U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5101

In cooperation with the U.S. Environmental Protection Agency

Evaluation of Water-Chemistry and Water-Level Data at the 

Henderson Road Superfund Site, Upper Merion Township, 

Montgomery County, Pennsylvania, 1991–2008
Cover.

Aerial photograph of the Henderson Road Site (bottom center) and the Upper Merion Reservoir (top center), 2005

Photograph courtesy of the Delaware Valley Regional Planning Commission (DVRPC). 
Evaluation of Water-Chemistry and 

Water-Level Data at the Henderson Road 

Superfund Site, Upper Merion Township, 

Montgomery County, Pennsylvania,

1991–2008

By Ronald A. Sloto

In cooperation with the U.S. Environmental Protection Agency

Scientific Investigations Report 2009-5101

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Sloto, R.A., 2009, Evaluation of water-chemistry and water-level data at the Henderson Road Superfund Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 1991–2008: U.S. Geological Survey Scientific Investigations 

Report 2009-5101, 96 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Shutdown-Rebound Tests ...................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Well-Numbering System......................................................................................................................4

Site Geology...........................................................................................................................................4

Evaluation of Water-Chemistry Data ..........................................................................................................4

Injection Well.........................................................................................................................................9

HR-2 Cluster Wells..............................................................................................................................11

HR-3 Cluster Wells and HR-26-457...................................................................................................15

HR-4 Cluster Wells..............................................................................................................................25

HR-6 Cluster Wells and HR-24-476...................................................................................................29

HR-7 Cluster Wells..............................................................................................................................32

HR-9 Cluster Wells..............................................................................................................................35

HR-12 Cluster Wells............................................................................................................................35

HR-14 Cluster Wells............................................................................................................................35

Well HR-18-190 ....................................................................................................................................38

Well RE-205 ..........................................................................................................................................38

Off-Site Downgradient Wells ............................................................................................................38

Upgradient Wells ................................................................................................................................42

Areal Distribution of Volatile Organic Compounds........................................................................42

Evaluation of Water-Level Data.................................................................................................................58

Temporal Changes in Water Levels .................................................................................................58

HR-3 Cluster Wells and HR-26-457..........................................................................................58

HR-4 Cluster Wells.....................................................................................................................58

HR-6 Cluster Wells and HR-24-476..........................................................................................58

HR-7 Cluster Wells.....................................................................................................................58

Other On-Site Wells...................................................................................................................64

Off-Site Wells..............................................................................................................................64

Potentiometric Surface......................................................................................................................64

June 16, 2003 (Full-Pumping Rate) ..........................................................................................64

July 10, 2006 (Reduced-Pumping Rate)..................................................................................64

February 25–29, 2008 (No Pumping)........................................................................................71

Movement of Contaminants..............................................................................................................71

Summary and Conclusions.........................................................................................................................81

Acknowledgments.......................................................................................................................................83

References Cited..........................................................................................................................................83
iv

Figures

1. Map showing location of the Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania...........................................................................................3

2. Sketch showing shutdown-rebound test time line at the Henderson Road Site,

Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008..........................4

3–4. Maps showing:

3. Location of wells at the Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania..................................................................................5

4. Geology in the vicinity of the Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania..................................................................................7

5–61. Graphs showing:

5. Concentrations of benzene and chlorobenzene in water samples from the

injection well, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008......................................................................................9

6. Concentrations of trichloroethylene and tetrachloroethylene in water samples

from the injection well, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1991–2008............................................................10

7. Concentrations of chlorobenzene,1,2-dichloropropane,

cis-1,2-dichloroethene, and trichloroethylene in water samples from the

injection well, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................10

8. Concentrations of benzene and 1,1-dichloroethane in water samples from

well HR-2-175, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–05........................................................................................11

9. Concentrations of benzene and 1,1-dichloroethane in water samples from well

HR-2-175, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2005....................................................................................12

10. Concentrations of total xylene in water samples from well HR-2-175,

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, 1991–2005 ..................................................................................................12

11. Median concentrations of benzene and 1,1-dichloroethane in water samples

from well HR-2-175, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1992–2005............................................................13

12. Concentrations of benzene and 1,1-dichloroethane in water samples from

well HR-2-195 Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1992–2008....................................................................................13

13. Median concentrations of benzene, chlorobenzene, and 1,1-dichloroethane

in water samples from well HR-2-195, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania, 1992–2008.........................................14

14. Concentrations of benzene and 1,1-dichloroethane in water samples from well

HR-2-295 Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, 1999–2008 ..................................................................................................14

15. Median concentrations of benzene and 1,1-dichloroethane in water samples

from well HR-2-295 Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1999–2008............................................................15

16. Concentrations of benzene in water samples from wells HR-3-255, HR-3-280,

and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................16
v

17. Median concentrations of benzene in water samples from wells HR-3-255,

HR-3-280, and HR-3-295, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1991–2008............................................................16

18. Concentrations of toluene in water samples from wells HR-3-255 and

HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................17

19. Concentrations of total xylene in water samples from wells HR-3-255 and

HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................17

20. Median concentrations of total xylene in water samples from wells HR-3-255

and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................18

21. Concentrations of chlorobenzene in water samples from wells HR-3-255,

HR-3-280, and HR-3-295, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 2003–08................................................................18

22. Median concentrations of chlorobenzene in water samples from wells

HR-3-255, HR-3-280, and HR-3-295, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania, 1991–2008.........................................19

23. Concentrations of 1,1-dichloroethane, 1,2-dichloroethane, and

cis-1,2-dichloroethene in water samples from wells HR-3-255, Henderson

Road Site, Upper Merion Township, Montgomery County, Pennsylvania,

2003–08 ................................................................................................................................20

24. Concentrations of 1,1-dichloroethane in water samples from wells HR-3-280

and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................20

25. Median concentrations of 1,1-dichloroethane in water samples from wells

HR-3-255, HR-3-280, and HR-3-295, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania, 1991–2008.........................................21

26. Concentrations of 1,2-dichloroethane in water samples from wells HR-3-280

and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................21

27. Median concentrations of 1,2-dichloroethane in water samples from wells

HR-3-255 and HR-3-280, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1991–2008............................................................22

28. Concentrations of ethylbenzene in water samples from wells HR-3-255 and

HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................23

29. Median concentrations of ethylbenzene in water samples from wells HR-3-255

and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................23

30. Concentrations of vinyl chloride in water samples from wells HR-3-255,

HR-3-280, and HR-3-295, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 2003–08................................................................24

31. Concentrations of benzene and chlorobenzene in water samples from well

HR-26-457, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................24

32. Median concentrations of benzene and chlorobenzene in water samples from

well HR-26-457, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1992–2008....................................................................................25
vi

33. Concentrations of 1,1-dichloroethane in water samples from wells HR-4-195 and 

HR-4-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................26

34. Concentrations of benzene in water samples from wells HR-4-195 and

HR-4-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................26

35. Concentrations of benzene in water samples from wells HR-4-195 and

HR-4-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................27

36. Median concentrations of benzene, 1,1-dichloroethane, and

1,2-dichloroethane in water samples from well HR-4-295, Henderson Road

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008......27

37. Concentrations of 1,1-dichloroethane, and 1,2-dichloroethane in water

samples from well HR-4-295, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 2003–08................................................................28

38. Concentrations of 1,2-dichloroethane in water samples from well

HR-4-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–08........................................................................................28

39. Concentrations of benzene in water samples from well HR-6-377, Henderson

Road Site, Upper Merion Township, Montgomery County, Pennsylvania,

2003–08 ................................................................................................................................29

40. Concentrations of benzene in water samples from wells HR-6-141,

HR-6-241,and HR-24-476, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 2003–08................................................................30

41. Concentrations of benzene in water samples from wells HR-6-241, HR-6-377,

and HR-24-476, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................30

42. Median concentrations of benzene in water samples from wells HR-6-377 and

HR-24-476, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008....................................................................................31

43. Concentrations of chlorobenzene in water samples from wells HR-6-141,

HR-6-241, HR-6-377, and HR-24-476, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania, 1991–2008.........................................31

44. Median concentrations of chlorobenzene in water samples from wells

HR-6-377 and HR-24-476, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1991–2008............................................................32

45. Concentrations of benzene in water samples from wells HR-7-163, HR-7-278,

and HR-7-383, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1998–2008....................................................................................33

46. Median concentrations of benzene in water samples from wells HR-7-163,

HR-7-278, and HR-7-383, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1998–2008............................................................33

47. Concentrations of chlorobenzene in water samples from wells HR-7-163,

HR-7-278, and HR-7-383, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1998–2008............................................................34

48. Median concentrations of chlorobenzene in water samples from wells

HR-7-163, HR-7-278, and HR-7-383, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania, 1998–2008.........................................34
vii

49. Concentrations of 1,1-dichloroethane in water samples from well

HR-9-191, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1992–2005....................................................................................35

50. Concentrations of vinyl chloride in water samples from well HR-9-191,

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, 1992–2005 ..................................................................................................36

51. Concentrations of benzene and 1,1-dichloroethane in water samples from well

HR-12-300, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 2003–06........................................................................................36

52. Concentrations of benzene and 1,1-dichloroethane in water samples from well

HR-14-178, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1993–2008....................................................................................37

53. Concentrations of benzene and chlorobenzene in water samples from well

HR-14-376, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1998–2008....................................................................................37

54. Median concentrations of benzene and chlorobenzene in water samples from

well HR-14-376, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1998–2008....................................................................................38

55. Concentrations of 1,1-dichoroethane and trichloroethylene in water samples

from well HR-18-190, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 2003–08................................................................39

56. Concentrations of 1,1-dichoroethane and trichloroethylene in water samples

from well HR-18-190, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1992–2008............................................................39

57. Median concentrations of trichloroethylene and 1,1-dichloroethane in water

samples from well HR-18-190, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1992–2008............................................................40

58. Concentrations of benzene and chlorobenzene in water samples from well

RE-205, Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, 1991–2008 ..................................................................................................40

59. Median concentrations of benzene, chlorobenzene, and 1,1-dichloroethane in

water samples from well RE-205, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania, 1991–2008.........................................41

60. Concentrations of benzene, chlorobenzene, 1,1-dichloroethane, and

1,2-dichloroethane in water samples from well HR-22-380, Henderson Road

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1999–2008......41

61. Median concentrations of benzene, chlorobenzene, 1,1-dichloroethane, and

1,2-dichloroethane in water samples from well HR-22-380, Henderson Road

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1999–2008......42

62. Map showing concentrations of benzene measured in water samples from wells,

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania,

February and March 2008..........................................................................................................46

63. Cross section showing concentrations of benzene measured in water samples

from wells, Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008................................................................................47

64. Map showing change in benzene concentration measured between July 2006 and

February 2008 in water samples from wells, Henderson Road Site, Upper Merion

Township, Montgomery County, Pennsylvania......................................................................48
viii

65. Map showing concentrations of chlorobenzene measured in water samples from

wells, Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008................................................................................50

66. Cross section showing concentrations of chlorobenzene in water samples from

wells along section A-B, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, February and March 2008 .........................................51

67–72. Maps showing:

67. Change in chlorobenzene concentration measured between July 2006 and

February 2008 in water samples from wells, Henderson Road Site, Upper

Merion Township, Montgomery County, Pennsylvania...............................................52

68. Concentrations of 1,1-dichloroethane measured in water samples from

wells, Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008.......................................................................53

69. Concentrations of cis-1,2-dichloroethene measured in water samples from

wells, Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008.......................................................................54

70. Concentrations of vinyl chloride measured in water samples from wells,

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008.......................................................................55

71. Concentrations of total xylene measured in water samples from wells,

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008.......................................................................56

72. Generalized approximate extent of area exceeding ARARs, Henderson Road

Site, Upper Merion Township, Montgomery County, Pennsylvania, February

and March 2008..................................................................................................................57

73. Graph showing water levels measured in wells HR-4-295, HR-6-377, and HR-17-170

at the Henderson Road Site; wells MW-1, MW-2, and MW-4 at the McCoy Quarry;

and U.S. Geological Survey observation wells BK-1020 and MG-917, 1996–2008 ...........60

74–79. Graphs showing:

74. Elevation of water levels measured in wells HR-3-255, HR-3-280, and

HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1997–2008....................................................................................61

75. Elevation of water levels measured in wells HR-4-195, HR-4-242, and

HR-4-295, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1997–2008....................................................................................61

76. Elevation of water levels measured in wells HR-6-141, HR-6-241, HR-6-377, and

HR-24-276, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1997–2008....................................................................................62

77. Elevation of water levels measured in wells HR-7-163, HR-7-278, and

HR-7-383, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1997–08........................................................................................62

78. Elevation of water levels measured in wells HR-6-377, HR-9-191, HR-14-178,

and HR-14-378, Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1997–2008....................................................................................63

79. Elevation of water levels measured in wells HR-3-280, HR-5-195, HR-6-377,

HR-17-170, and HR-22-380, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania, 1997–2008............................................................63

80–94. Maps showing:

80. Elevation of water levels measured in shallow wells at the Henderson Road Site,

Upper Merion Township, Montgomery County, Pennsylvania, June 16, 2003.........65
ix

81. Elevation of water levels measured in intermediate depth wells at the

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, June 16, 2003 ............................................................................................66

82. Elevation of water levels measured in deep wells at the Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania,

June 16, 2003 ......................................................................................................................67

83. Elevation of water levels measured in shallow wells at the Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania,

July 10, 2006........................................................................................................................68

84. Elevation of water levels measured in intermediate depth wells at the

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, July 10, 2006..............................................................................................69

85. Elevation of water levels measured in deep wells at the Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania,

July 10, 2006 .......................................................................................................................70

86. Elevation of water levels measured in shallow wells at the Henderson Road

Site, Upper Merion Township, Montgomery County, Pennsylvania, February

25–28, 2008 ..........................................................................................................................72

87. Elevation of water levels measured in intermediate depth wells at the

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February 25–28, 2008 ...............................................................................73

88. Elevation of water levels measured in deep wells at the Henderson Road

Site, Upper Merion Township, Montgomery County, Pennsylvania,

February 25–28, 2008 .........................................................................................................74

89. Concentrations of benzene measured in water samples from shallow wells

and generalized direction of ground-water flow, Henderson Road Site, Upper

Merion Township, Montgomery County, Pennsylvania, February and March

2008 ......................................................................................................................................75

90. Concentrations of benzene measured in water samples from

intermediate-depth wells and generalized direction of ground-water flow,

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008.......................................................................76

91. Concentrations of benzene measured in water samples from deep wells and

generalized direction of ground-water flow, Henderson Road Site, Upper

Merion Township, Montgomery County, Pennsylvania, February and

March 2008 .........................................................................................................................77

92. Concentrations of chlorobenzene measured in water samples from shallow

wells and generalized direction of ground-water flow, Henderson Road Site,

Upper Merion Township, Montgomery County, Pennsylvania, February and

March 2008 .........................................................................................................................78

93. Concentrations of chlorobenzene measured in water samples from

intermediate-depth wells and generalized direction of ground-water flow,

Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008.......................................................................79

94. Concentrations of chlorobenzene measured in water samples from deep

wells and generalized direction of ground-water flow, Henderson Road Site, 

Upper Merion Township, Montgomery County, Pennsylvania, February

and March 2008..................................................................................................................80
x

Tables

1. Record of wells at the Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania...................................................................................................................6

2. Compounds analyzed, applicable or relevant and appropriate requirements

(ARARs) set for volatile organic compounds at the Henderson Road Site in the

Record of Decision (U.S. Environmental Protection Agency, 1988a), and U.S.

Environmental Protection Agency maximum contaminant levels (MCLs) for

drinking water ...............................................................................................................................8

3. Wells sampled during the 2006–08 shutdown-rebound test, Henderson Road Site,

Upper Merion Township, Montgomery County, Pennsylvania..............................................8

4. Concentrations of selected volatile organic compounds in ground-water samples

from the Henderson Road Site, Upper Merion Township, Montgomery County,

Pennsylvania, February and March 2008................................................................................43

5. Change in concentration of selected volatile organic compounds between July

2006 and February and March 2008, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania.........................................................................................44

5. Change in concentration of selected volatile organic compounds between July

2006 and February and March 2008, Henderson Road Site, Upper Merion Township,

Montgomery County, Pennsylvania.........................................................................................45

6. Elevation of water level measured in wells at the Henderson Road Site, Upper

Merion Township, Montgomery County, Pennsylvania, for selected dates 2003–08 ......59

7. Summary of concentrations of selected volatile organic compounds in water

samples from the Henderson Road Site, Upper Merion Township, Montgomery

County, Pennsylvania, 1991–2008.............................................................................................86
xi

Conversion Factors, Abbreviations, and Datums

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

acre 0.4047 square hectometer (hm2

) 

acre 0.004047 square kilometer (km2

)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3

) 

million gallons (Mgal) 3,785 cubic meter (m3

)

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Hydraulic conductivity

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

Vertical coordinate information is referenced to a local site benchmark at the Henderson Road 

Site and is given in feet above mean sea level. All data collected at the site since the 1980s was 

referenced to this benchmark.

Horizontal coordinate information is referenced to the North American Datum of 1988 (NAD 88).

Altitude, as used in this report, refers to distance above the vertical datum.

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

or micrograms per liter (μg/L).

Abstract

Several shutdown-rebound tests have been conducted 

at the Henderson Road Superfund Site, which has been on 

the U.S. Environmental Protection Agency’s National Priorities List since 1984. For a given test, the extraction wells are 

turned off, and water samples are collected from selected 

monitor wells at regular intervals before and during cessation 

of pumping to monitor for changes in chemical concentrations. 

A long-term shutdown-rebound test began on July 17, 2006. 

In support of this test, the U.S. Geological Survey conducted 

this study to determine the effects of shutting down on-site 

extraction wells on concentrations of selected contaminants 

and water levels. Concentrations were compared to ARARs 

(applicable relevant and appropriate requirements), which 

were set as remediation goals in the Henderson Road Site 

Record of Decision.

Water from 10 wells in and near the source area and to 

the north, northeast, and northwest of the source area sampled 

in 2008 exceeded the 5.52 μg/L (micrograms per liter) ARAR 

for benzene. The greatest changes in benzene concentration 

between pre-shutdown samples collected in July 2006 and 

samples collected in February and March 2008 (19 months 

after the shutdown) were for wells in and north of the source 

area; increases in benzene concentration ranged from 1.5 to 

164 μg/L.

Water from five wells in the source area and to the north 

and northwest of the source area sampled in 2008 exceeded 

the 60 μg/L ARAR for chlorobenzene. The greatest changes in 

chlorobenzene concentration between pre-shutdown samples 

collected in July 2006 and samples collected in February and 

March 2008 were for wells north of the source area; increases 

in chlorobenzene concentration ranged from 6.9 to 99 μg/L. 

The highest concentrations of chlorobenzene were near or 

outside the northern site boundary, indicating chlorobenzene 

may have moved north away from the source area; however, no monitor well clusters are on the northern side of the 

Pennsylvania Turnpike, which is about 190 feet north of the 

source area. A much larger area was affected by chlorobenzene 

than benzene. Chlorobenzene concentrations decreased in the 

source area and increased at and beyond the site boundary.

Water from four wells in and northeast of the source 

area sampled in 2008 exceeded the 5.06 μg/L ARAR for 

1,1-dichloroethane (1,1-DCA). Increases in 1,1-DCA concentration between pre-shutdown samples collected in July 

2006 and samples collected in February 2008 ranged from 0.4 

to 20 μg/L. Water from two wells in the source area sampled 

in 2008 exceeded the 175 μg/L ARAR for total xylene. The 

1,1-DCA and xylene plumes appear to extend in an east-northeast direction from the source area.

Large drawdowns in the Upper Merion Reservoir during droughts in 1998 and 2001 affected water levels in the 

Chester Valley and at the Henderson Road Site, except for 

well HR-17-170. After the drought of 2001, water levels in 

the Chester Valley showed a protracted recovery lasting from 

September 2001 until June 2005 (46 months).

Water-level data were evaluated temporally for 1997–

2008 and spatially for (1) June 16, 2003, when the extraction 

wells were pumping at the full rate prior to the start of the 

June 2003 shutdown test; (2) July 10, 2006, during the period 

of reduced pumping after the June 2003 shutdown test; and 

(3) February 25–29, 2008, when the extraction wells were not 

pumping. Except for well HR-5-195, wells were categorized 

as shallow, intermediate-depth, and deep wells. The potentiometric surface for shallow wells did not appear to be affected 

by pumping of the extraction wells. The general direction of 

ground-water flow was to the north. The potentiometric surface for intermediate-depth wells showed a cone of depression 

when the extraction wells were pumping at the full rate but did 

not show a cone of depression when the extraction wells were 

pumping at the reduced rate. The ground-water-flow direction 

was toward the north and northeast, similar to that when the 

extraction wells were pumping.

Water-level data were available for only four on-site deep 

wells when the extraction wells were pumping. The available 

water-level data showed a flat hydraulic gradient. When the 

wells were pumping at the full rate, the ground-water-flow 

direction was to the Henderson Road Site from the northwest; 

when the wells were pumping at the reduced rate, the groundwater-flow direction was reversed, and flow was away from 

Evaluation of Water-Chemistry and Water-Level Data 

at the Henderson Road Superfund Site, Upper Merion 

Township, Montgomery County, Pennsylvania, 1991–2008

By Ronald A. Sloto
2 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

the Henderson Road Site to the northwest. When the extraction wells were not pumping, the ground-water-flow direction 

was away from the Henderson Road Site toward the north and 

northeast.

Benzene concentrations measured in water samples from 

shallow wells in February and March 2008 were above the 

ARAR only in the source area. Benzene concentrations measured in water samples from intermediate-depth wells were 

above the ARAR in the source area and beyond the northern 

site boundary. Benzene concentrations measured in water 

samples from deep wells were above the ARAR in the source 

area and at and beyond the northern site boundary. Benzene 

appears to have moved to the north away from the source area 

in the intermediate and deep zones.

Chlorobenzene concentrations measured in water samples 

from shallow wells collected in February and March 2008 

were above the ARAR beyond the northern site boundary 

northwest of the source area. Chlorobenzene concentrations 

measured in water samples from intermediate-depth wells 

were above the ARAR in the source area and beyond the 

northern site boundary northwest of the source area. Chlorobenzene concentrations measured in water samples from deep 

wells collected in February and March 2008 were above the 

ARAR at and beyond the northern site boundary. Chlorobenzene appears to have moved to the north away from the source 

area in the shallow, intermediate, and deep zones.

Off-site wells were drilled to monitor the possible movement of chemicals of concern from the Henderson Road Site. 

Concentrations of benzene and chlorobenzene above the 

ARARs were measured in water samples from well cluster 

HR-7 at the northern site boundary and well cluster HR-6 

beyond the northern site boundary on the southern side of the 

Pennsylvania Turnpike. No off-site monitor wells are located 

directly north of these well clusters on the northern side of the 

Pennsylvania Turnpike. Potentiometric-surface maps indicate 

the direction of ground-water flow from these well clusters 

is to the north. Additional monitor well clusters north of well 

clusters HR-6 and HR-7 on the northern side of the Pennsylvania Turnpike could help determine how far benzene or 

chlorobenzene have moved offsite and could be used to better 

define ground-water-flow directions north of the site.

Introduction

The Henderson Road Superfund Site, herein referred to 

as the Henderson Road Site, occupies approximately 7 acres 

in Upper Merion Township, Montgomery County, Pa. (fig. 1). 

Between December 1974 and March 1977, an on-site well 

(the injection well) was used to dispose of liquid industrial 

waste containing organic contaminants. In addition, an on-site 

landfill received industrial and municipal wastes. The site was 

listed on the U.S. Environmental Protection Agency (USEPA) 

National Priorities List on September 21, 1984.

A ground-water treatment plant was constructed and 

began operation in September 1991. The treatment plant 

utilized bioremediation to reduce organic contaminant levels 

and carbon adsorption to remove residual contaminants before 

the treated water was discharged to an adjacent intermittent 

stream. Initially, five ground-water extraction wells pumped 

contaminated ground water to the treatment plant.

Several shutdown-rebound tests were conducted on the 

site. The objective of a shutdown-rebound test is to determine 

whether chemical concentrations would increase or be stable 

in the absence of pumping. For a given test, the extraction 

wells are turned off, and water samples are collected from 

selected monitor wells at regular intervals before and during 

cessation of pumping to monitor for changes in chemical concentrations. A long-term shutdown-rebound test began on July 

17, 2006. The U.S. Geological Survey (USGS) conducted this 

study for the USEPA in support of this extended shutdownrebound test to determine the effects of shutting down the 

extraction wells on the concentrations of selected contaminants and on water levels.

All chemical and most water-level data used for this 

study were collected and furnished by RT Environmental 

Services, Inc., a contractor for the responsible parties at the 

Henderson Road Site. RT Environmental Services, Inc. has 

worked at the site since 1989. They designed and implemented 

the site-remediation system and operate the treatment plant.

Shutdown-Rebound Tests

In September 1991, the ground-water treatment plant 

began operation. Initially, five ground-water extraction 

wells (B-1, IW, HR-3-255, HR-3-295, and RE-205) pumped 

contaminated ground water to the treatment plant. Wells 

HR-24-476 and HR-26-457 were later added as extraction 

wells, and wells B-1 and HR-24-476 were discontinued as 

extraction wells.

Several shutdown-rebound tests were conducted to 

evaluate the effect of shutting down the extraction wells on 

chemical concentrations. Short tests (1 to 3 weeks in duration) 

were conducted in June 1995, April 1997, and April 1999. A 

longer, 5.5-month test was conducted from June 30 to December 12, 2003; this test is referred to as the 2003 shutdown test 

in this report. Following this test, the pumping rate for the 

extraction wells was reduced. A second, long-term shutdownrebound test was started on July 17, 2006; this test is called the 

2006–08 shutdown test in this report. The time line covered by 

this report is shown in figure 2.

Purpose and Scope

This report summarizes selected chemical and waterlevel data collected at the Henderson Road Site. Data for 

volatile organic compounds (VOCs) in ground-water samples 

collected from August 1991 to August 2008 and groundwater levels collected from May 1997 to August 2008 were 
Introduction 3

75°22’ 75°21’ 75°20’ 75°19’

40°05’

40°06’

276

US 202

Schuylkill River

UPPER MERION TOWNSHIP

PLYMOUTH

TOWNSHIP

WEST

NORRITON 

 TOWNSHIP

BRIDGEPORT

 BOROUGH

NORRISTOWN

 BOROUGH

UPPER MERION

 RESERVOIR

0 0.25 0.5 0.75 1 MILE

0 0.25 0.5 0.75 1 KILOMETER

McCOY QUARRY

HENDERSON ROAD SITE

Base from U.S. Geological Survey digital data,1972,

1:2,000,000 Albers Equal-Area Conic Projection.

Standard parallels 29°30’N, central meridian 75°00’W.

PENNSYLVANIA

MONTGOMERY

 COUNTY

MW-2

MW-1

MW-4

MW-1 McCOY QUARRY MONITOR WELL

 AND IDENTIFICATION NUMBER 

EXPLANATION

PENNSYLVANIA TURNPIKE

Figure 1. Location of the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania.
4 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

compared graphically. Median VOC concentrations in groundwater samples were compared. The effects of the 2006–08 

shutdown-rebound test on VOC concentrations and water 

levels in 41 monitor wells are discussed.

Well-Numbering System

The well-identification numbering system used in this 

report is that used by RT Environmental Services, Inc., to be 

consistent with previous site work. Most site well-identification numbers consist of the prefix HR (Henderson Road) 

followed by two numbers. The first number identifies the well 

cluster or group. The second number is the well depth. Well 

HR-6-377, for example, is a 377-ft deep well in well cluster 6. 

Other prefixes include RE (replacement well) and B (boring). 

The injection well is designated as IW. Well locations are 

shown on figure 3, and data for the wells are given in table 1. 

Wells south of the Pennsylvania Turnpike are considered to 

be on-site wells; wells north of the Pennsylvania Turnpike are 

considered to be off-site wells.

Site Geology

The Henderson Road Site is in a carbonate valley, known 

as Chester Valley (shown on fig. 4), in southwest Montgomery 

County near the Schuylkill River (fig. 1). The site is about 

2,100 ft south of the Upper Merion Reservoir (fig. 1), which 

is operated by Aqua Pennsylvania, Inc. The Upper Merion 

Reservoir is a former dolomite quarry now used as a source of 

public water supply. Aqua Pennsylvania, Inc. supplies water to 

much of the Philadelphia suburban area. The water is treated 

for removal of VOCs prior to distribution. A large active 

quarry, the McCoy Quarry, is northeast of the Henderson Road 

Site.

The Henderson Road Site is underlain by the Conestoga 

Limestone (fig. 4), which forms a complex, fractured, carbonate-rock aquifer. The Conestoga is a blue-gray, thin-bedded, 

argillaceous limestone with intervals of a purer, granular 

limestone. Mica coats most of the bedding and cleavage planes 

(Lyttle and Epstein, 1987). The impure part of the Conestoga 

has thin-bedded alterations of dark-gray, clayey, silty, slaty, 

micaceous layers and medium-gray, argillaceous limestone 

that impart a characteristic banded appearance to the rock. 

Some of the basal beds are a coarse limestone conglomerate containing large pebbles and irregular masses of coarse 

white marble in a gray limestone. The Conestoga Limestone 

is 500 to 800 ft thick and unconformably overlies the Elbrook 

Formation. At the Henderson Road Site, karst features such as 

solution channels, voids, and deep weathering are prevalent. 

Depth to water in wells on the Henderson Road Site measured 

in August 2008 ranged from 97 to 142 ft below land surface.

The Elbrook Formation lies between the Henderson Road 

Site and the Upper Merion Reservoir (fig. 4). The Elbrook is a 

light-gray to white, finely laminated, fine-grained, interbedded 

limestone and marble. The Elbrook is 300 to 800 ft thick. The 

lower contact is gradational with the Ledger Dolomite.

Ground-water flow in the region is influenced by the 

pumping of the Upper Merion Reservoir for water supply 

and by the McCoy Quarry for dewatering. The Upper Merion 

Reservoir and the McCoy Quarry are in the Ledger Dolomite 

(fig. 4). The Ledger is a white to light gray, massive to thickbedded, granular, relatively pure dolomite with a high magnesium content. The dolomite is interbedded with some siliceous 

beds and laminated limestone. The Ledger contains a few beds 

of marble with a high calcium content. The Ledger is 660 to 

1,000 ft thick.

Evaluation of Water-Chemistry Data

Wells at the Henderson Road Site have been sampled 

for VOCs (table 2) since 1991. Compounds analyzed and 

applicable or relevant and appropriate requirements (ARARs) 

set in the Record of Decision for the Henderson Road Site 

(U.S. Environmental Protection Agency, 1988a) are listed 

in table 2. Section 121(d) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 

(CERCLA) requires that on-site remedial actions attain or 

waive Federal environmental ARARs, or more stringent 

State environmental ARARs, upon completion of the remedial action. ARARs are identified on a site-by-site basis. A 

requirement under other environmental laws may be either 

 STOP

PUMPING

 6/30/03

 START

PUMPING

 12/12/03

 FULL

PUMPING

 RATE

REDUCED

 PUMPING

 RATE

 NO

PUMPING

 NO

PUMPING

1991 2001 2002 2003 2004 2005 2006 2007 2008

 STOP

PUMPING

 7/17/06

Figure 2. Shutdown-rebound test time line at the Henderson Road Site, Upper Merion Township, Montgomery County, 

Pennsylvania, 1991–2008.
Evaluation of Water-Chemistry Data

5

Figure 3. Location of wells at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

40°

05'

20”

40°

05'

15”

40°

05'

10”

HR-17-170

HR-22-300

HR-5-195

HR-10-180

HR-30-318

HR-23-350

HR-15-255

HR-6-141

HR-6-241 HR-6-377

HR-24-476

HR-16-304

HR-1-260

HR-1-276 HR-1-280

HR-20-155

HR-2-295

HR-25-325 HR-12-150

IW

RE-205

HR-3-255HR-3-295

HR-3-280

HR-2-175

HR-2-195

HR-11-133

HR-26-457 HR-12-300

HR-13-147

HR-7-383

HR-7-278

HR-7-163

HR-4-242

HR-14-376

HR-14-178

HR-4-295

HR-4-195

HR-18-190

HR-9-191

HR-9-333

HR-19-160

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

HR-6-377 LOCATION OF WELL AND WELL-

 IDENTIFICATION NUMBER

HR-B1 APPROXIMATE SITE BOUNDARY

75°21’30” 75°21’20” 75°21’10”
6 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Table 1. Record of wells at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania.

[—, no data; *, major water-bearing fracture; >, greater than; < less than]

Wellidentification 

number

Year 

drilled

Depth 

drilled 

(feet)

Depth 

cased 

(feet)

Yield

(gallons 

per

minute)

Depth of fracture or void

(feet below land surface)

Screened 

(S) or 

open-hole 

(OH)

Screened or 

open-hole 

interval

(feet below 

land surface)

Elevation of 

top of casing 

(feet above 

mean sea 

level)

B-1 1990 140 — — — — — 158.82

HR-1-260 1986 260 54 3 210, 215* OH 54–260 161.83

HR-1-276 1986 280 31 15 270* S 255.4–276.2 159.73

HR-1-280 1986 280 61 1 — OH 61–280 160.73

HR-2-175 1986 175 107.5 > 50 94–102, 132, 161–164* S 154.7–175.5 161.19

HR-2-195 1986 195 101 < 5 80–95, 108–112, 133–135 OH 101–158.3 161.35

HR-2-295 1986 300 101 > 30 148, 155*, 205–223, 278 S 274–294.8 161.01

HR-3-255 1986 255 137 < 1 67, 126* OH 137–255 161.67

HR-3-280 1986 280 140 1 260* OH 137–280 158.82

HR-3-295 1986 300 117 15 67, 132, 282* S 274.7–295 161.39

HR-4-195 1986 220 143 — 153–160 S 174.1–194.9 160.35

HR-4-242 1986 280 116 — 228–230 S 221.4–242.2 160.17

HR-4-295 1986 300 300 > 30 161, 177–178, 181*, 280–300 S 274.4–295.2 160.37

HR-5-195 1986 200 179.2 10 — S 181.3–192.1 156.20

HR-6-141 — — — — — — — 164

HR-6-241 1991 241 188 20 181, 201, 235* OH 188–241 164.31

HR-6-377 1991 377 295 8 161, 277, 314, 357 OH 295–377 165.11

HR-7-163 1991 163.5 105 1 150* OH 105–163.5 158.66

HR-7-278 1991 278 209 30 181, 221, 231, 261, 278* OH 209–278 159.30

HR-7-383 1991 383 301 46 201, 208, 241, 301, 383 OH 301–383 159.08

HR-9-191 1991 191 9.5 2 95-99.5, 140, 181, 191 OH 9.5–191 171.50

HR-9-333 1991 333 273 20 181, 241, 261, 281, 301 OH 273–333 170

HR-10-180 1990 180 133 10 — OH 133–180 173.81

HR-12-150 — — — — — — — 157.68

HR-12-300 1991 300 218 8 161, 171, 266* OH 218–300 157.81

HR-13-147 — 147 124 5 — OH 124–147 158.17

HR-14-178 1991 178.5 82 2 119, 129, 156, 178.5 OH 82–178.5 160.81

HR-14-376 1991 376 292.5 50 280, 336, 376 OH 292.5–376 158.87

HR-15-225 1991 225 200 10 160, 190, 200, 210, 215 OH 200–225 151.18

HR-16-304 1991 304 160 1.5 175, 185, 215, 250, 300 OH 160–304 —

HR-17-170 1991 170 69.5 3 86-93, 102–103 OH 69.5–154.55 151.20

HR-18-190 1991 190 35.5 1 109, 161, 190 OH 35.5–190 167.50

HR-19-160 1991 160 79 2 132, 160 OH 79–160 135.36

HR-20-155 1991 155 102 — 50–53, 59–61, 65–66, 89–95, 

100–107, 112–114, 124.5–151

S 102–132 152.06

HR-22-300 1992 300 219 3 275* OH 219–300 157.33

HR-23-350 — — — — — — — 174.47

HR-24-476 1992 476 78 60 195, 221, 260, 315* OH 78–476 164.34

HR-25-325 1992 330 284 — — OH 284–330 159.76

HR-26-457 1992 457 50 10 201, 260, 340, 357, 424 OH 50–457 158.50

HR-30-318 2007 318 285 8 296 S 297.5–318 174.72

IW (Injection 

well)

— 165.5 81 > 50 90-93, 97–102, 164–165.5 OH 81–165.5 159.79

RE-205 1986 280 103 30 203–205 OH 103–280 161.38
Evaluation of Water-Chemistry Data 7

Figure 4. Geology in the vicinity of the Henderson Road Site, Upper Merion Township, Montgomery County, 

Pennsylvania.

75°22’ 75°21’ 75°20’ 75°19’

40°05’

40°06’

276

US 202

Schuylkill River

UPPER MERION

 RESERVOIR

McCOY QUARRY

HENDERSON ROAD SITE

0 0.25 0.5 0.75 1 MILE

0 0.25 0.5 0.75 1 KILOMETER

Base from U.S. Geological Survey digital data,1972,

1:2,000,000 Albers Equal-Area Conic Projection. 

Standard parallels 29°30’N, central meridian 75°00’W.

Cl

OCc

Ce

NC

Cl

NC

Cl

Ce

OCc

EXPLANATION

LEDGER DOLOMITE

CONESTOGA LIMESTONE

ELBROOK FORMATION

NON-CARBONATE ROCKS

Geology from Miles and Whitfield (2001)

NC

CHESTER VALLEY

NC

PENNSYLVANIA TURNPIKE
8 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

“applicable” or “relevant and appropriate,” but not both. Identification of ARARs must be done on a site-specific basis and 

involves a two-part analysis: first, a determination whether 

a given requirement is applicable; then, if it is not applicable, 

a determination whether it is nevertheless both relevant and 

appropriate. Applicable requirements are those cleanup standards, standards of control, and other substantive environmental protection requirements, criteria, or limitations promulgated under Federal or State law that specifically address a 

hazardous substance, pollutant, contaminant, remedial action, 

location, or other circumstance at a CERCLA site. Relevant 

and appropriate requirements are those cleanup standards, 

standards of control, and other substantive environmental 

protection requirements, criteria, or limitations promulgated 

under Federal or State law that, although not “applicable” to a 

hazardous substance, pollutant, contaminant, remedial action, 

location, or other circumstance at a CERCLA site, address 

problems or situations sufficiently similar to those encountered 

at the CERCLA site that their use is well suited to the particular site (U.S. Environmental Protection Agency, 1988b).

Data for VOCs in ground water were provided by RT 

Environmental Services, Inc. The database consisted of 1,172 

VOC analyses of 29 compounds for 27 wells over a period 

of 18 years. Detection limits were not provided and are not 

known. Concentrations below the detection limit were given 

as 0 (zero). For the statistics presented in this report, zero 

was used for concentrations below the detection limit. For 

the 2006–08 shutdown test, 13 wells were sampled quarterly 

and an additional 12 wells were sampled twice (May 2007 

and February 2008) (table 3). Summary statistics for selected 

compounds are presented in table 7 (at the back of the report). 

Wells for which no compound exceeded the ARARs (HR-10-

180, HR-17-170, and HR-30-318) are not listed in table 7. Not 

all wells were sampled for all dates.

Grouping of data for statistical analysis depended on the 

number of analyses available. If enough analyses were available, data were grouped into four general categories:

(1) early full-pumping rate period, 1991 to 1999; (2) pre-2003 

shutdown full-pumping rate, 2000 to June 2003; (3) 2003 

shutdown test and pumping at the reduced rate, July 2003 

to January 2007; and (4) most recent samples, May 2007 to 

August 2008. For 25 wells sampled in 2008, ARARs were 

exceeded for benzene (10 wells), chlorobenzene (5 wells), 

1,1-dichloroethane (1,1-DCA) (4 wells), and total xylene (m-, 

p-, and o-xylene) (2 wells). No off-site downgradient well 

sampled during 2003–08 exceeded the ARARs.

Table 2. Compounds analyzed, applicable or relevant and 

appropriate requirements (ARARs) set for volatile organic 

compounds at the Henderson Road Site in the Record of 

Decision (U.S. Environmental Protection Agency, 1988a), and U.S. 

Environmental Protection Agency maximum contaminant levels 

(MCLs) for drinking water.

[μg/L, micrograms per liter; —, no ARAR or MCL set]

Compound ARAR

(μg/L)

U.S Environmental

Protection 

Agency MCL1

(μg/L)

Benzene 5.52 5

Bromodichloromethane 100 —

2-Butanone — —

Carbon disulfide — —

Carbon tetrachloride 5 5

Chlorobenzene 60 100

Chloroethane 19,000 —

Chloroform 100 —

Chloromethane — —

Dibromochloromethane 100 —

1,1-Dichloroethane (1,1-DCA) 5.06 —

1,2-Dichloroethane (1,2-DCA) 6.02 5

1,1-Dichloroethene 7 7

cis-1,2-Dichloroethene (cis-1,2-DCE) 70 70

1,2-Dichloroethene 70 —

1,2-Dichloropropane 6.28 5

Ethylbenzene 680 700

2-Hexanone — —

Methylene chloride 47 —

Styrene — 100

Tetrachloroethylene (PCE) 6.9 5

Toluene 2,000 1,000

Total xylene 175 10,000

1,1,1-Trichloroethane 200 200

Trichloroethylene (TCE) 25.8 5

Vinyl chloride 2 2

Trichloroflouromethane 12,000 —

1

U.S. Environmental Protection Agency (2009).

Table 3. Wells sampled during the 2006–08 shutdownrebound test, Henderson Road Site, Upper Merion Township, 

Montgomery County, Pennsylvania. (Well locations are shown 

on figure 3.)

Wells sampled quarterly Wells sampled in May 2007 

and February 2008

HR-3-280 HR-2-195

HR-4-295 HR-2-295

HR-6-141 HR-3-295

HR-6-241 HR-5-195

HR-6-377 HR-7-163

HR-7-383 HR-7-278

HR-14-376 HR-10-180

HR-17-170 HR-14-178

HR-18-190 HR-25-325

HR-20-155 HR-26-457

HR-22-380 Injection well

HR-24-476 RE-205

HR-30-318
Evaluation of Water-Chemistry Data 9

Injection Well

Between December 1974 and March 1977, an on-site 

well, known as the injection well (IW on fig. 3), was used to 

dispose of liquid industrial waste containing organic contaminants. In 1991, water samples from the injection well 

exceeded the ARARs for 13 of 22 compounds. In general, 

concentrations for all compounds except 1,2-dichloropropane 

and cis-1,2-dichloroethene (cis-1,2-DCE) have substantially 

decreased since the 1990s (table 7). The concentrations of 

most compounds increased around the time of the June 2003 

shutdown and then decreased (figs. 5 and 6). Median concentrations of most compounds have substantially decreased 

Figure 5. Concentrations of benzene and chlorobenzene in water samples from the injection well, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc.

since 1991 except for six compounds: chlorobenzene, 

cis-1,2-DCE, 1,2-dichloropropane, tetracloroethylene, tricloroethylene (TCE), and vinyl chloride (table 7, fig. 7).

Between May 2003 and August 2008, concentrations 

exceeded ARARs for nine compounds: benzene, chlorobenzene, 1,1-DCA, 1,2-dichloroethane (1,2-DCA), cis-1,2-DCE, 

1,2-dichloropropane, tetrachloroethylene (PCE), vinyl 

chloride, and total xylene (table 7). Median concentrations of 

benzene and 1,1-DCA exceeded the ARARs. The ARAR for 

vinyl chloride was exceeded in 41 percent of samples. For the 

two samples collected in 2007–08, the ARAR was exceeded 

only for benzene and total xylene.

BENZENE 

CHLOROBENZENE

0

50

100

150

200

250

300

350

400

450

500

550

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

Benzene concentration

1,500 μg/L on 8/28/1991

BENZENE ARAR

CHLOROBENZENE

 ARAR
10 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 6. Concentrations of trichloroethylene and tetrachloroethylene in water samples from the injection well, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 7. Concentrations of chlorobenzene,1,2-dichloropropane, cis-1,2-dichloroethene, and 

trichloroethylene in water samples from the injection well, Henderson Road Site, Upper Merion Township, 

Montgomery County, Pennsylvania, 1991–2008. Median concentrations of 1,2-dichloropropane, cis-1,2-

dichloroethene, and trichloroethylene were zero for 1991 to May 2003. ARARS for chlorobenzene, cis-1,2-

dichloroethene, and trichloroethylene are 60, 70, and 25.8 micrograms per liter, respectively. ARAR is the 

applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site 

(U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

5

10

15

20

12/91-5/03 7/03-2/08

CHLOROBENZENE

1,2-DICHLOROPROPANE

CIS-1,2-DICHLOROETHENE

TRICHLOROETHYLENE

1,2-DICHLOROPROPANE ARAR

0

10

20

30

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

 2003

January

2005

January

 2007

January

 2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

PCE ARAR

TRICLOROETHYLENE (TCE)

TETRACHLOROETHYENE (PCE)

TCE ARAR
Evaluation of Water-Chemistry Data 11

Figure 8. Concentrations of benzene and 1,1-dichloroethane in water samples from well HR-2-175, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003-05. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

HR-2 Cluster Wells

Well HR-2-175 was not sampled during the 2006–08 

shutdown test; it was last sampled on June 15, 2005. Between 

July 2003 and June 2005, concentrations in water samples 

from well HR-2-175 exceeded the ARARs for benzene, 

1,1-DCA (figs. 8 and 9), 1,2-dichloropropane, vinyl chloride 

(table 7), and total xylene (fig. 10). Median benzene concentrations were highest during 1992–99 (11 μg/L) (figs. 9 and 

11), declined during August 2000 to May 2003 (4.1 μg/L), 

and then increased to greater than the ARAR during the 2003 

shutdown test (7.5 μg/L) (fig. 11). Median concentrations 

of 1,1-DCA have remained about the same for the period 

1992–2005 (fig. 11). The concentration of total xylene in water 

samples from well HR-2-175 dropped below the ARAR on 

August 25, 2003, and remained below the ARAR from August 

2003 to June 2005 (fig. 10).

During the 2006–08 shutdown test, wells HR-2-195 

and HR-2-295 were sampled twice (May 2007 and February 

2008). Well HR-2-195 was sampled only three times prior 

to the June 2003 shutdown test; the benzene concentration 

was below the ARAR for all three samples. After the June 

2003 shutdown, well HR-2-195 was sampled four times; 

the benzene concentration exceeded the ARAR for all four 

samples (fig. 12). The median benzene concentration in 

water samples from well HR-2-195 for 2005–08 was 41 μg/L 

(fig. 13). The median concentration for chlorobenzene in water 

samples from well HR-2-195 increased from 0 for 1992 to 

May 2003 to 17 μg/L for June 2005 to February 2008 (fig. 13); 

however, concentrations did not exceed the ARAR. For 

1990–99, water samples from well HR-2-195 exceeded the 

ARARs for 1,1-DCA, cis-1,2-DCE, ethylbenzene, methylene 

chloride, toluene, and total xylene (table 7).

Well HR-2-295 was sampled three times prior to the June 

2003 shutdown test and four times thereafter. The ARAR for 

benzene was exceeded for two of the three water samples 

collected before the 2003 shutdown. The concentrations of 

benzene in the four water samples collected after the start of 

the June 2003 shutdown were below the ARAR (fig. 14). The 

concentration of 1,1-DCA in six of the seven water samples 

from well HR-2-295 exceeded the ARAR (fig. 14). The 

median concentrations of benzene and 1,1-DCA were compared before and after the June 2003 shutdown test (fig. 15). 

The median concentration of benzene decreased from 7.5 to 

3.4 μg/L, and the median concentration of 1,1-DCA increased 

from 5.8 to 6.2 μg/L.

CONCENTRATION, IN MICROGRAMS PER LITER 

 BENZENE ARAR

1,1-DICHLOROETHANE ARAR

0

5

10

15

20

BENZENE 

1,1-DICHLOROETHANE STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

2003 July2003 January2004 July2004 January2005 July2005 January2006 July2006 January2007 July2007 January2008 July2008
12 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 9. Concentrations of benzene and 1,1-dichloroethane in water samples from well HR-2-175, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2005. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 10. Concentrations of total xylene in water samples from well HR-2-175, Henderson Road Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 1991–2005. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). 

Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE 

1,1-DICHLOROETHANE

0

20

40

60

80

100

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

 BENZENE

 ARAR

1,1-DICHLOROETHANE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

0

100

200

300

400

500

600

700

XYLENE ARAR

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

SAMPLE 9/25/1991

CONCENTRATION = 5,700 μg/L
Evaluation of Water-Chemistry Data 13

Figure 11. Median concentrations of benzene and 1,1-dichloroethane in water samples from well 

HR-2-175, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1992–2005. 

ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) 

for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, 

Inc.

Figure 12. Concentrations of benzene and 1,1-dichloroethane in water samples from well HR-2-195 Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1992–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

2

4

6

8

10

12

1992-99 2000-5/03 7/03-05

BENZENE

1,1-DICHLOROETHANE

 BENZENE ARAR

1,1-DICHLOROETHANE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

0

20

40

60

80

100

BENZENE 

1,1-DICHLOROETHANE

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

SAMPLE 11/21/1992

CONCENTRATION = 230 μg/L

BENZENE AND 

1,1-DICHLOROETHANE ARARS
14 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 13. Median concentrations of benzene, chlorobenzene, and 1,1-dichloroethane in water 

samples from well HR-2-195, Henderson Road Site, Upper Merion Township, Montgomery County, 

Pennsylvania, 1992–2008. Median concentrations of benzene and chlorobenzene were zero for 1992 

to May 2003. ARAR is the applicable or relevant and appropriate requirement that is set in the Record 

of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT 

Environmental Services, Inc.

Figure 14. Concentrations of benzene and 1,1-dichloroethane in water samples from well HR-2-295 Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1999–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

CHLOROBENZENE

BENZENE

1,1-DICHLOROETHANE

0

5

10

15

20

25

30

35

40

45

1992-5/03 6/05-2/08 

 BENZENE

 ARAR

1,1-DICHLOROETHANE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE 

1,1-DICHLOROETHANE

0

5

10

15

January

2003 January2004 January2005 January2006 January2007 January2008 January

1998 January1999 January2000 January2009 January2001 January2002

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

 BENZENE ARAR

1,1-DICHLOROETHANE ARAR
Evaluation of Water-Chemistry Data 15

HR-3 Cluster Wells and HR-26-457

During the 2006–08 shutdown test, well HR-3-280 was 

sampled quarterly; wells HR-3-255 and HR-3-295 were sampled once in May 2007 and once in February 2008. Despite 

the close proximity and similar depths of wells HR-3-255, 

HR-3-280, and HR-3-295, temporal benzene concentrations do 

not show a relation (fig. 16). Concentrations in water samples 

from all three wells exceeded the benzene ARAR during 

2003–08. For well HR-3-255, the median benzene concentration was 110 μg/L for 1991–99, increased to 292 μg/L for May 

2000 to June 2003, remained about the same (278 μg/L) for 

July 2003 to January 2007, and increased to 482 μg/L for May 

2007 to February 2008 (table 7, fig. 17).

For well HR-3-280, the median benzene concentration 

was 285 μg/L for 1991–99, decreased to 29 μg/L for January 

2000 to June 2003, increased to 39 μg/L for July 2003 to January 2007, and increased again to 182 μg/L for May 2007 to 

August 2008 (table 7, fig. 17). For well HR-3-295, the median 

benzene concentration was 85 μg/L for 1991–99, increased to 

195 μg/L for May 2000 to June 2003, decreased to 19 μg/L 

for July 2003 to July 2006, and remained about the same 

(18 μg/L) for May 2007 to February 2008 (table 7, fig. 17).

Water samples from wells HR-3-255 and HR-3-295 also 

were elevated in the other BTX (benzene, toluene, xylene) 

compounds. Forty-two percent of the water samples from 

well HR-3-255 exceeded the ARAR for toluene between July 

2003 and February 2008 (fig. 18). All water samples collected 

from well HR-3-255 between July 2003 and February 2008 

exceeded the ARAR for total xylene (table 7, fig. 19); the maximum concentration was 32,100 μg/L. For well HR-3-255, the 

median total xylene concentration was 219 μg/L for 1991–99, 

increased to 1,360 μg/L for May 2000 to June 2003, increased 

to 9,145 μg/L for July 2003 to July 2006, and decreased to 

1,955 μg/L for May 2007 to February 2008 (table 7, fig. 20). 

In general, concentrations of total xylene have declined since 

2003 but remained substantially above the ARAR.

Water samples from wells HR-3-255 and HR-3-295 often 

exceeded the chlorobenzene ARAR during 2003–08 (fig. 21). 

Water samples from well HR-3-280 were below the chlorobenzene ARAR for most samples during 2003–08 (fig. 21). 

For well HR-3-255, the median chlorobenzene concentration was 65 μg/L for 1991–99, remained about the same 

(69 μg/L) for May 2000 to June 2003, increased to 94 μg/L 

for July 2003 to January 2007, and remained about the same 

(98 μg/L) for May 2007 to February 2008 (table 7, fig. 22). 

For well HR-3-280, the median chlorobenzene concentration 

was below the ARAR for 1991–2008. For well HR-3-295, the 

median chlorobenzene concentration was 52 μg/L for 1991–

99, remained about the same (47 μg/L) for May 2000 to June 

2003, increased to 117 μg/L for July 2003 to July 2006, and 

Figure 15. Median concentrations of benzene and 1,1-dichloroethane in water samples from 

well HR-2-295 Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 

1999–2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record 

of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT 

Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

1

2

3

4

5

6

7

8

1999-5/03 6/05-2/08 

BENZENE

1,1-DICHLOROETHANE

BENZENE ARAR

1,1-DICHLOROETHANE

ARAR
16 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 16. Concentrations of benzene in water samples from wells HR-3-255, HR-3-280, and HR-3-295, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 17. Median concentrations of benzene in water samples from wells HR-3-255, HR-3-280, and 

HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. 

ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision 

(ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental 

Services, Inc.

HR-3-295

HR-3-280 

HR-3-255

0

100

200

300

400

500

1991-99 2000-6/03 7/03-1/07 5/07-8/08

CONCENTRATION, IN MICROGRAMS PER LITER 

 BENZENE

ARAR

HR-3-295

HR-3-280 

HR-3-255

0

100

200

300

400

500

600

January

2003

January

2004

January

2005

January

2006

January

2007

January

2008

January

2009

CONCENTRATION, IN MICROGRAMS PER LITER 

 BENZENE ARAR

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06
Evaluation of Water-Chemistry Data 17

Figure 18. Concentrations of toluene in water samples from wells HR-3-255 and HR-3-295, Henderson Road Site, 

Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 19. Concentrations of total xylene in water samples from wells HR-3-255 and HR-3-295, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. The ARAR (the applicable or relevant and 

appropriate requirement) for xylene is 175 micrograms per liter. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). 

Data provided by RT Environmental Services, Inc.

TOLUENE ARAR

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

January

2003 July2003 January2004 July2004 January2005 July2005 January2006 July2006 January2007 July2007 January2008 July2008

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03 STOP 

PUMPING

START 7/17/06

PUMPING

12/12/03

HR-3-295

HR-3-255

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

January

2003 July2003 January2004 July2004 January2005 July2005 January2006 July2006 January2007 July2007 January2008 July2008

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

HR-3-295

HR-3-255
18 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 20. Median concentrations of total xylene in water samples from wells HR-3-255 and HR-3-295, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008 ARAR is 

the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for 

the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, 

Inc.

Figure 21. Concentrations of chlorobenzene in water samples from wells HR-3-255, HR-3-280, and HR-3-295, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the 

applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. 

Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

500

1,000

1,500

2,000

1991-99 2000-6/03 7/03-1/07 5/07-2/08

HR-3-255

HR-3-295 

MEDIAN = 9,145

TOTAL XYLENE

 ARAR

CHLOROBENZENE

 ARAR

HR-3-295

HR-3-280 

HR-3-255

0

60

120

180

240

January

2003 January2004 January2005 January2006 January2007 January2008 January2009

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06
Evaluation of Water-Chemistry Data 19

decreased to 8.6 μg/L for July 2007 to February 2008 (table 7, 

fig. 22).

For more than a year prior to the start of the June 2003 

shutdown test, the concentrations of 1,1-DCA in water 

samples from wells HR-3-255, HR-3-280, and HR-3-295 

were below the ARAR. During the June 2003 shutdown test, 

three of six water samples (50 percent) from well HR-3-255 

exceeded the ARAR; the maximum concentration was 

14 μg/L. Concentrations of 1,1-DCA in water samples from 

wells HR-3-280 and HR-3-295 were below the ARAR. When 

the extraction wells began pumping at the reduced rate in 

December 2003, the concentration of 1,1-DCA in water samples increased to a peak of 599 μg/L on February 24, 2004, 

for well HR-3-255 (fig. 23); increased to a peak of 68 μg/L on 

November 5, 2004, for well HR-3-280 (fig. 24); and increased 

to a peak of 135 μg/L on April 6, 2004, for well HR-3-295. 

Concentrations of 1,1-DCA in samples from all three wells 

have decreased since 2004. The concentration of 1,1-DCA in 

two water samples collected in 2007–08 from wells HR-3-255 

and HR-3-280 were below the ARAR. Three of four water 

samples (75 percent) collected from well HR-3-280 exceeded 

the ARAR for 1,1-DCA for May 2007 to February 2008 

(fig. 24).

For well HR-3-255, the median 1,1-DCA concentration 

was 5.7 μg/L for 1991–99, decreased to 1.1 μg/L for January 2000 to June 2003, increased to 93 μg/L for July 2003 to 

July 2006, and decreased to 1.1 μg/L for May 2007 to February 2008 (table 7, fig. 25). For well HR-3-280, the median 

1,1-DCA concentration was 114 μg/L for 1991–99, decreased 

to 4.3 μg/L for November 2000 to June 2003, increased to 

9.4 μg/L for July 2003 to January 2007, and increased again 

to 14 μg/L for May 2007 to August 2008. For well HR-3-295, 

the median 1,1-DCA concentration was 5.7 μg/L for 1991–99, 

decreased to 1.2 μg/L for May 2000 to June 2003, and 

remained about the same for July 2003 to July 2006 (2.5 μg/L) 

and May 2007 to February 2008 (1.9 μg/L) (table 7, fig. 25).

For more than a year prior to the start of the June 2003 

shutdown test and during the shutdown, the concentrations of 

1,2-DCA in water samples from wells HR-3-255, HR-3-280, 

and HR-3-295 were below the ARAR. When the extraction 

wells began pumping at the reduced rate in December 2003, 

the concentration of 1,2-DCA in water samples increased to a 

peak of 172 μg/L on February 24, 2004, for well HR-3-255; 

increased to a peak of 10.8 μg/L on February 2, 2005, for well 

HR-3-280; and increased to a peak of 27 μg/L on April 6, 

2004, for well HR-3-295 (fig. 26). Concentrations of 1,1-DCA 

in water samples from all three wells have decreased since 

Figure 22. Median concentrations of chlorobenzene in water samples from wells HR-3-255, HR-3-280, 

and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 

1991–2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record 

of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT 

Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

 CHLOROBENZENE

 ARAR

0

30

60

90

120

1991-99 2000-6/03 7/03-1/07 5/07-8/08

HR-3-295

HR-3-280 

HR-3-255
20 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 23. Concentrations of 1,1-dichloroethane, 1,2-dichloroethane, and cis-1,2-dichloroethene in water samples from well 

HR-3-255, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 24. Concentrations of 1,1-dichloroethane in water samples from wells HR-3-280 and HR-3-295, Henderson Road Site, 

Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data 

provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

100

200

300

400

500

600

January

2003 January2004 January2005 January2006 January2007 January2008

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

1,1-DICHLOROETHANE

1,2-DICHLOROETHANE

CIS-1,2-DICHLOROETHENE

January

2009

1,1-DICHLOROETHANE AND

1,2-DICHLOROETHANE ARAR

CIS-1,2-DICHLOROETHENE ARAR

HR-3-295

HR-3-280 

0

50

100

150

January

2003 January2004 January2005 January2006 January2007 January2008 January2009

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

1,2-DICHLOROETHANE

 ARAR
Evaluation of Water-Chemistry Data 21

Figure 25. Median concentrations of 1,1-dichloroethane in water samples from wells HR-3-255, 

HR-3-280, and HR-3-295, Henderson Road Site, Upper Merion Township, Montgomery County, 

Pennsylvania, 1991–2008. ARAR is the applicable or relevant and appropriate requirement that is set in 

the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided 

by RT Environmental Services, Inc.

Figure 26. Concentrations of 1,2-dichloroethane in water samples from wells HR-3-280 and HR-3-295, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the 

applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site 

(U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

1,1-DICHLOROETHANE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

0

25

50

75

100

125

1991-99 2000-6/03 7/03-1/07 5/07-8/08

HR-3-295

HR-3-280 

HR-3-255

HR-3-295

HR-3-280 

 1,2-DICHLOROETHANE ARAR

0

5

10

15

20

25

30

January

2003 January2004 January2005 January2006 January2007 January2008 January2009

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03
22 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

2005; samples collected in 2007–08 were below the ARAR 

(fig. 27).

Concentrations of ethylbenzene in water samples from 

wells HR-3-255 and HR-3-295 increased during the 2003 

shutdown test (fig. 28). The concentration of ethylbenzene 

in water samples from well HR-3-255 increased to a peak of 

7,490 μg/L on September 30, 2003, and the concentration of 

ethylbenzene in water samples from well HR-3-295 increased 

to a peak of 8,160 μg/L on July 30, 2003. The median concentration of ethylbenzene in water samples from well HR-3-255 

was greatest during July 2003 to July 2006 and exceeded the 

ARAR during that time (fig. 29).

Vinyl chloride concentrations increased substantially 

in water samples from wells HR-3-255, HR-3-280, and 

HR-3-295 following the restart of pumping in December 2003 

and then began to decline (fig. 30). From December 2003 to 

August 2008, the ARAR for vinyl chloride was exceeded for 

16 of 20 water samples (80 percent) from well HR-3-255. 

Concentrations of vinyl chloride in water samples collected 

from wells HR-3-255 and HR-3-295 since December 2003 

were higher than those collected during 1991 to November 

2003 when the extraction wells were pumped at the full rate 

(table 7).

Well HR-26-457 is in close proximity to the HR-3 well 

cluster. During the 2006–08 shutdown test, well HR-26-457 

was sampled once in May 2007 and once in February 2008. 

Chlorobenzene concentrations in water samples from well 

HR-26-457 for 2003–07 were highly variable and exceeded 

the ARAR some of the time (fig. 31). Benzene concentrations 

were below the ARAR during the June 2003 shutdown test, 

rose above the ARAR after the start of pumping at the reduced 

rate, and exceeded the ARAR for 75 percent of the samples. 

Median concentrations of benzene and chlorobenzene have 

decreased with time; however, median concentrations of benzene were above the ARAR (fig. 32).

Figure 27. Median concentrations of 1,2-dichloroethane in water samples from wells HR-3-255 and 

HR-3-280, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. 

Median concentrations of 1,2-dichloroethane were zero for 1991 to June 2003 and May 2007 to August 

2008 for well HR-3-255. The meidan concentrations of 1,2-dichloroethane were zero for May 2007 to August 

2008 for well HR-3-280. ARAR is the applicable or relevant and appropriate requirement that is set in the 

Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT 

Environmental Services, Inc.

HR-3-280 

HR-3-255

0

5

10

15

20

25

1991-99 2000-6/03 7/03-1/07 5/07-8/08

CONCENTRATION, IN MICROGRAMS PER LITER 

1,2-DICHLOROETHANE ARAR
Evaluation of Water-Chemistry Data 23

Figure 29. Median concentrations of ethylbenzene in water samples from wells HR-3-255 and HR-3-295, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. The 

median concentration of ethylbenzene was zero for July 2003 to July 2006 for well HR-3-295. ARAR is the 

applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site 

(U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 28. Concentrations of ethylbenzene in water samples from wells HR-3-255 and HR-3-295, Henderson Road Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and appropriate requirement that 

is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental 

Services, Inc.

 ETHYLBENZENE ARAR

HR-3-295

HR-3-255

0

200

400

600

800

1,000

1991-99 2000-6/03 7/03-7/06 5/07-2/08

CONCENTRATION, IN MICROGRAMS PER LITER 

 ETHYLBENZENE ARAR

HR-3-295

HR-3-255

 0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

January

2003 January2004 January2005 January2006 January2007 January2008

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

2009
24 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 30. Concentrations of vinyl chloride in water samples from wells HR-3-255, HR-3-280, and HR-3-295, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 31. Concentrations of benzene and chlorobenzene in water samples from well HR-26-457, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

VINYL CHLORIDE ARAR

HR-3-295

HR-3-280 

HR-3-255

0

20

40

60

80

100

120

140

January

2003 July2003 January2004 July2004 January2005 July2005 January2006 July2006 January2007 July2007 January2008 July2008

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

BENZENE 

CHLOROBENZENE

BENZENE ARAR

0

40

80

120

160

CHLOROBENZENE

 ARAR

January

2003 July2003 January2004 July2004 January2005 July2005 January2006 July2006 January2007 July2007 January2008 July2008

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03
Evaluation of Water-Chemistry Data 25

HR-4 Cluster Wells

During the 2006–08 shutdown test, well HR-4-295 was 

sampled quarterly. Wells HR-4-195 and HR-4-242 were not 

sampled for the 2006–08 shutdown test but were sampled during and after the June 2003 shutdown test. Water samples from 

well HR-4-242 did not exceed the ARARs. Water samples 

from well HR-4-195 did not exceed the ARAR for 1,1-DCA 

during 2003–06; however, this ARAR was exceeded during 

1991–93 and once in 2001 (fig. 33).

Water samples from well HR-4-295 exceeded the ARAR 

for benzene twice during 2003 (fig. 34). Since 2003, benzene 

concentrations have been decreasing. Benzene concentrations 

were greater prior to 1998 than after 1998 (fig. 35). For well 

HR-4-295, the median benzene concentration was 5.5 μg/L 

for 1991–99, decreased to 2.4 μg/L for November 2000 to 

June 2003, increased to 3.3 μg/L for June 2003 to January 

2007, and decreased to 1 μg/L for May 2007 to August 2008 

(table 7, fig. 36).

Thirteen out of 15 (87 percent) water samples from well 

HR-4-295 exceeded the ARAR for 1,1-DCA during November 

2003 to May 2007 (fig. 37). Since September 2007, the concentrations of 1,1-DCA in water samples from well HR-4-295 

have been below the ARAR. For well HR-4-295, the median 

1,1-DCA concentration was 3 μg/L for 1991–99, remained 

about the same (3.2 μg/L) for November 2000 to June 2003, 

increased to 7.4 μg/L for June 2003 to January 2007, and 

decreased to 4.5 μg/L for May 2007 to August 2008 (table 7, 

fig. 36).

The concentrations of 1,2-DCA in water samples from 

well HR-4-295 exceeded the ARAR following the June 2003 

and July 2006 shutdowns (fig. 38). Concentrations of 1,2-DCA 

have been below the ARAR since May 2007. For well 

HR-4-295, the median 1,2-DCA concentration was 0 μg/L for 

1991–99, remained about the same (0.7 μg/L) for November 

2000 to June 2003, increased to 5.2 μg/L for June 2003 to 

January 2007, and decreased to 0.3 μg/L for May 2007 to 

August 2008 (table 7, fig. 36).

Figure 32. Median concentrations of benzene and chlorobenzene in water samples from well HR-26-457, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1992–2008. ARAR is the 

applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site 

(U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

20

40

60

80

1992-1999 2000-6/03 7/03-2008

BENZENE

CHLOROBENZENE

BENZENE

 ARAR

CHLOROBENZENE ARAR
26 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 33. Concentrations of 1,1-dichloroethane in water samples from wells HR-4-195 and HR-4-295, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 34. Concentrations of benzene in water samples from wells HR-4-195 and HR-4-295, Henderson Road Site, 

Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data 

provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

HR-4-295 

HR-4-195

0

15

30

45

1,1-DICHOROETHANE ARAR

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

0

1

2

3

4

5

6

BENZENE ARAR

HR-4-295 

HR-4-195

January

2003 January2004 January2005 January2006 January2007 January2008

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

2009
Evaluation of Water-Chemistry Data 27

Figure 35. Concentrations of benzene in water samples from wells HR-4-195 and HR-4-295, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 36. Median concentrations of benzene, 1,1-dichloroethane, and 1,2-dichloroethane in water samples 

from well HR-4-295, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–

2008. Median concentration of 1,2-dichloroethane was zero for 1991-99. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

1

2

3

4

5

6

7

8

1991-99 2000-6/03 6/03-1/07 5/07-8/08

 BENZENE

1,1-DICHLOROETHANE

 1,2-DICHLOROETHANE

 BENZENE ARAR

1,1-DICHLOROETHANE ARAR

 1,2-DICHLOROETHANE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

0

20

40

60

140

BENZENE ARAR

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

HR-4-295 

HR-4-195
28 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 37. Concentrations of 1,1-dichloroethane, and 1,2-dichloroethane in water samples from well HR-4-295, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 38. Concentrations of 1,2-dichloroethane in water samples from well HR-4-295, Henderson Road Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data 

provided by RT Environmental Services, Inc.

1,1-DICHLOROETHANE

 ARAR

1,2-DICHLOROETHANE

 ARAR

0

5

10

15

January

2003 January2004 January2005 January2006 January2007 January2008 January2009

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

 1,2-DICHLOROETHANE ARAR

0

2

4

6

8

10

12

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03
Evaluation of Water-Chemistry Data 29

HR-6 Cluster Wells and HR-24-476

Wells HR-6-241, HR-6-377, and HR-24-476 were 

sampled quarterly during the 2006–08 shutdown test; 

well HR-6-141 was sampled once in 1999 and five times 

in 2007–08. The first water sample collected from well 

HR-6-241 was in May 2003. For May 2007 to August 2008, 

all six water samples from well HR-6-377 and five of the six 

(83 percent) water samples from well HR-6-241 exceeded 

the benzene ARAR (figs. 39 and 40). For well HR-6-241, 

the benzene concentration increased to above the ARAR 

during the 2003 shutdown test and then decreased to below 

the ARAR when pumping resumed. The benzene concentration increased to above the ARAR following the July 2006 

shutdown and remained above the ARAR except for the 

September 2007 sample (figs. 40 and 41). Concentrations of 

benzene in water samples from well HR-6-377 generally were 

greater for 2003–08 than for 1991–2002, and concentrations 

of benzene in water samples from well HR-24-476 generally 

were less for 2003–08 than for 1991–2002 (fig. 41). For well 

HR-6-377, the median benzene concentration was 23 μg/L for 

1991–99, decreased to 8.6 μg/L for November 2000 to June 

2003, increased to 231 μg/L for July 2003 to January 2007, 

and decreased to 129 μg/L for May 2007 to August 2008 

(table 7, fig. 42). For well HR-24-476, the median benzene 

concentration was 23 μg/L for 1991–99, decreased to 0.7 μg/L 

for March 2000 to May 2003, increased to 2 μg/L for August 

2003 to January 2007, and remained about the same (2.2 μg/L) 

for May 2007 to August 2008 (table 7, fig. 42).

For May 2007 to August 2008, all six water samples from 

wells HR-6-241 and HR-24-476 exceeded the chlorobenzene 

ARAR (table 7, fig. 43). Three out of five (60 percent) water 

samples from well HR-6-141 exceeded the chlorobenzene 

ARAR. Chlorobenzene concentrations were substantially 

greater after the June 2003 shutdown than before the shutdown. Since the start of the 2006–08 shutdown test, chlorobenzene concentrations in water samples from wells HR-6-241 

and HR-24-476 have been above the ARAR (fig. 43).

For well HR-6-377, the median chlorobenzene concentration was 11 μg/L for 1991–99, decreased to 7.1 μg/L for 

January 2000 to June 2003, increased to 50 μg/L for July 

2003 to January 2007, and decreased to 43 μg/L for May 

2007 to August 2008 (table 7, fig. 44). For well HR-24-476, 

the median chlorobenzene concentration was 12 μg/L for 

1991–99, decreased to 2.1 μg/L for November 2000 to May 

2003, increased to 52 μg/L for August 2003 to January 2007, 

and increased again to 104 μg/L for May 2007 to August 2008 

(table 7, fig. 44).

Figure 39. Concentrations of benzene in water samples from well HR-6-377, Henderson Road Site, Upper Merion Township, 

Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and appropriate requirement that is set in the 

Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, 

Inc.

January

2003 January2004 January2005 January2006 January2007 January2008 January2009

CONCENTRATION, IN MICROGRAMS PER LITER 

0

50

100

150

200

250

300

350

400

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

BENZENE ARAR
30 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 40. Concentrations of benzene in water samples from wells HR-6-141, HR-6-241,and HR-24-476, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc.

Figure 41. Concentrations of benzene in water samples from wells HR-6-241, HR-6-377, and HR-24-476, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

BENZENE ARAR

HR-6-241

HR-24-476

HR-6-141

0

10

20

30

40

50

January

2003 January2004 January2005 January2006 January2007 January2008 January2009

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

0

100

200

300

400

500

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

HR 6-241

HR-6-377 

HR-24-476

BENZENE ARAR
Evaluation of Water-Chemistry Data 31

Figure 42. Median concentrations of benzene in water samples from wells HR-6-377 and HR-24-476, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is 

the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the 

site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 43. Concentrations of chlorobenzene in water samples from wells HR-6-141, HR-6-241, HR-6-377, and 

HR-24-476, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is 

the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. 

Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

BENZENE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

0

60

120

180

240

1991−99 2000−6/03 7/03−1/07 5/07−8/08

HR-6-377 

HR-24-476

0

30

60

90

120

150

180

CHLOROBENZENE

 ARAR

HR-6-241

HR-6-377 

HR-24-476

HR-6-141

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 
32 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

HR-7 Cluster Wells

During the 2006–08 shutdown test, well HR-7-383 was 

sampled quarterly, and wells HR-7-163 and HR-7-278 were 

sampled once in May 2007 and once in February 2008. Well 

HR-7-278 was sampled 11 times since 1998. Water samples 

from well HR-7-278 exceeded the benzene ARAR three times 

prior to October 2003 and the chlorobenzene ARAR once 

(72 μg/L on September 29, 1998).

Since the start of the June 2003 shutdown test, the 

benzene concentration in water samples from well HR-7-383 

exceeded the benzene ARAR (fig. 45). Benzene concentrations 

in water samples from well HR-7-163 exceeded the ARAR 

during the June 2003 shutdown test and fell below the ARAR 

before the end of the test; concentrations have remained below 

the ARAR since then. For well HR-7-383, the median benzene 

concentration was 12 μg/L for 1998 to May 2003, increased 

to 60 μg/L for October 2003 to July 2006, and decreased to 

54 μg/L for May 2007 to February 2008 (table 7, fig. 46). 

For well HR-7-163, the median benzene concentration was 

80 μg/L for 1991–97, decreased to 0.1 μg/L for 1998 to June 

2003, increased to 7.6 μg/L for July 2003 to July 2006, and 

decreased to 4.5 μg/L for May 2007 to February 2008 (table 7, 

fig. 46).

The chlorobenzene concentration in water samples 

from well HR-7-383 began to increase in October 2006 and 

exceeded the ARAR in September 2007 (fig. 47). Median 

chlorobenzene concentrations in water samples from well 

HR-7-383 have been increasing (fig. 48). For well HR-7-383, 

the median chlorobenzene concentration was 7.1 μg/L for 

1998 to May 2003, increased to 24 μg/L for October 2003 to 

January 2007, and increased to 82 μg/L for May 2007 to February 2008 (table 7, fig. 48). Since 2000, the chlorobenzene 

concentration in water samples from well HR-7-163 exceeded 

the ARAR only once (62 μg/L on May 10, 2007).

Figure 44. Median concentrations of chlorobenzene in water samples from wells HR-6-377 and 

HR-24-476, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. 

ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision 

(ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental 

Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

CHLOROBENZENE ARAR

HR-6-377 

HR-24-476

0

30

60

90

120

1991-99 2000-6/03 7/03-1/07 5/07-5/08
Evaluation of Water-Chemistry Data 33

Figure 45. Concentrations of benzene in water samples from wells HR-7-163, HR-7-278, and HR-7-383, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1998–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc.

Figure 46. Median concentrations of benzene in water samples from wells HR-7-163, HR-7-278, and 

HR-7-383, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1998–2008. 

ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for 

the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

0

20

40

60

80

1998-5/03 10/03-1/07 5/07-8/08

CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE

 ARAR

HR-7-383

HR-7-278

HR-7-163

0

30

60

90

120

150

January

2003 January

2004 January2005 January

2006 January

2007 January

2008 January

1998 January1999 January

2000 January2009 January2001 January

2002

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

HR-7-383

HR-7-278 

HR-7-163

CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE

 ARAR
34 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 47. Concentrations of chlorobenzene in water samples from wells HR-7-163, HR-7-278, and HR-7-383, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1998–2008. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

Figure 48. Median concentrations of chlorobenzene in water samples from wells HR-7-163, HR-7-278, 

and HR-7-383, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 

1998–2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record 

of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT 

Environmental Services, Inc.

HR-7-383

HR-7-278

HR-7-163

0

30

60

90

1998-5/03 10/03-1/07 5/07-8/08

CONCENTRATION, IN MICROGRAMS PER LITER 

CHLOROBENZENE ARAR

0

30

60

90

120

CHLOROBENZENE ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

January

2003 January

2004 January2005 January2006 January2007 January

2008 January

1998 January1999 January2000 January2009 January

2001 January

2002

HR-7-383

HR-7-278 

HR-7-163 STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03
Evaluation of Water-Chemistry Data 35

HR-9 Cluster Wells

Wells HR-9-191 and HR-9-333 were not sampled during 

the 2006–08 shutdown test. Well HR-9-333 was sampled six 

times during 1998–2005; the water samples did not exceed 

the ARARs. Water samples from well HR-9-191 exceeded the 

ARAR for 1,1-DCA following the June 2003 shutdown test 

(fig. 49). Vinyl chloride concentrations in water samples from 

well HR-9-191 exceeded the ARAR in 1997. Vinyl chloride 

concentrations increased in 2005 (fig. 50).

HR-12 Cluster Wells

Wells HR-12-150 and HR-12-300 were not sampled 

during the 2006–08 shutdown test. Well HR-12-150 was 

sampled only twice (April 22, 1999, and April 16, 2001). 

Water samples from well HR-12-150 exceeded ARARs for 

benzene, 1,1-DCA, vinyl chloride, and total xylene in 1999 

and exceeded the ARAR for 1,1-DCA in 2001 (table 7). Well 

HR-12-300 was sampled 19 times during 2003–06. Seventeen 

of the 19 (89 percent) water samples exceeded the ARAR 

for 1,1-DCA (fig. 51); the median 1,1-DCA concentration 

was 10 μg/L (table 7). The concentration of benzene in water 

samples from well HR-12-300 generally exceeded the ARAR 

during the June 2003 shutdown test and exceeded the ARAR 

for four of nine samples (44 percent) since the end of the test 

(fig. 51).

HR-14 Cluster Wells

During the 2006–08 shutdown test, well HR-14-376 was 

sampled quarterly, and well HR-14-178 was sampled once 

in May 2007 and once in February 2008. Since the start of 

the June 2003 shutdown test, well HR-14-178 exceeded the 

ARAR for 1,1-DCA twice (fig. 52). The median concentration of 1,1-DCA in water samples from well HR-14-178 was 

0 μg/L for 1993–99, increased to 2.7 μg/L for November 2000 

to May 2003, decreased to 1.3 μg/L for October 2003 to July 

2006, and increased to 5.7 μg/L for May 2007 to February 

2008 (table 7).

All water samples from well HR-14-376 exceeded the 

benzene ARAR, except for one sample collected on October 

30, 2003 (fig. 53). Only 10 percent of water samples from 

well HR-14-376 exceeded the chlorobenzene ARAR (fig. 53). 

About 8 months after the December 2003 start of pumping at 

the reduced rate, benzene and chlorobenzene concentrations 

increased and then decreased (fig. 53).

 Median benzene and chlorobenzene concentrations in 

water samples from well HR-14-376 have been decreasing 

(table 7, fig. 54). For well HR-14-376, the median benzene 

concentration was 50 μg/L for 1998 to June 2003, decreased 

to 28 μg/L for July 2003 to January 2007, and decreased to 

13 μg/L for May 2007 to August 2008. For well HR-14-376, 

the median chlorobenzene concentration was 26 μg/L for 1998 

to June 2003, decreased to 21 μg/L for July 2003 to January 

2007, and decreased to 8.9 μg/L for May 2007 to August 2008.

Figure 49. Concentrations of 1,1-dichloroethane in water samples from well HR-9-191, Henderson Road Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 1992–2005. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data 

provided by RT Environmental Services, Inc.

1,1-DICHLOROETHANE

 ARAR

0

5

10

15

20

25

30

35

40

45

50

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 
36 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 50. Concentrations of vinyl chloride in water samples from well HR-9-191, Henderson Road Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 1992–2005. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data 

provided by RT Environmental Services, Inc.

Figure 51. Concentrations of benzene and 1,1-dichloroethane in water samples from well HR-12-300, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–06. ARAR is the applicable or relevant 

and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). Data provided by RT Environmental Services, Inc.

 VINYL CHLORIDE ARAR

0

2

4

6

8

10

12

14

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE 

1,1-DICHLOROETHANE

 BENZENE ARAR

1,1-DICHLOROETHANE ARAR

0

5

10

15

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

January

2003 July2003 January2004 July2004 January2005 July2005 January2006 July2006 January2007 July2007 January2008 July2008
Evaluation of Water-Chemistry Data 37

Figure 52. Concentrations of benzene and 1,1-dichloroethane in water samples from well HR-14-178, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1993–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc.

Figure 53. Concentrations of benzene and chlorobenzene in water samples from well HR-14-376, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1998–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

5

10

15

20

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

BENZENE 

1,1-DICHLOROETHANE (1,1-DCA)

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

BENZENE ARAR

1,1-DCA ARAR 

CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE ARAR

CHLOROBENZENE ARAR

0

20

40

60

80

100

January

2003 January2004 January2005 January2006 January2007 January2008 January

1998 January1999 January

2000 January

2009 January2001 January

2002

BENZENE 

CHLOROBENZENE

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03
38 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Well HR-18-190

During the 2006–08 shutdown test, well HR-18-190 was 

sampled quarterly. During 2003–08, water samples from well 

HR-18-190 exceeded the ARAR for 1,1-DCA much of the 

time (fig. 55). The TCE concentration, although below the 

ARAR, usually exceeded the USEPA maximum contaminant 

level (MCL) of 5 μg/L. Concentrations of 1,1-DCA and TCE 

were about the same after the June 2003 shutdown as before 

the shutdown (fig. 56). For well HR-18-190, the median 

1,1-DCA concentration was fairly stable; it was 6.2 μg/L for 

1992–99, 4.8 μg/L for May 2000 to May 2003, 6.1 μg/L for 

October 2003 to January 2007, and 5.5 μg/L for May 2007 

to August 2008 (table 7, fig. 57). The median TCE concentration was 7.1 μg/L for 1992–99, decreased to 2.9 μg/L for 

May 2000 to June 2003, increased to 9.7 μg/L for July 2003 

to January 2007, and remained about the same (9.3 μg/L) for 

May 2007 to August 2008 (fig. 57).

Well RE-205

During the 2006–08 shutdown test, well RE-205 was 

sampled once in May 2007 and once in February 2008; water 

samples did not exceed the ARARs. Concentrations of benzene and chlorobenzene in water samples from well RE-205 

exceeded the ARARs following the June 2003 shutdown 

(fig. 58). Median concentrations of benzene, chlorobenzene, 

and 1,1-DCA generally have been decreasing with time 

(table 7, fig. 59).

Off-Site Downgradient Wells

Off-site downgradient wells include wells HR-5-195, 

HR-11-133, HR-10-180, HR-17-170, HR-22-300, HR-23-350, 

and HR-30-318. Locations of these wells are shown on 

figure 3. No off-site downgradient well sampled during 

2003–08 exceeded the ARARs.

Well HR-22-300 was sampled four times during 1999–

2001, once in 2005, and quarterly during the 2006–08 shutdown test. For 1999–2001, the benzene ARAR was exceeded 

for three of four samples (75 percent) (fig. 60). For 2005–08, 

the benzene concentration was below the ARAR and was 

below the detection limit for the last seven samples. Concentrations of chlorobenzene, 1,1-DCA, and 1,2-DCA increased 

after the start of the 2006–08 shutdown test and then began 

to decline (fig. 60). Comparing the 1999–2001 samples with 

the 2005–08 samples, median concentrations of benzene and 

chlorobenzene decreased and median concentrations of 1,1-

DCA and 1,2-DCA increased (fig. 61).

Figure 54. Median concentrations of benzene and chlorobenzene in water samples from well HR-14-376, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1998–2008. ARAR is 

the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the 

site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

0

20

40

60

1998−6/03 7/03−1/07 5/07−8/08

CHLOROBENZENE

BENZENE

BENZENE

 ARAR
Evaluation of Water-Chemistry Data 39

Figure 55. Concentrations of 1,1-dichoroethane and trichloroethylene in water samples from well HR-18-190, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 2003–08. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). The ARAR for trichloroethylene is 25.8 micrograms per liter. Data provided by RT 

Environmental Services, Inc.

Figure 56. Concentrations of 1,1-dichoroethane and trichloroethylene in water samples from well HR-18-190, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1992–2008. ARAR is the applicable 

or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental 

Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

1,1-DICHLOROETHANE (1,1-DCA)

TRICHLOROETHYLENE

1,1-DCA ARAR

0

5

10

15

20

CONCENTRATION, IN MICROGRAMS PER LITER 

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

2003 January2004 January2005 January2006 January2007 January2008 January

2009

0

5

10

15

20

25

30

1,1-DICHLOROETHANE (1,1-DCA)

TRICHLOROETHYLENE

 1,1-DCA

 ARAR

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

TRICHLOROETHYLENE ARAR
40 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 57. Median concentrations of trichloroethylene and 1,1-dichloroethane in water samples from 

well HR-18-190, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 

1992–2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of 

Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). The ARAR for trichloroethylene 

is 25.8 micrograms per literData provided by RT Environmental Services, Inc.

Figure 58. Concentrations of benzene and chlorobenzene in water samples from well RE-205, Henderson Road 

Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. ARAR is the applicable or relevant and 

appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 

1988a). Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

TRICHLOROETHYLENE

1,1-DICHLOROETHANE (1,1-DCA)

0

5

10

15

1992−99 5/2000−5/03 10/03−1/07 5/07−8/08

 1,1-DCA ARAR

BENZENE 

CHLOROBENZENE

CHLOROBENZENE

 ARAR

0

60

120

180

240

300

January

1991

January

1993

January

1995

January

1997

January

1999

January

2001

January

2003

January

2005

January

2007

January

2009

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

CONCENTRATION, IN MICROGRAMS PER LITER 

BENZENE

 ARAR
Evaluation of Water-Chemistry Data 41

Figure 59. Median concentrations of benzene, chlorobenzene, and 1,1-dichloroethane in water samples 

from well RE-205, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 

1991–2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of 

Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). The ARAR for chlorobenzene is 

60 micrograms per liter. Data provided by RT Environmental Services, Inc.

Figure 60. Concentrations of benzene, chlorobenzene, 1,1-dichloroethane, and 1,2-dichloroethane in water samples 

from well HR-22-380, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1999–2008. 

ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the 

site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. The ARAR for 

chlorobenzene is 60 micrograms per liter. CONCENTRATION, IN MICROGRAMS PER LITER 

1,1-DICHLOROETHANE

CHLOROBENZENE

BENZENE

10

15

0

5

20

25

1991−99 2000−6/03 7/03−7/06 5/07−2/08

BENZENE

 ARAR

1,1-DICHLOROETHANE

 ARAR

CONCENTRATION, IN MICROGRAMS PER LITER 

0

5

10

15

20

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

January

1999

January

2001

January

2002

January

2003

January

2004

January

2005

January

2006

January

2007

January

2008

January

2000

January

2009

BENZENE 

CHLOROBENZENE

1,2-DICHLOROETHANE

BENZENE

ARAR 

1,1-DICHLOROETHANE

ARAR

1,2-DICHLOROETHANE

ARAR

1,1-DICHLOROETHANE
42 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Upgradient Wells

Upgradient wells include wells HR-1-260, HR-1-276, 

HR-1-280, HR-15-255, and HR-20-155. Locations of these 

wells are shown on figure 3. Only well HR-20-155 was 

sampled during the 2006–08 shutdown test. The concentration 

of total VOCs was less than 2 μg/L during 2006–08.

Areal Distribution of Volatile Organic 

Compounds

The areal distribution of benzene, chlorobenzene, 

chloroethane, 1,1-DCA, cis-1,2-DCA, vinyl chloride, and total 

xylene was evaluated using data from February and March 

2008 because more wells were sampled for that time period 

than for other dates. All wells, except wells HR-6-377 and 

HR-24-476, were sampled February 25–29; well HR-6-377 

was sampled on March 25, and well HR-24-476 was sampled 

on March 28, 2008. Data for February and March 2008 for 

these compounds are given in table 4. Changes in constituent 

concentrations between pre-shutdown samples collected in 

July 2006 and samples collected in February and March 2008 

are given in table 5.

The highest concentrations of benzene measured in 

water samples in February and March 2008 were from wells 

HR-3-255 (513 μg/L), HR-3-280 (178 μg/L), HR-6-377 

(133 μg/L), and HR-7-383 (56 μg/L) (table 4, fig. 62). The 

approximate area where the benzene ARAR was exceeded and 

the approximate area affected by benzene contamination are 

shown on figure 62. The benzene plume appears to extend in 

a northwestern direction from the source area (fig. 62). The 

source area, as used in this report, is the area around the injection well and the HR-3 well cluster. The map indicates the 

benzene has moved toward the north, but no monitor wells are 

directly north of the HR-6 and HR-7 well clusters. The downgradient extent of the benzene plume is unknown. Concentrations of benzene appear to be somewhat depth related, and the 

plume appears to be dipping to the north (fig. 63). The greatest 

changes in benzene concentration between the pre-shutdown 

samples collected in July 2006 and the samples collected 

in February and March 2008 were for wells HR-3-255 (an 

increase of 164 μg/L), HR-7-383 (an increase of 37 μg/L), 

the injection well (an increase of 26 μg/L), and HR-3-280 (a 

decrease of 79 μg/L) (table 5, fig. 64).

The highest concentrations of chlorobenzene measured in 

water samples in February and March 2008 were from wells 

HR-6-141 (145 μg/L), HR-6-241 (102 μg/L), HR-24-276 

(97 μg/L), HR-3-255 (95 μg/L), and HR-7-383 (87 μg/L) 

Figure 61. Median concentrations of benzene, chlorobenzene, 1,1-dichloroethane, and 

1,2-dichloroethane in water samples from well HR-22-380, Henderson Road Site, Upper Merion Township, 

Montgomery County, Pennsylvania, 1999–2008. ARAR is the applicable or relevant and appropriate 

requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection 

Agency, 1988a). The ARAR for chlorobenzene is 60 micrograms per liter. The median concentration of 

benzene was zero for July 2005 to August 2008. Data provided by RT Environmental Services, Inc. CONCENTRATION, IN MICROGRAMS PER LITER 

CHLOROBENZENE

BENZENE

1,1-DICHLOROETHANE

1,2-DICHLOROETHANE

0

1

2

3

4

5

6

7

8

9

4/1998−4/2001 7/2005−8/2008

BENZENE

ARAR 1,1-DICHLOROETHANE

ARAR

1,2-DICHLOROETHANE

ARAR
Evaluation of Water-Chemistry Data

43

Table 4. Concentrations of selected volatile organic compounds in ground-water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008.[ARAR, applicable or relevant and appropriate requirements; Concentrations in micrograms per liter; concentrations above ARAR are in bold type]

Compound ARAR

HR-2-195 HR-2-295 HR-3-255 HR-3-280 HR-3-295 HR-4-295 HR-5-195 HR-6-141 HR-6-241 HR-6-377

2/26/08 2/26/08 2/27/08 2/28/08 2/27/08 2/29/08 2/26/08 2/25/2008 2/25/2008 3/25/2008

Benzene 5.52 50 3 513 178 16 1 0 3.3 12 133

Chlorobenzene 60 16 3.2 95 28 10.9 2 2.6 145 102 43

Chloroethane 19,000 197 4.2 79 180 17 1.8 0 .83 43 4.1

1,1-Dichloroethane 5.06 2.1 7.1 .6 25 1.7 4.4 1.1 0 .39 0

cis-1,2-Dichloroethane 70 .73 1.8 0 .27 .46 .37 .32 0 0 0

Vinyl chloride 2 .74 1.1 0 .58 0 .75 0 0 0 0

Total xylene 175 82 .53 1,730 0 3.6 0 0 0 0 .51

Compound ARAR

HR-7-163 HR-7-278 HR-7-383 HR-10-180 HR-14-178 HR-14-376 HR-17-170 HR-18-190 HR-20-155 HR-22-300

02/28/08 2/28/08 2/28/08 2/29/08 2/26/08 2/26/2008 2/27/2008 2/29/2008 2/25/2008 2/27/2008

Benzene 5.52 4.8 3.4 56 0 0 14 0 0 0 0

Chlorobenzene 60 24 47 87 0 .44 10 0 .99 0 .21

Chloroethane 19,000 0 0 52 0 0 9.4 0 0 0 0

1,1-Dichloroethane 5.06 .68 .92 .56 0 5.4 8.4 0 9.5 0 2.4

cis-1,2-Dichloroethane 70 0 0 .32 0 3.6 .31 0 3.7 0 0

Vinyl chloride 2 0 0 0 0 0 0 0 .44 0 0

Total xylene 175 0 0 0 0 0 0 0 .92 0 0

Compound ARAR

HR-24-476 HR-26-457 HR-30-318 RE-205 Injection 

well

3/28/08 2/27/08 2/27/08 2/27/08 2/27/08

Benzene 5.52 1.5 21 0 0.93 36

Chlorobenzene 60 97 8.3 .53 3.6 46

Chloroethane 19,000 0 28 0 .35 53

1,1-Dichloroethane 5.06 .26 1.5 1.4 1.8 1.4

cis-1,2-Dichloroethane 70 0 .61 .48 .74 .95

Vinyl chloride 2 0 .32 0 1.1 .86

Total xylene 175 0 2.3 0 0 185
44 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 5. Change in concentration of selected volatile organic compounds between July 2006 and February and March 2008, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania. [Change given in micrograms per liter; ND, compound not detected in either sample; —, unable to compute statistic] Compound HR-2-195 HR-2-295 HR-3-255 HR-3-280 HR-3-295 HR-4-295 Change Percent change Change Percent change Change Percent change Change Percent change Change Percent change Change Percent change Benzene 18.9 61 -0.50 -14 164 47 -79 -31 8.1 100 -3.0 -75 Chlorobenzene -3.2 -17 .8 33 -4.3 -4 -51 -65 -8.3 -43 -2.9 -59 1,1-Dichloroethane 1.6 357 1.0 16 -1.9 -76 20 410 -.30 -15 -1.7 -28 cis-1,2-Dichloroethene .37 103 .10 6 -1.3 -100 -1.3 -83 -.54 -54 -.83 -69 Ethylbenzene 41 227 -.60 -100 -619 -95 -.39 -46 -.59 -49 ND ND Toluene 11 329 -1.3 -84 -447 -90 6.0 316 -.75 -68 ND ND Vinyl chloride .4 118 .10 10 -1 -100 -.72 -55 -.33 -100 -.45 -38 Total xylenes 37 83 -.08 -13 -1,410 -45 -278 -100 -3.1 -46 ND ND Compound HR-5-195 HR-6-241 HR-6-377 HR-7-163 HR-7-278 HR-7-383 Change Percent change Change Percent change Change Percent change Change Percent change Change Percent change Change Percent change Benzene ND ND 11 2,188 5.0 4 4.8

— -0.10 -3 37 198

Chlorobenzene 1.7 177 99 3,190 9.6 29 21 770 43 1,080 74 579

1,1-Dichloroethane -.20 -15 -2.1 -84 ND ND .4 143 -.58 -39 -.02 -3

cis-1,2-Dichloroethene -.18 -36 -.95 -100 ND ND ND ND -.77 -100 .09 39

Ethylbenzene ND ND ND ND -.09 -20 ND ND ND ND .31

—

Toluene ND ND .63

— -.20 -15 ND ND .02

— .97 422

Vinyl chloride ND ND -.64 -100 ND ND ND ND -.56 -100 ND ND

Total xylenes ND ND ND ND -.04 -7 ND ND ND ND ND ND
Evaluation of Water-Chemistry Data

45

Table 5. Change in concentration of selected volatile organic compounds between July 2006 and February and March 2008, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania. —Continued[Change given in micrograms per liter; ND, compound not detected in either sample; —, unable to compute statistic]

Compound

HR-10-180 HR-14-178 HR-14-376 HR-17-170 HR-18-190 HR-20-155

Change Percent change Change Percent change Change Percent change Change Percent change Change Percent change Change Percent change

Benzene ND ND ND ND -2.3 -14 ND ND ND ND ND ND

Chlorobenzene ND ND -0.04 -8 -18 -64 ND ND -0.61 -38 ND ND

1,1-Dichloroethane ND ND 3.7 218 6.2 282 ND ND 1.5 19 -0.51 -100

cis-1,2-Dichloroethene ND ND 3.1 567 .31 — ND ND 1.9 106 ND ND

Ethylbenzene ND ND ND ND ND ND ND ND ND ND ND ND

Toluene -0.43 -100 ND ND -.07 -20 ND ND ND ND ND ND

Vinyl Chloride ND ND ND ND ND ND ND ND -.17 -28 ND ND

Total Xylenes ND ND ND ND ND ND ND ND .92 — ND ND

Compound

HR-22-300 HR-24476 HR-25-325 HR-26-457 RE-205 Injection well

Change Percent 

change

Change Percent 

change

Change Percent 

change

Change Percent 

change

Change Percent 

change

Change Percent 

change

Benzene -0.46 -100 1.5 — -0.99 -100 5.2 22 -15 -94 26 253Chlorobenzene .21 — 95 3,958 -.27 -100 -63 -88 -51 -93 9.7 271,1-Dichloroethane 1.7 264 -1.0 -80 0 ND -.5 -21 -.7 -28 -.90 -39

cis-1,2-Dichloroethene ND ND -.75 -100 0 ND -.5 -42 -.36 -33 -.05 -5

Ethylbenzene ND ND ND ND 0 ND .9 15 -5.2 -100 56 1,114

Toluene ND ND ND ND -3.7 -100 77 6,425 -.63 -45 102 8,483

Vinyl Chloride ND ND ND ND ND ND .52 — 1.1 — .50 139Total Xylenes ND ND ND ND ND ND -19 -59 -28 -100 165 844
46 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 62. Concentrations of benzene measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Cross section along generalized line of section A-B is shown on figure 63. Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20”

40°

05'

20”

40°

05'

15”

40°

05'

10”

75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

36

0

50

3

178

513 16

3.3

0.9

0

1

12

21

0

4.8

3.4 133

56

0

0

0

14

0

0

1.5

A

B

LOCATION OF WELL AND BENZENE  CONCENTRATION, IN MICROGRAMS PER  LITER - Bold number indicates concentration above ARAR OF 5.52BENZENE CONCENTRATION  EXCEEDING ARARAPPROXIMATE EXTENT OF BENZENE 

A GENERALIZED LINE OF SECTION

50

513

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 133

APPROXIMATE SITEBOUNDARY

B

75°21'30”
Evaluation of Water-Chemistry Data 47

DISTANCE FROM THE INJECTION WELL, IN FEET

B

A

DEPTH, IN FEET BELOW LAND SURFACE

0 100 200 300 400 500 600 0

50

100150200250300350400450500

100

 12

0

133

 3.3

1.5

56

178

513

100

10 36

513

100

HR-3-255 WELL-IDENTIFICATION NUMBER

CLAY AND SURFICIAL MATERIAL

VOID

LIMESTONE AND/OR DOLOMITE

SCREENED OR OPEN INTERVAL

MEASURED WATER LEVEL

CONCENTRATION OF BENZENE, IN MICROGRAMS PER LITERCONCENTRATION CONTOUR, IN MICROGRAMS PER LITER –  Contour interval variable

500

16

HR-3-280 IW HR-3-295 HR-3-255

HR-7-383

HR-24-476

HR-6-141

HR-6-377 HR-6-241 HR-30-318

Figure 63. Concentrations of benzene measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Cross section along generalized line of section A-B is shown on figure 63. Data provided by RT Environmental Services, Inc.
48 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 64. Change in benzene concentration measured between July 2006 and February 2008 in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania. Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0

-0.5

0

0

11 5

1.5

0

-0.5

26

-15

8.1

164

-79

19

5.2

37

-0.1

4.8

-2.3

0

-3

0

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. ( 2005)

LOCATION OF WELL AND CHANGE IN BENZENE CONCENTRATION, IN  MICROGRAMS PER LITER

19

164

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 37

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Chemistry Data 49

(table 4, fig. 65). The approximate area where the chlorobenzene ARAR was exceeded and the approximate area affected 

by chlorobenzene contamination are shown on figure 65. A 

much larger area is affected by chlorobenzene than benzene. 

The chlorobenzene plume appears to extend northwest and 

north from the source area (fig. 65). The greatest concentrations of chlorobenzene are near and beyond the site boundary away from the source area (figs. 65 and 66). The map 

indicates chlorobenzene has moved toward the north, but no 

monitor wells are directly north of the HR-6 and HR-7 well 

clusters. The downgradient extent of the chlorobenzene plume 

is unknown. The greatest changes in chlorobenzene concentration between the pre-shutdown samples collected in July 

2006 and the samples collected in February and March 2008 

were for wells HR-6-241 (an increase of 99 μg/L), HR-24-476 

(an increase of 95 μg/L), HR-7-383 (an increase of 74 μg/L), 

HR-7-278 (an increase of 43 μg/L), HR-26-457 (a decrease of 

63 μg/L), HR-3-280 (a decrease of 51 μg/L), and RE-205 (a 

decrease of 51 μg/L) (table 5, fig. 67). Chlorobenzene concentrations decreased in the source area and increased at the 

northern site boundary at well clusters HR-6 and HR-7.

The highest concentrations of 1,1-DCA measured in 

water samples in February and March 2008 were from wells 

HR-3-280 (25 μg/L), HR-18-190 (9.5 μg/L), HR-14-376 

(8.4 μg/L), and HR-2-295 (7.1 μg/L) (table 4, fig. 68); the 

ARAR was exceeded in water samples from these wells. 

Increases in 1,1-DCA concentration between the pre-shutdown 

samples collected in July 2006 and the samples collected in 

February 2008 (19 months after the shutdown) ranged from 

0.4 to 20 μg/L. The greatest increases were measured in 

water samples from wells HR-3-280 (20 μg/L), HR-14-376 

(6.2 μg/L), and HR-14-178 (3.7 μg/L). The approximate area 

where the 1,1-DCA ARAR was exceeded and the approximate area affected by 1,1-DCA contamination are shown on 

figure 68. The area affected by 1,1-DCA appears to extend 

east-northeast from the source area (fig. 68). It is possible that 

the source of 1,1-DCA in water from well HR-18-190 is from 

the landfill south of the well.

Concentrations of TCE and PCE were below the ARAR 

for all water samples for 2003–08; however, breakdown products of TCE and PCE exceeded ARARs for 2003–08. Anaerobic bacteria convert PCE to TCE by reductive dechlorination. 

By the same process, TCE is reduced to cis-1,2-DCE and 

trans-1,2-DCE, which are reduced to vinyl chloride. For water 

samples collected on the Henderson Road Site during 1991–

2008, the TCE and PCE concentrations generally were below 

the detection limit. A water sample collected from the injection 

well in June 1979 contained 1,200 μg/L TCE and 2,900 μg/L 

PCE (BCM Engineers, 1988, p. 85), a water sample collected 

from well HR-2-175 in June 1986 contained 610 μg/L TCE 

and 291 μg/L PCE (BCM Engineers, 1988, p. 89), and a water 

sample collected from well HR-2-195 in June 1986 contained 

140 μg/L TCE and 9,800 μg/L PCE (BCM Engineers, 1988, 

p. 89). It appears that biodegradation has substantially reduced 

concentrations of TCE and PCE.

The highest concentrations of cis-1,2-DCA measured in 

water samples in February and March 2008 were from wells 

HR-18-190 (3.7 μg/L) and HR-14-178 (3.6 μg/L) (table 4, 

fig. 69). Concentrations of cis-1,2-DCA measured during February and March 2008 did not exceed the ARAR. The approximate area affected by cis-1,2-DCA contamination is shown on 

figure 69. The area affected by cis-1,2-DCA appears to extend 

north and northeast from the source area (fig. 69).

The highest concentrations of vinyl chloride measured in 

water samples in February and March 2008 were from wells 

HR-2-295 (1.1 μg/L) and RE-205 (1.1 μg/L) (table 4, fig. 70). 

Concentrations of vinyl chloride measured during February 

and March 2008 did not exceed the ARAR. The approximate 

area affected by vinyl chloride contamination is shown on figure 70. The area affected by vinyl chloride appears to extend 

east-northeast from the source area (fig. 70).

The highest concentrations of total xylene measured in 

water samples in February and March 2008 were from wells 

HR-3-255 (1,730 μg/L), the injection well (185 μg/L), and 

HR-2-195 (82 μg/L) (table 4, fig. 71); water samples from 

wells HR-3-255 and the injection well exceeded the ARAR 

for total xylene. The greatest change in total xylene concentration between the pre-shutdown samples collected in July 2006 

and the samples collected in February 2008 (19 months after 

the shutdown) was an increase of 165 μg/L in water samples 

from the injection well and a decrease of 1,410 μg/L in water 

samples from well HR-3-255. The approximate area where the 

total xylene ARAR was exceeded and the approximate area 

affected by xylene are shown on figure 71. The area affected 

by xylene appears to mainly extend east-northeast from the 

source area (fig. 71).

The concentration maps appear to show two overlapping plumes (fig. 72), a benzene-chlorobenzene plume and 

a PCE/TCE breakdown-products plume. The benzenechlorobenzene plume extends northeast and northwest from 

the source area. The PCE/TCE breakdown products plume 

extends east and northeast from the source area.
50 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 65. Concentrations of chlorobenzene measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Cross section along generalized line of section A-B is hsown on figure 66. Data provided by RT Environmental Services, Inc.

APPROXIMATE SITEBOUNDARY

A

B

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

87

0

97

11

2

2.6

145

102

46

24

47

0

0

1

10

LOCATION OF WELL AND CHLOROBENZENE  CONCENTRATION, IN MICROGRAMS PER  LITER - Bold number indicates concentration above ARAR OF 60CHLOROBENZENE CONCENTRATION  EXCEEDING ARARAPPROXIMATE EXTENT OF  CHLOROBENZENE 

A

B GENERALIZED LINE OF SECTION

46

102

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 97

95 3.2

8.3

16

3.6

28

43

0.4

0.5

0.2

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Chemistry Data

51

DISTANCE FROM THE INJECTION WELL, IN FEET B A

DEPTH, IN FEET BELOW LAND SURFACE

0 100 200 300 400 500 600 0

50

100150200250300350400450500

100

 102

0.5

43

 145

97

87

28

95

50

100

10

50

10

46

145

100

HR-3-255 WELL-IDENTIFICATION NUMBER

SCREENED OR OPEN INTERVALCONCENTRATION OF CHLOROBENZENE, IN MICROGRAMS PER LITERCONCENTRATION CONTOUR, IN MICROGRAMS PER LITER –  Contour interval variable

VOID

CLAY AND SURFICIAL MATERIALLIMESTONE AND/OR DOLOMITE

WATER LEVEL

11

IW HR-3-295 HR-3-255 HR-3-280 HR-7-383 HR-24-476

HR-6-141

HR-6-377 HR-6-241 HR-30-318

Figure 66. Concentrations of chlorobenzene in water samples from wells along section A-B, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). The ARAR for chlorobenzene is 60 micrograms per liter. Generalized line of section A-B is shown on figure 65. Data provided by RT Environmental Services, Inc.
52 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 67. Change in chlorobenzene concentration measured between July 2006 and February 2008 in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania. Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0

0.2

1.7

0

99 9.6

95

0

0.8

-51

9.7

-4.3

-8.3

-51

-3.2

-63

74

43

21

-18

0

-2.9

-0.6

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental, Inc. (2005)

LOCATION OF WELL AND CHANGE IN CHLOROBENZENE CONCENTRATION, IN MICROGRAMS PER LITER

9.7

99

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 95

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Chemistry Data

53

Figure 68. Concentrations of 1,1-dichloroethane measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20”

75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

8.4

5.4

4.4

0.4

2.1

0

7.1

1.1

0

1.4

0.61.7

0.6

1.5

0

0

9.5

0.9

0.7

2.4

0

1.4

1.8

0.3

APPROXIMATE SITEBOUNDARY

1,1-DICLOROETHANE CONCENTRATIONS EXCEEDING ARAR

APPROXIMATE EXTENT OF 

1,1-DICHLOROETHANE

LOCATION OF WELL AND 1,1-DICLOROETHANE

CONCENTRATION, IN MICROGRAMS PER LITER - Bold number indicatesconcentration above ARAR of 5.06

2.1

25

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 8.4

25

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
54 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 69. Concentrations of cis-1,2-dichloroethene measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

0.7

0.6

0.7

1.8

3.6

0.3

0.5

1

3.7

0.4

0.3

0 0

0

0

0

0.3

0.5

0

0.3

0

0

0

0

0

APPROXIMATE EXTENT OF 

CIS-1,2-DICHLOROETHENE 

LOCATION OF WELL AND CIS-1,2-DICHLOROETHENE CONCENTRATION, IN MICROGRAMS

PER LITER

3.6

1.8

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 0.3

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Chemistry Data

55

Figure 70. Concentrations of vinyl chloride measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. Data provided by RT Environmental Services, Inc.

APPROXIMATE SITEBOUNDARY

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.6

1.1

0.9

1.1

0.7

0.4

0.8

0.3

0

0

0

APPROXIMATE EXTENT OF 

VINYL CHLORIDE

LOCATION OF WELL AND VINYL CHLORIDE

CONCENTRATION, IN MICROGRAMSPER LITER

0.41.1

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 0.3

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
56 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 71. Concentrations of total xylene measured in water samples from wells, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. Data provided by RT Environmental Services, Inc.

APPROXIMATE SITEBOUNDARY

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

0.9

0

0

0

0.5 0 0

3.6

0

0.5

2.3

82 185 1,730

0

0 0

0

0

0

0

0

0

0

0

LOCATION OF WELL AND TOTAL XYLENEAPPROXIMATE EXTENT OF XYLENE 

CONCENTRATION, IN MICROGRAMSPER LITER

82

1,730

SHALLOW WELLINTERMEDIATE-DEPTH WELLDEEP WELL 2.3

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Chemistry Data

57

Figure 72. Generalized approximate extent of area exceeding ARARs, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. 2007

GENERALIZED APPROXIMATE EXTENT OF BENZENE-  CHLOROBENZENE PLUME EXCEEDING ARARs 

GENERALIZED APPROXIMATE EXTENT OF TRICHLOROETHYLENE BREAKDOWN PRODUCTS

PLUME EXCEEDING ARARs

AREA OF OVERLAP

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
58 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Evaluation of Water-Level Data

Water-level data for the Henderson Road Site were 

provided by RT Environmental Services, Inc. for May 1997 

through August 2008. The datum is a site benchmark at well 

HR-2-295, and water-level altitudes are referenced to that 

benchmark and reported in feet above mean sea level (see note 

on Conversion Factors page). Water-level data were evaluated 

temporally for 1997–2008 and spatially for June 16, 2003; 

July 10, 2006; and February 25–29, 2008. Water-level data for 

selected dates are given in table 6.

Water levels measured in Chester Valley were compared 

to water levels measured in USGS observation wells in Montgomery (well MG-917) and Bucks (well BK-1020) Counties 

(fig. 73). The USGS wells were plotted on figure 73 with an 

arbitrary datum; however, the range of fluctuation with respect 

to the Y-axis is correct. Water-level measurements made in the 

Upper Merion Reservoir on file at Aqua Pennsylvania, Inc. 

indicate that large drawdowns in the Upper Merion Reservoir 

occurred during droughts in 1998 and 2001. A long period of 

water-level recovery followed the drought of 2001. The hydrographs for the USGS observation wells do not show the same 

extended water-level recovery from drought as the water levels in the Chester Valley. For the drought of 2001, water levels 

in Chester Valley, except for McCoy Quarry monitor well 

MW-4 and well HR-17-170, show a protracted recovery from 

September 2001 until June 2005 (46 months). Water levels 

in wells MW-1 and MW-2 on the eastern side of the McCoy 

Quarry and water levels in wells at the Henderson Road Site, 

except for well HR-17-170, show the same extended recovery. 

This indicates the water level in the Upper Merion Reservoir 

affects water levels at the Henderson Road Site, except for 

well HR-17-170.

Temporal Changes in Water Levels

Water-level hydrographs for wells at the Henderson 

Road Site are presented for May 1997 through August 2008 

(figs. 74–79). Not all wells were measured for each point in 

time. For most wells, only one water-level measurement was 

available between February 1, 2004, and July 10, 2006. A few 

wells had two water-level measurements during this 30-month 

period.

HR-3 Cluster Wells and HR-26-457

The HR-3 well cluster includes wells HR-3-255, 

HR-3-280, and HR-3-295. Well HR-26-457 is in close proximity to the HR-3 well cluster. Water levels in the HR-3 well 

cluster and well HR-26-457 reflect the regional rise in water 

levels during and after the June 2003 shutdown test (fig. 74). 

Water levels measured on June 16, 2003, prior to the start of 

the June 2003 shutdown test, were compared to water levels measured February 25–29, 2008; the water level in well 

HR-3-280 was 23.5 ft higher, the water level in well HR-3-295 

was 23.76 ft higher, and the water level in well HR-26-457 

was 27.95 ft higher in February 2008 than on June 16, 2003. 

In February 2008, the water level in well HR-3-295 was 

1.88 ft lower than the water level in well HR-3-280 and 1.36 ft 

lower than the water level in well HR-26-457.

HR-4 Cluster Wells

The HR-4 well cluster includes wells HR-4-195, 

HR-4-242, and HR-4-295. Data were available for well 

HR-4-242 from December 29, 2003, to September 13, 2005, 

only. The water levels in wells HR-4-195 and HR-4-295 

reflect the regional rise in water levels during and after the 

June 2003 shutdown test (fig. 75). Water levels measured on 

June 16, 2003, prior to the start of the 2003 shutdown test, 

were compared to water levels measured February 25–29, 

2008; the water level in well HR-4-195 was 25.44 ft higher, 

and the water level in well HR-4-295 was 25.25 ft higher in 

February 2008 than on June 16, 2003. Water levels in wells 

HR-4-195 and HR-4-242 were within 0.3 ft of each other in 

February 2008; the water level in well HR-4-295 was about 

2 ft lower.

HR-6 Cluster Wells and HR-24-476

The HR-6 well cluster includes wells HR-6-141, 

HR-6-241, and HR-6-377. Well HR-24-476 is in close proximity to the HR-6 well cluster. Few water-level data were 

available for wells HR-6-241 and HR-24-276. The water level 

in well HR-6-377 reflects the regional rise in water levels 

during and after the June 2003 shutdown test (fig. 76). The 

water level measured in well HR-6-377 on June 16, 2003, 

prior to the start of the 2003 shutdown test, was compared to 

the water level measured February 25–29, 2008; the water 

level was 24.27 ft higher in February 2008 than on June 16, 

2003. In February 2008, the water level in well HR-6-141 was 

1.81, 1.18, and 1.05 ft lower than the water levels in wells 

HR-6-241, HR-6-377, and HR-24-476, respectively.

HR-7 Cluster Wells

The HR-7 well cluster includes wells HR-7-163, 

HR-7-278, and HR-7-383. No data were available for well 

HR-7-383 prior to December 29, 2003. The water level in 

wells HR-7-163 and HR-7-278 reflect the regional rise in 

water levels during and after the June 2003 shutdown test 

(fig. 77). Water levels measured on June 16, 2003, prior to 

the start of the 2003 shutdown test, were compared to water 

levels measured February 25–29, 2008; the water level in well 

HR-7-163 was 23.66 ft higher, and the water level in well 

HR-7-278 was 24.09 ft higher in February 2008 than on June 

16, 2003. In February 2008, the water level in well HR-7-383 

was 2.09 ft lower than the water level in well HR-7-163 and 

0.38 ft lower than the water level in well HR-7-278. The water 

levels indicate a downward hydraulic gradient at the HR-7 

well cluster.
Evaluation of Water-Level Data 59

Table 6. Elevation of water level measured in wells at the Henderson Road Site, Upper Merion Township, Montgomery County, 

Pennsylvania, for selected dates 2003–08.

[—, no measurement]

Wellidentification 

number

Date of water-level measurment Change in 

water level

between 

6/16/03 and 

2/27/08

(feet)

6/16/03 12/9/03 12/29/03 7/10/06 2/27/08 8/20/08

Water level, in feet above mean sea level

HR-1-260 — — — — 53.41 — —

HR-1-276 30.31 36.19 — 53.63 52.04 50.01 21.73

HR-1-280 — — — — 51.88 — —

HR-2-175 29.61 39.56 43.41 — 51.34 — 21.73

HR-2-195 — — — — 51.54 50.08 —

HR-2-295 26.01 36.83 39.65 45.53 49.91 48.44 23.90

HR-3-255 25.17 37.12 19.96 46.72 — — —

HR-3-280 26.82 37.76 39.72 47.92 50.32 49.07 23.50

HR-3-295 24.68 36.28 25.91 48.19 48.44 47.01 23.76

HR-4-195 17.05 28.33 31.73 42.05 42.49 — 25.44

HR-4-242 — — 26.50 — 42.79 — —

HR-4-295 15.34 25.98 30.06 40.94 40.59 38.46 25.25

HR-5-195 -6.10 6.74 — 19.00 16.41 14.38 22.51

HR-6-141 — — — — 47.01 45.32 —

HR-6-241 — — 37.58 46.73 45.20 43.61 —

HR-6-377 22.11 34.40 35.22 47.43 46.38 44.86 24.27

HR-7-163 24.95 35.86 37.79 47.10 48.61 47.23 23.66

HR-7-278 22.00 32.66 35.66 47.73 46.09 44.59 24.09

HR-7-383 — — 36.12 47.03 45.71 44.06 —

HR-9-191 22.80 33.29 48.50 48.35 47.04 25.55

HR-9-333 — — — — 35.94 — —

HR-10-280 — — — — 35.29 — —

HR-12-150 — — 36.64 50.97 — —

HR-12-300 20.93 33.25 36.30 48.10 49.25 48.26 28.32

HR-13-147 28.43 37.43 34.40 48.37 50.03 48.91 21.60

HR-14-178 21.41 34.22 35.64 46.86 46.77 45.20 25.36

HR-14-376 21.49 30.94 35.84 47.07 46.42 44.92 24.93

HR-15-255 — — 43.06 — 51.63 — —

HR-17-170 27.20 26.33 — 28.30 28.09 27.81 .89

HR-18-190 — — — — 48.69 46.23 —

HR-19-160 — — — — 53.26 — —

HR-20-155 — — — — 56.12 54.77 —

HR-22-380 — — — — 17.77 15.65 —

HR-23-350 — — — — 34.27 32.56 —

HR-24-476 — — — — 46.25 44.89 —

HR-25-325 — — — — 50.18 47.14 —

HR-26-457 21.85 35.69 33.17 — 49.80 48.34 27.95

HR-30-318 — — — — 36.55 34.99 —
60 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 73.

Water levels measured in wells HR-4-295, HR-6-377, and HR-17-170 at the Henderson Road Site; wells MW-1, MW-2, and MW-4 at the McCoy Quarry; and U.S. 

Geological Survey observation wells BK-1020 and MG-917, 1996–2008. Data provided by RT Environmental Services, Inc., and Glasgow, Inc.

McCOY MW-2

McCOY MW-4

McCOY MW-1

USGS BK-1020

USGS MG-917

HR-6-377

HR-4-295

 ELEVATION OF WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL

Lines dashed where dataare missing for some wells

HR-17-170

-20-40-60-80

0

604020

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

HR-5-195
Evaluation of Water-Level Data 61

Figure 74. Elevation of water levels measured in wells HR-3-255, HR-3-280, and HR-3-295, Henderson Road Site, 

Upper Merion Township, Montgomery County, Pennsylvania, 1997–2008. Data provided by RT Environmental Services, 

Inc.

Figure 75. Elevation of water levels measured in wells HR-4-195, HR-4-242, and HR-4-295, Henderson Road Site, Upper 

Merion Township, Montgomery County, Pennsylvania, 1997–2008. Data provided by RT Environmental Services, Inc. ELEVATION OF WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL

0

20

40

60

-20

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06

Lines dashed where data are missing

for some wells

HR-26-457

HR-3-255

HR-3-280 

HR-3-295

 ELEVATION OF WATER LEVEL, 

IN FEET ABOVE MEAN SEA LEVEL

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

HR-4-195

HR-4-242 

HR-4-295

Lines dashed where data are missing

for some wells

0

10

20

30

40

50

60

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06
62 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 76. Elevation of water levels measured in wells HR-6-141, HR-6-241, HR-6-377, and HR-24-276, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1997–2008. Data provided by RT 

Environmental Services, Inc.

Figure 77. Elevation of water levels measured in wells HR-7-163, HR-7-278, and HR-7-383, Henderson Road Site, 

Upper Merion Township, Montgomery County, Pennsylvania, 1997–08. Data provided by RT Environmental Services, 

Inc. ELEVATION OF WATER LEVEL, 

IN FEET ABOVE MEAN SEA LEVEL

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

10

20

30

40

50

60

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06

HR-6-241

HR-24-476 

HR-6-377

HR-6-141

Lines dashed where

data are missing

 ELEVATION OF WATER LEVEL, 

IN FEET ABOVE MEAN SEA LEVEL

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 0

20

40

60

80

STOP 

PUMPING

6/30/03

STOP 

PUMPING

7/17/06

START 

PUMPING

12/12/03

HR-7-383

HR-7-278 

HR-7-163

Lines dashed where

data are missing
Evaluation of Water-Level Data 63

Figure 78. Elevation of water levels measured in wells HR-6-377, HR-9-191, HR-14-178, and HR-14-378, Henderson 

Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1997–2008. Data provided by RT 

Environmental Services, Inc.

Figure 79. Elevation of water levels measured in wells HR-3-280, HR-5-195, HR-6-377, HR-17-170, and HR-22-380, 

Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1997–2008. Data provided by RT 

Environmental Services, Inc. ELEVATION OF WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

HR-14-376

HR-6-377

HR-9-191

HR-14-178

Lines dashed where

data are missing

10

20

30

40

50

60

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06

 ELEVATION OF WATER LEVEL, 

IN FEET ABOVE MEAN SEA LEVEL

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Lines dashed where data are missing

HR-17-170

HR-5-195

HR-22-300

HR-6-377

HR-3-280

-20

0

20

40

60

STOP 

PUMPING

6/30/03

START 

PUMPING

12/12/03

STOP 

PUMPING

7/17/06
64 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Other On-Site Wells

Sufficient data were available to plot hydrographs for 

wells HR-9-191, HR-14-178, and HR-14-376 (fig. 78). The 

hydrograph for well HR-6-377 is shown on figure 78 for comparison. The water level in wells HR-9-191, HR-14-178, and 

HR-14-376 reflect the regional recovery in water levels during 

and after the June 2003 shutdown test (fig. 78). Water levels 

measured on June 16, 2003, prior to the start of the 2003 shutdown test, were compared to water levels measured February 

25–29, 2008; the water level in well HR-9-191 was 25.55 ft 

higher, the water level in well HR-14-178 was 25.36 ft higher, 

and the water level in well HR-14-376 was 24.93 ft higher in 

February 2008 than on June 16, 2003.

Off-Site Wells

Few water-level data were available for off-site wells 

HR-10-180, HR-11-133, HR-19-160, HR-22-300, and 

HR-23-350. Hydrographs for wells HR-5-195 and HR-17-170 

and six available measurements for well HR-22-300 are shown 

on figure 79. The hydrograph for well HR-6-377 is shown 

on figure 79 for comparison. Water levels measured in well 

HR-17-170 did not show the regional recovery from 2001 to 

2005 that was shown by the water levels in all other wells at 

the Henderson Road site (figs. 73–79). Water levels measured 

on June 16, 2003, prior to the start of the 2003 shutdown test, 

were compared to water levels measured February 25–29, 

2008; the water level in well HR-17-170 was 0.89 ft higher 

in February 2008 than on June 16, 2003. The water-level 

fluctuations are similar to that of the McCoy Quarry monitor well MW-4 (fig. 73), which is on the southeastern side of 

the quarry (fig. 1) and does not appear to be influenced by the 

water level in the Upper Merion Reservoir. It is unlikely that 

well HR-17-170 is affected by the Upper Merion Reservoir or 

pumping at the Henderson Road Site.

Water levels in well HR-5-195 are much lower than 

water levels measured in other shallow wells; however, the 

water levels are similar to those measured in nearby deep well 

HR-22-300 (fig. 79). During drilling of well HR-5-195, 179 ft 

of clay was encountered overlying fractured bedrock. Well 

HR-5-195 may be hydraulically connected to a deeper flow 

system. Water levels measured in well HR-5-195 reflect the 

regional recovery in water levels, and the hydrograph from 

well HR-5-195 is similar to hydrographs from other Henderson Road Site wells. Water levels measured on June 16, 2003, 

prior to the start of the 2003 shutdown test, were compared to 

water levels measured February 25–29, 2008; the water level 

in well HR-5-195 was 22.51 ft higher in February 2008 than 

on June 16, 2003.

Potentiometric Surface

The potentiometric surface was contoured for (1) June 

16, 2003, when the extraction wells were pumping at the full 

rate prior to the start of the June 2003 shutdown; (2) July 10, 

2006, when the extraction wells were pumping at the reduced 

rate prior to the start of the July 2006 shutdown; and (3) February 25–29, 2008, during the 2006–08 shutdown test when 

the extraction wells were not pumping. Water levels in most 

wells on the site were measured during February 25–29, 2008. 

Except for well HR-5-195, wells were divided into shallow 

wells (less than 200 ft deep), intermediate-depth wells (200–

299 ft deep), and deep wells (greater than 299 ft deep) following the designations used by RT Environmental Services, Inc. 

(2004). Because the water level in well HR-5-195 is much 

deeper than water levels in other shallow wells and is similar 

to water levels in deep well HR-22-300, well HR-5-195 was 

grouped with the deep wells.

June 16, 2003 (Full-Pumping Rate)

The potentiometric surface was contoured for shallow 

wells (fig. 80), intermediate-depth wells (fig. 81), and deep 

wells (fig. 82) for June 16, 2003. The extraction wells were 

pumping at the former full-pumping rate. The potentiometric surface for shallow wells (fig. 80) does not appear to be 

affected by extraction-well pumping. The ground-water-flow 

direction was to the northeast and northwest. The potentiometric surface for intermediate-depth wells (fig. 81) shows a 

cone of depression caused by extraction-well pumping. The 

ground-water-flow direction was from the southwest toward 

the pumping wells and toward the northeast away from the 

pumping wells. Data for only four deep on-site wells were 

available. The available water-level data for the deep wells 

(fig. 82) show a flat gradient. The ground-water-flow direction 

was to the Henderson Road Site from the northwest.

July 10, 2006 (Reduced-Pumping Rate)

The potentiometric surface was contoured for shallow 

wells (fig. 83), intermediate-depth wells (fig. 84), and deep 

wells (fig. 85) for July 10, 2006. The recovery wells were 

pumping at the reduced rate. Water levels were measured prior 

to cessation of pumping for the 2006–08 shutdown test. Water 

levels are about 25 ft higher than those measured on June 16, 

2003. The potentiometric surface for shallow wells (fig. 83) 

does not appear to be affected by extraction-well pumping. 

The ground-water-flow direction was to the northeast. The pattern generally is similar to that when the extraction wells were 

pumping at the full rate (fig. 80). The potentiometric surface 

for intermediate-depth wells (fig. 84) does not show a cone of 

depression caused by extraction-well pumping as it did when 

the extraction wells were pumping at the full rate (fig. 81). The 

ground-water-flow direction was from the south-southwest 

toward the pumping wells and toward the northeast away from 

the pumping wells, similar to that when the extraction wells 

were pumping at the full rate. Data for only four deep on-site 

wells were available. The available water-level data for the 

deep wells (fig. 85) show a flat gradient. The ground-waterflow direction was to the northwest; this is the reverse of the 

flow direction when the extraction wells were pumping at the 

full rate.
Evaluation of Water-Level Data

65

Figure 80. Elevation of water levels measured in shallow wells (less than 200 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, June 16, 2003 (full-pumping rate). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

27.2

26.9

28.4

25.0

21.4

17.1

22.8

29.6

22

24

26

28

28

18

20

22

24

26

18 20

APPROXIMATE SITEBOUNDARY

22.8

24

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 2 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
66 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 81. Elevation of water levels measured in intermediate depth wells (200 to 299 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, June 16, 2003 (full-pumping rate). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

30.3

26.0

24.7

25.2

26.8

22.0

15.3

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

24

30

22

18 20 16

26

28

26

15.3

24

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 2 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

24

30

22

18

20

16

APPROXIMATE SITEBOUNDARY

28

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Level Data

67

Figure 82. Elevation of water levels measured in deep wells (greater than 299 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, June 16, 2003 (full-pumping rate). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

22.1

21.9 20.9

21.5

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

21

21

22

22

20.9

21

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Contour interval 1 foot. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

APPROXIMATE SITEBOUNDARY

-6.1

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
68 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 83. Elevation of water levels measured in shallow wells (less than 200 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, July 10, 2006 (reduced-pumping rate). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

28.3

48.37

47.10

46.86

42.05

48.50

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

44

48

46

48.50

44

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Contour interval 2 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

44

48

46

APPROXIMATE SITEBOUNDARY

40°

05'

20”

40°

05'

15”

40°

05'

10”

75°21'30”
Evaluation of Water-Level Data

69

Figure 84. Elevation of water levels measured in intermediate depth wells (200 to 299 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, July 10, 2006 (reduced-pumping rate). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

46.73

53.93

45.53

48.19

46.72

47.92

47.73

40.94

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

52

50

42

48

46

44

40.49

40

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 2 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

52

50

42

48

46

44

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
70 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 85. Elevation of water levels measured in deep wells (greater than 299 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, July 10, 2006 (reduced-pumping rate). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

47.43

48.1

47.03

47.07

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

48

48

19.00

APPROXIMATE SITEBOUNDARY

47

47

48.1

48

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 1 foot. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

40°

05'

20”

40°

05'

15”

40°

05'

10”

75°21'30”
Evaluation of Water-Level Data 71

February 25–29, 2008 (No Pumping)

The potentiometric surface was contoured for shallow 

wells (fig. 86), intermediate-depth wells (fig. 87), and deep 

wells (fig. 88) for February 25–28, 2008. This time period was 

chosen because water levels were measured in most wells on 

the site. The extraction wells were not pumping. The potentiometric surface for shallow wells (fig. 86) shows that the 

ground-water-flow direction was toward the north-northeast. 

The flow direction generally is similar to that when the extraction wells were pumping. Water-level altitudes are similar to 

those when the extraction wells were pumping at the reduced 

rate and about 24 ft higher than those measured on June 16, 

2003. The potentiometric surface for intermediate-depth wells 

(fig. 87) shows that the ground-water-flow direction was 

toward the north and northeast, similar to that when the extraction wells were pumping. Water-level altitudes are similar to 

those when the extraction wells were pumping at the reduced 

rate and about 24 ft higher than those measured on June 16, 

2003. Data for 12 deep wells were available. The potentiometric surface for deep wells (fig. 88) shows that the groundwater-flow direction was toward the north and northeast; this 

is the reverse of the flow direction when the extraction wells 

were pumping at the full rate (fig. 82).

Movement of Contaminants

Ground-water flow at and in the vicinity of the Henderson Road Site is through open fractures (bedding planes 

and joints) and solution features in the carbonate bedrock. 

Ground-water flow is controlled by hydraulic gradients created 

by recharge and discharge points. Because of the fractured 

nature of the bedrock, ground-water flow is unlikely to be in a 

straight line but instead follows the direction of bedding and 

fractures as it moves down the hydraulic gradient. Discharge 

points in the area include natural discharge points, such as 

the Schuylkill River, and human-made discharge points, such 

as pumping wells and quarries where water is withdrawn for 

water supply and dewatering, respectively. Differences in permeability among geologic materials also control ground-water 

movement.

Off-site wells were drilled to monitor the possible off-site 

movement of chemicals of concern. Wells HR-23-350 and 

HR-30-318 were drilled on a northwest-trending fracture (the 

northwest fracture) identified by RT Environmental Services, 

Inc. (2005, p. 7). During drilling of well HR-30-318, 296 ft 

of clay and weathered rock were encountered before competent bedrock was reached. The thick clay in the vicinity of 

well HR-30-318 may prevent contaminant migration to the 

northwest. Well HR-5-195 penetrated 179 ft of clay before 

encountering competent bedrock. It is possible that a thick 

clay north of the turnpike restricts movement of contaminants 

to the north. Well HR-10-180 was drilled approximately 

920 ft north-northwest of the injection well. Few water-level 

data were available for well HR-10-180, making it difficult to 

evaluate.

Off-site wells HR-22-300 and HR-17-170 were drilled on 

a northeast-trending fracture (the northeast fracture) identified by RT Environmental Services, Inc. (2005, p. 6). Well 

HR-5-195 appears to be drilled on a fracture that intersects 

the northeast fracture (RT Environmental Services, Inc., 2005, 

fig. 25). Water levels in well HR-5-195 are much lower than 

water levels measured in other shallow wells; however, the 

water levels are similar to those measured in nearby deep 

well HR-22-300. Well HR-5-195 may be hydraulically connected to a deeper flow system. Water levels measured in 

well HR-17-170 did not show the 2001–05 regional recovery 

shown by water levels in all other wells at the Henderson 

Road Site. The water-level fluctuations are similar to that of 

McCoy Quarry monitor well MW-4 (fig. 73), which is on the 

southeastern side of the quarry. It appears unlikely that well 

HR-17-170 is affected by the Upper Merion Reservoir or the 

Henderson Road Site. Few water levels were available for well 

HR-22-300, making it difficult to evaluate.

Benzene concentrations measured in water samples 

from shallow wells collected in February and March 2008 

were above the ARAR only in the source area (fig. 89). The 

direction of ground-water flow in the shallow zone is to the 

north-northeast (fig. 89). Benzene concentrations measured 

in water samples from intermediate-depth wells collected in 

February and March 2008 were above the ARAR in the source 

area and outside the northern site boundary northwest of the 

source area (fig. 90). The direction of ground-water flow in 

the intermediate zone is to the north-northeast and northeast 

(fig. 90). Benzene concentrations measured in water samples 

from deep wells collected in February and March 2008 were 

above the ARAR in the source area, at the northern site boundary northeast of the source area, and outside the site boundary 

north of the source area (fig. 91). The direction of groundwater flow in the deep zone is to the north-northwest, north, 

and north-northeast (fig. 91). Benzene appears to have moved 

to the north from the source area in the intermediate and deep 

zones.

Chlorobenzene concentrations measured in water samples 

from shallow wells collected in February and March 2008 are 

above the ARAR outside the northern site boundary northwest 

of the source area (fig. 92). The direction of ground-water 

flow in the shallow zone is to the north-northeast (fig. 92). 

Chlorobenzene concentrations measured in water samples 

from intermediate-depth wells collected in February and 

March 2008 were above the ARAR in the source area and 

outside the northern site boundary northwest of the source area 

(fig. 93). The direction of ground-water flow in the intermediate zone is to the north-northeast and northeast (fig. 93). Chlorobenzene concentrations measured in water samples from 

deep wells collected in February and March 2008 were above 

the ARAR at and outside the northern site boundary north of 

the source area (fig. 94). The direction of ground-water flow 

in the deep zone is to the north-northwest, north, and northnortheast (fig. 94). Chlorobenzene appears to have moved to 

the north from the source area in the shallow, intermediate, 

and deep zones.
72 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 86. Elevation of water levels measured in shallow wells (less than 200 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February 25–28, 2008 (no pumping). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

28.09

47.01

56.12

50.97

51.34

50.03

51.54

48.61

46.77

42.49

48.69

48.35

53.26

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

48

44

54

56

50

46

52

48.35

44

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows altitude of potentiometric  surface as defined by measured  water levels. Dashed where  approximately located. Contour  interval 2 feet. GENERALIZED DIRECTION OF GROUND-WATER FLOW – Arrow  points in direction of ground-water  flow.

48

44

54

56

50

46

52

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Level Data

73

Figure 87. Elevation of water levels measured in intermediate depth wells (200 to 299 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February 25–28, 2008 (no pumping). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

51.63

45.2

53.41 54.02 51.88

49.91

48.44

50.32

46.09

42.79

40.59

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

35.29

48

42

44

54

50

46

52

50.32

44

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 2 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

48

42

44

54

50

46

52

40

38

36

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
74 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 88. Elevation of water levels measured in deep wells (greater than 299 feet deep) at the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February 25–28, 2008 (no pumping). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

46.42

40

LOCATION OF WELL AND WATER LEVEL, IN FEET ABOVE MEAN  SEA LEVELPOTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 5 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

17.77

36.55

34.27

46.38

46.25

50.18

49.80 49.25

45.71

46.42 35.95

50

40

35

45

50

40

35

45

20

25

30

16.41

APPROXIMATE SITEBOUNDARY

20

25

30

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Level Data

75

Figure 89. Concentrations of benzene measured in water samples from shallow wells and generalized direction of ground-water flow, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

Base map modified from RT Environmental Services, Inc. (2005)

0

0

0

3.3

4.8

36

0

50

0 200 FEET 100

0 25 50 METERS

48

44

54

56

50

46

52

48

44

54

56

50

46

52

LOCATION OF WELL AND BENZENE  CONCENTRATION, IN MICROGRAMS PER  LITER - Bold number indicates concentration above 5.52 micrograms per liter ARARBENZENE CONCENTRATION  EXCEEDING ARAR

50

50

APPROXIMATE EXTENT OF BENZENE  MEASURED IN WATER SAMPLESPOTENTIOMETRIC CONTOUR – Shows altitude of potentiometric surface defined by measured water levels.  Dashed where approximately located.  Contour interval 2 feet. GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
76 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 90. Concentrations of benzene measured in water samples from intermediate-depth wells and generalized direction of ground-water flow, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

0

1

12

0.9

3.4

178

513

17

3 48

42

44

54

50

46

52

48

42

44

54

50

46

52

40

38

36

APPROXIMATE SITEBOUNDARY

LOCATION OF WELL AND BENZENE  CONCENTRATION IN, MICROGRAMS PER  LITER - Bold number indicates concentration above 5.52 micrograms per liter ARARBENZENE CONCENTRATION  EXCEEDING ARAR

14

50

APPROXIMATE EXTENT OF BENZENE  MEASURED IN WATER SAMPLES

POTENTIOMETRIC CONTOUR – Shows altitude of potentiometric surface as defined by measured water levels. Dashed where approximately located. Contour interval 2 feet.

GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

75°21'20”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Level Data

77

Figure 91. Concentrations of benzene measured in water samples from deep wells and generalized direction of ground-water flow, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20”

75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

0

0

133

14

56

1.5 21

50

40

35

45

50

40

35

45

20

25

30

0

APPROXIMATE SITEBOUNDARY

LOCATION OF WELL AND BENZENE  CONCENTRATION, IN MICROGRAMS PER  LITER - Bold number indicates concentration above 5.52 micrograms per liter BENZENE CONCENTRATION  EXCEEDING ARAR

14

40 POTENTIOMETRIC CONTOUR – Shows 

 altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 5 feet. 

GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

75°21'20”

40°

05'

20”

40°

05'

15”

40°

05'

10”
78 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 92. Concentrations of chlorobenzene measured in water samples from shallow wells and generalized direction of ground-water flow, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

Base map modified from RT Environmental Services, Inc. (2005)

0

16

145

46

24

0

1

10

0 200 FEET 100

0 25 50 METERS

48

44

54

56

50

46

52

48

44

54

56

50

46

52

LOCATION OF WELL AND CHLORO- BENZENE CONCENTRATION, IN  MICROGRAMS PER LITER - Bold  number indicates concentration aboveCHLOROBENZENE CONCENTRATION  EXCEEDING ARAR

60 micrograms per liter ARAR

145

POTENTIOMETRIC CONTOUR – Shows  altitude of potentiometric surface as  defined by measured water levels.  Dashed where approximately located.  Contour interval 2 feet. 

50

APPROXIMATE EXTENT OF CHLORO- BENZENE MEASURED IN WATER  SAMPLESGENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

APPROXIMATE SITEBOUNDARY

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Evaluation of Water-Level Data

79

Figure 93. Concentrations of chlorobenzene measured in water samples from intermediate-depth wells and generalized direction of ground-water flow, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

3.2 9528

11

2

102

48

0

3.6

48

42

44

54

50

46

52

48

42

44

54

50

46

52

40

38

36

LOCATION OF WELL AND CHLOROBENZENE  CONCENTRATION, IN MICROGRAMS PER  LITER - Bold number indicates concentration above 60 micrograms per literCHLOROBENZENE CONCENTRATION  EXCEEDING ARAR

95

POTENTIOMETRIC CONTOUR – Shows altitude of potentiometric surface as defined by measured water levels. Dashed where approximately located. Contour interval 2 feet.

50

APPROXIMATE EXTENT OF CHLOROBENZENE  MEASURED IN WATER SAMPLESGENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

0

APPROXIMATE SITEBOUNDARY

PENNSYLVANIA TURNPIKE

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
80 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

Figure 94. Concentrations of chlorobenzene measured in water samples from deep wells and generalized direction of ground-water flow, Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, February and March 2008. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.

PENNSYLVANIA TURNPIKE

HENDERSON ROAD

75°21'20” 75°21'10”

0 200 FEET 100

0 25 50 METERS

Base map modified from RT Environmental Services, Inc. (2005)

87

43

97

0.4

0.2

0.5

8.3

50

40

35

45

50

40

35

45

20

25

30

2.6

APPROXIMATE SITEBOUNDARY

LOCATION OF WELL AND CHLOROBENZENE  CONCENTRATION, IN MICROGRAMS PER  LITER - Bold number indicates concentration above 60 micrograms per literCHLOROBENZENE CONCENTRATION  EXCEEDING ARAR

97

50

APPROXIMATE EXTENT OF CHLOROBENZENE  MEASURED IN WATER SAMPLESPOTENTIOMETRIC CONTOUR – Shows altitude of potentiometric surface as defined by measured water levels. Dashed where approximately located. Contour interval 5 feet.GENERALIZED DIRECTION OF GROUND- WATER FLOW – Arrow points in direction of ground-water flow.

75°21'30”

40°

05'

20”

40°

05'

15”

40°

05'

10”
Summary and Conclusions 81

Concentrations of benzene and chlorobenzene above the 

ARARs were measured in water samples from the HR-6 and 

HR-7 well clusters at and near the northern site boundary on 

the south side of the Pennsylvania Turnpike (figs. 89 through 

94). Potentiometric-surface maps indicate the direction of 

ground-water flow from these well clusters is to the north; 

however, no off-site monitor wells are located directly north 

of these well clusters on the north side of the Pennsylvania 

Turnpike. Off-site well HR-10-180 is 180 ft deep and is about 

580 ft north of the HR-6 well cluster. Only three water levels 

were available for well HR-10-180 from 1997 to 2008; the 

depth to water was 138.52 ft in February 2008. The depth of 

water-bearing zones in well HR-10-180 is unknown. Well 

HR-10-180 may be too shallow to intercept contamination 

from the Henderson Road Site. Additional monitor well clusters north of well clusters HR-6 and HR-7 on the north side of 

the Pennsylvania Turnpike could help determine how far benzene and chlorobenzene have moved offsite and could be used 

to better define ground-water-flow directions north of the site.

Summary and Conclusions

Two shutdown-rebound tests were conducted from 2003 

to 2008 at the Henderson Road Site to determine whether 

concentrations of selected volatile organic compounds (VOCs) 

would stabilize or otherwise change when the extraction 

wells stopped pumping. A long-term shutdown-rebound test 

began on July 17, 2006. The U.S. Geological Survey (USGS) 

conducted this study for the U.S. Environmental Protection 

Agency (USEPA) in support of this test to determine the 

effects of shutting down the extraction wells on concentrations 

of selected contaminants and water levels. Concentrations 

were compared to ARARs (applicable relevant and appropriate requirements), which were set as remediation goals in the 

Henderson Road Site Record of Decision.

Wells at the Henderson Road Site have been sampled for 

VOCs since 1991. For 25 wells sampled in 2008, ARARs were 

exceeded for benzene (10 wells), chlorobenzene (5 wells), 

1,1-dichloroethane (1,1-DCA) (4 wells), and total xylene 

(2 wells). Water samples from off-site downgradient wells 

sampled during 2003–08 did not exceed ARARs. Chemical 

concentration maps show two overlapping plumes, a benzenechlorobenzene plume and a PCE/TCE (tetrachloroethylene/

trichloroethylene) breakdown-products plume. The benzenechlorobenzene plume extended northeast and northwest from 

the source area, and the PCE/TCE breakdown-products plume 

extended east and northeast from the source area; this plume 

may receive some input from the former landfill on the Henderson Road Site.

Water from 10 wells sampled in 2008 exceeded the 

5.52 μg/L ARAR for benzene. Concentrations of benzene 

exceeding the ARAR were measured in water samples from 

wells in and near the source area (injection well, HR-2-195, 

HR-3-255, HR-3-280, and HR-3-295) and to the north 

(HR-7-383), northeast (HR-14-376), and northwest (HR-6-241 

and HR-6-377) of the source area. The highest benzene 

concentrations measured in water samples from wells away 

from the source area were for wells HR-6-377 (133 μg/L) 

and HR-7-383 (56 μg/L). Benzene concentrations increased 

in water samples from wells HR-6-241 and HR-7-383. The 

greatest changes in benzene concentration between pre-shutdown samples collected in July 2006 and samples collected 

in February and March 2008 (19 months after the shutdown) 

were for source-area wells HR-3-255 and the injection well 

and wells north of the source area (HR-6 and HR-7 well 

clusters, except well HR-7-278); increases in benzene concentration ranged from 1.5 to 164 μg/L. The greatest increases 

in benzene concentration were in water samples from wells 

HR-3-255 (164 μg/L), HR-7-383 (37 μg/L), injection well 

(26 μg/L), and HR-6-241 (11 μg/L). Benzene appears to have 

moved from the source area to the north; however, no monitor 

well clusters are north of well clusters HR-6 and HR-7 on the 

north side of the Pennsylvania Turnpike. The 296-ft thick clay 

encountered at well HR-30-318 may prevent the plume from 

moving to the northwest.

Water from five wells sampled in 2008 exceeded the 60 

μg/L ARAR for chlorobenzene. Concentrations of chlorobenzene exceeding the ARAR were measured in wells in the 

source area (HR-3-255) and north (HR-7-383) and northwest 

(HR-6-141, HR-6-241 and HR-24-476) of the source area. 

The highest chlorobenzene concentrations in water samples 

from wells away from the source area were measured in wells 

HR-6-141 (180 μg/L), HR-24-476 (133 μg/L), HR-6-241 

(150 μg/L), HR-6-141 (136 μg/L), and HR-7-383 (87 μg/L). 

The greatest changes in chlorobenzene concentration between 

pre-shutdown samples collected in July 2006 and samples 

collected in February and March 2008 (19 months after the 

shutdown) were for wells north of the source area (HR-6 and 

HR-7 well clusters); increases in chlorobenzene concentration ranged from 6.9 to 99 μg/L. The greatest increases were 

in water samples from wells HR-6-241 (99 μg/L), HR-24-476 

(95 μg/L), and HR-7-383 (74 μg/L).

For May 2007 to August 2008, all six water samples from 

wells HR-6-241 and HR-24-476 and 60 percent of the water 

samples from well HR-6-141 exceeded the chlorobenzene 

ARAR. Chlorobenzene concentrations were substantially 

greater after the June 2003 shutdown test than before the 

test. Median chlorobenzene concentrations in water samples 

from well HR-7-383 have been increasing over time. For 

well HR-7-383, the median chlorobenzene concentration was 

7.1 μg/L for 1998 to May 2003, increased to 24 μg/L for October 2003 to January 2007, and increased to 82 μg/L from May 

2007 to February 2008. For well HR-24-476, the median chlorobenzene concentration was 12 μg/L for 1991–99, decreased 

to 2.1 μg/L for January 2000 to May 2003, increased to 

52 μg/L for August 2003 to January 2007, and increased again 

to 104 μg/L for May 2007 to February 2008.

Chlorobenzene appears to have moved from the source 

area to the north. The highest concentrations of chlorobenzene 

were near or outside the northern site boundary, indicating 
82 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site

chlorobenzene may have moved north away from the source 

area. A much larger area was affected by chlorobenzene than 

benzene. Chlorobenzene concentrations decreased in the 

source area and increased at the site boundary at well cluster 

HR-7 and beyond the site boundary at well cluster HR-6. 

No monitor well clusters are north of well clusters HR-6 and 

HR-7 on the north side of the Pennsylvania Turnpike. The 

296-ft thick clay encountered at well HR-30-318 may prevent 

the plume from moving to the northwest.

Water from four wells sampled in 2008 exceeded the 

5.06 μg/L ARAR for 1,1-DCA. Concentrations of 1,1-DCA 

exceeding the ARAR were measured in wells in and near the 

source area (HR-2-295 and HR-3-280) and northeast of the 

source area (HR-14-376 and HR-18-190). The highest concentrations were measured in water samples from wells HR-3-380 

(25 μg/L), HR-18-190 (9.5 μg/L), HR-14-376 (8.4 μg/L), 

HR-2-295 (7.1 μg/L), and HR-14-178 (5.4 μg/L). Increases 

in 1,1-DCA concentration between pre-shutdown samples 

collected in July 2006 and samples collected in February 2008 

(19 months after the shutdown) ranged from 0.4 to 20 μg/L. 

The greatest increases were measured in water samples 

from wells HR-3-280 (20 μg/L), HR-14-376 (6.2 μg/L), and 

HR-14-178 (3.7 μg/L). The concentration of 1,1-DCA in a 

water sample from off-site well HR-22-300 was 1.7 μg/L. The 

1,1-DCA plume extended in an east-northeast direction from 

the source area.

Water from two wells sampled in 2008 exceeded the 

175 μg/L ARAR for total xylene. Both wells (injection well 

and HR-3-255) are in the source area. The highest concentrations of total xylene measured in 2008 were in water samples 

from well HR-3-255 (1,730 μg/L) and the injection well 

(185 μg/L). The greatest changes in total xylene concentration between pre-shutdown samples collected in July 2006 

and samples collected in February 2008 (19 months after the 

shutdown) were an increase of 165 μg/L in water samples 

from the injection well and a decrease of 1,410 μg/L in water 

samples from well HR-2-155. The xylene plume extended in 

an east-northeast direction from the source area.

Large drawdowns in the Upper Merion Reservoir during 

droughts in 1998 and 2001 affected water levels in Chester 

Valley and at the Henderson Road Site. For the drought of 

2001, water levels in the Chester Valley, except for McCoy 

Quarry monitor well MW-4 and well HR-17-170, showed a 

protracted recovery from September 2001 until June 2005 

(46 months). Water levels in wells MW-1 and MW-2 on the 

eastern side of the McCoy Quarry and water levels in wells at 

the Henderson Road Site, except for well HR-17-170, showed 

the same extended recovery, indicating the water level in the 

Upper Merion Reservoir affected water levels on the Henderson Road Site, except for well HR-17-170.

Water-level data were evaluated temporally for 1997–

2008 and spatially for (1) June 16, 2003, when the extraction 

wells were pumping at the full rate prior to the start of the 

June 2003 shutdown test; (2) July 10, 2006, when the extraction wells were pumping at the reduced rate prior to the start 

of the July 2006 shutdown test; and (3) February 25–29, 2008, 

during the 2006–08 shutdown test when the extraction wells 

were not pumping. Except for well HR-5-195, wells were 

divided into shallow wells (less than 200 ft deep), intermediate-depth wells (200–299 ft deep), and deep wells (greater 

than 299 ft deep), following the designations used by RT 

Environmental Services, Inc. The potentiometric surface for 

shallow wells did not appear to be affected by pumping of the 

extraction wells. The general direction of ground-water flow in 

the shallow zone was to the north.

The potentiometric surface for intermediate-depth wells 

for June 16, 2003, showed a cone of depression caused by the 

extraction wells pumping at the full rate. The ground-waterflow direction was from the southwest toward the pumping 

wells and toward the northeast away from the pumping wells. 

During the period of reduced pumping (July 10, 2006), the 

potentiometric surface for intermediate-depth wells did not 

show a cone of depression as it did when the extraction wells 

were pumping at the full rate. The ground-water-flow direction 

was from the south-southwest toward the pumping wells and 

toward the northeast away from the pumping wells, similar to 

that when the extraction wells were pumping at the full rate. 

The ground-water-flow direction when the extraction wells 

were not pumping (February 25–29, 2008) was toward the 

north and northeast, similar to that when the extraction wells 

were pumping.

Water-level data were available for only four on-site 

deep wells for June 16, 2003 (full-pumping rate), and July 

10, 2006 (reduced-pumping rate), when the extraction wells 

were pumping. The available water-level data showed a flat 

hydraulic gradient. When the wells were pumping at the full 

rate (June 16, 2003), the ground-water-flow direction was to 

the Henderson Road Site from the northwest. When the wells 

were pumping at the reduced rate (July 10, 2006), the groundwater-flow direction was away from the Henderson Road Site 

to the northwest, the reverse of the direction of flow when the 

extraction wells were pumping at the full rate. During February 25–29, 2008, water levels in 11 deep wells were measured; 

the ground-water-flow direction was away from the Henderson 

Road Site toward the north and northeast.

Benzene concentrations measured in water samples collected in February and March 2008 from shallow wells were 

above the 5.52 μg/L ARAR for benzene only in the source 

area. Benzene concentrations measured in water samples from 

intermediate-depth wells were above the ARAR in the source 

area and beyond the northern site boundary northwest of the 

source area at well cluster HR-6; the direction of ground-water 

flow in the intermediate zone was to the north-northeast and 

northeast. Benzene concentrations measured in water samples 

from deep wells were above the ARAR in the source area, at 

the northern site boundary northeast of the source area at well 

cluster HR-7, and outside the site boundary north of the source 

area at well cluster HR-6. The general direction of groundwater flow in the deep zone is to the north. Benzene appears 

to have moved to the north away from the source area in the 

intermediate and deep zones.
References Cited 83

Chlorobenzene concentrations measured in water samples 

collected in February and March 2008 from shallow wells 

were above the 60 μg/L ARAR for chlorobenzene beyond the 

northern site boundary northwest of the source area at well 

cluster HR-6. Chlorobenzene concentrations measured in 

water samples from intermediate-depth wells were above the 

ARAR in the source area and beyond the northern site boundary northwest of the source area at well cluster HR-6. Chlorobenzene concentrations measured in water samples from deep 

wells were above the ARAR at the northern site boundary at 

well cluster HR-7 and beyond the northern site boundary at 

well cluster HR-6. Chlorobenzene appears to have moved to 

the north away from the source area in the shallow, intermediate, and deep zones.

Off-site wells were drilled to monitor the possible movement of chemicals of concern from the Henderson Road Site. 

Concentrations of benzene and chlorobenzene above the 

ARARs were measured in water samples from well cluster 

HR-7 at the northern site boundary and well cluster HR-6 

beyond the northern site boundary on the southern side of the 

Pennsylvania Turnpike. No off-site monitor wells are directly 

north of these well clusters on the northern side of the Pennsylvania Turnpike. Potentiometric-surface maps indicate the 

direction of ground-water flow from these well clusters was to 

the north. Off-site well HR-10-180 is about 580 ft north of the 

HR-6 well cluster; however, this well may be too shallow to 

intercept contamination from the Henderson Road Site. Additional monitor well clusters north of well clusters HR-6 and 

HR-7 on the northern side of the Pennsylvania Turnpike could 

help determine how far benzene or chlorobenzene have moved 

off-site and could be used to better define ground-water-flow 

directions north of the site.

During drilling of well HR-30-318, 296 ft of clay and 

weathered rock were encountered before competent bedrock 

was reached. Well HR-5-195 penetrated 179 ft of clay before 

encountering competent bedrock. It is possible that a thick 

clay north of the turnpike restricts movement of contaminants 

to the north.

Acknowledgments

Chemical and water-level data for the Henderson Road 

Site used in this study were provided by RT Environmental 

Services, Inc. In addition, RT Environmental Services, Inc. 

was kind enough to provide well-casing elevations and other 

data necessary for this study. Glasgow, Inc. provided waterlevel data for the McCoy Quarry monitor wells. Randall Conger and Melvin Mathes of the USGS provided critical reviews 

of this report.

References Cited

BCM Engineers, Inc., 1988, Final remedial investigation 

report injection well operable unit volume I for Henderson 

Road site Upper Merion Township, Montgomery Township, 

Pennsylvania: Plymouth Meeting, Pa., 221 p.

Lyttle, P.T., and Epstein, J.B., 1987, Geologic map of the 

Newark 1° × 2° quadrangle, New Jersey, Pennsylvania, and 

New York: U.S. Geological Survey Miscellaneous Investigations Series Map I-1715, 2 pl., scale 1:250,000.

Miles, C.E., and Whitfield, T.G., comps., 2001, Bedrock geology of Pennsylvania: Pennsylvania Geological Survey, 4th 

ser., digital dataset, scale 1:250,000.

RT Environmental Services, Inc., 2004, Shutdown/rebound 

test report Henderson Road Superfund Site: King of Prussia, Pa., 212 p.

RT Environmental Services, Inc., 2005, Technical support for 

request for remedy modification of the Henderson Road Site 

IWOU—ROD mandated reevaluation/application for TI 

wavier: King of Prussia, Pa., 24 p.

U.S. Environmental Protection Agency, 1988a, EPA superfund 

record of decision—Henderson Road: U.S. Environmental 

Protection Agency Report EPA/ROD/RO-3-88/049.

U.S. Environmental Protection Agency, 1988b, CERCLA 

Compliance with Other Laws Manual: U.S. Environmental Protection Agency Report EPA/540/G-89/006, variously 

paginated.

U.S. Environmental Protection Agency, 2009, National Primary Drinking Water Regulations: accessed January 6, 

2009, at http://www.epa.gov/safewater/contaminants/

index.html#listmcl
84 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc. [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) HR-2-175 4/90–11/99, n=21 HR-2-175 8/00–5/03, n=10 HR-2-175 7/03–6/05, n=16 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 900 11 2.6 8.1 4.1 2.2 18 7.5 Carbon tetrachloride 5 0 52 0 0 0 0 0 0 0 Chlorobenzene 60 0 230 6.2 2.6 13 4.9 4.1 12 8.5 1,1-Dichloroethane 5.06 0 210 2 1 3.5 1.9 1.3 13 2.2 1,2-Dichloroethane 6.02 0 100 0 0 0 0 0 1.5 0 1,1-Dichloroethene 7 0 470 0 0 0 0 0 .45 0 1,2-Dichloroethene 70 0 810 0 0 1.1 0 0 .45 0 1,2-Dichloropropane 6.28 0 .50 0 0 0 0 0 6.4 0 Ethylbenzene 680 0 2,600 21 0 61 2.7 0 29 0 Tetrachloroethylene 6.9 0 9.0 0 0 0 0 0 .51 0 Toluene 2,000 0 61,000 11 0 1.8 .32 0 .78 0 Total xylenes 175 0 5,700 54 0 379 7.6 0 374 4.0 Trichloroethylene 5 0 72 0 0 0 0 0 2.5 0 Vinyl chloride 2 0 200 0 0 1 0 0 3 .43 Compound ARAR (μg/L) HR-2-195 11/92–5/03, n=3 HR-2-195 6/05–2/08, n=4 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L)

Benzene 5.52 0 2.4 0 20 91 41

1,1-Dichloroethane 5.06 0 230 8.8 .46 19 3.2

cis-1,2-Dichloroethene 70 2.8 350 240 .36 5.8 .77

Ethylbenzene 680 8.1 930 480 5.2 59 14

Methylene chloride 47 0 170 2 .11 1.4 .96

Toluene 2,000 2.6 22,000 8,200 .49 15 3.2

Total xylenes 175 5.3 5,700 5,300 2 82 25
Table 7

85

Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, MontgomeryCounty, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued[n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type]

Compound ARAR (μg/L)

HR-2-295

4/99–5/03, n=3

HR-2-295

6/05–08, n=4

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 3.8 11 7.5 3.0 4.4 3.41,1-Dichloroethane 5.06 4.6 8.8 5.8 6.0 7.1 6.2

Compound ARAR (μg/L)

HR-3-255

8/91–11/99, n=35

HR-3-255

5/00–6/03, n=14

HR-3-255

7/03–7/06, n=24

HR-3-255

5/07–2/08, n=2

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 1,800 110 54 850 292 95 530 278 452 513 —Carbon tetrachloride 5 0 36 0 0 0 0 0 0 0 0 0 —Chlorobenzene 60 0 480 65 33 321 69 22 169 94 95 101 —1,1-Dichloroethane 5.06 0 1,100 5.7 0 279 1.1 0 599 93 .6 1.5 —1,2-Dichloroethane 6.02 0 250 0 0 34 0 0 172 2.2 0 0 —

1,1-Dichloroethene 7 0 300 0 0 0 0 0 .61 0 0 0 —cis-1,2-Dichloroethene 70 0 0 0 0 134 .35 0 774 42 0 .78 —

1,2-Dichloroethene 70 0 160 0 0 2.0 0 0 1.7 0 .40 .60 —1,2-Dichloropropane 6.28 0 160 0 0 75 0 0 462 16 0 5 —Ethylbenzene 680 0 3,400 63 41 5,130 446 178 7,490 944 30 186 —

Methylene chloride 47 0 67 0 0 28 2.0 0 60 3.3 0 0 —Tetrachloroethylene 6.9 0 11 0 0 .50 0 0 1.6 0 0 0 —Toluene 2,000 0 14,000 44 0 8,590 27 15 8,600 1,975 50 54 —

Total xylenes 175 0 28,880 219 216 18,100 1,360 192 32,100 9,145 1,730 2,180 —

Vinyl chloride 2 0 82 0 0 113 .25 0 128 41 0 1.0 —
86 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) HR-3-280 8/91–11/99, n=28 HR-3-280 11/00–6/03, n=12 HR-3-280 7/03–1/07, n=28 HR-3-280 5/07–8/08, n=6 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 2,300 285 0 99 29 11.2 298 39 174 198 182 Carbon tetrachloride 5 0 900 55 0 0 0 0 0 0 0 0 0 Chlorobenzene 60 0 430 26 2.1 23 12 3 79 5.8 24.4 49 32 Chloroform 100 0 1,400 6 0 64 0 0 .89 0 0 0 0 1,1-Dichloroethane 5.06 0 2,700 114 1.9 19 4.3 .38 68 9.4 .64 45 14 1,2-Dichloroethane 6.02 0 2,600 23 0 8.0 .50 0 11 2.4 0 0 0 1,1-Dichloroethene 7 0 5,200 0 0 0 0 0 0 0 0 0 0 1,2-Dichloroethene 70 0 200 0 0 1.0 0 0 1.4 0 0 1 .47 1,2-Dichloropropane 6.28 0 85 0 0 6.4 1.5 0 88 1.9 0 0 0 Ethylbenzene 680 0 4,500 434 .31 46 .57 0 20 .32 .45 2 .62 Methylene chloride 47 0 920 7 0 1.9 .98 0 9.6 1.0 0 1 .43 Tetrachloroethylene 6.9 0 91 0 0 0 0 0 .39 0 0 0 0 Toluene 2,000 0 54,000 1,270 .14 5.1 1.1 0 9.2 .20 .68 8 1.5 Total xylenes 175 0 14,000 445 0 91 .92 0 278 .79 0 0 .21 Vinyl chloride 2 0 86 1.9 0 1.8 0 0 28 1.8 0 4 .77
Table 7

87

Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, MontgomeryCounty, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued[n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type]

Compound ARAR (μg/L)

HR-3-295

8/91–11/99, n=37

HR-3-295

5/00–6/03, n=13

HR-3-295

7/03–7/06, n=24

HR-3-295

7/07–2/08, n=2

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 1,800 85 0.4 583 195 8.1 559 19 16 20 —

Carbon tetrachloride 5 0 33 0 0 0 0 0 0 0 0 0 —

Chlorobenzene 60 0 730 52 2.6 228 47 19.2 186 117 6.2 11 —

1,1-Dichloroethane 5.06 0 390 5.7 0 16 1.2 0 135 2.5 1.7 2 —

1,2-Dichloroethane 6.02 0 70 0 0 7 0 0 27 0 0 0 —

cis-1,2-Dichloroethene 70 0 1.9 0 0 112 .7 0 93 .89 .46 1 —

1,2-Dichloropropane 6.28 0 56 0 0 55 0 0 72 0 0 0 —

Ethylbenzene 680 0 3,800 40 0 4,790 181 0 8,160 0 .61 3 —

Methylene chloride 47 0 67 0 0 10 1.5 0 21 0 0 0 —

Tetrachloroethylene 6.9 0 10 0 0 .9 0 0 0 0 0 0 —

Toluene 2,000 0 19,000 11 0 8,920 14 0 2,550 .62 .35 48 —

Total xylenes 175 0 15,000 79 0 16,000 852 0 30,500 0 3.6 6 —

Vinyl chloride 2 0 18 0 0 29 0 0 73 .51 0 0 —
88 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) HR-4-195 8/91–11/99, n=37 HR-4-195 5/00–6/03, n=13 HR-4-195 7/03–7/06, n=24 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 27 0.70 0.30 1 0.54 0.22 0.6 0.44 1,1-Dichloroethane 5.06 0 42 4.0 0 27 2.0 .75 3.2 2.2 Methylene chloride 47 0 77 0 0 0 0 0 0 0 COMPOUND ARAR (μg/L) HR-4-295 10/91–11/99, n=19 HR-4-295 11/00–6/03, n=6 HR-4-295 6/03–1/07, n=23 HR-4-295 5/07–8/08, n=6 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 140 5.5 .90 4.9 2.4 2.0 5.8 3.3 .9 1.9 1.0 Chlorobenzene 60 0 100 3.9 .50 3.7 3.3 2.8 5.6 3.5 0 .5 0 1,1-Dichloroethane 5.06 0 14 3.0 2.8 7.8 3.2 3.2 12 7.4 4.3 6.8 4.5 1,2-Dichloroethane 6.02 0 12 0 0 4.8 .70 0 10 5.2 0 3.3 .28 1,1-Dichloroethene 7 0 38 0 0 0 0 0 0 0 0 0 0 Total xylenes 175 0 311 0 0 0 0 0 .50 0 0 0 0
Table 7

89

Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, MontgomeryCounty, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued[n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type]

Compound ARAR (μg/L)

HR-5-195

4/99–5/03, n=4

HR-5-195

7/05–2/08, n=7

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 51 0.21 0 1 0

Compound ARAR (μg/L)

HR-6-141

4/99–8/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 41 2.8Chlorobenzene 60 13 180 98

Compound ARAR (μg/L)

HR-6-241

5/03–01/07, n=17

HR-6-241

5/07–8/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 .36 49 6.9 4.6 14 7.6Chlorobenzene 60 3.0 106 46 73 150 105

Compound ARAR (μg/L)

HR-6-377

9/91–11/99, n=10

HR-6-377

11/00–6/03, n=8

HR-6-377

7/03–1/07, n=26

HR-6-377

5/07–8/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 500 23 2.1 17 8.6 15 396 231 38 168 129

Chlorobenzene 60 0 88 11 1.8 9.1 7.1 6.2 70 50 28 52 43Total xylenes 175 0 520 66 0 2.0 1.4 0 27 .54 0 .73 .26
90 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) HR-7-163 8/91–11/97, n=24 HR-7-163 9/98–6/03, n=16 HR-7-163 7/03–7/06, n=16 HR-7-163 5/07–2/08, n=2 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 860 80 0 15 0.10 0 19 7.6 4.1 4.8

—

Carbon tetrachloride 5 0 9.3 0 0 1.0 0 0 0 0 0 0 —

Chlorobenzene 60 0 400 35 0 62 1.2 0 59 32 24 62

—

1,1-Dichloroethane 5.06 0 23 0 0 9.2 2.9 0 2.0 .87 0 .68

—

1,2-Dichloroethane 6.02 0 11 0 0 1.3 0 0 .41 0 0 0 —

1,1-Dichloroethene 7 0 8.0 0 0 .40 0 0 0 0 0 0 —

Ethylbenzene 680 0 1,900 2.1 0 17 0 0 .18 0 0 0 —

Tetrachloroethylene 5 0 10 0 0 1.7 0 0 1.2 .11 0 0 —

Toluene 2,000 0 3,900 6.0 0 26 .20 0 .77 0 0 0 —

Total xylenes 175 0 4,530 27 0 74 0 0 .71 0 0 0 —

Vinyl chloride 2 0 2.2 0 0 1.2 0 0 .45 0 0 0 —

Compound ARAR (μg/L)

HR-7-278

9/98–5/03, n=3

HR-7-278

10/03–7/06, n=8

HR-7-278

5/07–2/08, n=2

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 9.1 11 10 .87 3.5 2.4 2.8 3.4

—

Chlorobenzene 60 1.6 72 4.9 .93 24 3.5 34 47

—
Table 7

91

Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, MontgomeryCounty, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued[n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type]

Compound ARAR (μg/L)

HR-7-383

9/98–5/03, n=4

HR-7-383

10/03–1/07, n=12

HR-7-383

5/07–2/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 2.9 67 12 19 75 60 34 131 54Chlorobenzene 60 1.6 70 7.1 3.4 62 24 38 99 82

Compound ARAR (μg/L)

HR-9-191

11/92–11/99, n=19

HR-9-191

8/00–6/03, n=6

HR-9-191

6/03–11/05, n=27

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 510 3.9 0 1.8 .80 0 2.6 .33Chlorobenzene 60 0 350 2.5 0 3.9 3.0 .72 4.0 2.61,1-Dichloroethane 5.06 0 46 3.2 1 6.2 2.6 1.0 24 3.41,2-Dichloroethane 6.02 0 3.6 1.4 0 7.1 2.1 0 3.2 2.51,1-Dichloroethene 7 0 11 0 0 0 0 0 0 0

Total xylenes 175 0 1,440 0 0 .20 0 0 .94 0

Vinyl chloride 2 0 12 0 0 .79 0 0 1.4 .40

Compound ARAR (μg/L)

HR-12-150

4/99–4/01, n=2

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 2.1 14 —1,1-Dichloroethane 5.06 17 40 —Total xylenes 175 0 730 —Vinyl chloride 2 .71 4 —
92 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) HR-12-300 5/03–2/06, n=19 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 6.5 5.4 1,1-Dichloroethane 5.06 1.1 12 10 Vinyl chloride 2 0 2.7 1.7 Compound ARAR (μg/L) HR-14-178 5/93–11/99, n=9 HR-14-178 11/00–5/03, n=6 HR-14-178 10/03–7/06, n=11 HR-14-178 5/07–2/08, n=2 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 16 0 0 4.0 0 0 0 0 0 0 — 1,1-Dichloroethane 5.06 0 11 0 2.7 9.4 2.7 1.3 4.7 1.3 5.4 6.0

—

Methylene chloride 47 0 1,500 0 0 0 0 0 0 0 0 0 —

Compound ARAR (μg/L)

HR-14-376

9/98–6/03, n=11

HR-14-376

7/03–1/07, n=23

HR-14-376

5/07–8/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 25 93 50 2.4 38 28 5.3 22 13

Chlorobenzene 60 19 84 26 .98 82 21 6.3 11 8.9

1,1-Dichloroethane 5.06 0 3.0 1.1 .4 3.0 1.5 1.5 8.4 5.2

Compound ARAR (μg/L)

HR-18-190

11/92–11/99, n=16

HR-18-190

5/00–5/03, n=13

HR-18-190

10/03–1/07, n=16

HR-18-190

5/07–8/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

1,1-Dichloroethane 5.06 0 13 6.2 0 9 4.8 0 9.2 6.1 1.1 10 5.51,2-Dichloroethane 6.02 0 6.3 0 0 4.5 1.9 0 2.4 1.8 0 2.8 1.7Vinyl chloride 2 0 3.0 0 0 1.3 0 0 .84 .13 0 0 0
Table 7

93

Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, MontgomeryCounty, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued[n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type]

Compound ARAR (μg/L)

HR-20-155

11/92–/08, n=39

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 6.0 01,2-Dichloroethane 6.02 0 12 0Vinyl chloride 2 0 36 0

Compound ARAR (μg/L)

HR-22-300

4/98–4/01, n=4

HR-22-300

7/05–8/08, n=10

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 1.9 20 8.1 0 4.3 01,1-Dichloroethane 5.06 0 11 .30 0 2.5 2.1

Compound ARAR (μg/L)

HR-24-476

12/92–11/99, n=25

HR-24-476

3/00–5/03, n=8

HR-24-476

8/03–1/07, n=19

HR-24-476

5/07–8/08, n=6

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 190 23 0 91 .74 0 5.6 2.0 0 4.0 2.2Carbon tetrachloride 5 0 6.0 0 0 0 0 0 0 0 0 0 0Chlorobenzene 60 0 96 12 .50 96 2.1 .54 168 52 83 110 104

1,1-Dichloroethane 5.06 0 28 3.0 1.8 6.5 3.0 0 1.6 .64 0 0 0

1,2-Dichloroethane 6.02 0 21 0 0 0 0 0 0 0 0 0 0

Total xylenes 175 0 394 8.0 0 11 0 0 0 0 0 0 0

Vinyl chloride 2 0 3.0 0 0 .70 .30 0 0 0 0 0 0
94 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) HR-26-457 12/92–11/99, n=29 HR-26-457 11/00–6/03, n=11 HR-26-457 7/03–2/08, n=27 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 6,000 72 0.94 66 24 0.79 42.6 12 Carbon tetrachloride 5 0 18 0 0 0 0 0 0 0 Chlorobenzene 60 0 430 54 2.9 92 33 2.5 156 8.3 1,1-Dichloroethane 5.06 0 82 12 0 6.4 3.5 1.3 21 3.1 1,2-Dichloroethane 6.02 0 140 0 0 1.3 0 0 2.4 0 1,1-Dichloroethene 7 0 12 0 0 .31 0 0 0 0 cis-1,2-Dichloroethene 70 0 4.1 0 0 2.2 .99 0 75 .76 1,2-Dichloropropane 6.28 0 11 0 0 2.6 0 0 7.8 0 Ethylbenzene 680 0 1,500 110 0 9.8 2.8 0 6.8 .3 Tetrachloroethylene 6.9 0 7.0 0 0 1.1 0 0 .68 0 Toluene 2,000 0 9,700 180 .39 6.7 1.6 0 78 0 Total xylenes 175 0 4,200 220 0 28 6.2 0 32 0 Vinyl chloride 2 0 5.9 0 0 .65 0 0 22 .52
Table 7

95

Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, MontgomeryCounty, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued[n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type]

Compound ARAR (μg/L)

IW

12/91–5/03, n=85

IW

7/03–2/08, n=25

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Benzene 5.52 0 1,500 41 1.1 141 14Carbon tetrachloride 5 0 580 1.5 0 0 0Chlorobenzene 60 0 530 15 3.2 99 161,1-Dichloroethane 5.06 0 4,200 43 0 60 5.81,2-Dichloroethane 6.02 0 520 5.5 0 21 01,1-Dichloroethene 7 0 190 0 0 .41 0cis-1,2-Dichloroethene 70 0 3.8 0 .92 95 4.11,2-Dichloroethene 70 0 320 0 0 .25 01,2-Dichloropropane 6.28 0 5.1 0 0 132 6.2Ethylbenzene 680 0 2,300 53 .44 100 16Methylene chloride 47 0 79 0 0 6.5 0Tetrachloroethylene 6.9 0 25 0 0 19 1.3Toluene 2,000 0 50,000 685 1.2 1,910 65

Total xylenes 175 0 5,500 125 .58 926 35

Vinyl chloride 2 0 97 0 .36 24 1.1
96 Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site Table 7. Summary of concentrations of selected volatile organic compounds in water samples from the Henderson Road Site, Upper Merion Township, Montgomery County, Pennsylvania, 1991–2008. Only compounds exceeding the applicable or relevant and appropriate requirement (ARAR) are included. ARAR is the applicable or relevant and appropriate requirement that is set in the Record of Decision (ROD) for the site (U.S. Environmental Protection Agency, 1988a). Data provided by RT Environmental Services, Inc.—Continued [n, number of samples; μg/L, micrograms per liter; —, too few data to compute statistic ;concentrations above ARAR are in bold type] Compound ARAR (μg/L) RE-205 12/91−5/03, n=85 RE-205 7/03−2/08, n=25 RE-205 12/91−5/03, n=85 RE-205 7/03−2/08, n=25 Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Minimum (μg/L) Maximum (μg/L) Median (μg/L) Benzene 5.52 0 156 15 0 14 6.7 0 287 1.8 0.93 1.1

—

Carbon tetrachloride 5 0 16 0 0 0 0 0 0 0 0 0 —

Chlorobenzene 60 0 134 6.0 2.2 33 5.2 1.7 142 4.7 2.4 3.6

—

1,1-Dichloroethane 5.06 0 210 23 0 7.1 2.4 1.1 165 2.8 1.7 1.8

—

1,2-Dichloroethane 6.02 0 24 0 0 0 0 0 41 0 0 0 —

1,1-Dichloroethene 7 0 67 0 0 .80 0 0 .56 0 0 0 —

cis-1,2-Dichloroethene 70 0 2.8 0 0 3.0 2 .26 209 1.7 .74 .94

—

1,2-Dichloropropane 6.28 0 3.0 0 0 0 0 0 283 0 0 0 —

Methylene chloride 47 0 73 0 0 0 0 0 16 0 0 0 —

Tetrachloroethylene 6.9 0 10 0 0 16 .6 0 19 .87 0 0 —

Toluene 2,000 0 2,300 108 0 16 4.5 0 2,260 0 .71 .77

—

Total xylenes 175 0 1,196 29 0 12 2.7 0 620 0 0 0 —

Vinyl chloride 2 0 46 0 0 1.0 .60 0 43 .99 1.1 1.5

—

Sloto—Evaluation of Water-Chemistry and Water-Level Data at the Henderson Road Superfund Site, 1991–2008—Scientific Investigations Report 2009–5101