You probably see stormwater control measures (SCM) every day – that deep and empty pond in your subdivision, the ditch planted with decorative grasses, a flowering garden dug down into a yard, and those pavers in the store parking lot. These features, in many cases required by regulations, reduce the amount of polluted stormwater that enter our creeks and streams.
When it rains, stormwater runs over lawns, roads, and other hard surfaces, picking up pollutants along the way. This polluted water then drains to our local waterways where it can impact aquatic life and threaten drinking water supplies.
If you have an SCM on your property, or on your HOA’s property, you are responsible for maintaining the feature and submitting annual maintenance reports to Metro if the grading permit requiring the SCM was issued after 2008. Properly maintained SCMs help prevent pollutants from reaching our waterways.
Most SCMs will fall into one of these categories:
- Bioretention, also called a rain garden, is a hole filled with native plantings and special soil mix. It collects and slows stormwater runoff and removes pollutants.
- Permeable Pavement allows stormwater runoff to drain through the pavement into the soil below where the water is filtered before it enters our system.
- Wet Retention Ponds allow pollutants to settle out of the water, encourage natural microbial activity that cleans the water, and reduce the overall amount of stormwater runoff.
- Dry Detention Ponds temporarily store and slowly release stormwater runoff and prevent downstream flooding. Sediment (soil), nutrients, heavy metals, and other pollutants settle out in the pond.
- Grassy Swales reduce and slow down the flow of stormwater runoff as well as filter out some pollutants.
- Water Quality Units are placed underground to filter pollutants out of stormwater runoff and release the treated water to the drainage system. The structures have limited pollutant storage and require frequent maintenance.
Just as privately-owned SCMs must be maintained, likewise, Metro Government is responsible for inspecting and maintaining such structures on its properties. Through a Memorandum of Understanding, Metro Water Services has agreed to annually inspect all SCMs under Metro’s purview. That includes 86 such structures operated by the Department of General Services.
Liz Stienstraw, General Services’ Landscape and Stormwater Infrastructure Manager, reviews the annual inspection reports. Reports contain photographs, engineering plans, an explanation of any problems, and a green-yellow-red ranking system.
| Green | Minor Maintenance Needs | All of the SCMs per the Grading Permit appear to be functioning. Continue routine maintenance. May be some notes of items to monitor. |
| Yellow | Moderate Maintenance Needs | One or all of the SCMs per the Grading Permit are functioning, but issues were noted that should be addressed in this calendar year to prevent further damage to the structure(s). |
| Red | Major Maintenance Needs | One or all of the SCMs per the Grading Permit are not functioning as designed and require prompt maintenance actions so their functions are restored. MWS will be following up with the department late Summer, to determine the status of the maintenance on these structures. |
Routine maintenance can include things like debris removal and removal of excessive sediment, while repair/ remediation can include change out of engineered soils, replacement of pervious pavers, and many more extensive procedures.
Liz uses the annual MWS reports to prioritize SCM projects. She conducts in-person visits to all yellow and red ranked SCMs, to verify scope of work to be completed. Visits are conducted after a significant rain event to assess performance and functionally. She then develops a plan for repair and maintenance, gets estimates from Metro-contracted vendors, and presents a proposal to departmental leadership for approval. Once projects are authorized, Liz walks through the scope of work with the vendor and ensures successful project completion. She then sends the list of remediated sites to Metro Water Services for their records.
If you are interested in learning more about SCMs, there are several resources available. Online SCM maintenance training, information about finding SCMs on your property, and directions for filing an annual maintenance report are available at scm.nashville.gov. For questions specific to your property, contact Metro Water Services’ Stormwater Division.
This blog is based on content created by Julie Berbiglia of Metro Water Services.