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Taking the center of Clements as a"start�ing3soinf'of'poteritial. itrate contamination, it would theoretically take: 2,640 ft 2.3 ftld1,148 days or 3.1 years lo traverse from under the center of the town, to the project site. --�_ ___.,_. The Well Completion Report indicates a significant sand stratum from 21 ft to 50 ft. Due to the thickness of this sand layer, it may be historical River accretion which may connect with the hydraulics of the River. he Well Completion Report does not TecifX when "first water"was ter encpuned;however, it is a� m ossibility that this stratucould be considered a perched water taPercolatig nitrate zayeeonter this stratum and if there is sufficient hydraulic anffi1j§ v ty,_ ay}!travelto-, or awl from the„ tier deperidiug„Qu-thc,.hydzauties,without impacting deeper aquifexs used fo-r domestic-purposes. ` 2. HYDROCHEMICAL BEHAVIOR OF NITRATE-NITROGEN Nitrate is the most common contaminant identified in groundwater. It is not limited by solubility constraints, and due to its anionic form, it is extremely mobile in groundwater. In groundwater that is strongly oxidizing, nitrate is in the stable form of dissolved nitrogen. Groundwater with a redox potential of 250 millivolts (mv) and a pH of 7 can promote denitrification. Although the redox potential of the water is unknown, it is known to have a pH of 7 at the 294 ft depth, with a slight increase in pH with increasing depth. The dissolved oxygen (D.O.) content of the well water may be tested upon well completion to determine redox potential. If D.O. does not exist, or is in very low concentrations, denitrification potential may certainly be enhanced. This is what may be occurring in the water depths ("aquifers") that were tested. !/ 3. SOURCE DETERMINATION OF NITRATE IN GROUNDWATER Although it was once common practice to sample well water from adjacent or surrounding parcels from a subject property under examination to quantify surrounding nitrate impact, the EHD no longer allows this practice due to several reasons. Consequently, nearby shallow domestic wells on surrounding properties were not sampled to ascertain the nitrate concentration existing on either the aforementioned shallow aquifers, or from the static water table depth of 140 feet. The two main sources of nitrate,that may occur in the Clements would be from on-site se tic systems and agricultural fertilizer in uts. A third source may potentially be historical organic matter contributions originating from the River. It may be that in the future, if nitrate concentrations begin to appear in the proposed on-site domestic well, source determinations can be made. The Delta "N nitrogen isotope technique can be used for possible determinations. Although there is no one technique that can exclusively determine the source of nitrate contamination, the Delta `sN isotope technique provides a theoretical correlation with the probable sources referenced (i.e., septic systems, fertilizers, organic soil N). The test is based on measuring the two stable isotopes of nitrogen 14N and "N in the nitrate found in a respective sample. Page -9- Chesney Consulting