Under the Clean Water Act, mining projects that result in the discharge of soil or other pollutants into navigable waters must comply with state 'water quality standards.' Mining projects that result in the discharge of soil and other pollutants into navigable waters require two Clean Water Act permits. Section 404 permits ensure that the discharge of dredged or fill material as a result of the mining project will not harm navigable waters. The Army Corps of Engineers issues those permits, but the EPA may deny the use of an area as a disposal site if a discharge at that site would 'have an unacceptable adverse effect' on certain water bodies, wildlife, or recreational areas. Section 402 permits - known also as National Pollutant Discharge Elimination System or NPDES permits - ensure that mining projects do not result in any other pollutants damaging States' water bodies. States decide whether to issue those permits, but EPA may object if the permit would not meet state water quality standards or other requirements of the Clean Water Act. The EPA and the Army Corps of Engineers agreed to an Enhanced Coordination Process where the EPA must run the applications through a database that compares the information in the permit application to the guidelines the Corps must consider when issuing permits. EPA identifies permits that could run afoul of the guidelines and notifies the Corps. Over 60 days, subject to extensions, EPA and the Corps, along with any interested parties, then discuss those permit applications. The Corps then decides whether to issue the permits. EPA also issued a Final Guidance document related to, Section 402 permits. The Final Guidance explained that recent peer-reviewed studies had found that surface coal mining raises the salinity of States' waters. The Final Guidance advises EPA staff to ask state permitting authorities to assess the potential for elevated conductivity in proposed Section 402 permits. For the Appalachian region, the Final Guidance recommends that water conductivity levels not exceed 300-500 µS/cm (microSiemens per centimeter). The States of West Virginia and later Kentucky, along with coal mining companies and trade associations (Ps) challenged the Enhanced Coordination Process and EPA's Final Guidance as exceeding EPA's authority under the Surface Mining Control and Reclamation Act and the Clean Water Act. The court granted summary judgment for Ps. McCarthy (D) appealed.