Landfill gas emergencies are on the rise at landfills nationwide, often due to lining and closure systems that are overly effective. To quickly mitigate the hazards of landfill gas buildups, officials are increasingly turning to the design/ build, or turnkey, approach for implementing an active gas extraction system.
Although landfill gas, or methane, is not directly harmful to health, it can explode if allowed to accumulate in confined spaces. Capped landfills are particularly susceptible to methane buildup because these systems block the methane from dispersing into the air through its normal route. Emergency situations develop when the trapped methane seeks outlets beyond the landfill boundaries, endangering neighboring homes and businesses.
One way to prevent an emergency is building an active gas extraction system, which consists of a series of wells and trenches constructed into a landfill's base. Wells and trenches are connected to a pump system that directs the gases to a flare, which then burns them at the top of a stack. More than 99 percent of methane reportedly can be destroyed through the flare system.
When the Milwaukee County Department of Public Works discovered that methane was seeping past the borders of its closed Franklin, Wis., landfill, officials decided to construct an active gas extraction system. Using the design/build approach, the entire Milwaukee County landfill's interim system was designed, permitted and constructed ahead of schedule - three months after the official notice to proceed. Initial methane readings from the landfill, taken since the start-up of the gas flare, have shown a significant decrease from 50 percent to less than two percent methane.
The design/build approach for both landfill gas extraction systems and landfill closure design offers several advantages, including "fast-track" scheduling, reduced bidding processes and decreased costs. In addition, once an engineer/construction firm is hired, the firm manages the project from start to finish, which relieves the burden on landfill officials.
With design/build, work on the project, such as ordering equipment and site preparation, also can begin while the system's final design and permits are still being prepared. The engineering processes are streamlined because construction bid documents and detailed specifications are no longer necessary. In general, design/ build can shave at least three months from the traditional design/bid/build schedule - one month for design and two for the bidding process.
In addition, because the engineer/constructor has full control over any equipment selection, he or she can choose the most appropriate vendor based on quality and not solely on price. Often, the engineer/constructor can even negotiate better prices because of his or her long-term relationship with the vendor.
A significant hurdle to overcome in design/build projects, however, is establishing a strong sense of trust. The engineer/constructor's function is profoundly different from its role in a traditional design/bid/build relationship.
In design/build the engineer/ constructor has a closer relationship with the client and is responsible for the entire project - there are no outside agents reviewing the work of the engineer/constructor. While this aspect of the design/ build relationship can be a challenge and often must be nurtured, many landfill officials have found that it ultimately benefits the client and its constituents.