Environmental Monitoring

Maui Wildfire Data: Coastal Sediment

Sediment is a solid material that contains sand, minerals, and other substances. Rain or wind often moves and deposits sediment in new locations. Ash from the Maui wildfires has entered sediment in ditches, streambeds, and along the shore. This ash may have settled from the air or may have been carried by stormwater runoff. Solid ash particles in water eventually settle into sediment.

DOH and partners continue to test sediment to understand how fire-related substances have moved through the environment. Sampling helps DOH determine the levels of fire-related substances in sediment, possible health and safety concerns, and whether remediation of contaminated sediment might be needed.

People could be exposed to fire-related substances if they stir up contaminated sediment during recreational activities in coastal waters. To date, significant levels of fire-related substances have not been identified in the sediment and there is not a health concern for recreational users.

Coastal Sediment Sampling

DOH is reviewing data from the following sampling efforts to evaluate sediment quality:

• DOH began collecting quarterly nearshore sediment samples from nine sites throughout Lahaina in May 2024.
• The Department of Land and Natural Resources (DLNR) collected 20 sediment samples from 17 sites at the Lahaina Small Boat Harbor on November 16, 2023. The fires burned vessels and boats in the Harbor, which may have released harmful substances and debris into nearby water and sediment. The primary purpose of the sampling was to determine whether it would be safe to dispose of sediment in upland areas. Samples were collected from sediment depths ranging from approximately 0.5 to 4 feet below the sea floor.
• U.S. Geological Survey (USGS) sampled numerous locations for a wide range of substances, including potentially fire-related substances. While the data provide context, they are preliminary and not suitable for decision-making. The USGS samples were not collected using DOH protocols for assessment of health risk and cannot be used to assess potential health risks. Nonetheless, the data do not suggest potentially significant health concerns.

Sediment 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.
Bolded numbers indicate exceedances of DOH’s EALs for unrestricted soils.
ND: Non-detect
¹Screening values represent soil EALs for commercial/industrial land use and unrestricted land use obtained from DOH’s TGM EAL Surfer (Tier 1 EALs) search function (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) at the time of data release (Fall 2024).
²Additional duplicate and triplicate samples were collected at Shark Pit – Puamana and Kahekili (Airport) Beach for quality assurance/quality control purposes.

DNLR collected sediment samples from 17 sites at the Harbor on November 16, 2023 (Figure 2).   

The samples were analyzed for more than 85 parameters, including metals, total petroleum hydrocarbons-diesel range organics (TPH-DRO), dioxins, and others. Table 2 presents a subset of the results, with a focus on fire-related substances of potential concern (substances known to stick to wildfire dust and ash) at sampling locations.

As shown in Table 2, reported levels are below DOH’s commercial/industrial EALs for direct soil exposure. The results of the initial screening indicate that sediments could be dredged and may be suitable for upland disposal and reuse at commercial or industrial sites as fill material or daily landfill cover. However, additional sampling and analysis are needed to evaluate final suitability decisions for sediment reuse.

Sediment data provided by DLNR.
DOH EAL: Hawaii DOH Environmental Action Level for screening. An entry of “—” means the analyte does not have an EAL.
TPH-DRO: Total petroleum hydrocarbons – diesel range organics
ND: Non-detect
TEQ Dioxins: “Toxic equivalent concentration” that allows the reporting of multiple dioxin/dioxin-like chemicals as a single value based on their relative toxicities.
¹Screening values represent soil EALs for commercial/industrial land use obtained from DOH’s TGM EAL Surfer (Tier 1 EALs) search function (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) at the time of data release (December 2023).

Grab sample sediment data provided by USGS; sampling locations are listed as presented by USGS as “marine sediment.”
An entry of “—” means the analyte does not have an EAL.
Data are provisional and not suitable for decision-making.
ND: Non-detect
TEQ Dioxins: “Toxic equivalent concentration” that allows the reporting of multiple dioxin/dioxin-like chemicals as a single value based on their relative toxicities.

Grab sample sediment data provided by USGS; sampling locations are listed as presented by USGS as “marine beach.”
An entry of “—” means the analyte does not have an EAL.
Data are provisional and not suitable for decision-making.
ND: Non-detect
TEQ Dioxins: “Toxic equivalent concentration” that allows the reporting of multiple dioxin/dioxin-like chemicals as a single value based on their relative toxicities.

Grab sample sediment data provided by USGS; sampling locations are listed as presented by USGS as “marine beach.”
An entry of “—” means the analyte does not have an EAL.
Data are provisional and not suitable for decision-making.
ND: Non-detect
TEQ Dioxins: “Toxic equivalent concentration” that allows the reporting of multiple dioxin/dioxin-like chemicals as a single value based on their relative toxicities.