autopsy of a small ust site in bedrock: implications for remedial effectiveness · 2013-05-11 ·...
TRANSCRIPT
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Autopsy of a Small UST Site in Bedrock: Implications for Remedial Effectiveness
Case Study, Devens, MA
Autopsy of a Small UST Site in Bedrock: Implications for Remedial Effectiveness
Case Study, Devens, MA
Federal Remediation Technology Roundtable Meeting Characterization and Remediation of Sites with Fractured Bedrock Washington, DC November 9, 2010
Federal Remediation Technology Roundtable Meeting Characterization and Remediation of Sites with Fractured Bedrock Washington, DC November 9, 2010
William C. Brandon, Hydrogeologist, US EPA Region 1William C. Brandon, Hydrogeologist, US EPA Region 1
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Acknowledgements
• Gannet Fleming Inc.• Army BRAC Office• HGL Inc.• EPA Region 1 Federal Facilities• EPA Region 1 OEME• Mass Development
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Geologic Setting
SITE
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Site Location
SITE
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Site Geology
Modified from Kopera, 2008
SITE
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Geologic History
• Silurian metasediments• Intrusion of Ayer Granodiorite (Devonian)• Intrusion of Chelmsford Granite (later
Devonian)• Deformation, faulting, metamorphism• Quaternary glaciation and de-glaciation
– Unloading, development of sheeting fractures– Deposition of outwash sand, gravel
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DRMO Site Plan
Source Area MW(Shallow Bedrock)
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POL Site Plan
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DRMO Site History• Defense Reutilization and Marketing Office (DRMO)
– Equipment Recycling ~ 1964-1995
– 5000 gal Waste Oil UST
• UST removed 1992• Limited soil removal (tank grave partially in BR) • COCs: TCE, DCB, VPH, As, Mn
• 1998-1999; LTMP (V_1.0) Initiated
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DRMO LTM Network Pre-2000
32M-92-06X
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COC Trends (Pre-2000)3 2 M - 9 2 -0 6 X
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
1 2 0 0
1 4 0 0
1 6 0 0
Nov-9
2Feb-
93M
ay-93
Aug-93
N ov-9
3Feb-
94M
ay-94
Aug-94
N ov-9
4Feb-9
5M
ay-95
Aug-95
N ov-9
5Feb-
96M
ay-96
Aug-9
6Nov
-96
Feb-97
May-9
7Aug-
97Nov-9
7Feb-9
8M
ay-98
Aug-98
Nov-98
D a te
Con
cent
ratio
n (u
g/l)
1 ,2 - D C B1 ,4 - D C B1 ,3 - D C BT C E
3 2 M - 9 2 - 0 6 X
2 4 3
2 4 4
2 4 5
2 4 6
2 4 7
2 4 8
2 4 9
2 5 0
Nov-92
Feb -93
May -9
3A ug-9
3
Nov-93
Feb -94
May -9
4A ug -9
4
Nov-94
F eb -95
May-9
5
Aug -95
Nov-95
F eb-96
May-9
6
Aug -96
Nov-9
6
F eb -97
May-9
7Aug -9
7
Nov-97
Feb -98
May-9
8A ug-9
8
Nov-98
GW
Ele
vato
n (fa
msl
)
W L
No Data
No Data
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Site History (Part II)
• Warehouse Construction Results in large-scale site alterations (2000-2001)– Bedrock Blasting/Cut-and-fill– Engineered Drainage (Storm sewers, Detention Basin)– Extensive area of impervious surface (Building, Parking lots)
• Site Hydrology Profoundly Altered
• 2001-2002; LTMP Revised (v.2), – Numerous new monitoring wells installed. – New baseline– Ongoing LTM and data evaluation (2002-2006)
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Site: Pre-construction (March 2000)
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Pre-Blast Bedrock Exposures at SE Corner of Building Area
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Fill Emplacement SW of Building Footprint
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Storm Drain Installation
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Subsurface Utilities
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LTM/CSM Issues (2002-2006)• “Moving Target” - Site Hydrology Slowly Evolving Post-
Construction
• Few COCs identified at POL after 2002, but
• “Down-gradient” directions uncertain
• Persistent Contamination in UST-13 Area
• Bedrock Affected, but Fracture Network not evaluated
• Adequacy of LTM network called into question
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Near-Term Objectives• Detailed evaluation of bedrock structural data from
outcrop mapping• Update CSM (Consensus)
– Bedrock Surface Map– Bedrock Fracture Data– Ground Water Flow Gradients
• Lateral/vertical• Source Areas/Downgradient of Source Areas• Long-term water level trends
– Configuration of Subsurface Hydrostratigraphic Units (2D/3D)– Detailed cross sections through each source area normal and
parallel to hydraulic gradient• Identify Data Gaps• Recommend Adjustments to GW Monitoring Network
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Longer-term Objectives
• Install New Monitoring Wells• Decommission Unnecessary Wells• New Baseline; Re-initiate Long-term
Monitoring• Evaluate time-series contaminant trends• Determine whether additional remedial
measures are needed• Site Closeout
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Site Plan with Existing Monitoring Well Locations
Source: MACTEC, 2006
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Elements of Bedrock Evaluation
• Configuration of top-of-bedrock surface• Geologic Mapping• Rock Type Identification• Foliation orientation Data• Joint Orientation Data• Structural Analysis
– Stereo-net analysis– Joint/Fracture Mapping
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Bedrock Elevation (Pre-Blast)
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Elevation of Bedrock Surface (Post-Blast)
Source: MACTEC, 2006
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Major Rock Types• Berwick Formation (S-O)
– Thick-bedded to massive Metaconglomerates, cg conglomeratic quartzite, fg feldspathic biotitic quartzite
– Thinly bedded to massive dark gray to brown calcareous and phyllitic siltstones and mg feldspar-qz-biotite schist
• Ayer Granite– Devens Long-Pond Facies– Massive gneissic equigranular to
porphyroblastic biotite granite and granodiorite
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Site Geology
Modified from Kopera, 2008
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Bedrock Geologic Map of the Shepley’s Hill Landfill Area
Source Harding ESE, 2003
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Blasting Presents Fresh Exposures
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Overview of Locations Where Structural Data Was Collected
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Foliation
• Primary layering in metamorphic rocks• Generally follows compositional layering• Consistent orientation at site-scale• Local evidence of minor folding
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Stereoplot of Foliation Orientations
N=49Strike ~ N3Dip ~ 52 W
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Plan View of Foliation Data NE Corner of Building
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Plan View of Foliation Data SE Corner of Building
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Stereoplot of Foliation indicating Fold Axis
Azimuth ~ N21EPlunge ~ 40
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Joints
• Generic Term for Planar discontinuity in Rock Mass (e.g., crack)
• Open joints may transmit water (oxidation)
• Greater Variability than Foliation
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Intersecting Joint Sets
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Stereo-plot of Joint Orientations
N=15666 stations
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Major and Minor Joint Sets
– N3E +/-, 50-60 W (parallel to foliation)– N45E +/-, 65-85 SE– Near-surface sheeting joints at various
orientations, Sub-parallel to former topography
– ~ N70W, Subvertical (weak)– ~ N30W, > 70-80 SE or SW Dips (weak)
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Interpretive Overburden Groundwater Surface Map, October 7, 2004
Source: MACTEC, 2006
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Interpretive Bedrock Groundwater Surface Map, October 7, 2004
Source: MACTEC, 2006
BR GW Divide
Down-Dip Smear Zone?
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N-S Hydrogeologic Cross Section – UST 13
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W-E Hydrogeologic Cross-Section UST 13 Area
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True-Scale Cross Section of UST- 13 Area Normal to Foliation, Illustrating Monitoring Gap
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Plan View of Site 32-43A Indicating Proposed Locations for New Monitoring Wells
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DPT Program - 2007
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UST-13
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UST-13
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Summary and Conclusions• Basic Geologic Analysis points to numerous
opportunities for LTM Improvements• Many existing MWs are no longer useful and should be
eliminated from the program• UST-13 Area Requires several new MWs
– Source area– True down-gradient directions– Water-table (BR/OB)
• Joints parallel to foliation may play a significant role in contaminant migration– Down-dip migration of NAPL (W/SW)– Dissolved COC migration along strike (S)
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Summary and Conclusions (Cont.)
• Systematic water table rise in the POL area
• Many existing MWs no longer screened optimally for water table monitoring
• Source area MWs needed• Several MWs needed to SW of source
area along primary flow pathways (SOB/DOB)
• Target SW-striking Bedrock Structure
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Recommendations and Outstanding Issues
• CSM Consensus• Install New Monitoring Wells• Decommission Unnecessary Wells• New Baseline; Re-initiate Long-term Monitoring• Evaluate time-series contaminant trends• Evaluate Perchlorate (Blasting)• Install Transducers to evaluate long-term water
level trends• Determine whether additional remedial
measures are needed
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2009 Persulfate Injection
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2009 Persulfate Injection
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2009 Persulfate Injection
• Focus on “hotspot” near 32M-01-18XBR• 3 shallow bedrock injection wells installed
around 32M-01-18XBR• Overburden injection well installed on Top-
of-bedrock in former tank grave• 1800 gallons of water/sodium persulfate
solution injected February 2009• sodium hydroxide used as catalyst
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Injection Pressure Response Far Field
Data Corrupted
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Injection Pressure Response Near Field
Transducer Malfunction
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Injection Conductivity Response Near Field
Discernable Conductivity Increase
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May 2010300 ug/l
Cleanup goal = 600 ug/l
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May 201059 ug/l
Cleanup goal = 40 ug/l
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Cleanup goal = 200 ug/l
May 2010300 ug/l
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Vertical LNAPL Distribution
• LNAPL penetrates below water table
• LNAPL and water coexist in pores
• Assumes LNAPL floats on water table
• Uniform LNAPL saturation
LNAPL
Water
Grains
Vertical EquilibriumPancake Model
No YesPancake Model vs. Vertical Equilibrium Model
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Water Levels - 32M-01-18XBR
234
236
238
240
242
244
246
248
Jan-0
2Mar-
02May
-02
Jul-0
2Sep
-02Nov
-02Ja
n-03
Mar-03
May-03
Jul-0
3Sep
-03Nov
-03Ja
n-04
Mar-04
May-04
Jul-0
4Sep
-04
Date
WL
Elev
atio
n - m
sl
Series1
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True-Scale Cross Section of UST- 13 Area Normal to Foliation, Illustrating Monitoring Gap
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Questions for Ongoing LTM
• Is the apparent COC attenuation real?• Or will the Oscillatory longer-term trends resume• Does the site behave as a typical “drowned
smear zone”?• Delivery: Will future remedial efforts need to
more carefully consider the bedrock fracture system?
• Deliverance: How might one increase the oxidant contact with residual contaminants?
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Next Steps• Install • Install Transducers to evaluate long-term water level
trends
• Determine whether additional remedial measures are needed
• Consider Injecting in down-dip directions
• Monitor in down gradient areas in consideration of bedrock ground water gradients and bedrock fabric
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2009 Persulfate InjectionINJECT HERE
MONITOR HERE
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• THANKS
• Question ??