Thursday, September 5, 2019

KDOT works to reduce and control stormwater runoff

By Lisa Knoll
Public Affairs Manager,
Southwest Kansas
There’s something about a rainy day that people love.  Maybe it’s that amazingly fresh smell that comes with rain, not having to water the lawn or the flowers that day or just an excuse to sleep in and binge watch Netflix.  Whatever it is, most people love a rainy day every now and then.

But with rain comes an often-overlooked issue: stormwater runoff.  Most water that falls to earth as rain or snow is usually absorbed by trees, plants and the soil, which naturally filters the water before it flows back into rivers, streams and waterways. 

However, the Federal Highway Administration reports that precipitation that occurs over highways and other impervious surfaces, like parking lots and driveways, results in stormwater runoff that can carry debris, sediment and chemicals into water sources such as rivers, streams and waterways— diminishing the quality of water sources. 

Because stormwater runoff can have devastating effects on the environment, KDOT works to reduce and control this runoff as much as possible during construction projects.  This includes implementing an approved stormwater pollution prevention plan (SWPPP) for each highway project that disturbs one acre or more of vegetation.   

According to Scott Shields, KDOT’s Environmental Program Administrator, a SWPPP will include both soil erosion and sediment erosion controls.  Perimeter controls are used during a project until all grade work is completed.  Perimeter controls are temporary barriers that ensure that sediment and contaminants are contained on the project site and do not end up contaminating surface water.  They include silt fences, erosion controls, rock checks and biodegradable logs.   

A silt fence may be used in highway construction projects to retain soil and sediment on a project site so that it does not run into natural water bodies.  Silt fences usually remain in place until revegetation and permanent soil stabilization begins.

Sediment controls are used to control the sediment until the vegetation grows back.  Sediment controls include perimeter controls, ditch checks and slope barriers.  These controls will control sediment runoff until native grasses grow back.  Native grasses work with the soil to slow down and filter runoff so that surface water does not become contaminated. 

Mulch can be used an erosion control device and is usually crimped in, as shown here, using a spade or roller.
An erosion control blanket is in place around a box/winged culvert providing protection from rain and wind erosion on highway projects. 

Shields said KDOT has several standard seed mixes. 

“Each mix is customized by district and includes cool season perennial grasses along with native grasses that grow well in the area,” said Shields. “Cool season perennial grasses will last one to two years until the native grasses become established.” 

He said native grasses are important because they grow naturally in an area, and provide benefits for pollinator insects, roadside aesthetics and natural landscapes. 

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