Investors are challenging 10 energy companies, including Chevron and Exxon Mobil, to release more information about how they do hydraulic fracturing, a process better known as "fracking," in which a mixture of chemicals and water is pumped underground to release natural gas trapped in shale deposits.

It's the third consecutive year that investors have filed shareholder resolutions seeking information about the process. In addition to Chevron and Exxon Mobil, resolutions this year were filed at Anadarko, Chesapeake Energy, EOG Resources, Exxon Mobil, Noble Energy, Penn Virginia, Range Resources, Stone Energy and Ultra Petroleum.

"Right now, companies are not providing investors, or the communities in which the companies operate, sufficient information on the steps they are taking to address and mitigate the risks associated with hydraulic fracturing operations, so shareholders are demanding increased transparency," said Larisa Ruoff, Director of Shareholder Advocacy for Green Century Capital Management.

Although fracking has been used for decades to extract energy, its use has increased dramatically since it's become more feasible to use the process to release huge deposits of natural gas in places including Pennsylvania, Ohio and New York. As that's happened, controversy over fracking has grown between residents and environmentalists who say the process has polluted drinking water and others who are benefiting economically from the gas being extracted and sold.

Meanwhile, energy companies maintain the process is safe. Some, like Exxon Mobil, say they have released details on fracking fluids. Exxon Mobil says their fluid consist of about 99 percent water and sand and about 1 percent chemical additives. The fluid is essential to the process of releasing gas trapped in shale rock and other deep underground formations, the company says.

"Investors are concerned about the financial risks associated with the environmental, health, and social impacts of fracking," said Michael Passoff, senior strategist for As You Sow, which has filed at ExxonMobil and Ultra Petroleum since 2010. "Concern about water sources, toxic chemicals and wastewater has led to new regulations in several states and proposed federal legislation. Explosions, contamination incidents, and millions of dollars in fines demonstrate that things can and do go wrong."


The lead filers on the resolutions are:
Anadarko-Trillium Asset Management
Chesapeake Energy-Mercy Investment Services
Chevron-Co-led by Green Century and the Sisters of St. Francis of Philadelphia
EOG-Green Century
ExxonMobil-As You Sow
Noble Energy-Green Century
Penn Virginia-Miller/Howard Investments
Range Resources-New York State Common Retirement Fund
Stone Energy-Miller/Howard Investments
Ultra Petroleum-As You Sow