Permeable Pavers from Recycled Auto Tires & Plastic Containers Pave Houston Parking Lot

The new parking lot for the Houston Parks Board facility was truncated from 60 spaces to 20. VAST composite permeable pavers were specified to meet the city?EUR??,,????'?????<

Asphalt, concrete, clay brick and stone are typically hardscape construction materials for cities. When it rains the runoff from these impervious surfaces can erode adjacent soils and carry all manner of pollutants and trash into drains and ultimately into waterways.

Research has shown that even a modest amount of impervious cover in a geographic area (less than 20 percent of the total area) is associated with degraded water quality.

Houston, Texas, like most large cities, has vast areas of imperious surfaces, so managing stormwater runoff is an ongoing battle. Houston and the Harris County Flood Control District require detention of runoff from parking lots as one element of its regional stormwater management efforts.

According to a 2004 study on surface infiltration rate of permeable pavements by the Interlocking Concrete Pavement Institute, permeable pavements do reduce runoff to a significant extent if these conditions are met: pavers sited in a sandy or loamy sand soil, site is located in soils without seasonally high water tables, the pavement is well-maintained, proper construction materials and techniques are followed and the pavement is essentially flat and away from disturbed clay soils.

Downsizing and Rebuilding the Parking Area
The Houston Parks Board (HPB) relocated in July 2009 to the former home of the Houston Police Mounted Patrol. The main building was left intact, but the offices and horse stalls were razed and plans made to reforest those spaces.

The parking lot in front of the building had room for 60 cars. The new parking lot was redesigned down to just 20 spaces and permeable paving specified to meet the city’s detention requirement, which would filter rain water into the ground, instead of allowing it to drain into Buffalo Bayou. Buffalo Bayou is a main waterway through Houston, flowing about 53 miles (85 km) east to the Houston Ship Channel and then into Galveston Bay and the Gulf of Mexico. Along the way, several significant tributaries feed Buffalo Bayou.

There were basic permeable choices: crushed granite, pervious concrete or asphalt and permeable concrete pavers.

While researching permeable pavers on line, Trent Rondot, project manager for the Houston Parks Board, read about composite permeable pavers, noting the composite pavers were 95 percent recycled auto tires and plastic containers.

Rondot’s selection came down to concrete permeable pavers or composite permeable pavers. Both, he felt, would be good choices, but he recommended the composite pavers because of its recycled content. After the Houston Parks Board analyzed the budget numbers, Roksan Okan-Vick, AIA, executive director of the board, endorsed the recommendation.

Installation and Permeability
While designers tend to just assume permeable pavers reduce runoff, certain conditions are necessary, according to a 2004 study on the surface infiltration rate of permeable pavements by the Interlocking Concrete Pavement Institute.

“Evidence suggests that, providing the following conditions are met, permeable pavements do reduce runoff to a significant extent: (1) the application is sited in a sandy or loamy sand soil, (2) is located in soils without seasonally high water tables, (3) the pavement is well-maintained, (4) proper construction materials and techniques are followed, (5) the pavement is essentially flat and away from disturbed clay soils.

Installation and Results
Gulf Coast Landscape Services did the parking lot installation. Mark Burzynski of Gulf Coast explained that preparation of the base is the same for any type of permeable paver installation. It begins with six inches of lime mixed into the site soil to stabilize it. Next is six inches of cement-stabilized sand and then a one-inch layer of sharp sand. The irregular, angular grains of sharp sand are good for drainage.

Manually aligning, spacing and leveling pavers is a time-consuming task. VAST has engineered an installation grid, which when laid atop the prepared base indicates the spacing and alignment for the pavers. Installation time was about the same as it would have been with concrete pavers, although the composite pavers weigh two-thirds less than concrete pavers. The project was completed with a 6-by-12 inch curb.