As part of a project to expand and modernize the city’s wastewater treatment plant, failure to turn off several valves put the plant into noncompliance with state pollution-discharge limits for a short period in April.
The city informed the state Department of Environmental Quality of the violations a few days later, and the DEQ’s environmental compliance inspector in Billings, Dan Freeland, said the city is unlikely to be penalized for the incident.
“They’ll receive a violation letter for those exceedances,” Freeland said. “Something like this is not likely to generate an enforcement action.”
The city itself, however, said in the “notice of noncompliance” sent to the DEQ that disciplinary action would be taken in the incident, which led to the release of relatively high levels of E. coli bacteria and “total suspended solids.”
Vern Heisler, deputy director of the Public Works Department, which operates the Billings Water Reclamation Facility, as it is formally known, said “corrective action” was taken after the incident. Asked for specifics, Heisler said that because the disciplinary action involved an individual employee or employees, “that’s something we don’t really talk about much.”
The treatment plant, which sits next to the Yellowstone River just downstream of MetraPark, is a little more than halfway through a two-year, $65 million expansion and upgrade.
In the notice of compliance, written by Louis Engels, the city’s utilities systems engineer, and sent to the DEQ on April 23, Engels explained that a pump station at the plant was shut down at about 5 p.m. on April 18 so that a new valve could be installed.
Heisler said it was thought the job would take only a couple of hours, but because it took longer than that, workers had to had to use a backup, or redundant pipeline to keep partially treated water moving through the plant. By 8 the next morning, the valve was installed and partially treated water was flowing through the main pipeline again.
However, valves on the backup pipeline were not shut off, as they should have been, and that caused some solid matter to overflow from one part of the plant to another, and partially treated effluents ultimately were discharged into the Yellowstone River. The valves were closed later in the morning.
On April 18 and 19, regular monitoring showed that total suspended solids were found at a level of 258 milligrams per liter of water, compared to a normal daily reading of 25 to 35 milligrams. Elevated levels of E. coli were also detected — 816,400 MPNs in a sample of 100 milliliters of water.
MPN stands for “most probable number.” Engels said the MPN refers to the number of E. coli colonies found in 100 milliliters of water, which is the size of the sample tested five days a week. On a typical day in April, the level might fluctuate from the teens to 50 MPNs or so.
A reading of 816,400 MPNs sounds high, Engels said, but the bacteria are so tiny and so numerous that a thimbleful of water generally contains more bacteria of different kinds than there are people on earth.
Also, he said, it is important for people to know that raw sewage was not being discharged into the river. At the stage of the treatment process that the water flows in question reached, most contaminants have already been consumed, and what is left are bacteria and other microorganisms, Engels said.
The last process is disinfection. The plant disinfects microorganisms by “scrambling” their DNA to keep them from reproducing. But, as in this case, Englels said, when too many microorganisms get sent to disinfection, it overwhelms the process and the water is insufficiently disinfected.
Engels’ letter to the DEQ said the treatment plant had already taken or was planning to take steps to prevent further occurrences of noncompliance. Those including revising standard operating procedures for using a redundant pipeline and increasing the sampling of effluent turbidity.
It also said the plant’s construction activities would be modifying the redundant pipeline to make sure the hydraulic conditions experienced in April could not occur again. The letter also said the city was “beginning the process for disciplinary action.”
Freeland said there probably wouldn’t be any enforcement action because “it was just a short-term thing and they realized the mistake.” He said another factor was the difficulty of the situation facing the city.
“They’re trying to operate the plant and expand it at the same time,” he said.