The state Department of Health is advising residents to avoid a drainage ditch near Nanakuli Beach Park following an 850-gallon sewage overflow from a manhole on Mano Avenue.

City crews were able to recover 350 gallons, but 500 gallons entered a ditch that flows to the beach park, according to the Health Department's Clean Water Branch.

A sandbar blocks the drainage ditch from entering the ocean.

Although not their responsibility, city and county crews freed the flow, cleaned up, and disinfected the manhole spill site.

A cement slab in the sewer line was determined to have caused the overflow.

The slab will be taken out later, officials said in a news release.