Ayres Associates provided construction engineering services for the reconstruction of 1.4 miles of Lacy Road from Research Park Drive to Syene Road in the City of Fitchburg, Wisconsin. What sets this project apart is a 400-foot test section of porous asphalt pavement along a shared use path that parallels the urban street, as well as permeable storm trenches along the majority of the project that allow much of the water in the storm sewer system to weep through perforated storm sewer pipes and into the ground rather than proceeding through the stormwater collection system.
The test section of porous pavement on the shared use path required a non-standard asphalt mixture that omits the sand particles that usually fill the gaps between larger rocks. The concept of the porous pavement is that rainwater can filter directly through the asphalt and through the thick open-graded stone bed underlying the pavement, thereby reducing runoff.
The City will look at the results of this test length of porous paving to determine whether it is suitable to use more in the future.
The project’s permeable storm trenches are a notable variation on standard storm sewer drainage systems in that the pipes are perforated and surrounded by open-graded stone, allowing stormwater to drip out of the pipes and seep through the stone and into the ground adjacent to the street. This is an alternative to stormwater treatment that typically guides all runoff to detention ponds or bio swales. Establishing a pond or swales on this project would have required acquiring additional right-of-way.
Ayres’ construction engineering work involved water main, sanitary sewer, storm sewer, asphalt roadway, curb and gutter, driveways, roundabout construction, the 10-foot-wide shared-use path, pavement markings, signage, and landscaping.