QUINCY — Unlike the public hearing back in 2011 where close to 50 people turned out to discuss issues pertaining to the Yahoo! proposal to expand its operations at the data center in Quincy, about half that number showed up Thursday night to meet with representatives.

Yahoo! is proposing to expand its operations at the Quincy data center. In order to expand, their air quality permit needs to be updated to ensure that human health and the environment are protected.

The Washington Department of Ecology is seeking comments on the updates to Yahoo!’s original permit that was issued in 2011. With the updated permit they can operate an additional 25 backup diesel generators. Ecology evaluates the levels of all pollutants during the permit review process. The ones most likely to be produced in high enough amounts to potentially affect the health are diesel exhaust particles and nitrogen dioxide.

Medical concerns based on increased diesel emissions were the main topic of concern, along with negative effects to nearby agriculture and air quality monitoring.

“We’re being required to trust people telling us that (the generators) will be running for X amount of time with no proof provided that in fact happens,” former Quincy mayor Patty Martin said. “If you were to talk to anyone that has lived in this community for a long time, they would tell when they look out at the Beezley Hills, they have to look through the haze. It never used to be like that.”

Diesel engine exhaust contains fine particles that can cause health problems for people who are exposed frequently and at high enough levels. The permit includes conditions to protect the public from air pollution including fuel limits and specified hours of operation for generators. The generators would only be used during the course of a power outage, said Mike Coleman, senior director of Data Center operations.

“It’s a very rare occurrence, but (the generators) are an insurance policy. We did have a four-hour outage during the Alcoa Fire in 2014. I can confirm that we did actually have an outage, but that’s the only one,” Coleman said. “It’s important for people to understand that we provide messaging and we provide mail, not only to this state, but to people all over the world. When there are natural disasters and people trying to get in touch with friends or family during those times, the telephone is long gone and the Internet has actually replaced it. These generators are very seldom used and only in the case of emergencies.”

The proposed Project Genesis will include:

— Direct evaporative cooling units

— Air cleaning systems

— Boiler heating

— A 196,969-square-foot building complex

— Twenty five new diesel-powered engines. Twenty will provide the main data center support and will be rated at 2.0 megawatt electrical capacity. The data center will also have four reserve engines rated at 2.75 and one administrative support engine rated at 2.75.

The permit, according to Yahoo!, includes conditions to protect the public from air pollution, including fuel limits and specified hours of operation for generators.

“They have to do what is called a fact analysis, which is the best way to control the pollutants into environment,” Martin said. “These are huge locomotive-sized engines. By not putting controls on the engines, we’re putting people at risk. The good thing is, the health study that is required is a result of our efforts. These permits have gotten more stringent because of our efforts.”

Data centers house servers that store digital data, handle email, manage instant messages and run applications for computers. Yahoo! uses backup generators powered by diesel engines to keep servers functioning in case of emergency.