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F <br /> i ) 1. <br /> M <br /> Ed) in , groundwater was computed based on the following <br /> assumptions : <br /> an average sewage loading of 150 gallons per day (gpd ) per <br /> unit ; �G • <br /> a total nitrogen concentration in the effluent of 40 <br /> milligrams per liter (mg/1 ) ; <br /> a deep rainfall percolation rate of 5 inches per year <br /> (rainfall less evapotranspiration) ; <br /> a background nitrogen concentration for percolating rainfall <br /> of 1 . 0 mg/1 ; and, <br /> a nitrate loss of 25% due to denitrification in the soil . <br /> Impacts from adjacent properties are not expected to raise <br /> this level because the surrounding density of development is <br /> generally less than that of the project. Results of this analysis <br /> projected long-ter`m nitrate-nitrogen concentrations of 4-.-& 6. 5 <br /> mg/l . A-ht h a ugh t h insCo v e'1 ' f s]Kw i.t Yi i n S t-a t o m d r i n-k i-n-g w-a-t e,r <br /> staridar-:a(iAcan be considered to be a significa t constraint to <br /> use of �ndivzdual septi tank/ilea held systems. These pro1ecte_d <br /> impacts can be considered to extend va�"nd the proiect site <br /> boundaries by approximately 200 feet depending upon groundwater <br /> mdgration and soil conditions, <br /> The feasibility of on-site sewage disposal for this project <br /> will primarily be dependent upon adequate soil percolation at <br /> each site . Subsurface soil conditions are relatively uniform <br /> throughout the site, however, percolation rates are likely to vary <br /> somewhat from lot to lot. If percolation rates are near the <br /> maximum allowable, these minor variations may present a ' <br /> constraint to use of individual systems. <br /> F <br /> The applicant reports that winter groundwater levels on the <br /> project site are approximately 50 feet. 4 Groundwater conditions <br /> such as this would not affect the use of horizontal leachfields. <br /> However, if percolation tests dictate the use of seepage pits, any <br /> seasonally high groundwater levels may become an issue. <br /> In the event soil and groundwater conditions do not permit <br /> the use of either leachfields or seepage pits for sewage disposal , <br /> alternative methods will have to be considered by the applicant. <br /> A common alternative is the use of a package treatment plant for <br /> the entire subdivision. Most available plants, however, would not <br /> likely be cost effective for a 39-unit subdivision. If <br /> development occurs on adjacent lands within the study area, a <br /> jointly-owned packaged treatment system could be considered and <br /> would be more cost effective. <br /> 44 <br />