Protecting public health and the environment

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  District Response to June 2008 High Flow Events

The Madison Metropolitan Sewerage District, along with other municipalities in southern Wisconsin, is recovering from the extraordinary precipitation events and subsequent flooding that took place in early June. The District measured its all-time high peak flow rate of 100,000 gallons per minute and its all-time high one-day wastewater volume of 106 million gallons on June 9. Typical volumes during periods of normal weather are about 40 million gallons per day.

The high flows resulted from rain water that leaked into basements and rain water that flooded streets and low areas and leaked into manholes and through defects in sewer lines. The excess flow from these sources overwhelmed the District’s conveyance system for a period of about 30 hours on June 8 and 9. Even though all pumping equipment was available and in operation during this entire event, many homes and businesses experienced basement back-ups from the sewer system. The District employed portable pumping equipment at two pumping stations to remove water from the sewer system and prevent further basement backups. Even so, the sewer system overflowed from manholes at several points. System overflows and the portable pump discharges ultimately reached nearby wetlands, streams, and the lakes.

Over the past fifteen years the District has experienced six or more significant storm events that have led to high flows in the sewer system. Many scientists now expect that storms of higher intensity and longer duration will be experienced more frequently in the future. To address this possibility and to lessen the likelihood of future events overwhelming the sewer system, the Madison Metropolitan Sewerage District is taking the following actions:

1. The District is reviewing its design standards for sizing interceptor sewers and pumping stations. The District currently provides an allowance for high flows in these facilities that varies from peak flow capacities 4.0 times greater than the average daily flows for facilities with average day design flows of one million gallons per day to peak flow capacities 2.5 times greater than the average daily flows for facilities with average day design flows of 20 million gallons per day. The review will include data from the storm events of the past fifteen years. If higher peaking factors are judged to be necessary, the schedule for construction of replacement interceptor sewers and pumping stations will need to be accelerated, and new and replaced facilities will be larger. This will lessen the likelihood of back-ups and overflows and will result in higher costs for service.
   
2. The District is reviewing its design standards for materials used in constructing interceptor sewers, including manholes, to assure that rain waters are less likely to leak into these facilities during heavy rains and floods.
   
3. The District is reviewing flow data and inspecting its existing interceptor sewers to identify and repair defects that allowed excessive rain water leakage into the District’s system.
   
4. The District is reviewing flow data from its customer communities collected during the recent high flow events. This review will identify likely areas in community sewer systems that experienced excessive leakage during the recent high flow events. The District will work with these communities to address these areas.
   
5. The District will make greater efforts to educate the public in the area of water conservation and how to prevent rain water from leaking into basements. Water conservation and reduced inflow will have positive impacts in both dry and wet weather.

Although the events of June were unprecedented, this will not be the last challenge of this type that we will face. The District is taking action now to better insure that future events will have less impact on the public and the environment.
   
Mercury Pollutant Minimization Program

Dental Amalgam BMPs Training Videos 1-4

Dental sector achieves 60% installation rate.  Click here to go to the mercury page.
   
 

MMSD Master Planning Project Presentations

District staff will be making brief presentations regarding the master planning project at several of our customer communities’ regularly scheduled monthly meetings.  The presentations will include the following topics: 

  • Background information on the District and it’s challenges
  • The master planning process and schedule
  • Future opportunities for the public to provide input to the planning process

District personnel and our consultants will be available to answer questions and listen to the thoughts and ideas presented by the meeting attendees.  To-date, we have 7 presentations scheduled in the months of February and March.  Click here for a list of currently scheduled meetings.
   
  Visions Goals and Strategies updated

The District recently updated its strategic plan, which is described in the Vision, Goals and Strategies (VGS) document. Click here for the most recent edition of the VGS document.
   


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