Experiences with batch detention systems
Experiences with batch detention systems
(OP)
Does anyone have experiences with batch detention systems they would like to share? I'm particularly interested in the design and modeling aspects of these systems. Since they involve active outlet controls (valves, gates, etc) they cannot be modeled with a standard head-dependent outlet device, such as a weir or orifice.
Here's a brief summary:
Batch detention basins capture and temporarily detain the water quality volume from a storm event using an automated controller and valve. They are intended to serve primarily as settling basins for the solids fraction, and as a means of limiting downstream erosion by controlling peak flow rates during erosive events. Batch detention basins may be constructed either online or offline, however, offline structures are preferred. Batch detention basins are designed to prevent clogging of the outflow structure and resuspension of captured sediment during a discharge. They also provide enhanced dissolved pollutant removal performance. The batch detention design typically incorporates a non-clogging outflow structure, such as an orifice protected by a trash rack, or a perforated riser pipe protected by riprap. Batch extended detention basins may be used in very small watersheds (no minimum size), since the discharge is regulated by a valve instead of an orifice. In addition, batch detention basins tend to accumulate debris deposits rapidly, making regular maintenance necessary to minimize aesthetic and performance problems. Batch detention basins can readily be combined with flood and erosion control detention basins by providing additional storage above the water quality volume.
Here's a brief summary:
Batch detention basins capture and temporarily detain the water quality volume from a storm event using an automated controller and valve. They are intended to serve primarily as settling basins for the solids fraction, and as a means of limiting downstream erosion by controlling peak flow rates during erosive events. Batch detention basins may be constructed either online or offline, however, offline structures are preferred. Batch detention basins are designed to prevent clogging of the outflow structure and resuspension of captured sediment during a discharge. They also provide enhanced dissolved pollutant removal performance. The batch detention design typically incorporates a non-clogging outflow structure, such as an orifice protected by a trash rack, or a perforated riser pipe protected by riprap. Batch extended detention basins may be used in very small watersheds (no minimum size), since the discharge is regulated by a valve instead of an orifice. In addition, batch detention basins tend to accumulate debris deposits rapidly, making regular maintenance necessary to minimize aesthetic and performance problems. Batch detention basins can readily be combined with flood and erosion control detention basins by providing additional storage above the water quality volume.
Peter Smart
HydroCAD Software
www.hydrocad.net
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RE: Experiences with batch detention systems
I haven't had to model one of these yet, because they're temporary BMPs, but if I did I'd probably just back calculate the orifice flow based on constant head and use a constant discharge in the routing.
In these batch systems, do the valves adjust based on head or something? I would think unless there was some kind of widget that changed the valve opening based on head, the discharge relationship would still be based on head.
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RE: Experiences with batch detention systems
RE: Experiences with batch detention systems
Don't think a constant outflow is an accurate way to model an orifice.
RE: Experiences with batch detention systems
1 Wait till WSE rises to target level (treatment volume)
2 Wait a further 12-48 hours for settling
3 Immediately lower control weir to current WSE
4 Gradually lower weir to empty pond at constant rate over desired draw-down time.
5 Reset weir for next event.
All monitored and managed by a smartphone app.
Peter Smart
HydroCAD Software
www.hydrocad.net