Page 20 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

Intr oduction 3

The reasons are not known, but perhaps the contractor or owner does not understand
the environmental impact that the lack of a pond may cause, therefore, installation of
one may not seem important.
Then there is the use of MTBE (methyl-tertiary-butyl ether) as an additive in
gasoline to improve air quality, which was a common practice in the 1990s. It was
considered to be a sound environmental practice with respect to air issues. However,
there were some unexpected consequences. Traditionally in the United States, gasoline
is made at a refinery, is transported and distributed through a network of petroleum
facilities, and ends up at the retail outlet, the gasoline station. Gasoline is usually
stored in underground tanks, for many reasons including safety, at this end resale
site. Underground tanks are currently fairly well regulated and monitored in the
United States, but that was not always the case. In many sites, gasoline has leaked
into the ground, and the product sits on or in the groundwater. Most constituents in
gasoline are nonpolar organics which do not dissolve readily in polar water, but might
prefer to adsorb to organic material in the soil. So even though the groundwater may
slowly flow off-site, most of the gasoline contaminants remain closer to the site.
However, MTBE is an ether, and ethers are more polar than many gasoline constituents
such as benzene. Polar organics tend to be more soluble in water and may have a
greater tendency to travel with the groundwater gradient. Therefore, there are many
places where some gasoline leakage in the soils at a site did not initially cause an off-
site concern until the MTBE was added and moved more rapidly off-site. In this way
a practice that is an environmental benefit for one system may not be as sustainable
in another.
There are several other green rating systems for vertical construction in the United
States, but the LEED system and the alternative Green Globes system are by far the
most prominent. Green Globes is distributed by the Green Building Initiative (GBI) in
the United States and is based on a system developed in Europe and later also used in
Canada. The European version is referred to as the Building Research Establishment’s
Environmental Assessment Method (BREEAM). Another similar initiative is the California
Green Building Standards (CALGreen) Code, which was in draft form in 2010 and
scheduled to become effective on January 1, 2011. It has been developed by the California
Building Standards Commission. This text is based on the LEED system, but this in no
way implies that the other systems are not useful and viable. The LEED rating system was
chosen as the focus of this text as it is currently more widespread in the United States. It
also does not allow for a self-certification method, which makes it more restrictive and
possibly more difficult to complete, but at the same time may also give greater control
and consistency to green building.
The text has a heavy focus on some of the civil and environmental aspects of the
rating system, since the author is first targeting this engineering community. However,
it also addresses in some fashion other issues in the rating system. One of the reasons
for its being more all encompassing in the topics reviewed is to educate the civil and
environmental engineers about the other credits and criteria so that they can effectively
work with other disciplines in a cooperative fashion to better implement sustainable
construction practices. Other engineering and nonengineering disciplines have found
the text useful, including mechanical engineering, computer science, architecture, and
construction management, just to name a few.
There is a need for further involvement from the civil and environmental engineering
community in the development of the LEED rating system. The evaluation of best