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.
Perfluoroalkyl and polyfluroalkyl substances (PFAS) and other emerging contaminants are becoming increasingly important for real estate transactions. Several states have adopted or proposed health guidelines or Maximum Contaminant Levels (MCLs) for PFAS in their state. States with adopted limits include CA, CT, CO, MN, NC, NH, NJ, and VT; and states with proposed limits include IL, MA, MI, and NY. You can track bills by state here.
The Wisconsin Department of Natural Resources (WDNR) and the Environmental Protection Agency (EPA) are focusing their attention on these contaminants. The WDNR recently issued letters to more than 3,000 responsible parties listed with open cases on the DNR’s Bureau for Remediation and Redevelopment Tracking System (BRRTS) requesting they review PFAS use at open sites. Read a sample of the DNR letter.
With WDNR’s increasing focus on PFAS, a lack of sufficient due diligence, which includes evaluations for PFAS, could lead to significant additional liability for property purchasers, developers, and lenders. In addition, a lack of sufficient assessment could lead to a delay in case closure even after responsible parties have addressed all other contaminants and potential exposure pathways at a site. A sufficient assessment for PFAS will depend on site-specific factors and should carefully consider the associated risks and liabilities.
For real estate buyers, owners, developers, lenders, brokers, and contractors the potential presence of PFAS at a property presents significant liabilities that need to be incorporated into due diligence procedures and safe work plans. The investigation and remediation of sites with PFAS contamination can be expensive, and the WDNR is working to define enforceable cleanup goals for soil and groundwater.
PFAS are often referred to as “forever chemicals” due to their inability to be broken down in the environment. Due to the very high toxicity of PFAS, the proposed groundwater standard is extremely low – in the parts per trillion, which is more than 100 times lower than the groundwater standards for other well-known toxic contaminants such as benzene from gasoline or tetrachloroethylene commonly used at dry cleaners and industrial facilities.
PFAS are found in a wide variety of products, including nonstick coatings (e.g., Teflon), water-repellent coatings used on clothing and food packaging, fume suppressants, and firefighting foams. Potential sources of PFAS include many types of manufacturing and processing facilities, locations where firefighting foams have been used, metal plating facilities, wastewater treatment plants, and many more.
PFAS systems can treat and clean sources and remediation solutions by environmental engineers can bring properties back to life; safe to build and live on.
Florida Environmental Network will host its 34th Annual Environmental Permitting Summer School on Marco Island, Florida, July 21-24, 2020.
Organizers are monitoring the COVID pandemic very carefully, and currently are proceeding with the conference, which will take place at the JW Marriott Marco Island Resort. There is also an option for Virtual attendance.
Meet SCS Engineers Professionals, who will be present — and presenting — at the permitting school, including
Florida Environmental Network, Inc. (FENI) is part of the Florida Chamber Foundation’s ongoing effort to keep its members and other business organizations informed of the numerous environmental and growth management laws and regulations affecting Florida’s citizens and businesses. Each year, FENI produces the long-standing and popular seminar called the Environmental Permitting Summer School, which focuses on finding solutions to Florida’s environmental challenges, development and research, and working in partnership with state business leaders to secure Florida’s future.
The land development industry, contracting for nearly a decade is now on the rise again. In urban areas, where available parcels are environmentally impacted, the land is prepared by addressing structural and environmental issues as part of the design and permitting of the proposed development.
Old dumps and lake fills are particularly interesting because a geotechnical investigation and evaluation are required to address subsurface substandard conditions. In most cases, the land is purchased from the original owner who carried out operations resulting in environmental impacts to the property, even if staying with compliance regulations at the time. Experienced developers and engineers use dynamic compaction to compress the subsurface material increasing its ability to withstand the future loading from structures developed on the surface. Developers extract the cost of preparing the land for development from the purchase price. Those who have not experienced the development of brownfields need to have an experienced engineer on their side to proceed through the challenging assessments to establish accurately a price for the land.
The cost of land preparation may involve addressing multiple issues, such as:
Addressing groundwater impacts alone requires an intimate knowledge of cleanup technologies, applicable rules, familiarity with regulators and application reviewers, ability to design methodologies to handle significant amounts of contaminated water coming out of the ground in the case of pumping groundwater for treatment, and experience with developing cost-effective designs that the developer can afford in its development proforma.
SCS was one of the few firms that started working on making undevelopable parcels of land into developable properties when it began its operations nearly fifty years ago. SCS’s experience covers various types of impacted properties with a record of successful and award-winning projects throughout the country resulting in these revitalized parcels of land redeveloped into economically sustainable properties, such as:
SCS supports real estate developers, landowners, banks, and the insurance industry interested in identifying and reducing the environmental risks associated with properties with a past. SCS can provide estimates for remediating the property in preparation for and during construction and support permitting and compliance challenges for financing. Developers retain experienced engineers to assist throughout the design and permitting process, to maximize savings before and after construction begins.
Author: Dr. Ali Khatami
SCS Engineers ranks 4th on the Los Angeles Business Journal’s list of the top 25 largest environmental services firms in the Los Angeles region. “We’re very proud of our environmental work in California and across the nation,“ stated Pat Sullivan, BCES, CPP, REPA, and a Senior Vice President of SCS Engineers. “It’s especially rewarding to know that we make a positive difference in our backyard and for the regional economy.”
SCS Engineers – highly ranked for environmental consulting – San Diego Business Journal
The San Diego Business Journal listed SCS Engineers as one of the top Environmental Consultants in the region. The listing was researched and compiled by Courtney Shamrell of SDBJ. Environmental services covered by the list include; site assessments, environmental sciences, NEPA/CEQA activities, environmental remediation, work for federal and local governments, work for commercial enterprises, and other environmental engineering projects.
Thank you to our clients and to our environmental professionals who put SCS sustainable environmental solutions to work.