|Name||USA: Idaho: West Page Swamp Wetland Restoration Project (Bunker Hill)|
|Executive Summary||The West Page Swamp wetland restoration project lies within the Bunker Hill, Idaho superfund site. This individual restoration project was set up as a research site to evaluate the use of a cap of biosolids (including compost, wood ash, and wood waste) over soils contaminated by heavy metals as a result of mining. It appears that these methods are useful. These new soils limit the bioavailability of lead to plants and animals and also provide nutrients for plant growth. This site was being monitored as of 2005 and will probably continue to be monitored. If this method of remediation is successful, it may be used in further restorations both in the Bunker Hill (Idaho) superfund site and elsewhere.|
|Original Ecosystem||This site is an approximately 11 hectare wetlands that was part of the Cour d’Alene River basin in Idaho. Not much has been written about the original ecosystem of the area. Almost certainly, it used to be an important stopover site for waterfowl as well as habitat for many species of wildlife.
This site is located in Shoshone County, Northern Idaho and is contained within the Bunker Hill CERCLA (Superfund) site.
|Specific Country||United States of America|
|Pre Disturbance Condition||Unknown.|
|Degradation Description||Starting in 1916 and into the 1980s, the Bunker Hill site was used for the mining and smelting of lead (Pb) and Zinc (Zn). The West Page Swamp site was used for direct tailings deposition between 1918 and 1929. This resulted in contamination from Lead, Zinc, Cadmium (Cd), and Arsenic (As). Mine tailings reached depths of 18 inches to 10 feet, vegetation was sparse, and the soil was found to be contaminated with very high metal concentrations (lead was found at about 30,000 mg/kg; zinc at concentrations of about 15,000 mg/kg; and cadmium at concentrations of roughly 100 mg/kg).
Because of the mining activity, the soil on site lacked vegetation due to the poor physical properties of the soil, acidity, salts, and metal toxicity. Additionally, this ecosystem had an elevated lead level, endangering any waterfowl that may use these wetlands for feeding or nesting.
|Stakeholder Involvement||University of Washington
U.S. Environmental Protection Agency, Region 10
Coeur d’Alene Indian Tribe
Mining companies listed as potentially responsible parties (PRPs)
Idaho Department of Environmental Quality
U.S. Fish and Wildlife
|Project Desc||The West Page Swamp wetland restoration is a small part of the large Bunker Hill superfund site. This site was set up as a scientific research site to determine whether or not the use of a mixture of natural components could be a solution to the problem of contaminated soils in wetlands. The scientists used a combination of compost (to add nutrients), wood ash/lime (to reduce pH), and wood waste (Carbon rich residuals that limit Nitrogen availability).
In order to restore this site to a functioning part of the ecosystem, some contaminated soil would have to be removed. Soils amendments would have to be made both to allow vegetation to grow and to reduce the bioavailability of lead to wildlife on site. Plans were made to add approximately 15 cm of soil to the site. This addition would allow plants to reestablish in the area without rooting in the contaminated lower soil. The additional soil horizon also makes sure that feeding waterfowl ingest less lead-contaminated soil in the course of their natural activities.
Researchers at the University of Washington evaluated their methods of using biosolids and compost along with other residuals to remediate lead-contaminated sediment and increase the rate of revegetation.
|Project Goals||The goals of the West Page Swamp wetland restoration project were:
• Test the effectiveness of using compost and organic residuals to remediate lead-contaminated sediment so that these techniques and components could be used on similar sites.
• Establish a place where native vegetation could grow and thrive
• Reduce the bioavailability of lead and other contaminants to animal species
If these goals are attained, then the site will have better ecosystem function and not pose a hazard to life currently or in the future.
|Project Activities||• This site was set up as a research site, to determine the usefulness of this type of remediation as a solution to contaminated soils in wetlands
• Tailings in the area were removed to a depth of 0.7 meters
• About 15 cm of compost and wood ash were spread over the site using heavy equipment
• Significant problems arose with rising groundwater and poor accessibility so that they constructed a road for heavy equipment and used a blower to spread the new soil
• But in September of 2000, the remaining area were covered by the new soil
• The outlet end of the wetland was closed to make sure a water depth of 2 feet was maintained.
• The movement and settling of the treatment was monitored at 12 and 24 months
• The effluent quality (suspended solids, pH, species, and water quality) was monitored monthly
• Plant establishment and their uptake of metals was monitored
• Carbon and Nitrogen dynamics were monitored at 6, 12, and 24 months
• A greenhouse study was implemented to determine differences between treated and untreated soil including: bioaccessibility of sediment lead, plant growth, and metal uptake.
• Monitoring for metal bioavailability continued at least until 2005
|Funding Description||Funding for the project was provided by US EPA Environmental Response Team, a division of CERCLA.|
|Project Duration||3 years with ongoing monitoring|
|Project Stage Id||Completed (3)|
|Project Start Date||Jun 1, 1997|
|Project End Date||Sep 30, 2000|
|Recovery To Date||This appears to be an effective method of remediating lead contaminated soils. Plants grown in the treatment area (with added soil) had less lead mg/kg than plants grown in the control areas (without added soil).|
|Recovery Limits||Using biosolids is a good decision economically. This method is cheaper than other methods such as capping with non-biological substances or removing the soil. Biosolids are also easily obtainable because they are just recycled by-products of other human activities.
Future monitoring will be needed at this site to ensure this method is a permanent solution since the contaminants are still on site.
|Human Well Being||Remediation of this site minimizes the amount of lead and other contaminants that could enter the human food supply through consumption of waterfowl that have used this site.
This research site also provided scientific evidence on the efficacy of this treatment.
|Long Term Mgmt||Mining, the major reason for the degradation of this site, is not longer practiced in this area.|
|Evaluation||Application of simple, recycled, natural materials including wood ash, compost, and wood waste seems to have provided the nutrients to encourage vegetative cover and reduced the bioavailability of lead to plants and waterfowl.
This site will continue to be monitored and the lessons learned will probably be implemented at larger sites.
|Case References||Sally Brown
Research Assistant Professor
University of Washington
University of Washington
Harry Compton and Scott Fredericks
US EPA Environmental Response Team
US EPA Region 10
Main page for project http://faculty.washington.edu/clh/wet.html
Journal article http://jeq.scijournals.org/cgi/content/full/32/3/851?ck=nck
Presentation at meeting http://www.rtdf.org/PUBLIC/iinert/minutes/062399.htm
|Created At||May 24, 2007|