Preventative measures begin at 20 feet

The Hannibal Board of Public Works (HBPW) began its flood prevention preparations soon after the Mississippi River began its latest rise.

The HBPW's flood plan, which was drafted about five years ago and reviewed every couple years, includes preventative measures for electric, water, sanitary sewer and storm water. The plan goes into effect when the river is at 20 feet and rising.

Possibly the biggest concern during a flood is keeping the pumphouse operational. It is located along the river between the railroad bridge in U.S. 72 bridge.

"It has flooding issues at 20 feet and higher," HBPW General Manager Heath Hall said. "Thankfully there was a floodwall added to the structure after 1993, and it takes care of most of the concerns. But there is some prep work that has to be done to get it ready."

When the river reaches 24 feet or higher, as it is expected to do over the next few days, daily inspections at the pumphouse are performed by a three-man crew in a boat.

Also high on the HBPW's watchlist during a flood is the sanitary sewer lift station located near Bear Creek, off of Ely Street. Precautions at that facility began when the river is at 22 feet. Like at the pumphouse, on-site inspections are performed daily by a crew in a boat at river levels above 24 feet.

"The station is inspected for flooding and to ensure the sewer lift pumps are operating correctly. We do have alarms on key items so we can be notified if something goes wrong between inspections," Hall said.

While the HBPW does not set the floodgates in place, it has duties to perform in conjunction with their installation. Sanitary sewer valves are shut when the floodgates are installed. Some storm water valves along the floodwall are also closed to prevent water from backing up into the protected area. Some electricity is also turned off outside the floodwall.

Hall said that the HBPW typically does not have too many issues with substations or electrical infrastructure during river flooding.

"We have relocated most of our key facilities out of the danger area or constructed redundant facilities," he said.

An Ameren substation, which supplies power to the city, is located south of the city near Mark Twain Cave and can have flooding issues when the river climbs above 25 feet.

"In the past, sandbagging (at the substation) has prevented any substantial damage," Hall said.

The city's aging sanitary sewer system can present problems, depending on how high the river rises and how long it stays elevated.

"It gets overloaded with floodwater, and overflows and basement backups can occur. We do our best to prevent them, but the system can only handle so much water," Hall said.

As the river approached its major flood level of 24 feet, Hall expressed confidence that the HBPW is ready.

"We have made our preparations and it should not be a problem. Unfortunately we are getting pretty good at taking these precautionary measures. It is become part of our normal routine work," he said.



danny.henley@courierpost.com