The bridges rest on concrete abutments, and the structures themselves were set using cranes from Phoenix Crane. These single-span structures were constructed by subcontractor Steadfast Bridges, based in Fort Payne, Ala. In addition to construction of the new pathway, this project included construction of three major bridges on the Rottenwood Creek portion of the trail. Proper finishing of the pervious concrete was important, too, as too much finishing can bring the paste to the surface and adversely affect the pervious qualities of the finished pavement.Īfter final finishing, the newly placed concrete was then covered with plastic, which remained in place for seven days to allow the concrete to cure. Final finishing was achieved using long-handled steel rollers. Winches and cables pulled the screed along as the concrete finishing moved ahead. The screed included a vibratory system, though only a small amount of vibration was required during placement. Lewallen's custom screed, which the contractor fabricated for this job by modifying anexisting screed, traveled by riding on the edges of the form boards. It arrived at the site in ready mix trucks, which carefully backed down the trail route to the work area and discharged the mix directly onto the prepared base.Īs soon as the concrete was discharged, Lewallen's crew went to work with a custom-made screed to level and finish the concrete. The pervious concrete used on the project - a total of about 1,400 cubic yards was required over the course of the project - was supplied by Thomas Concrete. Then, in preparation for concrete placement, crews installed forming strips along the edges of the trail route. However, the Rottenwood Creek portion of the trail involved new construction - and with it some challenging clearing work.Īs a section of trail was cleared and graded, crews placed and spread 6.5 inches of graded aggregate base. Along the Chattahoochee River, the new trail follows the route of an earlier trail. To construct the trail, contractor Lewallen Construction first cleared and graded the trail route. The main portion of the trail, running along the Chattahoochee River, has a width of 12 feet a side trail following Rottenwood Creek is 10 feet wide. Because of that ability to regulate runoff, pervious concrete is ideal for projects in environmentally sensitive areas where surges of storm runoff must be minimized.ĭuring the course of this project, pervious concrete was used to construct much of the 2.1 miles of new trail. The result is a porous mix with an open-cell structure which allows water to quickly pass through and then soak into the underlying ground instead of running off quickly into nearby waterways. However, unlike conventional concrete, pervious concrete mixes include little or no sand. Pervious concrete, like conventional concrete, consists of cement, coarse aggregates and water. This became apparent from the moment of the initial walk-through and remained a factor throughout the course of the project. In fact, the very thing that makes this area so popular with visitors - its decidedly urban yet relatively remote and ruggedly scenic topography - also brought challenges to the construction team. "Projects like this one are fun projects," says Larry Lewallen, "but they can be challenging too." Moreland Altobelli designed the project, which is part of Cobb County's trail system. Lewallen Construction, based in Marietta, Ga., served as the contractor on the project. This $3.6-million trail project enhances their experience by providing a greatly improved trail surface, and the pervious concrete used in trail construction will be a major factor in controlling runoff and thus minimizing river impacts during rain events.
41.ĬRNRA draws visitors year-round, and hiking along the river and through the surrounding countryside is a popular activity. The trail extends from Interstate Parkway and Interstate North Circle near I-285 and I-75 and continues into the Chattahoochee River National Recreation Area (CRNRA) off U.S.
Pervious concrete, steel bridges and attention to the environment have been key elements during construction of the Bob Callan Trail, a new 2.1-mile multi-use trail along the Chattahoochee River and Rottenwood Creek in northwest Atlanta.
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