New webpage launches to advance cesspool conversion

A user-friendly webpage to help homeowners and policymakers address the critical issues surrounding Hawai‘i’s 83,000 cesspools is now publicly available. 

The webpage,, is a collaboration between the University of Hawai‘i Sea Grant College Program (Hawai‘i Sea Grant), UH Water Resources Research Center (WRRC), and the Hawai‘i State Department of Health (DOH) Wastewater Branch.  

A suite of free resources are available on the page, including the Hawai‘i Cesspool Prioritization Tool (HCPT), an interactive map-based tool that displays each cesspool’s prioritization level and indicates the urgency of conversion based on geographic location. This is essential information for homeowners because, as of 2017 when Act 125 Session Laws of Hawai‘i (2017) passed, all of the state’s 83,000 cesspools are required to be upgraded, converted, or connected to sewer before 2050. 

Christopher Shuler, a hydrologist and researcher with WRRC, led the tool’s creation. He noted “We were privileged to receive so many essential contributions from an incredible array of scientists, wastewater experts, and a number of students that allowed us to explore every angle we could as we sought to make the HCPT a comprehensive, yet easy-to-use tool.” 

The HCPT is an essential resource for coastal communities and policymakers statewide. The DOH will use the HCPT to plan for the conversion of cesspools and in the distribution of funding assistance to homeowners. Homeowners have the ability to input their tax map key (TMK) or physical address to determine the conversion priority level from one to three based on their location. Even members of the community who do not have a cesspool can use the tool to visualize the scale and effects of untreated sewage discharges occurring in neighboring areas. 

In addition to the HCPT tool, the website offers a series of place-based videos explaining what cesspools are and why some have particularly acute and hazardous impacts on human and ecosystem health, and step-by-step instructions on how to use the prioritization tool. It also includes helpful links and resources including the 2022 report, ‘Hawai‘i Cesspool Hazard Assessment & Prioritization Tool’ which details the process of creating the HCPT. 

Melanie Lander, Hawai’i Sea Grant community planning and design extension agent, led the project’s outreach efforts. “Upgrading Hawai‘i’s cesspools to modern and effective forms of wastewater treatment is one of the state’s most critical priorities, especially with climate change and sea-level rise intensifying in the coming years. Our educational materials focus on informing Hawai’i’s communities about the human health and ecosystem risks that cesspools pose.” 

Darren T. Lerner, director of Hawai‘i Sea Grant and a member of the Cesspool Conversion Working Group, said “We worked closely with experts from the state and departments throughout the University of Hawai‘i at Mānoa for several years to develop the prioritization tool, and are so proud to share the information with the community and with policymakers now. This website truly has something for everyone.” 

To determine your cesspool’s level of conversion priority, visit For more information on the HCPT, contact Christopher Shuler at To discuss educational opportunities and outreach products, contact Melanie Lander at

This project was funded by the Hawai‘i State DOH Wastewater Branch.