2004-10-26_PWETC_AgendaPacket - Laserfiche WebLink

Home

Roseville Public Works and Transportation Commission Agenda Item Date: October 26, 2004 Item No: 5 Item Description: Metropolitan Council Infiltration and Inflow Taskforce Report Background: The entire City of Roseville is within the Metropolitan Urban Service Area (MUSA), therefore the Metropolitan Council Environmental Services (MCES) provides treatment plant and interceptor service. There are approximately 180 miles of public sanitary sewers providing service to 17,258 households and businesses. Trnnk sewers and 13 lift stations collect wastewater and deliver it to the MCES interceptor sewers. The MCES interceptors serving the City of Roseville include RV-430, RV-431, RV-432 and RV-433. All of the interceptors flow south and eastward where they connect to RV-430, which delivers the waste to the Pigs Eye Wastewater Treatment Plant in St. Paul. Operated by the MCES, this plant accepted 1.8 billion gallons of wastewater from Roseville in 1997 and an estimated 1.95 billion gallons in 1999. By contract with the City, MCES provides and maintains the interceptor sewers. We believe that clear groundwater and surface water is leaking into the city's sewer pipes. Once in the system, it flows to the regional interceptor sewers, and then on to wastewater plants for treatment. Because Roseville is charged for the nmnber of gallons of wastewater they contribute to the system, we are paying for the treatment of clear water. In addition to the cost of treating clear water, 1/1 can also impact the regional system. Many sections in the MCES interceptor system will not have adequate capacity for future development if the amount of clear water entering the system is not reduced. Another concern is the ability to meet future environmental regulations if reduction is not achieved. The problem is that clear gronndwater and surface water enter sanitary sewer pipes and take up space needed to convey wastewater. Groundwater, for example, may get in through old, cracked pipes (infiltration). Surface flooding during heavy rains can run into sewer pipe access holes (inflow). To address these issues, the Metropolitan Council in April 2003 appointed an Infiltration and Inflow Task Force. The group's charge was to propose strategies to reduce excessive infiltration and inflow (III) in local and regional wastewater collection systems. The extent of the problem varies from year to year, depending on overall rainfall and the severity of particular rains. The excess water from some commnnities is cunently exceeding the design of several major interceptors. If excessive wet weather flows are not reduced, the risk of overflows (and backups into homes) will increase each year as more homes and businesses are added to the system. The Met Council estimates that not conecting the problem could cost the region an additional $300 to $400 million to construct relief sewers and pump stations to handle the excess flow.