Trends in Green (Sustainable Innovations on Campus)

Options in Stormwater Management

To the university of New Hampshire (UNH) faculty, staff and visitors who park outside the Elliott Alumni Center, the area may seem like just another parking lot: 53,000 square feet of black asphalt, white lines and never enough empty spaces.

But to Tom Ballestero, director of the UNH Stormwater Center (UNHSC), the parking lot is innovative infrastructure, providing not just parking but also improved water quality and research data.

Pervious pavements let stormwater drain through the parking lot instead of sitting on the surface. UNH has made a commitment to sustainability, stormwater management and long-term planning by installing similar parking areas at five locations around the Durham campus. UNH, in collaboration with the UNHSC, has demonstrated the effective use of a range of pervious pavements… and all in a northern climate.

An Effective System

The research and implementation projects conducted by the UNHSC have proven that pervious pavements are a very effective approach to stormwater management in terms of both quality and quantity. Data produced by UNHSC proves that pervious pavement treatment systems can infiltrate large volumes of water — in some areas, over 97 percent — while filtering out large amounts of sediment, oils, metals (>90 percent) and phosphorus (>60 percent). Unlike retention ponds, pervious pavement systems do not require large amounts of additional space. The marginal cost between standard and porous asphalt is typically less than the associated drainage infrastructure (curb, catch basins, piping and ponds) for standard impervious pavements.

With porous asphalt, rainfall filters through the system and infiltrates back into the ground, which significantly reduces runoff volume, lowers peak flows, decreases summer runoff temperatures and improves water quality. Researchers at UNH have also found that pervious pavements speed snow and ice melt in cold climates and virtually eliminate black ice development, reducing salt requirements for winter maintenance.

Part of a Commitment

The change in approach to stormwater management has not come overnight, but is a large part of the university’s long-term planning efforts. UNH has a long-standing tradition of and commitment to sustainability. “Sustainability is a core value of the university. There is an extensive history of advancing our sustainable principles and carefully implementing them to serve our mission through a wide range of planning, design and construction initiatives,” says Doug Bencks, university architect and director of Campus Planning. Dirk Timmons, director of transportation, says that supporting UNH’s research and academic mission was a major factor in his allocation of the extra funding to replace some of UNH’s standard parking lots with a pervious surface.

A Range of Possibilities

Pervious pavement, like most low-impact development stormwater practices, is suitable for a wide range of locations. Its usage typically includes parking lots, driveways, sidewalks, low-use roadways and developments with large areas of impervious surface, a versatility that UNH has taken advantage of. Since the technology’s introduction in 2004, UNH has used it to convert more than six acres of otherwise impervious parking lots and sidewalks to pervious alternatives, setting a high bar for alternative water resource management throughout the state and region.

The effectiveness of pervious pavements has been demonstrated over a wide range of land uses and conditions at UNH, including those with winter freezing, thawing and snowplowing. Studies at UNH have shown pervious pavement to be especially effective in cold climates, given its durability and capacity to reduce the salt needed for deicing in winter conditions. Improvements in pervious pavement designs and installation practices are continually advancing. The UNHSC has recently updated its specification for porous asphalt installations, which is a standard that is used throughout the country. The specification is available for download at

The demonstrated performance combined with added requirements for infiltration and higher stormwater quality treatment standards has placed UNH in a good position to economically deal with current and impending stormwater regulations, in addition to establishing a sound environmental track record.

The UNHSC, part of the Environmental Research Group and the department of civil engineering at UNH, has pioneered the use of permeable pavements in the Northeast, serving as an advisor on many paving projects throughout the region and conducting workshops for civic leaders, municipal officials, designers and stormwater managers on the use of this rapidly expanding technology.

This article originally appeared in the issue of .

About the Author

James Houle, MA, CPSWQ, is program manager for the UNH Stormwater Center (