Portland Cement Pervious Concrete Pavement on Highway Shoulders - Stormwater Quality and Quantity Assessment

Focus Area

Water Quality/Wetlands


Natural Resources






Over 3 years

Research Idea Scope

Background: This research proposal seeks to study Portland Cement Pervious Concrete’s (PCPC) ability to remove pollutants, particularly heavy metals, and reduce surface volume flows from highway runoff. This study will monitor the stormwater treatment effectiveness of PCPC pavement installed along the highway shoulder at select study sites. PCPC pavement has been in existence in the United States for nearly 50 years. Though not a widely used product, when properly designed and constructed, PCPC has proven effective in removing pollutants and reducing surface runoff volume from parking lots, low-volume roadways, and pedestrian walkways. Although there have been many studies conducted on PCPC pavement and its applications, we are still learning its potential benefits. There are few studies regarding PCPC pavement’s use in highway applications, particularly on high-traffic volume highways, and fewer still when narrowed down to using PCPC pavement on highway shoulders. Starting in the late 1980s, efforts to address polluted stormwater runoff have increased significantly, and requirements for treating highway runoff have become more stringent. Not long ago, the objective was just sediment removal, and most highway runoff could be treated using a few simple treatment methods such as bioswales, wet ponds, or vegetated filter strips. More recently, however, treatment requirements have been shifting to include the removal of specific pollutants, such as dissolved metals and nutrients. Heavy metals (total and dissolved) in stormwater are becoming more of a concern to regulatory agencies as well as developers, particularly in highly urbanized areas where land values and lack of available space limit treatment options. There are a number of currently available best management practices (BMPs) that are effective in removing heavy metal pollutants, but the effectiveness of these treatments relies on the availability of sufficient space to accommodate them. There is an urgent need for effective BMPs that can achieve stormwater treatment goals in urban areas without the need to purchase additional right of way. PCPC shoulders have high potential to meet these environmental constraints and provide a viable, cost-effective treatment option. Research Objective The goal in this research is to install PCPC on highway shoulders to study: • PCPC’s ability to remove pollutants from highway runoff, especially heavy metals such as copper and zinc; • PCPC’s ability to reduce surface runoff volume; • PCPC’s ability to work with another treatment BMP (e.g., roadway ditch, bioswale, vegetated filter strip) in a treatment train to improve its capacity for pollutant removal; • the operation and maintenance requirements of PCPC on highway shoulders; • PCPC’s ability to withstand freeze and thaw cycles in western Washington; • PCPC’s load bearing capacity over time; and • PCPC’s ability to produce sheet flow conditions where stormwater runoff will discharge from the downstream edge of the PCPC shoulder to the roadway embankment side slope. WSDOT will follow the Washington State Department of Ecology’s Technical Guidance Manual for Evaluating Emerging Stormwater Treatment Technologies: Technology Assessment Protocol – Ecology (TAPE) (Ecology 2011) to determine if PCPC pavement on highway shoulders can meet the TAPE basic and enhanced treatment requirements.

Urgency and Payoff

Regulatory agencies require state departments of transportation, local governments, and other developers to provide treatment BMPs that can remove sediment, heavy metals, and other pollutants from stormwater runoff. There is increasing demand for effective BMPs that can fit into existing roadway prisms, especially in urbanized areas where available space is limited. If monitoring shows PCPC pavement installed along highway shoulders can remove sediment, heavy metals, and other pollutants from highway runoff, huge benefits will be seen for transportation agencies, local governments, developers, and the environment. Project proponents will have one more cost-effective tool to fulfill environmental regulatory requirements. If PCPC pavement can provide treatment, the cost of building expensive detention systems and treatment facilities may be eliminated.

Suggested By

Le Chi Nguyen Washington State Department of Transportation 206.440.5070

[email protected]