Q&A: How did the integration of the site/civil, geotechnical, and environmental engineering bring added value to the Bayshore Technology Park project?

About the Project
Bayshore Technology Park was built in the late 1990s on an 85-acre waterfront property that was a former landfill from the 1940s to 1970s. Located in Redwood Shores, the Park contains 20 office buildings that are supported on deep foundations, which extend through the landfill and into bay mud (thick deposits of soft, unconsolidated silty clay).

Bayshore Technology Park, Redwood City, CA

Bayshore Technology Park, Redwood City, CA

The original design anticipated future settlement of the site due to the degradation of landfill waste and the consolidation of the bay mud. Our services address American with Disabilities Act (ADA) compliance to resolve differential settlement between the building structures and walkways leading to the buildings.

Solutions to Challenges
The integration of our site/civil, geotechnical, and environmental disciplines is key to addressing the main challenges facing the site in an efficient and cost-effective manner. Surface slopes and utilities (site/civil), excavation and grading (geotechnical), and clay cap and landfill gas building protection systems (environmental) are all intertwined issues that demand a collaborative design approach.

Our multidisciplinary engineering team delivers constant responsiveness to clients, as all three disciplines are communicated via a single point of contact: our multi-disciplined project manager. Client communication during the design process is critical — especially on projects such Bayshore Technology Park, where the final product needs to be functional, cost-effective, and aesthetically pleasing. The multi-disciplinary team works together closely on each improvement project to develop new designs to address varying situations.

On several projects, our team designed and implemented a unique “floating” footing for the new ADA stairs and ramps. Through ongoing monitoring and maintenance, this footing will prolong the life of the improvements by separating the structure from site settlement. Also, the removal and replacement of existing soil with lightweight fill on many projects reduces the surface weight over the landfill and subsequently reduces future site settlement.

Answer provided by DJ Hodson, PE, LEED AP, California Site/Civil Practice Leader
DJ Hodson is a principal in Langan’s San Francisco office and has over 20 years of national and international site/civil engineering experience. He provides expertise in master-plan engineering, site analysis and design, utility assessment and design, hydrologic and hyrdraulic analysis and design, stormwater-management analysis and design, streetscape, waterfront and redevelopment site projects, as well as geotechnical, traffic, and environmental engineering and permitting.

Q&A: Langan designs foundations for some of the tallest towers around the world. How does the firm provide its expertise in so many locations?

Kingdom Tower, Jeddah, KSA

Kingdom Tower, Jeddah, KSA

Langan’s core values of technical excellence, practical experience, and client responsiveness are desirable qualities that export well around the world. The technical excellence starts with a roster of geotechnical engineers that are trained at world class universities. This deep knowledge of soil mechanics, engineering geology, and foundation design allows us to apply fundamental and advanced engineering principles in any type of geology.

As for practical experience, it is essential when adapting to local construction equipment, workmanship, and materials. Many times, foundation options available in North America are not economically feasible in emerging economies.  We find that labor is less expensive compared to construction materials, where the opposite is often true in the U.S.

Last is client responsiveness. We find, especially in emerging markets, that few design teams can outpace Western project teams from concept design all the way through contract documents. Our international clients welcome this accelerated pace of work, because no matter where you are, time is money.

About Alan Poeppel, PE
Alan has over 20 years of diversified experience in geotechnical engineering projects involving the management, investigation, instrumentation, design, and construction of projects in the United States and overseas. He has spearheaded  a number of high-rise “super” towers projects in India and the Middle East including Kuala Lumpur City Center and the 1,000-meter-tall super structure, Kingdom Tower, in Saudi Arabia.

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

Q&A: How do ground improvement techniques affect infrastructure in areas with highly-compressible soils?

Earthwork diagram illustrating the amount of fill and adjustments for compaction and settlement.

Earthwork diagram illustrating the volumes of fill needed for a project.

As major cities in Latin America grow and evolve, land developers are looking to complex and challenging sites to meet their development needs. In general, existing conditions such as low-quality soil present various development challenges. For example, sites in low-lying areas with highly-compressible, saturated clays complicate the development process. In these cases, ground improvement solutions such as wick drains combined with temporary surcharge facilitate development by significantly accelerating the time frame in which total and differential settlement would otherwise occur gradually over an extended period of time before reaching the required clay consolidation suitable for development. These accelerated ground improvement time periods are critical to developer schedules.

Prefabricated vertical wick drains

Prefabricated vertical wick drains

Depending on the wick drain spacing and the thickness of the clay stratum, ground improvements in these areas become necessary to properly support low-rise buildings and infrastructure. Storm drainage, sanitary sewer, potable water, and roadway systems constructed in improved soils minimize the risk of critical infrastructure failure by addressing and resolving issues related to differential settlement that could affect the overall performance of the infrastructure system.

About Ing. Aurelio Escalona 
Aurelio has over 20 years of diversified experience in land development engineering projects involving utility improvements, permitting, earthwork, hydraulics and hydrology, roadways, storm drainage, potable water systems, and sanitary sewer systems. As an associate at Langan he manages the firm’s regional office in Panama City, Panama and serves as the practice leader for hospitality, residential, and mixed-use projects in Latin America and the Caribbean.

Q&A: What are the unique engineering challenges for San Francisco’s burgeoning downtown area?

706 Mission, San Francisco, CA

706 Mission, San Francisco, CA

Background Information

Langan Treadwell Rollo is performing engineering services for several new high-rise residential developments in downtown San Francisco: 706 Mission Street, Transbay Blocks 6/7 and Block 8, 201 Folsom Street, and 41 Tehama Street, among others. These projects address both the city’s lack of land space (only 7 miles wide by 7 miles long) and desire for smaller units (an estimated 38% of residents are single occupants). According to the San Francisco Planning Department’s 2014 Housing Inventory Report, the production of new housing has increased by 50% from 2013.

What makes all this interesting — and challenging — to an environmental scientist is these projects focus on sky-high vertical growth built on land that our ancestors extended horizontally.

Solutions to Challenges
As a result of the 1906 earthquake and subsequent fire and the preceding Gold Rush era, many of the new downtown developments exist on, or are close to, infill. Rubble, wreckage, old wharves and piers, and abandoned ships can be within these infills.


Remnants of an old ship found during an excavation in downtown San Francisco.

Given the nature of infill, we recognize that contamination and historical concerns will likely result in additional costs for soil handling and disposal. San Francisco’s infill is the reason why the city created the Maher Ordinance (Article 22A of the San Francisco Health Code), regulated by the city’s Department of Public Health (SFDPH). This city code mandates stricter protocols, including site history, soil sampling, and site mitigation, which SFDPH oversees and approves.

Another challenge we face when excavating is the discovery of potential artifacts. These areas within the excavation are then left undisturbed so archaeologists can investigate. While this process can delay a project, it can be quite interesting. During recent excavations, we encountered remnants of an old ship as well as a lighter boat that originated from New England. Our construction crews have discovered items of interest that were as deep as 60 feet below ground so they likely existed several thousand years ago. Some of these artifacts are now displayed in museums. This is why I like the more complex projects: the more challenges we face, the more fascinating these projects become.

Answer provided by Peter J. Cusack
Peter Cusack is an environmental scientist who has worked on San Francisco and other Bay Area projects for the last 26 years. He manages and implements hazardous waste characterization and remediation projects. His experience includes pre-acquisition site assessments, site investigations, underground storage tanks removal, Phase II investigations, soil and groundwater sampling and remediation, development of soil management plans, aquifer pumping tests, contractor oversight, and field inspection for numerous construction projects. His work is often done in coordination with our geotechnical practice. He has extensive experience in site investigations and regulatory agency interaction prior to new construction/development.

Q&A: What are some major seismic design challenges in the Middle East?

As with most regions of the world, the challenge to evaluating seismic hazards is proper quantification of seismicity of the region of interest. Because of the Middle East’s tremendous size, spanning from Western India to North Africa and Turkey and Central Asia to the Southern Arabian Peninsula, it encompasses a region of very different seismic environments. Not only is the seismicity in the region tremendously varied from the highly seismic region of Turkey, Armenia, Azerbaijan, and Iran to low seismicity in the Southern Gulf region, but the cultural and language barriers provide unique challenges for projects in the region.

Langan provided seismic hazard assessments for the structures at Basrah Sports City in Iraq.

Langan provided seismic hazard assessments for the structures at Basrah Sports City in Iraq.
(Rendering courtesy of HOK)

With the high rate of signature developments in the Middle East and the prevalence of Performance-Based Design, appropriately quantified site-specific seismic criteria is imperative for effective and efficient design. Proper quantification of seismic load demands on structures provides the best value engineering that Langan can provide. As such, understanding of the geology and seismic histories of the particular region of interest is critical in seismic evaluations. Another equally important factor is quality, quantity, and appropriateness of locally developed subsurface information used in the development of site-specific seismic design criteria. It is critical to provide seismic recommendations that properly evaluate geologic, geotechnical, and seismologic conditions, that are appropriate, and not overly conservative.

Langan completed a geotechnical earthquake engineering study for Abu Dhabi Media Zone.

Langan completed a geotechnical earthquake engineering study for Abu Dhabi Media Zone.


About Ramin Golesorkhi, PhD, PE, GE
Dr. Golesorkhi, with over 28 years of experience in international seismic analysis and foundation engineering, is the director of seismic engineering services at Langan. He has developed seismic and geotechnical design criteria appropriate for industrial, residential, private and government office buildings, hospitals and healthcare facilities, bridges, elevated freeways and viaducts, structures with energy dissipation systems such as base-isolators and dampers, tunnels, and seismic strengthening of existing structures.