Monday, March 31, 2008

Best Management Practices for Storm Water Pollution

Storm water Management is most affective when it involves a system of BMP’s
that targets each stage of the erosion process to ensure success from construction
activities. The most efficient approach involves minimizing the likely sources from
outwash. This means the less disturbance to a land area the better. BMP’s should also
involve controlling the amount of runoff and its ability to carry sediment by diverting incoming flows and stopping inner flows. And finally, BMP’s should be able to attain certain sediments that are picked up on the way through the use of sediment-capturing devices. Above all BMP’s are best performed using advance planning and good scheduling.
A system intended to eliminate storm water pollution should include at least one
example of each of the following categories : surface stabilization, runoff control
measures, runoff conveyance measures, outlet protection, sediment traps and barriers, and stream protection.
As far as surface stabilization goes the best method seems to be Surface Roughening.
Surface Roughening is crapping up a bare, sloped soil surface with horizontal grooves or benches running across the slope. Grooves can be large-scale, such as stair-step grading with small benches or terraces, or small-scale, such as grooving with disks, tillers, or other machinery, or with heavy tracked machinery which should be reserved for sandy, non compressible soils.
Runoff control measures are usually used in a way called Runoff Diversion. This
may be described as a structure that channels upward slope runoff away from erosion
source areas, diverts sediment-laden runoff to appropriate traps or stable outlets, or captures runoff before it leaves the site, diverting it to locations where it can be used or released without erosion or flood damage.
Hardened Channel is the next best BMP phase in which a channel with erosion-resistant linings of riprap, paving, or other structural material designed for the conveyance and safe disposal of excess water without erosion. Channels assist in the second, conveyance stage of a BMP system.
Level Spreader is the next step to a successful Storm water Management system and it is an outlet designed to convert concentrated runoff to sheet flow and disperse it uniformly across a slope without causing erosion. This structure is very good for returning natural sheet flows to exiting drainage that has been altered by development, especially for returning sheet flows to receiving ecosystems such as wetlands where dispersed flow may be important for maintain pre-existing hydrologic regimes. Alternative designs to minimize such channeling include hardened structures, stiff grass hedges, and segmenting discharge flows into a number of smaller, adjacent spreaders. The level spreader is often used as an outlet for runoff diversions. Level spreaders assist in the second, conveyance stage of a BMP system.
The best idea for a sediment drop or barrier is the Sediment Trap, A small,temporary ponding basin formed by an embankment or excavation to capture sediment from runoff. Traps are most commonly used at the outer areas of diversions, channels,slope drains, or other runoff carrier that give off sedimentful water. The pond outlet should be a stone section designed as the low point. Sediment traps assist in the third,capture, stage of a BMP system. With the correct combination of the devices explained storm water pollution can be easily controlled. These are not the only ways but the most effective strategies to manage the problem.

Information on erosion control pre-viewed

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