Former Potrero Power Plant Site Remediation

WELCOMEPG&E Community Open House

Offshore Sediment Area Investigation Findings

November 20, 2013

Former Potrero Power Plant Site Remediation

Former Potrero Power Plant Site

Photo taken: March 2012.

Former Potrero Power Plant Site Remediation

GA

S

RESIDENCES

STREET LAMPS

BUSINESSES

MANUFACTURINGPROCESS

GAS HOLDER

COAL OR OIL

What is a Manufactured Gas Plant (MGP)?

Former Potrero Power Plant Site Remediation

Goals

Fulfill our commitment to address impacts from historic MGP and power plant operations.

Protect human health and the environment.

Work collaboratively with stakeholders and the community.

Protect the safety of the community and site workers.

Allow for the productive re-use of the site.

Former Potrero Power Plant Site Remediation

Timeline-Sediment Remediation

1990

20002010

1995

20052015

202019

9620

0619

9120

0120

1120

1619

9720

0719

9220

0220

1220

1719

9820

0819

9320

0320

1320

1819

9920

0919

9420

0420

1420

19

1990–PresentEnvironmental Investigations. Site Wide Soil and Groundwater Sampling.

2014–2015Offshore Sediment Remedial Action Plan Process

2013–2014Offshore Sediment Feasibility Study Process (including public participation process)

2015–2016Offshore Sediment Cleanup Design

2014–2016Offshore Sediment Permitting

2009–2013Offshore Sediment Remedial Investigations and Survey

2016Off-shore Sediment Construction and Field Work

Former Potrero Power Plant Site Remediation

1870

1920

1970

1880

1930

1980

1890

1940

1990

1900

1950

200019

1019

602015

2010

Timeline-Operations

1999PG&E sells Potrero Power Plant to Southern Company.

1870s–1930sAn MGP operated on Potrero Property.

1910s–1970sPG&E operates Potrero Power Plant Station A (Units 1 and 2).

1965–1999PG&E operates Potrero Power Plant Unit 3.

PG&E

March 2011Potrero Power Plant shuts down.

NRG

1999–2013Southern Co. (subsequently, Mirant Corp., then GenOn and now NRG Potrero, LLC) owns Potrero Power Plant Unit 3.

2007–2010Trans Bay Cable Project completed.

Former Potrero Power Plant Site Remediation

Project Site

Approximate boundaries shown. Map not to scale.

23RD ST.

22ND ST.

ILLINO

IS ST.

3RD

ST.

TEN

NE

SSEE

ST.

OFFSHORE INVESTIGATION AREA

280

PG&E-Owned Properties NRG Potrero, LLC Owned Properties Port of San Francisco Property Impacted by Historical MGP Activities

N

Port Property

Station A

Tank Farm

Switchyard/Construction Yard Northeast

Area

Hoe Down Yard

Former Power Generation Facility

Approx. 500 ft.

Former Potrero Power Plant Site Remediation

Offshore Sediment Remedial Investigation Report

• Summarizes findings of four phases of investigations

• Characterizes impacts of former MGP, power plant and other industrial activities

• Identifies areas that may require remediation

• Investigations included the following:−− 88 surface sediment samples

−− 64 sediment cores

−− 96 profiles using advanced TarGOST technology

−− 50 sediment profile imaging stations

−− 10 benthic community evaluation stations

−− 27 bioaccumulation stations

−− 9 stations for sedimentation rate evaluation

−− Survey of depth to sediment surface

Extensive sampling was conducted during four phases of sediment investigations.

Former Potrero Power Plant Site Remediation

A Typical Healthy Marine Ecosystem

• Benthic organisms include a variety of invertebrates that live on or in underwater sediments

• They serve as an important food source for bottom-feeding fish and some birds

• The presence of an abundant and diverse benthic community is one sign of a healthy marine ecosystem

For illustrative purposes only. Image not to scale.

Water

Healthy Benthic Community

Oxidized Sediment

Former Potrero Power Plant Site Remediation

Offshore Sediment Remedial Investigation Report Findings

• Majority of impacts located close to shoreline and in some isolated, deep sediment areas further from shore (more than 15 feet below sediment surface)

• No current human health risk

• No toxicity to sediment organisms; bioaccumulation occurring in some areas

• Healthy, abundant and diverse benthic community currently exists

In the absence of chemical or physical disturbance, benthic organisms burrow into soft sediment, feeding on bacteria and oxidizing the sediment, providing a better habitat for a diversity of organisms, such as the sea pens so abundant in the Potrero offshore sediments.

For illustrative purposes. Images not to scale.

Healthier Benthic CommunityLess-Healthy Benthic Community Abundant Sea Pens in Offshore Sediments

Oxidized Sediment

Oxidized Sediment

Un-oxidized Sediment

Un-oxidized Sediment

Water Water

Former Potrero Power Plant Site Remediation

Remedial Investigation Report Recommendations

Port Property

Station A

Tank FarmNortheastArea

NRG Potrero, LLC Owned Properties

Port of San Francisco Property Impacted by Historical MGP Activities

Areas of Benthic Organism Bioaccumulation Above Ambient Conditions

Shoreline and Nearshore Areas Where Impacts Will be Addressed

Approximate boundaries shown. Map not to scale.

Former Power Generation Facility

N

• Remove impacts in the shoreline and nearshore area

• Reduce potential for bioaccumulation in benthic organisms where it is above ambient bioaccumulation levels

• Minimize disturbance to the remainder of the benthic community

• These recommendations are supported by state and federal regulatory oversight agencies

OFFSHORE INVESTIGATION AREA

280