DALLAS After a four-day investigation, the City of Dallas discovered a custodian at a local middle school is apparently responsible for the disgusting odor and cloudy appearance of the Dixon Branch of White Rock Lake.

The City of Dallas issued a formal Notice of Violation to the Richardson Independent School District for the illegal dumping of water, floor wax and floor stripper chemicals into a storm drain on campus Monday afternoon.

A city official going manhole-to-manhole and looking for possible construction site dumpers observed the custodian and snapped a photo of the culprit as he pushed a mop bucket and carried a hose back toward the school building.

Brad Young, a long-time resident along the creek, recently reported a foul odor, dead fish and cloudy water on the Dixon Branch of White Rock Lake near Plano Road and Northwest Highway. At least four others alerted officials with similar reports.

It was brown with gray on top, and it smelled like sewage to me, Young said.

Richardson ISD told News 8 the custodians have been cleaning the floors at Lake Highlands Junior High since June 7.

Upon being notified of the illegal dumping, the district immediately suspended that work and launched an internal investigation to discover how widespread the practice is.

The RISD promises to clean it up.

If we're responsible for any kind of mess in the neighborhood or any kind of contamination to a creek bed or anything else, we want to do the right thing and be part of the solution, said district spokesman Tim Clark.

Used floor stripper solution is supposed to be poured in the sanitary sewer, Clark said. Why it wasn't is one of the questions RISD is trying to answer.

The district said it's also trying to find out how much of the product was used at Lake Highlands Junior High. Empty boxes of the floor chemicals overflowed the school's dumpster late Tuesday afternoon.

Though polluters often face fines, Dallas said it would likely ask the district to just clean it up.

I really couldn't believe it was the junior high, because the funny thing is the junior high is where most of the kids come from that play in that creek, Young said.

He and others hope the district keeps its word on remediation, and acts fast to preserve the fragile and seldom-seen ecosystem.

E-mail jwhitely@wfaa.com