PROTECTING PARADISE: CMOM COMES TO YOSEMITE NATIONAL PARK

Nearly 4 million visitors enjoy the splendor of Yosemite National Park each year, with over 22,000 visitors on an average day during the peak season. Unseen by these visitors is the infrastructure necessary to support a small city. U.S. National Park Service (Park Service) staff are responsible for the operation and maintenance of approximately 34 miles of wastewater collection system, 3 major sewage lift stations, 4 major grease interceptors, and a 1 million gallon-per-day tertiary wastewater treatment plant serving Yosemite Valley, as well as numerous smaller developed areas outside of the Valley.Park engineering and utilities staff face unique challenges in operating and maintaining this infrastructure. Increased visitation and changing use patterns require Park staff to continually adjust and adapt. Much of the park's sewer infrastructure dates from the 1930's, and funding for large capital projects requires Congressional approval and an extraordinary level of public review. Maintenance and repair schedules are hampered by access during the peak tourist season and by weather during much of the remainder of the year. Many of the park concessionaire employees are seasonal, and require re-education on proper system use (i.e grease management) each year. Visitors often misuse park restrooms for garbage disposal. Over-riding all of these engineering, administrative, and operational concerns are the consequences of a significant sanitary sewer overflow (SSO) discharging to the Merced River – a designated National Wild and Scenic River.A catastrophic flood in January 1997 highlighted the vulnerabilities of the sewer infrastructure. Several critical elements of the collection system and interceptor from Yosemite Valley to the El Portal Wastewater Treatment Facility were destroyed. Park Service staff responded with a fast-track designbuild project that replaced the damaged pipelines, and began a concerted effort to upgrade the entire collection system. Concurrently, the Park Service has adopted the Merced Wild and Scenic River Plan and the Yosemite Valley Plan to guide future land use decisions in the Valley.In the past year, the Park Service has launched a comprehensive and systematic program to mitigate factors that might result in a sewage discharge to the Merced River. The program addresses capacity, management, operations and maintenance of the Yosemite Valley and El Portal wastewater collection systems. This aggressive program encompasses four main elements: condition and capacity assessments; spill prevention and response planning; pre-treatment, including grease and garbage management; and public education.A review of specific program elements and lessons learned in addressing the unique challenges of the national park environment provides a strong foundation for compliance with pending federal and state SSO regulations.