Hawaii Route 580 is a 6.68-mile State Highway located on the island of Kauai. This corridor follows Kuamoo Road from Hawaii Route 56 (Kuhio Highway) near the Wailua River west to the Keahua Stream Bridge in Lihue-Koloa Forest Reserve.
Kuamoo Road was part of a series of roadways which were used to access the site of the Wailua Reservoir. Modern Kuamoo Road was constructed in 1936, and the corridor would be assigned as Hawaii Route 58 when the Hawaii Route System was extended to Kauai in 1955. Hawaii Route 58 originally terminated at the Wailua Reservoir and ultimately the corridor was renumbered as Hawaii Route 580 to denote it as a secondary highway.
By the 1980s Hawaii Route 580 was extended to a concrete ford at Keahua Stream. This then new terminus was once planned to connect with a never constructed extension of Hawaii Route 583. Hawaii Route 580 has become a popular highway used by hikers out of the Keahua Arboretum. The Keahua Stream ford was replaced by a prefabricated bridge which was installed at the site in 2017.
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Part 1; the history of Hawaii Route 580
Modern Hawaii Route 580 is fully aligned over Kuamoo Road from Hawaii Route 56 near the Wailua River Bridges west to Keahua Stream Bridge in the Lihue-Koloa Forest Reserve. The first segment of Kuamoo Road to be constructed was from Opaekaa Road west to the site of the Wailua Reservoir. In 1919 the Opaekaa Stream Bridge was constructed which facilitated vehicle access to the future reservoir site. The Wailua Reservoir would be completed in 1920 and would be the locale of a Hawaii Agricultural Experiment Station.
The 1919-era Opaekaa Stream Bridge can be seen below as it was in November 2009 in a Craig Philpott photo. Originally traffic would descend eastward from the Wailua Reservoir following much of modern Kauai County Route 581 towards Kapaa via the Puuopae Bridge (constructed in 1915) and Olohena Road.
The Opaekaa Stream Bridge had been fabricated by a company called Motherwell in Scottland circa 1890. It isn't fully clear if the span was used elsewhere prior to being installed at Opaekaa Stream. The structure was added to the National Register of Historical Places in 1983.
Ultimately the Opaekaa Stream Bridge received a retrofit in 2020 which was conducted by KAI Hawaii Incorporated. The original steel truss members were repaired and incorporated into a modernized structure.
Modern Kuamoo Road east of Opaekaa Road to Kuhio Highway (Hawaii Route 56) was constructed in 1936. During said year a bridge was constructed at Opaekaa Stream where it empties into the Wailua River. This Tee Beam span can be seen below from the Wailua River.
The terminus of Hawaii Route 58 at the Wailua Reservoir can be seen on the 1963 United States Geological Survey map of Kapaa. During the late 1960s the corridor of Kuamoo Road would be renumbered as Hawaii Route 580. This renumbering was intended to denote Kuamoo Road as secondary State Highway. The designation of Hawaii Route 58 was recycled along Nawiliwili Road which was originally Hawaii Route 501.
Hawaii Route 580 was eventually extended west of the Wailua Reservoir approximately 1.7 miles to Keahua Stream in the Lihue-Koloa Forest Reserve. The end of State Highway maintenance was located at a concrete ford which was installed in Keahua Stream. This extension was made to connect Hawaii Route 580 with the once planned extension of Hawaii Route 583 to Hawaii Route 56 near Princeville.
Hawaii Route 580 can be seen ending at Keahua Stream on the 1983 United States Geological Survey map of Waialeale.
The terminus of Hawaii Route 580 would ultimately serve several trailheads in Lihue-Koloa Forest Reserve. The ford at Keahua Stream would often prove inadequate as the water level was prone to rise unexpectedly and strand hikers. Ultimately a Acrow Bridge Company sourced 110-foot-long prefabricated span was installed at Keahua Stream in 2017. Following installation of the Acrow bridge the ford in Keahua Stream was washed out via flooding during April 2018.
Hawaii Route 580 appears on the current inventory of roads maintained by the Hawaii Department of Transportation.
Part 2; a drive on Hawaii Route 580
Westbound Hawaii Route 580 begins as Hawaii Route 56 intersects Kuamoo Road north of the Wailua River.
Hawaii Route 580 climbs westward and passes an overlook of Opaekaa Falls.
Across the highway from Opaekaa Falls another overlook can be found which faces south over the Wailua River. The Wailua River is the only such body in Hawaii to have a navigable portion by large ships. Navigable segment of the river can be used to reach Fern Grotto in Wailua River State Park.
Hawaii Route 580 continues west and passes Kauai County Route 581 at Kamalu Road.
Hawaii Route 580 narrows approaching the Wailua Reservoir.
Hawaii Route 580 continues west just below the dam at the Wailua Reservoir. The highway continues to climb and terminates at the Keahua Stream Bridge in Lihue-Koloa Forest Reserve. This area is known as the Keahua Arboretum and has numerous accessible trailheads.
The scar of the Keahua Stream ford is still plainly visible underneath the Acrow sourced bridge.
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