Green Alleys of St. Louis

Fall 2014

Pilot projects to evaluate PICP

Elizabeth Ecker Bandy

By

Green Alleys of St. Louis

Taking cues from the successes of projects in cities like Chicago, St. Louis has installed several green alley projects since 2007 utilizing permeable pavers and interlocking concrete pavement. The Tower Grove Heights Green Alley Paver Project was completed in two phases from 2011 to 2014. It updated 400-year-old alleys with permeable pavers through a federal Community Development Block Grant, a state Department of Natural Resources grant, and local tax-based funding. PICP was used to reduce stormwater runoff and maintain the historic appearance of the alley, originally laid in brick over clay.

In 2009, the City of St. Louis commissioned a Pilot Green Alley project using donated materials and labor. Three alleys were installed that year with pervious concrete, porous asphalt and PICP. The performance of the city-owned alleys is being evaluated over time. All of these are built over open-graded aggregate reservoirs, allowing stormwater to drain through the system per the City’s specifications.

“We helped fund a portion of them because of the experimental nature of the materials at the time,” says John Grimm, of the Metropolitan Sewer District. St. Louis also used tax funds for the $41,000 Cherokee Green Alley Concrete Project, a 150-ft long by 12-ft wide alley completed in 2009. The pilot project’s outcomes are still being tested, with MSD conducting a report on flow measurements scheduled for completion at the end of 2015.

Green alleys are not unique to St. Louis, but the city’s history and layout with centuries-old alleyways and roads lends to more paver installations in the future, Mr. Grimm says. “There are some suburbs that have alley arrangements, but they are not as prevalent,” he says. “It’s mainly particular to the city.” 

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