This page provides a discussion of operation and maintenance (O&M) considerations when incorporating vegetation into stormwater practices.
Identifying vegetation operations and maintenance considerations is a critical item in a successful stormwater management project. Proper planning at the beginning of a project can save time and money over the life of the project. When designing vegetation for a BMP it is essential to understand the maintenance requirements needed to maintain plant selections.
It is critical to understand what maintenance is required for a successful and fully vegetated BMP. Specific considerations are unique to each site and should ask the following questions, at a minimum:
Answering each of these and any other relevant questions will help guide the specific maintenance needs and better ensure the success of a project.
1. Which maintenance items are needed?
Maintenance can vary depending on the characteristics of the site and the specific vegetation to be managed. Typical tasks include mowing, hand weeding, spot spraying with herbicide, woody plant removal, mulching, and adding or replacing plants. Some maintenance may be specific to the function of a BMP, but not all maintenance is necessary or appropriate for every project’s goal and budget. For example, selective removal of an aggressive species from a large retention pond it may not be necessary for the hydraulic or water quality function of the BMP but it may add habitat and ecosystem value. A landscape architect, restoration specialist, or other trained professional can assist with determining appropriate maintenance tasks by vegetation type. Careful determination of tasks and timing at the planning stage can result in an efficient scope, budget, and execution. BMP specific maintenance activities and schedule should be considered before developing a planting plan. For information on bmp-specific operation and maintenance guidance, link here.
2. How often should each maintenance item occur?
Carefully evaluate the vegetation being established on the site, what the best practices for maintenance include, and how often those need to be included to establish a plan prior to installation. Some examples of considerations that would affect inspection and maintenance timing include seasonal rainfall, irrigation requirements, weeds and other vegetative pressures, heat and cold, aspect, and herbivory. The planned maintenance and maintenance staff should match the requirements of each vegetative type.
Example: watering requirements for new trees can be in excess of 2” of water per week during the middle of the summer. Depending on timing, the required maintenance for irrigation alone may require multiple trips to a site each week and may require the use of a truck equipped with a water tank if irrigation water is not available on site.
3. What is the schedule and timing of inspection and maintenance? What communication and reporting requirements are required?
Maintenance timing again should be based on the type of vegetation being established and the site conditions. Consider how often maintenance should occur, as determined in the previous step, and create a plan and schedule for the maintenance at the planning stage. Typical maintenance periods are daily, weekly, monthly during the growing season, annually, or otherwise.
Additionally, it is important to understand how reporting will need to occur and what personnel should perform the reporting. Standard forms or checklists are a beneficial tool to have for reporting inspection and maintenance. A communication plan is also helpful in determining which personnel, how often, what methods to use, and contact information for maintenance coordination throughout the project.
4. What personnel are required to perform the maintenance? Do they have the necessary qualifications and equipment to perform the work?
It is important to consider the type of maintenance required throughout the design of the project. Specially trained or certified personnel such as arborists, herbicide/pesticide applicators, and prescribed burn managers may be appropriate depending on the vegetation and project goals. These requirements should be considered in evaluating and hiring contractors to perform maintenance.
5. What are the methods and benchmarks for evaluating success?
What determines success varies by vegetation. For example, a successful sodded turfgrass area is very different from a successful native wetland planting. The time from installation to evaluation of success will vary as well by cover type. Proxy measures for evaluating success may be appropriate based on the evaluation period and timing.
6. What are the costs?
Consider the project budget when evaluating the duration of maintenance, short- and long-term goals (e.g., number of plants in a selected area, no bare areas, etc.), number of planned maintenance site visits, creating a maintenance plan, reporting, and other site-specific needs when determining the cost of the maintenance. Ensure the project budget considers maintenance. A line-item for maintenance in the contract can ensure successful execution of vegetative establishment.
The following sections are specific considerations to help evaluate vegetation operations and maintenance needs throughout the design and establishment phases of a project.
Developing a vegetation management plan that addresses the identified operations and maintenance considerations is a critical item in a successful stormwater management project. Proper planning at the beginning of a project can save time and money over the life of the project. This section outlines some of the major considerations that need to be considered in developing restoration maintenance plan and considerations when designing stormwater BMPs.
Typically, a vegetation management plan will include the following.
In the process of selecting vegetation, think through and address goals you would like to achieve in short and long term management of the BMP vegetation or within the whole project. These goals can vary widely, based on a number of different drivers. For example, your plant selection and management goals may be affected by regulatory requirements, as in the case of projects funded by Clean Water Act allocations. Some funding sources may even necessitate vegetation management for a set number of years as part of their requirements. Defining clear goals will assist you in selecting appropriate plants for your project. They will also help you consider longer term maintenance needs and allow you to plan for the commitment (financial and physical) that it will take to reach your desired goals.
Some typical goals may include the following items
Adaptive management is a tool that can be utilized to determine what maintenance is required, how often it may be needed, and how successful that maintenance is within a project. The adaptive management process is a decision-making tool that works to reduce uncertainty and complexity on a project through an iterative monitoring, evaluation, and adjustment. The repetitive nature of the adaptive management process allows for flexibility in management or maintenance implementation throughout the life of a project and in the face of unforeseen uncertainties (see adaptive management figure).
As noted in the introduction, identifying vegetation operations and maintenance is a critical step in a successful BMP project. Adaptive management can plan a key role in defining and maintaining success, especially on larger scale vegetative projects.
For more resources on adaptive management and how to apply the concept in a project visit the following links.
When selecting vegetation for a project, it is important to determine the type and amount of management that will be required to allow the project to reach its defined vegetative management goals. To better get a grasp what vegetation might be best suited to help reach the projects goals, the following should be considered:
In the process of setting plant selection goals, you will also want to consider site context and stressors. These are additional factors that influence the plants you choose to incorporate into your design. Site context and stressors should focus on the conditions that could negatively impact the vegetation you have selected for the BMP design. Potential considerations include:
Soils affect stormwater and stormwater management in two ways.
The types of stormwater practices that can be implemented at a site are largely determined by soil conditions. Of particular importance are soil suitability for infiltration, suitability for implementing vegetated practices, and suitability for retaining pollutants. Understanding the type of soil on your BMP can help you to select plant material that will be best suited for your site.
Below are useful links to additional information on soil and effects of soil on vegetation. To learn more about how soil can impact the vegetation on your site the overview and role of soil in stormwater management at the link below.
Before plant selection you should understand how much, how often, and how long the BMP is designed to hold water. Too much or too little water can have a drastic and significant impact on plant survival and maintenance needs.
A Minimal Impact Design Standards (MIDS) best management practice (BMP) calculator was developed to assist designers and regulators in determining conformance to the MIDS performance goals. The MIDS BMP calculator is a tool used to determine stormwater runoff volume and pollutant reduction capabilities of various low impact development (LID) BMPs.
How much – bounce within BMP Water level will have a significant impact on the plant selection within the BMP. It is important to consider and select a plant that will be able to handle the hydraulic conditions in which it is planted. Before selecting a plant, you will want to know the location of the highwater or inundation level within your BMP and the potential water level fluctuations (bounce) within a bmp. This will help you select plants that can either tolerate periods of time with inundated roots or plants that cannot. Other questions that might be helpful to ask when reviewing plant material for your BMP include the following.
How long – length of inundation In addition to understanding the highwater or inundation level of your BMP you will also want to understand the length of inundation. Length of inundation, or the given time in which your BMP is at a high-water level, will help you best determine what types of plants will best be suited to thrive within your BMP. It will also help you determine the successful locations for plants with regard to their ability to tolerate longer periods of inundation. Other questions that might be helpful to ask when reviewing plant material for your BMP include the following.
How often - duration between rain events Finally, it is important to understand how often rain events occur that will raise the water level of your BMP to a high-water level elevation. This will help narrow the choice of plant selection and help determine plant varieties that are best suited for to the BMP design. Questions that might be helpful to ask when reviewing plant material for your BMP include the following.
In the process of plant selection, you will want to consider the location of your BMP and the potential for excessive pollutants or nutrients to enter and potentially physically harm the vegetation in your design. Considerations include salt, sediment, trash.
Excessive nutrients can be directly harmful to vegetation. Excessive amounts of nitrogen or phosphorus can create significant alterations to a given habitat, providing more increased opportunities for invasive or other aggressive species to out compete, or become introduced to a habitat. Additionally, excess nutrients can hinder some plant’s ability to grow and develop. The following links provide a greater background on excess nutrient loads on plants.
In the process of plant selection, you will want to consider the location of your BMP for the potential for invasive species pressure. Invasive species can make long-term maintenance a challenge. Not only can it require more physical work it may also be challenging for maintenance crews to distinguish between invasive and native plants. When considering planting of your BMP it is important to understand the likelihood that you will be dealing with invasive species in your design. Consider the following in vegetation selection.
If you have a dedicated maintenance staff, you can start to learn to identify invasive species at the links below. Depending upon the BMP project, location, and likelihood of invasive maintenance required it may also be helpful to consult with a professional.
Some of the most common invasive plants that might find in or around a BMP include common buckthorn, smooth brome, spotted knapweed, thistle, purple loosestrife, and reed canary grass. Learn more about identifying invasive species at the following links
When considering plant selection for long-term maintenance it is worth considering what types of human and herbivory pressure may be found at your site. Considerations may include the following.
In consideration of plant material, you will want to investigate the infrastructural needs and design of your BMP. Placing a tree directly next to a stormwater catch basin would be a cause for future maintenance issues. Placement and vegetative growth of a selected plant should be taken into consideration in BMP design. Additionally, plant selection, placement, and growth should be taken into consideration when thinking about management activity and access needs to maintain the stormwater infrastructure. Questions to consider include the following.
When considering long-term planting success, you will want to consider the growth and life cycle of the plant material selected in your design. For example, a tree may be an excellent choice as a part of a BMP design but over time and with growth of the tree, it may easily shade plant material within the BMP. The shade from the tree could become a maintenance issue if other plant material was selected for full sun conditions. Actively planning for the growth and succession of plant material will strengthen the long-term maintenance success of the design and function of the BMP. Questions to consider include the following.
The following links can help guide the process of selecting a tree for a BMP. Trees and shrubs can be a big investment, both monetary and maintenance but they can provide significant benefits in a project. Selecting the correct plants can be key to a successful design.
In the process of plant selection consideration of the following should be taken over the lifecycle of the plant selected. In the process of investigating these questions a designer will be able to determine if the owner, client, or caretaker should prepare to replace a plant within a given time frame or if they will need to perform maintenance tasks to prevent the plant from spreading and taking over a given area.
Pruning vegetation can be a helpful tool in long-term maintenance and can also be a consideration when selecting plant material. Pruning can act as a preventative measure for both insect and disease damage, maintain an intended purpose for specific plants in a landscape, and approve appearance of plants.
Plant succession is the change in vegetation that occurs over time or after a disturbance. Disturbances can include grazing, flooding, fire, or other human-related activities. In the process of selecting vegetation for a BMP, depending upon the size and goals within the project, the project may greatly benefit from a plant selection that focuses on a species successional approach. A common practice in restoration, a species succession can be a useful practice in cultivating a preferred vegetation community.
Over time, plant communities fluctuate. A change in a plant community could be due to a plant’s lifecycle, outside pressures such as introduction of invasive species, or any other number of factors. Although, many native plant communities have the ability to adapt through the process of a natural plant succession, specifically through a disturbance that was common to that communities given habitat. Introducing specific and timely disturbances allows for a plant community to meet establishment requirements for a regenerative plant succession and create a weed resistant plant community. For more information on plant succession visit the following links:
Irrigation is the primary requirement that most vegetative operations and maintenance plans must focus on. The goal is to provide consistent plant-available soil moisture for the duration of the establishment period. Water need not be potable but should be free of nutrients and pollutants. Initial irrigation requirements will be high but will lessen as the vegetation becomes established and well-rooted. Consider the following in establishing the operations and maintenance needs for irrigation.
|Which irrigation system?|
|How will the irrigation be delivered?|
|Is the irrigation system permanent or temporary?|
|Are there water sources available on site?|
|Are there water sources available off site?|
A resilient planting design is a design that can withstand or recover from changing circumstances. When thinking about plant selection it is important consider serval aspects of a resilient design to ensure the continued success of a BMP design and function. When considering a resilient design, it is important to consider the climate change, pests and disease, and your maintenance needs on a project.
Our climate is changing due to human impacts on the environment. Increased heat, drought, larger rain events, and changing winter conditions are all associated changes taking place with climate change. Planning for these changes within your plant selections will help reduce the amount and expense of maintenance needed on a project. Learn more about climate change here: What Is Climate Change? (United Nations) or Climate Change and Global Warming (NASA)
When selecting plant material, it is important to understand and consider what pests and diseases are associated with potential plant choices. Selection of a plant that has a known pest or disease moving through a given geographical area increase the risk and cost of future maintenance and or replacement of a given plant. It is important to understand the known pests and diseases that might have an impact in your site and given location. In a similar fashion, a planting design without diversity is more susceptible to pest and disease. Although a monoculture design may be easy to maintain it is also at a higher risk for concern if there is an associated health or climate adjustment that creates a problem for the given plant. Therefore, it is important to design with a diversity of plants and species to allow for a greater resistance to future health and climate changes.
Planning for a maintenance budget is a key part of a resilient design. Long-term maintenance can be expensive and challenging to sustain but is also crucial for a successful project. When selecting plant species, it is important to consider the funds and resources available to the owner, client, or caretaker to continually maintain the design. Consider the following questions.
To help determine high-level planning and cost considerations visit the links below.
|Establishment period O&M considerations|
|Temporary cover crop||Vegetation, usually seeded, for protecting bare soil surfaces from erosion during the construction process and protecting seeded surfaces post-construction during the establishment of permanent vegetative cover.|
|Erosion and Sediment Control||Practices to prevent erosion or control sediment loss and protect the soil surface until cover has been established.|
|Irrigation||Water artificially delivered to vegetation to provide consistent plant-available soil moisture for the duration of the establishment period.|
|Off-line BMPs||Stormwater systems adjacent to the main stormwater system that indirectly receive stormwater runoff through diversion and that do not directly affect the functioning of the whole system.|
|Fencing||Fencing around vegetation to protect the vegetation from construction equipment and operations and/or from herbivory.|
Establishment Period refers to the time period immediately after installation, during which plants must be maintained to better ensure their success. The recommended time period for establishment varies depending on what is planted (seed, plugs, trees, etc.). The length of this period can also be affected by project goals and budgets. If a project is completed in phases, vegetative establishment may also incorporate phasing. Temporary covers can often provide interim stabilization between phases. This section will cover several vegetation establishment strategies increasing the success of a BMP and reducing the chance for potential pollutants to enter waterways. These are summarized in the adjacent table.
Temporary cover crops, or temporary covers, are vegetation established to provide temporary stabilization of sites and prevent erosion during the establishment period. This vegetation, usually seeded, has two main roles in stormwater management: a) protecting bare soil surfaces from erosion during the construction process, and b) protecting seeded surfaces post-construction during the establishment of permanent vegetative cover. Temporary cover establishes rapidly and the root structure provided firmly anchors the soil surface to prevent detachment and transport of sediment.
Both short- and long-term considerations in selecting cover crops should consider seed type, location/aspect, slope, duration of cover, and how the cover will be applied. These considerations should also incorporate any sediment and erosion control measures, regulatory requirements, and any Stormwater Pollution Prevention Plan (SWPPP) plan requirements. Selected cover crop must specifically address the season installed. Oats are appropriate for installation during the spring and summer. Winter wheat is appropriate for installation during the fall for winter cover. Mn/DOT Seeding Manual has specific seed mix and rates for your goals.
Cover crop needs to be reapplied every growing season. For example, cover seeded in the fall needs to be re-seeded in the spring on an active site or one that has not achieved final growth and cover requirements of final stabilization. Cover crop may need to be applied multiple times in phased projects.
Depending on the duration of time between project phases, a permanent cover may be required for temporary stabilization. Consider this approach when the project earthwork spans multiple years or where there is one or more dormant seasons between phases. See Construction stormwater best management practice – Site stabilization for additional discussion on application of temporary and permanent covers.
Erosion protection and sediment control strategies ensure continued stormwater protection for the duration of the project. Erosion prevention practices and sediment control practices combine to protect the soil surface until cover has been established. Careful consideration of the following practices should be weighed against the site constraints and management goals in protection of establishing vegetation.
Mulch types application rates benefits, and limitations
Link to this table
|Mulch Type||Application Rate||Benefits||Limitations|
|Straw, hay, or other grasses||1.5 to 2.5 tons per acre||Readily available and inexpensive; very effective in controlling erosion; can be applied on large sites via blower||Can carry unwanted seeds; might need tackifier or anchoring,
especially on steep slopes
|Wood chips, bark, sawdust||5 to 8 tons per acre||Very low cost in some locations; chips can be effective on slopes up to 30%||High nitrogen demand when decomposing; can float away or blow away during rain storms|
|Rock||200 to 500 tons per acre||Could be inexpensive and readily available in some locales; might be suitable for smaller sites||Inhibits plant growth; adds no nutrients to the soil; can be costly to apply on slopes and large sites; adds hardened look to slopes|
|Hydraulically applied mulches||1.5 to 2.5 tons per acre||Easily and rapidly applied with sprayer equipment; can include seed, fertilizer, flexible/fibrous mulches, and soil binders||Could be too expensive for small or very remote sites; after application, must dry for at least 24 hours before rainfall|
Types of mulch products typically used on construction sites
Link to this table
|Mulch type||Description||Application Method|
|Straw, hay, or other grasses||Wheat, oat, or pine straw; rolled or baled pasture grasses also used in some cases||Hand scattering for small areas; chopper/blower used for larger areas, sometimes with co-applied tackifying agent to promote adhesion|
|Wood chips, bark, sawdust||Waste product from sawmills and other timber harvest and processing operations||Hand scattering or mechanized spreader|
|Rock||Can include all classes of aggregate, riprap, and large stone; used for permanent erosion protection||Placement by hand or equipment (e.g., track-hoe, skidder, front-end loader)|
|Hydraulically applied mulches||Bonded fiber matrix products, including those manufactured with natural and/or synthetic fibers, cellulose, or other materials||Spray application via high-pressure pumping from the mixing tank, through a hose and nozzle apparatus|
All vegetation used for erosion and sediment control should consider the length and phasing of the project, as well as any necessary operations and maintenance before, during, and after the project. Multiple applications of temporary cover may be necessary to provide interim site stabilization throughout the progress of the project.
BMPs can be categorized as online and offline. Online systems directly receive and control stormwater as part of a chain. Offline systems are adjacent to the main stormwater system, acting as a supplementary feature but do not directly affect the functioning of the whole system. When practicable, designing offline BMPs affords vegetation a significant advantage in establishing outside of fluctuating stormwater levels. One full growing season offline is recommended. Irrigation must be considered when establishing vegetation in offline BMPs. Operation and maintenance should include consideration for connecting features after establishment.
Temporary fencing serves two main functions in site vegetation establishment: (1) protecting vegetation from construction equipment and operations; and (2) protecting vegetation from herbivory. Temporary fencing can be categorized as tree (or vegetation) protection fencing, or animal exclusion fencing. Tree protection fencing is generally made of snow fence and metal t-stakes. This is to be installed as required to protect existing sensitive vegetation (usually trees) or new vegetation on the site. Operations and maintenance should consider when this is to be removed, generally at the end of the construction activities. Animal exclusion fencing is also generally composed of snow fence and/or silt fence and metal t-stakes. This also can incorporate a metal mesh such as hardware cloth when necessary for additional rodent protection. This is generally installed after vegetation has been installed but will remain in place for the duration of the establishment period after construction activities have been completed. Operations and maintenance should consider implementation and removal of animal exclusion fencing, as well as on-going inspection and repair to maintain an intact barrier.
This page was last edited on 7 February 2023, at 14:52.