Challenges of Redeveloping Landfills Can Be Overcome

By Mike McLaughlin and Dan Johnson

There is much recent interest in reclaiming real estate formerly occupied by municipal landfills in many jurisdictions. For years, closed landfill sites were used, if at all, primarily for passive recreation. Over the last 25 years, however, an increasing number of closed landfills have been used for a variety of industrial, commercial, and residential purposes.

Throughout North America, agencies of federal, state, and local governments have begun new initiatives (“brownfields”) to redevelop sites that are environmentally “tainted.” In many respects, closed landfills are classic brownfields opportunities, as they are often near good transportation and other public infrastructure.

Colma Home Depot Retail Center

Consider this recent landfill project. At the closed Junipero Serra (Colma) landfill in San Mateo County, CA, refuse depths varied up to 130 ft. After the site was selected by Bocci-Schneider Interests to be developed as a Home Depot, the civil engineering firm of Brian Kangas Faulk (now BKF Engineers) and DPA Associates prepared one of the most innovative approaches ever undertaken for redevelopment of a landfill site. Included was a deep pile foundation through buried waste to support the building, a landfill gas protection system, and an unusual hinged slab to connect the building to the parking areas supported by waste.

The completed project was presented at National Solid Wastes Management Association’s WasteTech ’96 Conference. Many in the audience wondered how the project would work in the “real world.” More than eight years later, the results are in, and the Colma Home Depot is doing very well. Sales are good - the store has been one of the highest-grossing Home Depot stores on a per-square-foot basis - and the innovative environmental systems have worked almost better than expected.

Operation, monitoring, and maintenance services for the landfill gas extraction, treatment, and sensor systems were provided by SCS Field services. This work also included design, permitting, and installation of a replacement gas flare. In addition, SCS provided health and safety support and construction oversight for below-grade repairs to site utilities and the hinged slab that doubles as a store entrance. Fewer repairs have been necessary than originally anticipated, and the average shopper would not know the store sits atop a closed landfill.

Despite the success of this and other landfill redevelopment projects, however, closed landfill sites often are regarded as being too affected by environmental challenges to be successfully redeveloped. Experience shows otherwise, if legal and technical issues are properly addressed.

Recent changes to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or Superfund) offer some liability protection for those who qualify as bona fide prospective purchasers of property where historical releases of hazardous substances may have occurred. Under Section 222 of the Small Business Liability Relief and Brownfields Revitalization Act, a bona fide prospective purchaser can receive liability protections if specific conditions are met. A prospective purchaser of a closed landfill site probably can meet these conditions, provided that they take reasonable steps to mitigate the hazards presented by developing such a site.

Municipalities face liabilities under a variety of theories if they allow development on "the old town dump" without requiring appropriate mitigation measures, including those to address technical problems presented by settlement, foundation support, and gas generation. Los Angeles has had a specific program governing construction near closed landfills and other sources of potentially explosive gases for more than 25 years. Alexandria, VA also has had such an ordinance since the mid-1970s, and Texas has a statewide program governing redevelopment of closed landfills. The more established regulatory programs require developers to have mitigation measures designed by engineers experienced in such projects.

Westport Office Park - Before Redevelopment

Westport Office Park - After Redevelopment

The $150 million Westport Office Park in Redwood City, CA is considered one of the most ambitious, technically-challenging redevelopment projects ever undertaken on a former landfill site. The 85-acre property was used as a municipal waste landfill from the 1940s until 1970.

In 1998, the general contractor retained SCS Engineers to provide various landfill engineering, permitting, and construction management services. The presence of underlying refuse created challenging engineering issues for site development, including protection of structures from explosive gases, site settlement, special design for site utilities, and preservation of the landfill clay liner. Design plans and specifications for protecting site structures from potential explosive hazards associated with landfill gas infiltration were prepared. Key protection and monitoring features were incorporated into the development.

Today, Westport Office Park is a successful 20-building, 980,000-sq. ft. campus situated in a park-like setting. The development encompasses research and development, office, and biotech uses. The Westport project illustrates how creative solutions can be used for even the most technically-challenging landfill redevelopment projects. One common challenge in particular is protecting structures from landfill gas. Several approaches are available, including such active control technologies as landfill gas extraction to remove landfill gases before they reach structures and air injection, or air curtain systems, to create positive pressures to drive landfill gases away from structures. Passive control technologies include membrane barriers and vents to prevent gases from entering structures, and monitoring and alarm systems to warn of accumulating gases.

Scores of closed landfills across the United States have been successfully developed into productive land uses. Development ranges from institutional and residential, to a wide variety of commercial, retail, and industrial land uses, in addition to the more traditional passive recreation or golf course uses. The legal and technical challenges inherent in development of a closed landfill can be overcome if these challenges are addressed thoughtfully and strategically.

Mike McLaughlin is a senior vice president and head of the Environmental Services practice at SCS Engineers, Reston, VA and may be reached at 703-471-6150, Ext. 204, or at MmcLaughlin@scsengineers.com

Dan Johnson is principal of Environmental Business Solutions (EBS), which functions as the San Diego, CA office of SCS Engineers and may be reached at 858-571-5500, Ext. 234.