OPINION: Gravel Pit Wars…Part Two

Read Part One…

A Land Use Change Application for a permit to surface mine in an area zoned rural inevitably pits neighbor against neighbor, especially if the rural area has been developed with upscale subdivisions. Chaffee County is no exception, and the pit war is on.

The ACA/Holman Major Impact Review for the RB gravel pit is posted on line. At this date there are 24 documents associated with this pending land use application. You can view these documents by going to this county page, and scrolling down to the Pending Land Use Applications.

I’ve read through these documents. My observation is that in some instances there’s wiggle room built into the application and reports, and there’s some out and out claims that can not be substantiated. For example:

The change in land use (from grazing to surface mining) shall not cause any impacts to the surrounding area.

Opacity from the pit is limited to 20% so it will not cause any more dust than the current vacant land.

Here’s an example of what 20% opacity looks like, comparatively, in the case of smoke.

However, according to the Example of ACA Pit Permit with Opacity report in the ACA/Holman Major Impact Review, there are brief periods (6 minutes every 60 minutes) during certain phases of construction that allow for 30% opacity.

The following statements (some paraphrased) were taken from the Major Impact Review documents, and provide more detail about the proposed RB gravel pit:

There is no intention to use explosives on this property.

Equipment used on site will include a loader, dozer, blade, excavator and water truck.  Processing equipment will include a generator, jaw crusher, cone crusher, conveyor belting and JCI screen.

Crushing activities will take place for approximately one month during the winter… the material that is being crushed has a high plasticity index and will have a high moisture content, therefore, it will only emit minimal dust or particulates…. there will be no water or chemicals used in this processing…

There will be no concrete plant and no need for equipment washing. There is also no asphalt plant planned for permitted area.

The estimated average truck traffic for the RB pit is 550 round-trips per year, annually occurring from May 1 through September 30. That is an average of 10 transport trucks per weekday, spread relatively evenly between the hours of 8 a.m. and 5 p.m. Variability in daily trip generation is likely due to fluctuating demand. Transport truck trips will rarely occur outside of these hours.  The transport  trucks will proceed from the pit to CR 140, and then half split off at CR 250 to Highway 50, and half continue on CR 140 to Highway 285.

Two sharp curves on CR 140 will need to be widened so that semi-trucks don’t encroach on coming traffic.  Applicant will bear the cost.

Then there is the somewhat bizarre Holman/ACA Major Impact Review document “MSHA Guide for Noise Control” available on the Chaffee County website.

Instead of linking to a MSHA (Mine Safety and Health Administration) document, it links to Decibel Trivia and a decibel comparison chart posted by Hearing Education and Risk for Rockers. My hunch is that they are talking Led Zepplin, not mining. Applicant ACA Products did scribble some MSHA noise exposure levels on the Rocker info sheet. Acceptable MSHA levels are less than a piano fortissimo, which is rated at 92-95 decibels. Stone crushers aren’t rated on the Decibel Trivia chart, but my research indicates that they rate over 90 decibels at close proximity.

Stone crusher or piano fortissimo? Let me think about that. Too much of either would wear on my ear drums after a while.

I’d like to revisit two claims made in the Major Impact Review Application:

The change in land use (from grazing to surface mining) shall not cause any impacts to the surrounding area.

Opacity from the pit is limited to 20% so it will not cause any more dust than the current vacant land.

These claims, stated in absolute terms, leave me speechless, and give me pause as to how credible other aspects of the application and associated documents are.

It’s a fact that surface mining of aggregates is a source of increased dust and noise. That is why surface mining noise levels and dust levels are regulated. The question is, how much will dust and noise increase, and what distances will be affected? We know how windy it can be. The wind generally blows from the west, which would be toward the CR 140 corridor. Sound travels uphill and is also affected by the wind.

The answer is, we don’t know. But we do know there will be some level of impact.

I found the San Luis Obispo County (CA) Noise Analysis for a proposed rock quarry to be an informative approach to noise analysis.

Here’s some excerpts from this 35-page report on the existing acoustic environmental setting of the proposed Las Pilitas Rock Quarry project:

Something resembling the following text is standard for many environmental impact reports:

1 dBA increase in sound level is perceived as a barely audible increase by most people and is usually not judged to be significant.

3 dBA increase in sound level, is clearly perceived and is a clearly audible increase, considered to be a “significant” impact under some planning standards and threshold evaluations.

10 dBA increase in sound level, is perceived as a “doubling” of sound levels.

There is evidence that the annoyance associated with changes in sound exposure is related to the current level of ambient noise.

Transitory atmospheric effects; wind, humidity and temperature and temperature gradients affect sound transmission and these become increasingly significant with distance. Noise forecasting models developed by the US military include not just a single estimate of noise levels but an estimate of the range of variability around an average. This study does not include estimates of these variations but it is certain that there will be variations and that these will increase with distance from the source.

There is also a question of how to best characterize noise from thirty years of quarrying activity since the location of sources changes over time and the topography changes too.

While rock crushing involves use of very heavy equipment the sound character is not “heavy” in its low frequency content. It is a mid-range clicking of rock against rock. The low frequency content of operations comes with the diesel trucks and excavators. The higher register sounds are the OSHA warning beepers with their intermittent tones in the 1000 – 3000 Hz range.

On occasion, sounds from quarry operations can be clearly distinguished from the background; a distant backup beeper, a thump when a load of stone is dropped into an empty truck bed or the run-up of a diesel engine. These events have a marginal effect on noise level as measured by a sound level meter but they are a continuing reminder of the ongoing excavation activity.

There is no technological way to make distinctions between sounds that are appropriate or inappropriate for rural settings. It can only be noted that there will be some level of community annoyance whenever the sounds of quarry operations are audible and that sounds will be audible even when they are within the limits set by County standards.

There is a contrary argument to the FICON and FTA criteria. This relates to the value people place on maintaining the “natural soundscape”. Studies by the National Park Service had indicated that people that come to enjoy an outdoor experience are quite bothered by even the smallest intrusion of man made sound. As noted, people can detect individual specific sound sources even when they are less than background levels. The noted psychoacoustician Hugo Fastel has commented on the fact that, “people can be bothered by sounds if they hear them.”

Read Part Three…

Cynda Green

Cynda Green is an investigative reporter who enjoys writing about various and sundry topics, least of which is politics. But someone has to do it. Contact: cyndagreen@gmail.com