What are your top tips to best manage the risks of contaminated fill during construction projects?

Tip #1: Know that there are risks and liabilities for the owner, developer, contractor and consultants.

Management of known or potentially contaminated fill (and recycled material/debris) poses risks and liabilities to all involved: owners, developers, contractors, and consultants.  There are federal, state, and often local regulations and requirements that apply to managing fill and recycled materials. The site owner, developer,  contractor, and even the consultant who were involved in generating and arranging for the management of exported fill/materials could be liable for its handling and management under federal and state law.

Tip #2: Assess the likelihood of contaminated fill on your project at the outset in the concept development stage.

Construction contracts often presume that excess soil and demolition debris represents only a nominal cost or is viewed as a commodity in the bidding stage of a project. Completing a Phase I Environmental Site Assessment in compliance with the ASTM standard is prudent and can offer some valuable information and liability protection, but is not always adequate to assess potential project impacts related to managing potentially contaminated materials.  Understand the cut/fill balance well in advance of contractor bidding and construction.

Tip #3: Plan ahead to minimize costs and delays.

A fill management plan incorporated into project bid documents, contracts, and construction documents designates responsibility and can be used to allocate costs. Characterizing fill early allows time for practical solutions such as treating material in place or in piles, segregating and routing material to lower cost facilities, consolidating/blending material on-site or re-working the site design. Insuring that your bidders have reviewed the plan and are experienced in the management of fill will get you a price without an “uncertainty premium” (high rates to buffer unknowns) or overly broad exclusions that lead to change orders.

Answer provided by Jeff Smith, PG, Associate
Jeff has over 24 years of experience with property assessments, pre-remedial investigation and strategy, RI/FS, FD/RA, alternative remedial strategies, amended RODs, and exposure pathway and vapor intrusion assessments. His career has required the mitigation of complex technical, regulatory, and legal issues, resulting in development of alternative, cost-effective, practical solutions to environmental problems.

Why is everyone talking about emerging contaminants?

So-called emerging contaminants (ECs) like 1,4-dioxane and per- and poly- fluorinated substances (PFAS) have been receiving much press and public attention lately.  Keeping-up with related news, science and policy developments may seem like an overwhelming challenge, and to some it may be tempting to overlook ECs as a sensational “issue du jour” that will pass with the next news cycle.  However, there are plenty of reasons why everyone is talking and why remediation professionals of all stripes should pay attention.  Here are a few of them.

  1. Inconsistent and Unclear Policies & Regulations. State and federal policy makers have been unable to agree on how (or even whether) to regulate ECs.  It has been almost 20 years since the USEPA promulgated or modified a Maximum Contaminant Level (MCL) for a synthetic organic contaminant under the Safe Drinking Water Act (SWDA).  In the interim, the USEPA has issued unenforceable “health advisory levels” for numerous ECs (like PFAS), and many states have reacted to public pressure by establishing their own, often divergent, numerical threshold values.  The resulting tangle of unclear and inconsistent policies and regulations has confused the regulated community and the general public about actual risks and legal obligations, which in turn has set the stage for controversy and conflict.
  1. Potential for “Re-Opening” Sites. ECs are sparking renewed interest in sites that were previously approved for “closure”.  Previously approved remedies may not have considered ECs for myriad reasons:  a) they were unregulated or not known to be hazardous at the time, b) standards have become more stringent, and c) suitable analytical techniques were either unavailable or unable to resolve concentrations at the levels now being regulated or considered for regulation, some of which are in the parts per trillion (ppt) range (i.e., < 0.1 µg/L).  Regulators have expressed concerns that historically approved remedies should be revisited to consider ECs, to ensure that those remedies remain adequately protective.
  1. Business Environmental Risk. Beyond the attendant regulatory risks and uncertainties, ECs may pose new and potentially significant business environmental risks.  The specter of EC-related toxic tort claims is raising questions about:  a) whether and how companies should assess exposure to EC-related risks, b) whether and to what extent ECs should be considered in transactional due diligence, and c) whether EC-related risks are adequately insured and eligible for claims.
  1. Treatment/Remediation Challenges. By their physical and chemical nature, many ECs do not respond as favorably (or at all) to common, conventional treatment and remediation technologies.  For example, 1,4-dioxane cannot be effectively removed from water via air stripping, while granular active carbon (GAC) is only mildly effective for removing 1,4-dioxane.  Additionally, PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are mobile in the environment and are not known to degrade at meaningful rates by natural chemical or biological process.  Treating to ppt levels also presents technical challenges and limitations.
  1. Prevalence. Occurrence studies by the USEPA, USGS and various state agencies have identified detectable concentrations of ECs in a significant proportion of public water supplies (PWS) and surface water bodies. For example:
    • 1,4-dioxane was detected in 22% of the PWS tested from 2013 through 2015 pursuant to the USEPA’s Unregulated Contaminant Monitoring Rule (UCMR).
    • PFAS have been detected in a relatively smaller proportion of PWS nationally (2%) but occur more frequently in some regions like New Jersey (detected in 67% of PWS sampled from 2006-2010; see Occurrence of Perfluorinated Chemicals in Untreated New Jersey Drinking Water Sources, NJDEP Division of Water Supply and Geoscience, April 2014).

Additionally, many ECs are not rare or unusual; they have been used extensively in manufacturing processes and consumer products and therefore may have entered the environment from a variety of potential sources.

Answered by Adam Hackenberg, PG
Adam has over 20 years of diverse experience investigating and remediating environmentally distressed sites under various state programs, CERCLA/Superfund, and RCRA. He has been recognized for teaming with clients to evaluate project drivers, define goals and objectives, and develop cost-effective exit/management strategies.

Langan Remediation Summit Recap: “Managing Risk at Legacy Sites – Insights for Success”

The three-day Summit highlighted the latest technical and scientific developments with an emphasis on practical experience and solutions for remediation and redevelopment.

“All presenters were asked to share positive developments and insights in their presentations.  We wanted attendees to understand not only the new issues that we face in remediation, but also the progress taking place to address difficult sites,” said Nick DeRose on the goals for the Summit.  This goal was evident in a collaborative and lively session on “emerging contaminants” (more information on this below), as well as a presentation on current research trends in “Methods for Minimizing Contaminant Rebound Including Current Developments in Back Diffusion Phenomena Research,” a critical concern for on-going remediation projects.

A presentation on “Remediation Risk Management, Including Risk Financing and/or Risk Transfer” offered insights into creative mechanisms to manage remediation liability.

For more information on the presentations, and including obtaining copies, please contact Nick DeRose, Managing Principal at Langan, at nderose@langan.com or 215-491-6510 .

View the Emerging Contaminants presentation.

View the full agenda and see what you missed!

What were some of the challenges and rewards associated with working in the Golden Gate National Recreation Area and specifically the Presidio of San Francisco?

The most rewarding aspect of working within the Golden Gate National Recreation Area (GGNRA), and specifically the Presidio, is being part of a team that transformed a former US Army base into a spectacular National Park.

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Battery East – Before

Our role as the environmental consultant began more than 16 years ago. At that time, the US Army base at the Presidio had recently transferred to the National Park Service with the Presidio Trust in charge of managing the interior park lands. The National Park Service  would control coastal lands.

Some of our projects included assessing and achieving clean closure at landfills on or near the coast of the Presidio, cleaning up soil impacted with lead near the Golden Gate Bridge, assessing water quality in habitat ponds to support the resurgence of the red-legged frog, and performing remediation on former landfills to assist in bicycle and pedestrian trail development.


Battery East – After

Our biggest challenge was navigating the complex regulatory structure associated with working within the park to clean-up previously contaminated sites and obtain closure. Some of the government agencies with jurisdiction in the GGNRA are the Regional Water Quality Control Board, Department of Toxic Substance Control, Golden Gate Bridge Highway and Transportation District, National Park Service, and Presidio Trust. Another critical component to successfully manage a park project is to understand land use and applicable cleanup standards, whether they be commercial, ecological, recreation, or residential. Different areas of the park have different cleanup criteria, which are based on land use, exposure assumptions, and background conditions.

The GGNRA now consists of over 80,000 acres of ecologically and historically significant landscapes in the greater San Francisco Bay Area.  Over 14 million people visit and enjoy the GGNRA each year making it one of the largest urban parks in the world. We at Langan are proud to have helped open many areas to the public.

About Joshua Graber, CHMM
Joshua is a senior project manager with nearly 20 years of environmental consulting experience.  His responsibilities include geologic, hydrogeologic, and chemical analytical evaluations; Superfund site management; vapor intrusion assessments and mitigation; soil and groundwater remediation; litigation support; remedial excavation, waste classification, and disposal; and technical report preparation. He currently manages the Presidio-wide groundwater monitoring program, GGNRA projects, in addition to other projects in Northern California.

Q&A: Aren’t sediments just wet soils? Is sand capping appropriate to isolate contaminated sediments?

Sediments are NOT just wet soils.

Sediments deposited underwater in modern geological times are categorically different than wet soils.  Ignoring those differences could lead to major errors in remedial investigations, evaluation of regulatory requirements, and assessment of environmental liabilities.  These differences may include:

  • High susceptibility to water transport (e.g. tides, storm induced flows)
  • Temporal variations existing over hours to decades
  • Large spatial heterogeneities, and
    • Low percent solids
    • High organic carbon
    • Wide range in particle sizes
    • Strong biological influences
    • Debris
  • Contaminant reservoirs in many forms
  • Complex geochemical changes over short (centimeter scale) vertical intervals
  • Ground water and surface water pathways
16 minutes later with 2, 4, and 6-inch sand caps

16 minutes later with 2, 4, and 6-inch sand caps; and sharp interfaces (<2 millimeters)

Soft, fluffy sediment

Soft, fluffy sediment

Sand caps can be utilized to isolate contamination even in very soft “fluffy” sediment.

The key to designing and constructing sand caps on top of very soft sediment is to use fine sands to minimize initial density differences and to add the sand very gently.  Soft sediment is easily disturbed and can be displaced in mud “waves” when sand is introduced quickly in large volumes or clumps.  These clumps impact the soft sediment as large single “stones” instead of a gentle rain of small particles.  The following figures illustrate the very sharp interface (<2 millimeters) that can occur between a sand cap and very soft sediment using a well-designed and engineered approach to sand placement.

About Rick Beach
Rick Beach brings nearly 45 years of experience with sediment projects and programs where he has managed, directed, and implemented site investigations, data gap evaluations, feasibility studies, remedial designs, remediation services, project optimizations, third-party reviews, potentially responsible party (PRP) identification, litigation support, and expert testimony.

Q&A: What are the design considerations for landfill gas mitigation during site redevelopment?

Over the past two decades, the United States has seen a substantial increase in development on closed municipal-waste landfills. The construction value of these projects could be substantial in addition to the numerous end-use benefits such as tax revenues and new jobs. Redeveloping landfills is particularly challenging not only because of the issues associated with cleanup, but also because of the environmental and geotechnical issues of building on refuse. Landfill gas containing elevated levels of methane poses a significant risk of fire and explosion. Other landfill gases such as sulfur-based corrosives like hydrogen sulfide and volatile organic compound vapors pose significant exposure risks to human health, safety and the environment. Hydrogen sulfide can also cause significant odor issues.

Langan performed all aspects of monitoring, remedial planning, and landfill closure for this Contra Costa Waster Service NPL site.

Langan performs all aspects of monitoring, remedial planning, and landfill closure for various landfill sites.

To be effective, design strategies for mitigating landfill gas, must incorporate the site’s architectural, structural, and geotechnical features. Applying pilot testing and pneumatic air-flow computational modeling tools is good engineering practice to determine key parameters, including air intrinsic permeability of the refuse, radius of influence, well network, desired air-flow rates, vacuum propagation, and pore-air volume exchanges, for cost-effective designs and more reliable predictions of the mitigation system performance. Detailed evaluation of long-term remedial benefits, potential refuse settlement, seismic hazards, fire and explosion hazards, odor problems, and corrosive-gas impacts on the system constructability and performance should also be performed during the design phase.

Although redevelopment of landfills holds great potential, the means and methods used to design and implement gas mitigation systems are such that human health, safety and the environment are protected for the life of the project. Our ability to effectively remediate such sites means that redeveloping closed landfills for sanctioned use will continue for years to come.

About Omer Uppal, PE 
Omer has more than 15 years of experience in the environmental remediation and consulting industry. As Senior Project Engineer at Langan, he is responsible for soil, sediment, and groundwater investigations, field pilot testing, groundwater flow and contaminant transport modeling, risk-based closure and remedial strategy development, and full-scale engineering design. He is experienced in various remedial technologies including in-situ bioremediation, soil vapor extraction (SVE), multi-phase extraction (MPE), air sparging, chemical oxidation, treatment barriers, vapor intrusion, mitigation, and landfill gas mitigation systems.

Q&A: What are the unique engineering challenges for the Sutter Health CPMC project on Cathedral Hill?

CPMC Van Ness and Geary, located in the bottom left of the image, is on Cathedral Hill in San Francisco, CA

CPMC Van Ness and Geary (bottom left of the image) is on Cathedral Hill in San Francisco, CA.

The Sutter Health CPMC Van Ness and Geary Campus is highly visible: it is located in the heart of city, considered to be a future flagship medical center, and involves demolitions, deep excavations, and constructing an underground tunnel. This year, our geotechnical and environmental engineers focused heavily on the hospital excavation and the tunnel construction underneath one of San Francisco’s most congested and centrally located roadways, U.S. Highway 101/ Van Ness Avenue.

Closing down the road for the initial stage of the tunnel construction was the foremost challenge, but it was a necessary component. Earlier this year, the development team obtained the City and County of San Francisco’s approval and coordinated extensively with Caltrans to close down Van Ness between Geary and Post for three 72-hour periods, from Friday at 12:01 a.m. to Sunday at 11:59 p.m. The first two closures were completed last spring and the final closure will occur later this year.

During the first two closure periods, our field staff worked around-the-clock in rotating eight-hour shifts to help ensure that every necessary task was completed within the allotted time frame. Soldier beams were installed on either side of the tunnel to provide temporary excavation support and also to support temporary, traffic-rated decking atop them. During the first two closure periods, the construction team installed all soldier piles and completed an excavation of about 5 feet below Van Ness Avenue. As the excavation progressed, timber lagging boards were installed between the soldier piles. The tunnel excavation work then moved to the hospital side, where hand-digging equipment is being used to complete the tunnel, which will bottom approximately 25 feet below Van Ness Avenue.

Construction on the CPMC Van Ness and Geary site in San Francisco, CA

Construction on the CPMC Van Ness and Geary site in San Francisco, CA

The entire project team, including architects, engineers, contractors, and subcontractors, has also been dedicated to sustainability. For example, an estimated 51,000 tons of concrete and 5,000 tons of steel were recycled from the hotel demolition. The team is aiming for LEED Silver certification for this project, which will make Sutter Health CPMC Van Ness and Geary one of the largest LEED-certified hospital campuses in the world and only the fourth LEED-certified hospital in California.

Bringing this extraordinary project to fruition has required close coordination, efficient project integration, and creative problem solving. Our focus has been highly responsive and we have completed tasks on, or ahead of, schedule. We are eager to see this project come to life and serve the community.

Answer provided by Cary E. Ronan, PE, GE
Cary has over 18 years of experience performing and managing geotechnical investigations and construction observation services for numerous projects throughout the San Francisco Bay Area. She provides project management and supervision services during investigations for commercial, retail, and residential developments, including high-rise developments as well as healthcare, school, university, and museum facilities.

Cary directs subsurface investigations, designs and evaluates foundations systems, performs engineering analyses, and directs field and office personnel. She has performed engineering analyses to determine settlement behavior of soil under loading, bearing capacity for shallow foundations, lateral and vertical capacity for deep foundations, and evaluated slope stability and seismic hazards including liquefaction potential.

Photography: ©2015 Brian Haux – SkyHawk Photography