Water Quality Studies of Hawaiʻi
A database of water quality research conducted in the Hawaiian Islands
What are Cesspools?
Cesspools are a type of wastewater disposal method that is essentially a hole in the ground with an open bottom. Wastewater from the building flows into the cesspool and enters the environment with no treatment. Watch the video below to learn more!
Video Credit: Hawaiʻi Dept. of Health (DOH), University of Hawaiʻi Sea Grant College Program (Hawaiʻi Sea Grant)
The Cesspool Issue in Hawaiʻi
Hawaiʻi has ~83,000 cesspools that discharges over 52 million gallons of untreated sewage per day into Hawaiʻiʻs waters. Leachate from cesspools contaminates both drinking water and underground aquifers, as well as pollutes the marine environment.
To assess the environmental and public health risks posed by cesspools, UH Sea Grant and UH Water Resources Research Center (WRRC) conducted a study that categorized each cesspool in the islands using a Priority Ranking based on their potential hazards to public health and the environment.
Priority 1 areas require the most urgent replacement with improved wastewater systems. Zoom in on the map to view the priority level of your neighborhood or any area of interest!
Cesspools are classified into Priority 1 , Priority 2, and Priority 3 based on 14 types of data, encompassing geologic, public health, and environmental factors.
However, measurements of wastewater pollution in the environment were not included due to the lack of a statewide water quality study with the required resolution. This led to the development of this tool, which allows users to view various water quality studies on a single map!
Water Quality Studies in the Hawaiian Islands
Explore the maps below to gain insights into water quality studies conducted across Hawaiʻi's watersheds. As a living document, this map will be updated with additional studies and information, so be sure to check back regularly!
Hawai'i Island Water Quality Studies
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Puakō, Hawaiʻi
The Puakō community, home to hundreds of houses built on porous lava rock near a once-thriving coral reef ecosystem, faces pollution issues due to cesspools and poorly functioning individual wastewater systems (IWS). Tests have shown a transit time of as little as 6 hours from flush to reef. While the community is eager to close cesspools and transition to a community-scale system, financial and logistical obstacles present challenges.
Photo Credit: Ethan Tweedie Photography
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Hilo, Hawaiʻi
Hilo Bay is susceptible to pollution buildup due to its restricted water circulation. There are thousands of cesspools in the four watersheds that drain into the bay and other land-based pollution sources, such as waste from feral animals. The municipal sewer system, in desperate need of repair, disposes treated wastewater via an outfall pipe situated about 1 mile offshore.
Photo Credit: University of Hawai'i at Hilo
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Kailua Kona, Hawaiʻi
Numerous neighborhoods and communities along the Kona Coast rely on cesspools for wastewater disposal. Kailua-Kona also has a wastewater treatment plant (WWTP) that discharges waste into aerated lagoons. There is interest in upgrading the WWTP for water reuse, and recent research indicates that cesspool conversion is a key factor in enhancing reef resilience along this remarkable coral reef coastline.
Photo credit: Hawaii Tourism Authority (HTA) / Heather Goodman
Maui Water Quality Studies
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Maʻalaea, Maui
In Maʻalaea, shoreline condominiums inject wastewater into the ground, which eventually seeps into the bay. This results in algal overgrowth nearshore due to high nutrient concentrations. Maʻalaea also faces water quality issues from sedimentation, which can cause the bay to turn brown during heavy rainfall events. These sedimentation issues are worsened by deforestation and invasive species.
Photo credit: Dante Parducci
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Kihei, Maui
Wastewater pollution in Kihei originates from a nearby wastewater treatment plant and has been conclusively connected to declining coral health and impaired water quality.
Picture credit: Jad Limcaco
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Kahului, Maui
The Kahului Wastewater Reclamation Facility and numerous cesspools in the area contribute to wastewater pollution in Kahului. Kahului is a Priority 1 area for cesspool conversion according to the DOH prioritization tool. Studies have identified wastewater pollution in coastal waters through the use of algal analysis.
Photo credit: Mike7777777 | Dreamstime.com
O'ahu Water Quality Studies
Oʻahu Watersheds and Water Quality Studies
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Kūpikipikiʻō (Black Point), Oʻahu
Cesspools in the Black Point neighborhood of Diamond Head, Oʻahu, release pollutants into the nearshore ocean below. Richardson et al. (2017) found that up to 8% of the groundwater received by the adjacent coral reef is actually wastewater. These cesspools are challenging to convert to better systems due to the slope of the streets and high housing density in the neighborhood, but innovative solutions are possible.
Picture credit: Jeremy Huang
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Waimānalo, Hawaiʻi
The Waimānalo area includes an area of Hawaiian Homelands housing, dense residential housing, and rural farms. Pollution from the cesspools here has been detected by multiple studies in the nearshore marine environment, with unknown effects on the local fisheries and safety of the water at this popular local swimming and fishing beach.
Photo credit: Dan V.
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Kahaluʻu, Hawaiʻi
In Kahaluʻu, cesspools cause pollution in both the stream and Kaneʻohe Bay. Numerous cases of skin infections have occurred due to exposure to the polluted water. Moreover, the pollution negatively impacts the patch reefs of Kaneʻohe Bay which function as essential habitats for reef fish and shark nurseries.
Photo credit: Svetlana Day
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Haleʻiwa, Hawaiʻi
On Oʻahu's North shore, cesspools, agricultural pollution, and feral mammals collectively contribute to persistent water pollution in Haleʻiwa. The Surfrider Foundation Blue Water Task Force (BWTF) Oʻahu program found that the water's fecal indicator bacteria (FIB) content exceeds the Department of Health limits more than 70% of the time.
Photo credit: Rayn Noeker
Kauai'i Water Quality Studies
Kauaʻi Watersheds and Water Quality Studies
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Hanalei, Kauaʻi
The region between Haʻena and Hanalei on Kauaʻi has approximately 554 cesspools in use. However, studies in this area have found that the main source of nitrate pollution in Hanalei Bay is fertilizer rather than wastewater.
Picture credit: Backyard Productions
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Nawiliwili, Kauaʻi
Lihūʻe, Kauaʻi's main city, is situated in the Nawiliwili watershed, an area that accommodates commercial activities such as the harbor and airport. Although comprehensive coastal water quality research is limited, instances of cesspool pollution in the area's streams have been recorded.
Picture credit: Faina Gurevich
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Poʻipū, Kauaʻi
Koloa-Pouʻpū, with 671 cesspools, is classified as a Priority 2 area for cesspool conversion. A water quality study by Smith et al. (2021) revealed that wastewater serves as the primary contributor of nitrogen in the coastal waters of this region.
Photo credit: Mathias Alwart
Hawaiʻi State Beach Monitoring Program
In Hawaiʻi, enterococci bacteria are used to monitor recreational water quality and detect possible harmful microbes that could cause illness. The concentration of enterococci is measured in units, either as colony forming units (CFU) or most probable number (MPN) per 100mL, based on the testing technique. According to Hawaiʻi's water safety standards, the average enterococci level in recreational waters must not surpass 35 units per 100mL over a 30-day span. Additionally, no more than 10% of water samples collected within that same 30-day period should contain enterococci levels exceeding 130 units per 100mL.
The State of Hawai’i Department of Health Clean Water Branch (CWB) performs routine monitoring of Hawaii’s beaches which encompass sample collection, field measurements, and field observations. CWB analyzes water samples for enterococcus and utilizes a beach action value (BAV) of 130 CFU/100mL (equivalent to EPAs STV) to enact management action.
If the BAV is not exceeded during CWB routine monitoring then no action is required and routine monitoring is resumed. However, if the BAV is exceeded, CWB collects additional confirmatory sample and issues a notice on CWB Water Quality Notification and Advisories website. If the confirmatory sample shows that the BAV is not exceeded then the notification is updated with no advisory issued but if exceeded, CWB issues an advisory for the affected beach.
CWB also issues advisories for confirmed sewage spills and brown water events. However, during brown water events all water sampling is suspended.
Subscribe to CWB Water Quality Notification and Advisories website to stay up to date!
