We're big fans of the Presidio and Crissy Field here at Curbed SF. Welcome to In the Presidio, a weekly series covering what's going on at what may be the country's most far-ranging and complex examples of adaptive re-use.
Poor Mountain Lake. The first Spanish campsite in the Presidio– back in the days when it was coastal meadow– it would become the source of San Francisco's water in the 19th Century. The 2,000-year-old spring-fed body of water has fallen on hard times since, mostly due to toxic runoff from Route 1, the WPA-era highway project connecting to the Golden Gate Bridge which also reduced the lake by 40%. Across the lake is the Army's 1897 golf course, contributing a century of fertilizer runoff. Fouled by pollution, overrun with non-native species, and now only nine feet deep instead of its historic 27 feet, the Presidio Trust will start dredging this fall to restore the lake as habitat, a $5.5M effort twelve years in the planning and paid for by Caltrans. For next year they've planned restoration of the small marsh at the eastern end, paid for by SFO in exchange for those longer runways. In the meantime, the Trust is evacuating the current residents (fish included) to the Sonoma County Reptile Rescue, which will relocate them to vineyard ponds and private lakes.
We had a chat with the Trust's Ecological Restoration intern Jon Young, a biology graduate student rescuing the current denizens, who explained that along with getting filled in and polluted by runoff, Mountain Lake has been damaged by smaller human interventions. The lake was stocked with bass for sports fisherman, and decades of pet shop turtles were released there, no doubt by well-meaning parents who wanted to return them to the wild– critters whose natural life span is sixty years and adult length is ten inches. The fishermen used crayfish for bait, and apparently enough jumped their hooks to breed into a sizable population. Along with fouling the water, crayfish eat tadpoles, which, along with eucalyptus crowding the shore and the decline of the marsh, is why the native California Red-Legged Frog has disappeared there. The native Western Pond turtles have been replaced by the more aggressive Red-Eared Slider Turtle (the pet shop turtle of choice) plus there are those pet shop goldfish which turned out to be koi and have grown to almost three feet long.
Frankly, looking at the lake, you can't help but admire the residents' ability to survive in such a bad neighborhood, although they'll probably love their new digs up north. Dredging starts in August, and the Route 1 shore will eventually get a bioswale to moderate the highway's runoff. The project has nothing to do with Mountain Lake Park, the adjacent city-run park.
· Mountain Lake Remediation & Restoration [The Presidio Trust]
· Sonoma County Reptile Rescue [SCRR]