Scoring points for the environment

April 2012 » Features » PROGRESSIVE ENGINEERING
Wastewater treatment approaches are key to meeting LEED standards.
Dennis Hallahan, P.E.
An engineered wetland serves a school. The wetland vegetation provides a natural buffer and attracts wildlife.

New municipal regulations and public awareness increasingly are guiding environmentally sound construction practices for commercial and residential development. This is elevating the appeal to owners and tenants of green building, and catalyzing support from communities for Smart Growth. Engineers, developers, and architects increasingly are looking toward improved ecological approaches for construction materials and systems and seeing the value in pursuing the U.S. Green Building Council—€™s (USGBC) Leadership in Energy and Environmental Design (LEED) credit programs to validate and quantify each project—€™s environmental attributes.

The USGBC is working with the commercial real estate market to promote the business advantages of green building and its adoption in new and existing buildings and tenant spaces. There are several options in place to obtain LEED points for commercial, mixed use, and residential building projects including the LEED for New Construction (LEED-NC) rating system, the LEED for Neighborhood Development (LEED-ND) rating system, and the LEED Volume Program for organizations planning to certify a large number of design and construction projects or existing buildings.

A 2010 study by Jonathan Wiley, Justin Benefield, and Ken Johnson published in the Journal of Real Estate Finance and Economics —€” —€œGreen Design and the Market for Commercial Office Space—€ —€” concluded that green buildings, and specifically those that are LEED-certified, achieve superior rents, sustain significantly higher occupancy, and garner premium selling prices.

According to the USGBC, the LEED-NC rating system distinguishes high-performance commercial and institutional projects, including office buildings, high-rise residential buildings, government buildings, recreational facilities, manufacturing plants, and laboratories.

The LEED-ND rating system, the first national rating system for neighborhood design, focuses on entire communities, not just individual buildings, with a focus on integrated, Smart Growth developments. LEED-ND points are given based on a set of established criteria including location, reducing auto dependency, incorporating community green space, and energy, water, and natural resource conservation.

The LEED Volume Program, aimed at increasing the efficiency of LEED certification and lowering the associated costs, allows national chains to submit plans for a prototype store, office, bank, or restaurant for LEED certification. If the design, construction, and building-management plan meet LEED standards, the council will waive the evaluation of each new store as it is built and instead conduct random audits as certified prototypes go up in city after city, state after state.

Wastewater treatment and LEED
As regulations continue to tighten, those wanting to pursue development in heavily regulated and environmentally sensitive areas are benefiting by designing projects that qualify for LEED points, even if the project as a whole does not achieve certification. Within the current LEED rating standards, one of the opportunities gaining attention is wastewater treatment, water conservation, and water efficiency. In fact, the LEED credits under the LEED-NC program for Innovative Wastewater Technologies were reweighted in 2010 from one to two points.

In areas where centralized wastewater treatment is not available or where the treatment facility is at capacity, the use of evolved wastewater treatment technology and —€œsmart sewers—€ are viable options that also align with the LEED standards. Chamber drainfield systems or other alternative technologies, including engineered aggregate manufactured from recycled materials, are options that allow for a smaller overall footprint for the development.

Another LEED rating standard that can be impacted directly by the choice of a wastewater treatment system is to leave 40 percent of the building lot undisturbed by the construction. Again, this is where advanced treatment technologies can provide a huge advantage because of their smaller size and the ability for installation without severe disruption of the existing landscape.

Rainwater capture and water reuse also offer potential to achieve LEED credits under the rating systems.

Additionally, the increasing popularity of cluster or community wastewater treatment systems is good news for sustainable development as are advanced products designed for difficult sites. Improvements in monitoring equipment and ongoing management practices for decentralized systems offer the opportunity to provide better, environmentally sound solutions protecting public health while being cost effective for the building community. Core technologies that make cluster systems a viable option today are scalable wastewater treatment technologies and pumping systems, which offer both reliability and ease of maintenance. These technologies allow design professionals the opportunity to work with projects of all sizes —€” from single lot systems to small communities.

Hot applications for decentralized treatment
Three hot applications for decentralized treatment using chambers are community systems, smart sewers, and reuse.

Community systems —€” Community or cluster systems promote sustainable development, protect and enhance community character, and provide high-quality, cost-effective wastewater management to a wide range of wastewater challenges. Often, chamber technology and engineered wetlands are designed together in community system or cluster applications. The cluster system approach, often employing engineered wetlands designed with subsurface chambers, is a viable alternative even for large developments, and allows for preservation of community open space. These systems allow communities and developers to meet treatment requirements and economic goals. In addition, cluster wastewater systems can easily be landscaped to integrate into open space viewsheds.

ABOVE: The efficiency of the chamber system allows a smaller overall footprint; therefore, more of the site can remain in its natural vegetated state.
BELOW: A community cluster system is constructed within the green space of a golf course fairway, saving other areas from having to be cut and cleared.

These community septic systems generally serve multiple residential dwellings or commercial establishments and often use technologically advanced collection and treatment systems, monitoring capability, and engineered infiltration chambers to provide a higher level of treatment. By definition and goal, these systems treat wastewater and return it to the ground in close proximity to where the wastewater was generated as opposed to transporting it long distances to a centralized sewer facility.

Cluster systems also may reduce each lot—€™s required footprint area as compared with individual septic tanks and leachfields. This directly aligns with the new LEED-ND commitment to better use of land as part of a neighborhood setting.

Smart sewers —€” Smart sewer is a term given to a new storage application within a centralized system. Many sewer systems are at or beyond capacity, but it is extremely costly to expand the treatment plant. Established treatment plants are constricted to their peak design flow, which typically only occurs during a short period each day. If some of the flow can be detained and then released during low-flow periods, the plant would be able to assimilate the flow without having to spend millions of dollars on upgrades.

This practice is already common at treatment plants that utilize large storage tanks to store peak flows or to store flows due to stormwater infiltration. In some cases, there is no space for large storage tanks so an effective strategy is to provide remote storage in the form of individual tanks installed at each facility, which release flows at off-peak operating hours.

Reuse —€” Another application gaining momentum is water reuse. This can be reuse for agriculture and landscape irrigation and even grey water reuse for non-potable applications such as toilet flushing. Systems also can be designed to reuse water for industrial applications. Many of the solutions being developed are novel approaches. In the absence of sewers, onsite wastewater treatment systems are being designed to allow high water usage facilities to reuse wastewater. The systems discharge to the subsurface, thereby replenishing dwindling groundwater supplies, and reuse treated wastewater for toilet flushing.

Reuse can be classified as either indirect or direct. Indirect reuse occurs when the water receives enough treatment to be discharged back into the ground to build up the water table or prevent seawater encroachment. Direct reuse requires that the treated wastewater be transported directly to a point of reuse.

Monitoring and management
Cluster systems can provide the advantage of development in areas that were previously not an option, but these systems do require a much higher level of management. At this time, many local governments are not equipped to manage these systems and are looking for management companies that can ensure that the proper ongoing maintenance practices are followed.

Another option for system monitoring is to incorporate an intelligent control panel such as Infiltrator System—€™s Aquaworx Tracker to monitor system events. This enables management professionals to securely access the panel to monitor system events through a password-protected website, allowing for accurate, real-time liquid levels 24-hours a day, seven days a week. This level of monitoring is necessary to facilitate future growth within the advanced treatment market.

Conclusion
Community systems for wastewater treatment will be a leading approach for wastewater treatment in LEED projects and have been at the forefront of new approaches to environmental sustainability in development. Reuse also will be a key factor, particularly in areas where water cost and shortages are an issue daily. Existing LEED standards and the new LEED-ND standard will reward builders and developers who consider advanced alternatives in building systems that ultimately increase community appeal, environmental sustainability, and open space.

Onsite wastewater treatment and reuse aids quest for LEED certification

The National Great Rivers Research and Education Center and Field Station (www.ngrrec.org) in Alton, Ill., is tracking for LEED Gold or Platinum certification with a two-phase construction process that will result in a 32,000-square-foot facility. The center, which sits on approximately eight acres leased from the U.S. Army Corps of Engineers, will provide scientific resources and public outreach related to improving the sustainable management of large rivers.

The building is a symbol of innovation in design and construction of green technologies and can be used to educate the public on the importance of environmentally friendly applications through construction. It also is a state-of-the-art research center that will provide a platform to educate future generations on sustainable management of the environment. The physical location of the building at the confluence of three major rivers adds to the educational aspect, allowing for real-time experiments to collect data that can be used to effect government policies and standards.

Design challenges
The major challenge for the design team, which included civil engineers Sheppard, Morgan & Schwaab Inc. and architects from AAIC, was taking innovative technologies and applying them to the building in a way that all worked congruently to achieve a highly functional structure. The project is located within a flood levee on federal property, which added difficulty to the permitting and construction process.

The project includes numerous technologies that are new to the construction industry. The architectural design of the façade was intended to mimic the Mississippi river bluffs of the area through the use of limestone and the unique installation process of —€œdry-stacking—€ and grouting from above and behind. The footprint of the structure itself was designed to flow with its surroundings and to provide the sense of a natural arrangement. The living green roof and the outdoor rooftop classroom provide an energy efficient structure with the capability of educating the public on green roof construction and the sustainability issues relevant to this geographical area. Water efficiency innovations minimize the use of domestic water through an onsite wastewater treatment and reuse system and the reuse of captured rainwater.

A key component in the design is the natural system to treat wastewater onsite that also will support water reuse and allow for water features to be incorporated into the new building. As well as qualifying for LEED points, the natural treatment system fit well given the unique ecosystem that is created by the confluence of the three rivers at the site and the organic building design.

The wastewater treatment and reuse system design is the outcome of a feasibility analysis completed by Jacques Whitford NAWE, now Naturally Wallace Consulting. The wastewater treatment design is an engineered wetland treatment system that includes 56 Infiltrator Quick4 Equalizer 36 chambers installed in seven rows in the infiltration bed disposal system that enables the return of the treated wastewater into the soil. The reuse system design features a two-stage tertiary and secondary wetland treatment system with ultraviolet disinfection, with the subsurface wetland cells incorporating native plants in the design. The chambers, manufactured entirely from recycled materials, are utilized at the influent (front) and effluent (back) ends of the engineered wetland system.

After sewage is cleansed through the tertiary and secondary wetland systems, the water is sent through the ultraviolet filter and stored in a 5,000-gallon grey water storage tank. The storage tank is treated with an environmentally friendly chemical to keep the water fresh. That water is then pressurized and pumped into the building to flush all toilets and urinals.

A wetland cell at the National Great Rivers Research and Education Center —€” containing Infiltrator Chambers to optimize treatment performance —€” is graded and ready for planting.

A water feature will be filled with captured rainwater, grey water, river water, or domestic water. Additionally, 100 percent of the rooftop rainwater will be captured and stored in a 10,000-gallon storage tank. That water is pressurized and pumped to all hose bibs onsite for the garage (truck/boat washing) and exterior bibs and a rooftop hose bib for landscape irrigation.

Once phase two is complete, the project will be submitted under LEED version 2.2 in several categories, including Innovative Wastewater Technologies, Sustainable Sites, Indoor Environmental Quality, Water Efficiency, Material Resources, and Energy and Atmosphere.

Dennis F. Hallahan, P.E., is technical director with Infiltrator Systems Inc., Old Saybrook, Conn., responsible for government relations and technology transfer between the company and the regulatory and design communities. He has more than 20 years of experience with onsite wastewater treatment systems design and construction and oversees a staff that is responsible for product research and testing for universities and private consultants. He can be contacted at dhallahan@infiltratorsystems.net.

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