CRAIG T. KOJIMA / CKOJIMA@STARBULLETIN.COM
It could take more than a week to find out what caused the sewage leak at Sand Island last week. Shown here yesterday is the exploratory shaft that city workers made to find out where the sewer pipe was broken. From this location, the workers found where they needed to dig to repair the line.
City trying to figure out
why sewage pipe burst
It could be a week or more before city workers can determine what caused a 66-inch sewage pipe to rupture last week and pour almost 2 million gallons of raw sewage into the ocean before sewage was diverted away from the pipe.
Workers will continue work today that will allow them access to the underground pipe on Sand Island.
"Everything we're doing is below the water table," said Frank Doyle, director of the city's Department of Environmental Services.
Workers were to reduce the amount of soil and ground water surrounding the pipe, then drill 40 to 50 feet and inject cement into the soil.
The soil will harden in five to seven days, allowing workers to reach the pipe and determine what caused it to rupture. Possible causes include corrosion, stress failure, structural damage due to settlement of the pipe or a combination of factors.
It is unknown at this time how long it will take to repair the pipe, Doyle said.
The largest sewage spill on Oahu was in November 1996 at Sand Island when 9 million gallons of raw sewage spilled into the ocean after a weir broke during heavy rain, said Ross Tanimoto, head of the department's Monitoring and Compliance Branch.
Water samples taken off Sand Island yesterday indicated the ocean water had returned to normal, he said.
Severe storms pushed rainfall totals on Oahu well above average last month, according to National Weather Service data, causing several sewage spills and large amounts of runoff.
Signs warning the public of possible water contamination remain posted at Puha Stream, Kawa Stream, Kaneohe Bay, Kaelepulu Stream, Kailua Bay, Keehi Lagoon, Sand Island State Recreation Area, Kakaako Waterfront Park and Point Panic at Kewalo Basin.
Signs were removed yesterday from Waimanalo and Bellows beaches, Blaisdell Park in Waimalu and Kalihi Stream.
