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Paving our Way to a Greener Future

Summer is fast approaching and soon will be upon us before we know it. Summer around here means heading down to the river. Whether you are walking on the dike, taking the boat out to fish or being pulled behind the boat on a tube, we cannot spend enough time on or near the river. And while we value our time spent on the waves, when Clinton was founded 150 years ago, the river was valued for a much different reason. Our town’s proximity to the river and the rivers ability to transport goods for commerce made this a prime location for the lumber industry to thrive. The City’s first sewer system was installed, and everything drained directly into the river. During that time, it was a common practice for river towns to direct their wastewater, runoff, and toxic waste into the river. This system of sewers that connect both waste from homes as well as collecting storm water from the streets became known as a combined sewer. At that time there was little concern about anything being dumped into the river and there were no regulations on it.

IMG_2685It wasn’t until 1970 when the Environmental Protection Agency was established that people began to worry about the hazards of polluting rivers and waterways. In 1972, the EPA established the Clean Water Act which became the foundation for the elimination of combined sewer overflows. The issue of combined sewers was finally addressed in 1989 when the EPA mandated they could no longer used.

Sewer designs have changed over the years with new practices being put into place and other dated practices, (like combined sewers) being eliminated, but all of this takes time. Even now Clinton experiences combined sewer overflow (CSO) events where untreated waste is discharged into the river. These CSO events happen during extreme wet weather (such as large amounts of steady rainfalls over a period of days or hours, or excess snow melt) entering the storm sewer system.

Correcting these problems has already begun. You may recall projects over the last few years such as the 25th Ave N Pump station, 20th Ave N pump station and the Main Ave Sewer project just to name a few. All of these played a role in Clinton’s goal to separate the sewer and storm water, and this summer’s 25th Ave North project will continue this work. The designs for 25th Ave North, like the work on Main Ave, will incorporate green infrastructure or BMP (Best Management Practices) features. Green Infrastructure are features that focus not only conveying storm water to its proper location but also treating the water by removing debris and contaminates or retaining it on site long enough so the sewer system doesn’t become overwhelmed. These practices are called green infrastructure because they attempt to replicate the natural drainage conditions.

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This project will be a large undertaking, with the complete reconstruction of nine blocks of paved roadway and the installation of over one mile of sewer pipes. Storm water and sanitary waste will be separated, and this will eliminate the possibility of combined sewer overflows into the river and backups into basements in this area. Some trees will be removed, more trees will be planted, 

a new bike path will be constructed and ADA accessible handicap ramps will be installed at every corner.   The existing road surface will be replaced with full curb and gutter, and 31’ wide permeable concrete pavers (similar to the brick pavers on Main Ave). These pavers, as well as a bio-retention cell, are the green infrastructure practices. In Figure 1, as the rain falls on the pavers it is able to infiltrate the open graded subbase. An open graded subbase has voids in it that normally would be filled with fine particles, by eliminating these fine particles it provides a place to temporarily store water. After the water is stored for a short duration it then is conveyed to the storm sewer via the slotted sub drain that is installed below the pavers. The bio-retention cell works in a similar manner as the concrete pavers by slowing allowing the water to filter through the soil and aggregate to the slotted sub-drain where the water is conveyed to the sewer system.

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The Mississippi River has been important to Clinton for many years. Local industries still depend on the river, but when someone mentions the river today we conjure images of walking the dike, riding bikes, eating from a food cart, theatrical performances, musicians at the band shell or taking the boat out after work. On the surface this it may only seem like this project is fixing the road for a smoother drive, but in reality, this project goes much deeper than that. It, like many other things in town, leads back to the river and focuses on maintaining our greatest resource.