During hydraulic fracturing (commonly known as fracking), pump trucks produce significant low frequency noise levels. For this reason, compliance with the COGCC noise limits is usually most difficult during fracking. The COGCC noise limits are designed to control two measures of noise. These are:
The noise levels that must be achieved vary by land use. The A-weighted noise level below must be achieved 350 feet from the facility (or the property line, if a greater distance), or 25 feet from structures closer than 350 feet. Sound levels must be measured for a period of at least 15 minutes and averaged. For permanent installations, the noise levels to be achieved are as follows:
The C-weighted level must not exceed 65 dBC when measured 25 feet from the nearest structure. Short term operations, such as drilling, fracking and workover operations are subject to the compliance with the light industrial zone standards.
Achieving compliance with the A-weighted standards is usually relatively easy, and exceedances of these limits are rare. Unfortunately, the same cannot be said of the C-weighted limits. Low frequency noise travels around, and through, noise barriers with relative ease. Low frequency noise is also not as quickly attenuated with distance traveled in the atmosphere compared to high frequency sounds. These effects combine to make this noise a serious challenge to deal with. Judging from the noise complaints on projects we’ve been involved with, this low frequency tends to be the problem residents are most concerned with, especially during drilling and fracking.