League of Wilderness Defenders and other environmental groups (LWD) challenged a United States Forest Service (USFS) aerial pesticide spraying program, alleging that USFS failed to obtain a National Pollution Discharge Elimination System (NPDES) permit and prepared an inadequate Environmental Impact Statement (EIS) under the National Environmental Policy Act (NEPA). The district court granted summary judgment for USFS, and LWD appealed. Upon review the Ninth Circuit reversed and remanded to the district court to enjoin USFS from aerial pesticides spraying until it obtained a NPDES permit and conducted an adequate EIS.
In the 1970s an outbreak of the Douglas fir tussock moth (Orgyia pseudotsugata) ravaged hundreds of thousands of acres throughout Oregon, Washington, and Idaho. Fearing that another outbreak would cause further damage to forests, USFS created a warning system to predict outbreaks and a pesticide spraying program to limit resulting damage. Such an outbreak was predicted for 2000-2002, and USFS began aerial pesticide spraying.
LWD first challenged USFS's spraying program for failure to obtain a NPDES permit. Under the Clean Water Act (CWA), an agency must get a permit before discharging any pollutant into navigable waters from any point source. A point source is defined as "any discernable, confined and discrete conveyance, including but not limited to any . . . floating craft from which pollutants are or may be discharged." USFS, stipulating that the insecticide qualifies as a pollutant, argued that aerial forest spraying to control pests is not a point source as defined by federal regulation. USFS claimed that under 40 C.F.R. section 122.27, aerial spraying did not qualify as a point source because "[s]ilvicultural point source . . . does not include non-point source silvicultural activities such as . . . pest and fire control . . . ." The Ninth Circuit rejected this argument, holding that an airplane spraying pesticide is clearly a point source under the CWA definition. The court stated that when the intent of Congress is clear in an act, an agency cannot circumvent that intent through interpretation of administrative regulations. Further, the court found that the language of the administrative regulation indicated that nonpoint sources were those "from which there is natural runoff," and the regulation was not intended to apply to pest control spraying that directly discharges pollutants over waterways. USFS also argued that the listing of four particular point sources in the regulation excluded any other activity from being defined as a point source. However, the Ninth Circuit found that a contextual reading of the statute indicated those activities were listed to clarify that they remained subject to NPDES requirements, not to exclude other activities from being defined as a point source. The Ninth Circuit also found uncompelling two Environmental Protection Agency (EPA) letters and a guidance document offered by USFS as evidence supporting its interpretation of the regulation because the clarity of legislative intent in the CWA closed the door on USFS or EPA authority to interpret the regulation differently. The Ninth Circuit reversed the district court, requiring USFS to obtain a NPDES permit before undertaking any further aerial spraying.
On appeal, LWD also challenged USFS's spraying program for failure to prepare an adequate EIS. Under NEPA, an EIS must be prepared for any major federal action that significantly affects the environment. Although USFS did prepare an EIS, LWD argued it was insufficient because it did not adequately consider the drift of pesticides outside the spraying area. In response, USFS reasoned that because the EIS accounted for drift with mitigation measures--such as a one-mile buffer between the target area and wilderness areas and wind speed requirements for spraying--it was sufficient. The Ninth Circuit held that the mitigation measures did not substitute for a consideration of the impact of inevitable drift of pesticides into areas not designated wilderness or for a showing of the distance the pesticide could drift. Thus, the Ninth Circuit remanded the issue to the district court with instructions to enjoin the program until USFS obtains a NPDES permit and completes a new EIS.
 League of Wilderness Defenders/Blue Mountains Biodiversity Project v. Forsgren, 309 F.3d 1181, 1185-86 (9th Cir. 2002) (applying Chevron U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837 (1984)).