Regulating Environmental Noise in Minnesota

Popular version of paper 1aNCd2
Presented Monday Morning, Oct. 17, 2005
ASA/NOISE-CON 2005 Meeting, Minneapolis, MN

The Minnesota Pollution Control Agency (MPCA) regulates environmental noise in Minnesota. The regulation has several interesting features. Like many states, Minnesota regulates both daytime (7:00 a.m.-10:00 p.m.) and nighttime (10:00 p.m. to 7:00 a.m.) noise. The MPCA noise rule (Minnesota Rules Chapter 7030) classifies land uses into three categories or noise area classifications. These noise area classifications group areas according to noise sensitivity. The state noise rule identifies maximum allowable noise levels using the L10 and L50 values. These are statistical values that represent the noise level exceeded 10% of the time and 50% of the time in an hour. So the limits below can be exceeded for six minutes per hour (L10) and for 30 minutes per hour (L50). Table 1 presents the numeric limits found in MN Rules 7030.0040. The noise limits are not dramatically different than in other states that regulate daytime and nighttime noise.

Table 1: MPCA Maximum Allowable Noise Levels

Text in this section of the rule states that “these standards do not, by themselves, identify the limiting levels of impulsive noise needed for the preservation of public health and welfare.” The topic of impulsive noise is discussed later in this paper.

Unlike most states, Minnesota applies the state noise regulation to highway traffic noise. Rush hour traffic in the Twin Cities metro area can be pretty loud between 6 and 7:00 a.m., which is considered the loudest nighttime hour in the context of the state noise rule. Minnesota Department of Transportation (Mn/DOT) has to comply with the MPCA noise rule. Mn/DOT has a lot of noise walls in the Metro area, but the maximum wall height for noise mitigation purposes is 20 feet. When a 20 feet tall noise wall doesn’t reduce traffic noise to levels that comply with the MPCA noise rule, Mn/DOT has to apply for an exemption. This is an unusual feature of the state noise rule.

The MPCA noise rule also requires municipalities with jurisdiction over land uses to ensure that when new developments are erected, noise levels comply with the state noise limits. In practice, municipalities require developers to have noise analyses performed. Sometimes developers have to build noise walls or berms to reduce outdoor noise levels in areas of frequent human activity.

The basis for the MPCA noise rule exists in a Minnesota Statute. The statue says:

The Pollution Control Agency shall also adopt standards describing the maximum levels of noise in terms of sound pressure level which may occur in the outdoor atmosphere, recognizing that due to variable factors no single standard of sound pressure is applicable to all areas of the state. Such standards shall give due consideration to such factors as the intensity of noises, the types of noises, the frequency with which noises recur, the time period for which noises continue, the times of day during which noises occur, and such other factors as could affect the extent to which noises may be injurious to human health or welfare, animal or plant life, or property, or could interfere unreasonably with the enjoyment of life or property.

This sets some pretty ambitious goals for MPCA’s noise rule. One of the problems it creates is that it can be interpreted to apply to impulsive noise. Impulsive noise, like noise from pile driving, jack hammering, certain industrial and mining activities, etc. may not be loud enough to exceed the numeric noise limits. However, impulsive noise can be very annoying by virtue of its nature. Ground-borne noise, often associated with impulsive activities, can also be very annoying. Ground-borne noise occurs, for example, when energy from pile driving travels through the ground, is absorbed by a foundation, radiates through the structural members inside the wall, and is released when the wall vibrates. Plates, windows, hanging pictures often rattle – this is ground-borne noise.

Impulsive noise is regulated in few states. Illinois has a very detailed and site-specific impulsive noise rule that actually identifies specific equipment and specific locations, and limits the hours of operation of those items. It is analogous to the way the US Environmental Protection Agency controls air pollution from certain new equipment – in the New Source Performance Standards (NSPS). This NSPS-like approach works in Illinois to control impulsive and ground-borne noise from metal stamping plants located in residential areas.

Theoretically, then – this approach could work in Minnesota. The MPCA studied impulsive noise sources in Minnesota, and also reviewed regulations used to limit impulsive noise. MPCA summarized these efforts in a report. That report concluded that it might not be realistic to change the MPCA noise rule and regulate impulsive noise sources. It also recommended further review and study of impulsive noise issues. This author is surprised by those conclusions, and has first-hand experience dealing with ground-borne and impulsive noise problems that could have been resolved if MPCA adopted a regulatory strategy similar to how impulsive and ground-borne noise is regulated in Illinois. When non-noise-compatible land uses are allowed to exist next to each other, it creates potential land use conflicts. Often the conflict involves impulsive or ground borne noise. Good land use planning and a more meaningful noise regulatory program would eliminate many of these conflicts.

This author suggests that the MPCA noise rule does not fulfill its statutory goals because it does not regulate impulsive and ground-borne noise. The Minnesota Attorney General agreed. Yet the MPCA Commissioner eliminated the MPCA noise program. This move, which further reduces the environmental noise control efforts in Minnesota, was based on the governor's environmental priorities and funding limitations.