Report adds details in Mattawa wastewater treatment facility fire

MATTAWA — The exact cause of the fire at the Mattawa Wastewater Treatment Facility, which occurred in January, is unknown. Over the months since the fire, it has been speculated that the fire started in the building’s electrical panel.

In the early morning hours of Jan. 9, the Mattawa Wastewater Treatment Facility suffered a fire that destroyed the facility’s blower room and associated equipment. The exact time the fire started is unknown, but City of Mattawa Public Works Director Juan Ledezma has stated in past interviews with the Sun Tribune that officials estimate it to have started around 2 or 3 a.m., based on the size of the room destroyed and how hot the fire was when the fire department arrived on scene.

The investigation of the fire was conducted by Fire Investigator Ron Trogdon of EFI Global. Trogdon was asked to evaluate the cause and origin of the fire, not to collect any evidence and prepare a summary report of his findings. The examination was concluded Jan. 13.

In the fire summary report recently obtained by the Columbia Basin Herald, it was stated that two electrical boxes were located on the north side of the wall that divided the building in half. The larger of the two boxes housed the breakers and relays “that controlled the three 20-year-old motors.” The smaller box ran an additional motor. The report stated that the one of the relays in the larger box was completely destroyed, while the others were damaged.

“There were oxidation patterns on all surfaces of the two electrical boxes and to the metal conduit supplying electricity to the relays and from the relays to the motors that drove the blowers,” stated the report.

The night of the fire, the power to the facility, and other parts of Mattawa and Desert Aire, went out. In the report, Trogdon stated the representative for Grant County PUD had not been available for him to interview. However, he did interview Taylor Bendt, an electrical engineer with EFI Global.

“Electromechanical contactors are widely used in industrial applications to control the operation of machines,” Bendt is credited with saying in the report. “These devices operate using an electromagnet which pulls against a spring to close a contact, like a switch, to turn on a motor.”

Bendt explained that when voltage sags, during such events as storms, the reduced voltage weakens the electromagnet, causing the circuit to have a high-resistance connection. While the machinery attached to the circuit is able to operate normally, the reduction in voltage “will generate considerable heat in the conductor.” Normally, the device will fail from the heat, but in some cases, a fire can occur if the low voltage level “is sustained for a long period of time or other ignitable material is nearby.”

In the report, Trogdon also noted that “a large pile of burned material,” such as plastic buckets, old electrical conductors, a gas-powered pressure washer, ruptured aerosol cans, gypsum wall board and other items that were unidentifiable had been removed from the north portion of the building that had been destroyed.

The report concluded that the fire originated inside the north half of the wastewater treatment facility building. It also stated that “a failure within the heavily damaged motor control relay,” as well as “an unidentified ignition source that was consumed by the fire,” could neither be “excluded as a source of ignition.”