SCM Operation & Maintenance

Stormwater Control Measures (SCMs) are permanent structural devices that are designed, constructed, and maintained to remove pollutants from stormwater runoff before the water reaches our streams and drinking water supply reservoirs.  Some examples of SCMs include wet ponds, bioretention cells, infiltration systems, stormwater wetlands, permeable pavement, and sand filters. 

SCMs require regular operation and maintenance to function properly over the long term.  Important information about SCM Operation & Maintenance:

  • SCMs do not work unless they are maintained properly.
  • The type of maintenance that is needed depends on the type of SCM.
  • SCMs should be inspected on a quarterly basis at a minimum.  It is also a good idea to inspect SCMs after larger storm events (exceeding 1 inch over a 24-hour period). 

This site provides a description of each SCM, an inspection form, and an webinar to instruct you about how to conduct an inspection.

General Topics: SCM Maintenance 

Wet Pond

Wet ponds improve stormwater quality by holding stormwater over a two to five day period.  A wet pond includes a forebay, a permanent pool, and a temporary pool.  A forebay is a separate smaller pond that is placed upstream of the main portion of the pond to trap suspended solids.  A permanent pool is water that stays in the pond between storms to slow down stormwater and allow pollutants to settle out. A temporary pool is additional depth of water that is held and released over slowly after a storm. 

Wet Pond Inspection Form                 
Wet Pond Operation & Maintenance Webinar

Bioretention Cell

A bioretention cell is an excavated area that is filled with a specialized soil media and plants, or grass/sod. It is designed to temporarily hold and filter stormwater. Bioretention cells are one of the most versatile SCMs: They can be installed in a variety of soil types from clay to sand and in a wide variety of sites. They are also one of the most effective SCMs for removing pollutants, because they use many different pollutant removal mechanisms, including infiltration, absorption, adsorption, evapotranspiration, microbial action, plant uptake, sedimentation, and filtration.

Bioretention Cell Inspection Form                
Bioretention Cell Operation & Maintenance Webinar

Infiltration System

An infiltration system captures stormwater runoff and allows it to infiltrate into the soil. This SCM (along with permeable pavement) is typically the work horse of a runoff volume match site because it helps the site to mimic pre-development hydrology and therefore helps to protect the structure of the receiving stream. Infiltration systems work best when their drainage areas are mostly impervious, as pervious surfaces can contribute fines that clog the soil.

  • Infiltration Basins are depressions that capture, store and allow stormwater to infiltrate into the soils.
    Infiltration Basin Inspection Form                                 
    Infiltration Basin Operation & Maintenance Webinar
  • Infiltration Trenches are filled with stone or other media to store stormwater in the voids between. Some infiltration trenches use precast concrete vaults with open bottoms to provide a large storage volume to hold stormwater for infiltration into the soil. 
    Infiltration Trench Inspection Form                                
    Infiltration Trench Operation & Maintenance Webinar (coming soon!)   

Stormwater Wetland

Stormwater wetlands are designed to reproduce the exceptional pollutant removal capability of natural wetlands. Stormwater that is captured by the wetland area first enters a micropool or forebay, which is a relatively deep pool that promotes initial settling of larger pollutant particles. The stormwater slowly flows through the shallow areas of the wetland where the wetland plants filter suspended pollutants and reduce nutrient pollution through uptake.

Stormwater Wetland Inspection Form                   
Stormwater Wetland Operation & Maintenance Webinar             

Permeable Pavement

Permeable pavement has openings in its surface that allow stormwater to soak through the pavement and be captured in a stone layer that is located beneath the pavement's surface. From the stone layer, stormwater is either soaked into the ground below or is held and released over a period of two to five days.  Permeable pavement is useful in existing urban development where the need to expand parking areas is hindered by lack of space needed for stormwater management. Permeable pavement is also useful in new developments with limited space where land costs are high,

Permeable Pavement Inspection Form                      
Permeable Pavement Operation & Maintenance Webinar   

Sand Filter

A sand filter is a surface or subsurface device that percolates stormwater through a sand media where pollutants are filtered out. Sand filter effluent is usually discharged. Sand filters are capable of removing a wide variety of pollutant concentrations in stormwater via settling, filtering, and adsorption processes. Since sand filters can be installed as basins or can be located underground.  If they are located underground, they should be inspected by a professional knowledgeable in confined space entry.  The materials below are intended to be used for sand filters designed as basins.

Sand Filter Inspection Form                     
Sand Filter Operation & Maintenance Webinar