The City of Evanston’s parking lot outside of the Morton Civic Center sees plenty of traffic in its role as a hub of local government activity. But over the past year, the parking lot got an upgrade. No longer is the parking lot a mass of traditional concrete and asphalt – instead, the parking lot is now a pioneer of green infrastructure in the City.
Last October, the City completed construction on the Morton Civic Center parking lot, making it Evanston’s first City-owned sustainable public parking lot. The lot now has two electric vehicle charging stations, as well as three new permeable pavements, rain gardens and native plants that will work together to reduce the volume of storm water run-off into the City’s sewers.
“Permeable-paving materials help promote storm water to drain through the pavement structure and infiltrate into the underlying native soils,” says Dan Manis, a civil engineer with the City of Evanston and the project’s senior manager. ““The primary benefit of these sustainable materials is the reduction of stormwater reaching the sewer system which reduces the frequency and magnitude of sewer backups due to sewer surcharging.” Additional environmental benefits include the cleaning of stormwater runoff through natural biological processes and groundwater recharge.
The three new permeable materials in the parking lot are interlocking concrete blocks, porous asphalt and porous concrete.
Interlocking Concrete Blocks
(Interlocking concrete blocks right after installation in the Morton Civic Center parking lot/ Image courtesy of Dan Manis)
Interlocking concrete blocks are the most expensive of the three materials used in the project. (Approximately half of the parking lot project’s $1.4 million cost was funded by a grant through the Metropolitan Water Reclamation District of Greater Chicago, the public agency responsible for managing stormwater and collecting and treating wastewater generated by most Cook County municipalities.) The concrete blocks were spaced by a machine an equal distance apart from each other, and then the cracks between them were filled with loose rock to allow water to slip through.
Porous Concrete and Porous Asphalt
(Porous concrete is pictured here above the traditional concrete in the parking lot/ Image courtesy of Dan Manis)
The porous concrete and porous asphalt are not too different from their traditional counterparts. The largest difference is that the porous materials lack fine aggregates such as sand. Instead, the porous concrete and porous asphalt mixtures only contain open graded larger rocks producing a porous pavement structure.
The Morton Civic Center parking lot also features rain gardens around the edges of the parking lot. The gardens are designed to keep as much water as possible in the native soil. In the fall, the City planted a seed mix of native grasses, shrubs and wildflowers that have long roots to trap more water deep in the soil than their short-rooted counterparts. The plant root systems also serve as a filtration system — removing nutrients, sediments and pollutants from the rainwater before it seeps down into Evanston’s groundwater and waterways.
The rain gardens will be composed of native plants, which are plants that existed in the Evanston ecosystem before European settlement. Native plants are beneficial to the environment because they require minimal care once planted, they provide food and shelter to local wildlife and they help prevent erosion and water pollution. The flowers and grasses around the parking lot will begin blooming this spring.
Electric Vehicle Charging Stations
The Civic Center parking lot now also features two free charging stations for electrical vehicles. Each charging station has two ports, so four electric vehicles can be charged simultaneously at zero expense for the driver. The City also installed electric vehicle charging stations in the Maple Avenue Garage, the Sherman Plaza Garage and the Evanston Public Library. The City also has a fleet of electric vehicles to minimize the City’s carbon footprint and negative impact on the environment.
For the Future
The City is monitoring the success of each of the three pavement materials “to gauge the long-term durability of each to make decisions for future City projects,” Manis said. Another City-owned parking lot in the 1600 block of Oak was built this past October using interlocking concrete blocks.
Currently, the City of Evanston is planning to apply for grants to rehabilitate seven more parking lots using sustainable infrastructure techniques in the coming years. Manis said that the consultants hired to design the lots will need to come up with a system to provide quantitative data on the benefits of sustainable pavements versus conventional pavements.