Transcript Our Presentation

Project Update
Groundwater Remediation Project
Hinkley Gas Compressor Station
Presentation to the
Lahontan Regional Water Quality Control Board
June 8, 2011
Our
Presentation
• 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
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Goals for
Hinkley
Site
• 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
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Feasibility Study of Cleanup Options
Alternatives assembled from array of proven effective technologies
• 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
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Evaluation of Remedial Alternatives
Range of options considered and estimated years to completion
Alternative
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50 ppb
MCL
80% Mass
Removal
3.1 ppb
Background
4B
Aggressive in-situ treatment and beneficial
agricultural use with targeted pumping
6
10
40
4A
Aggressive in-situ treatment
and beneficial agricultural use
6
10
75
6
Combined alternative
28
18
90
5
Plume-wide pump and treat
50
37
140
4
Core in-situ treatment
and beneficial agricultural use
6
13
150
3
Plume-wide in-situ treatment
8
10
110
2
Containment
120
95
260
1
No action
750 – 1000
>780
>1000
Conceptual Plan
of Final Remedy
Agriculture
Area
Containment
Extraction
Multiple remedial components
target specific areas of plume
Fresh Water
Injection
Agricultural Treatment
Hinkley
Compressor
Station
Fresh Water Injection
In-situ
Treatment
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Locations approximate and not to scale
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
Initial Chromium
Concentrations
After 10 Years
of Remediation
After 20 Years
of Remediation
Computer generated estimates of 10-year and 20-year results
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Benefits of Final Remedy Concept
Technically sound remediation plus multiple local / regional benefits
• 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
8
March 9, 2011 Public Comments
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.”
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March 9, 2011 Public Comments
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
Groundwater typically flows about 300 feet toward
extraction wells during spring, summer and fall pumping
Groundwater may flow 100 feet away from
extraction wells during winter pumping
The net annual movement of
groundwater is about 200 feet
toward extraction wells
• 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
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DTSC Review of Feasibility Study
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
We will work with the Water Board
to address reviewer suggestions
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“DTSC also
recommends
consideration of
focus areas for
remediation goals
and strategy”
Diffuse Plume
North of Hwy 58,
chromium concentrations
are below 50 ppb
• Diffuse plume strategy:
Immediately contain, and
treat via extraction
Plume Core
South of Hwy 58,
chromium concentrations
are above 50 ppb
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Locations approximate and not to scale
Hinkley
Compressor
Station
• Plume core strategy:
Immediately cut off
continuing source to diffuse
plume, and treat in place
for maximum speed
Our
Presentation
• 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
Summerset Rd
Mountain View Rd
Thompson Rd
Plume Containment, Treatment,
and Monitoring
Desert View
Dairy Land
Treatment
Unit
Fresh
Water
Injection
Central
Area IRZ
South Central
Reinjection
Area
DVD, SCRIA Extraction Wells
MW-62A Action Plan Wells
Source
Area IRZ
Agricultural Unit & LTU Wells
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14
Locations approximate and not to scale
2011
Hinkley
Compressor
Station
• 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
Gorman
Property
Pumping
Desert View
Dairy Land
Treatment
Unit
2009
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:
Central
Area IRZ
• Containment pumping and
agricultural treatment at DVD
South Central
Reinjection
Area
• Source reduction through
large-scale in-situ treatment
Source
Area IRZ
15
Locations approximate and not to scale
Hinkley
Compressor
Station
Former
Gorman
Property
2010
New Activities:
Desert View
Dairy Land
Treatment
Unit
• PG&E purchases Gorman
property to control pumping
• Approval and implementation
of MW-62A Response Plan
• New monitoring wells confirm
thin layer near Summerset
Fresh
Water
Injection
Central
Area IRZ
Ongoing Activities:
South Central
Reinjection
Area
Source
Area IRZ
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Locations approximate and not to scale
• Containment pumping and
agricultural treatment at DVD
• Source reduction through
large-scale in-situ treatment
Hinkley
Compressor
Station
Summerset Rd
Mountain View Rd
Thompson Rd
Desert View
Dairy Land
Treatment
Unit
2011
New Measures:
• Ag Unit G North
• Ag Unit G South
• Ag Unit C
• Ranch Ag Unit
Fresh
Water
Injection
• Western Ag Unit (in process)
Central
Area IRZ
South Central
Reinjection
Area
DVD, SCRIA Extraction Wells
MW-62A Action Plan Wells
Source
Area IRZ
Agricultural Unit & LTU Wells
17
Locations approximate and not to scale
Hinkley
Compressor
Station
• Additional Ag Unit (in process)
• Additional DVD extraction wells
• Additional in-situ treatment work
• Additional monitoring wells
Significant Increase in Pumping to
Increase Control of the Plume
MW-62A Response Measures:
Increase in pumping
• Purchase Gorman property
1350
950
650
450
345
• New extraction wells
• Increase in pumping rates
Additional Measures:
• More extraction wells
• Additional piping on standby
• Additional injection wells
Nov.
2009
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• Increase agricultural treatment
In-Situ Remediation Effectiveness to Date
Encouraging results indicate source reduction within core of the plume
Rapid decrease
of chromium concentrations
2011
Chromium (µg/L)
2007
2008
Data shown
are from
upper aquifer
19
2009
2010
Our
Presentation
• 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
Trindall Rd
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
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Property Purchase
Program Area
• 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
Program Area
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• Properties appraised as if
the chromium plume is not
present, and comparable
home values are from
communities outside
Hinkley
Community Advisory Committee
• 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
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Thank You
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