Stormwater SCM inspections include a thorough evaluation of the primary features of SCMs in place. Particular attention is placed on the following areas:
Dam and Emergency Spillway
The dam and emergency spillway are very important in protecting lives and property downstream in the event of a catastrophic failure. Too much woody vegetation or too many mature shrubs and trees can degrade the integrity of a dam if their root structure gets into the dam foundation. Burrowing animals, such as muskrats and mice, can cause even more degradation. Dams must be inspected for any cracks, seepage, or excessive erosion that may cause a failure of the pond. The emergency spillway should be maintained from any excessive woody vegetation or significant erosion as well.
Inlets and Outlets
The inlets and outlets to and from the pond may become clogged with sediment, trash or debris. Structural failure of the inlet or outlet may occur as a result of blockages or improper installation. Blockages should be removed and pipes should be repaired or replaced as needed. The riser pipe and orifice holes should be visually inspected from shore to ensure they are not blocked and that the pond appears to be draining properly.
Erosion can be of minimal importance or it can be the most significant problem associated with the pond. Minor erosion should be noted and can be corrected by revegetating. Major erosion on the dam or spillway, or where it impairs the sediment storage capacity of the pond, should be corrected by regrading and vegetating or dredging. Erosion of side slopes may occur if the slopes are too steep and/or if there is limited vegetation to stabilize the slopes. On slopes with less than a 3:1 ratio, revegetation of the side slopes is recommended to prevent erosion. On steep slopes, regrading the slope to less than a 3:1 ratio and then revegetating that slope should prevent erosion.
Sediment Storage Capacity
One of the major functions of the wet detention pond is to trap pollutants, including sediment. Periodic sediment removal is required to ensure that stormwater runoff is treated. A visual inspection of the pond forebay should reveal any excessive sedimentation problem. If a pond requires sediment removal, sediment capacity calculations should be used to determine the extent of removal necessary to restore the pond to designed conditions.
Water quality problems in ponds may result from needed maintenance, upstream influences, or urban runoff. Algae or sedimentation is the most likely problem, but on occasion, stagnation or fish kills may result for no apparent reason. Other problems, such as oil, trash, and bacterial growth, will occur as well. Commonly, algae will grow when sedimentation has begun to fill in the pond and the nutrients do not have enough room to settle out and be treated. Dredging to remove the sediment usually resolves this issue. General appearance and overall function should be visually inspected to ensure proper function.
Upon the completion of a pond inspection, an inspection report will be generated in a letter format with any recommendations or requirements necessary to improve water quality or return the SCM to design specifications. This inspection report is mailed directly to the owner with a completion date (generally 90 days) for all recommended/required items.
No Recommendations -- If no problems were noted and no recommendations or requirements are to be made, a letter will be sent to the owner stating that the SCM was inspected, was in good condition and that no recommendations or requirements will be made at this time.
Recommendations -- If recommendations have been made, a letter will be sent to the owner with specific actions needed to restore the pond and a date to complete the maintenance items.
Required Items -- Items that would be required by the owner include items that directly relate to the safety and primary design function of the SCM. If the required items are complex, expensive, or a need a substantial amount of time to complete, a written corrective action plan should be submitted with estimated time frames for completion.
If an owner does not complete the recommended or required items during the original 90 days, a second letter will be sent by certified mail to the owner, allowing an additional 30 days to comply with the recommended or required maintenance items. If the recommended items are not completed by the end of that second time period, a letter will be sent to the owner stating that the maintenance of SCMs is the sole responsibility of the owner and the City of Greensboro accepts no liability in the event of failure. If required items are not completed by the end of the second time period and all attempts to cooperatively work with the owner have failed, the owner will be sent a notification letter that the work may be completed by the City's chosen contractor -- at the owner's expense, and an assessment against the owner will be filed with the City Financial & Administrative Services Department. This process will be in accordance with Chapter 30 (Watershed Regulations) and follow all applicable guidelines.