Cleaning the Piped System and Catch Basins
Routine cleaning and preventive maintenance of the 570-mile piped stormwater system and catch basins is required to facilitate proper functioning of the system and relatively trouble-free operation of the stormwater structures. These structures must be kept free of obstructing debris and built-up sediments. Experience has shown that routine catch basin, pipe segment and connecting line cleaning helps reduce storm system overflow and street flooding during periods of heavy precipitation. Cleaning is also done to reduce the amount of contaminants reaching waterways and to minimize surface flooding.
The Subsurface Maintenance Team routinely cleans catch basins, pipe segments and manholes on improved streets. The cleaning program utilizes specialized sewer jet/vacuum trucks to collect sediments and debris, as well as pressure jet open the system’s connecting lines. Any piped system inlet structures that are obstructed by debris or materials that cannot be vacuumed are cleaned by hand. The obstructing material is then removed from the site by truck. Collected material is placed in a storage container and eventually deposited at the regional stormwater waste management facility for drying and pretreatment prior to land filling.
Scheduling of Cleaning
If needed, catch basins, pipe segments and manholes may be cleaned concurrently. Scheduling is based on the city stormwater grid maps with a goal of cleaning 50% of the city’s catch basins annually. Historic problem areas and seasonal influences are also controlling factors. The fiscal year 2012 Work Plan projects cleaning about 7,500 catch basins this year.
Catch basins, pipe segments and manholes constructed privately for the purpose of draining private lots are not cleaned by city crews. Lines connecting private catch basins or pipe segments into the city storm system are not the maintenance responsibility of the city; however, catch basins connected to private pipes will often allow material from the private system to migrate into a public catch basin as it is cleaned. When this occurs, the private line as it enters the public system is cleaned to prevent further migration of debris and sediment.