Metro Center Warwick

Type: Permeable pavement and rain garden

Use: Commercial

Installer: Fleet Construction, Cumberland, RI

Designer/Developer: Dennis Diprete of DiPrete Engineering

Installation Date: October 2007

Address: 117 Metro Center Blvd., Warwick, RI 02886


Greg Guglielmo

DiPrete Engineering

Porous asphalt and rain gardens were used on this commercial facility. The porous asphalt has been in place since October, 2007 and is visually monitored on a regular basis to detect any problems. The porous pavement is designed to infiltrate the 100 year storm from the 6 acre parking area and 2.8 acre rooftop. Building runoff is conveyed directly under the parking lot and then infiltrated. The 450 space parking lot and drainage design, is sized to accommodate a second building to be built in the future.

The site is a former gravel bank with an average water table of 6 – 8 ft. and good infiltration rates of (1.3 – 15.5 in/hr). Additional fill used in development will provide greater separation to groundwater. In lieu of the originally designed 4 ft of base stone across the entire parking lot area, the design was modified during construction to reduce the stone coverage to 2 ft in some areas, stepping the stone infiltration bed under the pavement. This allowed the bottom of the stone infiltration zone below the pavement to be laid flat; areas of shallower stone base are sloped toward the deeper stone areas. This saved a substantial amount of stone, reduced cost, and appears to be working well.

To ensure proper stormwater management in case efficiency of the porous asphalt is reduced over time, a redundant drainage system was installed. Catch basins with infiltration pipes allow stormwater to enter the stone infiltration bed directly. Roof leaders are also piped into the stone infiltration zone. Stone trenches located along the edge of the parking areas are also tied to the stone bed at several places to provide additional opportunities for infiltration. Finally, rain gardens along the westerly boarder of the property treat water flowing onto the property as well as on-site landscaped areas.

Visit the DiPrete Engineering website for more information.

Metro Center Warwick

Address: 117 Metro Center Blvd., Warwick, RI 02886