DENVER - As oil and gas drilling grows in Colorado, so do the number of spills.
Since January 1, 2015, oil and gas companies have reported 35 spills to the Colorado Oil and Gas Conservation Commission, the state agency that regulates natural gas drilling.
Three-quarters of those spills occurred in just four counties:
4 in Rio Blanco County
5 in Garfield County
6 in Las Animas County
12 in Weld County
Companies also reported one spill in each of the following counties: Moffat, Yuma, Washington, Adams, La Plata, and Elbert. Two spills were reported in Jackson County.
The COGCC requires oil and gas companies to report spills ranging 210 gallons -- the equivalent of five "barrels" -- to incidents involving thousands of gallons that could contaminate waterways. The reporting threshold is smaller when a spill leaks out of a storage tank and out of secondary containment.
If a spill is smaller than 210 gallons but is stopped by secondary containment, the state does not require formal reporting but does expect companies to properly clean it up.
Records show in 2014 companies reported 712 spills in Colorado, in all, releasing more than a million gallons of oil and other contaminants.