drainage & Flood Control
Sediment Basin Surface Drains Maximize Settling
M
any states have come to the same conclusion North Carolina did several years ago:
Conventional sediment basins do not work very
well. This is not surprising because the outlets (perforated
risers or stone filters) typically do not adequately regulate
outflow to ensure that the basin fills; then they drain the
basin from the bottom, releasing the muddiest water in
the basin. Research has found that these types of basins
capture only 50% of the sediment entering them. Releasing
water from near the surface—the water with the least sediment in it—would improve sediment-trapping efficiency.
The Faircloth Skimmer surface drain for sediment basins
does this and regulates the draining so that the initial
runoff fills the basin to create conditions that allow gravity
settling to occur. Then the skimmer releases the cleanest
water in the basin at a uniform rate over several days to
maximize settling.
Alabama is one of several states to adopt this sediment
basin design to improve performance. A basin built in
Alabama to demonstrate efficiency is shown in the photograph. Research at North Carolina State University has
shown that with basins that are properly sized and shaped
and that
utilize
porous
baffles
to slow
the flow
through
the basin
and prevent dead
zones, trapping efficiencies of 90% to 95% can be achieved. Even with
high-trapping efficiency, outflow will still be turbid with clay
soils. The Faircloth Skimmer enhances the use of a flocculent
on clay particles that will not settle by gravity alone and will
pass through the basin. The skimmer will capture the initial
runoff with the flocculent in the water and hold it, giving the
sediment time to settle and creating a clean layer of water
on the surface that is released through the skimmer. SWS
J.W. Faircloth & Son Inc.
919.732.1244 • www.fairclothskimmer.com
Write in 816
Surface DrainS
for
SeDiment BaSinS
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PVc skimmer floats on the surface,
releasing the cleanest water
Drains from the basin’s Surface
instead of the bottom
improves basin performance
Simple, automatic, gravity operation
Works in basins with risers or
sediment traps with spillway
Sizes, flow rates, prices, illustrations and instructions
are available at www.FairclothSkimmer.com
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replaces perforated risers and
stone outlets as the basin’s drain
convenient for use in a detention
basin as a temporary sediment
basin during construction
8 sizes available
inlet orifice easily adjusted for
drawdown requirements
JW Faircloth & Son Inc.
Hillsborough, nc 27278 | 919.732.1244 | 919.732.1266 fax
Write in 766
26 • S T O R M W A T E R S O L U T I O N S • 2 0 1 3 – 2 0 1 4 C ase B oo k