Introduction
Objectives
Biosolids Demonstration
Research Plots
Research Results
New Research Plots
Cooperators
Other Associated Projects
Upper Arkansas River
Alluvium Remediation
Biosolids Demonstration
Biosolids Demonstration
Leadville, CO
Autumn, 2000
Introduction
Historic mining activities near Leadville resulted in deposition of mine tailings in the Arkansas River. Over the years, these high pyrite wastes have been eroded and redeposited along an 11-mile stretch of the river, contaminating a number of areas. The fluctuating water table has resulted in alternating reducing and oxidizing conditions. Oxidation of the reduced sulfur has resulted in extremely acidic soil pH (1.5-4.5). As a function of the fluctuating water table and the acidic conditions, Zn and Pb form soluble salts and wick to the soil surface during dry portions of the year. A metal salt crust forms on the soil surface with measured Zn concentrations of up to 90,000 mg/kg.
 |
Mine tailings washed down and accumulated in deposits up to and exceeding 2'. |
Deposits are toxic to riparian vegetation. |
 |
 |
Contaminated soils, barren of vegetation, are highly susceptible to continued erosion by the river. |
Objectives
|
The overall objective:
Specific objectives:
|
|
Biosolids
Demonstration
Biosolids have been used both alone and in combination with other materials to restore soils that have been disturbed by a wide range of activities including coal and gravel mining. Research has consistently demonstrated that biosolids are highly effective, in many cases more so than topsoil replacement, for restoration of disturbed ecosystems. Biosolids, applied at restoration rates (generally greater than 50 tons/ac) provide sufficient organic matter to improve soil physical properties and soil nutrient status, while reducing metal availability. To correct active & residual, plus potential acidity, lime or other alkaline materials is mixed with the biosolids.
Demonstration treatments. Biosolids from Denver Metro were applied at 100 dry tons/ac by August 1998. Lime was mixed with the biosolids, also at around100 tons/ac, calculated from soil properties as shown inthe following table. Amendments were tilled into the soil to a depth of 12".
Seeding. In September 1998, plots were seeded with a mixture of native seed and ryegrass. Due to the a variety of climatic conditions, little germination was evident by July 1999. Reseeding took place in August 1999 by drilling seeds, followed by daily irrigation.
Research Plots
Selected plots in July 1999 . . . . . . . . . Plots
immediately after installation
A small plot study was installed in September 1998 to help design future operational sites. This study tests different mixtures of soil amendments. Treatments were tilled in, left fallow over the winter, and seeded with annual rye in June, 1999.
 |
Soil and plant samples were taken in August 1999, and analyzed for pH, and extractable metals (soils), and metal uptake (plants). |
 |
Research Results
pH and exchangeable metals in soil after one year.
Plant elemental concentrations one year after application.
New Research Plots
Two new research studies were installed July, 2000. The first was designed to investigate the effect of combining varying amounts of woody material with the biosolids to achieve soil amendments that favor different native plant communities.
The second set of plots investigates which type of liming
material will achieve the best short and long term correction
of soil acidity. Also, movement of lime down the soil profile
by water is being monitored.
Cooperators
|
Profs. Sally
Brown and Chuck
Henry Mike Zimmerman and Bob Brobst Harry Compton and Scott Fredericks Bernard Smith Rufus Chaney Jan Christner Denver Metro |
 |
 |
  |
Other Associated Projects
Bunker Hill, Idaho: Ecological Restoration Demonstration
Coeur d'Alene River Basin West Page Swamp Wetland Restoration Project