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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - Summer 1993

H3: The Island Interstate

by Craig Sanders

To those on the mainland United States, visions of Hawaii usually bring thoughts of relaxing on a white, sandy beach during the long, warm, tropical days, sipping on a fruity drink while an exhilarating equatorial breeze gently whisks away the stress and worries common to everyday life.

While these peaceful images of Hawaii may hold true for the two-week tourist, we who live in and around the city of Honolulu on the island of Oahu, which houses 80 percent of Hawaii's residents, must deal with the big city problems of population and traffic congestion. In the last 20 years, the population has increased 44 percent while the number of motor vehicles on the highway has risen 111 percent. Interstate route H-3 is part of the Hawaii Department of Transportation's (HDOT) integrated long range transportation plan to accommodate the island's growing population.

How can any highway on an island be designated as an interstate? In 1959, after Hawaii became a state, Congress felt both Alaska and Hawaii needed to be included in the interstate highway system, granting the new state of Hawaii 50 miles of this high-speed, limited access freeway for the highly populated island of Oahu. So, by nature of its designation and funding, we have an interstate system in Hawaii separated from the next nearest state by a 2000-mile stretch of the Pacific Ocean.

The 52-mile-long interstate system was planned to solve Oahu's projected traffic demands and connect the island's major military centers. This network consists of three freeways: H-1, H-2 and H-3.

H-1, 27 miles long and now complete, connects the Hawaii National Guard at Fort Ruger to the Barbers Point Naval Air Station and runs through the middle of Honolulu. H-2, also complete and only eight miles long, joins Pearl Harbor Naval Base and Hickam Air Force Base to Wheeler Air Force Base. H-2 also serves as a partial connection from H-1 to the North Shore of the island. The 15-mile-long H-3 will connect the Kaneohe Marine Corps Air Station to the Pearl Harbor defense bases, passing through the Koolau Mountains to join the windward towns of Kailua and Kaneohe to the leeward cities of Pearl City and Honolulu.


Construction on the Kaneohe interchange which is one of 20 contracts for the H-3 project. The shear windward side of the Koolau Mountains is in the background.


H-3 will provide much needed relief to the other two trans-Koolau routes -- the Likelike and Pali highways -- which have long been operating at capacity during the morning and evening rush hours. When H-3 is opened, it is predicted that one-third of the present traffic crossing the mountains will use H-3, one-third will use the Likelike Highway, and one-third the Pali Highway.

H-3 is the biggest construction and the largest public works project ever undertaken by the state of Hawaii. This immense goal, consisting of 20 separate contracts, includes both leeward and windward viaducts joined by a 5,000-foot trans-Koolau tunnel, bridges, interchanges, access roads, and more. The planning and construction of H-3 has been costly, lengthy, and anything but easy. At times it seemed that there was no end to the environmental, archaeological, legal, and engineering challenges. However, it has been an invaluable learning experience for HDOT.

Although the planning for H-3 began much earlier, the passage of the National Environmental Policy Act of 1970 required the state to file its first Environmental Impact Statement (EIS). The law demands the study, documentation, and possible mitigation measures of significant impacts on the environment caused by any projects using federal funds. At the time, the concept of putting environmental concerns ahead of engineering issues was rarely considered on most projects.

HDOT conducted specialized studies for different areas of concern, including archaeology, plants and animals, and air and noise quality. To validate these studies, experts in each of the involved fields -- botany; zoology; archaeology; Hawaiian culture; and water, air, and noise quality -- were hired.

When all the environmental questions had been answered and the studies completed, the results were compiled into a huge, several-volume EIS document. These findings were discussed with the public, evaluated by the state and federal governments, and finally incorporated into the planning and design of the H-3 project. Although much time and money was spent on the preparation of the EIS, HDOT had its first experience with the new law and had planned and designed a project with the environment as a prime consideration.

An often overlooked benefit of the H-3 project is the wealth of archaeological knowledge uncovered. The proposed H-3 corridors routed the freeway through undeveloped lands on the island. Recognizing the possibility of unearthing artifacts of the ancient Hawaiians, HDOT hired archaeological experts from the Bishop Museum in Hawaii to find, survey, and study archaeological sites. After the important areas were identified, H-3's alignment was designed to avoid any adverse impacts. A section of the Moanalua Valley, once considered a possible corridor for H-3, was even placed on the National Register of Historic Places. A Bishop Museum archaeologist declared that the H-3 process saved these priceless sites from private development. The examination of the sites is ongoing, and much more is expected to be learned about the early Hawaiians.


The Coast Guard Omega Station located on the windward side of the Koolaus near the mouth of the Trans-Koolau Tunnels. This station causes large, insulated objects nearby to become charges, posing the threat of shocks to workers and users of H-3. Several countermeasures have been taken to eliminate this problem.


The Coast Guard Omega Station (OMSTA) presented a unique challenge. The station, located on the windward side near the mouth of the Trans-Koolau Tunnels, is part of an eight-station, worldwide network which allows any aircraft or ship to determine its location to within a mile. OMSTA causes large insulated objects near the station to become energized, providing a small shock to anyone coming in contact with these items. HDOT was concerned that "surprise shocks" to workers on H-3 might result in a fall or other accident. In some cases, workers in sensitive areas were required to wear gloves or rubber boots. To prevent any effect on H-3 travelers, a device known as a Faraday Shield was installed over a short section of the highway near the mouth of the tunnels to reduce the electric field. The shield consists of six three-eighth-inch-diameter wires on each side of the road spaced one vertical meter apart and eight three-eighth-inch-diameter wires overhead. A wire mesh is incorporated into the pavement below to complete the shield.

Hoomaluhia Park on the windward (east) side of the Koolau Mountains was developed in conjunction with the H-3 alignment. The Department of Parks and HDOT worked together to produce a park which would be partially bordered by H-3. However, a legal challenge stemming from this shared border delayed the construction of the freeway for more than two years.

A small group of opponents to the highway saw the shared border as an opportunity to use the park and Section 4f of the U.S. Department of Transportation Act to stop the construction of H-3. Section 4f protects some public lands and historic sites. On August 21, 1984, the Ninth Circuit Court of Appeals determined that there had been "constructive" taking of park land, effectively stopping all construction activity on H-3. Although no park land was actually taken, the more abstract "constructive" possesion of the park land was defined as the overall reduction in the environmental quality of the park as a result of the 1.7-mile border with H-3. State attorneys appealed this ruling but were unsuccessful in overturning the injunction.

Finally, it was decided to pursue an exemption to Section 4f by presenting the case to the U.S. Congress. After a constant bombardment of phone calls, letters, petitions, and meetings with subcommittee members in support of H-3, Congress approved and President Reagan signed an exemption into law in October 1986. Then, after more than two years of delay, the U.S. District Court dismissed all injunctions against the construction of H-3.

With the lifting of the injunction, construction began on the five-mile, $8.5-million North Halawa Valley access road. Many obstacles had to be overcome to build this road. For example, everyday, surveyors had to be airlifted deep into the beautiful but rugged North Halawa Valley to set the road alignment, gather topographical information, and build a landing pad for their return ride in the evening.

At the completion of the access road in 1989, work began to relocate Hawaii's unique animal quarantine station and to construct a short "cut and cover" tunnel, viaducts, and the trans-Koolau tunnels. Unfortunately, the best alignment of H-3 routed it through the middle of the state's animal quarantine station. This was the only facility capable of holding animals in accordance with the state law requiring a 120-day quarantine of all potential carriers of rabies imported into Hawaii. The station was relocated using federal funds allowed for "functional replacement," meaning that the relocated facilities could be designed and built to current codes but could only perform the same functions as the existing facilities. The new AQS was completed in 1991 for $20 million.


The Hospital Rock "cut and cover" tunnels.


Hospital Rock Tunnel is a 690-foot "cut and cover" with separate inbound and outbound tunnels. A cut and cover tunnel is cut completely away to daylight, the tunnel constructed, and the cover backfilled around the concrete tunnel section. These tunnels cost nearly $18 million.

The real showcases of H-3 are the North Halawa and Windward Viaducts and the connecting mile-long Trans-Koolau Tunnel.


The twin Windward Viaducts looking away from the tunnels.
The portal buildings on the windward side.
The outbound, windward side portal structure.


H-3 passes through the majestic Koolau Mountains via the mile-long Trans-Koolau twin tunnels. The construction of the tunnels involves six different contracts, including ones for an exploratory tunnel, ventilation, control and support systems, finishing, and tunneling. All contracts are expected to be completed by December 1994.

When the North Halawa Valley was opened up by the newly built access road in January 1989, the boring of an 14-foot-wide exploratory tunnel began through the Koolau Mountains. An exploratory tunnel is used by engineers to provide geological information and assist in the design of the main tunnel. Although this exploratory tunnel, finished in March 1990, cost $12 million, it has been proven that an exploratory tunnel saves money in the long run by reducing the expense of the main tunnel.

The actual tunneling work for the main tunnels was split between two contracts -- one beginning on the leeward or North Halawa side and one starting from the windward or Haiku side. A joint venture of contractors, called H-3 Tunnelers, began tunneling from the Halawa side in January 1991 for a contract price of $89 million. Another joint venture, named Trans-Koolau, began tunneling from the Haiku side in October 1990 for a price tag of $108 million. The tunnelers used the "drill and blast" method of tunnel excavation, following with shotcreting and rock bolting for temporary support. A soft ground type called sapprolite was encountered for the first 300 feet into the Halawa side of the tunnels. The rest of the tunneling was done in good rock. Although the H-3 tunnels are above the groundwater table, rain water filters through the porous rock and poses the problem of nuisance drips. To alleviate this problem, a waterproof membrane seals the shotcrete to a 14-inch-thick concrete lining, which is being constructed using a 50-foot-long moving form.


Construction of the North Halawa Valley Viaducts piers and stream bank protection.


The tunnel section is horseshoe shaped with an invert width of 48 feet for two lanes of traffic and an excavated height of 38 feet. The profile has a maximum grade of 6 percent; the Haiku and a Halawa portal elevations are 840 and 1,305 feet above sea level, respectively. The rock cover above the tunnel ranges from 600 to 1,385 feet. The top of the Koolau Range reaches an elevation of 3,760 feet. Included in the design of the tunnel are 10 horseshoe-shaped cross-passages, which are excavated 10 feet wide by 24 feet high and are from 115 to 226 feet in length.

There are two portal structures on each side of the mountain -- one for the inbound and one for the outbound lanes. These are four-level concrete buildings designed to house the ventilation and control systems, including electrical switchgear for power, transformers, communications equipment, lighting, air supply and exhaust fans, water supply for fire protection, service and emergency vehicles, and more.


(Top) A view of the steel cantilevered truss used to construct the North Halawa Valley Viaducts.

(Bottom) An up-close look at pier 17 outbound and the truss.


The control building, separate from the portal structures, is located at the Halawa mouth of the tunnels. It is the "brain" of the H-3 tunnel operations, housing the computer equipment, variable message sign controls, emergency generator, closed circuit television equipment, fire and intrusion alarms, carbon monoxide monitoring system, and AM/FM rebroadcast system.

The ventilation for the tunnels is accomplished by a false, flat concrete ceiling which runs for the entire length of the tunnels. The area between the arch of the tunnel and the false ceiling is separated into two sections by a concrete divider, with one compartment used for inhaling exhaust air and one compartment used for distributing fresh air. Large fans either draw or blow air the into the separated compartments.

The Windward Viaducts are spectacular, one-mile-long twin structures connecting the Haiku side of the Trans-Koolau Tunnels to the cut and cover Hospital Rock Tunnel. Through a contractor-submitted Value Engineering Contract Proposal (VECP), the design of these structures was changed from segmentally constructed, cast-in-place to segmentally constructed, precast, prestressed boxgirder viaducts. This request also included a change from precast driven to drilled shaft piles. After those critical design issues were resolved, the VECP was accepted by the state. This resulted in a savings of $2.2 million split equally by the state and the contractor for this $136-million contract.

The viaducts have 23 sets of piers, each supported by six three-foot-diameter drilled shaft piles 40 to 140 feet long. The piers vary from 12 to 160 feet in height and have a double box cross section with walls 18 inches thick. These massive piers measure 22 feet long by 14 feet wide and are topped by pier tables. The superstructures are made up of the precast, single box girder sections with 24 to 30 segments per span. The segment depths vary from eight feet at mid-span to 16 feet at the piers giving the superstructures an arched span appearance.

The construction of the superstructure for each viaduct involved the use of a specially designed, twin, self-launching, steel erection truss system. This system physically picks up the precast girder segment and helps set it into place in the viaduct, allowing the then in-place section to be prestressed with steel tendons. This 384-foot-long truss enabled the construction of the inbound and outbound structures simultaneously.

A precasting yard was constructed near the job site to produce the precast segments. The yard produced an average of four segments per day, manufacturing a total of 1,338 for the viaducts.

Although the construction of the twin structures is now substantially complete, delamination problems with the three-inch deck overlay are expected to delay its finishing until the end of 1993.

The twin, mile-long North Halawa Valley inbound and outbound viaducts on the Halawa side of the tunnels will also be impressive structures. Although there was the option to build precast superstructures like the Windward Viaducts, the contractor for these viaducts chose to build cast-in-place, prestressed, segmental superstructures as originally designed for a bid price of $141 million.

The superstructures are supported by 17 outbound and 19 inbound double celled box piers, whose heights range from 27 to 105 feet. The piers' cross section measures 23 feet long by 10 feet wide with 18-inch-thick walls and is supported underneath by five to nine five-foot-diameter drilled shaft piles, 35 to 65 feet in length. The cast-in-place superstructure segments range in height from 18 feet at the pier to eight feet at the midspan with a wall thickness of eight to 27 inches and a bottom width of 23 feet. The concrete overlayed decks vary from 41 to 53 feet in width.

Three specially designed, steel cantilevered trusses are being used to construct the superstructures. One truss began construction at one end of the viaducts, and the other two started from the opposite end. The contractor has been averaging a segment turnaround time of 14 hours.

Unusually large boulders encountered during the boring for the drilled shaft piles have added another $6 million to the cost of the project. Although the contract specified two- to three-foot boulders were likely to be encountered during the drilling, the contractor had to deal with boulders the size of automobiles.

The North Halawa Valley Viaducts are expected to be completed by December 1994.

H-3 required a great deal of time, money, and political support, but the highland highway is almost a reality. The freeway, envisioned more then 30 years ago, will soon be in service to ease the trans-Koolau traffic crunch. Total cost of this extraordinary project, which should be completed by 1996, is expected to come close to $1 billion dollars. Hawaii may never again have the opportunity to "experience" a project of this magnitude and complexity.


1. Parsons Brinkerhoff--Hirota Associates. "Interstate Route H-3 Trans-Koolau Tunnels Facilities Study Report," October 1984.

2. "H-3/Haiku Omega Collection Studies," Hawaii Department of Transportation, April 1984.

3. "Final -- Section 4(f) Statement for the H-3 Windward Highway and Ho'omaluhia Park," Federal Highway Administration and Hawaii Department of Transportation.

4. Parsons Brinkerhoff -- Hirota Associates. "H-3 Tunnel Facts," January 1993.

5. "The H-3 Interstate Highway Video," Hawaii Department of Transportation.

6. "Executive Summary -- H-3 Briefing Halawa Interchange to Halekou Interchange," Hawaii Department of Transportation.

7. Richard M. Sato & Associates, Inc. "Basis for Design -- Animal Quarantine Station Functional Replacement," August 1984.

8. Plans and Specifications for I-H3 contracts: I-H3-1(71), I-H3-1(61,64), I-H3-1(57,58), I-H3-1(53).

9. "Why We Need H-3," Carrier, newsletter of the Hawaii Department of Transportation, Vol. 20, Issue 5, November 1984.

10. "Staff Analysis -- Interstate H-3 and existing Trans-Koolau Highway Alternatives," Federal Highway Administration, Region 9, San Francisco, California, October 1979.

11. J.D. Stokes. "Hawaii's Interstate H-3 Windward Viaduct," April 19, 1992.

Craig Sanders is on the FHWA's Highway Engineer Training Program (HETP), currently assigned to the small and busy Hawaii division office. The Hawaii division office is responsible for the islands of O'ahu, Kaua'i, Maui,