Determination of Appropriate Monitoring Level(s) for a Stormwater Treatment Practice
Determination of Appropriate Monitoring Level(s) for a Stormwater Treatment Practice.
Link to this table
| Level | Should I perform this assessment? | Advantages | Requirements/limitations | Recommended frequency | Can this be used to obtaina stormwater credit? |
|---|---|---|---|---|---|
| Visual inspection | Recommended for all practices | Quick and cost-effective | Available personnel. Does not necessarily identify causes of poor performance. | ≥ 1x / year, at start of rainy season | No |
| Capacity testing | If there are suspected filtration rate problems with the practice, or to determine if the media has capacity for phosphorus removal | Applicable for practices of all sizes, quickly identify specific areas that require maintenance, less time and expense than monitoring | A Modified Philip-Dunne Infiltrometer is recommended for filtration rate testing. | Every few years | Consult with MPCA or regulatory agency to determine eligibility |
| Synthetic runoff testing | If there are suspected problems with filtration or pollutant removal, or to establish a baseline performance level | Controlled method to accurately measure drain time and/or pollutant removal efficiency | Testing will be limited by available water supply.
Must be able to plug or measure all outflow paths other than filtration. Must be able to continuously measure water surface elevation in practice during test. Recommended for small stormwater treatment practices. May require authorization to conduct testing with targeted pollutants. |
Every few years | Consult with MPCA or regulatory agency to determine eligibility |
| Monitoring | Goals include obtaining stormwater credits, assessing performance results and life of filter media, or complying with a permit or regulatory agency | Most comprehensive assessment technique and measures the response to natural rainfall events | Requires the most time, labor, and equipment of the four assessment techniques. Variations in weather, pollutant loading, and flows require correct and simultaneous operation of all instrumentation. | Continuously from construction of the IESF | Yes |