skip to main content

Natural Resources and Parks

King County, Washington

For questions about King County Natural Resources and Parks website, please contact Fred Bentler, webmaster.

Oct. 8, 2009

Keep a lid on it! Wastewater agency warns against opening manholes during flooding

To protect public safety, King County is warning emergency responders, public works employees and community members to not open sewer manholes during flooding.

The issue has become especially urgent with the increased possibility of flooding in the Green River Valley related to Howard Hanson Dam. An earthen bank next to the dam was damaged after record high water last winter, meaning the dam won’t be able to store as much water this flood season.

“An open manhole could have deadly consequences. There is a very real risk for someone to fall into the rapidly rushing water inside the pipe,” said Wastewater Treatment Division Director Christie True.

True said opening manholes would do little to alleviate floodwater in inundated areas. However, it would increase the volume of water in overwhelmed pipes and cause more sewer backups that could damage property and injure people.

King County also reminds people that floodwaters can obscure many hazards such as open manholes, damaged roads and debris, and recommends that people protect themselves by staying out of flooded areas.
Additional information about flood preparedness is available on the Web at as well as and clicking on ”Wastewater” under “Frequently Asked Questions.”

People enjoy clean water and a healthy environment because of King County's wastewater treatment program. The county’s Wastewater Treatment Division protects public health and water quality by serving 17 cities, 17 local sewer districts and more than 1.4 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for more than 40 years.

Related information

Prepare now for floods

Flood preparation for the Green River Valley

Flooding FAQs about Wastewater

King County Wastewater Treatment