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Green and Gray Infrastructure Research

Water infrastructure may be considered “gray” or “green.” Gray infrastructure refers to traditional practices for stormwater management and wastewater treatment, such as pipes and sewers. Green infrastructure refers to sustainable pollution reducing practices that also provide other ecosystem services.

Gray Infrastructure

Gray infrastructure takes wastewater away from our fields, homes and businesses. In cities and towns, we rely on sewers to move and treat human or commercial waste. Storm sewers carry rain and snowmelt. Often this water contains:

  • pathogens and bacteria from human and animal waste,
  • chemicals and heavy metals from our industries,
  • gas & oil from roads, and
  • fertilizers and pesticides from farms and gardens.

There are convenient ways to ferry water out of town and into the nearest water body. Unfortunately, the idea that “dilution is the solution to pollution” is not the way to get away from stormwater and its pollutants.

Structural Integrity Monitoring (SIM)

Water supply is typically carried in pipes under pressure. Wastewater is conveyed in sewers at atmospheric pressure. Structural integrity of water mains refers to:

  • the soundness of the pipe wall and joints for carrying water to its intended locations, and
  • preventing water leaks, pressure loss, and contamination.

Water main breaks have caused:

  • water quality degradation,
  • waterborne disease,
  • wasting of water and other resources (e.g., labor and funds),
  • accidents,
  • loss of service, and
  • property damage.

A barrier to cost-effective water main break prevention is the inability to accurately predict location and time of main breaks.

Reducing Water Main Breaks

Structural smart pipes can potentially enable improved prediction of the time and location of water main breaks. These predictions can be used to efficiently schedule pre-failure maintenance, rehabilitation, or replacement. An ideal structural smart pipe system consists of:

  • a pipe (or coating or liner);
  • structural parameter monitoring capability;
  • data transmission and storage capability; and
  • Central processing and analysis capability.

The analysis capability could be utilized to:

  • determine the history and status of pipeline structural condition and loading at all points on the inner and outer surface;
  • estimate deterioration rate; and
  • Predict pipe strength-time series, pipe loading-time series, and time and location of main breaks.

Structural smart pipes will enable the baseline condition of the pipeline to be updated, so predictions of times-to-failure can be based on recent measured condition of the pipe, not rough estimates from either initial conditions or infrequent inspections.

Improving Drinking Water Mains

Inadequate structural integrity monitoring (SIM) capability for water mains can cause repair, rehabilitation, or replacement (R3) to be scheduled either late or early. Late R3 can mean serious deterioration and main breaks. Early R3 is inefficient, which adversely affects system maintenance priorities and funding. Existing SIM technologies inadequately characterize various combinations of pipe materials, configurations, and failure modes. Fortunately, substantial research to improve SIM is underway for high risk, non-drinking water applications. Acceleration of SIM improvement research is especially important at this time, since:

  • for the next 30+ years a steep rise in R3 decision-making is projected for aging water mains;
  • multiple technology transfer, collaboration, and leveraging opportunities exist; and,
  • SIM improvement takes time.

White Paper on Improvement of Structural Integrity Monitoring for Drinking Water Mains.

Green Infrastructure

Green infrastructure is a general name given to an approach using environmentally friendly techniques to manage stormwater. EPA’s risk management green infrastructure research includes:

  • Green roofs project: Design/construction of a green roof demonstration site at the Edison Environmental Center (EEC).

  • Porous/permeable pavement project: EPA has installed a full-scale, 110-space porous pavement parking lot. It is instrumented and monitored for a number of water quantity and quality parameters. This demonstration provides improved design and performance information on three permeable surfaces. The study monitors side-by-side porous asphalt, porous concrete, and permeable interlocking concrete paver systems. The porous pavement parking areas have sections lined with an impermeable liner to collect the runoff. Other sections will allow the runoff to infiltrate to the underlying soil. Each monitored parking row has four impermeable and five permeable sections for each porous pavement type. The factors that will be monitored include volume, solids, microorganisms, nutrients, metals, and semi-volatile organic compounds.

    Design/Construction of a Permeable Pavement Demonstration Site at the Edison Environmental Center (PDF)
    (2 pp, 268 KB) (EPA/600/F-09/038) October 2009 | Opening ceremony and demonstration of the parking lot (Video)

  • Swale management (infiltration trenches): Swales are “engineered ditches” that route stormwater runoff. Swales are a green, low cost drainage option for highways, farms, industrial, and commercial areas. Swales mitigate the pollutants carried by the runoff. They can also reduce both the runoff volume and peak stormwater runoff rate that can damage streams.

    Brochure: Stormwater Best Management Practices - Swales (PDF) (2 pp, 320 Kb)

  • Rain gardens and rainwater barrels

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