SU0002228 SSNL - Laserfiche WebLink

Home Browse Search

Now, wcurately estimating the quantity of recharge waters is 2.5 -it data dcarly evident,particularly in cases of higher nitrogen load- W=150 9911day/d.•IIIng unit which ing and lower denitrification rates. N np=t.0 m0/L nitrar In Figure 2,the critical minimum gross acreage per lot, H 2.0 :sen A,is plotted against the annual rate of rainfall recharge, R, , select- for a selected range of values for nW and d, with nb = 1.0 ons of mg/I as before. In this instance the long-term waste-water v 1.5 N 0 flow, W, is assumed equal to 150 gal/day per DU, on the 0 o Titrate- basis of an average expected occupancy of three persons per 0 1.0 `� o �� '.o t(1)is residence and 50 gal/person/day.The U.S.EPA(1980)cites a a o ion of 45 gal/day as the typical per capita flow for residential o for a dwellings.The influence of climate and the water balance is 0.5 vaste- seen to be significant,particularly for lower ranges of R,i.e., rogen drier climates.Thus,in desert areas,very large lots may be I,and necessary. 0 0 S 10 15 20 25 30 Ild be In typical new developments of single family resi- NATURAL RAINFALL RECHARGE. R. In/yr gnifi- dences, practical lot size limits exist because of minimum Fig.2.Influence of effluent quality,denitrification,and rainfall rks), space requirements for site development, disposal fields, recharge on critical lot size. Ogen roadways,open space,etc.These limits may be on the order sults of 0.25 to 1.0 gross acres per dwelling unit, depending on ects, local codes and specific development plans. As seen in ---_-------- td d. Figure 2, such practical or statutory limits may often be = 40 more stringent than the critical minimum gross acreage per 'ely. lot, A, determined from equation (2). This is particularly s by true as R values increase. g/l. - oo == ==- I CHICO AREA I be Case Study Examples age To demonstrate and test their validity, the preceding to methods for assessing nitrate impacts were compared ------------ of against the actual ground-water quality data for three California communities.All three of these communities rely ==e o uH s= =_MESA O on individual on-site systems for sewage disposal. In each case ground-water contamination by nitrates has been docu- mented b extensive monitoring programs.The three com- _-=-==_--____ Y gP g --_=__:- _===--==__=_--_ munities reviewed here as case study examples are: (1) the Bolinas Mesa area in Marin County; (2) the Chico area in 8 Y W 000 LOS s o s o s Butte County; and (3) the Baywood-Los Osos area in San =__ -________________________-::___ Luis Obispo County(Figure 3). =====-