Oil and gas have contaminated groundwater in 17 percent of the
2,078 spills and slow releases that companies reported to state
regulators over the past five years, state data show. The damage
is worse in Weld County, where 40 percent of spills reach
groundwater, the data show. Most of the spills are happening
less than 30 feet underground — not in the deep well bores that
carry drilling fluids into rock. State regulators say oil and
gas crews typically are working on storage tanks or pipelines
when they discover that petroleum material, which can contain
cancer-causing benzene, has seeped into soil and reached
groundwater. Companies respond with vacuum trucks or by
excavating tainted soil. Contamination of groundwater — along
with air emissions, truck traffic and changed landscapes — has
spurred public concerns about drilling along Colorado's Front
Range. There are 49,236 active wells statewide, up 31 percent
since 2008, with 17,844 in Weld County. Starting Monday,
Colorado Oil and Gas Conservation Commission