KENNEWICK (AP) — Workers have removed about 129 tons of concentrated chromium from the soil along the Columbia River near the Tri-Cities.

The Tri-City Herald reports that sodium dichromate was added to water that cooled Hanford nuclear reactors. The form of chromium left in the soil can cause cancer in humans and is highly toxic to fish and other aquatic life.

Workers recently dug massive holes at the former reactor sites to excavate soil and prevent groundwater contamination.

Hanford officials say they found the "mother lode" of chromium near the D and DR reactors, where the concentration was so high that it stained the soil a yellow-green color.

An Environmental Protection Agency official says soil cleanup at most reactor areas is "very, very close" to being finished.

Chromium near the K West and East reactors may still need attention.

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