HI SB3259

Municipal solid waste combustor ash (fly ash, bottom ash, or combined ash) must be disposed of only in double-lined municipal solid waste or hazardous waste landfills.

Beginning December 31, 2026, incinerator ash is prohibited from being used as alternative daily cover material on landfills, roadbuilding, fill, or other construction material.

Waimanalo Gulch Sanitary Landfill cells constructed and in use by December 31, 2025 are exempted from the double-liner requirement.

Current federal testing procedures for incinerator ash only measure substances that leach at pH levels where toxic metals like lead, cadmium, and arsenic are not expected to leach, failing to capture real-world landfill conditions.

The EPA acknowledged in December 2025 that non-hazardous municipal solid waste ash may still pose risks through inhalation, ingestion, or skin contact pathways for workers.