SRI's Envirotechnical Program supported the Federal Aviation Administration (FAA) in development of a new Air Route Surveillance Radar, Model 4 (ARSR-4) to replace an existing outdated radar located at Ajo, Arizona. The original radar was constructed in the 1960s. Since that time, the FAA radar site and nearby lands have been incorporated into the Cabeza-Prieta National Wildlife Refuge, greatly complicating development of the new ARSR-4. The Envirotechnical Program prepared a National Environmental Policy Act (NEPA) environmental assessment analyzing potential environmental effects of construction and operation of the ARSR-4. This effort required delicate negotiations with the U.S. Fish and Wildlife Service (USFWS) to identify measures, such as construction timing, to prevent harm to listed species and a careful analysis under Section 4(f) of the Department of Transportation Act. The NEPA document was well received and approved by the FAA, and the USFWS issued permits to allow construction of the ARSR-4 within the refuge.