- Program Areas
- Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Climate Change
- Weapons Systems and Platforms
A Flexible Permeable Reactive Barrier for Protection of Wetland Sediments from Heavy Metals in Runoff Water
Small arms firing ranges (SAFRs) located on Department of Defense (DoD) facilities are, in many cases, constructed next to wetland areas, including ponds, lakes, and streams. These wetlands, which may be seasonal, intermittent, freshwater, brackish, or estuarine, represent a potential point of regulatory interest as they are at risk of heavy metal contamination in the runoff water from the adjacent active ranges. Access to wetland areas (especially forested wetlands) is typically limited due to a lack of roads. Standard environmental remedial options and monitoring techniques are expensive to implement due to the nature of the terrain and seasonal changes in water flow and salinity. The objective of this project is to demonstrate a relatively low-cost, passive, in situ treatment technology for exclusion of toxic metals in runoff water that can meet the needs of the variable terrain and salinity requirements.
This technology combines the proven use of geotextile fabric woven into a tubular shape (a “sock”) with the addition of innovative amendments to adsorb from surface water cationic (such as lead [Pb], zinc [Zn], and copper [Cu]) and anionic (such as antimony [Sb]) metals, metalloids, and metals bound to suspended solids. The filter sock is National Pollutant Discharge Elimination System (NPDES)-approved for use on construction sites in order to control transport of sediment in surface water. This project will address the contamination of surface receiving waters by metal-contaminated runoff water from training ranges. Several amendments will be evaluated for use in the sock—phosphate minerals and salts, iron and magnesium oxides, and an innovative combination of mesoscale biogenic phosphate carrier and nanoscale reactive chemicals. The latter combination results in a mesoscale material that is easy to handle and recover while retaining nanoscale reactivity for the stabilization of metals. The different geotextiles have varying porosity, photodegradability, and life expectancy that must be matched to the site requirements and the amendments. The weight of a filled sock (approximately 40 lb/linear ft for an 8-inch diameter, depending on the fill material) should effectively prevent sediment migration beneath the sock. Given the large land area to be covered, and the high cost to install and maintain most runoff water management BMPs for metals, the low-cost, easy-to-use filter socks may offer a solution for improving the quality of surface receiving waters located adjacent to training ranges.
The expected benefits to DoD include a reduced potential for impact on surface receiving waters. It is estimated that there are more than 3000 active SAFRs at DoD facilities in the United States used for both military training and recreational purposes. The principal life-cycle cost advantage of the technology is that it could be rapidly installed in areas (i.e., watersheds) that could be impacted by sediment runoff containing metals. Once the lifetime of the filter sock has been reached, the fill material can be removed, properly disposed of, and replaced if necessary. There is the potential that the sand with the proper amendments will pass the Toxicity Characteristic Leaching Procedure (TCLP) evaluation and the material can be disposed of in a nonhazardous waste landfill or left in place, significantly reducing disposal costs. Combining the filter sock geotextile with amendments for metal immobilization creates a containment system for metals, metalloids, and metals bound to suspended solids found in surface water runoff from training ranges that is flexible, transportable, inexpensive, and easy to replace. (Anticipated Project Completion - 2015)
Points of Contact
Dr. Steven Larson
U.S. Army Engineer Research and Development Center (ERDC)
SERDP and ESTCP
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