The Grade-Controlled Landfill
Colorado landfill operator takes advantage of GNSS to optimize cell construction and airspace utilization
The Front Range Landfill is a Municipal Solid Waste (MSW) landfill that opened in 1996 in Erie, Colorado to serve the disposal needs of the northern Colorado Front Range region. Permitted by the Colorado Department of Public Health and Environment and Weld County, the landfill has a footprint of 326 acres on the 460-acre site with a 70 million cubic yard capacity. It is expected to operate through 2051.
Like other MSW landfills, Front Range Landfill strives to optimize capacity of the permitted airspace and operations with environmentally responsible and efficient material handling. Effective airspace utilization requires skilled operators, good equipment and sound planning.
For improved operational efficiency and accurate constructing of cells, Front Range installed Trimble GNSS technology on its compactors and cover dozers and also utilizes a rover unit for operations staff to facilitate real-time slope and drainage management that increases the efficiency of their airspace utilization program.
The Front Range solution includes:
- CCS900 - Trimble Compaction Control System on Caterpillar 836 Landfill compactors
- GCS900 - Trimble Grade Control System on Caterpillar D6 dozer
- SCS900 - Trimble Site Controller Software – Trimble GNSS rover
- Trimble Connected Community
- Get the right survey measurements at the right time to keep operations on track
- Give the operators visibility of their machine’s current location relative to the design
- Highly accurate lift construction, slopes and tie-ins
- Improved drainage
The effective management of a Municipal Solid Waste (MSW) landfill is much more than pushing trash into place and packing it down.
Typical landfill cells range in size from a few acres to as large as 20+ acres. The best managed landfills deliver longer landfill life and better amortization of such major capital expenditures as liners and closure/post-closure. Constructing cell slopes and tie-ins per the engineered specifications has long been based on experience, intuition and operator approximations.
Dennis Stover, lead operator for Front Range Landfill and a certified Solid Waste Association of North America (SWANA) Manager of Landfill Operations, said, “It’s all about safety, cost and time efficiency in the waste management space. In our case, we’re moving up to 10,000 tons of waste a day—and our operators don’t have time to waste. While our team is very experienced and very good at building accurate slope (typically a 3:1), even small errors are costly in the long run.”
Building a cell with a slope that is off by just a small amount directly effects the entire cell’s life.
“Some of these cells are 200-feet tall,” Stover explained. “If we get off track with the slope down low, we can easily lose out on 10-feet of fill by the time we reach the top, that small error down low could make the difference in months for the life of cells.”
Like other landfill organizations, Front Range relied on third-party surveyors to help keep the compactors working in the permitted airspace and for building accurate slopes. For instance, Front Range regularly relied on surveyors to stake the toe of its slopes before building on a cell. From there the slope was maintained by experienced operators. A surveyor needed to come back on site to validate that the operators were on grade – but it isn’t always practical to get a surveyor on site for every situation that would benefit from it.
Once the slopes are built, it’s very difficult—and costly—to correct. Rework often requires the removal of dirt, backfill of waste material and recovering with dirt. It is extremely time consuming and difficult to get good compaction on a backfilled slope.
“It’s really important for us to build planned slopes right the first time to optimize landfill space,” confirmed Stover.
With his experience with GNSS and machine control in the construction industry, Stover knew the same technology could bring accuracy and productivity gains to landfill cell construction and airspace utilization.
More Efficient Operations
The Front Range system includes the Trimble CCS900 on three landfill compactors, Trimble GSC900 on the CAT D6 cover dozer, a Trimble rover with SCS900 Site Controller Software and Trimble Connected Community (TCC).
Trimble Connected Community is used to wirelessly transfer the engineer’s lift plans to the GNSS rover and in cab computer on the machines.
“With design guidance on the machines, we don’t need surveyors on site to keep the machines moving in the right direction,” Stover adds. “The operators get real-time feedback without any guesswork. They know where material is supposed to be placed and when they have reached the top of waste for the current lift—so we’re always building cell slopes to the correct grade and in the correct location and filling all of the permitted airspace.”
Having the same designs in the GNSS rover allows for the operations staff to make spot checks, create sloping planes in the field and set location or grade stakes when required for machines that do not have GNSS systems.
When it’s time to cover the cell with a layer of soil to prevent the interaction between the waste and the air and reduce odors, the cover dozer operator relies on the GCS900 Trimble Grade Control System with automatic blade control to place cover material to specified design. Because the compactors are using CCS900 to bring the waste material to top of waste design, the amount of cover soil used is minimized.
Stover adds, “Consistent and accurate cover aids in controlling drainage and optimizes cover material used and airspace consumed.”
Here’s how it works.
In the cab of the compactor, the operator sees current and design elevation. For instance, in Figure 1, the operator can see that there is about one foot left to fill to get the material to grade based on the elevation of the front drums of the compactor.
“It’s a simple matter of filling to the prescribed line,” explained Stover. “Our operators don’t have time to study a screen—they need something that is easy to see so they can continue at normal operating speed to complete a job.”
In addition to the machine indicate system on the compactors, Front Range installed the Trimble GCS900 Grade Control System the D6 cover dozer dozers.
“With this system, our dozer operator uses a model that is vertically offset from the one the compactor operators use,” said Stover. “Because the compactor operator places waste to the top of waste design and the dozer places dirt to the permitted airspace design, the operators are able to maintain the correct cover thickness, volume of cover dirt is optimized, and airspace is maximized.”
Since installing the grade control system in mid-2017, Front Range Landfill has realized improved productivity, efficiency and cost savings—and more accurate slopes.
Stover concluded, “We’re in so much better shape with this technology. It has paid for itself just by eliminating the need for third party surveyors. We haven’t had surveyors out here to guide operations since we installed the system. Most importantly, we’re getting all the permitted airspace in every cell just because we have instant knowledge about slopes. It’s such a small investment for the value derived.”