Temporary vs. Permanent Stabilization
By Don Abresch // 2020-08-13
Surface stabilization is an important principle of erosion and sediment control because reducing erosion at the source is more effective and efficient than trying to clean up sediment after it has eroded. Minimizing the disturbance and length of time bare soil is left at the site greatly reduces the potential for erosion and off-site sediment damage. A reduction in sediment load or erosion on a site can also reduce the frequency and expense of maintenance operations. Construction site stabilization, or lack thereof, can have large impacts on sediment discharges related to stormwater. Sites that are well stabilized benefit from clean inlets, clean streets, and little sedimentation at discharge points. Poorly stabilized sites face sedimentation challenges daily. The Minnesota Construction General Permit provides guidance for site stabilization.
"Stabilize", "Stabilized", "Stabilization" means the exposed ground surface has been covered by appropriate materials such as mulch, staked sod, riprap, erosion control blanket, mats or other material that prevents erosion from occurring. Grass seeding, agricultural crop seeding, or other seeding alone is not stabilization. Mulch materials must achieve approximately 90 percent ground coverage (typically 2 ton/acre). [Minn. R. 7090] 25.30
Temporary seeding involves the establishment of rapid growing annual grasses or small grains to stabilize disturbed areas until such time as a permanent cover can be established. The main purposes are to provide vegetative cover where permanent seeding is not desirable or practical, to reduce erosion and sedimentation damage by stabilizing disturbed areas, to reduce problems associated with sedimentation, erosion, and dust from unvegetated soil surfaces during construction and to improve visual aesthetics of construction areas.
Minnesota Guidelines for Permanent Stabilization
Permittees must complete all construction activity and must install permanent cover over all areas prior to submitting the NOT. Vegetative cover must consist of a uniform perennial vegetation with a density of 70 percent of its expected final growth. Vegetation is not required where the function of a specific area dictates no vegetation, such as impervious surfaces or the base of a sand filter. [Minn. R. 7090] 13.2
The purpose of permanent perennial seeding is to prevent erosion, remove sediment from runoff, reduce the volume of runoff, and improve water quality. Permanent seeding involves the establishment of a permanent vegetative cover to protect soils from erosive forces, to provide permanent vegetative cover and improve long term visual aesthetics of a project site. Slow growing Native plants are typically used to provide long term stabilization due to their deep root structure, and ability to hold soils together, and the low maintenance associated.
Benefits of Native Plantings
- Native plantings compete with undesirable vegetation and noxious weeds.
- Vegetation absorbs water, reducing the volume of stormwater runoff.
- Vegetation filters out sediment and other pollutants, improving water quality.
- Provides an aesthetically pleasing, finished look to the site.
[Minn. R. 7090] 25.30
[Minn. R. 7090] 13.2