A.J. Erickson, B.C. Asleson, J.S. Gulliver, R.M. Hozalski
It is recommended that visual inspection and any associated maintenance be performed at least once per year for all biologically enhanced practices. If, based on assessment goals, an assessment of runoff volume reduction potential or remaining sediment storage capacity is warranted, capacity testing is recommended because, as long as the number of test locations is sufficient, this level of assessment provides accurate and location–specific data. Since capacity testing only assesses infiltration rates or volumes of retained sediment, synthetic runoff testing is recommended for bioretention practices and constructed wetlands when pollutant retention assessment is desired and there is an adequate available water supply. Monitoring will be required for assessment of the larger practices, and can assess performance of the biologically enhanced practice within the drainage basin.
Biologically enhanced practices, which can be effective in reducing stormwater runoff volume, as well as retaining suspended solids and dissolved pollutants require regular maintenance if they are to remain effective. The required frequency of inspection and maintenance is dependent on the watershed land use (e.g. urban, rural, farm, etc.), construction practices in the watershed and rainfall amounts and intensity.
For any biologically enhanced stormwater treatment practice it is important to maintain the desired vegetation in a healthy state at appropriate densities. For systems that infiltrate stormwater it may be periodically necessary to break up the soil surface to allow infiltration to occur. Other practices, such as constructed wetlands, may need to have accumulated sediment removed if solid removal rates are unacceptable. For detailed recommendations on maintenance activities and when such activities are warranted, see Maintenance.