Big Green Vactor Preventative Maintenance Program

The City of Madison Engineering Division's "Big Green Vactor Preventive Maintenance Program" is an aggressive approach to maintaining and cleaning the City's sanitary and storm sewer.

The "Big Green Vactor"

The Big Green Vactors that you see around town are the City’s primary tool to clean and maintain the City Sewer system.  Cleaning and televising the City sanitary sewer mains prevents interruption in sanitary sewer service (backups) for customers and Sanitary Sewer Overflows (SSOs) which are our priorities as a Utility. In the event that there is a problem with the City sewer, we will remove the blockage quickly and minimize the impact on homes or buildings and the environment. This is the reason for an aggressive cleaning and CCTV schedule that we have here at Engineering.

The City of Madison-Engineering Department has 10 Vactor trucks (9 Vactor 2100 Series Combo Units and 1 Vactor Jetter Unit) and 1 Sewer Rodding Machine.

The Vactors use high pressure water pushed through a 1” flex hose and specially designed nozzle to propel itself through the underground sewer main. Once the nozzle has reached the upstream sanitary structure, the operator draws the hose and nozzle back through a sophisticated hydraulic system that controls the speed and water pressure. As the nozzle comes back slowly, it scours the pipe and pulls any debris in the main back to the sanitary structure that the truck is working out of. The Vactors have a powerful vacuum that is connected to 8” tubes that will then vacuum up the debris. By scouring the main and vacuuming up the debris, it keeps the mains operating correctly to help prevent any sanitary sewer backups or overflows.

The advantages of the Vactors is the superior cleaning they do compared to mechanical means such as sewer rodding or bucket machines. Vactors do not use any chemicals to clean, just high pressure water. Vactors are capable of cleaning thousands of linear feet per day, depending on sanitary main size and how dirty it is. Vactors, even though they carry 1500 gallons of water, are able to work in extreme cold temperatures. The Vactors are equipped with a water recirculating system to help prevent freezing, which is much needed with Wisconsin winters.

Strategy

We measure success by the number of backups. Sewer backups are very costly and a health hazard for our customers. One backup is too many.  Prior to ramping our preventative maintenance efforts, we had problem areas in the City.

The City schedules maintenance cleaning with the Sewer Vactors based on the condition of the sewer mains in an area, tendency for the sewer to have root obstructions, and the history of a sewer accumulating grease. Scheduled sewer cleaning maintenance has two categories: Sanitary Sewer Area Clean (AC) and Preventative Maintenance (PM) Program. Sewer mains on the Area Clean (AC) Schedule are cleaned once every  three years.  This is the City’s standard cleaning cycle for sanitary sewers.  There are 2.7 million feet are in this category. Sewer mains that have a history of problems (sewer backups, root problems, grease) require additional cleaning.  These sewer mains are on the Preventative Maintenance (PM) Schedule and are cleaned 1-12 times per year. There are 1.5 million feet of sewer main in this category.

The City cleans our 29 lift station up to 3 times per year depending on weekly inspections done by Madison Metropolitan Sewerage District (MMSD).

Basin, Grate Cleaning

• Biannual Catch Basin Cleanings
  • Engineering crews clean 1,200 catch basins every April and October
  • On average, 480 tons of debris are removed each cleaning season
• Priority Grate Cleaning
  • Prior and after each rain event, crews clean 763 structures that range from inlets, dead ends and big grates