Faced with an old stormwater system and heavy rains that are becoming ever more common, Green Bay officials are looking to spend well over $100 million on an extensive improvements meant to combat flooding.
Officials at the Green Bay Department of Public Works officials stated in a recent internal memo that they are aware of residential flooding in 450 places throughout the city. The public has complained of everything from flooding within a street right of way to the formation of small “ponds” on residential properties, wrote Matthew Heckenlaible, assistant city engineer.
In response, public works officials have proposed embarking on a massive, $150 million project to replace storm sewers in the worst-hit parts of the city.
Most of the recent flooding, he said, can be traced back to heavy rains, which became more frequent occurrences between 2010 and 2015. Public works officials specifically pointed to a spate of bad weather that dropped 3.6 inches of rain over the course of five days in December.
The rains “continued to saturate the already moist ground, causing significant drainage issues within the city of Green Bay but also in the surrounding communities,” Heckenlaible wrote in the memo.
The department logged 125 complaints during that time. Of those, 50 were of flooded basements.
The memo also made note of another likely source of flooding: The submergence of various pipes normally used to discharge water from the city’s sewer system.
Green Bay, because of its proximity to large bodies of water, might be more exposed to flooding than many other places. But its troubles are far from unique, especially amid climate change and the increasing development of urban areas.
Heavy rains have become more common in both Wisconsin and the rest of the country, said Kevin Shafer, executive director of the Milwaukee Metropolitan Sewerage District, a governmental agency that provides water treatment and flood management in 28 municipalities in the Greater Milwaukee area.
“Since around 2000, (they’re) seeing shorter duration, higher intensity of rainfall, which is really stressing the stormwater systems in the entire state,” he said.
Shafer said district officials have come to realize that one of the best ways to combat flooding is to control what happens upstream. To that end, much is being done to encourage residents and local officials to install bioswales, rain gardens and rain barrels. The goal is to capture excess runoff before it can cause harm elsewhere.
As an example of what can be accomplished, sewerage district officials have made special note of rain gardens installed recently at residential properties in West Allis.
Flooding, meanwhile, can also result from development.
Bob Bartel, executive director of the Wisconsin Underground Contractors Association Inc., said projects involving a lot of concrete structures and paved surfaces give rainwater fewer opportunities to seep into the ground. Having no other place to go, runoff flows into storm sewers, which are then put under even more stress.
“The more pavement you put down, the less places you have for water to absorb or run off into,” he said.
In Green Bay, much of the current development is going on around Lambeau Field, home to the Green Bay Packers organization. Foreseeing possible troubles, local officials have been working with the team the past few year to revise the stormwater-management plan for the site.
To detain stormwater before it enters public sewer systems, Packers representatives have proposing installing an approximately 150-foot-by-300-foot storm tank underground. The project is expected to cost the city about $3 million.
Existing sewers are also inadequate. Some of the worst sections can be found in an area once known as the town of Preble. A part of Green Bay since the 1960s, the former Preble has storm sewers that are barely large enough to prevent flooding during what local officials deem a two-year inclement weather event, meaning the accumulation of 2.5 inches of precipitation over the course of 24 hours.
That’s far below current standards. To now be in compliance, sewers must be able to discharge the runoff generated when 3.8 inches of precipitation fall within 24 hours.
The city’s memo, meanwhile, places some of the blame for the flooding on residents. When people do not dispose of yard waste, grass clippings, leaves and seeds properly, the debris can block sewer inlets, leading to backups.
“These types of blockages are the direct result of inappropriate behavior by the general public and no amount of improvements to the storm sewer system will change those scenarios,” Heckenlaible writes.
The document also warns of what can happen when residents try to deal with flooding on their own. City officials say they know of instances – mainly in the southwestern part of the city – when people have removed manhole covers to try to give standing water a place to go..
Many times, the manholes lead to sanitary sewers. In some cases, neighbors’ basements have been flooded. Follow @alexzank