U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 02-4119

Prepared in cooperation with

Department of the Navy

Engineering Field Activity, Northwest

Naval Facilities Engineering Command

Natural Attenuation of Chlorinated Volatile

Organic Compounds in Ground Water at

Operable Unit 1, Naval Undersea Warfare

Center, Division Keyport, Washington

science for a changing world

SR

308

SR

303

BRO

WNSV LI LE H GI HWAY

L I B E R T Y

B A Y

Dogfish Bay

Shallow

lagoon

Tide

flats

KEYPORT

VIRGINIA

POINT

Landfill

(Operable Unit 1)

P o r t

O r c h a r d

Naval Undersea

Warfare Center, Keyport
U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4119

Natural Attenuation of Chlorinated Volatile

Organic Compounds in Ground Water at

Operable Unit 1, Naval Undersea Warfare

Center, Division Keyport, Washington

Prepared in cooperation with

DEPARTMENT OF THE NAVY

ENGINEERING FIELD ACTIVITY, NORTHWEST

NAVAL FACILITIES ENGINEERING COMMAND

By R.S. Dinicola, S.E. Cox, J.E. Landmeyer, and P.M. Bradley

Tacoma, Washington

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information write to:

District Chief

U.S. Geological Survey

1201 Pacific Avenue – Suite 600

Tacoma, Washington 98402

http://wa.water.usgs.gov

Copies of this report can be purchased

from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

District Chief

U.S. Geological Survey

1201 Pacific Avenue – Suite 600

Tacoma, Washington 98402

http://wa.water.usgs.gov
Contents iii

CONTENTS

Executive Summary .......................................................................................................................................... 1

Abstract ............................................................................................................................................................. 5

Introduction ....................................................................................................................................................... 5

Purpose and Scope ................................................................................................................................... 7

Description of the Study Area.................................................................................................................. 7

Hydrogeologic Setting .................................................................................................................... 9

Surface-Water and Ground-Water Flow ......................................................................................... 12

Contamination and Remediation..................................................................................................... 15

Acknowledgments.................................................................................................................................... 20

Redox Conditions in Contaminated Ground Water .......................................................................................... 23

Natural Attenuation in Ground Water............................................................................................................... 25

Destructive Attenuation Processes........................................................................................................... 25

Trichloroethene and Other Chlorinated Ethenes............................................................................. 25

1,1,1-Trichloroethane and Other Chlorinated Ethanes ................................................................... 27

Nondestructive Attenuation Processes..................................................................................................... 27

Methods and Data Analysis............................................................................................................................... 28

Hydrogeologic Data Collection................................................................................................................ 28

Chemical Sampling and Analyses............................................................................................................ 29

Calculation of Contaminant Mass-Degradation Rates in Ground Water and 

Discharge to Surface Water......................................................................................................... 30

Calculation of Contaminant Attenuation Rates........................................................................................ 32

Hydrogeologic and Geochemical Characterization for Natural Attenuation.................................................... 32

Ground-Water Flow Directions and Rates............................................................................................... 32

Ground-Water Flowpaths Between the Upper and Intermediate Aquifers..................................... 33

Ground-Water Flow Rates in the Intermediate Aquifer.................................................................. 38

Changes in Ground-Water Flow from Phytoremediation Activities .............................................. 39

Redox Conditions in Ground Water......................................................................................................... 39

Upper Aquifer ................................................................................................................................. 40

Changes in Upper-Aquifer Redox Conditions from Phytoremediation Activities ......................... 40

Intermediate Aquifer ....................................................................................................................... 45

Distribution of Chlorinated VOCs in Upper-Aquifer Ground Water and Surface Water........................ 45

Evaluation of Natural Attenuation .................................................................................................................... 49

Natural Attenuation in the Upper Aquifer Beneath the Northern Plantation........................................... 49

Changes in CVOC Concentrations Over Time............................................................................... 49

Changes in CVOC and Geochemical Concentrations Along Flowpaths........................................ 51

Natural Attenuation in the Upper Aquifer Beneath the Southern Plantation........................................... 54

Changes in CVOC Concentrations Over Time............................................................................... 54

Changes in CVOC and Geochemical Concentrations Along Flowpaths........................................ 57

Natural Attenuation in the Intermediate Aquifer ..................................................................................... 59

Changes in CVOC Concentrations Over Time............................................................................... 61

Changes in CVOC and Geochemical Concentrations Along Flowpaths........................................ 61

Natural Attenuation in Surface Water...................................................................................................... 64

Changes in CVOC Concentrations Over Time............................................................................... 64

Changes in CVOC Concentrations Along Flowpaths..................................................................... 64
iv Contents

Degradation Rates of Chlorinated Ethene Mass in Ground Water and Mass Discharge 

to Surface Water.......................................................................................................................... 66

Chlorinated Ethene Attenuation Rates..................................................................................................... 69

Effectiveness of Natural Attenuation at Meeting Remediation Goals..................................................... 70

Conclusions ....................................................................................................................................................... 72

Current Understanding of Natural Attenuation at OU 1 .......................................................................... 72

Current Impacts of Phytoremediation Activities on Natural Attenuation................................................ 75

Continued Monitoring of Natural Attenuation......................................................................................... 75

References Cited ............................................................................................................................................... 76

Appendix A. Quality Assurance and Control of U.S. Geological Survey Geochemical Sampling.................. 112
Figures v

FIGURES

Figure 1. Map showing location of the Operable Unit 1 study area, Naval Undersea Warfare 

Center (NUWC), Division Keyport, Washington.............................................................................. 6

Figure 2. Map showing location of the former landfill and other features and of the 

data-collection sites at Operable Unit 1, Naval Undersea Warfare Center (NUWC), 

Division Keyport, Washington .......................................................................................................... 8

Figure 3. Map showing location of the hydrogeologic sections shown in figure 4, Operable 

Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington......................... 10

Figure 4. Hydrogeologic sections showing the six primary hydrogeologic units at Operable 

Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington......................... 11

Figure 5. Map showing ground-water levels and flow in the shallow aquifer during a low 

tide, September 1996, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), 

Division Keyport, Washington .......................................................................................................... 13

Figure 6. Map showing ground-water levels and flow in the shallow aquifer during a high 

tide, September 1996, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), 

Division Keyport, Washington .......................................................................................................... 14

Figure 7. Map showing ground-water levels and flow in the intermediate aquifer during a low 

tide, September 1996, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), 

Division Keyport, Washington .......................................................................................................... 16

Figure 8. Map showing ground-water levels and flow in the intermediate aquifer during a high 

tide, September 1996, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), 

Division Keyport, Washington .......................................................................................................... 17

Figure 9. Map showing ground-water flow directions and flow rates in the upper aquifer at 

Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington ......... 18

Figure 10. Map showing ground-water flow directions and flow rates in the intermediate aquifer 

at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington ..... 19

Figure 11. Map showing concentrations of chlorinated volatile organic compounds (CVOCs) in 

surface water and upper-aquifer ground water, 1996, at Operable Unit 1, Naval Undersea 

Warfare Center (NUWC), Division Keyport, Washington................................................................ 21

Figure 12. Map showing concentrations of chlorinated volatile organic compounds (CVOCs) in

intermediate-aquifer ground water, 1996, at Operable Unit 1, Naval Undersea Warfare 

Center (NUWC), Division Keyport, Washington.............................................................................. 22

Figure 13. Diagram showing possible degradation pathways for trichloroethene and for 

1,1,1-trichloroethane.......................................................................................................................... 26

Figure 14. Graph showing concentrations of oxygen-18 and hydrogen-2 isotopes in ground water 

in selected wells, June 2000, at Operable Unit 1, Naval Undersea Warfare Center, 

Division Keyport, Washington .......................................................................................................... 34

Figure 15. Trilinear diagrams showing (A) differences in ionic composition of water at selected 

wells and (B) mixing of ground waters along two flowpaths at Operable Unit 1, Naval 

Undersea Warfare Center, Division Keyport, Washington ............................................................... 36
vi Figures

Figure 16. Map showing average dissolved hydrogen (H2) concentrations at sampled wells and 

delineated redox conditions in the upper aquifer at Operable Unit 1, Naval Undersea 

Warfare Center (NUWC), Division Keyport, Washington................................................................ 41

Figure 17. Map showing concentrations of total organic carbon in ground water, 1999, at Operable 

Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington......................... 42

Figure 18. Graphs showing concentrations of manganese, iron (II), total organic carbon, and 

hydrogen (H2), 1996–2000, in wells MW1-4, MW1-5, and MW1-16 in the southern 

plantation at Operable Unit 1, Naval Undersea Warfare Center, Division 

Keyport, Washington ......................................................................................................................... 43

Figure 19. Graphs showing concentrations of manganese, iron (II), total organic carbon, and 

hydrogen (H2), 1996–2000, in wells MW1-2, 1MW-1, and MW1-14/41 in the northern 

plantation at Operable Unit 1, Naval Undersea Warfare Center, Division 

Keyport, Washington ......................................................................................................................... 44

Figure 20. Map showing average dissolved hydrogen (H2) concentrations at sampled wells and 

delineated redox conditions in the intermediate aquifer at Operable Unit 1, Naval Undersea 

Warfare Center (NUWC), Division Keyport, Washington................................................................ 46

Figure 21. Graphs showing concentrations of manganese, iron (II), total organic carbon, and 

hydrogen, 1996–2000, in selected intermediate-aquifer wells at Operable Unit 1, Naval 

Undersea Warfare Center, Division Keyport, Washington ............................................................... 47

Figure 22. Map showing concentrations of chlorinated volatile organic compounds (CVOCs)

in upper-aquifer ground water, 1999, at Operable Unit 1, Naval Undersea Warfare Center

(NUWC), Division Keyport, Washington ......................................................................................... 48

Figure 23. Graphs showing concentrations of chlorinated ethenes in wells 1MW-1 and MW1-2

in the northern plantation, 1991–2000, at Operable Unit 1, Naval Undersea Warfare 

Center, Division Keyport, Washington.............................................................................................. 50

Figure 24. Map showing locations of ground-water flow paths used to evaluate natural 

attenuation at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division 

Keyport, Washington ......................................................................................................................... 52

Figure 25. Graphs showing concentrations of chlorinated ethenes, 1999, along ground-water 

flowpaths A and B and along an averaged flowpath in the northern plantation at Operable 

Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington......................................... 53

Figure 26. Graphs showing concentrations of redox-sensitive compounds, 1999, along ground-water 

flowpaths A and B and along an averaged flowpath in the northern plantation at Operable 

Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington......................................... 55

Figure 27. Graphs showing chlorinated ethenes, 1991–2000, in wells MW1-4, MW1-5, and MW1-16

in the southern plantation at Operable Unit 1, Naval Undersea Warfare Center, 

Division Keyport, Washington .......................................................................................................... 56

Figure 28. Graphs showing concentrations of chlorinated ethenes, 1999, along ground-water 

flowpaths C, D, and E in the southern plantation at Operable Unit 1, Naval Undersea 

Warfare Center, Divison Keyport, Washington................................................................................. 58

Figure 29. Graphs showing concentrations of redox-sensitive compounds, 1999, along ground-water 

flowpaths C, D, and E in the southern plantation at Operable Unit 1, Naval Undersea 

Warfare Center, Division Keyport, Washington................................................................................ 60

Figure 30. Graphs showing concentrations of chlorinated ethenes, 1991–2000, in intermediate-aquifer 

wells 1MW-4, MW1-25, and MW1-28 in the southern plantation at Operable Unit 1, Naval 

Undersea Warfare Center, Division Keyport, Washington ............................................................... 62
Figures vii

Figure 31. Graphs showing concentrations of chlorinated ethenes and redox-sensitive compounds 

along flowpath F in the intermediate aquifer at Operable Unit 1, Naval Undersea Warfare 

Center, Division Keyport, Washington.............................................................................................. 63

Figure 32. Graphs showing concentrations of chlorinated ethenes, 1991–2000, for surface-water 

stations MA-12, MA01/MA-11, and MA-09 at Operable Unit 1, Naval Undersea Warfare 

Center, Division Keyport, Washington.............................................................................................. 65

Figure 33. Graph showing concentrations of chlorinated ethenes in surface water as it flows through 

the marsh and across the tideflats at Operable Unit 1, Naval Undersea Warfare Center, 

Division Keyport, Washington .......................................................................................................... 66
viii Tables

TABLES

Table 1. Characteristic dissolved-hydrogen concentrations for different anaerobic redox conditions 

in ground water ................................................................................................................................. 24

Table 2. Age dates calculated using tritium/helium data from ground water sampled 

September 19, 1996, at Operable Unit 1, Naval Undersea Warfare Center, Division 

Keyport, Washington ........................................................................................................................ 38

Table 3. Degradation rates of chlorinated ethene mass and discharge to surface water at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ........................ 68

Table 4. Results of alternate method of estimating chlorinated ethene discharge to the marsh at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ........................ 69

Table 5. First-order attenuation half-lives of chlorinated ethene for segments of selected 

flowpaths at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ...71

Table 6. Numerical remediation goals for concentrations of chlorinated volatile organic 

compounds in ground water and surface water at Operable Unit 1, Naval Undersea 

Warfare Center, Division Keyport, Washington ............................................................................... 72

Table 7. Predominant redox conditions at selected wells and ground-water chemistry data 

collected from 1996 to 2000, at Operable Unit 1, Naval Undersea Warfare Center, 

Division Keyport, Washington ......................................................................................................... 82

Table 8. Concentrations of chlorinated volatile organic compounds in ground water at Operable 

Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ........................................ 86

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile 

organic compounds in ground and surface water, 1991–2000, from selected sites at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ........................ 88

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile 

organic compounds in ground and surface water, 1991–2000, from selected sites at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ........................ 98

Table 11. Data used to calculate degradation rates of chlorinated ethene mass and discharge to 

surface water at Operable Unit 1, Naval Undersea Warfare Center, Division 

Keyport, Washington ........................................................................................................................108

Table 12. Data used to calculate first-order attenuation half-lives of chlorinated ethene for 

segments of selected flowpaths at Operable Unit 1, Naval Undersea Warfare Center, 

Division Keyport, Washington .........................................................................................................109

Table A1. Quality assurance and control data collected by the U.S. Geological Survey at Operable 

Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington ........................................114
Conversion Factors ix

CONVERSION FACTORS AND VERTICAL DATUM

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=1.8 °C+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of

1929)--a geodetic datum derived from a general adjustment of the first-order level nets of both the

United States and Canada, formerly called Sea Level Datum of 1929.

Altitude, as used in this report, refers to distance above or below sea level.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or

micrograms per liter (μg/L).

Multiply By To obtain

Length

inch (in) 2.54 centimeter

inch (in) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

acre 4,047 square meter

acre 0.004047 square kilometer

Flow rate

foot per day (ft/d) 0.3048 meter per day

foot per year (ft/yr) 0.3048 meter per year

Mass

gram (g) 0.03527 ounce, avoirdupois 
Executive Summary 1

Natural Attenuation of Chlorinated Volatile Organic 

Compounds in Ground Water at Operable Unit 1, Naval 

Undersea Warfare Center, Division Keyport, Washington

By R.S. Dinicola, S.E. Cox, J.E. Landmeyer, and P.M. Bradley

EXECUTIVE SUMMARY

The U.S. Geological Survey (USGS) 

evaluated the natural attenuation of chlorinated 

volatile organic compounds (CVOCs) in ground 

water beneath the former landfill at Operable Unit 

1 (OU 1), Naval Undersea Warfare Center, 

Division Keyport, Washington. The predominant 

contaminants in ground water are trichloroethene 

(TCE) and its degradation byproducts cis-1,2-

dichloroethene (cisDCE) and vinyl chloride (VC). 

The Navy planted two hybrid poplar plantations on 

the landfill in spring of 1999 to remove and control 

the migration of CVOCs in shallow ground water. 

Previous studies provided evidence that microbial 

degradation processes also reduce CVOC 

concentrations in ground water at OU 1, so 

monitored natural attenuation is a potential 

alternative remedy if phytoremediation is 

ineffective. This report describes the current 

(2000) understanding of natural attenuation of 

CVOCs in ground water at OU 1 and the impacts 

that phytoremediation activities to date have had 

on attenuation processes. The evaluation is based 

on ground-water and surface-water chemistry data 

and hydrogeologic data collected at the site by the 

USGS and Navy contractors between 1991 and 

2000. Previously unpublished data collected by the 

USGS during 1996–2000 are presented. 

Natural attenuation of CVOCs in shallow 

ground water at OU 1 is substantial. For 1999–

2000 conditions, approximately 70 percent of the 

mass of dissolved chlorinated ethenes that was 

available to migrate from the landfill was 

completely degraded in shallow ground water 

before it could migrate to the intermediate aquifer 

or discharge to surface water. Attenuation of 

CVOC concentrations appears also to be 

substantial in the intermediate aquifer, but 

biodegradation appears to be less significant; those 

conclusions are less certain because of the paucity 

of data downgradient of the landfill beneath the 

tide flats. Attenuation of CVOC concentrations is 

also substantial in surface water as it flows through 

the adjacent marsh and out to the tide flats. 

Attenuation processes other than dilution reduce 

the CVOC flux in marsh surface water by about 

40 percent by the time the water discharges to the 

tide flats. Despite the importance of natural 

attenuation processes at reducing both the 

contaminant concentrations and the contaminant 

mass at OU 1, natural attenuation alone was not 

effective enough in the year 2000 to meet current 

numerical remediation goals for the site. That was 

in part due to the relatively short distance between 

the landfill and the adjacent marsh, and in part due 

to the extremely high CVOC concentrations 

directly beneath the landfill.

Additional hydrogeologic and geochemical 

characterization was completed as part of this 

investigation to improve our understanding of the 

fate and transport of CVOCs at OU 1. Oxygenand hydrogen-isotope and common-ion data were 

interpreted to identify two distinct flowpaths for 

contaminant migration into the intermediate 

aquifer, one through the middle aquitard and 

downgradient to the slightly contaminated 

intermediate-aquifer well beneath the Highway 

308 causeway, and the other through a permeable 

window in the middle aquitard to currently 

uncontaminated deeper intermediate-aquifer wells 

beneath Highway 308. 
2 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

A more detailed distribution of total CVOCs in 

shallow ground water was determined by 

integrating data from existing monitoring wells 

with new data from piezometers in the landfill and 

diffusion samplers in the adjacent marsh. The 

refined distribution shows that the highest CVOC 

concentrations beneath the landfill are about four 

times greater than previously thought, and that the 

pattern of CVOC concentrations in shallow marsh 

ground water correlates well with the pattern 

observed beneath the landfill. The latter 

observation was evidence that the diffusion 

samplers used to collect marsh CVOC samples 

worked as intended and reasonably represent 

shallow ground-water conditions.

Ground-water redox conditions beneath the 

former landfill were found to be generally 

favorable for complete degradation of CVOCs 

through either reductive dechlorination alone or 

through the combined processes of reductive 

dechlorination and mineralization. Redox 

conditions were determined by quantifying 

oxidized and reduced inorganic compounds as 

well as steady-state dissolved hydrogen (H2) 

concentrations throughout the contaminant plume. 

Two areas of strongly reducing (sulfate reduction 

or methanogenesis) ground water favorable for 

reductive dechlorination were identified beneath 

the landfill—one beneath the northern part of the 

landfill and one beneath the southern part. Those 

areas were surrounded by mildly reducing (iron or 

manganese reducing) ground waters that are 

possibly more favorable for mineralization of less 

chlorinated CVOCs. The landfill is a substantial 

source of organic carbon in shallow ground water, 

and the correlation between high organic carbon 

concentration and strongly reducing conditions is 

clear evidence that redox conditions are being 

controlled by microbially mediated processes. 

Ground-water redox conditions within the 

intermediate aquifer were generally less favorable 

for reductive dechlorination, but were possibly 

favorable for mineralization of less chlorinated 

CVOCs. Organic carbon concentrations were 

elevated in contaminated intermediate aquifer 

wells, but were substantially lower than those 

found in shallow ground water beneath the 

landfill. 

The evaluation of natural attenuation found 

consistent evidence for both partial and complete 

degradation of CVOCs in upper-aquifer ground 

water at OU 1. Temporal changes in CVOC 

concentrations between 1991 and 2000 at shallow 

wells beneath the landfill, and changes in recent 

(1999-2000) CVOC and redox-sensitive 

geochemical concentrations along shallow groundwater flowpaths indicated substantial attenuation 

and degradation beneath the landfill. Total CVOC 

concentrations continued to attenuate along 

ground-water flowpaths between the landfill and 

the marsh, and the proportions of CVOCs changed 

from predominantly highly chlorinated 

compounds to less chlorinated compounds along 

selected flowpaths. Concentrations of redoxsensitive compounds also changed, following a 

pattern consistent with active reductive 

dechlorination along those same flowpaths. 

Overall, the evidence indicated the most 

substantial attenuation and degradation occurred 

beneath the southern part of the northern 

plantation and beneath the northern part of the 

southern plantation. 

The evaluation found evidence for limited 

attenuation and degradation in the intermediate 

aquifer. Temporal changes in CVOC 

concentrations at individual wells in the most 

contaminated part of the intermediate aquifer 

indicated limited attenuation and degradation, 

whereas changes in CVOC and geochemical 

concentrations along ground-water flowpaths 

between the upper aquifer and the main body of 

the intermediate aquifer indicated substantial 

attenuation but uncertain biodegradation. Further 

downgradient of the landfill, it could only be 

concluded that contaminants have not migrated to 

beneath the Highway 308 causeway in the main 

body of the intermediate aquifer. 
Executive Summary 3

That could be a result of biodegradation, dilution, 

or discharge of ground water to the tide flats 

upgradient of Highway 308; or it could simply be 

that not enough time has passed for the 

contaminants to reach the deeper wells at the 

Highway 308 causeway. Along the newly 

identified ground-water flowpath between the 

upper aquifer and the sole contaminated Highway 

308 well, the evidence suggested substantial 

attenuation, but the causes of the attenuation were 

uncertain because of the lack of observation points 

beneath the tide flats. 

There have been no clear long-term changes 

in CVOC concentrations at individual surfacewater sites in the marsh, but there has been 

substantial attenuation of concentrations in surface 

water as it flows through the marsh and out to the 

tide flats. Biodegradation is likely insignificant in 

surface water, but volatilization (as well as 

dilution) substantially attenuate contaminant 

concentrations in the downstream direction.

Flux-based contaminant-mass-degradation 

rate calculations indicate that the majority of 

dissolved chlorinated ethenes in landfill ground 

water are degraded in ground water before they 

have an opportunity to migrate to the intermediate 

aquifer or discharge to surface water. Of the mass 

of dissolved chlorinated ethenes available to 

migrate from the landfill, nearly all TCE is 

degraded, about 60 percent of the cisDCE is 

degraded, and about 40 percent of the VC is 

degraded before discharging to surface water. 

Additional calculations using surface-water 

concentration data suggest that the actual fluxes of 

TCE and cisDCE to the marsh may be about 100 

and 30 percent greater, respectively, than the fluxbased estimates, because the diffusion samplers 

did not fully represent contaminant discharge to 

the southeastern portion of the marsh. The surfacewater-based calculations also suggest there was a 

net loss of about 30 percent of the TCE flux, 

40 percent of the cisDCE flux, and 50 percent of 

the VC flux as surface water flows through the 

marsh and out to the tide flats. The losses were 

likely due to nondestructive attenuation processes 

such as volatilization.

Comparison of calculated attenuation rates 

of chlorinated ethene concentrations for different 

ground-water flowpaths confirmed the previous 

findings regarding where biodegradation is most 

effective at OU 1. Attenuation rates varied 

throughout the upper aquifer beneath the landfill 

in close accordance with the location of favorable 

redox conditions, and attenuation rates in the 

intermediate aquifer were substantially slower 

than those calculate for the upper aquifer.

Based on data collected through June 2000, 

natural attenuation alone was not effective enough 

to meet the numerical remediation goals for 

ground water or surface water at OU 1. CVOC 

concentration goals were not met in upper-aquifer 

ground water beneath the landfill in five wells 

sampled as part of the long-term monitoring 

program and in all nine piezometers sampled 

during this investigation. CVOC concentrations in 

intermediate aquifer ground water were greatly 

attenuated when compared to landfill 

concentrations; nevertheless, ground-water 

remediation goals for cisDCE and/or VC were not 

met in three intermediate-aquifer wells. CVOC 

concentrations in marsh ground water also were 

greatly attenuated when compared to landfill 

concentrations, but the VC ground-water 

remediation goal for the protection of surface 

water was not met in nine of the 16 diffusion 

samplers. And finally, CVOC concentrations in 

surface water were also greatly attenuated when 

compared to landfill concentrations, but surfacewater remediation goals for VC were not met at 

three of the five surface-water sites that are part of 

the long-term monitoring program, and the TCE 

remediation goal was not met at one site.

Phytoremediation activities had some 

apparent effect on contaminant concentrations in 

ground water and surface water, but ground-water 

redox conditions to date (2000) were not affected 

by the February 1999 asphalt removal for tree 

planting. Water-level monitoring by the Navy 

during 1999 and 2000 showed that ground-water 

flow directions and gradients were consistent with 

those found previous to asphalt removal. 
4 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

The poplar trees in the phytoremediation 

plantations were not yet mature in 2000, so the 

lack of discernible changes to date is 

understandable. Redox conditions in the upper 

aquifer did not change substantially after the 

initiation of phytoremediation activities. However, 

concentrations of some redox-sensitive 

compounds did decrease, suggesting that increased 

recharge following asphalt removal diluted 

ambient landfill ground water or led to 

precipitation of oxidized iron and manganese 

compounds. There was no evidence of 

geochemical changes in the intermediate aquifer 

as a result of asphalt removal. CVOC 

concentrations increased in some downgradient 

wells in both the northern and southern plantations 

after asphalt removal, whereas CVOC 

concentrations decreased in some upgradient wells 

in the southern plantation. There was no evidence 

for CVOC changes in the intermediate aquifer that 

could be attributed to asphalt removal. A clear 

increase in CVOC concentrations in marsh surface 

water followed asphalt removal, apparently from 

increased contaminant discharge in ground water 

beneath the southern plantation.

The results of the natural attenuation 

evaluation suggest than minor modifications to the 

current sampling plan may be beneficial to 

understanding the future impacts of 

phytoremediation and natural attenuation on the 

fate and distribution of CVOCs at OU 1. Current 

plans call for sampling analytes related to natural 

attenuation at eight wells once every year through 

2004 and once every 5 years after 2004. With 

regard to sampling frequency, it would be 

informative to sample in March and September 

during at least a single year after the plantation 

canopy closes and tree roots have reached the 

water table. Those data would give more 

convincing evidence about effects of 

phytoremediation activities on ground-water redox 

conditions. Also, the decision to switch to a 5-year 

sampling cycle could best be made nearer the year 

2004, when additional data will be available to 

evaluate whether ground-water conditions are 

relatively stable. With regard to the number of 

wells sampled, the eight wells identified for 

sampling may be inadequate. Adding at least one 

upgradient well in the upper aquifer and one in the 

intermediate aquifer would provide comparison 

data to determine how geochemical conditions 

change as water flows to beneath the landfill. In 

addition, the landfill piezometers are located in the 

most contaminated parts of the landfill, so it would 

be worthwhile to sample CVOCs and 

geochemistry at those sites at least every other 

year through 2004. It would be worthwhile to 

sample the CVOCs and geochemistry in a deeper 

intermediate-aquifer well at the Highway 308 

causeway to monitor possible contaminant 

migration in the main body of that aquifer. The 

passive diffusion samplers provided very valuable 

information on overall contaminant attenuation in 

ground water, and it would be worthwhile to 

sample those same sites (with a few modifications) 

a few years after the plantation canopy closes. It 

would be informative to deploy diffusion samplers 

in March and September to coincide with the 

proposed one-time seasonal sampling, but 

sampling CVOCs in surface water could be used 

as a reasonable proxy for those seasonal data. With 

regard to analytes sampled, the list of 

geochemicals identified is adequate. DOC is 

thought to be a somewhat better measure of 

bioavailable organic carbon, so future sampling 

could include DOC rather than TOC. It would be 

useful to measure redox-sensitive compounds in 

diffusion samplers if that capability is available in 

the near future, and it would be useful to measure 

surface-water discharge directly in the marsh 

during the proposed seasonal sampling events or 

during the year when diffusion samplers are 

deployed. Those data could be used to confirm the 

hypothesis of seasonal or no ground-water 

discharge to the marsh from the northern part of 

the landfill.
Abstract 5

ABSTRACT

The U.S. Geological Survey (USGS) evaluated 

the natural attenuation of chlorinated volatile organic 

compounds (CVOCs) in ground water beneath the 

former landfill at Operable Unit 1 (OU 1), Naval 

Undersea Warfare Center, Division Keyport, 

Washington. The predominant contaminants in ground 

water are trichloroethene (TCE) and its degradation 

byproducts cis-1,2-dichloroethene (cisDCE) and vinyl 

chloride (VC). The Navy planted two hybrid poplar 

plantations on the landfill in spring of 1999 to remove 

and control the migration of CVOCs in shallow ground 

water. Previous studies provided evidence that 

microbial degradation processes also reduce CVOC 

concentrations in ground water at OU 1, so monitored 

natural attenuation is a potential alternative remedy if 

phytoremediation is ineffective. This report describes 

the current (2000) understanding of natural attenuation 

of CVOCs in ground water at OU 1 and the impacts 

that phytoremediation activities to date have had on 

attenuation processes. The evaluation is based on 

ground-water and surface-water chemistry data and 

hydrogeologic data collected at the site by the USGS 

and Navy contractors between 1991 and 2000. 

Previously unpublished data collected by the USGS 

during 1996-2000 are presented. 

Natural attenuation of CVOCs in shallow ground 

water at OU 1 is substantial. For 1999-2000 conditions, 

approximately 70 percent of the mass of dissolved 

chlorinated ethenes that was available to migrate from 

the landfill was completely degraded in shallow ground 

water before it could migrate to the intermediate 

aquifer or discharge to surface water. Attenuation of 

CVOC concentrations appears also to be substantial in 

the intermediate aquifer, but biodegradation appears to 

be less significant; those conclusions are less certain 

because of the paucity of data downgradient of the 

landfill beneath the tide flats. Attenuation of CVOC 

concentrations is also substantial in surface water as it 

flows through the adjacent marsh and out to the tide 

flats. Attenuation processes other than dilution reduce 

the CVOC flux in marsh surface water by about 

40 percent by the time the water discharges to the tide 

flats. Despite the importance of natural attenuation 

processes at reducing both the contaminant 

concentrations and the contaminant mass at OU 1, 

natural attenuation alone was not effective enough in 

the year 2000 to meet current numerical remediation 

goals for the site. That was in part due to the relatively 

short distance between the landfill and the adjacent 

marsh, and in part due to the extremely high CVOC 

concentrations directly beneath the landfill.

Phytoremediation activities had some apparent 

effect on contaminant concentrations in ground water 

and surface water, but ground-water redox conditions 

to date (2000) were not affected by the February 1999 

asphalt removal for tree planting. The poplar trees in 

the phytoremediation plantations were not yet mature 

in 2000, so the lack of discernible changes to date is 

understandable. Concentration changes of some redoxsensitive compounds suggest that increased recharge 

following asphalt removal diluted ambient landfill 

ground water. CVOC concentrations increased in some 

downgradient wells in both the northern and southern 

plantations after asphalt removal, whereas CVOC 

concentrations decreased in some upgradient wells in 

the southern plantation. A clear increase in CVOC 

concentrations in marsh surface water followed asphalt 

removal, apparently from increased contaminant 

discharge in ground water beneath the southern 

plantation.

The results of the natural attenuation evaluation 

suggest than minor modifications to the current 

sampling plan may be beneficial to understanding the 

future impacts of phytoremediation and natural 

attenuation on the fate and distribution of CVOCs at 

OU 1.

INTRODUCTION

Chlorinated volatile organic compounds 

(CVOCs) have migrated to ground water beneath the 

9-acre former landfill at Operable Unit 1 (OU 1), Naval 

Undersea Warfare Center (NUWC), Division Keyport 

(referred to in this report as NUWC Keyport), Wash. 

(fig. 1). The predominant contaminants in ground water 

are trichloroethene (TCE) and its degradation 

byproducts cis-1,2-dichloroethene (cisDCE) and vinyl 

chloride (VC); the compound 1,1,1-trichloroethane 

(TCA) and its degradation byproducts 1,1-

dichloroethane (1,1-DCA), 1,1-dichloroethene (1,1-

DCE) and chloroethane (CA) are of concern at a few 

locations at the site. A need for remedial action was 

identified because those hazardous compounds present 

a potential risk to humans, primarily through drinking 

contaminated ground water or through ingesting 

seafood harvested from contaminated surface water 

(URS Consultants, Inc., 1998).
6 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

SR

308

BROWNSVILLE

HIGHWAY

SR

303

1000 2000 3000 FEET

0 900 METERS

0

300 600

42'

42'

30"

47° 

42'

40"

37' 122°36'30"

47° 

41'

10"

41'

30"

122°38'20" 38' 37'30"

T.

26

N.

T.

25

N.

R.1 E. Base map modified from URS Consultants, Inc., 1997a.

WASHINGTON

Seattle

Bremerton

Figure

location

Location of figure 2 

L I B E R T Y B A Y

Dogfish Bay

Shallow

lagoon

Tide

flats

Marsh

KEYPORT

VIRGINIA POINT

Landfill

(Operable Unit 1)

P o r t

O r c h a r d

Naval Undersea

Warfare Center,

Keyport

Figure 1. Location of the Operable Unit 1 study area, Naval Undersea Warfare Center (NUWC), Division Keyport, 

Washington.
Introduction 7

In spring of 1999 two hybrid poplar plantations 

were planted on the northern and southern parts of the 

OU 1 landfill (fig. 2) to remove and destroy CVOCs 

from shallow ground water and to reduce the potential 

for CVOC migration from the site (URS Greiner, Inc., 

1999). If that phytoremediation strategy is later 

determined to be ineffective at the site, the Record of 

Decision (ROD) specifies that monitored natural 

attenuation should be evaluated as an alternative 

remedy (URS Consultants, Inc., 1998). The ROD also 

specifies that potentially adverse impacts of 

phytoremediation activities (which included removing 

asphalt cover from parts of the landfill) on in-situ 

microbial degradation of contaminants be evaluated.

The Navy began a cooperative effort with the 

U.S. Geological Survey (USGS) in 1995 to investigate 

various natural attenuation mechanisms at OU 1. 

Results from previous field and laboratory studies have 

provided evidence that microbial degradation processes 

can reduce CVOC concentrations in ground water at 

OU 1 (Bradley and others, 1998; URS Consultants, 

Inc., 1997a). Ground-water reduction-oxidation 

(redox) conditions are favorable for microbially 

mediated CVOC degradation beneath OU 1, the 

concentrations and distributions of parent compounds 

and degradation products are in general accord with 

expected degradation processes, and laboratory 

experiments demonstrated that microorganisms 

indigenous to the site can successfully biodegrade 

selected contaminants of concern under ambient 

ground-water conditions. Since those preliminary 

investigations in 1998, the USGS has collected 

additional natural-attenuation data both before and 

after the initial phytoremediation activities, and 

methods for collecting and interpreting those data have 

improved. The U.S. Navy is interested in documenting 

the current understanding of natural attenuation of 

CVOCs in ground water at OU 1 and identifying if 

phytoremediation activities to date (2000) have had any 

adverse impacts on attenuation processes.

Purpose and Scope

The purpose of this report is to present the results 

of evaluating natural attenuation in the study area 

including: (1) a description of the current (2000) 

understanding of natural attenuation of CVOCs in 

ground water at OU 1, NUWC Keyport, and (2) an 

evaluation of whether phytoremediation activities have 

had any adverse impacts on attenuation processes. The 

data used for the evaluation of natural attenuation 

included hydrogeologic, contaminant chemistry, 

geochemistry, and environmental tracer data collected 

by the USGS from 1996 to 2000 and by the Navy from 

1991 to 2000. 

Description of the Study Area

NUWC Keyport is located mostly on a small 

peninsula in Kitsap County, Wash., in an extension of 

Puget Sound called Liberty Bay (fig. 1). The NUWC 

occupies the eastern half of the peninsula and the town 

of Keyport occupies the western half. The highest point 

on the Keyport peninsula (about 43 feet above sea 

level) is located near the center, and the peninsula is 

connected to the mainland by a narrow strip of land just 

above sea level that was mostly tidal wetland before 

much of it was filled in by the Navy by the 1940s. The 

mainland to the southwest of Keyport peninsula rises 

steeply to rolling uplands 200–400 feet above sea level.

The 9-acre former landfill at OU 1, located on 

the narrow strip of connecting land, is between 9 and 

14 feet above sea level and is essentially flat. It is 

adjacent to some tide flats that are an extension of 

Dogfish Bay and Liberty Bay. Most of the landfill was 

formerly a marshland extending inland from the tide 

flats, and a portion of the original marsh remains to the 

west and south of the landfill. The landfill is unlined at 

the bottom, and the southern two-thirds of its surface 

was covered with asphalt when this investigation began 

(1996). Some of the asphalt cover was removed during 

February 1999 in order to plant hybrid poplar trees for 

phytoremediation.

Keyport has a temperate marine climate 

characterized by warm, dry summers and cool, wet 

winters (Washington State University, 1968). Mean 

annual temperature is about 51 degrees Fahrenheit; 

January is the coolest month and July is the warmest. 

Mean annual precipitation is about 31 inches, 

77 percent of which falls from October through March. 

Snowfall is infrequent and rainfall is generally not 

intense.

More-detailed discussions of the study area and 

its setting can be found in the Remedial Investigation 

(RI) report (URS Consultants, 1993) and the Summary 

Data Assessment Report (URS Consultants, 1997a).
8 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

Landfill

DOGFISH BAY

Shallow

lagoon

NUWC

Keyport

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 42'

41'

50"

47° 41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

?

?

N-1

N-2

N-3

N-5 N-4

N-7 N-6

N-8

C-1

C-2

C-3

S-1

S-2

S-3

S-4

S-5

S-6

DB-14

TF19

MA09

MA11

MA10

MA12

MA13

MW1-22

MW1-30

PZ1-5

MW1-23

MW1-24

1MW-4

MW1-36

MW1-37

MW1-39

MW1-38

MW1-32

MW1-21

MW1-29

MW1-40

MW1-25

MW1-28

MW1-9

PZ1-2

PZ1-4

MW1-7

MW1-31

MW1-27 MW1-11

MW1-33

PZ1-3

1MW-5

MW22-7

MW1-19

MW1-18

MW22-6

MW1-3

MW1-17

1MW-1 MW1-15

MW1-2

PZ1-1

Private

Well 1

Private

Well 2

MW1-10

MW1-14

MW1-41

P1-1

P1-2 P1-3

MW1-6 MW1-35

MW22-5

MW3-5

MW22-1

MW1-20

MW22-2

MW1-34

MW1-8

P1-4 P1-5

P1-6

P1-7

P1-8

P1-9

P1-10

MW1-5

MW1-16

MW1-4

MW1-1

Diffusion sampler

Surface-water sampling site

EXPLANATION

NUWC, Keyport 

Former landfill

Phytoremediation plantation

Surface water

Approximate extents of

 windows in middle aquitard

Approximate location of former

 waste paint and solvent

 disposal area

Monitoring well or piezometer

 in upper aquifer

Monitoring well in intermediate

 aquifer

Base map modified from URS Consultants, Inc., 1997a.

Figure 2. Location of the former landfill and other features and of the data-collection sites at Operable Unit 1, 

Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.
Introduction 9

Hydrogeologic Setting

NUWC Keyport lies within the Puget Sound 

Lowland, a topographic and structural depression 

between the Cascade Range on the east and the 

Olympic Mountains on the west. The Keyport 

peninsula and surrounding areas are composed 

primarily of unconsolidated Pleistocene glacial and 

interglacial deposits overlying Tertiary and older 

bedrock (Blunt and others, 1987). A veneer of more 

recent alluvium, including stream, beach, landslide, 

and marsh deposits, covers the youngest glacial 

deposits in some areas. The unconsolidated deposits 

are more than 1,500 feet thick beneath the Keyport 

peninsula (Jones, 1999).

Ground water beneath OU 1 occurs within a 

series of aquifers that are composed of permeable sand, 

gravel, or fill materials separated by finer-grained silt 

or clay layers. Contamination at OU 1 is known to 

occur only in about the top 60 feet of the 

unconsolidated deposits, so those units are described in 

this report; recent information on deeper sediments can 

be found in Kahle (1998) and Jones (1999). Twentyone stratigraphic units and six primary hydrogeologic 

units were identified beneath the study area (URS 

Consultants, Inc., 1997a). The hydrogeologic units, 

from top to bottom, are referred to as the unsaturated 

zone, upper aquifer, middle aquitard, intermediate 

aquifer, Clover Park aquitard, and Clover Park coarsegrained zone (figs. 3 and 4). Those six units are 

described below. Additional cross sections, original 

borehole logs, and a discussion of the relation between 

stratigraphic and hydrogeologic units can be found in a 

report by URS Consultants, Inc. (1997a).

The unsaturated zone at OU 1 consists primarily 

of fill materials including a mix of silt, sand, gravel, 

clay, and trash debris. The unit also includes organicrich silt or silty-sand marsh deposits and silt or siltysand estuary and tide flats deposits. The unit ranges 

from 0 to about 20 feet thick. The permeability of this 

zone is highly variable due its heterogeneity.

The upper aquifer at OU 1 consists primarily of 

sand or silty-sand and gravel with localized zones of 

marsh, estuary, and tide flats deposits. The saturated 

portion of the OU 1 landfill materials is also included 

in this unit. The unit is nearly continuous across OU 1 

and ranges from about 4 to 22 feet thick. The 

permeability of the upper aquifer is relatively high 

where coarse-grained, although scattered deposits of 

finer-grained materials suggest that preferential flow 

pathways are likely over short distances. The unit is 

less permeable near the northern tip of the landfill, and 

the unit is essentially absent west of the landfill in the 

vicinity of well MW1-8, where it is truncated by finegrained glaciolacustrine clay and silt deposits. 

Estimated hydraulic conductivity for the upper aquifer 

ranges from 0.2 to 4.1 feet per day (ft/d) (URS 

Consultants, Inc., 1997a).

The middle aquitard at OU 1 separates the upper 

and intermediate aquifers and consists primarily of silt, 

clay, and fine sand with localized peat. The unit is 

nearly continuous across OU 1 and ranges from about 1 

to 40 feet thick. The middle aquitard is notably absent 

beneath the central part of the landfill; an eroded 

window of about 1 acre extends northwest for about 

500 feet from the southeastern edge of the landfill 

(fig. 2). The unit is also essentially absent where it 

grades into more permeable silt and sand interbeds in 

the vicinity of well MW1-18 at the northwestern 

margin of the landfill. The permeability of the middle 

aquitard is mostly very low, with an estimated vertical 

hydraulic conductivity of 0.0001 ft/d (URS 

Consultants, Inc., 1993).

The intermediate aquifer at OU 1 consists 

primarily of sand and gravel with localized silt and 

glacial till lenses. The unit is continuous across OU 1 

except in the vicinity of well MW1-7, where it is 

truncated by fine-grained glaciolacustrine clay and silt 

deposits. The intermediate aquifer thins to less than 1 

foot and is indistinct near well MW1-18 at the 

northwestern margin of the landfill where fine-grained 

sediments predominate. It increases to about 30–40 feet 

in thickness upgradient (south) and downgradient 

(northwest) of the landfill. Somewhere beneath the tide 

flats and in the vicinity of the Highway 308 causeway, 

the aquifer is divided into an upper and lower 

permeable zone by as much as 16 feet of a compacted 

glacial till deposit. The permeability of the 

intermediate aquifer is relatively high, with an 

estimated hydraulic conductivity of 3.3 ft/d (URS 

Consultants, Inc., 1997a).

The Clover Park aquitard is a regionally 

extensive unit consisting of hard silt, peat, and clay. It 

is continuous beneath OU 1 and ranges from 100 to 

200 feet thick. Localized permeable zones occur in the 

aquitard and were distinguished as a separate 

hydrogeologic unit. The permeability of the Clover 

Park aquitard is mostly very low, with an estimated 

vertical hydraulic conductivity of 0.01 to 0.0001 ft/d 

(URS Consultants, Inc., 1993).
10 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

SR

308

SR

303

Keys Road

BROWNSVILLE HIGHWAY

Shapely Road

Bradley Road

Tide flats

Shallow

lagoon

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 42'

41'

50"

47° 41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

MW1-24

1MW-4

MW1-39 MW1-38

MW1-29

MW1-25

MW1-28

MW1-9

MW1-7

MW1-33

MW1-19

MW1-18

MW1-15

MW1-2

MW1-10

MW1-34

MW1-8

MW1-16

MW1-4

MW1-1

EXPLANATION

Monitoring well or

 piezometer in

 upper aquifer

Trace of hydro-

 geologic section

Monitoring well in

 intermediate aquifer

Borehole

A A'

A

A'

B

B'

TP #8

TP #5

SB1-41

W-1

HA #5

HA #4

HA #1

B-13

B-3

B-4 B-9

B-12 B-11

W-6

TP #9

Figure 3. Location of the hydrogeologic sections shown in figure 4, Operable Unit 1, Naval Undersea 

Warfare Center (NUWC), Division Keyport, Washington.
Introduction 11

SEA LEVEL

1010202030

SOUTH

FEET

30405060

A

HA #4

HA #5

W-1

SB1-41

TP #5

TP #8

SECTION

B-B'

Marsh Creek

Marsh

Landfill

Marsh

Marsh Creek

Highway 308

MW1-1

MW1-4 projected

MW1-16

MW1-2

HA #1 projected

MW1-34

MW1-33

B-13

B-3

B-4

B-9 & B-11 projected

B-12

W-6

MW1-15

MW1-25

MW1-38

MW1-39

0 100 200 300 400 500 600 FEET

0 30 60 90 120 150 180 KILOMETERS

VERTICAL EXAGGERA

Tide Flats

D

Shapley Road

Keys Road

Keys Road

Shapley Road

Keys Road

MW1-34

MW1-33

MW1-7

MW1-8

MW1-29

MW1-28

MW1-25

MW1-18

1MW-4

MW1-19

MW1-24

MW1-10

MW1-9

SEA LEVEL

1010202030

SOUTH

FEET

30405060

B

Interbedded

sand / silt

Clover Park Aquitard

Clover Park Aquitard

Middle Aquitard

Middle Aqu

Unsaturated Zone Upper Aquifer

Upper Aquifer

Intermediate Aquifer

Interm

A

Intermediate Aquifer

SECTION

B-B'

BEND IN SECTION

Glaciolacustrine

clay / silt

Upper A

Clover Park Aquitard

Middle Aquitard

Middle Aquitard

Upper Aquifer

Intermediate Aquifer

Intermediate Aquifer

SECTION

A-A'

SECTION

A-A'

BEND IN SECTION

BEND IN SECTION

Interbedded

sand / silt

sil

(Includes discontinuous deposits of

Clover Park Coarse-Grained Zone)

Modified from URS Consultants, Inc., 1997a.

Figure 4. The six primary hydrogeologic units at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division KeyportModified from URS Consultants, Inc., 1997a.)
12 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

The Clover Park coarse-grained zone consists of 

large discontinuous deposits of sand and gravel with 

silt embedded throughout the Clover Park aquitard. The 

unit was identified in a few borings at OU 1, but the 

coarse-grained lenses are not thought to be 

interconnected. Selected lenses may be hydraulically 

connected to the intermediate aquifer.

The NUWC Keyport water-supply well and a 

nearby Kitsap Public Utility District water-supply well 

are completed in a deeper aquifer 700 to 800 feet below 

sea level. A thorough inventory of private wells, 

completed in 1996-97, showed no water-supply wells 

completed in shallower units at locations downgradient 

from OU 1 (URS Consultants, Inc., 1997a).

Surface-Water and Ground-Water Flow

The descriptions of surface-water and groundwater flow and their interaction are summarized from 

two reports by URS Consultants, Inc. (1993 and 

1997a). The reports relied on data from multiple waterlevel measurements from wells and piezometers and 

surface-water stations collected during 1995-96, hourly 

observations of water level and salinity collected 

during a 48-hour tidal/salinity investigation in July 

1996, and rising-head slug-test data collected from 

monitoring wells between 1991–96.

Two perennial freshwater creeks drain into the 

marsh adjacent to the OU 1 landfill (fig. 2). The eastern 

creek begins in a partly emergent wetland area located 

immediately south of the landfill, and the western creek 

drains the upland area to the southwest of OU 1. Both 

creeks flow into a perennial marsh pond that feeds a 

single outlet creek. The outlet creek flows past the 

northern part of the landfill, through a culvert and tide 

gate, and into the tide flats. Most storm-water runoff 

from the OU 1 landfill drains directly into the marsh, 

and limited amounts of storm-water runoff from other 

parts of NUWC Keyport flow into the marsh at points 

just south of the landfill and near the mouth of the 

outlet creek. Storm-water runoff also enters the marsh 

from the creek draining the western uplands. During 

periods of no runoff, surface water in the marsh is 

entirely ground-water discharge.

Surface water in the tide flats and upstream to the 

marsh pond is affected by the 10- to12-ft diurnal tidal 

fluctuations in Dogfish Bay. During high tides, water 

levels in the tide flats are at the same water-level 

elevation as Dogfish Bay. However, the tide gate at the 

marsh outlet automatically closes during a rising tide 

and limits the flow of seawater into the marsh. As a 

result, the high-tide surface-water level at the marsh 

outlet is generally 1.5 to 2.5 ft less than the water level 

in the tide flats. The incoming seawater rarely extends 

upstream beyond the marsh pond, where the tidal 

fluctuation is less than 0.5 ft. On a falling tide, surface 

water from the marsh again drains into the tide flats 

and the tide flats drain to Dogfish Bay. When the waterlevel elevation in Dogfish Bay drops below about -2 ft, 

a sill beneath the Highway 308 bridge limits the 

discharge to Dogfish Bay and maintains the water level 

in the tide flats at about -2 ft. The water-level elevation 

in Dogfish Bay falls below -2 ft about one-third of the 

time. On a rising tide the situation is reversed; seawater 

from Dogfish Bay flows into the tide flats once the 

water-level elevation in the Bay exceeds -2 ft, and 

seawater from tide-flats flows into the marsh once the 

tide flats water level elevation exceeds about 0.5 ft.

Ground water in the unconfined upper aquifer 

beneath the OU 1 landfill generally flows from east to 

west (figs. 5 and 6). All of the upper-aquifer ground 

water beneath the landfill was previously thought to 

discharge primarily to the marsh, because of an 

inferred ground-water flow divide beneath Keys Road, 

the elevated roadway that separates the marsh from the 

tide flats. New data presented in the section 

"Evaluation of Natural Attenuation" suggest, however, 

that at least during part of the year, ground water from 

the northern half of the landfill flows beneath the marsh 

and discharges directly to the tide flats. A ground-water 

flow divide east of the landfill separates westward 

ground-water flow from eastward groundwater flow 

beneath the neck of the Keyport peninsula. The primary 

source of upper-aquifer ground water is recharge of 

precipitation through the landfill itself and through 

pervious areas to the immediate east and northeast of 

the landfill. The removal of asphalt from the 

phytoremediation plantations in February 1999 has 

likely resulted in increased recharge through the 

landfill itself, but no discernable changes in flow 

directions or gradients had been observed by the year 

2000 (CH2MHill Constructors, Inc., 2001). Although 

upper-aquifer water levels and flow directions beneath 

the northwestern part of the landfill are influenced by 

tidal changes, there does not appear to be a substantial 

flux of seawater into the upper aquifer during high 

tides. Ground water in wells MW1-2 and 1MW-1 is not 

saline, and the salinity did not fluctuate as a function of 

tide during the 24-hour tidal study.
Introduction 13

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47°

42'

41'

50"

47°

41'

40"

122°37'40" 30" 122°37'20"

Shallow

lagoon

T.

26

N.

R.1 E.

SW-1

-1.55

SW-2

1.76

SW-5

2.89

SW-7

5.36

SW-6

4.30

SW-4

2.68

SW-3

2.55

EXPLANATION

Plantation

Surface water

Ground-water flow direction

Water-level contours–Show

 altitude of ground water,

 in feet above sea level.

 Contour interval 1 foot

Monitoring well or piezometer

 and water level, in feet

 above sea level

Surface-water measuring

 point and water level, in

 feet above sea level

8

PZ1-3

42.58

1MW-5

9.44

MW22-7

10.87

MW1-19

7.76 MW1-18

2.98

MW22-6

7.71

MW1-3

8.38

MW1-17

3.59

MW1-15

5.95

1MW-1

3.14

MW1-2

1.92

PZ1-1

40.68

Private

Well 1

41.02

Private

Well 2

1.93

MW1-10

4.67

MW1-14

5.58

MW1-6

3.85

MW1-35

6.96

MW22-5

9.36

MW3-5

4.75

MW22-1

6.36

MW1-20

6.19

MW22-2

6.29

MW1-34

9.79

MW1-8

3.18

MW1-5

4.27

MW1-16

5.31

MW1-4

5.53

MW1-1

15.49

3

2

10 -1

4

6

5

3

3

2

2

10

4

4

4

5

6

5

11

10

9

8

10

9

7

8

6

5

12

14

16

8

6

5

6

Figure 5. Ground-water levels and flow in the shallow aquifer during a low tide, September 1996, at 

Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.

(Modified from URS Consultants, Inc., 1997a.)
14 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

EXPLANATION

Plantation

Surface water

Ground-water flow direction

Water-level contours–Show

 altitude of ground water,

 in feet above sea level.

 Contour interval 1 foot

Monitoring well or piezometer

 and water level, in feet

 above sea level

Surface-water measuring

 point and water level, in

 feet above sea level

8

6

4

3

4

5

5

7

8

8

9

10

10

11

6

12

14

16

5

6

9

8

7

6

5

4

5

4

5

10

PZ1-3

42.58

1MW-5

9.44

MW22-7

10.86

MW1-19

7.80

MW1-18

4.06

MW22-6

7.71

MW1-3

8.38

MW1-17

3.66

MW1-15

5.96

1MW-1

3.50

MW1-2

4.16

PZ1-1

40.68

Private

Well 1

41.00

Private

Well 2

2.23

MW1-10

4.71

MW1-14

5.59

MW1-6

3.84

MW1-35

6.96

MW22-5

9.35

MW3-5

4.78

MW22-1

6.36

MW1-20

6.20

MW22-2

6.33

MW1-34

9.82

MW1-8

3.17

MW1-5

4.30 MW1-16

5.33

MW1-4

5.55

MW1-1

15.51

SW-1

5.67

SW-2

3.52

SW-5

3.01

SW-7

5.36

SW-6

4.32

SW-4

3.04

SW-3

3.11

Figure 6. Ground-water levels and flow in the shallow aquifer during a high tide, September 1996, at 

Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.

(Modified from URS Consultants, Inc., 1997a.)
Introduction 15

Ground water in the predominantly confined 

intermediate aquifer beneath the OU 1 landfill 

generally flows from the south and west to the 

northwest (figs. 7 and 8). Ground-water flow in this 

aquifer converges beneath the tide flats and Dogfish 

Bay from three directions and ultimately discharges 

directly to seawater. The primary sources of ground 

water in the intermediate aquifer are recharge of 

precipitation in areas more than 1,000 ft south of the 

landfill where the middle aquitard is absent, and 

downward flow from the upper aquifer in areas within 

and northeast of OU 1 where permeable windows 

penetrate the middle aquitard. Ground-water levels and 

flow directions in the intermediate aquifer beneath and 

adjacent to the tide flats are influenced by tidal 

changes, however the flux of seawater into and out of 

the aquifer beneath OU 1 during a single tidal cycle is 

negligible. Observed changes in intermediate-aquifer 

water levels result from a pressure wave that 

propagates inland because of the increased load of 

seawater on aquifer sediments during a high tide. Over 

a timescale of perhaps centuries, there has been a flux 

of saline water (or possibly a flux of dissolved solids 

only through dispersion) into the intermediate aquifer. 

Ground water in the intermediate aquifer upgradient of 

the landfill is fresh; at the down-gradient margin of the 

landfill it is somewhat brackish; and further 

downgradient at Highway 308 it is brackish north of 

the bridge, somewhat brackish in the lower part of the 

aquifer south of the bridge, and not brackish in the 

upper part of the aquifer south of the bridge (well 

MW1-39). Together, these observations and 

interpretation of new data presented in this report 

suggest that the downgradient well MW1-39 is 

hydraulically connected to the upper aquifer and is not 

screened within the main body of the intermediate 

aquifer, as previously inferred.

Some ground water in the contaminated portion 

of the upper aquifer flows downward into the 

intermediate aquifer. Observed water levels indicate 

that there is a downward gradient for ground-water 

flow between the upper and intermediate aquifers 

beneath the northeastern third of the landfill, and that 

there is an upward gradient beneath the remainder of 

the landfill and perhaps the entire marsh. The 

delineated zone of downward gradient partially 

overlaps both of the identified windows in the middle 

aquitard (fig. 2). 

Ground-water flow rates along multiple flow 

paths in the upper and intermediate aquifers (figs. 9 and 

10) were estimated using observed water levels and 

calculated hydraulic conductivities from slug-tests in 

monitoring wells. In the upper aquifer, ground-water 

flow rates were estimated to be 29 to 83 ft/yr for the 

five east-west flowpaths shown on figure 9. In the 

intermediate aquifer, ground-water flow rates were 

estimated to be 28 to 89 ft/yr beneath the landfill and 

10 ft/yr beneath the tide flats (fig. 10). These estimates 

are used later in this report for calculating contaminant 

mass degradation rates and field attenuation rates at 

OU 1. The USGS collected additional data related to 

ground-water flow rates in the intermediate aquifer, 

and they too are presented in this report.

Contamination and Remediation

The OU 1 landfill was the primary disposal area 

for both domestic and industrial wastes generated by 

NUWC Keyport from the 1930s through 1973. Mixed 

trash and demolition debris were burned at the northern 

end of the landfill from the 1930's to the 1960's, and 

unburned or partially burned materials were buried in 

the landfill or pushed into the marsh. Paints, thinners, 

solvents, acids, dried sludge from a wastewater 

treatment plant, and other industrial wastes were 

disposed of at various locations in the landfill from the 

1930s through 1973. The most concentrated disposal 

area for waste paints and solvents was located at the 

southern end of the landfill (fig. 2). That location 

coincides with the highest observed concentrations of 

CVOCs in ground water at OU 1. Few, if any, intact 

and full drums of waste were thought to be buried in 

the landfill. Instead, most drum contents were emptied 

into the landfill and the drums were then reused or 

crushed and buried.

The CVOCs identified as chemicals of concern 

at OU 1 are tetrachloroethene (PCE), TCE, cisDCE, 

trans-1,2-dichloroethene (transDCE), VC, TCA, 1,2-

dichloroethane (1,2-DCA), 1,1-DCA, and 1,1-DCE. 

The primary CVOCs originally disposed of were likely 

PCE, TCE, TCA, and 1,2-DCA. The other 

contaminants are known degradation products of those 

original contaminants and likely developed within the 

landfill itself.
16 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

SR

308

SR

303

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

EXPLANATION

Plantation

Surface water

Ground-water flow direction

Water-level contours–Show

 altitude of ground water,

 in feet above sea level.

 Contour interval variable

 and dashed where inferred

8

5

6

6

7

8

9

10

12

14

16

18

20

5

4

4

3

3

2

2

1

1

0

0

7

8

9

MW1-22

5.59

MW1-30

-0.56

PZ1-5

8.08

MW1-23

2.92

MW1-24

7.27

1MW-4

4.34

MW1-36

-0.64

MW1-37

-0.59 MW1-39

-0.53

MW1-38

-0.42

MW1-32

3.44

MW1-21

3.42

MW1-29

1.63

MW1-40

2.21

MW1-25

1.71

MW1-28

1.63

MW1-9

4.72

PZ1-2

5.79

PZ1-4

19.24

MW1-7

8.85

MW1-31

6.46

MW1-27

6.82

MW1-33

10.22

Figure 7. Ground-water levels and flow in the intermediate aquifer during a low tide, September 1996, at 

Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.

(Modified from URS Consultants, Inc., 1997a.)
Introduction 17

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47°

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

Shallow

lagoon

T.

26

N.

R.1 E.

EXPLANATION

Plantation

Surface water

Ground-water flow direction

Water-level contours-–Show

 altitude of ground water,

 in feet above sea level.

 Contour interval variable

 and dashed where inferred

8

5

4

6

7

8

9

6

7

8

9

16

14

18

20

12

10

5

4

5

4

MW1-22

6.51

MW1-30

5.42

PZ1-5

8.14

MW1-23

5.14

MW1-24

1MW-4 7.37

4.86

MW1-36

5.69

MW1-37

5.73 MW1-39

5.72

MW1-38

5.66

MW1-32

3.96

MW1-21

3.93

MW1-29

4.37

MW1-40

3.65

MW1-25

4.89

MW1-28

4.77

MW1-9

4.92

PZ1-2

5.79

PZ1-4

19.29

MW1-7

8.93

MW1-31

6.49

MW1-27

6.86

MW1-33

10.26

Figure 8. Ground-water levels and flow in the intermediate aquifer during a high tide, September 1996, at 

Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.

(Modified from URS Consultants, Inc., 1997a.)
18 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

Shallow

lagoon

T.

26

N.

R.1 E.

83

65

59

41

29

PZ1-3

42.58

1MW-5

9.44

MW22-7

10.87

MW1-19

7.76 MW1-18

2.98

MW22-6

7.71

MW1-3

8.38

MW1-17

3.59

MW1-15

1MW-1 5.95

3.14

MW1-2

1.92

PZ1-1

40.68

Private

Well 1

41.02

Private

Well 2

1.93

MW1-10

4.67

MW1-14

5.58

MW1-6

3.85

MW1-35

6.96

MW22-5

9.36

MW3-5

4.75

MW22-1

6.36

MW1-20

6.19

MW22-2

6.29

MW1-34

9.79

MW1-8

3.18

MW1-5

4.27

MW1-16

5.31

MW1-4

5.53

MW1-1

15.49

3

2

10 -1

4

6

5

3

3

2

2

10

4

4

4

6

5

5

11

10

9

8

10

9

7

8

6

5

12

14

16

8

6

5

6

EXPLANATION

Plantation

Surface water

Ground-water flow direction

Water-level contours–Show

 altitude of ground-water,

 in feet above sea level.

 Contour interval 1 foot

8

Line of measured gradients

 and estimated ground-water 29 flow rate, in feet per year.

Figure 9. Ground-water flow directions and flow rates in the upper aquifer at Operable Unit 1, Naval 

Undersea Warfare Center (NUWC), Division Keyport, Washington.

(Modified from URS Consultants, Inc., 1997a.)
Introduction 19

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

8

EXPLANATION

Plantation

Surface water

Ground-water flow direction

Water-level contours–Show

 altitude of ground water,

 in feet above sea level.

 Contour interval 1 foot

Line of measured gradients

 and estimated ground-water

89 flow rate, in feet per year.

28

33

89

10

10

10

10

5

6

6

7

8

9

10

12

14

16

18

20

5

4

4

3

3

2

2

1

1

0

0

7

8

9

MW1-22

5.59

MW1-30

-0.56

PZ1-5

8.08

MW1-23

2.92

MW1-24

7.27

1MW-4

4.34

MW1-36

-0.64

MW1-37

-0.59 MW1-39

-0.53

MW1-38

-0.42

MW1-32

3.44

MW1-21

3.42

MW1-29

1.63

MW1-40

2.21

MW1-25

1.71

MW1-28

1.63

MW1-9

4.72

PZ1-2

5.79

PZ1-4

19.24

MW1-7

8.85

MW1-31

6.46

MW1-27

6.82

MW1-33

10.22

Figure 10. Ground-water flow directions and flow rates in the intermediate aquifer at Operable Unit 1, Naval 

Undersea Warfare Center (NUWC), Division Keyport, Washington.

(Modified from URS Consultants, Inc., 1997a.)
20 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Chlorinated VOCs are present in the upper and 

intermediate aquifers and in surface water at OU 1. The 

highest contaminant concentrations are found in the 

upper aquifer beneath the southern part of the landfill 

(fig. 11). Less is known about contaminant 

concentrations in the intermediate aquifer beneath the 

landfill, although the contaminant plume downgradient 

of the landfill is well characterized (fig. 12). Based on 

the disposal history and observed contaminant 

concentrations, some contaminants probably are 

present in the upper aquifer in their non-dissolved 

phase as non-aqueous phase liquids (NAPLs).

The remediation strategy selected by the Navy 

for CVOCs at OU 1 includes removal and treatment of 

the contaminants from the upper aquifer by 

phytoremediation with hybrid poplar trees, retaining 

the asphalt cover over the remaining paved portions of 

the landfill to minimize ground-water recharge, shortterm process monitoring, long-term performance 

monitoring, and institutional controls to prevent undue 

exposures to landfill contaminants (URS Consultants, 

Inc., 1998). Two plantations of hybrid poplar trees were 

planted in spring of 1999. Asphalt was removed, about 

1 to 2 feet of topsoil was added, and the sites were 

prepared for planting during February 1999. 

Performance monitoring during 1999 and 2000 showed 

the trees were overall in good health, and ground-water 

flow directions and gradients are consistent with 

historical findings (URS Greiner, Inc., 2000). The trees 

were not yet mature in 2000 and the roots had not 

reached the water table, so the lack of discernible 

water-level changes was expected. Changes in 

contaminant concentrations in upper-aquifer ground 

water and in surface water have been observed after the 

introduction of phytoremediation (CH2MHill 

Constructors, Inc., 2001). Those changes are described 

and interpreted later in this report in section 

"Evaluation of Natural Attenuation".

Acknowledgments

The authors thank the many people and agencies 

for their important contributions to the study. Renee 

Wallis, Sandra Keinhholz, and Matthew Butler of the 

Naval Facilities Engineering Command, Engineering 

Field Activity, Northwest (EFANW) provided guidance 

and funding for the investigation. Diane Jennings and 

Gene Ellis of NUWC Keyport and James Reeves of 

EFANW provided logistic support for field activities. 

Daryl Jech, Mark Dagl, and Thomas Dube of Science 

Applications International Corporation; David Tonkin 

and Michael Meyer of URS Corporation; and Bernard 

Wong of CH2M Hill Constructors, Incorporated, 

provided logistic support and additional data. 

Katherine Greene, Raegan Huffman, CG Laird, and 

Daniel Smith of USGS in Tacoma, Wash., assisted the 

authors with field data collection and processing. 

Robert Crist and Sharon Wahlstrom of USGS, Tacoma, 

Wash., prepared the illustrations, tables, and 

manuscript for publication.
Introduction 21

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

?

?

EXPLANATION

Surface water

Not detected

Approximate extents of

 windows in middle aquitard

Line of equal concentration of

 CVOCs, in micrograms per liter

Monitoring well 45

nd

10

Plantation

10

?

1,000

100

10

1,000

10,000

100 10

MW1-2

1,700

SP1-1

160

1MW-1

1,300

MW1-15

2.7

MW1-17

8.7

MW1-10

nd

MW1-6

5.6

MW1-8

nd

MW1-5

1,900

MW1-16

42,000

MW1-4

19,000

MW1-34

nd

MW1-20

nd

MW1-35

nd

MW1-3

nd

MW1-14

0.53

MW1-18

45

MW1-19

14

1MW-5

nd

Figure 11. Concentrations of chlorinated volatile organic compounds (CVOCs) in surface water and upperaquifer ground water, 1996, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, 

Washington.

(Modified from URS Consultants, Inc., 1997a).
22 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

?

?

MW1-22

nd

MW1-30

nd

MW1-23

nd

MW1-24

nd

1MW-4

26

MW1-36

nd

MW1-37

nd MW1-39

0.8

MW1-38

nd

MW1-32

0.5

MW1-21

nd

MW1-29

nd

MW1-40

nd

MW1-25

2,200

MW1-28

2,200

MW1-9

nd

MW1-7

nd

MW1-31

nd

MW1-27

nd

MW1-33

nd

1

10

100

1000

EXPLANATION

Surface water

Not detected

Approximate extents of

 windows in middle aquitard

Line of equal concentration of

 CVOCs, in micrograms per liter

45 Monitoring well

nd

10

Plantation

Figure 12. Concentrations of chlorinated volatile organic compounds (CVOCs) in intermediate-aquifer 

ground water, 1996, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, 

Washington.

(Modified from URS Consultants, Inc., 1997a).
Redox Conditions in Contaminated Ground Water 23

REDOX CONDITIONS IN CONTAMINATED 

GROUND WATER

Evaluation of redox conditions in ground-water 

contaminant plumes is a prerequisite for understanding 

the behavior of contaminants and for evaluating the 

effectiveness of natural attenuation processes. That is 

because ground-water redox conditions greatly control 

the occurrence and rate of nearly all biodegradation 

processes.

Most biodegradation processes involve redox 

reactions in which electrons are transferred from one 

compound (the electron donor) to another (the electron 

acceptor). Depending on the particular compound and 

redox condition, CVOCs can serve as either electron 

donors or electron acceptors. Possible electron donors 

in contaminated ground water include various organiccarbon compounds in landfill leachate, and 

hydrocarbon fuels. The less chlorinated VOCs, such as 

VC and dichlorinated ethenes and ethanes, can also act 

as electron donors under aerobic or mildly reducing 

redox conditions. Possible electron acceptors include 

the inorganic constituents oxygen, nitrate, manganese 

(IV), iron (III), sulfate, and carbon dioxide, as well as 

highly chlorinated VOCs such as PCE, TCE, and TCA. 

VC and dichlorinated ethenes and ethanes may also act 

as electron acceptors under strongly reducing redox 

conditions.

Indigenous microorganisms that require carbon 

and energy to sustain their growth facilitate most 

ground-water redox reactions. A variety of 

microorganisms often compete for the supply of 

available electron-donating organic carbon in ground 

water, but they are more specialized in their use of the 

different electron acceptors. Oxygen-reducing 

microorganisms (those that use oxygen as an electron 

acceptor) can out-compete all others when dissolved 

oxygen (DO) is present. However, if the supply of DO 

in ground water is depleted and electron-donating 

compounds are still available, oxygen reducers will 

become dormant and nitrate reducers will predominate 

until the supply of nitrate is depleted. This sequence 

continues through manganese reduction, iron 

reduction, sulfate reduction, and carbon-dioxide 

reduction (methanogenesis). The result of this 

competitive exclusion is the formation of somewhat 

discrete redox zones in an aquifer.

Redox conditions are named according to the 

inorganic compound that is acting as the predominant 

electron acceptor in a given portion of an aquifer. Thus, 

the common redox conditions in ground water are 

oxygen reducing (or aerobic), nitrate reducing, 

manganese reducing, iron reducing, sulfate reducing, 

and carbon-dioxide reducing (methanogenic). Nitrate 

reduction, manganese reduction, and iron reduction are 

often together referred to as mildly reducing 

conditions, whereas sulfate reduction and 

methanogenesis are often referred to as strongly 

reducing conditions. That distinction is made because 

different types of biodegradation processes are favored 

under mildly and strongly reducing conditions.

Determination of redox conditions in 

contaminated ground water is not a simple task and no 

universally accepted procedures exist. The rationale 

behind characterizing redox conditions in ground water 

at Keyport is summarized here. Additional information 

about characterizing redox conditions can be found in 

Cozzarelli and others (2000), Christensen and others 

(2000), Wiedemeier and Chappelle (1998), and 

Weidemeier and others (1998).

Redox conditions in contaminated ground water 

can sometimes be deduced by quantifying various 

oxidized and reduced inorganic compounds in ground 

water samples (Cozzarelli and others, 2000; 

Christensen and others, 2000; Wiedemeier and 

Chappelle, 1998). The identification of aerobic 

conditions is relatively simple; they are predominant if 

DO concentrations in ground water are greater than 

about 1 milligram per liter (mg/L). Identification of the 

various anaerobic redox conditions (in which DO 

concentrations are less than 1 mg/L) is more difficult. If 

nitrate concentrations exceed about 0.5 mg/L in 

anaerobic ground water, then nitrate reduction is likely. 

If anaerobic ground water lacks nitrate, and if reduced 

manganese (Mn(II)) or iron (Fe(II)) concentrations 

increase along a ground-water flow path, then 

manganese or iron reduction is indicated. If anaerobic 

ground water lacks nitrate, if sulfate (oxidized sulfur) 

concentrations decrease along a ground-water flow 

path, and if concentrations of hydrogen sulfide 

(reduced sulfur) exceed about 0.05 mg/L, then sulfate 

reduction is indicated. Finally, if anaerobic ground 

water lacks nitrate, sulfate, and hydrogen sulfide, and if 

methane concentrations exceed about 0.2 mg/L, then 

carbon dioxide reduction (methanogenesis) is 

indicated.
24 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Many conditions at the OU 1 landfill complicate 

the determination of redox conditions. Contaminated 

ground water beneath landfills often is not at a 

thermodynamic steady-state or chemical equilibrium, 

so several electron-accepting processes may be 

occurring simultaneously (Cozzarelli and others, 2000; 

Christensen and others, 2000). As fresh ground water 

mixes with saline ground water in a near shore 

environment such as the OU 1 landfill, the natural 

supply of sulfate may increase substantially along a 

flowpath and effectively mask any sulfate consumption 

by redox reactions. Redox-sensitive compounds such 

as sulfate, methane, or iron (II) may leach to ground 

water from many locations in a landfill, and could also 

mask any concentration changes resulting from redox 

reactions in the local ground water. Redox-sensitive 

species such as methane, iron (II), or manganese (II) 

often migrate away from where they were produced, 

blurring the interpretation of where one redox zone 

ends and another begins. Precipitation of iron, 

manganese, and sulfur species can also affect the 

identification of a redox condition at a given point. And 

finally, redox conditions and concentrations of redoxsensitive compounds can change dramatically over 

very short distances in contaminant plumes, making it 

difficult to obtain a ground-water sample that 

represents a single discrete redox zone even in 

monitoring wells with relatively short (5-foot) open 

intervals. These confounding conditions cannot be 

avoided, but an awareness of them can put the 

interpretation and use of the identified redox zones into 

proper perspective.

An alternative method for identifying the 

predominant redox processes in anaerobic ground 

water is through direct measurement and interpretation 

of dissolved-hydrogen (H2) concentrations in ground 

water. Hydrogen is continuously produced and 

consumed by different microorganisms during 

anaerobic decomposition of organic matter, and for 

natural ground waters the different microorganisms 

that facilitate nitrate-, manganese-, iron-, sulfate-, and 

carbon dioxide-reduction reactions exhibit different 

efficiencies in utilizing H2 (Lovely and Goodwin, 

1988). Nitrate-reducers are very efficient at utilizing 

H2, so they keep H2 concentrations in ground water at 

very low levels of less than 0.1 nanomolar (nM). 

Manganese- and iron-reducers use H2 less efficiently, 

so they keep H2 concentrations between 0.1–0.2 and 

0.2–0.8 nM, respectively. Sulfate-reducers are less 

efficient still, so they keep H2 concentrations at 

between 1 and 4 nM, and carbon-dioxide reducers are 

relatively inefficient, resulting in H2 concentrations 

greater than 5 nM. The result of that competition for H2

is that each anaerobic redox condition is characterized 

by a distinct H2 concentration in ground water (table 1) 

(Chapelle and others, 1995; Lovely and others, 1994).

It has more recently been argued that identifying 

redox conditions from specific steady-state H2

concentrations is not applicable to all contaminant 

plumes (Hoehler and others, 1998; Jakobsen and 

others, 1998; Christensen and others, 2000). 

Uncertainties arise from observations that H2

concentrations alone do not account for complicating 

effects from different absolute concentrations of 

dissolved redox species, that there is much variability 

in the iron-oxide minerals that can serve as electron 

acceptors, that ground-water temperature affects 

equilibrium H2 concentrations, and that redox 

conditions may be overlapping and not exclusive. 

Despite those limitations, H2 concentrations do 

indicate redox conditions in a relative sense, in that 

higher H2 concentrations are consistently found in 

more strongly reduced ground waters. And in terms of 

contaminant biodegradation, identifying the presence 

of strongly reducing conditions or knowing where H2

concentrations exceed 1 nM may be more important 

than knowing the specific inorganic compound that is 

the predominant electron acceptor. Thus, quantifying 

oxidized and reduced inorganic compounds as well as 

steady-state H2 concentrations throughout a 

contaminant plume can be used with reasonable 

confidence to identify favorable and less favorable 

conditions for contaminant biodegradation. 

Table 1. Characteristic dissolved-hydrogen concentrations 

for different anaerobic redox conditions in ground water

Redox condition

Characteristic dissolvedhydrogen concentration 

(nanomolar)

Nitrate reduction Less than 0.1

Manganese reduction 0.1 − 0.2

Iron reduction 0.2 − 0.8

Sulfate reduction 1 − 4

Methanogenesis Greater than 5
Natural Attenuation in Ground Water 25

NATURAL ATTENUATION IN GROUND 

WATER

Natural attenuation refers to a variety of 

physical, chemical, and biological processes that act 

without human intervention to reduce the mass, 

toxicity, mobility, volume, or concentration of 

contaminants in soil or ground water (U.S. 

Environmental Protection Agency, 1997). Processes 

relevant to natural attenuation of CVOCs in ground 

water include destructive processes such as abiotic and 

biotic degradation and non-destructive processes such 

as dispersion, sorption, and volatilization. Destructive 

processes are preferred when relying on natural 

attenuation for site remediation (U.S. Environmental 

Protection Agency, 1997), so contaminant degradation 

was a primary focus of this investigation. Processes 

that could naturally attenuate chlorinated ethenes and 

ethanes in ground water at the OU 1 landfill are 

summarized here.

Destructive Attenuation Processes

Contaminant degradation is the transformation of 

a chemical compound (the parent compound) into one 

or more other compounds (the daughter products). 

Biodegradation reactions are mediated by subsurface 

microorganisms, whereas abiotic degradation reactions 

are not. Daughter products resulting from degradation 

of CVOCs may be more or less toxic than the parent 

compound, but most intermediate daughter products 

can be further degraded into nontoxic compounds. 

From a remediation standpoint, degradation is most 

desirable when a contaminant is ultimately transformed 

into innocuous inorganic by-products such as carbon 

dioxide, water, and chloride.

Over the past two decades, numerous field and 

laboratory studies have shown that microbes 

indigenous to ground-water systems can degrade 

chlorinated ethenes and ethanes. It has also been shown 

that local subsurface redox conditions are a primary 

factor controlling the occurrence and rate of 

biodegradation reactions, although the occurrence and 

rate of abiotic degradation reactions are usually 

independent of redox conditions. The most important 

degradation reactions for the chlorinated ethenes TCE, 

DCE, cisDCE, and VC and the chlorinated ethanes 

TCA, 1,1-DCA, and chloroethane (CA) are presented 

here.

Trichloroethene and Other Chlorinated Ethenes

Abiotic degradation of chlorinated ethenes 

occurs very slowly under conditions commonly found 

in aquifers (Vogel, 1994). Although considerable 

discrepancies exist, half-lives for abiotic degradation of 

TCE and DCE have been reported to be as long as 

106–108 years (Jeffers and others, 1989). Abiotic 

degradation half-lives of TCE can be as short as 

minutes to a few days in systems amended with an 

abundance of zero-valent iron (Gillham and 

O'Hannesin, 1994), but abundant zero-valent iron is 

uncommon in natural settings.

Biodegradation of chlorinated ethenes can be 

very rapid under conditions often found in aquifers, 

and at least two pathways for complete biodegradation 

of chlorinated ethenes have been demonstrated in field 

and laboratory studies (fig. 13). The first pathway 

consists solely of sequential dechlorination reactions in 

which the chlorinated ethenes serve as electron 

acceptors. TCE can be rapidly degraded to ethene by 

this pathway, but the dechlorination often slows or 

stops at cisDCE or VC in many ground-water systems. 

The second pathway consists of a partial sequence of 

dechlorination reactions, followed by mineralization of 

the resulting cisDCE or VC. Mineralization (or direct 

oxidation) is the process in which organic compounds 

are transformed into inorganic by-products. In 

mineralization reactions, cisDCE and VC serve as 

electron donors. This combination of dechlorination of 

TCE followed by mineralization of cisDCE and VC has 

been shown to result in complete biodegradation of 

chlorinated ethene contaminants in many ground-water 

systems (Weidemeier and Chappelle, 1998).

Reductive dechlorination of TCE by 

microorganisms requires anaerobic ground-water redox 

conditions. TCE serves as an electron acceptor during 

this process, and a chlorine atom is removed and 

replaced with a hydrogen atom to form (primarily) 

cisDCE. All three isomers of dichloroethene can 

theoretically be produced, but cisDCE is by far the 

most common daughter product (Bouwer, 1994). 

Because TCE is reduced during this process, the 

reaction must be coupled with the oxidation of another 

compound. Organic compounds such as natural organic 

matter, fuel hydrocarbons, or various compounds found 

in landfill leachate are common electron donors that are 

oxidized during the reduction of TCE. 
26 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Reductive dechlorination of TCE has been 

demonstrated under all anaerobic conditions, but it is 

reported to be most efficient under the strongly 

reducing conditions of sulfate reduction (Gossett and 

Zinder, 1996) or methanogenesis (McCarty and 

Semprini, 1994). Reductive dechlorination can also 

degrade cisDCE to VC to ethene, but the sequence 

often is interrupted because of a change to mildly 

reducing redox conditions as contaminants are 

transported downgradient by ground-water flow. TCE 

is the chlorinated ethene most susceptible to reductive 

dechlorination, followed by cisDCE and then VC.

Microbially mediated mineralization of all DCE 

isomers or VC can occur in either aerobic or mildly 

reducing anaerobic ground water. The CVOCs serve as 

electron donors during this process and are degraded to 

carbon dioxide, water, and chloride. Because DCE or 

VC is oxidized in this process, the reactions must be 

coupled with the reduction of another compound. 

Oxygen, manganese (IV), and iron (III) are common 

electron acceptors that can be reduced during 

mineralization of DCE and VC (Bradley and others, 

1998; Bradley and Chapelle, 1996, 1997, and 1998; 

Davis and Carpenter, 1990). Mineralization of DCE 

and VC is most efficient under aerobic conditions, is 

moderately efficient under iron or manganese reducing 

conditions, and is negligible under sulfate reducing and 

methanogenic conditions. The rates of DCE 

mineralization are usually somewhat less than those for 

VC mineralization, and TCE is not readily mineralized.

EXPLANATION

Organic daughter compounds

Abiotic reaction

Inorganic daughter compounds

Mineralization reaction

Parent compound

Reductive dechlorination

Trichlorethene

(TCE)

1,1,1-Trichlorethane

(TCA)

Vinyl Chloride

(VC)

Chloroethane

(CA) Acetate

Ethene

Carbon Dioxide,

Water,

Chloride

cis-1,2-Dichloroethene

(cisDCE)

1,1-Dichloroethene

(DCE)

1,1-Dichloroethane

(DCA)

Figure 13. Possible degradation pathways for trichloroethene and for 1,1,1-trichloroethane.
Natural Attenuation in Ground Water 27

Given the above processes, the complete 

degradation of TCE into carbon dioxide, water, and 

chloride is most effective in aquifers that are either (1) 

sulfate reducing or methanogenic throughout the extent 

of contamination, or (2) sulfate reducing or 

methanogenic near the TCE source area, and become 

aerobic or manganese or iron reducing downgradient of 

the source area (Chapelle, 1996). The first situation is 

favorable for complete reductive dechlorination of 

TCE, cisDCE, and VC, whereas the second situation is 

favorable for reductive dechlorination of TCE and 

possibly cisDCE, followed by mineralization of the 

resulting cisDCE and VC. Both situations require a 

substantial source of organic carbon to create strongly 

reducing conditions near the TCE source area.

1,1,1-Trichloroethane and Other Chlorinated 

Ethanes

In contrast to TCE, the chlorinated ethane 1,1,1- 

TCA can be degraded at significant rates by both 

abiotic and biotic reactions. Abiotic degradation of 

TCA can occur through two different pathways 

(fig. 13). Reported half-lives for the abiotic degradation 

of TCA into acetate range from 0.5–1.7 years and halflives for abiotic degradation of TCA into DCE range 

from 0.8–2.5 years (Vogel and McCarty, 1987). Those 

half-lives reflect conditions at a temperature of 20 

degrees Celsius (°C). Expected field half-lives for TCA 

at 15°C, a representative ground-water temperature for 

Area 6, would be about twice as long (1.6 to 5 years) 

based on data from Jeffers and others (1989). Abiotic 

degradation of TCA is essentially independent of redox 

conditions or pH, so it occurs throughout most 

aquifers. Abiotic degradation of 1,1-DCA and 1,2-

DCA is not an important natural attenuation process 

(Jeffers and others, 1989)—their reported half-lives are 

about 60 to 70 times greater than those for TCA. 

However, abiotic degradation of CA is very rapid, with 

a reported half-life of only 0.12 year at 20°C (Bouwer 

and McCarty, 1983).

Reductive dechlorination of chlorinated ethanes 

is similar to the process for chlorinated ethenes. TCA 

can be reductively dechlorinated to 1,1-DCA and then 

to CA. The process occurs under anaerobic conditions 

only, and is most effective under the more strongly 

reducing conditions of sulfate reduction and 

methanogenesis. TCA is more susceptible to reductive 

dechlorination than are 1,1-DCA and CA. Less is 

known about mineralization of chlorinated ethanes. 

Mineralization of 1,2-DCA under aerobic conditions 

(Klecka and others, 1998) and under anaerobic 

conditions (Dinicola and others, 2000) has been 

demonstrated previously. Mineralization of 1,1-DCA 

has been inferred but not well studied, and 

mineralization of CA is suspected to be much slower 

than abiotic degradation of that compound.

Similar to the degradation of TCE, the complete 

degradation of TCA into carbon dioxide, water, and 

chloride is also most efficient in aquifers that are either 

(1) sulfate reducing or methanogenic throughout the 

extent of contamination, or (2) sulfate reducing or 

methanogenic near the TCA source area, and become 

aerobic or manganese or iron reducing downgradient of 

the source area. However, the potential for substantial 

abiotic degradation of TCA suggests that even in an 

aerobic aquifer, TCA can degrade into acetate and 1,1-

DCE, which could subsequently be degraded into 

innocuous daughter products. Given that degradation of 

1,1-DCE (a known carcinogen) could possibly be a 

rate-limiting step in the process, a fully aerobic aquifer 

system would probably not be as conducive to TCA 

degradation as would an aquifer system that is 

anaerobic at the source area.

Nondestructive Attenuation Processes

Nondestructive natural attenuation processes 

include those that reduce contaminant concentration 

but do not reduce the total contaminant mass in a 

system. The most important nondestructive attenuation 

processes for CVOCs in ground water are 

volatilization, dispersion, and sorption.

With regard to natural attenuation of 

contaminants in ground water, volatilization is a 

transfer of contaminants from ground water to soil gas. 

Volatilization can reduce the total contaminant mass in 

ground water, but only by transferring the mass to soil 

gas and the atmosphere. Volatilized chemicals in soil 

gas can also be transferred back to ground water by 

infiltrating water, resulting in little loss of mass but an 

attenuation of chemical concentrations. Volatilization 

can be a very important mechanism for the loss of 

chemicals from the soil to the air or from surface water 

to the air, but volatilization of chemicals from ground 

water is constrained much more by the rate of vapor 

transport upward through the unsaturated zone. 
28 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

The rate at which a chemical volatilizes from ground 

water is affected by many factors, such as soil 

properties, chemical properties, and environmental 

conditions, and commonly used methods used to 

estimate volatilization are not particularly accurate 

(Rathbun, 1998).

Dispersion is the mixing of different waters due 

to effects of heterogeneity in the permeability of 

aquifer materials. It causes a contaminant plume to 

spread out in directions that are longitudinal and 

transverse to the direction of ground-water flow. 

Dispersion is relevant to natural attenuation because it 

dilutes contaminant concentrations by spreading the 

contaminant into a larger volume of aquifer. Dispersion 

is attributed to both mechanical and molecular 

diffusion processes, but mechanical dispersion is the 

dominant process at normal ground-water flow 

velocities (Davis and others, 1993). Dispersion is 

greater in more heterogeneous aquifer materials. 

Sorption is the partitioning of dissolved solutes 

from the ground water onto sediment particles. 

Sorption is relevant to natural attenuation because it 

retards the movement of a contaminant plume. 

Sorption is largely a reversible process, so 

contaminants may not be permanently removed from 

solution. Sorption is a complex process than includes 

several mechanisms, but sorption of CVOCs is 

primarily dependent on the amount of organic carbon 

present in the aquifer materials and the hydrophobicity 

of the contaminant. The amount of sorption is often 

quantified by a distribution coefficient (Kd). A Kd for a 

given contaminant in a given material is defined as the 

ratio of the sorbed contaminant concentration to the 

dissolved contaminant concentration, and Kd increases 

directly with the total organic carbon content of aquifer 

materials (Schwarzenbach and Westall, 1981). The 

equilibrium distribution of contaminants between the 

sorbed and dissolved phases generally can be described 

by a linear sorption isotherm, where Kd is always equal 

to the amount of contaminant sorbed to the solid phase 

divided by the amount in solution. Although such an 

equilibrium between contaminant concentrations in the 

sorbed and solution phases is often assumed, numerous 

experiments have shown that desorption can be ratelimiting, and previously sorbed contaminants can be 

slowly released into solution over a period of weeks or 

months (Harmon and others, 1989).

METHODS AND DATA ANALYSIS

This evaluation of natural attenuation at OU 1 

was patterned after existing guidelines and protocols 

from Wiedemeier and Chapelle (1998), Weidemeier 

and others (1998), and U.S. Environmental Protection 

Agency (1997). The data used for the evaluation 

included hydrogeologic, contaminant chemistry, 

geochemistry, and environmental tracer data collected 

by the Navy during 1991-2000 and by the USGS 

during 1996-2000. The focus was on documenting and 

quantifying contaminant degradation in ground water, 

although data on contaminant attenuation in surface 

water are also presented.

The evaluation considered the following 

evidence. First, ground-water CVOC concentration 

data from 1991-2000 were examined to ascertain any 

long-term trends in contaminant concentrations. 

Temporal changes in concentration attributed to natural 

attenuation were identified separately from changes 

that could be attributed to recent phytoremediation 

activities. Temporal changes in the relative amounts of 

parent compounds and daughter compounds were also 

examined to help ascertain the importance of 

biodegradation over other attenuation mechanisms. 

Changes in CVOC concentrations and redox-sensitive 

geochemicals along selected ground-water flow paths 

for recent (1999–2000) conditions were then examined 

to determine the magnitude of natural attenuation and 

the importance of degradation in creating the observed 

changes. The rate at which the dissolved contaminant 

mass at OU 1 is degraded in ground water, and the rate 

at which contaminants are discharged to surface water, 

were then estimated for recent (1999–2000) conditions. 

Contaminant attenuation rates, which are a measure of 

the attenuation of contaminant concentrations rather 

than mass, were also calculated from observed data 

along selected ground-water flowpaths. And finally, the 

overall effectiveness of natural attenuation at meeting 

site remediation goals was evaluated.

Hydrogeologic Data Collection

The Navy has routinely measured water-level 

altitudes in wells, piezometers, and nearby streams 

since 1991 (URS Consultants, 1993 and 1997a; URS 

Greiner, Inc., 2000; CH2M Hill Constructors, Inc., 

2001). 
Methods and Data Analysis 29

Measurement points were all surveyed and referenced 

to existing NUWC Keyport benchmarks, and all 

altitudes were referenced to sea level as defined by the 

National Geodetic Vertical Datum of 1929. The Navy 

conducted rising-head slug tests in most wells to 

estimate the hydraulic conductivity of subsurface 

materials, and those hydraulic conductivity values were 

calculated using the Hvorslev (1951) method.

Chemical Sampling and Analyses

The Navy collected and analyzed ground-water 

and surface-water chemical samples at NUWC Keyport 

during 1991-2000. The USGS collected and analyzed 

ground-water chemical samples at NUWC Keyport 

during 1996-2000.

The Navy's ground-water chemistry data were 

collected from a varying network of monitoring wells 

(fig. 2). The specific wells sampled at different times 

and the methods and analyses used by the Navy for 

collecting and analyzing ground-water samples are 

described by URS Consultants, Inc. (1993 and 1997a), 

URS Greiner, Inc. (2000), and CH2M Hill 

Constructors, Inc. (2001). In general, samples were 

collected with bottom-filling bailers during 1991, and 

with submersible or peristaltic pumps after 1991. 

Bailer samples were collected after purging at least 

three well volumes of water from the wells. Pumped 

samples were collected using a modification of the Puls 

and Barcelona (1996) low-flow sampling method in 

which dedicated pumps were not used. Samples were 

collected after allowing ground-water temperature, pH, 

specific conductance, and turbidity measurements to 

stabilize to within 10 percent. The Navy's ground-water 

analytical results that were used in this investigation 

included concentrations of VOCs, total metals, and 

dissolved metals determined using the U.S. 

Environmental Protection Agency's Contract 

Laboratory Program (CLP) methods that were 

applicable at the time of sampling.

The Navy's surface-water chemistry data were 

collected from a network of sampling sites located 

along the creek that flows through the marsh, the marsh 

pond, the tide flats, and into Dogfish Bay (fig. 2). The 

specific sites that were sampled at different times and 

the methods and analyses used for collecting and 

analyzing surface-water samples are described by URS 

Consultants, Inc. (1993 and 1997a) and CH2M Hill 

Constructors, Inc. (2001). In general, all surface-water 

samples were single-grab samples collected by hand in 

small containers. The Navy's surface-water analytical 

results used in this investigation also included 

determinations for VOCs, total metals, and dissolved 

metals using the U.S. Environmental Protection 

Agency's CLP methods that were applicable at the time 

of sampling.

The USGS collected ground-water samples from 

various wells and piezometers between 1996 and 2000. 

All samples were collected with a peristaltic pump 

after purging at least three well volumes of water from 

the wells. Most samples were collected after allowing 

ground-water temperature, pH, specific conductance, 

and DO measured in a flow-through chamber to 

stabilize to within 10 percent; purge water from wells 

sampled from September 1996 through March 1998 

was not monitored.

Usually, ground-water temperature, specific 

conductance, and pH were measured in the field 

immediately before collection of unfiltered samples; 

DO was always measured in the field. Specific 

conductance and temperature were measured using a 

temperature-compensated probe and meter that were 

checked daily with standard reference solutions. The 

pH was measured using a temperature-compensated 

meter calibrated daily with two pH standards. 

Dissolved oxygen was measured using one or more 

methods, including a modified Winkler titration 

(Radtke and others, 1998), a temperature-compensated 

meter that was calibrated daily with water-saturated air, 

or 0–1 mg/L CHEMettes Rhodazine-D colorimeteric 

ampules. Multiple DO analyses were often done to 

confirm concentrations of less than 1 mg/L. Alkalinity 

was measured by field titration of an unfiltered sample 

and concentration of the bicarbonate ion (HCO3

-

) was 

calculated.

Concentration of manganese, iron (II), total iron, 

and hydrogen sulfide were measured in the field 

immediately after collection and filtration of samples 

through a 0.45-micrometer membrane filter. Analyses 

were made using a Hach Model 2010 

spectrophotometer, according to Hach analytical 

method numbers 8039, 8034, 8146, 8008, and 8131 

(Hach Company, 1998). Selected samples also were 

filtered into polyethylene bottles, acidified with nitric 

acid to a pH of less than 2, chilled, and sent to the 

USGS National Water Quality Laboratory (NWQL) for 

measurement of manganese and iron using inductively 

coupled plasma (ICP) spectroscopy. 
30 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Those lab analyses were done to check the accuracy of 

the field analyses, and the data were found to be 

comparable to the field analyses (data not shown). 

Samples for sulfate and chloride analyses were filtered 

into polyethylene bottles with no preservatives added, 

and analyte concentrations were measured using ion 

chromatography at the NWQL or at the USGS 

Microbial Studies Group Laboratory (MSGL) in 

Columbia, S.C.

VOC samples were collected in 40-mL glass 

vials, acidified to a pH of less than 2 with hydrochloric 

acid, sealed, placed on ice, and shipped to one of three 

laboratories for analysis using EPA Method 8260A: the 

MSGL, the NWQL, and a NWQL contract laboratory 

(Quanterra) in Denver, Colo. Total organic carbon 

(TOC) was measured in the USGS laboratory in Ocala, 

Fla., using EPA Method 415.1. The unfiltered TOC 

samples were collected in amber glass bottles and 

chilled to less than 4°C before shipment to the 

laboratory. Dissolved methane, ethene, and ethane 

samples were collected in serum bottles and sealed 

with Teflon septa. The samples were preserved with 

mercuric chloride, chilled, and analyzed using gas 

chromatography (Kampbell and others, 1989) at the 

MSGL or at Transglobal Environmental Geosciences 

Northwest, Inc., in Lacey, Wash. 

Dissolved H2 in ground water was sampled using 

the bubble-strip method of Chapelle and others (1997) 

and concentrations were measured in the field using a 

gas chromatograph equipped with a reduction gas 

detector. Initial gas samples were collected and 

analyzed after 20 minutes of stripping; subsequent 

samples were collected and analyzed at about 5-minute 

intervals until measured H2 concentrations stabilized to 

within 10 percent.

Oxygen-18 and hydrogen-2 (deuterium) samples 

were unfiltered and were collected in 250-mL 

polyethylene bottles. Oxygen-18 concentrations were 

measured using the CO2 equilibration technique (25°C) 

of Epstein and Mayeda (1953). Deuterium 

concentrations were measured using a hydrogen 

equilibration technique (Coplen and others, 1991).

Samples for tritium/helium age dating were 

collected in 12-inch-long, 3/8-inch-diameter copper 

tubes. The tubes were crimped closed while the 

contents were under pressure from the sampling pump 

to eliminate atmospheric contamination. The analyses 

for tritium and helium isotopes and the estimated age 

dates for each sample were determined at LamontDoherty Earth Observatory of Columbia University, 

Palisades, N.Y. (Ludin and others, 2001).

VOCs in shallow ground water directly beneath 

the marsh stream and pond were sampled at 17 

locations (fig. 2) using passive diffusion samplers. 

Such sampling devices have proven to be effective in 

sampling ground water in wells (Vroblesky, 2001), and 

there is no theoretical reason that they would not be 

equally effective at sampling ground water directly in 

saturated sediments. The samplers consisted of 

8-in-long by 2-in-diameter polyethylene lay-flat tubing 

that was filled with deionized water and heat sealed at 

both ends; they were constructed by the USGS in 

Tacoma, Wash. The filled bags were inserted into 

plastic mesh sleeves to protect them from damage. 

Sixteen samplers were buried by hand in about 12-in of 

mud beneath the marsh creek and pond, and one 

sampler was buried beneath an isolated puddle. The 

holes were backfilled with native materials and tamped 

down and left to equilibrate with pore water for more 

than 2 weeks. The locations of the samplers were 

marked with wooden stakes and approximately located 

on a site map. Samplers were retrieved by hand and 

immediately processed. A corner of each bag was cut 

and three 40-mL glass VOC vials were filled, acidified 

to a pH of less than 2 with HCl, sealed, and kept on ice 

for shipment to the NWQL.

Calculation of Contaminant MassDegradation Rates in Ground Water and 

Discharge to Surface Water

The rate at which the contaminant mass at OU 1 

was degraded in ground water and the rate at which 

contaminants were discharged to surface water were 

calculated for recent (1999–2000) conditions using 

mass-balance equations. Comparison of the two rates 

provides a measure of the effectiveness of destructive 

attenuation mechanisms. The mass degradation and 

discharge rates represent recent conditions only and are 

not appropriate for extrapolating contaminant 

degradation long into the future; if ground-water flow 

rates change or if the mass of dissolved contaminants in 

ground water decreases due to phytoremediation, the 

mass degradation and discharge rates may also change. 

However, the rates presented in this report can in the 

future be compared to rates calculated from additional 

data collected after phtytoremediation is fully 

implemented to provide insight into the effects of 

phytoremediation.
Methods and Data Analysis 31

The mass degradation and discharge rates were 

calculated using a flux-based approach that accounts 

for the entire dissolved mass of chlorinated ethenes in 

ground water. The approach compared the flux of 

chlorinated ethenes that is available to migrate from the 

landfill to the flux that actually migrates from the 

landfill to beneath the marsh, to the intermediate 

aquifer, and ultimately to surface water. The difference 

between the flux available to migrate from the landfill 

and the flux that actually migrates is an estimate of the 

mass of contaminants degraded in ground water over a 

given duration. Data used for the calculations included 

contaminant concentration data primarily from 1999 

and 2000, and ground-water flux estimates from a 

previous site-characterization investigation (URS 

Consultants Inc., 1997b). The mass of non-dissolved 

contaminants in the landfill (such as that sorbed to 

sediment or present as non-aqueous phase liquids) is 

unknown, so the calculations considered only 

contaminants dissolved in ground water.

Chlorinated ethene fluxes across three separate 

transects positioned approximately perpendicular to 

ground-water flow were calculated by multiplying 

ground-water fluxes determined by URS Consultants 

Inc. (1997b) by observed contaminant concentrations, 

with the appropriate unit conversions. The flux across 

the most upgradient transect represented the mass of 

contaminants available to migrate from the landfill; the 

upgradient transect was oriented north to south beneath 

the landfill and connected the most highly 

contaminated wells in the upper aquifer (specific wells 

used are identified in the tables presenting the flux 

calculations and results). The flux across a 

downgradient transect in the upper aquifer represented 

the mass of contaminants that actually migrates from 

the landfill in the upper aquifer; that transect was 

oriented north to south beneath the marsh and 

connected the line of diffusion sampler sites. Finally, 

the flux across a downgradient transect in the 

intermediate aquifer transect represented the mass of 

contaminants that actually migrates from the landfill in 

that deeper unit; that transect was oriented northeast to 

southwest in the intermediate aquifer downgradient 

from the landfill and connected the row of intermediate 

aquifer wells at that location.

Once the chlorinated ethene fluxes were 

calculated for the three transects, the mass degraded in 

ground water per day was calculated as the difference 

between the flux across the upgradient (landfill) 

transect and the sum of the fluxes across the 

downgradient (marsh and intermediate aquifer) 

transects. There were too few data to estimate mass 

degradation beyond the marsh and intermediate aquifer 

transects, so it was conservatively assumed that all 

chlorinated ethenes that flowed past those 

downgradient transects discharged to surface water. 

The validity of the mass balance calculations was 

partly assessed by independently calculating the flux of 

chlorinated ethenes into the marsh using available 

surface-water flow and contaminant concentration data. 

No similar data were available to calculate the actual 

flux of contaminants to the tide flats and Dogfish Bay.

The flux-based mass balance was based on the 

following assumptions. First, the ground-water 

sampling locations were assumed to adequately 

represent conditions throughout the site. That 

assumption is reasonable for the relatively dense 

network of wells and piezometers in the landfill and 

intermediate aquifer, although it is less certain that the 

diffusion samplers adequately represent shallow 

ground water beneath the marsh. It was also assumed 

that steady-state conditions applied to ground-water 

flow, the supply of dissolved contaminants, and 

contaminant degradation rates. Historical and recent 

water-level data suggest that ground-water flow was at 

or near steady-state conditions (URS Greiner, Inc., 

2000). Generally stable or slowly decreasing CVOC 

concentrations in the most contaminated landfill wells 

suggest that the supply of dissolved contaminants has 

been relatively steady. Less is known about the history 

of contaminant degradation rates, although the landfill 

has been closed for many years and enough time has 

passed for redox conditions to stabilize and the 

microbial community to acclimate. The final 

assumption was that there was no substantial 

contaminant loss in ground water through sorption or 

volatilization. Volatilization losses were probably 

minimal because volatilization of chemicals from 

ground water is greatly constrained by the rate of vapor 

transport upward through the unsaturated zone. 

Sorption losses may have been important in the 

organic-rich marsh sediments, but contaminants have 

been flowing through those sediments for many 

decades, so the bulk of the sorption capacity was 

probably filled long ago. Contaminant losses through 

both of these mechanisms are inherently included in 

the reported calculated mass degradation rates.
32 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Calculation of Contaminant Attenuation 

Rates

The contaminant attenuation rate is the firstorder approximation of the rate at which ground-water 

contaminant concentrations decrease in the 

downgradient direction. The calculated attenuation 

rates could change as a result of changing redox 

conditions, but the rates are more appropriate than 

mass degradation rates for extrapolating contaminant 

degradation into the future because they are not 

dependent on the absolute concentrations of CVOCs. 

The attenuation rates presented in this report can also 

be compared in the future with similarly calculated 

results based on new data that could be collected after 

phtytoremediation is fully implemented to provide 

insight into the effects of phytoremediation on CVOC 

degradation.

 The attenuation rates are presented as half-lives 

(T1/2), in years, which are measures of the time 

required to reduce the concentration of a contaminant 

to one-half of its initial value. Attenuation rates were 

estimated using the simple one-dimensional first-order 

rate equation

 , (1)

where

If Co and Cx are known, the equation can be rearranged 

as follows to solve for k;

(2)

k can be converted to a half-life (T1/2) by

(3)

and

(4)

The concentration values used in the equation were 

from individual sampling locations along presumed 

flow paths, or were from average concentrations for 

transects aligned perpendicular to the ground-water 

flow direction (specific wells used are identified in the 

tables presenting the attenuation rate calculations and 

results). Transect averages were used to overcome 

uncertainties about whether individual wells lie exactly 

along the centerline of a flowpath. Estimates of 

ground-water travel-times used in the calculations were 

from URS Consultants, Inc. (1997a) and from data 

presented in this report.

HYDROGEOLOGIC AND GEOCHEMICAL 

CHARACTERIZATION FOR NATURAL 

ATTENUATION

Site characteristics used to evaluate natural 

attenuation included the direction and rate of groundwater flow, the redox conditions of ground water, and 

the distribution of the various CVOCs. The Navy did 

much of the hydrogeologic and contaminant 

characterization at the site (URS Consultants, Inc., 

1997a). The focus of this section of the report is on new 

data and interpretations concerning ground-water flow 

directions, the rates and distribution of contaminants, 

and ground-water redox conditions.

Ground-Water Flow Directions and Rates

Previous estimates of ground-water flow 

directions and rates at Area 1 are shown in figures 9

and 10. Some important uncertainties regarding 

ground-water flowpaths and flow rates in the 

intermediate aquifer remained after publication of 

those estimates (URS Consultants, Inc., 1997a). 

Although the human health risk from contaminants in 

the intermediate aquifer was demonstrated to be 

minimal, the contaminants are still a concern because 

they are migrating beyond the landfill and may 

eventually pose an environmental risk in the marine 

environment.

Cx is the contaminant concentration at a distance x

feet downgradient of Co,

Co is the contaminant concentration at an upgradient 

location,

t is time required for contaminants to travel 

distance x, and 

k is the first-order rate constant.

Cx Coe

–kt =

k lnCo/Cx = [ ] ( ) /t

T1/2 = ln 2( )/k

T1/2 = 0.693/k
Hydrogeologic and Geochemical Characterization for Natural Attenuation 33

Ground-Water Flowpaths Between the Upper and 

Intermediate Aquifers

The flowpath followed by contaminants from the 

landfill out to the intermediate aquifer well MW1-39 

beneath the Highway 308 causeway is uncertain, in 

large because the chemistry of ground water in well 

MW1-39 is substantially different from that in the other 

three wells on the causeway. In particular, detectable 

concentrations of CVOCs have been found only in 

MW1-39, and ground water at MW1-39 has a specific 

conductance that is 65 to 95 percent lower than that 

observed at the three nearby wells. The specific 

conductance in well MW1-39 is also 60 to 80 percent 

lower than that observed at the contaminated 

intermediate-aquifer wells closer to the landfill (MW1-

25 and MW1-28) that are presumably upgradient from 

MW1-39. URS Consultants, Inc. (1997a) suggested 

two possible flowpaths from the landfill that could 

explain the data. One flowpath presumed the 

contaminants migrated in the top layer of the 

intermediate aquifer above more saline ground water 

represented by MW1-25 and MW1-28, and the other 

presumed contaminated ground water from MW1-25 

and MW1-28 mixed with fresh uncontaminated ground 

water flowing beneath the tide flats from the southwest. 

The flowpath that contaminants follow from the landfill 

to MW1-39 was further examined in this study using 

new common-ion, oxygen-18 (18O), and hydrogen-2 

(deuterium or 2H) data.

Details about the hydrogeologic setting and well 

characteristics of the area between the landfill and 

Highway 308 are as follows. Four intermediate-aquifer 

wells are located near the center of the Highway 308 

causeway: MW1-36, MW1-37, MW1-38, and MW1-39 

(fig. 2). Wells MW1-37 and MW1-39 are screened 

immediately below the approximately 5-ft-thick middle 

aquitard at a depth of about 27 feet, whereas wells 

MW1-36 and MW1-38 are screened about 12 feet 

below that altitude at the bottom of the intermediate 

aquifer. All wells have 5-ft-long screen intervals. Of 

the shallower wells, MW1-39 is screened in a nonglacial silty sand and MW1-37 is screened in a glacial 

sand and gravel; both are underlain by a relatively silty 

subunit within the intermediate aquifer (fig. 4). Both of 

the deeper wells, MW1-36 and MW1-38, are screened 

in a glacial sand and gravel that is similar to the unit 

screened by the intermediate-aquifer wells MW1-25 

and MW1-28 nearer the landfill. Between the two pairs 

of wells on the causeway, the specific conductance of 

ground water is substantially higher northeast of the 

highway bridge, and within each well pair, the specific 

conductance is higher in the deeper wells.

2H and 18O isotope samples were collected 

during June 2000 in eight wells at OU 1, including an 

uncontaminated upgradient intermediate-aquifer well 

(MW1-33), two upper-aquifer wells in the landfill 

(MW1-16 and MW1-41), three intermediate-aquifer 

wells near the downgradient margin of the landfill 

(MW1-29, MW1-28, and MW1-25), and two 

downgradient wells on the causeway at Highway 308 

(MW1-38 and MW1-39). 2H and 18O isotopes are ideal 

conservative tracers for ground water because they are 

chemically stable and are physically a part of the water 

molecule. The isotope "signature" of a specific type of 

ground water is simply its concentration of 2H and 18O. 

Isotope concentrations are reported as so-called "delta" 

values in units of parts per thousand relative to Vienna 

Standard Mean Ocean Water, and a negative delta value 

indicates that water is depleted in the heavy isotope 

relative to the standard. 

Analysis of the isotope data suggests that the 

deeper well MW1-38 is on the primary intermediateaquifer flowpath that originates at MW1-33 and passes 

through MW1-25 and MW1-28, but the shallower well 

MW1-39 is part of a different flowpath (fig. 14). 

Ground water at MW1-39, the only contaminated well 

on the causeway, is isotopically distinct from ground 

water at all the other wells sampled, whereas ground 

water in the deeper uncontaminated deeper well MW1-

38 is isotopically similar to contaminated intermediateaquifer ground water nearer the landfill (MW1-25 and 

28) as well as uncontaminated upgradient water 

(MW1-33). The ground water at MW1-39 is 

isotopically distinct in that it is relatively depleted in 

the heavier isotopes. It is beyond the scope of this 

report to fully investigate the cause of that depletion, 

but one documented mechanism that can deplete 

heavier isotopes in ground-water systems is ultrafiltration through fine-grained geologic materials such 

as a confining bed (Coplen and Hanshaw, 1973). 
34 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

That possible mechanism suggests an alternate 

flowpath for contamination to reach Highway 308 from 

the landfill: percolation of contaminated upper-aquifer 

ground water from the northern part of the landfill 

directly through the fine-grained middle aquitard to the 

layer screened by MW1-39.

Ground water at well MW1-41, the only upperaquifer well sampled for isotopes in the northern part 

of the landfill, is also isotopically distinct from that at 

all other wells sampled because it is enriched in the 

heavier isotopes. Isotope enrichment from evaporation 

during recharge is the likely cause of that difference; 

the well is located in the northern plantation in an area 

where ponded water and saturated surface soils have 

inhibited tree growth. Ground water in upper-aquifer 

well MW1-16 in the southern plantation is more 

similar in composition to ground water in the 

intermediate-aquifer wells, and no ponded water has 

been noted at its location. Given that contaminants are 

able to migrate directly from the upper aquifer to the 

main body of the intermediate aquifer through the 

window in the middle aquitard beneath the central 

landfill, it is likely that contaminants in MW1-25 and 

MW1-28 have followed that flowpath. The results of 

the isotope analysis suggest the hypothesis of two 

distinct flowpaths for contaminants in the intermediate 

aquifer, one through the aquitard itself to MW1-39 and 

the other through the aquitard window to MW1-25 and 

28. This hypothesis was further explored by an 

evaluation of common-ion data collected in June 2000.

The common-ion data highlight a number of 

known and hypothesized characteristics of groundwater flowpaths at OU 1. Common-ion data from 

selected wells were plotted on a variation of a trilinear 

diagram (fig. 15a) , a graphical tool that illustrates 

differences in the ionic composition of various samples 

as well as the effects of mixing waters with different 

ionic compositions (Hill 1940; Piper 1944). The 

diameters of the circles around individual points in the 

diagram are directly proportional to the concentration 

of total dissolved solids (TDS) in the sample.

DELTA 18O, IN PARTS PER THOUSAND

DELTA 2H, IN PARTS PER THOUSAND

-82

-80

-78

-76

-74

-72

-70

-68

-66

-12 -11.5 -10.5 -9.5 -10

-84

-11

MW1-39

MW1-29

MW1-16

MW1-16 duplicate

MW1-25

MW1-38

MW1-33

MW1-41

MW1-28

Figure 14. Concentrations of oxygen-18 and hydrogen-2 isotopes in ground water in selected wells, June 2000, 

at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
Hydrogeologic and Geochemical Characterization for Natural Attenuation 35

The trilinear diagram shows clear differences 

between ground water at different locations. 

Uncontaminated intermediate-aquifer water that is not 

affected by seawater (light blue symbols on fig. 15) is 

calcium/magnesium-bicarbonate type with relatively 

low TDS concentration, which is typical for 

uncontaminated ground water in Kitsap County, Wash. 

(Greene, 1997). The exception in this group is well 

MW1-7 which is screened in a fine-grained unit that is 

not truly part of the intermediate aquifer; the 

contaminated intermediate-aquifer well 1MW-4 is also 

screened in finer-grained materials and plots closely to 

MW1-7. Uncontaminated (or minimally contaminated) 

upper-aquifer water (purple symbols on fig. 15) is also 

calcium/magnesium-bicarbonate type except where 

wells are screened in finer-grained materials (such as 

MW1-35 and MW1-20). Contaminated upper-aquifer 

water beneath most of the landfill (red symbols on 

fig. 15) is usually somewhat enriched in sodium and 

potassium and consistently has elevated TDS 

concentrations due to mixing with landfill leachate. 

Contaminated upper-aquifer wells near the 

downgradient margin of the northern part of the landfill 

(1MW-1, MW1-2 and MW1-19; grey symbols on 

fig. 15) are substantially enriched in sodium and 

potassium and have elevated TDS concentrations due 

to mixing with landfill leachate of a different 

composition. And finally, intermediate-aquifer water 

downgradient of the landfill (green symbols for wells 

near landfill and pink symbols for wells near the 

Highway 308 causeway on fig. 15) is enriched with 

chloride and sodium as a result of mixing with 

seawater—the ionic composition of seawater (without 

the TDS circle) is shown on fig. 15 for comparison. 

Specific differences between seawater—affected wells 

in the intermediate aquifer are discussed below.

The observed ionic differences support the 

hypothesis that there are two distinct flowpaths for 

contaminants to reach intermediate-aquifer wells. 

Mixing of two different waters is illustrated by a 

straight line joining two points on a trilinear diagram 

(assuming ions are not added or removed by processes 

such as ion exchange, precipitation, or dissolution of 

salts). Line "AA" in figure 15b illustrates the 

salinization of intermediate-aquifer ground water when 

uncontaminated intermediate-aquifer water flows from 

the upgradient area to the south of OU 1 

(MW1-33), to beneath the southern tip of the tide flats 

shoreline (MW1-29), and eventually towards seawater 

in Dogfish Bay. Lines labeled BB illustrate the 

contamination and salinization of intermediate-aquifer 

water by mixing with two different waters; 

uncontaminated intermediate-aquifer water from south 

of the landfill (MW1-33) mixes with contaminated 

upper-aquifer water from the central part of the landfill 

(1MW-1 and MW1-16), and the resulting mix flows 

towards seawater past MW1-25 out to MW1-36 or 

MW1-37. Similar lines that included MW1-28 rather 

than MW1-25 could be drawn. Sodium and potassium 

concentrations in MW1-25 and MW1-28 are elevated 

above the level expected for straight mixing of 

intermediate-aquifer water with seawater (line AA), 

suggesting that sodium/potassium-enriched upperaquifer water from the northern plantation is part of the 

mix. Lines labeled CC illustrate the contamination and 

salinization of intermediate-aquifer ground water by 

mixing with one (or possibly two) different waters 

along the newly hypothesized flowpath; contaminated 

sodium/potassium-enriched upper-aquifer water from 

the northern part of the landfill (1MW-1 or MW1-2) 

diffuses through the middle aquitard and mixes with 

seawater as it flows out towards Highway 308 

(MW1-39). Water at MW1-39 has a lower TDS 

concentration than contaminated landfill water, so the 

landfill water may also be mixed along the flowpath 

with a third, unidentified type of water with lower 

TDS concentration. The lower TDS concentration in 

MW1-39 may also be a result of dissolved solids 

removal from the landfill water by ultra-filtration or 

precipitation within the fine-grained unit, or it may 

reflect a preferential flowpath between the landfill and 

MW1-39 that is not reflected in the chemistry found in 

existing landfill wells. Although the isotope and 

common-ion data are not definitive, they do support 

the hypotheses that contaminated ground water in 

MW1-39 comes directly from the northern part of the 

landfill and not from the main body of the intermediate 

aquifer represented by MW1-25 and MW1-28. 
36 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Calcium + Magnesium

Sulfate

Sulfate + Chloride

Carbonate + Bicarbonate

Sodium + Potassium

Magnesium

C A T I O N S A N I O N S Percent milliequivalent per liter

Calcium Chloride

80

60

40

20

20

40

60

80

80

60

40

20

20

0

40

60

80

100

20

40

60

80

80

60

40

20

20

0

40

60

80

20

40

60

80

80

100

100

100

100

100

100

60

40

20

0

0

80

60

40

20

0

0

0

100

0

100

0

100

0

Total Dissolved Solids (Parts Per Million)

1,00001,0002,0003,0004,0005,0006,0007,0008,000

MW1-38

MW1-37

MW1-39

MW1-36

Seawater

Intermediate aquifer,

(near Highway 308)

minimally contaminated,

seawater influence

1MW-1

MW1-2

MW1-19

1MW-4

MW1-9

MW1-28

MW1-29

MW1-25

Intermediate aquifer,

(near landfill)

some contaminated,

seawater influence

Upper aquifer,

(northwestern landfill)

contaminated,

no seawater influence

MW1-22

MW1-24

MW1-23

MW1-33

MW1-31

MW1-21

MW1-11

MW1-32

MW1-7

MW1-3

MW1-10

MW1-35

MW1-20

MW1-15

MW1-5

P1-9

MW1-6

MW1-17

P1-7

MW1-16

P1-10

MW1-4

MW1-14

Intermediate aquifer,

uncontaminated,

no seawater influence

Upper aquifer,

minimally contaminated,

no seawater influence

Upper aquifer,

contaminated,

no seawater influence

Monitoring well or piezometer

A. EXPLANATION

Figure 15. Trilinear diagrams showing (A) differences in ionic composition of water at selected wells and (B) mixing of ground 

waters along two flowpaths at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
Hydrogeologic and Geochemical Characterization for Natural Attenuation 37

MW1-37

MW1-39

MW1-36

Seawater

Intermediate aquifer,

(near Highway 308)

minimally contaminated,

seawater influence

Mixing lines for ground

waters flowing towards

seawater

1MW-1

MW1-2

MW1-28

MW1-29

MW1-25

Intermediate aquifer,

(near landfill)

some contaminated,

seawater influence

Upper aquifer,

(northwestern landfill)

contaminated,

no seawater influence

MW1-33

MW1-16

Intermediate aquifer,

uncontaminated,

no seawater influence

Upper aquifer,

contaminated,

no seawater influence

Monitoring well or piezometer

EXPLANATION

MW1-37

MW1-39

MW1-36

Seawater

1MW-1

MW1-2

MW1-28

MW1-29

MW1-25

MW1-33

MW1-16

AA

BB

BB

BB

BB

CC

CC

Sulfate + Chloride

20

0

40

60

80

100

Calcium + Magnesium

20

40

60

80

100

0

Carbonate + Bicarbonate

100

80

60

40

20

0

Sodium + Potassium

80

100

60

40

20

0

Total Dissolved Solids (Parts Per Million)

1,00001,0002,0003,0004,0005,0006,0007,0008,000

B.

Figure 15. Continued
38 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Ground-Water Flow Rates in the Intermediate 

Aquifer

Previous flow-rate estimates for ground water in 

the intermediate aquifer downgradient of the landfill 

were inconsistent. The USGS previously collected and 

interpreted tritium data from selected wells at OU 1 

and estimated that the flow rate in the intermediate 

aquifer between the landfill margin and Highway 308 

was about 25 ft/yr (Appendix A in URS Consultants, 

Inc., 1997a). That estimate was more than twice the 

10 ft/yr rate estimated using hydraulic-gradient and 

conductivity data (fig. 10). For this study, the USGS 

collected and analyzed data for use in a more accurate 

tritium/helium age-dating method (Solomon and Cook, 

2000) to derive independent estimates of ground-water 

flow rates in the intermediate aquifer. The 

tritium/helium method allows age-date estimation not 

only by quantifying the amount of tritium in a sample, 

but also by quantifying the amount of the 3helium 

isotope in a sample that resulted from radioactive decay 

of tritium. An expanded discussion with references on 

the theory and application of tritium/helium age dating 

can be found in Solomon and Cook (2000) and is not 

repeated in this report.

The previous flow-rate estimates and the new 

tritium/helium flow-rate estimate are consistent if the 

newly hypothesized flowpath out to well MW1-39 is 

presumed true. Tritium/helium age dates were 

calculated for ground-water samples collected by 

USGS in September 1996 from intermediate-aquifer 

wells MW1-31, MW1-25, and MW1-39 (table 2). A 

sample was also collected from shallow well MW1-15, 

but it was contaminated in the laboratory and unusable. 

The calculated tritium/helium age dates of ground 

water (a measure of the time between when the ground 

water was recharged and when it was sampled) were 

11 years for MW1-31, 24 years for MW1-25, and 

38 years for MW1-39. Ground-water flow rates were 

estimated by dividing the distance traveled between 

wells by the difference in age dates for water from two 

wells. The distance between upgradient well MW1-31 

and MW1-25 is 660 ft. Assuming that upper-aquifer 

water does not mix with intermediate-aquifer water 

along the flow path from MW1-31 to MW1-25, the 

estimated ground-water flow rate would be about 

50 ft/yr, which is faster than rate of 33 ft/yr estimated 

in 1997. However, some "younger" upper-aquifer water 

is know to reach the intermediate aquifer between the 

two wells (MW1-25 is contaminated), so the 50 ft/yr 

flow rate estimate must be too high and the actual flow 

rate is more likely similar to the hydraulics-based 

estimate of 33 ft/yr. The tritium/helium flow rate 

beneath the tide flats between wells MW1-25 and 

MW1-39 was similarly calculated to be 36 ft/yr 

[500 ft / (38 yrs – 24 yrs)], but those two wells are now 

hypothesized to be on different flowpaths. The 

calculated flow rate from tritium age dates reported in 

1997 was similar (25 ft/yr), but that estimate was also 

based on the erroneous assumption that the wells are on 

the same flowpath. Both of those age-date-based 

estimates are much higher than the hydraulics-based 

estimate of 10 ft/yr. However, presuming that MW1-39 

is on a more shallow flowpath coming from the upper 

aquifer (as indicated by isotope and common-ion data), 

and assuming that the upper-aquifer water at the 

margin of the landfill is about 5 years old, then the 

tritium/helium based flow rate beneath the tide flats 

between wells MW1-2 and MW1-39 would be about 

15 ft/yr [500 ft / (38 yr - 5 yr)]. 

Table 2. Age dates calculated using tritium/helium data from ground water sampled 

September 19, 1996, at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, 

Washington

[TU, tritium unit; ccSTPg-1, cubic centimeters at standard temperature and pressure per gram]

Well

identification

No.

Tritium

(TU)

3Helium/

4Helium

10-6

4Helium

10-8

Neon

(ccSTPg-1)

Uncorrected

age

(years)

Corrected

age

(years)

MW1-31 5.92 1.63 5.13 21.9 12 11

MW1-25 5.91 2.03 5.24 20.9 22 24

MW1-39 1.64 1.56 7.17 24.6 27 38
Hydrogeologic and Geochemical Characterization for Natural Attenuation 39

That estimate is similar to the 1997 hydraulicsestimated rates of 10 ft/yr. No tritium/helium data were 

collected at other wells located on the Highway 308 

causeway that are likely on the same flowpath as 

MW1-25, so the hydraulics-based estimate of about 

10 ft/yr is the only estimate available for the main body 

of the intermediate aquifer.

Changes in Ground-Water Flow from 

Phytoremediation Activities

Performance monitoring of the phytoremediation 

activities by the Navy during 1999 and 2000 showed 

that ground-water flow directions and gradients are 

consistent with historical findings (URS Greiner, Inc., 

2000). The poplar trees in the phytoremediation 

plantations were not yet mature in 2000, so the lack of 

discrenable water-level changes to date is not 

unexpected. Thus, for this report, it is presumed that 

the overall ground-water flow directions and rates have 

not yet been affected by phytoremediation activities.

Redox Conditions in Ground Water

Characterizing ground-water redox conditions 

was required because redox conditions greatly control 

the occurrence and rate of nearly all contaminant 

biodegradation processes. The redox conditions of 

ground water in the upper and intermediate aquifers at 

OU 1 were characterized using ground-water 

geochemistry data collected by the USGS between 

during 1996-2000 (table 7, back of report). The 

geochemical data were not always consistent with 

theory or easy to interpret for reasons previously 

described in this report. The two approaches for 

identifying redox conditions described in the methods 

section of this report were generally followed, except in 

the following three cases.

1. A reliable DO concentration of greater than 1 mg/L 

indicated aerobic conditions, and the reliability of a 

DO measurement was determined by comparing the 

measurement with dissolved iron and manganese 

concentrations. It is relatively easy to contaminate 

an anaerobic ground-water sample with oxygen and 

is quite difficult to contaminate an aerobic sample 

with dissolved iron and manganese. Thus, a sample 

with a measured DO concentration greater than 1 

mg/L that also had dissolved iron (II) or manganese 

concentrations exceeding about 0.2 mg/L was 

considered to be anaerobic. Conflicting DO and 

dissolved metals data were most frequent in the 

September 1996 data, and most wells with DO 

concentrations greater than 1 mg/L in 1996 were 

found to be anaerobic in all subsequent sampling 

rounds. The suspect 1996 DO data most likely result 

from inadequate well purging before sampling 

(purging was done up to 24 hours prior to sampling 

in 1996 only), or from inadvertent sample aeration 

during collection.

2. The unique relationship between dissolved H2

concentrations and redox conditions shown in 

table 1 was assumed to be reasonable for ground 

water at OU 1. However, it was recognized that a 

pumped sample from a well screened 5 ft or longer 

likely included ground water from different redox 

zones in the highly heterogeneous environment of 

the landfill. Thus, additional geochemistry data 

were often used to assign a redox condition different 

than the condition indicated by dissolved H2

concentration alone. In particular, if sulfide and iron 

(II) were detected in the same sample at elevated 

concentrations, sulfate-reducing conditions were 

assigned even if dissolved H2 concentrations were 

less than 1 nM. This was justified in part because the 

temperature of ground water at Keyport (12–15°C) 

is colder than that on which the equilibrium H2

concentrations are based. It was also justified 

because iron (II) and sulfide are expected to react 

quite rapidly and precipitate from solution, so a 

detection of both analytes in a sample suggested ongoing production of sulfide through sulfate 

reduction.

3. The detection of methane in a well was not 

necessarily interpreted as signifying methanogenic 

conditions at that well. Elevated methane 

concentrations were found throughout the landfill, 

indicating that methanogenic conditions in OU 1 

ground water are common but perhaps limited to 

small areas distributed throughout the landfill. 

Methane is relatively mobile in ground water, so 

elevated methane concentrations in wells located 

near the margin or downgradient of the landfill were 

not considered conclusive evidence for 

methanogenic conditions in those downgradient 

locations.
40 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Upper Aquifer

Redox conditions in many of the wells in the 

upper aquifer varied widely over time (table 7, back of 

report). Some of that variability may be actual changes 

in redox conditions over time, but some of it can be 

attributed to technical shortcomings in sampling highly 

heterogeneous ground water or to non-equilibrium 

redox conditions.

Despite the variability in geochemistry sample 

data, a consistent spatial pattern of redox conditions in 

the upper aquifer was ascertained from the data. There 

were two areas of strongly reducing ground water 

beneath the OU 1 landfill—one in the vicinity of the 

northern plantation and one in the southern plantationand those areas were surrounded by mildly reducing 

ground waters. The site-wide redox conditions can be 

shown by mapping the average dissolved H2

concentrations from all sampling rounds for each well, 

and then delineating zones of aerobic ground water, 

mildly reducing ground water (dissolved H2

concentrations less than 1 nM), and strongly reducing 

ground water (dissolved H2 concentrations greater than 

1 nM) (fig. 16). Those three redox classifications are 

particularly relevant to natural attenuation because 

biodegradation through reductive dechlorination is 

generally limited to strongly reducing ground water, 

and biodegradation through direct mineralization is 

most effective in aerobic or mildly reducing ground 

water.

The distribution of redox conditions in the upper 

aquifer corresponds well to the distribution of total 

organic carbon in ground water (fig. 17). It is clear that 

the landfill is a substantial source of organic carbon in 

shallow ground water, and the former waste-paint 

disposal area at the southern end of the landfill is a 

particularly abundant source of organic carbon. 

Because organic carbon is a basic necessity for 

microbial respiration, the correlation between organic 

carbon and redox conditions is clear evidence that 

microbially mediated processes are controlling redox 

conditions. Specific organic acids were analyzed in 

September 1996 ground-water samples, and organicacid concentrations (particularly acetic acid) in 

southern plantation well MW1-16 were more than 

three orders of magnitude greater than those found in 

any other well (data not shown). Organic acids are 

compounds that can be readily metabolized by 

microorganisms, whereas TOC includes many carbon 

compounds that are not so easily metabolized.

Changes in Upper-Aquifer Redox Conditions from 

Phytoremediation Activities 

The overall spatial pattern of redox conditions in 

the upper aquifer has not changed substantially over the 

six sampling rounds, but concentration changes in 

some redox-sensitive compounds suggest that groundwater chemistry was somewhat affected after asphalt 

was removed in February 1999. Beneath the southern 

plantation, a greater than 50-percent reduction in the 

concentrations of the relatively mobile compounds 

manganese, iron (II), and TOC between October 1998 

and June 2000 may indicate a flushing or dilution of 

those analytes near the northern margin of the 

plantation near MW1-16 (fig. 18). A post-asphalt 

removal decrease in specific conductance at MW1-16 

from 3,370 microseimens per centimeter (μS/cm) to 

902 μS/cm (table 7, back of report) supports that 

hypothesis, as do decreased contaminant 

concentrations described later in this report. Specific 

conductance also decreased substantially in MW1-5 

after asphalt removal, although concentration changes 

in redox analytes were not consistent, which suggests 

that all geochemical changes were not related to 

dilution alone. Beneath the northern plantation, a 

similar response to asphalt removal was not evident 

(fig. 19), probably because much of that area was not 

paved prior to phytoremediation. There was little 

evidence indicating a change in the historically strong 

reducing conditions beneath the centers of the 

plantations as a result of asphalt removal (see dissolved 

H2 trends in figs. 18 and 19), although the piezometers 

with the high H2 concentrations were not installed until 

after the asphalt removal. A substantial change in redox 

conditions is unlikely because even with the observed 

decrease in TOC after asphalt removal, there remained 

abundant organic carbon to quickly consume any 

additional dissolved oxygen that might be carried 

downward with increased recharge. Additional data 

would be needed to track the changes into the future, 

but ground-water consumption by the maturing poplar 

trees may induce more substantial changes in groundwater chemistry.
Hydrogeologic and Geochemical Characterization for Natural Attenuation 41

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

?

?

MW1-18

0.7

MW1-3

0.5

MW1-17

0.9

MW1-15

1.3

1MW-1

0.3

MW1-2

0.5 MW1-14

0.9

MW1-41

1.1

P1-1

0.7 P1-3

0.4

MW1-6

0.6

MW1-35

MW1-20

0.7

P1-4

0.7

P1-5

3.0

P1-6

1.8

P1-7

1.2

P1-8

1.8

P1-9

19

P1-10

0.7

MW1-5

1.1

MW1-16

4.0

MW1-4

0.7

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

EXPLANATION

Plantation

Surface water

Strongly reducing

Aerobic

Monitoring well or piezometer

 with dissolved hydrogen

 concentration, in nanomoles

 per liter

1.3

Figure 16. Average dissolved hydrogen (H2) concentrations at sampled wells and delineated redox 

conditions in the upper aquifer at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division 

Keyport, Washington. 

Ground water not delineated as strongly reducing or aerobic is mildly reducing.
42 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

EXPLANATION

Plantation

Surface water

Line of equal concentration

 of total organic carbon,

 in milligrams per liter

Upper aquifer

Intermediate aquifer

10

2

Monitoring well or piezometer

 with total organic carbon 

 concentration, in milligrams

 per liter.

100

10

MW1-32

0.8

MW1-37

6.1

MW1-36

2.4

MW1-39

3.5

MW1-38

5.6

1MW-4

23

MW1-31

5.6

MW1-33

0.7

MW1-28

9.3

MW1-25

7.3

MW1-3

2

P1-7

19.3

P1-9

10.4

MW1-4

4.9

P1-10

7.2

MW1-16

297

MW1-5

14.5

MW1-20

2.2

MW1-35

2.2 MW1-6

33

MW1-17

17

1MW-1

9.1

MW1-15

41.5

MW1-41

22

MW1-14

39

MW1-2

6

MW1-18

28

Figure 17. Concentrations of total organic carbon in ground water, 1999, at Operable Unit 1, Naval Undersea 

Warfare Center (NUWC), Division Keyport, Washington.
Hydrogeologic and Geochemical Characterization for Natural Attenuation 43

048

121620

Dec. 95 Dec. 97 Dec. 98 Dec. 99 Dec. 00 Dec. 96

MW1-4MW1-5MW1-16

CONCENTRATION, IN MILLIGRAMS PER LITER

MANGANESE

0

4080

120160200

Dec. 95 Dec. 97 Dec. 98 

Dec. 96

MW1-4MW1-5MW1-16

CONCENTRATION, IN

MILLIGRAMS PER LITER

0

100200300400500

Dec. 95 Dec. 97 Dec. 98 Dec. 99 Dec. 00 Dec. 96

MW1-4MW1-5MW1-16

TOTALORGANICCARBON

0123456789

1011

Dec. 95 Dec. 96 Dec. 97 Dec. 98 

MW1-4MW1-5MW1-16

CONCENTRATION, IN

NANOMOLES PER LITER

Figure 18. Concentrations of manganese, iron (II), total organic carbon, and hydrogen (H2), 1996–2000, in wells MW1-4, MW1-5, a

plantation at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
44 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

04286

1012

Dec. 95 Dec. 97 Dec. 98 Dec. 99 Dec. 00 Dec. 96

MANGANESE MW1-2

1MW-1MW1-14/41

0

40208060

100

Dec. 95 Dec. 97 Dec. 98 

Dec. 96

IRON (II)

0

2010403050

Dec. 95 Dec. 97 Dec. 98 Dec. 99 Dec. 00 Dec. 96

MW1-21MW-1MW1-14/41

CONCENTRATION, IN MILLIGRAMS PER LITER TOTAL ORGANIC CARBON

CONCENTRATION, IN

MILLIGRAMS PER LITER 0

123456

Dec. 95 Dec. 96 Dec. 97 Dec. 98 

CONCENTRATION, IN

NANOMOLES PER LITER

HYDROGEN (H2)

Figure 19. Concentrations of manganese, iron (II), total organic carbon, and hydrogen (H2), 1996–2000, in wells MW1-2, 1MW-1, an

plantation at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
Hydrogeologic and Geochemical Characterization for Natural Attenuation 45

Intermediate Aquifer

Background redox conditions in the intermediate 

aquifer are aerobic to the south of the landfill (MW1-

33) and are iron or manganese reducing to the east of 

the landfill (MW1-31) and to the southwest of the tide 

flats (MW1-32) (table 7, back of report). At the 

downgradient margin of the landfill, conditions range 

from strongly reducing near the northern tip of the 

landfill (1MW-4) to iron or manganese reducing near 

the central landfill (MW1-25, MW1-28, and MW1-29) 

(fig. 20), and TOC concentrations are elevated in the 

wells contaminated with leachate (wells MW1-25, 

MW1-28, and 1MW-4 in fig. 17). Redox conditions 

have been more variable further downgradient in the 

intermediate aquifer beneath Highway 308 (fig. 21). 

The upper part of the intermediate aquifer at that 

location (MW1-37 and MW1-39) appears to switch 

between iron- and sulfate-reducing conditions, whereas 

the lower part of the aquifer (MW1-36 and MW1-38) 

appears to be consistently iron or manganese reducing. 

The alternating redox conditions may be related to 

tidal-induced changes in the intermediate aquifer 

(water levels in the wells along Highway 308 fluctuate 

in close accordance to tide level), but the specific 

mechanism causing the variability is unknown. It was 

observed that stronger reducing conditions were 

present in MW1-39 when samples were taken on a 

falling tide within 2 hours of the high tide. As would be 

expected in this deeper aquifer, there was no evidence 

that the redox conditions were affected by asphalt 

removal or other phytoremediation activities.

Distribution of Chlorinated VOCs in UpperAquifer Ground Water and Surface Water

The Navy has monitored the distribution of 

CVOCs in ground water at OU 1 since 1991. In this 

section of the report, some of those historical data are 

integrated with new CVOC data collected by the USGS 

from piezometers at the northern and southern 

plantations, and from passive diffusion samplers within 

the marsh. The distribution of CVOCs in ground water 

is required to evaluate natural attenuation because 

decreasing concentrations along flowpaths are 

evidence for natural attenuation, and because 

increasing predominance of degradation products 

relative to parent compounds along flowpaths is 

evidence that biodegradation is a contributor to the 

attenuation. Interpretation of historical and new CVOC 

data is presented later in the "Evaluation of Natural 

Attenuation."

A more detailed distribution of total CVOCs in 

the upper aquifer was determined by integrating data 

from monitoring wells, piezometers, and diffusion 

samplers (fig. 22). The data shown were collected 

primarily in June 1999 for wells and piezometers, and 

in June 2000 for diffusion samplers; some data from 

April 1997 are included for wells that were not 

sampled more recently (table 8, back of report). 

Although the data are from different times, they 

reasonably represent the distribution of CVOCs in the 

landfill at about the time that phytoremediation 

activities began. As will be described in the following 

section of this report, changes in CVOC concentrations 

attributed to the first 2 years of phytoremediation 

activities have been noticeable in only a few selected 

wells. The distribution of CVOCs in the intermediate 

aquifer has changed little from that shown previously 

in figure 12.

The more detailed distribution of CVOCs in the 

upper aquifer is similar to the distribution determined 

previously (fig. 11), with a few notable exceptions. 

First, data from piezometers in the north and south 

plantations show that the highest CVOC concentrations 

in the shallow aquifer are about four times greater than 

previously thought. Because CVOC concentrations in 

most monitoring wells have changed little over time, 

the refined distribution reflects the increased number of 

measurement points rather than any substantial change 

in site CVOC concentrations. The overall pattern of 

CVOC concentrations in shallow ground water beneath 

the marsh correlates well with the pattern observed 

beneath the landfill. That is evidence that the passive 

diffusion samplers used to collect marsh CVOC 

samples worked as intended and are representative of 

shallow ground-water conditions. 
46 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

?

?

?

?

?

?

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

Shallow

lagoon

T.

26

N.

R.1 E.

EXPLANATION

Plantation

Surface water

Strongly reducing

Aerobic

Monitoring well with dissolved

 hydrogen concentration, in

 nanomoles per liter

MW1-36

0.5

MW1-37

MW1-39 0.9

1.2

MW1-38

0.1

MW1-32

0.3

MW1-33

1MW-4

1.2

MW1-29

0.3

MW1-25

0.4

MW1-28

0.5

1.2

Figure 20. Average dissolved hydrogen (H2) concentrations at sampled wells and delineated redox 

conditions in the intermediate aquifer at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division 

Keyport, Washington.

Ground water not delineated as strongly reducing or aerobic is midly reducing.
Hydrogeologic and Geochemical Characterization for Natural Attenuation 47

CONCENTRATION, IN MILLIGRAMS PER LITER

MANGANESE

CONCENTRATION, IN

MILLIGRAMS PER LITER

IRON (II)

TOTAL ORGANIC CARBON

CONCENTRATION, IN

NANOMOLES PER LITER

HYDROGEN (H2)

0

0.20.40.60.81.0

Dec. 95 Dec. 97 Dec. 98 Dec. 99 Dec. 00 Dec. 96

MW1-25MW1-28MW1-36MW1-37MW1-38MW1-39

0246351

Dec. 95 Dec. 97 Dec. 98 

Dec. 96 

MW1-25MW1-28MW1-37MW1-39

024

14

6

1012

8

Dec. 95 Dec. 96 Dec. 97 Dec. 98 Dec. 00 Dec. 99

0246351

Dec. 95 Dec. 96 Dec. 97 Dec. 98 

Figure 21. Concentrations of manganese, iron (II), total organic carbon, and hydrogen, 1996–2000, in selected intermediate-aquifer Naval Undersea Warfare Center, Division Keyport, Washington.
48 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

DOGFISH BAY

Shallow

lagoon

Landfill

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

100

100

1000

1000

10

10,000

100,000

10

?

?

MW1-17

15

MW1-15

0

1MW-1

1,500

MW1-14

100

MW1-41

1

MW1-6

130

MW1-5

300

MW1-4

16,300

N-5

N-7 15

10

N-4

18

N-8

11

N-2

136

N-3

596

N-1

1

C-1

1

C-2

16

C-3

3 S-1

40

S-2

32

S-3

730

S-4

25,000

S-5

150

S-6

10

MW1-19

14

MW1-18

75

MW1-2

1,200

P1-1

17

P1-4

5,600

P1-3

630

P1-5

870

P1-6

23,400

MW1-16

28,300

P1-8

28,800

P1-10

50,800

P1-9

144,000

P1-7

64,300

EXPLANATION

Surface water

Approximate extents of

 windows in middle aquitard

Line of equal concentration of

 CVOCs, in micrograms per liter

10

Plantation

Monitoring well or piezometer

Diffusion sampler

Figure 22. Concentrations of chlorinated volatile organic compounds (CVOCs) in upper-aquifer ground 

water, 1999, at Operable Unit 1, Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.
Evaluation of Natural Attenuation 49

EVALUATION OF NATURAL 

ATTENUATION

 The first step in evaluating natural attenuation at 

OU 1 was to look for trends over time in the 

contaminant concentration data from 1991–2000. 

Decreasing contaminant concentrations over time were 

evidence for natural attenuation, and an increasing 

predominance over time of degradation products 

relative to parent compounds were evidence for 

biodegradation. The changes in concentration over time 

were divided into those attributable to post-1998 

phytoremediation activities and those attributable to 

natural attenuation. The second step was to examine 

changes in CVOC concentrations and redox-sensitive 

compounds along selected ground-water flowpaths at a 

specific time. Again, decreasing contaminant 

concentrations along a flowpath were evidence for 

natural attenuation, and an increasing predominance of 

degradation products relative to parent compounds 

along a flowpath were evidence for biodegradation. 

The evidence is presented separately for the upper 

aquifer beneath the northern plantation, the upper 

aquifer beneath the southern plantation, the 

intermediate aquifer, and surface water. 

There is clear evidence for substantial natural 

attenuation and degradation of CVOCs in ground water 

at OU 1. The rate of degradation was quantified by 

calculating how much dissolved contaminant mass was 

degraded in ground water each day assuming recent 

(1999-2000) site conditions. For comparison, the mass 

of dissolved contaminants that were discharged to 

surface water each day was also calculated. The rate of 

natural attenuation was also quantified by calculating 

the first-order attenuation rates for contaminant 

concentrations along selected ground-water flowpaths. 

The rate calculations are presented for OU 1 as a whole 

and for specific locations.

Natural Attenuation in the Upper Aquifer 

Beneath the Northern Plantation

Changes in contaminant and geochemical 

concentrations over time and along ground-water 

flowpaths indicate that natural attenuation and 

degradation are substantial beneath the northern 

plantation, particularly at its southern end. Flowpath 

data also indicate that there is continued contaminant 

attenuation between the landfill and the marsh, and 

possibly between the landfill and intermediate-aquifer 

well MW1-39 at the Highway 308 causeway. Some of 

the post-1998 decrease in contaminant concentrations 

can be attributed to the effects of asphalt removal for 

phytoremediation.

Changes in CVOC Concentrations Over Time

Evaluation of 1991-2000 CVOC data (tables 9

and 10, back of report) for northern plantation wells 

showed decreasing CVOC concentrations over the long 

term at the southern end of the plantation that are 

attributed to biodegradation. Increased concentrations 

after 1998 beneath the southwestern corner of the 

plantation are attributed to the effects of asphalt 

removal. CVOC concentrations have been relatively 

stable beneath the northern part of the plantation, 

which indicates biodegradation has been less active and 

attenuation has been less pronounced. The northern 

part of the plantation was never paved and post-1998 

changes were not evident.

Total chlorinated ethene concentrations at 

1MW-1, just outside the southwestern corner of the 

northern plantation, steadily decreased from 1991 

through March 1998, but that trend reversed after 

asphalt removal during February 1999 (fig. 23). The 

proportion of VC relative to TCE and cisDCE has 

steadily increased since 1991, which is evidence for 

VC production from the reductive dechlorination of 

TCE and cisDCE. The absolute concentration of VC 

has not increased over the long term, which is evidence 

for reductive dechlorination and(or) mineralization of 

VC. The post-1998 increase in concentration at 1MW-1 

was coincidental with asphalt removal over the 

southern part of the plantation, which suggests that the 

resulting increase in recharge may have flushed some 

additional contamination from the unsaturated zone 

into ground water. Chlorinated ethanes (and the TCA 

abiotic degradation compound 1,1-DCE) have also 

been above concentrations of concern at 1MW-1, and 

the temporal changes in ethane concentrations have 

been similar to those observed for chlorinated ethenes. 

There has been a long-term decrease in total 

chlorinated ethane concentrations since 1991, followed 

by an increase after 1998. There has also been a 

noticeable increase in the proportion of the daughter 

product DCA and a noticeable decrease in the 

proportion of the abiotic degradation product 1,1-DCE.
50 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

TCE as a percentage of total ethenes

VC as a percentage of total ethenes

cisDCE as a percentage of total ethenes

Total ethenes concentration

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

0

10

20

30

40

50

60

70

80

90

100

0

500

1000

1500

2000

2500

0

10

20

30

40

50

60

70

80

90

100

CONCENTRATION OF TOTAL CHLORINATED ETHENES, IN MICROGRAMS PER LITER

PERCENTAGE OF TOTAL CHLORINATED ETHENES

Well 1MW-1

Well MW1-2

Figure 23. Concentrations of chlorinated ethenes in wells 1MW-1 and MW1-2 in the northern plantation, 

1991–2000, at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
Evaluation of Natural Attenuation 51

Beneath the northern part of the plantation at 

well MW1-2, there has been a more subtle decrease in 

total chlorinated ethene concentrations between 1991 

and 2000 and little change in the predominance of 

cisDCE (fig. 23). Those observations suggest that 

biodegradation has been less active at MW1-2, and that 

much of the degradation of TCE to cisDCE and some 

VC occurs upgradient of the well. The only chlorinated 

ethane-related compound of concern at MW1-2 has 

been the abiotic degradation product 1,1-DCE. The 

lack of the TCA biodegradation products DCA and CA 

at MW1-2 further indicates that reductive 

dechlorination has been less active. No consistent 

changes due to post-1998 asphalt removal were evident 

at MW1-2, likely because the northern part of the 

northern plantation had never been paved. There are no 

long-term observations of CVOC concentrations 

upgradient from the western margin of the northern 

plantation available to evaluate trends.

Changes in CVOC and Geochemical 

Concentrations Along Flowpaths 

Changes in CVOC and geochemical 

concentrations along ground-water flowpaths beneath 

the northern plantation show additional evidence for 

natural attenuation and biodegradation, and the data 

confirm that biodegradation has been most active 

beneath the southern part of the plantation. Flowpath 

data also indicate continued attenuation of CVOCs 

between the landfill and the marsh, and possibly 

between the landfill and intermediate-aquifer well 

MW1-39 at the Highway 308 causeway.

Two specific point-to-point flowpaths were 

evaluated for the northern plantation (fig. 24), as well 

as a transect-to-transect averaged flowpath. Flowpath 

A is located along the northern margin of the northern 

plantation and is assumed to terminate in the marsh or 

extend beneath the tide flats to MW1-39. Flowpath B is 

located along the southern margin of the plantation and 

likely terminates in the marsh near N-7, although some 

ground water along this path may also continue on to 

MW1-39. The transect-to-transect flowpath consists of 

four 300-ft-wide north-south transects oriented 

perpendicular to the direction of ground-water flow. 

The upgradient and easternmost transect is represented 

by the upgradient well MW1-3. The next downgradient 

transect includes sites MW1-14, P1-1, MW1-41, P1-5, 

and MW1-15, followed by the third transect that 

includes MW1-2, P1-3, P1-4, and 1MW-1. The final 

and westernmost transect includes all diffusion 

samplers between N-2 and N-8. Well MW1-39 

represents an alternative possible end point for the 

transect-to-transect flowpath. Data used for the 

flowpath evaluations were collected primarily during 

June 1999 from the wells and piezometers, and during 

June 2000 from the diffusion samplers (tables 7 and 8, 

back of report); data collected at other times were used 

only for wells where 1999 or 2000 data were not 

available. The transect-to-transect flowpath was 

evaluated to overcome uncertainties in the assumption 

that specific wells on the point-to-point flowpaths are 

indeed on the same flowpath. The average 

concentrations for each transect were estimated by 

weighting the observed concentrations at individual 

points by the proportion of a transect's length 

represented by each sampling point. The transect-totransect approach does mask the observed differences 

between the northern and southern parts of the 

plantation, but it was found to reasonably represent 

conditions beneath the plantation as a whole.

CVOC concentrations increase substantially as 

ground water flows beneath the plantation, but then 

decrease as ground water flows beneath the marsh and 

the tide flats (fig. 25). The predominant ethene 

compound changes from TCE to cisDCE or VC in the 

downgradient direction, indicating reductive 

dechlorination of TCE and cisDCE along the 

flowpaths. The short-lived degradation product ethene 

was detected at 1MW-1 (at 8.6 μg/L) during June 2000 

(table 9, back of report), indicating active reductive 

dechlorination of VC beneath the southern part of the 

plantation. Only 0.2 μg/L of ethene was detected at 

MW1-2, indicating limited reductive dechlorination of 

VC beneath the northern part of the plantation. The 

average total CVOC concentrations decreased by more 

than a factor of 20 between the downgradient margin of 

the landfill and the marsh, indicating continued 

contaminant attenuation beyond the landfill. 

Downgradient of the marsh and tide flats at MW1-39, 

the detection of only trace amounts of cisDCE and VC 

and the switch to VC as the predominant ethene 

compound may indicate continued reductive 

dechlorination of TCE and cisDCE beneath the tide 

flats, although there are alternative explanations for the 

observations. It is possible that TCE and cisDCE have 

been sorbed more effectively than VC has; for the same 

aquifer materials, TCE sorption may be as much as 

10 times greater and cisDCE sorption up to 3 times 

greater than VC sorption (Howard, 1993). 
52 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Keys Road

BROWNSVILLE HIGHWAY

Bradley Road

Shapely Road

SR

308

SR

303

Tide flats

Marsh

NUWC

Keyport

Landfill

DOGFISH BAY

Shallow

lagoon

50 200 250 METERS 100 150

200

0

0 400 800 FEET 600

47° 

42'

41'

50"

47° 

41'

40"

122°37'40" 30" 122°37'20"

T.

26

N.

R.1 E.

?

?

A

B

C

D

E

F

N-2 N-3

N-4

N-5

N-7

N-8

S-2

S-4

S-5

S-6

MW1-36

MW1-39

MW1-38

MW1-25

MW1-28

MW1-3

MW1-17

1MW-1

MW1-2

MW1-14

MW1-41

P1-1

P1-2

P1-3

MW1-20

P1-4

P1-5

P1-7

P1-8

P1-9

P1-10

MW1-5

MW1-16

MW1-4

Diffusion sampler

EXPLANATION

Phytoremediation plantation

Surface water

Approximate extents of

 windows in middle aquitard

Monitoring well or piezometer

 in upper aquifer

Monitoring well in intermediate

 aquifer

Flowpath in upper aquifer

Flowpath in intermediate

 aquifer

Figure 24. Locations of ground-water flow paths used to evaluate natural attenuation at Operable Unit 1, 

Naval Undersea Warfare Center (NUWC), Division Keyport, Washington.

Flowpaths A through E are in the upper aquifer and flowpath F is in the intermediate aquifer.
Evaluation of Natural Attenuation 53

0.01

0.1

10

1

100

1000

10,000

0.01

0.1

10

1

100

1000

10,000

0.01

0.1

10

1

100

1000

10,000

0 400 600 800 100 200 0

DOWNGRADIENT DISTANCE, IN FEET

Flowpath A

Flowpath B

MW1-3 MW1-3

P1-1 P1-5

P1-4

Averaged flowpath

MW1-2

1MW-1

Transect 2

Transect 3

Transect 4

N-3

N-7

MW1-39 MW1-39 MW1-39

Transect 1

CONCENTRATION OF CHLORINATED ETHENES , IN MICROGRAMS PER LITER

EXPLANATION

TCE

VC

cisDCE

Figure 25. Concentrations of chlorinated ethenes, 1999, along ground-water flowpaths A and B and along an 

averaged flowpath in the northern plantation at Operable Unit 1, Naval Undersea Warfare Center, Division 

Keyport, Washington.
54 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

It is also possible that not enough time has passed for 

the core of the CVOC plume to reach MW1-39. The 

estimated travel time of ground water between the 

landfill and the well is 20-25 years, but the contaminant 

travel time may be longer due to retardation from 

sorption. Given the paucity of hydrogeologic 

information from beneath the tide flats, continued longterm monitoring would be the most certain way to 

determine the actual attenuation downgradient from the 

marsh.

 Changes in concentrations of redox-sensitive 

compounds along the northern flow paths provide 

additional evidence for active biodegradation, and they 

again indicate that biodegradation is most active 

beneath the southern part of the plantation (fig. 26). 

(Redox-sensitive compounds could not be measured in 

the diffusion samplers because of the sampler design 

used.) The increase in total organic carbon (TOC) 

beneath the plantation correlates well with the 

enhanced microbial activity, and the subsequent 

downgradient decrease in TOC illustrates consumption 

of the organic carbon by microorganisms. The increase 

in H2 concentrations beneath the southern part of the 

plantation indicates favorable conditions for reductive 

dechlorination. The increase in HCO3

-

 beneath the 

plantation indicates production of carbon dioxide by 

microbial mineralization of organic compounds, 

possibly including cisDCE and VC. The increase in 

reduced iron (II) and sulfide and the decrease in sulfate 

indicate that the electron acceptors iron (III) and sulfate 

are being consumed. The increase in specific 

conductance (SC) beneath the plantation indicates 

landfill leachate reaching ground water, and the 

downgradient decrease in specific conductance of 

about 50 percent between the marsh and MW1-39 

suggests that perhaps half of the observed 

downgradient attenuation can be attributed to dilution 

of contaminants through mixing with lesscontaminated water. There were not enough methane 

data to show on the flowpath illustrations, but the data 

in table 7 (back of report) indicate substantial methane 

production beneath the northern plantation, particularly 

at or near 1MW-1.

Natural Attenuation in the Upper Aquifer 

Beneath the Southern Plantation

Changes in contaminant and geochemical 

concentrations over time and along ground-water 

flowpaths suggest that natural attenuation, including 

both abiotic and biotic degradation, is also substantial 

beneath the southern plantation, although the data are 

quite variable. Attenuation and degradation have been 

substantial beneath the northern part of the southern 

plantation. Biodegradation processes are less effective 

beneath the southern part of the plantation, due in part 

to lower H2 concentrations that are less favorable for 

sustained reductive dechlorination. Attenuation 

processes in general also appear to be less effective 

along ground-water flowpaths because remaining 

NAPL is likely an on-going source of dissolved 

contaminants. Contaminant concentrations continued 

to decrease at a possibly accelerated rate beneath the 

northern part of the plantation after the1999 asphalt 

removal, but concentrations were highly variable 

beneath the southern part of the plantation after 1998.

Changes in CVOC Concentrations Over Time

Evaluation of the 1991-2000 CVOC data 

(tables 9 and 10, back of report) showed that long-term 

concentrations have overall, but inconsistently, 

decreased beneath the northern part of the southern 

plantation, whereas concentrations tended to increase 

beneath the southern part. Much of the long-term 

decrease beneath the northern part of the plantation can 

be attributed to biodegradation, although changes after 

1998 are likely due in part to asphalt removal for 

phytoremediation. Changes in CVOC concentrations 

were inconsistent after asphalt removal beneath the 

southern part of the plantation.

Near the northwest corner of the southern 

plantation at MW1-5, total chlorinated ethene 

concentrations decreased over the long term, and the 

predominant compound by far has been VC (fig. 27). 

Total ethene concentrations continued to decrease after 

the asphalt removal. Total chlorinated ethane 

concentrations also decreased over the long and short 

term. At MW1-5, DCA was increasingly the 

predominant ethane compound through 1998, after 

which it has alternated with chloroethane in 

predominance. Those observations are clear evidence 

for reductive dechlorination of both chlorinated 

ethenes and ethanes.

Near the northern margin of the plantation at 

MW1-16, total chlorinated ethene and ethane 

concentrations have varied but have generally 

decreased over the long term (fig. 27). The 1999 

asphalt removal appears to have enhanced the 

concentration decrease. 
Evaluation of Natural Attenuation 55

0.01

0.1

10

1

100

0.01

0.1

10

1

100

0.01

0.1

10

1

100

0 400 600 800 1000 200

DOWNGRADIENT DISTANCE, IN FEET

MW1-3 MW1-3

P1-1 P1-5

P1-4

MW1-2

1MW-1

Transect 2

Transect 3

MW1-39 MW1-39 MW1-39

Transect 1

CONCENTRATION OF REDOX-SENSITIVE COMPOUNDS,

IN MILLIGRAMS PER LITER, OR NANOMOLAR, OR MILLISIEMENS PER CENTIMETER

TOC

Iron (II)

H2

Sulfide

SC

HCO3

-

Sulfate

EXPLANATION

Flowpath A

Flowpath B

Averaged flowpath

Figure 26. Concentrations of redox-sensitive compounds, 1999, along ground-water flowpaths A and B 

and along an averaged flowpath in the northern plantation at Operable Unit 1, Naval Undersea Warfare 

Center, Division Keyport, Washington.
56 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

EXPLANATION

cisDCE as a percentage

 of total ethenes

VC as a percentage

 of total ethenes

Total ethenes

 concentration

TCE as a percentage

 of total ethenes

0 0

5000

15,000

10,000

20,000

25,000

30,000

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

0

10,000

20,000

30,000

40,000

50,000

60,000

0

200

1000

500

3500

3000

4500

2500

2000

1500

5000

80

90

100

0

10

20

30

40

50

60

70

80

90

100

CONCENTRATION OF CHLORINATED ETHENES , IN MICROGRAMS PER LITER

PERCENTAGE OF TOTAL CHLORINATED ETHENES

Well MW1-5

Well MW1-16

Well MW1-4

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Figure 27. Chlorinated ethenes, 1991–2000, in wells MW1-4, MW1-5, and MW1-16 in the southern plantation at Operable Unit 

1, Naval Undersea Warfare Center, Division Keyport, Washington.
Evaluation of Natural Attenuation 57

At MW1-16, cisDCE was the predominant ethene 

compound, and DCA was the predominant ethane 

compound. The observations clearly show that the 

historically high chlorinated ethene and ethane 

concentrations have been greatly attenuated in the 

vicinity of MW1-16, and that biodegradation has been 

the reason for at least part of that attenuation.

In contrast, in the southern part of the plantation 

chlorinated ethene concentrations have increased over 

the long term at MW1-4 (fig. 27). TCE was 

consistently the predominant compound before 1999 

and has since alternated with cisDCE for 

predominance. Chlorinated ethane concentrations have 

been sporadic and relatively low over the long term at 

MW1-4, and the abiotic degradation product 1,1-DCE 

has been predominant. Those observations indicate that 

biodegradation at MW1-4 has not been rapid enough to 

fully attenuate the incoming contaminant flux. The 

1999 asphalt removal was followed by a sharp rise and 

then a fall in concentrations, which is difficult to 

interpret with the available data.

 There are no long-term observations of CVOC 

concentrations from the newer piezometers throughout 

the plantation, but the limited available data from 1999-

2000 indicate that CVOC concentrations beneath the 

southern part of the plantation (P1-7 and P1-9) 

increased slightly during the year. CVOC 

concentrations beneath the eastern part of the 

plantation (P1-10) decreased by about a factor of two 

during the same year.

The effects of asphalt removal on CVOC 

concentrations beneath the southern plantation have 

varied, depending on the specific location. However, 

recent increased CVOC concentration changes in the 

marsh surface water (described later in this section) 

indicate that, overall, the asphalt removal has resulted 

in increased chlorinated ethene flux to the marsh from 

the southern plantation.

Changes in CVOC and Geochemical 

Concentrations Along Flowpaths 

Changes in CVOC and geochemical 

concentrations along ground-water flowpaths beneath 

the southern plantation show evidence for substantial 

attenuation and biodegradation, particularly toward the 

northern margin of the plantation. Biodegradation 

processes are less effective beneath the southern part of 

the plantation, due in part to lower H2 concentrations 

that are less favorable for sustained reductive 

dechlorination, but attenuation processes in general 

also appear to be less effective along ground-water 

flowpaths because remaining NAPL is likely an ongoing source of dissolved contaminants.

Point-to-point ground-water flowpaths were 

difficult to define beneath the southern plantation, in 

part because of the large spatial variation in 

concentrations of CVOC and redox-sensitive 

geochemicals observed in wells and piezometers. 

Ground-water flow is east to west beneath the 

plantation, except near the southern landfill margin 

where the lower-altitude marshlands induce a more 

southerly flow direction. Flow direction and 

geochemistry data were used to delineate three 

presumed point-to-point flowpaths beneath the 

southern plantation (fig. 24). Flowpath C is an eastwest track beneath the northern part of the plantation, 

flowpath D is an east-west track beginning nearer the 

center of the plantation, and flowpath E is a northeastsouthwest track beneath the southeastern corner of the 

plantation. All flow paths were assumed to terminate in 

the marsh. An averaged transect-to-transect flowpath 

was not constructed for the southern plantation.

There is a substantial increase in CVOC 

concentrations as ground water flows into the southern 

plantation, and the magnitude of subsequent 

downgradient attenuation varies greatly between the 

three flowpaths evaluated (fig. 28). There is substantial 

attenuation and biodegradation of CVOCs beneath the 

northern part of the plantation and marsh along 

flowpath C. TCE was consistently the least abundant 

ethene, and the switch in predominance from cisDCE 

to VC at MW1-5 indicates active reductive 

dechlorination along the flow path. The short-lived 

degradation product ethene was detected in MW-16 (at 

70 μg/L) and MW1-5 (at 8.6 μg/L) during June 2000 

(table 9, back of report), also indicating active 

reductive dechlorination of VC. The total chlorinated 

ethene concentrations decreased by about a factor of 

100 between the center of flowpath C and the margin of 

the landfill in June 1999; before the February 1999 

asphalt removal the decrease was still substantial at 

about a factor of 20-30. The total chlorinated ethene 

concentrations decreased by about an additional factor 

of 10 to less than 16 μg/L between the margin of the 

landfill and the marsh. Those decreases all indicate 

sustained attenuation along flowpath C. 
58 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington CONCENTRATION OF CHLORINATED ETHENES , IN MICROGRAMS PER LITER

Flowpath C

Flowpath D

Flowpath E

P1-8

MW1-16

P1-10 P1-10

MW1-4

MW1-5

S-2

MW1-20 MW1-20 MW1-20

S-5

P1-9

P1-7

S-4

0.1

10

1

10,000

100,000

1000

100

0.1

10

1

10,000

100,000

1000

100

0.1

10

1

10,000

100,000

1000

100

0 40 240 280 320 360 80 120 160 200

DOWNGRADIENT DISTANCE, IN FEET

EXPLANATION

TCE

VC

cisDCE

Figure 28. Concentrations of chlorinated ethenes, 1999, along ground-water flowpaths C, D, and E in the 

southern plantation at Operable Unit 1, Naval Undersea Warfare Center, Divison Keyport, Washington.
Evaluation of Natural Attenuation 59

Chlorinated ethane concentrations were high enough to 

be of concern along this flowpath (table 10, back of 

report), and attenuation (including biodegradation) of 

those compounds is similar to the ethenes. Chlorinated 

ethane concentrations decreased substantially along 

flowpath C, the relative abundance of the intermediate 

products DCA and CA increased along the flowpath, 

and the short-lived ethane was detected at 3.6 - 

6.6 μg/L.

There is less attenuation of CVOCs beneath the 

southern part of the plantation and marsh along 

flowpaths D and E, perhaps because remaining NAPL 

is an on-going source of dissolved contaminants. TCE 

is less abundant than cisDCE, but more abundant than 

VC, which suggests less-complete reductive 

dechlorination along the flow paths. However, the 

short-lived degradation product ethene was detected 

along flowpath D in P1-10, P1-9, and P1-7 at 2, 37, and 

69 μg/L, respectively, during June 2000 (table 9, back 

of report), and was also detected along flowpath E in 

P1-10 and MW1-4 at 2 and 12 μg/L. Those detections 

of ethene indicate active reductive dechlorination of 

VC along both flowpaths. The total chlorinated ethene 

concentrations decreased somewhat along flowpaths D 

and E beneath the landfill, and they decreased more 

substantially between the margin of the landfill and the 

marsh. The attenuation along flowpath D between the 

landfill and the marsh is likely due both to accelerated 

biodegradation of TCE and cisDCE in the organic-rich 

marsh sediments and to preferential sorption of TCE in 

the sediments. The more substantial attenuation shown 

for flowpath E is likely an artifact of the marsh 

sampling locations. Site S-5 may not adequately 

represent ground-water discharge coming from MW1-4 

because there are saturated marshlands between the 

landfill margin and S-5 where more highly 

contaminated ground water may discharge. The TCE 

concentration at surface-water station MA12 during 

June 2000 was about twice as high as that observed at 

S-5 or any other diffusion sampler site, which indicates 

an unmeasured discharge of TCE to the marsh. 

Chlorinated ethanes are far less abundant than ethenes 

(and of less concern) along flowpaths D and E.

Changes in concentrations of redox-sensitive 

compounds along flow paths in the southern plantation 

(fig. 29) provide additional evidence for active 

biodegradation, particularly in the northern part of the 

southern plantation. The increase in total organic 

carbon (TOC) beneath the plantation indicates a reason 

for the enhanced microbial activity. Subsequent 

downgradient decrease in TOC along the northern 

flowpath illustrates consumption of the electron-donor 

material by microorganisms, whereas the continuing 

increase in TOC along the southern flowpaths indicates 

continuing sources of organic carbon. Increasing H2

concentrations along flowpaths C and D reflect 

increasingly anaerobic conditions, and the 

concentrations are high enough to sustain reductive 

dechlorination. H2 concentrations along the 

southernmost flowpath E are lower and less favorable 

for sustained reductive dechlorination. The increase in 

HCO3

-

 along the northern flowpath indicates 

production of carbon dioxide by microbial 

mineralization of organic compounds, possibly 

including cisDCE and VC. The increase in reduced 

iron (II) and sulfides along flowpath C and the decrease 

in sulfate indicate that the electron acceptors iron (III) 

and sulfate are being consumed. Although sulfate 

decreases along the southern flowpaths D and E, no 

coincident increase in sulfide was observed; the sulfide 

and iron (II) may be precipitating along those paths. 

The downgradient decrease in specific conductance 

(SC) of about 50 percent along flowpath C suggests 

that perhaps half of the observed attenuation could be 

attributed to dilution of contaminants through recharge 

of relatively clean water.

Natural Attenuation in the Intermediate 

Aquifer

Changes in contaminant and geochemical 

concentrations over time and along ground-water 

flowpaths indicate that attenuation is substantial but 

degradation is uncertain in the most contaminated part 

of the intermediate aquifer. CVOC concentrations have 

decreased slightly over the long term beneath the 

downgradient margin of the landfill, but the lack of 

observation points beneath the tide flats indicates only 

that contaminants have not migrated to beneath 

Highway 308. That may reflect either biodegradation, 

dilution, discharge of ground water to the tide flats 

upgradient of Highway 308, or simply that not enough 

time has passed for the contaminants to reach most 

Highway 308 wells. There is no evidence for changes 

in the intermediate aquifer that could be attributed to 

asphalt removal.
60 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

0.001

0.01

0.1

10

1

10,000

1000

100

0.001

0.01

0.1

10

1

10,000

1000

100

0.1

0 40 240 280 320 360 80 120 160 200

DOWNGRADIENT DISTANCE, IN FEET

Flowpath C

Flowpath D

P1-8

Flowpath E

MW1-16

P1-10 P1-10

MW1-4

MW1-5

MW1-20 MW1-20 MW1-20

P1-9

P1-7

0.001

0.01

10

1

10,000

1000

100

TOC

Iron (II)

H2

Sulfide

SC

HCO3

-

Methane

Sulfate

EXPLANATION

CONCENTRATION OF REDOX-SENSITIVE COMPOUNDS,

IN MILLIGRAMS PER LITER, OR NANOMOLAR, OR MILLISIEMENS PER CENTIMETER

Figure 29. Concentrations of redox-sensitive compounds, 1999, along ground-water flowpaths C, D, and E in 

the southern plantation at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
Evaluation of Natural Attenuation 61

Changes in CVOC Concentrations Over Time

Evaluation of CVOC data from 1991-2000 for 

intermediate aquifer wells indicates a substantial longterm decrease in concentrations at the moderately 

contaminated well 1MW-4, but only a small long-term 

decrease in concentrations at the highly contaminated 

wells MW1-25 and MW1-28 (fig. 30). The 

predominant compound has generally been VC at 

1MW-4, and had been consistently been cisDCE at 

MW1-25 and MW1-28. The data indicate that VC has 

been effectively biodegraded at 1MW-4. The reason for 

the apparent increase in cisDCE at 1MW-4 in 1996–97 

is unknown. Redox conditions at 1MW-4 were 

identified as strongly reducing during 1996 and 1997, 

and methane concentrations were some of the highest 

observed at OU 1, so it does not appear that the 

elevated 1996-97 cisDCE concentrations resulted from 

less favorable conditions for biodegradation. 

The predominance of cisDCE in the intermediate 

aquifer indicates that most of the transformation of 

TCE to cisDCE and VC occurs upgradient, likely in the 

upper aquifer. The continued biodegradation (and 

attenuation in general) of CVOCs in the most 

contaminated part of the intermediate aquifer is not 

evident in the long-term data at MW1-25 and MW1-28. 

The stable concentrations and predominance of 

cisDCE do not provide much insight into attenuation 

and biodegradation in the intermediate aquifer. 

Changes in CVOC concentrations along ground-water 

flow paths, as described below, do suggest continued 

attenuation in the intermediate aquifer, but continued 

biodegradation is uncertain. There is no evidence for 

CVOC changes in the intermediate aquifer that could 

be attributed to asphalt removal.

Changes in CVOC and Geochemical 

Concentrations Along Flowpaths

Because there were no intermediate-aquifer 

observation points beneath the tide flats, point-to-point 

ground-water flowpaths indicate only that the 

contaminants have not migrated to beneath Highway 

308. That may be because of biodegradation, dilution 

through mixing with seawater, or discharge of ground 

water to the tide flats upgradient of Highway 308.

A single flowpath was evaluated for the 

intermediate aquifer (F on fig. 24). The precise location 

of the contaminant source for the flowpath is unknown, 

so the contaminants and geochemical concentrations 

from two wells (1MW-1 and MW1-16) at opposite 

ends of the window through the middle aquitard were 

averaged and assumed to be representative of the 

source water. The flowpath is assumed to begin in the 

upper aquifer, although it is recognized that some 

uncontaminated and aerobic water from upgradient 

parts of the intermediate aquifer contributes to the 

flowpath. The contaminant and geochemical 

concentrations at wells MW1-25 and MW1-28 were 

averaged to represent the second point along the 

flowpath; the chemical composition of ground water is 

quite similar in the two wells. The flowpath is shown to 

continue beneath the tide flats to well MW1-36 or 

MW1-38, the deeper wells of each of the nested pairs 

on either side of the Highway 308 bridge. It is 

recognized that some intermediate-aquifer ground 

water may actually discharge into the tide flats and 

never flow as far as the Highway 308 wells.

There is substantial attenuation of CVOCs along 

the presumed intermediate aquifer flowpath (fig. 31), 

although much of the attenuation is likely due to 

mixing with uncontaminated water. TCE 

concentrations decrease by about a factor of 10 

between the upper and intermediate aquifers, cisDCE 

concentrations decrease by a factor of 2, and VC 

concentrations decrease by a factor of 3. Those data 

suggest some additional reductive dechlorination of 

TCE between the two aquifers, although H2

concentrations within the intermediate aquifer are 

likely too low to sustain additional reductive 

dechlorination. A 25-percent increase in HCO3

-

concentrations between the upper and intermediate 

aquifer wells (fig. 31) is most likely due mixing with 

seawater, although some of the increase could also be 

due to mineralization of cisDCE and VC along the 

flowpath. Other changes in geochemistry indicate a 

gradual decrease in the strength of reducing conditions 

and mixing with seawater. Changes in common-ion 

concentrations between wells MW1-25 and MW1-28 

and wells MW1-36 and MW1-38 also indicate mixing 

with seawater beneath the tide flats (see fig. 15).
62 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

EXPLANATION

CONCENTRATION OF CHLORINATED ETHENES , IN MICROGRAMS PER LITER

PERCENTAGE OF TOTAL CHLORINATED ETHENES

cisDCE as a percentage

 of total ethenes

VC as a percentage

 of total ethenes

Total ethenes

 concentration

TCE as a percentage

 of total ethenes

0 0

500

1500

1000

2000

2500

3000

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

0

1000

500

1500

2000

2500

3000

3500

0

20

120

100

140

80

60

40

160

80

90

100

0

10

20

30

40

50

60

70

80

90

100

Well 1MW-4

Well MW1-28

Well MW1-25

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

Figure 30. Concentrations of chlorinated ethenes, 1991–2000, in intermediate-aquifer wells 1MW-4, MW1-25, and MW1-28 in 

the southern plantation at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
Evaluation of Natural Attenuation 63

0.01

0.001

0.1

10

1

100

0 400 600 800 1000 200

CONCENTRATION OF REDOX-SENSITIVE

COMPOUNDS, IN MILLIGRAMS PER LITER, OR

NANOMOLAR, OR MILLISIEMENS PER CENTIMETER

Sulfide

TOC

H2

EXPLANATION

SC

Methane

Iron (II)

Sulfate

HCO3

-

0

500

2000

1000

1500

2500

3000

3500

4000

0 400 600 800 1000 200

DOWNGRADIENT DISTANCE, IN FEET

1MW-1/16

MW1-25/28

MW1-36/38

1MW-1/16

MW1-25/28

MW1-36/38

CONCENTRATION OF CHLORINATED ETHENES,

IN MICROGRAMS PER LITER

EXPLANATION

TCE

VC

cisDCE

DOWNGRADIENT DISTANCE, IN FEET

Flowpath F

Flowpath F

Figure 31. Concentrations of chlorinated ethenes and redox-sensitive compounds along flowpath F in the intermediate 

aquifer at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
64 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Natural Attenuation in Surface Water

There have been no clear long-term changes in 

contaminant concentrations at surface-water sites in the 

marsh, but there is substantial attenuation of 

concentrations in surface water as it flows through the 

marsh and across the tide flats. An increase in surfacewater contaminant concentrations after 1998 can be 

attributed to increased discharge of ground-water 

contaminants to surface water after asphalt removal 

from the southern plantation.

Changes in CVOC Concentrations Over Time

The presence of a pattern of long-term trends in 

CVOC data for 1991-2000 for surface-water sites in 

the marsh is inconclusive, but a clear increase in 

concentrations after 1998 (tables 9 and 10, back of 

report) can be attributed to increased discharge of 

ground-water contaminants to surface water after 

asphalt removal in the southern plantation (fig. 32). 

cisDCE has been the predominant ethene compound at 

the most highly contaminated upstream site, MA-12, 

although the relative abundance of VC has been 

increasing. Likewise, DCA has been the predominant 

ethane compound at MA-12, although the relative 

abundance of CA has also been increasing. As 

expected, those observations correspond with the 

observed temporal pattern of daughter product 

predominance in most southern plantation wells. 

Biodegradation is likely insignificant in surface water, 

but dilution of contaminant concentrations from other 

surface-water inflows to the marsh, and contaminant 

loss presumably through volatilization, result in a 

substantial change in concentrations in the downstream 

direction, as described below. 

Changes in CVOC Concentrations Along 

Flowpaths

There is substantial attenuation of CVOC 

concentrations in surface water as it flows through the 

marsh and across the tide flats (fig. 33). The data 

shown are from June 2000, and the total chlorinated 

ethene concentration in shallow ground water beneath 

the marsh creek and pond is included for comparison. 

The data confirm that most surface-water 

contamination results from ground-water discharge to 

the marsh from beneath the southern plantation. 

Standing water and saturated soils persist year around 

in the marshland adjacent to the southern plantation, 

which indicates perennial ground-water discharge to 

the southern marsh.

In contrast, the marshland adjacent to the 

northern plantation is not consistently saturated at the 

surface. For example, diffusion sampler N-6 was 

buried in saturated soils beneath a small pond near the 

north-central landfill margin in late June 2000, but the 

pond was dry and the soil surrounding the sampler was 

unsaturated when the sampler was retrieved 2 weeks 

later. Those observations suggest that ground water 

from the northern plantation may not be discharging to 

the marsh, and that conclusion is supported by the lack 

of an observable increase in surface-water contaminant 

concentrations where the marsh ground-water 

contaminant concentrations increase between 

downgradient distances of 800 to 1,200 feet. Flowpath 

A (fig. 24) crosses the marsh in the vicinity where 

ground-water discharge to the surface may be absent, 

which further explains why contaminated ground water 

continues flowing westward out to well MW1-39.

Concentrations of surface-water contaminants 

increased slightly between the most downgradient 

marsh station (MA-09) and the discharge point to the 

tide flats (TF19). This increase has been observed 

consistently since 1996, and upper-aquifer 

contamination at the far northern tip of the landfill is 

the most likely cause for it.

The predominance of cisDCE in surface water 

confirms that biodegradation of chlorinated ethenes is 

not complete in upper-aquifer ground water, and the 

consistent ratios of TCE, cisDCE, and VC indicate that 

biodegradation ceases in surface water. The observed 

attenuation of CVOCs is thus a result of volatilization, 

dispersion, and mixing.
Evaluation of Natural Attenuation 65

0 0

5

10

15

20

25

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70

0

200

400

600

800

1000

1200

80

90

100

0

10

20

30

40

50

60

70

80

90

100

Well MA-12

Well MA-09

Well MA-01/MA-11

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

CONCENTRATION OF CHLORINATED ETHENES , IN MICROGRAMS PER LITER

PERCENTAGE OF TOTAL CHLORINATED ETHENES

EXPLANATION

cisDCE as a percentage

 of total ethenes

VC as a percentage

 of total ethenes

Total ethenes

 concentration

TCE as a percentage

 of total ethenes

Figure 32. Concentrations of chlorinated ethenes, 1991–2000, for surface-water stations MA-12, MA01/MA-11, and MA-09 at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.
66 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Degradation Rates of Chlorinated Ethene 

Mass in Ground Water and Mass 

Discharge to Surface Water 

The rate at which the dissolved contaminant 

mass is degraded in ground water, and the rate at which 

the remaining contaminant mass is discharged to 

surface water, were estimated for recent (2000) 

conditions at OU 1 using the approach described in the 

"Methods and Data Analysis" section of this report. 

The data used to estimate those rates were primarily 

from June 1999 and 2000, and the results are thought to 

represent conditions at OU 1 before phytoremediation 

activities have substantially affected ground water. 

Ranges in mass-degradation rates were reported for 

cisDCE and VC. The minimum rates were based only 

on the observed differences in fluxes between transects 

for a specific compound. The maximum rates for 

cisDCE were calculated by assuming that the estimated 

mass of TCE that was degraded produced an equivalent 

number of moles of cisDCE that were also degraded. 

Likewise, the maximum rates for VC were calculated 

by assuming the estimated mass of cisDCE that was 

degraded produced an equivalent number of moles of 

VC that were also degraded. Only one mass removal 

rate is reported for TCE because the amount of PCE 

available to degrade into TCE was negligible. The 

calculations were done only for the chlorinated 

ethenes; the mass of chlorinated ethanes in the landfill 

is substantially less.

1.0

0.1

1,000.0

10.0

100.0

10,000.0

100,000.0

0 1000 1500 2000 500

DOWNGRADIENT DISTANCE, IN FEET

MA-12

MA-11

MA-09

CONCENTRATION OF CHLORINATED ETHENES,

IN MICROGRAMS PER LITER

TCE in surface water

Total chlorinated ethenes in ground water

VC in surface water

cisDCE in surface water TF-19

DB-14

Figure 33. Concentrations of chlorinated ethenes in surface water as it flows through the marsh and across the 

tideflats at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington.

Total chlorinated ethene concentration in ground water beneath the marsh creek and pond is included for 

comparison.
Evaluation of Natural Attenuation 67

Overall, the results indicate that the majority of 

dissolved chlorinated ethenes are degraded in ground 

water before they have an opportunity to discharge to 

surface water (table 3; additional data in table 11 at 

back of report). Of the 71 grams per day (g/d) of 

chlorinated ethenes available to migrate from the 

landfill (table 11), only about 27 percent (19 g/d) 

actually migrates past downgradient transects and 

discharges to surface water (table 3). Thus, 73 percent 

of the dissolved contaminant mass is degraded in 

ground water.

Of the 24 g/d of TCE available to migrate from 

the landfill, less than 1 percent (0.2 g/d) actually 

migrates past downgradient transects and discharges to 

surface water. The degradation of dissolved TCE in 

landfill ground water appeared to be very effective, but 

the amount degraded is likely overestimated. Probably, 

not all of the TCE that migrates from the southern 

plantation to the marsh was measured in the diffusion 

samplers because no samplers were located directly 

adjacent to the southernmost margin of the landfill.

The degradation of dissolved cisDCE appeared 

to be somewhat less effective than that of TCE; of the 

41 g/d of cisDCE that is originally available to migrate 

from the landfill, almost 40 percent (16 g/d) migrates 

past downgradient transects and discharges to surface 

water. However, the total mass of cisDCE degraded 

each day (25 to 43 g/d) is greater than the mass of TCE 

degraded. That is because initially there was more 

cisDCE available to degrade, and because the 

degradation of TCE is an ongoing source for additional 

cisDCE. About three-quarters of the cisDCE that is not 

degraded migrates to the intermediate aquifer and 

likely discharges to the tide flats and Dogfish Bay.

The degradation of dissolved VC appeared to be 

least efficient of the compounds examined; of the 

5.5 g/d of VC that is originally available to migrate 

from the landfill, 60 percent (3.4 g/d) migrates past 

downgradient transects and discharges to surface water. 

The mass of VC degraded each day (2.2 to 18 g/d) is 

the least of all of the compounds examined, but the 

total mass of VC discharging to surface water is still 

much less than the mass of cisDCE that discharges. 

An alternate estimate of chlorinated ethene 

discharge to the marsh was made by summing the 

appropriate ground-water and surface-water fluxes to 

the marsh upstream of two surface-water monitoring 

sites (MA-12 and TF-19) and multiplying those total 

streamflow estimates by the average chlorinated ethene 

concentrations measured at the surface-water sites. 

Streamflow has not been measured directly at OU 1, so 

the ground-water and surface-water discharge 

estimates were instead used to represent non-storm 

period streamflow through the marsh.

The results of the alternative estimate (table 4) 

suggest that discharge of TCE and cisDCE to surface 

water from the southern plantation may be about 

98 and 27 percent greater, respectively, than that 

calculated using the flux-based approach. Those results 

are consistent with the hypothesis that the diffusion 

samplers did not fully represent contaminant discharge 

to the southeastern portion of the marsh; TCE and 

cisDCE are the predominant contaminants in well 

MW1-4 along the margin of the landfill in that vicinity. 

The two estimates of VC discharge from the southern 

plantation are in close agreement.

The results of the alternative estimate also 

suggest there is a net loss of contaminants in marsh 

surface water as it flows from MA-12 to the outlet at 

TF-19. About 30 percent of the TCE flux, 40 percent of 

the cisDCE flux, and 50 percent of the VC flux flowing 

past the upstream site are lost to other destructive 

attenuation processes such as volatilization before 

discharging to the tide flats.
68 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Table 3. Degradation rates of chlorinated ethene mass and discharge to surface water at Operable Unit 1, Naval Undersea Warfare C

Washington[Chlorinated ethene mass removal rate between landfill transect and downgradient transects: cisDCE, Upper range estimate for cisDCE mas removal rate assumes converted to cisDCE; VC, Upper range estimate for VC mass removal rate assumes all cisDCE mass removed was converted to VC. TCE, trichloroethene; cisDCE, cis-1chloride; ft, feet; g/d, grams per day; –, not applicable]

Sub-transect 

name

Ground-water 

sample sites in 

transects

Chlorinated ethene mass removal 

rate between landfill transect and 

downgradient transects

Chlorinated ethene discharge to 

marsh

Chlorinated 

fla

TCE (g/d) cisDCE (g/d) VC (g/d) TCE (g/d) cisDCE (g/d) VC (g/d) TCE (g/d) 

1 – Landfill

North MW1-18 -0.002 0.006 0.010 – – – – North-central MW1-2, P1-3, P1-4 0.4 6.7 – 7 0.4 – 4.7 – – – – Central MW1-17 0.001 -0.008 0.01 -0.02 – – – – South-central MW1-6 0.2 0.02 – 0.2 0.01 – 0.03 – – – – South P1-6, P1-7, MW1-4 23.9.9 18 – 35 1.8 – 13 – – – – 

Subtotals 24 25 – 43 2.2 - 18 – – – – 

2 – Marsh

North N1 – – – – – – – 0.0001 North-central N2, N3, N4, N5, N7, N8 – – – – – – – 0.02 Central C1, C2 – – – 0.0001 0.009 0.01 – South-central C3 – – – 0.0001 0.004 0.001 – South S1, S2, S3, S4, S5, S6 – – – 0.02 3.5 1.1 – 

Subtotals – – – 0.02 3.5 1.1 0.02 

3 – Intermediate aquifer

North1 1MW-1 – – – – – – 0.002 North-central2 1MW-4, MW1-25 – – – – – – 0.01 South-central3 MW1-25 – – – – – – 0.2 South4 MW1-28 – – – – – – 0.0 

– – – – Subtotals – – – – – – 0.2 

TOTALS 24 25 – 43 2.2 – 18 0.02 3.5 1.1 0.2 

1North intermediate-aquifer CVOC flux comes from northern part of the landfill 2North-central intermediate-aquifer CVOC flux comes from northern part of the landfill (0.6 percent) and the north-central part (99.4 percent). 3South-central intermediate-aquifer CVOC flux comes from north-central part of the landfill (50 percent) and southern part (50 percent). 4South intermediate-aquifer CVOC flux comes from north-central part of the landfill (50 percent) and southern part (50 percent).
Evaluation of Natural Attenuation 69

Chlorinated Ethene Attenuation Rates

The approximate first-order rates at which 

CVOC concentrations are attenuated in ground water 

were also estimated for recent conditions at OU 1. The 

data used to calculate attenuation rates using equations 

(2) and (3) were primarily from June 1999 for ground 

water beneath the landfill and in the intermediate 

aquifer, and from June 2000 for ground water beneath 

the marsh. Like the mass degradation rate estimates, 

the results presented are thought to represent natural 

attenuation rates at OU 1 before phytoremediation 

activities have substantially affected ground water, 

although some of the initial effects of asphalt removal, 

site preparation, and tree planting are inherent in the 

estimates.

Attenuation rates were calculated for TCE, 

cisDCE, and VC (table 5; additional data in table 12 at 

back of report) between pairs of sampling locations 

(segments) along ground-water flowpaths shown on 

figure 24. Attenuation rates were not calculated for the 

first segment of most flowpaths between upgradient 

wells and landfill wells where contaminant 

concentrations consistently increased. The negative 

half-lives calculated for a few segments indicate there 

was a net gain in downgradient concentration due to 

additional source material. Ranges in attenuation 

degradation rates are reported for cisDCE and VC 

when the two estimates were significantly different. 

The minimum rates were calculated using only the 

point-to-point concentration changes observed for a 

flowpath segment. 

Table 4. Results of alternate method of estimating chlorinated ethene discharge to the marsh at Operable Unit 1, Naval 

Undersea Warfare Center, Division Keyport, Washington

[Water flux: Ground-water and surface-water flux estimates not shown in table 11 were from Appendix F, URS Inc., 1997b. Observed chlorinated ethene 

concentrations: Chlorinated ethene data from table 9 (sites MA-12 and TF-19) and table 8 (diffusion sampler transects). TCE, trichloroethene; cisDCE, cis1,2-dichloroethene; VC, vinyl chloride; gal/min, gallons per minute; μg/L, micrograms per liter; g/d, grams per day]

Location

Water

flux 

(gal/min)

Observed chlorinated 

ethene concentration

Calculated and observed 

chlorinated ethene flux

TCE 

(μg/L)

cisDCE

(μg/L)

VC

(μg/L)

TCE

(g/d)

cisDCE

(g/d)

VC

(g/d)

Upstream of station MA-12

Ground water from south side of marsh 1.1 0 0 0 0 0 0

Ground water from landfill 0.2 16 3,200 980 0.02 3.5 1.1

Calculated flux to surface water upstream of MA-12 1.3 0.02 3.5 1.1

Observed flux in surface-water at MA-12 1.3 110 670 140 0.8 4.7 1.0

Percent difference between calculated and observed 98 27 -7

Upstream of station TF-19

Surface water from creek draining lands west of 

marsh

40 0 0 0 0 0 0

Ground water from west of marsh pond 0.6 0 0 0 0 0 0

Ground water from south-central landfill 0.3 0.05 2.2 0.44 0.0001 0.004 0.001

Ground water from central landfill 0.4 0.06 4.1 6.1 0.0001 0.009 0.01

Calculated flux to surface water upstream of TF-19 43 0.02 3.5 1.1

Observed flux in surface-water at TF-19 43 2.3 12 2 0.5 2.8 0.5

Percent difference between calculated and observed 97 -25 -121

Percent difference observed between MA-12 and TF-19 31 41 51
70 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

The maximum rates for cisDCE were calculated by 

assuming that all TCE lost along a flowpath segment 

produced an equivalent number of moles of cisDCE, 

and the maximum rates for VC were calculated by 

assuming that all cisDCE lost along a flowpath 

segment produced an equivalent number of moles of 

VC. That approach assumes that TCE and cisDCE are 

attenuated by reductive dechlorination only. Only one 

attenuation rate is reported for TCE because the 

amount of PCE remaining in the landfill was 

negligible. The calculations were done only for the 

chlorinated ethenes.

Comparison of calculated attenuation rates for 

different flowpaths (table 5 and table 12) confirms the 

previous findings regarding where biodegradation is 

most effective at OU 1. Beneath the southern part of 

the northern plantation, relatively short TCE and 

cisDCE half-lives were estimated (flowpath B, 

segment 2) where redox conditions were favorable for 

reductive dechlorination. In contrast, longer TCE and 

cisDCE half-lives and shorter VC half-lives were 

calculated at the downgradient margin of the northern 

part of landfill (flowpath A, segment 2; flowpath B, 

segment 3) where redox conditions were less favorable 

for reductive dechlorination, but were more favorable 

for mineralization of VC. Attenuation half-lives for the 

flowpath segments from the marsh to Highway 308 

were substantially longer than those determined for 

upgradient segments, which suggest that contaminant 

degradation slows substantially once ground water 

leaves the organic-carbon-rich aquifer beneath the 

landfill.

In the southern plantation, the longest 

attenuation half-lives were most often found along the 

more southern flowpaths D and E. For flowpath D, 

segment 2, the likely cause of the long half-life for 

TCE is that there is an additional source for TCE along 

the segment; redox conditions are very favorable for 

reductive dechlorination along the segment. For 

flowpath E, segment 2, the relatively long TCE halflife is likely due to limited reductive dechlorination; 

redox conditions along the segment are less favorable 

for that degradation mechanism. For the more northern 

flowpath C, redox conditions are very favorable for 

reductive dechlorination of TCE and cisDCE along the 

upgradient segment of the flowpath, and redox 

conditions may be favorable for mineralization of VC 

along downgradient segments. Those conditions are 

reflected in TCE half-lives that increase and VC halflives that decrease in the downgradient direction. The 

negative half-life for TCE at the beginning of flowpath 

C indicates that an additional source of TCE is 

available along the segment.

In the intermediate aquifer, the calculated 

attenuation half-lives are substantially longer than 

those determined for the upper aquifer, which again 

suggests a decrease in contaminant degradation once 

ground water leaves the organic-carbon-rich aquifer 

beneath the landfill. Rates could not be calculated for 

the flowpath segment between MW1-25/28 and 

Highway 308 because contaminants have not been 

detected in the downgradient wells as of 2000.

Effectiveness of Natural Attenuation at 

Meeting Remediation Goals

There is clear evidence for substantial 

degradation and overall attenuation of CVOCs at 

OU 1. However, for natural attenuation to be an 

effective sole remedy under the 1998 Record of 

Decision, it would need to meet the specific 

remediation goals for a site. The numerical remediation 

goals related to chlorinated VOCs in ground water and 

surface water at OU 1 are shown in table 6. 

In June 2000, natural attenuation alone was not 

effective enough to meet the numerical remediation 

goals for ground water or surface water at OU 1. 

Chlorinated VOC concentrations in upper-aquifer 

ground water beneath the landfill substantially 

exceeded remediation goals; multiple ground-water 

remediation goals were exceeded in five wells that 

were sampled as part of the long-term monitoring 

program (1MW-1, MW1-2, MW1-4, MW1-5, and 

MW1-16)(CH2MHill Constructors, Inc., 2001), and 

one or more ground-water remediation goals were 

exceeded at all nine upper-aquifer piezometers sampled 

during this investigation.

Chlorinated VOC concentrations in 

intermediate-aquifer ground water were greatly 

attenuated when compared to landfill concentrations, 

but ground-water remediation goals for cisDCE and 

VC were still notably exceeded in two intermediateaquifer wells (MW1-25 and MW1-28), and the goal for 

VC was slightly exceeded in a downgradient well 

(MW1-39).
Evaluation of Natural Attenuation 71

Chlorinated VOC concentrations in marsh 

ground water were also greatly attenuated when 

compared to landfill concentrations, but the VC 

ground-water remediation goal for the protection of 

surface water was exceeded in eight of the 16 diffusion 

samplers (N-2, N-3, N-4, N-8, C-2, S-3, S-4, and S-5); 

the remediation goal for 1,1-DCE was also exceeded in 

the S-4 diffusion sampler.

And finally, CVOC concentrations in surface 

water were also greatly attenuated when compared to 

landfill concentrations, but surface-water remediation 

goals for VC were exceeded at three of the five 

surface-water sites that are part of the long-term 

monitoring program (MA-12, MA-11, and TF-19). The 

TCE goal was also exceeded at site MA-12 near the 

southern plantation where the VC exceedance was 

most substantial.

Table 5. First-order attenuation half-lives of chlorinated ethene for segments of selected 

flowpaths at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

[TCE, trichloroethene; cisDCE, cis-1,2-dichloroethene; VC, vinyl chloride]

Flowpath and segment

First-order attentuation half-life T1/2

TCE (years) cisDCE (years) VC (years)

Upper Aquifer

North landfill to marsh

Flowpath A, segment 2 0.5 0.3 1.3 – 0.1

Flowpath B, segment 2 0.1 0.1 -0.5 – 0.3

Flowpath B, segment 3 -0.1 0.2 0.2

Average flowpath, segment 2 0.3 0.2 0.3 – 0.2

Marsh to Highway 308

Flowpath A, segment 3 2.7 3.6 – 3.5 5.5 – 4.2

Average flowpath, segment 3 2.6 3.9 6.5 – 4.8

South landfill to marsh

Flowpath C, segment 2 -0.9 0.7 1.3 – 0.4

Flowpath C, segment 3 0.3 0.3 1 – 0.5

Flowpath C, segment 4 0.4 -2.5 – -13 0.1

Flowpath D, segment 2 1.4 1 – 0.8 1.1 – 0.3

Flowpath D, segment 3 0.1 1.5 – 0.8 -1.5 – 0.7

Flowpath E, segment 2 1.0 1.6 – 1.3 3.3 – 0.6

Flowpath E, segment 3 0.5 0.4 0.4 – 0.3

Intermediate aquifer

Upper aquifer to intermediate aquifer

Flowpath F, segment 1 1.7 5.6 – 5.1 3.5 – 2

Intermediate aquifer to Highway 308 3.9 2.7 3.0 – 2.7
72 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

CONCLUSIONS

Current Understanding of Natural 

Attenuation at OU 1

Natural attenuation of CVOCs in shallow ground 

water at OU 1 is substantial. Approximately 70 percent 

of the mass of dissolved chlorinated ethenes that is 

available to migrate from the landfill is completely 

degraded in shallow ground water and does not migrate 

to the intermediate aquifer or discharge to surface 

water. Attenuation of CVOC concentrations appears 

also to be substantial in the intermediate aquifer, but 

biodegradation appears to be less active. The 

conclusions regarding the intermediate aquifer are less 

certain and more difficult to quantify because of the 

paucity of data downgradient of the landfill beneath the 

tide flats. Attenuation of CVOC concentrations also is 

substantial in surface water as it flows through the 

adjacent marsh and out to the tide flats. Attenuation 

processes other than dilution reduce the flux of CVOCs 

in marsh surface water by about 40 percent by the time 

the water discharges to the tide flats. Despite the 

importance of natural attenuation processes at reducing 

both the contaminant concentrations and the 

contaminant mass at OU 1, natural attenuation alone 

was not effective enough in the year 2000 to meet 

current numerical remediation goals for the site. That 

was due in part to the relatively short distance between 

the landfill and the adjacent marsh, and in part to the 

high CVOC concentrations beneath the landfill.

Most of the data needed to characterize the 

hydrogeology were collected and reasonably 

interpreted before this investigation. Additional 

interpretation of existing data and new data collected 

for this study, including stable-isotope and commonion concentrations, suggest that there are likely two 

distinct flowpaths for contaminant migration into the 

intermediate aquifer. The first flowpath begins with 

contaminated shallow ground water beneath the 

northern plantation and flows through the middle 

aquitard and downgradient to the slightly contaminated 

intermediate well MW1-39. The second flowpath 

begins with contaminated shallow ground water from 

beneath perhaps both plantations and flows through a 

permeable window in the middle aquitard to the 

moderately contaminated intermediate aquifer wells 

MW1-25 and 28. 

Table 6. Numerical remediation goals for concentrations of chlorinated 

volatile organic compounds in ground water and surface water at Operable Unit 

1, Naval Undersea Warfare Center, Division Keyport, Washington

[μg/L, micrograms per liter; –, no criterion]

Chemical of concern

Ground-water 

remediation 

goal for 

drinking-water 

protection 

(μg/L)

Ground-water 

remediation 

goal for 

surface-water 

protection 

(μg/L)

Surfacewater 

remediation 

goal (μg/L)

Tetrachloroethene 5 4.2 4.2

Trichloroethene 5 56 56

cis-1,2-dichloroethene 70 – –

trans-1,2-dichloroethene 100 33,000 33,000

Vinyl chloride 0.5 2.9 2.9

1,1,1-trichloroethane 200 41,700 41,700

1,1-dichloroethane 800 – –

1,2-dichloroethane 5 59 59

1,1-dichloroethene 0.5 1.9 1.9
Conclusions 73

The second flowpath likely continues downgradient to 

currently uncontaminated wells screened deeper in the 

intermediate aquifer (MW1-36 or MW1-38), but it may 

flow upward to discharge into the tide flats. 

Interpretation of new ground-water age-date estimates 

based on tritium/helium analysis reconciled some past 

discrepancies between ground-water flow rates in the 

intermediate aquifer that were estimated using different 

techniques.

With regard to geochemical characterization, the 

distribution of total CVOCs in shallow ground water 

was determined in greater detail by integrating data 

from existing monitoring wells with newly collected 

data from piezometers in the landfill and diffusion 

samplers beneath the adjacent marsh. The refined 

distribution shows that the highest CVOC 

concentrations beneath the landfill are about four times 

greater than previously thought, and that the pattern of 

CVOC concentrations in shallow marsh ground water 

correlates well with the pattern observed beneath the 

landfill. The latter observation was evidence that the 

diffusion samplers used to collect CVOC samples from 

the marsh worked as intended and are representative of 

shallow ground-water conditions.

Also with regard to geochemical 

characterization, ground-water redox conditions 

beneath the former landfill were found to be generally 

favorable for complete degradation of CVOCs through 

either reductive dechlorination alone or through the 

combined processes of reductive dechlorination and 

mineralization. Two areas of strongly reducing ground 

water (sulfate reduction or methanogenesis) that are 

favorable for reductive dechlorination were delineated 

beneath the landfill—one in the vicinity of the northern 

plantation and one in the southern plantation. Those 

areas were surrounded by mildly reducing ground 

waters (iron or manganese reducing) that may be 

favorable for mineralization of CVOCs. The landfill is 

a substantial source of organic carbon in shallow 

ground water, and the correlation between organic 

carbon and redox conditions is clear evidence that 

microbially mediated processes are controlling redox 

conditions.

Ground-water redox conditions within the 

intermediate aquifer were generally less favorable for 

reductive dechlorination, but were somewhat favorable 

for mineralization of CVOCs. Redox conditions in 

contaminated intermediate aquifer wells ranged from 

strongly reducing to mildly reducing. Organic carbon 

concentrations were somewhat elevated in 

contaminated intermediate-aquifer wells, but were 

substantially less than those found in shallow ground 

water beneath the landfill. 

The evaluation of natural attenuation found 

consistent evidence for both partial and complete 

degradation of CVOCs in ground water at OU 1, 

particularly within the upper aquifer beneath the 

landfill. The evidence included temporal changes in 

CVOC concentrations at individual wells between 

1991 and 2000 and changes in 1999 CVOC 

concentrations and redox-sensitive geochemicals along 

ground-water flowpaths.

Temporal changes in CVOC concentrations at 

individual wells in shallow ground water beneath the 

landfill indicated substantial attenuation and 

degradation of CVOCs. Beneath the northern 

plantation, CVOC concentrations decreased beneath 

the southern part of the plantation due to 

biodegradation, but were unchanged beneath the 

northern part. Beneath the southern plantation, CVOC 

concentrations generally decreased beneath the 

northern part of the plantation, but increased beneath 

the southern part. Much of the long-term concentration 

decrease could be attributed to biodegradation. 

Changes in CVOC and geochemical 

concentrations along ground-water flowpaths beneath 

the landfill also indicated substantial attenuation and 

degradation. Total CVOC concentrations decreased 

along ground-water flowpaths between the landfill and 

the marsh, and along many flowpaths the predominant 

CVOC switched from a more highly chlorinated 

compound to a less chlorinated compound. That switch 

indicates active reductive dechlorination. Also along 

many flowpaths, concentrations of redox-sensitive 

compounds such as H2, HCO3

-

, iron (II), and sulfide 

increased while TOC and sulfate concentrations 

decreased. That pattern is consistent with conditions 

suitable for active reductive dechlorination. Similar to 

the historical CVOC evidence, the flowpath evidence 

indicated more substantial attenuation and degradation 

beneath the southern part of the northern plantation, 

and beneath the beneath the northern part of the 

southern plantation. 

Temporal changes in CVOC concentrations at 

individual wells in the most contaminated part of the 

intermediate aquifer indicated little attenuation or 

degradation. There was substantial attenuation and 

degradation beneath the far northern margin of the 

landfill in the intermediate aquifer where CVOC 

concentrations were much lower to begin with.
74 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Changes in CVOC and geochemical concentrations 

along ground-water flowpaths between the upper 

aquifer and the main body of the intermediate aquifer 

indicated substantial attenuation but uncertain 

degradation; H2 concentrations in the main body of the 

intermediate aquifer were not indicative of the strongly 

reducing conditions needed to sustain reductive 

dechlorination. Along flowpath segments farther 

downgradient of the landfill in the main body of the 

intermediate aquifer, it could only be concluded that 

contaminants have not migrated to beneath Highway 

308. The lack of observation points beneath the tide 

flats did not allow rigorous evaluation of attenuation 

processes, and the available data could reflect either 

biodegradation, dilution, discharge of ground water to 

the tide flats upgradient of Highway 308, or simply that 

not enough time has passed for the contaminants to 

reach most Highway 308 wells. Along the newly 

identified ground-water flowpath between the upper 

aquifer and the Highway 308 intermediate aquifer well 

MW1-39 at the Highway 309 bridge, the evidence 

suggested substantial attenuation but was again 

uncertain because of the lack of observation points 

beneath the tide flats. 

There have been no clear long-term changes in 

CVOC concentrations at surface-water sites in the 

marsh, but there is substantial attenuation of 

concentrations in surface water as it flows through the 

marsh and across the tide flats. The predominant 

ethenes and ethanes in surface water have been cisDCE 

and DCA, respectively, but the relative abundance of 

VC and CA has been increasing. Those observations 

reflect the observed temporal pattern of ethene and 

ethane predominance in most southern plantation wells 

where most surface-water contaminants originate. 

Biodegradation is likely insignificant in surface water, 

but dilution and volatilization substantially attenuate 

contaminant concentrations in the downstream 

direction.

Flux-based calculations of the degradation rates 

of contaminant mass indicate that the majority of 

dissolved chlorinated ethenes in landfill ground water 

are degraded in ground water before they have an 

opportunity to discharge to surface water. Of the mass 

of dissolved chlorinated ethenes available to migrate 

from the landfill, an estimated 73 percent is degraded 

in ground water and only 27 percent actually 

discharges to surface water. Nearly all TCE is 

degraded, about 60 percent of the cisDCE is degraded, 

and about 40 percent of the VC is degraded. An 

alternate estimate of chlorinated ethene discharge to the 

marsh indicated that the actual TCE and cisDCE 

discharge rates might be about 100 and 30 percent 

greater, respectively, than the flux-based estimates. The 

flux-based estimates were low because the diffusion 

samplers did not fully represent contaminant discharge 

to the southeastern portion of the marsh. Additional 

calculations suggest there was a net loss of about 

30 percent of the TCE flux, 40 percent of the cisDCE 

flux, and 50 percent of the VC flux contaminants in 

surface water as it flows through the marsh and out to 

the tide flats. The loss was likely due to nondestructive 

attenuation processes such as volatilization before 

discharging to the tide flats.

Comparison of calculated attenuation rates of 

chlorinated ethene concentration for different groundwater flowpaths confirmed the previous findings 

regarding where biodegradation is most effective at 

OU 1. Attenuation rates varied throughout the upper 

aquifer beneath the landfill in close accordance with 

the location of favorable redox conditions, and 

attenuation rates in the intermediate aquifer were 

substantially slower.

Based on data collected through June 2000, 

natural attenuation alone was not effective enough to 

meet the numerical remediation goals for ground water 

or surface water at OU 1. CVOC concentrations in 

upper-aquifer ground water beneath the landfill 

substantially exceeded remediation goals; multiple 

remediation goals were exceeded in five wells that 

were sampled as part of the long-term monitoring 

program, and one or more remediation goals were 

exceeded at all nine upper aquifer piezometers sampled 

during this investigation. CVOC concentrations in 

intermediate-aquifer ground water were greatly 

attenuated when compared to landfill concentrations, 

but ground-water remediation goals for cisDCE and 

VC were still notably exceeded in two intermediateaquifer wells, and the goal for VC was slightly 

exceeded in a third well. CVOC concentrations in 

marsh ground water were also greatly attenuated when 

compared to landfill concentrations, but the groundwater remediation goal for VC for the protection of 

surface water was exceeded in eight of the 16 diffusion 

samplers. 
Conclusions 75

And finally, CVOC concentrations in surface 

water were also greatly attenuated when compared to 

landfill concentrations, but surface-water remediation 

goals for VC were exceeded at three of the five 

surface-water sites that are part of the long-term 

monitoring program, and the TCE remediation goal 

was exceeded at one site.

Current Impacts of Phytoremediation 

Activities on Natural Attenuation

Phytoremediation activities apparently had some 

impact on contaminant concentrations in ground water 

and surface water, but ground-water redox conditions 

to date (2000) were not affected by the removal of 

asphalt in February 1999 for tree planting. Performance 

monitoring by the Navy during 1999 and 2000 showed 

that ground-water flow directions and gradients were 

consistent with historical findings. The poplar trees in 

the phytoremediation plantations were not yet mature 

in 2000, so the lack of discernable changes to date is 

not unexpected.

Redox conditions in the upper aquifer did not 

change substantially after the initiation of 

phytoremediation activities, but decreased 

concentrations of some redox-sensitive compounds 

suggest that increased recharge following the February 

1999 asphalt removal somewhat diluted ambient 

landfill ground water. In selected southern plantation 

wells, concentrations of the relatively mobile 

compounds manganese, iron (II), and TOC decreased 

by more than 50 percent between October 1998 and 

June 2000. A similar response to asphalt removal was 

not evident in the northern plantation, likely because 

much of that area was not paved prior to 

phytoremediation. There was no evidence of 

geochemical changes in the intermediate aquifer as a 

result of asphalt removal.

Increases in CVOC concentrations after 1998 in 

downgradient wells in the northern and southern 

plantations were coincidental with asphalt removal for 

phytoremediation. The northern part of the northern 

plantation was never paved, so post-1998 changes were 

not evident. Decreases in CVOC concentrations after 

1998 in upgradient wells in the southern plantation 

were also coincidental with asphalt removal for 

phytoremediation.

There was no evidence for CVOC changes in the 

intermediate aquifer that could be attributed to asphalt 

removal. A distinct post-1998 increase in CVOC 

concentrations in marsh surface water was coincidental 

with the asphalt removal, and the increase appeared to 

have resulted from increased contaminant discharge 

from the southern plantation.

Continued Monitoring of Natural 

Attenuation

Current plans call for sampling of analytes 

related to natural attenuation at eight wells once every 

year through 2004 and once every 5 years after 2004. 

The wells identified for sampling are 1MW-1 and 

MW1-2 in the northern plantation; MW1-4, MW1-5, 

and MW1-6 in the southern plantation; and MW1-25, 

MW1-28, and MW1-39 in the intermediate aquifer. 

The analytes identified for sampling are those shown in 

tables 7 and 8 of this report. The Navy and regulatory 

agencies may mutually agree to adjust the sampling 

locations, frequencies, and analytes.

With regard to sampling frequency, it would be 

informative to sample in March and September during 

at least a single year after the plantation canopy is 

closed completely and tree roots have reached the 

water table. The first possible year for that will likely 

be 2002. Data from seasonal sampling would give 

more definitive evidence on effects of 

phytoremediation activities on ground-water redox 

conditions. The growing season begins and the 

recharge season ends in March, and both the growing 

season and dry season are nearly over in September. 

Also, the decision to switch to a 5-year sampling cycle 

would best be made nearer the year 2004 when 

additional data will be available to evaluate whether 

ground-water conditions are relatively stable. 

With regard to sampling locations, the eight 

wells identified for sampling may be too few. Past 

natural-attenuation sampling rounds have included 12 

to 20 wells or piezometers to fully characterize site 

redox conditions. Including at least one upgradient well 

in the upper aquifer (MW1-3 or MW1-20) and one in 

the intermediate aquifer (MW1-33) will provide 

comparison data to assess how geochemical conditions 

change beneath the landfill. 
76 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

The landfill piezometers are also located in the most 

contaminated parts of the landfill, so it would be 

beneficial to sample VOCs and geochemistry at those 

sites at least every other year through 2004. And given 

the newly hypothesized flowpaths for the intermediate 

aquifer, it would be worthwhile to sample the VOCs 

and geochemistry in another intermediate aquifer well 

at Highway 308 (MW1-38) to monitor possible 

contaminant migration from MW1-25 and MW1-28. 

The passive diffusion samplers provided valuable 

information on overall contaminant attenuation in 

ground water, and it would be useful to sample those 

same sites (with a few modifications to better monitor 

ground-water discharge in the vicinity of MW1-4) a 

few years after the plantation canopy is closed and tree 

roots have reached the water table. Multilevel diffusion 

samplers (referred to as "peepers") rather than single 

samplers would allow better documentation of 

attenuation processes in marsh sediments. It would be 

informative to deploy diffusion samplers or peepers in 

March and September to coincide with the proposed 

one-time seasonal sampling, but sampling VOCs in 

surface water could be used as a reasonable proxy for 

those seasonal data.

With regard to analytes sampled, the list of 

geochemicals identified is adequate. In June 2001, the 

USGS collected and analyzed both total and dissolved 

organic carbon (TOC and DOC) at 19 wells. DOC is 

thought to be a somewhat better measure of 

bioavailable organic carbon, so future sampling could 

include DOC rather than TOC with little loss of 

continuity. It would be useful to measure redoxsensitive compounds in diffusion samplers if that 

capability is available in the near future; the capability 

is available now to measure dissolved oxygen and 

possibly methane in diffusion samplers. And it would 

be useful to measure surface-water discharge directly 

in the marsh during the proposed seasonal sampling 

events, or at least during the year when diffusion 

samplers are deployed. Those data could be used to 

confirm the hypothesis of seasonal or no ground-water 

discharge to the marsh from the northern part of the 

landfill.

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80 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

TABLES 7, 8, 9, 10, 11, AND 12
T

ables7,8,9,10,11,and1281

Table 7. Predominant redox conditions at selected wells and ground-water chemistry data collected from 1996 to 2000, at Operable UniWarfare Center, Division Keyport, Washington—Continued

Well 

identification 

No.

Date 

sampled

Hydrogeologic 

unit

Predominant 

redox 

condition

Ground-water chemistry data

Dissolved 

H2 (nM)

Dissolved 

oxygen 

(mg/L)

Total 

organic 

carbon 

(mg/L)

Nitrate 

(mg/L)

Dissolved 

manganese 

(mg/L)

Dissolved 

iron (II) 

(mg/L)

Dissolved 

sulfate 

(mg/L)

Dissolved 

sulfide 

(mg/L)

Dissolved 

methane 

(mg/L)

T

b

bo

(m

1MW-1 09-17-96 U Fe 0.4 2.8 7.0 <0.02 0.18 0.24 7.5 0.00 10 

04-16-97 Fe 0.8 0.4 – 0.11 – 8.0 1.4 0.01 29 103-05-98 Fe/S 0.2 0.1 8.3 – 0.39 12 .– 0.06 .– 10-09-98 Fe 0.2 0.5 – – 0.08 0.39 .– 0.01 .– 06-21-00 Mn/Fe 0.1 0.5 12 <0.05 0.96 13 0.9 0.00 0.39 

1MW-4 09-17-96 I S/M 0.6 1.6 23 <0.02 0.77 1.4 0.04 0.00 16 

04-16-97 S/M 1.8 0.0 – 0.03 – 1.7 0.36 0.02 47 1

MW1-2 09-17-96 U Fe 0.5 2.4 6.0 <0.02 0.05 0.23 4.6 0.00 1.2 

04-16-97 S 1.1 0.2 – <0.02 – 0.13 4.6 0.00 2.5 103-02-98 Fe 0.3 0.1 – – – 0.16 .– .– .– 10-07-98 Fe 0.1 0.1 – – 0.05 0.14 .– 0.00 .– 06-09-99 Fe 0.9 0.2 – – 0.08 0.09 .– 0.00 .– 06-21-00 Fe 0.3 0.1 6.0 <0.05 0.06 0.10 4.3 0.00 0.04 

MW1-3 06-09-99 U1 Fe 0.8 0.4 – – 0.07 <0.01 .– 0.01 .– 

06-20-00 Fe 0.2 0.3 2.0 0.99 0.08 <0.01 13 0.00 0.02 

MW1-4 09-17-96 U Fe 0.5 2.8 2.0 <0.02 0.28 1.8 7.1 0.00 1.2 

04-16-97 Fe 0.6 0.4 – 0.24 – 0.00 8.6 0.00 0.70 03-03-98 S 1.7 0.2 4.0 – 0.10 0.01 .– 0.00 .– 10-08-98 Fe 0.2 0.5 – – – 0.28 .– 0.00 .– 06-07-99 Fe 0.9 0.1 – – 0.20 1.2 .– 0.00 .– 06-22-00 Fe 0.2 0.1 8.6 – 0.70 .– 5.5 0.00 0.56 

MW1-5 09-17-96 U S 1.2 0.0 15 <0.02 1.6 19 6.4 0.01 2.4 

04-16-97 Fe 0.5 0.0 – 0.08 – 3.1 2.8 0.03 18 103-04-98 Fe 0.7 0.0 12 – 1.3 4.5 .– 0.00 .– 10-08-98 S 2.4 0.0 – – 1.5 11 .– 0.00 .– 06-08-99 Fe 0.6 0.3 – – 1.2 30 .– 0.01 .– 06-22-00 Fe .– 0.0 17 – 1.5 39 6.4 0.01 1.1 

Table 7. Predominant redox conditions at selected wells and ground-water chemistry data collected from 1996 to 2000, at Operable Unit Warfare Center, Division Keyport, Washington [U, upper aquifer; I, intermediate aquifer; Fe, iron reducing; S, sulfate reducing; Mn, manganese reducing; M, methanogenic; A, aerobic; H2, hydrogen; nM, nanomolar; m

μS/cm, microsiemens per centimeter; <, less than; >, greater than; –, not analyzed]
82 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington MW1-6 09-17-96

U S 1.1 0.0 33 1.2 1.2 30 0.10 0.00 7.0 

04-16-97 S 0.5 0.0 – 0.07 – 36 4.2 0.15 14 10-08-98 Fe 0.2 0.0 – – 1.1 32 .– 0.01 .– 

MW1-14 09-17-96

U S/M 0.6 0.0 42 <0.02 2.0 67 0.27 0.00 9.2 

04-16-97 S/M 0.7 0.0 – 0.05 – 78 0.13 0.00 46 03-04-98 Fe/S .– 0.1 36 – 11 68 .– 0.05 .– 10-07-98 S 1.2 0.0 – – 1.5 48 .– 0.01 .– 06-09-99 S 1.0 0.3 – – 0.30 57 .– 0.36 .– 

MW1-15 09-16-96

U S/M 0.2 0.0 50 <0.02 5.7 68 0.11 0.00 8.8 

04-16-97 S/M 0.8 0.0 – <0.02 – 77 0.08 0.03 44 03-05-98 S 1.2 0.0 33 – 18 51 .– 0.00 .– 10-09-98 S 2.9 0.0 – – 5.8 64 .– 0.01 .– 

MW1-16 09-17-96

U S 2.1 0.0 480 <0.02 3.9 130 0.17 0.00 4.3 

04-16-97 S/M 1.0 0.0 – <0.02 – 120 2.0 0.06 29 03-04-98 Fe 0.7 0.3 350 – 18 100 .– 0.01 .– 10-08-98

M 9.6 0.0 – – 5.4 180 .– 0.01 .– 

06-07-99

M 6.8 0.6 – – >5 140 .– 0.12 .– 

06-22-00 S .– 0.1 61 – 1.9 60 1.2 0.02 1.2 

MW1-17 09-17-96

U Fe/S 0.9 0.0 23 <0.02 1.3 62 4.3 0.00 8.9 

04-16-97 Fe 0.6 0.0 – <0.02 – 37 68 0.02 23 10-09-98 Fe .– 0.0 – – 0.80 56 .– 0.02 .– 06-22-00 S 1.2 0.0 11 – – 68 .– 0.02 2.8 

MW1-18 09-17-96

U Fe/S 1.0 0.3 28 <0.02 4.0 12 4.6 0.00 11 

04-16-97 Fe 0.5 0.0 – 0.05 – 23 8.2 0.00 52 10-07-98 Fe .– 0.2 – – 0.77 3.3 .– 0.01 .– 

MW1-20 06-08-99

U1 Fe 0.9 0.3 – – 0.35 0.03 .– 0.01 .– 

06-21-00 Fe 0.4 0.0 2.2 <0.05 0.24 0.11 16 0.00 0.01 

MW1-25 09-17-96 I Fe 0.4 2.7 7.4 0.14 0.16 0.74 16 0.01 3.6 

04-17-97 Fe 0.8 0.1 – <0.02 – 0.88 15 0.01 7.9 03-05-98 Fe 0.3 0.3 7.9 – 0.20 0.73 .– 0.00 .– 10-05-98 Fe 0.2 0.1 – – 0.19 0.99 .– 0.01 .– 

Table 7. Predominant redox conditions at selected wells and ground-water chemistry data collected from 1996 to 2000, at Operable U

Warfare Center, Division Keyport, Washington—Continued

Well 

identification 

No.

Date 

sampled

Hydrogeologic 

unit

Predominant 

redox 

condition

Ground-water chemistry data

Dissolved 

H2 (nM)

Dissolved 

oxygen 

(mg/L)

Total 

organic 

carbon 

(mg/L)

Nitrate 

(mg/L)

Dissolved 

manganese 

(mg/L)

Dissolved 

iron (II) 

(mg/L)

Dissolved 

sulfate 

(mg/L)

Dissolved 

sulfide 

(mg/L)

Dissolved 

methane 

(mg/L)
Tables 7, 8, 9, 10, 11, and 12 83

MW1-25 06-22-00 Fe 0.4 0.2 6.5 – 0.16 0.80 12 0.00 0.79 MW1-28 09-16-96 I Fe 0.5 2.1 7.2 <0.02 0.20 1.0 48 0.00 1.7 

04-17-97 Fe 1.0 0.0 – 0.04 – 0.99 51 0.01 5.3 03-05-98 Fe 0.4 0.5 7.7 – 0.20 0.67 .– 0.00 .– 10-07-98 Fe 0.6 0.0 – – 0.19 1.0 .– 0.02 .– 06-22-00 Fe 0.3 0.0 13 – 0.16 0.66 44 0.01 0.45 

MW1-29 09-16-96 I Mn/Fe 0.0 1.9 – <0.02 0.86 2.0 1.8 0.02 8.1 

04-17-97 Fe 0.7 0.0 – 0.29 – 2.1 1.1 0.01 18 

MW1-31 09-16-96 I1 Mn/Fe – .– 5.6 – 3.6 0.32 .– .– .– MW1-32 09-16-96 I2 Fe 0.5 2.7 0.8 0.07 0.23 1.3 16 0.01 <0.01 

04-17-97 Fe – 1.2 – 0.17 – 0.87 17 0.01 <0.01 03-02-98 Fe – <1.0 – – 0.10 1.1 .– 0.01 .– 10-05-98 Fe 0.1 0.0 – – 0.36 1.0 .– 0.01 .– 

MW1-33 10-07-98 I1 A – 3.3 0.1 – 0.003 0.0 .– 0.01 .– 

06-21-00 A – 3.8 0.7 1.3 <0.002 0.0 7.5 0.00 0.05 

MW1-35 10-07-98 U1 A – 2.4 1.9 – 0.15 0.0 .– 0.00 .– 

06-08-99 A – 2.1 – – – -- .– .– .– 06-20-00 A – 3.0 2.2 0.16 <0.002 0.0 3.9 0.00 0.01 

MW1-36 10-09-98 I3 Fe – 0.0 – – 0.30 3.6 .– 0.01 .– 

06-20-00 Fe 0.5 0.1 2.4 <0.05 0.28 3.2 180 0.02 0.01 

MW1-37 09-16-96 I4 Fe 0.8 1.2 6.9 <0.02 0.12 0.48 23 0.03 0.30 

04-17-97 S 3.3 0.0 – <0.02 – 0.80 27 0.02 0.90 03-03-98 Fe 0.4 0.4 5.7 – 0.10 0.86 .– 0.00 .– 10-09-98 Fe 0.4 0.0 – – <0.01 0.43 .– 0.01 .– 06-07-99 Fe 0.4 0.4 – – 0.10 0.32 .– 0.03 .– 06-20-00 Fe 0.1 0.1 5.8 <0.05 0.13 0.30 28 0.02 0.07 

MW1-38 10-09-98 I3 Fe – 0.1 – – 0.20 0.08 .– 0.02 .– 

06-20-00 Fe 0.1 0.2 5.6 <0.05 0.08 0.10 2.3 0.03 0.10 

Table 7. Predominant redox conditions at selected wells and ground-water chemistry data collected from 1996 to 2000, at Operable U

Warfare Center, Division Keyport, Washington—Continued

Well 

identification 

No.

Date 

sampled

Hydrogeologic 

unit

Predominant 

redox 

condition

Ground-water chemistry data

Dissolved 

H2 (nM)

Dissolved 

oxygen 

(mg/L)

Total 

organic 

carbon 

(mg/L)

Nitrate 

(mg/L)

Dissolved 

manganese 

(mg/L)

Dissolved 

iron (II) 

(mg/L)

Dissolved 

sulfate 

(mg/L)

Dissolved 

sulfide 

(mg/L)

Dissolved 

methane 

(mg/L)
84 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington MW1-39 09-16-96 I

4 Fe 0.6 2.0 4.4 <0.02 0.02 0.0 0.71 0.04 1.6 

04-17-97 S 4.5 0.0 – <0.02 – 0.05 13 0.06 6.1 03-03-98 Fe 0.3 0.3 3.7 – 0.10 0.03 .– 0.05 .– 10-09-98 Fe/S 0.5 0.0 – – <0.01 0.04 .– 0.07 .– 06-07-99 Fe/S 1.0 0.3 – – 0.10 0.02 .– 0.00 .– 06-20-00 S 0.5 0.1 2.4 <0.05 0.01 0.10 0.2 0.08 0.41 

MW1-41 06-09-99

U S 1.0 0.3 – – 2.2 60 .– 0.01 .– 

06-21-00 S/M 1.2 0.1 22 <0.05 3.5 55 <0.3 0.00 1.9 

P1-1 06-09-99

U Fe 0.7 0.4 – – 4.0 59 .– 0.00 .– 

P1-3 06-09-99

U Fe 0.4 0.2 – – 1.0 19 .– 0.04 .– 

P1-4 06-09-99

U Fe 0.7 0.3 – – 0.34 2.6 .– 0.02 .– 

P1-5 06-08-99

U S 3.0 0.3 – – 3.1 72 .– 0.01 .– 

P1-6 06-08-99

U S 1.8 0.1 – – 0.12 0.02 .– 0.04 .– 

P1-7 06-08-99

U S 1.2 0.1 – – 0.61 2.09 .– 0.00 .– 

06-22-00 Fe – 0.1 19 – 2.6 3.8 24 0.00 1.5 

P1-8 06-07-99

U S 1.8 0.0 – – 0.20 0.08 .– 0.01 .– 

P1-9 06-08-99

U

M 19 0.3 – – 0.90 0.03 .– 0.00 .– 

06-22-00 S/M – 0.1 10 – 0.69 0.20 6.6 0.00 1.7 

P1-10 06-07-99

U Fe 0.7 0.3 – – 0.10 0.11 .– 0.00 .– 

06-22-00 S/M – 0.0 7.2 – 0.03 0.30 <0.31 0.01 1.3 

1Background well2Cross-gradient well, uncontaminated3Lower part of intermediate aquifer4Upper part of intermediate aquifer.

Table 7. Predominant redox conditions at selected wells and ground-water chemistry data collected from 1996 to 2000, at Operable UWarfare Center, Division Keyport, Washington—Continued

Well 

identification 

No.

Date 

sampled

Hydrogeologic 

unit

Predominant 

redox 

condition

Ground-water chemistry data

Dissolved 

H2 (nM)

Dissolved 

oxygen 

(mg/L)

Total 

organic 

carbon 

(mg/L)

Nitrate 

(mg/L)

Dissolved 

manganese 

(mg/L)

Dissolved 

iron (II) 

(mg/L)

Dissolved 

sulfate 

(mg/L)

Dissolved 

sulfide 

(mg/L)

Dissolved 

methane 

(mg/L)
Tables 7, 8, 9, 10, 11, and 12 85

Table 8. Concentrations of chlorinated volatile organic compounds in ground water at Operable Unit 1, Naval Undersea Warfare Cent

Washington—Continued

Well

identification 

No.

Date 

sampled PCE (μg/L) TCE (μg/L) cisDCE (μg/L) transDCE (μg/L) VC (μg/L) 1,1,1-TCA (μg/L) 1,1-DCA (μg/L) CA (μg/L) 1,1-DC

(μg/L

1MW-1 06-11-99 <3 <3 310 170 960 <3 19 9.0 4.0 1MW-4 04-16-97 <3.3 <2.6 11 <1.9 <1.3 – – – <1.9 MW1-2 06-11-99 <3 27 980 26 160 <3 <3 <3 5.0 MW1-3 10-20-99 <0.5 0.70 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-4 06-14-99 4.0 2,600 12,000 140 1,500 <3 2.0 2.0 24 MW1-5 06-14-99 <3 2 9.0 2.0 260 <3 9.0 18 <3 MW1-6 04-16-97 <3.3 108 16 <1.9 9.4 – – – <1.9 MW1-14 04-16-97 <3.3 <2.6 <1.9 <1.9 <1.3 – – – <1.9 MW1-15 04-16-97 <3.3 <2.6 <1.9 <1.9 <1.3 – – – <1.9 MW1-16 06-14-99 1.0 530 6,800 160 1,700 140 15,000 3,900 48 MW1-17 04-16-97 <3.3 <2.6 16 <1.9 <1.3 – – – <1.9 MW1-18 04-16-97 <3.3 <2.6 47 <1.9 28 – – – <1.9 MW1-20 10-20-99 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-25 03-04-98 <0.5 56 1,700 35 210 <0.5 2.4 <0.5 5.3 MW1-28 03-04-98 <0.5 0.98 1,500 64 400 <0.5 1.3 <0.5 4.3 MW1-29 04-17-97 <3.3 <2.6 <1.9 <1.9 <1.3 – – – <1.9 MW1-31 09-12-96 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-32 03-02-98 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-33 06-24-96 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-35 09-09-96 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-36 09-11-96 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-37 06-07-99 <1 <1 <1 <0.5 <2 <1 <1 <2 <1 MW1-38 09-10-96 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 MW1-39 06-07-99 <1 <1 0.28 <0.5 1.2 <1 <1 <2 <1 MW1-41 10-20-99 <0.5 <0.5 0.60 <0.5 <0.5 <0.5 <0.5 – – 

Table 8. Concentrations of chlorinated volatile organic compounds in ground water at Operable Unit 1, Naval Undersea Warfare Cent

Washington

[Laboratory data qualifier codes, such as “J” for estimated value and “D” for dilution, are not shown. PCE, tetrachloroethene; TCE, trichloroethene; cisDCE, cis-1,2-d

1,2-dichloroethene; VC, vinyl chloride; 1,1,1-TCA, 1,1,1-trichloroethane; 1,1,-DCA, 1,1-dichloroethane; CA, chloroethane; 1,1-DCE, 1,1-dichloroethene; BTEX, bxylenes; CVOCs, chlorinated volatile organic compounds; μg/L, micrograms per liter; <, less than; –, not analyzed or calculated; nd, none detected at unspecified l
86 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington P1-1 06-09-99 <2 11 6.1 <1 <4 <2 0.24 <4 <2 

P1-3 06-09-99 <16 35 450 20 120 <16 <16 3.6 <16 P1-4 06-09-99 <130 160 4,800 56 540 <130 <130 <270 <130 P1-5 06-08-99 <13 440 400 3.5 11.0 <13 <13 15 <13 P1-6 06-08-99 <400 74 16,000 170 5,400 <400 1,500 300 <400 P1-7 06-08-99 <670 26,000 35,000 210 3,100 <670 <670 <1,300 <670 P1-8 06-07-99 <710 190 25,000 210 3,400 <710 <710 <1,400 <710 P1-9 06-08-99 <2,000 48,000 88,000 470 7,200 <2,000 <2,000 <4,000 <2,000 P1-10 06-07-99 <1,000 14,000 34,000 270 2,500 <1,000 <1,000 <2,000 <1,000 S1 07-07-00 <0.1 1.4 8.2 0.69 1.5 <0.1 4.7 24 <0.1 S2 07-07-00 <0.1 0.60 11 1.3 2.8 <0.1 6.1 10 <0.1 S3 07-07-00 <0.1 0.63 9.9 9.5 220 <0.1 460 36 <0.1 S4 07-07-00 <0.1 45 19,000 140 5,600 <0.1 0.91 20 76 S5 07-07-00 <0.1 49 80 1.3 17 <0.1 <0.1 – 0.17 S6 07-07-00 <0.1 0.24 8.0 0.22 1.1 <0.1 <0.1 – <0.1 C1 07-07-00 <0.1 <0.1 0.51 0.28 0.25 <0.1 <0.1 – <0.1 C2 07-07-00 <0.1 0.11 3.8 0.25 12 <0.1 0.11 – <0.1 C3 07-07-00 <0.1 <0.1 2.2 <0.1 0.44 <0.1 <0.1 – <0.1 N1 07-07-00 <0.1 0.13 0.68 <0.1 <0.2 <0.1 <0.1 – <0.1 N2 07-07-00 <0.1 0.42 46 2.5 86 <0.1 1.61 – <0.1 N3 07-07-00 <0.1 16 410 13 130 <0.1 <0.1 – 1.2 N4 07-07-00 <0.1 0.77 13 0.72 3.4 <0.1 <0.1 – <0.1 N5 07-07-00 <0.1 0.83 13 0.35 0.24 <0.1 0.22 – <0.1 N7 07-07-00 <0.1 0.91 6.7 0.23 1.9 <0.1 0.15 – <0.1 N8 07-07-00 <0.1 0.12 7.6 0.23 3.2 <0.1 0.12 – <0.1 

Table 8. Concentrations of chlorinated volatile organic compounds in ground water at Operable Unit 1, Naval Undersea Warfare CenteWashington—Continued Well identi- fication No. Date sampled PCE (μg/L) TCE (μg/L) cisDCE 

(μg/L)

transDCE 

(μg/L) VC (μg/L) 1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) 1,1-DCE 

(μg/L)
Tables, 7, 8, 9, 10, 11, and 12 87

1

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well or 

site No. 

Date 

sampled

Data 

source 

code

Ethene compounds Specific chlorina

percentage of 

PCE (μg/L) TCE (μg/L) cisDCE (μg/L) transDCE (μg/L) VC (μg/L) Ethene (μm, or μg/L) Total (μg/L) Percentage of TCE Percen

of tra

and cis

Monitoring wells

1MW-1 07-09-91 1 <0.01 15 2,300 – 1,500 – 3,800 0 60 

01-20-92 1 <10 45 1,900 – 1,100 – 3,000 1 62 08-25-95 2 <1 <1 590 180 1,000 – 1,800 0 43 12-06-95 3 <1 <1 87 7.7 210 – 300 0 31 03-12-96 4 <0.5 0.62 450 120 710 – 1,300 0 45 06-26-96 5 <0.5 0.51 460 220 1,200 – 1,900 0 36 09-17-96 7 <3.3 <2.6 410 160 500 <1 1,100 0 53 04-16-97 7 <3.3 <2.6 450 120 1,000 <1 1,600 0 36 03-03-98 8 <0.5 <0.5 81 34 250 – 360 0 31 06-11-99 9 <3 <3 310 170 960 – 1,400 0 33 10-20-99 9 <0.5 <0.5 320 190 970 – 1,500 0 34 04-26-00 9 <0.5 <0.5 380 210 1,200 – 1,800 0 33 06-21-00 10 <0.5 0.58 240 210 1,200 8.6 1,700 0 27 07-24-00 9 <25 <25 380 210 920 – 1,500 0 39 10-31-00 9 <1 <1 270 160 1,300 – 1,700 0 25 

1MW-4 07-09-91 1 <0.01 <0.01 1.0 – 100 – 100 0 1 

01-21-92 1 <10 <10 <10 – 140 – 140 0 0 08-21-95 2 <1 <1 <1 <1 62 – 62 0 0 12-05-95 3 <1 <1 <1 <1 21 – 21 0 0 03-12-96 4 <0.5 <0.5 <0.5 <0.5 16 – 16 0 0 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface wselected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington[Data source code: 1, URS Consultants, Inc., 1993. 2, URS Consultants, Inc., 1997a; Round 1. 3, URS Consultants, Inc., 1997a; Round 2. 4, URS Consultants, Inc., 19

Inc., 1997a; Round 4. 6 , URS Consultants, Inc., 1997a; Round 5. 7, USGS, this report; 1996-97 data from Microbial Studies Group Laboratory, Columbia, SC by gas c

ionization detector. 1999-2000 data from Quanterra laboratory, EPA methods SW846 8260B, except ethene and ethane from Transglobal Env. Geo. NW, Inc., by modifi

ROD sampling Round 6; personal communication, Renee Wallis; U.S. Navy, EFA NW, Poulsbo, WA; EPA Method 8260. 9, URS Greiner, Inc., 2000. 10, CH2MHill Co

Ethene data for September 1996 and April 1997 are reported as micromoles (μM) in the headspace of the sample vial. They are suitable for comparison between wells sa

Laboratory data qualifier codes, such as “J” for estimated value and “D” for dilution, are not shown. Acroymns: PCE, tetrachloroethene; TCE, trichloroethene; cisDC

transDCE, trans-1,2-dichloroethene; VC, vinyl chloride; 1,1,1-TCA, 1,1,1-trichloroethane; CA, chloroethane; 1,1-DCE, 1,1-dichloroethene; BTEX, benzene, tolue

CVOCs, chlorinated volatile organic compounds. Abbreviations: μg/L, micrograms per liter. Symbols: <, less than; --, not analyzed or calculated; nd, none detect
88 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued 1MW-4 06-26-96 5 <0.5 <0.5 <0.5 <0.5 6.2 – 6.2 0 0 

09-17-96 7 <3.3 <2.6 54 <2 <1.4 <1 54 0 100 04-16-97 7 <3.3 <2.6 11 <2 <1.4 <1 11 0 100 

MW1-2 06-19-91 1 <0.01 83 960 – 190 – 1,200 7 78 

01-20-92 1 <10 70 1,300 – 160 – 1,500 5 85 08-28-95 2 <1 36 1,400 23 150 – 1,600 2 88 12-06-95 3 <1 35 1,300 22 140 – 1,500 2 88 03-11-96 4 <0.5 41 1,800 26 170 – 2,000 2 90 06-25-96 5 <0.5 43 1,500 31 180 – 1,800 2 87 09-17-96 7 <3.3 28 1,100 21 87 <1 1,200 2 91 04-16-97 7 <3.3 30 1,100 30 160 <1 1,300 2 86 03-02-98 8 <0.5 29 1,200 21 110 – 1,400 2 90 06-11-99 9 <3 27 980 26 160 – 1,200 2 84 10-20-99 9 <0.5 23 1,000 21 110 – 1,200 2 88 04-26-00 9 <0.5 13 1,900 49 230 – 2,200 1 89 06-21-00 10 <0.5 22 890 21 110 0.26 1,000 2 87 07-24-00 9 <25 <25 750 <25 87 – 840 0 89 10-31-00 9 <1 12 810 15 84 – 920 1 90 

MW1-3 06-20-91 1 <0.01 <0.01 <5 – <0.01 – nd – – 

01-20-92 1 <10 <10 <10 – <10 – nd – – 03-08-96 4 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-21-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-11-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 10-20-99 9 <0.5 0.70 <0.5 <0.5 <0.5 – 0.7 100 0 04-26-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-20-00 7 – – – – – 0.12 – – – 07-24-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 10-31-00 9 <1 <1 <1 <1 <1 – nd – – 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE 

(μg/L)

transDCE 

(μg/L) VC (μg/L)

Ethene 

(μm, or

μg/L)

Total 

(μg/L)

Percentage 

of TCE

Percent

of tra

and cis
Tables, 7, 8, 9, 10, 11, and 12 89

Monitoring wells—Continued

MW1-4 06-19-91 1 <0.01 5,600 1,900 – 800 – 8,300 67 23 

01-23-92 1 <10 1,300 700 – 690 – 2,700 48 26 08-23-95 2 2.2 11,000 6,400 80 2,000 – 19,000 56 33 12-05-95 3 1.7 8,600 3,900 <500 2,800 – 15,000 55 27 03-05-96 4 0.96 6,300 3,500 56 1,100 – 11,000 58 32 06-20-96 5 4.0 22,000 5,900 41 970 – 29,000 76 21 09-17-96 7 20 7,800 7,300 109 970 2.0 16,000 48 46 04-16-97 7 <3.3 3,300 1,200 24 410 <1 4,900 67 25 03-03-98 8 3.8 22,000 13,000 140 1,900 – 37,000 59 35 06-14-99 9 4.0 2,600 12,000 140 1,500 – 16,000 16 75 10-20-99 9 0.70 3,600 5,300 70 1,100 – 10,000 36 53 04-26-00 9 2.9 19,000 8,500 160 1,300 – 29,000 66 30 06-22-00 10 <250 38,000 15,000 100 1,300 12 54,000 70 28 07-24-00 9 <250 18,000 8,500 <250 860 – 27,000 65 31 11-09-00 9 <1 490 660 12 160 – 1,300 37 51 

MW1-5 06-25-91 1 <0.01 <0.01 370 – 1,762 – 2,100 0 17 

01-23-92 1 <10 23 95 – 1,500 – 1,600 1 6 08-23-95 2 <1 1.9 17 1.3 140 – 160 1 11 12-05-95 3 <1 7.3 74 16 4,300 – 4,400 0 2 03-06-96 4 <0.5 3.0 60 7.0 1,100 – 1,200 0 6 06-20-96 5 <0.5 1.7 93 6.5 1,500 – 1,600 0 6 09-17-96 7 <3.3 292 709 <2 560 2.0 1,600 19 45 04-16-97 7 <3.3 285 60 <2 140 <1 490 59 13 03-04-98 8 <0.5 1.6 8.9 7.2 1,000 – 1,000 0 2 06-14-99 9 <3 2.0 9.0 2.0 260 – 270 1 4 10-20-99 9 <0.5 <0.5 0.50 <0.5 18 – 19 0 3 04-26-00 9 <0.5 <0.5 1.2 <0.5 30 – 31 0 5 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well or 

site No. 

Date 

sampled

Data 

source 

code

Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE (μg/L) transDCE (μg/L) VC (μg/L) Ethene (μm, or μg/L) Total (μg/L) Percentage of TCE Percent

of tra

and cis
90 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued MW1-5 06-22-00 10 <0.5 1.6 1.8 0.64 22 8.6 26 6 9 

07-25-00 9 <0.5 <0.5 3.4 <0.5 31 – 34 0 10 11-06-00 9 <1 <1 <1 <1 7.0 – 7.0 0 0 

MW1-6 06-25-91 1 <0.01 <0.01 2.0 – <0.01 – 2.0 0 100 

01-23-92 1 <10 <10 <10 – <10 – nd – – 08-24-95 2 <1 <1 <1 <1 <1 – nd – – 12-12-95 3 <1 <1 <1 <1 <1 – nd – – 03-07-96 4 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-20-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-17-96 7 <3.3 150 290 <2 89 <1 530 28 55 04-16-97 7 <3.3 110 16 <2 9.4 <1 140 81 12 

MW1-14 08-28-95 2 <1 <1 <1 <1 0.53 – 0.53 0 0 

09-17-96 7 <3.3 <2.6 99 <1.9 <1.2 <1 99 0 100 04-16-97 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 

MW1-15 08-30-95 2 <1 <1 <1 <1 0.53 – 0.53 0 0 

09-16-96 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 04-16-97 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 

MW1-16 08-31-95 2 0.51 250 14,000 520 12,000 – 27,000 1 54 

06-20-96 5 1.3 34 3,100 180 2,200 – 5,500 1 59 09-17-96 7 <3.3 11 1,100 29 1,200 12 2,300 0 48 04-16-97 7 45 126 220 46 240 25 630 20 42 03-04-98 8 1.5 3,900 18,000 180 3,900 – 26,000 15 70 06-14-99 9 1.0 530 6,800 160 1,700 – 9,200 6 76 10-20-99 9 1.2 9.2 28 26 28 – 91 10 59 04-26-00 9 0.69 3.3 70 7.4 4.3 – 85 4 91 06-22-00 10 1.0 20 13 12 6.6 70 52 39 48 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE 

(μg/L)

transDCE 

(μg/L) VC (μg/L)

Ethene 

(μm, or

μg/L)

Total 

(μg/L)

Percentage 

of TCE

Percent

of tra

and cis
Tables, 7, 8, 9, 10, 11, and 12 91

Monitoring wells—Continued

MW1-16 07-25-00 9 <50 <50 <50 <50 <50 – nd – – 

11-06-00 9 <1 4.1 12 16 0.5 – 33 12 86 

MW1-17 08-29-95 2 <1 <1 6.4 0.94 6.9 – 14 0 50 

12-04-95 3 <1 <1 5.1 <1 4.3 – 9.4 0 54 03-06-96 4 <0.5 <0.5 0.32 0.29 0.47 – 1.1 0 46 06-24-96 5 <0.5 <0.5 1.4 0.51 1.2 – 3.1 0 57 09-17-96 7 <3.3 <2.6 34 <2 52 <1 86 0 40 04-16-97 7 <3.3 <2.6 16 <2 0.62 <1 16 0 90 06-22-00 10 <0.5 0.30 0.25 0.64 0.25 <0.1 1.4 21 62 

MW1-18 08-28-95 2 <1 <1 <1 <1 34 – 34 0 0 

12-05-95 3 <1 <1 <1 <1 35 – 35 0 0 03-12-96 4 <0.5 <0.5 <0.5 <0.5 66 – 66 0 0 06-26-96 5 <0.5 <0.5 <0.5 <0.5 45 – 45 0 0 09-17-96 7 <3.3 <2.6 137 <1.9 0.62 <1 140 0 99 04-16-97 7 <3.3 <2.6 47 <1.9 28 <1 75 0 63 

MW1-20 08-30-95 2 <1 <1 <1 <1 <1 – nd – – 

12-08-95 3 <1 <1 <1 <1 <1 – nd – – 03-11-96 4 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-27-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 10-20-99 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 04-26-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-21-00 7 – – – – -- <0.1 nd – – 07-25-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 10-31-00 9 <1 <1 <1 <1 <1 – nd – – 

MW1-25 08-17-95 2 <1 100 2,500 49 440 – 3,100 3 83 

12-06-95 3 <1 74 2,200 38 240 – 2,600 3 88 03-11-96 4 <0.5 11 470 6.3 52 – 540 2 88 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well or 

site No. 

Date 

sampled

Data 

source 

code

Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE (μg/L) transDCE (μg/L) VC (μg/L) Ethene (μm, or μg/L) Total (μg/L) Percentage of TCE Percent

of tra

and cis
92 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued MW1-25 06-25-96 5 <0.5 70 2,200 51 300 – 2,600 3 86 

09-17-96 7 <3.3 62 1,800 39 150 <1 2,100 3 90 04-17-97 7 <3.3 64 1,400 46 270 <1 1,800 4 81 03-04-98 8 <0.5 56 1,700 35 210 – 2,000 3 87 06-22-00 10 <0.5 39 2,000 41 260 5.8 2,300 2 87 

MW1-28 12-07-95 3 <1 2.3 1,600 61 450 – 2,100 0 79 

03-08-96 4 <0.5 1.6 1,600 94 540 – 2,200 0 76 06-25-96 5 <0.5 2.2 1,700 85 620 – 2,400 0 74 09-09-96 6 <0.5 1.2 1,400 58 480 – 1,900 0 75 09-16-96 7 <3.3 <2.6 1,165 49 220 <1 1,400 0 85 04-17-97 7 <3.3 <2.6 1,065 75 520 <1 1,700 0 69 03-04-98 8 <0.5 0.98 1,500 64 400 – 2,000 0 80 06-22-00 10 <0.5 0.81 1,300 74 520 2.6 1,900 0 73 

MW1-29 12-07-95 3 <1 <1 <1 <1 <1 – nd – – 

03-08-96 4 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-18-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-09-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-16-96 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 04-17-97 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 

MW1-31 12-11-95 3 <1 <1 <1 <1 <1 – nd – – 

03-13-96 4 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-21-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-12-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

MW1-32 03-18-96 4 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

06-18-96 5 <0.5 0.46 <0.5 <0.5 <0.5 – 0.46 100 0 09-12-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-16-96 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 04-17-97 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 03-02-98 8 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE 

(μg/L)

transDCE 

(μg/L) VC (μg/L)

Ethene 

(μm, or

μg/L)

Total 

(μg/L)

Percentage 

of TCE

Percent

of tra

and cis
Tables, 7, 8, 9, 10, 11, and 12 93

Monitoring wells—Continued

MW1-33 06-24-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

06-21-00 7 – – – – – 0.18 nd – – 

MW1-35 06-25-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

09-09-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-20-00 7 – – – – – 0.37 nd – – 

MW1-36 06-17-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

09-11-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-20-00 7 – – – – – <0.1 nd – – 

MW1-37 06-17-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

09-10-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-16-96 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 04-17-97 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 06-07-99 7 <1 <1 <1 <0.5 <2 – nd – – 06-20-00 7 – – – – – – nd – – 

MW1-38 06-19-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

09-10-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 06-20-00 7 – – – – – 0.57 nd – – 

MW1-39 06-17-96 5 <0.5 <0.5 <0.5 <0.5 0.80 – 0.80 0 0 

09-10-96 6 <0.5 <0.5 <0.5 <0.5 0.76 – 0.76 0 0 09-16-96 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 04-17-97 7 <3.3 <2.6 <1.9 <1.9 <1.2 <1 nd – – 03-03-98 8 <0.5 <0.5 0.34 <0.5 1.40 – 1.7 0 20 06-07-99 7 <1 <1 0.28 <0.5 1.20 – 1.5 0 19 06-20-00 10 <0.5 <0.5 0.40 <0.5 2.00 0.26 2.7 0 17 

MW1-41 10-20-99 9 <0.5 <0.5 0.60 <0.5 <0.5 – 0.60 0 100 

04-26-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well or 

site No. 

Date 

sampled

Data 

source 

code

Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE (μg/L) transDCE (μg/L) VC (μg/L) Ethene (μm, or μg/L) Total (μg/L) Percentage of TCE Percent

of tra

and cis
94 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued MW1-41 06-21-00 10 <0.5 <0.5 0.82 <0.5 0.53 <0.1 1.3 0 0 

07-24-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 11-02-00 9 <1 <1 <1 <1 <1 – nd – – 

Piezometers P1-1 06-09-99 7 <2 11 6.10 <1 <4 – 17 65 35 

P1-3 06-09-99 7 <16 35 450 20 120 – 620 6 75 P1-4 06-09-99 7 <130 160 4,800 56 540 – 5,600 3 87 P1-5 06-08-99 7 <13 440 400 3.5 11 – 860 51 47 P1-6 06-08-99 7 <400 74 16,000 170 5,400 – 22,000 0 75 P1-7 06-08-99 7 <670 26,000 35,000 210 3,100 – 64,000 40 55 

06-22-00 7 3.61 26,600 44,000 220 3,800 69 75,000 36 59 

P1-8 06-07-99 7 <710 190 25,000 210 3,400 – 29,000 1 88 P1-9 06-08-99 7 <2,000 48,000 88,000 470 7,200 – 140,000 33 62 

06-22-00 7 4.99 88,000 64,000 320 5,800 37 160,000 56 41 

P1-10 06-07-99 7 <1,000 14,000 34,000 270 2,500 – 51,000 28 68 

06-22-00 7 1.04 8,730 13,000 100 2,260 2.3 24,000 36 54 

Seep SP1-1 05-16-90 1 <5 <5 <5 – <5 – nd – – 

07-01-91 1 <0.01 <0.01 14 – 59 – 73 0 19 01-22-92 1 <10 <10 55 – 160 – 210 0 26 09-05-95 2 <1 <1 <1 <1 0.66 – 0.66 0 0 12-05-95 3 <1 <1 <1 <1 <1 – nd – – 03-13-96 4 <0.5 <0.5 170 1.8 420 – 590 0 29 07-02-96 5 <0.5 <0.5 7.4 0.76 31 – 39 0 21 09-10-96 6 <0.5 <0.5 0.33 <0.5 1.1 – 1.1 0 23 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE 

(μg/L)

transDCE 

(μg/L) VC (μg/L)

Ethene 

(μm, or

μg/L)

Total 

(μg/L)

Percentage 

of TCE

Percent

of tra

and cis
Tables, 7, 8, 9, 10, 11, and 12 95

Seep—Continued

SP1-1 06-11-99 9 <3 <3 4.0 <3 32 – 36 0 11 

10-20-99 9 <0.5 <0.5 0.60 <0.5 0.25 – 0.85 0 100 04-26-00 9 <0.5 1.7 32 2.5 210 – 250 1 14 07-25-00 9 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 11-09-00 9 <1 <1 <1 <1 <1 – nd – – 

Surface-water sites in downstream order

MA01 06-10-91 1 <5 5.0 39 – 22 – 66 8 59 

08-21-91 1 <5 <5 4.0 – <10 – 4.0 0 100 01-14-92 1 <10 <10 10 – 3.0 – 13 0 77 

MA09 09-05-95 2 <1 <1 4.0 <1 1.3 – 5.3 0 75 

12-05-95 3 <1 <1 14 <1 5.4 – 19 0 72 03-14-96 4 <0.5 1.2 11 <0.5 8.0 – 20 6 55 07-02-96 5 <0.5 <0.5 0.79 <0.5 <0.5 – 0.79 0 100 03-03-98 8 <0.5 <0.5 1.5 <0.5 0.30 – 1.8 0 83 06-01-00 10 <0.5 0.63 3.0 <0.5 0.64 – 4.3 15 70 

MA10 09-06-95 2 <1 <1 1.9 <1 0.64 – 2.5 0 76 

12-06-95 3 <1 2.5 36 <1 17 – 56 4 65 03-13-96 4 <0.5 3.2 30 0.36 15 – 49 7 63 07-02-96 5 <0.5 0.49 6.3 <0.5 1.2 – 7.5 6 79 

MA11 09-06-95 2 <1 <1 0.51 <1 <1 – 0.51 0 100 

12-06-95 3 <1 <1 10 <1 3.5 – 14 3 74 03-13-96 4 <0.5 1.6 13 <0.5 5.9 – 21 8 64 07-02-96 5 <0.5 <0.5 0.52 <0.5 <0.5 – 0.52 0 100 06-01-00 10 <0.5 7.9 33 0.56 9.2 – 51 16 66 

MA12 03-14-96 4 <0.5 26 180 1.6 <0.5 – 210 13 87 

07-01-96 5 <0.5 64 480 3.5 <0.5 – 550 12 88 03-04-98 8 <0.5 45 200 1.6 49 – 300 15 68 06-11-99 7 <3 130 710 8.0 150 – 1,000 13 72 10-20-99 9 <0.5 110 600 5.5 130 – 850 13 72 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well or 

site No. 

Date 

sampled

Data 

source 

code

Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE (μg/L) transDCE (μg/L) VC (μg/L) Ethene (μm, or μg/L) Total (μg/L) Percentage of TCE Percent

of tra

and cis
96 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Surface-water sites in downstream order—Continued MA12 04-26-00 9 <0.5 190 630 10 250 – 1,100 18 59 

06-01-00 10 <0.5 110 670 5.5 140 – 930 12 73 07-25-00 9 <25 180 750 <25 140 – 1,100 17 70 11-09-00 9 <1 170 680 4.6 140 – 1,000 17 69 

TF16 06-11-91 1 <5 <5 <5 – <10 – nd – – 

08-21-91 1 <5 <5 <5 – <10 – nd – – 01-14-92 1 <5 <5 3.0 – <10 – 3.0 – – 

TF19 09-05-95 2 <1 <1 4.0 <1 0.92 – 4.9 0 80 

12-04-95 3 <1 <1 8.7 <1 3.1 – 12 0 74 03-12-96 4 <0.5 1.3 19 0.26 19 – 40 3 49 07-01-96 5 <0.5 0.70 5.9 <0.5 2.4 – 9.0 8 65 09-10-96 6 <0.5 <0.5 1.4 <0.5 <0.5 – 1.4 0 100 03-03-98 8 <0.5 2.6 16 0.31 6.1 – 25 10 65 06-01-00 10 <0.5 2.3 12 0.20 3.1 – 18 13 69 

DB14 09-05-95 2 <1 <1 <1 <1 <1 – nd – – 

12-04-95 3 <1 <1 1.9 <1 <1 – 1.9 – – 03-13-96 4 <0.5 <0.5 0.35 <0.5 <0.5 – nd – – 07-01-96 5 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 09-10-96 6 <0.5 <0.5 <0.5 <0.5 <0.5 – nd – – 03-03-98 8 <0.5 <0.5 1.50 <0.5 0.58 – 2.1 – – 06-01-00 10 <0.5 <0.5 0.59 <0.5 <0.5 – 0.59 – – 

Table 9. Cumulative summary of concentrations of chlorinated ethenes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethene compounds Specific chlorinate

percentage of to

PCE (μg/L) TCE (μg/L) cisDCE 

(μg/L)

transDCE 

(μg/L) VC (μg/L)

Ethene 

(μm, or

μg/L)

Total 

(μg/L)

Percentage 

of TCE

Percent

of tra

and cis
Tables 7, 8, 9, 10, 11, and 12 97

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface wa

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well

or site No. 

Date 

sampled

Data 

source 

code

Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes an

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane (μg/L) 1,1-DCE (μg/L) Total (μg/L) Percentage TCA Percentage DCA 

Monitoring wells

1MW-1 07-09-91 1 <5 20 11 – 13 44 5 43 

01-20-92 1 <10 18 9.0 – 14 41 11 39 08-25-95 2 <1 14 <1 – 5.1 19 2 70 12-06-95 3 <1 1.0 2.2 – <1 3.2 12 24 03-12-96 4 <0.5 8.5 <0.5 – 2.6 11 2 73 06-26-96 5 <0.5 15 0.50 – 3.2 19 1 79 09-17-96 7 – – – – <2 – – – 04-16-97 7 – – – – 7.8 7.8 0 0 03-03-98 8 <0.5 4.5 1.3 – 0.40 6.2 4 70 06-11-99 9 1.5 19 9.0 – 4.0 34 4 57 10-20-99 9 <3 17 – – 2.9 20 0 85 04-26-00 9 <0.5 18 6.9 – 3.1 28 1 64 06-21-00 10 <0.5 13 5.8 19 1.7 39 1 63 07-24-00 9 <0.5 <25 – – <25 nd – – 10-31-00 9 <1 <1 – – 2.0 2.0 0 0 

1MW-4 07-09-91 1 <5 <5 <10 – <5 nd – – 

01-21-92 1 <10 <10 <10 – <10 nd – – 08-21-95 2 <1 <1 <1 – <1 nd – – 12-05-95 3 <1 <1 <1 – <1 nd – – 03-12-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface wa

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

[Data source code: 1, URS Consultants, Inc., 1993. 2, URS Consultants, Inc., 1997a; Round 1. 3, URS Consultants, Inc., 1997a; Round 2. 4, URS Consultants, Inc., 1997a

Inc., 1997a; Round 4. 6 , URS Consultants, Inc., 1997a; Round 5. 7, USGS, this report; 1996-97 data from Microbial Studies Group Laboratory, Columbia, SC by gas chroionization detector. 1999-2000 data from Quanterra laboratory, EPA methods SW846 8260B, except ethene and ethane from Transglobal Env. Geo. NW, Inc., by modified 

ROD sampling Round 6; personal communication, Renee Wallis; U.S. Navy, EFA NW, Poulsbo, WA; EPA Method 8260. 9, URS Greiner, Inc., 2000. 10, CH2MHill ConsEthene data for September 1996 and April 1997 are reported as micromoles (μM) in the headspace of the sample vial. They are suitable for comparison between wells sampLaboratory data qualifier codes, such as “J” for estimated value and “D” for dilution, are not shown. Acroymns: 1,1-DCE, 1,1-dichloroethene; 1,1,1-TCA, 1,1,1-trichlor

1,1-dichloroethane; CA, chloroethane; Abbreviations: μg/L, micrograms per liter. Symbols: <, less than; –, not analyzed or calculated; nd, none detected at unspecif
98 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued 1MW-4 06-26-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

09-17-96 7 – – – – <1.9 – – – 04-16-97 7 – – – – <1.9 – – – 

MW1-2 06-19-91 1 <5 <5 1.0 – 2.0 3.0 0 0 

01-20-92 1 <10 <10 <10 – 4.0 4.0 0 0 08-28-95 2 <1 <1 <1 – 4.2 4.2 0 0 12-06-95 3 <1 <1 <1 – 3.5 3.5 0 0 03-11-96 4 <0.5 <0.5 <0.5 – 4.8 4.8 0 0 06-25-96 5 <0.5 0.23 <0.5 – 5.1 5.3 0 4 09-17-96 7 – – – – <1.9 – – – 04-16-97 7 – – – – 7.8 – – – 03-02-98 8 <0.5 <0.5 <0.5 – 3.4 3.4 0 0 06-11-99 9 <3 <3 <3 – 5.0 5.0 0 0 10-20-99 9 <0.5 <0.5 – – 3.4 3.4 0 0 04-26-00 9 <0.5 <0.5 <0.5 – 6.0 6.0 0 0 06-21-00 10 <0.5 0.30 0.30 0.24 3.2 4.0 0 8 07-24-00 9 <25 <25 – – <25 nd – – 10-31-00 9 <1 <1 – – 2.2 2.2 0 0 

MW1-3 06-20-91 1 <0.01 <5 <10 – <5 nd – – 

01-20-92 1 <10 <10 <10 – <10 nd – – 03-08-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 06-21-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-11-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 10-20-99 9 <0.5 <0.5 – – <0.5 nd – – 04-26-00 9 <0.5 <0.5 <0.5 – <0.5 nd – – 06-20-00 7 – – – 0.19 – 0.19 – – 07-24-00 9 <0.5 <0.5 – – <0.5 nd – – 10-31-00 9 <1 <1 – – <1 nd – – 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane 

(μg/L)

1,1-DCE 

(μg/L) Total (μg/L) Percentage TCA Percentage DCA 
Tables 7, 8, 9, 10, 11, and 12 99

Monitoring wells—Continued

MW1-4 06-19-91 1 <5 1.0 2.0 – 5.0 8.0 24 10 

01-23-92 1 <10 <10 <10 – <10 nd – – 08-23-95 2 <1 <1 <1 – 7.7 7.7 0 0 12-05-95 3 <1 <1 <1 – 5.2 5.2 0 0 03-05-96 4 <0.5 0.67 <0.5 – 5.6 5.6 0 7 06-20-96 5 <0.5 0.64 <0.5 – 13 14 0 5 09-17-96 7 – – – – 27 – – – 04-16-97 7 – – – – <2 – – – 03-03-98 8 <0.5 <0.5 <0.5 – 16 16 0 1 06-14-99 9 <3 2.0 2.0 – 24 28 0 7 

– 10-20-99 9 <0.5 0.80 – – 10 11 0 7 

04-26-00 9 <0.5 16 0.84 – 16 33 0 48 06-22-00 10 <250 <250 <250 4.1 <250 4.1 – – 07-24-00 9 <250 <250 – – <250 nd – – 11-09-00 9 <1 <1 – – 0.9 0.9 0 0 

MW1-5 06-25-91 1 <5 13 9.0 – <5 22 0 59 

01-23-92 1 <10 30 8.0 – <10 38 0 79 08-23-95 2 <1 5.8 2.8 – <1 8.6 0 67 12-05-95 3 <1 110 <1 – <1 110 0 100 03-06-96 4 <0.5 34 <0.5 – <0.5 34 0 100 06-20-96 5 <0.5 29 <0.5 – <0.5 29 0 100 09-17-96 7 – – – – <2 – – – 04-16-97 7 – – – – <2 – – – 03-04-98 8 <0.5 67 2.8 – <0.5 70 0 96 06-14-99 9 <3 9.0 18 – <3 27 0 33 10-20-99 9 <0.5 9.6 – – <0.5 10 0 100 04-26-00 9 >0.5 1.1 11 – >0.5 12 0 10 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well

or site No. 

Date 

sampled

Data 

source 

code

Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane (μg/L) 1,1-DCE (μg/L) Total (μg/L) Percentage TCA Percentage DCA 
100 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued MW1-5 06-22-00 10 <0.5 6.9 9.3 3.6 <0.5 20 0 34 

07-25-00 9 <0.5 1.8 – – <0.5 1.8 0 100 11-06-00 9 <1 1.7 – – <1 1.7 0 100 

MW1-6 06-25-91 1 <0.01 <5 12 – <5 12 0 0 

01-23-92 1 <10 <10 12 – <10 12 0 0 08-24-95 2 <1 <1 6.7 – <1 6.7 0 0 12-12-95 3 <1 <1 4.4 – <1 4.4 0 0 03-07-96 4 <0.5 <0.5 4.1 – <0.5 4.1 0 0 06-20-96 5 <0.5 <0.5 6.9 – <0.5 6.9 0 0 09-17-96 7 – – – – <2 – – – 04-16-97 7 – – – – <2 – – – 

– MW1-14 08-28-95 2 <1 <1 <1 – <1 nd – – 

09-17-96 7 – – – – <1.9 – – – 04-16-97 7 – – – – <1.9 – – – 

MW1-15 08-30-95 2 <1 <1 <1 – <1 nd – – 

09-16-96 7 – – – – <1.9 – – – 04-16-97 7 – – – – <1.9 – – – 

MW1-16 08-31-95 2 5,600 12,000 44 – 680 18,000 31 65 

06-20-96 5 430 30,000 1,900 – 180 33,000 1 92 09-17-96 7 – – – – 99 – – – 04-16-97 7 – – – – 72 – – – 03-04-98 8 840 24,000 3,800 – 110 29,000 3 83 06-14-99 9 140 15,000 3,900 – 48 19,000 1 79 10-20-99 9 23 6,500 – – 5.0 6,500 0 100 04-26-00 9 16 1,700 430 – <0.5 2,100 1 79 06-22-00 10 29 2,500 590 6.6 2.0 3,100 1 80 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well

or site No. 

Date 

sampled

Data 

source 

code

Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes an

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane 

(μg/L)

1,1-DCE 

(μg/L) Total (μg/L) Percentage TCA Percentage DCA 
Tables 7, 8, 9, 10, 11, and 12 101

Monitoring wells—Continued

MW1-16 07-25-00 9 25 2,300 – – <50 2,300 1 98 

11-06-00 9 21 3,900 – – <1 3,900 1 99 

MW1-17 08-29-95 2 <1 <1 0.86 – <1 0.86 0 0 

12-04-95 3 <1 <1 2.2 – <1 2.2 0 0 03-06-96 4 <0.5 <0.5 2.5 – <0.5 2.5 0 0 06-24-96 5 <0.5 <0.5 3.3 – <0.5 3.3 0 0 09-17-96 7 – – – – <1.9 – – – 

– 04-16-97 7 – -- – – <1.9 – – – 

06-22-00 10 <0.5 0.10 1.3 17 <0.5 18 0 0 

MW1-18 08-28-95 2 <1 <1 <1 – <1 nd – – 

12-05-95 3 <1 <1 <1 – <1 nd – – 03-12-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 06-26-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-17-96 7 – – – – <1.9 – – – 04-16-97 7 – – – – <1.9 – – – 

– MW1-20 08-30-95 2 <1 <1 <1 – <1 nd – – 

12-08-95 3 <1 <1 <1 – <1 nd – – 03-11-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 06-27-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 10-20-99 9 <0.5 <0.5 – – <0.5 nd – – 04-26-00 9 <0.5 <0.5 <0.5 – <0.5 nd – – 06-21-00 7 – – – <0.1 – nd – – 07-25-00 9 <0.5 <0.5 – – <0.5 nd – – 10-31-00 9 <1 <1 – – <1 nd – – 

MW1-25 08-17-95 2 <1 4.8 <1 – 7.3 12 0 40 

12-06-95 3 <1 3.9 <1 – 6.1 10 0 39 03-11-96 4 <0.5 1.1 <0.5 -- 0.98 2.1 0 53 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well

or site No. 

Date 

sampled

Data 

source 

code

Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane (μg/L) 1,1-DCE (μg/L) Total (μg/L) Percentage TCA Percentage DCA 
102 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued MW1-25 06-25-96 5 <0.5 4.7 <0.5 – 7.5 12 0 37 

09-17-96 7 – – – – <1.9 – – – 04-17-97 7 – – – – <1.9 – – – 03-04-98 8 <0.5 2.4 <0.5 – 5.3 7.7 0 34 06-22-00 10 <0.5 6.9 2.3 1.6 7.2 18 0 38 

MW1-28 12-07-95 3 <1 1.1 <1 – 5.1 6.2 0 16 

03-08-96 4 <0.5 2.1 <0.5 – 5.0 7.1 0 29 06-25-96 5 <0.5 2.4 <0.5 – 6.3 8.7 0 28 09-09-96 6 <0.5 2.3 <0.5 – 5.4 7.7 0 29 09-16-96 7 – – – – <1.9 – – – 04-17-97 7 – – – – <1.9 – – – 03-04-98 8 <0.5 1.3 <0.5 – 4.3 5.6 0 23 06-22-00 10 <0.5 3.2 0.97 0.67 5.1 10 0 32 

MW1-29 12-07-95 3 <1 <1 <1 – <1 nd – – 

03-08-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 06-18-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-09-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 09-16-96 7 – – – – <1.9 – – – 04-17-97 7 – – – – <1.9 – – – 

MW1-31 12-11-95 3 <1 <1 <1 – <1 nd – – 

03-13-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 06-21-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-12-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 

MW1-32 03-18-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 

06-18-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-12-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 09-16-96 7 – – – – <1.9 – – – 04-17-97 7 – – – – <1.9 – – – 03-02-98 8 <0.5 <0.5 <0.5 – <0.5 nd – – 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane 

(μg/L)

1,1-DCE 

(μg/L) Total (μg/L) Percentage TCA Percentage DCA 
Tables 7, 8, 9, 10, 11, and 12 103

Monitoring wells—Continued

MW1-33 06-24-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

06-21-00 7 – – – 11 – 11 – – 

MW1-35 06-25-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

09-09-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 06-20-00 7 – – – <0.1 – nd – – 

MW1-36 06-17-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

09-11-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 06-20-00 7 – – – <0.1 – nd – – 

MW1-37 06-17-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

09-10-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 09-16-96 7 – – – – <1.9 – – – 04-17-97 7 – – – – <1.9 – – – 06-07-99 7 <1 <1 <2 – <1 nd – – 06-20-00 7 – – – – – – – – 

MW1-38 06-19-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

09-10-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 06-20-00 7 – – – 1.7 – – – – 

MW1-39 06-17-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 

09-10-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 09-16-96 7 – – – – <1.9 – – – 04-17-97 7 – – – – <1.9 – – – 03-03-98 8 <0.5 <0.5 <0.5 – <0.5 nd – – 06-07-99 7 <1 <1 <2 – <1 nd – – 06-20-00 10 <0.5 <0.5 <0.5 <0.1 <0.5 nd – – 

MW1-41 10-20-99 9 <0.5 <0.5 – – <0.5 nd – – 

04-26-00 9 <0.5 <0.5 1.8 – <0.5 1.8 0 0 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well

or site No. 

Date 

sampled

Data 

source 

code

Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane (μg/L) 1,1-DCE (μg/L) Total (μg/L) Percentage TCA Percentage DCA 
104 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Monitoring wells—Continued MW1-41 06-21-00 10 <0.5 0.20 1.9 1.4 <0.5 3.5 0 6 

07-24-00 9 <0.5 <0.5 – – <0.5 nd – – 11-02-00 9 <1 <1 – – <1 nd – – 

Piezometers P1-1 06-09-99 7 <2 0.24 <4 – <2 0.2 0 100 

P1-3 06-09-99 7 <16 <16 3.6 – <16 3.6 0 100 P1-4 06-09-99 7 <130 <130 <270 – <130 nd – – P1-5 06-08-99 7 <13 <13 15 – <13 15 0 0 P1-6 06-08-99 7 <400 1,500 300 – <400 1,800 0 83 P1-7 06-08-99 7 <670 <670 <1,300 – <670 nd – – 

06-22-00 7 0.24 17 8.4 11 72 110 0 16 

P1-8 06-07-99 7 <710 <710 <1,400 – <710 nd – – P1-9 06-08-99 7 <2,000 <2,000 <4,000 – <2,000 nd – – 

06-22-00 7 <10 2.6 <20 <1.0 47 49 0 4 

P1-10 06-07-99 7 <1,000 <1,000 <2,000 – <1,000 nd – – 

06-22-00 7 <0.1 1.2 0.13 0.42 16 17 0 7 

Seep SP1-1 05-16-90 1 <5 <5 <10 – <5 nd – – 

07-01-91 1 <5 <5 3.0 – <5 3.0 – – 01-22-92 1 <10 <10 <10 – <10 nd – – 09-05-95 2 <1 <1 1.3 – <1 1.3 – – 12-05-95 3 <1 <1 <1 – <1 nd – – 03-13-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 07-02-96 5 <0.5 <0.5 0.20 – <0.5 nd – – 09-10-96 6 <0.5 <0.5 1.8 – <0.5 1.8 – – 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane 

(μg/L)

1,1-DCE 

(μg/L) Total (μg/L) Percentage TCA Percentage DCA 
Tables 7, 8, 9, 10, 11, and 12 105

Seep—Continued

SP1-1 06-11-99 9 <3 <3 2.0 – <3 2.0 – – 

10-20-99 9 <0.5 <0.5 – – <0.5 nd – – 04-26-00 9 <0.5 <0.5 2.1 – <0.5 2.1 – – 07-25-00 9 <0.5 <0.5 – – <0.5 nd – – 

11-09/00 9 <1 <1 – – <1 nd – – 

Surface-water sites in downstream order

MA01 06-10-91 1 <5 1.0 <10 – <5 nd – – 

08-21-91 1 <5 <5 <10 – <5 nd – – 01-14-92 1 <10 <10 <10 – <10 nd – – 

MA09 09-05-95 2 <1 <1 <1 – <1 nd – – 

12-05-95 3 <1 <1 <1 – <1 nd – – 03-14-96 4 <0.5 0.29 <0.5 – <0.5 0.29 – – 07-02-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 03-03-98 8 <0.5 <0.5 <0.5 – <0.5 nd – – 06-01-00 10 <0.5 <0.5 <0.5 – <0.5 nd – – 

MA10 09-06-95 2 <1 <1 <1 – <1 nd – – 

12-06-95 3 <1 1.2 <1 – <1 1.2 – – 03-13-96 4 <0.5 0.93 <0.5 – <0.5 0.93 – – 07-02-96 5 <0.5 0.23 <0.5 – <0.5 0.23 – – 

MA11 09-06-95 2 <1 <1 <1 – <1 nd – – 

12-06-95 3 <1 <1 <1 – <1 nd – – 03-13-96 4 <0.5 0.43 <0.5 – <0.5 0.44 – – 07-02-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 06-01-00 10 <0.5 1.2 <0.5 – <0.5 1.2 – – 

MA12 03-14-96 4 <0.5 <5 0.52 – 0.56 1.1 – – 

07-01-96 5 <0.5 11 0.54 – 1.0 13 – – 03-04-98 8 <0.5 3.9 <0.5 – <0.5 3.9 – – 06-11-99 7 <3 15 3.0 – 2.0 20 – – 10-20-99 9 <0.5 12 – – 1.9 14 – – 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Well

or site No. 

Date 

sampled

Data 

source 

code

Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane (μg/L) 1,1-DCE (μg/L) Total (μg/L) Percentage TCA Percentage DCA 
106 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Surface-water sites in downstream order—Continued MA12 04-26-00 9 <0.5 21 5.0 – 1.3 27 – – 

06-01-00 10 <0.5 16 7.3 – <0.5 23 – – 07-25-00 9 <25 <25 – – <25 nd – – 11-09-00 9 <1 14 – – 1.2 15 – – 

TF16 06-11-91 1 <5 <5 <10 – <5 nd – – 

08-21-91 1 <5 <5 <10 – <5 nd – – 01-14-92 1 <5 <5 <10 – <5 nd – – 

TF19 09-05-95 2 <1 <1 <1 – <1 nd – – 

12-04-95 3 <1 <1 <1 – <1 nd – – 03-12-96 4 <0.5 0.43 <0.5 – <0.5 0.43 – – 07-01-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-10-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 03-03-98 8 <0.5 <0.5 <0.5 – <0.5 nd – – 06-01-00 10 <0.5 0.40 <0.5 – <0.5 0.40 – – 

DB14 09-05-95 2 <1 <1 <1 – <1 nd – – 

12-04-95 3 <1 <1 <1 – <1 nd – – 03-13-96 4 <0.5 <0.5 <0.5 – <0.5 nd – – 07-01-96 5 <0.5 <0.5 <0.5 – <0.5 nd – – 09-10-96 6 <0.5 <0.5 <0.5 – <0.5 nd – – 03-03-98 8 <0.5 <0.5 <0.5 – <0.5 nd – – 06-01-00 10 <0.5 <0.5 <0.5 – <0.5 nd – – 

Table 10. Cumulative summary of concentrations of chlorinated ethanes and other volatile organic compounds in ground and surface w

selected sites at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued Well or site No. Date sampled Data source code Ethane compounds and 1,1-DCE Specific chlorinated ethane and 

total ethanes a

1,1,1-TCA 

(μg/L)

1,1-DCA 

(μg/L) CA (μg/L) Ethane 

(μg/L)

1,1-DCE 

(μg/L) Total (μg/L) Percentage TCA Percentage DCA 
Tables 7, 8, 9, 10, 11, and 12 107

Table 11. Data used to calculate degradation rates of chlorinated ethene mass and discharge to surface water at Operable Unit 1, Naval Division Keyport, Washington[Transect length and ground-wate flux: Cross-section length and ground-water flux estimates from Table 3-11, URS Inc., 1997a. Average chlorinated ethene concent

from table 8, this report; VC, vinyl chloride; ft, feet; gal/min, gallons per minute; μg/L, micrograms per liter; g/d, grams per day;–, not applicable]

Sub-transect 

name

Ground-water sample 

sites in transects

Transect 

length (ft)

Groundwater flux 

(gal/min)

Average chlorinated ethene concentration Chlorinated ethene 

TCE (μg/L) cisDCE (μg/L) VC (μg/L) TCE (g/d) cisDC

1 – Landfill

North MW1-18 275 0.1 0.50 46 28 0.0003 0.0North-central MW1-2, P1-3, P1-4 315 1.2 72. 2,000 260 0.5 13 Central MW1-17 300 0.4 0.30 0.25 0.25 0.001 0.0South-central MW1-6 250 0.3 110 16 9.4 0.2 0.0South P1-6, P1-7, MW1-4 225 0.2 22,000 25,000 3,500 23 27 

Subtotals 1,365 2.2 – – – 24 41 

2 – Marsh

North N1 275 0.1 0.13 0.68 0.1 0.00007 0.0North-central N2, N3, N4, N5, N7, N8 315 1.2 3.2 82 38 0.02 0.5 Central C1, C2 300 0.4 0.06 4.1 6.1 0.0001 0.0South-central C3 250 0.3 0.05 2.2 0.44 0.0001 0.0South S1, S2, S3, S4, S5, S6 225 0.2 16 3,200 980 0.02 3.5 

Subtotals 1,365 2.2 – – – 0.04 4.0 

3 – Intermediate aquifer

North1 1MW-1 160 0.3 1.3 11 0.72 0.002 0.0North-central2 1MW-4, MW1-25 110 0.1 20. 1,000 130 0.01 0.5South-central3 MW1-25 185 0.8 39 2,000 260 0.2 9.2 South4 MW1-28 130 0.3 0.81 1,300 520 0.001 2.0 

Subtotals 585 1.5 – – – 0.2 12 

TOTALS – – – – – – – 

1North intermediate aquifer CVOC flux comes from northern part of the landfill.2North-central intermediate aquifer CVOC flux comes from northern part of the landfill (0.6 percent) and the northcentral part (99.4 percent).3South-central intermediate aquifer CVOC flux comes from north-central part of the landfill (50 percent) and southern part (50 percent).4South intermediate aquifer CVOC flux comes from north-central part of the landfill (50 percent) and southern part (50 percent).
108 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Table 12. Data used to calculate first-order attenuation half-lives of chlorinated ethene for segments of selected flowpaths at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

[TCE, trichloroethene; cisDCE, cis-1,2-dichloroethene; VC, vinyl chloride; CVOC, chlorinated volatile organic compound; ft, feet; μg/L, micrograms per 

liter; ft/d, feet per day]

Flowpath and segment Upgradient sample sites

Upgradient CVOC concentration CO

TCE (μg/L) cisDCE (μg/L) VC (μg/L)

Upper aquifer

North landfill to marsh

Flowpath A, segment 2 MW1-2 27 980 160

Flowpath B, segment 2 P1-4 160 4,800 540

Flowpath B, segment 3 1MW-1 0.001 310 960

Average flowpath, segment 2 MW1-2, P1-3, P1-4, 1MW-1 51 1,500 440

Marsh to Highway 308

Flowpath A, segment 3 N3 16 410 130

Average flowpath, segment 3 N2, N3, N4, N5, N7, N8 4.5 82 38

South landfill to marsh

Flowpath C, segment 2 P1-8 190 25,000 3,400

Flowpath C, segment 3 MW1-16 530 6,800 1,700

Flowpath C, segment 4 MW1-5 2 9 260

Flowpath D, segment 2 P1-9 48,000 88,000 7,200

Flowpath D, segment 3 P1-7 26,000 35,000 3,100

Flowpath E, segment 2 P1-10 14,000 34,000 3,100

Flowpath E, segment 3 MW1-4 2,600 12,000 1,500

Intermediate aquifer

Upper aquifer to intermediate aquifer 

Flowpath F, segment 1 MW1-16, 1MW-1 265 3,600 1,300

Intermediate aquifer to Highway 308

Flowpath F, segment 2 MW1-25, MW1-28 20 1,600 390
Tables 7, 8, 9, 10, 11, and 12 109

Table 12. Data used to calculate first-order attenuation half-lives of chlorinated ethene for segments of selected flowpaths at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Flowpath and segment Upgradient sample sites

Downgradient CVOC concentration CX

TCE (μg/L) cisDCE (μg/L) VC (μg/L)

Upper aquifer

North landfill to marsh

Flowpath A, segment 2 N3 16 410 130

Flowpath B, segment 2 1MW-1 0.58 240 1,200

Flowpath B, segment 3 N7 9 6.7 1.9

Average flowpath, segment 2 N2, N3, N4, N5, N7, N8 4.5 82 38

Marsh to Highway 308

Flowpath A, segment 3 MW1-39 0.001 0.28 1.2

Average flowpath, segment 3 MW1-39 0.001 0.28 1.2

South landfill to marsh

Flowpath C, segment 2 MW1-16 530 6,800 1,700

Flowpath C, segment 3 MW1-5 2 9 260

Flowpath C, segment 4 S2 0.60 11 2.8

Flowpath D, segment 2 P1-7 26,000 35,000 3,100

Flowpath D, segment 3 S4 45 19,000 5,600

Flowpath E, segment 2 MW1-4 2,600 12,000 1,500

Flowpath E, segment 3 S5 49 80 17

Intermediate aquifer

Upper to intermediate

Flowpath F, segment 1 MW1-25, MW1-28 20 1,600 390

Intermediate to Highway 308

Flowpath F, segment 2 MW1-37 0.001 0.001 0.001
110 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

Table 12. Data used to calculate first-order attenuation half-lives of chlorinated ethene for segments of selected flowpaths at 

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington—Continued

Flowpath and segment

Downgradient 

distance x 

(ft)

Groundwater flow 

rate (ft/d)

Travel time 

t (days)

First-order attenuation half-life T1/2

TCE (years) cisDCE 

(years) VC (years)

Upper aquifer

North landfill to marsh

Flowpath A, segment 2 45 0.34 132 0.5 0.3 1.3 – 0.1

Flowpath B, segment 2 65 0.34 191 0.1 0.1 -0.5 – 0.3

Flowpath B, segment 3 170 0.34 500 -0.1 0.2 0.2

Average flowpath, segment 2 127 0.34 374 0.3 0.2 0.3 – 0.2

Marsh to Highway 308

Flowpath A, segment 3 560 0.04 13,659 2.7 3.6 – 3.5 5.5 – 4.2

Average flowpath, segment 3 481 0.04 11,732 2.6 3.9 6.5 – 4.8

South landfill to marsh

Flowpath C, segment 2 45 0.10 474 -0.9 0.7 1.3 – 0.4

Flowpath C, segment 3 150 0.15 1,000 0.3 0.3 1 – 0.5

Flowpath C, segment 4 35 0.15 233 0.4 -2.5 – -13 0.1

Flowpath D, segment 2 70 0.15 467 1.4 1 – 0.8 1.1 – 0.3

Flowpath D, segment 2 70 0.15 467 0.1 1.5 – 0.8 -1.5 – 0.7

Flowpath E, segment 2 85 0.10 895 1.0 1.6 – 1.3 3.3 – 0.6

Flowpath E, segment 3 150 0.15 1,000 0.5 0.4 0.4 – 0.3

Intermediate aquifer

Upper to intermediate

Flowpath F, segment 1 450 0.2 2,250 1.7 5.6 – 5.1 3.5 – 2

Intermediate to Highway 308

Flowpath F, segment 2 550 0.03 20,370 3.9 2.7 3.0 – 2.7
Appendix A. Quality Assurance and Control of U.S. Geological Survey Geochemical Sampling 111

APPENDIX A. QUALITY ASSURANCE AND CONTROL OF 

U.S. GEOLOGICAL SURVEY GEOCHEMICAL SAMPLING
112 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington

APPENDIX A. QUALITY ASSURANCE AND 

CONTROL OF U.S. GEOLOGICAL SURVEY 

GEOCHEMICAL SAMPLING

Quality assurance and control of geochemical 

sampling included collecting duplicate samples for 

redox-sensitive analytes and VOCs and analyzing field 

blank samples for VOCs. Duplicates were collected for 

various redox-sensitive analytes during all sampling 

events, and were collected for VOCs only during the 

four events when numerous VOC samples were 

collected. A field blank collected during June 1999 was 

collected by pumping VOC-free water through 

previously used and cleaned tubing. Those results 

represent possible sampling contamination in samples 

collected at known contaminated wells only; new 

tubing was used to sample from wells that were known 

to be uncontaminated or slightly contaminated and 

from piezometers sampled for the first time. A 

diffusion sampler field blank was collected from an 

extra passive diffusion sampler that was carried along 

in the backpack with other samplers during the entire 

day of sampler installation. All diffusion samplers 

including the field blank were filled with deionized, 

rather than VOC-free water. Those blank results 

represent possible sampling contamination in diffusion 

samples that could result from many sources during the 

course of sampler installation, such as the ambient 

environment, or from VOCs present in the deionized 

water. Selected laboratory quality assurance and 

control data, including the method blank results for 

methane, ethene, and ethane analyses done by 

Transglobal Environmental Geosciences Northwest, 

Inc., in Lacey, Wash., are provided in table A1. The 

complete data set is on file in the USGS office in 

Tacoma, Wash. 

Duplicate sample results compared favorably for 

all constituents (table A1). The relatively high variation 

in duplicate sulfide analyses from October 1998 and 

June 1999 was attributed to a delay in adding reagents 

to the samples after filling the sample vials; sulfide 

concentrations can change substantially in just a few 

minutes once anaerobic ground water is exposed to the 

atmosphere. Dissolved H2 concentrations in samples 

from some wells during some sampling events changed 

upward and downward and failed to stabilize around a 

single value, even after repeated sampling and analysis 

for more than 3 hours. Repeated H2 analyses for a 

given sample were consistent, so analytical errors were 

not the cause of the variation. The variation may reflect 

the likely heterogeneity of redox conditions beneath the 

landfill. As more water was pumped during extended 

sampling, ground water with different H2

concentrations and redox conditions from slightly 

different zones in the aquifer may have been sampled. 

Variability in H2 and sulfide analyses adds some 

uncertainty to the determination of redox conditions for 

a given well at a specific time. However, that 

uncertainty was reduced by considering multiple 

redox-sensitive constituents in determining redox 

conditions, and by sampling redox constituents 

multiple times at most wells.

Trace amounts of chlorinated ethenes and BTEX 

compounds were detected in the field blank sample of 

pumped VOC-free water (MW1-14FB). As previously 

mentioned, this blank was collected by pumping 

VOC-free water through previously used and cleaned 

tubing, so those results represent possible sampling 

contamination only in samples collected at known 

contaminated wells. A trace amount of cisDCE 

detected in the diffusion sampler field blank (S-1FB) 

could have come from the deionized water used in the 

sampler, or it could have diffused into the sampler from 

the ambient air above the marsh. Finally, a trace 

amount of methane was detected in the June 2000 

method blank, indicating low-level contamination at 

the laboratory.
Appendix A. Quality Assurance and Control of U.S. Geological Survey Geochemical Sampling 113

Table A1. Quality assurance and control data collected by the U.S. Geological Survey at Operable Unit 1, Naval Undersea Warfare CenWashington[Laboratory data qualifier codes, such as “J” for estimated value and “D” for dilution, are not shown. Well identification No.: D denotes duplicate sample; FB denotes fiMultiple dissolved H2 samples were analyzed at all wells. The duplicate data shown are the lowest and highest concentrations measured at wells where consecutive concconsistent value. Ethene: Ethene data for September 1996 and April 1997 are reported as micromoles (μM) in the headspace of the sample vial. They are suitable for comduring the same times only. nM, nanomolar; mg/L, milligrams per liter; μg/L, micrograms per liter; μM, micromolar; PCE, tetrachloroethene; TCE, trichloroethene; cisDtransDCE, trans-1,2-dichloroethene; VC, vinyl chloride; TCA, 1,1,1-trichloroethane; 1,1-DCA, 1,1-dichloroethane; CA, chloroethane; 1,1-DCE, 1,1-dichloroethene; BTethylbenzene, and xylenes; <, less than; nd, none detected; –, not analyzed

Well

identification 

No.

Date sampled

Dissolved 

H2 (nM)

Dissolved 

oxygen 

(mg/L)

Dissolved 

nitrate (mg/L)

Dissolved 

manganes 

(mg/L)

Dissolved 

iron 

(mg/L

Dissolved 

iron (II) 

(mg/L)

Dissolved 

sulfate 

(mg/L)

Dissolved 

sulfide 

(mg/L)

Dissolved 

methane 

(mg/L)

p

(un

MW1-2 September 1996 – 2.4 <0.02 – – 0.23 4.6 <0.01 1.2 6MW1-2D September 1996 – 1.9 <0.02 – – 0.18 5.1 <0.01 0.9 6

-- --- --- -- -- -- -- -- -- -- 

MW1-6 September 1996 0.9 0.0 1.2 – – 30 0.10 <0.01 7.0 6MW1-6D September 1996 1.1 0.0 0.81 – – 35 <0.01 <0.01 7.1 6

-- --- -- -- -- -- -- -- -- -- 

MW1-16 April 1997 0.8 0.0 – – – 120 – 0.06 29 6MW1-16D April 1997 1.0 0.0 – – – 110 – 0.06 29 6

-- -- -- -- -- -- -- -- -- -- 

MW1-2 March 1998 – – – – 0.19 0.16 – – – – MW1-2D March 1998 – – – – 0.18 0.12 – – – – 

-- -- -- -- -- -- -- -- -- -- 

MW1-14 October 1998 – 0.0 – 1.5 – 48 – 0.01 – 6MW1-14D October 1998 – 0.0 – 1.4 – 43 – 0.03 – 6

-- -- -- -- -- -- -- -- -- -- 

MW1-28 October 1998 0.1 – – – – – – – – – MW1-28D October 1998 0.6 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- -- 

MW1-14 June 1999 – – – 0.30 – 57 – 0.4 – – MW1-14D June 1999 – – – 0.20 – 64 – 0.03 – – 

-- -- -- -- -- -- -- -- -- -- 

MW1-16 June 1999 2.5 – – – – – – – – – MW1-16D June 1999 6.8 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- -- 

P1-1 June 1999 – – – – – – – – – – P1-1D June 1999 – – – – – – – – – – 

-- -- -- -- -- -- -- -- -- -- 

P1-7 June 1999 0.6 – – – – – – – – – P1-7D June 1999 1.2 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- -- 

MW1-14FB June 1999 – – – – – – – – – – 
114 Natural Attenuation of CVOCs in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington Table A1. Quality assurance and control data collected by the U.S. Geological Survey at Operable Unit 1, Naval Undersea Warfare Cen

Washington—Continued Well identification No. Date sampled PCE

(μg/L)

TCE

(μg/L)

cisDCE

(μg/L)

transDCE

(μg/L)

VC

(μg/L)

Ethene

(μM or

μg/L)

TCA

(μg/L)

1,1-DCA

(μg/L)

CA

(μg/L)

1,1

(μ

-- -- -- -- -- -- -- -- -- 

MW1-2 September 1996 <3.3 28 1,100 21 87 <10 – – – <MW1-2D September 1996 <3.3 26 1,100 19 88 <10 – – – <

-- -- -- -- -- -- -- -- -- 

MW1-6 September 1996 <3.3 150 290 <1.9 89 <10 – – – <MW1-6D September 1996 <3.3 140 240 <1.9 66 6.0 – – – <

-- -- -- -- -- -- -- -- -- 

MW1-16 April 1997 45 130 220 46 240 25 – – – 7MW1-16D April 1997 38 87 160 42 210 25 – – – 6

-- -- -- -- -- -- -- -- -- 

MW1-2 March 1998 – – – – – – – – – MW1-2D March 1998 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-14 October 1998 – – – – – – – – – MW1-14D October 1998 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-28 October 1998 – – – – – – – – – MW1-28D October 1998 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-14 June 1999 – – – – – – – – – MW1-14D June 1999 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-16 June 1999 – – – – – – – – – MW1-16D June 1999 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

P1-1 June 1999 <2 11 6.1 <1 <4 <2 0.24 <4 <P1-1D June 1999 <2 11 5.7 <1 <4 <2 0.23 <4 <

-- -- -- -- -- -- -- -- -- 

P1-7 June 1999 – – – – – – – – – P1-7D June 1999 – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-14FB June 1999 <1 0.34 1.4 0.17 <2 – <1 <1 <2 <
Appendix A. Quality Assurance and Control of U.S. Geological Survey Geochemical Sampling 115

Table A1. Quality assurance and control data collected by the U.S. Geological Survey at Operable Unit 1, Naval Undersea Warfare Cen

Washington—Continued

Well

identification 

No.

Date sampled

Dissolved 

H2 (nM)

Dissolved 

oxygen 

(mg/L)

Dissolved 

nitrate (mg/L)

Dissolved 

manganes 

(mg/L)

Dissolved 

iron 

(mg/L

Dissolved 

iron (II) 

(mg/L)

Dissolved 

sulfate 

(mg/L)

Dissolved 

sulfide 

(mg/L)

Dissolved 

methane 

(mg/L)

p

(u

MW1-17 June 2000 – – – – – – – – 2.8 – MW1-17D June 2000 – – – – – – – – 1.8 – 

-- -- -- -- -- -- -- -- -- 

MW1-20 June 2000 0.1 – – – – – – – 0.008 – MW1-20D June 2000 0.5 – – – – – – – 0.007 – 

-- -- -- -- -- -- -- -- -- 

MW1-36 June 2000 – – – – – – – 0.02 0.009 – MW1-36D June 2000 – – – – – – – 0.02 0.009 – 

-- -- -- -- -- -- -- -- -- 

MW1-37 June 2000 – – – – – – – 0.02 – – MW1-37D June 2000 – – – – – – – 0.02 – – 

-- -- -- -- -- -- -- -- -- 

S-1FB June 2000 – – – – – – – – – – Method Blank June 2000 – – – – – – – – 0.002 – 

Well

identification 

No.

Date sampled PCE

(μg/L)

TCE

(μg/L)

cisDCE

(μg/L)

transDC

E

(μg/L)

VC

(μg/L)

Ethene

(μM or

μg/L)

TCA

(μg/L)

1,1-DCA

(μg/L)

CA

(μg/L)

1,1-

(μ

MW1-17 June 2000 – – – – – <0.1 – – – – MW1-17D June 2000 – – – – – <0.1 – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-20 June 2000 – – – – – <0.1 – – – – MW1-20D June 2000 – – – – – <0.1 – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-36 June 2000 – – – – – <0.1 – – – – MW1-36D June 2000 – – – – – <0.1 – – – – 

-- -- -- -- -- -- -- -- -- 

MW1-37 June 2000 – – – – – – – – – – MW1-37D June 2000 – – – – – – – – – – 

-- -- -- -- -- -- -- -- -- 

S-1FB June 2000 <0.1 <0.1 0.13 <0.1 <0.2 -- <0.1 <0.1 -- <0Method Blank June 2000 – – – – – <0.1 – – – – 
R. S. Dinicola and others USGS-WRIR 02-4119

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Natural Attenuation of Chlorinated Volatile Organic Compounds in Ground Water at

Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington