Red Hill: UH Lends its Expertise to an Engineering Marvel

While the sheer volume of its fuel capacity is impressive, it was the project’s engineering and design, considered radical and innovative at that time, which ultimately qualified the Red Hill Underground Fuel Storage Facility to be named as a National Historic Civil Engineering Landmark in 1995.

Shrouded in secrecy until the late 1990s, the U.S. Navy’s Red Hill Underground Fuel Storage Facility on the island of O‘ahu, Hawai‘i, could arguably be considered as one of the most innovative and unique engineering projects in the world. Located under a mountain ridge about three miles from Joint Base Pearl Harbor-Hickam, the massive facility utilized novel design and construction techniques for the 1940s era—that still remain significant in today’s modern engineering.  


In response to the growing threat of war with Japan in the late 1930s, the Roosevelt administration authorized the construction of a top secret underground fuel storage facility in realization that above ground fuel storage tanks made easy targets for enemy air attack. Up to that point, underground fuel storage for naval bases involved the utilization of several, relatively small 20,000 gallon tanks buried in shallow trenches. By comparison, the final plans of the Red Hill Underground Fuel Storage Facility, which broke ground on December 26, 1940, called for the construction of two rows of 10 tanks, 250 feet high and 100 feet in diameter, each approximately 110 to 174 feet below the surface to protect them from bombardment. With a storage capacity of approximately 12.5 million gallons in each tank, the total fuel storage capacity of the Red Hill facility is 250 million gallons, a staggering volume that remains unmatched even by today’s standards.

Outside of the Box Engineering

While the sheer volume of its fuel capacity is impressive, it was the project’s engineering and design, considered radical and innovative at that time, which ultimately qualified the Red Hill Underground Fuel Storage Facility to being named as a National Historic Civil Engineering Landmark in 1995.  Here are some of those key features:

Vertical Tanks

By building vertical tanks in lieu of horizontally oriented ones, construction and excavation could occur simultaneously—made possible by a vertical shaft drilled through the centerline of the tank allowing excavated rock to be funneled down onto a series of conveyor belts in the lower access tunnel to be taken away for use as aggregate. This process eliminated the need for heavy equipment and a larger workforce to haul the material away, greatly reducing the cost of the project and shortening its timeline for completion. The project broke ground in December 1940 with the first tank completed in September 1942. The remaining 19 tanks were finished a year later, nine months ahead of schedule and coming in at a cost of $43 million dollars.

Gravity-Fed Pipelines

Since Red Hill is located at a higher elevation in relation to Joint Base Pearl Harbor-Hickam, three gravity-fed pipelines are used to carry bunker and jet fuel for ships and aircraft based there or for further distribution to U.S. Air Force, U.S. Marine Corps, U.S. Army and U.S. Coast Guard bases on the island.  Powered pumps are used only to transfer fuel between tanks for routine maintenance or in case of an emergency.

“Mined” Into the Mountain

To compensate for the greater hydrostatic pressure found inside of a filled vertical tank than that of a horizontal tank, engineers lined the tank with ¼ inch thick steel plates and filling the gaps between the steel and rock with concrete. Since it was anticipated that the concrete would pull away from the rock as it cured, high-pressure grout was pumped into the gaps to prestress the lining to prevent cracks and permanently bind the sides of tank to the surrounding rock wall—fortifying them to withstand the pressure from within the tank and at the same time, making them almost impenetrable to attack from above.

Ship in a Bottle

As with any aging structure or facility, constant and vigilant maintenance efforts are needed to keep the operation in top shape. However, the Red Hill facility’s unique engineering design poses significant challenges to its upkeep. Since the back of the tanks are literally imbedded into the rock, visual scans for corrosion on the steel walls are impossible. As a result, specialty contractors on suspended scaffolding inside the tank—similar to those used by window washers, must painstakingly and methodically search for corrosion using hand-held ultrasonic scanners that would detect any thinning of the steel. Repairs are done by welding new ¼ inch patch plates over the affected areas on the inside of the tank and to ensure its integrity, undergo stringent testing. 

Unfortunately, a spill of 27,000 gallons of jet fuel occurred in January 2014 from a tank that was just put back on line after repairs were completed the previous month—catching the attention of public interest groups and regulators, as well as stirring public emotion—because the Red Hill facility is built over a vast aquifer that supplies a good portion of drinking water to greater Honolulu and to a section of Joint Base Pearl

Fortunately, the release was contained and did not permeate into the aquifer. The following year, officials from the U.S. Navy, U.S. Environmental Protection Agency and the Hawai‘i State Department of Health signed an administrative order of consent (AOC) to address the cleanup of the leak. It also required the Navy to research and evaluate methods of upgrades to the Red Hill tanks to decrease the threat of future leaks and to upgrade the tanks with the “best available technology” by 2045 or have the fuel removed and the facility shut down.

One suggestion has been repeatedly brought up is to retrofit the existing tanks with secondary containment or a double wall. While this would seem relatively simple, existing retrofitting technologies of double-wall/secondary containment were designed for shorter, above-ground tanks with significantly lower pressure, making them unsuitable for use at the Red Hill facility. Also, most tanks are not locked into a mountain, with access further restricted by a narrow walkway—making it virtually impossible to move large structures in for repairs.

“To some degree, figuring out double-wall equivalency or secondary containment here is akin to building a ship in a bottle,” said Captain Marc R. Delao, commanding officer of Naval Facilities Engineering Command Hawai‘i. “There are certainly some engineering challenges, but we have some incredibly gifted scientists and engineers working on this from the Navy, industry and now—researchers from the University of Hawai‘i (UH), to help ensure that the facility remains absolutely safe today and well into the future.”

Engaging UH Research—Letting the Science and Facts Speak for Themselves

Already familiar with the University of Hawai‘i’s expertise in science and engineering through a number of collaborative projects over the years, the Navy turned to UH to independently assess the current condition of the tanks and to help develop technologies to improve on what it refers to as TIRM (testing, inspection, repair and maintain). Led by UH Vice President of Research and Innovation Vassilis L. Syrmos, a team of UH researchers and officials traveled to the Naval Facilities Engineering and Expeditionary Warfare Center at Port Hueneme, California last December to present a comprehensive proposal that involves the College of Engineering and School of Ocean and Earth Sciences and Technology at University of Hawai‘i at Mānoa (UH Mānoa), Applied Research Laboratory at UH (ARL at UH) and funding by the Office of Naval Research. The proposal has been funded and work will commence this summer.

“In the current situation, a more careful long-term, scientific-based strategy is needed to achieve a balance between preserving both national security and O‘ahu’s water infrastructure,” said Syrmos. “By forming a strategic partnership with UH, the Navy has expressed their willingness and confidence in our researchers to deliver unbiased assessments, while providing the necessary expertise to explore current and future technologies in the areas of corrosion prevention, surface coatings, groundwater monitoring and double-wall containment.”

To begin the multi-phase project, corrosion research experts from the UH Mānoa College of Engineering will assess the current situation of the tanks using data collected by the Navy and by performing additional independent analysis. In addition to researching methods to measure the minimum thickness of the existing steel more accurately, they must also devise a protocol for measuring the in situ corrosion rate of the tank wall to help determine safe time intervals for repair and maintenance.

In subsequent stages of the project, the researchers plan to machine-in known defects (mimicking corrosion) into steel lab sample plates to analyze and verify the limits of detection of non-destructive testing (NDT) methods, then backfill the defects with specific types of corrosion products to determine if the same defects could be identified or if the signals were affected by the corrosion products—to improve the interpretation of NDT data to identify corrosion defects and estimate remaining plate thickness more accurately. They also plan to investigate tank-wall repair protocols, and investigate the feasibility of heat-resistant coatings that can withstand welding on a repair plate to enhance resistance to corrosion and crevice corrosion.

“Storage tanks are similar to airplanes, in that both are both are subjected to internal pressure and external elements,” said UH Mānoa College of Engineering Dean Brennon Morioka. “However, unlike aircraft, access to the entire structure of the Red Hill tanks is not possible, making the reliance on accurate scans of steel—taking into account any effects to the readings by any corrosion products—of extreme importance.”

Other researchers from the UH Mānoa College of Engineering will also be conducting research on NDT using drones and magnetic robot crawlers for both empty and fuel-submerged tanks; inspection of concrete degradation; and novel leak detection by analyzing products of microbial degradation; while the School of Ocean and Earth Sciences and Technology will further examine geologic conditions and conduct soil vapor monitoring; while ARL at UH will be concentrating their efforts on real-time sensor development and display, data analysis and information assurance work. 

“We will be developing various sensor packages to increase the Navy’s ability to sense the environment in and around the tanks,” said ARL at UH Director Margo Edwards.  “Our team will also be looking at ways to incorporate machine learning to securely distill data into a user-friendly dashboard for the decision-makers, while at the same time—working to deliver a communications system to help create more transparency for the general public about the facility.”

“As scientists, we want the science and facts to speak for themselves,” said Morioka, who also traveled to Point Hueneme to present his college’s capabilities. “Because there is so much emotion surrounding the future of the Red Hill facility, the role of UH as an independent arbiter will hopefully go a long way in ultimately validating the results to bring greater objectivity among all parties involved.” Morioka added, “Many of our faculty involved in this partnership are long-time residents of the potentially affected communities and also share a vested interest in preserving the safety of the aquifer.”