Abandoned Mine Site Investigation & Reclamation
Former Coal Strip Mine
Wapello County, Iowa
Regulatory Agencies Involved
Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation, Mines and Minerals Bureau
U.S. Army Corps of Engineers
Trihydro was contracted with the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation, Mines and Minerals Bureau (Bureau) to develop reclamation plans for the abandoned mine land (AML) site identified as the Teach AML Reclamation Site. The site was a former coal strip mine area consisting of polluted water, a large water-inundated pit, vertical highwall, large spoil/overburden piles, and clogged streams.
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Trihydro performed a site investigation to document and assess the condition and hazards associated with site features. Feature mapping, aerial photos, LiDAR topographic mapping, and digital photos taken during the field investigation were compiled into a web-based project management portal that included a site-specific GIS application. Trihydro developed conceptual and preliminary reclamation plans for review by the Bureau and landowners. To aid in the development of the site plans, a natural resource survey and geotechnical investigation were performed to identify potential Waters of the US, wetland areas, water quality, depth of spoil material, and surface soil composition. This investigation included wetland delineations, geotechnical drilling, soil, and surface water sampling and analysis.
The final reclamation design for the site incorporated geomorphically stable design concepts (landform grading) using Carlson’s Natural Regrade software. This site is one of Iowa’s first AML sites to be designed completely using the landform grading approach. Trihydro prepared final construction plans and specifications, developed an engineer’s estimate, prepared bid documents, conducted the pre-bid meeting and tour, and assisted the Bureau with Bid Adjudication. The construction plans included the project location, landownership/permit boundaries, survey control, existing site features, proposed grading, proposed cross-sections and profiles, construction details, and a stormwater pollution prevention plan (SWPPP). Construction specifications included specifications for mobilization/demobilization, safety, utility locates, and construction documentation; earthwork; debris removal; drainage and erosion control; pit dewatering; soil amendments to address acidic materials; and revegetation.
Trihydro and the Bureau coordinated with landowners and the U.S. Army Corps of Engineers to develop a design that provided for the abatement of the polluted drainages from the area and eliminated recognized public safety and other environmental concerns, while mitigating disturbance to wetlands and Waters of the U.S.
Trihydro was then retained to provide construction management and perform onsite construction monitoring. Reclamation generated approximately 210,000 cubic yards of fill material, which was mainly used to fill the pit and construct ridges and valleys to create sub-watersheds within the site. Trihydro completed reclamation grading, acidic soil amendments, and revegetation.