Evaluating the Effects of the Blennerhassett Island Bridge Crossing (Ohio River) on Soil, Vegetation, and Wildlife.

摘要

Corridor D was one of the original 23 highway corridors selected by the Appalachian Highway Development System in 1965 and stretches from Bridgeport, West Virginia to Cincinnati, Ohio. The last piece of Corridor D to be completed was the Blennerhassett Island Bridge which crosses over the Ohio River and Blennerhassett Island near Parkersburg, West Virginia and Belpre, Ohio. The Blennerhassett Island Bridge is a tied-arch style bridge about 1,220 m in length and 24 m above the ground and water surface. Construction of the bridge began in March 2005 and the bridge was opened to the public in June 2008. This study examined environmental impacts of the Blennerhassett Island Bridge to comply with mitigation requirements for the West Virginia Department of Transportation, Division of Highways in accordinance with the Blennerhassett Island Bridge Final Environmental Impact Statement. From October 2007 through July 2009, I researched the impacts of the Blennerhassett Island Bridge upon vegetation, soil, and the following wildlife groups: waterbirds, songbirds, anurans, turtles, small mammals, and furbearers. Comparisons were made to two other islands (Buckley Island [bridge crossing present for about 45 years] and Muskingum Island [no bridge crossing]), to three distances from the bridge (0 [under], 100, and 300 m), and to pre-construction data collected during the 1985--1987 and 1998--2000 time periods.;Over the course of this study, 170 plant, 19 waterbird, 60 songbird, 7 anuran, 5 turtle, 9 small mammal, and 4 furbearer species were detected among the three islands. Also, 19 soil variables were analyzed. Vegetative communities were different under the bridge compared to other sampling distances and pre-construction data. Vegetative communities were composed of species from the seed mixture used for reclamation, exotic and invasive species, and disturbance tolerant species with low herbaceous cover and minimal woody plants. Thirteen soil variables (phosphorus, bray II phosphorus, potassium, sodium, calcium, manganese, soluble sulfur, zinc, aluminum, copper, total exchange capacity, organic matter, and estimated nitrogen released) had altered levels under the Blennerhassett Island Bridge and/or Buckley Island Bridge. Great blue heron (Ardea herodias) abundances were lower at islands with bridges. Songbird abundances were lower under the bridge and species composition differed compared to other distances with generalist species present under the bridge. Carolina chickadee (Poecile carolinensis), Carolina wren (Thryothorus ludovicianus), and common yellowthroat (Geothlypis trichas) abundances were lower under the bridge and rock pigeon (Columba livia), cliff swallow ( Petrochelidon pyrrhonota), and European starling (Sturnus vulgaris) abundances were highest under bridges. Overall small mammal abundance, richness, and diversity were lower under the new bridge compared to other distances and abundances of Peromyscus spp. were lower under the new bridge. Raccoon (Procyon lotor) occurrences were lower under the new bridge compared to other sites and distances. Anurans and turtles showed no differences among islands and distances.;The Blennerhassett Island Bridge was found to have some impacts to vegetation, soil, and wildlife. These impacts, however, are minor in scale and are mostly limited to the area directly under the bridge and did not impact large portions of Blennerhassett Island or the adjacent mainlands. Some of these impacts under the bridge include: altered soil chemistry, altered amount and type of vegetation, attraction of exotic and non-native vegetation, lower abundances and different composition of songbirds, attraction of urbanized songbird species, lower abundance, richness, and diversity of small mammals, and changes and alteration in habitat. I recommend that all possible care should be taken during future bridge construction to minimize environmental impacts to vegetation, soil, and wildlife and to restore the impacted land back to previous conditions. I also suggest that vegetation, soil, songbirds, and small mammals should continually be monitored at the Blennerhassett Island site to determine if these impacts found in this study are temporary or permanent.