Posted on May 23, 2020
Dane County this summer is kicking off an expansive four-year effort to dredge the Yahara River and reduce future risks of flooding like the county experienced two years ago — potentially lowering the river’s chain of lakes by a foot.
The county’s Sediment Removal Project will target the stretch of the Yahara River between Lake Monona and Lake Waubesa in a first phase this summer and fall, removing up to 40,000 cubic yards of sediment, or 3,000 dump trucks worth of soil, before dredging the river further downstream in future years.
The project is expected to wrap up in the fourth summer on the river’s stretch between Lake Mendota and Lake Monona where it cuts across Madison’s Isthmus.
In response to devastating flooding in August 2018, the dredging effort is aimed at improving the lakes’ water flow and increasing their storage capacity. It is expected to cost the county between $10 million and $15 million when complete.
While residents of central Michigan continue to grapple with severe flooding from recent rains that overtook dams, the current risk of flooding remains low in Dane County, said John Reimer, assistant director of the county’s Land and Water Resources Department.
Lake Monona is 2.3 feet below the 100-year flood level and 3.2 feet lower than the height it hit in 2018, he said.
“Over the past couple of years in particular, we certainly have seen a manifestation of the effects of climate change, we’re seeing more rain events, we’re seeing rain events of greater intensity and greater duration,” Dane County Executive Joe Parisi said at a news conference Thursday at the Lottes Park boat launch in Monona, where dredging equipment is being set up.
The county awarded a $3.25 million contract to Houston-based Dredgit Corp. to remove sediment between lakes Monona and Waubesa this year.
But going forward, the county intends to purchase its own hydraulic dredging equipment and hire four employees to complete the sediment removal south of Lake Waubesa up to Dane County’s border with Rock County and finishing off between lakes Mendota and Monona.
The work is being divided into five phases.
The project is one of several efforts launched by Dane County and other municipalities to mitigate the risk of flooding after a deluge of rain nearly two years ago killed a man, swamped thousands of homes and businesses and threatened to submerge large swaths of the Isthmus.
On Aug. 20, 2018, a powerful storm parked over Dane County and dropped more than a foot of rain in places, causing rivers and creeks to run their banks in the western half of the county and flash flooding in urban areas.
Source: Madison
