Permeable Interlocking Concrete Pavement Project Profiles

For more information on these project profiles and additional case studies, click here.

Pavement that Detains
and Infiltrates Runoff

Like infiltration trenches, permeable interlocking concrete pavements (PICPs) are highly effective in providing infiltration, detention and treatment of storm water pollution. The base can be designed to filter, treat and slowly release water into a storm sewer or water course while providing a walking and driving surface. PICPs limit the amount of impervious cover flowing into storm drains working at capacity, or when sites have limited space for detention ponds.

The U.S. Environmental Protection Agency (EPA) and several state agencies consider PICPs an infiltration Best Management Practice (BMP). An increasing number of cities, counties and states are incorporating them into land development and runoff standards, low-impact development guidelines and design manuals on stormwater control. With proper design, material selection, construction and routine maintenance, PICP is a sustainable low-impact BMP used by landscape architects, architects, engineers, developers and public agencies.

PICPs have been widely used across Europe, especially Germany since the early 1990s. The projects demonstrate runoff reduction and improved water quality in a range of climates, soils, hydrological and regulatory environments.

Morton Arboretum Visitor's Center Parking Lot
Lisle, Illinois

When Morton Arboretum in suburban Chicago decided to build a new visitor's center, it also developed a new entrance, parking lot and bus passenger drop off area. The need for detention facilities to capture runoff from these areas was unacceptable to the Arboretum. Permeable pavers were instead chosen to protect water quality, manage stormwater and provide a durable surface for vehicle traffic. The Arboretum wanted to implement as many BMPs as possible into their new parking lot design since runoff from the project is being monitored under the EPA Section 319 National Runoff Monitoring Program. The parking lot consists of 173,000 sf (16,000 m²) mechanically installed PICPs and 32,000 sf (2,970 m²) of interlocking concrete pavement. Constructed in 2003 and 2004, the paving units used custom color blends selected by the Arboretum's staff.  
 

Wal-Mart Parking Lot
Rehobeth Beach, Delaware

Rehobeth Beach is situated along the Atlantic coast just north of the mouth of the Chesapeake Bay. When the shopping center owner needed to expand parking behind a Wal-Mart in 2002, there wasn't sufficient space for the parking lot and a separate detention pond. PICPs combined the two functions. PICP enabled partial exfiltration from the base to the soil, using perforated pipe and surface drains for saturated conditions from heavy rainstorms.   

Due to the size of the project the pavement at this Wal-Mart was mechanically installed.  

Robson Center
Gainesville, Georgia
Formerly known as the Southern Heritage Building, the Robson Center's 8,200 sf (760 m²) parking lot represents one of the first pavements of its type in the region. The Robson Center pavement was installed in order to meet a new municipal limitation on impervious cover, while getting full economic development from the site's acreage. The pavement surface located in the development's entry lanes used colored brick red to match the building.

The base course or 'base reservoir' is made with open-graded No. 57 crushed granite rock, which has void space of 30%+ and very high permeability. The bedding layer and joint fill is similar but smaller No. 89 aggregate, which also has high porosity and permeability. The combination gives the pavement high permeability and water storage capacity.

Since the soil was largely clay fill that had to be compacted, very little infiltration into the soil is expected. Instead, a perforated pipe at the bottom of the base reservoir drains to the city's storm sewer system. A previously installed stormwater detention basin had been designed for impervious surfaces throughout the development. This pavement's permeability and in-pavement storage are expected to make the project's stormwater performance exceed the design expectations. In the unlikely event the pavement should generate surface runoff due to an extremely intense storm or clogging occur somewhere in the system, the runoff will drain to grate inlets at the side of the pavement, then into the conventional storm sewer system.

Hilton Garden Inn
Calabasas, California

PICPs at this hotel in Southern California capture and treat the first flush from the parking lot. The curbs are recessed to allow overflows to run into an adjacent grass swale.

The Hilton Garden Inn designers chose PICP to satisfy the City of Calabasas stormwater management requirements. These mandated at least 30% pervious cover to control the quantity and quality of runoff from the site, specifically by containing the "first flush" or the initial ¼ in. (6 mm) of rain water within a 24-hour period. The site meets this requirement with PICP that runoff filter into an open-graded base, temporarily detaining water before passing to the storm drain system.  

A color blend of cream/brown, cream/charcoal and solid brown was selected for the 12,000 sf (1,110 m²) project completed in June 2002. This maintains some reflectivity without blinding pedestrians on sunny days.  The pavement covers the hotel driveway, entry area and parking lot.

The position of the pavers changed over the design stages of the project. Instead of laying the pavers at the lower side, away from the building, they were installed on the uphill side next to the hotel. Placement of pavers next to the hotel entry provided a visually pleasing appearance, but reduced the total amount of water infiltrated by the pavement's surface. Other measures were implemented to treat runoff which included a grassy swale to filter runoff next to the asphalt pavement and a filter in the catch basin.

Multnomah Arts Center
Portland, Oregon

Built as a school in 1913, the City of Portland Parks and Recreation Department purchased the building in 1979 and converted it to an art center. The parking lot required expansion and the City wanted a permeable pavement with a pedestrian-friendly surface that would withstand parked cars. The 10,500 sf (975 m²) was completed in three phases each taking 10 to 12 days. The pavement was sloped toward a bio swale to handle excess water.

Jordan Cove Watershed
Waterford, Connecticut

Runoff and pollution monitoring of PICPs in the EPA funded Jordan Cove Urban Watershed National Monitoring Project. Driveways and municipal streets were paved in this low-impact, environmentally sensitive residential development.

This watershed that drains to an estuary in Long Island Sound is participating in a 10-year monitoring project of runoff from a traditional subdivision, a single-family home development built with a conventional pavements and stormwater management system and a low-impact development built with runoff and pollutant-reducing BMPs. These include grass swales, bio-retention areas and PICP. The EPA Section 319 National Monitoring Program supports the monitoring project conducted by the University of Connecticut.

Built in 2001, the Glen Brook Green subdivision within the watershed features more than 15,000 sf (1,400 m²) of PICPs in a street and 12 residential driveways that recharge the local aquifer, slow runoff velocities, oxidizes and filters some pollutants, filters suspended solids and cools water before it enters the estuary. Maintenance includes periodic sweeping and vacuuming with the same equipment used on other streets. An annual inspection ensures no ponding and aggregate is replaced in the pavement openings as needed.

The 2003 annual report of the multi-year monitoring project demonstrates the effectiveness of PICPs in reducing runoff and pollutants.  Runoff quantity and quality from asphalt, PICPs (with a dense-graded base) and crushed stone driveways entering single family homes were studied for 12 months in 2003. 

Besides lower infiltration rates than asphalt, PICPs demonstrated lower concentrations of pollutants in runoff and similar concentrations to that from driveways with crushed stone. Concentrations are statistically significantly lower for all pollutants from PICP compared to asphalt. Pollutant levels in PICPs are similar to that from the driveways with crushed stone.

Engineering/Computer Science Building Entrance
Victoria University, British Columbia
Home to more than 18,000 students and 4,000 staff, the university follows an integrated campus plan that incorporates sustainable practices in construction and operation of all new buildings and facilities. A natural fit are PICPs at a new pedestrian drop off and short-term parking for the expanding Engineering/Computer Science building. Completed in March 2004, University officials asked the design engineer to create the 8,000 sf (743 m2) parking area to exceed LEED criteria, specifically reducing the rate and quantity of runoff by 25% from a 2-year, 24 hour design storm. The open joints and notches in the paver surface enabled full infiltration of commonly occurring storms through a clean crushed jointing and bedding material.

The PICP pattern achieved a welcoming entrance with six parking spaces for disabled persons and six standard parking spaces. The pavement and subgrade sloped gently to one end of the site where perforated pipe at the bottom of the subbase drains it within 24 hours. Existing catch basins handle overflows from extreme storm events.

According to Sarah Webb, the University's Sustainability Coordinator, "The paving stones have exceeded our expectations. Students, faculty and staff have commented on how aesthetically pleasing the drop off is. We have had no problems with wheelchair access, and the stones have continued to perform under our heaviest west coast rains. Maintenance has been minimal and deicers kept ice from the surface during the occasional winter freeze, nor have their been any problems from freezethaw cycles. Ms. Webb also noted that, Paving stones, and other permeable products, will continued to be used on the campus as a part of our green building program and our commitment in the university's Integrated Stormwater Management Plan to reduce water runoff and improve water quality."


Harbourfront Fire Station
Toronto, Ontario
Located on a Lake Ontario, the Harbourfront Fire Station features 11,000 sf (1,022 m2) of PICP in its entrance and parking lot. Built in the winter of 1998, the City of Toronto required a pavement that would reduce runoff pollution to Lake Ontario through infiltration while providing a parking lot in a highly urbanized area.

Built with a dense-graded base, the project exemplifies the ability of PICPs to withstand heavy loads from fire trucks in a winter environment with deep penetration of frost in pavements. The pavement is plowed and salted in the winter, but not sanded to prevent clogging of the aggregate in the openings and reduced infi ltration. The lack of raised curbs enables snow plows to push snow directly off the pavement.

For more information on these project profiles and additional case studies, click here. To speak to an ICPI staff member on the technical aspects of PICPs, please (202) 712-9036 or e-mail icpi@icpi.org.