Popping manhole covers have HECO double-checking fixes
By Walter Wright
Advertiser Staff Writer
Three covers have been blown off Hawaiian Electric Co. manholes on Punchbowl Street in as many weeks, the company said yesterday after the third incident occurred at 10:30 a.m.
In one of the incidents, police said, the cast-iron cover flew an estimated 12 feet into the air, striking branches of a tree in front of the state Circuit Court building.
In the other two cases, the covers appear to have been lifted only slightly out of the ground and pushed only a few inches away, Hawaiian Electric spokeswoman Lynne Unemori said.
Unemori said the company did not anticipate the first explosion May 29 and thought it had dealt with the problem before the second incident June 2 and before yesterday's case.
Unemori said HECO yesterday cut power to the circuit and sent crews in to immediately replace old cable with new in the area.
"Because the circuit is de-energized, there is no danger to anybody," she said. "We are also planning to send people out to double-check manhole covers tomorrow and find out if there are any other unvented covers and, if so, change them out as quickly as possible."
In addition, she said, the company will explore early replacement of cable on the entire circuit.
"We don't want to take any chances," she said.
HECO has experienced similar problems before. In 1996, two blasts on Oct. 4 blew covers off a manhole and a utility vault on Richards Street, almost at the doorstep of HECO's corporate headquarters.
The 150-pound manhole cover in that case narrowly missed a pedestrian, landed 20 feet away in the middle of the intersection of Merchant and Richards streets and snapped in two.
The pedestrian and one HECO employee exposed to fumes and smoke were injured and downtown was without power for several hours.
That was the first of a series of five more mishaps through January 1997, which prompted HECO to rewire the downtown circuit and begin replacing all 2000 of its solid manhole covers with the vented type, initially downtown, in Kaka'ako, and in Waikiki.
Vented covers are designed to allow any gases in the manhole to escape, and help dissipate the force of any explosion that might occur, Unemori said.
But the covers on Punchbowl — where the circuits have not shown signs of trouble — had not been replaced, Unemori said.
She said the solid cover in the May 29 case lifted several feet into the air, and was replaced with a vented model.
Unemori said HECO crews reported all three incidents involved different manhole covers, the first on Punchbowl between Ala Moana and Pohukaina, the second between Pohukaina and Halekauwila, and the third farther mauka toward Halekauwila.
Unemori said the incidents have occurred along a circuit along Ala Moana Boulevard onto Punchbowl that serves the Aloha Tower Marketplace, Restaurant Row and about 90 other customers in the area.
Power was restored to all customers except the Hawai'i Maritime Center after a brief time yesterday, she said.
Technicians have said covers have been lifted from the manholes by pressure when accumulated gases generated by burning insulation have exploded, or from pressure generated by arcing of electricity from short-circuits on a line.
