Dam outfall before removal. Photo: California Water Audit
York Creek Uncorked
Mar 30, 2021 at 2:20pm
Over the summer, while most of the Bay Area was figuring out how to navigate the COVID-induced shelter-in-place orders, 1,933 heavy truckloads laden with 22,000 yards of material wound their way away from Napa County’s York Creek, and were dumped into two nearby landfills. Extracting these spoils was the last step in the York Creek Dam removal project, the culmination of decades of effort by the city of St. Helena to take down a small earthen dam with a big ecological impact. The dam blocked fish from spawning in the creek’s 4.4-square-mile-watershed.
Though the project seemed straightforward, no one involved in its conception could have imagined the convoluted path to its completion forty years later, nor just how difficult and expensive it would turn out to be for a small city to tackle a heavily regulated dam removal project and watershed.
The former dam site is to the southwest of Spring Mountain Road, which tightly wends its way up a grape growing valley snuggled in the Mayacamas Mountains. The descent of the creek is steep and fast — at its head its banks are lined by a cool redwood-dominant mixed evergreen forest, which, by the time it arrives at the elevation of the dam site, becomes more of a transitional chaparral forest that smells like summer where the sun hits the manzanita. What’s as notable as the soft gurgle of the creek washing its way through the dam site on the way downstream, is that most of the watershed is still heavily singed as a result of the Glass Fire last fall, which consumed 67,484 acres in Napa County. All along Spring Mountain Road, piles of burnt logs and other debris are stacked along the guardrails. At the dam removal site itself, bright green willow shoots are popping out of black, scorched earth.
Today, York Creek flows freely from its headwaters in the hills above the Napa River, which the creek feeds. The dam site is about two-and-a-half-miles upstream from that confluence and was first constructed in 1900 to create a reservoir for residents of St. Helena and the surrounding vineyards. Amber Manfree, a Napa Valley native and geographer, remembers as a kid in the 1980s that the reservoir still kind of looked like a reservoir.
By the time the dam was removed in 2020, a forest of alder, willow, and invasive ivy had grown in the sediment infill behind the barrier, rendering it useless for water storage. There are hundreds of obsolete, small dams just like York Creek’s scattered across California’s watersheds. These aging dams show the same issues — they no longer provide water supply, they trap increasingly scarce sediment upstream, and they obstruct fish passage to spawning grounds.