February 17, 2005

Potrero Hill’s Hidden Streams

By Alison Fromme
Special to the Neighborhood Newswire

“Once in southeastern San Francisco [there were] bodies of water that have as completely disappeared as has mythical Atlantis… Unlike Atlantis, submerged in water by a cataclysm of nature, these waters have been smothered in earth debris deposited in them by the hand of man.”
--William Crittenden Sharpsteen, California Historical Society Quarterly, Vol. XXI, No. 2, June 1941.

Water flowing down Potrero Hill follows the path of least resistance: around rocks, through gardens, via sewers, and — in some cases — under houses. When resident Don Stannard-Friel bought his house on the 200-block of Connecticut Street, a seasonal creek ran straight through the basement.

“The stream was about the diameter of a fire hose,” he said. Water entered through a hole in the wall, traveled through a concrete gutter, and exited another hole. Today, Stannard-Friel has opted for a closed system of pipes to channel the water, thereby keeping the basement drier, and allowing for better use of space. Luckily, his “family of plumbers” helped with the project, saving him several thousand dollars.

Throughout Potrero Hill, like most San Francisco neighborhoods, water seeps into basements, out of cliff-sides, and over sidewalks. Although Stannard-Friel’s basement stream is a live concern, water flowed through the property long before the house was built in 1919.

Throughout the 19th century, San Francisco’s coastline was molded and extended, creeks were filled in and built over, and water found new routes to the bay. Prior to intensive human habitation, water nearly surrounded Potrero Hill and Potrero Point. Mission Creek wound its way past the west and north sides of the hill, while Islais, Precita, and Pollywog creeks bordered the south side. Marshes encircled the waterways for hundreds of feet.

Today, it’s difficult to imagine that Jackson Park’s playground and ball fields were home to a 30-foot-wide pond surrounded by wetlands, where the late resident Julius Salvotti collected watercress for his mother in the early 1900s. Likewise, automobile traffic through the intersection of Cesar Chavez and Vermont doesn’t evoke the creek that used to flow there, although PVC pipe lining the ditches of a construction project suggests that water still lurks somewhere nearby. The families who will soon move into this new development may scarcely believe that their predecessors played in open waterways.

“We used to build rafts out of the leftover lumber from the mills and use sticks to push ourselves down the creeks,” said resident Peter Luskatoff. For a boy in the 1930s and ‘40s, swimming in the bay and looking for tadpoles in the aptly named Pollywog Creek down by the train tunnel at Texas and Sierra streets provided endless entertainment.

“When it rained, it was a raging creek,” said Jack Wickert who grew up on the hill in the 1940s. Building small makeshift dams and sloshing around in the water were regular pastimes. He recalls that the creek even froze over during one cold snap, and he slid across it as if he were on ice skates.

Historically, natural waterways drained the land. Culverts today serve the same function, but constraining water in concrete deprives local vegetation — such as maples, redwoods, and willows — of water and sometimes actually inhibits proper drainage.
If current residents want to try to mitigate such problems by, for example, building culverts on their property, they must first get approval from the State Water Resources Control Board to ensure that the changes don’t cause more problems for erosion, wildlife, or downstream residents.

Basement leaks and cliff-side seepage have made some residents wonder if underground streams are hiding below Potrero Hill. But that idea is misleading, according to Karen Grove, San Francisco State University geology professor and former Potrero Hill resident.

Geologically, the hill stands out from neighboring areas as a sturdy, 300-foot-tall lump of greenish serpentine rock. During its formation millions of years ago, cracks spread through it, creating small spaces where water collects today. The water doesn’t flow like a river through the cracks, but it follows the fractures and comes out the cliffs, according to Grove.

Seepage isn’t a sign of weakened serpentine, but it is a reminder that water flows underground as well as on the surface. In the early 1900s, residents tapped into groundwater for industrial and home use with wells that pumped more than 250,000 gallons of water per day in and around the hill, according to a Department of Public Works report.

“People forget where they are with respect to topography,” said Grove. Development masks the hill’s contours that would otherwise reveal where water naturally flows. But by looking at a topographic map, the small valleys that are likely to funnel surface runoff become apparent. Potrero Hill is roughly “Y” –shaped, and water, pulled by gravity, flows between the ridges.

Satellite photos of the hill reveal lush backyards in the valleys compared with neighboring ridges, said Christopher Richard, curator of aquatic biology at the Oakland Museum of California. This plant growth indicates that water is still winding its way down the hill north to Jackson Park, east to Potrero del Sol Park, and south down Connecticut to Cesar Chavez.

“We pretend we’ve overpowered Mother Nature,” said Grove, explaining that paving over streams and building houses in the path of seasonal water flows doesn’t get rid of the water. “The water will come out someplace.”

Apparently, Stannard-Friel’s basement is one of those places.