Holly Holder, PE, PSC Principal and PSC’s Public Works Sector Director, recently received PSC’s Trusted Adviser Award. I recently spoke to him about his passion for public works, interesting trends regarding landfills and advice for engineers and architects who want to become trusted advisers for their clients. Here is a condensed article about our conversation.

Q: What drives your passion for working in landfills and solid waste engineering?

Holly Holder: Engineering solid waste facilities includes everything that you study to obtain a civil engineering degree. It begins with selecting a site that would be suitable for a landfill. It includes studying the site’s hydrogeology and geology in looking at the soil stratas. This includes slope stability, geotechnical aspects of the site, stormwater runoff and run-on design, and roadways. We design pumping systems for leachate management, including evaporation ponds for removal of leachate. We build the sites to prevent the migration of landfill gas both to protect offsite structures and buildings as well as underlying aquifers. Annually, we perform volumetric calculations for owners so they know the life of their facility and can plan for future expansions.

Q: How does the environmental aspect come into play in how you love this field?

HH: Everything we do has the goal to protect the environment, to protect our groundwater, to protect surface water, to protect our air.

Q: How do landfills help protect our groundwater?

HH: We design dual liner systems that are called composite liners. The regulatory prescriptive liner is a two-foot-thick compacted clay liner with a minimum permeability of 1 x 10-7 centimeters per second, and that’s overlain by a 60-mil-thick high density polyethylene geomembrane that is welded together to create what we call a ‘bathtub.’ Then we overlay that with a geocomposite drainage layer which allows leachate to migrate and be removed. That’s covered with a two-foot thick soil cover to protect the whole lining system.

About 20 years ago a product became available called geosynthetic clay, which consists of a powder bentonite sandwiched in between two layers of geotextile fabric. It has an extremely low permeability and we use that in place of the two-foot-thick clay layer. This is still overlain with the 60-mil geomembrane.

We design systems that protect human health and safety and the environment.

Q: Are there any new innovations in solid waste management?

Frank Pugsley has engineered a project in Denton where they are creating a sustainable landfill. This involves pumping water into the landfill waste mass to accelerate the biological activity which increases the rate of decomposition. This accelerates methane production which they can then use to produce electricity. Eventually, when all the waste has broken down and is no longer producing methane, they will re-enter that cell and mine it for metals, plastics, and glass, which is recycled. Then the process starts all over again, thus creating a sustainable landfill.

Q: You mentioned methane earlier, how do you help landfills deal with methane?

HH: Landfill gas is typically is made up of carbon dioxide and methane. These two compunds comprise 72 percent of the whole landfill gas — more than 50 percent of that is methane. Methane is explosive and its is a problem if it migrates offsite. This predominantly occurs in older, unlined facilities and not modern landfills that are engineered. Methane that migrates offsite, can move beneath buildings and become an explosive hazard. Methane can also contaminate underground acquifer and require remediation to clean up the groundwater.

Q: Are people recycling more than we used to?

HH: The most recent data that I saw shows the amount of trash that people in Texas throw away has increased in the last 20 years, instead of decreasing. With all the talk of recycling and how everybody wants to be good stewards, we’re actually doing a worse job now than we were 20 years ago as far as how we handle trash in the United States.

Nationally, the average disposal rate is 5 pounds of trash per person per day. Howaever in Texas, we are above that rate. For example, in 2007-09, the Texas disposal rate was over 7 pounds of trash per person, per day. This has dropped somewhat, for instance, in 2014 we were  at 6.58 pounds per person/day, but in 2015 the disposal rate was 6.67 pounds per person per day.

Q: So what is your passion as far as being an engineer? I’ve spoken with others that say they just love to fix things.

HH: It is a natural trait of engineers to be drawn to fix things. It begins at a young age, with taking your toys apart and putting them back to together to see how they work. Engineers need that mindset of ‘how do things work.’ That understanding of how to take blank sheet of paper and be able to design something that you can actually physically build, maintain and operate.

Q: You were recently named at PSCU, the Trusted Adviser of the Year. What advice would you give to a young engineer?

HH: Talk to your clients. Don’t text them, don’t email them, TALK to them. Find out what is really important to them and listen to them. When you listen to someone speak, you can hear their passion in and understand what is really driving them. You just can’t get from reading a text message or email.