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4 VII. CONCLUSIONS The results of this study indicate the need for careful management of septic effluent nitrogen originating from the proposed project due to preexisting nitrate impact to the underlying # groundwater. The following conclusions and recommendations are made in this regard. It is our opinion, nitrate impact to the underlying groundwater has originated from intense t agricultural production in the area along with a high density of upgradient domestic septic systems. This housing density can be denoted on the attached USGS map. A nitrogen stable isotope ratio test may differentiate the nitrate origination; however, this of course, is after the fact. Sampling and analysis of encountered aquifers which will supply water to the Kingdom Hall during �= the drilling of the well should be done. If deep aquifers can be found which have not been nitrate impacted, then the well should be extended to these depths, with a 200-foot grout seal. After well development, if nitrate concentrations continue over the drinking water standard of 45 ppm NO3i women Parishioners who are pregnant and infants should not drink the well water. Either bottled water should be supplied or a reverse osmosis treatment system installed. Since the project is located in essentially a groundwater recharge area, we are recommending the wells tested for this study, be analyzed yearly after project development. If there are significant increases in the nitrate and/or chloride concentrations, a nitrogen stable isotope ratio analysis of the groundwater should be conducted to detect the nitrate source. If the ratio analysis suggests sewage influence then consideration should be made to placing a re-circulating sand filter in the area where effluent is discharged from the second septic tank. This will force the nitrogen to convert to nitrate (nitrification). Denitrification will then be accomplished either by anaerobic bacteria that coexist in anaerobic microenvironments within the filter bed, or an engineered nitrogen removal system. A landscape professional should be consulted for the types of trees and shrubs that may be planted in the leachfield and seepage pit areas for nitrogen utilization. As referenced earlier, nitrogen in sewage effluent is predominately in the organic or ammonium form. Plants use two forms of nitrogen: ammonium and nitrate. However, ammonium excess can be toxic to many species of trees and shrubs. Additionally, plant roots may infiltrate leachlines and seepage pits. Conifer trees, especially cedar trees are known to readily plug leachlines. Root problems are usually worse in �. leachlines which are used intermittently since the roots seek any available water. 8 Valley Ag Ppearck