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Characterizing Contaminant Flux at the Groundwater- Surface Water - - PowerPoint PPT Presentation

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Characterizing Contaminant Flux at the Groundwater- Surface Water Interface Robert Ford USEPA Office of Research and Development Cincinnati, OH Collaborators: Steve Acree, Randall Ross, Bob Lien Office of Research and Development National

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SLIDE 1

Characterizing Contaminant Flux at the Groundwater- Surface Water Interface

Robert Ford USEPA Office of Research and Development Cincinnati, OH Collaborators: Steve Acree, Randall Ross, Bob Lien

Office of Research and Development National Risk Management Research Laboratory, Cincinnati, OH USEPA Ground Water Forum Meeting, August 8, 2019

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SLIDE 2

Disclaimer

1

The findings and conclusions in this presentation have not been formally disseminated by the U.S. EPA and should not be construed to represent any agency determination or policy.

SHC 3.61.1 Contaminated Sites - Technical Support

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SLIDE 3

Plan for Presentation

2

  • Context for evaluating water and

contaminant flux from upland groundwater to downgradient surface water bodies (CSM)

  • Assessing hydraulic pathway from

groundwater to surface water

  • Assessing factors controlling

contaminant flux to surface water

SHC 3.61.1 Contaminated Sites - Technical Support

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SLIDE 4

Conceptual Site Model

3 SHC 3.61.1 Contaminated Sites - Technical Support

Understand Interaction Between GW & SW

  • Water flux of GW and SW at interface will

govern processes controlling contaminant fate

  • Dominant chemical processes will be

governed by the mass of contaminant and reactive constituents delivered to and mixed at the interface

  • Net result of processes will likely vary in

time (seasonal) and space (geology)

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SLIDE 5

Conceptual Site Model

4 SHC 3.61.1 Contaminated Sites - Technical Support

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SLIDE 6

Conceptual Site Model

5 SHC 3.61.1 Contaminated Sites - Technical Support

Effective CSMs - Site Hydrology Issues

  • Hydraulic connection between contaminated GW

and surface water body ‒ Does it exist? ‒ If so, is it continuous or episodic? ‒ When connected, does the direction of water exchange vary?

  • Questions need to be addressed to understand

timing and location of contaminant discharge

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SLIDE 7

Conceptual Site Model

6 SHC 3.61.1 Contaminated Sites - Technical Support

  • Site topography and

stream morphology influence GW flow direction and magnitude

  • May need to

characterize this spatial variability relative to GW plume dimension

  • GW is not a static

system, but may respond more slowly to changes in water budget (continuous logging)

L a t i t u d e Longitude E l e v a t i

  • n

Stream Aquifer

GW Potentiometric Surface

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Conceptual Site Model

7 SHC 3.61.1 Contaminated Sites - Technical Support

  • An effective CSM depends on understanding

contaminant transport from source area(s) to SW and dynamics at GW-SW interface

  • Contaminant non-detects that occur along some

assumed flow path could mean two things: ‒ Contaminated GW does not reach SW ‒ Monitoring location is not in the flow path

  • Hydrologic & chemical measurements across

the GW-SW interface bridge upland GW-to-SW transport pathway

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SLIDE 9

Assessing Hydrology

8 SHC 3.61.1 Contaminated Sites - Technical Support

  • Site topography and

stream morphology influence GW flow direction and magnitude adjacent to surface water body

  • Characterizing local flow

field across GW-SW interface important for understanding dynamic processes governing water exchange & contaminant flux

Discharge Recharge

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SLIDE 10

P

Assessing Hydrology

9 SHC 3.61.1 Contaminated Sites - Technical Support

  • Hand-Deployed Devices

‒ Piezometer (P) ‒ Piezometer-Stilling Well (PS) ‒ Temperature Profiler (TP) ‒ Permeameter (Pm)

  • Provide for assessment of the

direction and magnitude of water exchange

  • Logging sensors allow

assessment of variability over time

P PS PS Pm TP

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SLIDE 11

P

Assessing Hydrology

10 SHC 3.61.1 Contaminated Sites - Technical Support

Temperature Profile Measurements Installation of Piezometer-Stilling Well & Temperature Profiler Vertical Gradient Piezometer-Stilling Well

PS PS TP TP

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SLIDE 12

Assessing Hydrology

11

Develop Integrated Knowledge of GW-SW Interface

  • Localized monitoring network used to understand

dynamics of flow system with time (seasonal) ‒ Horizontal gradient ‒ Vertical gradient ‒ Horizontal/vertical water flux

  • Basis for comprehending processes controlling

contaminant flux and fate at GW-SW interface

  • Baseline analysis of system provides the basis for

interpreting whether upgradient remedial actions are performing as desired

SHC 3.61.1 Contaminated Sites - Technical Support

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Factors Affecting Contaminant Transport

12 SHC 3.61.1 Contaminated Sites - Technical Support

Inorganic Contaminant Properties & Mass Flux

  • Contaminant properties influence types of processes

active in controlling fate (adsorption, precipitation, chemical speciation)

  • GW-SW interface is typically a zone with major changes

in chemistry over distance due to mixing of reactive constituents delivered by GW and SW

  • Contaminants with chemical fate sensitive to changes in

pH and redox may show changing patterns with season

  • Contaminants sequestered in sediments may become a

secondary source of contaminant flux to SW

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Factors Affecting Contaminant Transport

13 SHC 3.61.1 Contaminated Sites - Technical Support

Reduced GW Plume

  • SW body with varying

water depth in which

  • xygen reaches

sediments in shallow locations but not deep

  • Oxidation & attenuation of

Fe and As in sediments for shallow depths

  • Unhindered transport of

As into SW for deeper depths

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Case Study

14

  • Arsenic plume

flowing from landfill toward cove

  • Nested

piezometers used to evaluate magnitude & distribution of arsenic flux

SHC 3.61.1 Contaminated Sites - Technical Support EPA-600-R-09-063

N

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Case Study

15 SHC 3.61.1 Contaminated Sites - Technical Support

Picture of cove from north shore Picture at central cove from boat next to contaminated seepage area

April 2007 April 2007

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SLIDE 17

Case Study

16

  • Sediment arsenic

concentrations variable within cove – correlate with iron

  • PZ5 location shows

sustained discharge with plume chemistry signature in deep SW

  • PZ13 in location of low

discharge & no plume chemistry signature in deep SW

SHC 3.61.1 Contaminated Sites - Technical Support EPA-600-R-09-063

192215 192220 192225 192230 192235 208 210 212 214 216 218

MC SW02B SW04

RCTW 4 RCTW 9 RCTW 10

Contaminated Sediment

GW Discharge

High As, Fe, K Low DO

Sediment Recycling

High As, Fe – Low K Variable DO

9 9

PZ5 PZ13

What influences SW concentrations?

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Case Study

17 SHC 3.61.1 Contaminated Sites - Technical Support

Median Flux Reduction Factors Flow 2.9 Barium 7.6 Arsenic 4.3 Ammonium 12.8

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 0.00 0.04 0.08 0.12 0.16 0.20 Barrier Wall

Calendar Year

Groundwater Flux, m / d

25 50 75 100 125 150

GW Arsenic Flux, mg / d-m2 Measured Interpolated

Upland GW

N

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Case Study

18 SHC 3.61.1 Contaminated Sites - Technical Support

Sediment Temperature Profile Method Comparison

  • ver entire

monitoring period…

170 180 190 200 210 220 230 240 5 10 15 20

Middle of Cove ( June - August ) Pre-Installation ( 2008 ) Post-Installation ( 2014 ) Upland GW Flux

Calculated Seepage Flux (cm/d) Calendar Day

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 5 10 15 20 25

GW Flux Seepage Flux

Water Flux, cm/d Calendar Year

GW-SW Interface

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Case Study

19 SHC 3.61.1 Contaminated Sites - Technical Support

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 25 50 75 100 125 150

Calendar Year Interpolated GW Arsenic Flux, mg / d-m2 Measured Cove Arsenic Flux, mg / d-m2

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Case Study

20 SHC 3.61.1 Contaminated Sites - Technical Support

Outcome

  • GW plume diverted away

from cove by hydraulic barrier

  • Performance metric of GW

contaminant flux reduction was realized and could be assessed in multiple ways

  • Episodic exceedances of

AWQC (As) during late Summer / early Fall, but…

  • Spring fish nest building
  • bserved immediately after

remedy and continues (2014- 2018)

BEFORE AFTER

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Closing Remarks

21

  • Methods to assess GW flow and seepage flux

are relatively easy to implement and provide flexibility to monitor the GW-SW interface

  • Knowledge of water flux dynamics improves

understanding of processes controlling contaminant fate

  • Comprehension of baseline contaminant flux

dynamics across the GW-SW interface are critical to assessing response to upland remediation

SHC 3.61.1 Contaminated Sites - Technical Support

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Acknowledgements

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Engineering Technical Support Center John McKernan, mckernan.john@eda.gov Ed Barth (Acting), barth.edwin@epa.gov Groundwater Technical Support Center David Burden, burden.david@epa.gov EPA Region 1 – Carol Keating, Bill Brandon, Ginny Lombardo, Jerry Keefe, Dan Boudreau, Tim Bridges, Rick Sugatt, David Chaffin (State of Massachusetts) Workbook Beta Testing – Region 1 (Bill Brandon, Marcel Belaval, Jan Szaro), Region 4 (Richard Hall, Becky Allenbach), Region 7 (Kurt Limesand, Robert Weber), Region 10 (Lee Thomas, Kira Lynch, Bruce Duncan, Piper Peterson, Ted Repasky), Henning Larsen and Erin McDonnell (State of Oregon) EPA ORD – Jonathon Ricketts, Patrick Clark (retired!), Kirk Scheckel, Todd Luxton, Mark White, Lynda Callaway, Cherri Adair, Barbara Butler, Alice Gilliland US Army – Robert Simeone Don Rosenberry (USGS – Lakewood, CO) – verification studies at Shingobee Headwaters Aquatic Ecosystems Project

SHC 3.61.1 Contaminated Sites - Technical Support