Plugging and reclaiming 4,000 old wells in Colorado has allowed the oil and natural gas sector to slash ozone-causing pollutants, the Colorado Oil and Gas Association (COGA) reported on Monday.

Colorado has significantly reduced its ozone emissions in recent years and is beginning another summer campaign keep the emissions in check, according to COGA.

Using Colorado Air Pollution Control Division measurement methods, the state has cut volatile organic compound (VOC) emissions by the equivalent of taking 208,000 cars off the road. A COGA spokesperson said there is no “silver bullet” for cutting the the emissions, but the actions taken by the exploration and production (E&P) sector are important.

Last year COGA member companies plugged and reclaimed an estimated 1,850 wells, and they plan to plug and reclaim an added 2,150 wells this year.

Combining plugged and reclaimed wells, 4,000 wells will be closed by the end of this year, COGA said.

“The wells being taken offline and properly reclaimed will further improve our air quality,” COGA CEO Dan Haley said. “Of course, new production facilities continue to be built, but operators are using innovative, clean technologies and practices that are resulting in a net gain for the environment.”

According to COGA, plugging and reclaiming the wells should result in sharp emissions reductions for the three biggest ozone precursors, VOCs, nitrogen oxide (NOx) and carbon monoxide (CO):

The industry’s well plugging and reclamation is critical, particularly as it relates to reducing emissions that lead to ozone formation in Colorado’s Front Range, which is a designated nonattainment area, Haley said.

Ozone is a secondary pollutant formed when VOCs and NOx combine in the presence of sunlight and heat. It is tracked by the Regional Air Quality Council, which noted that weather plays a key role, with the highest ozone levels usually recorded in summer months.

In addition to the oil and gas sector, emissions also come from the transportation sector, industrial plants, lawn/garden equipment and household products, such as paints, solvents and hair spray.

Additional information on Colorado’s ozone is available from COGA, which is also promoting a public education initiative by the Regional Air Quality Council.