The oldest parts of Navy Pier date back nearly a 100 years, with a significant expansion taking place during World War II. For almost a century, this major U.S. Navy maritime supply hub has literally been through the ringer.
Now that the USS Midway Museum and the Port of San Diego are transforming the pier into Freedom Park at Burnham Navy Pier, significant work has been done to guarantee it endures for countless decades to come.
This work isn’t easy or glamorous, but it needs to be done. To ensure Navy Pier is strong enough to start construction of Freedom Park, an important stabilization project was undertaken to reenforce a section of underwater soil, known as a “mole,” that sits directly beneath the eastern portion of the pier. A process known as jet grouting was employed to fortify the subsurface.
“Our goal was to strengthen this ground location by injecting at high pressure and high velocity a mixture of concrete, water and air to create columns of strength in the soil,” said Len Santiago, Midway’s chief engineer who is overseeing the Freedom Park’s construction for the museum. “This was a very unique project and a first for me.”
As the Navy’s footprint and role in San Diego grew in the years before the Second World War, the service needed to build a larger pier on the east side of the bay to support increased resupply operations for naval warships. A series of wooden pillars were driven into the mole to add structural strength to the soil as the pier was expanded. Those pilings have suffered at the hands of time over the past 80 years.
“The structural engineering report indicated the wooden pillars that supported this particular area under the pier had degraded over time,” said Len. “The bay’s salt water, adverse microbiological conditions, sea termites and other deteriorating factors took their toll on those support columns. In order to sustain the surface structure of Navy Pier for Freedom Park, we needed to take care of the foundation of the pier just like you’d reinforce the foundation of a very old house.”
The four-month jet grouting process for Navy Pier involved drilling 58 macro holes that were 10-feet in diameter into the soil and rock formation under the pier to a depth of approximately 20 feet. An additional 52 smaller holes were also bored into the subsurface. These holes were then injected with the concrete grout mixture creating solid “soilcrete” columns.
As with any significant construction project, unexpected challenges emerged that required patience and timely problem solving to overcome.
“Unfortunately, we had to work with old pier engineering drawings that were not always complete,” said Len. “The pier was built with really good dense American concrete and steel rebar back in the day, and it was so hard we busted several drill bits. As we proceeded, we ended up finding a set of rail road tracks buried in the middle of the pier that we didn’t know were there. On top of that, the environmental requirements of the project didn’t allow us to leak a single drop of concrete grout mixture into the bay. Even faced with those obstacles, we got it done.”
With the jet grouting successfully completed and the subsurface soil beneath the pier stabilized, the door is now open to move on to next and most exciting phase of the project – the actual construction of Freedom Park.
Comments are closed.