The excessive noise levels experienced in cities around the world can cause hearing loss, disrupt sleep and induce stress, and with a growing body of evidence linking noise pollution to a variety of negative health impacts, many cities are starting to take the issue more seriously.
But when is a noise violation not a noise violation? It’s a question that residents of north Denver neighborhoods like Globeville and Elyria-Swansea have learned the answer to over the past year or so.
Construction on the Central 70 project, a controversial $1.3 billion overhaul of a ten-mile stretch of Interstate 70 in north Denver that began last year, needs to take place at night in order to drastically shorten the project’s timeline — and nighttime construction means the project needs a variance from Denver’s noise ordinance. Denver’s Board of Public Health and Environment granted a one-year variance to Kiewit Infrastructure Company, the project’s contractor, in September 2018.
Earlier this month, at a hearing on Kiewit’s request to extend the variance for another three years, city health officials reported that no noise violations had been recorded since construction began last summer. But during a public comment period, residents repeatedly raised an issue that Denver’s noise ordinance doesn’t cover: low, rumbling vibrations from construction and traffic related to the project, which they say have kept them up at night, rattled their walls and potentially even damaged their homes.
“The vibrations keep me up, the noise keeps me up; I can’t sleep,” Sanjuana Romero told boardmembers. “It’s really hard to live through this. I’m sleep-deprived. My head hurts all the time.”
“My main concern is vibration,” said Raquel Casillas. “Vibration that has been so intense that at 3 a.m., my eight-year-old woke me up to alert me of an earthquake that we were having.”
“I have been woken up many times,” said Drew Dutcher. “My bed is shaking, my walls are shaking. I live in a masonry house built in 1890. Masonry doesn’t take vibration.”
The health board granted another one-year variance instead of the three-year term that Kiewit had requested, and city staff from the Department of Public Health and Environment told residents and the board that they would study the vibration issue going forward.
"We’re researching how this is handled in other jurisdictions and will report out on it by end of year," says DDPHE spokesperson Tammy Vigil. The process, which is being handled by the department's Public Health Investigations unit, will make its findings public, but any changes to the city's noise ordinance would have to be approved by Denver City Council.
Matt Sanman, a spokesman for Kiewit, says that in the absence of municipal regulations, the company has taken steps to mitigate the potential risks posed by "vibratory impacts" associated with the Central 70 project.
"Construction in and of itself has vibratory operations and impacts that are essential to building a quality product, especially for stabilizing the earth and placement of asphalt to ensure the public has a smooth roadway," Sanman writes in an email to Westword. "Although there are currently no regulations for vibration as it relates to construction activities, the team tries to be very proactive in how we build, monitor and document our impacts to the public."
While removing concrete from the surface of Brighton Boulevard earlier this year, the project received a complaint about vibration and made changes to the process to minimize those impacts, Sanman says. "The team is very cognizant of what types of equipment and operations have vibratory impacts and we consciously avoid these impacts during nighttime hours whenever possible," he adds.
Nearly all cities have ordinances prohibiting excessive noise; Chapter 36 of the Denver municipal code, for example, is meant to “promote the health, safety, welfare, peace and quiet for the citizens of the city through the reduction, control, and prevention of noise.”
But a growing number of cities are expanding their noise ordinances to regulate vibrations from construction and other activities, too. A bill passed by Greenwood Village City Council in 2012 amended the city’s noise ordinance to regulate “excessive sound and vibration.”
"Noise and vibration are regulated together in other municipalities, because they are both generated by many of the same activities and are widely acknowledged to have similar negative effects on human health," Ava Farouche, an attorney with the environmental group Earthjustice, told health board members at this month's hearing.
Measuring vibrations, however, can be complicated. Denver’s noise ordinance, like nearly all others, is based on decibel levels, a common and easily understood measure of volume. There’s no simple, standardized metric used to compare construction vibrations, though a measure known as peak particle velocity (PPV), expressed in millimeters per second, is the most common.
“In terms of creating some set of standards to require [Kiewit] to adhere to, we’re not in a position to say what standards currently exist,” Danica Lee, director of DDPHE’s public health investigations unit, told the health board. “There’s not a common consensus out there among regulatory agencies about how to approach this.”
Chicago’s noise and vibration ordinance simply prohibits “earthshaking vibrations that create a nuisance or hazard,” while allowing for a number of exceptions. Municipal codes in Santa Clara, California, Cambridge, Massachusetts and other cities prohibit activities that are “above the vibration perception threshold,” defined as the minimum level necessary to cause a ”reasonable person of average sensitiveness to be aware of the vibration.”
In addition to public health impacts, construction vibrations are also known to sometimes cause structural damage, particularly to older buildings. "We have completed some vibration monitoring to ensure we’re within a reasonable threshold, minimizing the likelihood of structural damage," says Sanman.
“There are some cracks in my foundation,” resident Joe Elliott told boardmembers at this month's hearing. “And that’s the kind of issue I’m concerned about, if we’re looking at another few years of construction, and probably much heavier [construction] in that time. I would like to see you guys take a better look into that, because I think it will become more of an issue as time goes on."