Since the primary purpose of a SMF is to remove sediment and other pollutants (which are usually attached to sediment) from stormwater, sediment will naturally accumulate in a SMF and eventually need to be removed. Facilities vary so dramatically in terms of removal requirements that there are no fast rules of thumb to guide responsible parties. For instance, dry ponds should be cleared of sediment once a significant portion of the SMF volume (25-50%) has been filled. For wet ponds, a minimum water depth of approximately 3 feet is desirable. Sediment and pollutants will need to be discarded.
The best solution is to have an onsite area or a site adjacent to the facility (outside a floodplain) set aside for sediment. When sediment is stored near the facility, it is important to protect the stockpile against erosion. If onsite disposal is not an option, transportation and landfill tipping fees can greatly increase sediment removal costs. Once the sediment is removed, the facility should be quickly restabilized, either through revegetation or, in the case of a sand filter, replacement of sand and other filter media if necessary. Finally, wet sediment is more difficult and expensive to remove than dry sediment. In some cases, the entire facility can be drained and allowed to dry so that heavy equipment can remove sediment from the bottom. In other cases, it may be necessary to remove sediment from the shoreline or by hydraulic dredging from the surface. A permit may be required for removal and proper disposal of sediment. Contact your local government for assistance.