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U NIVERSITY OF M INNESOTA <br />Room 173 McNeal Hall <br />Onsite Sewage Treatment Program <br />1985 Buford Avenue <br />Water Resources Center <br />St. Paul, MN 55108 <br />University of Minnesota <br />Extension Service <br />800-322-8642 <br />Fax: 612-624-6434 <br />septic.umn.edu <br />To:RollingHillsHomeownerAssociation <br />From:Dr.SaraHeger <br />Date:11/10/20 <br />RE:Replacementsepticsystem <br />TheOnsiteSewageTreatmentProgram(OSTP)isservingasaresourceforRollingHillsIƚƒĻƚǞƓĻƩ͸ƭ <br />Association(RHHA)helpingtheAssociationdesignandoverseeinstallationofanewsubsurface <br />sewagetreatmentsystem(SSTS).Ontwooccasions,ourstaff,includingasoilscientistandan <br />engineer,havemetonsitetoevaluatethesoilandsiteconditionsatvariouslocationsownedbythe <br />RHHAwiththehireddesigner/consultant.Belowisasummaryofthetwovisits: <br />1. OnSeptember23,2020,thefocuswasonthealternativeareanearthecurrentdrainfield <br />area.Thesoilsinthisareawould ƓƚƷ allowforTypeIsoiltreatmentduetoshallow <br />periodicallysaturatedsoilconditions,soilcompactionandimpactsfromtheexisting <br />drainfield.ThesesoilevaluationsalsoindicatedthatthecurrentsystemisͻCğźƌźƓŭtoProtect <br />DƩƚǒƓķǞğƷĻƩͼaccordingtoMinnesotaRulesChapter7080.Thelocationofthecurrent <br />systemintotheseperiodicallysaturatedsoilconditionsislikelyoneofthereasonsithas <br />beenproblematic.Thisdrainfieldareaalsorequiresa200footsetbacktoanydrinkingwater <br />well,duetothedailywastewaterflowvolumewithintheSSTS.Anotherpotentialareainthe <br />woodedhillslopewaslookedatbutnotfullyevaluatedatthistimeduetoonlyslightly <br />bettersoilconditions,limitedarea,andproximitytothepropertyline.OSTPrecommends <br />thattheconsultantdetermineifthenewsystemwouldfitintheexistingdrainfield, <br />consideringthepotentialforgroundwatermounding(anelevatedwaterlevelduetothe <br />additionsofwastewater).Thelimitedsystemlayoutoptionsandthecorresponding <br />moundingevaluationindicatedthatthissiteishighriskforsurfacingofeffluentand <br />thereforeotherlocationsshouldbeconsidered.Thesoilfromthisareacannotsimplybe <br />removedandreplacedtosolvetheproblems.Therearemanyfeetofclay,compactedsoils <br />andwetlandsoilscoveringtheentireareaandthisdoesnotimprovetheperiodically <br />saturatedsoilelevation.Inaddition,theğƩĻğ͸ƭflattopographyandsurroundingsoil <br />conditionswillexacerbatewetnessatthissiteΑevenifthesoilwasreplaced.Thesystemis <br />currentlydischargingapproximately9,000gpdthatmustbesafelyreturnedtothe <br />environmentwithpropertreatmentandremainbelowthegroundsurface. <br /> <br />