Owner/Operator Maintenance Requirements

Maintenance of the BMPs is critical to optimize their effectiveness in reducing pollutants from entering our streams, creeks, and lakes. Owners and operators of these properties are required to conduct regular maintenance activities and annual inspections. The following details on specific BMPs provide guidance on how to stay in compliance.

Bioretention

Bioretention basins (also known as rain gardens) are landscaped depressions or shallow basins used to slow and treat onsite stormwater runoff using engineered soils, vegetation (plants and grasses) and an underdrain system that conveys the excess runoff to a discharge point.

Bioretention(JPG, 349KB)

Maintenance suggestions

  • Inspect the infiltrating surface at least annually and following major precipitation events to determine if the area is providing acceptable infiltration.
  • Remove debris and litter from the infiltrating surface to minimize clogging of the media. Remove debris and litter from the overflow structure. Ensure that the contributing drainage area, inlets, and facility surface are clear of debris.
  • Weeds should be removed before they flower. The frequency of weeding will depend on the planting scheme and cover. When the growing media is covered with mulch or densely vegetated, less frequent weeding will be required. Remove volunteer trees that start to grow in the vicinity of the basin.
  • Adjust irrigation throughout the growing season to provide the proper irrigation application rate to maintain healthy vegetation. Check for broken sprinkler heads and repair them, as needed. Completely drain the irrigation system before the first winter freeze each year.
  • Replace top layers (stone/topsoil/mulch/etc.) and filter fabric as needed if clogged. If ponded water is observed in the basin more than 48 hours after the end of a runoff event, check underdrain outfall locations and clean-outs for blockages.
  • Maintenance activities to restore infiltration capacity of basin will vary with the degree and nature of the clogging. If clogging is primarily related to sediment accumulation on the filter surface, infiltration may be improved by removing excess accumulated sediment and scarifying the surface of the filter with a rake. If the clogging is due to migration of sediments deeper into the pore spaces of the media, removal and replacement of all or a portion of the media may be required. The frequency of media replacement will depend on site-specific pollutant loading characteristics.
  • Repair undercut and eroded areas around and within basin area.

Retention Pond

A retention basin, sometimes called a wet pond, wet detention basin or stormwater management pond, is an artificial pond with a permanent pool of water in its design. It is used to manage stormwater runoff to prevent flooding and improve water quality in an adjacent river, stream, lake or bay.

Retention Pond(JPG, 313KB)

Maintenance suggestions

Inspect the pond at least annually. Note the amount of sediment in any forebays and look for debris at the outlet structure.

Remove debris and litter from the pond as needed. This includes floating debris that could clog the outlet or overflow structure.

Mosquito control may be necessary if mosquitoes are found to be breeding in the BMP. The most effective mosquito control programs include weekly inspection for signs of mosquito breeding with treatment provided when breeding is found.

Remove sediment from the forebay before it becomes a significant source of pollutants for the remainder of the pond. For dry forebays, sediment removal should occur once a year. Sediment removal in wet forebays should occur approximately once every four years or when buildup of sediment results in excessive algae growth or mosquito production.

Removal of sediment from the bottom of the pond may be required every 5 to 10 years to maintain volume and deter algae growth. This typically requires heavy equipment, designated corridors, and considerable expense. Harvesting of vegetation may also be desirable for nutrient removal.

Inspect the condition of stormwater inlets/outlet structures to the pond for material damage, erosion or undercutting.

Inspect internal and external side slopes of the pond for evidence of sparse vegetative cover, erosion, or slumping, and make needed repairs immediately.

Extended Detention Basin

Extended detention basins, also called dry ponds or detention cells, are designed to intercept a volume of stormwater runoff, infiltrate some of the water and pollutants, then temporarily hold the water for gradual release. Detention basins are normally dry and designed to completely empty out between storm events, typically within 48 hours. In certain situations, the land may also function as a recreational facility.

Extended Detention Basin(JPG, 107KB)

Maintenance suggestions

  • Detention basins are designed to be completely drained 48 hours after the end of a storm event – look for standing water after this time as it may indicate a drainage problem.
  • Remove debris and litter from the detention area as required to minimize clogging of inlet/outlet structure(s).
  • Control excess vegetation by mowing and removing dead vegetation on an annual basis.
  • Remove small volunteer trees from the basin as needed. Unwanted tree growth can damage the basin’s structures and side slopes, as well as reduce the amount of stormwater storage capacity.
  • Remove sediment from the bottom of the basin when accumulated sediment occupies about 20% of the water quality design volume or when sediment accumulation results in poor drainage within the basin.
  • Repair basin inlets, outlets, trickle channels, and all other structural components required for the basin to operate as intended. Repair and vegetate eroded areas as needed following inspection.
  • Inspect internal and external side slopes of the pond for evidence of sparse vegetative cover, erosion, or slumping, and make needed repairs immediately.

Vegetative Buffer

Vegetative Buffers (also called filter strips or buffers), are densely vegetated, often grassed practices that accept sheet flow runoff from adjacent surfaces. They slow runoff; filter out sediment and other pollutants; and enhance infiltration of surface water runoff.

Vegetative Buffer(JPG, 302KB)

Maintenance suggestions

Sediment and debris should be routinely removed when buildup exceeds 2 inches in depth in either the strip itself or the level spreader. If erosion is observed, measures should be taken to improve the level spreader or other dispersion method to address the source of erosion.

Perform periodic mowing to keep grasses at acceptable levels and to minimize the growth of successional vegetation. It is recommended that mowing be performed perpendicular to the slope to help minimize the development of rills. It is important to avoid the use of herbicides and fertilizers on grassed portions of the strip, since these applications can directly contribute undesirable pollutants to waterways.

Inspect buffers for evidence of sparse vegetative cover, erosion, or slumping, and make needed repairs immediately.

Inspect any inlet/outlet structures for blockages and damage.

Remove trash and litter on a continual basis.

If applicable, check for broken sprinkler heads and repair them as needed. Completely drain the irrigation system before the first winter freeze each year.

Grassed Swale

Grassed swales (also called grassed channels or drainage ditches) consist of a shallow channel or swale that conveys stormwater down a slight gradient away from its source. The vegetation and soil media filter out sediment and other pollutants and then release the stormwater to a discharge point.

Grassed Swale(JPG, 304KB)

Maintenance suggestions

  • Add reinforcement planting to maintain 90% turf cover. Reseed any vegetation.
  • Remove any accumulated sand or sediment deposits behind check dams and inflow points.
  • Inspect upstream and downstream of check dams for evidence of undercutting or erosion and remove and trash or blockages at weep holes.
  • Examine channel bottom for evidence of erosion, braiding, excessive ponding or dead grass.
  • Inspect side slopes for evidence of rill or gully erosion and repair.
  • Remove weeds and mow overgrown vegetation as needed

Green Roof

A green roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. The planting medium filters out sediment and other pollutants and reduces the temperature of rooftop stormwater runoff.

Green Roof(JPG, 462KB)

Maintenance suggestions

Green roof inspection should be conducted at least three times per year.

Inspect joints, borders, waterproof membrane or other features that pass through the roof to remove roots and identify damage that could lead to leaks. For example, inspect abutting vertical walls, roof vent pipes, outlets, air conditioning units, and perimeter areas. Joints with facades must provide open access for inspection, maintenance, and upkeep.

A vegetation-free zone of approximately one foot should be maintained at the border of roof edges and at drain openings on the roof. Vegetation-free zones should be lined with pavers, stones, or gravel. Drains must remain free of vegetation and foreign objects. In order to allow for regular inspections and maintenance, drains on a green roof must remain permanently accessible.

Because of the severe consequences of drain backups, inspection of drainage flow paths is crucial. Remove the inlet cover and visually inspect drainage pipes for roots or other material that could impede the flow of water.

Plants are susceptible to poor drainage in the soil. If too much water is present and unable to drain, the plants will drown or rot. Routine inspections of drains should take place approximately three times per year as well as after precipitation events of 0.6 inches or more.

Inspect the irrigation system for leaks or malfunctions. Uneven vegetative growth or dying plants should serve as indicators of potential irrigation system problems.

Mow or trim plantings in early Spring of each year as needed.

Remove weeds on a continual basis.

Infiltration Planter

Infiltration planters are raised structural planting beds that filter and infiltrate runoff from surrounding rooftops, parking lots, or sidewalks.

Infiltration Planter(JPG, 51KB)

Maintenance suggestions

  • Debris and Litter shall be removed to prevent channelization, clogging, and interference with plant growth. Fallen leaves and debris from deciduous plant foliage shall be raked and removed.
  • Erosion Damage shall be identified and controlled when native soil is exposed, or erosion channels are forming.
  • Filter Media consisting of sand and/or topsoil shall be tested to ensure stormwater percolates through the planter. Remove and replace sand and/or topsoil to correct percolation deficiencies.
  • Infiltrating Stormwater Planters shall be excavated and cleaned, and gravel or soil shall be replaced to correct low infiltration rates. Water should drain through the planter within 3-4 hours after a storm event.
  • Inlets/outlets shall be cleared when conveyance capacity is plugged to ensure unrestricted stormwater flow to the rain garden.
  • Mulch shall be replenished as needed to ensure healthy plant growth.
  • Nuisance and Prohibited Vegetation shall be removed when discovered.
  • Piping shall be cleared of sediment and debris to maintain conveyance capacity.
  • Planter Walls shall be examined for deficiencies, such as rot, cracks, and failure, and repaired as needed. Holes that are not consistent with the design and allow water to flow directly through the planter to the ground shall be plugged.
  • Sedimentation build-up near or exceeding 2” in depth shall be handremoved with minimum damage to vegetation using proper erosion control measures. Sediment shall be removed if it is more than 4 inches thick or so thick as to damage or kill vegetation.
  • Vegetation shall be healthy and dense enough to provide filtering while protecting underlying soils from erosion. Dead vegetation shall be removed to maintain less than 10% of area coverage or when vegetative filter function is impaired. Vegetation shall be replaced immediately to control erosion where soils are exposed and within 3 months to maintain cover density.

Native Vegetation

Native vegetation used as a BMP is the act of planting, seeding, and/or not disturbing vegetation on the property in order to infiltrate stormwater and reduce runoff. The deep-rooted vegetation is native to the area, which is naturally adapted to the soils and climate.

Native Vegetation(JPG, 353KB)

Maintenance suggestions

Inspect area for signs of over mowing. Clearly mark areas with stakes and signs that show boundaries of areas that are not to be mowed. If mowing is needed, make sure the vegetation is mowed to the correct height.

Perform periodic weeding as needed to reduce weed competition. Check for noxious weeds and remove as needed.

Reseed bare and thin areas as needed during spring and fall. Check seed mixtures for correct formula.

Inspect areas for signs of erosion (gulley, rills, etc.). repair/regrade/reseed as needed.

Controlled burning is not allowed within City of Lincoln limits. Check local regulations before performing any type of burnings.

Avoid using fertilizers whenever possible.

Permeable Pavement

Permeable pavement, also known as pervious pavement, allows precipitation to infiltrate by way of vertical pore spaces in the paving material where water is temporarily stored and treated in the gravel layer underneath. It is often installed within parking lots, streets, and high foot traffic areas. Permeable pavements include an underdrain.

Permeable Pavement(JPG, 177KB)

Maintenance suggestions

  • Always read the manufactures specifications first and follow as directed.
  • Inspect pavement condition and observe infiltration at least annually, either during a rain event or with a garden hose to ensure that water infiltrates into the surface. Video, photographs, or notes can be helpful in measuring loss of infiltration over time.
  • Debris should be removed, routinely, as a source control measure. Typically, sites that require frequent sweeping already plan for this activity as part of their ongoing maintenance program. For example, a grocery store may sweep weekly or monthly. Although this type of sweeper can be effective at removing solids and debris from the surface, it will not remove solids from the void space of a permeable pavement. Use a vacuum or regenerative air sweeper to help maintain or restore infiltration.
  • Permeable Interlocking Concrete Pavers, Concrete Grid Pavements (with aggregate infill), Pervious Concrete, and Porous Asphalt: Use a regenerative air or vacuum sweeper after any significant site work (e.g., landscaping) and approximately twice per year to maintain infiltration rates.
  • In general, permeable pavements do not form ice to the same extent as conventional pavements. Additionally, conventional liquid treatments (deicers) will not stay at the surface of a permeable pavement as needed for the treatment to be effective. Sand should not be applied to a permeable pavement as it can reduce infiltration. Plowing is the recommended snow removal process. Conventional plowing operations should not cause damage to the pavements.

Rain Barrels and Cisterns

A rain barrel is any above-ground container modified to receive, store, and distribute rooftop runoff for non-potable uses. Rain cisterns are similar systems designed for below-ground use, but typically provide much greater storage and more complex construction techniques.

Rain Barrels and Cisterns(JPG, 183KB)

Maintenance suggestions

Cleaning Rain Barrels

Drain, then disconnect the rain barrel from the down spout that is feeding the barrel. Place barrel to the side.

Start at the gutter canal that feeds the rain barrel to make sure that the gutter is clean and clear from debris.

View the interior of the downspout to be sure that there is no material blocking the downspout that could end up in the rain barrel.

Remove and clean or replace the mesh screen on the rain barrel. Be sure the mesh is in good condition to handle the new season. This screen is to filter out smaller debris from entering into your rain barrel, thereby reducing overall maintenance. This screen also keeps insects or critters from entering your rain barrel.

Inspect the inside of the rain barrel for general condition, looking for cracks in the barrel, debris on the bottom, or algae growth on the interior.

If you need to scrub the interior of the barrel a long handled brush will work well. Using a mixture of vinegar and water, or a light bleach and water solution; scrub the interior of the barrel’s walls and bottom with the brush. Then rinse the barrel again and let dry.

Inspect the spigot of the barrel to make sure it is functioning well. Clean if necessary.

Considering moving barrel indoors during winter months to avoid freeze damage.

Cleaning Cisterns
  • Clean the catchment area (for example, rooftop and gutters) and remove all debris and water.
  • Scrub the inside with a stiff brush and a solution of 1 cup (about 0.25 liter) of unscented liquid household bleach (5%-8.25%) mixed with 10 gallons (about 38 liters) of water.
  • Rinse cistern with clean, safe water, then drain, refill the cistern with clean, safe water.
  • Consider installing a treatment system to improve the quality and safety of cistern water. Measure the chlorine residual regularly; chlorine test kits can be found at most swimming pool supply stores. Maintain a free chlorine residual between 0.2 ppm to 2.0 ppm to prevent microbial growth.

Soil Conditioning

Soil Conditioning, also known as soil amending, is the act of adding natural materials to soil. The natural materials improve both the health and structure of the soil by increasing the space between particles, allowing the soil to absorb and retain more moisture and nutrients. The amended soil creates deeper rooting grass that infiltrates more stormwater on site.

Soil Conditioning(JPG, 342KB)

Maintenance suggestions

  • Inspect the condition of the soil at least annually. If poor vegetation growth and/or drainage is observed, soil testing is recommended. Decide how many soil samples are necessary for your landscape. One sample is usually sufficient for most landscapes unless there are obvious soil differences, then each unique area should be sampled separately. Choose a test that will give results for residual nitrogen, phosphorus, potassium, organic matter, cation exchange capacity (CEC) and soil pH. Add amendments as needed.
  • Depending on the application, aerating may be needed on heavily compacted soils.
  • If soils begin to lack nutrients and erode, adding mulch is an easy way to retain water, inhibit weed growth, and prevent erosion. Mulch is any material, such as wood chips, grass clippings, leaves or compost, even rock, newspaper or shredded tires, that is spread over the surface of soil to retain water, inhibit weed growth and keep temperature moderate. Organic mulches are preferred as they break down overtime and encourage earthworms and beneficial insects to live in your garden.
  • Before reseeding/re-planting, it's important to thoroughly work the soil. Amend poor soils, such as heavy clay, by adding organic matter. Sources include compost, rotted manure, peat, and quality topsoil Incorporate these materials into the existing soil, rather than layering them on the surface. A goal is to have six inches or more of wellprepared soil, and beyond that is impractical around large trees where many roots are found within the dripline.

Stormwater Treatment Train

A stormwater treatment train incorporates at least two practices (BMPs) to maximize the control of pollutant runoff from the site. An example might include a project installing a green roof on the building, permeable pavement for the parking lot, and a detention basin along the perimeter. All these practices work together with the purpose of treating and retaining stormwater.

Stormwater Treatment Train(JPG, 210KB)

Underground BMP

Underground stormwater BMPs include proprietary and non-proprietary devices installed below ground (ex. Underneath a parking lot) that provide stormwater quality treatment via sedimentation, screening, filtration, and other physical and chemical processes.

Underground BMP(JPG, 221KB)

Maintenance suggestions

  • Always follow the manufacturer's recommended maintenance requirements and inspection frequency schedule.
  • A good rule to follow is to inspect underground BMPs at least quarterly for the first two years of operation and then two to three times a year for the life of the BMP.
  • Check for debris that could cause the structure to bypass water quality flows. Strong odors may also indicate that the facility is not draining properly.
  • Inspect inlet areas frequently; at a minimum, inspect after every storm event exceeding 0.6 inches. Removal of flow blocking debris is critical for flood control.
  • Remove sediment/debris as needed depending on manufactures recommendations. Vac trucks may be needed depending on application.

Urban Forest

Urban forest used as a BMP is the planting, maintaining, and protection of tree populations in urban settings. Urban forests come in many different shapes and sizes, including: urban parks, street trees, landscaped boulevards, greenways, river corridors, wetlands, and nature preserves. Tree canopy vegetation can hold stormwater and release it over a longer duration of time vs non-treed areas.

Urban Forests(JPG, 513KB)

Maintenance suggestions

Inspect vegetation for signs of overgrowth and/or noxious weeds, which may outcompete young seedlings.

Remove trash/litter from the area on a continuous basis. If the area is in public place with frequent foot traffic, trash containment containers might be warranted if littering is evident.

After initial planting, periodically check tree growth for any signs that may be preventing the trees from reaching maturity (soil condition, watering amounts, fertilizing etc.)

Inspect trees for signs of disease and insect damage. Consult a local arborist for more information on treatment/prevention.

Vegetated Bioswale

Vegetated swales are basically a filter strip located along a gentle ditch known as a “swale”. Drainage swales that are planted with native vegetation are commonly called bioswales. Swales have gently sloping sides and are used to infiltrate and convey the overland flow of stormwater down a low gradient.

Vegetated Bioswale(JPG, 39KB)

Maintenance suggestions

  • Inspect the infiltrating surface at least annually and following major precipitation events to determine if the area is providing acceptable infiltration.
  • Remove debris and litter from the infiltrating surface to minimize clogging of the media. Remove debris and litter from the overflow structure. Ensure that the contributing drainage area, inlets, and facility surface are clear of debris.
  • Weeds should be removed before they flower. The frequency of weeding will depend on the planting scheme and cover. When the growing media is covered with mulch or densely vegetated, less frequent weeding will be required. Remove volunteer trees that start to grow in the vicinity of the basin.
  • Adjust irrigation (if applicable) throughout the growing season to provide the proper irrigation application rate to maintain healthy vegetation. Check for broken sprinkler heads and repair them, as needed. Completely drain the irrigation system before the first winter freeze each year.
  • Replace top layers (stone/topsoil/mulch/etc.) and filter fabric as needed if clogged. If ponded water is observed in the basin more than 48 hours after the end of a runoff event.
  • Maintenance activities to restore infiltration capacity of swale will vary with the degree and nature of the clogging. If clogging is primarily related to sediment accumulation on the filter surface, infiltration may be improved by removing excess accumulated sediment and scarifying the surface of the filter with a rake. If the clogging is due to migration of sediments deeper into the pore spaces of the media, removal and replacement of all or a portion of the media may be required. The frequency of media replacement will depend on site-specific pollutant loading characteristics.
  • Repair undercut and eroded areas within the swale including the swale slopes and base.

Constructed Wetlands

Wetlands are shallow marsh systems planted with emergent vegetation that are designed to naturally treat stormwater runoff. While they are one of the best BMPs for pollutant removal, stormwater wetlands may also mitigate peak rates and sometimes reduce runoff volume.

Constructed Wetlands(JPG, 103KB)

Maintenance suggestions

Inspect the wetland area at least annually. Note the amount of sediment accumulation and look for debris at the outlet areas.

Remove debris and litter from the wetland area as needed. This includes floating debris that could clog the inlet/outlet areas or overflow structure.

If a reduction in cattails is desired, harvest them annually, especially in areas of new growth. Cut them at the base of the plant just below the waterline, or slowly pull the shoot out from the base. Cattail removal should be done during late summer to deprive the roots of food and reduce their ability to survive winter.

Mosquito control may be necessary if mosquitoes are found to be breeding in the BMP. The most effective mosquito control programs include weekly inspection for signs of mosquito breeding with treatment provided when breeding is found. These inspections and treatment can be performed by a mosquito control service and typically start in mid-May and extend to mid-September. The use of larvicidal briquettes or "dunks" is not recommended for ponds due to their relatively large size and configuration.

For constructed wetland ponds, reestablish growth zone depths and replant if necessary.

Hydrodynamic Separator

Hydrodynamic separators are stormwater management devices that use cyclonic separation to control water pollution. They are designed as flow-through structures with a settling or separation unit to remove sediment and other pollutants and are used to treat and pre-treat stormwater runoff.

Hydrodynamic Separator(JPG, 254KB)

Maintenance suggestions

  • Before commencing maintenance activities, refer to the manufacturer of the device for any specific maintenance instructions.
  • Typically, the maintenance of most hydrodynamic separators requires the use of a vacuum truck equipped with a water supply and a high pressure water spray. With that type of equipment, the accumulated solids may be removed through the manufacturer supplies access to the sump of the device. During and after the vacuum operation a high pressure water spray should be used to wash sediment and debris from all surfaces of the device into the sump where it may be vacuumed out.
  • Inspect device frequently to check for obstructions and the amount of its sediment or floatable pollutant storage capacity. If sediment and debris are observed to be over capacity, the device will need to be cleaned out.
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