Military Brownfields Demand Explosive Considerations
by Don Plenderleith

Uncle Sam’s sell-off of former military bases under the Base Realignment and Closure (BRAC) program continues under 2005 recommendations that may affect some 800 installations. Some sites are relatively pristine, while others, impacted by years of military use, are literally rife with explosive issues. Though many of these sites face conventional brownfield problems, such as groundwater tainted by diesel oil and PCBs, other environmental issues are exclusive to military bases. These may be as diverse as chemical-warfare residue, spent target-range munitions and unexploded ordnance.

Recent work at a former military landfill site near Ottawa, Canada, reflects some of the unique factors and engineering remedies that might come into play when remediating a military base for continued military use or eventual sale. Each site poses its own set of special challenges based on past usage.

Military History and Unique Considerations
Between 2002 and 2006, the environmental and geotechnical firm Golder Associates Ltd. was contracted to provide engineering supervision and support at a former waste disposal area on the Connaught Ranges and Primary Training Centre, a five-acre site adjacent to the Ottawa River. The work included environmental site investigations, ecological and human risk assessments, remedial options analysis and recommendations, and the development of the remediation plan. It also involved developing the technical scope of work, monitoring excavations of contaminated zones, quality control, wildlife protection measures, and final project delivery.

Once site investigation began, plans changed quickly and engineers found themselves implementing some not-so-traditional engineering and safety measures. An additional consideration typical of any but military brownfield cleanups was the fact that parts of the Connaught Ranges continued to be used for live fire exercises during the remediation process. Employees were required to sign in and out, and stay strictly within the site boundaries.

Over the 40 years that the site was in operation, it was used for disposal of a wide range of military waste—none more dangerous than unexploded ordnance. Initial site investigation also found evidence of hospital laboratory waste, which raised the spectre of chemical and biological hazards. Other contamination came from hydrocarbons, including accelerants used to burn waste such as diesel and stove fuel.

Contaminated soil was excavated from three zones identified as requiring remediation and the areas were backfilled with clean material. Special precautions taken during the work included continuous monitoring to detect explosives, excavating soil by six-inch layers and visually inspecting the exposed soil after each layer was removed.

In all, some 2,400 U.S. tons of impacted soil was removed from the site. Inert wastes such as concrete, bricks and steel—about 550 U.S. tons—were separated from the contaminated soil and re-buried onsite, thus reducing disposal costs and saving landfill space.

A permeable landfill cap of sand and silt was installed, incorporating a slope of 4 degrees for drainage, covered with topsoil and planted with trees and grass. Shoreline protection was engineered to protect the cap during flood conditions.

Between the threat of unexploded ordnance in the landfill and the promise of live fire overhead, little consideration was given to local wildlife that might pose a safety issue, both to itself and the integrity of the landfill cap, until it was discovered that portions of the landfill served as a turtle nesting site.

Stakeholders determined that it might be possible for the turtles to dig through the landfill cap to build their nests and expose contaminated soil.

The decision to relocate the nesting habitat to a safer area was easy. Finding ways to encourage the turtles to use the new digs rather than the area covered by the cap was more challenging.

Through a literature review, bioscientists determined the best aggregate to use as nesting material—a specific mix of sand and gravel, rounded to protect the turtles’ feet from cuts. Because the aggregate mix was not available from any local supplier, it had to be custom-prepared.

Because the landfill site borders the Ottawa River, erosion control measures along the shoreline included Rip Rap—large angular rocks supported below by filter cloth and a finer aggregate. The erosion control measures would have been difficult or impossible for the turtles to traverse to reach the new nesting site from the water, so a sand-covered turtle pathway was built through the Rip Rap to the newly constructed nesting site.

Much to everyone’s relief, the turtles liked their new digs. In the spring of 2006, 20 nests with hatched eggs were found in the alternative nesting habitat. Now the only indication that there is a small landfill still present is a slight rise in the topography. The landfill cap is vegetated with grass and shrubs to consolidate the soil cover layers and prevent their erosion.

Given that the site is behind the target area for one of the firing ranges, it does not get much human traffic, but its landscape is in keeping with the surrounding area and the site no longer poses a threat to the local ecosystem.

Multiple Stakeholders, High Standards
In many such projects, there are multiple stakeholders—in this case, military authorities as well as various levels of civilian authority. Each have an interest in making sure that the work is done to a high standard due to their positions as holders of the public trust.

On the Connaught project, Golder found itself working with Public Works and Government Services Canada, which manages many of the military bases in the Ottawa region on behalf of the Department of National Defence. But the project also needed to meet a wide range of federal and provincial requirements.

A federally protected migratory bird sanctuary, the site is a designated area of natural and scientific interest by the Ministry of Natural Resources of the Province of Ontario. Some of the property is classified as Class 1 provincially significant wetlands.

While all construction work must meet environmental regulations—including wildlife protection measures—close scrutiny from the media, nongovernmental organizations and political entities makes it essential that military brownfield redevelopment maintain a high level of environmental responsibility.

One of the keys to success in this arena is outreach and communication. Each government entity must keep its stakeholders—including elected politicians—informed on the progress and issues associated with such a redevelopment. Success on the Connaught Ranges project was based on good communications, solid planning, a good understanding of the client’s needs, and the combination of several disciplines, including the biosciences, to reach the best result.

Don Plenderleith, P.E., is a senior project manager and federal client service team leader with Golder Associates Ltd., in Ottawa, Ontario.