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WETLANDS CONSTRUCTION Wetlands Mitigation Approximately 3.1 acres of wetlands mitigation were created and enhanced on a design/build basis at a reclaimed mine area site located near Glenville, Gilmer County, West Virginia. Freshwater wetlands totaling 2.5 acres were created and 0.6 acres of existing onsite seasonally saturated forested and scrub-shrub wetlands were enhanced.
The Louis Berger Company served as the engineer for the design/build project. The advantages of the design/build process are primarily that the project can be more expeditiously implemented and allows the design to be verified or modified in response to observations made onsite during construction of a dynamic ecosystem. Geo-Con was chosen by Louis Berger Company to construct this wetland based on Geo-Con's wetland experience and the ability to work with Louis Berger Company on a design/build basis.
All of the wetlands areas lie within a reclaimed mine area and are characterized as palustrine wetlands functioning primarily to receive rain water and surface water runoff from elevated areas and to retain floodwaters during periods of heavy rainfall. The wetland design allows this water to be retained in the ponded areas that were constructed by Geo-Con and then drain offsite into Duck Run.
Considerations that affected the design included location of existing gas well lines, underground pipelines, the stability of the slopes surrounding the mitigation area, the stability of the site under high energy hydraulic loads during major storms and erosion control requirements.
The project included excavating existing soil in the wetland area to an elevation two feet below the proposed finish elevation. The excavated topsoil was saved for reuse. The balance of the material was sorted through to remove all large rocks and debris. The material was then placed in the area to be constructed and compacted to hold the water. Berms were constructed around the perimeter of the wetland area. The topsoil was then replaced. There was also excavation required for channels, rip-rap stabilization across and an outlet structure at the site. The excess material that was excavated was placed in low-lying areas of the site to direct offsite upland water onto the site. To prevent erosion of the areas, existing rock was used to channel the water. The newer-type structure was placed at the end of the site to control the water surface elevation within the wetland mitigation area.
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