1.10 BMP C123 - Plastic Covering
Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas.
Plastic covering may be used on disturbed areas that require cover measures for less than 30 days, except as stated below.
Plastic is particularly useful for protecting cut and fill slopes and stockpiles.
The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term (greater than six months) applications.
Due to rapid runoff caused by plastic covering, this method shall not be used upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes.
Whenever plastic is used to protect slopes, water collection measures must be installed at the base of the slope. These measures include plastic-covered berms, channels, and pipes used to convey clean rainwater away from bare soil and disturbed areas. At no time is clean runoff from a plastic covered slope to be mixed with dirty runoff from a project.
Other uses for plastic include:
Pond liner in temporary sediment pond;
Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored;
Emergency slope protection during heavy rains; and
Temporary conveyance used to direct stormwater and surface water.
1.10.3 Design and Installation Specifications
Plastic slope cover must be installed as follows:
Run plastic up and down slope, not across slope.
Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet.
Minimum of 8-inch overlap at seams.
On long or wide slopes, or slopes subject to wind, all seams should be taped.
Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath.
Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and pound a wooden stake through each to hold them in place. Alternative options for holding plastic in place exist and may be considered with COT approval.
Inspect plastic for rips, tears, and open seams regularly and repair immediately. This prevents high velocity runoff from contacting bare soil, which causes extreme erosion;
Plastic sheeting shall have a minimum thickness of 6 mil.
If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff.
Torn sheets must be replaced and open seams repaired.
If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and replaced.
When the plastic is no longer needed, it shall be completely removed.