Phase II of the Clean Water Act requires stormwater surface flows that are captured meet higher standards prior to being discharged into public waterways. One manner in which this is achieved is by installing some type of a Water Quality Unit (WQU).
There are a variety of WQU available from various manufactures however all require a maintenance program to ensure proper function. Here are some examples of the types of WQU commonly used:
• Aqua Swirl Hydrodynamic Separator
• Continuous Deflective Separation (CDS)
• ADS HDPE Water Quality Unit
The technical specifications of when these units must be cleaned can sometimes be confusing, thus many local regulations mandate the system be checked and/or cleaned annually. Failure to inspect and clean, along with maintain proper documentation of the maintenance, can result in a Notice of Violation being levied against the owner.
It is recommended these units be inspected on a quarterly basis and during this time, the floating debris should be removed from the system. A sludge judge is used to then determine the amount of sediment collected in the unit. It is important to properly document this procedure and include date stamp photographs for verification.
The annual cleaning usually consists of removing the liquid and sediment by use of a vacuum truck. The inside is washed down and any hydrocarbon pads or screens should be replaced. Additionally, the inside of the unit is inspected by properly trained personnel entering under a confined space permit.
Following this maintenance plan can help ensure you are properly treating your stormwater runoff while maintaining the proper operation of your WQU.