Suit Alleges Denver Airport Underestimates Overflight Noise

JULY 3, 2018

Denver International Airport has knowingly used an outdated noise-monitoring system that for years has underestimated the impact from overhead aircraft on airport-area residents, according to a lawsuit Adams County filed Monday against the City of Denver. And that under-reporting, the suit claims, has allowed DIA to avoid making related payments to Adams County and its cities, like Thornton, Aurora, and Commerce City.

The county is asking a judge to order DIA to recalculate and re-report noise impacts for every year going back to 2014, and that the new data be used to enforce the noise standards agreed to by Denver and Adams County in a 1988 agreement that paved the way for the construction of DIA. The airport opened in 1995 on land that was annexed from Adams County into Denver. The lawsuit Monday was filed in Jefferson County District Court, as required by the agreement signed by both parties 30 years ago.

At the heart of Adams County’s complaint is the contention that Denver relied on a noise modeling approach that was never tested for its accuracy in terms of how it compared to actual noise data collected on the ground. It described the system “as being an outdated, archaic aircraft noise modeling system” that was “abandoned years ago by all users except DIA.” It went further, saying Denver “actively kept secret any data or evaluations of the data” produced by its system. Adams County wants DIA to put into place a noise monitoring system “that complies with current industry standards and the state of the art, and that such system be validated by initial and by annual testing.”

Monday’s legal action was not the first taken by Adams County against Denver over noise at DIA. The county sued the city as far back as 1992 — three years before the airport opened — in protest of DIA’s plan at the time to use a noise modeling approach rather than actual measurements by monitoring equipment.

DIA accuses Adams County of “making numerous unfounded allegations that are based on unproven and imprecise noise collection and measurement methods.” Airport spokeswoman Stacey Stegman said DIA has “diligently monitored noise in Adams County since the airport opened.” She contends that advances in aircraft engine technology and more precise flight technology have resulted in many fewer noise violations in recent years.

According to Stegman, in the 23 years DIA has been operating it has paid Adams County around $40 million for exceeding agreed upon noise thresholds. The last payment, of $1.25 million, was made for noise violations recorded seven years ago, she said. She said Adams County rejected an offer from DIA to pay for a pilot program to explore new noise-monitoring systems. “Unfortunately, Adams County walked away from these discussions and filed a lawsuit instead,” she said.

Adams County commissioner Mary Hodge sees it differently, saying on Monday that the county did everything to avoid going to court. “Denver got their airport while moving the noise impacts associated with an airport out of their city and into our municipalities,” she said. “We have to make sure they’re sticking with the spirit and language of that original pact.”