Water Science and Technology Board
National Research Council
Alternatives for Managing the
Nation’s Complex Contaminated
Groundwater Sites
Webinar
1 pm Eastern Time Zone
Committee on Future Options for Management in
the Nation’s Subsurface Remediation Effort
MICHAEL KAVANAUGH, NAE, Chair, Geosyntec WILLIAM ARNOLD, University of Minnesota BARBARA BECK, Gradient Corporation
YU-PING CHIN, The Ohio State University ZAID CHOWDHURY, Malcolm Pirnie
DAVID ELLIS, DuPont Engineering
TISSA ILLANGASEKARE, Colorado School of Mines PAUL JOHNSON, Arizona State University
MOHSEN MEHRAN, Rubicon Engineering Corporation
JAMES MERCER, Tetra Tech GEO
KURT PENNEL, Tufts University
ALAN RABIDEAU, State University of New York, Buffalo ALLEN SHAPIRO, U.S. Geological Survey
Background
• For 30 years, remediation has eliminated or controlled acute risks; many hazardous waste sites with contaminated groundwater now “closed”.
• But, reaching unlimited use and unrestricted exposure (UU/UE) (i.e., drinking water standards or highest beneficial use) remains a
significant challenge.
• A substantial number of sites exhibit attributes that make restoration unlikely for many decades.
• DoD has invested heavily in addressing legacy contamination in groundwater ($30 billion to date).
Stringfellow, CA, cerca 1995
34 million gallons of liquid hazardous waste released
Site placed on NPL in 1983
Exposure pathways controlled
Restoration will take ~ 500 yrs
Future cost in excess of $200 million; Cost to Date > $500 M.
State is RP. Have requested a TI Waiver for two of the four “zones”. ROD 5 in progress.
Statement of Task
•
What is the size of the nation’s hazardous waste
problem?
•
How much contamination can current technologies
remove?
•
What is the future of treatment technologies
?
•
Can mass removal be better correlated with
site-specific risk?
Magnitude of the Problem
• Estimated the number of sites that have not yet reached “closure”
• Tabulated remediation costs expended to date
• Summarized costs estimated by others to reach “closure” as
defined by regulatory program
• Estimated number of sites affecting public water supply sources
Information listed above was not available for some programs
• DoD
• Other federal sites
• State Sites
Estimated Number of Sites/Facilities with Conditions not
allowing for Closure and Costs to Complete
Program/Agency Number of Facilities Number of Sites Estimated Cost to Complete ($B)
DoD 4,329 $12.8
CERCLA 1,364 $16 -23
RCRA 2,844 $32.4
UST 87,983 $11
DOE 3,650 $17.3 – 20.9
Other Federal Sites >3,000 $15 - 22
State Sites >23,000 $5
TOTALS >126,000 $110 - 127
Chapter 2 Main Conclusions
• 126,000 sites that have not yet reached closure is likely an
underestimate.
• Could not determine the total number of sites with residual
contamination above levels allowing for UU/UE (must be > 126,000).
• More than 12,000 sites are “complex”.
• Estimated future cost of $110-127 billion likely an underestimate.
• ~10% of Superfund sites affect drinking water supply sources.
• Nomenclature for site closure inconsistent between federal
agencies, the states, and the private sector; confusing for public.
Analysis of 80 NPL-Delisted Groundwater Sites
• The Committee evaluated 80 contaminated groundwater sites, identified by EPA personnel, already deleted from the NPL.
• Site documents* were queried to consider several questions:
– What were the remedial goals? (e.g., MCLs or other)
– Contaminants of concern?
– Were MCLs met? If not, what levels were achieved?
– What remedial actions were used?
– Does monitoring continue?
– Were alternative strategies used? (e.g., TI Waivers)
14
MCLs Achieved: Active Remedy, No LTM
MCLs Achieved: Active Remedy, LTM
MCLs Not Achieved: LTM MCLs Not Achieved: Deleted
Based on Risk Assessment: No LTM MCLs Not Achieved: Deleted
Based on Risk Assessment: LTM Remedial Objective
Other Than Meeting MCLs
MCL Achievement Unknown Not a Groundwater Site
MCLs Achieved: No Active Remedy, No LTM
Chapter 2 Main Conclusions
• 126,000 sites that have not yet reached closure is likely an underestimate.
• Could not determine the total number of sites with residual contamination above levels allowing for UU/UE (must be > 126,000).
• More than 12,000 sites are “complex”.
• Estimated future cost of $110-127 billion likely an underestimate.
• ~10% of Superfund sites affect drinking water supply sources.
• Nomenclature for site closure inconsistent between federal
agencies, the states, and the private sector; confusing for public.
Capabilities of Current Technologies – An Update
• Thermal Treatment
• In Situ Chemical Oxidation
• Surfactant and Co-solvent Flushing
• In Situ Bioremediation
• Pump and Treat for hydraulic containment
• Physical Containment
• Permeable Reactive Barriers
• Monitored Natural Attenuation
• Combined Remedies
Thermal Treatment <10X to 100000X concentration and flux reduction; 95 to 99+ percent mass reduction of what is captured
In Situ Chemical Oxidation
55 to 90 percent mass reduction
Surfactant Flushing 65 to 90+ percent mass recovery
Chapter 4 Conclusions
• While significant reductions in mass, mass discharge, and
concentration are reported, significant technical limitations persist
that make achievement of MCLs throughout the aquifer unlikely at most complex groundwater sites for many decades.
• There are limited data upon which to base a scientifically
supportable comparison of remedial technology performance.
– Since NRC (2005), only thermal and ISCO have undergone a thorough independent review
– Additional independent reviews needed on most promising technologies
Implications of Contamination Remaining in Place
• Potential failure of engineering and institutional controls.
• Changes in toxicity and dose-response relationships (e.g., TCE) could result in site reopeners.
• New contaminants (e.g., NDMA/1,4-dioxane/nano) and exposure pathways (vapor intrusion) may emerge.
• Legal/economic issues like Natural Resource Damage and trespass may need to be addressed.
• Risks associated with well head treatment to prevent exposure.
Technology Development to Support
Long Term Management
• R&D investments have been unable to keep pace with the needs of practitioners conducting remediation.
• There is no national strategy for technology development to support long-term management of complex sites.
• It is not clear that the pertinent federal agencies will be capable of providing the funding and other support for R&D.
A comprehensive assessment of future research needs, involving coordination between federal agencies, would allow research
Innovations to Support Long-Term Management
Need research in several areas to meet the requirements of effective long-term management of complex sites
Monitoring
– Sensors and other tools to assess vapor intrusion risks
– Molecular biological and isotope diagnostic tools – “precision treatment” – and to quantify the transformation capacity of subsurface
Modeling
– More accurate estimates of time-to-reach-restoration goals
– Better accounting for back-diffusion and desorption
Remediation Technologies
Better Decision Making: Overview
• Attainment of MCLs unlikely for decades or longer at large number of complex sites.
• Where costs are incurred with a diminishing reduction in concentration or risk, alternative strategies are needed.
• When the effectiveness of optimum site remediation reaches a point of diminishing returns prior to reaching cleanup goals, a “Transition Assessment” should be conducted.
• The Transition Assessment, which is like a Focused Feasibility Study, determines the appropriate “end state” for the site.
EPA Recognizes Alternate Approaches Are Needed for
Sites Where Restoration is Unlikely
EPA
Key Decision Points in the
Transition Assessment
•
Is a new remedy warranted and not precluded by a
legal release?
•
On case-by-case basis, is active or passive long-term
management appropriate?
•
Evaluate each alternative based on
– protectiveness
– ability to attain remedial action objectives
– implementability (including costs)
– more comprehensive risk analysis
Is a New Remedy Warranted?
•
Only if no legal release from future liability applies or
PRP offers to perform new remedy.
•
Yes, under the following conditions:
– New technology satisfies remedy selection criteria and will meet RAOs in reasonable time frame.
•
No, under the following conditions:
What are the Costs and Risks of Alternatives?
•
Cost considerations should expand beyond typical
net present value comparisons
– Appropriate net discount rate for current and future economic conditions
– Consideration of probabilistic cost models
•
Risk analysis should expand beyond traditional
methodologies
– Risk reduction over time
– Risk analysis if residual contamination unavoidable
Is Passive Long-Term Management Appropriate?
•
If Active LTM not appropriate, evaluate Passive LTM.
•
Decision should consider the following factors:
– Potential use of MNA time frame beyond 100 years
– Optimum monitoring program to ensure protectiveness and confirm degradation
• New diagnostic tools (e.g., CSIA, molecular biological tools, etc.)
– Effective institutional controls
Transition Assessment – Other Factors to Consider
•
Requires continued and transparent communication with
community advisory groups (e.g., EPA CAGs, DoD RABs).
•
Could utilize data and information from the five-year review
process.
•
MNA may eventually transition to natural attenuation
without monitoring.
Summary of Key Points
• ~ 12,000 of the 126,000 remaining sites are complex and unlikely to reach UU/UE within 50 – 100 years with current technologies.
• No major technological breakthroughs anticipated.
• When the active remedy reaches a point of diminishing returns prior to reaching cleanup goals, conduct Transition Assessment to accelerate decision for long-term management. Transition
Assessment will require renewed community involvement.
• Cost savings anticipated from implementation of Transition Assessment but funding will still be needed for long-term
management at these complex sites.
