A recent discovery from a Dane County study found that targeting residual sludge might be the key to mitigating phosphorus pollution in the waterways of southern Wisconsin. This has spurred immediate action by the county, and a new plan by Dane County Executive, Joe Parisi may make waves in Wisconsin environmental efforts.
According to the study, unregulated farming practices that were used many years ago has caused phosphorus to build up in Wisconsin waterways. Now, that phosphorus is slowly and steadily leaching back into lakes, in particular the Madison area chain of lakes. This so called “legacy” phosphorus would continue pollute lakes at levels higher than the state’s maximum regulation for the next 60 years, even if no additional phosphorus was added.
This is why Joe Parasi put a $12 million project in the budget. This project will to remove 870,000 pounds of phosphorus from 33 miles of waterways.
According to Parasi, “This is a breakthrough that we believe will allow us to achieve clean lakes in our lifetime instead of our grandchildren’s lifetime.”
Phosphorus is harmful to water ecosystems because it is an incredibly nutrient-rich element, so when it is introduced, it causes a boom of algae and weeds. These limit recreation activities and block sunlight from other organisms. When the organisms ultimately die, decomposers use the water’s oxygen to break them down. This can deplete oxygen, which limits the amount of future organisms that can exist in the lakes.
This extreme problem has been a Wisconsin priority for years. Since the clean water act in 1972, the levels of water pollutants have been heavily regulated by the state. Governmental grants have funded things like barn roofs and created infrastructure to reduce farm runoff. Other efforts to plant vegetation to clean out streams have also been employed to mitigate phosphorus pollution. While these efforts have helped, phosphorus has continued to cause problems in Wisconsin.
Joe Parasi’s initiative is designed to largely remove legacy phosphorus. The new plan proposes a strategy similar to a Fox River PCB (polychlorinated biphenyl) cleanup project in 2004. A hydraulic dredge will be used to vacuum up over 200 cubic yards of sediment. The dredge would be attached to a pipeline that would temporarily collect phosphorus in bags.
The question is what to do with the extracted phosphorus. One method of disposal is quite similar to septic tank designs. It would put the sediment in containers made of materials that would slowly allow the nutrient-rich substance to leak into the ground. Another method would convert the collected sediment into fertilizer for farms and gardens. Ultimately, this plan is projected to cut phosphorus pollution in half and expose gravel stream beds that may allow for the growth of new fish species.
According to a 2015 DNR memo, phosphorus dredging may harm wildlife. Many of the waterways proposed for cleanup are surrounded by delicate wetlands, which raises the stakes for the endeavor. DRN water quality engineer, Mike Sorge, made it very clear that the process will need to be watched carefully to ensure that ecosystems aren’t damaged.
This plan passed as part of the 2017 Dane County budget proposal. It is a $12 million initiative, projected to take about five years to complete. Supporters of the proposal like Jeff Endres, chair of the Yahara Pride Farms Conservation Board feel that this project is a big step for Wisconsin lakes. Endres told the Wisconsin State Journal “If we don't strategically remove this legacy phosphorus from our stream, we will never be able to meet our water quality goals."
The Wisconsin State Journal
The Capital Times; Madison.com