As large tracts of geographically desirable vacant land become scarcer, residential and commercial property developers are increasingly turning to old landfills or former dumps. However, such redevelopment is complex and rife with uncertainties. When compared to greenfield development, the land acquisition costs are lower. Still, any savings are typically offset by greater environmental and infrastructure costs associated with the foundation, landfill gas management, stormwater management, groundwater impacts, meeting closure requirements, and multiple regulatory agency coordination. Therefore, it is important to maximize the developable area while providing engineering solutions to make the project economically feasible. In this blog, we identify some options to reuse challenging sites and lessons learned to contribute to successful redevelopment projects.
Deep Dynamic Compaction
Old landfills or dumps present some unique soil stability challenges. Deep dynamic compaction (DDC) is a ground stabilization technique that has gained popularity in recent years to improve subsurface soil conditions. DDC involves dropping 6 to 30-ton weights from a height between 30 and 75 feet to achieve the desired soil compaction. DDC can effectively apply to a range of subsurface materials, including former C&D debris or municipal solid waste dumps.
DDC provides a stable foundation for future development, minimizes differential settlement while leaving the landfill waste in place, and eliminates the costs associated with removing, transporting, and disposing of buried waste, costing millions of dollars. For simplicity’s sake, let’s consider a 1-acre old landfill or a dumpsite with an average of 15 feet of waste. If excavating the waste and replacing it with clean fill, the disposal fee costs for the excavated waste alone could exceed $400,000. Alternatively, DDC costs range from $1.50 to $2.00 per square foot or $65,000 to $87,120 per acre, excluding mobilization, which costs around $30,000.
Gas Mitigation Systems
Constructing buildings on top of dynamically compacted areas generally requires a combustible gas barrier layer below the building foundation to manage subsurface combustible gases (typically methane). The barrier is required because the waste remains in place. In its simplified form, gas mitigation systems include:
These gas mitigation systems can be either a passive or an active system with a blower. The cost of such systems varies depending on the size of the building, location, and type of liner system used. Typical capital costs for passive systems are in the range of $7 to $9 per square foot for the spray-applied liner and $3 to $4 per square foot for the HDPE liner. For an active system using blowers, add $3 to $4 per square foot. The designer configures a system from these options to address the client’s risk preference and considering future tenant preferences.
Using innovative approaches, impaired lands are increasingly attractive to developers. Beyond the cost-saving benefits to developers realized through DDC and an appropriate gas mitigation system, such projects also create local jobs, increase the tax base, and protect public health and the environment.
About the Authors:
Somshekhar Kundral – Mr. Kundralis, PE, is a Senior Project Manager with over 12 years of broad and diverse environmental engineering experience that includes projects in landfill redevelopment, landfill gas management system design, site assessment, groundwater remediation system design, stormwater management, and injection well system construction. Som is experienced with site permitting, compliance reporting and construction administration services, and remediation systems’ operation and management.
Manuel J. Hernandez – Mr. Hernandez, PE, BCEE, is a Project Director with 21 years of experience in the environmental field. Manny focuses on solid waste management, and he is an expert in local and federal environmental regulations. His experience includes comprehensive project development, including planning, evaluation, contract negotiations, permitting, design, construction administration, and public outreach. He is known for his leadership, mentoring and team-building skills within multicultural teams.
Both engineer’s environmental works include public and private clients. SCS Engineers is a member of the U.S. Green Building Council and the Center for Creative Land Recycling.
At SCS, we’re proud that our services, vision, and corporate citizenship support community revitalization through brownfield redevelopment and land reuse.
The U.S. Environmental Protection Agency in 2017 estimated that roughly 40 percent of all Americans, including a quarter of all children, live within 3 miles of a brownfield site that has received EPA funding. This is a conservative estimate, as only 5.5% of brownfields nationwide have benefited from EPA resources. But these striking numbers clarify the degree to which remediating and repurposing contaminated and underutilized properties has transformative potential to protect our residents’ health and safety.
SCS firmly believes that all blighted, abandoned, and underutilized properties have a future as community assets. We support this vision through the services we provide as well as through our corporate citizenship. The partnership of SCS technology and environmental know-how with CCLR is powerful. There is no shortage of possibilities for brownfields now; ski resorts, parks, mixed-use properties, solar farms, really almost any infrastructure is possible.
SCS is proud to support the Center for Creative Land Recycling (CCLR, or “See Clear”), the leading national nonprofit dedicated to transforming communities through land recycling. Over the past two decades, CCLR has convened, navigated, and influenced the redevelopment industry. Their programs educate the public and community stakeholders to clean up and repurpose underutilized and environmentally impacted properties in a sustainable, equitable and responsible manner.
CCLR and SCS share the belief that with the right training, incentives, and conditions — chiefly, an active corporate partner/investor, community support, and municipal leadership — the redevelopment of brownfields changes communities for the better. CCLR has produced two videos, “About CCLR” and “What is Land Recycling?,” which provide important perspectives about CCLR’s mission and accomplishments.
Dan Johnson, Jim Ritchie, and Amy Dzialowski are among the SCS staff who have worked with CCLR. They have spoken on panels at CCLR’s California Land Recycling Conference, participated in vapor intrusion study groups, teamed with CCLR on providing technical support to West Sacramento and other municipalities, and serve on the planning committee for the Brownfields 2021 Conference together.
At SCS, we understand that brownfield redevelopment is inherently complex and multifaceted, and we appreciate that productive, successful land recycling requires all hands on deck. We’re proud to play a part on the road to redevelopment and thank CCLR for their national leadership in transforming communities through land recycling.
For more information about CCLR, brownfields, and property remediation, contact , or Jean Hamerman, Acting Executive Director of CCLR.