In its first few meetings, Honolulu’s new Climate Change Commission has heard from a slew of city agency heads about the status of their respective agencies’ efforts to plan for climate change effects. Some agencies have gone further than others. At the commission’s meeting last month, the Honolulu Board of Water Supply proved that it’s gone the furthest, by far.
“It’s only going to get worse,” said Board of Water Supply program administrator Barry Usagawa of street flooding in various parts of O‘ahu during high tide (especially Waikiki and Mapunapuna), which modeling predicts will get deeper and spread further with climate change-induced sea level rise. Already, he told the commission, his agency has had to wait until low tide to pump floodwaters exacerbated by three recent water-main breaks in urban Honolulu. Until the tide receded, there was nowhere to pump the water, he said.
In addition to more flooding, the BWS also expects sea level rise to threaten its transmission infrastructure. The increased groundwater and salinity levels near the coast will likely worsen corrosion of the BWS’s pipelines, the agency’s newly adopted long-range financial plan states.
Usagawa noted that the BWS’s network of 2,100 miles of pipelines supplies 145 million gallons of water a day to about a million people on the island. A lot of those pipes are metallic and will corrode in salt water, he said, adding that even the plastic pipes are connected with metallic fittings, which are also vulnerable to corrosion.
What’s more, the transmission system includes about two dozen low-elevation coastal pipe bridge crossings that may be subject to coastal erosion effects, he said.
Perhaps most concerning are the potential effects on water supplies. Currently, two types of modeling – statistical and dynamical – have been done to predict how climate change will affect weather and precipitation in Hawai‘i with one painting a much rosier picture than the other. In the worst-case scenario, Usagawa said, the sustainable yield (SY) of groundwater aquifers on the island could decrease by 34 percent, from a histori- cal average of 407 mgd to 267 mgd.
“Altogether, assets that could be impacted from climate change include some water resources, some pump stations, and coastal pipes. All this might drive the need for mandatory conservation,” the financial plan states. It’s also likely to require the BWS, which is self-supported, to raise its rates to increase revenue. “[I]n the near term, no appreciable difference in revenue requirements is seen. However, over the long term, revenue requirements would begin to increase as assets had to be replaced sooner than originally planned, possibly by six percent over the base case by the 30th year,” the plan states.
In addition to including a climate change scenario in its financial plan, the BWS is in the midst of preparing an adaptation plan with the help of the Water Research Foundation and the engineering firm of Brown and Caldwell. Brown and Caldwell has an $838,771 contract to further evaluate climate change effects on the BWS and its assets and to develop the agency’s response plan, a preliminary draft of which has already been prepared.
“Climate change adaptation involves erring on the side of caution and planning well in advance,” Usagawa said. Right now, however, his agency still has a lot of questions that will hopefully be answered in the final plan. “Where do we start? … Lewers (in Waikiki)? Mapunapuna? What are the triggers for CIP [capital improvement projects]? Nuisance flooding?” he asked.
The agency is already looking into increasing the use of recycled water from the Honouliuli, Mililani, Wahiawa, and Schofield wastewater treatment plants. Desalinization is also, and has long been, another consideration.
“This is a huge impact,” Usagawa said of the projected loss in sustainable yield. He said the BWS would continue to monitor water levels and try to detect any downward trends as soon as they start, since “it takes ten years to get these [mitigation projects] moving.”
At the commission’s first meeting, Department of Planning and Permitting (DPP) acting administrator Kathy Sokugawa noted that the proposed revision of the O‘ahu General Plan, approved by the Planning Commission earlier this year, incorporates climate change and sea level rise considerations.
“[A]ll public and private organizations [are called on] to prepare for the future problems caused by rises in sea level, rises in groundwater levels, and more frequent and severe storms, shifts in local rainfall patterns, and higher urban temperatures,” the proposed revision states.
In contrast, the city’s regional community development plans have not taken those concerns into account and at the rate they’re being updated, they won’t anytime soon. At the commission’s meeting, however, Brad Romine, who works both with the University of Hawai‘i Sea Grant program and the state Department of Land and Natural Resources’ Office of Conservation and Coastal Lands (OCCL), announced that he is preparing a white paper for the DPP on how to incorporate sea level rise predictions into the Primary Urban Center Community Development Plan, which has not been updated since 2004. The plan covers the region extending from Pearl City to Kahala and across the south shore, where most of the island’s population resides.
Romine, who is working on the white paper with Tetra Tech, Inc., said it would take both the National Oceanic and Atmospheric Administration’s recent guidance on climate change resilience and downscaled sea level rise predictions for the area into account.
“State and county agencies should consider potential long-term cost savings from implementing sea level rise adaption measures as early as possible (e.g., relocating infrastructure sooner than later) compared to the cost of maintaining and repairing chronically threatened public infrastructure in place over the next 30 to 70 years,” states the December 2017 Sea Level Rise Vulnerability and Adaptation Report (SLR report) prepared by Tetra Tech and the OCCL.
According to Department of Environmental Services director Laurie Kahikina, whose agency manages the island’s wastewater treatment system, hundreds of agency projects are already in the planning, design, and construction phases, so her agency just “can’t go back” and reconfigure them to address climate change concerns.
The SLR report identified those areas throughout the state (SLR-XA) that are vulnerable to sea level rise effects under various scenarios. “While no wastewater treatment facilities on O‘ahu are located within the SLR-XA with 3.2 feet of sea level rise, sea level rise may impact wastewater stabilization ponds immediately surrounding the Sand Island and Kahuku Wastewater Treatment Plants. Flooding of these ponds would have the potential of releasing wastewater into nearshore waters,” it states.
At the same time the city is undertaking an $800 million upgrade to the Sand Island plant as a result of a consent decree over water pollution, the facility’s pipes are vulnerable to sea water infiltration, said deputy director Timothy Houghton. He added that the wastewater system also includes 70 pump stations, a large number of which are located close to shore.
“We can’t just pick them up and move them,” he said, adding later, “If we get an opportunity to re-route lines … how do we do that? Pieces are tied together. Once you start moving, you’ve got to move lots.”
While the department is not yet prepared to relocate its entire wastewater system to avoid the effects of sea level rise, Houghton said it instructs its contractors whenever it can to consider sea level rise in ongoing projects.
“We do lots of borrowing and bond rat- ers have asked us, ‘How are you looking at climate change?’ It’s important to the bond raters. They’re happy we’re looking at it and talking about it. If we didn’t, we would take a hit,” he said.
Ross Sasamura, head of the city’s Department of Facility Maintenance, told the commission that his agency may have the same problem the BWS has had with pumping areas flooded by water main breaks that are already flooded by high tides. As rising seas infiltrate more and more of the city’s stormwater management system, runoff could have nowhere but the streets to go at some point.
“Pumps and pump systems can be problematic,” Sasamura said. As an alternative to simply pumping floodwaters, he suggested what he admitted might be viewed as a hare-brained idea: capping outfalls, connecting regional systems using old abandoned pipes, and potentially using that trapped water as a non-potable resource, if necessary.
“I don’t ever see us reconfiguring the storm drain systems, which are mostly developer-constructed,” he said.
— Teresa Dawson