Closing Thoughts from APWA Sustainability in Public Works

We concluded our time at the American Public Works Association’s (APWA) Sustainability in Public Works Conference today with a day of focused sessions and capped off with closing remarks from the organizers.

The sessions I attended pertained to green infrastructure and biomass-to-energy, while other sessions addressed facility energy use, pervious concrete, success indicators, urban ecosystem management, the “people” side of sustainability measures and work, and recycled materials in road construction.

GREEN VS GRAY

The first session, “Green Infrastructure Master Implementation Plan for Indianapolis, Indiana,” was presented by Ted Blahnik, P.E., from Williams Creek Consulting, Inc. It was, to say the least, a discussion that grabbed the group. The overflow crowd had many questions and shared a number of stories from their parts of the country. The liveliness of the discussion was stimulating, but it did prevent us from finishing the presentation, as APWA eventually cut us off at 30 minutes beyond time.

Blahnik’s talk addressed not just types of green infrastructure design–such as pervious pavers in alleys–but cost estimations on effect (in terms of sq. ft. of impervious surfaced treated by installation of pervious surfaces). He contrasted frequently gray (or traditional hard) infrastructure with green. For example, gray stormwater management is based around managing events, such as a 10-year storm event. Green infrastructure is designed for annual volume, which means not just the potential of big storms but managing all of the small stuff too. Gray is concerned with "the pipe onward"; that is, the process of diversion. Green is “pre-pipe.”

Without going into the entirety of the presentation, it may suffice to say that green infrastructure is no longer an option–it is becoming a required practice. The EPA is moving to expand the areas of stormwater management guided by federal rules. New regulations are expected to come into effect in 2012. This will involve significant requirements on retrofitting, which is one of the reasons that Blahnik’s talk generated so much open discussion in the session.

Geosynthetics professionals will be happy to know that green infrastructure utilizes many geosynthetic materials, but often in smaller applications, such as wrapping stone and perforated pipes with geotextile or installing geocomposite drains in green roof systems. Still, the scope on which these projects are being conducted means plenty of interaction with the geosynthetics field. In Indianapolis, for example, 7,800 acres are being transitioned to green infrastructure designs.

Perhaps the greatest notion to take from our unfinished time with Blahnik are the lessons that green infrastructure is often quite economical, if not more so than traditional gray options; and that there’s no reason not to switch to green when you are doing your normal maintenance. If a street is already being torn up, why not use that as a way to “green” that street’s stormwater design?

Retrofitting is a viable, affordable option, and it doesn’t have to mean lesser performance. It can be better.

A BRIGHT FUTURE

After a visit to the exhibit hall for an increasing amount of business card exchanges, we turned back to the session rooms. My next stop was in the “Municipal Biomass-to-Energy Options” session expertly led by Wayne McFarland of GDH.

His talk was a primer for nearly all of us on the great many form of biomass-to-energy methods, energy outputs, advantages, disadvantages, world utilization rates, and trends. We all appreciated how easily (and with a bit of humor) he spoke about this very complex topic.

McFarland took us from little facts, such as the 2.2-watt output of the human heart (pretty much the same as a cell phone) to the 14,000 mW it takes to launch the Space Shuttle into orbit–the latter fact of which is equivalent to the output of about 12 nuclear power plants.

Energy is a fascinating issue, and with greener methods gaining momentum, government grants and subsidies, and to some extent official mandates, it’s a subject extending well beyond public works and which engineers, contractors, planners and others must acknowledge.

Harvesting methane from landfills, for example, has become a steady source for renewable energy in capped sites. Combined with flexible, thin-film photovoltaic cells on exposed geomembrane landfill caps, even more power is generated.

Anaerobic digestion, such as beneath geomembrane covers, has become a major issue with large farms and industrial processing facilities.

Dewatering sludge to gather biosolids at wastewater treatment plants (WWTPs) is a vastly underutilized technology, McFarland noted. Municipal solid waste can be burned to produce 4,000 Btu/lb, but dried sludge from biosolids generate even more: 6,000. And, if separated out, WWTP biosolids involve many other energy-producing elements: grit, 4,000 Btus; screenings, 9,000 Btus; grease, 16,000 Btus (which is more than gasoline).

If wastewater could be really used properly, the power necessary to treat wastewater in the current non-utilized way would be significant. Wastewater treatment uses approximately 3% of the United States energy consumption. Combined with the amount of energy it takes to pump all that water to and from WWTPs, it comes close to 7%. California’s energy need for wastewater is actually quite a bit higher than that 7% rate.

This ties McFarland’s talk closely with Blahnik’s on the importance of green infrastructure over gray infrastructure. We can turn our waste into renewable energy; but we can also significantly reduce our waste.

THANK YOU

It would be impossible to sum-up everything of value within the APWA Sustainability in Public Works Conference without simply repeating the lectures, the side discussions, etc. It was an outstanding event with high-quality and attendees. It’s left my brain buzzing on all of these issues of stormwater management, erosion control, brownfields remediation, energy conversion, containment, pollution control and so much more.

I’d like to thank the staff of APWA for granting me this opportunity and for their fine work on site. We appreciate you.

And I’d like to thank the exhibitors for their time and support of the event. They are:

As soon as information is available on the next APWA sustainability gathering, Geosynthetica will pass it on to our readers too. It’s an event and group well-worth getting involved with. And stay up to date on APWA’s activities at the association website.

Chris Kelsey is the editorial director for Geosynthetica. He can be reached at chris@geosynthetica.net.