These days, the 100-year flood seems to be happening nearly every year. Cases in point: Tropical Storm Allison in 2001, Hurricane Katrina in 2005, the Mid-Atlantic floods of 2006 and 2011, flooding in the Midwest in 2007-2008 and again in 2010-2011, the Red River flood of 2009, the Midwest flooding again in 2013, and of course Hurricane Sandy. 

While floodwaters are indiscriminate, riverside wastewater treatment infrastructure is especially vulnerable. Losing facilities to high water can be disastrous for communities and the water environment. 

Prepare for the worst

As a precaution, many facilities are taking steps to guard against flooding. In the District of Columbia, DC Water is investing millions to protect the city’s 370 mgd Blue Plains Advanced Wastewater Treatment Plant from sea level rise, storm surge, and the type of destruction brought by Sandy. 

Construction has already begun on a 17.2-foot-high sea wall designed to protect the plant — located along the Potomac River — from a 500-year storm surge. The project includes a steel wall backed by reinforced concrete that connects to buildings to eventually form a continuous wall. It will cost an estimated $13.2 million and plant personnel expect it to be completed in 2021. 

“We’ve never seen the 500-year flood, but we’ve had lesser inundations,” says Jonathan Reeves, manager of DC Water’s office of emergency management. “We see the wall as a prudent response. It will run around the riverside edge of the plant, and back to the contour (on higher ground).” 

The wall is being funded out of DC Water’s discretionary capital projects budget, and is being constructed in phases to strategically coincide with DC Water projects along the waterfront. 

Firsthand experience

On the other hand, the Cedar Rapids (Iowa) Water Pollution Control facility has had firsthand experience with flooding. In 2008, a catastrophic flood on the Cedar River knocked the plant off line for 12 days and prevented it from returning to full service for nearly three months. During part of that time, some local businesses brought in portable restrooms for their employees. 

Largely federally funded by FEMA, a new $21 million project will surround the plant with a floodwall and earthen levee, in some places reaching 12 to 15 feet above the existing grade at the plant. The wall will contain a pump station, which will enable the plant to pump out effluent as well as stormwater during flood events. New valving inside the plant will prevent stormwater from backing up through the plant’s return sewer. 

Andrew Lundy, process and facilities engineering manager, says the wall is expected to be complete by next October. 

Be prepared

If your community is not investing in or can’t afford the megabucks to build flood protection, you can still ensure emergency measures are in place to mitigate the effects of natural and manmade disasters. 

According to Jack Moyer, national water security and preparedness practice leader for URS Corp. and past chair of AWWA’s committee on emergency preparedness, clean water professionals need to be prepared for worst-case scenarios — “things that have never happened to us before,” as he puts it. 

Effective measures don’t have to be expensive, just well thought out, he says. The most important thing is to have an up-to-date emergency plan and be sure your employees are trained in emergency response. 

Beyond that, he says, emergency generators and the fuel to operate them are critical. Power outages are usually the reason treatment plants get knocked out of service, he says. 

Easy-to-follow guidelines

The State of Montana offers a very complete yet succinct set of instructions on flooding that treatment plants nationwide can use as a reference. In addition to emergency contact lists, the Montana DEQ recommends plants know — before flooding occurs — what equipment is available from other treatment plants in the area that might not be affected. The department also advises that plants be able to move vital records and critical equipment to higher levels, and that they immediately report any discharge of partial or untreated sewage. 

During flooding, the DEQ advises plants to keep stormwater infrastructure clear of debris, use preventive measures to reduce I&I into the collection system, lower levels in lagoons if possible to provide additional hydraulic capacity, and preserve the biological system by isolating one treatment train and protecting it against washout. 

Most important, the Montana DEQ says: “Document all decisions, actions and correspondence which should include, but is not limited to, maintaining copies of all reports.” 

Taking the necessary steps to protect your wastewater infrastructure during floods and other disasters is critical. “Utilities are a priority,” Reeves says. “We’ve seen events like the Red River flooding that have been devastating to the utilities and their communities. We don’t have enough funding available to replace wastewater treatment facilities. The cost of mitigation is far less than the cost of replacement.”