Construction site Sediment control

When people modify the landscape, oftentimes the soil underlying the construction site is bared. This allows the land to become more susceptible to erosion, allowing sediments to flow into our waterways and negatively affect water quality.

In order to mitigate these effects, there are Best Management Practices (BMPs) defined by Wisconsin’s Department of Natural Resources. Construction BMPs can be split into two different groups: Erosion Control BMPs and Sediment Control BMPs.

Sediment Control BMPs “Aid in removal of sediments from water after the erosion process has already begun . This is accomplished by using barriers, containments, or other devices to filter or reduce the velocity of the water so soil particles can no longer remain suspended.” - Wisconsin Costruction Site Erosion Control Field Guide. Read on to learn a bit more about Sediment Control BMPs.

 
 

BMP 1: De-Watering

De-watering allows water to be trapped in a settling basin or filter so that the sediments that it would carry from the construction site can be retained.

“I. Definition A compartmented container, settling basin, filter, or other appropriate best management practice through which sediment-laden water is conveyed to trap and retain the sediment.

II. Purposes The purpose of this standard is to determine appropriate methods and means to remove sediment from water generated during dewatering activities prior to discharging off-site or to waters of the state. Practices identified in this standard shall be deemed to meet the de-watering performance standard to prevent the discharge of sediment to the maximum extent practicable (MEP) as defined in NR 151.11(6)(c). “

 

BMP 2: Sediment Bale Barrier

Sediment bale barriers slow or stop sheet flow and erosion by reducing the length of the slope of the exposed site. The hay or straw bales are anchored to the slope in rows, slowing the flow of water and the removal of sediment.

“I. Definition A temporary sediment barrier consisting of a row of entrenched and anchored straw bales, hay bales or equivalent material used to intercept sediment-laden sheet flow from small drainage areas of disturbed soil.

II. Purpose The purpose of this practice is to reduce slope length of the disturbed area and to intercept and retain transported sediment from disturbed areas.”

 

BMP 3: Sediment Basin

Sediment basins capture and slow runoff from the site in an excavated ditch, allowing sediments to settle before the water leaves the site through an permeable outlet.

“I. Definition A sediment control device constructed with an engineered outlet, formed by excavation or embankment to intercept sediment-laden runoff and retain the sediment.

II. Purposes Detain sediment-laden runoff from disturbed areas for sufficient time to allow the majority of the sediment to settle out.”

 

BMP 4: Sediment Trap

Sediment traps allow sediment to settle out of runoff water so that it does not leave the site.

“I. Definition A temporary1 sediment control device formed by excavation and/or embankment to intercept sediment-laden runoff and to retain the sediment.

II. Purposes To detain sediment-laden runoff from disturbed areas for sufficient time to allow the majority of the sediment to settle out”

 

BMP 5: Silt Curtain

A silt curtain captures sediments already in a waterway by creating a permeable barrier perpendicular or parallel to the flow of water behind which sediments can drop from the water column.

“I. Definition A temporary permeable fabric installed in a waterway or waterbody to minimize sediment transport. A silt curtain does not extend to the bottom of the channel and is placed parallel or perpendicular to the direction of flow.

II. Purposes The purpose of this practice is to provide sediment containment while construction activities are occurring in or directly adjacent to a waterway or waterbody.”

 

BMP 6: Silt Fence

A silt fence, like a sediment bale barrier, shortens slope length and reduces the velocity of sheet flow, allowing eroded sediments to settle behind a permeable geotextile fabric.

“I. Definition Silt fence is a temporary sediment barrier of entrenched permeable geotextile fabric designed to intercept and slow the flow of sediment-laden sheet flow runoff from small areas of disturbed soil.

II. Purpose The purpose of this practice is to reduce slope length of the disturbed area and to intercept and retain transported sediment from disturbed areas.”

 

BMP 7: Storm Drain Inlet Protection for Construction Sites

A storm drain inlet protection creates a barrier around a storm drain to prevent sediments from entering the storm sewers.

“I. Definition A temporary device installed in or around a storm drain inlet, drop inlet, or curb inlet.

II. Purposes This practice is intended to minimize sediment from entering storm drainage systems in areas where the contributing drainage area is temporarily disturbed.”

 

BMP 8: Turbidity Barrier

Turbidity barriers are similar to silt curtains, but are less permeable and therefore cannot be placed perpendicular to the direction of flow. They contain sediment within a waterbody or waterway.

“I. Definition A temporary fabric barrier with very low permeability, installed in or near the bed of a waterway or waterbody to minimize sediment transport and is installed parallel to flow. Turbidity barrier cannot be installed perpendicular to a moving channel.

II. Purposes The purpose of this practice is to provide sediment containment while construction activities are occurring in or directly adjacent to a waterway or waterbody.”

 

BMP 9: Water Application of Additives for Sediment Control

Additives for sediment control, such as polyacrylamide and other water soluble additives, are added to water to clarify it before it is allowed to leave the site, leaving behind sediments.

“l. Definition The water application of products containing watersoluble additives to remove suspended solids in sediment control structures (water clarification). Products include additives such as polyacrylamide (PAM) and other polymers.

ll. Purpose The purpose of this practice is to clarify water prior to discharge by settling suspended sediment within sediment control structures for construction or post-construction process systems.”

 

BMP 10: Interim Manufactured Perimeter Control and Slope Interruption Products

Interim manufactured perimeter control and slope interruption products are other types of barriers similar to sediment bale barriers and silt fences. They shorten slope lengths and reduce the velocity of runoff to allow any eroded sediments to settle.

“I. Definition Manufactured perimeter control and slope interruption products include a variety of products designed to detain or slow the flow of sediment-laden sheet flow runoff from small areas of disturbed soil. This definition does not include sediment bale barriers or silt fence which are covered under Conservation Practice Standards 1055 and 1056 respectively.

II. Purpose The purpose of the installation of these products is to reduce uninterrupted slope length to slow the velocity of runoff so as to retain transported sediment from disturbed areas.”