BISMARCK, N.D. (AP) -- State health officials are working this week to verify that a 20,000-barrel oil spill in northwestern North Dakota didn't contaminate groundwater.
Tesoro Corp. earlier did testing and found no contamination. State Environmental Health Chief Dave Glatt says state officials are taking their own samples to verify Tesoro's findings.
The pipeline rupture discovered in September sent oil across a wheat field. Tesoro is working on cleanup, and Glatt says about 5,000 barrels of oil have been recovered. He says most of the rest will have to be baked out of the soil, and the soil renewed and replaced. He says that could take a couple of years.
Glatt says Tesoro is doing more soil boring as part of the cleanup, but he doesn't expect the spill size estimate to change much.