Costa Mesa Sanitary District officials want the Orange County district attorney’s office to prosecute a contractor the district alleges poured cement into the sewage system.

Residents reported Feb. 27 that an employee from Luna & Sons Concrete Inc. had used a wheelbarrow to dump what appeared to be cement down a manhole in front of 1625 Sandalwood St. in Costa Mesa.

Sanitary district staff and Costa Mesa police investigated and found evidence that the contractor had done so, according to district General Manager Scott Carroll.

The district’s incident report includes statements from two witnesses along with pictures showing that someone had used a pickaxe to remove the manhole cover.

A call seeking comment from Luna & Sons was not immediately returned Thursday.

Sanitary district board members voted unanimously Tuesday to ask the district attorney’s office to prosecute Luna & Sons on allegations of violating the district’s operations code, which states it’s unlawful to dump unauthorized materials into the sewer system.

Carroll said the offense would be a misdemeanor. The district also hopes to recover $1,882 in costs it incurred because of the incident, Carroll said.

Though it’s not uncommon for people to discard things into the sewer system — Carroll recalled discovering a bowling ball there once — he said it’s rare to catch the perpetrators.

Carroll thanked the residents who reported the Feb. 27 incident.

“If it wasn’t for our residents, we would never have known this happened,” he said. “We’re thankful to them for being our additional eyes and ears out there in the community.”

luke.money@latimes.com

Twitter @LukeMMoney