Permeable Paving Made with Recycled Tires Helps a Historic Cemetery Preserve Its Heritage
Greenwood Cemetery covers more than 30 acres in the village of Hillsdale, Missouri, part of the St. Louis metropolitan area. Established in 1874, the cemetery was the first African-American non-sectarian cemetery in St. Louis. More than 50,000 people are buried here, including some 5,000 formerly enslaved people.
The road leading to the cemetery’s rear section traverses a roughly 10% slope; gravel washout occurred after almost every big rainfall. Drivers visiting the gravesites of loved ones in this part of the cemetery would leave deep tire trenches, often making the road impassable.
Making a tangible improvement to the road had long been a priority. So, members of the cemetery association reached out to Civil Design Inc. for guidance, and CDI in turn reached out to Engineers Without Borders USA’s (EWB-USA) domestic program (known as Community Engineering Corps / CECorps) and its Gateway Professional Chapter, as well as the joint engineering program at the University of Missouri St. Louis (UMSL) and Washington University.
Together, this team of professionals and engineering students began with a site assessment, which included using ground-penetrating radar to help pinpoint the location of unmarked gravestones close to the road. The students used the data to develop a preliminary design. When the design was 90% complete it was handed off to CDI to finalize for construction.
As part of their work, students prepared an alternatives analysis that considered a range of options and cost estimates. Traditional asphalt and concrete pavement options were considered but rejected because both materials would have created an impermeable surface, leaving unresolved the roadway’s storm runoff issues.
The most expensive option was to rebuild the road and include a rain garden to intercept runoff and a stormwater pipe replacement. This design carried an estimated cost of $320,000.
The adopted solution had a cost estimate of $183,000 and specified the use of permeable pavers made with recycled tires- designed by ASPIRE
These innovative pavers, generously supplied as in-kind donations from the American Chemistry Council, are 4x8-in. And set in a 16 sq. in. grid that weighs around 15 lbs. The pavers allow rainwater to percolate through the joints and infiltrate into the underlying layers. And, the pavers have a peak compressive strength of 2,000 psi, based on ASTM C140-09 Section 7 standards; their ultimate flexural strength is 695 psi.
The use of the pavers on the cemetery’s steep slopes required approval by the Metropolitan Sewer District (MSD). As part of its review, the District required that a water storage system be installed beneath the road to manage runoff. In turn, the CECorps team helped secure a grant from MSD to help defray the infrastructure costs.
In the final design, the 2.4 in. thick pavers were installed atop bedding sand and a subbase. An underlying layer of crushed rock formed a water storage bed interlaced with 6 in. perforated pipe. On the sections of the roadway where slopes reached 10%, vertical concrete anchor beams were placed every 120 ft. These beams had a minimum width of 8 in. and were sunk to a minimum depth of 36 in.
The access road is the first outcome of a collaboration announced in January 2023 in which America’s Plastic Makers committed to contribute $1 million in funding and materials to help EWB-USA uplift underserved communities and advance U.S. infrastructure.
The rebuilt roadway represents a sustainable solution, managing stormwater effectively while also ensuring the cemetery remains accessible for generations to come.