Gov. Neil Abercrombie signed an executive order Wednesday granting Hawaii County its portion of Chain of Craters Road.
The county is in the early stages of building an alternate route along the roadway for lower Puna residents impacted by the June 27 lava flow.
Nearly 8 miles of the road is covered by lava rock from past flows, though it presents itself as potentially the only means in and out of lower Puna if the current flow crosses Highway 130 as well as other alternate routes along Railroad Avenue and Government Beach Road.
Lower Puna is home to more than 9,000 residents.
The state’s portion of Chain of Craters Road consisted of 3.68 miles, though it wasn’t immediately clear how much of that is covered by lava rock. The rest is in Hawaii Volcanoes National Park.
County Public Works Director Warren Lee said crews will smooth out a path over the surface rather than digging through to the original roadway.
Most of the flows from Puu Oo’s ongoing 31-year eruption crossed the roadway. For now, that area is considered out of the path of the current flow.
Hawaiian Volcano Observatory is not providing an estimate for when lava could reach Railroad Avenue, which will initially serve as the main alternate route, since the flow remains relatively weak.
If it does return to previous flow rates, Mayor Billy Kenoi in conference calls with reporters said the lava could reach the highway in 15 days and Railroad Avenue in 38 days.
Like the other routes, Chain of Craters Road will be packed aggregate. Officials say the park can only allow one-lane access as part of an emergency route within its boundaries, and Kenoi said he is continuing to pursue a presidential declaration or other means to get two-lane access.
“We’re committed to a two-lane road,” he said.
“It’s not something we want … it’s something we absolutely need to have for our residents of lower Puna.”
About 5.4 miles of the buried road is in the park.
The route is expected to take between 45 and 60 days and between $12 million and $14 million to complete.
Kenoi said the county is covering the cost upfront to avoid delays, though it could seek reimbursement from the state or federal sources later.
He said work will be expedited if needed to get it done before lava reaches Railroad Avenue.
A bulldozer began preparing a path on the Kalapana side of the road Sept. 23.
It had progressed about a quarter mile, Lee said, and three more bulldozers will join it today.
HVO spokeswoman Janet Babb said in an email the lava rock is up to 147 feet thick above the original roadway and on average 49 feet thick.
There also are 10 major lava tubes under the route, which could present a challenge to road crews using heavy machinery. The tubes could be up to 16 feet wide.
Lee said road crews have experience working with the presence of shallow lava tubes and know how to deal with the issue.
The drive to Hilo from Pahoa on that route would be approximately 64 miles. It is currently about 17 miles.
Lee said Railroad Avenue is “substantially complete” and ready for use should the flow reach the highway.
The approximately 7-mile route runs parallel to the highway about 4 miles makai and mostly along a former railroad grade between Nanawale Estates and Hawaiian Paradise Park.
Lee said there will be a 20 mph speed limit for the two-lane, 60-foot-wide packed aggregate surface between subdivisions. Drive times from Nanawale Estates to HPP could be between 20 and 30 minutes in nonpeak hours and an hour or more during rush hour.
It won’t be opened unless lava reaches the highway.
Between 7,000 and 11,800 vehicles use the highway near Pahoa each day. Lee said maintenance crews will be on hand to patch up the road as needed.
Government Beach Road further makai would be available also as a one-lane gravel road with turnouts.
Together, both roads are estimated to cost $3 million.
That’s roughly double earlier estimates. Lee said the presence of “blue rock,” which is the hardest found on the island, increased construction costs.
Email Tom Callis at tcallis@hawaiitribune-herald.com.