Hold your nose if you must but don’t look away if you love the ocean or swim in it. This story is about cesspools in Hawaiʻi, a problem that was kicked down the road for decades but one we are finally dealing with. We also look at the common ways to replace cesspools and one bold new technology.



cesspool is just a hole in the ground” and that hole is usually not lined, says Sina Pruder, chief of the state’s Wastewater Branch. That means the human waste and wastewater that is dumped into cesspools often leaches into local streams, groundwater and, eventually, the ocean.

There are 88,000 such holes in the ground in Hawai‘i, mostly in rural areas, according to a state Department of Health estimate. And every day people dump more than 53 million gallons of human waste and partially treated wastewater into them – that’s equivalent to 80 Olympic-size swimming pools daily.

Here’s another way to understand the scale of this pollution: Think back to 2006 when so much raw sewage was dumped into the Ala Wai Canal that Waikīkī Beach was closed for a week and Hawai‘i tourism was humiliated in the global media. That massive dump was 48 million gallons, less than what’s dumped into local cesspools in a single ordinary day.

Cesspools range from 20 to 40 feet deep. “If you’re in close proximity with the ocean, cesspools are actually dug deep enough to hit the groundwater,” Pruder explains. “It’s actually a conduit that kind of takes wastewater sewage and transfers it to the ocean or possibly to a drinking water source.”

The resulting pollution can make you sick, harm coral reefs and lead to all kinds of ecological damage.

State Rep. Chris Lee says, “In Hawai‘i, we are the best example of a developed nation which still has some of the worst sewage disposal and contamination problems that have been affecting our freshwater supply, our streams and nearshore marine environments.”

Most states banned cesspools decades ago, but Hawai‘i was the last state to allow new ones to be built. But over the last three years, new state laws were passed to change the situation. In 2016, a coalition of environmental groups, government agencies and health advocates supported the passage of Act 120. The law banned construction of new cesspools and offered homeowners $10,000 tax breaks to upgrade their systems. Act 125 was passed in 2017, mandating the upgrade of all existing cesspools by 2050. The law also required the state Department of Health to complete an extensive report and develop a method of prioritizing which areas should be upgraded first.

Soon after the report was released in 2018, Gov. David Ige signed Act 132 into law, creating the Cesspool Conversion Working Group. Pruder helps lead the group, which includes representatives from the state Department of Health, its Wastewater Branch and other state and county agencies, plus UH researchers, environmental advocates, legislative leaders, bankers and real estate brokers. (Disclosure: The author is a member of the group.) The group’s goal is to develop a comprehensive plan on how, where and when to convert the state’s 88,000 cesspools. Most aren’t registered with the state, Pruder says, so it would be good to identify all of the cesspools and manage that inventory on a database.

Some of the biggest questions that remain: What are the best replacements for cesspools and who will pay for the upgrades – homeowners, the counties, the state or some combination? The Department of Health estimates that an average upgrade costs more than $20,000, making this an almost $2 billion issue in Hawai‘i. Before diving into new technological solutions, it may help to get a brief history of wastewater treatment.

Starting in the late 19th century, the U.S. and other developed nations created vast and expensive sewer systems in major cities to collect waste. But many people outside cities had to create their own individual wastewater systems. “Currently, somewhere between 30% and 40% of Americans are on on-site systems that are not connected to a private or public treatment plant,” says Roger Babcock, a sanitation engineer and professor of civil engineering at UH Mānoa.

Babcock says cesspools were the cheapest and most common forms of individual wastewater systems, but they were least effective for treating pathogens and removing harmful chemicals and nutrients. “The cesspool was kind of the first thing, and it’s just an infiltration system. It can provide some kind of benefit, depending on the type of soil, and it removes solids at least. But other than that, it doesn’t really do much.”

The next level of individual wastewater system evolved into the modern septic system, which includes an underground tank made of concrete, fiberglass or plastic and a leach field or absorption bed. After a household’s waste is pumped into the tank, the solids settle at the bottom and begin slowly breaking down. The clearer liquids rise to the top and are funneled into the leach field, where they percolate into the soil and are naturally digested by bacteria in the system.

Septic tanks provide little bacterial treatment or digestion, says Babcock. The leach field does most of the treatment, but its effectiveness depends on the type of soil, geology and hydrology. Under ideal conditions, the leach field will remove most of the pathogens. “But other times, if it’s raining hard or the soil is not good … it will do a very minimal amount of treatment.” Also, septic systems do little to remove heavy concentrations of nitrogen and phosphorus, which harm marine life and can create “dead zones” in nearshore waters.

In wetter areas like Kahalu‘u on O‘ahu’s Windward Coast, heavy rain will wash out leach fields before they can treat the waste. The resulting wastewater runoff and sediment pollutes the bay below. In dry Leeward shoreline areas like Puakō on Hawai‘i Island, the volcanic soil is close to groundwater and not deep enough to treat waste effectively.

Based on research from UH and The Nature Conservancy, the Coral Reef Alliance reports that high levels of nutrients like nitrogen in the runoff from cesspools and septic systems are likely damaging coral reefs.

Places like Kahalu‘u and Upcountry Maui are listed as Priority One areas by the Wastewater Branch because cesspools there threaten groundwater and drinking water. Cesspools in these areas will need to be converted or upgraded before 2050, Pruder says, but exact deadlines have not yet been set.

“In areas where we know the depth to groundwater is shallow, there is a potential for creating additional contamination. So we’ve been requiring new systems that could potentially impact nearshore waters to upgrade. A septic tank wouldn’t be allowed. Right now, they are required to put in an advanced treatment unit,” like aerobic treatment units or ATUs, Pruder says.

“The ATU is basically the same thing you’ll see at a wastewater treatment plant, just a miniature form that sits in your house,” says Babcock. Like a large treatment plant, there are primary and secondary treatments that use aerobic and anaerobic processes to treat the waste before funneling it into a more extensive leach field. But ATUs and high-end septic systems can be expensive.

Costs vary depending on how many people live in the house, the size of the leach field, the soil type and construction rates. “They can be about $25,000 to $40,000,” says Pruder. “They can even exceed $40,000.” Most homeowners will need financial assistance to install such a system and government will need to make sure the new systems are properly maintained.

“There should be a program to track when septic tank systems are being properly pumped,” says Pruder. “Homeowners with septic tanks are required to have an operation and maintenance manual for their septic tank system, but we’re finding that a lot of homeowners are not following it. It is recommended that they should be pumping out their solids every three to five years, and that’s not being done.” One homeowner on O‘ahu’s Windward Side reported that whenever there is heavy rain, she sees brown wastewater spilling out of her neighbor’s property, across the road and into the ocean.

Research shows that even the best and most expensive on-site systems like ATUs can leach harmful effluent into nearby water. “Dye tracer studies conducted by the University of Hawai‘i at Hilo found that sewage from cesspools, septic tanks and ATUs enters the marine environment through groundwater along the shore within five hours to 10 days – and there is no difference between systems,” says Jos Hill, associate program director at the Coral Reef Alliance. “What is more important is the geology and the connectivity of groundwater to the coastline.”

However, there may be other options for individual wastewater systems. “First of all, I think it’s a very exciting time to be involved with sewage,” says Roger Babcock. “This ban is a great thing because we set the bar high and forced the technology to catch up. I don’t know what’s going to happen with that, but luckily, we have another 30 years.”

Mandatory conversions aren’t required for most areas until 2050, but some homeowners may choose to act faster if they want to sell their home or refinance with a 30-year mortgage. (A 30-year mortgage taken in 2021 or later will extend past the conversion deadline.) Such states as Rhode Island have mandated that cesspool conversions take place when properties are sold. This allows sellers to negotiate shared costs with buyers, who could include the added expense into their home loans.

“We have the opportunity to finally solve our cesspool problem, and we don’t want to flush this opportunity down the toilet.” Chris Lee, State Representative

“It’s a crappy situation,” says Lee, the state representative, unable to resist the puns. “But we have the opportunity to finally solve our cesspool problem, and we don’t want to flush this opportunity down the toilet.” In November 2018, Lee says, he attended the Bill & Melinda Gates Foundation’s Reinvented Toilet Expo in Beijing, saw the next generation of toilet technology and talked with experts and industry leaders about the challenges of converting Hawai‘i’s 88,000 cesspools.

Because poor sanitation is one of the leading causes of disease and death in the developing world, the Gates Foundation has invested over $200 million into research and development of new sanitation systems that are efficient, eco-friendly and affordable. Most developing countries can’t afford extensive sewer systems and treatment plants, so the Gates Foundation is focusing on stand-alone toilets and decentralized package plants.

Most of the Reinvented Toilet technology separates liquids and solids, uses the dry solids for fuel to burn away the pathogens and then uses the resulting heat to pasteurize the wastewater. Then equipment can produce pathogen-free, odorless biochar that can be used as fertilizer plus clean water that can be used for irrigation or other purposes. Some technology even produces net energy, which can be used for other purposes or sold to a utility.

Brian Arbogast, director of the Gates Foundation’s water, sanitation and hygiene program, believes its technology will change the future of sanitation. “The reinvented toilet is basically its own treatment plant,” says Arbogast. “It is inexpensive to buy and easy to operate on a day-to-day basis that doesn’t take a lot of energy. And you don’t need a sewer system. In fact, you don’t need any further treatment. The toilet produces safe liquids and safe solids that you could happily put on your garden.”

Arbogast hopes the new technology can provide a less expensive alternative to cesspool conversion but did not estimate what that price would be. “I believe that household reinvented toilets would be a much more cost-effective way to solve the problem,” he says. “I think there’s a tremendous opportunity for local companies to step up and be the local partners of these international product developers.”

“The reinvented toilet is basically its own treatment plant. It is inexpensive to buy and easy to operate on a day-to-day basis that doesn’t take a lot of energy. And you don’t need a sewer system.” Brian Arbogast, Director of the water, sanitation and hygiene program at the Gates Foundation

The Gates Foundation plans to introduce the technology in Honolulu in 2019. “That will be an opportunity to show the progress our partners have made and to better understand the challenges and opportunities in serving the Hawai‘i market,” Arbogast says. “I’m excited about Hawai‘i being a cutting-edge market for reinvented toilet companies.

“I think it’s an important message for the entire world to realize that new innovations may see their first trials in Hawai‘i and have the potential to completely transform the world.”

Lee thinks this new technology could be a great opportunity for Hawai‘i. “We have 88,000 cesspools, many of which are leaching contaminants into the environment and our water system. This is something the state has struggled to deal with for decades. So, if we can take advantage of this technology and prove it works, imagine what we can do for other communities around the country.”