Stormwater retention pond inspections (BMP) and maintenance are necessary for a stormwater pond to operate as designed on a long-term basis. The pollutant removal, channel protection, and flood control capabilities of ponds will decrease if:
- Permanent pool elevations fluctuate;
- Debris blocks the outlet structure;
- Pipes or the riser are damaged;
- Invasive plants out-compete the wetland plants;
- Sediment accumulates in the pond, reducing the storage volume;
- Slope stabilizing vegetation is lost; or
- The structural integrity of the embankment, weir, or riser is compromised.
Pond maintenance activities range in terms of the level of effort and expertise required to perform them. Routine pond and wetland maintenance, such as mowing and removing debris or trash, is needed multiple times each year. More significant maintenance such as removing accumulated sediment is needed less frequently, but requires more skilled labor and special equipment. Stormwater Retention Pond Inspections and repair of critical structural features such as embankments and risers, needs to be performed by a qualified professional (e.g., structural engineer) that has experience in the construction, inspection, and repair of these features:
- Adequate access must be provided for inspection, maintenance, and landscaping upkeep, including appropriate equipment and vehicles. It is Recommendedthat a maintenance right of way or easement extend to ponds from a public or private road.
- It is Highly Recommendedthat ponds be inspected annually during winter freeze periods to look for signs of improper operation.
- It is Highly Recommendedthat sediment removal in the forebay and permanent pool occur every 2 to 7 years or after 50 percent of total forebay or permanent pool capacity has been lost. In areas where road sand is used, an inspection of the forebay and permanent pool should be scheduled after the spring melt to determine if clean-out is necessary.
- Sediments excavated from stormwater ponds that do not receive runoff from confirmed hotspots are generally not considered toxic or hazardous material, and can be safely disposed by either land application or land filling. Sediment testing may be necessary prior to sediment disposal when a confirmed hotspot land use is present.
- Periodic mowing of the pond buffer is Highly Recommendedalong maintenance rights-of-way and the embankment. The remaining buffer can be managed as a meadow (mowing every other year), prairie, or forest.
- Ponds should not be drained during the spring, as temperature stratification and high chloride concentrations at the bottom can occur, which could result in negative downstream effects.
- Care should be exercised while draining the pond to prevent rapid release and minimize the discharge of sediments or anoxic water. The approving jurisdiction should be notified before draining a pond.