Road to Hana Historic Bridges

By 1900, the cultivation, irrigation and transportation of raw sugar cane stimulated the construction of roadway and bridges along the Hāna Belt Road (aka Road to Hāna).   In 1926, the completion of the road aided the economic development of east Maui and provided overland access for residents and plantation workers.

The early pioneering bridges along the Road to Hāna’s historic district were constructed of stone, which was plentiful; however stone bridges required skilled labor, which was scarce.  Wood bridges were also constructed; however, they were continually damaged by floods and termites.   As early as 1884, the Kingdom of Hawai’i imported steel truss bridges from America to permanently replace the wooden structures.  Unfortunately, the steel truss bridges were vulnerable to the harsh corrosive marine environment and maintenance proved too costly.

Between 1908 and 1947 several different materials were used for the 74 historic “spans” along the Road to Hāna.   In the earliest bridges, native basalt lava rock was either dry-laid, cut-into blocks, or mortared using Concrete Rubble Masonry (CRM).  As early 20th century building material, technology and architectural design progressed, the use of reinforced, cast-in-place concrete was utilized.

The following is some basic bridge terminology to help you better understand and therefore enjoy the historical bridges on the Road to Hāna.

In a “Deck” bridge configuration, traffic travels on top of the main bridge structure.

“Arch Deck Bridges” are designed in a way that the traffic deck rests upon the supporting arch(s) and the area between the arch(s) and deck is called the “spandrel”.  Spandrel design can be one of two types; solid spandrel (barrel arch) or open spandrel (rib arch) construction.

The “parapets” are the walls above the road deck and contain the date of bridge construction and in some cases, bridge names.  Parapet design can also be of solid or open (baluster) construction.

An “abutment” is a structure where the bridge slab adjoins the roadway and transmits the load to the bridge’s foundations, including the floor of a valley or riverbed.  Retaining walls are often used as abutments and “wing walls” are retaining walls that extend laterally to stabilize the banks of the stream.

A “span” is a distance between bridge supports. “T-beams” or “girders” are used for short, flat concrete slab spans.

Most bridges along the road are one lane and the spans range from 12’6” – 20’6” wide.  They come in 4 basic styles, Masonry Arch, Reinforced Concrete Arch, Reinforced Concrete Deck (including flat slab, T-beam and girder spans), and Culverts.

Masonry Arch Bridges

Masonry Arch 1910 Hāhālawe Bridge MM 43 (After Hāna)

The first type of bridge, Masonry Arch Bridges, are some of the oldest along the road and are constructed from dry-laid rock or cut-block masonry.   Two rare surviving examples can be found past Hāna at MM 43.5 (Wai’ele Bridge) and MM 43 (Hāhālawe Bridge).  The arches and abutments are superbly crafted from the local basalt (lava) rock and may have even been constructed earlier than the solid concrete parapets and 1910 inscription date.

Concrete Arch Bridges

Concrete Arch Solid Spandrel Open Parapet 1916 Ohe’o Bridge located inside Haleakalā National Park MM 42.1 (After Hāna)

The second type of bridge, Reinforced Concrete Arch Bridges, appears in 2 varieties, “solid spandrel” (barrel arch) and “open spandrel” (rib arch).  Two examples of solid spandrel concrete arch bridges, can be seen before Hāna, the 1926 Hanawī Bridge at MM 24 and the 1926 Kūhiwa Bridge at MM 25.2.  A third example, the famous 1916 ‘Ohe’o Bridge at MM42.1 can be seen after Hāna in Haleakalā National Park.

Concrete Arch Open Spandrel Open Parapet 1926 Waikani Bridge spanning Waikani Falls (a.k.a. 3 Bears) MM 19.4 (Before Hana)

 

The second variety, the open spandrel, provided lighter, yet larger more eye pleasing structures such as the 2 most famous bridges along the Road to Hāna, the 1926 Waikani Bridge at MM 19.4 (before Hāna) and the last bridge in the historic district, the 1911 Koukou’ai (Kaukau’ai) Bridge at MM 40.6 (after Hāna) just south of Haleakalā National Park.  Construction of these five Concrete Arch Bridges demonstrated that Maui could keep pace with the rest of the world in modern architectural bridge designs of the times.

Concrete Deck Bridges

Concrete Flat Slab T-Beam Open Diamond Parapet 1910 Pu’uhaoa Bridge MM 43.8 (After Hāna)

The third type of bridge is the Reinforced Concrete Deck (including flat slab, T-beam and girder spans).  Constructed from concrete casted on-site, they are the most common bridges along the road and were both economical and strong over short spans.   The 1912 Waikamoi Bridge at MM 9.9 before Hāna is one of the earliest examples of a 2-span reinforced concrete flat slab girder bridge and the 1910 Pu’uhaoa Bridge at MM 43.8 after Hana is one of the earliest examples of a 1-span reinforced concrete flat slab T-beam bridge.

Culverts

The fourth type of bridge is a Culvert.  East Maui’s rainforests and watersheds are the island’s major water producers.  Massive drainage and flash flooding jeopardize road and bridge stability so culverts are used to channel water from streams under the roadway. Culverts have a floor and are circular, rectangular, elliptical, or even square in size.  If the length of the culvert’s span is greater than 20 feet, it is officially categorized as a bridge.

Bridge Replacement

East Maui residents are concerned that as the historical bridges deteriorate, wider and more modern bridges that meet federal, state and county building codes will be used to replace them.

Pony Truss Steel Bridge Replacement Pa’ihi Bridge MM 44 (After Hana)

To preserve the area’s rural character, officials revised bridge policies to favor preservation of the one-lane bridges or replace them with structures of similar design; however, in 2009, the 1911 reinforced concrete T-beam Pa’ihi Bridge damaged by the 2006 earthquake was replaced by an inappropriate Bailey truss steel bridge constructed by the Army Corps of Engineers that does not complement the road’s historic character.