U.S. EPA has released revised guidance materials on the use of diesel fuel in hydraulic fracturing activities. "EPA is issuing the guidance alongside an interpretive memorandum, which clarifies that class II UIC requirements apply to hydraulic fracturing activities using diesel fuels, and defines the statutory term diesel fuel by reference to five chemical abstract services registry numbers. The guidance outlines for EPA permit writers, where EPA is the permitting authority, existing class II requirements for diesel fuels used for hydraulic fracturing wells, and technical recommendations for permitting those wells consistently with these requirements." (EPA News Release)
For a copy of the guidance document itself, see here.