San Francisco Redoing its Sewage System
By Morgane Byloos
In San Francisco, rain and sewage flow through more than 1,000 miles of pipes connected to three treatment plants, the largest of which is located on Phelps Street. The Southeast Treatment Plant, built in 1952, cleans roughly 80 percent of the City’s effluent. All in all, about 40 billion gallons of dirty water is processed annually before it’s discharged into the Bay or the Pacific Ocean. The remnants of San Francisco’s eight watersheds—including Islais Creek and Channel—soak up rainwater and runoff that isn’t captured by the human-made system.
The system is stressed by its age, regular flooding, the need for seismic and other retrofits, and climate change. Sixty percent of the pipes are at least 70 years old, with 30 percent roughly 100 years old. According to the San Francisco Public Utilities Commission (SFPUC) a water pipe should last about 50 years. And climate change-related sea level rise is pushing salty water back into the pipes, compromising their durability and shortening their lifespan.
The system is at the early stages of a $2.7 billion makeover, called the Sewer System Improvement Program that’s expected to take upward of 20 years to complete. According to Rachel Kraai, SFPUC planning and regulatory urban watershed specialist, the City has applied “Band-Aid fixes” through the years, but now wants “holistic” upgrades, including addressing upstream issues in ways that take care of downstream challenges.
SFPUC has identified two types of strategies to heal the City’s watersheds: grey and green. Grey infrastructure includes pipes, tunnels, transport and storage structures, pump stations, storm drains and outfalls to the Bay and the Pacific Ocean. Green consists of flow-through planters, porous alleys, green roofs, sidewalk trees and bulb-outs, and cisterns, among other improvements. Gardens—which have been heavily deployed in Portland, Oregon, as part of that city’s renewed system—retain runoff so that it doesn’t flood the streets; porous basketball courts are used in Philadelphia for a similar purpose.
SFPUC started evaluating watershed challenges in 2011, with the goal of launching its construction plan in 2015. The agency is testing green technologies in each of the eight watersheds to evaluate their effectiveness, including at the Mission and Valencia Green Gateway and the Wiggle Neighborhood Green Corridor. Urban Watershed Assessment community workshops are being held to better understand San Franciscans’ green infrastructure preferences.
More than 90 people attended a bayside meeting held last fall. Conveyance pipes, rain gardens, and permeable pavements were some of the most popular options the attendees identified for Islais Creek. Residents were also concerned about disruptions caused by the project, and hoped that the SFPUC would work cooperatively with other City agencies to coordinate construction activities. Kraai said that SFPUC is already engaged in “synergistic projects” with the San Francisco Municipal Transportation Agency and the Department of Public Works.
According to Alex Lantsberg, who holds the Environmental Justice seat on the SFPUC’s Citizens’ Advisory Committee, and who attended the November meeting, the workshops help people understand the water linkages between neighborhoods, as well as how upstream activities affect downstream areas, and vice versa.
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