Members and committees of EWRI typically gain quite a bit through the institute by means of networking, new information in their field of work, and other helpful opportunities. While there is much to gain through the organization, those involved tend to give back in the form of research and the shared results of said studies. The Low Impact Development (LID) committee of the Urban Water Resources Research Council (UWRRC) has recently began the opening stages of several initiatives. These efforts include the topics of Green Roof technology, Porous and Permeable Pavement, and Rainwater Harvesting technology. The following summaries indicate the purposes and general goals of each of the individual efforts:

The EWRI Green Roof Technology Initiative

The use of green roofs as a tool in sustainable development is rapidly spreading in the US.  Green roof technology originally developed in Europe, and has been in use in Germany for over 30 years. The US experience with green roofs is still relatively new. 

Green roof systems may be modular, with drainage layers, filter cloth, growing media and plants already prepared in movable, interlocking grids, or, each component of the system may be installed separately. Figure 1 illustrates the basic components.

Figure 1. Green Roof Cross-section               Source: American Wick Drain Corp.

Green technology provides a wide range of benefits and involves the application of numerous technical specialties, such as structural and mechanical engineering, storm water management, horticulture, air quality, economics and marketing.  

The potential benefits associated with the use of green roofs can be both private and public. Private benefits can be economic, technical, and aesthetic. A few of these potential benefits are listed below:

• Longer roof life can result in lowered life cycle costs
• Potential savings on energy heating and cooling costs
• Improved sound insulation
• Potential to meet regulatory requirements for stormwater management
• The aesthetic appeal can improve marketability of building
• Can provide amenity space for day care, meetings, and recreation

For more information on this initiative, please contact Dr. William Hunt of North Carolina State University at bill_hunt@ncsu.edu.

The EWRI Porous and Permeable Pavement Initiative

Pavements are a dominant feature of urban environments. In urban watersheds they produce two thirds of the excess runoff, are responsible for essentially all the hydrocarbon pollutants, produce two thirds of the groundwater decline and the resulting local water shortages, and produce two thirds of the temperature increase in the urban “heat island” (Ferguson, 2005). They can also determine whether urban trees extend their roots and live, or die.

Porous pavements are those that have built-in networks of void spaces where water and air pass through. Although some porous paving materials are nearly indistinguishable from nonporous materials in construction and superficial appearance, their environmental effects are qualitatively different. They cause air, water and heat to enter different parts of the environment, there to undergo qualitatively different processes of storage, treatment and flow. Figure 2 illustrates various permeable pavement systems.

Figure 2. Various permeable pavement systems Source: NC State University – Biological and Agricultural Engineering Department

Porous pavements can allow the oils from cars and trucks to biodegrade safely, the rainwater to infiltrate the soil, the heat of the sun to dissipate, the groundwater to be replenished, the roots of trees to breathe, and the streams to flow in dry summers.

In spite of these environmental advantages of porous pavements, in North America, they are outside the ordinary conventions of urban design and construction. Very few state and local agencies have standards or guidelines that can be used for the design of these systems.

Figure 3. Porous Pavement Application               Source: Cahill and Associates

Anyone interested in participating in this effort can contact Michael Clar, chair of the LID committee at: mclar@nccde.org.

The EWRI Rainwater Harvesting Technology Initiative

The US is witnessing an increasing interest in the collection and reuse of rainwater as an element of stormwater management. This trend is the result of a number of interrelated developments which include an increasing focus on sustainability in the built environment and green building initiatives, an increasing awareness of the need for water conservation and realization that rainwater should be perceived as a resource rather than a nuisance, and an increasing interest in managing the increased volume of runoff from impervious surfaces rather than just focusing on the peak rates of discharge.

Rainwater harvesting is a way to capture the rain water when it rains and storing that water either above or below ground for later use. Common uses of captured rain water include watering of trees, lawns and other landscape features, as well as both potable and grey water re-use. Some parts of the world such as New Zealand, parts of Australia, and numerous Caribbean countries rely on the capture and filtering of rain water as their primary source of potable water. In addition a number of projects in the US use captured rain water for non potable water uses such as flushing toilets.

Figure 4. Rainwater Harvesting System Schematic Source: NC State University Stormwater Management Research Group (http://www.bae.ncsu.edu/people/faculty/hunt/#Current%20Research)

This capture and reuse of rain water can help to substantially lower water bills, help reduce local flooding and reduce landscaping and property maintenance needs.

Rain water harvesting is not new and is becoming increasingly important on a global level. A number of organizations have sprung up around the world that provide information on this topic including; The Center for Science and Environment (CSI), the International Rainwater Harvesting Association (IRHA), the International Rainwater Catchment Systems Association (IRCSA), and the American Rainwater Catchment Systems Association (ARCSA).  A number of states and local governments have published water harvesting guidance manuals including the Texas Manual on Rainwater Harvesting.

In spite of the benefits provided by rainwater harvesting technology, in North America, this technology remains largely outside the ordinary conventions of urban design and construction. Very few state and local agencies have standards or guidelines that can be used for the design of these systems.

Anyone interested in participating in this effort can contact Michael Clar, chair of the Low Impact Development committee at: mclar@nccde.org.

EWRI recently launched these three initiatives through the activities of the Low Impact Development committee of the Urban Water Resources Research Council by co-sponsoring several related technical sessions as part of the 2nd National Conference on Low Impact Technology held in Wilmington, NC. More information on the conference can be found at: http://www.soil.ncsu.edu/swetc/lid/home.htm.

Recognizing that, currently, technical guidance with respect to the benefits of these technologies is limited, the LID committee is forming the Green Roofs technical committee, Porous and Permeable Pavement Technology committee, and the Rainwater Harvesting Technology Technical Committee. These committees will review the available data on these specific technologies and develop the following committee products; 1) a review and summary of the current literature related to the stormwater benefits of this technology (Phase 1); 2) a committee report of these technologies as tools to harness stormwater (Phase 2); 3) the development of national guidelines for the use of the individual topics for stormwater management (Phase 3); and 4) the planning and execution of a mini-symposium or specialty conference on these Low Impact Development technologies.