San Francisco is planning to upgrade its sewers to the tune of $4 billion. In the process it will restore a little freedom to some creeks that were covered in an effort to create as much housing as possible during the years after the Gold Rush. In some cases, people didn’t even know the creeks were there—until all that water under the buildings caused flooding.

In most cases, these creeks were diverted into the sewage system, so when water levels rose too high they overwhelmed the sewer system and pushed sewage into San Francisco Bay.

Such “daylighting” of urban creeks is being embraced in cities throughout the world. Seattle, Portland, Oregon, Yonkers, New York, Providence, Rhode Island, as well as Zurich are among many places reopening long hidden waterways. Resurrecting old creeks can help remove hundreds of millions of gallons (liters) of storm water from sewer systems each year—meaning fewer sewage spills and cleaner water.

Covered up during and after the Gold Rush when the city’s booming population created demand for housing, San Francisco’s many creeks were diverted and sent underground into the sewer system—parts of it still utilizing 1850s-era brick pipes. The water is mixed with the waste and sent to a treatment plant before being expelled into San Francisco Bay or the Pacific Ocean.

Right now these projects are still in the planning phase, with work possibly beginning in 5 to 10 years.

Islais Creek, which starts in the city’s Glen Park neighborhood, and Mission Creek, which runs beneath the trendy Mission and South of Market districts, are likely the first candidates.

Both creeks flow toward the bay through densely packed neighborhoods, which could expose the water to pollutants such as auto runoff and garbage.

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Still, regulators say with proper monitoring and natural filters, opening the creeks can actually improve overall water quality by reducing raw sewage overflows.

How Is This Restoration?

Aside from the fact that the projects won’t begin work for years—possibly never, if California’s budget crisis continues, though sewers are a pretty essential service—this kind of recovery of waterways is the beginning stage of restoration. I doubt that city officials plan to liberate the entire length of these creeks or to restore them to anything resembling their original condition. But free-flowing water flowing through a riparian area that filtered pollutants is much better than a creek under concrete.

Source: “Plans Percolate to Revive Some U.S. Native Creeks,” by Jason Dearen, Associated Press, April 27, 2010