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11.09.2006 12:00AM
Impact of Towers on Birds May Affect Tower Lighting Specifications
At last week's open commission meeting, the FCC adopted a Notice of Propose Rulemaking in the Matter of Effects of Communications Towers on Migratory Birds. In the NPRM, the FCC seeks comment "on the extent of any effect of communications towers on migratory birds and whether any such effect warrants regulations specifically designed to protect migratory birds."

The NPRM summarizes studies on bird deaths due to collisions with towers and lists some of the actions it may take to protect migratory birds. At the top of the list is tower lighting--studies showed more than three times as many bird deaths at 380-480 foot towers using red steady lights than at towers at the same heights with other lighting configurations.

"We tentatively conclude that for any newly constructed or modified communications tower that must meet lighting specifications under Part 17 of the commission's rules, medium intensity white strobe lights for nighttime conspicuity is to be considered the preferred system over red obstruction lighting systems to the maximum extent possible without compromising aircraft navigation safety," the commission said.

Studies showed there were more avian collisions with guyed towers than self-supporting towers. In considering possible restrictions on guyed towers, the NPRM recognizes this could cause other problems. For example, if a greater number of smaller self-supporting towers or a self-supporting tower with a larger physical footprint was required to provide the same coverage as one guyed tower, would this result in "additional adverse impact on environmental matters that do not pertain to migratory birds, such as historic properties, wetlands, or endangered species?" The FCC asked for help on deciding these issues.

A somewhat simpler option would be to adopt requirements relating to marking guy wires, but, as the NPRM notes, there are problems with that option because from an engineering perspective, wire marking devices that physically enlarge the wire, such as those used on power lines, "commonly act as wind-catching objects and may increase the risk of wire breaks due to the line tension, vibration and stress loads."

Reduced tower height minimizes the impact of the tower on migratory birds. As with restrictions on guyed towers, reduced tower heights might lead to a greater number of towers. It could also hinder deployment of public safety communications services. In its NPRM the commission asked whether it should "regulate towers over 200 feet in order to minimize the use of lights."

The potential solutions are not as clear when it comes to tower location. Some commented that towers "should not be sited in certain locations such as migratory bird habitats or in migration corridors on ridgelines."

It was reported that most collisions occur on nights with low visibility conditions, but there had been no similar finding with regard to the effect that locating towers on ridges or in wetlands might have on avian mortality.

The FCC asked if it should adopt additional requirements to promote tower collocation. One possible requirement, the NPRM states, would be to require certification that "collocation opportunities are unavailable and/or describe collocation alternatives that the licensee explored."

Many applications for new communications facilities require certification that the facility would not be a significant environmental action as defined by Section 1.1307(a) of the FCC rules or, if it is a significant action, preparation of an environmental assessment is required. Some responded to the Notice of Inquiry that "considering the evidence of mass bird mortalities at communications towers, the commission should also expressly require an EA (environmental assessment) for proposed facilities that would have potential effects on migratory birds." In the NPRM, the FCC said that its existing rules provide for consideration of factors not specifically identified in Section 1.1307(a), including the facility's effect on migratory birds, "to the extent the commission independently determines that there may be a significant environment effect in a particular case." The NPRM seeks comment on whether the FCC should adopt an EA addressing this effect for all new tower construction.

Finally, the NPRM sought comment "on whether there are other possible substantive or procedural measures the commission could take to minimize migratory bird collisions that are not discussed above."

Many broadcasters needing tall towers or high elevation locations to provide a reliable signal over a wide area would certainly be affected by any new rules protecting migratory birds. For more information, read the Notice of Propose Rulemaking in the Matter of Effects of Communications Towers on Migratory Birds.


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