A reclaimed 175-acre section within the larger Rocky Flats National Wildlife Refuge in Jefferson County, Colorado, west of Denver, was home to a nuclear testing facility for 40 years. The area’s combination of rolling topography, high winds and incidents of heavy rain and snow increase the likelihood of soil erosion. Given the site’s past use, it’s important to keep soils on-site to minimize risks of contamination.
Nilex GeoRidge in a drainage area of Rocky Flats National Wildlife Refuge. Photograph courtesy of Nilex Inc.
Conditions ideal for soil erosion can build on each other, forming channels that further encourage movement of soil off-site. Sites as large as Rocky Flats present numerous areas where these channels can form, so choices around erosion control need to be easy to transport and install, as well as durable enough to rely on once placed; large sites take time to inspect, and time equals expense.
What was needed for the site was a permeable high-density polyethylene (HDPE) berm designed for erosion and sediment control. The contractor chose Nilex GeoRidge®, a lightweight, sustainable alternative to conventional check dams. When used with erosion control blankets, such permeable HDPE berms are effective in reducing water velocity, trapping sediment and aiding in vegetation establishment. Once native grasses have had a chance to take root with the support of the berms, natural erosion control is significantly enhanced. Many separate areas across the site required erosion control, so it was easy for the contractor to put in place the lightweight, portable berm sections as the installers moved across the 175-acre section.
In 2016 the U.S. Department of Energy purchased 1,340 sections of the HDPE berms, and the contractor has been installing it with crews of two, using 10-inch (25-cm) landscaping spikes. It was installed both in drainage channels to slow water velocity and limit erosion, and along the contours of slopes to control sheet erosion, which is generally harder to control because it can take longer to recognize.
Work on the site continues to date. The HDPE berms choice will save the U.S. Department of Energy money during installation compared to other methods, such as coir logs and rock check dams, which require more labor, materials and hauling costs.