La Verne residents who have recently noticed a foul, sewage-like smell, I now have an answer about its source.

The odor is coming from materials produced during the drinking water treatment process at the F.E. Weymouth Water Treatment Plant, according to a statement from Metropolitan Water District of Southern California.

Residents have been discussing the smell on social media, with some saying they have noticed it repeatedly for weeks, particularly later in the day.

City Manager Ken Domer said the City was notified about the odor Monday, Sept. 14. The staff member responsible for the City’s sewer system inspected manholes and checked for odors but did not identify the sewer system as the source.

City staff then contacted Metropolitan, which confirmed the smell was coming from its facilities, Domer said.

Metropolitan said dirt, silt and organic matter are removed from water during the treatment process. Those materials can produce an odor while being stored or prepared for disposal, particularly during hotter summer months.

“As it begins getting cooler, this issue should dissipate significantly,” Metropolitan said in the statement emailed to La Verne Daily News on Tuesday.

The agency said it is working to move and dispose of the materials as quickly as possible to minimize odors around the plant while continuing to provide safe, reliable drinking water.

For people who regularly spend time near the plant, the odor has been difficult to ignore.

Lisa Vaporis, whose children have attended Bright Beginnings Preschool on Wheeler Avenue for years, said she's noticed this type of odor in the area before. "There is sometimes a faint smell, especially after rain with the riverbed, but never consistent like this."

She described the odor as resembling rancid or rotten sewage. Although she has occasionally noticed a faint smell in the area after rain, she said it has never been this persistent.

Kobi Gonzalez, center director at Bright Beginnings Preschool, said staff first noticed the odor around the end of July. Because plumbing had backed up at a home across the street, they initially thought that might be the cause.

“It hasn’t gone away since then,” Gonzalez said. “It seems to come randomly, normally mid-dayish.”

Gonzalez said the smell varies from day to day. Sometimes it resembles backed-up sewage; other times, it smells like something rotting. Staff members have also reported smelling it farther south near Bonita and Allen avenues.

“It’s worse on some days, but sometimes it’s better, and sometimes you don’t smell it at all,” Gonzalez said.

The preschool’s children generally have not been outdoors during the afternoon because of the heat, limiting their exposure to the smell, Gonzalez said.

The Weymouth plant began treating and delivering water in 1941 and can treat up to 520 million gallons per day, according to Metropolitan’s website.

Residents can report unusual odors by calling La Verne City Hall at (909) 596-8726. On weekends, residents can call the La Verne Police Department’s nonemergency line at (909) 593-2531.