The City of Dubuque’s Green Alley Project is an infrastructure improvement project focusing on storm water runoff reduction. Between 1999 and 2011, Dubuque, IA was the site of six flood-related Presidential Disaster Declarations with total damages nearing the $70 million mark. In response to these repeated disasters, funding was secured to resurface approximately 240 alleys in the Bee Branch watershed with permeable pavement. The project is expected to reduce runoff in the watershed by 80% and help protect water quality in the Mississippi River. The Green Alleys project is phase 6 of a 12-phase flood mitigation effort currently under way in the watershed.
Because of their superior durability and aesthetic appeal, concrete permeable pavers were chosen over alternative pervious pavement options for the alley renovation. County Materials Corporation is supplying the majority of the pavers for the project. “We like the durability, and we like the look of them,” comments city engineer Jon Dienst of the 4”x8” H20 Pro Pavers®, adding that the uniformity of the units also makes them ideal for mechanical installation.
On a project of this scope, that is no small concern. Three local contractors are involved in the installation, each typically laying well over 3,000 units per day. The pavers can be laid one layer at a time, with a typical pallet of 8 layers taking just 6-7 minutes to install. This helps the project progress at an optimum rate. County Materials has stepped up to the challenge of keeping ahead of the contractors’ needs by maintaining careful communication between dispatchers, plant foremen and contractors. “They are installing a significant amount of pavers to meet project goals,” says County Materials’ sales representative Jon Schroetke. “It’s our job to make sure we are delivering what they need within a realistic, quicker time frame.”
The base materials used for the project are larger gravel size than typical sandset paver applications. The larger sized stone is less labor intensive to vibrate in, and easier to maintain. It is also far more cost effective for the city. Instead of paying for 1/4” granite chip at $200-300 per ton, the City of Dubuque is able to use 3/8” clean limestone gravel at just $18-20 per ton. This results in a mechanical installed price of under $4 per square foot.
“(The pavers) are the best bang for the buck. They’re consistent. It’s easier to remove debris out of these paver joints,” says Dienst. “And they’re cost effective, so we’re not overly burdening the citizens of Dubuque,” he adds, referring to the property assessment that is supplementing funding for the project.
As an added bonus to citizens, the pavers help extend seasonal access to the alleys. Like most Midwestern cities, Dubuque does not plow its alleys. The pavers eliminate water puddles and freezing in winter. Therefore they keep the alleys far more clear of snow than traditional paving, and minimize water accumulation in the spring.
At first, the City’s engineering department fielded some pushback about the assessment for alley reconstruction. However, as residents watched the transformation happening in their alleys, the nature of the phone calls changed. Now, people are calling up and asking whether their alleys are next. The City is using the popularity of the alleys to help educate the public about watershed best practices.
Despite the speed at which the work is progressing, the Green Alleys project is a long-term endeavor. Twenty-three alleys were completed in 2014 with another 50 scheduled for 2015 and 2016. Reconstruction of the remaining alleys in the Bee Branch Watershed is scheduled to take place between 2024 and 2038. However, the City of Dubuque may not stop there. “At some point,” says Dienst, “we’d like to extend to areas outside the Bee Branch watershed. We expect other areas of city will also want their alleys redone.”
Photos courtesy of the City of Dubuque.
