Article Summary:

The Will County Landfill Committee received a comprehensive technical update on the site investigation for the planned horizontal expansion of the county landfill, confirming the project remains on schedule. Consultants presented detailed findings from the completed geological and hydrogeological fieldwork, which will inform the final engineering and design of the new landfill area to ensure public and environmental safety.

Landfill Expansion Key Points:

• Drilling of nine new borings and continuous soil and bedrock sampling for the expansion area is complete, with samples being sent for extensive laboratory analysis.

• Fourteen new piezometers, or monitoring wells, have been installed to characterize groundwater conditions and will be used for an impact evaluation model.

• Engineers are refining the expansion’s design, including adjusting the northern boundary to maximize airspace and designing a V-notched base for efficient leachate collection.

• Despite the fieldwork phase taking slightly longer than anticipated, project consultants confirmed the overall expansion timeline has not been delayed.

The Will County Landfill Committee on Thursday received a detailed update on the extensive site investigation for the planned expansion of the county landfill, learning that the project remains on schedule as engineers begin analyzing a trove of geological data.

A consultant for the project, Mr. Fallon, walked committee members through the now-completed fieldwork phase, which involved drilling nine borings as deep as 140 feet to characterize the soil, clay, and bedrock at the proposed expansion site. He explained that the purpose of the in-depth investigation is to provide engineers with the necessary data to design a site that protects public health, safety, and welfare.

“We have logged and continuously sampled nine additional borings to supplement that information at the existing facility,” Fallon stated. “Those samples have all been delivered to the lab. And actually… we have already received back I would say about 75% of those analytical results.”

The investigation included collecting undisturbed soil samples using Shelby tubes and rock cores to conduct a battery of laboratory tests. These tests, Fallon explained, measure properties like soil density, moisture content, permeability, and shear strength. The results are critical for engineering calculations that ensure the stability of the landfill’s slopes and foundation.

In addition to soil stability, the investigation is focused on groundwater. Fourteen new piezometers—small-diameter wells—have been installed at various depths to monitor different water-bearing zones. This data will be used to create a groundwater impact evaluation model.

“We’ll take the landfill design once it’s once our engineers have developed that and then we’ll… place it into the into the geologic system,” Fallon said in response to a question from member Dawn Bullock. “And then we’ll assume that it’s leaking and we’ll evaluate… after 100 years after closure what are the what are the concentrations of this hypothetical plume at the zone of attenuation.”

Fallon noted that this modeling is a state requirement for the sighting application.

The data is already informing design tweaks. Stormwater modeling has shown that the planned retention ponds are larger than necessary, allowing engineers to push the landfill’s northern boundary slightly to “eek out a little more airspace.” They are also designing the base grades with a “V-notch design” to better channel leachate to a sump location for extraction.

County Board Speaker Joe VanDuyne asked if the water from the underlying aquifer could be utilized by the county. Fallon explained that this would be out of the question, citing both the unsuitability of the small monitoring wells for water supply and a deed restriction on the property. “We have a deed restriction we’re not allowed to use any of the water for drinking purposes,” he said.

Vice-Chair Kelly Hickey, who chaired the meeting, asked if there were any changes to the project’s timeline.

“We haven’t had a delay in the project yet,” Fallon responded. “The field investigation did take a little longer than we than we had thought it would… but within the larger framework of the project, I feel like we’re still on schedule.”