Tunneling is an extreme and energy-intensive process that can have significant site and cost bearing on a project and community. Traditional tunneling requires the use of massive equipment and machinery, and substantial consumption of materials and natural resources.
The constant need for innovative methods and technology keep the industry moving at a pioneering rate. It is no surprise that the major environmental impacts of the tunneling process include energy consumption, materials and resources and site disturbance. But are these factors driving the machine or are they simply being buried in the muck?
Photo courtesy MWH
There are some inherent sustainable design practices that occur with tunneling procedures, like the increased life expectancy of the tunnel – as compared to surface treatments – and even the reduced energy consumption via use of local material delivery, reuse and disposal. However, other than these inherent benefits, not much is done to advance environmental stewardship and lessen the impacts of a typical tunneling project. Sustainable design not only saves money and the environment, but also promotes a positive community perception for local development.
Tactics to consider
Here are 10 tactics for enhancing the process:
1. Excavated water reuse — Utilize for surface dust control or aquifer recharge;
2. Geothermal renewable energy system — Ground source heat pump to heat/cool surface buildings and take advantage of excavation that is already in place for tunnel or shafts;
3. Low impact development (lid) opportunities — Maintain pre-development hydrologic configurations;
4. Muck reuse — Local disposal to reduce transportation emissions and cost; reuse at surface sites to raise grade or to prevent flooding; reuse high quality muck rocks for construction aggregate, community road base and concrete mixes;
5. Fly ash/slag — Local by-products used in concrete mix. For precast segments, manufacture locally to reduce greenhouse gas emissions and cost from transportation;
6. Inclined tunneling (uphill or steep grade) — Gravity assistance in muck removal to reduce energy (uphill); hauler braking converted into electricity or batteries (steep grade);
7. Green power — Construction activities powered by green power from utility provider;
8. Biodiesel — Burns cleaner and reduces emissions from machinery, trucks and muck cars;
9. Renewable hydropower — Harness water power during excavation; and
10. Restore habitat — Recharge disturbed areas with native vegetation and reduce ecosystem impact.
Photo courtesy MWH.
ABOUT THE AUTHOR: Cara Hlad is an architect and LEED AP at MWH Global. She serves as the Sustainable Design Director in the DESIGN Group, and teaches sustainable architecture courses at a local college, in Denver, CO. She can be contacted at Cara.A.Hlad@us.mwhglobal.com.