AMD Remediation Case Study, Raccoon Creek Watershed Project
|The Raccoon Creek Watershed drains 683 square miles in the southeastern Ohio counties of Athens, Gallia, Hocking, Jackson, Meigs, and Vinton. Natural resource extraction industries, particularly coal, have had a tremendous effect upon water quality, the landscape, and communities within the watershed. The Ohio Division of Wildlife performed the first basin-wide study of Raccoon Creek in the early 1950s, but found little aquatic life due to abandoned coal mines and acid producing wastes. 350 million tons of coal was mined in the watershed between 1820 and 1993, affecting nearly 40,000 acres.
Until the 1970s companies were not required to properly dispose of the vast amount of waste generated during mining. As a result, thousands of tons of toxic coal refuse lies scattered throughout the watershed contributing to increased rates of erosion and the generation of acid mine drainage. The main cause of acid mine drainage is an unstable mineral called iron pyrite, which when exposed to oxygen and water produces sulfuric acid. This acid, once generated, will leach naturally occurring metals such as iron and aluminum from the surrounding coal wastes and bedrock. This chemical soup drastically changes the water quality of local streams and inevitably alters aquatic communities.
Interest in restoring Raccoon Creek first began nearly 20 years ago with a number of citizens from Gallia County forming the Raccoon Creek Improvement Committee. The group started with a number of small projects, such as trash cleanups and logjam removals. However, members realized the problems reached much farther than the borders of their county. The group expanded by inviting citizens from the other six counties in the watershed, as well as several state and local agencies.
Blue = Surface Mining
In 1996, the Ohio Department of Natural Resources, National Resources Conservation Service, Ohio Valley Resource Conservation and Development, Vinton Soil & Water Conservation District, and the Raccoon Creek Improvement Committee partnered to implement an OEPA 319 grant to remediate acid mine drainage in key areas along Little Raccoon Creek. Specifically, in addition to a number of water quality education and outreach activities, the grant funded two acid mine drainage abatement projects in Little Raccoon Creek; State Route 124 Seeps Project and the Buckeye Furnace Project. These two AMD abatement projects were among the first activities of the newly formed Raccoon Creek technical partnership, which is referred to today as the Raccoon Creek Watershed Project. A more recent project utilized 319 grant funds to implement a Raccoon Creek Headwaters Restoration Project.
State Route 124 Seeps Project
The State Route 124 Seeps Project involves an unnamed tributary to Little Raccoon Creek in Milton Township, Jackson County Ohio. The headwaters of this unnamed tributary were extensively surface mined (? 42 acres) for coal prior to the federal Surface Mining Control and Reclamation Act (SMCRA).of 1977. The post-mining condition of the site included a mix of sandy overburden and acid-producing coal refuse haphazardly disposed of on the mine pit floor. The unreclaimed mine spoil was poorly vegetated with rills and gullies indicating high rates of erosion. Two lakes formed near the highwall, on top of the impervious pit floor. This stored water was slowly released into the toxic mining waste throughout the year, producing a continuous source of abandoned mine drainage (AMD). Little Raccoon Creek is most susceptible to this type of AMD generation because production is continuous, particularly during drier periods when there is less dilution and buffering capacity in the stream. Pre-reclamation water quality can be characterized as having low pH (2.5 - 3.5), high acidity loads (23 - 650 lbs/day), and abundant heavy metals (aluminum 1 - 60 lbs/day). The mean acidity load was on the order of 41 tons/year.
The focus of the State Route 124 Seeps Project included both reclamation and treatment components. Reclamation activities included eliminating the impounding lakes, establishing positive surface water drainage, clay-capping the mining wastes, and reestablishing vegetation. Approximately 4100 feet of limestone riprap was installed along stream channels draining the mine as means to treat any residual AMD leaving the site. An open limestone channel is a relatively inexpensive way to treat acid mine drainage, but essentially must be over- designed to contend with varying neutralization efficiencies.
The Vinton SWCD has continued to monitor the water quality at the site since project completion in spring 2001. The post-reclamation water quality has a higher pH (4.2 - 6.0), lower acidity loads (1 - 50 lbs/day), and lower heavy metals (aluminum 0.09 - 9 lbs/day). The mean acidity load has dropped to 2 tons/year, which translates to a 95% reduction in acidity.
Buckeye Furnace Project
The Buckeye Furnace Project includes extensive reclamation and treatment efforts along Buffer Run, a tributary to Little Raccoon Creek in Milton Township, Jackson County. The post-mining condition of this 1.9 acre basin includes numerous abandoned underground mines and an abandoned strip mine with 65-acres of barren coal refuse. High rates of erosion off the strip mine had literally buried the floodplain of Buffer Run in sediment and eliminated any semblance of a normal stream channel. Abandoned mine drainage (AMD) was continually discharging from numerous underground mine entrances and within the strip mine after heavy rain and snowstorms. The Little Raccoon Creek Abandoned Mine Drainage Abatement and Treatment (AMDAT) Plan identified Buffer Run as one of the top AMD producers in the entire Little Raccoon Creek basin. It was not uncommon for Buffer Run to be generating 25% of the total acid load in Little Raccoon Creek. Pre-reclamation water quality can be characterized as having low pH (2.5 - 3.5), high acidity load (900 - 4000 lbs/day), and abundant heavy metals (aluminum 23 - 320 lbs/day). The mean acidity load was on the order of 373 tons/year.
Reclamation and treatment involved a combination of source control measures (reshaping and recontouring of the coal refuse, capping the refuse with clay and soil, and placement of BYPRO (by product of Mead/WesVaco paper company) to reestablish vegetation) and passive treatment systems (successive alkalinity-producing system (SAPS), anoxic limestone drain (ALD), and steel slag leach beds). The SAPS and ALD systems are being used to treat drainage from the underground mines, while the steel slag leach beds are used generate additional alkalinity for the entire subwatershed.
One of the difficulties in treating AMD is the large load of heavy metals, which can precipitate and clog the limestone used to treat and neutralize the mine drainage. One way to eliminate this hazard is remove dissolved oxygen from the mine water before it enters the limestone treatment. Removing the oxygen allows acidity to be neutralized without forming the metal (hydroxide) precipitate. The SAPS system utilizes mushroom compost to remove dissolved oxygen, while the ALD employs an insulating membrane to isolate the system from atmospheric conditions. Freshwater runoff is harvested and used to charge the two steel slag leach beds, which generates additional alkalinity (? 2,000 mg/l) for Buffer Run. The post-reclamation water quality has a higher pH (2.7 - 6.1), lower acidity loads (130 - 290 lbs/day), and lower heavy metals (aluminum 8 - 45 lbs/day). The mean acidity load has dropped to 50 tons/year, which translates to an 87% reduction in acidity.
Partners move forward with implementation
As the initial implementation projects began construction in 1997, the partners entered into a phase of planning that would continue through September of 2003. At the request of ODNR, Division of Mineral Resource Management (DMRM), the partners began characterizing water quality and land use in the watershed to create a prioritized list of AMD problems, along with a treatment scenario that resulted in Abandoned Mine Drainage Abatement and Treatment (AMDAT) Plans. Three AMDATs were completed, beginning with the Little Raccoon Creek AMDAT (submitted in June of 2000), followed by the Headwaters of Raccoon Creek AMDAT (January 2002), and culminating with the Middle Basin of Raccoon Creek AMDAT (September 2003). As these plans were submitted and approved, avenues of funding for AMD remediation began to open and the partners developed more AMD grant projects.
As of December 2003 the Partners have successfully completed four AMD projects, two more are in the final days of construction (the Mulga Run AMD and Carbondale II projects), and the East Branch/Brushy Fork Project, Middleton Run Project, Flint Run Project and Hope Clay Mine Project have all received funds for construction and are in different stages of design. These efforts have also drawn new partners into the project as both private sector (MeadWestvaco) and public sector (OSU Extension, United States Forest Service) partners play important roles in the new AMD projects.
Carbondale II Project
The Raccoon Creek Headwaters includes all areas that drain into the mainstem from river mile 111.9 (the confluence of the East and West Branches of Raccoon Creek) to river mile 80.6 (US Route 50). This portion of the watershed drains approximately 200 square miles in portions of Athens, Hocking, and Vinton Counties. Hewett Fork is a large headwater tributary (15.4 miles) to Raccoon creek, which drains approximately 40.4 square miles of western Athens County and northeastern Vinton County. This area of the watershed has been extensively mined for coal during the last 100 years. Abandoned underground mines that date before the turn of the 20th century underlie many of the hills. Area ridgetops and valley floors were extensively surface mined from the 1950s through the 1970s.
One of the largest sources of AMD in the Hewett Fork watershed is the 33-acre Rice Hocking Mine (AS-14) or Carbondale Mine. The underground mine complex discharges from two former entrances (named the east and west sources). The following is the median water quality for the east source: pH 3.96, acidity 160 tons/yr, iron 40 tons/yr, and aluminum 13 tons/year (Shimala 2000). The following is the median water quality for the west source: pH 3.52, acidity 58 tons/yr, iron 13 tons/yr, and aluminum 5 tons/yr (Shimala 2000). The Carbondale Mine discharges an average acidity load of 218 tons per year.
The Ohio Department of Natural Resources Division of Mineral Resource Management (ODNR DMRM) constructed a series of artificial wetland cells at the Carbondale Mine in 1989 - 1990 as way of treating the acidic mine discharge. This rudimentary treatment system consisted of 7 wetland cells and a polishing pond for the precipitation of metals. Each wetland cell was filled with 9 inches of lime substrate, 12 inches of mushroom compost, and planted with cattails. The wetland system was used primarily to increase the residence time of the mine drainage in an effort to allow natural biogenic processes to neutralize acidity and precipitate heavy metals. The Carbondale Wetland treatment system was reevaluated in 1999 and was found to be eliminating 21% acidity, 63% iron, and 23% aluminum (Shimala 2000). System failure was due in part to the shear volume of metal precipitate in the cells and the presence of burrowing animals (muskrat), which short-circuited the cells and effectively decreasing the residence time. The Raccoon Creek partners agreed in 1997 that a new treatment design was a priority for the Carbondale Mine and Hewett Fork.
Design criteria for constructing a more efficient treatment system for the Carbondale Mine included the following points:
The construction of the in-stream lime-dosing unit, referred to as the Carbondale Doser or Carbondale II, was completed in December 2003. The Carbondale doser requires no electricity to operate and is literally powered by the mine discharge. A portion of the water is routed from the mine entrance to an AQUAFIX water wheel, which resembles a miniature water-powered mill. As the water wheel makes one revolution, an auger injects a prescribed amount of alkaline material into the mine discharge. The alkaline material is stored in a 75-ton storage overhead, which is then gravity fed to the auger. The efficiency of treatment can be fine tuned by adjusting the flow of water into the water wheel unit or by regulating the amount treatment exiting the storage silo.
Recent lab analyzed samples taken at the Carbondale II discharge in May and June 2004 show elevated pH values (11.0 -11.2), elevated alkalinity concentrations (166 - 203 mg/l), and no measurable acidity. During the June 2004 sampling event, the Carbondale Mine was producing 811-lbs/day acidity and 246-lbs/day dissolved iron. The Carbondale II treated effluent showed no measurable acidity, 632-lbs/day alkalinity, and 5.3 lbs/day dissolved iron. This implies that we have exceeded our goal of neutralizing 30% of the acidity or 65 tons per year (based on average load of 218 tons per year) and also significantly reduced the metal loads to Hewett Fork. There is evidence that excess alkalinity added to Hewett Fork is also treating two nearby AMD sources emanating from Carbondale Creek and Trace Run. The combined acid load being treated by the Carbondale II doser may be in the neighborhood of 300-400 tons per year.
Partners move forward with planning
In April of 2000 the Institute of Local Government Administration and Rural Development (ILGARD) at Ohio University led the partners in the production of a Non Point Source Management Plan for the Raccoon Creek Watershed. This plan was subsequently the first endorsed watershed management plan in the State of Ohio, when it received approval in June of 2003.
The recovery of Raccoon Creek
|It will likely take a decade for the effect of remediation on the water quality and biology of Raccoon Creek to result in pronounced changes in the health of the stream. 100 years of habitat and chemical degradation will not be turned around by one or two projects. But Partners do have reason to have faith in their actions. Initial biologic studies done by the USGS for the Little Raccoon Creek AMDAT, led to the conclusion that the stream has improved as the result of reclamation in the watershed from the 1980's and undergone substantial improvement since the 1950s. The collection of aquatic insects and fish, while not overly abundant in numbers, show a diversity that is poised for rebounding, water chemistry and aquatic habitat improve. The partners are focusing new AMD projects on those reaches of stream that are currently listed as not meeting their current use attainment and AMD is listed as the primary reason for impairment. Projects are located in Mulga Run, Middleton Run, and Flint Run basins located near Wellston, Ohio and will directly affect a reach of stream in Little Raccoon Creek that is currently listed as fair in terms of biologic community performance. Projects located in East Branch and Brushy Fork will reduce the pollution along a reach of Raccoon that is in poor condition and currently listed as Limited Resource Water - AMD. The Carbondale II Project will reduce pollution received by Hewett Fork, also a stream with a poorly performing biological community.|