Monroe, WA

Five Mile Quarry Company

U.S. Environmental Protection Agency (EPA) Noise Criteria:

The EPA has established non-statutory guidelines for evaluating noise increases caused by a project over ambient sound levels.  Noise increases of 0-5 dBA are considered a slight impact, 5-10 dBA a significant impact, and over 10 dBA a serious impact.


Our scope of work with the Five Mile Quarry includes completing an environmental noise assessment for the Environmental Impact Statement, as well as conducting quarterly monitoring of noise levels in accordance with Snohomish County.  Our evaluation included noise generated from activities on the site, located along Route 203 in Monroe, Washington, including blasting and equipment and the addition of truck traffic to the surrounding community.


The equipment operating at the site consists of crusher (Pegson), screen (Chieftain), Backhoe (Caterpillar 980F), Excavator, and dump trucks.  Applicable noise limits, which are contained in Chapter 10.01 of the Snohomish County Noise Ordinance, set the allowable limits for an Industrial source and Rural receiver at 57 dBA during daytime hours and 47 dBA during nighttime hours.  A quarry is defined as Industrial, and the nearby residential receivers are considered Rural. The Snohomish County noise limits are based on the district of the source and receiving properties.

Solutions and Measurement Equipment:

Continuous noise measurements were conducted to determine the spectrum of each piece of equipment operating at the site for noise modeling purposes.  The noise measurements were taken using a Larson Davis spectrum analyzer 2900.  Measurements and monitoring were completed at the nearest property lines with respect to the DNS requirements, and mitigation recommendations were made when necessary to reduce noise levels to within Snohomish County Noise Code.  Sound levels were also measured using a Larson-Davis Model 820 Precision Integrated Sound Level Meter with a Larson-Davis microphone and professional grade windscreen.  The microphone and sound level meter were calibrated using a Larson-Davis Type CAL200 acoustic calibrator.  The measurement equipment was calibrated before and after measurement sessions, and conforms to American National Standards Institute (ANSI) requirements for Type 1 instruments.