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Life Cycle Cost Analysis

Tuesday, March 24, 2015

While catching up on the news today, there was an article of interest that Boston had a record snowfall this year totaling 108.6 inches!  I am sure Boston residents are wondering what surprises await them after the big melt.  How that affects what we do as civil engineers, particularly in transportation is the subject of my comments this month.

I grew up in Indianapolis and went to Purdue University.  It seemed like the entire time I was in school we had bone chilling winters with a decent amount of snow.  Every spring, travelling up and down I-65, through the streets of West Lafayette and Indianapolis, there was a sea of potholes.  As my education progressed I learned about frost heave, ice lenses in subgrade, and freeze thaw effects. On the positive side air entrained concrete and asphalt VMA were proportioned to minimize environmental impacts.  All these criteria and more need to be to be considered by the design engineer when developing plans for a project.

After leaving Purdue, I worked in Indianapolis for 10 years and constructed pavements for parking lots, roadways, and airports.  Generally, a normal duty pavement for a collector street consisted of a something like compacted subgrade, 10" of crushed stone, and 8" of asphalt.  Underdrains were the norm rather than the exception.  Now that I am in Tampa, Florida after working in Tennessee and Virginia, a standard pavement section is 12" of stabilized base, 8" of crushed stone, and 2-3" of asphalt with no underdrains. Quite a difference on materials due to temperature and the lack of freezing.  However, I still see asphalt pavements oxidizing and becoming brittle, which leads to cracking and potholes.  Just can't get away from crumbling infrastructure.

Back to my lead in.  There are ways to design and construct infrastructure to mitigate environmental damage and still be within a reasonable budget.  We as engineers all exercise care in our designs and take into account the impacts of local conditions on our infrastructure.  ASCE is leading an effort to encourage the use of life cycle cost analysis to look at total costs of infrastructure.  This includes sustainability, resilience, environmental, and other costs associated with the project.  T&DI supports and encourages all our members to learn methods of life cycle cost analysis and provide the best long-term value for your clients, public or private.

Brian McKeehan, P.E., F.ASCE