Community Assessment Report - Onsite Sewage Treatment ...

Table 4: Estimated Permitting Flow Rates for AlternativesTotal DailyAlternative andTreatment System TypePropertiesIncludedPermitting FlowGallons/Day* Permit Type Required**Alternative 1: ISTS 14 6,375 County ISTSAlternative 2:Cluster LISTS + ISTS 14 6,534County Large ISTS+ County ISTSAlternative 3: Cluster MSTS 14 5,930 County MSTS*The permitting flow is not the actual flow, but rather is a design flow that dictates the level of permitting effortrequired for the system. The permitting flow takes into account allowed reduction in flow for cluster systems withover 10 dwellings and increases in flow for infiltration and inflow into the collection system.**The permit type required for ISTS assumes that the individual property owners are the owners/managers of theISTS. A midsized-SSTS (MSTS) is a cluster system with a daily permitting flow between 5,000 and 10,000 gallonsper day.Using 2011 Minnesota Rules, Part 7081.0120, an average daily flow for each system orwastewater generator is estimated using a formula specified in the rule. This formula calculates aflow based on the number of bedrooms in each of the residences, the treatment system type(individual or cluster), and the total number of wastewater generating parcels included in eachsystem.To provide the analysis in this report, we have assumed an average of 3 bedrooms per residenceand a Class I dwelling status for homes included in the cluster system analysis which did not fillout a homeowner survey. Three bedroom homes have an average daily flow of 450 gpd for aClass 1 dwelling (150 gpd/bedroom). Residences indicating only one bedroom were included indesign analysis as two bedroom dwellings, as directed in 2011 Minnesota Rules, Part 7080.1860.In the future, when a design plan is created an actual flow for a selected cluster system wouldneed to be determined based on the actual number of bedrooms in each home. Design flowconsiderations for properties not included in the CAR area that desire to be included in theselected wastewater system would also be required. Design flows shown included additions forinfiltration and inflow into a collection system as well as allowed reductions in estimation ofdaily flows when the number of residential wastewater generating properties connected to acluster treatment system exceeds 10.T:\2797-01 Chisago County\CAR\ROLLINGS SHORES CAR 090712.docx3-9