Study ranks
rock slide areasRoads near Makapuu and
Waimea are the riskiest on OahuTop 10 Oahu sites
In a report ranking potential rock slides near state highways and roads on Oahu, Kalanianaole Highway at Makapuu Point leads a list of top 10 rock fall hazard sites.
The report, based on a study by Earth Tech Inc., was released this morning by the state Department of Transportation.
Kamehameha Highway near Waimea Bay, where a rock slide in 2000 led to closure of the highway for more than two weeks and prompted the study, is ranked second on the list.
The study, commissioned for $290,000, was conducted June 2000 to November 2002 and has since been under review by the DOT.
"Now that the report is complete and approved by the Attorney General's office, we will be proactive in implementing a plan to mitigate the rock fall situation," state DOT Director Rod Haraga said in a news release.
"Once the plan is set, we will work as quickly as possible in constructing catchment devices to deal with the issue."
The state completed a $1.5 million project this week at Makapuu to protect drivers from falling rocks. An Oct. 15 rock slide there accelerated DOT plans to do safety work at the site.
The completed Makapuu project scaled back 870 cubic yards of rock and placed steel netting along the slope to catch any falling rocks. Additional work is planned for Makapuu next year.
The DOT first promised a study of Oahu rock fall dangers after a March 6, 2000, slide onto the Kamehameha Highway at Waimea Bay hit two cars . There was a public outcry about rock slide danger and complaints about traffic inconvenience while DOT closed the highway for more than two weeks.
Haraga said in the news release that the department's preliminary plan includes:
>> Allocating $1 million per year for design work of higher-priority Oahu rock fall mitigation projects.
>> Installing additional warning signs along higher-priority rock fall sites.
>>Asking the Oahu Metropolitan Policy Organization, which coordinates intergovernmental roadway projects, to approve the list and seek federal funding for the projects.
>> Installing lower-cost mitigation measures at smaller rock fall sites not on the top ten list.
Haraga stressed that factors other than rock fall likelihood will be considered as the department plans the order of construction projects for the top rock slide sites. Those include construction costs and funding availability, what type of rock catchment device is needed, and whether a second access or detour road is available for motorists near each construction site, he said.
The state report deals only with 117 potential rock fall sites near state highways and roads on Oahu.
Scoring of the sites was based on several criteria, including rock fall history at each site, slope height, width and proximity of the nearby roadway, structural rock conditions, erosion rate, climate, and the presence of water on the slope.
Though there have not been highway deaths in recent years due to falling rocks, there have been some close calls. And the death of 26-year-old Dara Rei Onishi, who died in her bed when a six-ton boulder crashed into her Nuuanu home Aug. 9, highlighted the danger of falling rocks.
Other recent incidents that have highlighted the instability of Hawaii's hillsides and cliffs include evacuation of a section of Hawaii Kai townhomes after a boulder rolled onto a resident's car Nov. 28. On Feb. 14, a 4-by-3-foot boulder rumbled down a hillside in Waialae Nui and came to rest 20 feet from a house.
State geologist Glenn Bauer has noted in the past that falling rocks and boulders are quite common in Hawaii's geography. "It happens on a fairly regular basis, and we don't see it because it happens where people are not living. It's a natural process."
State Department of Transportation
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Top 10 rockfall
hazard sites on Oahu
The scores were determined by considering rockfall history, slope height, width of nearby roadway, rock condition, erosion rate and climate.
Location Score 1. Kalanianaole Highway at Makapuu 638 2. Kamehameha Highway near Waimea Bay 628 3. Kamehameha Highway near Kahuku 582 4. Pali Highway, Kailua bound, 576 side of roadway past Castle Junction 5. Pali Highway, Kaneohe side of roadway at Castle Juntion 568 6. Kamehameha Highway near Kipapa Gulch Bridge 519 7. Kamehameha Highway near Wahiawa 512 8. Pali Highway just before Kailua Town 497 9. Farrington Highway before Yokohama Bay 494 10. Kamehameha Highway near Wahiawa 493 Source: Earth Tech Inc. study for the State Dept. of Transportation