09/02/2008 Council Packet - Laserfiche WebLink

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• Sanitary Sewer System Design Criteria: Water use varies with population more than any other parameter, and in particular, per capita consumption is the industry standard for computing water use and, therefore, wastewater flow generated. Both the Minnesota Pollution Control Agency (MPCA) and the Metropolitan Council Environmental Services (MCES) have compiled and documented extensive data that relates wastewater flow generation to population and land -use. This information has been used as our basis for estimating the wastewater design flows and peaking design conditions to determine the capacity of the existing and future sewer systems. MCES has established 274 gallons per day (gpd) to be the average daily wastewater production from a typical residential equivalent unit (1 REU = 274 gpd). The following parameters were used for the wastewater flow projections throughout this Plan: Residential Equivalent Unit (REU) = 274 gpd or 100,000 gallons per year Commercial /Industrial Development: 40 gpd per employee Correctional Facility: 110 gpd per resident Design flows for piping and pumping facilities are based on peak wastewater flow conditions. Peaking factors vary with the total contributing population. The greater the population in the service area the less variable the wastewater flow condition is with time. Standard peaking factors developed by the MCES were utilized to estimate peak flows. The resulting flow projections by sewer district are shown on Table 7 -2 Summary of Projected Flows - Ultimate Development. • Lino Lakes Sanitary Sewer System: • The existing City sanitary sewer system is shown on Figure 7 -1 Existing Sanitary Sewer System Map. For sewer planning purposes, the City has been divided into several Sewer Districts and Sub - Districts, as shown on Figure 7 -2 Sewer District Map. District boundaries are based on the areas that can potentially be served by the various existing and future regional facilities serving the City. Individual Sewage Treatment Systems (ISTS). The City currently also contains extensive areas of Low - Density Residential and Rural Land -Use areas not served by the public sewer system. Residences and businesses in these areas are served by individual on -site systems. There are no package treatment plants or group on -site systems currently existing within the City. The City's policy is to permit unsewered residential properties to remain as long -term land uses, and to extend sanitary sewers into unsewered subdivisions only at the request of the property owners or as a trunk line extension. New installations of on -site systems will generally be restricted to rural land uses with a minimum lot size of 10 acres. Figure 7 -4. Sanitary Service Types shows areas of rural and low density unsewered residential land use as of May 2008. Within these areas, on -site systems are in use. The City assumes that most of these unsewered areas will become sewered by the time of ultimate development. However, many areas will remain unsewered through at least 2030 and a few areas will remain unsewered beyond that time. The City's Individual Sewage Treatment Systems Ordinance requires biennial inspections of on -site systems. The ordinance establishes notification and reporting procedures and requirements for repairs and re- inspection. Properties with failed systems must connect to the municipal sanitary sewer system if service is available. The City will also consider establishment of a "point of sale" inspection requirement. 7 -9