What lies beneath? As Kakaako develops up, questions raised about infrastructure below


From a pair of sinkholes at a beach park to emergency work on major roadways, several incidents have raised questions about the stability of the roads around Kakaako.

So what’s going on beneath the surface, and what needs to be done to prevent future issues?

The recent road problems have been caught by state and county agencies in the nick of time, requiring some serious short- and long-term fixes. We asked what’s going on underground, and what’s being done to watch out for and fix other at-risk areas of this fast-growing part of town.

Driving through Kakaako lately has meant navigating a maze of emergency road work after underground near-collapses and even sink holes have popped up in the area.

“We have so many streets,” explained Panos Prevedouros, a University of Hawaii civil and environmental engineering professor, “so many likelihoods of a potential sinkhole.”

That’s because Kakaako was once a low-lying marsh, perfect for fishponds, salt, rice, and taro, but trickier for roadways and urban development we see now.

UH experts Always Investigating spoke with say the buckling roads are giving us signs of three things to watch out for:

  1. Age of infrastructure like underground drainage culverts;
  2. Rising sea levels and groundwater; and
  3. Soil problems common to coastal areas.

“We have clay and sand, things that are easy to dissolve,” said Prevedouros, “and then because we have intrusion of sea water, or perhaps pipes, storm drains, and even sewers breaking, all that has the effect of diluting the soil and creating all kinds of cavities which pose a major threat to public safety.”

But why now?

“We have developed a lot and of course the more population you have, the more concentrated the drainage channels, the more overloaded they get,” Prevedouros said, “and of course they get older, and as they get older, they crack. They fail, and then you have all kinds of problems with underwater flows that are out of our control.”

A routine state bridge inspection caught signs of a compromised culvert beneath Ala Moana Boulevard in February. The state Department of Transportation lightened allowed loads on that stretch until jacks could shore it up, followed by this fall’s permanent fix.

“The Ala Moana Boulevard drainage culvert project is replacing the top slab of the existing concrete segment that has deteriorated since it was constructed more than 45 years ago,” explained state DOT spokesman Tim Sakahara.

A city storm drain inspection near Pensacola Street found deteriorated culvert concrete top slabs and six feet of salt water and sediment in the 8-by-8-foot boxes.

“They were a little bit shocked at how significant it was,” said Robert Kroning, director of the Honolulu Department of Design and Construction. “It was a lot more than we had anticipated. The top slab had shown significant spalling, which basically means the concrete was flaking away from the reinforcing bar that is within the concrete.”

The city gave us video showing scuba divers deep in the muck. After months of work, they’ve got that area up on more than 1,000 jacks and it can be driven on, a $5 million temporary fix. A permanent solution is being designed for the area to replace the double culverts with stainless steel boxes from Kapiolani Boulevard all the way down to the Ala Moana canal outflow, even going under one of the high-rises.

They’re slating $50 million in the CIP (capital improvements program) budget for work that could start in 2020 or the year after.

“The danger to pedestrian or cars driving over, it wasn’t significant,” Kroning said. “You don’t hear of cave-ins on culverts really anywhere. It’s not a catastrophic problem. If they do decay and start falling apart, it’s something we’ll see signs of and we’ll be able to react to fast enough.”

All of this is happening in a neighborhood that’s been on a big building swing lately, a stark juxtaposition of glitzy high-rises and aging industrial facilities. The Howard Hughes Corp. is among them, building up in a master-planned, 60-acre section.

“A lot of our buildings, the actual building level starts higher that street level and that’s to work itself out of the flood plain,” said Todd Apo, vice president of community development for Howard Hughes. “We’ll make sure when we do generator equipment and those type of safety issues for the building, they’re not placed below ground level.”

Experts agree the new structures are built to last and take all coastal-zone geographical challenges into account.

“The newer the buildings, the safer they are,” Prevedouros said. “The older buildings, they may start having problems with their foundations and they may have some tilting. Eventually they will have to have significant repairs and eventually demolition and reconstruction.”

Whether you rent or own in Kakaako or just drive through, there’s a big public benefit taking place as the new buildings go up: Utility, road, sidewalk and even lighting improvements are being done by Howard Hughes alongside their structures, which may help catch and fix some of the same problems seen on other area roadways.

“A lot of the new roads in this area are because we were doing the construction work. That means there’s brand-new infrastructure, less likely to break for our whole city and county,” Apo said. “The city and state have a lot more they have under their purview, so figuring out how to prioritize that and catch up on that is something they’re needing to do.”

Taking just those culverts as an example, there are thousands of them around the island, and we wanted to know from the public agencies, what lessons have been learned from these recent incidents and can more be done to check and shore things up?

“Because this has come to our attention now, we do plan on checking all the other drainage systems in the area that are similar to Pensacola,” Kroning said. “What they’ll do is they’ll add some additional checks now to take care of the Kakaako area and the north-south roads that cross Kapiolani Boulevard.”

That’s instead of the about once-every-five-year cycle the Department of Facility Maintenance would reach each culvert in their ongoing inspection cycle.

As for the state, it doesn’t plan any changes to inspection routines in the area.

“HDOT follows the American Association of State Highway and Transportation Officials guidelines for bridge inspections every two years,” Sakahara said. “The deterioration was discovered during routine inspections of the structure as it is designed to do. We will continue inspecting this and our other bridges as part of our bridge inspection program, as it is the current process that found the issue.”

“In a perfect world, we would be having very consistent maintenance of these things, particularly now,” Prevedouros said. “We have robotic equipment that can go and crawl into that and find out what’s wrong, but again, these are ‘cha-ching’ kinds of issues.”

Issues that can be ameliorated from what’s learned as rail makes it way toward Ala Moana, since it’s rare that any one project will produce as big of a stretch of studies and engineering.

“One of the side benefits of the rail project is they can help us with the geo-technical investigations they have done,” Prevedouros said, “and actually they can inform the neighborhood as to the stability of the soils, because they have to do it for their own foundations. Unless you plan to put a big rail or a big road in the area, you cannot simply start poking holes. It’s simply too expensive.”

We’ll follow up with the Honolulu Authority for Rapid Transportation as it compiles the area studies, to see what can be used for broader public roadway maintenance, and what area property owners and builders might benefit from knowing.

State Ala Moana Boulevard Project

Remaining closures:

  • Lanes will be closed from 5 a.m. on Saturday, Nov. 4, 2017, through 5 a.m. on Monday, Nov. 6, 2017
  • Lanes will be closed from 5 a.m. on Saturday, Nov. 11, 2017, through 5 a.m. on Monday, Nov. 13, 2017 (tentative)
  • In anticipation of the holiday season, HDOT will not schedule weekend closures on this project from Thanksgiving through early January 2018.

Per HDOT: “This culvert is inspected as part of our bridge inspection program. The inspection in February found that repairs were necessary, temporary shoring was done, and our crews continued to inspect on a regular basis while working on the permanent fix. A similar process would occur if any of our bridge facilities were found to be in need of repair. A February 2017 inspection found that immediate repairs were necessary to the facility and HDOT placed a load restriction on this section of Ala Moana Boulevard. HDOT contractors completed installation of steel jacks to temporarily increase the load carrying ability of the concrete slab and lifted the load restriction in April. The current work is the permanent fix to replace the concrete slab.

Construction crews will replace the top segment of a double box culvert that runs beneath Ala Moana Boulevard. Construction will remove the existing pavement and median, replace the top slab of the culvert and then restore the pavement and median to match the existing roadway.”

City Pensacola Street Project and Culvert Information

Per Honolulu Department of Facility Maintenance director Ross Sasamura: “The box culverts under the jurisdiction of the City and County of Honolulu are spot checked or monitored when there are indications of restrictions, blockage, or damage that may arise when crews are performing maintenance in or around the culverts, the streets above, adjoining storm drain structures or after receiving reports from the community.”

  • There are 2,581 box culvert “segments” under the jurisdiction of the City and County of Honolulu.
  • The “segments” are not necessarily physical pieces that were assembled into a length of box culvert, they are typically the means by which a “run” of box culvert is categorized by cross-streets above it or through other defining physical attributes.
  • A length of box culvert like the one under Pensacola Street consists of several “segments.”

According to a city press release: “Emergency repairs began on April 20 and forced the closure of traffic lanes on Pensacola Street between Kapiolani Boulevard and Waimanu Street. As of Sept. 15, cleaning and shoring work was completed and all traffic lanes were reopened.

“The work involved the cleaning of 734 linear feet of culvert and the installation of 1,038 support jacks. The Department of Design and Construction issued an emergency procurement to initiate the repairs, which were necessary because of the deteriorated condition of two parallel box culverts constructed in 1971 below Pensacola Street.

“In the long-term, the departments of Design and Construction and Facility Maintenance are requesting funds for future permanent repairs.”

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