Work on the second phase of cleanup at the Waipahu Ash Landfill site is expected to begin in the coming weeks after the city and the Environmental Protection Agency signed a new agreement.

The EPA pressed the city to make the improvements at the location along the Waipio Peninsula, identified as being within the Pearl Harbor Superfund site, due to concerns that dioxins and heavy metals in the former landfill’s sediments pose a risk to nearby wetlands.

The ash landfill, which served the Waipahu Incinerator that burned muncipal solid waste from 1972 to 1991, is nearby the Pouhala Marsh Wildlife Sanctuary.

The first phase of the cleanup included excavation and relocation of ash refuse, grading and erosion control, installation of a liner and soil cover, and installation of a passive gas well system and groundwater monitoring wells.

The second phase will include identifying residual contamination at or from the site, determining any human health and ecological risks, and evaluating potential cleanup alternatives. The city will also analyze remaining ash in the soil and sediment and, if necessary, install additional monitoring wells that will sample groundwater to evaluate future impacts from the site.

The work is expected to take several years.