Study by BoDean Co. asphalt plant confirms it exceeds Santa Rosa’s noise limits

The BoDean Co. asphalt plant in Santa Rosa routinely exceeds the noise limits set by the city, a study commissioned by the company has found. The new study confirms the findings of a June analysis paid for by a group of neighbors who for years have complained about noise, dust and noxious odors from the Maxwell Drive operation.

Both studies were conducted by professional sound engineering firms taking measurements from residential areas around the plant. Both reached the conclusion that noise from the plant exceeded city standards during daytime and nighttime hours when measured from the homes closest to the plant.

“There is no discrepancy as far as the results between the two studies,” BoDean general manager Bill Williams said.

That initial analysis, paid for by Citizens for Safe Neighborhoods, and a series of code enforcement complaints lodged against the facility by neighbors caused the city to open an investigation into the matter over the summer.

The first analysis, conducted by Petaluma acoustics firm Illingworth & Rodkin Inc., showed the plant exceeded the daytime limit of 60 decibels by up to 4 decibels. It exceeded the evening limit of 55 decibels by up to 9 decibels, and exceeded the nighttime limit of 50 decibels by up to 14 decibels.

The city’s noise thresholds are considered exceeded when levels are more than 5 decibels above the ambient noise levels established for various types of land uses.

As part of the investigation, the city asked BoDean to conduct its own study. The company hired RDG Acoustics of Larkspur and submitted a six-page preliminary analysis to the city this week.

That analysis was slightly different but still found that the plant violated the daytime and evening noise standards. The study found the plant exceeded the noise limits by up to 7 decibels during the daytime and 13 decibels at night.

But there is a potentially significant difference between the two studies.

The neighborhood-funded study concludes that the plant needs to conform to a lower decibel level, 55 decibels in the evening and 50 in the night, arguing that the areas where there readings were taken are covered by the strictest residential standards.

But the BoDean-funded study argues that slightly less restrictive standards apply because the area where the readings were taken, which has a mixture of single-family homes and apartments, is actually in a multifamily zoned area.

Such zones are covered by slightly less restrictive limits of 60 decibels in the daytime and evening, and 55 at night.

In either case, Williams said it is clear the plant has some work to do to come into compliance with the city’s noise ordinance.

“We’re committed to doing what it takes to get the noise levels down to meeting the city standards,” Williams said Thursday.

The plant is now performing additional studies to figure out how to do that. Adding complexity to the issue is that the noise at the plant is not produced by any single piece of equipment, but rather from the accumulation of noise from various machinery.

The report, which Williams stresses is preliminary, suggests reducing the noise created by eight different pieces of machinery at the plant between 10 and 20 decibels each.

The company will be exploring a number of possible solutions, such as muffling exhaust vents, installing new, quieter equipment or installing sound barriers. It has made no decisions and will present a plan to the city as soon as possible, Williams said.

Allen Thomas, the West End resident leading the opposition to the plant, said he was “pleasantly surprised” to hear the second study confirmed the findings of his group’s analysis. Thomas has questioned the plant’s claim that it has a legal right, because of its status as a grandfathered site, to operate 24/7 and has pushed for restrictions. Thomas said the solution seems pretty clear to him.

“Obviously, the thing that jumps out at me is for them to limit their hours of operation,” he said.

Editor’s note: This story has been revised to clarify that the city’s noise ordinance is only considered to have been violated if the noise levels in an area exceed the ambient noise criteria, which vary by land use, by more than 5 decibels.

You can reach Staff Writer Kevin McCallum at 521-5207 or kevin.mccallum@pressdemocrat.com. On Twitter @srcitybeat.