Post tracks noise zones; terrain, weather key factors
March 7, 2012
By VINCE LITTLE
Fort Benning's newest range opened Thursday along the installation's northern border, bringing another layer of noise management for post planners to contend with. But they said an effective strategy already is in place to monitor range activity and limit any impact on local homes, schools and churches.
Soldiers are set to use Oscar Range for small-arms training with rifles, pistols and .50-caliber machine guns. Meanwhile, Hastings Range remains under construction and slated for completion July 1. It will accommodate tank, howitzer and cannon fire.
The Environmental Management Division monitors three noise zones across Fort Benning, said Robert Thomas, geospatial program manager for the Directorate of Public Works. Terrain and weather are the biggest dynamics to consider in the noise-mitigation measures Fort Benning takes to keep sound inside installation borders.
He said training planners use computer modeling noise maps to show where the environment is incompatible with noise-sensitive land uses. Automated remote sensors provide usable data that further beefs up noise-reduction efforts.
"We're trying to be good neighbors as best we can," he said.
"Weather makes noise and the sound wave bounce and carry, so the zones can shift, depending on various factors. It also depends on weaponry as far as what noise signatures are going to look like. But weather and terrain, more than anything, will influence how far noise is going to travel."
Decibels less than 65 fall in Noise Zone I, which is normally acceptable for most noise-sensitive land uses, Thomas said. Noise Zone II contains sound signatures between 65 and 75 decibels, while Noise Zone III is the most severe with decibels exceeding 75.
Fort Benning is home to 95 training ranges, and noise zones are determined by the type of large or small-arms fire conducted on each, said Ellis Leeder, the post's noise and environmental management system program manager.
"Large-caliber noise is hard to stop because it has a different impulse," he said.
"The sound wave coming at a barrier will find ways to flow around it. … Under certain weather conditions, sound travels well. A blast that may rattle windows on an overcast day might not even be heard on a clear day."
Thomas said Fort Benning's terrain level rises from 220 feet along the Chattahoochee River in the southern portion of the installation to 700 feet in the northern part.
The elevation change -- combined with the hills, trees and buildings that sit in between -- also affects noise dispersion. Flatter land adds distance to sound, he said.
Reforestation and planting more trees on major tracts of land across post is a small percentage of noise abatement but contributes to the aggregate, Leeder said. The hilly terrain and timberland around the Malone ranges is a particularly effective natural noise buffer.
He said the majority of training ranges are located on Fort Benning's interior, with tubes and barrel locations pointing inward -- whether they're designed for large- or small-caliber weapons.
Leeder said all the ranges have been evaluated for noise considerations, accounting for terrain, tube and barrel locations, and firing points.
The installation operational noise management plan outlines a strategy that includes education, complaint management, noise and vibration mitigation, and noise-abatement procedures.
Leeder said Fort Benning's final environmental impact statement released in 2009 highlights all expansion and construction plans, which covers training ranges.
Public input was encouraged during the draft phase of the EIS.
"That helps us realistically address issues and plan," he said. "Keeping our local communities informed about our missions here is very important."