Dane County initiative cleans 60,000 pounds of phosphorus from Lake Mendota watershed

Crews extracted tens of thousands of tons of sludge to curb summer-time algae blooms and stormwater floods from waterways around Madison this year, Dane County Executive Joe Parisi announced on Thursday.

The county pulled 60,000 pounds of phosphorus and 25,000 tons of sediment from streams that feed into Lake Mendota between Waunakee and Middleton, county officials said. The “Suck the Muck” initiative targeted phosphorus because it provides nutrients for algae, which eat up oxygen and block sunlight from underwater plants.

The initiative is meant to address both algae blooms and floods due to increased runoff and frequent storms, county officials said. The county bought hydraulic dredging equipment and hired staff dedicated to removing sludge that causes lakes to rise faster with intense rains, reacting to floodwaters and overflow in 2018.

“With an ever-changing climate that we know is increasingly less predictable, we know it’s important to prepare now to increase our resiliency for what lies ahead,” Parisi said in a statement. The county executive added the work done now would hopefully minimize property damage in the future as bigger storms and heavier rains occur more frequently.

The crew removed 18,500 cubic yards of ooze from an area between Babcock Dam on Lake Waubesa and Lower Mud Lake, a “choke point” in the Yahara River where water flow slows and lake levels rise upstream, officials said. Dane County is on track to remove over 40 million gallons of muck that contributed to flooding concerns by the end of 2023, they added.

The County Executive’s 2023 budget includes $2 million for planning another scooping project for built-up sediment inside the Door Creek Wetlands in the southeast part of the county, county officials said. So far, the program dredged 60,000 tons of sludge containing around 180,000 pounds of phosphorus from Dorn, Token and Six Mile Creeks – just one pound can grow almost 500 pounds of algae.

James Tye, the executive director of Clean Lakes Alliance, praised the county for its effort to break up phosphorus flow in surrounding lakes. “Despite climate change and increased runoff making water quality recovering all the more challenging, the county continues to lead with bold but targeted action to protect our greatest natural assets,” he said.

Dredge teams will focus on an area of the river between Lafollette Dam along Lake Kegonsa and Highway B in 2023, county officials said. Hydraulic dredging will start as soon as possible as the weather thaws in the spring.

“Whether it’s cleaning our waters or preventing them from rising and doing damage, we know the work we’re doing is one important part of overall solutions needed to keep our lakes, streams, and rivers healthy,” Parisi said. “We are fortunate to live in a community that places such a high priority on water quality and look forward to continuing to do all we can in the coming year and beyond.”