Operation and maintenance of wet swale (wetland channel)
This page is in development
The most frequently cited maintenance concern for wet swales is that they provide a breeding ground for mosquitoes. Common operational problems include:
- blockage by debris and vegetation;
- sediment accumulates in the swale, reducing the storage volume;
- slope stabilizing vegetation is lost; and
- invasive plants out-compete native vegetation
Design phase maintenance
Implicit in the design guidance is the fact that many design elements of filtering systems can minimize the maintenance burden and maintain pollutant removal efficiency. Key examples include:
- limiting drainage area;
- providing easy site access (REQUIRED);
- providing pretreatment (RECOMMENDED); and
- utilizing native plantings (see Plants for Stormwater Design).
Wet swales can be designed, constructed and maintained to minimize the likelihood of being desirable habitat for mosquito populations. Designs that incorporate constant inflows and outflows, habitat for natural predators, and constant permanent pool elevations limit the conditions typical of mosquito breeding habitat (see section on mosquito control). For more information on design information for wet swales, link here.
Construction phase maintenance
Proper construction methods and sequencing play a significant role in reducing problems with operation and maintenance (O&M). Inspections during construction are needed to ensure that the wet swale practice is built in accordance with the approved design standards and specifications. Detailed inspection checklists should be used that include sign-offs by qualified individuals at critical stages of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. An example construction phase inspection checklist is provided below.
Wet swale construction inspection checklist.
Link to this table
To access an Excel version of form (for field use), click here.
| Project: | ||
| Location: | ||
| Site Status: | ||
| Date: | ||
| Time: | ||
| Inspector: | ||
| Construction Sequence | Satisfactory / Unsatisfactory | Comments |
|---|---|---|
| 1. Pre-Construction | ||
| Pre-construction meeting | ||
| Runoff diverted (Note type of bypass) | ||
| Facility area cleared | ||
| Project benchmark near site | ||
| Facility location staked out | ||
| Temporary erosion and sediment protection properly installed | ||
| 2. Excavation | ||
| Size, location, and inverts per plans | ||
| Side slopes stable | ||
| Lateral slopes completely level | ||
| Longitudinal slopes within design range | ||
| Groundwater/bedrock verified | ||
| Stockpile location not adjacent to excavation area and stabilized with vegetation and/ or silt fence | ||
| Verify stockpile is not eroding | ||
| 3. Structural Components | ||
| Outlets installed pre plans | ||
| Pretreatment devices installed per plans | ||
| Soil bed composition and texture conforms to specifications | ||
| Inlets installed per plans | ||
| 4. Vegetation | ||
| For native wet swales, plants and materials ordered 6 months prior to construction | ||
| For native wet swales, construction planned to allow for adequate planting and establishment of plant community | ||
| Complies with planting specs | ||
| Topsoil complies with specs in composition and placement | ||
| Soil properly stabilized for permanent erosion control | ||
| 5. Final Inspection | ||
| Project: | ||
| Dimensions per plans | ||
| Check dams operational | ||
| Pre-treatment operational | ||
| Inlet/outlet operational | ||
| Effective stand of vegetation stabilized per specifications | ||
| Construction generated sediments removed | ||
| Contributing watershed stabilized before flow is diverted to the practice | ||
| Comments: | ||
| Actions to be taken: | ||