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.

dsc03964

Confidential Project, 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.

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

9

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.

213_3

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
IMG_3865r1-blog

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.

SFMOMA - 1213

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.

How important is community engagement in construction or remediation projects?

Including the local community in construction or remediation projects is extremely beneficial for all involved and can result in acceptance versus opposition. Although this may not always be a regulatory requirement or even considered to be “critical” to a project’s success, often times this type of proactive inclusion can result in time and money saved, and reduced liability.

Picture10-LM pick-ok for safety

Environmental remediation at a Langan project

Most individuals are curious about ongoing construction projects that are taking place in their own (or neighboring) towns and they wonder about the rationale or ultimate purpose of the project, yet they rarely have any information. Individuals potentially impacted by remediation projects have greater concerns and fears.  The lack of knowledge frequently raises questions, doubts, or even cynicism about the project, especially if the project causes inconveniences that disrupt their daily routines, such as commuting or even being able to send a child out to play.  On the other hand, if the impacted community has the facts about the nature of the project, and understands the benefits or risks to their families, friends, and lifestyle they are less likely to be frustrated and confrontational.  For these reasons, any type of proactive information sharing and allowing residents to feel included in major project stages is of key importance to project management success. Additionally, proactively sharing information (possibly in the form of a fact sheet) also allows the party conducting the work control of the message and can dispel concerns.

Gaining greater project acceptance, and more importantly, obtaining the least community resistance, is your goal. This can only happen by voluntarily sharing information. While it is important to do so with the general public, it is equally, if not more, important to include community leaders – both elected and those who are simply well known and trusted civic leaders. Communication may occur formally (newspapers, planning committee meetings) or informally (social media, social gatherings). Taking steps to proactively educate supporters and opponents will help garner support for your project.

The key components to be communicated include, but are not limited to:

  • The nature of the final project, such as new stores, office buildings, a park or housing
  • The reason for the project, the ultimate purpose/rationale
  • The temporary impacts of construction regarding inconveniences, detours, delays, etc.
  • Permanent changes beyond the construction phase including land use/loss and transportation issues such as roadway changes, traffic, noise
  • Benefits such as increased jobs, easier access to stores, better housing, a cleaner environment, increased revenues and improved transportation
  • The most critical component of community relations is allowing for open discussions, and truly listening to concerns as every community has different needs and issues
  • Ultimately providing feedback on a timely basis, and incorporating appropriate components of their recommendations into a final project

By building strong relationships within your project’s community and easing concerns, the project team can save time, money, unwanted bad press, reduce liability, and pave the way for future successful projects in neighboring communities.

About Irene S. Kropp, Senior Environmental Consultant 
A universally respected leader in the New Jersey environmental community, Irene Kropp brings 30 years of regulatory, technical, administrative, and management experience in all areas of environmental protection to Langan’s environmental practice. Prior to joining Langan, Kropp served as the Deputy Commissioner of the New Jersey Department of Environmental Protection. Additionally, she managed multiple offices in the NJDEP including Water Resources, Compliance and Enforcement, Information Resources Management, Management and Budget, and Science and Site Remediation. She has worked closely with other state agencies, the legislature, local governments, the USEPA, other state environmental agencies, developers, corporations, and many New Jersey business and industry associations.

What challenges have you faced applying SWPPP regulations to projects?

The initial challenge is ensuring our clients understand what a SWPPP (storm water pollution prevention program) is and how it affects construction.

20160304_080108

Langan provided Qualified SWPPP Practitioner (QSP) services during the construction of the Equinix SV10 development.

SWPPP provides instructions on how to treat stormwater prior to leaving a construction site. This isn’t new. For many years, cities have required sites to have SWPPPs, however the programs were unenforced and remained unopened throughout construction.

In 2009, the state’s General Permit mandated a SWPPP monitoring and compliance program. Every construction site that disturbs over one acre must have a project-specific SWPPP that the state has reviewed. Also, the construction team is responsible for appointing someone to monitor the site for SWPPP compliance throughout construction. SWPPPs may remain in effect for a few months up to several years, depending on the project’s construction timeline.

Some requirements are as simple as collecting trash and storing it in covered bins; while others require intricate systems to divert stormwater and remove sediment prior to entering the storm drain system.

While SWPPP is a great tool, it has created some confusion. Misunderstandings among different levels of government, contractors, and the property owners have placed us, as the consultants, right in the middle.

Part of our “middle man” role is ensuring clients and property owners understand their responsibilities as well as ours. For example, the party who develops and writes the SWPPP does not have to be the same party monitoring and inspecting the site for compliance.

Whether it’s writing the SWPPP, obtaining state approval, or overseeing the contractors during construction, Langan can play all roles, relieving the client from the burden of keeping up with the evolving regulations and staying on top of multiple contractors.

Even though we may be in charge of SWPPP, we still stress that all involved parties know what it is and its intent, which leads to the most common question we get asked: what’s up with all the acronyms? While there are too many to list here (the state’s General Permit lists them all), I provide a few key ones below:

SWPPP­­ — Storm Water Pollution Prevention Program

QSD — Qualified SWPPP Developer (writes the SWPPP)

QSP — Qualified SWPPP Practitioner (oversees the SWPPP inspections)

LRP — Legally Responsible Person (usually the owner or contractor; cannot be QSD or QSP)

REAP — Rain Event Action Plan (instructions for the contractor to follow prior to a rain event)

SMARTS — Storm Water Multi-Application and Report Tracking System (the state’s portal for submitting SWPPP documents)

Answer provided by Vitina Mandella, PE, LEED AP, QSD/P, Senior Project Manager
Vitina manages project teams from design through construction for land development, site design, and infill projects. She has extensive experience with stormwater management throughout the construction process and after completion as well as designing and implementing stormwater controls. Vitina has prepared stormwater pollution prevention plans (SWPPPs) as well as site and off-site plans for street improvements, traffic, LEED designation, Americans With Disabilities Act (ADA) compliance, and historical preservation.

How can consultants help clients reduce costs and tighten schedules on Latin American development projects?

Through more effective and efficient designs that are tailor-made for developers’ specific needs. 

SMG17

Santa Maria Golf & Country Club, Panama City, Panama

While geotechnical engineering principles are the same in Latin America as in the rest of the world, it is important to understand that each site has its own set of unique challenges and solutions. At Langan, we have helped clients save time and money by evaluating and recommending the most up-to-date and suitable ground improvement procedures for their specific site conditions. Examples of cost-effective considerations include re-evaluating seismic site conditions and improving the design criteria, modifying foundation support systems to more efficient designs, and re-evaluating and improving slope stability and stabilization procedures.

It is also imperative that consultants provide designs that are not only efficient and technically sound, but constructible in the region of the project.  This requires in-depth knowledge and understanding of local construction practices and limitations.  When you combine these key ingredients for project delivery, it helps clients in Latin America tighten schedules and reduce costs.

About Roger Archabal, PE
Roger has over 30 years of geotechnical engineering experience throughout the United States and abroad, focusing on the Gulf of Mexico regions, Florida, Central America, and the Caribbean. He specializes in complex foundations in coastal environments, performing hundreds of geotechnical explorations of varied size and scope.

Q&A: What were the unique engineering challenges for the Alameda Landing Redevelopment project?

Transforming the former U.S. Navy property into a mixed-use development encountered several challenges including complex subsurface conditions, former land uses and improvements, multiple stakeholders, and sensitivity of adjacent improvements.

The Alameda Landing Redevelopment project sits on approximately 80 acres of marshland and tidal flats that were reclaimed with hydraulic fill. Reclamation and development of the site began in the early 1900s. Over the last 100 years, the site has been used by the Tacoma Beer Company, Golden State Miners Iron Works, San Francisco Bay Airdrome, and, most recently, U.S. Navy Fleet Industrial Supply Center.

Alameda

Alameda Landing, Alameda, CA

The site is bound by settlement-sensitive improvements including buildings, tunnels, roadways, and utilities (above and below ground that could not be adversely impacted by the proposed development.) Redevelopment involved construction of residential office, and retail structures, and new public infrastructure (roadways and underground utilities). In addition, existing adjacent roadways were widened and rehabilitated as part of the project due to the increased traffic and condition of the roadways.

The complicated subsurface conditions, former land uses and improvements, and settlement sensitive adjacent improvements presented multiple challenges. The challenges included undocumented liquefiable hydraulic fill and compressible marine clay (Bay Mud) that varies in thickness. These challenges were further complicated by the necessity to raise the site grades by several feet to meet projected future sea-level rise. In addition, the presence of shallow groundwater and environmental impacted soil and groundwater were also present, which necessitated additional considerations and interaction with local, state, and federal regulators.    Along with these issues, the project involved a great deal of coordination and interaction with the project team and multiple stakeholders.  These stakeholders included local, state, and federal regulators, adjacent property owners, multiple contractors, architects, structural engineers, and multiple developers and tenants. The schedule, construction phasing, cost-constraints, and specific performance criteria of each developer and tenant required precision in phasing of the construction and ground improvement operations.

Langan evaluated and provided recommendations for multiple foundation types (shallow and deep foundations) and ground improvement techniques to meet the project goals. Ground improvement techniques included pre-consolidation using soil surcharges and pre-fabricated vertical drains, densification, reinforced earth pads, and lightweight fills.

Answer Provided by Haze M. Rodgers, PE, GE, Senior Project Engineer 
Haze has more than 12 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.