HI SB446

Prohibits construction, modification, or expansion of landfill units mauka (inland) of the underground injection control line without establishing a buffer zone of at least one-quarter mile around the landfill unit, effective July 1, 2025.

Applies buffer zone requirement to both municipal solid waste landfill units and construction and demolition landfill units, with exemptions for continued operation of existing properly permitted landfills that do not require physical expansion.

Prohibits the use of fly ash, bottom ash, or combined fly and bottom ash from municipal waste combustors for road building, construction, or as alternative daily cover material on landfills; requires such ash be disposed of only in double-lined and duly licensed municipal solid waste or hazardous waste landfills.

Defines "buffer zone" as the distance between the edge of waste activity and the nearest residential, school, or hospital property line.

Takes effect December 31, 2050.