2 employees are assigned each summer to operate the high-pressure jet to clean sanitary sewers within the City. Each year 1/3 of the system is cleaned as routine maintenance. Several specific locations are cleaned annually.
The annual cleaning is done around restaurants and other businesses that may be introducing grease or other such waste into the collection system. Generally, in a sanitary sewer pipe the material is more of a grease and/or sludge type material and is usually washed down and left in the pipe to be dealt with at the Wastewater Treatment Plant. Though the crew has found sand, gravel and rocks in the sanitary sewers, it is rare. Special procedures must be followed when dealing with materials removed from a sanitary sewer in accordance with the Minnesota Pollution Control Agency rules and regulations.
Routine Jet Cleaning
Routinely "jetting" sewer lines accomplish a couple of different objectives. First, the cleaning reduces the possibility of a sludge build up in the pipes that may in time create a blockage. Secondly, any more severe problems that are developing may be detected early before a major problem affects any home or business owners.
Since the purchase and implementation of a specialized "jet / vacuum" sewer cleaning truck in 1992, the number of sewer back-ups and other associated sewer problems have been reduced substantially. In fact, during the entire year 2000, there were no reported sewer back-ups linked to a City sewer main. However, in the few years before that, there were several potential problems found by the "jet" crew and repaired before any serious consequence occurred.
No routine cleaning of storm sewer lines are done. Problems occurring in any storm sewer are dealt with as needed.
Because storm sewers are only handling clean water (storm runoff) they are considered self-cleaning. For the most part this is true, however, as we all know this runoff may, at times, carry quite a bit of solid material with it (depending on the circumstances).
Occasionally, solids introduced into these storm drains accumulate to the point of plugging a pipe. When this occurs, the "jet / vacuum" truck and crew are dispatched to remove the material and eliminate the problem. More often than not, the vacuum portion of the truck is used in this situation. Most of these problems occur in the catch basin where the material can be vacuumed out and hauled away. This material is not considered hazardous waste.