CC PACKET 01061998 - Laserfiche WebLink

Home Browse Search

Statement of Understanding It is our understanding that the City of St.Anthony has identified clear water(infiltration and inflow) in the collection system as one of the factors in recent backups problems. The City has made efforts to reduce clear water from"public" sources but the private property sources have not been addressed thus far. "Infiltration" and "inflow" are different classifications of clear water in general "engineering" terminology,but for practical purposes and analysis they are generally combined into one term and called infiltration/inflow or I/I for short. I/I has always been a concern in sanitary sewer collection and treatment facilities. I/1 is relatively clean, runoff or ground water, and it does not require the extensive treatment that is necessary for wastewater. However, once I/I enters a sanitary sewer system it becomes mixed with the wastewater and it must be processed at a treatment facility before discharging it to a receiving stream. The I/I uses capacity in the collection system and the treatment facility that could be used by additional service connections from homes or businesses, and results in increase treatment charges to the City. Wastewater from the City of St. Anthony is treated at a Metropolitan Council Environmental Services(MCES)facility,and the City is charged a fee for each gallon that is treated. The MCES has been encouraging communities to reduce I/I by offering a grant/loan program. Information on the MCES program will be included in the "funding" section of this letter. There are many potential sources of I/1 ranging in size from minor pipe joint leaks, providing less • than one gallon per day to catch basins and roof drains, which can contribute hundreds of gallons per minute. Flow from extremely large I/1 sources quickly and regularly exceed the capacity of the available sanitary sewer pipes and,as a result,these sources are generally removed shortly after they are identified. Smaller sources spread throughout the system are more difficult to identify and remove. These sources include leaking manholes, damaged pipe, leaking joints, foundation drain tiles, sump pumps and down spouts from roof gutters. Routine system operation and maintenance procedures provide the opportunity for the City Staff to identify and correct some I/I sources in the City or"public"system,but the private property sources are generally overlooked unless specifically targeted. Private property sources include foundation drainage tiles, sump pumps and down spouts from roof gutters. These sources can contribute significant quantities of I/I very quickly , or over a long period of time, depending on the type of construction, the soil conditions, and the precipitation event. Foundation drains are normally difficult to identify and difficult to remove from the system. Sump pumps and down spouts are relatively easy to identify and disconnect. The pump discharge line can be routed outside the basement and discharged on the ground away from the foundation. The water from the sump is basically clean and can be discharged on the ground surface without difficulty in most cases. However, it is important to discharge the water several feet from the foundation to reduce the potential for recirculating it back to the tile and sump pump system. Occasionally problems with surface discharge occur in situations where the pump is required to operate frequently over long periods of time, or during freezing conditions. In these cases special consideration of the discharge method may be necessary. The City of St. Anthony has been working on identifying and removing I/I sources in the public • sewer system and it is necessary to expand the program to the private property area to increase I/I reduction. In most communities, sump pumps are the most common"private property" source and Page/ F-WPW/MPROPOSAD059 97Ipropow/