The beaches were spotted with used syringes, catheters, raw sewage and other garbage.

West Oahu Land Filled Special Project Badge

In late 2010 and early 2011, heavy rains caused a Leeward reservoir to overflow above Oahu’s only municipal landfill, Waimanalo Gulch. The landfill’s filtration system and backup retention ponds were overwhelmed, and millions of gallons of contaminated water flooded the sands of Ko Olina resort and nearby beaches, from Ewa to Nanakuli.

The U.S. Environmental Protection Agency sued the owner of the landfill, and the operators were indicted for “knowingly discharging pollutants into U.S. waters,” and repeatedly lying to federal and state health officials about having an adequate stormwater system. The landfill operators pleaded guilty to criminal violations of the Clean Water Act, paid $400,000 in criminal fines, $200,000 in restitution to local businesses and spent thousands of dollars upgrading their stormwater drainage system in the following years.

Waimanalo Gulch Sanitary Landfill Stormwater System
In January 2011, the filtration system at Waimanalo Gulch was overwhelmed with stormwater and debris that ultimately emptied out to Westside beaches. Ku‘u Kauanoe/Civil Beat/2021

The landfill manager called the two storms that flooded the landfill in December 2010 and January 2011 “two back-to-back, 100-year storms,” but climate change is expected to make such storms more frequent and possibly even more intense.

The City and County of Honolulu is in the process of picking the location of Oahu’s next landfill, raising questions about which site will be least impacted by climate change and what additional infrastructure is needed to protect the environment from a warming world.

Preparing For The Future By Learning From The Past

Hawaii’s rainfall and trade winds are caused by pockets of warm air circulating from the equator to the poles and back again. Rising temperatures will change those patterns, and the state has already seen a decrease in the frequency and intensity of northeast trade winds since 1973.

Warmer temperatures lead to more ocean evaporation, which means more moisture in the atmosphere and heavier rainfall. According to Hawaii climatologist Pao-Shin Chu, there’s a 7% increase in atmospheric moisture for every 1 degree increase in ocean temperatures. Over the past 50 years, there’s already been an increase in extreme rain events in the islands, and research suggests that southern Oahu should brace for even more periods of heavy rainfall.

But when atmospheric winds shift and carry moisture-laden clouds away from the islands, those same increased temperatures dry out soil and vegetation, making periods of drought longer and more intense. Hawaii has already seen increased periods of drought since 2008.

Put together, climate change means that there will be more water when it isn’t as needed and less when it is.

While there are complex and highly accurate models for predicting climate impacts on a global scale, pinpointing the possible change in precipitation in a specific, small area is incredibly difficult.

The location of Oahu’s new landfill is restricted to the uncolored locations on this map, according to the city’s Department of Environmental Services. City & County of Honolulu

“Regardless of where the next landfill is going to be, we’re already talking about what redundant measures we can install at the landfill to protect the surrounding environment from increased rainfall and potential hazardous runoff,” said Michael O’Keefe, deputy director of the Honolulu Department of Environmental Services.

There are four potential areas where the island’s next landfill could be built, and multiple potential sites within each area.

Two large swaths on the North Shore are up for consideration, an issue the North Shore Neighborhood Board will be discussing in January.

One is near Wheeler Army Airfield. Another is between the hills of Makakilo and Kunia. Kapolei Neighborhood Board Chair Anthony Makana Paris indicated that the board’s Environmental Justice subcommittee has received concerns from community members about the potential new sites’ proximity to the Ewa aquifer, Honouliuli National Historic Site and the University of Hawaii West Oahu campus.

The nine-member board has until Dec. 31, 2022, to recommend a location for the new landfill. At its next meeting on Feb. 7, the committee will finalize the list of criteria that will be used to score and rank potential landfill sites. The draft list has a site’s potential impact on groundwater evaluated alongside the site’s distance from H-Power, construction costs, landfill capacity and effect of precipitation among other considerations.

Civil Beat requested interviews with every member of the advisory committee about how they were considering the impact of climate change in their decision-making. Markus Owens, a spokesman for the Honolulu Department of Environmental Services, said in an email that most felt it was “way too early” in the process to discuss climate impacts.

The impact of increased precipitation was a hot topic at the latest committee meeting in mid-December after the Board of Water Supply expressed concerns that the next landfill could contaminate the island’s groundwater.

Due to overlapping local, state and federal regulations, all four of the potential landfill areas are above drinking water aquifers. Mike Kaiser, a senior project manager with HDR, a construction company that’s consulting with the city on the new landfill, gave a presentation at the meeting on the many safety elements that are built into a modern landfill.

These include pipes underneath the landfill that collect leachate or the contaminated water that seeps out of a landfill. Leachate is regularly pumped out and regulations don’t allow for more than 12 inches of the contaminated water to be in those pipes at any given time.

But Cynthia Rezentes, a member of the committee and a former member of the National Environmental Justice Advisory Council, pointed out that the same regulations were in place before the 2010-2011 storms, and the landfill operators knowingly broke many rules.

In 2013, Waimanalo Gulch and the city also paid a $1.1 million civil penalty after emitting air toxics, organic compounds and potent greenhouse gas methane from 2002 to 2005, which violated the Clean Air Act.

“I’ll be the first to admit we have made a lot of mistakes in the past and we’re definitely trying to learn from them,” city planner Josh Nagashima said in response to Rezentes’ questions about leachate.

Making A ‘More Robust’ Landfill

“Waimanalo Gulch landfill has a really robust catchment system that was made even more robust after the whole fiasco with the spillage at Ko Olina,” said O’Keefe, of the Department of Environmental Services. “But for the new landfill, we would look at making it even more robust.”

The city is pushing for the new landfill to have a double liner system, which surpasses federal requirements and could significantly increase costs. Waimanalo Gulch Sanitary Landfill opened with a single-liner system in 1989, but since 2010 all new construction at the site has used a double-liner system.

Waimanalo Gulch Sanitary Landfill, Oahu’s only municipal landfill, sits inland of Ko Olina resort, Kapolei’s Honokai Hale community and Campbell Industrial Park.

Waimanalo Gulch currently has nine monitoring wells, where water and soil samples are periodically tested to see if any contaminants have leached out of the landfill. There haven’t been any detected leaks at Waimanalo Gulch, and O’Keefe wants the next landfill to have even more monitoring wells.

“There is concern about the landfill being close to sensitive natural resources, including our freshwater drinking system,” he said.

But every additional protection brings additional costs.

Before the 2010-2011 storm, Waimanalo Gulch had invested $15 million in a new dam and stormwater diversion system. After the overflow, thousands of dollars in additional upgrades have been made.

And after the 2013 Clean Air Act settlement, the landfill operator said it spent $1.5 million to design and construct a gas collection and control system.

“Because we don’t have a site yet, we have no real idea about how much such measures would cost,” O’Keefe said. “Depending on the site, the mitigation measures vary greatly, actually.”

Drought is less of a concern but would also lead to increased costs. Landfill workers constantly spray water over the site to tamp down dust and keep particulates from blowing into surrounding areas. A long period of drought could impact the cost of water, but O’Keefe said from a purely management perspective, a dry area is much preferable to a wet one.

“Of all of the climate change-related impacts that we could be faced with, drought might be the one that’s most easily able to be dealt with,” he said. “The main challenge of landfill management is stormwater that leads to leachate. So the less rain, the less leachate runoff and potentially the easier job.”

Most recent estimates anticipate the new landfill to cost $210 million, span 80 acres and be open for 20 years. That’s part of the reason the Department of Environmental Services is dedicating a significant portion of 2022 to reducing waste, extending the life of the landfill and trying to reduce the carbon footprint of the island’s waste management system.

A sankey chart showing the flow of waste on Oahu. Most municipal waste goes to H-Power or is recycled, with a small amount going right to the landfill. Ash from H-Power goes to the landfill. Most construction and demolition waste is recycled, with only a small amount going to the landfill. Overall, about 84% of Oahu's waste was diverted from the landfill in 2020.
Claire Caulfield/Civil Beat/2021 • Source: City and County of Honolulu, Department of Environmental Services • Diagram created using SankeyMATIC 

Mitigating The Effects Of Climate Change

Although transportation and energy production produces the bulk of Hawaii’s carbon emissions, waste management still has a significant impact on the state’s carbon footprint.

To counter his sector’s emissions, O’Keefe is focusing on reducing the amount of waste that needs to be brought to H-Power, the island’s waste-to-power incinerator.

“H-Power saves literally hundreds and hundreds and hundreds of thousands of tons of waste from having to be landfilled every year,” he said. “But the combustion process that occurs does emit greenhouse gases.”

H-Power generates about 10% of the island’s electricity, and emitted 746,228 metric tons of greenhouse gasses in 2020, making it the state’s 4th highest emitter. The garbage trucks that bring 94% of the island’s waste to H-Power and then transport the remaining ash to the landfill consume a lot of gasoline, and the Waimanalo landfill emitted 25,602 metric tons of methane last year.

“So that’s why in the new year, we’re going to be convening a source reduction working group that’s going to come together and discuss how we can affect policy to minimize the amount of waste that’s generated to begin with,” O’Keefe said.

The group will look into opportunities to compost food waste, reduce packaging and use food waste and sewage to generate electricity, O’Keefe said.

“We really want to get to initiatives that will mitigate the impacts of climate change,” he said.

This report was made possible in part by the Fund for Environmental Journalism of the Society of Environmental Journalists.

Help power our public service journalism

As a local newsroom, Civil Beat has a unique public service role in times of crisis.

That’s why we’re committed to a paywall-free website and subscription-free content, so we can get vital information out to everyone, from all communities.

We are deploying a significant amount of our resources to covering the Maui fires, and your support ensures that we can pivot when these types of emergencies arise.

Make a gift to Civil Beat today and help power our nonprofit newsroom.

About the Authors