Presentation to the Lahontan Regional Water Quality Control Board June 8, 2011 Project Update Groundwater Remediation Project Hinkley Gas Compressor Station

Feasibility study for comprehensive final groundwater cleanup plan Progress of current remedial actions and containment activities PG&E’s bottled drinking water program and other community initiatives Our Presentation 2

Protect human health and the environment Contain and clean up the plume Apply green and sustainable practices Enhance and restore beneficial use of groundwater Create opportunities for beneficial reuse of land Contribute to economic vitality of the community Goals for Hinkley Site 3

Submitted to Water Board August 2010 Over 60 remedial technologies evaluated: In-situ reactive zones (multiple configurations) Agricultural land treatment units Pump and treat (multiple technologies) Infiltration galleries Direct push amendment delivery Freshwater injection Review of on-site pilot studies is included Alternatives assembled for detailed analysis 4 Feasibility Study of Cleanup Options Alternatives assembled from array of proven effective technologies

Evaluation of Remedial Alternatives Range of options considered and estimated years to completion Alternative 50 ppb MCL 80% Mass Removal 3.1 ppb Background 4B Aggressive in-situ treatment and beneficial agricultural use with targeted pumping A Aggressive in-situ treatment and beneficial agricultural use Combined alternative Plume-wide pump and treat Core in-situ treatment and beneficial agricultural use Plume-wide in-situ treatment Containment No action 750 – 1000>780>1000 5

Conceptual Plan of Final Remedy Multiple remedial components target specific areas of plume Fresh Water Injection In-situ Treatment In-situ Treatment Agriculture Area Containment Extraction Fresh Water Injection 6 Agricultural Treatment In-situ Treatment

Cleanup Under Proposed Remedy (4B): In-Situ Treatment and Beneficial Agricultural Use Core plume remediated in 6 years; only traces left after 20 years Computer generated estimates of 10-year and 20-year results 7 Initial Chromium Concentrations After 10 Years of Remediation After 20 Years of Remediation

Achieves plume containment Provides rapid remediation of plume core Offers beneficial land and aquifer use for farming Promotes a “green” / sustainable remedial approach Improves legacy nitrate issues Benefits of Final Remedy Concept Technically sound remediation plus multiple local / regional benefits 8

Primary public questions: Did the Feasibility Study consider enough technologies?  Yes. 60 technologies were evaluated, including use of a treatment plant and resins as in municipal facilities  DTSC stated in their review: “DTSC agrees that Table 6-1 and 6-2 of the FS provided a reasonable list of processes and technologies available for the remediation of groundwater contaminated with hexavalent chromium. We believe that the ‘best available technology’ for remediation of the site would likely be a combination of the processes and treatment parameters presented in the two FS addenda.” March 9, 2011 Public Comments 9

Primary public questions: Do agricultural units allow plume escape during winter months?  No. Pumping rates vary by season but net direction of groundwater flow is toward extraction wells all year 10 March 9, 2011 Public Comments Groundwater typically flows about 300 feet toward extraction wells during spring, summer and fall pumping The net annual movement of groundwater is about 200 feet toward extraction wells Groundwater may flow 100 feet away from extraction wells during winter pumping Is chromium conversion in soil permanent?  Chromium-6 converts to chromium-3, binds to the existing soil, and then becomes the same as natural chromium-3

Additional DTSC suggestions include: Update computer model runs to current plume Allow flexibility for future plume understanding Provide additional level of cost details Provide particle track analysis in addition to current fate and transport model Review issues surrounding seasonality of pumping, and develop contingency plans should capture be inadequate Document permanence of chromium conversion in soil 11 DTSC Review of Feasibility Study We will work with the Water Board to address reviewer suggestions

“DTSC also recommends consideration of focus areas for remediation goals and strategy” Diffuse plume strategy: Immediately contain, and treat via extraction Plume core strategy: Immediately cut off continuing source to diffuse plume, and treat in place for maximum speed 12 Plume Core South of Hwy 58, chromium concentrations are above 50 ppb Plume Core South of Hwy 58, chromium concentrations are above 50 ppb Diffuse Plume North of Hwy 58, chromium concentrations are below 50 ppb Diffuse Plume North of Hwy 58, chromium concentrations are below 50 ppb

Feasibility study for comprehensive final groundwater cleanup plan Progress of current remedial actions and containment activities PG&E’s bottled drinking water program and other community initiatives 13 Our Presentation

ppb DVD, SCRIA Extraction Wells MW-62A Action Plan Wells Agricultural Unit & LTU Wells South Central Reinjection Area Central Area IRZ Source Area IRZ Plume Containment, Treatment, and Monitoring Control leading edge of plume with freshwater injection Contain plume with groundwater extraction and agricultural land treatment Treat plume core and source areas with in-situ remediation Groundwater and Land Use Management Accomplished through property acquisition and restoration Land use/pumping agreements

New Activities: Trend identified at MW-62A Additional talks with Gorman of need to control pumping Additional extraction wells installed to increase control Ongoing Activities: Containment pumping and agricultural treatment at DVD Source reduction through large-scale in-situ treatment 50 ppb South Central Reinjection Area Source Area IRZ Central Area IRZ

50 ppb 3.1 ppb 2010 New Activities: PG&E purchases Gorman property to control pumping Approval and implementation of MW-62A Response Plan New monitoring wells confirm thin layer near Summerset Ongoing Activities: Containment pumping and agricultural treatment at DVD Source reduction through large-scale in-situ treatment 16 South Central Reinjection Area Central Area IRZ Source Area IRZ

New Measures: Ag Unit G North Ag Unit G South Ag Unit C Ranch Ag Unit Western Ag Unit (in process) Additional Ag Unit (in process) Additional DVD extraction wells Additional in-situ treatment work Additional monitoring wells ppb DVD, SCRIA Extraction Wells MW-62A Action Plan Wells Agricultural Unit & LTU Wells South Central Reinjection Area Central Area IRZ Source Area IRZ 17

MW-62A Response Measures: Purchase Gorman property New extraction wells Increase in pumping rates Additional Measures: More extraction wells Additional piping on standby Additional injection wells Increase agricultural treatment Significant Increase in Pumping to Increase Control of the Plume Increase in pumping Nov

19 In-Situ Remediation Effectiveness to Date Encouraging results indicate source reduction within core of the plume Data shown are from upper aquifer Rapid decrease of chromium concentrations Rapid decrease of chromium concentrations Chromium (µg/L)

Feasibility study for comprehensive final groundwater cleanup plan Progress of current remedial actions and containment activities PG&E’s bottled drinking water program and other community initiatives 20 Our Presentation

Bottled Drinking Water Program Area Boundaries Bottled water provided to all residences up to approximately ½-mile surrounding the plume Separate Water Board mandated program applies to domestic wells found to be above background levels Water currently supplied to about 80 residents plus Hinkley School and Senior Center PG&E program boundaries are periodically reviewed 21

Domestic Wells Sampling Areas Long-standing PG&E program expanded in 2010 to include properties up to ½-mile beyond bottled water program area 22

Property Purchase Program Area 23 Program intended for homes or properties: On or next to the plume Located where agricultural pumping and/or other activities could potentially affect the plume Located in an area that could be needed for future remediation activities Properties appraised as if the chromium plume is not present, and comparable home values are from communities outside Hinkley Program Area

Mission is to advise, share concerns with, and provide direct input to PG&E on its environmental and community programs in Hinkley Membership will reflect the composition, diversity, and interests of the Hinkley community All meetings open to the public and announced in local newspaper and other media Community Advisory Committee 24

Thank You 25