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.

How did Langan’s expertise assist with the design of Zuckerberg San Francisco General Hospital and Trauma Center’s base-isolated foundation?

The Zuckerberg San Francisco General Hospital and Trauma Center (ZSFG) is the first hospital in San Francisco to be built with a base-isolated foundation — the latest technology for protecting buildings during seismic activity. ZSFG is the only Level One trauma center in San Francisco, so maintaining operations during a natural disaster is critical.

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Zuckerberg San Francisco General Hospital & Trauma Center
(photo credit: Agnieszka Jakubowicz)

By incorporating a base isolation system at the foundation level, the building can move freely up to 33 inches during the Maximum Considered Earthquake (MCE). This free movement reduces the seismically-induced forces in the structure, resulting in an enhanced seismic performance and lowering the cost of the structure.

To accommodate the movements, Langan recommended a void space (commonly referred to as a moat) be constructed between the structure’s basement wall and the adjacent permanent perimeter retaining wall (moat wall).  The moat wall is a permanently tied-back retaining wall ranging from 25 to 41 feet in height.

As the seismic engineers on this project, Langan also developed earthquake ground motions and estimated ground deformations during and following the MCE shaking for use in the structural evaluations and design of the base isolation system and the superstructure.

In addition, we performed nonlinear time series Soil-Structure Interaction (SSI) analyses to estimate seismic forces and displacements of the moat wall as a result of shaking during an MCE event. We used the results to evaluate the potential of out-of-phase motion between the moat and basement walls during the MCE event.

It was very rewarding to be part of this project team and assist with the design and evaluation of the base-isolated foundation, the most earthquake-resistant design known today.

Answer provided by Haze M. Rodgers, PE, GE, Senior Project Engineer 
Haze has nearly 15 years of experience providing geotechnical consulting services, including subsurface exploration, laboratory testing, and construction observation. During design, he provides soil structure interaction evaluations (static and dynamic), ground improvement evaluations, slope stability, and foundation designs. His projects include commercial and residential structures, deep excavations, infrastructure (roadways and utilities), marine and waterfront developments (piers, wharves, and harbors), seismic strengthening, and landslide stabilizations

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!

Is soil liquefaction a risk in the Middle East?

Soil liquefaction is a phenomenon primarily associated with saturated loose granular soils such as sands, some gravels, and non-plastic silts located close to the ground surface where in situ confining stresses are relatively low.  During earthquake shaking, loose, saturated granular soils tend to contract which can cause an increase in the pore water pressure of the soil particles.  If the shaking is strong enough to increase the pore water pressure beyond the effective confining stress of the soil, the pressure may force the soil particles apart and the soil will then behave similar to a liquid – hence the term “liquefaction”.  Liquefaction can result in a significant reduction in the soil’s shear strength, as well as other ground distress such as sand boils, excessive settlement, and lateral movements.

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Yas South Development, Abu Dhabi, UAE

Soil liquefaction can be a risk in the Middle East as groundwater levels are typically high within one to two kilometers of the coast.  The phenomenon is potentially problematic in man-made land reclamation zones, as well as in areas where natural coastal loose sand deposits are encountered.

The liquefaction risk is often exaggerated, as engineers tend to overlook several risk mitigating circumstances, like the high content of fines (silt and clay) within the soil material; the additional surcharge (and hence increased confining stress) due to the subsequent construction of embankments; and also the existence of a surficial crust of dense sand that prevents the liquefaction induced settlement from reaching the surface. In some cases the relatively small thickness of the liquefiable sand layers means that even under a design earthquake event, the actual induced settlements are manageable from a serviceability perspective. Reclaimed areas may or may not be susceptible to liquefaction, depending on the quality of the sand compaction during reclamation and the content of the sand in fines.  Typically, the reclamation can be performed in wet conditions by use of the hydraulic fill method, where the material is deposited by a flowing stream of water, or in dry conditions by compacting the imported fill material in layers. In the first case, the compaction of the reclaimed material typically takes place by use of the vibro-compaction method, while in the second case by the use of impact or vibration rollers. Hydraulic fills tend to be more susceptible to liquefaction, as the material usually lacks fines and as the compaction is performed following fill placement, so is therefore more difficult to achieve. Conversely, reclamation fill placed in dry conditions tend to be less susceptible to liquefaction as the material is compacted in layers and the compaction quality control is performed during fill construction.

In a recent case in Abu Dhabi, authorities accepted Langan’s view that the above mentioned mitigating circumstances eradicated the soil liquefaction risk, which resulted in cost savings of millions of dollars in ground improvement related construction costs.

About Alexandros Yiagos, Ph.D 
U.S. educated (Princeton University) and native of Athens, Greece, Alexandros has 25 years of experience in the design and construction of earth dams, highways (embankments, slopes, and bridges), buildings, thermal power plants, refineries, hydraulic structures, marine structures, airports, wind farms, mines and environmental projects. As a senior project manager for Langan International in Dubai during the past three years, he has been involved in geotechnical engineering consulting for the design of high-rise and low-rise residential, office, hotel, hospital, and education buildings in the United Arab Emirates, Saudi Arabia, Oman, Qatar and India.

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.

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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.

How do multi-disciplinary firms help solve the challenges of complex PPP (concession) projects overseas?

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Langan serves as technical advisor to the lenders (LTA) for EKPPT Motorway in Peloponnese, Greece.

By nature, public–private partnership (PPP or 3P or P3) projects are collaborative and multi-disciplinary. PPP projects have numerous stakeholders, multiple success criteria, longer time horizons, and greater risks in procurement and delivery. The ultimate goal is achieving a balance between risk and return. Therefore, the PPP project model requires numerous specialists to access and address a variety of technical, environmental, contractual, and financial aspects.

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EKPPT Motorway will link Athens and Korinthos to the western end of the Peloponnese.

The role of the Lender’s Technical Adviser in a PPP not only requires excellent technical background, but also an understanding of the bigger picture.  During the tender and construction phases, Langan liaises with the involved parties and provides lenders with risk assessments for environmental permitting, designs and construction methods, project schedule, and robustness of CAPEX and OPEX. As a multidisciplinary firm with extensive experience in complex construction projects, Langan has been able to provide high quality Lender’s Technical Adviser services, help cross-disciplinary and cross-functional conflicts, and move the project forward.

About Tasos Papathanasiou, PE
Tasos has over 18 years of diversified experience managing large scale multi-disciplinary projects, including geotechnical and environmental investigations, site evaluations, foundation design, bulkhead design, construction oversight, and stormwater management. He has provided technical advisory services for motorway and airport concession projects in Greece, Cyprus, and Eastern Europe.

What challenges did you encounter while working on the SFMOMA project?

Project Background and Challenges
The expanded San Francisco Museum of Modern Art (SFMOMA), designed by lead architect Snøhetta, opened last month. The 10-story steel-framed structure stands 210 feet above the adjacent streets.

Originally designed in 1991, the museum’s foundation system consisted of a relatively thin mat that extended beyond the structure’s limits to support a future seven-story expansion. Two decades later, expansion plans revealed that the museum needed more space than originally planned.

The expansion combines the existing mat foundation with the new foundation. The project also added a basement, which required a 30-foot-deep excavation in a heavily dense urban area.

Langan faced the following geotechnical challenges:

  • Differential settlement between the existing and new foundations
  • Temporary support of the adjacent 32-story W Hotel during the planned excavation for the new basement
  • Weak and potentially liquefiable soil underlying the new mat foundation
  • Presence of relatively thick deposit of moderately compressible soil
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Construction at the SFMOMA site.

Our Solutions
Langan was a key member of the project team, working closely with Magnusson Klemencic Associates (project structural engineer) and Webcor Builders (project general contractor). As the geotechnical, earthquake, and environmental engineers, we developed performance-based seismic design criteria and foundation solutions so the project could move forward.

To address the geotechnical challenges, we recommended deep soil-cement mixing (DSM) to improve the ground beneath the new basement and provide temporary shoring. The objective of the ground improvement was to: (1) reduce the potential for liquefaction, (2) reduce the potential for disturbing the weak underlying soils during construction, and (3) transfer building loads to deeper competent layers.

The DSM panels provided appropriate subgrade bearing for the mat and brought the anticipated differential settlement to acceptable levels. For the original mat foundation, MKA developed a system of stiff shear walls through the basement to spread heavy column loads to meet Langan’s geotechnical and foundation design criteria. This structural system not only supported the original mat without overstressing it, but it also allowed the structural connection to the new mat foundation.

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SFMOMA reopened in May 2016. The transformed museum, with its new (white) addition visible behind the distinctive original building, has twice the amount of exhibition space as before. (Credit: Michael Layefsky)

For the required 30-foot-deep excavation, we developed geotechnical design criteria for a stiff soldier beam and raker system to support the neighboring 32-story W Hotel. Ground improvement was also used to strengthen and stiffen the subgrade soil supporting the shoring. Small measured excavation-induced displacements confirmed the success of this approach.

With our interactive solution-oriented approach with the design and construction teams, we overcame project challenges. The majestic SFMOMA is a testament to our innovative and adaptable foundations systems.

Answer provided by Scott Walker, PE, GE, Associate
Scott has over 17 years of experience in providing geotechnical investigation, design, consultation, earthquake engineering, and construction observation services for projects throughout California and southwestern Montana. He specializes in providing innovative geotechnical solutions to challenging sites. His experience includes: commercial and residential buildings, high-rises, sports facilities, museums, schools, and resort development.