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Pier Reconfiguration—A Seismic Focus

Pier Reconfiguration—A Seismic Focus

Pier 4

Pier 4 completed with cranes installed. Photo: The Northwest Seaport Alliance

Local ports must evolve to meet industry needs, or ships and jobs will simply go elsewhere. The Northwest Seaport Alliance (the Ports of Tacoma and Seattle) needed to accommodate some of the largest shipping vessels in the world. A 18,000 twenty-foot equivalent unit (TEU) Ultra-Large Container Ship is longer than two Space Needles, and the Port of Tacoma’s General Central Peninsula couldn’t accommodate such a vessel. Part of the reason was that Pier 4 stuck out diagonally into the Blair Waterway, narrowing the waterway and creating a chokepoint.

Pier 4 had to be completely reconfigured and aligned with Pier 3 to create a single 3,000-foot-long berth. This required demolition of the existing pier structure and cutting back the shoreline to accommodate the reconfiguration.

Hart Crowser supported multi-discipline engineering firm KPFF Consulting Engineers on this project, which involved demolishing the existing wharf, dredging 460,000 cubic yards of sediment (a volume equivalent to a football field stacked with 215 feet of sediment), constructing a new 1,750-foot-long concrete wharf structure, erecting a new 7,000-square-foot, two-story marine operations building, and improving utilities throughout the site.

Brand-New Seismic Code for Wharves and Piers

Cranes arriving

Eight new post-Panamax cranes came from overseas. Photo: KPFF

The Port of Tacoma Pier 4 Reconfiguration project was the first major port development in the Pacific Northwest to follow the new code standard. The new code standard for seismic design of piers and wharves (ASCE 61-14 ) encourages using “performance-based seismic design” to calculate how the soil and structures will act and interact during an earthquake.

It’s usually the differential deformation (the difference in movement from one location of the structure or soil to another location) that makes a structure unusable after an earthquake. Hart Crowser used dynamic finite element modeling and close collaboration with KPFF engineers to analyze the forces and displacement in the structure caused by earthquake ground motions. Hart Crowser’s work was used to provide input to KPFF’s structural analysis and to optimize the stone column ground improvement layout. This analysis makes the resulting design safer, more resilient, and less expensive than alternative design methods.

Ground Improvement for Seismic Stability

Stone column installation

Installing stone columns to strengthen soil.

The soil at port and waterfront sites is often weak, and the Port of Tacoma is no exception. In many places there are river deposits or large areas of fill that have been deposited in the past. To strengthen the soil, the team installed stone columns, which are basically pillars of rock inserted into the ground. A hollow probe (or tube) is vibrated into the soft ground to the specified depth then filled with gravel which is injected into the surrounding soil. This vibration and volumetric displacement makes the surrounding soil denser and stronger. When the probe is removed, the gravel stays behind, forming underground columns. This can mitigate earthquake-induced liquefaction—in other words, keep the soil from turning to quicksand in an earthquake, and keep the underwater slope from failing in an earthquake.

The ability to design and install stone columns is not common and requires knowledge and experience. Plus, some stone columns needed to be installed on land and some in water, and there was a high water table to contend with. Construction had to be timed for dealing with tides so that workers could get close enough to create the hole before the tide came in. During the stone column installation, old undocumented pier structures were found. Hart Crowser made recommendations for over excavation of the structures in some places and a revised stone column layout to avoid underground obstructions in other places.

A Successful Outcome

The American Council of Engineering Companies of Washington awarded Hart Crowser a 2019 Silver Best in State Award for complexity for this project. The reconfigured dock now supports the largest container cranes on the West Coast and can accommodate some of the largest container vessels in the world. These new ships use 35 percent less fuel per box than smaller vessels and produce around 50 percent less carbon emissions. Hart Crowser was honored to be a part of the new Pier 4 – a world class marine cargo facility that will serve the Port of Tacoma, the Northwest Seaport Alliance, and the community for many years to come.

You Shall Not Pass

Chinook Salmon

Removing Fish Barriers

In 1969, a burning river helped draw attention to the polluted state of many United States waterways. Since then, much progress has been made to clean them up, allowing wildlife to thrive in habitats that were once dead. It’s only more recently that attention has migrated (pun intended) to fish passage problems.

According to NOAA, In the United States, more than 2 million dams and barriers block fish from migrating upstream to spawning and rearing habitat. The Washington State Department of Transportation (WSDOT) says that a little under two thousand culverts block fish passage along Washington highways. As of last year, WSDOT completed 319 fish passage projects, but there is still much to accomplish.
Read on for an example of a recent project, what services are needed to clear the way, and information about Washington, Oregon, Hawaii, and Alaska organizations that are trying to make a difference.

Example of a Fish Passage Project—Rue Creek

Before construction

Rue Creek before construction.

After construction

Rue Creek after construction.

The Pacific Conservation District received a Washington Coastal Restoration Initiative grant from the Washington State Recreation and Conservation Office. Hart Crowser supported the Pacific Conservation District with design and development of two culvert replacements on Rue Road in Pacific County.

Fish passage and flow conveyance capacity were restored by removing the existing culverts and overlying fill, and installing a 50-foot bridge that met design requirements in the Washington Department of Fish and Wildlife’s Water Crossing Design Guidelines and Washington State Department of Transportation’s Standard Specifications for Road, Bridge and Municipal Construction and Design Manual. Staff then used the stream simulation approach (one of the methods to size and design culverts that is an option in the Washington Department of Fish and Wildlife’s Water Crossing Design Guidelines) to design the pattern, dimensions, and other features of the stream channel at the crossing, which would enable safe passage of juvenile and adult salmonids both upstream and downstream. An added benefit was that the replacement should prevent the creek from flooding Rue Creek Road and nearby residences.

Services Needed for Fish Passage Projects

These projects can require:

  • Hydraulic engineering
  • Geotechnical engineering
  • Stream reach assessment
  • Wetland delineation
  • Permit applications to comply with Section 404 of the Clean Water Act, Section 7 of the Endangered Species Act, and other federal, state, and local permit requirements. For the Rue Creek example above, this included preparation of a JARPA, SEPA checklist, ESA Section 7 Biological Assessment, Essential Fish Habitat assessment, and Stewardship Plan.

Action on the Local Level

Washington

In 2014, the Washington State Legislature created the Fish Passage Barrier Removal Board to develop a coordinated barrier removal strategy and provide the framework for a fish barrier grant program. Its stated mission is to “identify and expedite the removal of human-made or caused impediments to anadromous fish passage in the most efficient manner practical through the development of a coordinated approach and schedule that identifies and prioritizes the projects necessary to eliminate fish passage barriers caused by state and local roads and highways and barriers owned by private parties.”
The board has monthly meetings; agenda and meeting handouts are available on its website. It advanced its first project list to the legislature, which has been funded.

Oregon

The Oregon Department of Fish and Wildlife has a nine-member Fish Passage Task Force, which “advises the Oregon Department of Fish and Wildlife and the Fish and Wildlife Commission on matters related to fish passage. These matters include, but are not limited to, rulemaking to implement statutes, funding and special conditions for passage projects, and exemptions and waivers.” The most recent agendas and minutes are at the link above; older ones are here.

Hawaii

The Pacific Islands Fish and Wildlife Office of The US Fish and Wildlife Service says that the Hawaii Fish Habitat Partnership “is composed of a diverse group of partners that have the capacity to plan and implement a technically sound statewide aquatic habitat restoration program. The partnership is committed to implementing aquatic habitat restoration in the appropriate landscape scale to achieve conservation benefits.”

They list “instream structures and barriers including stream diversions, dams, channel alteration, and road crossings” as one of eight key threats to freshwater species and habitat.
See the Pacific Islands Fish & Wildlife Office annual report for fiscal year 2017 for more information.

Alaska

The Alaska Department of Fish and Game has a fish passage inventory database with information about 2,500 stream crossings. They have partnered with other organizations to complete at least 33 culvert replacements.

You Shall Pass

A blocked river isn’t as dramatic as a burning river, which makes it harder to draw attention to the plight of the remaining blocked fish. But the hope is that continued effort will forward the progress that is already being made.

Performance-Based Seismic Design for Safer High-Rises

F5 Tower

The City of Seattle knows that building codes for downtown Seattle are not safe for tall buildings in a strong earthquake. That’s why it now requires performance-based seismic design for all buildings over 240 feet tall.

What is Performance-Based Seismic Design?

Seismic design usually follows a prescriptive code, sort of like following a cookbook. Performance-based seismic design is a more rigorous seismic analysis, performed by a team of experienced geotechnical and structural engineers. Because the design doesn’t follow the cookbook code, this alternate design procedure must be done by top engineers, so that it meets the intent of the code while also going beyond the code in certain respects. It must also be peer-reviewed by experienced engineers—often the people who participated in developing the code in the first place.

Doug Lindquist, a principal geotechnical engineer with Hart Crowser, describes it this way: “Performance-based design is a design method where the geotechnical and structural engineers proactively evaluate the performance of a structure in terms of displacements, forces, moments, and damage level. Performance-based design often results in a more resilient, constructible, and valuable structure compared to prescriptive/reactive methods.”

In the early 2000s, Hart Crowser was the first local geotechnical firm to use modern performance-based seismic design methods in the Pacific Northwest. Our engineers have incrementally improved on our proprietary methods and procedures over the last 18 years.

When and Where is Performance-Based Seismic Design Used?

Performance-based seismic design is used for buildings taller than 240 feet—around twenty-four stories or higher. It is used in areas zoned for high-rises, and only when allowed by the local permitting jurisdiction (e.g., Seattle and Bellevue).

Examples of our 20+ performance-based seismic design projects include:

  • Rainier Square Tower, Seattle (850 feet tall)
  • F5 Tower, Seattle (660 feet tall)
  • Russell Investments Center, Seattle (598 feet tall)
  • Lincoln Square Expansion, Bellevue (two towers, 450 feet tall)
  • Cirrus, Seattle (440 feet tall)
  • Midtown 21, Seattle (322 feet tall)

Major western United States cities allowing performance-based seismic design include Seattle, Bellevue, Portland, San Francisco, San Jose, Oakland, Los Angeles, and San Diego.

Advantages

Safer Design

Typical building design following the International Building Code (IBC) is based on the Design Earthquake (DE), which is defined as two-thirds of hazard level of the Risk-Adjusted Maximum Considered Earthquake (MCER). Using performance-based seismic design, the geotechnical engineer works closely with the structural engineers to analyze the building under both the DE and the MCER hazard levels. Because the building is analyzed under the higher MCER loading, the engineers have a better understanding of how the building will behave when subjected to strong ground motions. After review of many performance-based design projects, the City of Seattle identified deficiencies in the typical building design methods and now requires performance-based seismic design for all buildings taller than 240 feet.

Faster Construction and Lower Development Costs

When a building is so tall, the building code requires a dual seismic restraint system. This is like wearing both a belt and suspenders. If it’s a good belt, you don’t need the suspenders, and vice versa. Using performance-based seismic design allows you to build using one or the other. Just as it’s faster and more economical to dress donning only one fashion accessory, it’s faster and more economical to build only one structural system. This is allowed when the design engineers perform detailed analyses showing that the single system achieves the desired performance goals of the structure.

Improved Views and Higher Building Value

Eliminating cross-bracing or other exterior seismic restraint systems improves the building’s views, allowing floor-to-ceiling windows, which make the building more desirable to tenants.

Recent Advances

ASCE 7-16

Although it will not be required for use until 2020, improved methods in ASCE 7-16 have been used by Hart Crowser engineers since 2015. Certain provisions of this new code document allow for the removal of some of the extra conservatism built into the current building code. Hart Crowser was the first to use these methods in the Pacific Northwest, which result in reduced construction costs compared to older methods.

Ground Motions

Horizontal pairs of ground motions are provided by the geotechnical engineer to the structural engineer, who simulates the seismic response of the building subjected to these motions using a building model in the PERFORM 3D. There are thousands of ground motions in multiple public databases for geotechnical engineers to choose from to give to the structural engineer for design. Over the last 18 years, Hart Crowser has developed tools and techniques to identify, select, and scale the optimum ground motions that meet the source characteristics (e.g., magnitude, mechanism, spectral shape, site conditions, and source-to-site distance) and reduce the error between the target spectrum and ground motion spectra. This eliminates unnecessary conservatism and reduces construction cost compared to using less ideal ground motions.

Seattle Basin Amplification

The Seattle Basin amplifies ground motions compared to motions outside of a basin. Hart Crowser has been at the forefront of the practical implementation of research on the Seattle Basin into building design. Doug Lindquist has presented at both the 2013 and 2018 workshops on the subject organized by USGS and the City of Seattle.

Future Improvements

Future improvements will include enhanced scenario modeling to determine the strength of shaking at a building site (e.g., the M9 project) and additional advancements on incorporating basin amplification into design.

Lincoln Square Expansion

Lincoln Square Expansion in Bellevue, Washington.

There’s a Volcano on our Project Site

Water is the life blood of any city, but its systems are not always pretty. So the two-million-gallon Forest Park Low Tank was embedded into the hillside to preserve the natural character of the area and leave unfettered views. However, this presented engineering challenges. Overcoming those challenges helped us win a 2017 Grand Award from the American Council of Engineering Companies (ACEC).

Wait—What’s Down There?

The subsurface conditions were quite unusual. Maps showed them as hard volcanic rock, but our geotechnical explorations discovered a new volcanic vent, as yet unmapped. Although of great interest to geologists, volcanic vents are rarely built on. A search of case histories did not find any information to guide the process. We embarked upon an exploration and laboratory testing program to determine if the 100-foot plus pile of cinders would support the tank. We determined that the cinders were fairly uniform across the area, resulting in uniform support for the tank. Our testing further determined the magnitude of loading the cinders could support. With this information we were able to design a foundation that did not require expensive subgrade improvements or pile foundations.

Our high-tech analyses confirmed a low-tech approach would work.

Burying Infrastructure to Preserve the Natural Beauty

In many places, water tanks are constructed within large cuts that many may view as eyesores and which permanently remove natural habitat. This has been accepted over decades as a necessary compromise to provide a robust water supply to our cities. However, this compromise does not need to be accepted. Much like the trend of burying power, communications, and other utilities that were once also overhead, the Forest Park Low Tank demonstrates that water infrastructure can be adapted similarly.

Making the Water Supply Safe

Water is a critical resource in any disaster that disrupts our infrastructure. It’s common knowledge that we cannot survive for more than three days without water. During any natural disaster, it is imperative that our water remain safe and accessible. We completed a site specific seismic hazard (SSSH) as part of our work, so the tank and appurtenant facilities will withstand the next “Big One.”

Defining Ingenuity

Sometimes ingenuity is not devising something new, but applying simple methods to solve a problem. We used performance-based results to guide changes in shoring design, and confirmed landslide mitigation approaches during construction. We avoided designing expensive foundation alternatives, installing bulletproof (and expensive) secant shoring walls, and over-analyzing slope stability prior to construction. And then we buried our best work.

The one thing to remember about this project is that we did not blow our top over an unexpected volcanic vent; instead, we persevered and worked with the design and construction teams to build a successful project…and then buried it out of “site.”Finished project

The Game of Thrones Wall—An Engineering Perspective

Game of Thrones Wall

Photo: HBO

The Game of Thrones (the HBO series based on George R. R. Martin’s books, A Song of Fire and Ice) features a giant wall made of ice. Seven hundred feet high. It’s an imposing structure, but it has to be, in order to keep out the terrifying dead people who inhabit the north.

According to Martin, “You could see it from miles off, a pale blue line across the northern horizon, stretching away to the east and west and vanishing in the far distance, immense and unbroken. This is the end of the world, it seemed to say.”

Such an extraordinary structure couldn’t help but draw attention from our geotechnical engineers and staff, who responded to some of the quotes from the books.

“The wall is a hundred leagues long.”

A league was supposed to be the distance that a person could walk in one hour. An English league, once upon a time was about three miles long, which would make the wall three hundred miles long.

“The wall is 700 feet high.”

This is almost as tall as the 1201 Third Avenue Building in Seattle, a 55-story building, which coincidentally has beautiful blue coloring as well. Certainly it takes a lot of work to design and build a high-rise—imagine building so many adjacent high-rises that they would stretch for 300 miles. That’s never been done.

At a height of 700 feet and a unit weight of 57.4 pounds per cubic foot (pcf) for fresh water ice, the base contact pressure on the underlying soil/rock would be on the order of 40,000 pounds per square foot (psf). (Compare that to a high-rise on glacial till at 14,000 psf).

“The wall has stood for, what, eight thousand years?”

Assuming a coefficient of secondary compression, C-alpha, of 0.02 and assuming that the base upon which the wall is built is comprised of some reasonable thickness of compressible organic muskeg (say ten feet), and assuming the wall was built over a period of one hundered years, the wall will likely have settled about three to five feet under its own weight.

“The top wide enough for a dozen armored knights to ride abreast.”

How wide is an armored knight? Say five feet? 5 x 12 = 60 feet wide? To safely travel, there would need to be at least three feet between riders so the total width (including four feet on either side for shoulders and jersey barriers) would be 101 feet.

“The gaunt outlines of huge catapults and monstrous wooden cranes stood sentry up there, like the skeletons of great birds, and among them walked men as small as ants.”

To anchor the catapults and cranes, it is likely that the overturning and uplift forces on the catapults and cranes would control the design. The overturning forces associated with the action of the catapults and the wind loads on the structures (resulting from the unobstructed exposure to the predominant winds due to the height of the wall) could be resisted by using high-capacity drilled micropiles.

“It was older than the Seven Kingdoms and when he stood beneath it and looked up, it made Jon dizzy. He could feel the great weight of all that ice pressing down on him, as if it were about to topple, and somehow Jon knew that if it fell, the world fell with it.”

One of the Seattle-Tacoma International Airport Third Runway walls (135 feet tall) was built stepped in, in order to avoid this feeling when you stand at the base of it. However, typically, a tall wall looks shorter when looking up than when it does when looking down. Jon is a weenie.

“Eight hundred feet above the forest floor, a good third of that was earth and stone rather than ice.”

It seems that people got creative over the years, sometimes making use of on-site materials, a good practice to save cost, time, and the environment. It also makes sense, when you are building a structure with a contact bearing pressure equal to 40,000 psf, to do overexcavation and replacement with densely compacted (i.e., 95 percent of the maximum dry density, within two percent plus or minus of optimum moisture content, as determined by ASTM D1557 Test Procedure) well-graded sand and gravel with less than five percent passing the U.S. No. 200 sieve based on the minus three-quarter-inch fraction.

Have questions about the geotechnical design of other giant structures? Need a dragon or two? Contact Garry “the Hound” Horvitz.

Why an Earthquake Warning System Should Not Be a Priority In The Pacific Northwest

Earthquake_damage_Cadillac_Hotel,_2001_SmallerThe newest and hottest topics when it comes to disaster discussions in Oregon and Washington, as well as on the national level, are an earthquake warning system and earthquake prediction possibilities. They are the new obsession that has come on the heels of the New Yorker articles this summer. While we don’t object to advancing both of these methods to better warn of impending quakes and hopefully save lives, we do think that the discussion is premature, especially here in the northwest.

The first reason is that an earthquake warning system like that in Japan has to be implemented only with a comprehensive, aggressive, and continuous public education program. Without a full understanding of what you should do when your phone emits an ear piercing shriek warning of impending shaking, we risk even greater panic and possibly more casualties. Running out of buildings with unreinforced masonry or weak facades just before the shaking could put people at more risk of falling hazards outside of the buildings. It could also cause major traffic hazards as drivers try desperately to get across or get off bridges and overpasses. Unless we develop a much better awareness of what the public should do when they receive the warning, it may cause more problems than it solves.

But the real issue is that these technologies are acting as the bright shiny objects that are distracting all of us, from the public to the president, from the real issue: our infrastructure is in dire need of upgrades not only to prevent casualties, but also to encourage long term recovery.  We doubt 30 seconds of warning will seem as beneficial when the public doesn’t have wastewater for one to three years.  Further, a warning system that stops surgery or an elevator is not as important as making sure that the hospital or building itself is designed to withstand shaking. Especially in Oregon and Washington, all of our energy and funds need to be focused first on comprehensive and intelligent infrastructure improvements that increase our community resilience. And that needs to happen as quickly as possible. We implore you not to follow the flashing light! Urge our government to focus on the real issues, and encourage your colleagues and neighbors to personally prepare.

For more information contact Allison Pyrch at (360) 816-7398 or Allison.pyrch@hartcrowser.com

Oregon Public Broadcasting’s Resiliency Blitz Starts January 26

Allison Pyrch of Hart Crowser

Allison Pyrch at a base isolated hospital near Ishinomaki, Japan, talking to Ed Jahn, OPB Producer. With Jay Wilson, Clackamas County Emergency Manager (left) and the hospital engineer. Listen January 26-28 on OPB radio’s Morning Edition between 7 and 9 am and at www.OPBnews.org.

For the last year, Allison Pyrch, a geotechnical engineer with Hart Crowser in Portland, Oregon has been the American Society of Civil Engineers representative to support Oregon Public Broadcasting in the preparation of a 2015 “media blitz” highlighting Oregon’s dire need for improved seismic resiliency.

Allison, the section secretary and a member of the ASCE Technical Committee on Lifeline Earthquake Engineering, travelled to Japan with the OPB Field Guide crew in September to highlight the damage and engineering successes that were observed after the 2011 subduction zone earthquake and tsunami.

The Japan footage, as well as footage from within Oregon, will be used throughout the year to bring awareness to the need for seismic resiliency here at home. The work will culminate with an hour-long documentary in October 2015.

The first segment of coverage will air January 26-28 on OPB radio’s morning Edition between 7 and 9 am can be found now on the OPB website here and here. The series will discuss critical structures in tsunami zones. The January 28th segment will feature Allison and cover how Japan constructs base isolated hospitals that are ready for business immediately after a major seismic event. Tune in and listen!