BILLINGS — A former chemist at the city of Billings Water Treatment Plant laboratory is accused of contaminating water test samples conducted by a coworker in 2015, costing the city its state certification.
Michelle Henderson was set to make her initial appearance in Yellowstone County Justice Court Wednesday on one count of tampering with public records or information.
Henderson was employed with the city of Billings as a chemist in 2015.
She worked in a lab with two other chemists, who rotated on a three-month basis to separate testing duties in the lab.
One chemist began testing on inorganics, nutrient and total organic carbon while Henderson and the third chemist performed other tests.
The chemist testing for inorganics began experiencing failed tests on a near daily basis beginning in May of 2015 and ending in September of that same year.
On one occasion, the chemist left her testing sample and work station for less than five minutes and returned to find the test had failed.
Henderson and the other chemist did not experience an inordinate number of failed tests during this same time period, according to court documents.
The chemist with all the failed tests notified her supervisor, who watched as the chemist performed tests.
The supervisor determined the chemist was conducting tests properly.
The supervisor contacted the Hach Company, known worldwide as a leader in testing equipment and testing methods, to help troubleshoot the issue.
The company could not determine any explanation for the failed tests.
While Henderson was on vacation in July of 2015, none of the chemist’s tests failed.
When Henderson returned from vacation, the chemist’s tests failed again.
The public works director installed surveillance cameras in the lab in August.
When the chemist left her work station one day, she returned about 10 minutes later to find a white powder around the rim of a funnel she had been using to filter the samples she collected.
The chemist saved the white powder as evidence.
Supervisors reviewed surveillance footage and saw Henderson handling the other chemist’s samples while the woman was out to lunch.
Henderson was seen in the video spiking the chemist’s samples with a substance then discarding the materials in the trash.
When confronted about the misconduct, Henderson replied “oh” and did not explain why she had allegedly contaminated the samples.
Henderson was placed on leave before she ultimately resigned, at which point no further tests resulted in failures.
The city of Billings was required to spend thousands of dollars to investigate the contamination as a result of Henderson’s alleged actions.
The continuous sample failures also resulted in the City of Billings failing its State Certification that year.
Henderson is being held at the Yellowstone County jail.