Concern For Cultural Sites Slows Plan To Build Mounds

A plan to build earthen mounds over some contaminated Hanford Nuclear Reservation sites is being slowed by concerns about disturbing American Indian religious and cultural areas.

A study by Bechtel Hanford Inc. shows that just two of seven potential basalt-quarry sites on or near the reservation were not used by mid-Columbia Indian tribes.

Basalt is a volcanic rock that would keep water away from the wastes.

The plan is to build barrier mounds of soil and rock over areas contaminated by radioactive or chemical wastes.

The mounds - 15 feet high and possibly covering acres - would keep rain, plant roots, burrowing animals and curious people out of the contaminated spots for at least 1,000 years, allowing most radioactive materials to decay to safe levels.

The Bechtel study estimates 16.2 million cubic yards of basalt, enough to cover 3,037 football fields under a yard of the volcanic rock, would be needed.

The study estimated the cost of mining and hauling the rock would be $49 million to $163 million, depending on where the quarry site is located.

A prototype barrier is being tested in the central part of the 560-square-mile government reservation. It consists of several layers of soils and gravel over a 5-foot-thick layer of basalt to keep out rain and halt wind and water erosion.

The U.S. Department of Energy had hoped to have the necessary environmental studies of the barrier mounds finished by Feb. 15, but the deadline probably will be extended as Hanford officials look for additional basalt-quarry sites.