Stormwater Maintenance Operations

What We Do

Water gushing from storm sewer following very heavy rains.

We provide resources to maintain the storm drainage system through inspections and preventative maintenance services throughout the city's drainage system. Activities include:

Storm Pipe System

Storm water drainage systems need to be cleaned regularly.  While cleaning is necessary for all storm drain systems, there are limitations. Here are five things to know about storm drain cleaning:

  • Clogged drains can cause an overflow of water, leading to increased erosion and dangerous driving conditions. Areas with relatively flat grades or low water flow often require special attention as they rarely achieve high enough water flows to flush themselves.
  • Cleaning storm drains by flushing is more successful for smaller pipes.
  • Since storm drainage systems direct rain water into sources of fresh water such as lakes and rivers, it is important to use environmentally safe products to clean the storm drains.
  • The efficiency of storm system flushing decreases as the length of pipe between flushing points increase.
  • High-pressure water jetting or hydro jetting is one of the most effective ways to clean storm drains and clear away debris and buildup.
Two differnt views of clogged stormdrains.
An unclogged stormdrain and drawing of a truck unclogging a stormdrain.

Inlets and Storm Grates

Many inlets have gratings or grids to prevent people, vehicles, large objects or debris from falling into the storm drain. Grate bars are spaced so that the flow of water is not impeded, but sediment and many small objects can also fall through. However, if grate bars are too far apart, the openings may present a risk to pedestrians, bicyclists, and others in the vicinity. Storm drains in streets and parking areas must be strong enough to support the weight of vehicles, and are often made of cast iron and reinforced concrete.

Three different types of stormdrain inlets and grates.

Roadside Shouldering/Ditch Cleaning

Roadside ditches and channels are immediately adjacent to the roadway. The design of a traversable ditch section depends on the amount of run-off, the grade of the roadway, slope and soil conditions and speed of vehicles on the road. Many are designed to ensure a vehicle or bicycle can pass over the ditch or channel at the road way speed without abruptly stopping, losing control or rolling over. Roadside ditches require maintenance to remove debris and prevent erosion that can create roadside hazards and/or reducing the effectiveness of the drainage system. It is important when repairing eroded earth ditches and shoulders to restore them to their original safety shapes.

Roadside ditches.

Detention Ponds

Detention ponds have become one of the most common solutions for storm water management. They do a great job of slowing runoff, contain sediment, collect trash, and remove pollutants. These ponds are in need of basic maintenance, Things like mowing, trash and litter clean up; removing sediment and slope stabilization with vegetation as well as disposal of these pollutants collected in ponds. Ensuring proper flow and function of a pond not only helps neighborhood drainage, but prevents downstream flooding and property damage, and in dry seasons function as a playground and environmental sanctuary.

Two types of detention ponds.

Drainage Channels

Channels and drainage ways are maintained to avoid obstruction and maintain flow. Channel cleaning includes use of heavy equipment for excess vegetation, loading, hauling, and disposing of materials. Fill material and rock may be imported to repair eroded channel walls and for restoring flow line to original specifications. Rock and concrete can be used for check dams, to control erosion in channels.

Two types of drainage channels.


  • Clean catch basins, storm drain inlets, and other conveyance structures, including detention ponds, in high pollutant load areas before the wet season to remove sediments and debris accumulated during dry weather.
  • Drainage ditches and creeks are also cleared of vegetation and debris to improve hydraulics, increase pollutant removal, and enhance aesthetics and habitat value.
  • During routine maintenance of the conveyance system and drainage structures, field staff should look for evidence of illegal discharges or illicit connections:
    • Is there evidence of spills such as paints, discoloring, etc.?
    • Are there any odors associated with the drainage system?
  • Record locations of apparent illegal discharges/illicit connections for further investigation per the processes described in the Illicit Discharge webpage located here.
  • For more information on stormwater maintenance, see Chapter 6 of the Mile High Flood District Criteria Manual.

The Storm Drainage Program is designed to provide resources to maintain the storm drainage system, which protects the integrity of drainageways and streets to prevent hazards and stormwater damage.

Why We Do It

To safely convey stormwater and minimize the risk of flooding and damage to public and private property.