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Presidio Journal

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Mountain Lake: A Restored Natural Jewel

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History, Tour Presidio

If you had visited Mountain Lake 20 years ago, you would have been underwhelmed. This small urban lake at the southern tip of the Presidio was severely polluted and choked with algae. Resident bird and fish populations were dying off. It was a sad state of affairs for one of the most important natural and historical sites in the city.

Today, after a decade of careful remediation and restoration, Mountain Lake is once again a haven for native wildlife, a resting stop for migrating birds, and a lovely spot for San Franciscans and visitors to enjoy the beauty and history of the city.

Mountain Lake is one of a very few remaining natural lakes in San Francisco and the only natural lake located in the Golden Gate National Recreation Area. For thousands of years before the arrival of Europeans, Mountain Lake provided fresh water and many other resources for the native Ohlone. They built houses and boats from the tule reeds growing on the shoreline. When Captain Juan Bautista de Anza arrived with his Spanish soldiers in 1776, they camped by Mountain Lake while deciding where to build their new military outpost (presidio).

In the 1930s, construction of Highway 1 nearby dumped tons of sediment into the water. Water running off the highway and the Presidio Golf Course brought in toxic pollutants, fertilizers, and pesticides. Local residents dropped off their unwanted pet fish, turtles – even an alligator – which multiplied and crowded out native species.

Reversing the damage and restoring the ecosystem

Starting in 2013, the Presidio Trust started dredging the lake to remove contaminated soil. This massive 2-year effort removed nearly 17 tons of potentially toxic sediments from the lake. Systems to catch potentially toxic runoff from the nearby road and golf course were installed to ensure that the water will stay clean.

Along with the lake bed remediation, invasive species had to be cleared out. Teams of scientists, graduate students, and volunteers helped catch non-native carp, crayfish, large-mouthed bass, and turtles.

Once the lake was clean and safe from non-native predators, scientists planted carefully chosen native aquatic plants to establish safe habitats and food at the base of the ecosystem. Starting in 2015, native species of freshwater mussels, fish, frogs, newts and turtles are being reintroduced. Each step of the restoration plan is carefully calibrated to build a thriving natural ecosystem that has not been seen here since the last century. The effort to restore Mountain Lake is providing lessons for habitat restoration in urban environments that will guide similar efforts in cities around the globe.

Mountain Lake today

Mountain Lake and the parklands around it are a treasured favorite of Richmond neighborhood residents. Birders come here to spot native and migratory bird species. Locals visit to picnic, jog, walk their dogs, and play with their kids at the new playground. Hiking trails connect Mountain Lake to the network of trails throughout the Presidio and the GGNRA. It is about 1.5 miles away from the Inn at the Presidio via the Mountain Lake trail.