Best Management Practices for Storm water Pollution

Best Management Practices or , BMP’s, are defined as general good

housekeeping practices, schedules of activities, pollution prevention techniques,

educational practices, maintenance procedures, prohibitions of practices and other

management practices(1). BMP’s also include treatment practices, operating procedures,

and practices to control site runoff, spillage or leaks, sludge or water disposal, or drainage

from raw materials storage.

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. Diversions such thins as Surface Roughening.

Runoff diversions assist in the second, conveyance stage of a BMP system.

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.

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