Downey_MG_Maryland_Tt format

Quantitative Metrics to Gage the Effects of an Enhanced Biodegradation Program Iowa Army Ammunitions Plant, Middletown, Iowa

Melisa Geraghty, Brian Caldwell, PG; Dr. Tiffany Downey, Dr. Ronnie Britto, and Dr. Rick Arnseth

Site History Iowa Army Ammunition Plant (IAAAP) - located

in Des Moines County, Iowa Munitions production and testing beginning in

1941 Resulted in contamination of the soil,

groundwater, and surface water with explosives – Extensive offsite Royal Demolition Explosive

(RDX) groundwater plume sourced by RDX in surface water runoff.

Off-Site Plume map here

Remediation Plan To enhance biodegradation and expedite the

natural attenuation of the RDX plume using an enhanced degradation process (sodium acetate injection) – 11 designed-injection wells upgradient of the

highest concentration plume core. – Analytically modeled injection rates and locations – Five injection events between October 2007

and April 2009• initial event employed all 11 injection wells. • Subsequent events customized injected mass

and number of injection points based on analytical data

Development of Evaluation Metrics Remedial progress metrics developed to

account for temporal and spatial comparisons in order to maintain optimal reducing conditions– Quantitative analysis of plume configuration

– Statistical analysis of the RDX concentrations from individual sampling events

Evaluation Metrics Include Point by point comparisons

– Statistical trend analysis – First-order kinetics concentration change

analysis • degradation rates and times to achieve

remediation goals. Plume wide analysis

– Representative population using differential analysis

– Central Tendency Analysis– Change in overall plume core mass.

Mann-Kendall Trend Analysis Non-parametric statistical test (the data are not

required to be normally distributed) Assesses point changes in a data set over time for an

increasing or decreasing trend at a given statistical confidence level. – Designed to assess four to eighteen rounds of data at

an 80% confidence level– Determines if the data can be used to estimate a first

order degradation or augmentation rate – To avoid biasing the MK test, the same value for all ND

results was used (one half of the detection limit from the round with the lowest detection limit for that well).

– For wells that did not exhibit a increasing or decreasing trend at an 80% confidence level the coefficient of variation was used to determine if the well was stable or unstable

Mann-Kendall Trend Analysis Con’t For wells that did not have a minimum of four

sampling events or did not exhibit an overall trend at 80% confidence, the last three measurements were used to approximate the direction of the concentration change. 

The point-by-point analysis results indicate an overall decreasing trend in a majority of the wells. – 18 wells trended

• 8 = decreasing• 1 = increasing • 9 = stable

Quantifying a Decreasing Trend Plotting of the log-transformed concentrations versus a linear

unit of time (days were used). Finite source degradation is described by an exponential degradation curve when plotted on a linear scale. In order to use linear regression to calculate the slope (the degradation rate), the data were log-transformed and plotted on a linear scale.

Performing linear regression calculations on Step 1 by plotting a trend line (least-squares fit trend line) that minimizes the variance (squared deviations) of all of the data points from the line.

Using the slope of the equation represented by the least-squares trend line as the fractional change per day. This was then used to calculate a half-life expressed in days, and to develop a degradation curve that predicts the time at which the concentrations at that sampling point will reach 2 ppb.

Example Output

DATE RDX (ug/L) Ln Conc. (ug/L)Degradation Rate

(% per day)09/28/2007 104 4.644390899 1.02176599812/19/2007 95.8 4.562262685 1.00369779102/13/2008 76.9 4.342505877 0.95535129312/09/2008 41.3 3.7208625 0.81858975

First-order Degradation Rate (day-1) = 0.0022Half Life (days) = 315.05Mann Kendall Statistic (S) = -6.0Number of Rounds (n) = 4Average = 79.50Standard Deviation = 27.880Coefficient of Variation(CV)= 0.351Trend ≥ 80% Confidence Level DECREASINGTrend ≥ 90% Confidence Level DECREASING

Example Output Graphs - Decreasing

3930

0

3940

0

3950

0

3960

0

3970

0

3980

0

3990

0

0

20

40

60

80

100

120

f(x) = − 0.144037624628416 x + 5771.56772215897R² = 0.973120132443412

EMW-06

Date

RD

X ug

/L

3930

0

3940

0

3950

0

3960

0

3970

0

3980

0

3990

0

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

f(x) = − 0.00217427496108336 x + 90.2403354244016R² = 0.987992540092612

EMW-06

Date

Ln R

DX

ug/L

0 200 400 600 800 1000 1200 1400 16000

5

10

15

20

25

30

35

40

45

Degradation Curve

Time (days)

Conc

entra

tion

(ug/

L)

Example Output Graphs – Stable or Non-Stable

11/0

9/20

04

02/1

7/20

05

05/2

8/20

05

09/0

5/20

05

12/1

4/20

05

03/2

4/20

06

07/0

2/20

06

0

10

20

30

40

50

60

70

f(x) = 0.014359634334823 x − 506.668356346557R² = 0.0768510632675288

IW-05

Date

RD

X ug

/L

04/0

8/20

05

05/2

8/20

05

07/1

7/20

05

09/0

5/20

05

10/2

5/20

05

12/1

4/20

05

02/0

2/20

06

03/2

4/20

06

05/1

3/20

06

0

10

20

30

40

50

60

f(x) = 0.0523149703166883 x − 1978.16565832776R² = 0.924461506594045

IW-05

Date

RD

X ug

/L

Example Output Graphs - Increasing

08/0

6/20

07

11/1

4/20

07

02/2

2/20

08

06/0

1/20

08

09/0

9/20

08

12/1

8/20

08

03/2

8/20

09

07/0

6/20

09

10/1

4/20

09

01/2

2/20

10

0

0.5

1

1.5

2

2.5

3

3.5

f(x) = 0.00350760288795276 x − 138.069184305981R² = 0.740959616062104

EMW-08

Date

RD

X ug

/L

Plume Wide Analysis

Plume Core Mass

Plume Event

Number of wells sampled

RDX mass(g)

Change in mass from Previous events

(g)Percent Change

1 16 3,693,903.46 N/A N/A

2 24 61,897,939.34 58,204,035.88 1576%

3 24 61,815,101.54 -82,837.80 0%

4 26 57,380,772.09 -4,434,329.45 -7%

Insert example of plume core mass wksheet

Statistical Mean The plume-wide statistical mean decreased

from 101 ppb at baseline in October 2007 to 42.38 ppb in December 2008

Between December 2008 and December 2009, there was a 70.0% decrease in UCL means to 12.73 ppb.

However, based on the differential test (Kolmogorov-Smirnov), the change in populations is not statistically significant at a 95% confidence level. All data sets result from the same population