LID may be most appropriately used in institutional, industrial, commercial and governmental developments, as these facilities are more likely than residential developments to receive maintenance on LID features over residential developments. When maintenance is required, additional easements may be necessary to facilitate maintenance access. In residential developments the landowners or homeowners association are often responsible for any required maintenance. Regular inspections, by or for the responsible party, must be completed to ensure LID and conventional stormwater control features continue to operate properly.
Wetland Setbacks should be inspected regularly to ensure that the Wetland Setbacks are being maintained in a natural state and have not been mowed, treated with herbicide (except as used to control invasive species), or developed. Wetland Setbacks and the wetlands they surround should be placed in a conservation easement to protect these resources in perpetuity. Easements should be regularly monitored and violations of easement agreements addressed in order to insure long-term protection.
This includes removal of temporary risers used for sediment control and reseeding bare soil or establishing wetland vegetation in designated areas within the pond.
While maintenance is inevitable, the amount of maintenance required and its cost can vary considerably depending on the initial design of a pond. A number of design features are helpful in this regard:
Sediment Storage – Reduce the frequency of sediment cleanout easily by increasing the volume available for sediment storage. Increasing the permanent pool volume by 20% or according to the predicted sediment loads is recommended. Ponds used for sediment control during construction should be cleaned out when the site is stabilized, as the cost of cleanout will be considerably less expensive during construction than in the future.
On-Site Disposal – Transporting dredged sediment is often the largest cost associated with pond cleanout. This can be avoided by providing an area on-site for future sediment disposal. A disposal site should be designated during site design.
Forebay – Trapping most sediment in a confined, easily accessible forebay can reduce maintenance costs.
Maintenance Easements – Maintenance easements must be established to allow access to the pond, particularly to the forebays, embankment, outlet structure and sediment disposal areas.
Disposal of Pollutants – Water quality treatment practices are intended to trap pollutants. The fate of these pollutants must be considered. Trapped sediment is usually clean enough for on-site use. The large volume of sediment poses the most common disposal problem. Sediments may also have high concentrations of hydrocarbons, nutrients and heavy metals. Soil tests should be done if the pond has received spills, is in a highly industrial area, or if the watershed has intensive traffic.
Sediment should be spoiled in areas, which will keep pollutants bound in the sediment (e.g., metals and phosphorous). To avoid these pollutants from becoming soluble, acid and anaerobic conditions, such as wetlands, should be avoided.
Twice per year:
Check observation wells following 3 days of dry weather. Failure to percolate within this timeCheck observation wells following 3 days of dry weather. Failure to percolate within this time period indicates clogging.
Inspect pretreatment devices and diversion structures for sediment build-up and structural damage.
Remove sediment and oil/grease from pretreatment devices as well as overflow structure.
Total rehabilitation of the trench should be conducted to maintain storage capacity within 67% of the design treatment volume and 72-hour exfiltration rate limit.
Trench walls should be excavated to expose clean soil.
Trim adjacent trees to assure that drip-line does not extend over the surface of the infiltration trench.
Filter systems require frequent maintenance. Two design considerations that can help reduce maintenance problems are:
Where observation wells and grates are used, lifting rings or threaded sockets should be provided to allow for easy removal by lifting equipment. Access for the lifting equipment must be provided. Any long-term maintenance plan for sand and organic filters should include regular inspections for each of the following items:
Annual and/or After Major Storms
Proper functioning of a bioretention practice is dependent on the planting soil continuing to drain and plant survival. Most maintenance activities influence these goals. Maintaining the pretreatment area and minimizing erosion will extend the function of the planting soil. Bioretention areas are a landscaped feature of a site and regular attention to the plants is necessary. Take measures to insure winter snow plowing does not pile snow on trees or shrubs in the landscaped ponding area.
Over time (3-10 years); fine sediments may accumulate in the top few inches of planting soil. This is expected and can be corrected by replacing a portion of the planting soil or replacing all the planting soil and the filter layer until better permeability is achieved.
2-10 years / As needed
Pervious pavements require maintenance to provide stormwater benefits over a long time period. Because pervious pavements convey water through the pavement and also effectively trap fine materials, the majority of maintenance efforts will be to keep the system permeable (unclogged) and to manage pollutants such as salts that might effect groundwater. Therefore regular inspection will evaluate whether the surface and the bed of the pavement are functioning as intended. In other words, water should continue to move through the pavement, not pond into the pavement layer, and drain from the reservoir layer in sufficient time. Maintenance of the pavement will remove fine materials as they collect in the surface and prevent winter deicing materials from being overused or clogging the system.
Effective management includes educating the property owner, landscapers, maintenance staff, snow removal personnel and general users. In this regard, an operation and maintenance plan, signage, maintenance agreements, and contracts will serve as important points of reference for these audiences. Each document should reflect the appropriate actions to take and those to avoid for the appropriate audience. For example, landscaping personnel that work adjacent to the pavement area should be required to keep landscaping materials, such as soil, mulch or plants off the pavement and to use adequate sediment control and/or stabilization for bare areas. Snow removal, pavement repair and similar contracts should include notes regarding appropriate and inappropriate actions regarding the pervious pavement area. Because pervious pavements will be maintained and managed differently than traditional pavements, signage at pervious pavement installations is recommended. This will promote its prolonged use and prevent conventional pavement management from damaging the system. An example of this includes preventing seal coating of porous asphalt or allowing snow to be stockpiled on a pervious pavement.
An operation and maintenance plan should be prepared by the designer and provided to the owner and the stormwater authority as well as the property manager and maintenance personnel. An operation and maintenance plan for pervious pavement should detail specific actions that must be performed and their timing and/or frequency. It also describes potential damaging actions and measures to take to prevent damage to the pervious pavement. The operation and maintenance plan should also provide detailed information regarding the observation well and the depth or elevations of the underdrain system and outlet, so that the water levels under the pavement can be monitored and compared to the designed function of the system. The operation and maintenance plan should provide the normal drain time (hours) of the pavement.
Three main strategies dominate pervious pavement operation and maintenance:
Prevent clogging of the pavement and regularly remove accumulated fines. Vacuum sweeping is necessary to remove grit, leaves and other debris collecting at the pavement surface. This should be done two to four times a year. Times that especially will have an accumulation of material include after winter snow melt and after leaf drop in the fall. Vacuums used on paver systems with bedding material should be able to remove sediments and organic matter without removing the bedding aggregate. If bedding aggregate is removed, it should be replaced. Preventing clogging also involves managing adjacent vegetated and landscaped areas. These area should be maintained in healthy vegetation. Soil, mulch and other landscaping materials should never be stored or stockpiled directly on the pavement. Construction equipment should not be driven over or stored on the pavement
Snow and Ice Removal. No sand or cinders should be used on pervious pavements. Instead winter maintenance should focus on timely snow plowing and judicious use of deicing materials. Deicing materials present a problem in any pavement system due to their solubility and history of building up to levels that are toxic to plant and animal life. In pervious pavements, high salt use has an increased potential of reaching groundwater sources, but case studies of pervious pavements have shown a reduced need for deicing material to be applied to pervious pavements due to the effects of a warmer subbase. The operation and maintenance plan should provide guidelines for reduced salt use responsive to the actual ice on the pavement rather than typical rates applied on conventional pavements in the Midwest. Snow should not be stockpiled on the pavement. The operation and maintenance plan should show where snow will be pushed or stockpiled during plowing. The operation and maintenance plan should detail the blade depth that plow operators should use, because in some instances, such as grid pavements, snow plow operators may need to raise the blade slightly to avoid dislodging the surface. In every case, care should be taken with snow plowing to keep from gouging the pavement or dislodging aggregate or pavers.
Repair pervious pavements appropriately. Areas may be repaired using the same treatment as the original pervious pavement application or, in the case of porous asphalt or pervious concrete, small areas (not the lowest area on a sloping section) can be replaced with standard (impermeable) pavement. In that case the stone bed of the entire pavement will continue to provide storage and infiltration as designed. In no case should seal coats or new impermeable pavement layers be applied, as is typical in traditional asphalt pavements.
The following are suggested items for inspection and are adapted from CSN, 2010:
Using the observation well, observe the rate of drawdown in the practice. Measure the water level in the observation well following a storm event exceeding one half inch of rainfall. This should be done immediately after the storm, recording the precipitation amount, the time of the measurement and the water level in the well. Observe and record the water level after 24, 48 and 72 hours. Actual expected performance will depend on the soils and the intended performance of the design. If the subgrade soils were hydrologic soil group D, there may still be water standing in the reservoir layer after 48 or 72 hours. There should not be standing water above the elevation of the underdrain, and this would indicate problems with the outlet or underdrain system being clogged. Assess potential clogging of the subgrade soils and geotextile by comparing the actual drawdown rate to the intended or design performance of the reservoir layer.
Observe the pavement surface during and after rain for evidence of ponding, deposited sediments, leaves or debris. Address any signs of clogging or accumulated fine material by performing vacuum maintenance.
Inspect the structural integrity of the pavement surface for damage such as missing infill material or broken pavers, spalling, rutting, or slumping of the surface. Any adversely affected areas should be repaired as soon as possible.
Check contributing impervious areas and their associated pretreatment or runoff control structures for sediment buildup and structural damage. Remove sediment as needed.
Inspect adjacent and contributing drainage area for sources of sediment or areas that may need better stabilization with erosion control.
All SCMs require inspection to determine when routine and non‐routine maintenance shall be performed. Routine maintenance may include items such as removing accumulated sediment from the SCM, removal of debris blocking inlets or outlet pipes within the SCM, pruning or replacing plant material or mowing designated grass areas of the SCM. Some routine maintenance items may have a seasonal frequency requirement such as leaf debris removal, mulching or plant material maintenance (i.e. pruning, mowing, transplanting or plant replacement). Non‐routine maintenance may include repair or replacement of key components of the SCM such as specialized soil mixes, damaged inlets, outlets or drain pipes or removal of significant amounts of accumulated sediment and debris that are clogging the SCM and compromising the SCM’s functionality. Listed below are common issues that, if observed within the SCM, may indicate the need for SCM maintenance. A brief description of each common issue is also listed along with the particular SCMs that can be affected by the issue.
The following section lists general recommendations for routine and non‐routine maintenance items. Some routine maintenance items are completed on a seasonal basis, others require greater frequency. Non‐routine maintenance items often require professional expertise and assistance before appropriate corrective measures can be determined. Resources for professional assistance are listed in Appendix 3.
Dry Pond or Dry Extended Detention Basin
Wet Pond or Wet Extended Detention Basin
Vegetated Infiltration Swale
Non‐Structural SCMs: Riparian & Wetland Setbacks and Conservation Areas
Rain Barrels & Cisterns
Sand Filter System
* Do not enter sand filter chambers to inspect system unless Occupational Safety & Health Administration (OSHA) regulations for confined space entry are followed.
* Follow inspection and maintenance instructions and schedules provided by system manufacturer and installer.
* Properly dispose of all wastes removed from the sand filter system.
* Do not enter underground detention manholes to inspect system unless Occupational Safety & Health Administration (OSHA) regulations for confined space entry are followed.
* Follow inspection and maintenance instructions and schedules provided by system manufacturer and installer.
* Properly dispose of all wastes.
* Do not enter systems unless Occupational Safety & Health Administration (OSHA) regulations
for confined space entry are followed.
* Follow inspection and maintenance instructions and schedules provided by system
manufacturer and installer.
* Properly dispose of all wastes.
Rainwater and Land Development: Ohio’s Standards for Stormwater Management, Land Development and Urban Stream Protection
Ohio Post Construction Stormwater Management Practices (2018 updates)