Thursday, May 16, 2013
The words Esto Perpetua engraved in the capstone above the entrance to Grotto Spring in Eureka Springs represent the belief at the time that water from this spring would flow forth forever. But the spring that once produced large amounts of water was disrupted, possibly by nearby road construction, and now only a trickle flows through this once productive spring.
“Just the smallest digging can potentially disturb a spring in karst terrain because it is so fragile,” Barbara Harmony, director of the National Water Center, said. “I am very concerned about the proposals by SWEPCO to put a high transmission power line through our fragile karst terrain. The extent of the drilling they propose to put in their transmission towers is very extreme. They could hit an underground stream that leads to a spring, and then that spring would stop flowing. You can easily lose a spring by earth moving or blasting.”
Karst terrain refers to limestone formations below ground with channels that have been tunneled out by erosion. It results in an area rich with springs, caves and sinkholes. Harmony is concerned that both springs and caves could be destroyed, and that SWEPCO won’t be able to tell from the surface how to avoid these special features.
Karst aquifers and caves are underground and out of sight, but certainly their water flow and quality are impacted by deforestation, excavation and fill, and herbicides. And it is in this underground world where rare and endangered cave species dwell.
“I just don’t think they realize how fragile the karst is, and that there is no filtration with karst,” Harmony said.
SWEPCO spokesman Peter Main said, “Karst features will be an important factor in the project design and construction. For the approved route, structure locations will be selected after a careful survey that will specifically identify and avoid sinkholes or other karst features. Throughout the construction project, care will be taken to avoid impacts in karst areas.
“Our transmission project team and the engineering and environmental consulting firm that prepared our environmental impact study are experienced in working in Northwest Arkansas. Our consulting firm’s experience with karst topography includes northwest Arkansas and other parts of the country.”
Pat Costner, a local retired scientist who is an internationally recognized authority on dioxins, has been investigating the process involved in setting 150-foot-tall power line poles.
“It's pretty horrendous, a process that causes extensive damage both short- and long-term,” Costner said. “It seems certain that many caves and springs in our area will be destroyed. During the process, our fragile karst terrain will be like a war zone.”
Costner, who works with the citizen group, Save The Ozarks, said the project would involve drilling holes for more than 300 single-pole towers that are 10 to 15 stories in height.
“For each pole, truck-mounted augers or tracked vehicles equipped with power augers would drill boreholes 7-10 feet in diameter and 30-40 feet deep, and site leveling would require bulldozers or front-end loaders,” said Costner, whose home property north of Eureka Springs is on the path of the preferred SWEPCO routes. “This process can be expected to disturb about 12,500 square feet on the surface and cause extensive damage to sub-surface features such as caves, underground streams and springs. In some cases, reinforced concrete foundations may be necessary, requiring additional special trucks and equipment. The poles will be put in place by helicopters or heavy ground equipment. Perpetual access for trucks and other heavy equipment will be required for on-going maintenance of the line, poles and corridor.”
Another concern is the steep terrain. Combined with the karst geology, the terrain presents both hazards to actual destruction/construction activities and environmental problems during and forever after in the corridor. Experts are concerned the hollows are the uppermost parts of the watershed, and are particularly susceptible to erosion, blockage of springs and sedimentation.
Dr. Andrea J. Radwell, research assistant professor with the Department of Biological Sciences, University of Arkansas, Fayetteville, said major concerns with regard to construction is the production of fine sediments that are known to impact benthic organisms, those found in the interstices of gravel bed streams.
“Deposition of fine sediment has been shown to decrease both abundance and diversity of aquatic insect larvae and other small organisms critical to development of fish,” Radwell said. “I expect that the power company is prepared to say they will take every precaution to prevent sedimentation, but a project of that magnitude will inevitably produce sediment during construction since it will involve the removal of trees from a large swath of land.”
Radwell said herbicides used to maintain this treeless landscape would work their way through the karst and enter streams and rivers.
“While there are some studies that suggest at least some herbicides are not harmful to fauna, there are studies that have documented the ‘inert’ ingredients used to broadcast herbicides are harmful to invertebrates,” she said. “Even though concentrations of herbicides may be very low when they enter waterways, application will be in perpetuity.”
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