Inflow Points. Inflow Points or Outfalls into EDBs are the point source of the stormwater discharge into the facility. An inflow point is commonly a storm sewer pipe with a flared end section that discharges into the EDB. In some instances, an inflow point could be a drainage channel or ditch that flows into the facility. An energy dissipater (riprap or hard armor protection) is typically immediately downstream of the discharge point into the EDB to protect from erosion. In some cases, the storm sewer outfall can have a toe-wall or cut-off wall immediately below the structure to prevent undercutting of the outfall from erosion. The typical maintenance items found with inflow points are as follows:
Inflow Points. Inflow points are the points of stormwater discharge into the swale or buffer. Inflow points are typically pipe outfalls, other grass xxxxxx or buffers, or curb cuts from upstream impervious areas, such as parking lots. Some form of energy dissipation is typically provided immediately downstream of the inflow point into the grass swale or buffer. Energy dissipation devices may include riprap aprons, or flow spreader devices. The typical maintenance items required at inflow points are as follows:
Inflow Points. Inflow points or outfalls into BRCs/PLDs are the point of stormwater discharge into the facility. An inflow point is commonly a curb cut with a concrete or riprap rundown. In limited cases, a storm sewer pipe outfall with a flared end section may be the inflow point into the BRC/PLD. An energy dissipater (riprap or concrete wall) is typically immediately downstream of the discharge point into the BRC/PLD to protect the BRC/PLD from erosion. In some cases, the storm sewer outfall can have a toe-wall or cut- off wall immediately below the structure to prevent undercutting of the outfall from erosion. The typical maintenance items required at inflow points are as follows:
Inflow Points. Splitter Box 4 SFB-2.3.2 Sedimentation Chamber 5 SBF-2.3.3 Filter Media 6 SFB-2.3.4 Underdrain System 7 SFB-2.3.5 Overflow Outlet Works 7 SFB-2.3.6 Embankments 8 SFB-2.3.7 Emergency Overflow 9 SFB-2.3.8 Miscellaneous 9 SFB-2.4 Inspection Forms 10 SFB-3 MAINTAINING SAND FILTER BASINS (SFBs) 10 SFB-3.1 Maintenance Personnel 10 SFB-3.2 Equipment 10 SFB-3.3 Safety 11 SFB-3.4 SFB Maintenance Forms 11 SFB-3.5 SFB Maintenance Categories and Activities 12 SFB-3.6 Routine Maintenance Activities 12 SFB-3.6.1 Mowing 13 SFB-3.6.2 Trash/Debris Removal 13 SFB-3.6.3 Splitter Box/Overflow Outlet Works Cleaning 13 SFB- 3.6.4 Woody Growth Control/Weed Removal 14 SFB-3.7 Minor Maintenance Activities 14 SFB-3.7.1 Sediment Removal/Pollutant Removal 14 SFB-3.7.2 Erosion Repair 16 SFB-3.7.3 Jet-Vac/Clearing Drains 16 SFB-3.8 Major Maintenance Activities 16 SFB-3.8.1 Major Sediment/Pollutant Removal 17 SFB-3.8.2 Major Erosion Repair 18 SFB-3.8.3 Structural Repair 18 SFB-3.8.4 SFB Rebuild 18 SFB-1 BACKGROUND Sand Filter Basins (SFBs) are a common type of Stormwater Management facility utilized within the Front Range of Colorado. A SFB consists of a sedimentation chamber, a flat surfaced area of sand (sometimes covered with grass or sod), a filtration chamber, and a flat sand filter bed with an underdrain system. A surcharge zone exists within the sedimentation and filtration xxxxxxxx for temporary storage of the Water Quality Capture Volume (WQCV). During a storm, runoff enters the sedimentation chamber, where the majority of sediments are deposited. The runoff then enters the filtration chamber where it ponds above the sand bed and gradually infiltrates into the underlying sand filter, filling the void spaces of the sand. The underdrain gradually xxxxxxxx the sand bed and discharges the runoff to a nearby channel, swale, or storm sewer. SFBs provide for filtering and absorption of pollutants in the stormwater3. The popularity of SFBs has grown because they allow the WQCV to be provided on a site that has little open area available for stormwater management. However, there are limitations on their use due to potential clogging from large amounts of sediment. SFB-2 INSPECTING SAND FILTER BASINS (SFBs) SFB-2.1 Access and Easements Inspection and maintenance personnel may utilize the stormwater facility map located in Appendix G containing the locations of the access points and maintenance easements of the SFBs within this development. SFB-2.2 Stormwater Management Facilities Locatio...
Inflow Points. Splitter Box Inflow points or outfalls into SFBs are the point of stormwater discharge into the facility. An inflow point is commonly a curb cut with a concrete or riprap rundown or a storm sewer pipe outfall with a flared end section. In some instances SFBs are designed to treat only the WQCV. The WQCV is a volume of water that runs off a site during an 80th percentile event. Any amount over the WQCV is allowed to go to a detention facility without water quality treatment. The splitter box is generally constructed of reinforced concrete. The splitter box typically has a lower wall height that will trap the required WQCV. Volumes over the WQCV are allowed to spill over the wall and enter a storm sewer system that conveys the runoff to a detention facility. Proper inspection and maintenance of the splitter box is essential in ensuring the long-term operation of the SFB. An energy dissipater is typically immediately downstream of the splitter box, at the discharge point into the SFB, to protect the sedimentation and filtration xxxxxxxx from erosion. In some cases, the splitter box outfall can have a toe-wall or cut-off wall immediately below the structure to prevent undercutting of the outfall from erosion. Where there is detention included with the SFB an energy dissipater (riprap or hard armor protection) is typically immediately downstream of the discharge point into the SFB to protect from erosion. In some cases, the storm sewer outfall can have a toe-wall or cut-off wall immediately below the structure to prevent undercutting of the outfall from erosion. The typical maintenance activities required at inflow points are as follows:
