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Page -9- Concern about this i ir-imar-, sej�aiat ion distance is due To the fa.' thlit it takes approximat--ly 3 feet of unsaturated soil iraterial to properly treat the epti�- tank effluent. Once the tic tank effluent reaches a watertable trc .t.faaent of the of .if�erii Ceases.- This resuT-f s inn *fie -r res- encc� off' a-=xTl�u`t water near t eut'e. uicl it Tonal inputs ut effluent and ,tatural water in the area :.av result in surfacinc of the effluent and,'or the backing up of the effluent intf. the house. This cre- ates not only a nuisance to the home owner, but can also pose a health hazard if the surrounding area is well polurlate.,. Tile best i ;cator available for :leterminink the maximu"I height of .a seasonal wa,ertable which often occurs in the soils of Hennepin County is the presence of soil mottles. %ttling is a distinctive coloration of grey with red and yellow splotches in the subsoil. :Viv investigation of a proposed soil absorption l:treatment system site sF.;.ul,: include a determination of the depth at which soil anottles occur. With this back• ground the potential of the original soils mapped in this development area for treatment of septic tank effiucia will be discussej. :areas of Marsh soils :.adicated by bark blue on the accc..q-wnying soils overlay are found in wetlands. the watertable in these organic sails is above or near the surface the entire near. these areas are unsuitable for the installation of any soil absorption system. The Glencoe and flaixl soils indicated by the rx'dium blue color or the soils overlay have the highes, watertable during the year either at or within 1 foot of the surface. This water m ay persist for several rxmt�Ls during the year. Installation of any subsurface soil absorption system in this soil obvi-,xisly would not allow the minimcrr recom vended separat ifir:. The round system is dcsigmtj for soils with periodic high watertables. liowever, the' watertable must not be higher they, 2 fret below the surface for the mound system to ffrnct ion effectively. Instal ia_t ion of _ .env soil absorpt ion system on this soil type is not. recorR:x�e3: `' _. Areas of Cor&A-a and 1undas soils are indicated by the lig!it Mue color on the soils overlay. The maxims height of the .CaSMIjI wa-.e•rtable In this soil as indicated by the presence of Mottles is usually between 1 and a feet. if the mottling occur, at less than a ' foot depth installation of aanv so afi%orp ton system i not recownendr-d. __Ts t{te most I ►ne occurs at y dt-,,t gres r t irn rrt s iu T l�v<Cew arty iUnLt to" properly. Messy1 soils colored light giccn on the .-oils overla% coa>wim IT have a seastmal watertable at a depth of t to S feet. It the soil qottline in- di.ate, Ti at the d-pth of Ox- watertable i% 3 fee* the reiowvwxled icpit at ion !x•tween the ix)ttcm of the bet"ge trench .and the hatertable c:xin►,t be msintainaxi. In this case, installation of am submarfaeu systen is not recon r►.led. "rnwo,•er, a MtMW sv.t. An fia tion properly. If the wottlinc indicates tht watertable ;present at the S foot 3epth them a --hallow t ren.•h .y--teri .ou id provide k1equrats- treatment. The NavrMe •oil . colored med iias green on the acconpaanv ing owrl.ay offers t h. mo. t not ent ia l for im a st e t reatzrit . , cn. e ) f T to .e.a w na l u at e r table as often below the 3 foot depth. ;' pal ' .il lo% the ih,T.il l it Of tht tarwtrrJ eat► w f.kr d �t.'�. +a� , • ,� e% ideme of soil saottIing at a s tc • , :ri .�