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Potrero Power Plant

Cleanup Areas and Recent Activities

Former Potrero Power Plant | Site Overview | Cleanup Areas & Recent Activities | FAQ | Archive

To expedite the remediation process, we designated seven separate work areas. This allows us to investigate and remediate each area independently, so that while we conduct work in one area, we do not delay or hold back activities aimed at redevelopment in other areas of the Site.

Potrero Site Aerial View (JPG, 175 KB)

We have made significant progress on the environmental investigation and remediation of the site. In 2012, we completed remediation in two of the seven project areas: the PG&E owned Hoe Down Yard, and the Switchyard and Construction Yard Area. PG&E, NRG Potrero, LLC (NRG) and the Water Board are working together to finalize closure documents for the Station A Area, another large area of the site.

This leaves work in four remaining areas: the Northeast Area and a southeast portion of - the adjacent Pier 70 on Port Property (which is considered one area and is shown in green in the Site map above), the Offshore Sediment Area, the Tank Farm and the Power Generation Facility.

Recent Area-by-Area remediation milestones include:


Northeast Area and a Portion of Pier 70 (NRG Potrero, LLC and Port of San Francisco Owned)

This area includes the northeastern corner of the Potrero Power Plant property owned by NRG and a portion of Pier 70 (as illustrated above), which is owned by the Port of San Francisco. An extensive soil and groundwater investigation of the area is now complete.

In December 2012, a Feasibility Study of various cleanup options that provided a recommendation for a preferred cleanup approach, was approved by the Water Board.

The cleanup method approved by the Water Board (Solidification with Limited Excavation) is a well-accepted remediation approach, wherein a portion of MGP residues at the Power Plant property will be solidified in place using a cement mix. This method will address MGP residues in the area that extend deep below the ground surface and are difficult to excavate. Excavation on the Port property will be used to address MGP residues at a shallower depth.

The approved cleanup option also includes the incorporation of a durable cover in both areas where solidified soil is present or MGP residues are present in substantially smaller quantities. The durable cover will prevent exposure to the remaining residues. The durable cover included installing a wear–resistant material (such as paving, buildings, clean soil with vegetation) over the area to contain the soil in place and prevent contact with underground residues.

After implementation of the cleanup, monitoring will be conducted to confirm that groundwater is being protected. Institutional controls will also be used, including a Land Use Covenant (LUC) and a Risk Management Plan (RMP). The RMP will set forth procedures for maintaining the protectiveness of the cleanup efforts, provide safety guidelines for workers to use during future construction and maintenance activities, as well as future site users (based on property owners’ redevelopment plans).

Upcoming activities in the Northeast Area, and the portion of the Port Property will focus on refining the remedial design. In May, we conducted a Pilot Test of the solidification remediation technology in the Northeast Area. As stated above, this technology uses cement with various additives to solidify contaminated soils in-place and minimize its mobility. The Pilot Test helped refine the cement mix formula and confirmed the equipment needed for mixing it into the soil. The in-place solidification of the soil will be both protective of human health and allow for future redevelopment of the property.

Click here to view a Close-Out Report summarizing the work completed as part of the Pilot Test and anticipated next steps for cleanup of the Northeast Area. (PDF, 899 KB)

(Northeast Area)


Offshore Sediment Area

This approximate 16-acre area includes sediments in the San Francisco Bay near the former power plant property and also along the Pier 70 property.

In 2010, PG&E conducted an interim cleanup action along a portion of the shoreline adjacent to the NRG and Pier 70 properties. MGP residues (asphalt-like material) exposed along the shoreline were removed to prevent them from eroding and entering the Bay. With the residues removed, the shoreline was restored and further protected from erosion by placing a specialized fabric layer over the ground surface followed by pieces of stabilizing rock (also known as rip rap).

Four phases of investigation have been performed in the Offshore Sediment Area since 2009. In 2013, PG&E presented a comprehensive report (called the Potrero Offshore Sediment Area Remedial Investigation Report) to the Water Board summarizing the investigation findings. Specifically, the report outlines the potential impacts of the former MGP, former power plant and other industrial operations. Upon approval by the Water Board, the report will be made available for public review.

The results of the investigations indicate the presence of impacts likely to be the result of PG&E's historic operations. The majority of impacts are located close to the shoreline and in some isolated deep sediment areas further from shore (more than 15 feet below the sediment surface). Current data shows that the health of the organisms living in the sediments is not impacted and that a healthy, abundant and diverse benthic community exits offshore.

However, potential exposure of fish to sediment contaminants (through the consumption of sediment organisms) may occur in areas near the shoreline. As a result, the report recommends conducting remediation activities along and near the shoreline, while minimizing any disturbance to the mature, stable benthic community.

In November 2013, PG&E hosted an open house to share the investigation findings and answer questions from community members.

A Feasibility Study and Remedial Action Plan for the area will be finalized next year (2015). The public will be invited to comment on the Feasibility Study by the Water Board in advance of its final approval.

Cleanup design and permitting activities will take place during 2015 and 2016. Active remediation of the area is anticipated to take place in 2017.

(Sediments Study Area)


Switchyard and General Construction Yard Areas (PG&E Owned)

The Switchyard and General Construction Yard remain an integral part of San Francisco's electrical infrastructure. In 2012, the Water Board issued a completion (i.e., No Further Action) letter for environmental work on this portion of the site, indicating that no further remediation work is needed.



Hoe Down Yard (PG&E Owned)

Environmental remediation work for the Hoe Down Yard (a PG&E construction and equipment storage area) has been completed and approved by the Water Board. In 2012, the Water Board issued a completion (i.e., No Further Action) letter for environmental work on this portion of the site, indicating that no further remediation work is needed. The public may see additional work on the property if the ownership and land use of the Hoe Down Yard changes in the future.

(Hoe Down Yard)


Station A Area (NRG Potrero, LLC Owned)

Site investigations are complete and a Human Health Risk Assessment was approved by the Water Board in February 2012. PG&E, NRG and the Water Board are working together to finalize closure documents for the Station A Area. These documents, which include a Risk Management Plan and a Land Use Covenant, will describe the engineering and institutional controls proposed to effectively manage the environmental impacts within the Station A Area. The documents are expected to be available for public review and comment this fall, prior to being finalized by the Water Board.

(Station A)

Power Generation Facility (NRG Potrero, LLC Owned)

This area includes the Unit 3 power plant (which was shut down in 2011) and immediate surroundings. Some soil and groundwater investigations have already been conducted in this area and additional investigations will take place once the former power plant structure has been removed by NRG, the property owner.

(Unit 3)

Tank Farm Area (NRG Potrero, LLC Owned)

This area includes three large above-ground fuel tanks formerly used to house fuel oil. Limited soil and groundwater investigations have been conducted in this area. Additional investigations are anticipated once the above ground tanks are removed by NRG, the property owner.

(Tank Farm)

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