Rainscaping Iowa - Permeable Pavement Projects
Rainscaping Iowa, an educational campaign that promotes urban stormwater management practices, encourages the use of permeable pavement by featuring successful installations in the state. By gathering feedback on previous projects, Rainscaping Iowa simultaneously highlights the environmental benefits of permeable surfaces and provides lessons for future installations and maintenance. Importantly, the campaign’s literature describes how permeable paving surfaces can help reduce runoff and improve water quality in the face of changing precipitation and increasing heavy rainfall events.
Rainscaping Iowa’s featured projects utilize two types of permeable paving surfaces: porous asphalt and modular permeable paver blocks. Porous asphalt is a paving surface that allows water on the surface to infiltrate through the asphalt to storage bed of limestone below. Modular permeable paver blocks are individual blocks that fit together to create a surface with funnel-like openings that lead to a limestone storage bed.
The project site includes several examples of different types of permeable pavement installations on both public and private property. For example, the Green Alley program in Dubuque reconstructs city alleyways using permeable pavements. In one project, porous asphalt was installed in an alley between White and Jackson Streets. The alley manages rainfall and runoff well, and it clears up faster than other alleys after winter storms despite not being plowed by the city. There have been problems with debris from neighboring driveways, although such problems can be avoided with more frequent cleaning. The city has also installed wider collars along the alley to block debris. The city recommends informing neighbors ahead of time about the benefits and maintenance of porous asphalt alleys. In Dubuque, they mark such alleys with Green Alley stamps at both ends and distribute pamphlets to nearby residents that explain maintenance requirements and warn against pouring certain substances (e.g. oil, antifreeze) onto the porous asphalt. In a different featured alley, the City of Dubuque installed interlocking concrete pavers. This alley is also performing well, with nearby residents taking some responsibility for keeping the area clear of debris.
To manage stormwater around private parking areas, one business owner in Pleasant Hill installed 1600 square feet of porous asphalt in a new parking lot. The pavement absorbs and infiltrates direct rainfall and stormwater from adjacent driveways, parking lots, and rooftops. The owner emphasizes the need to keep the pavement clear of debris and recommends completing construction on a site before installing porous pavement.
Okoboji, Iowa has also utilized permeable pavement on both public and private property. The city installed two permeable paver sections, along with bio-retention cells, when they reconstructed an urban street. The first 1.25 inches of storm water runoff at the site are cool-filtered and treated. The permeable pavers required maintenance when the aggregate filling the void between paver stones became clogged and was not percolating properly. Overall, the city has seen an improvement in the quality of runoff form the site.
Also in Okoboji, a city ordinance requiring 421 cubic feet of storage for the first 1.25 inches of runoff led property owners adjacent to a lake to install low impact development features, including permeable pavers in the patio and driveway. With little space surrounding the residence on which to install LID features, the permeable pavers helped achieve the required storage in a limited area.
Overall, the projects compiled by Rainscaping Iowa illustrate how, with proper design and maintenance, permeable paving surfaces can consistently improve runoff infiltration and water quality. Such benefits also show how permeable paving surfaces can help protect local water supplies faced with changes in precipitation or extreme weather due to climate change.
Rainscaping Iowa is funded by its partners and stakeholders, namely the Iowa Department of Natural Resources, Department of Agricultural and Land Stewardship, Department of Economic Development, Department of Transportation – Living Roadway Trust, the Iowa Storm Water Education Program, and the Polk Soil and Water Conservation District.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on March 18, 2015.
Publication Date: 2010
- Rainscaping Iowa
- Iowa Department of Natural Resources
- Best practice
- Case study