The stench can be overpowering. A rotten egg cloud so sour it causes headaches and watery eyes. Residents weep as they describe the feelings of nausea and helplessness, sick with the frustration of suffering this miasma.

Because if you live next to the Annapolis Water Reclamation Facility, you have to expect this sort of thing. I mean, it’s sewage, right?

“Please remember, this is a wastewater treatment plant,” said Chris Biggerstaff, the engineer who runs the plant on the edge of the city. “There is no eliminating the odor.”

Biggerstaff and his bosses at the Anne Arundel Department of Public Works couldn’t have known that the affluent neighbors who organized the Clean Air Action Group last year brought a special set of skills to their cause.

A physician focused on respiratory health. A Johns Hopkins University scientist studying air monitoring. A small-business executive who brings people together for a common purpose. A retired Marine Corps general.

And Sharon Hockenberry, who spent three decades creating ways to analyze problems for clients such as the National Security Agency, the Department of Health and Human Services, corporations and state governments.

Hockenberry found the one element crucial to the group’s success so far — technology that convinced the county that something was rotten in Annapolis.

“I think I was Googling air quality, wastewater treatment plants,” Hockenberry said. “Smell and health outcomes. I was Googling all those things and technology because I knew that we needed to be able to get the data. How do I get the data?

“I stumbled across that Smell My City app, and I thought, Oh my gosh! Then I started reading.”

To its credit, Anne Arundel County, after initially pooh-poohing the idea that anything was wrong, looked at what the app gave them — more than 2,600 individual reports on air quality — and admitted that their neighbors were on to something.

“Beyond our trust in the data is where you start building a relationship of trust,” said Beth O’Connell, deputy public works director. “It’s a little bit more substantial.”

Complaints about smell are more than an on-the-nose gripe about something unpleasant. There is an evolving acknowledgment of the connection between a stinky sniff and health.

Open-pit storage of liquid leftovers from animal slaughter and processing has made life miserable on parts of the Eastern Shore. Curtis Bay and Brooklyn Park residents have long complained about the reek of industrial plants concentrated around South Baltimore.

It just takes a while to grasp the ephemeral value of smell.

Biggerstaff and his team at the Annapolis wastewater plant might not have noticed that its stench had grown worse because they just accepted it as a given. Weather and wind change, and the sickening aroma of decay — hydrogen sulfide in the case of processing sewage into treated water — wafts away.

But people who live near sources of bad air can also lack the power to address it, for reasons of education, income, political representation or a lack of trust.

“It takes some time for governments to realize there may be a difference between data and the lived experiences of people they get through complaints,” said Ana Hoffman, director of air quality engagement at CREATE Lab in Pittsburgh.

That was the incentive for CREATE Lab, part of Carnegie Mellon University, to develop the Smell Pittsburgh app in 2016.

Atmospheric inversion can trap air in the Appalachian hollows and valleys around the city and Western Pennsylvania. Near one coke-smelting plant in the area, neighbors were often stuck breathing in noxious emissions.

Pennsylvania interprets the federal Clean Air Act to mean smells must stay within a facility’s fence line. The sulfurous charcoal smell of coke smelting was a clear sign that something was amiss. By allowing users to record individual complaints of smell, rated in a five-point scale, the app quantified what neighbors were experiencing.

In 2019, Hoffman and CREATE Lab realized the potential wider power of their app. Backed by private investment, they released Smell My City as a free download. It’s been used in places including Portland, Oregon, and Louisville, Kentucky.

Unlike Pennsylvania, Maryland regulates pollutants going into the air but not necessarily odor.

You can report complaints to the Maryland Department of the Environment or local agencies; it got more than 300 in the last fiscal year. It refers them to appropriate agencies, which might send an inspector to look for underlying issues such as air quality permit violations, illegal businesses or dumping — rather than treating a bad smell as the problem.

“The Department of Health does receive odor complaints, but it’s usually an accessory to the true nature of the complaint,” said Megan Pringle, a spokesperson for the department. “For example, we might get complaints about septic failure, dog waste, excessive trash, or rats and mentioned in the complaint is odor.”

Public Works investigated 46 calls over the last two years involving sewer smells, a department spokesperson said. Sometimes, the source was a county pumping station or sewer line, but more often it turned out to be inside the caller’s house or vanished before a work crew arrived.

The MDE doesn’t automatically regulate smells from sewer plants, but it is trying in Annapolis.

Yen-Der Cheng, chief of the municipal discharge section of the MDE wastewater division, said that in response to more than 100 complaints on the permit, his department proposed adding odor management to the plant’s new wastewater permit.

In an email to members of the Clean Air Action Group, he explained it would require regular monitoring at the fence line and an annual report. Public Works is pushing back, arguing that a wastewater permit is not the place to regulate air quality. More hearings are planned before a final decision.

“It just doesn’t belong in our permit,” said Karen Henry, county director of public works.

On Monday night, Henry, Biggerstaff, O’Connell and others from the department packed into a library meeting room with 75 neighbors of the Annapolis plant.

They acknowledged two areas at the plant need attention. Both clogged grit screens and an open backwash pit may be contributing to the worse-than-normal stench.

But there was a disconnect — not surprising when one side measures in parts-per-billion and the other counts poolside parties ruined, business lost and holidays spoiled.

It took some time for neighbors of the plant to agree that this campaign was worth the trouble. Condos where organizers of Clean Air Action Group live overlook the Chesapeake Bay, with two pools and a private marina.

It doesn’t smell every day. The setting is beautiful. Why not just sell, some residents asked, and let someone else deal with it?

“People understandably have mixed feelings about this,” said Dr. Alec Chester, an internist who focuses on respiratory medicine and founded of the group. “If you create an enormous amount of public attention about this, that’s not going to do a lot for property values.

“My feeling is that the smell is quite apparent, and having a group of people working on this is a plus for this community.”

In the end, for some, that argument won. It was probably helped by a new waterfront park just down the street, Elktonia/Carr’s Beach Heritage Park. The plant and the surrounding homes are actually built on the site of a former Black resort the park represents.

It wasn’t just the app that convinced the county that there was a problem.

It was Hockenberry’s creation of a platform that collates and presents the findings to make a coherent argument. It was her neighbor, Lisa Culver, who created a Facebook page and door hangers that helped recruit volunteers.

Although the county hired a consultant and started fixes — it wants more data over the summer. And time. Major upgrades could take years.

Even in Pittsburgh, it turns out that making smells go away takes more than recording them.

“It can take decades,” said Hoffman, the CREATE Lab director. “It hasn’t been completely effective.”