ABSTRACT
Transmission lines for electric current, pipelines for oil and natural gas, and routes for highways and railroads transect landscapes, cutting across geographic and geologic regions. Each of these modes of transmission or transport consists of a corridor having a width determined by requirements for construction and maintenance as well as by the size of the structure itself. The process of siting corridors is convoluted. Among considerations are (1) directness of routes and efficiency of transport, (2) economics of construction, (3) economic benefits or liabilities to communities along routes, (4) safety, and (5) potential environmental impacts. Unfortunately, site selection is commonly influenced by political and socio-economic factors and these are often the deciding elements rather than sound scientific and technical studies on feasibility.
Existing corridors cross every sizable karst area in the United States. Most were constructed years ago when the vulnerability of karst to environmental hazards and degradation was little known, studied, or understood. Consequently, there have been numerous cases where karst features have been damaged or outrightly destroyed and where water quality in karst has been reduced through contamination of surface streams and groundwater. The situation has improved through the years. The Federal government and most states now require site evaluations and statements or assessments of environmental impact during the planning stages. Outcrops of carbonate and other soluble rocks are now mapped and for some projects karst features such as caves and dolines are routinely inventoried. Disappointingly, some mapping and inventories along corridors are performed hastily, sporadically, or superficially, and miss many features.
A major karst area in southwestern Virginia and southeastern West Virginia is currently under simultaneous consideration for routing of a 765-kilovolt power transmission line and several highways, including a major new interstate. For each project, several proposed alternative corridors cross the New River Valley drainage basin, including areas of karst in Montgomery, Craig, Giles, and Bland counties in Virginia and Monroe County in West Virginia. Karst has been mapped in the case of the power lines, albeit the level of detail is wanting. Karst has not been seriously considered during site evaluation for the proposed highways. Power-line and highway corridors coincide in some areas and not in others. Composite maps compiled by citizens action groups and this author indicate potentially threatening environmental problems in the region.
