Remediation Evaluation of Site ST-14 at Joint Base Andrews

Michael H. Flinn, Ph.D., PMP, REP
22 March 2012
Remediation Evaluation of Site ST-14
Joint Base Andrews:
A Detective Story

Introduction
Restoration Branch of the Air Force Center for Engineering and the
Environment Technical Directorate (AFCEE/TDV) performed an
Environmental Restoration Program – Optimization (ERP-O) visit at
Joint Base Andrews Naval Air Facility Washington (JBA)
ERP-O Team recommended that the Site ST-14 remedy be reviewed
– Evaluate for effectiveness
– Recommend a path forward
Conducting the evaluation was like reading a detective story. The
available documentation had several red herrings and false leads.
Multiple lines of evidence (clues) had to be pieced together to reach a
full understanding of the site situation.

Introduction (Concluded)
It is a capital mistake to theorise [sic] before one
has data. Insensibly one begins to twist facts to
suit theories, instead of theories to suit facts.
Sherlock Holmes in “A Scandal in Bohemia” by Sir
Arthur Conan Doyle

The Scene - Joint Base Andrews
Formerly known as
Andrews Air Force
Base
Located southeast
of Washington, D.C.
JBA

The Scene - Site ST-14 (Continued)
Location of the former East
Side Service Station
Two 10,000 gallon USTs
removed in 1983
Approximately 20,000 gallons
of gasoline recovered
Other contaminant sources
include aircraft and vehicle
washracks Draft ST-14 Second Long-Term Monitoring Report, Andrews Air Force Base. June 2010

The Scene – Hydrogeology (Continued)
Unconfined aquifer comprised of three stratigraphic lithologies of the
Brandywine Formation Upland Deposits
– Shallow Zone: clayey, gravelly silt (range 0 – 28’ bgs, avg. 14’ bgs)
– Intermediate Zone: sand and gravel (range 10 – 38’ bgs, avg. 26’ bgs)
– Deep Zone: silty fine sand (range 15 – 40’ bgs, avg. 33’ bgs)
Average depth to water is 17’ bgs
Estimates of Intermediate K range from 0.24 – 3.5’ per day
Hydraulic gradient = 0.007 – 0.02
Underlain by Calvert Formation (range 38 – 40’ bgs, outcrops at northeast)
– Described as a regional aquitard (Final ST-14 Feasibility Study Report,
January 2007)

The Scene - Hydrogeology (Concluded)
Derived from Draft ST-14 Second Long-Term Monitoring Report, Andrews Air Force Base. June 2010

The Suspects – TCE, BTEX, CCl4
(Baseline – MAR 2006)
62 Acre TCE Plume
5.5 Acre CCl4 Plume 6.4 Acre BTEX Plume
62 Acre TCE Plume
5.5 Acre CCl4 Plume 6.4 Acre BTEX Plume

The Tools: TCE and CCl4 Remediation –
Reductive Dechlorination
Sodium lactate (6% solution) injected to promote reductive dechlorination
– Ten injection events between October 2007 and November 2009
– Ten injection “barriers”
– 210 injection points (max. depth 45’ bgs)
– Total of 239,250 gallons of sodium lactate solution injected
 Emulsified vegetable oil (EOS®)
– One injection event between May and June 2010
– 250 gallons of 4-6% EOS injected per injection point
– Total of 25,000 gallons of EOS added

The Tools: BTEX Remediation –
Aerobic Respiration
PermeOx® Plus injections (time released calcium peroxide powder)
120 pounds of PermeOx® Plus in 120 gallons of water per point
One foot increments from 32’ to 19’ bgs
Three injection events
– October 2007 (40 points, 4,800 lbs PermeOx® Plus)
– July 2009 (10 points, 1,200 lbs PermeOx® Plus)
– May 2010 (8 points, 960 lbs PermeOx® Plus)
Total = 6,960 lbs

Injection Event 1 Locations
(OCT 2007)
4,800 pounds of
PermeOx® Plus
49,500 gallons of
Sodium Lactate
1
2
3
4
5
6
7

(DEC 2007 – JAN 2008)
47,000 gallons of
Sodium Lactate
1
2
3
4
5
6
7

(FEB 2008 – MAR 2008)
45,500 gallons of
Sodium Lactate
1
2
3
5
6
4
7
6

(APR 2008 – MAY 2008)
33,000 gallons of
Sodium Lactate
1
2
3
4
5
6
7

(JUL 2008)
30,750 gallons of
Sodium Lactate
1 2
3
4
5
6
7

(NOV 2008)
19,000 gallons of
Sodium Lactate
1
2
3
4
5
6
7

(JUN 2009)
3,000 gallons of
Sodium Lactate
1
2
3
4
5
6
7

(JUL 2009)
3,500 gallons of
Sodium Lactate
1,200 pounds of
PermeOx® Plus
1
2
3
4
5
6
7
8
9
10

(SEP 2009)
5,000 gallons of
Sodium Lactate
1
2
3
4
5
6 7
8
9
10

(NOV 2009)
3,000 gallons of
Sodium Lactate
1
2
3
4
5
6
7
8
9
10

(MAY - JUN 2010)
960 pounds of
PermeOx® Plus
25,000 gallons
of EOS®
1
2
3
4
5
6
7
10
9
8

Contractor’s Conclusion
The groundwater analytical data and geochemical
parameters at Site ST-14 suggest that the remedial actions
performed at the site, including the PermeOx® Plus and
sodium lactate injections, generated favorable conditions in
the treatment area conducive to the biodegradation of the
primary [contaminants of concern].
And,
The data collected during the second long term monitoring
event showed that the remedial actions implemented at ST-
14 have had positive results in most of the targeted areas.

Evidence of Success?
The contractor cited the following lines of
evidence to demonstrate the success of the
injections:
–Reductions in plume size
–Mann-Kendall analysis
–Regression analysis
–Reductions in contaminant concentrations
–Phospholipid Fatty Acid (PLFA) analysis for
percent biomass (Firmicutes)

Clues from Changes in TCE Plume Size
(MAR 2006)
Draft ST-14 Second Long-Term Monitoring Report, Andrews Air Force Base. June 2010

(APR 2010)

(APR 2010)
Letter to Maryland Department of Environmental Quality, 2011

Clues from Mann Kendall
and Regression Analyses
Mann Kendall analysis were conducted using the
Monitoring and Remediation Optimization System
(MAROS) software to identify general trends
(increasing, decreasing, stable, no trend)
Regression analyses were conducted on
selected wells to predict when contaminants
would meet maximum contaminant limits (MCLs)

TCE Regression Analysis (Red Herrings)

Clues from Injection Barrier Monitoring Well Data
Injection Barrier Wells
– Injection Barrier 1: Monitor Well (MW) 17
– Injection Barrier 3: MW 11
– Injection Barrier 5: MW 12 and MW 19 (well pair)
– Injection Barrier 6: MW 23 and MW 24 (well pair)
Downgradient Monitoring Wells
– MW 16
– MW 37
– MW 07

Injection Barrier 1 - MW 17 Data
(Evidence of Incomplete Degradation)

Injection Barrier 3 - MW 11 Data
(Evidence of Incomplete Degradation)

Injection Barrier 5 - MWs 12 (Deep?) and 19 (Shallow)
Data (Evidence of Incomplete Degradation)

Injection Barrier 6 - MWs 23 (Deep) and 24 (Shallow?)
Data (Evidence of Incomplete Degradation)

Downgradient Wells - MWs 16 and 37 Data
(Evidence of Displacement)
Similar Response
Pattern
Mounding

Downgradient Wells – MW 07 Data
(Smoking Gun for Displacement)
4,800lbs
1,200lbs
PermeOx
Mounding

Calvert Formation a Regional Aquitard?
(False Lead)

(False Lead)
Boring logs
indicate that
Calvert
Formation in
area of Site
ST-14
consists of
sandy clay

(False Lead)
The Calvert is a silty clay with local sand beds. It is reported to be
a poor aquifer and considered to be a confining bed in southern
Maryland (Chapelle and Drummond, 1983). Locally, it may yield
small amounts of water to farm or domestic wells. Recharge to the
Calvert is probably transmitted from overlying units and discharge
is likely directed either to local surface waters or to water-bearing
units at greater depth. Water in the Calvert may exist under water
table or artesian (confined) conditions [emphasis added].
“Installation Restoration Program Phase I Records Search” (June
1985)

Clues from Changes in CCl4 Plume Size
(MAR 2006)

Clues from Changes in CCl4 Plume Size
(APR 2010)

Clues from CCl4 Regression Analysis

Clues From CCl4 Well Data – MWs 23, 24, and 01
5
6 7

Evidence of CCl4 Displacement
0
2
4
6
8
10
12
14
16
18
20
Jan‐08
Feb‐08
Mar‐08
Apr‐08
May‐08
Jun‐08
Jul‐08
Aug‐08
Sep‐08
Oct‐08
Nov‐08
Dec‐08
Jan‐09
Feb‐09
Mar‐09
Apr‐09
May‐09
Jun‐09
Jul‐09
Aug‐09
Sep‐09
Oct‐09
Nov‐09
Dec‐09
Jan‐10
Feb‐10
Mar‐10
Apr‐10
Concentration
Sample Date
MW 24 DO and CT Concentrations
DO
(mg/L)
CT
(ug/L)
6,000gal(5,6)
12,500gal(5,6,7)
2,000gal(5,6)
6,000gal(5,6)
6,500gal(5,7)
4,500gal(6,7)
Sodium Lactate

Clues from Changes in BTEX Plume Size
(MAR 2006)

Clues from Changes in BTEX Plume Size
(APR 2010)

Clues from Benzene Regression Analysis
(Red Herrings)

Clues from Ethylbenzene, Toluene, and Total
Xylene Regression Analysis (Red Herrings)

Clues From BTEX Well Data –
MWs 10 and 04
3 4
9
8

7,500 gal (3)
4,800 lbs
7,500 gal (3)
4,000 gal (3,8,9)
2,500 gal (8,9)
2,500 gal (8,9)
Substrate Competition
0
10
20
30
40
50
60
70
Concentration in mg/L
Sample Date
MW 10 Total BTEX and DO Concentrations
DO
Total
BTEX
20,000 gal (3,4)
20,000 gal (3,4)
12,000 gal (3)
7,500 gal (3)
1,200 lbs
980 lbs
Sodium Lactate
PermeOx

Conclusion – What can we deduce from
the available evidence?
The preponderance of the evidence suggests that:
– Remediation of contaminants at Site ST-14 was only marginally effective
• Limited in extent and duration
• Contaminant reductions primarily the result of displacement and dilution
– Reductive dechlorination appears to be limited by recharge of oxygenated
water through the Calvert Formation, low pH (avg. 4.88), and the method of
substrate addition
• Difficulty in establishing and maintaining low DO concentrations
• pH of 4.88 is suboptimal for Dehalococcoides
• Inconsistent production of microbial biomass
• Reductive dechlorination of TCE generally stalls at DCE
– BTEX remediation was limited due to substrate competition

Lessons Learned (Site Characterization)
Fit the theory to the facts, not the facts to the
theory
–Calvert Formation was considered a regional
aquitard in spite of available data that suggested
otherwise
–Demonstrates the need for a complete and
accurate conceptual site model

Lessons Learned (Substrate Injections)
When designing a remedial approach involving
substrate injections:
–Ensure groundwater flow gradient is sufficient to
overcome injection-related mounding effects
–Consider limiting perpendicular injections to laterally
limited hydrogeologic systems (e.g. paleochannels)

Lessons Learned (Remediation)
Begin remediation activities within short period of
establishing baseline conditions
Do not try to promote aerobic respiration of
certain contaminants (BTEX) while simultaneously
trying to promote reductive dechlorination of other
compounds (TCE) in close proximity

Lessons Learned (Data Analyses)
Statistics and trend analyses do not always tell
the whole story and can be misleading
When evaluating the performance of reductive
dechlorination, consider changes in concentration
of the daughter products in addition to the primary
contaminant of concern
Site conditions are dynamic and change with time,
groundwater movement, and remedial activity

Lessons Learned (Plume Depictions)
Contaminant plume depictions are generated
based on kriging algorithms found in the individual
software systems
–Results influenced by contaminant
concentrations, and data quality and density
–Use professional judgment when drawing
conclusion for software generated plume maps

Lessons Learned (Third Party Review)
An independent third party review can be useful in
providing an objective assessment of the available
data to provide an alternative perspective

Closing Argument
It is an old maxim of mine that when you have
excluded the impossible, whatever remains,
however improbable, must be the truth.
Sherlock Holmes in “The Adventure of the Beryl
Coronet” by Sir Arthur Conan Doyle

Acknowledgments
Dr. Arturo Riojas
Dr. Sabina Chowdhury
Mr. Sriram Madahbushi

Remediation Evaluation of Site ST-14 at Joint Base Andrews

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