The Innovator’s Angle: Engineered Fills for Waste Management

By Mark Williams

The Innovator's Angle logoSince AMW first adapted its GPS machine control software for landfills in the early 2000s, I’ve had the pleasure of speaking with numerous waste management professionals around the world. Based on my own decades of experience in construction, and through hundreds of conversations with landfill operators, I’ve come to understand these six points as the most important rules of engineered fills:

Know the material. Understand the waste stream, and its fluctuations of quantity and makeup.

Measure the moisture content precisely, and know how it relates to the current waste stream.

Control the lift thickness with as much accuracy as modern technology allows.

Understand the mechanical part of the compaction process, and use it to your advantage.

Measure and document the density, moisture and the waste content. Analyze the data, and trust the results.

Use precise data to predict the result of settlement and know how that reflects on the planned airspace.

None of the above is new regarding engineered fills, in general, but it is certainly all applicable to landfills. It is the way that engineered fills have been built for years, if not centuries. Successful or failed earthen dams are a good example: One of the most famous failures caused the Johnstown, Pennsylvania flood of the late 1880’s, with 20 million tons of water released from Lake Conemaugh. In an attempt to shore up an already failing structure, materials was basically thrown in to breach the gap. During a very wet period, the water rose to a level that reached the unconsolidated fill. And the rest, as they say, is history.

When building an engineered fill it is often necessary to mix materials once they reach the fill. Earthen materials with different moisture levels and particle sizes are placed in controlled thicknesses, disked, mixed, dried or watered, and compacted to their maximum density and stability. The application of the above-mentioned rules are often overlooked in non-engineered fills, such as overburden and tailing fills. All goes well until moisture or settlement upsets the stability, resulting in disastrous failures. Almost any sizable fill has the ability to cause problems and should be looked at with these rules in mind.

A BOMAG compactor in action.
Photo courtesy of BOMAG Americas, Inc.

Using modern GPS technology and in-depth data analysis to follow these rules, landfills can profit from increased efficiency in these ways:

1. More overall capacity

2. Lower indemnification costs

3. LFG production revenues

4. Lower end-of-life maintenance costs

5. Intentional, cost-effective repurposing of the area

6. Public Relations, community support, and trust in the operator

Mark Williams started his construction career in 1971, building roads for his father’s West Michigan-based company. Despite his numerous technological inventions for the machine control industry, he is most proud of the bicycle-driven lawnmower he built at ten years old.