Oso Creek Trail began in April 1997 as a community collaboration in Mission Viejo, where volunteers gather in late spring to celebrate the Earth and the arts. Set along the riparian corridor of Oso Creek Valley, it connects residences to city facilities, the commercial core, and surrounding neighborhoods, and reflects community and city efforts to create a backbone trail system for long-term public benefit. The trail includes amenities and features intended to educate and honor the community, including the Peace Obelisk honoring victims of 9/11, the mosaic history walls in the Character Garden, painted butterflies, the Celebration Garden, the Wave Wall on the Upper Oso Creek Trail, and murals around the Village Green. As a walking garden, it exposes users to local plant and animal life and to the workings of the local ecosystem. Oso Creek flows from north of the Santa Ana Mountains, joins Trabuco Creek, and ultimately reaches the Pacific Ocean. The valley also yielded rare fossils preserved by the Mission Viejo Company, including baleen and toothed whales, long-snouted dolphins, primitive sea lions, sharks, rays, and bony fish. After creek grading was completed, the channel was engineered to carry increased storm water, and reclaimed water lines were installed along the eastern side to move recycled water from the Upper Oso Reservoir to residential areas for landscape beautification. The creek edge was replanted with indigenous riparian species including coyote bush, mulefat, Mexican elderberry, toyon, and willows, and over time natural change in vegetation has helped bring wildlife back to the creek edge, including house finch, song sparrow, goldfinch, Costa's hummingbird, turtles, great blue herons, and great egrets. The trail was created with both riparian and drought-tolerant plant material sustained with minimal irrigation, with over 60 plant varieties contributing to its walking garden. Significant trees along the trail include the California sycamore, the coast live oak, and the olive tree. Oso Creek is the main route through which water travels in most of Mission Viejo within the 133.9-square-mile San Juan Creek watershed, which extends from the Santa Ana Mountains to Doheny State Beach. Water moving through this watershed travels by streets, pipes, creeks, and rivers to the ocean. Once dry through most of the year, Oso Creek now flows year-round largely because of human activities such as over-irrigation and residential car washing, and that water can carry pollutants including pet waste, litter, bacteria, fertilizer, and pesticides untreated through storm drains to the ocean. In the late 1970s, the Oso Creek Barrier and Return Water Pump Station was installed just north of Oso Parkway to capture dry-weather flow, send it to the Upper Oso Reservoir for storage, and later reuse it mostly to irrigate city-owned landscaped areas; currently, over 70% of Mission Viejo's landscaped areas are irrigated with reclaimed water.