As the California legislature returned from its month-long recess Monday, the backers of a bill (AB 591) to mandate chemical disclosures on hydraulic fracturing (fracking) fluid held a press conference at the state Capitol in Sacramento, releasing the signatures of "roughly 50,000" voters supporting the measure.

Contending that information on the fracking process is "badly lacking," AB 591 author Assemblyman Bob Wieckowski sought to pressure the state and regional oil and gas producers' associations that are still opposed to the measure. The bill went to the Senate Appropriations Committee but is not expected to be voted on until Aug. 26, according to Wieckowski's spokesperson.

Wieckowski was joined by two leaders in the lower house Assembly and several environmental groups: the Environmental Working Group, California League of Conservation Voters, Clean Water Action, Natural Resources Defense Council and the Environmental Defense Fund.

AB 591, according to supporters, will ensure that the state Division of Oil, Gas and Geothermal Resources gathers what they contend is important information on the chemicals used, along with the volume and source of water, in the fracking process. They are calling the bill a "landmark" piece of legislation.

Wieckowski's spokesperson said the use of fracking has become controversial this year because of "the possibility of contamination to water supplies." He said the final committee decision on the measure in the Senate will come next week.

Saying it is time to "pull back the curtain and shed more light on fracking," Wieckowski said roughly 50,000 Californians have now signed online petitions expressing their support for his bill.