City of Clinton Public Works Department

Situated near the Mississippi River, Clinton, Iowa, recently celebrated the 135th anniversary of the city’s incorporation. In an effort to increase the location’s economic growth as well as local jobs, city officials determined that sewer system and road improvements, as well as construction of a new wastewater treatment facility, were long overdue. Much of the city of Clinton’s combined sewer system is in need of separation.

“When the sewer system was originally designed and constructed, the storm intakes were connected directly into the sanitary system,” City Engineer Jason Craft says. “These cross connections cause surcharging of the smaller sewers during heavy rainfalls.”

The city of Clinton has completed several sewer separation projects over the last five years. The latest project was completed in 2010. The 22nd Avenue North sewer separation was a 12-block project that separated all storm and sanitary sewers, in addition to reconstructing the streets with concrete. With the new system, stormwater is discharged straight to the Mississippi River while the sanitary sewer discharge is routed to a wastewater treatment plant for decontamination.

“This was a pretty standard sewer installation,” Craft claims. As an added bonus, the city planners were encouraged by the price of the bids they received from the contractors. Budgeted at $1.9 million, a project bid of $1.4 million from Eas­t­ern Iowa Excavating & Concrete was accepted by the city. “With the cost savings, we were able to resurface additional roads,” he says.

Reusing the Roads

To revamp as much roadway as possible, engineers looked into alter­nate methods of asphalt paving that would save money and recycle the existing pavement. Instead of removing and disposing of the surface pavement layer, the city implemented a hot-in-place recycling method that involved heating and softening the top two inches of asphalt. 

The exposed surface is scarified while a recycling agent that rejuvenates the asphalt binder is mixed into the heated, recycled asphalt. After the recycling process, the street is then treated with a thin asphalt overlay or microsurfacing. “Though we will have to do full-depth patching in some places, this method will allow us to save money, conserve energy and get more roads paved,” Craft notes. “It will be the first time we will use hot-in-place and microsurfacing on Clinton’s streets.” This portion of the project is slated to begin in September 2010.

In addition to Hot-In-Place Recycling, the city of Clinton is using another method of asphalt road recycling called full-depth reclamation. This is a road rehabilitation technique in which the full thickness of asphalt pavement and base material is uniformly pulverized and blended to provide a homogenous and more stable pavement base. In some cases, fly ash is added to the reclaimed material to further stabilize the road base. 

After this reclaimed road base is graded, a driving surface is constructed. The city of Clinton plans to use a three-inch asphalt overlay or a double- chip seal as surface, depending on anticipated traffic loads.

Perhaps the largest street reconstruction endeavor in the city of Clinton’s recent history is the Highway 30 reconstruction project through the heart of the town. The plan involves a partnership between the Iowa DOT and the city to replace an old four-lane, two-way asphalt-paved roadway with a new concrete parallel one-way couplet. Phase I of the project included constructing the new concrete, one-way eastbound street and restriping the old asphalt highway for use as the westbound, one-way lanes. Phase I of the project is substantially complete; it is scheduled to be completed fall 2010, once trees are planted throughout the new corridor. Phase II, scheduled to begin in 2012, will involve constructing the new concrete, one-way westbound lane. The finished project will be a divided one-way couplet system with a large green space in be­t­ween that the city will redevelop.

The city of Clinton’s No. 1 transportation project is the planned extension of 19th Ave­nue North approximately 1.85 miles from High­way 136 Mississippi River Bridge (connecting Iowa to Illinois) to the Mill Creek Parkway on the west edge of Clinton. The new roadway will offer travelers a more efficient route through Clinton between major highways in Iowa and Illinois. “We’re trying to route more traffic through Clinton in an effort to spur the city’s economic growth,” Craft explains.

New Wastewater Facility

Construction of a $37 million wastewater treatment facility on a 40-acre site began in April 2010. Scheduled to be completed in September 2012, the new facility will incorporate poured concrete floors with precast walls and roofs. The new facility will house the entire operation from the head pumps that deliver the wastewater to rotary presses and then to aeration basins. Final clarifying systems eliminate any remaining contamination and the clean water will then be discharged into the river.

“We’re incorporating very new, energy efficient technologies for the blowers in the aeration basin,” Public Works Director Gary Schellhorn says. “The turbine acts like a jet en­gine so it’s much more efficient at moving the air than the blowers used in the old facility.” He notes that these blowers are ordinarily the lar­gest energy user in the plant. The new system will save approximately $100,000 per year in energy consumption costs.

In addition to the $37 million price of the fac­ility, almost two miles of pipeline will have to be placed both to and from the old facility to the new one. “This will put the costs for the en­tire project at about $50 million,” Schellhorn estimates. He adds that there will be 27,000 feet of pipeline within the new facility itself to move flow to the various tanks.

Designed to treat up to 12 million gallons per day, Clinton designed its plant to accommodate wastewater from neighboring cities Low Moor and Camanche, Iowa. “Both of those cities had outdated wastewater facilities,” Schellhorn notes. “The other two cities combined need less than 1 million gallons of water treated per day, so they will save money by not having to construct or maintain wastewater facilities and Clinton will benefit from the revenue earned.”

Additionally, the old wastewater treatment facility also will be used as a backup system for instances when excess rainfall must be treated. “In all, both facilities at full capacity will be able to handle 15 million gallons per day.” Built to accommodate future industrial growth, the new facility will also be able to accommodate wastewater from any companies that build plants in Clinton in the near future.  

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