Environmental Monitoring

Maui Wildfire Data: Nearshore Coastal Water Quality

Ash from the Lahaina wildfires may enter coastal water through surface water runoff and windblown ash. The ash may contain substances including arsenic, other metals, and asbestos, which can be harmful to human health. Stormwater best management practices (BMPs) throughout Lahaina have helped prevent runoff from carrying ash to the ocean, and spraying Soiltac® on soil and other surfaces has helped prevent winds from blowing ash into the ocean.  

DOH and partners continue to monitor the quality of nearshore coastal waters. This monitoring helps to answer the following questions:

• Have the Maui wildfires affected nearshore water quality?
• Is it safe for people to swim, fish, and enjoy other forms of recreation in waters near Lahaina without significant health impacts caused by the wildfires?
• Do additional steps need to be taken to prevent the settled ash in Lahaina from entering the ocean?

• DOH collects routine water quality indicators every week from nearshore monitoring sites. These indicators include dissolved oxygen, pH, salinity, and turbidity. A summary of recent DOH data is presented here. DOH is also collecting nearshore water quality data for metals (total and dissolved), nutrients, and other water quality indicators to further evaluate potential impacts from the wildfires.
• Hui O Ka Wai Ola (HOKWO) has collected water chemistry and nutrient data monthly or bimonthly from 12 sites in the Lahaina area. They will be assisting DOH in collecting upcoming quarterly monitoring for metals and nutrients. A summary of recent Hui O Ka Wai Ola data is presented here.
• The Surfrider Foundation’s Maui Chapter collected grab ocean water samples on January 10, 2024, following a heavy rainfall event and analyzed the samples for metals and polycyclic aromatic hydrocarbons (PAHs). Surfrider also collected samples on June 4, 2024, this time using DOH sample collection guidance to evaluate fire-related metals. The most recent Surfrider sampling data can be found here.

• The University of Hawaii at Manoa is conducting ongoing research on coastal water quality following the Lahaina fires. The UH results are summarized in a YouTube video from a public presentation on March 11, 2024.
• U.S. Geological Survey (USGS) conducted limited water quality sampling and DOH is currently receiving and reviewing data from these sampling efforts. While the data provide context, they are preliminary and not suitable for decision-making. These data were not collected using DOH protocols or EPA protocols and methods, so DOH cannot verify the quality or representativeness of the samples or the analytical data. DOH is not using these data to inform decision-making.

To evaluate impacts from the wildfires, DOH and partners collect nearshore water samples from nine sites near Lahaina (Figure 1). The sampling occurs at seven beaches and two surf breaks.

Tables 1 through 3 present the summaries of coastal water quality sampling data collected by DOH during August 2024 for total and dissolved metals, nutrients, and conventional water quality parameters. Table 4 shows water quality data from various locations for temperature, salinity, dissolved oxygen, pH, and turbidity, comparing overall water quality data before and after the Lahaina fires.

DOH will continue to collect nearshore water quality samples and will post sampling results to this page.

Coastal water quality samples were collected by DOH in accordance with DOH protocols.
DOH EAL: Hawaii DOH Environmental Action Level for screening. An entry of “—” means the analyte does not have an EAL.
The table shows valid sampling results from the sites, including duplicate and triplicate samples collected for quality assurance purposes.
Concentrations higher than DOH EALs are shown in bold font.
ND: Non-detect
*Values were J flagged in the laboratory report, indicating that the result should be considered as an estimated rather than quantitative value.
¹Surface water EALs are for marine habitats and primarily consider potential harm to aquatic habitats or the potential for substances to accumulate in aquatic species. The EALs are from Table D-2b of DOH’s TGM EAL Surfer (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) from Spring 2024. Recreational water criteria for human health are based on bacteria levels in the water. See “What Do the Data Tell Us?” for explanations of why the levels shown here do not pose a risk to people using these waters for recreation.

Coastal water quality samples were collected by DOH in accordance with DOH protocols.
DOH EAL: Hawaii DOH Environmental Action Level for screening. An entry of “—” means the analyte does not have an EAL.
The table shows valid sampling results from the sites, including duplicate and triplicate samples collected for quality assurance purposes.
Concentrations higher than DOH EALs are shown in bold font.
ND: Non-detect
*Values were J flagged in the laboratory report, indicating that the result should be considered as an estimated rather than quantitative value.
¹Surface water EALs are for marine habitats and primarily consider potential harm to aquatic habitats or the potential for substances to accumulate in aquatic species. The EALs are from Table D-2b of DOH’s TGM EAL Surfer (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) from Spring 2024. Recreational water criteria for human health are based on bacteria levels in the water. See “What Do the Data Tell Us?” for explanations of why the levels shown here do not pose a risk to people using these waters for recreation.

Coastal water quality samples were collected by DOH in accordance with DOH protocols.
DOH does not currently have Environmental Action Levels (EALs) for the parameters listed in the table.
The table shows valid sampling results from the sites, including duplicate and triplicate samples collected for quality assurance purposes.
Note that recreational water criteria for human health are based on bacteria levels in the water.
ND: Non-detect
*Values were J flagged in the laboratory report, indicating that the result should be considered as an estimated rather than quantitative value.

¹Pre-fire data range is from August 1, 2022, to August 7, 2023. Post-fire data range is from August 8, 2023, to March 31, 2024.
²Water quality data are based on DOH and Hui O Ka Wai Ola monitoring efforts.

Water quality data provided from the Surfrider Foundation monitoring efforts.
DOH EAL: Hawaii DOH Environmental Action Level for screening. An entry of “—” means the analyte does not have an EAL.
Concentrations higher than DOH EALs are shown in bold font.
ND: Non-detect
PAH samples not collected for Canoe Beach 2 site
¹Surface water EALs are for marine habitats and primarily consider potential harm to aquatic habitats or the potential for substances to accumulate in aquatic species. The EALs are from Table D-2b of DOH’s TGM EAL Surfer (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) from Spring 2024. Recreational water criteria for human health are based on bacteria levels in the water. See “What Do the Data Tell Us?” for explanations of why the levels shown here do not pose a risk to people using these waters for recreation.