Big Bertha – Slow and Steady Wins the Race

This article was written for a construction magazine. It was a complex article to write because it merged history, project management, and construction equipment into one piece. It also touched lightly on the controversy over the project without being political.

*****

Big construction requires big ideas, big money – and mammoth equipment. The Washington State Department of Transportation (WSDOT) proposed a project back in 2009 to replace the Alaskan Way Viaduct. Their big idea was to dig a tunnel under the city of Seattle. The equipment needed to do this didn’t exist. WSDOT needed a tunnel boring machine (TBM) massive enough to breakthrough 1.7 miles of rock and soil 200 feet below a populous city. A Japanese company, Hitachi Zosen Sakai Works,  built the machine that was ultimately named after the 1920s Seattle mayor Bertha Knight Landes. The TBM measured 57 feet in diameter and weighed more than 6,559 tons. The 326-foot long TBM cost $80 million. Given her size (the TBM; not the mayor), Bertha came to be known as “Big Bertha.” Before Bertha, Becky was the biggest and baddest TBM around. She was used to divert part of the Niagara river to a hydroelectric plant in Canada. Becky had a 45-foot cutting head and weighed “just” 4,000 tons.

The Fabulous Fifties

Back in the mid-1930s, it was the Alaskan Way Viaduct that was the big idea to solve Seattle’s growing traffic problem.

In early 1950, work began on the viaduct. It opened to traffic in 1953. By 1959 the Battery Street Tunnel and an extension to the viaduct were completed.

A 3.4-mile-long freeway was built south of the West Seattle Bridge and headed north to the downtown waterfront. The freeway begins as a standard surface road and ramps up to a double-decker viaduct that comprises about half of the thoroughfare. The upper tier runs north; the lower tier runs south. Eventually, traffic moves into the Battery Street Tunnel. With the tunnel, the total route is 3.8 miles. A relatively short way to travel, but incredibly complex.

The Earthquake Reveal

There’s nothing like a natural disaster to reveal the flaws in a structure. In 2001, the 6.8 Nisqually earthquake damaged the viaduct. Warnings from engineers in the 1990s that the viaduct would not likely withstand a 7.5 magnitude quake had been ignored. Years were spent debating whether to repair, replace, or eliminate the viaduct. Well before Nisqually, the roadways in and out of downtown Seattle were stressed by increasing traffic. When the viaduct was built in the 1950s, it was estimated that 65,000 cars a day would travel on its roadways. In the early 2000s, it was handling an average of 110,000 cars a day.

In contrast, the SR 99 tunnel can handle about a 9.0-magnitude earthquake. All equipment in the tunnel has gone through a seismic analysis. Geotechnical and structural engineers agree that being in the tunnel during an earthquake is your safest bet as the seismic waves are greatest above the surface. Tunnels, with the help of the joints between its rings, move with the soil while above-ground structures sway to and fro. Moreover, when the earthquake is over, the tunnel will remain watertight. This allows people to safely evacuate.

Back to Bertha

Since Bertha was built in Japan, she could not be shipped fully assembled to the United States. In April 2013, Bertha arrived in 41 pieces and was reassembled at the bottom of an 80-foot deep, concrete-lined pit on the waterfront.

Bertha is deceiving from the outside. Inside, she has catwalks, ladders, and stairs. There is a control room and even a pair of break rooms. Bertha is highly automated – it only takes about two dozen workers to keep her moving. But it takes thousands of feet of cables and pipes to supply Bertha with the power, water, and conditioner she needs.

Bertha’s cutterhead covers the entire front of the machine. The cutterhead alone weighed 2,000 tons. It has 260 steel teeth that break up soft soil. The soil moves through gaps inside the cutterhead. Some teeth rotate so that the right tooth is matched with the right task, such as grinding up big boulders. The cutterhead rotates up to 1.2 rpm using a 18,600-kW electrical system. The machine moves approximately 35 feet a day.

How much water is in the soil affects Bertha’s ability to move forward. If there isn’t enough water, the machine can break up the soil by injecting it with a mix of water and a soapy conditioner. Of course, if there’s too much water the cutterhead cranks away, but to no avail. The liquid mud prevents it from moving at all.

A Challenging Environment

Although Bertha didn’t have to bore through solid rock, she had an environment as much – if not more – challenging. Over hundreds of thousands of years, Seattle developed in such a way that eight types of soil formed the ground under the city center. Worse, since the project was near the waterfront, Bertha was operating below the waterline. She had to bore her way through 10 geological zones and come out of a hillside where the soil is very dry.

It gets worse. After well over a century of building, Seattle was a tangle of foundations, pilings, cellars, and sewage lines. Not to mention railway, road, and pedestrian tunnels. Bertha could not begin her journey until old deposits of fill soils were removed. Areas were strengthened so Bertha could do her work without destroying everything around her.

Under Pressure

For Bertha to move the excavated soil where it belonged, the cutterhead was pressurized up to 5.6 atmospheres. This kept the soil slurry in the cutterhead until it was removed. The amount of pressure had to be enough to keep slurry from churning away inside the cutterhead and causing the front face of the tunnel to fall in. With too much pressure, the machine would push a bunch of slurry ahead of itself. The pressure had to be maintained. When the cutterhead needed to be serviced, workers must dove through an airlock and worked inside a pressurized bubble within the cutterhead.

This huge TBM used a 3-foot diameter steel tube to allow the slurry to move safely through it via an Archimedean screw onto a conveyor belt. This tiny tube prevented the slurry from blasting into the digging machine with five atmospheres of pressure behind it. The soil was moved back to the end of the tunnel out to a barge on a nearby pier.

To Shield and Protect

Bertha’s shield was part of her power. This cylindrical hull at the front of the TBM allowed Bertha to move forward by holding up the sides of the tunnel wall. The shield protected her – and the workers – from muck and water.

56 hydraulic jacks formed a ring inside the shield. This pushed Bertha forward as she cut by pressing against the reinforced concrete walls lined along the previously bored section of the tunnel. The wall is comprised of two-foot thick concrete panels. As Bertha slowly inched forward, other jacks aligned and steered the shield.

The lining rings consist of 10 concrete panels. Each ring weighs an astounding 360,000 pounds and is lined with rubber gaskets to keep water out. Behind each panel is forced grouting. This stabilizes the tunnel. Some of the work was automated: A pair of robotic erector arms collected panels from an electric tram. It then placed them against the inner wall of the steel shield. The two arms enabled Bertha to lay down panels at double the speed compared to other machines.

Inside the shield was the control room. Workers monitored and guided Bertha and looked out for any problems that may have arisen. For example, a particularly large boulder may have had to be broken down manually. Or, they may have had to respond quickly to shifting earth.

Working Inside a Giant Machine

The SR 99 project has required legions of workers from many disciplines from truck drivers to engineers. In a project this complex, it’s critical to account for every person. Before starting their shift, each worker picksx up a metal tag that tracked their entering and leaving the tunnel.

During the time Bertha was tunneling, she would push forward, then stop to build the outer wall. This was done one ring at a time. A tunnel ring is comprised of 10 segments, each weighing about 18 tons. An enormous suction vacuum lifted and placed each segment. It played a different tune while in motion to alert nearby workers. Each segment was leveled with a hand tool and secured using a bolt and drill.

The employee restrooms and a kitchen were located inside Bertha’s trailing gear, which rested on huge rollers.

What Could Stop Bertha?

Bertha started boring in July 2013 with an estimated completion date for the tunnel of December 2015. About four months into the project, Bertha was taken offline. At first, the workers believed she had hit a steel pipe. (The pipe was installed in 2002 to measure groundwater around the viaduct.) Turns out that damage to portions of her main bearing seal system caused the bearing to overheat. It took two years to dig a recovery pit so the cutterhead could be lifted and repaired.

Even the red Mammoet tower crane brought in to pick her up encountered problems. The tower gantry planned for the operation was to rest on piles used for stabilizing the tunnel. But the piles were not designed to support a crane of any height. The risk was that uneven distribution could destabilize the tower gantry. The design of the gantry was in some ways as innovative as Bertha herself. It could slide and tilt lifted objects. 48 hydraulic cylinders were used to evenly disperse the load. It was the first gantry full supported by hydraulics.

In December 2015, work resumed. Unfortunately, the project was further delayed when a tethered barge in Elliott Bay damaged piers. The barge, loaded with excavated dirt, started to lean over. To avoid damaging the conveyer that moves the dirt from the tunnel to the dock, workers set the barge adrift. The barge hit a nearby pier and terminal, which damaged the barge and the dock. To make things really interesting, a sinkhole opened up near the site.

All tunnel work was halted in January 2016. Ultimately, citing safety concerns, Governor Inslee ordered maintenance and inspections. Finally, work resumed a couple of months later. Bertha completed tunnel boring in April of 2017.

Beyond Bertha

Replacing the viaduct with the tunnel is just the first step in a much larger construction project.

Removing the Alaskan Way Viaduct

The Alaskan Way Viaduct must be removed. First, it’s considered an eyesore by many. It’s also a safety hazard as it was not built to withstand a major earthquake. Its removal paves the way for Seattle’s Waterfront Program.

Removal of the viaduct began earlier this year and is expected to take several months. (Track the project’s progress here: https://www.wsdot.wa.gov/Projects/Viaduct/demolition/tracker) Once the viaduct removal is complete, the area will be restored and turned over to the City of Seattle’s Waterfront Seattle Program. In addition to the demolition of the viaduct, a new temporary pedestrian bridge will be built.

The viaduct is removed frame by frame beginning with the upper deck. Crews will use impact hammers to remove the roadway deck. Then, hydraulic munchers remove the supporting girders and columns. Some pieces of the viaduct will be lifted and removed with cranes. Finally, the viaducts foundations are removed and the site is restored.

The (Not So) Mighty Seawall

The original seawall was built between 1916 and 1934. The 20,000 old growth timber piles proved inadequate against rising tides and population. The Seattle Seawall Project shored up the structure. Although the new seawall is designed to withstand earthquakes and tsunamis, the SR 99 tunnel has a backup plan. Should a tsunami take place during very high tide (an event likely to occur only once in 6,000 to 24,000 years), Washington state’s early warning system and the tunnel’s real-time traffic technology kick in. Vehicles will be stopped from entering the tunnel. Drains and pumps will immediately remove any water from within the tunnel at a rate of 300 gallons per minute.

A Better Tunnel

Safe and Sound

In the rare event of an evacuation, the SR 99 tunnel has doors every 650 feet leading out to safe areas to either take cover or exit the tunnel. There is a pathway that runs along the entire tunnel equipped with ventilation and fire suppression systems. 300 cameras provide tunnel operators with real-time information 24/7.

The roadways have eight-foot wide shoulders, allowing ample space for vehicles to safely pull over in the case of an emergency. It also provides a pathway for emergency vehicles.

The tunnel itself is environmentally friendly. Three different types of fans keep fresh air flowing through the tunnel. They remove fumes from engines. In fact, it’s the vehicles themselves that push fresh air through the tunnel. Monitoring stations can detect increasing particulates in the air and jet fans are automatically activated to provide additional air flow.

In Case of Emergency

If there is a fire, eight huge extraction fans pull smoke out through vents in the tunnel wall. Simultaneously, the jet fans push fresh air inside. Smoke is ultimately pushed out of the tunnel’s ventilation stacks on top of the operations buildings located at both ends of the tunnel. Maintenance fans provide pressurization to prevent smoke from engulfing the tunnel’s emergency exit area.

The emergency walkways have their own ventilation and fire control systems. These run parallel to both the upper and lower tunnel roadways. Concrete walls and fire-resistant doors keep the emergency areas separate from the roadways. For those travelers who cannot use the stairwells to escape, there are “refuge” areas that will accommodate them. Emergency phones and cameras allow first responders to help those waiting in the refuge areas.

Should there be a power failure, generators power critical tunnel systems.

The Work is Never Done

Completion of the SR 99 tunnel is just the beginning. There is a lot more work to be done.

Closing the Battery Street Tunnel

The mechanical and electrical systems were removed. Now contractor Kiewit will close down the old Battery Street Tunnel with the concrete rubble from the viaduct demolition. Steel rebar was removed from the rubble and the concrete was crushed into small pieces. Funnels are used to send the rubble inside the tunnel. A vibratory roller is used to compact the fill. The tunnel is not completely filled up – about seven feet of space will be left at the top.

On the Waterfront

The waterfront above the tunnel should be more peaceful. A promenade 12 to 40 feet wide will be built and beautified with trees and flowers. Visitors can safely ride on a private bike trail. Overlook Walk is a public path that will connect the waterfront to Pike Place Market. It will provide expansive views of Elliott Bay and the city skyline. (See a complete list of projects, budget, and schedule: https://waterfrontseattle.org/budget-schedule.)

Pay Day

Later this year, commuters will pay a toll to enter the tunnel. This will pay off the construction debt and fund a maintenance account. It will also reduce the tunnel traffic by more than fifty percent.

Dismantling a Giant

It made sense in 2015 to lift Bertha above ground in one piece to be repaired. They needed Bertha whole then – it was worth the cost and time to provide the land, ground reinforcement, and assembly the Mammoet crane required. When her work was done in 2017, she was broken up into pieces that would never again be reassembled. The cutting disc was carved into eight sections. Then each section was chopped into smaller pieces – under the 20-ton maximum weight allowable to haul her away truckload by truckload on Seattle’s city streets. In order to ensure a balanced lift, engineers located the center of mass for each steel slice to determine where fastening loops should be attached.

Using torches, scaffolds, and power tools, it took months to dismantle Bertha.

As much of Bertha as possible will be re-used, including 24 electric motors, movable arms, and miles of hoses, wires, and conveyer belts. The rest of Bertha will be melted down and recycled. The remaining pieces of her cutting head were taken to a scrap-metal yard. The Port of Seattle held onto a few chunks to display to the public.

Lessons Learned

Despite some delays and cost overruns, the SR 99 tunnel project can certainly be called a success. On-site innovations by equipment manufacturers, engineers, and workers will improve the way large construction projects are handled in the future.

 

 

 

 

 

Resources:

https://www.seattlemag.com/news-and-features/tunnel-vision-360-look-bertha-underground

https://www.wsdot.wa.gov/Projects/Viaduct/tunnelsafety

https://www.mammoet.com/cases/project-bertha/

https://www.enr.com/blogs/15-evergreen/post/14092-damaged-main-bearing-seals-cause-of-bertha-overheating-shutdown

https://newatlas.com/bertha-boring-machine-seattle/48862/

“Big Becky” Boring Machine is Key to Canada’s Energy Goals

https://komonews.com/news/sr-99-tunnel/take-a-drive-down-memory-lane-with-the-historical-story-of-the-alaskan-way-viaduct

https://waterfrontseattle.org/seawall

https://komonews.com/news/sr-99-tunnel/from-the-vault-alaskan-way-viaduct-opens

https://www.seattletimes.com/seattle-news/transportation/a-look-back-at-the-alaskan-way-viaduct-as-its-demise-nears-and-the-new-highway-99-tunnel/

https://www.wsdot.wa.gov/Projects/Viaduct/library/advisories-and-updates/know-before-you-go-the-sr-99-tunnel%E2%80%99s-new-ramp-intersections

What You Must Know Before You Hire a Heavy Hauler

This is another example of an article I wrote on a topic I knew absolutely nothing about when I started. A writer doesn’t necessarily need to be a subject matter expert to write a compelling article. The client’s feedback? “Great job on the heavy haul article.” Then he gave me an assignment on foundation drilling rigs.

*****

Moving stuff isn’t generally a big deal. Even moving a piano can be accomplished fairly easily. You call a piano mover, they come and carefully disassemble it. Then, a few strong people pick it up, put it in a truck, and take it to its new destination and carefully reassemble it. But a 12-ton back hoe ain’t a piano. Transporting one requires a lot of coordination, paperwork, and most importantly – expertise. For construction equipment and materials, you may need to hire a heavy hauler.

Do You Need a Heavy Hauler?

What you’re moving may be big and heavy – but not enough to require you to hire a heavy hauler. Get the specific weight and dimensions of the load. You may not need a special truck or permits.

Weight Limitations

As trucks and the loads they carried got bigger and heavier, states needed to implement weight limitations to protect roads and bridges. In 1975, Congress enacted the Bridge Formula. Generally, it sets weight limitations based on the type of axle as follows:

• Steer axles: Up to 12,000 pounds
• Single axles: Up to 20,000 pounds
• Drive axles: Up to 34,000 pounds
• Tandem axles: Up to 34,000 pounds

For loads beyond these limits, special heavy haul equipment with additional axles is necessary. The formula is used to limit the weight-to-length ratio by adding axles or increasing the distance between axles. This prevents the truck from over-stressing bridge members and possibly causing the bridge to collapse.

Not for Nothing

These weight limits are serious. And usually posted on the bridge. Recently, an historic bridge in North Dakota (built in 1906) collapsed under the weight of 25 tons of dry beans. The sign on the bridge the trucker blew by listed the weight limit as 14 tons. An overload citation of $11,400 was issued. Which is nothing compared to the million dollars it will cost to replace the bridge.

Safety

Federal law mandates certain travel accommodations and requirements, including:

• Oversized Load Banners
• Safety Flags
• Specialty Lights
• Pilot Cars
• Police Escort

The heavy hauler should know exactly what is needed to meet the requirements. Additionally, you should take the time to check the company’s safety record. Accidents do indeed happen, but they should be few and far between.

Route Limitations

The heavy hauler you hire must know the specific route that meets all the rules of all the roads. Think about it: Too high and you can’t get under a bridge. Too heavy and you can’t travel over the bridge. Too wide and you can only travel with an escort vehicle on certain roads during certain hours. Every state, county, city, and municipality has developed different rules over the decades. Break them and it will cost you.

Required Permits

If you are crossing state, county, or city lines, you may need different permits. It gets complicated. For example, in Ohio, special consideration is given to the type of load. They will provide a 90-Day Regional heavy haul permit for steel or aluminum coils where the GVW of the vehicle and load is under 120,000 pounds. In Louisiana, any oversized and / or overweight load cannot drive through any of the tunnels in the state. The heavy hauler must know these details.

Tracking the Shipment

You want to know where your load is as it moves from Point A to Point B. The last thing you want to do is call the hauling company so they can call the driver then wait for them to call you with status. These days, any heavy hauler should use GPS for tracking shipments.

Insurance

What insurance is offered? Don’t cheap out on insurance! If anything happens to that load, the cost to you is beyond the actual equipment and materials. Job delays cost money.

Price

Obviously, you need to know the cost. You should get a few quotes. But price should not be your primary consideration. There’s usually a reason you’re paying less. You know, like a less experienced company with a spotty safety record. You don’t want to lose money in the long run because of a lost or damaged shipment. Insurance will cover the item, but not the financial hit to the project.

Basic Company Research

Select 4-5 companies to research. You’ll get quotes from the top 2-3. Try to get referrals from others in your industry. Don’t rely on the reference. Check it out.

Better Business Bureau (https://www.bbb.org/)

• How long has the company been in business?
• Number and type of complaints. If any, how were they handled?

Reviews

• Testimonials on their website
• Public reviews on Yelp, YP.com.

Safety Record

The U.S. Department of Transportation’s Federal Motor Carrier Safety Administration (FMCSA) manages a website to research safety records: https://safer.fmcsa.dot.gov/CompanySnapshot.aspx. All you need is the DOT number, MC/MX number or company name. Use of the Safety and Fitness Electronic Records (SAFER) system is free.

The Heavy Hauler Checklist

Use this checklist to ask the right questions. This information will help you make an informed choice on which heavy hauler to hire:

1. Is your company insured and bonded?
2. What is the best route?
3. What kind of truck will your use?
4. How will you track my shipment? Will I get automatic status? How often?
5. Do you specialize in transporting my load? When’s the last time you moved a load like mine? Can I get a reference? Then contact them.
6. What memberships and certifications do you have?
7. What type of insurance do you offer? How much does it cost?
8. What is the total cost of my shipment? Have the company list out all fees, taxes, etc. When is payment due?
9. How is your safety record? When’s the last time there was an accident? Then look it up. If they lied, move on.

Whatever agreements you make on price, route, and other details of the job, be sure to get it all in writing!

You Can Do It

Moving heavy equipment and materials is complex. But companies do it every day. To find a reputable and competent heavy haul company, do some basic research, ask the right questions, and don’t focus solely on price. Select a quality company and your stuff will make it from Point A to Point B safely and securely.

Helpful Resources:

https://oversize.io/regulations/axle-weight-calculator

https://ops.fhwa.dot.gov/freight/publications/brdg_frm_wghts/#table

 

 

Article Resources:

http://heavyhaultrucking.com/hiring-a-heavy-haul-trucking-company/

http://www.dot.state.oh.us/Divisions/Operations/Maintenance/Permits/Documents/Regional%20Heavy%20Haul%20Permits2.pdf

http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Multimodal/trucking/Documents%20%20Trucking/RegBook2013.pdf

https://www.wikiwand.com/en/Federal_Bridge_Gross_Weight_Formula

https://moffittservices.com/heavy-haul-services-need-know/

https://ops.fhwa.dot.gov/freight/publications/brdg_frm_wghts/

https://www.fmcsa.dot.gov/safety/company-safety-records

https://www.nbcnews.com/news/us-news/too-heavy-big-rig-collapses-100-year-old-bridge-north-n1032676

https://www.reference.com/home-garden/much-backhoe-weigh-a1b0087fec755340

http://www.accuratetowingservice.com/hiring-heavy-hauling-company/