PG&E Proposes Potrero Power Plant Remediation Strategy to Water Board
Pacific Gas and Electric Company (PG&E) held an open house at Dogpatch CafО last month to brief community members on its proposed environmental remediation plan for the Potrero Power Plant site. The investor-owned utility intends to submit the latest version of its preferred clean-up option to the San Francisco Regional Water Quality Control Board this month, which will make the final decision as to which remediation approach is adopted.
PG&E’s preferred option consists principally of solidifying the contaminants in the ground, using augers and a cement-type mixture to eventually form a cement block. In addition, contaminants would be excavated from a portion of the property, and a durable cover would be placed over the entire site, which includes a part of Pier 70 and the northeast section of the power plant property.
According to Mark Johnson, an engineering geologist with the Water Board, the public can comment on PG&E’s proposal this month and next. He said the Water Board will distribute fact sheets about the option chosen, which will include links to PG&E’s entire proposal. The Water Board will also host community meetings to allow residents to share their concerns. “We'll hear what others have to say. And it changes things,” Johnson said. “We do modify things because of the public's comments.”
In addition to its preferred option, PG&E considered other approaches, such as excavation-only, solidification-only, extraction-only, and a barrier wall. But the utility asserts that its proposal is the safest and most environmentally sustainable, eliminating most of the contaminants and allowing for future development. According to PG&E, extraction would remove only half the pollutants, possibly limit future development, necessitate ongoing maintenance, and require more than 10 years of pumping. An excavation-only strategy would require 8,800 trucks to travel through the neighborhood. According to Johnson, the process is technically challenging, with the possibility of the Bay being contaminated if a mistake is made.
Under PG&E’s proposal most of the affected property would be solidified, though one area would be excavated to a depth of roughly 20 feet — rather than 45 to 55 feet — because solidifying that area would be “difficult to implement around existing subsurface structures on Port property,” according to information conveyed at the meeting. Using a barrier wall as the only option would require future maintenance and may limit development, according to PG&E. Zeynep Ungun, PG&E's project manager, said the soil in the impacted area has a consistency “like molasses. It's not feasible to extract all of it by pumping.”
The Potrero Hill Power Plant — which was purchased by a company now called “GenOn” in 1999 — stopped generating electricity in 2011. PG&E is responsible for cleaning up operations that occurred during its ownership, which stretches back to the 19th century. From the 1870s until the 1930s, the company used oil and coal to manufacture gas to fuel businesses, homes, and gas lamps around San Francisco; hence the name “gas light district.” Pollutants created during this period will be the principal focus of PG&E’s remediation efforts.
According to Carol Bach, Port of San Francisco’s environmental manager, the site is contaminated, but PG&E is “…taking a very thorough approach” to remediation.
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