(October 7, 2019, 12:22 PM EDT) -- DENVER — Hydraulic fracturing companies on Sept. 20 filed a brief in Colorado federal court intervening in a lawsuit filed by environmental advocacy groups against the U.S. Bureau of Land Management (BLM) in which the groups contend that the agency violated federal law when it approved fracking permits in the Bull Mountain area of Colorado. The intervenors maintain that the BLM complied with federal law (Citizens for a Healthy Community, et al. v. United States Bureau of Land Management, et al., No. 17-2519, D. Colo.)....