While Acid Mine Drainage (AMD) isn’t making headlines like it used to do in the 1980s, it is still affecting streams in Jefferson and Clarion counties.
Groups such as the Mill Creek Coalition have been working to minimize AMD’s impact and bring life back to area streams. The Coalition has been working in the Mill Creek Watershed, which traverses both counties, for a good number of years, addressing about two dozen sites.
The group’s first site on Mill Creek was in 1990 at Howe Bridge Road, in the upper reaches of the watershed. A passive treatment system was placed and has been successful in improving the water there and downstream. This standard type of system includes “locating a discrete AMD source and guiding it into a large covered pile of high quality limestone (i.e., nearly all calcium carbonate) where alkalinity is generated to address the acidity of the AMD. If the limestone was left uncovered, the metals in the AMD would react with the oxygen in the air, then cover over the limestone, inhibiting its ability to dissolve and generate alkalinity. The increase in alkalinity should neutralize all the acidity within the AMD and even perhaps provide excess alkalinity, which after entering the stream can address potential acidity problems there,” according to a news release from Peter Dalby, the president of the Mill Creek Coalition.
The news release explained that “the alkalinity creates the correct type of aquatic environment that when the treated water is exposed to the air or a well aerated stream, the metals (iron and perhaps other minerals such as manganese and aluminum) are oxidized to a particulate form. Adjacent to the underground limestone bed of a passive treatment system is usually a pond or two where much of the metal particulates settle to the bottom, and thus don’t enter into the receiving stream.”
While these sites have been successful, it is time to upgrade them by replacing the original limestone. They stone is “still working well,” Dalby noted, adding that it’s about 25 years that the system has been in place. Since the systems usually have a lifespan of 25-30 years, these systems – while still working – are not as efficient as they once were. Replacing the limestone will address that efficiency. It will be the highest grade of limestone available, Dalby noted, adding that the old stone will be utilized elsewhere.
Three other sites are also scheduled to be upgraded as well along Mill Creek. Two grants from the state Department of Environmental Protection worth about $400,000 were approved for this year to upgrade the two passive water systems.
While much as been done to improve the quality of the Mill Creek, Dalby said, the coalition noted that despite its hard work the last several miles of the creek is still being impacted by acid mine drainage. The culprits are Jones Run and Douglas Run but parts of the watershed, according to Dalby, “do not lend themselves to the standard ways of treating Acid Mine Drainage (AMD).”
These two runs flow together and into Mill Creek in Clarion County, about five miles upstream from where Mill Creek flows into the Clarion River.
“Parts of this approximately 11 square mile divided tributary do not allow the above pattern of treatment. Some of the AMD seeps out of the ground over a generalized area, not as one discrete flow, as it enters into a stream. In addition, even a discrete flow might be located where the topography is too steep or irregular to provide sufficient space for a standard passive treatment system,” the news release noted.
“When Jones/Douglass empties into Mill Creek, it only contributes about 10 percent of the flow, but is responsible for approximately 60 percent of the acidity, iron, and manganese, and 80 percent of the aluminum to Mill Creek,” Dalby noted. “The result is that the final five miles of Mill Creek is largely uninhabitable for trout and other fishes.”
The news release noted that in streams of this nature “manufactured and somewhat expensive saturated lime solutions or agricultural lime are fed directly into the stream. However, in both cases, a mixing plant is necessary and frequently a plant operator to ensure that the proper amount of these materials is moving at the correct rate into the stream. As a result, there is a larger cost associated with these methods. To circumvent these issues, researchers, watershed groups, and the DEP have investigated the use of limestone of various sizes and purity placed directly into a stream.
“The result from these studies demonstrates that high grade limestone (i.e., around 95+ percent purity) of calcium carbonate is necessary. In addition, the particle size of this limestone must be small: a mixture of powder, sand, and grit-sized material (chips) is necessary so that the dissolution of these limestone fines will provide the appropriate alkalinity to the AMD affected stream. This sized material is considered a waste product in the limestone mining industry, so therefore the cost is much less than larger sized material. The major expense is trucking costs. To determine the correct amount of limestone fines necessary to address the AMD affected stream for a substantial period of time, such as a year, investigators take in consideration the chemistry of the stream and the stream’s watershed area.
“Another important criterion is that the stream must have sufficient velocity in its flow and a steep stream gradient to disperse the limestone fines over a considerable length of the stream. The number of high water events during the year assist in the dispersal process.”
In this study, one of the sub-tributaries referred to as the West Jones Run was selected for the placement of the limestone fines. The Douglass Run component of Jones/Douglass has AMD problems that can be addressed by the traditional passive treatment systems. Of the two forks of Jones Run, the west branch, located in Clarion Township, is the worst and is easily accessible. Roughly the first mile of this stream flows through a low gradient agricultural and wooded area and old mining lands. Where the stream crosses Carney Road via a four foot diameter culvert, the gradient for the final one mile journey consists of a mix of fast flowing riffles and pools to meet the more gently flowing south branch. The flow at the culvert can be less than 100 gpm at low flows to 300-400 gpms or more during rainy events.
On October 12, about 20 tons of limestone fines was brought to the Carney Road site by triaxle and directly placed into the stream. This was the first of 180 tons that has been placed into the stream to address the acid waters for the first year of treatment. While 180 tons of limestone is a lot, the amount needed the second year of treatment is expected to be about 60 tons, or three filled triaxles. Dalby noted that this is a long-term project. As the stream dissolves the limestone and storm events push the material further downstream, smaller dump-sized trucks will add more material over the project, he said.
Dalby explained that the “Carney Road tributary typically has a pH of 4.5 or lower, more than 100 times more acidic than neutrality. Adding the limestone fines causes the pH to quickly rise to 5.5-6.5, but as the water courses through the lower parts of the stream, the alkalinity drops and the pH lowers. This emphasizes the importance of having the limestone fines distributed throughout the tributary to maintain the desired pH.”
Dalby noted that the water would be sampled along the stream towards the Clarion River to see if the new project is working. Involved in the study are members of the Mill Creek Coalition and environmental students at Clarion University. “If the results of the study prove that indeed this is a successful design for Jones Run, a long term commitment will occur with a possible addition of other treatment sites within the Jones/Douglass subwatershed.”
Dalby noted that the project has been financed through several small grants. “Financial support of a $2,000 mini-grant for this project was provided by the Dominion Energy Charitable Foundation and the grant program was administered by the Western Pennsylvania Conservancy. The WPC also provided a consultant prior to the development of the proposal to Dominion Energy. Two matching mini-grants of $2,000 were also critical to meeting the financial needs for the project. One was from the Foundation for PA Watersheds, and the other was from The Pennsylvania Wildlife Federation, the educational arm of the Pennsylvania Federation of Sportsmen’s Clubs.
In the almost 30 years the coalition has been working to clean up the AMD along Mill Creek, about $11-12 million has been invested into the 60-mile watershed to address the AMD problems that come from the days of strip mining coal in the area, before new methods of environmental protection were developed. The money has come from conservation districts from both counties, local sources, foundations, the DEP and federal agencies. Because of these efforts and the resulting water quality improvement, the Pennsylvania Fish and Boat Commission are stocking more Brook trout in the watershed. In fact the number of stocked trout has doubled to about 4,500.