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The approximation of nitrate concentrations obtained Typical Solutions from equation 1]).1 igmrres dispersion.lateral no..and Solution of the loregoingcquations rrquacif input data mixing with ground- ter flow from upgradient areas, for several dispssal%ystem and site variables,ail of which Ibese procc n would generally contribute to additional can haw a significant effect on the predicted nitrate- reduction of mirate-nnrogen crosexntratiom in ground nitrogen concentration.Graphical solutions are presented water to the extent that the nitrate-nitrogen eornanitalion herr for typical antes of these vuiaMes,m an ad in ulect- of ground-water flow from upgadienl areas is lower, ing appropriate saline, and in identifying situations of Equation(1)thus prtrvidn a conservative(worst case)first potential concern, approxnmauon of ground-water nitrate-mlfogea con centra- The predicted resultant avnagc ground-water nitrate- tion resulting from the combined effect of on-site sewage nitrogen concentration,n,,computed from equation(1)is ditf—I systems and precipitation.Thu is for estimation of plotted for convenience in Figure 1 against the fraction or Inng-term rffrtts(i e.wet years)on ground-water quaiiy, waste-wvier recharic,1.relatisc to rainfall recharge,R.fora and is not intended for prediction of seasonal changm elected range of values for soil denitrification,it,and waste- A common land use planning dilemma is that of water mtri gro loading,n..Background nuau-nitrogen determining aaepmble development densities,sometimes loading.ns.typicaltyfalls in the range of0.5 to lA mgtl,and mfermt to as the carrying capacity of the land.From the a assumed here to be 1.0 mg;I.Exceptions to this would be standpoint of ground-water nitam-rutrogcn impacts,the tithearea haxlarge numbers ofconfinedliveanxkonignifi- crirical minimum gross acreage per developed lot,A,may be cant expanses of(endued Tops or turf areas(c.g,parks), defined at that which would result in a value ofn,equal to 10 which would lend to increase background nitrate-nitrogen mg71,the commonly xccapted drinking-water limit.By set- loadings above the typical values suggested here.The molt% ling I-0 013"W A and n,-10 mg;I,and then martang plated in Figure I%how a wide range of potential effccs. ing equation(1).A k then given by highly sensitive to the initial selmion of values for n.and d. Two tuner are plotted for the average slue of n.=al 0 01344%(n.-des. 10) mg;I,with denitrification rate%of 0 and 0.25,mpectivcly. RI10 tie) typical resgeis rcpresented on the A----- (2) The ty hi and low sdea by nhigh the turves for(a)n.=50 mg;I,d-0 and(b)n,=30 mg,I, in which A is espies-1 in terms ofgross acrnldwe0ing unit d-0.25.71¢curve for n.=a0 mgrl and d=0.25 would he (DI I),W is the average daily waste-water Bow per dwelling comidered the most representative of typical on-site sewage unit,in gallons;and ODIW is a conversion factor having disposal situations(U.S.FPA,1480;1981).In addition to units acre inch day DU yr'gal-', ptuper selection of values of n,and d,the importance til .o a o.an r s y ao as a so aw ae arM�ew tW u /; 'X°T,M=f I' ao•an,a.ores i o - to •..e 4N e.ee s.oe tie tie raa ..so roc waarawafaa aseaaaea aasanve TO aam•ase aaewaaea.va F ia.I.Re h.nr fv xr ,stn nitnrr-Nvopa OanaaYatlm as a fumum+or rmi-vit gwWf.Mwsrificatioe,and 1I g. 04; �C I NCC_