Line 132: | Line 132: | ||
<tr> | <tr> | ||
− | Remove any stormwater diversion or barriers once seedlings are established. | + | <tr> |
− | Once | + | <td>Remove any stormwater diversion or barriers once seedlings are established. |
− | When plants are sufficiently established | + | <td>Once |
− | 1-2 hours | + | <td>When plants are sufficiently established |
− | 1,2,3,4,5 | + | <td>1-2 hours |
− | + | <td>1,2,3,4,5 | |
− | + | </tr> | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
+ | <tr> | ||
+ | <td>Install protective barriers (e.g. chicken wire) to protect growing vegetation from wildlife | ||
+ | <td>As needed | ||
+ | <td>First growing season | ||
+ | <td>8 hours | ||
+ | <td>1,2,3,5 | ||
+ | </tr> | ||
− | 3,4 | + | <tr> |
− | Remove and replace dead plants | + | <td>Check for signs of burrowing animals and incorporate gravel or rock in problem areas to discourage burrowing. |
− | As needed | + | <td>As needed |
− | First growing season | + | <td>First growing season |
− | 2-4 hours | + | <td>1-2 hours |
− | 2,3,4,5,6 | + | <td>5 |
− | Spot reseeding of bare patches and eroding areas | + | </tr> |
− | As needed | + | |
− | First growing season | + | <tr> |
− | 2-4 hours | + | <td>Check that water is moving as planned through the wetland. Identify and fix any stagnant zones. |
− | 1,2,3,4,5,6 | + | <td>As needed |
− | After First Year of Operation | + | <td>During first 2 months |
− | Activity | + | <td>4 hours |
− | Frequency | + | <td>1 |
− | Time Period | + | </tr> |
− | Level of Effort per Visit | + | |
− | O&M Benefit* | + | <tr> |
− | Check that there is no ponding in the pre-treatment device | + | <td>Mow dikes frequently to establish deep rooted ground cover |
− | Biannually | + | <td>Biweekly or as needed |
− | Any time when ground is not frozen | + | <td>First growing season |
− | 1-2 hours | + | <td> |
− | 1 | + | <td>3,4 |
− | Check for evidence of clogging in the pre-treatment device and/or in any conveyance structures. | + | </tr> |
− | Biannually | + | |
− | In spring and fall | + | <tr> |
− | 1-2 hours | + | <td>Remove and replace dead plants |
− | 1 | + | <td>As needed |
− | Remove trash and debris from the pre-treatment device and/or in the main treatment area. | + | <td>First growing season |
− | Monthly | + | <td>2-4 hours |
− | All year long | + | <td>2,3,4,5,6 |
− | 1-2 hours | + | </tr> |
− | 1,5 | + | |
− | Inspect for and remove excess sediment in the pre-treatment device and/or in the main treatment area. | + | <tr> |
− | Monthly | + | <td>Spot reseeding of bare patches and eroding areas |
− | All year long | + | <td>As needed |
− | 4 hours if removal is needed | + | <td>First growing season |
− | 1 | + | <td>2-4 hours |
− | Check and repair eroded areas | + | <td>1,2,3,4,5,6 |
− | Annually | + | <tr> |
− | In fall or spring when vegetation has died down | + | |
− | 4 hours if repairs are needed | + | <tr> |
− | 1,2,3,4,5 | + | <th colspan=5>After First Year of Operation |
− | Weed and remove invasive plants | + | </tr> |
− | Twice during growing season | + | <tr> |
− | During growing season | + | <th>Activity |
− | 1-2 hours | + | <th>Frequency |
− | 2,3,4,5 | + | <th>Time Period |
− | Inspect plant composition and health and replace as needed to maintain >50% coverage. | + | <th>Level of Effort per Visit |
− | Biannually | + | <th>O&M Benefit* |
− | In fall or spring | + | </tr> |
− | 4-8 hours, more if plant replacement is needed | + | |
− | 2,3,4,5,6 | + | <tr> |
− | Remove woody vegetation on or near embankments, forebays, spillways, and outlets | + | <td>Check that there is no ponding in the pre-treatment device |
− | Annually | + | <td>Biannually |
− | In fall or spring | + | <td>Any time when ground is not frozen |
− | 4 hours | + | <td>1-2 hours |
− | 1,2,3, 4,5,6 | + | <td>1 |
− | Check for signs of burrowing animals and incorporate gravel or rock in problem areas to discourage burrowing. | + | </tr> |
− | As needed | + | |
− | During growing season | + | <tr> |
− | 1-2 hours | + | <td>Check for evidence of clogging in the pre-treatment device and/or in any conveyance structures. |
− | 1,2,5 | + | <td>Biannually |
− | Inspect for and repair broken inlets, pipes, or other water control structures | + | <td>In spring and fall |
− | Biannually | + | <td>1-2 hours |
− | After high flows and ice breakup | + | <td>1 |
− | 2 hours, more if repairs are needed | + | </tr> |
− | 1 | + | |
− | Mow dikes and remove any shrubs or trees growing on dikes | + | <tr> |
− | As needed | + | <td>Remove trash and debris from the pre-treatment device and/or in the main treatment area. |
− | During growing season | + | <td>Monthly |
− | 1-2 hours | + | <td>All year long |
− | 1,5 | + | <td>1-2 hours |
− | Monitor operating range of water level | + | <td>1,5 |
− | Daily (collect data continuously, use information to diagnose issues) | + | </tr> |
− | Any time | + | |
− | 1-2 hours | + | <tr> |
− | 1,2,4,6 | + | <td>Inspect for and remove excess sediment in the pre-treatment device and/or in the main treatment area. |
− | Check that water is moving as planned through the wetland. Identify and fix any stagnant zones | + | <td>Monthly |
− | Annually | + | <td>All year long |
− | During growing season | + | <td>4 hours if removal is needed |
− | 4 hours | + | <td>1 |
− | 1,2,3,4,5 | + | </tr> |
− | Inspect sediment accumulation in forebay and treatment areas. Remove if hydrology is impacted or if less than 50% of forebay capacity remains. | + | |
− | Annually | + | <tr> |
− | Fall | + | <td>Check and repair eroded areas |
− | 2 hours | + | <td>Annually |
− | 1,4,6 | + | <td>In fall or spring when vegetation has died down |
− | Harvest wetland plants | + | <td>4 hours if repairs are needed |
− | Once every 2-3 years | + | <td>1,2,3,4,5 |
− | After growing season | + | </tr> |
− | 4-8 hours | + | |
− | 1,4,5,6 | + | <tr> |
− | Remove sediment from forebay | + | <td>Weed and remove invasive plants |
− | Once every 2-7 years, or when less than 50% forebay capacity remains | + | <td>Twice during growing season |
− | As needed | + | <td>During growing season |
− | Varies | + | <td>1-2 hours |
− | 1,4,5,6 | + | <td>2,3,4,5 |
− | After 5+ Years of Operation (non-routine maintenance) | + | </tr> |
− | Activity | + | |
− | Frequency | + | <tr> |
− | Time Period | + | <td>Inspect plant composition and health and replace as needed to maintain >50% coverage. |
− | Level of Effort per Visit | + | <td>Biannually |
− | O&M Benefit* | + | <td>In fall or spring |
− | Remote inspection of all conveyance structures (e.g. pipes, underdrains, etc.) | + | <td>4-8 hours, more if plant replacement is needed |
− | Every 10 years | + | <td>2,3,4,5,6 |
− | Any time | + | </tr> |
− | Varies | + | |
− | 1 | + | <tr> |
− | After long term operation of the practice, some occasional and infrequent maintenance activities might be required, such as bigger repairs or redesign of key elements of the practice. Replacement of concrete components (e.g. pipes, risers, may be required after 25-50 years. | + | <td>Remove woody vegetation on or near embankments, forebays, spillways, and outlets |
− | As needed | + | <td>Annually |
− | As needed | + | <td>In fall or spring |
− | Could be significant depending on the activity | + | <td>4 hours |
− | 1,2,3,4,5,6 | + | <td>1,2,3,4,5,6 |
− | + | </tr> | |
− | Proper stormwater flow and infiltration | + | |
− | Creation and maintenance of wildlife habitat | + | <tr> |
− | Creation and maintenance of pollinator habitat | + | <td>Check for signs of burrowing animals and incorporate gravel or rock in problem areas to discourage burrowing. |
− | Nutrient cycling and storage | + | <td>As needed |
− | Aesthetics and public enjoyment | + | <td>During growing season |
− | Carbon sequestration | + | <td>1-2 hours |
+ | <td>1,2,5 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Inspect for and repair broken inlets, pipes, or other water control structures | ||
+ | <td>Biannually | ||
+ | <td>After high flows and ice breakup | ||
+ | <td>2 hours, more if repairs are needed | ||
+ | <td>1 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Mow dikes and remove any shrubs or trees growing on dikes | ||
+ | <td>As needed | ||
+ | <td>During growing season | ||
+ | <td>1-2 hours | ||
+ | <td>1,5 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Monitor operating range of water level | ||
+ | <td>Daily (collect data continuously, use information to diagnose issues) | ||
+ | <td>Any time | ||
+ | <td>1-2 hours | ||
+ | <td>1,2,4,6 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Check that water is moving as planned through the wetland. Identify and fix any stagnant zones | ||
+ | <td>Annually | ||
+ | <td>During growing season | ||
+ | <td>4 hours | ||
+ | <td>1,2,3,4,5 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Inspect sediment accumulation in forebay and treatment areas. Remove if hydrology is impacted or if less than 50% of forebay capacity remains. | ||
+ | <td>Annually | ||
+ | <td>Fall | ||
+ | <td>2 hours | ||
+ | <td>1,4,6 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Harvest wetland plants | ||
+ | <td>Once every 2-3 years | ||
+ | <td>After growing season | ||
+ | <td>4-8 hours | ||
+ | <td>1,4,5,6 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Remove sediment from forebay | ||
+ | <td>Once every 2-7 years, or when less than 50% forebay capacity remains | ||
+ | <td>As needed | ||
+ | <td>Varies | ||
+ | <td>1,4,5,6 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <th colspan=5>After 5+ Years of Operation (non-routine maintenance) | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <th>Activity | ||
+ | <th>Frequency | ||
+ | <th>Time Period | ||
+ | <th>Level of Effort per Visit | ||
+ | <th>O&M Benefit* | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Remote inspection of all conveyance structures (e.g. pipes, underdrains, etc.) | ||
+ | <td>Every 10 years | ||
+ | <td>Any time | ||
+ | <td>Varies | ||
+ | <td>1 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>After long term operation of the practice, some occasional and infrequent maintenance activities might be required, such as bigger repairs or redesign of key elements of the practice. Replacement of concrete components (e.g. pipes, risers, may be required after 25-50 years. | ||
+ | <td>As needed | ||
+ | <td>As needed | ||
+ | <td>Could be significant depending on the activity | ||
+ | <td>1,2,3,4,5,6 | ||
+ | </tr> | ||
+ | |||
+ | <tr> | ||
+ | <td>Key to Maintenance Benefits: | ||
+ | *Proper stormwater flow and infiltration | ||
+ | *Creation and maintenance of wildlife habitat | ||
+ | *Creation and maintenance of pollinator habitat | ||
+ | *Nutrient cycling and storage | ||
+ | *Aesthetics and public enjoyment | ||
+ | *Carbon sequestration | ||
+ | </tr> |
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:
Effective short and long-term operation of stormwater treatment wetland practices requires dedicated and routine maintenance. Proper maintenance will not only increase the expected lifespan of the facility but will improve ecological function, aesthetics, and property value. Important post-construction considerations are provided below.
The table below provides an overview and schedule of general maintenance activities.
First Year of Operation | ||||
---|---|---|---|---|
Activity | Frequency | Time Period | Level of Effort | O&M Benefit* |
Check that there is no ponding in the pre-treatment device. | At least twice after storm events > 0.5 inches | Within the first 6 months | 1-2 hours | 1 |
Check for evidence of clogging in the pre-treatment device and/or in any conveyance structures | At least twice after storm events > 0.5 inches | Within the first 6 months | 1-2 hours | 1 |
Maintain proper water level for establishing vegetation (may require supplemental source) | 1/week initially | During first 2 months | 1-2 hours | 2,3,4,5,6 |
As needed | First growing season | 1-2 hours | ||
Remove any stormwater diversion or barriers once seedlings are established. | Once | When plants are sufficiently established | 1-2 hours | 1,2,3,4,5 |
Install protective barriers (e.g. chicken wire) to protect growing vegetation from wildlife | As needed | First growing season | 8 hours | 1,2,3,5 |
Check for signs of burrowing animals and incorporate gravel or rock in problem areas to discourage burrowing. | As needed | First growing season | 1-2 hours | 5 |
Check that water is moving as planned through the wetland. Identify and fix any stagnant zones. | As needed | During first 2 months | 4 hours | 1 |
Mow dikes frequently to establish deep rooted ground cover | Biweekly or as needed | First growing season | 3,4 | |
Remove and replace dead plants | As needed | First growing season | 2-4 hours | 2,3,4,5,6 |
Spot reseeding of bare patches and eroding areas | As needed | First growing season | 2-4 hours | 1,2,3,4,5,6 |
After First Year of Operation | ||||
Activity | Frequency | Time Period | Level of Effort per Visit | O&M Benefit* |
Check that there is no ponding in the pre-treatment device | Biannually | Any time when ground is not frozen | 1-2 hours | 1 |
Check for evidence of clogging in the pre-treatment device and/or in any conveyance structures. | Biannually | In spring and fall | 1-2 hours | 1 |
Remove trash and debris from the pre-treatment device and/or in the main treatment area. | Monthly | All year long | 1-2 hours | 1,5 |
Inspect for and remove excess sediment in the pre-treatment device and/or in the main treatment area. | Monthly | All year long | 4 hours if removal is needed | 1 |
Check and repair eroded areas | Annually | In fall or spring when vegetation has died down | 4 hours if repairs are needed | 1,2,3,4,5 |
Weed and remove invasive plants | Twice during growing season | During growing season | 1-2 hours | 2,3,4,5 |
Inspect plant composition and health and replace as needed to maintain >50% coverage. | Biannually | In fall or spring | 4-8 hours, more if plant replacement is needed | 2,3,4,5,6 |
Remove woody vegetation on or near embankments, forebays, spillways, and outlets | Annually | In fall or spring | 4 hours | 1,2,3,4,5,6 |
Check for signs of burrowing animals and incorporate gravel or rock in problem areas to discourage burrowing. | As needed | During growing season | 1-2 hours | 1,2,5 |
Inspect for and repair broken inlets, pipes, or other water control structures | Biannually | After high flows and ice breakup | 2 hours, more if repairs are needed | 1 |
Mow dikes and remove any shrubs or trees growing on dikes | As needed | During growing season | 1-2 hours | 1,5 |
Monitor operating range of water level | Daily (collect data continuously, use information to diagnose issues) | Any time | 1-2 hours | 1,2,4,6 |
Check that water is moving as planned through the wetland. Identify and fix any stagnant zones | Annually | During growing season | 4 hours | 1,2,3,4,5 |
Inspect sediment accumulation in forebay and treatment areas. Remove if hydrology is impacted or if less than 50% of forebay capacity remains. | Annually | Fall | 2 hours | 1,4,6 |
Harvest wetland plants | Once every 2-3 years | After growing season | 4-8 hours | 1,4,5,6 |
Remove sediment from forebay | Once every 2-7 years, or when less than 50% forebay capacity remains | As needed | Varies | 1,4,5,6 |
After 5+ Years of Operation (non-routine maintenance) | ||||
Activity | Frequency | Time Period | Level of Effort per Visit | O&M Benefit* |
Remote inspection of all conveyance structures (e.g. pipes, underdrains, etc.) | Every 10 years | Any time | Varies | 1 |
After long term operation of the practice, some occasional and infrequent maintenance activities might be required, such as bigger repairs or redesign of key elements of the practice. Replacement of concrete components (e.g. pipes, risers, may be required after 25-50 years. | As needed | As needed | Could be significant depending on the activity | 1,2,3,4,5,6 |
Key to Maintenance Benefits:
|