Evaluating Transmission Line Clearing Methods for Minimizing Changes in Wetland Function

Julia W. Gaskin and Wade L. Nutter

Little information is available on the changes in wetland function due to transmission line clearing and construction. This type of information is critical to document minimal effects as may be required for laws regulating jurisdictional wetlands in the United States. The newly developed functional assessment methodology (the Hydrogeomorphic Approach or HGM) was used to evaluate and compare changes in wetland function in mineral flat wetlands in southeast Georgia due to various mechanized land clearing techniques. Functional assessments were conducted on wetlands before a proposed Right-of-Way (ROW) was cleared or at least 30 m off the existing ROW to provide reference data. Functional assessments were conducted in five mineral flat wetlands that were cleared by different mechanized techniques including clearing and grubbing of stumps by track crawlers, feller-buncher clearing and removal of trees with skidders (no stumps grubbed), and clearing and tree removal with low ground pressure (LGP) track crawlers. The HGM assessment indicated clearing the ROW by track crawlers and grubbing stumps created the greatest changes to wetland function. The least change in function was predicted for the wetland cleared with LGP track crawlers when the water table was at least 70 cm below the surface. The results of the HGM assessment suggests mineral flat wetlands in southeast Georgia can be cleared with minimal effects using LGP equipment under dry conditions; consequently, mitigation under Nationwide Permit 12 or an Individual 404 Permit should not be required.

Keywords: Jurisdictional wetlands, wetland function, hydrogeomorphic approach, transmission line construction, minimal effects