate from the application of nitrogenous _ fertilizers to crops. If conditions are favorable, a percentage of nitrogen applications may undergo complex biological transformations with the product being nitrate molecules. Plants use nitrogen in the form of the ammonium molecule (the nitrate precursor) and the nitrate molecule itself. Excess nitrogen applications and/or ideal environmental factors may contribute to nitrate contamination of the groundwater. Dairies have also been recognized by the State of California as nitrate pollution sources. Certain crops grown on dairies such as alfalfa use or fix atmospheric nitrogen for cellular composition. Excess nitrates from manure or wastewater applications can leach into the groundwater. Nitrates _ can also form naturally, for example in geological formations or in atmospheric phenomena such as lightning. And of course, septic systems can contribute to nitrate contamination. M. GROUNDWATER AND SURFACE RATER INFORMATION Groundwater is the ultimate "sink" for nitrate concentration. Therefore, the higher the groundwater _ elevation is in relation to the surface of the ground, the higher potential for nitrate impact. At present, the zone of saturation under the subject property extends downward starting from 3 vaffey Ag TZ search