By Claude Goguen, P.E., LEED AP
When we talk about sustainability in the construction industry, there is a tendency to focus on buildings and above-ground structures. When we hear about LEED projects, we imagine elaborately designed buildings that harvest rainwater through grassy rooftops. However, we need to shine the green spotlight on the unseen workhorses of the precast concrete industry – the underground structures – as well.
Marketing a product requires you to first identify values and strengths. You know you make a strong and durable product. But can you talk about its sustainable properties? Twenty years ago, those attributes would not be worth mentioning, but oh how the world has changed. Whether you sell to homeowners, contractors, developers or engineers, chances are good you will come across someone who values sustainability and will base their decision partially on that criteria. They may simply ask how you make a sustainable product or go even further and ask for proof in the form of an Environmental Product Declaration. Michael Tidwell, president of Bartow Precast in Cartersville, Ga., recently reported that a customer asked for an EPD for a grease interceptor project in Florida. This is a glaring example of things to come.
Whether you make pipe or panels, manholes or modular buildings, tanks or T-beams, you will likely face this situation, and being prepared may give you an edge over your competitors.
How are underground products sustainable?
You may already be using materials and products that are inherently sustainable. For example, the use of fly ash or slag reduces the amount of energy required to make a product simply by reducing the cement content. It also diverts materials otherwise bound for landfills to your product. Fly ash and slag are also proven to enhance the hardened properties of a product, which makes it more durable.
The reinforcement used in precast concrete structures is typically made of 90% to 100% recycled steel. Raw materials for precast underground structures – cement, water and aggregates – are extracted and manufactured locally, thereby reducing environmental impacts associated with transporting products to distant plants. Locally manufactured structures also benefit the local economy, which is often overlooked.
Looking at performance, precast concrete has a proven track record of durability. According to the U.S. Army Corps of Engineers Manual 1110-2-2902 – Section 1-4 Life Cycle Design, “Most studies estimated product service life for concrete pipe to be between 70 and 100 years. Of nine state highway departments, three listed the life as 100 years, five states stated between 70 and 100 years, and one state gave 50 years.” These structures must endure significant loads and stresses while withstanding extreme interior environmental conditions. A long life cycle is a core sustainable attribute.1
Precast concrete underground structures require minimal to no maintenance and do not burn, rust or rot. They can also be recycled at end of use. The following is a more detailed look at specific sustainable attributes for pipe, manholes, wastewater tanks, stormwater treatment structures and utility structures:
Concrete pipe is synonymous with durability, longevity and resiliency – giving it an advantage over alternative materials. The energy used, emissions released and traffic congestion caused during construction to maintain and replace pipe is significant. Many times, months or years of infiltration or exfiltration will precede required service on these alternative material pipes, and that can also result in serious damage to the local ecosystem. However, concrete pipe is usually backfilled with native soil and does not require imported material.
Precast concrete manholes are designed and built to withstand many extreme loads including traffic, soils and water. Similar to pipe, precast manholes are durable, resilient, require less maintenance and lower the environmental impact of construction and traffic disruptions. Manholes are modular, manufactured to meet specific needs and install easier and faster. Less time installing decreases emissions from machinery. Precast concrete manholes have watertight joints and connections to keep harmful, untreated wastewater from getting out.
Decentralized wastewater treatment is increasing in North America. Centralized sewer systems are already beyond their limits, can’t support additional loading and require a lot of energy to run. For this reason, structures used in wastewater treatment must be reliable and effective as well as sustainable. Diverting wastewater from sewers is already a sustainable milestone. Treating stormwater and wastewater on site is becoming more important as the green building movement gains momentum. Precast tanks withstand significant loads due to traffic and soils and are designed and manufactured to provide a long service life. Tanks manufactured with alternative materials that face strength or buoyancy issues lead to more construction and pollution. Precast tanks can be customized to meet specific needs for advanced treatment or other site conditions resulting once again in faster installation and less impact.
Stormwater treatment structures
Treatment of stormwater prior to releasing harmful elements to sewer systems is key to sustainability. Precast stormwater treatment structures are modular and can fit any design situation. Precast stormwater management components are watertight, resilient during storage and transportation, easy to install, less vulnerable to damage during backfill and environmentally safe during operation.
Precast concrete utility structures are ideal for communications, electrical, gas or steam systems since they protect vital connections and controls for utility distribution. Precast structures can be manufactured to fit any design situation, requiring less time on site performing modifications. Precast concrete utility structures are noncombustible, can withstand high temperatures. They are also nontoxic, environmentally safe and have a long life cycle. Precast structures are installed much quicker than cast-in-place alternatives reducing site impacts and pollution.
Use sustainability to your advantage
Underground structure manufacturers have no excuse for not using sustainability in their marketing. Sustainability applies to the entire job site from the pipe to the carpeting. Competing materials are recognizing the importance of sustainability. Recently, an environmental study surfaced that was commissioned by plastic tank manufacturers making the claim that plastic structures have significantly less impact than precast concrete. These companies are seeing greener pastures ahead.
The good news is your product already has inherent sustainable attributes, whether you know it or not. You may be able to implement some new practices to make them even more sustainable. Retaining and growing your market share could depend on your ability to recognize how green your product is and how much greener it can be.
Claude Goguen, P.E., LEED AP, is NPCA’s director of sustainability and technical education.
1 A life cycle assessment is a scientific method of evaluating the environmental impacts of a product over its full life, including raw material acquisition, manufacturing use and disposal or recycling. A LCA of precast concrete underground products can be found at precast.org/sustainability/LCA.