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For more design information for stormwater wetlands practices, see the “design criteria for stormwater wetlands” page. | For more design information for stormwater wetlands practices, see the “design criteria for stormwater wetlands” page. | ||
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+ | ==Construction Phase O&M Considerations== | ||
+ | Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include: | ||
+ | *Before construction begins: | ||
+ | **Develop a planting schedule that meets the needs of the selected species. Planting during fall dormancy or early spring is usually successful. | ||
+ | **Ensure that the contributing drainage area is fully stabilized with vegetation prior to the beginning of construction. Also make sure that impervious areas in the contributing drainage area are clean. If this is not possible, use barriers or diversions to direct stormwater flows from the contributing drainage area away from the practice. | ||
+ | **Install any needed erosion and sediment controls in your construction site and prepare a storm water pollution prevention plan (SWPPP). | ||
+ | **Designate a stormwater supervisor to make sure someone is responsible for erosion and sediment control. | ||
+ | Hold a pre-construction meeting with the designer and the installer to review the construction plans and the sequencing of construction. | ||
+ | *During construction: | ||
+ | **Construct any pre-treatment devices before constructing the main wetland area. | ||
+ | **Decompact and prepare treatment beds. Allow an extended wetted settling period to soften up soil if possible. | ||
+ | **Ensure heavy equipment does not enter the footprint of the practice after any vegetation has been seeded or planted. | ||
+ | **Store any soil or gravel media downstream of the practice footprint to avoid filling in any depressions and clogging any inlets and pools. If this is not possible, store soil or gravel media in some type of covered or contained structure. | ||
+ | **Inspect the practice during construction to ensure that it is built in accordance with the approved design and standards and specifications. This includes verification of the media composition and depths. Use a detailed inspection checklists 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. Example construction phase inspection checklists are provided further down below. | ||
+ | **Ensure that the plant and vegetation mix conforms to the vegetation design plan, particularly if the vegetation was selected to provide ecological function (such as pollinator habitat). | ||
+ | *After construction: | ||
+ | **Verify that the wetland was built in accordance with the approved design and standards and specifications, including the pre-treatment devices as well as the main practice. | ||
+ | **Verify that the contributing drainage area and any slopes are fully stabilized with vegetation prior to removing any barriers, diversions, or erosion and sediment control measures. | ||
+ | **Verify that the inlet structures capture the intended runoff. Conduct a full inundation test to inspect the outflow and any bypass functions. | ||
+ | **Verify that the practice reduces nutrient loads. Collect inflow and outflow storm water samples and have them analyzed for nutrient concentrations. | ||
+ | **Use a detailed inspection checklist that includes sign-offs by qualified individuals at the completion of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. **Example construction phase inspection checklists are provided further down below. | ||
+ | **Review and discuss the plant warranty/establishment period with the plant provider to understand the conditions under which failing plants will be replaced. | ||
+ | **Determine if stormwater should be kept offline from the practice until the seedlings are established. | ||
+ | The design/construction team should provide the O&M team with the following information to be included in the O&M plan: | ||
+ | **The plant warranty . | ||
+ | **The “as-built” plans of the practice | ||
+ | **A list of conditions that might cause failure of the practice if not properly maintained. |
Operation and Maintenance of Stormwater Treatment Wetland Practices
Stormwater treatment wetland practices are constructed depressions and pools planted with emergent aquatic or wetland vegetation. Wetlands typically remain wet due to relatively impervious sublayers and have retention times that allow pollutants to settle out of stormwater and into the sediment. The vegetated pools can provide excellent wildlife habitat, enhance nutrient cycling, sequester carbon, and offer aesthetic improvements to urban and rural areas if properly maintained.
Wetlands can provide stormwater and other ecosystem services for many years if they are properly maintained. Typical lifespans range between 25 and 75 years, depending on local conditions and ongoing maintenance to the systems (Torres et al., 2015). The most common O&M concerns for stormwater wetland practices include:
The sections below describe best practices to prevent or minimize these and other common problems.
Designers should design stormwater treatment wetland practices in ways that prevent or minimize O&M issues. In general, wetland designs should mimic natural wetlands and introduce few complex components. Design phase O&M considerations include:
Designers should consult and include any local requirements regarding green infrastructure. O&M considerations often depend on whether the practice is located on public land, private land, or in the public right of way. For example, exterior plantings in the public right of way that conflict with any traffic safety considerations (e.g. sight lines) could require increased O&M, such as pruning or complete removal.
Designers should also recognize the need to perform frequent landscaping maintenance to remove trash, check for clogging, and maintain vigorous and healthy vegetation. Designers can incorporate design solutions to facilitate maintenance activities. Examples include:
The designer should also provide a site-specific O&M plan that includes the following:
For more design information for stormwater wetlands practices, see the “design criteria for stormwater wetlands” page.
Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include:
Hold a pre-construction meeting with the designer and the installer to review the construction plans and the sequencing of construction.
The design/construction team should provide the O&M team with the following information to be included in the O&M plan: