Letter to the Editor: Mine opposition part 2

Editor’s note: This is the second in a three-part series by Portola resident Valari Simison, whose residence is 60 feet south and 200 feet west of the mine property under consideration for expansion. 

In my previous “Letter to the Editor,” the hazardous and harmful effects of this proposed Portola industrial mine in a residential area were discussed. Depletion of our aquifer and water contamination were highlighted along with air quality degradation. There are six more concerns on our petition to be addressed. This second installment will examine the issues of noise and light pollution.

Noise is the third concern relating to this possible “sand/aggregate” mine operation. Noise is also an issue in every General Plan for cities and counties. It is a contention that repeatedly comes up in lawsuits where mine operations and residential lifestyles meet. Earthmoving equipment–bulldozers, scrapers, excavators–are loud. Rock crushers are loud. Blasting is loud. Semi-truck end dumps transporting material are loud. How much equipment will be used to create enough material to fill end-dumps to reach the 700 round trips daily that this permit requires. This information is not forthcoming in the permit. Since noise is loud, travels, and affects people’s health, it is important to understand how sound waves that create noise operate. Noise is measured in decibels. A decibel is a logarithmic unit rather than a linear one. For every 3 dB increase, the sound doubles in intensity. That is:

  • 1 dB difference is not noticeable.
  • 2 dB difference is slightly obvious.
  • 3 dB difference is pronounced.
  • 6 dB difference is twice as loud.
  • 10 dB difference is very significant.

The Occupational Safety and Health Administration (OHSA) has addressed the issue ofsound intensity and sustained exposure relating to the workplace. Studies have proven that just a few decibels increase shortens one’s time of exposure before hearing damage occurs. For every 3 dB over 85 dBA, the permissible exposure before possible hearing damage occurs is cut in half. Recovery time for exposure to 85 dBA is a minimum of 10 hours.


This information highlights the importance of not only sound intensity, but exposure as well. For example, if the train whistle blows in town and stops. It is an entirely different issue if that same whistle blows nonstop for an hour…or 12 hours. Sustained noise at even lower decibels is annoying as well as damaging. Thus large numbers of earthmoving equipment along with blasting and rock crushing operations 12 hours a day and even listed in permit as possible 24 hours a day would fit this definition of annoying with damaging health consequences–mental, emotional, and physical.

Each piece of equipment and operation requested in this permit has a decibel level:

  • Bulldozer (newer models) 93-96
  • Earthmover 90-96
  • Front End Loader 86-94
  • Backhoe 84-93
  • Rock Crushing 75-90
  • Blasting 94-98
  • Industrial Generators 75 to 120 (older models) 107

Since there is no listing in the permit regarding numbers for large equipment, it is hard to estimate what decibel levels combined operations would reach. However, since decibels are a logarithmic unit, the units are not simply added together. For example, 90 dB + 90 dB do not equal 180 dB. Instead through a mathematical equation, the answer would be 93 dB. Additionally adding another 90 dB rating would bring the total to 96 dB. Thus it is cumulative but at a specific mathematical-equation level.

Noise travels. On moving to Plumas County from an urban area, it soon became noticeable how sound travels, even very low decibel sound. From our deck, conversation 300 feet away can be heard. This proposed mine operation is about 200 feet from our house. At 300 feet, a bulldozer is easily heard and loud. While the sound level pressure (SPL) would decrease with distance, this 96 dB rated piece of equipment would still reach 60 dB at our house. Add more machinery and other proposed operations, the (SPL) continues to rise. This would be sustained noise 12 hours to 24 hours daily.


The outside ambient noise level at our house measured with a NIOSH Sound Level Meter is 35 dB to 40 db. A sound level of 60 dB is 100 times louder than 40 dB. Given its logarithmic nature, sound measurement intensifies on the scale in powers of ten. Every increase of 10 dB on the scale is equivalent to a 10-fold increase in sound intensity (loudness). To continue this data, a reading of 100 db is 10,000 times louder than 60 dB and 1,000,000 louder than 40 dB. Consequently, this proposed mining operation with high decibel level equipment and operations working at sustained durations (12 to 24 hours daily, 6 days a week, 260 days a year) would greatly impact our quiet, rural environment This impact on the environment would have direct effects on the mental, physical, and emotional health of residents.

Impacted, sustained exposure to elevated noise levels definitely has an effect on hearing and hearing loss. It extends farther than that. Elevated noise levels affect the ability to understand speech, interferes with concentration, increases stress, lowers morale, reduces efficiency, creates irritability, and hinders sleep. For children, it can also impede development of speech and hearing. The EPA guidelines cite 45 dB to 50 dB for residential limits.

It is clear that this proposed mine operation offers a tremendous risk to the well-being of local residents. Elevated noise levels will also lower property values.There is no local official agency

with the necessary funding to adequately monitor this facility and its noise effects on the local residents. Nor is there an active local agency to whom the local citizenry can address their concerns and get results when such noise levels become intolerable which will be daily. The concept of allowing this “sand/aggregate” miine in a residential area is preposterous.


Light Pollution
Our dark night skies are important for several reasons which all tie back together to safeguarding human well-being and the environment. 24-hour exposure to light has environmental impacts on residents, wildlife, and domestic animals.

If the proposed mine functions during the “night time” hours using artificial lighting, all of the proceeding concerns in this letter are magnified: increased use of water and its degradation; increased contamination to air quality; and increased noise. See the above sections to review these hazards. Since the aforementioned sections address mostly human health and lifestyle, it is necessary to also examine the effects of light pollution on wildlife and domestic animals. All animal and plant species depend on the circadian rhythms. If the nocturnal segment of the day is eliminated, animal life patterns are compromised. Animal migration, feeding, reproduction, and communication will suffer. There is no reference in the permit to artificial light monitoring or mitigation.

Furthermore, as our population continues to increase creating the demand for more nighttime illumination, “dark skies” are disappearing. The ability to embrace the astronomical wonders of the night sky is a privilege that few people can enjoy. Why destroy this unique character of our county by allowing such detrimental astronomical pollution?

The last installment will study air & ground vibrations, erosion, fire, and community safety.


Valari Simison