The Pierce Run AMD treatment project will entail construction of passive AMD treatment systems at two sites: the Oreton Seep location in an unnamed tributary to Pierce Run and a wetland enhancement in Pierce Run near Radcliff.
The Oreton Seep is located in the former town of Oreton along SR 160 in Vinton County and is the most consistent and largest acid loader within the Pierce Run watershed. The source of the seep is a 116 acre underground coal mine (Clarion 4a seam) which was abandoned by the Oreton Mining Company in October of 1924. The seep appears to originate from a collapsed abandoned entry in an upper valley of a small unnamed tributary. The property is owned by the Scioto Land Company and an active surface mine is in operation by the Waterloo Coal Company upstream (South and West) of the Oreton Seep. A permitted sediment storage pond for the active mine is located approximately 200 ft upstream of the Oreton Seep. The Oreton seep discharges into a shallow wetland where it mixes with the upstream pond water for several hundred feet. Flow then enters a channel through a mine spoil pile from pre-law contour surface mining which blocks the majority of the valley. The stream channel descends approximately 15 ft into the lower valley into another wetland (approximately 3.5 acres) with large amounts of iron (red/orange) and aluminum (white) precipitate 2 to 3 feet deep in places. The channel diffuses through the wetland but eventually enters into Pierce Run through one overflow channel during low flow and three overflow channels during higher flows.
The existing wetland area in Pierce Run is located at RM 1.7 just upstream of the town of Radcliff in Vinton County. The wetland appears to have been created by beaver activity in the stream channel and the adjoining low lying floodplain. Contour surface mining also took place in this vicinity on the southern hillside and floodplain and may have also led to the current channel condition, which is a braided channel. Approximately 20 acres are available for wetland enhancement at the site. The wetland site contains no buildings or roads and is entirely owned by the Scioto Land Company.
The Conceptual Design
The conceptual design is to add alkalinity at the Oreton Seep with a steel slag leach bed (SLB), and to enhance the existing wetland in the mainstem of Pierce Run, downstream of Oreton, near the town of Radcliff at river mile 1.7. This wetland will be used to capture and store precipitated metals (iron and aluminum) to keep them from entering the mainstem of Raccoon Creek. Data in Pierce Run shows that a high level of dilution occurs in Pierce Run due to many non-AMD impacted tributaries between Oreton and Radcliff. Thus the treatment design will be to only treat the amount of acid necessary to produce consistent year round net-alkaline water at the proposed Radcliff wetland in Pierce Run and thus into Raccoon Creek. The overall result of the project will be net-alkaline, low dissolved metal water discharging into Raccoon Creek.
The proposed treatment at the Oreton Seep will consist of passive treatment via a steel slag leach bed. Fresh water from an existing clean-water tributary downstream of the Oreton Seep will be used to run the steel slag leach bed. Water samples from the stream showed water quality (pH 6.5 and low metals) sufficient for use in a steel slag leach bed. A steel slag leach bed will be created downstream of the tributary and steel slag will be placed in the bed to a depth of 4 feet with 1 – 2 feet of water over the slag. Plumbing in the leach bed will ensure adequate reaction time in the bed. Water from the steel slag leach bed (proven to generate highly alkaline water between 500 – 2,000 mg/l) will be discharged through a pipe to instantly mix with acid waters in the mainstem of Pierce Run.
Radcliff Wetland Enhancement - Wetland portion of the project was postponed due to increased flooding concerns.
The wetland enhancement project located in Pierce Run near Radcliff would consist of installing limestone dikes across the valley to create a shallow water / wetland environment. A series of 4 limestone dikes, approximately 500 - 600 feet in length, will be placed perpendicular to the flow in Pierce Run (see image) to slow the flow of water and create a shallow wetland type habitat for precipitated metal storage. The limestone will be placed until a sufficient elevation is achieved to create a consistent shallow water environment throughout the site. Surveying will be done on the wetland to determine the maximum height of the wetland dikes to accommodate flood water storage in the valley and not affect nearby buildings or residences. The treatment purpose of the 20 acre wetland is to collect and store metal precipitates from the Oreton Seep project site and from other small AMD sources in the basin. Furthermore, the wetland will allow for higher residence time and better mixing of alkaline and acidic waters to ensure further neutralization and precipitation.