HRS DOCUMENTATION RECORD COVER SHEET

Name of Site: Dwyer Property Ground Water Plume

EPA ID No. : MDD985366756

Contact Persons

Site Investigation: Arthur O’Connell Chief, Brownfields/Superfund Division Maryland Department of the Environm ent 1800 Washington Boulevard Baltimore, Maryland 21230

- 1719 (410) 537

- 3493 aoconnell@mde.state.md.us

HRS Documentation Record: Lorie Baker NPL Coordinator/ Site Assessment Manage r U.S. Environmental Protection Agency 1650 Arch Street Philadelphia, Pennsylvania 19103

- 2029 (215) 814

- 3355 Lorie.Baker@epa.gov

Pathways, Components, or Threats Not Scored

The Dwyer P roperty Ground Water Plume site is being evaluated as an area of ground water contamination with unknown sources. Preliminary scores for the surface water migration, air migration, and soil exposure pathways indicated minimal contribution of these to the overall site score; therefore, these pathways have not been included in this HRS documentation record. The surface water migration pathway ground water to surface water component score was low due to the lack of hazardous substances with high bioaccumulat ion factor values. Additionally, an overland runoff pathway likely does not exist. The lack of documented observed contamination and resident targets limit the soil exposure pathway scores. No observed release to the air has been documented within a 4 -m ile radius of the ground water plume.

Surface Water Overland Migration Pathway

The surface water pathway was not scored. The ground water pathway was sufficient to list the site.

Soil Exposure Pathway

The soil exposure pathway was not scored. The gro und water pathway was sufficient to list the site.

Air Migration Pathway

The air migration pathway was not scored. The ground water pathway was sufficient to list the site.GEN -1 HRS DOCUMENTATION RECORD

Name of Site: Dwyer Property Ground Water Plume Date Prepared: October 2010

EP A Region: 3

Street Address of Site*: The Dwyer Property Ground Water Plume site is located north east of the intersection of Maryland Route 545 and Maryland Route 279 (Elkton Road) in Elkton, Cecil Coun ty, Maryland, as shown in Reference 3.

City, County, State, Zip Code: Elkton, Cecil County, Maryland 21921

General Location in the State: Northeast corner of Maryland

Topographic Map : Elkton, Maryland

Latitude: 39.612007 North Longitude:

- 75.844474 West (Ref. 3; Ref. 4; Ref. 5)

The latitude and longitude were measured at the north west corner of the building shown in Reference 4.

* The street address, coordinates, and contaminant locations presented in this HRS documentation record identify the ge neral area the site is located. They represent one or more locations EPA considers to be part of the site based on the screening information EPA used to evaluate the site for NPL listing. EPA lists national priorities among the known "releases or threatened releases" of hazardous substances; thus, the focus is on the release, not precisely delineated boundaries. A site is defined as where a hazardous substance has been "deposited, stored, placed, or otherwise come to be located." Generally, HRS scoring an d the subsequent listing of a release merely represent the initial determination that a certain area may need to be addressed under the Comprehensive Environmental Response, Compensation, and Liability Act. Accordingly, EPA contemplates that the prelimina ry description of facility boundaries at the time of scoring will be refined as more information is developed as to where the contamination has come to be located.

Air Pathway Not scored Scores

Ground Water Pathway 100 Soil Exposure Pathway Not scored Su rface Water Pathway Not scored

HRS SITE SCORE : 50 .00GEN -2 WORKSHEET FOR COMPUTING HRS SITE SCORE

S S 2

1. Ground Water Migration Pathway Score (S gw ) 100 10,000

2a. Surface Water Over land/Flood Migration Component (from Table 4

- 1, line 30) Not Scored

2b. Ground Water to Surface Water Migration Component (from Table 4

- 25, line 28) Not Scored

2c. Surface Water Migration Pathway Score (S sw Enter the larger of lines 2a a nd 2b as the pathway score. ) Not Scored

3. Soil Exposure Pathway Score (S s (from Table 5

- 1, line 22) ) Not Scored

4. Air Migration Pathway Score (S a (from Table 6

- 1, line 12) ) Not Scored

5. Total of S gw 2 + S sw 2 + S s 2 + S a 2 100

6. HRS Site Score Divide the value on line 5 by 4 and take the square root 50 .00GEN -3 HR S Table 3- 1

– Ground Water Migration Pathway Scoresheet

Factor Categories and Factors Maximum
Value Value Assigned Likelihood of Release to an Aquifer:

1. Obs erved Release 550 550

2. Potential to Release:

2a. Containment 10
2b. Net Precipitation 10
2c. Depth to Aquifer 5
2d. Travel Time 35
2e. Potential to Release [lines 2a x (2b + 2c + 2 d)] 500
3. Likelihood of Release (higher of lines 1 and 2e) 550 550
Waste Characteristics:
4. Toxicity/Mobility (a) 10,000
5. Hazardous Waste Quantity (a) 10,000
6. Waste Characteristics 100 100 Targets : 7. Nearest Well 50 9
8. Population:
8a. Level I Concentrations (b)
8b. Level II Concentrations (b)
8c. Potential Contamination (b) 209 8d. Population (lines 8a + 8b + 8c) (b) 209
9. Resources 5 5
10. Wellhead Protection Area 20 5
11. T argets (lines 7 + 8d + 9 + 10) (b) 22 8 Ground Water Migration Score For An Aquifer:
12. Aquifer Score c [(lines 3 x 6 x 11)/82,500] 100 100
G round Water Migration Pathway Score:
13. Pathway Score (S gw ),

c (highest value from line 12 for al l a quifers evaluated) 100 100

a. b.

c. Maximum value applies to waste characteristics category. Maximum value not applicable. Do not round to nearest integer.GEN -4 REFERENCES Ref. No. Description of the Reference

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2. EPA. Superfund Chemical Data Matrix. ( Note: A complete copy of SCDM is available at On

Line Address: http://www.epa.gov/superfund/sites/npl/hrsres/tools/scdm.htm. ) Excerpt 16 pages.

3. Tetra Tech EM Inc. (Tetra Tech). Ground Water Plume

, Elkton, Cecil County, Maryland. Site Location Map. October 22, 2009. 1 page.

4. Tetra Tech EM Inc. Project Note for the Dwyer Property. Subject Latitude and Longitude of the Dwyer Property using Google Earth ©

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6. EPA. Safe Drinking Water Information System for Cecil County. Accessed on January 22, 2010

. On

- Line Address: http://www.epa.gov/enviro/html/sdwis/sdwis_query.html . 9 pages.

7. Tetra Tech. 4

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. Record of Telephone Conversation. Between Alicia Shultz, Tetra T ech, HRS Specialist , and Kim Kamp, Town of Elkton. November 5 , 2009. 1 page.

10. Tetra Tech. Population Served by the Town of Elkton Wells. January 22, 2010. 1 page.

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- Line Address: http://factfinder.census.gov/servlet/ACSSAFFFacts?_event=Search&geo_id=&_geoContext=&_st reet=&_county=cecil&_cityTown=cecil&_state=04000US24&_zip=&_lang=en&_sse=on&pctxt= fp h&pgsl=010

.

13. Tetra Tech Inc. Final Remedial Investigation Report. Remedial Investigation and Feasibility Study. Volume 1 of 2. Dwyer Site (MD 313), Elkton, Cecil County, Maryland ( i ncludes full copies of several reports as Appendices). August 2005 . 5 10 pages.

14. MDE. Site Investigation, Dwyer Property, MD

- 313, Routes 279 and 545, Elkton, Cecil County, Maryland. November 2002. 1 96 pages.GEN -5 15. MDE. A Screening Site Inspection of Dwyer Property, Elkton, Maryland (MD

- 313), Final Report, Dece mber 1989. 6 9 pages.

16. MDE. A Preliminary Assessment of Dwyer Property, Elkton, Maryland (MD

- 313). Final Report. March

. 1989. 30 pages.

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18

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21. MDE. Community Supply Wells. January 22, 2010. 1 page.

22. Tetra Tech. Record of Conversation. Between David Black, Cecil County Department of Planning and Zoning, Geographic Information System ( GIS ) Coordinator and Alicia Shultz, HRS Specialist. October 10, 2009. 1 page.

23. Town and County Mobile Home Park. Annual Drinking Water Quality Report. 2009. 2 pages.

24. Forest View Village and Sherwood Forest Mobile Home Park. Annual Drinking Water Quality Report. June 23, 2009. 4 pages.

25. MDE. Wellhead Protection. Accessed on January 22, 2010. 1 page. On

- Line A ddress: h ttp://www.mde.state.md.us/Programs/WaterPrograms/Water_Supply/sourcewaterassessment/well head.asp

.

26. TechLaw, Inc. Final Report, Site Operations/Ownership History, Cecil Industrial Park Site, Elkton, Maryland (Formerly Triumph Explosives, Inc., Site). Prepared for U.S. Army Corps of Engineers. Contract No. DACA45

- 89 -D- 0512. September 1, 1992. 48 pages.

27. Chesapeake GeoSciences, Inc. (CGS)

. Comprehensive Groundwater Monitoring Well Data. MDE

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28. Tetra Tech. Aerial Photograph of the Area Surrounding Maryland Route 279 and Route 545. March 2 , 2010. 1 sheet.

29. CGS. Dwyer Property and Extension, Blue Ball, Elkton and Singerly Roads, Elkton, Maryland. Figure 1, MIP Boring and Monitori ng Well Location Map

. September 2009. 1 sheet.

30. Agency for Toxic Substances and Disease Control (ATSDR). Toxicological Profile for Trichloroethylene. September 1997. Excerpt 9 pages (original page numbers referenced)

. (D ocument available at: http://www.atsdr.cdc.gov/toxprofiles/tp19.pdf ).

31. Kueper, Bernard H. and Kathyrn L. Davies. EPA. Ground Water Issue, Assessment and Delineation of DNAPL Source Zones at Hazardous Waste Si tes. September 2009. 20 pages.GEN -6 32. Tetra Tech. Record of Conversation. Between Alicia Shultz, HRS Specialist, and Phill Anderson, MDE, Dwyer Property Project Manager. October 8, 2009. 1 page.

33. Buddemeier, R.W. and J.A. Schloss. Ground Water Storage and Flow. November 21, 2000. 3
pages. (excerpt from Schloss, J.A., Buddemeier, R.W., and Wilson, B.B., An Atlas of the Kansas High Plains Aquifer, Kansas Geological Survey, Educational Series No. 14, 2000, 92 pages, available at: http://www.kgs.ku.edu/HighPlains/atlas/apgengw.htm ).

34. Buddemeier, R.W. and J.A. Schloss. Saturated Thickness – Concepts and Measurements. November 9, 2000. 2 pages. (excerpt from Schloss, J.A ., Buddemeier, R.W., and Wilson, B.B., An Atlas of the Kansas High Plains Aquifer, Kansas Geological Survey, Educational Series No. 14, 2000, 92 pages available at http://www.kgs.ku.edu/HighPlains/atlas/apst.htm ).

35. Tetra Tech. Mean Water Column Deep Monitoring Wells. May 12 , 2010. 1 page.

36. McFarland, E. Randolph and Bruce, T. Scott. The Virginia Coast Plain Hydrogeologic Framework. Professional Paper 1731. 2006. Excerpt 3 pa ges. (document available at: http://pubs.usgs.gov/pp/2006/1731/pp1731_download.htm ).

37. A merican Society for Testing and Materials. Unified Soil Classification System. 1985. 1 p age.

38. Tetra Tech. Mean Water Column for Shallow Ground Water. May 12, 2010. 1 page.

39. Tetra Tech. The Area of the Shallow and Deep Ground Water Plume s , Elkton, Cecil County, Maryland

. May 11, 2010. 1 page.

40. Michael Baker Corp., Inc. 10 0% Design Report for Operable Unit 3, Groundwater Interceptor Trench, Maryland Sand, Gravel and Stone Site , Elkton, Cecil County, Maryland. December 2006. Excerpt 3 pages.

41. MDE . Voluntary Cleanup/Brownfields Division. VICON PROPERTY, Route 213 an d Dogwood Road, Elkton, Cecil County, Maryland. Fact Sheet. Not dated. 2 pages.

42. EPA. Mid

- Atlantic Superfund Current Facility Information D atabase for Sand, Gravel, and Stone. Accessed on January 7, 2010 . 3 pages. On

- Line Address: http://www.epa.gov/reg3hscd/npl/MDD980705164.htm

.

43. Tetra Tech. Record of Conversation. Between Alicia Shultz, HRS Specialist and Phill Anderson, MDE, Dwyer Property Project Manager Regarding Wellhe ad Protection Areas. October 10, 2009. 2 pages.

44. Office of Cecil County, Economic Development. Agriculture. Accessed on March 1, 2010. 1
page. On -L ine Address: http://www.cecilbusiness.org/business_agriculture.cfm

.

45. CGS. Work Plans for Ground w ater Gauging, Ground w ater Sampling, Monitoring Well Installation, Surveying, Clearing, Disposal of Investigative Derived Waste, and Source Identification. Dated: December 8, 2006 (file CG

- P06

- 0283 Work Plan #6); August 21, 2007 (file CG

- P07

- 0407 Work Plan #9); October 15, 2008 (file CG

- P08

- 0527R Work Plan #12); February 5, 2009 (file CG

- P09

- 0581 Work Plan #16); June 10, 2009 (file CG

- P09

- 0646R Work Plan #18); June 24, 2009 (file CG

- P09

- 0666 Work Plan #19). 43 pages.GEN -7 46. CGS. Dwyer Property, CGS Project No. CG

- 06

- 0109. Well Gauging, Purging, and Sampling. April 2009. 71 pages.

47. Maryland Geological Survey. Bulletin 34, Water Resources and Estimated Effects of Ground

wate r Development, Cecily County, Maryland. 1988. Bound Report.

48. Maryland Geological Survey. Geologic Map of Cecil County, Maryland. 1986. 1 sheet.

49. USGS. The Regional Aquifer System Underlying the Northern Atlantic Coastal Plain in Parts of North Carolina, Virginia, Maryland, Delaware, New Jersey, and New York – Summary. USGS Professional Paper 1404

- A. 1992. Bound Report.

50. Driscoll, Fletcher, G. Groundwater and Wells

. Second Edition. 1986. Excerpt 5 pages.

51. Envirosystems, Inc. Analytical Data Package f or samples Received April 15, 2009, Dwyer Property, Report No. R 0905039. April 15, 2009. 42 pages.

52. EPA. Method 8260B, Volatile Organic Compounds by Gas Chromatography, Mass Spectrometry (GC/MS). December 1996. 9 pa ges. On

- Line Address : http://www.epa.gov/waste/hazard/testmethods/sw846/pdfs/8260b.pdf

53. Envirosystems, Inc. Analytical Data Package f or Samples Received April 22, 20 09, MDE – LRP Dwyer Property, Report No. R 0905047. April 22, 2009. 72 pages.

54. Air, Water, and Soil Laboratories , Inc. Certificate of Analysis, Final Report, Laboratory Order ID 09090603. December 4, 2009. 27 pages.

55. Air, Water, and Soil La boratories , Inc . Certificate of Analysis, Final Report, Laboratory Order ID 09090472. December 4, 2009. 32 pages.

56. Envirosystems, Inc. Analytical Data Package f or Samples Received April 17, 2009, Dwyer Property, Report No. R 0905046. April 17, 2009. 43 pages.

57. Envirosystems, Inc. Analytical Data Package f or Samples Received April 28, 2009, Dwyer Property, Report No. R 0905045. April 28, 2009. 58 pages.

58. Air, Water, and Soil Laboratories , Inc . Certificate of Analysis, Final Report, Laboratory Order ID 09090045. December 4, 2009. 17 pages.

59. Air, Water, and Soil Laboratories , Inc . Certificate of Analysis, Final Report, Laboratory Order ID 09090105. December 4, 2009. 24 pages.

60. Air, Water, and Soil Laboratories , Inc . Certificate of Analysis, Final Report, Laboratory Order ID 09090178. December 4, 2009. 18 pages.

61. Air, Water, and Soil Laboratories , Inc . Certificate of Analysis, Final Report, Laboratory Order ID 09090194. December 4, 2009. 27 pages.

62. CGS. Groun d Water Contour Map – Perched Monitoring Wells. September 14, 2009. 1 sheet.GEN -8 63. CGS. Ground Water Contour Map – Shallow Monitoring Wells. September 14, 2009 . 1 sheet.

64. CGS. Ground Water Contour Map – Deep Monitoring Wells. September 14, 20 09 . 1 sheet.

65. CGS. TCE Isoconcentration Map – Perched Monitoring Wells. September 2009 . 1 sheet.

66. CGS. TCE Isoconcentration Map – Shallow Monitoring Wells. April 2009. 1 sheet.

67. CGS. TCE Isoconcentration Map – Deep Monitoring Wells. April 2009. 1 sheet.

68. Envirosystems, Inc. MDL Study: LOW SOM1.2, Matrix Water. August 15, 2008. 2 pages.

69. Tetra Tech. Record of Telephone Conversation Between Alicia Shultz, HRS Specialist and Emile Shaw, Quality Assurance Officer, Air, Water, and Soil Laboratories. February 22, 200 9 . 1 page.

70. Maryland Hazardous and Solid Waste Management Administration. A Preliminary Assessment of Central Chemical Corporation Elkton, Maryland. MD

- 325. November 1989. 49 pages.

71. CGS. Expand ed Remedial Investigation, Dwyer Property, MD

- 313, Routes 279 and 545, Elkton, Cecil County, Maryland. March 2010. Excerpt. 101 pages.

72. Maryland Geological Survey. Hydrogeology of the Upper Chesapeake Bay Area, Maryland, with Emphasis on Aquifers in the Potomac Group. Report of Investigations No. 39. 1984. Bound Report.

73. MDE . Waste Management Administration. Focused Site Inspection of the National Fireworks Site Elkton, Maryland. (MD

- 386) Final Report, Volume I. September 1994. 66 pages

.

74. Baloochestani, Farshad. Estimation of Hydraulic Properties of the Shallow Aquifer System for Selected Basins in the Blue Ridge and the Piedmont Physiographic Provinces of the Southeastern U.S. Using Streamflow Recession and Baseflow Data. Georgia State University College of Art and Sciences Doctoral Dissertation. 2008. Excerpt 2 pages.

75. Gonthier, Gerald J. and Gregory C. Mayer. “Slug

- Test Results from a Well Completed in Fractured Crystalline Rock, U.S. Air Force Plant 6, Marietta, Georg ia.” Proceedings of the 2003 Georgia Water Resources Conference , April 23

- 24, 2003

. 4 pages.

76. MDE, Hazardous and Solid Waste Management Administration. A Preliminary Assessment of National Fireworks Site Elkton, Maryland (MD

- 386) . January 1990. 50 pages.

77. Martel Laboratories Inc. ATK Tactical Systems Comp. LLC Final Lab Report. April 15, 2009. 7 pages.

78. Atlantic Coast Laboratories, Inc. Report of Analysis Alliant Techsystems, Inc. April 2, 2009. 33 pages.

79. Martel Laboratories Inc. ATK Tactical Systems Comp. LLC Final Lab Report . September 8, 2009. 7 pages.

80. Atlantic Coast Laboratories, Inc. Report of Analysis Alliant Techsystems, Inc. September 14, 2009. 38 pages.GEN -9 81. Advanced Land and Water, Inc. Groundwater Supply Exploration and Development, Municipal Well No. 4, Town of Elkton, Cecily County, Maryland. ALWI Project No. CE1E141. October 23, 2009. 13 pages.

82. Envirosystems, Inc. Analytical Data Package, For Samples Received April 24 , 2009, MDE – LRP Dwyer Property, Report No. 0905048. April 24, 2009. 48 pages.

83. Tetra Tech. Ground Water Plume, Elkton, Cecil County, Maryland. Site Layout Map. November 6, 2009. 1 page.

84. Columbia Technologies, LLC. Subsurface Characterization Using Membrane Interface (MIP) and Soil Conductivity (SC) Technologies, Dwyer Property MD

- 313, Elkton, Maryland. September 24, 2009. Excerpt 53 pages.

85. Tetra Tech. Dwyer Ground Water Plume Volume Calculations. Project Note Prepared by Jordan Vaughn, Geologist. Ma y 12, 2010. 7 pages.

86. MDE. W.L. Gore (Left Bank) Site (MDE

- 303), Elkton, Maryland. Undated

. On

- Line Address: http://www.mde.maryland.gov/assets/document/brownfiel ds/WLGore.pdf

. 2 pages.

87. Maryland Geological Survey. “ The Geology of Cecil County, Maryland .” Bulletin 37

. 1990. Bound Report.

88. USGS. “Hydrogeologic Framework of the Coastal Plain of Maryland, Delaware, and the District of Columbia.” US GS Professional Paper 1404

- E. January 1, 1991. Bound Report.

89. MDE. Water for Maryland’s Future: What We Must Do Today. Final Report of the Advisory Committee on the Management and Protection of the State’s Water Resources. Volume 2: Appendices . July 1, 2008. Excerpt 2 pages. (Document available at: http://www.mde.state.md.us/Water/wolman_fullreport.asp ).

90. MDE (MDE). Well Construction Logs, Appendices E, I, J, L, O, R, and U. 2007

- 2009. 274
pages.

91. Tetra Tech. Record of Telephone Conversation Between Alicia Shultz, HRS Specialist and Gary Schold, MDE, Voluntary Cleanup Program, Project Manager. Regarding Vicon Property

. October 30, 2009. 1 page.

92. MDE. Home Well Questionnaire for RW

- 1 and RW

- 2. Undated. 17 pages.

93. Martel Laboratories Inc. ATK Tactical Systems Comp. LLC Final Lab Report. January 11, 2010. 37
pages.

94. Atlantic Coast Laboratories, Inc. Report of Analysis Alliant Techsyst ems, Inc. December 17, 2009. 36 pages.

95. Geraghty & Miller, Inc. Phase I: Task 1 Report – History of Land, TCE/Solvent, and Ground

- Water Use On and Near the Morton Thiokol, Inc., Elkton Division Facility, Elkton, Maryland. August 12, 1987. 43 pag es.GEN

- 10 96. MDE . Waste Management Administration. Preliminary Assessment/Site Inspection of New Jersey Fireworks. March 2001. 40 pages.

97. MDE . Waste Management Administration. Expanded Site Inspection of the Route 7 Chemical Dump (MD

- 75)/New Jersey Fireworks Site. May 2005. 47 pages.

98. Maryland Hazardous and Solid Waste Management Administration. A Preliminary Assessment of Iron Hill Road Site Elk t on, Cecil County, Maryland , MD

- 254, Final Report. October 1998. 12 pages.

99. EPA. Approval by Edwin Erickson of a Removal Action Elkton Farm Site

, Elkton, Cecil County, Maryland. January 15, 1992. 8 pages.

100. MDE . Waste Management Administration. Environmental Response and Restoration Program. Site Assessment Division. Preliminary Assessm ent of the Elkton Farm (MD

- 433). September 1993. 2 8
pages. (pages 11 and 12 are missing from the original report).

101. MDE . Waste Management Administration. Formerly Used Defense Site Inspection of the Elkton Farm Firehole (MD

- 433). November 2003 . 2 6 pages.

102. Reference Reserved.

103. MDE . Hazardous and Solid Waste Management Administration. A Screening Site Inspection of Crouse Brothers Excavating, Elkton, Maryland (MD

- 314) Volume I. September 1990. 40 pages.

104. Little Creek Reuse C ommittee. The Little Elk Creek, Maryland, Area Wide One

- Cleanup Program Pilot. January 12, 2004. 1 sheet.

105. CGS. Monitoring Well Sample Collection Form s

. Various Dates including September 1, 3, 4, 8, 9, 2009, and August 31, 2009

. 48 pages.

106. C GS. Monitoring Well Sample Collection Form. Various Dates including September 21 through 25, 2009. 29 pages.

107. Johnson, A.I. “Specific Yield – Compilation of Specific Yield for Various Materials.” USGS Water

- Supply Paper 1662

- D. 1967. 2 page s.

10 8. Tetra Tech. Letter Regarding Dwyer Property, Data Quality Reports with Appendices. From Josh Cope, Chemist. To Lorie Baker, Site Assessment Manager, EPA. March 22, 2010. 197 pages.

109. EPA Evaluating Ground Water Plumes Under the Hazard Ranking System. EPA

- 540/F

- 95/034. September 1998. 5 pages.

110. Whispering Pines Mobile Home Park. Annual Drinking Water Quality Report. 2009. 2 pages.GEN

- 11 SITE DESCRIPTION

The Dwyer Property Ground Water P lume site is located north of the intersection of Maryland Route 545 (Blue Ball Road) and Maryland Route 279 (Elkton Road) in Elkton, Cecil County, Maryland, as shown in Reference 3 9 and Figure 1

. The ground water plume underlies a property known as the Dwyer Property. The location of the Dwyer Property is shown in Reference 3. The Dwyer Property Ground Water Plume is located in the area of a former explosive devices manufacturing facility (Ref. 3; Ref. 13, p. 9; Ref. 28; Ref. 83 ; Ref. 104). The explosive facility was operated by Triumph Explosives, which manufactured products for the military. The explosives facility encompassed over 180 acres that included the Dwyer Property (Ref. 26, p p

. 2c, 12). The extent of the explosives facility is illustrated in Reference 104 and Figure 1 of the HRS documentation record

. Land use adjacent to the ground water plume is residential and commercial to the north and east; commercial, industrial, and agricultural to the south; and industrial to the west. Dogwood Run flows to the southwest along the w est ern portion of the Dwyer P roperty Ground Water Plume facility property into Little Elk Creek. An apartment complex (Rudy Park Development) is located adjacent and southeast of the Dwyer P roperty Ground Water Plume (Ref. 3; Ref. 13, p. 9; Ref. 28; Ref. 3 9; Ref. 83).

The site encompasses a trichloroethylene (TCE) ground water plume. A specific source of the TCE ground water plume has not been identified (Ref. 13, p. 46 ; Ref. 71, p. 48 ). The TCE ground water plume was initially identified by the Maryland Department of the Environment (MDE) during the following investigations: a preliminary assessment (PA) in March 1989 (Ref. 16, pp. 1, 17) ; a screening site inspection (SSI) in February 1989 (Ref. 15, pp. 1, 19); an expanded site inspection (ESI) in April 2000 (Ref. 8, pp. 3, 10); and a site inspection (SI) in April 2002 (Ref. 14, pp. 1, 7). To identify the source of the ground water plume, MDE or MDE contractors conducted a passive soil

- gas investigation , test pit investigations, membrane interface probe (MIP) surveys , direct

- push soil boring investigation s , ground
water sampling, and a soil vapor investigation (Ref. 13, p. 7; Appendix B

- 2, p. 209; Appendix C, pp. 220, 223; Ref. 84, pp. 1, 4). None of these investigations identified the original source o f the plume (Ref. 13, pp. 28, 46 ) . In response, MDE contactors conducted a remedial investigation and feasibility study (RI/FS) in June 2004 (Ref. 13, pp. 7, 23, 46). The MDE RI/FS included a review of the earlier investigations and additional sampling i n an attempt to delineate the plume and source of the plume (Ref. 13 , pp. 1, 7, 8, 9, 46 ). The RI/FS did not identify the source of the plume (Ref. 13, p. 46). MDE contractors completed a n

e xpanded r emedial i nvestigation (ERI) in March 2010 (Ref. 71 , p.1 ) . The ERI did not identify the source of the plume (Ref. 71, p. 48). Summaries of the investigations completed to identify the source of the ground water plume are provided later in this section.

Historic Land Use of the Dwyer Property and Surrounding Area

In 1992, t he U.S. Army Corp s of Engineers (USACE) environmental consultant conducted investigations of operations and ownership of the Cecil Industrial Park (Formerly Triumph Explosives, Inc.) in Elkton, Maryland

, which includes the location of the Dwyer Property Ground Water P lume. The USACE report (Reference 26) documenting operations previously conducted at the property describes historic land uses in the area of the ground water plume (Ref. 26, p. 10). The Triumph Fusee and Fireworks plant

manu factured fireworks and fusees (similar to roadside flares) on a 5

- acre plot of land on the east side of Blue Ball Road (later identified as the Dwyer Property) from 1933 until 1935 (Ref. 26, p. 10; Ref. 7 ; Ref. 18; Ref. 39 ). Materials used by Triumph Fus ee and Fireworks in the manufactur e of fireworks and fusees include d powdered metals, perchlorate, chlorate mixes, barium nitrate, charcoal, sulfur, sulfur mixes, saltpeter, carbon tetrachloride, hexachlorobenzene, alcohol, picric acid, stearine, dextrine, and potassium perchlorate (Ref. 26, pp. 10, 11).

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. co m. S o m e s h a ll ow a nd d ee p o b se r ve d r e l ease we ll s a r e in clu s t e r s (a t th e s am e l oca ti o n )

. Th e s h a ll ow we ll i de ntifi ca ti o n app e ar s f i r s t , f o ll owe d b y th e d ee p we lL O nl y we ll s that m ee t t he o b served release cr it eri a a pp ea r o n t h i s f ig ur e. Approximate Site Location = •

Maryland 

### Ground Water Plume Elkton

, Cecil COlUlty

, Maryland 

### Figure 1 The Area of the Shallow and Deep Ground Water Plumes

TDD No. E43- 0 3 0

- 09 -1O- 00 1 M a p cre a ted o n Ma y 11
, 2 010 EPA C ont ra ct No. EP-S3- 0 5- 0 2 b y D. C all

, Tet ra Tech EM Inc

.GEN

- 13 In 1935, Triumph Fusee and Fireworks entered into a contract with the U.S. Navy to produce floatlights. A floatlight is a device used both as a marker and a device to judge wind direction over water. All production was performed on the east side of Blue Ball Road. Triumph Fusee and Fireworks was a prototypical “backyard operation.” The workers at the plant consisted mainly of two families. The production area consisted of small one

- room bu ildings (Ref. 26, p. 11).

In 1938, Triumph Fusee and Fireworks began to perform contract work for the U.S. Army in response to the needs of a growing defense industry. On April 18, 1938, Triumph Fusee and Fireworks changed its name to Triumph Explosives . The new purpose of the company was to produce naval, military, and aeronautical pyrotechnics and signal devices, commercial explosives, shells, projectiles, bombs, grenades, fuses, and other forms of naval, military, and aeronautical munitions. A research laboratory and trinitrotoluene ( TNT ) melt

- pour system was added to the operations (Ref. 26, p. 11). Triumph Explosives reportedly manufacture d 81 millimeter ( mm ) mortar shells (Ref. 26, p. 11), anti

- tank mines, ordnance, and pentolite (Ref. 26, p. 12) . Pentolite contains a mixture of pentaerythritol tetranitrate (P.E.T.N.) and TNT (Ref. 26, p. 16).

Triumph Explosives operated on both the east and west sides of Blue Ball Road. Documentation refers to
t he west side a s the Navy side and the east side as the Army side because the west side was used to manufacture products for the Navy and the east side was used to manufacture products for the Army (Ref. 26, pp. 12, 14). The Army side was also referred to as the Incendiary or the Pyrotechnics Area (Ref. 26, pp. 12, 13). The relationship between the two sides is not explained in site documentation. Approximately 12,000 persons operated at the two plants between approximately 1941 and 1946 (Ref. 26, p p

. 12, 13 , 18, 20, 21 ).

According to one of Triumph Explosives’ employees, all wastes were disposed of in an area known as the firehole, including wastes from the Army and Navy sides of the plant (Ref. 26, p. 17). The firehole was a pit several feet deep and very broad located about 2 miles from the plant , near Zeitler Road. The exact location of the firehole has not been identified (Ref. 26, p. 17). The waste included fireworks chemicals that could no longer be used, such as barium nitrate, perchlorate, chlorate mixes, and sulfur mixes. According to a Triumph News Topics a rticle, there were two colors for waste disposal drums at Triumph Explosives. Red drums were for explosives waste, and yellow drums were for other waste. According to one of Triumph Explosives’ employees, the contents of the red barrels were always kept wet with ether or alcohol. The red barrels also had markings designating specific explosives. Some types of explosives were dangerous to mix and were kept separate. Workers were cautioned against overfilling the barrels because spil led mix could eventually dry and be dangerous. These barrels were also taken to the firehole for disposal (Ref. 26, p. 17).

The wet waste explosive mixes disposed of at the firehole w ere spread out thinly so that they did not form piles that would ex plode instead of burn, and so that they would dry quickly. The drums were rinsed with water at the firehole to remove explosive residues . T he explosives would th en be lit and allowed to burn. W atch houses were established to ensure that fire did not breach the confines of the firehole (Ref. 26, pp. 17, 18).

In 1942
, Triumph Explosives was seized by the Navy allegedly due to contract padding. The plant was to be returned to private control when corporate officers acceptable to both the Army and the Nav y could be installed (Ref. 26, p. 20). Triumph Explosives ceased operations on the east side of Blue Ball Road at the end of World War II. On June 1, 1946, the property was sold to Bowers Battery and Spark Plug Company (Bowers). The limited available information regarding the Bowers operations indicates that it was active from 1946 until 1948 (Ref. 26, p. 21)

. On April 20, 1948, Bowers sold the property to Aerial Products, Inc. (Aerial) (Ref. 26, p. 22).GEN

- 14 Mr. Martin Dwyer was the Vice President and ow ner of Aerial, which was active on the property from 1948 to 1958. Aerial conducted operations on both the east and west sides of Blue Ball Road. The facilit y encompassed 225 acres , occupied by numerous production buildings including seven warehouses

. A erial referred to plant facilities on the Army side of Blue Ball Road as Plant 1 and on the Navy side as Plant 2. A variety of munitions, components, signal flares, distress signals, and other items were manufactured in these buildings (Ref. 26, p. 25). A third plant, Plant 3 was constructed on the east side of Blue Ball road to produce 20

- mm shells for the Navy from 1952 to 1953 (Ref. 26, p. 25).

The exact types and amounts of hazardous materials handled during Aerial site operations are not documente d. Solvents, metals cleaners, and metal degreasers were reportedly used in the machine sh o p. S olvents were also reportedly used to clean work areas and machinery. A erial employees indicated that “carbon tet” (carbon tetrachloride) was used for cleaning certain areas. The solvents were kept in drums (Ref. 26, pp. 26, 32, 34).

Mr. Martin Dwyer, former Vice President of Aerial, purchased the property in 1958 when Aerial filed for bankruptcy. Mr. Dwyer used the property for production of incendiary flare s and grazing land for cattle until 1972

, when all operations terminated. In 1986, the ownership of the property transferred to Mr. Dwyer’s heirs (Ref. 13, p. 1 0 ).

Numerous environmental investigations have been complet ed between 198 9 and 20 10 in an attempt to identify the source of the ground water plume. Investigations conducted to identify the source of the ground water plume have focused on the Dwyer Property because the highest concentrations of TCE in ground water were identified from monitoring wells installed on this property. A brief summary of each investigation completed is provided in the sections below . The summary of each i nvestigat ion presented below focuses on the results related to the TCE ground water plume. Other contaminants identified in ground water during these investigations, such as metals or perchlorates, are not discussed because the purpose of summarizing the investigations is to provide evidence of significant attempts to identify the

sourc e of the TCE ground water plume. Ground Water Plume Investigations

Preliminary Assessment – March 1989

In March 1989, MDE conducted a PA at the Dwyer Property (Ref. 16, pp. 1, 3, 17). The PA was conducted because the property had been a former munitions manufacturing plant. During the PA, the property was observed to be wooded with demolished buildings and evidence of dumping (Ref. 16, pp. 2, 3, 5). According to the PA report , a consultant to Mr. Dwyer installed three monitoring wells on the property: Well 1 on the southern portion of the property, at 20 feet (ft) below ground surface (bgs); Well 2, north of Well 1, to 15 ft bgs; and Well 3, in the northern portion of the property, to 19 ft bgs. MDE obtain ed split samples of ground water collected from the se wells. The ground water s ampl ing results showed contamination of trans

- 1,2

- dichloroethene (DCE) up to 19,200 micrograms per liter ( μg/L ) , TCE up to 15,800 μg/L, and tetrachloroethylene ( PCE ) up to 360 μg/L. MDE sampled f ive private wells located north of the Dwyer Property along Dogwood Road. The private well samples did not contain these contaminants or any other volatile organic compounds (VOC) (Ref. 16, pp. 2, 14, 17, 23). A 1- ft

- deep well, possibly hand dug, located on the Dwyer Property contained contamination including TCE (43 μg/L), PCE (4 μg/L), and trans

- 1,2

- DCE (31 μg/L) (Ref. 16, pp. 2, 17, 23). A source of the chlorinated organic carbon contamination was not identified during the PA (Ref. 16, pp. 15, 16).GEN

- 15 Screening Site Inspection – February 1989

As part of a 1989 SSI , MDE sampled the three monitoring wells on the Dwyer Property. The samples were split with Mr. Dwyer’s consultant. MDE also sampled five domestic wells located on Dogwood Road immediately north of the Dwyer Property. The monitoring well samples cont ained trans

- 1,2

- DCE up to 19,200 μg/L, TCE up to 1 5,8 00 μg/L, and PCE up to 360 μg/L. The residential wells did not contain
any VOCs or chlorinated organics (Ref. 15, pp. 19, 20, 21, 34, 35, 47, 48, 53, 54, 56, 57).

Expanded Site Inspection – April 2000

In April 2000, MDE conducted an ESI (Ref. 8, p p. 3, 4, 10). The investigation included collection of six ground water , five sediment

, four surface water

, and nine surface a nd subsurface soil samples . All of the samples were analyze d for target compound l ist ( TCL ) and target analyte list ( TAL ) constituents ; aqueous samples were also analyzed for dissolved metals (Ref. 8, pp. 10, 11, 18). The ground water and surface water sampling locations are shown on Figure 9 (page 30) and Figure 10 (page 31), respecti vely, of Reference 8. A soil sampling location map is not provided in the ESI report, but Table 4 of that report lists the sampling locations (Ref. 8, p. 11). No VOC s were detected in any of the 9 soil samples. E stimated concentration s of PCE (1 microgr am per kilogram [ μg/kg ] ) and TCE (2 μg/kg) were detected in subsurface soil sample s 2A and 3A (Ref. 8, pp. 11, 12 , 18 ). The subsurface soil samples were collected at depths from 4 to 6 ft bgs (Ref. 8, p. 19). The low concentrations of PCE and TCE in the soil samples may be attributable to contaminated shallow ground water impacting the overlying soil. These chlorinated VOCs were detected in a 1

- ft

- deep shallow well located on the Dwyer Property (Ref. 16, pp. 2, 17, 23). Ground
water samples collected fr om the monitoring wells contained carbon tetrachloride (up to 18 μg/L), chloroform (up to 10 μg/L), cis

- 1,2

- DCE (up to 1 μg/L), PCE (up to 91 μg/L), and TCE up to (78 μg/L). The concentrations of PCE and TCE were data qualified with a specification of “E,” indicating exc e edance of a theoretically greater value (Ref. 8, p. 11). Three surface water samples collected downs tream or adjacent to the Dwyer P roperty from Dogwood Creek (which flows along the northern boundary of the Dwyer P roperty) contained TCE a t concentrations of 11, 6, and 5 μg/L (Ref. 8, pp. 11, 31).

Site Investigation – April 2002

The April 2002 MDE SI report documented conditions of the property at the time of sampling to be h eavily wooded with young hardwood trees; approximately 100 buildi ngs of various sizes and conditions (partially standing, foundation only, collapsed); presence of 55

- gallon drums; piles of shell casing s ; and tin cans. The SI report also cited the use of degreasers on the property when the property had been utilized for manufacturing incendiary devices and munitions between the 1930s and the 1950s (Ref. 14, pp. 1, 3, 5, 23 through 28 )

S urface soil, exploratory soil boring, ground water , and surface water samples were collected in support of the SI (Ref. 14, pp. 1, 6, 7, 8). The sampling locations are specified in Reference 14, pages 47, 49, and 51. The sampling included the collection of five surficial soil samples (4 to 6 inches below grade) for VOCs

, semivolatile organic compounds ( SVOC ), and priority pollutant metals analys es ; and eight subsurface soil boring samples collected for x

- ray fluorescence (XRF) analysis . Nine ground water samples collected from open boreholes and three surface water samples were analyzed for VOC s (Ref. 14, pp. 7, 8, 49, 63, 65). The SI re port indicates TCE was detected i n one surface soil sample (S

- 4 [94]) and one subsurface soil sample (S

- 3A [00]) at concentrations of 0.001 and 0.002 mg/kg, respectively, and PCE was detected in one surface soil sample (S

- 1 [94]) and one subsurface soil sa mple (S

- 2A [00]) at concentrations of 0.002 and 0.001 mg/kg, respectively (Ref. 14, pp. 9, 14). The SI does not indicate when these soil samples were collected and analyzed, but these events appear to have occurred during an earlier investigation (Ref. 14

, pp. 128 through 142). This small area of soil contamination is expected to be due to historical use becauseGEN

- 16 the size of the area was small and the concentrations detected were low (Ref. 14, pp. 9, 14). Ground water samples collected during the SI conta ined carbon tetrachloride, cis

- 1,2 - DCE, PCE, and TCE (Ref. 14, p. 9). The analytical data for the ground water samples are not provided in the SI. No VOCs were detected in the surface water samples (Ref. 14, pp. 10, 13, 139 through 143).

The subsurfac e soil investigation completed during the SI provided the following information regarding the underlying geology/stratigraphy: a continuous confining layer, which would act to inhibit downward migration of the dissolved

- phase contamination, was not identi fied and the detection of dissolved

- phase contamination below the overburden/saprolite interface suggests that a continuous confining layer is not present (Ref. 14, pp. 14, 53, 55, 57, 59, and soil borings pages 80 th r ough 117). An interpretation of the

a nalytical data included in the SI report indicated that the presence of dissolved

- phase VOC contamination in most of the area investigated suggested that multiple sources of contamination likely contributed to the VOC contamination (Ref. 14, p. 14).

Memb rane Interface Probe (MIP ) Direct

- Push Investigation s – 2003 and 2004

In 2003 and 2004, direct

- push investigations utilizing MIP and soil conductivity (SC) technology, were conducted to characterize subsurface soil in the vadose zone of the ground water pl ume. The investigation was used to more accurately define the extent of impacted soil and ground water . A total of 42 MIP borings were completed in the area of the ground water plume at biased locations

, including at the boundary of another potential sou rce of the TCE, the adjacent Vicon property (Ref. 13, p. 18 and Appendix C [Figure 1, p. 227]). The Vicon property is located northeast of the Dwyer Property (Ref. 18). A discussion of the Vicon property is provided in the Attribution section of this HRS documentation record. The depths of the borings ranged from 20 to 70 ft bgs . The MIP investigation indicated two distinct areas of TCE contamination. One area is located near MW -2A and the other is located near the Vicon property boundary (Ref. 13, p. 25 and Appendix C, p. 226, Figures 1 through 7, pp. 226 through 237).

Remedial Investigation/Feasibility Study – August 2005

The August 2005 MDE RI/FS include d a review of existing data

, a test pit investigation and associated soil sampling , and the col lection of ground water from 15 monitoring wells. The test pit investigation was performed in areas where underground storage tanks (UST) or other fluid storage containers were suspected, near a suspected drum dump, and at areas with tin can piles and flare canisters. The direct

- push soil boring investigation and associated soil sampling occurred at a 50 - by 70

- ft area possibly used as a solvent pit. The ground water samples were collected from 15 existing monitoring wells located on the Dwyer Property a nd analyzed for VOCs, perchlorate, and explosi ves (Ref. 13, pp. 16, 17, 18, 19, 20, 299 ).

The test pits were examined for visual signs of contamination such as soil discoloration and staining

. Soil samples were collected from areas of visible contamination. The test pit locations are shown o n Figure 3

- 1 of Reference 13 (Ref. 13, pp. 7, 16, 17 , 54 ). Seven test pits were excavated to a maximum depth of 8 ft bgs

. Soil samples from t he seven test pit s were collected using Encore devices and were analyzed for VOCs ( EPA analytical method SW8 4 6 5035), perchlorate (EPA 314), and explosives ( EPA analytical method SW846 8330) (Ref. 13, p. 17). Results from the soil sample analysis are provided in Table 4

- 1 of Reference 13 , p. 65

. TCE was not detected in any of the soil samples. PCE was detected in one soil sample collected from test pit TP

- 4 at 18 μg/L (Ref. 13, pp. 24, 308 and Figure 3

- 1, p. 54). This sample was collected at 5 ft bgs (Ref. 13, p. 54). The low concentration of PCE detected in this sample may be attributable to contaminated shallow ground water. PCE was detected in a 1

- ft

- deep shallow well (Ref. 16, pp. 2, 17, 23)

.GEN

- 17 Five direct

- push soil borings were completed to the water table in an area allegedly previously used as a solvent pit (see Figure 3-1 , page 54, of Reference 13 ) ( Ref. 13, pp. 7, 17). Six soil samples were collected from intervals with visible contamination or where VOCs had been detected via a photoionization detector (PID). The soil samples were analyzed for VOCs (SW8 4 6 5035), pe rchlorate (EPA 314), and explosives (SW846 8330) (Ref. 13, p. 17, 300). No VOCs were detected in the subsurface soil samples (Ref. 13, pp. 24, 30 6 ).

Surface soil samples were collected from locations on the Dwyer Property where historical information in dicated possible sources of contamination. The soil samples were collected using Encore devices and analyzed using EPA Method 8270 (Ref. 13, p. 17). No VOCs were detected in surface soil samples (Ref. 13, p. 24).

The three monitoring wells installed d u ring the RI/FS were completed in the Potomac Group Formation (Ref. 13, p. 19). (The RI/FS identifies the sediments at the Dwyer Property as the Columbia Formation, but more recent and in

- depth investigations have determined that the sediments are the Potomac Group [Ref. 71, pp. 38, 39]; therefore, these sediments will be referred to as the Potomac Group.) The Potomac Group Formation overlies the bedrock underlying the Dwyer Property (Ref. 71, p. 39). The monitoring well locations were selected in order to delineate the contaminant plume and to assess ground water contamination close to the Vicon property, identified as another possible source of the TCE ground water plume

. Reference 13, Figure 2 -1 , page 53 shows the locations of the monitoring wells (Ref. 13, p. 19). T en ground water samples were collected from the monitoring wells and were analyzed for VOCs (Ref. 13, p. 20). TCE was detected in all wells except MW

- 6D. The concentrations ranged from an estimated concentration of 0.2 μg/L detected in MW

- 5D to 18,000 μg/L in MW

- 8 (Ref. 13, pp. 27, 286, 287, 290, 297). The RI/FS concluded that a source of the TCE ground water plume could not be identified from t he analytical results obtained during the RI/FS or the review of data collected during previous investigations (Ref. 13, pp. 7, 28, 29, 46).

Perchlorate was detected in five monitoring wells. The highest concentration was detected in MW

- 2A (16 μg/L). This well was considered to be off site, not on the Dwyer Property. Perchlorate was detected in

a reas where high concentrations of TCE were identified (Ref. 13, p. 28).

Expanded Remedial Investigation – March 20 10

The ERI report submitted in March 2010 documents an interactive series of field investigation activities performed at the Dwyer Property and on nearby properties between January 2006 and January 2010. These activities included the installation of 44 monitoring wells, well and wellhead replacement activities, five groundwater sampling events, five additional MIP surveys, establishment of fi ve stream gauge stations, installation of 33 soil borings, and a series of monitoring well and stream gauge station gauging events (Ref. 71, p. 9 ). The ERI did not identify a source of the ground water plume (Ref. 71, p. 48). Results from the ERI are discussed in detail in Section 3.0 of this HRS documentation record.Source No: 1 Source Characterization

GEN

- 18 2.2 SOURCE CHARACTERIZATION

2.2.1 SOURCE IDENTIFICATION

Source Number: 1

Source Type: Ground water plume with no identified source (other)

Description and Location of Source (wit h reference to a map of the site):

The Dwyer Property Ground Water P lume site consists of a plume of contaminated ground water as presented in Reference 39 and Figure 1

. The plume includes a shallow ground water plume (shown in Reference 39 as blue) and a deep ground water plume (shown in Reference 39 as red). The plumes were delineated by using data obtained from monitoring well s for which an observed release to ground water has been documented (see Section 3.1.1 of this HRS documentation record ). Alth ough the aquifers within and underlying the ground water plume are interconnected, a shallow and deep ground water plume was delineated for purposes of determining a volume calculation for the ground water plume (Ref. 85). As documented in Reference 85, the water column, the saturated thickness, and the specific yield for each well

are needed to determine the volume of the plume. These values are significantly different for shallow and deep wells (Ref. 85). Therefore, volume s for each well depth (plume d epth), shallow and deep, w ere determined. The area of the ground water plume was completed in accordance with Reference 109, Evaluating Ground Water Plumes Under the HRS.

As shown in Reference 39

, the TCE ground water plume is located between Maryland State Routes 545 and 213

, and on the north and south side s of State Route 279. Numerous sampling investigations were conducted to identify the source of the ground water contamination; however, none of the investigations

were able to attribute the ground water contamination to any known source, as documented in the Site Description section of this HRS documentation record. As stated in the HRS documentation record, the plume itself will be considered the source (Ref. 1, Section 1.1).

Investigations conducted to identify the source of the ground water plume have focused on the Dwyer Property because the highest concentrations of TCE in ground water were identified from monitoring wells installed on this property. Investigations at the Dwyer Property hav e included collection of soil samples at biased locations where historical information indicated that sources of contamination may have existed (Ref. 13, pp. 16, 17: Ref. 8, pp. 10, 11, 12, 18; Ref. 14, pp. 7, 8, 49, 63; Ref. 71, p. 9 ). The soil sampling investigations have not identified a significant source of TCE contamination (Ref. 13, p. 24 ; Ref. 71, p. 48 ). A small number of subsurface soil samples have contained TCE or other chlorinated compounds. However, these samples were collected at the same depths as shallow ground water (Ref. 8, pp. 11, 12, 19; Ref. 14, pp. 7, 8, 9, 14, 49, 63; Ref. 13, pp. 7, 16, 17, 24, 54, 308; Ref. 27, p. 4), leading to a conclusion that the probable source of the soil contamination is ground water contamination. The ve ry low number of detections of TCE in soil samples indicates a source of TCE soil contamination does not currently exist on the Dwyer Property.

The most recent investigation s completed on the Dwyer Property in the area of the ground water plume (summari zed in the March 2010 ERI report) suggest s that TCE has been present in ground water without significant degradation, consistent with the absence of an existing source of TCE and the presence of TCE in the ground water for a long period of time (Ref. 71, p. 46). The ERI investigation did not identify a source of TCE (Ref. 71, p. 48). The ERI investigation identified two ground water plumes and determined the areas of the plumes (Ref. 71, pp. 44, 47). Theses plume areas were not used to determine the volu me of the Dwyer Property plume because the wells used to identify the area of the ground water plume in the ERI (Reference 71) do not meet the criteria for documenting an observed release to ground water (Ref. 1, Table 2

- 3; Ref. 109).Source No: 1 Source Characterization

GEN

- 19 Documentation in Section 3.0 of this HRS documentation record, such as the direction of ground water flow and TCE isoconcentrations, supports the interpretation that a ground water plume is present with no identifiable source.

MDE conducted an extensive ground water invest igation at the Dwyer Property in 2009. The data generated from the investigation are used to identify and characterize the ground water plume shown in Reference 39 and Figure 1 (Ref. 27; Ref. 29; Ref. 71). Section 3.1.1 of this documentation record descr ibes the plume area and discusses the field investigation, sample analysis, sampling locations, and observed release samples. The volume of the plume is documented in Reference 85 in accordance with Reference 109

.

2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH SOURCE 1

The site is being scored as a ground water plume with no identified source (Ref. 1, Section 1.1). The ground water samples collected from the plume and their respective detection limits are provided in Section 3.1.1. The hazardous substance associated with the ground water plume is TCE (see Section 3.1.1). Reference 39 and Figure 1 show t he location of the ground water plume and the background and release monitoring wells

. As shown in Reference 39 and Figure 1, Source No. 1 includes a pl ume in shallow and deep ground water. Monitoring wells are completed within shallow and deep portions of the aquifer (Ref. 71, p. 10). To establish an observed release to ground water, shallow and deep background wells were identified to document background concentrations within the same relative depth of the shallow and deep release wells.

Table GEN1 provides a summary of the release and background wells and the concentration of TCE detected in each well. An observed release to both the shallow and deep monitoring wells (aquifers) has been documented. Shallow wells screen the upper portion of the water table aquifer or unconsolidated unit . Deep wells screen lower portions of the water table aquifer within the unconsolidated unit and the saprolite (weathered bedrock)

. None of the wells penetrate bedrock (Ref. 71, p. 18). The monitoring well locations are shown on Figure 3, Reference 71 , p. 82 and Reference 29. On

- site wells have a “DP” label

, indicating wells located on the Dwyer Property . Nearby wel ls (wells not on the Dwyer Property) have the following labels: “RP” for the well installed on the Ruddy property; “EGWS” for the Elkton Ground Water Study wells installed on the Terumo and City Pharmacy properties; and “VP” for the Vicon property wells (R ef. 71, p. 10). The water table aquifer is known as the Potomac aquifer, as documented in Section 3.1.1 of this documentation record.Source No: 1 Source Characterization

GEN

- 20 TABLE

- GEN1 GROUND WATER PLUME – BACKGROUND AND RELEASE MONITORING WELLS

Monitoring Well

Identification Hazardous S ubstances Date Sampled Conc. (μg/L) References for Well Depth and Location Reference for Concentrations Detected Shallow Aquifer

- Background wells

DP

- MW

- 09 Trichloroethylene 4/16/2009 5 U 27, pp. 1, 2, 6; 29 46, pp. 2, 39; 56, pp. 7, 17 ; 108, pp. 27

- 29

EGWS

- MW

- 01 Trichloroethylene 4/16/2009 5 U 27, pp. 1, 2, 6; 29 46, pp. 2, 10, 11; 56, pp. 7, 19; 108, pp. 27

- 29

VP

- MW

- 08 Trichloroethylene 4/16/2009 5 U 27, pp. 1, 2, 6; 29 46, pp. 2, 38; 56, pp. 7, 15; 108, pp. 27

- 29 Shallow Aquifer

- Release Wells

DP

- MW

- 01 Trichloroethylene 4/22/2009 2 1 0 27, pp. 1, 2, 6; 29 46, pp. 1, 8, 9; 53, pp. 7, 45 ; 108, pp. 30

- 47

DP

- MW

- 08 Trichloroethylene 4/23/2009 4,100 27, pp. 1, 2, 6; 29 46, pp. 1, 36, 37; 82, pp. 7, 32; 108, pp. 48

- 69

DP

- MW

- 10 Trichloroethylene 4 /23/2009 1,300 27, pp. 1, 2, 6; 29 46, pp. 2, 40, 41; 82, pp. 7, 34; 108, pp. 48

- 69

DP

- MW

- 12A Trichloroethylene 9/9/2009 252 27, pp. 1, 2, 6; 29 105, pp. 7, 8; 61, pp. 17, 26; 108, pp. 113

- 139

DP

- MW

- 14A Trichloroethylene 9/8/2009 1,060 27, pp. 1, 2, 6; 29; 90, pp. 32 to 37 105, pp. 13, 14; 61, pp. 12, 26; 108, pp. 113

- 139

DP

- MW

- 17B Trichloroethylene 4/24/2009 80 27, pp. 1, 2, 6; 29; 90, pp. 145 to 148 46, pp. 3, 65, 66; 82, pp. 7, 24; 108, pp. 48

- 69

DP

- MW

- 25A Trichloroethylene 9/1/2009 117 27, pp. 1, 2, 6; 29; 90, pp. 190 to 193 105, pp. 17, 18; 58, pp. 12, 16; 108, pp. 81

- 83

DP

- MW

- 26A Trichloroethylene 9/2/2009 112 27, pp. 1, 2, 6; 29; 90, pp. 201 to 204 105, pp. 21, 22; 59, pp. 7, 23; 108, pp. 85

- 108

DP

- MW

- 27A Trichloroethylene 9/3/2009 211 27, pp. 1, 2, 6; 29; 90, pp. 210 to 214 105, pp. 25, 26; 59, pp. 12, 23; 108, pp. 85

- 108

DP

- MW

- 28A Trichloroethylene 9/4/2009 1,350 27, pp. 1, 2, 6; 29; 90, pp. 221 to 225 105, pp. 29, 30; 60, pp. 9, 17; 108, pp. 109

- 111

DP

- MW

- 29A Trichloroethylen e 9/3/2009 907 27, pp. 1, 2, 6; 29; 90, pp. 232 to 236 105, pp. 33, 34; 59, pp. 17, 23; 108, pp. 85

- 108

DP

- MW

- 30A Trichloroethylene 9/4/2009 279 27, pp. 1, 2, 6; 29; 90, pp. 24 3 to 2 47 105, pp. 37, 38; 60, pp. 4, 17; 108, pp. 109

- 111

DP

- MW

- 31A Trichloroethylene 9/1/2009 120 27, pp. 1, 2, 6; 29; 90, pp. 25 4 to 257 105, pp. 41, 42; 58, pp. 8, 16; 108, pp. 81

- 83Source No: 1 Source Characterization

GEN

- 21 VP

- MW

- 07 Trichloroethylene 4/27/2009 4,100 27, pp. 1, 2, 6; 29 46, p. 2, 34, 35; 57, pp 7, 23; 108, pp. 70

- 80

EGWSQ

- MW

- 03 Trichloroethyle ne 4/17/2009 11 27, pp. 1, 2, 6; 29 46, pp. 1, 21, 22; 56, pp. 7, 21; 108, pp. 26

- 28 Deep Aquifer

- Background Wells

DP

- MW

- 03A Trichloroethylene 4/15/2009 6.9 27, pp. 1, 2, 6; 2 9 46, pp. 1, 18, 19; 51, pp. 6, 31; 108, pp. 2

- 25

DP

- MW

- 15C Trichloroeth ylene 4/28/2009 8.6 27, pp. 1, 2, 6; 2 9 ; 90, pp. 135 to 140 46, p. 2; 57, pp. 6, 35* ; 108, pp. 70

- 80 Deep Aquifer

- Release Wells

DP

- MW

- 02A Trichloroethylene 4/17/2009 55 27, pp. 1, 2, 6; 29 46, pp. 1, 14, 15; 56, pp. 7, 25; 108, pp. 26

- 28

DP

- MW

- 04 Trichloroethylene 4/21/2009 5,900 27, pp. 1, 2, 6; 29 46, pp. 1, 24, 25; 53, pp. 7, 33; 108, pp. 30

- 47

DP

- MW

- 04A Trichloroethylene 4/21/2009 6,800 27, pp. 1, 2, 6; 29 46, pp. 23, 24; 53, pp. 7, 39 ; 108, pp. 30

- 47

DP

- MW

- 07 Trichloroethylene 4/17/20 09 59 27, pp. 1, 2, 6; 29 46, pp. 1, 32, 33; 56, pp. 7, 23; 108, pp. 26

- 28

DP

- MW

- 12B Trichloroethylene 9/9/2009 320 27, pp. 1, 2, 6; 29; 90, pp. 1 8 to 25 105, pp. 9, 10; 61, pp. 19, 26; 108, pp. 113

- 139

DP

- MW

- 13A Trichloroethylene 4/21/2009 3,200 27, pp. 1, 2, 6; 29; 90, pp. 2 6 to 31 46, pp. 2, 52, 53; 53, pp. 7, 25; 108, pp. 30

- 47

DP

- MW

- 14B Trichloroethylene 9/8/2009 22,300 27, pp. 1, 2, 6; 29; 90, pp. 38 to 44 105, pp. 15, 16; 61, pp. 1 4 , 26 ; 108, pp. 113

- 139

DP

- MW

- 17C Trichloroethylene 4/24/2 009 120 27, pp. 1, 2, 6; 29; 90, pp. 149 to 154 46, pp. 3, 67; 82, pp. 7, 26 ; 108, pp. 48

- 69

DP

- MW

- 26B Trichloroethylene 9/2/2009 902 27, pp. 1, 2, 6; 29; 90, pp. 205 to 209 105, pp. 23, 24; 59, pp. 10, 23; 108, pp. 85

- 108

DP

- MW

- 27B Trichloroethylene 9/3/2009 11,900 27, pp. 1, 2, 6; 29; 90, pp. 215 to 220 105, pp. 27, 28; 59, pp. 12, 23; 108, pp. 85

- 108

DP

- MW

- 28B Trichloroethylene 9/4/2009 13, 2 00 27, pp. 1, 2, 6; 29; 90, pp. 226 to 231 105, pp. 31, 32; 60, pp. 11, 17; 108, pp. 110

- 112

DP

- MW

- 29B Trichloroethylene 9/3/2009 15,800 27, pp. 1, 2, 6; 29; 90, pp. 237 to 242 105, pp. 35, 36; 59, pp. 19, 23; 108, pp. 85

- 108

DP

- MW

- 30B Trichloroethylene 9/4/2009 12,200 27, pp. 1, 2, 6; 29; 90, pp. 248 to 25 3 105, pp. 39, 40; 60, pp. 6, 17; 108, pp. 110

- 112

DP

- MW

- 31B Trichloroethylene 9/1/2009 335 27, pp. 1, 2, 6; 29; 90, pp. 258 to 264 105, pp. 43, 44; 58, pp. 10, 16; 108, pp. 81

- 84Source No: 1 Source Characterization

GEN

- 22 DP

- MW

- 32B Trichloroethylene 8/31/2009 46.9 27, pp. 1, 2, 6; 29; 90, pp. 268 to 274 105, pp. 47, 48; 58, pp. 5, 16 ; 108, pp. 81

- 84

EGWS

- MW

- 02A Trichloroethylene 9/9/2009 17,100 27, pp. 1, 2, 6; 29 105, pp. 1, 2; 61, pp. 22, 26; 108, pp. 113

- 139

Notes: * For sample DP

- MW

- 15C, the collection form is missing and the chain of cus tody incorrectly identifies the sampl e as DP

- MW - 15B. μg/L = Micrograms per liter Conc. = Concentration DP = Dwyer Property EGWS = Elkton Ground Water Study

MW = Monitoring well

U = Analyte was analyzed for but not detected. The result reported is the adjusted reporting limit for the analyte

L = Potential l ow bias due to holding time violations, value is an estimate

VP = Vicon Property

List of Hazardous Substances Associated with Source

Trichloroethylene (TCE)

2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY

Containment Description Containment Factor Value References

Gas release to air: Not Scored (NS)

Particulate release to air: NS

Release to ground water: 10 1, Table 3 -2

Release via overland migration and/ or flood: NS

Notes: The Contaminant Factor Value for the ground water migration pathway was evaluated for “All Sources” for evidence of hazardous substance migration f ro m the source area ( “ source area ” includes the source and any associated containment structures). A containment factor value of 10 has been assigned based on existing analytical evidence of both hazardous substance migration (contamination detected in ground water samples) ( s ee Section 3.1.1 of this HRS documentation record; Ref. 1, T able 3

- 2).Source No: 1 Source Hazardous Waste Quantity

GEN

- 23 2.4.2 HAZARDOUS WASTE QUANTITY

2.4.2.1.1 Hazardous Constituent Quantity

Description

The information available is not sufficient to evaluate Tier A source hazardous waste quantity, as required in Section 2.4.2.1.1 of the HRS (Ref. 1). As a result, hazardous constituent quantity is not scored and the evaluation of source hazardous waste quantity proceeds to Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1).

Hazardous Constituent Quantity Assigned Value: Not scored

2.4.2.1.2 Hazardous Wastestream Quantity

Description

The information available is not sufficient to evaluate Tier B source hazardous wastestream quantity, as required in Section 2.4.2.1.2 of the HRS (Ref. 1). As a result, hazardous wastestream quantit y is not scored and the evaluation of source hazardous waste quantity proceeds to Tier C, volume (Ref. 1, Section 2.4.2.1.2).

Hazardous Wastestream Quantity Assigned Value: Not scored

2.4.2.1.3 Volume

Description

The volume of the ground water pl ume is documented in Reference 85

, and the area is illustrated in Reference 39. To determine the hazardous waste quantity assigned value, 650,733 cubic yards is divided by 2.5, which equals 260,293 (Ref.1, Table 2

- 5). References 33, 34, 35, 38, 50, 107, and 109 were used to assist with determining the volume of the ground water plume.

Source Type Description (Volume of Plume) Units ( cubic yards [ yd 3 ]/ gal lon [gal] ) References

Other See References 39 and 85 650,733 39; 85

Sum (yd 3 Equation for Assigning Value (Ref. 1, Table 2

- 5): other source type, divide by 2.5 = 260,293 ): 650,733 (R ef . 85)

Volume Assigned Value: 260,293Source No: 1 Source Hazardous Waste Quantity

GEN

- 24 2.4.2.1.4 Area

Description

Area, Tier D, is not available for scoring for source type “other” (Ref. 1, Table 2

- 5).

Area Assigned Value: 0

2.4.2.1.5 Source Hazardous Waste Quantity Value

The source hazardous waste quantity value for Source 1 is the volume assigned value of 260,293 (Ref . 1, Sections 2.4.2.1.5).

Highest assigned value assigned from Ref erence 1, Table 2

- 5: 260,293Summary of Source Descriptions

GEN

- 25 SUMMARY OF SOURCE DESCRIPTIONS

Source

No. Source Hazardous Waste Quantity

Value Source Hazardous Constituent

Quantity Complete? (Y/N) Containment Factor Value by Pathway

Ground Water(G W) (Ref. 1, Table 3

- 2) Surf ace Water (SW) Air

Overland/flood (Ref. 1, Table 4

- 2) GW to SW (Ref. 1, Table 3

- 2) Gas (Ref. 1, Table

6

- 3) Particulate (Ref. 1, Table 6

- 9)

1 260,293 No 10 Not scored Not scored Not scored Not scoredGW

- General

GW

- 1 3.0 GROUND WATER MIGRATION PATHWAY

3.0.1 GENERAL CONSIDERATIONS

Ground Water Migration Pathway Description

Regional Geology

The ground water plume is located in the Coastal Plain physiographic province of Cecil County, Maryland, just south of the Fall Line (or Fall Zone). The Fall Line is the boundary separating the Coastal Plain and the Piedmont physiographic province, located to the southeast and northwest, respectively, of the ground water plume (Ref. 7; Ref. 47, p.10; Ref. 48; Ref. 71, p. 37). The Coastal Plain physiographic province of Cecil County, Maryland, consists of a wedge of unconsolidated layers of clay, silt, sand, and gravel increasing in thickness from less than 1 ft at the Fall Line to about 1,600 ft beneath the southeastern corner of Cecil County (Ref. 47, p. 1). The Piedmont physiographic province consists of crystalline igneous and metamorphic rock (Ref. 47, p. 9). Southwest of the Fall Line the surface of the Piedmont crystalline rocks slopes southeastward beneath progressivel y thicker Coastal Plain strata (Ref. 47, pp. 9, 12). Beneath the Coastal Plain sediments the upper portion of the crystalline rocks has weathered to a thick mantle of saprolite (Ref. 47, p. 14). The location and trend of the Fall Line in Cecil County and a geologic cross section depicting the relationship between crystalline rocks of the Piedmont physiographic province and sediments of the Coastal Plain physiographic province is depicted on Figure 5 of Reference 47 and Figure 2, Reference 36, page 3 (Ref. 47, p. 10; Ref. 36, p. 3).

Crystalline rocks, present at depth beneath the location of the ground water plume, outcrop at the surface northwest of the Fall Line (Ref. 7; Ref. 48). Crystalline rocks exposed at the surface nearby include metavolcanics (including schistose to massive amphibolite, granofels, diamicticite, and metabasalt) of the James Run Formation, gneiss classified as Gneiss at Rolling Mill, and gabbro and serpentinite named Gabbro and Serpentinite at Grays Hill (Ref. 48).

Sediments identified as the Quaternary age Talbot Formation and Tertiary age Pensauken Formation are mapped at the surface in the vicinity of the ground water plume. Talbot Formation sediments are described

as coarse

- grained sands and gravels to finer

- grained sands and l oam (coarse

- grained facies) and thin

bedded silts and fine sands (fine

- grained facies). Pensauken Formation sediments are described as poorly

sorted polymict gravels, sands, and loam (Ref. 48). Where present, Talbot and Pensauken Formation sediments are deposited as a thin veneer over older Coastal Plain sediments such as the Potomac Group (Ref. 88, p. 38).

Reference 48 is a geologic map of Cecil County. The geologic map depicts Potomac Group sediments at the location of the ground water plume and shows James Run Formation metavolcanics and Talbot and Pensauken Formation sediments northwest and southeast, respectively, of the ground water plume (Ref. 7; Ref. 48). The geologic map also provides a nor thwest

- southeast oriented cross

- section through Cecil Co unty. The cross

- section depicts deformed crystalline rocks of the Piedmont physiographic province, which are overlain in the southeast part of the county by a thin wedge of Potomac Group sediments that thickens towards the south (Ref. 48).GW

- General

GW

- 2 Site -S pecifi c Geology

The ground water plume is in Cretaceous age Potomac Group unconsolidated sediments followed by saprolite . The monitoring wells are completed within both the Potomac Group sediments and saprolite (Ref. 7; Ref. 48; Ref. 71, p p

. 18, 33, 34, 39). T he monitoring wells documenting an observed release to ground water and defining the area of the plume are summarized in Tables GW4 and GW8. These wells include well clusters consisting of one well screened within the unconsolidated unit immediately above the hard saprolite (weathered bedrock) (“A” designated wells) and one well screened within the hard saprolite (weathered bedrock) immediately above competent bedrock (“B” designated wells). The deeper well of each cluster (“B” designated wells) was insta lled first to the depth of auger refusal. Continuous split

- spoon soil samples were collected from the deeper well boring to the completion depth. Split

- spoon sampling was not performed during advancement of the shallower well boring. The shallower wells were installed to the depth of the base of the unconsolidated unit as determined from logging of the deeper well boring. Auger refusal was encountered 3 feet below the base of the unconsolidated unit in the DP

- MW

- 13 boring. Because of the relative thinn ess of the hard saprolite/weathered bedrock in the DP

- MW

- 13 boring, one well (DP

- MW

- 13A), screened within the unconsolidated unit and the hard saprolite/weathered bedrock,

w as installed to the depth of auger refusal at this location (Ref. 71, p. 18). Refe rence 71, pages 98 and 99, provides cross

- sections showing the stratigraphy of the well locations

The unconsolidated unit ( sediments ) in which the monitoring wells are completed is characterized as interbedded sand, silt, clay, and gravel with interspers ed layers of medium to coarse sand and gravel (Ref. 47, p. 23; Ref. 71, pp. 39, 40, 41). In 2002, soil borings were completed in the area of the ground water plume. From 2007 through 2009, monitoring wells were also installed in the area of the ground wa ter plume. Lithologic descriptions from soil borings and monitoring wells show that interbedded sands, silts, clays, and gravels, likely belonging to the Potomac Group, extend from ground surface to between 35 and 107 ft bgs (Ref. 48; Ref. 13, p. 86, Figures 7 to 10, pp. 123 to 126; Ref. 90; Ref. 71, p. 33). Cross sections prepared from soil boring logs illustrate the limited horizontal extent of silt and clay lenses, as well as the southeastward sloping of the Potomac Group

- saprolite contact (Ref. 13, Fi gures 7 to 10, pp. 123 to 126; Ref. 27, p. 1; Ref. 37; Ref. 71, pp. 98, 99). Soil boring and monitoring well lithologic descriptions indicate that saprolite was encountered below the sediments at depths between 24 and 107 ft bgs (Ref. 13, p. 86, pp. 133 t o 17 0 ; Ref. 90; Ref. 27, p. 1; Ref. 37; Ref. 71, p. 40). No soil borings and only a few monitoring wells were completed through the entire thickness of the saprolite. In deeper monitoring wells that penetrate the entire saprolite, bedrock is encountered between 31 and 115 ft bgs (Ref. 90; Ref. 27, p. 1; Ref. 37; Ref. 71, p. 34 , 35 ). Elsewhere in Cecil County, the median thickness of saprolite encountered in wells has been calculated at approximately 41 ft (Ref. 47, pp. 14, 15). The ground water plume

mo nitoring well logs label crystalline rock as “bedrock” (Ref. 90, pp. 11, 24, 25, 31, 43, 44; Ref. 27, p. 1; Ref. 37; Ref. 71, p. 40). However, in one log, bedrock is further described as containing mica, suggesting that bedrock beneath the ground water pl ume may belong to schistose amphibolite ( which is mica

- ric h) of the Frenchtown Member of the James Run Formation (Ref. 48; Ref. 90, pp. 24, 25).

The ERI report for the Dwyer Property describes the geology of the area of the ground water plume. The strati graphy of the overburden layer above competent bedrock at the Dwyer Property is comprised of weathered bedrock, saprolite, and a fluvial unit that was formed in a highly complex river system depositional environment. Saprolite is a highly weathered bedroc k remnant that ranges in consistency with respect to the degree of weathering. The lower and upper portions of the saprolite encountered at the Dwyer Property have been designated herein as “hard” and “soft,” respectively, according to the degree of weath ering. Because of their similar consistency, the weathered bedrock and hard saprolite are often grouped together herein for the purpose of discussion. Because of their often granular consistency, the softGW

- General

GW

- 3 saprolite and the fluvial unit are frequently dis cussed as a single unit herein and are collectively referred to as the “unconsolidated unit” (Ref. 71, pp. 9, 10, 39, 40, 41). The ERI report provides an extensive geologic description of the Dwyer Property (Ref. 71, pp. 38 through 47).

Hydrogeology

Hyd rogeology of the ground water plume is influenced by characteristics of both the Potomac and Crystalline Rock aquifers. A description of the aquifers is provided here.

Aquifer 1: Potomac Aquifer

The Potomac aquifer is the uppermost aquifer of the ground water plume (Ref. 47, p. 23; Ref. 71, pp. 40, 41). Ground water within the Potomac aquifer occurs within the Potomac Group (Ref. 47, p. 22). Regionally, the Potomac aquifer can be divided in some areas into three hydrogeologic units: the upper Potomac aquifer; middle Potomac confining unit; and lower Potomac aquifers (Ref. 47, p. 21). (The names of these units are not consistent in publications. Reference 49, page A8, provides a summary of the different names and their relationship to each other). The upper Potomac aquifer is absent within 4 miles of the center of the ground water plume (Ref. 47, p. 21). Based on the surface expression and depth of the Potomac confining unit (middle Potomac confining unit), the Potomac confining unit is absent within 4 miles of the center of the ground water plume and the Potomac aquifer is not confined (Ref. 88, pp. E- 11, E- 12, E

- 13, and E

- 14; Ref. 49, Plate 7; Ref. 47, p. 47; Ref. 7). Therefore, the hydrogeologic unit of the Potomac aquifer at the location of the g round water plume is the Lower Potomac aquifer. The Lower Potomac aquifer sediments outcrop at the surface at the Dwyer Property and in a northeast

- southwest trending swath in and around the Town of Elkton (Ref. 47, pp. 21 to 24; Ref. 48 ; Ref. 88, pp. E -1 1, E

- 12, E- 13, and E

- 14 ). (The Lower Potomac aquifer also is known as the Patuxent aquifer [Ref. 49, p. A8]).

Where the Potomac Group outcrops at the surface, as it does at the location of the ground water plume, the Lower Potomac aquifer is unconfined (R ef. 47, pp. 21 to 24; Ref. 81, pp. 4 to 5; Ref. 88, p. E11; Ref. 89, p. 1). To the southeast of the ground water plume , the Potomac Group is directly overlain by sediments of the Talbot and Pensauken Formations . The composition of these sediments indicates that the Potomac aquifer is unconfined at this location (Ref. 81, pp. 4, 5; Ref. 89, p. 1 ; Ref. 48 ). Unconfined areas of the Potomac aquifer , including the location of the ground water plume, serve as recharge areas to the confined Potomac aquifer in the Coastal Plain. The confined portion of the Potomac aquifer is located greater than 4 miles from the center of the ground water plume (Ref. 81, pp. 4, 5; Ref. 88, pp. E11, E12, E13, and E14; Ref. 89, p. 1 ; Ref. 7 ). A general schematic depicting ground water recharge from shallow unconfined areas of the aquifer to deeper confined areas of the aquifer is shown on Figure 2 of Reference 49 (Ref. 49, p. A

- 13).

The sediments of the Potomac Group were deposited in a river

- delta environment. The type of sedime nts constitute a transitional series from coarse channel deposits, characteristic of alluvial valleys, to thick clay, and fine to medium sand and silt beds characteristic of back

- swamps and flood

- plain deposits. These depositional environments shi f t laterally, coalescing with other migration depositional environments within a large river

- delta system. Because of this, individual lithologic units usually have little lateral continuity (Ref. 72, p. 12). The many water wells drilled in the Potomac aquifer h ave penetrated no consistent correlatable succession of clay, silt, sand, or gravel (Ref. 87, p. 128). Attempts have been made to subdivide the Potomac Group into smaller units on the basis of stratigraphy; however, the results of studies showed that indi vidual sand or clay units could not be successfully correlated over even short distances (Ref. 88, p. E3). The beds form a multilayer aquifer system (Ref. 88, p. E11). (The Potomac aquifer, inGW

- General

GW

- 4 which the ground water plume is located, also is known as the Patuxent aquifer [Ref. 47, p. 21; Ref. 49, p. A8]).

Sediments of the Potomac aquifer consist of interbedded sand, silt, clay, and gravel (Ref. 47, p. 23; Ref. 71, pp. 40, 41). Silt and clay lenses limit vertical ground water flow locally, but silt and clay lenses are laterally discontinuous and do not impede vertical ground water flow within the 4 mile s of the center of the ground water plume (Ref. 49, Figure 10, p. 126; Ref. 87, p. 124). Ground water is stored between grains in the sediment. Saturate d sand and gravel constitute the aquifer (Ref. 47, p. 1). Depth to water in the Potomac a quifer at the location of the ground water plume is as shallow as 1 ft bgs (Ref. 27, p. 4).

The thickness of the Potomac a quifer ranges from less than 1 ft at the Fall Line to nearly 1,200 ft at the southeastern corner of Cecil County (Ref. 47, p. 23). Hydraulic characteristic vary greatly within the aquifer. Transmissivity values range from 60 to 3,900 square feet per day (ft 2 /d) (Ref. 47, pp. 26, 27). Storage co efficient values range from 0.00005 to 0.004 (Ref. 47, pp. 26, 27). Hydraulic conductivity (K) values range from 40 to 210 feet per day (ft/d) (Ref. 72, p. 16). Precipitation recharges the Potomac aquifer (Ref. 47, pp. 77, 83). Conceptual site models of the Potomac aquifer indicate that there is both upward and downward leakage through the middle confining unit that would both recharge and deplete ground water stored in the confined portions of the Lower Potomac aquifer (Ref. 47, pp. 78, 80).

Based on the description of the monitoring wells logs and the locations of the wells documenting an observed release to ground water, the background and release monitoring wells have been completed in the Potomac a quifer or at the base of the Potomac aquifer (saprolite) beneath the ground water plume ( Ref. 71, pp. 18 , 98, 99; Ref. 90; Ref. 27, p. 4). Depth to water in these wells fluctuates seasonally and is encountered as shallow as 1 ft bgs (Ref. 27, p. 4). Town of Elkton wells 1 and 3, currently utilized for

wa ter supply to the Town, and Town of Elkton well 4, newly installed and not currently in production, are completed in the Potomac Aquifer (Ref. 81, p. 1). Well 1 is located approximately 1.5 miles southeast of the ground water plume; well 3 is located 2.75 miles southeast of the ground water plume; well 4 is located approximately 3 miles northeast of the ground water plume (Ref. 7).

Aquifer 2: Crystalline Rock Aquifer

The Crystalline Rock a quifer is found stratigraphically below the Potomac aquifer. The aquifer is comprised of fractured igneous and metamorphic crystalline rocks overlain by a mantle of weathered rock called saprolite (Ref. 47, pp. 1, 12). The crystalline rock itself yields little water; ground water is contained in fractures and in the saprolite mantle, which serves as a storage reservoir to underlying fracture systems (Ref. 47, p. 14).

Geologic units that make up the C rystalline R ock aquifer outcrop at the surface northwest of the Fall Line (Ref. 48). Southeast of the Fall Line, the su rface of the C rystalline R ock aquifer dips gently beneath the overlying aquifers of the Coastal Plain (Ref. 47, p. 10). Beneath the ground water plume, the saprolite component of the C rystalline R ock aquifer is encountered between 24 and 107 ft bgs, and t he crystalline rock component is encountered between 31 and 115 ft bgs (Ref. 13, pp. 133 to 170; Ref. 90, pp. 5, 10, 11, 17, 24, 25, 31, 43
, 44, 58, 61, 65; Ref. 71, p p

. 34, 35, 40).

Although ground water may be confined within an individual rock fractur e of the C rystalline R ock aquifer, the network of fractures and saprolite mantle ( which constitute the C rystalline Rock aquifer ) are considered
a water

- table, or unconfined, system (Ref. 47, p. 12). Ground water is recharge d to the C rystalline R ock aquife r from water infiltrating through overlying sediments (Potomac Group) or through fractures andGW

- General

GW

- 5 weathered rock joining the C rystalline R ock aquifer at depth with crystalline rock exposed at the surface (Ref. 47, pp. 10 to 14).

In the Piedmont physiographi c province of Cecil County, wells that have been completed in the C rystalline R ock aquifer range in depth from 11 to 575 ft bgs (Ref. 47, p. 21). Depth to water is encountered as shallow as 1 ft bgs and as deep as 200 ft bgs (Ref. 47, p. 17).

Ground wat er flow within the crystalline rock varies greatly depending on the amount of weathering, the number of fractures, the size of the fracture openings, and the interconnection of the fractures (Ref. 47, p. 12). Hydraulic conductivity for the C rystalline R oc k aquifer is reported between 1.3 3 and 9.4 ft/d (Ref. 74, p. 2 ; Ref. 75, p. 1). (Both References 74 and 75 report hydraulic conductivities for the Piedmont C rystalline R ock aquifer from locations outside Maryland.) Transmissivity values for the C rystalli ne R ock aquifer range from 2 to 1,400 ft 2 /d (Ref. 47, p. 18). Storage coefficient values range from less than 0.1 to 4.4 (Ref. 47, p. 17). Specific yield for the saprolite component of the crystalline rock aquifer is estimated at 0.08; specific yield for the upper 200 feet of the fractured rock component of the aquifer is 0.05 (Ref. 47, p. 15).

Monitoring wells have been completed in both the saprolite and fractured rock components of the crystalline rock aquifer at the ground water plume (Ref. 71, p. 40 ; Ref. 90; Ref. 27, pp. 1, 4). Nearby county and private water supply wells (private wells are located on Dogwood Lane [Ref. 7]) are completed in the C rystalline R ock aquifer (Ref. 47, pp. 37 to 40; Ref. 92, p. 7).

3.0.1.2.1 Aquifer Interconnectivity

Hydr ologic interconnection is established within the Potomac Aquifer, within the components of the Crystalline Rock a quifer, and between the Potomac and Crystalline Rock a quifers. Potomac sediments at the ground water plume are described as interbedded sand, silt, clay, and gravel (Ref. 47, p. 23; Ref. 27, p. 1; Ref. 71, p. 40). While clay and silt lenses present in Potomac aquifer sediments likely slow vertical ground water flow, cross

- sections prepared for the ground water plume indicate that finer

- grained materials are generally laterally discontinuous (Ref. 13, pp. 56 to 59, Figures 4

- 1 to 4

- 3; Ref. 13, Figures 7 to 10, pp. 123 to 126; Ref. 71, pp. 97, 98, 99). Additionally, elevated VOC measurements (for example, 34 parts per million [ppm] VOCs were foun d at 93 feet bgs in MW

- 14B) were recorded at the top of bedrock during monitoring well drilling, indicating that VOCs had infiltrated the entire thickness of Potomac sediments to reach bedrock (Ref. 90, p. 43). Finally, TCE and similar chlorinated solvent s including PCE, cis

- 1,2

- DCE, and trans

- 1,2

- DCE are found in ground water plume monitoring wells completed at the base of the Potomac aquifer (Ref. 27, pp. 1, 8; Ref. 13, p. 112, Table 11; Tables GW8 and GW9 of the HRS documentation record). Chlorinated solvents, specifically PCE, are also found in Town of Elkton Well 1, which is located southeast of the ground water plume and completed in the Potomac aquifer (Ref. 7; Ref. 19, p. 4; Ref. 11, pp. 1, 2). These contaminants are not naturally occurring (Ref. 30, p. 185 ). The presence of TCE at the base of the Potomac aquifer beneath the ground water plume and the presence of PCE in the Town of Elkton well 1 is evidence of interconnection (see the chemical analysis section of this HRS d ocumentation r ecord).

As described earlier, the C rystalline R ock aquifer is considered a water table ( or unconfined ) aquifer

, meaning that in the Piedmont physiographic province and at locations where the C rystalline R ock aquifer is overlain by other unconfined aquifers, there is interconnectivity between the surface, overlying sediments of the Potomac (where present), and the C rystalline R ock aquifer (Ref. 47, p. 12). This is illustrated in Reference 36, page 3. Chlorinated solvents are also found in monitoring wells at the g roundGW

- General

GW

- 6 water plume completed in the saprolite component of the C rystalline R ock aquifer (Ref. 27, pp. 1, 8; Ref. 13, p. 112, Table 11; Tables GW8 and GW9 of this HRS documentation record). In Piedmont crystalline rocks, the saprolite acts as a storage rese rvoir to underlying fracture systems of the C rystalline R ock aquifer (Ref. 47, p. 14). The presence of TCE and other chlorinated solvents in saprolite monitoring wells and the connection between the saprolite and underlying crystalline rocks are indications of interconnection between the surface, the Potomac aquifer, and the C rystalline Rock aquifer.

3.0.1.2.2 Aquifer Discontinuities within Target Distance Limit

No aquifer discontinuities have been identified within the 4

- mile radius of the ground water plume. The ground water plume is located within the Coastal Plain physiographic province of Cecil County, Maryland. The province consists of a wedge of unconsolidated layers of clay, silt, sand, and gravel increasing in thickness from less than 1 ft at the Fall Line to about 1,600 ft beneath the southeastern corner of Cecil County (Ref. 47, p. 1) lying on the Piedmont physiographic province consisting of crystalline igneous and metamorphic rock (Ref. 47, p. 9). Southwest of the Fall Line and the ground w ater plume, the surface of the Piedmont crystalline rocks slopes southeastward beneath progressively thicker Coastal Plain strata (Ref. 47, pp. 9, 12). Based on the stratigraphy of the sediments and bedrock, no barriers to ground water flow have been identified. This is illustrated in Reference 36, page 3. The surface expression of the two provinces is illustrated on the Geologic Map of Cecil County (Ref. 48).

TABLE GW1 SUMMARY OF AQUIFER(S) BEING EVALUATED

Aquifer No. Aquifer Name Is Aquifer Intercon nected with Upper Aquifer within 2 miles? (Yes [Y]/No

[N]/Not Available [NA]) Is Aquifer Continuous within 4

- mile Target Distance

Limit? (Y/N) Is Aquifer Karst? (Y/N)

1 Potomac NA Y N
2 Crystalline Rock Y Y N

As documented in the Aquifer Interconnect ion section of this documentation record, the Potomac and Crystalline Rock aquifers are interconnected and are therefore evaluated as one aquifer (Ref. 1, Section 3.0.1.1)GW

- Likelihood of Release

GW

- 7 3.1 LIKELIHOOD OF RELEASE

3.1.1 OBSERVED RELEASE

Aquifer Being Evaluated: Surfi cial/Potomac/Saprolite/Crystalline

Chemical Analysis

Establishing an observed release by chemical analysis requires analytical evidence of a hazardous substance in the media at a concentration significantly above the background level. If the background concentration is not detected (or is less than the detection limit), an observed release is established when the sample measurement equals or exceeds it s own sample quantitation limit (SQL) and that of the background sample. I f the SQL cannot be established, the EPA contract

- required quantitation limit (CRQL) is used in place of the SQL for sample analyses performed under the EPA Contract Laboratory Program (CLP), or the detection limit for sample analyses not performed under the EPA CLP (Ref. 1, Section 2.3, Table 2

- 3). All hazardous substances listed in the ground water observed release tables were above the background level SQL and its SQL or were three times the background level. These substances
met the observed release criteria.

The ground water s amples used to document an observed release to ground water were collected in April and September 2009 and were analyzed by Envirosystems, Inc. and Air, Water, and Soil Laboratories (Ref. 51; Ref. 53 through 61). Envirosystems, Inc.

, used EPA Method 8260 to analyze the samples (Ref. 51 pp. 1, 6; Ref. 53, p. 7; Ref. 54, p. 26; Ref. 55, p. 30; Ref. 56, p. 7; Ref. 57, p. 7; Ref. 58, p. 16; Ref. 59, p. 23; Ref. 60, p. 17; Ref. 61, p. 26). The data validation report is provided in Reference 108.

The ground w ater sampling results used to document an observed release to ground water (aquifer being evaluated) are described in the ERI report , Reference 71. The ERI report documents an interactive series of field investigation activities at the Dwyer Property and on nearby properties between January 2006 and January 2010, as completed for MDE. These activities include installation of ground water monitoring wells, well and wellhead replacement activities, five ground water sampling events, five additional phases

o f the MIP survey (Phases 2 through 6), establishment of five stream gauge stations, a soil boring program involving advancement of 33 soil borings, and a series of monitoring well and stream gauge station gauging events (Ref. 71, p. 9).

I nformation regarding the 65 Dwyer Property wells and nearby ground water monitoring wells is included in Table 1 of Reference 71, page 51

, and Reference 27, which show ground water monitoring wells designated as shallow or deep. Shallow wells screen the upper portion of the water table aquifer. Deep wells screen lower portions of the water table aquifer. The monitoring well locations are shown on Figure 3, page 82, Reference 71 and Reference 29. On

- site wells have a “DP” label. Nearby wells (wells not on the Dwyer Property) have the following labels: “RP” for the well installed on the Ruddy property; “EGWS” for the Elkton Ground Water Study wells installed on the Terumo and City Pharmacy properties; and “VP” for the Vicon property wells (Ref. 71, p. 10).

Table 1, pag e 51, of Reference 71, and Reference 27 present the following information for each well: well identifi er , well designation, the respective study area and study sub

- area, well installation and replacement/repair date, well survey and construction data, and information regarding the stratigraphy of the screened interval and the target well depth. Table 1 also presents the ground water monitoring well gauging data, the corresponding ground water elevation data, and a summary of TCE ground waterGW

- Likelihood of Release

GW

- 8 analytical da ta generated during the course of this investigation. The listing is sorted according to study area, well designation, study sub

- area, and by well identifi er (Ref. 71, p. 10). A release to the shallow and deep water

- bearing zones is described in the sections below. Each zone has a different background well completed within the same relative water

- bearing zone.

The locations of all the monitoring wells samples are illustrated in Reference 29.

Expanded Remedial Investigation (ERI) Field Investigations

G round water samples collected during April 2009 and September 2009, documented in the ERI (Reference 71), were collected in accordance with methodologies described in Sections 2.2.1 and 2.5.1 of Reference 71 (Ref. 71, pp. 12, 26, 33). The monitoring wells were gauged prior to sampling and purged according to low

- flow methodology using a variable speed

, submersible pump and disposable tubing, and monitored using a water quality meter and flow

- through cell, until field parameters stabilized . Field parameter s (dissolved oxygen [DO], oxidation

- reduction potential, conductivity, pH, turbidity, and temperature) were recorded in ground water sampling logs during well purging. The ground water samples were then collected from the submersible pump discharge stream

. The samples and one field blank were submitted to Phase Separation Science (PSS) in Baltimore, Maryland, for laboratory analysis for VOCs via EPA Method 8260. Well purge water was collected and placed into a 55

- gallon drum that was staged at the Dwyer Property for temporary storage (Ref. 71, pp. 12, 14).

The April 2009 ground water sampling event was performed as discussed in Referen ce 45, Work Plan #16, page 20. Ground water samples were collected between April 14 and 28, 2009, from the 36 monitoring wells at the Dwyer Property and on the Terumo, City Pharmacy, Vicon, and Ruddy properties (Ref. 71, p. 28). The September 2009 ground water sampling was completed in accordance with Reference 45, Work Plan #18, page 28 (Ref. 71, p. 33).

M onitoring Well Summary

The majority of monitoring wells used to document an observed release to the shallow and deep portion of the aquifer were installed as part of the 2009 ERI. Monitoring well clusters were installed during the ERI using a hollow

- stem auger (HSA) , t ruck

- mounted drilling rig. The clusters consist of one well screened within the unconsolidated unit immediately above the hard saprolite/weathered bedrock (“A” designated wells) and one well screened within the hard saprolite/weathered bedrock immediately above competent bedrock (“B” designated wells). The deeper well of each cluster (“B” designated wells) was installed first to the depth of auger refusal. Continuous split

- spoon soil samples were collected from the deeper well boring to the completion depth. Split

- spoon sampling was not performed during advancement of the shallower well boring. The shallower wells were installed to the depth of the base of the unconsolidated unit as determined from logging of the deeper well boring. Auger refusal was e ncountered three feet below the base of the unconsolidated unit in the DP

- MW

- 13 boring. Due to the relative thinness of the hard saprolite/weathered bedrock in the DP

- MW

- 13 boring, one well (DP

- MW

- 13A), screened within the unconsolidated unit and the hard saprolite/weathered bedrock, was installed to the depth of auger refusal at this location (Ref. 71, p. 18).

Other wells used to document an observe release to ground water include t wo ground water monitoring wells (DP

- MW

- 01 and DP

- MW

- 02 ) installed during a site inspection for MDE (Ref. 14) , t wo ground water monitoring wells (VP

- MW

- 07 and VP

- MW

- 08) installed by environmental consultants for Vicon on the Vicon property north of Dwyer and t hree ground water monitoring wells installed as part of the Elkto nGW

- Likelihood of Release

GW

- 9 Ground Water Study (EGWS

- MW

- 01, EGWS

- MW

- 02A, and EGWS

- MW

- 03) . EGWS

- MW

- 02A and EGWS

- MW

- 03 were installed on the Terumo Medical Corporation (Terumo) property, which is located southeast of the Dwyer property, and EGWS

- MW

- 01 (also known as MW

- 51) was installed on the City Pharmacy property, which is located east of the Dwyer property. MDE installed ten ground water monitoring wells (DP

- MW

- 01A, DP

- MW

- 02A, DP

- MW

- 03A, DP

- MW

- 04, DP

- MW

- 04A, DP

- MW

- 05, DP

- MW

- 05A, DP

- MW

- 06, DPMW

- 06A, and DP

- MW

- 07) at Dwyer in Apri l 2003. ENSAT installed three ground water monitoring wells (DP

- MW

- 08, DP

- MW

- 09, and DPMW - 10) at Dwyer in August 2004 to better define the nature and extent of ground water contamination on the northern portion of Dwyer, near the adjacent Vicon property where TCE ground water contamination had been detected (Ref. 71, pp. 7, 8). Monitoring well logs for these wells were reviewed to determine whether the wells were completed in the shallow or deep portions of the aquifer.

SHALLOW GROUND WATER

This section documents an observed release to shallow ground water. The shallow background and contaminated ground well construction details are provided in Tables GW2 and GW4, respectively. The TCE concentrations in the background and contaminated ground well (o bserved release) are summarized in T ables GW3 and GW5, respectively. The tables are provided at the end of this section.

Shallow Background and Release Monitoring Well Construction Details and TCE Concentrations

Reference 27, Comprehensive Ground Water M onitoring Data, was used to identify shallow background wells for shallow contaminated (release) wells. The criteria used in the ERI (Reference 71) was used to identify shallow and deep wells because the criteria ensure s that the background and release we lls are completed (screened) within the same relative depths of the aquifer and draw ground water from similar depths in the aquifer

. T he designation of shallow wells was made based on two factors: the elevation of the bottom of the well and the height of the water column. Shallow wells are those wells where the water column is less than (<) or equal (=) to 25 ft, and where the elevation at the bottom of the well is more than (>) - 7 ft above mean sea level (amsl) (Ref. 27, p. 9). Three background wells were identified (DP

- MW09, EGWS

- MW

- 01, and VP

- MW

- 08). Construction details for the shallow background and contaminated wells

─ including well depths, well screen intervals, and ground water elevations

─ are summarized in Tables GW2 and GW4, respectively. Locations of the background and contaminated wells are shown in Reference 29. Ground water elevations of the background and contaminated wells are summarized in Reference 27, p. 6

, and illustrated on Reference 63. Reference 66, Shallow Ground Water TCE Isoconcentratio ns Map, illustrates the TCE concentrations in shallow ground water.

As Reference 63 shows, the contaminate d wells are located hydrogeologically downgradient of the background wells. Ground water flows from the direction of the background wells towards the contaminated wells, primarily from the northeast to the south / southwest. Although some of the background well ground water elevations are lower than the contaminated well elevations, the background wells are upgradient of the contaminated wells because the ground water flows primarily to the south.

The background wells are considered to be background becau se:

**•** The wells are screened at the same relative depth as the contaminated wells.

**•** The background and contaminated well screen lengths are similar.GW

- Likelihood of Release

GW

- 10 **•** The background wells are screened within the same relative portion of the aquifer as the contaminated wells (see Tables GW2 and GW4).

**•** The wells were sampled using the same procedures as the contaminated wells (Ref. 45; Ref. 71, pp. 28, 33).

**•** The wells were sampled during the same timeframe as the contaminated wells (Ref. 51, p. 6; Ref. 54, p. 26; Ref. 55, p. 30; Ref. 56, p. 7; Ref. 57, p. 7; Ref. 58, p. 16; Ref. 59, p. 23; Ref. 60, p. 17; Ref. 61, p. 26).

**•** The wells were analyzed using the same methods (Ref. 51, p. 6; Ref. 54, p. 26; Ref. 55, p. 30; Ref. 56, p. 7; Ref. 57, p. 7; Ref. 58, p. 16; Ref. 59, p. 23; Ref. 60, p. 17; Ref. 61, p. 26).

Shallow ground water is documented to flow from the northeast to the south/southwest based on ground water elevations presented in Reference 27, page 6, and the ground water contour maps shown in Reference 63 (Ref. 71, p. 41). References 29 and 39 illustrate that the three background wells are outside the ground water plume. The background wells (DP

- MW

- 09, EGWS

- MW

- 01, and VP

- MW

- 08) document ground water conditions northeast, north, and east of the ground water plume (Ref. 29).

As Tables GW3 and GW5 show, background wells were not sampled during the September 2009 sampling investigation. This investigation included the collection of ground water samples primarily from the contaminated wells (see Tables GW3 and GW5). The backg round and contaminated ground water samples were collected 5 months apart. No other background wells have been identified for the September 2009 sampling date. Therefore, the April 2009 samples are used to document background concentrations for the September 2009 ground water samples. Additionally, TCE is not naturally occurring (Ref. 30, p. 185). MDE representatives indicated TCE had never been detected in residential wells samples located on Dogwood Lane upgradient of the plume. The residential wells have been sampled periodically to determine if the TCE ground water plume extended to the north / northeast (Ref. 32; Ref. 15, pp. 21, 47, 48, 53, 54, 56, 57; Ref. 16, pp. 2, 14, 17, 23; Ref. 92). Residential well sampling results provide evidence that

no source of TCE is outside the ground water plume.

The ground water sample collection forms for each sample used to document an observed release to ground water are provided in References 46, 105, and 106. The work plans followed for sample collection

are provided in Reference 45. The logbook notes for the ground water investigation are extensive and available at EPA.

Envirosystems, Inc.

, used EPA Method 8260 to analyze the ground water samples, and Air, Water, and Soil followed SW

- 846 methodology (Ref. 51 pp. 1, 6; Ref. 53, p. 7; Ref. 54, pp. 1, 26; Ref. 55, pp. 1, 30; Ref. 56, p. 7; Ref. 57, p. 7; Ref. 58, p. 16; Ref. 59, p. 23; Ref. 60, p. 17; Ref. 61, p. 26). Envirosystems, Inc.
, indicated that all quality control (QC) criteria were met (Ref. 51, p. 1). Envirosystems, Inc.

, laboratory data sheets provide the reporting limit when a compound is not detected (Ref. 51, p. 4). The reporting limit for TCE is 5 μg/L (Ref. 51, p. 17). The reporting limit corresponds to the Method 8260 estimated quantitation limit (EQL) (Ref. 52, pp. 1, 9). The EQL is generally 5 to 10 times the method detection limit (MDL). The EQL is the lowest concentration that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operati ng conditions (Ref. 52, p. 9). Envirosystems, Inc.

, laboratories provided the EPA Method 8260 MDL for TCE is 1.955 μg/L (Ref. 68, p. 1). The reporting limits are provided as the detection limits because concentrations below the reportingGW

- Likelihood of Release

GW

- 11 limits are identified on the laboratory data sheets as “ not detected ,” and represent detection limits achievable by Envirosystems, Inc. (Ref. 51, p. 4).

Air, Water, and Soil data sheets provide a limit of detection (LOD) and limit of quantitation (LOQ) for the detection l imits. The LOQ is the limit that the laboratory can quantify. LOQ is the concentration at which quantitative results can be reported with a high degree of confidence (Ref. 69). T he LOQ is higher that the LOD on the analytical data sheets (Ref. 54, pp. 1 2, 14, 19, 22; Ref. 55, pp. 3, 6, 7, 10, 14, 17, 24, 29).

The data validation reports for the ground water sample analysis are provided in Reference 10 8

.GW

- Likelihood of Release

GW

- 12 TABLE GW2 SHALLOW BACKGROUND MONITORING WELL CONSTRUCTION

Well ID Well Designation (1) Location W ell Diameter (in) Elev. Top of Screened Interval From Log (ft) * Elev. Bottom of Screened Interval

From Log (ft) * Total Measured Depth of

Well BTOC

(ft) Total Measured Depth of

Well BTOC

(ft) Total Measured Depth of

Well BTOC

(ft) Elevation of Ground wate r (ft) * Elevation of Ground water (ft) * Elevation of Ground water (ft) * References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09 DP

- MW

09 Shallow Northern 2 19.97 9.97 57.30 57.40 56.69 32.34 32.69 32.51 27, pp. 1, 2, 6; 29 EGWS

MW

- 01 Shallow N orthern 2 30.44 10.44 52.79 52.11 51.93 27.01 30.32 27.33 27, pp. 1, 2, 6; 29

VP

- MW

08 Shallow Northern

, Vicon Property 2 31.01 21.01 52.98 52.20 52.25 32.95 33.30 33.12 27, pp. 1, 2, 6; 29 ; 71, p. 7
Notes:

* Elevations are measure d as above mean sea level (amsl) (Ref. 27, p. 9).

Reference 2 9 provides the location of the wells

.

1 The designation of Shallow and Deep wells was made based on two factors: the elevation of the bottom of the well and the hei ght of the water column. Shallow w ells are those

where the water column is < or = to 25 ft and where the elevation at the bottom of the well is >

- 7 ft amsl. Deep wells are those where the water column is > 25 ft and where the elevation at the bottom of the well is <

- 7 ft amsl. The exce ption is well DP

- MW

- 15C
, where the water column is > 25 ft but where the bottom of well elevation is >

- 7 ft amsl. For this well

, solely t he height of the water column was used to assign the well designation. These designations were made to group wells drawing from the same relative depth of the aquifer.

BTOC = Below Top of Casing DP = Dwyer Property EGWS = Elkton Ground Water Study Elev. = Elevation f t = F eet ID = Identification In = I nches VP = Vicon PropertyGW

- Likelihood of Release

GW

- 13 Notes:

The analytical method used to analyze the samples was EPA Method 8260 by Envir osystems, Inc . (Ref. 56 pp. 1, 7 ). The laboratory data sheets provide the reporting limit when a compound is not detected (Ref. 5 6 , p. 5 ). The adjusted reporting limit for TCE is 5 μg/L (Ref. 56 , p. 1 9 ). The reporting limit corresponds to the Method 8260 estimated quantitation limit (EQL) (Ref. 52, pp. 1, 9). The EQL is generally 5 to 10 times the method detection limit ( MDL )

. The EQL is the lowest concentration that can be reliably achieved with in specified limits of precision and accuracy during routin e laboratory operating condition s (Ref. 52, p. 9).

μg/L = Micrograms per liter Conc. = Concentration DP = Dwyer Property EGWS = Elkton Ground Water Study ID = Identification MW = Monitoring Well NS = Not sampled VP = Vicon Property U = Analyte was analyz ed for but not detected. The result reported is the adjusted reporting limit for the analyte

. TABLE GW3 SHALLOW BACKGROUND WELL TRICHLOROETHYLENE (TCE) CONCENTRATIONS

Sample ID Hazardous Substance Sampling Date Conc. (μg/L) Reporting Limit (μg/L) References

DP

- MW

- 09 Trichloroethylene 4/16/2009 5 U 5 46, pp. 2, 39; 56, pp. 7, 17 ; 108, pp. 27

- 29

EGWS

- MW

- 01 Trichloroethylene 4/16/2009 5 U 5 46, pp. 2, 10, 11; 56, pp. 7, 19 ; 108, pp. 27

- 29

VP

- MW

- 08 Trichloroethylene 4/16/2009 5 U 5 46, pp. 2, 38; 56, pp. 7, 15 ; 108, pp. 27

- 29GW

- Likelihood of Release

GW

- 14 TABLE GW4 SHALLOW CONTAMINATED GROUND WATER MONITORING WELL CONSTRUCTION

Well ID Well Designation Location Well Diameter (in) Elev. Top of Screened In terval From Log (ft) * Elev. Bottom of Screened Interval From Log (ft) * Total Measured Depth of

Well BTOC (ft) Total Measured Depth of

Well BTOC (ft) Total Measured Depth of

Well BTOC (ft) Elevation of Ground W ater (ft) Elevation of Ground W ater (ft) Elev ation of Ground W ater (ft) References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09

DP

- MW

- 01 Shallow Southern 4 29.14 14.14 21.09 20.46 20.45 20.68 20.90 20.87 27, pp. 1, 2, 6; 29

DP

- MW

- 08 Shallow Northern 2 22.20 12.20 45.18 44.98 44.96 30.63 3 0.96 30.86 27, pp. 1, 2, 6; 29

DP

- MW

- 10 Shallow Northern 2 21.81 16.81 35.99 35.35 35.34 32.54 32.80 32.62 27, pp. 1, 2, 6; 29

DP

- MW

- 12A Shallow Southern 2 7.00

- 3.01 92.21 91.73 91.53 23.34 23.82 23.74 27, pp. 1, 2, 6; 29

DP

- MW

- 14A Shallow Southern

2 8.12

- 1.88 83.72 83.04 89.90 18.72 19.16 19.18 27, pp. 1, 2, 6; 29; 90, pp. 32 to 37

DP

- MW

- 17B Shallow Northern

2 35.45 15.45 53.77 53.03 53.14 29.96 30.32 30.22 27, pp. 1, 2, 6; 29; 90, pp. 145 to 148

DP

- MW

- 25A Shallow Southern

2 22.91 2.91 NA NA 51 .18 NM NM 19.24 27, pp. 1, 2, 6; 29; 90, pp. 190 to 193

DP

- MW

- 26A Shallow Southern

2 32.51 12.51 NA 49.51 50.30 NM 19.55 19.45 27, pp. 1, 2, 6; 29; 90, pp. 201 to 204GW

- Likelihood of Release

GW

- 15 Notes:

* Elevations are above mean sea level (amsl) (Ref. 27, p. 9). Reference 29 provides the locations of the wells. Well logs for DP

- MW

- 01, 08, 10, 12A and VP

- MW

- 07 and EGWS

- MW

- 03 have not been located. BTOC = Below Top of Casing DP = Dwyer Property Elev. = Elevation EGWS = Elkton Ground Water Study TABLE GW4 SHALLOW CONTAMINATED GROUND WTER MONITORING WELL CONSTRUCTION

Well ID Well Designation Location Well Diameter (in) Elev. Top of Screened Interval

From Log (ft) * Elev. Bottom of Screened Interval

From Log (ft) * Total Measured Depth of

Well BTOC

(ft) Total Measured Depth of

Well BTOC

(ft) Total Measured Depth of

Well BTOC

(f

t) Elevation of Ground W ater

(ft) * Elevation of Ground W ater

(ft) * Elevation of Ground W ater

(ft) * References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09

DP

MW

27A Shallow Southern

2 25.48 5.48 NA 66.56 67.06 NM 20.14 19.71 27, pp. 1, 2, 6; 29; 90, pp. 210

to 214

DP

MW

28A Shallow Southern

2 30.74 10.74 NA NA 67.06 NM NM 19.64 27, pp. 1, 2, 6; 29; 90, pp. 221

to 225

DP

MW

29A Shallow Southern

2 22.70 2.70 NA 70.44 71.15 NM 21.08 20.58 27, pp. 1, 2, 6; 29; 90, pp. 232

to 236

DP

MW

30A Sha llow Southern

2 25.89 5.89 NA NA 69.44 NM NM 19.23 27, pp. 1, 2, 6; 29; 90, pp. 24 3

to 2 47

DP

MW

31A Shallow Southern

2 22.14 2.14 NA NA 54.98 NM NM 18.85 27, pp. 1, 2, 6; 29; 90, pp. 25 4

to 257 VP

MW

- 07 Shallow Northern 2 26.36 21.36 37.76 37.17 37 .11 32.58 32.96 32.77 27, pp. 1, 2, 6; 29 EGWS

MW

- 03 Shallow Southern 2 13.32

- 6.68 31.23 30.62 30.48 11.89 12.07 12.14 27, pp. 1, 2, 6; 29GW

- Likelihood of Release

GW

- 16 f t = F eet ID = Identification i n = Inch MW = Monitori ng Well NM = Not Measured NA = Not Applicable (i.e., w ell had not been installed or repaired as of this date) TOC = Top of Casing of Monitoring Well VP = Vicon PropertyGW

- Likelihood of Release

GW

- 17 Notes:

a The analytical method used to analyze the samples was EPA Method 8 260 by Envirosystems, Inc. (Ref. 56 pp. 1, 7). The laboratory data sheets provide the reporting limit when a compound is not detected (Ref. 56, p.5). The adjusted reporting limit for TCE is 5 μg/L (Ref. 56, p. 19). The reporting limit corresponds to the Method 8260 estimated quantitation limit (EQL) (Ref. 52, pp. 1, 9). The EQL is generally 5 to 10 times the method detection limit (MDL). The EQL is the lowest concentration that can be reliably achieved within specified limits of precision and accuracy d uring routine laboratory operating conditions (Ref. 52, p. 9).

b Air, Water, and Soil Laboratories data sheets specify the LOD and the LOQ for the detection limits. The LOQ is the limit that the laboratory can quantify. LOQ is the concentration at which quantitative results can be reported with a high degree of confidence (Ref. 69). Because the LOQ is higher that the LOD on the analytical data sheets, the LOQ used as the detection limit as a conservative approach (Ref. 55, pp. 3, 6, 7, 10, 14, 17, 24, 2 9; Ref. 58, pp. 10, 16; Ref. 59, pp. 59, pp. 10, 12; Ref. 60, pp. 6, 11; Ref. 61, pp. 5, 7, 10, 12, 19, 22).

μg/L = Microgram s per liter TABLE GW5 SHALLOW CON T AMINATED GROUND WATER CONCENTRATIONS OBSERVED RELEASE TRICHLOROETHYLENE ( TCE ) CONCENTRATIONS

Sample ID Hazardous Substance Sample Date Conc. (μ g/L) Reporting Limit (μ g/L) a, b Reference

DP

- MW

- 01 Trichloroethylene 4/22/2009 210 10 (DF 2) 46, pp. 1, 8, 9; 53, pp. 7, 45 ; 108, pp. 30

- 47

DP

- MW

- 08 Trichloroethyl ene 4/23/2009 4,100 1000 (DF 200) 46, pp. 1, 36, 37; 82, pp. 7, 32 ; 108, pp. 48

- 69

DP

- MW

- 10 Trichloroethylene 4/23/2009 1,300 50 (DF 10) 46, pp. 2, 40, 41; 82, pp. 7, 34 ; 108, pp. 48

- 69

DP

- MW

- 17B Trichloroethylene 4/24/2009 80 5 46, pp. 3, 65, 66; 82, pp. 7, 24 ; 108, pp. 48

- 69

EGWS

- MW

- 03 Trichloroethylene 4/17/2009 11 5 46, pp. 2 , 21, 22; 56, pp. 7, 21 ; 108, pp. 26

- 28

VP

- MW

- 07 Trichloroethylene 4/27/2009 4,100 250 (DF 50) 46, p. 2, 34, 35; 57, pp 7, 23 ; 108, pp. 70

- 80

DP

- MW

- 08 Trichloroethylene 9 /25/2009 2,270 20 (DF 20) 106, pp. 4, 5; 54, pp. 7, 26 ; 108, pp. 172

- 197

DP

- MW

- 12A Trichloroethylene 9/09/2009 252 1 105, pp. 7, 8; 61, pp. 17, 26 ; 108, pp. 113

- 139

DP

- MW

- 14A Trichloroethylene 9/08/2009 1,060 10 (DF 10) 105, pp. 13, 14; 61, pp. 12, 26 ; 108, pp. 113

- 139

DP

- MW

- 25A Trichloroethylene 9/01/2009 117 1 105, pp. 17, 18; 58, pp. 12, 16 ; 108, pp. 81

- 83

DP

- MW

- 26A Trichloroethylene 9/02/2009 112 1 105, pp. 21, 22; 59, pp. 7, 23 ; 108, pp. 85

- 108

DP

- MW

- 27A Trichloroethylene 9/03/2009 211 1 105, pp. 25, 26; 59, pp. 12, 23 ; 108, pp. 85

- 108

DP

- MW

- 28A Trichloroethylene 9/04/2009 1,350 20 (DF 20) 105, pp. 29, 30; 60, pp. 9, 17 ; 108, pp. 109

- 111

DP

- MW

- 29A Trichloroethylene 9/03/2009 907 20 (DF 20) 105, pp. 33, 34; 59, pp. 17, 23 ; 108, pp. 85

- 108

DP

- MW

- 30A Trichloroethylene 9/04/2009 279 1 105, pp. 37, 38; 60, pp. 4, 17 ; 108, pp. 109

- 111

DP

- MW

- 31A Trichloroethylene 9/01/2009 120 1 105, pp. 41, 42; 58, pp. 8, 16 ; 108, pp. 81

- 83GW

- Likelihood of Release

GW

- 18 Conc. = Concentration DF = Dilution factor (the detection limit is adjusted by multiplying the detection limit [5] by the DF). DP = Dwyer Property EGWS = Elkton Ground Water Study ID = Identification MW = Monitoring W ell VP = Vicon PropertyGW

- Likelihood of Release

GW

- 19 DEEP GROUND WATER

This section documents an observed release to deep ground water. The deep background and contaminated grou nd water well construction details are provided in Tables GW6 and GW7, respectively. The deep background and contaminated ground water well (observed release) TCE concentrations are summarized in T ables GW8 and GW9, respectively. The tables are provided a t the end of this section.

Deep Background and Release Monitoring Well Construction Details and TCE Concentrations

Reference 27, Comprehensive Ground Water Monitoring Data, was used to identify deep background wells for deep contaminated (release) wells. The criteria used in the ERI (Reference 71) was used to identify shallow and deep wells because the criteria ensure s that the background and release wells are completed (screened) within the same relative depths of the aquifer and draw ground water from similar depths in the aquifer

. The designation of deep wells was made based on two factors: the elevation of the bottom of the well and the height of the water column. Deep wells are those where the water column is > 25 ft and where the elevation at the bottom of the well is below

- 7 ft amsl. The exception is well DP

- MW

15C, where the water column is > 25 ft but the bottom of well elevation is >

- 7 ft amsl. (Ref. 27, p. 5) For this well, solely the height of the water column was used to assign the well designation as deep (see Table GW6). Three background wells were identified (DP

- MW

- 03A, DP

- MW

- 06A, and DP

- MW

- 15C) (Ref. 27, p. 1 ; Ref. 39 ). The construction details for the deep background and contaminated wells including well depths, well screen intervals, and ground water elevations are summarized in Tables GW6 and GW8. Locations of the background wells are shown in Reference 29. Ground water elevations of the background and contaminated wells are summarized in Reference 27, p. 6 and illustrated on Reference 64. As these references show, the ground water elevations in the deep contaminated wells are lower than those in the deep background wells. Therefore, the contaminated wells are located hydrogeologically downgradient of the background wells. The background wells capture the conditions of ground water hydrogeologically upgradient of the contaminated wells.

The background wells are considered to be background wells because:

**•** The wells are screened with the same relative depth as the contaminated we lls.

**•** The well screen lengths are similar.

**•** The background wells are screened within the same relative portion of the aquifer as the contaminated wells (see Tables GW6 and GW8).

**•** The wells were sampled using the same procedures (Ref. 45; Ref. 71, pp. 28, 33)

.

**•** The wells were sampled during the same time frame (See Tables GW7 and GW9).

**•** The wells were analyzed using the same methods (Ref. 51, p. 6; Ref. 53, p. 7; Ref. 55, p. 30; Ref. 56, p. 7; Ref. 58, p. 16; Ref. 59, p. 23; Ref. 60, p. 17; Ref. 61, p. 26).

**•** The wells are located outside of the source, the ground water plume (Ref. 39; Ref. 67).

Additionally, deep ground water is documented to flow from the northeast to the south

- southwest based on ground water elevations presented in Reference 27, page 6, and t he ground water contour map shown in Reference 64 (Ref. 71, p. 41). References 29, 39, and 67 illustrate that the three background wells are outside the ground water plume. Ground water elevations in the background wells are higher than theGW

- Likelihood of Release

GW

- 20 elevations in the contaminated wells, as documented in Tables GW6 and GW8. The background wells indicate ground water conditions northeast, north, and southeast of the ground water plume.

As Tables GW7 and GW9 show, background wells were not sampled during the September 2009 sampling investigation. This investigation included the collection of ground water samples primarily from the contaminated wells (see Tables GW7 and GW9). The background and contaminated ground water samples were collected 5 months apart. No ot her background wells have been identified for this sampling date. Therefore, the April 2009 samples are used to document background concentrations for the September 2009 ground water samples. Based on the physical properties of TCE, it is not likely that these background wells would have become contaminated between April 2009 and September 2009 (Ref. 31, p. 1). Moreover, TCE is not naturally occurring (Ref. 30, p. 185). MDE representatives indicated TCE had never been detected in residential wells samples located on Dogwood Lane upgradient of the plume. The residential wells have been sampled periodically to determine whether the TCE ground water plume extended to the north / northeast (Ref. 32; Ref. 15, pp. 21, 47, 48, 53, 54, 56, 57; Ref. 16, pp. 2, 14, 17, 23; Ref. 92). This provides evidence that no source of TCE is outside the ground water plume.

The ground water sample collection forms for each ground water sample used to document an observed release to ground water are provided in References 46, 105, and 106. The work plans followed for sample collection are provided in Reference 45. The logbook notes for investigation are extensive and available at EPA.

Envirosystems, Inc.

, used EPA Method 8260 to analyze the samples, and Air, Water, and Soil followed SW

- 846 methodology (Ref. 51 pp. 1, 6; Ref. 53, p. 7; Ref. 55, pp. 1, 30; Ref. 56, p. 7; Ref. 58, p. 16; Ref. 59, p. 23; Ref. 60, p. 17; Ref. 61, p. 26). Envirosystems, Inc.

, indicated that all QC criteria were met (Ref. 51, p. 1). Envirosystems , Inc.
, laboratory data sheets provide the reporting limit when a compound is not detected (Ref. 51, p. 4). The reporting limit for TCE is 5 μg/L (Ref. 51, p. 17). The reporting limit corresponds to the Method 8260 EQL (Ref. 52, pp. 1, 9). The EQL is ge nerally 5 to 10 times the MDL. The EQL is the lowest concentration that can be reliably achieved with specified limits of precision and accuracy during routine laboratory operating condition s (Ref. 52, p. 9). Envirosystems, Inc.

, laboratories presumed th e EPA Method 8260 MDL for TCE is 1.955 μg/L (Ref. 68, p. 1). The reporting limits are provided as the detection limits because concentrations below the reporting limits are identified on the laboratory data sheets as not detected and represent detection limits achievable by Envirosystems, Inc. (Ref. 51, p. 4). Because the reporting limits are higher than the MDLs, this is a conservative approach.

Air, Water, and Soil data sheets specify the LOD and the LOQ for the detection limits. The LOQ is the limit that the laboratory can quantify. LOQ is the concentration at which quantitative results can be reported with a high degree of confidence (Ref. 69). Because the LOQ is higher that the LOD on the analytical data sheets, the LOQ used as the detection limit as a conservative approach (Ref. 55, pp. 3, 6, 7, 10, 14, 17, 24, 29; Ref. 58, pp. 10, 16; Ref. 59, pp. 59, pp. 10, 12; Ref. 60, pp. 6, 11; Ref. 61, pp. 5, 7, 10, 12, 19, 22).

The data validation report for the ground water samples is presented in Refere nce 10 8

.GW

- Likelihood of Release

GW

- 21 TABLE GW6 DEEP BACKGROUND MONITORING WELL CONSTRUCTION DETAILS

Well ID Well Designation Location Well Diameter (in) Elev. Top of Screened Interval

From Log (ft) * Elev. Bottom of Screened Interval

From Log (ft) * Total Measured Depth of

Well BT OC

(ft) Total Measured Depth of

Well BTOC

(ft) Total Measured Depth of

Well BTOC

(ft) Elevation of Ground water (ft) * Elevation of Ground water (ft) * Elevation of Ground water (ft) * References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09
DP

- MW

03 A Deep Northern 2

- 6.72

- 16.72 63.73 63.06 63.05 29.84 29.91 29.89 27, pp. 1, 2, 6; 29

DP

- MW

15C Deep Northern 2 14.49

- 0.51 83.35 82.84 82.73 26.69 27.13 27.05 27, pp. 1, 2, 6; 29 ; 90, pp. 135 to 140

Notes:

* Elevations are above mean sea level (amsl) (Ref. 27, p. 9). Reference 29 provides the locations of the wells. Well logs for DP

- MW

- 03A and 06A have not been located.

BTOC = Below Top of Casing DP = Dwyer Property f t = Feet ID = Identification i n = Inch MW = Monitoring WellGW

- Likelihood of Release

GW

- 22 TABLE GW7 DEEP BACKGROUND GROUND WATER CONCENTRATIONS

Well ID Hazardous Substance Sampling Date Conc (μg/L) Reporting Limit (μg/L) a References

DP

- MW

- 03A Trichloroethylene 4/15/2009 6.9 5 46, pp. 1, 18, 19; 51, pp. 6, 31; 108, pp. 2

- 25

DP

- MW

- 15C Trichlor oethylene 4/28/2009 8.6 5 46, p. 2 , 59, 60 ; 57,
pp. 7 , 35 (the chain of custody and collection form incorrectly identifies the sample

as DP

- MW - 15B );

108, pp. 70

- 80

Notes:

a The analytical method used to analyze the samples was EPA Method 8260 by Envi rosystems, Inc

. (Ref. 51 p. 6).

The laboratory indicted that all quality control (QC) criteria were met (Ref. 51, p. 1). The laboratory data sheets provide the reporting limit when a compound is not detected (Ref. 51, p. 4). The reporting limit for tri chloroethylene is 5 μg/L (Ref. 51, p. 17). The reporting limit corresponds to the Method 8260 estimated quantitation limit (Ref. 52, pp. 1, 9). The estimated quantitation limit (EQL) is generally 5 to 10 times the method detection limit ( MDL ) . The EQL i s the lowest concentration that can be reliably achieved with in specified limits of precision and accuracy during routine laboratory operating condition s (Ref. 52, p. 9).

μg/L = Microgram s per liter Conc. = Concentration DP = Dwyer Property ID = Identi fication NA = Not available MW = Monitoring WellGW

- Likelihood of Release

GW

- 23 - Contaminated Samples: Deep Monitoring Wells

TABLE GW8 DEEP CONTAMINATED GROUND WATER MONITORING WELL CONSTRUCTION DETAILS

Well ID Location Well Diameter (in) Elev. Top of Screened Interval

From Log (ft) * Elev. Bottom of Screened Interval

From Log (ft) * Total Measured Depth of

Well BTOC (ft) Total Measured Depth of

Well BTOC (ft) Total Measured Depth of Well BTOC (ft) Elevation of Ground Water (ft) * Elevation of Ground Water (ft) * Elevation of Ground Water (ft) * References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09 DP

- MW

01A Southern 2

- 10.83

- 20.83 58.90 58.25 58.26 17.26 17.59 17.61 27, pp. 1, 2, 6; 29 DP

- MW

02A Northern 2

- 6.94

- 16.94 62.61 62.09 62.01 27.44 27.73 27.63 27, pp. 1, 2, 6 ; 29

DP

- MW

- 04 Southern 2

- 4.62

- 14.62 72.19 71.50 71.43 18.25 18.55 18.57 27, pp. 1, 2, 6; 29 DP

- MW

04A Southern 2

- 20.13

- 30.13 89.80 90.44 89.43 18.21 18.38 18.58 27, pp. 1, 2, 6; 29

DP

- MW

- 07 Northern 2

- 5.87

- 15.87 72.81 72.34 72.15 26.67 27.01 26.85 27, pp. 1, 2, 6; 29

DP

- MW

12B South ern
2

- 19.98

- 29.98 123.00 122.65 122.19 23.34 23.76 23.57 27, pp. 1, 2, 6; 29; 90, pp. 1 8 to 25

DP

- MW

13A Southern

2

- 8.34

- 18.34 92.76 92.11 91.80 21.76 22.17 22.02 27, pp. 1, 2, 6; 29; 90, pp. 2 6 to 31GW

- Likelihood of Release

GW

- 24 TA BLE GW8 (Continued) DEEP CONTAMINATED GROUND WATER MONITORING WELL CONSTRUCTION DETAILS

Well ID Location Well Diameter (in) Elev. Top of Screened Interval

From Log (ft) Elev. Bottom of Screened Interval

From Log (ft) Total Measured Depth of

Well BTOC (f t) Total Measured Depth of

Well BTOC (ft) Total Measured Depth of

Well BTOC (ft) Elevation of Ground Water (ft) Elevation of Ground Water (ft) Elevation of Ground Water (ft) References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09

DP

- MW

14B Souther n
2

- 10.86

- 20.86 106.83 106.23 105.86 18.85 19.37 19.25 27, pp. 1, 2, 6; 29; 90, pp. 38 to 44

DP

- MW

17C Northern

2 1.49

- 13.51 83.62 82.97 82.94 30.01 30.27 30.18 27, pp. 1, 2, 6; 29; 90, pp. 149 to 154

DP

- MW

26B Southern

2

- 1.79

- 11.79 NM 72.29 73.44 NM 19.31 19.38 27, pp. 1, 2, 6; 29; 90, pp. 205 to 209

DP

- MW

27B Southern

2

- 5.10

- 15.10 NM 87.43 87.92 NM 20.14 19.75 27, pp. 1, 2, 6; 29; 90, pp. 215 to 220

DP

- MW

28B Southern

2

- 4.24

- 14.24 NM N M 91.09 NM NM 20.79 27, pp. 1, 2, 6; 29; 90, pp. 226 to 231

DP

- MW

29B Southern

2

- 15.15

- 25.15 NM 98.01 98.42 NM 21.47 20.90 27, pp. 1, 2, 6; 29; 90,
pp . 237 to 242GW

- Likelihood of Release

GW

- 25 TABLE GW8 (Continued) DEEP CONTAMINATED GROUND WATER MONITORING WELL CONSTRUCTION DETAILS

Well ID Location Well Diameter (in) Elev. Top of Screened Interval

From Log (ft) Elev. Bottom of Screened Interval

From Log (ft) Total Measured Depth of

Well BTOC

(ft) Total Measured Depth of

Well BTOC (ft) Total Measured Depth of

Well BTOC (ft) Elevation of Ground Water (ft) Elevation of Ground Water (ft) Elevation of Ground Water (ft) References

4/9/09 8/10/09 9/14/09 4/9/09 8/10/09 9/14/09

DP

- MW

- 30B Southern

2

- 8.91

- 18.91 N M NM 94.44 NM NM 19.30 27, pp. 1, 2, 6; 29; 90, pp. 248

to 25 3

DP

- MW

- 31B Southern

2

- 45.59

- 55.59 NM NM 113.24 NM NM 18.84 27, pp. 1, 2, 6; 29; 90, pp. 258

to 264

DP

- MW

- 32B Southern

2

- 64.11

- 74.11 NM NM 114.14 NM NM 17.71 27, pp. 1, 2, 6; 29; 90, pp. 268

to 274

EGWS

- MW

- 02A Southern 2 10.70

- 9.30 45.65 44.86 44.85 16.99 17.30 17.18 27, pp. 1, 2, 6; 29 No tes:

* Elevations are above mean sea level (amsl) (Ref. 27, p. 9). Reference 29 provides the locations of the wells. Well logs for DP

- MW

- 01A, 02A, 04, 04A, and 07 have not been located.

BTOC = Below Top of Casing f t = Feet MW = Monitoring well DP = Dwyer Property ID = Identification EGWS = Elkton Ground Water Study in = Inch Elev. = Elevation NM = Not measuredGW

- Likelihood of Release

GW

- 26 TABLE GW9 DEEP CONTAMINATED GROUND WATER TRICHLOROETHYLENE (TCE) CONCENTRATIONS

Well ID Hazardous Substance Sampling Date Conc. (μg/L) Reporting Limit (μg/L) a , b References

DP

- MW

- 02A Trichloroethylene 4/17/2009 55 5 46, pp. 1, 14, 15; 56, pp. 7, 25; 108, pp. 26

- 28

DP

- MW

- 04 Trichloroethylene 4/21/2009 5,900 250 (DF 50) 46, pp. 1, 24, 25; 53, pp. 7, 35; 108, pp. 30

- 47

DP

- MW

- 04A Trichloroethylene 4/21/2009 6,800 250 (DF 50) 46, pp. 1, 23; 53, pp. 7, 39; 108, pp. 30

- 47

DP

- MW

- 07 Trichloroethylene 4/17/2009 59 5 46, pp. 1, 32, 33; 56, pp. 7, 23; 108, pp. 26

- 28

DP

- MW

- 13A Trichloroethylene 4/21/2009 3,200 1,00 (DF 20) 46, pp. 2, 52, 53; 53, pp. 7, 27; 108, pp. 30

- 47

DP

- MW

- 14B Trichloroethylene 4/2 2 /2009 21,000 1,000 (DF 200) 46, pp. 2, 56, 57; 53, pp. 7, 49; 108, pp. 30

- 47

DP

- MW

- 17C Trichloroethylene 4/24/2009 120 5 46, pp. 3, 67 ; 82, pp. 7, 26 ; 108, pp. 48

- 69

EGWS

- MW

02A Trichloroeth ylene 4/22/2009 16,000 500 (DF 100) 46, pp. 2, 16, 17; 53, pp. 7, 47; 108, pp. 30

- 47

RP- MW

- 01A Trichloroethylene 9/22/2009 70.2 1 106, pp. 28, 29; 55, pp. 22, 30; 108, pp. 140

- 170

DP

- MW

- 04 Trichloroethylene 9/08/2009 4,500 50 (DF 50) 105, pp. 3, 4; 61, pp. 7, 26; 108, pp. 113

- 139

DP

- MW

- 04A Trichloroethylene 9/09/2009 6,000 50 (DF 50) 105, pp. 5, 6; 61, pp. 10, 26; 108, pp. 113

- 139

DP

- MW

- 12B Trichloroethylene 9/09/2009 320 1 105, pp. 9, 10; 61, pp. 19, 26; 108, pp. 113

- 139

DP

- MW

- 13A Trichloroethylene 9 /08/2009 2,640 20 (DF 20) 105, pp. 11, 12; 61, pp. 5, 26; 108, pp. 113

- 139

DP

- MW

- 14B Trichloroethylene 9/08/2009 22,300 200 (DF 200) 105, pp. 15, 16; 61, pp. 1 4 , 26 ; 108, pp. 113

- 139GW

- Likelihood of Release

GW

- 27 Notes:

a The analytical method used to analyze the samples was EPA Method 8260 by Envirosystems, Inc. (Ref. 56 pp. 1, 7). The laboratory data sheets provide the reporting limit when a compound is not detected (Ref. 56, p.5). The adjusted reporting limit for TCE is 5 μg/L (Ref. 56, p. 19). The reporting limit corresponds to the Method 8260 estimated quantitation limit (EQL) (Ref. 52, pp. 1, 9). The EQL is generally 5 to 10 times the method detection limit (MDL). The EQL is the lowest concentration that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operating conditions (Ref. 52, p. 9).

b Air, Water, and Soil Laboratories data sheets specify the LOD and the LOQ for the detection limits. The LOQ is the limit that the laboratory can quantify. LOQ is the concentration at which quantitative results can be reported with a high degree of confidence (Ref. 69). Because the LOQ is higher that the LOD on the analytical data sheets, the LOQ used as the detection limit as a conservative approach (Ref. 55, pp. 3, 6, 7, 10, 14, 17, 24, 29; Re f. 58, pp. 10, 16; Ref. 59, pp. 59, pp. 10, 12; Ref. 60, pp. 6, 11; Ref. 61, pp. 5, 7, 10, 12, 19, 22).

The highest background well trichloroethylene concentration in Table GW 7 is used to establish the background level . This is a conservative approach.

μg/L = Microgram s per liter Conc. = Concentration TABLE GW9 (continued) DEEP CONTAMINATED GROUND WATER TRICHLOROETHYLEN E (TCE) CONCENTRATIONS

Well ID Hazardous Substance Sampling Date Conc. (μg/L) Reporting Limit (μg/L) a References

DP

- MW

- 26B Trichloroethylene 9/02/2009 902 20 (DF 20) 105, pp. 23, 24; 59, pp. 10, 23; 108, pp. 85

- 108

DP

- MW

- 27B Trichloroethylene 9/03/200 9 11,900 200 (DF 200) 105, pp. 27, 28; 59, pp. 1 4 , 23 ; 108, pp. 85

- 108

DP

- MW

- 28B Trichloroethylene 9/04/2009 13, 2 00 50 (DF 50) 105, pp. 31, 32; 60, pp. 11, 17; 108, pp. 110

- 112

DP

- MW

- 29B Trichloroethylene 9/03/2009 15,800 200 (DF 200) 105, pp. 35, 36; 59
, pp. 19, 23; 108, pp. 85

- 108

DP

- MW

- 30B Trichloroethylene 9/04/2009 12,200 50 (DF 50) 105, pp. 39, 40; 60, pp. 6, 17; 108, pp. 110

- 112

DP

- MW

- 31B Trichloroethylene 9/1/2009 335 1 105, pp. 43, 44; 58, pp. 10, 16; 108. pp. 81

- 84

DP

- MW

- 32B Trichloroethylene 8/31/2009 46.9 1 105, pp. 47, 48; 58, pp. 5, 16; 108. pp. 81

- 84

EGWS

- MW

02A Trichloroethylene 9/09/2009 17,100 50 (DF 50) 105, pp. 1, 2; 61, pp. 22, 26; 108, pp. 113

- 139GW

- Likelihood of Release

GW

- 28 DF = Dilution factor (the detection limit is adjusted by multiplying the detection limit [5] by the DF). DP = Dwyer Property RP = Ruddy Property EGWS = Elkton Ground Water Study ID = Identification NA = N ot available MW = Monitoring Well

Trichloroethylene Product in Monitoring Wells

During ground water investigations at the Dwyer Property, TCE product was measured in monitoring wells DP

- MW

- 15A and DP

- MW

- 21. DP

- MW

- 15A had the following thicknesses of TCE product detected on the following dates : 2.69 feet (5/11/2009), 1.59 ft (6/10/2009), 1.63 ft (7/10/2009), 2.02 ft (8/10/2009), and 2.02 ft (9/14/2009) (Ref. 27, p. 5). TCE product was found in DP

- MW

- 21 at 2.45 ft on 9/14/2009 (Ref. 27, p. 5) . A review of available ground water data indicates that TCE dense, non

- aqueous phase liquid (DNAPL) occurs in the area of DP

- MW

- 15A and DP

- MW

- 17A (Ref. 71, pp. 45, 47 ).

Rationale for Plume :
Because the source is a contaminated groun d water plume with no identifia ble source of contamination, attribution has not been determined (Ref. 1, Section 3.1.1). This section describes the physical properties of TCE, the original source of which has not been identified, and describes facilities within Elkton, Maryland, that h ave been investigated as possible sources of contamination.

Physical Properties of TCE

An observed release of TCE to ground water has been established based on sampling of monitoring wells in the area of the ground water plume. The physical properties of TCE are documented in the following paragraphs.

Because TCE is heavier tha n water, TCE migrates downward from the original source to zones of low permeability. TCE remains in ground water for long periods of time. TCE has low solubility in water and a density greater than that of water. Therefore, TCE may exist in the subsurface as DNAPL and could migrate as a separate liquid phase to significant distances below the water table in both unconsolidated materials and fractured bedrock. Because of their physicochemical properties, DNAPLs can migrate selectively through the subsurface. Subsurface DNAPL acts as a long

- term source for dissolved

- phase contamination and determines the spatial distribution and persistence of contaminant concentrations within the dissolved

- phase plume. The DNAPL source zone is the overall volume of the subsurface containing residual and pooled DNAPL. In addition to the DNAPL, significant amounts of contaminant mass may have diffused into low permeability zones. Back diffusio n of contaminant mass from these zones may sustain dissolved

- phase plumes for significant periods of time, even after removal of DNAPL. Flow of ground water past residual and pooled DNAPL will result in dissolved

- phase plumes of contamination. Complete d issolution of most DNAPLs as a result of natural ground water flow is expected to take from several decades to hundreds of years (Ref. 31, pp. 1, 2, 3; Ref. 13, p. 27 , 33 ).

The presence of a contiguous and persistent plume extending from suspected release locations downgradient of the Dwyer property is evidence of a continuing source (e.g., DNAPL). If sufficient time” has passed since the last possible introduction of the contaminant to the subsurface and the plume has notGW

- Likelihood of Release

GW

- 29 “detached” itself from the suspected release locations, a DNAPL source may be present. The “sufficient time” depends on site

- specific conditions such as ground water velocity and the amount of sorption occurring (Ref. 31, p. 6; Ref. 13, p. 27). Abrupt reversals of ground water contamin ant concentration levels with depth or increasing concentrations with depth can indicate the presence of DNAPL (Ref. 31, p. 6). The Dwyer property ground water plume has these characteristics (Ref. 13, p. 27).

TCE may slowly biodegrade under anaerobic c onditions, suggesting that a slow biodegradation process may occur in subsurface environmental regions. In regions where volatilization is not viable, TCE may be relatively persistent. The biodegradation products from TCE are DCE and vinyl chloride (Ref. 30, pp. 2, 202, 203).

TCE is commonly used in vapor degreasing of fabricated metal parts, which is a process that is closely associated with the automotive and metals industries. TCE is an excellent extraction solvent for greases, oils, fats, waxes, and tars, and is used by the textile processing industry to scour cotton, wool, and other fabrics. The textile industry also uses TCE as a solvent in waterless dying and finishing operations. As a general solvent or as a component of solvent blends, TCE is used with adhesives, lubricants, paints, varnishes, paint strippers, pesticides, and cold metal cleaners. Approximately 10 million pounds of TCE is used annually as a chain transfer agent in the production of polyvinyl chloride. Other chemical intermediat e uses of TCE include production of pharmaceuticals, polychlorinated aliphatics, flame

retardant chemicals, and insecticides. TCE is used as a refrigerant for low

- temperature heat transfer and in the aerospace industry for flushing liquid oxygen. Various consumer products found to contain TCE include typewriter correction fluids, paint removers/strippers, adhesives, spot removers, and rug

- cleaning fluids (Ref. 30, p. 188).

TCE is a manmade chemical that is not known to occur in nature (Ref. 30, p. 18 5 ).

Land use in the area overlying the ground water plume include s mixed industrial and commercial development (Ref s. 3; 28 ; Figure 1of HRS documentation record). Locations of industrial and commercial facilities and operations, as well as environmental conditions in the area of the plume, are discussed below.

Facilities in Elkton, Maryland

Although the source of TCE in the ground water plume has not been identified, numerous industrial facilities are in the area of the ground water plume, as documente d below and shown in Reference 18.

ATK Tactical Systems Comp. LLC 55 Thiokol Road Elkton, Maryland

ATK/Thiokol (ATK) (formerly known as Morton Thiokol, Inc.) is a 467

- acre industrial site used for manufacture of rocket fuel and systems. TCE was used as solvent for degreasing metal components from 1959 to 1974. ATK discovered TCE contamination in production wells in 1984. This was the first time the wells were analyzed for VOCs and it is not know how long the wells had been contaminated. This prompted the testing of other wells in the vicinity of the facility. The facility also is contaminated with pesticides and PCE in the soil, surface water, and ground water. A pump and treat system is in use to address the ground water contamination, and further site investigations under the auspices of the EPA are ongoing (Ref. 17, p. 4; Ref. 95, pp. 3, 4).GW

- Likelihood of Release

GW

- 30 After the discovery of TCE at the facility, other wells in the vicinity were investigated. TCE was found in six on

- site wells and 16 off

- site wells. A plume identified by MDE extends from areas on the ATK property across Nottingham Road and Route 40 (Ref. 95, p. 3 , 4 ).

A historical survey generated information that indicates a number of potential sources of TCE and trace VOCs in the vicinity of the TCE ground water plume on and near the ATK facility. The most likely sources of contamination are divided into three groups: those north of Little Elk Creek and Laurel Run, those south of Little Elk Creek but north of Route 40, and those along Route 40. Based on aerial photographs and surveys of land ownership, 11 likely users of TCE or solvents have been or are north of Little Elk Creek, six have been or are south of Little Elk Creek, and four have been or are along Route 40. Many possible sources of TCE contami nation have been identified on and near the ATK facility, including other industries that own or lease property in the area of the facility and that have handled or used hazardous materials and/or solvents (Ref. 95, pp. 1, 5, 10).

On September 22, 1997, th e MDE renewed and modified the Permit for ATK Tactical Systems Company LLC, formerly Thiokol Corporation and later Thiokol Propulsion Controlled Hazardous Substances Storage and Treatment Facility; this action extended the corrective action permit issued t o ATK on October 8, 1989 (overseen by EPA). The permit requires ATK to sample the ground water and/or soil to determine whether releases of hazardous waste/constituents have occurred or are likely to occur from solid waste management units (SWMU). The permit also requires ATK to conduct a Resource Conservation and Recovery Act (RCRA) Facility Investigation to characterize the subsurface conditions and nature and extent of any releases based on the results of the sampling investigations. The third requirement of the permit tasks ATK to implement minor corrective measures at three SWMUs; this stems from submittal of results of an initial source identification / TCE ground water investigation resulting from contamination of two production drinking wells detect ed in December 1984 (Ref. 17, p. 9 ).

Limited SWMU investigations have identified pesticides, volatile organics, inorganics, and other contamination in the soil, surface water, and ground water. A ground water plume migrating from the central portion of the facility towards the southeast is contaminated with TCE and its degradation products. In October 1998, ATK sampled on

- site wells for the solvent constituents of concern and perchlorate. Perchlorate was detected at 500 parts per billion (ppb) in the facility production well (Ref. 17, p. 9 ).

Ground water samples were collected in March, August, and December 2009. Results showed detections and/or exceedences of perchlorates ( 10,100 μg/L (Ref. 93, p. 32 ) , 1,1,1

- trichloroethane (44,100 μg/L) (Ref. 78, p. 2) , 1,1,2

- trichloroethane (3.9 μg/L) (Ref. 78, p. 2), 1,1

- dichloroethane (2,480 μg/L) (Ref. 78, p. 2) , 1,1

- dichloroethene (2,670 μg/L) (Ref. 94, p. 2) , chlorobenzene (82.4 μg/L) (Ref. 80, p. 3)

, chloroethane (387 μg/L) (Ref. 78, p. 2) , chloroform (60.5 μg/ L) ( Ref. 78, p. 2) , methylene chloride (17.1 μg/L) (Ref. 80, p. 3) , PCE (280 μg/L) (Ref. 94, p. 6) , toluene (up to 19.6 μg/L) (Ref. 80, p. 3), TCE ( 249 μg/L) (Ref. 78, p. 14 ) , and vinyl chloride (87.2 μg/L) (Ref. 78, p. 7) . The analytical data reports and chain of custody records for the ground water samples are provide d in References 77 through 80 and References 93 and 94.

ATK is located approximately 1.3 miles southwest of the ground water plume (Dwyer Property) (Ref. 18; Ref. 62 through 64; Ref. 71, p. 41).GW

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- 31 Central Chemical Corporation Trinco Industrial Park Zientler Lane Elkton, Maryland

Central Chemical Corporation (Central Chemical) purchased the facility from the Elkton Company in September 1966. During the late 1960s, the facility was constructe d for herbicide and pesticide blending and air hammer milling operations conducted for client companies (Ref. 70, p. 1
, 7 ). Central Chemical ceased operations in 2003 and sold the property in 2004 to Aquafin, Inc. Aquafin, Inc.

, produces concrete sealing products (Ref. 17, p. 1 2 ).

During Central Chemical’s period of ownership, several incidents were reported of wastewater and lubricating oil spills from the facility into water channels connected to major streams in the State of Maryland, which prompted an order issued in April 1970. Under the order, Central Chemical was required to submit plans for implementing wastewater collection, treatment, and disposal from the facility; design, install, and maintain wastewater collection and treatment and disposal a ctivities for all wastewaters originating from the facility; provide storage facilities for empty bags and containers to prevent “wash down” of chemical residues from the storage area; supply a plan of improved surface drainage to control erosion and sedim ent transport resulting from rain; establish vegetative cover for berms, embankments, and other exposed areas; and train employees to use proper procedures when performing all wastewater collection, treatment, and disposal operations (Ref. 70, p p

. 2, 8, 9 )

. According to the 1989 preliminary assessment of the facility, Central Chemical did not generate any known hazardous wastes at the facility. Non

- hazardous materials generated at the facility were primarily ashes from incineration of bags, boxes, and dr ums that had contained herbicide and pesticide powder (Ref. 70, p. 18 ). The detected chlorinated solvent contamination was unlikely to have resulted from on

- site activities at the facility. The contamination most likely migrated from an off

- site source ( Ref. 17, p. 1 1 ).

Central Chemical is located approximately 1 mile west of the ground water plume (Dwyer Property) (Ref. 18; Ref. 62 through 64; Ref. 71, p p . 41 , 94, 95, 96 ).

Crouse Brothers Excavating 415 West Pulaski Highway Elkton, Maryland

Crouse Br others Excavating facility is an approximately 11

- acre commercial property used as a contractor’s yard for equipment storage and parts. It is located 1,000 feet west of the Route 40 intersection with Route 279. A privately owned rubble landfill extended approximately 2,000 feet towards the north from behind the buildings at the facility (Ref. 17, p. 1 2 ). The Crouse Brothers Excavating facility is located approximately 1.2 miles southwest of the Dwyer Property (Ref. 18).

The Crouse Brothers Excavating facility was acquired as two separate parcels. The southern parcel was purchased in 1972. The buildings along Route 40 were used for several decades as a maintenance shop for excavation vehicles and for repair and maintenance of heating/ventilation/air co nditioning units. In 1981, the second parcel was purchased from Gilpin Manor Development Corporation. The nature of Glipin Manor D evelopment C orporation ’s use of the property is unknown (Ref. 17, p. 1 2 ).

The rubble landfill was discovered in 1986 during an investigation of residential wells. D umping is believed to have occurred at the landfill after 1970. Site inspections by Maryland Department of Health and Mental Hygiene in 1986 found numerous regulated wastes in the landfill at the Crouse BrothersGW

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- 32 Ex cavating facility. The Maryland Department of Health and Mental Hygiene issued a Site Complaint to cease and desist all landfilling, other than tree stumps, brush, concrete, and clean fill dirt

, because the facility was unpermitted. Additional inspections were conducted and the facility submitted information requested by the Department to support a claim that the unacceptable materials found in the landfill had been removed. During the investigation of the ground water wells, the highest concentrations o f TCE were found in wells downgradient of the facility (Ref. 17, p p. 1 2, 13 ).

MDE collected ground water samples from six monitoring wells and three residential wells on January 3, 1990. A figure of the well locations was not provided in the information reviewed; therefore, it is unknown which wells were located near the Crouse Brothers Excavating facility. TCE was detected on site in monitoring wells at concentrations up to 2,200 μg/L, and in residential wells at up to 3,200 μg/L (Ref. 103, pp. 34, 35)

. Crouse Brothers is located approximately 1 mile southwest of the ground water plume (Dwyer Property) (Ref. 18; Ref. 62 through 64; Ref. 71, p p . 41 , 94, 95, 96 ).

Elkton Farm 183 Zeitler Road Elkton, Maryland

The Elkton Farm facility is located approximately 1.5 miles northwest of the Dwyer P roperty (Ref. 18). The facility was purchased from Triumph Explosives in 1945 and encompasses 323 acres. The facility was primarily used for farming and raising livestock. Elkton Farms has a history of use for m unitions waste disposal at the firehole, a rocket motor cleaning and recovery area; in the early 1980s, wastes from Galaxy Chemical plant were disposed of and/or stored at Elkton Farm (Ref. 100, p. 4, 5; Ref. 101, p p . 7
, 12 ).

The facility includes four are as where hazardous wastes were previously handled. Area 1 is located at 183 Zeitler Road and includes an outbuilding with an earthen floor and a barn used to house dairy cattle. In 1992, 17 drums of flammable paint wastes in the barn and 36 drums of vari ous organic wastes in the outbuilding were removed. The drums in the barn were in fair condition. The drums in the outbuilding were in poor condition and contained unknown materials. Many of the drums appeared to be leaking. The owner’s home is located about 200 feet south of the barn (Ref. 100, p p

. 4 , 6, 7; Ref. 101, p p . 7, 12 ).

Area 2 is a Word War II

- era waste ordnance combustion pit known as the f irehole , which was used by Triumph Explosives in the 1940s. The f irehole was defined as an area for the disposal of waste explosives materials generated by the operations at Triumph Explosives. This waste was collected in drums and kept wetted with alcohol or ether. The waste was then carried to a shallow pit off Zeitler Road, spread thinly, and burned. Plant personnel monitored the burn until the waste explosive was consumed. Total quantity of hazardous waste disposed of in the f irehole is unknown. Observations indicated that the f irehole is not one discrete area but a series of burn pits located acros s the property within approximately a 32

- acre area (Ref. 101, pp. 7
, 12 ).

Area 3 is located approximately along the western border of the property. It was a 1

- acre plot of land leased by Thiokol Corporation between the 1950s and 1960s. The area was used for testing rocket fuel (Ref. 101, p. 12, 13 ).GW

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- 33 Area 4 is located near the confluence of Little Elk Creek and Laurel Run. Evidently, it was a dumping ground for hazardous and non

- hazardous waste in the 1970s. The most significant of these wastes, accord ing to a 1979 inventory, were approximately 22 55

- gallon drums of printing ink, 400 to 500 30

- gallon drums of ashes from a burning area operated by Thiokol Corporation, and an estimated 6 cubic yards of 40

- mm projectile wastes (Ref. 100, p. 4).

In 1991, the facility owner informed MDE that drums of unknown materials were staged at the facility. In the 1970s, the facility owner collected the drums from Galaxy Chemical. The facility owner transported the drums to a landfill; however, the landfill refused to accept them. The facility owner then tried returning the drums to Galaxy Chemical; however, Galaxy Chemical was no longer operating. The property owner then placed the drums in the shed and barn on the facility’s property (Ref. 100, p. 5).

Between February 25 and 29, 1992, a Removal Action (RA) occurred at all areas. Drums were removed from the facility and transported to an approved disposal facility. The drums were tested and results showed that 24 drums contained flammable organic liquids, 25 RC RA inert solids, one drum of caustic, and one drum of halogenated organic fluid. An estimated 10 tons of contaminated soil was excavated from the outbuilding and stored in a roll

- off box. On June 17, 1992, drums were labeled and marked for transportation and disposal. On June 23, 1992, the contaminated soil was disposed of off site (Ref. 100, p. 6).

Prior to the 1992 cleanup, a RA had occurred in 1979. Between 400 and 500 drums of ashes containing aluminum oxide had been disposed of in a c ounty landfi ll. Approximately 975 gallons of lithographers printing ink was pumped from 22 55

- gallon drums and incinerated (Ref. 100, p. 7).

In October 2002, MDE collected soil, surface water, and ground water samples from the area believed to be the f irehole. Analy ses of samples showed elevated concentrations of lead, mercury, arsenic, TCE, polychlorinated biphenyls (PCB), and trinitrotoluene (TNT). A ground water sample collected downgradient of the soil sampling at the f irehole area contained TCE at 160 μg/L (Ref . 101, p 8 ).

In May 2003, additional ground water samples were collected from five wells located across the facility. In two of the wells, TCE was present at levels greater than three times the background, MDE Cleanup Standards, and EPA Risk

- Based Concen trations. In addition, 1,1,2

- trichloroethane was present at levels exceeding the EPA Risk

- Based Concentration. Trace levels of cis

- 1,2

- DCE and bis(2

- ethylexyl)phthalate were detected in some of the samples. Pesticides, PCBs, and perchlorates were not detected in any of the samples (Ref. 101, p. 27 ).

Elkton Farm is located approximately 1.25 mile s northwest of the Dwyer Property (Ref. 18; Ref. 71, pp. 94, 95, 96)

.

Iron Hill Road Facility 117 Iron Hill Road Elkton, Maryland

The Iron Hill Road facility e ncompasses approximately 4 acres and is approximately 300 feet from the Maryland/Delaware border. The facility was the location of a chemical recycling firm and had been used for other unknown projects during the 1970s and early 1980s. According to land record information, the site is owned by B & G Associates, Inc. (Ref. 98 , p p . 2, 3). During 1981, Methods Engineering, Inc., manufactured high

- density plastic drain liners. After that, the company closed and the facility was leased. Since 1981, other sm all companies have leased the facility, including an auto body shop and PyronicsGW

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- 34 Incorporated. The facility operated most recently under the name of Pyronics Incorporated. The following wastes were generated at the facility: osmium oxide, sodium azide, 2- chlorophenol, cresols, methanol, phenol, and 1,1,2,2

- tetrachloroethane (Ref. 98, pp. 3 and 4).

On February 10, 1987, MDE attempted to conduct a general inspection of the facility. The facility was found abandoned and surrounded by a locked fence. Drums observed inside of the fence were noted to be in poor and deteriorating condition and were leaking materials. On February 13, 1987, an initial assessment was conducted by the Maryland Waste Management Administration. Soil samples were collected from the areas where leaching of waste had occurred through the fence. At the time of the assessment, the facility consisted of four buildings with approximately 300 drums and containers. Some were in poor condition and leaking. Sample results revealed high con centrations of phenol and volatile organic solvents in surface soils near the leaking drums, as well as potential fire and explosion hazards (Ref. 98, p p . 3, 4).

In March 1987, approximately 300 drums and 1,100 cubic yards of contaminated soil were removed from site, due to a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Removal Cleanup action initiated by the EPA. Ten monitoring wells were installed to investigate shallow ground water contamination. Contamination found in six of the 10 wells included chlorinated hydrocarbons, aromatic compounds, chlorinated phenols, phthalates, and other organic compounds (Ref. 98, p p . 4, 5).

Additional monitoring wells were installed in February 1988. Three shallow and three deep wells were installed. Ground water samples were collected from all of the monitoring wells at the facility, as well as from 15 nearby residential wells. Ground water contamination found in a shallow sand and gravel aquifer consisted of chlorinated VOCs, aroma tic compounds, and phenols. A plume of contamination approximately 400 feet long extended off site to the southeast. None of the analytes was found in the residential wells. No shallow wells were in the path of the plume (Ref. 98, pp. 7, 8, 9).

TCE was not detected in the ground water samples collected at the Iron Hill Road facility. Iron Hill Road facility is located to the northeast of the ground water plume (Dwyer Property) (Ref. 18; Ref. 62 through 64; Ref. 98).

National Fireworks 900

- 1000 Block of Singerly Road (Rt. 213) Elkton, Maryland

National Fireworks is a former munitions and fireworks production facility that operated between the early 1940s and 1965 (Ref. 76, p. 2). Aerial photographs show that the facility shared a road connected to th e Vicon property, which suggests that these facilities operated as one integrated munitions production facility (Ref. 73, p. 5). The facility is located along the northeast boundary of the Dwyer Property ground water plume (Ref. 18).

During the period between the 1940s and 1960s, munitions facilities like Victory Fireworks and Specialty Company and Vicon used or produced different hazardous materials. Heavy metals used to produce different colored fireworks included aluminum, antimony, barium, cadium, chromium, cobalt, copper, magnesium, nickel, sodium, and zinc. Base/neutral and acid compounds used in the production of chemical munitions included 2,4 - and 2,6

- dinitrotoluene; hexachloroethane; chloroacetophenone; nitrobenzene; 2,4,6

- TNT; hexachlorobenze ne; dinitrobenzene; diphenylamine; 1,3,5

- trinitrobenzene; andGW

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- 35 alkane hydryocarbons. Volatile solvents used to clean and degrease equipment included TCE, PCE, and acetone (Ref. 76, pp. 2 4 , 2 5 ).

In 1990, the facility property owner contracted a company to c onduct an environmental risk assessment of the facility because the land had been proposed for residential development. Three separate phases of sampling were conducted to characterize the waste at the property (Ref. 73, p p

. 14, 15). Four soil samples

an d one composite sample were collected during the first phase of sampling. Each of the four soil samples was analyzed for VOCs, and the composite sample was analyzed for total metals and explosives. VOCs were not detected in the four samples; however, mea surable quantities (in the ppm range) of nitrobenzene, cyclotrimethylenetrinitramine (RDX), and tetryl were detected. In addition, 2,4

- dinitrobenzene was detected, but at levels below the reporting limit. Metals were found in the composite sample at

conc entrations above the reporting limit for ambient soil. Metals detected in the composite sample included arsenic, chromium, lead, zinc, cadium, copper, and nickel (Ref. 76, p p . 2 1, 22 ).

For the second phase of sampling, the property was divided into 21 s eparate zones, with each zone divided into four quadrants. Soil samples were collected from each of the quadrants. Composite samples containing soil from the four quadrants in each of the zones were analyzed for explosives only. Nine of the 21 composite samples contained levels of explosives analytes 2,4

- dinitrotoluene and 1,3,5

- trinitrobenzene (Ref. 76, p. 2 2 ).

During the third phase of sampling, the nine contaminated zones were resampled. Each of the nine zones was divided into four separate areas and samples were collected from each area (36 total samples). Five explosive s analytes were detected each of the 36 samples: 1,3

- dinitrobenzene; nitrobenzene; tetrahexamine tetranitramine (HMX); 1,3,5

- trinitrobenzene; and RDX (Ref. 7 6 , p. 23 ).

Because of th e plans for residential development on the property, the facility was referred to the State Superfund program for a remediation assessment (Ref. 73, p. 15). Three separate contaminated soil removals were conducted during the State Superfund cleanup of the facility. Two soil removals completed in 1991 involved removal of 79 and 84 tons of metal

- contaminated soils, respectively. In 1993, an estimated 900 to 1,100 tons of contaminated soil and burned waste was removed from target areas of the facility (Ref. 73, p. 7). Between 1991 and 1993, between 1,100 and 1,200 tons of contaminated soil was removed from the property (Ref. 73, p. 14).

In March 1994, soil, sediment, surface water, and ground water samples were collected from the property and within its vic inity. Manganese and lead were detected in two monitoring wells sampled; however, no organic contaminants detected in ground water samples exceeded the EPA benchmark for tap water. No organic analytes exceeded EPA benchmarks for tap water or residential soil in any of the sediment and surface water samples; however, manganese was detected at elevated levels in both sediment and surface water samples. No organic analytes detected in the soil samples exceeded EPA benchmarks for residential soil. Five inor ganic compounds (arsenic, barium, beryllium, manganese, and antimony) were detected at elevated levels. All five inorganic compounds exceeded EPA benchmarks for residential soil, and three analytes (antimony, barium, and manganese) were detected at levels more than three times the concentration of the off

- site background sample (Ref. 73, p p . 18, 19 ).

TCE was not identified in any samples collected on the National Fireworks facility (Ref. 73, pp. 7, 15, 18, 24, 31, 35)

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- 36 New Jersey Fireworks/Route 7 Dump 1726 Old Philadelphia Road (Route 7) Elkton, MD

The New Jersey Fireworks, Route 7 Dump facility is located approximately 2 to 2.5 miles southwest of the Dwyer property (Ref. 18). In the early 1900s, the Route 7 Dump portion of the facility was utilized as a clay quarry that supplied a brick manufacturer. During the World War II period, by

- products of nearby munitions production, as well as scrap rubber from the Bayshore Rubber Plant, were disposed of in the former clay quarry (Ref. 96, p. 3 ). In 1956, the New Jersey Fireworks Company purchased the property to manufacture “Class C” fireworks. Manufacturing occurred on the eastern portion of the facility’s property, and waste from the production of the fireworks was deposited in a pond formerly used as a clay quarry located at the western portion of the facility’s property. This was known as the Route 7 Dump (Ref. 17, pp. 23 and 24). In 1993, manufacturing of fireworks ended. In June 1999, the facility was transferred from New Jersey Fireworks to Sun and Star, LLC. Extensive cleanup of the facility was initiated after the transfer. Buildings, trailers, and hazardous materials were removed from the facility, and a new office building and warehouse were constructed. Currently, the facility’s operations consist primarily of repacking imported fireworks (Ref. 96, p p

. 3, 4 ).

In 1988, the New Jersey Fireworks facility was identified as a hazardous waste generator by the MDE. During an inspection in May 1999, MDE found large amounts of fireworks and black powder stored in an unsafe manner. Raw materials such as black powder, oxidizers, fuels, binders, and other fireworks components were found throughout the building. Rusted 33

- gallon and 55

- gallon drums contained potassium perchlorate. A waste disposal area found in the southwest portion of the facility included wooden pallets, drums, aerosol cans, oil containers, auto parts, cinders, and other debris. In April 2000, MDE collected ground water, surface water, sediment, and soil samples to assess potenti al contamination at the facility. Additional sampling was conducted in August 2004 (Ref. 17, p p

. 19, 20 ; Ref. 96, pp. 6, 7).

The April 2000 sampling event was conducted in accordance with the EPA R outine Analytic Services. Samples were analyzed for VOCs, SVOCs, PCBs, total metals, and cyanide. Some samples were analyzed for perchlorates (Ref. 96 , p. 1 0 ). The results were compared to Maryland Maximum Concentration Limits (MCL). For ground water sampling, only one sample, collected from beneath the waste pile, contained contamination above the MCL screening values. Arsenic (267 μg/L), beryllium (27.5 μg/L), chromium (1
, 450 μg/L), and lead (122 μg/L) were detected above MCLs. All of the inorganic analytes except copper were detected at levels three times greater than background. Perchlorate was not detected in the ground water samples; however, the holding time of the samples was exceeded (Ref. 96, p. 1 7 ).

Soil samples were screened against EPA Risk

- Based Concentration l evels. Four samples were anal yzed for perchlorates. The low levels of inorganic and organic contaminants detected in the soil samples did not exceed benchmark values; however, aluminum, antimony, arsenic, barium, chromium, cobalt, copper, iron, nickel, thallium, vanadium, and zinc we re detected at levels greater than three times the background levels. Perchlorate was not detected in the soil samples; however, the holding time of the samples was exceeded (Ref. 96, p. 1 8 ).

Additional sampling was conducted between 2001 and 2004 at the f acility. In December 2001, soil samples were collected to further characterize the burn pit area and areas near the buildings and trailers that still contained potentially hazardous wastes. Results showed elevated levels of antimony at the entrances of the two buildings. Additional field screening samples were collected in March 2002, approximately 10 to 20 feet from the building entrances to determine if metals contamination was restricted to those areas. An area near the former sparkler manufacturing building was sampled, andGW

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- 37 results showed elevated levels of barium ( 35,400 ppm and 39,300 ppm). In May 2003, perchlorate contamination was found in community wells near the facility. Sample results showed perchlorate contamination at 5 ppb in one of the wells and 2 8 ppb and 3 ppb in two additional community wells. Due to these levels, the MDE conducted two phases of sampling in September and November 2003, which included the New Jersey Fireworks facility production well. The production well had perchlor ate contamination at 202 ppb in September 2003 and 790 ppb in November 2003 (Ref. 97, p. 16 ).

An ESI conducted at the New Jersey Fireworks facility on August 3

- 5, 2004, evaluated potential impacts on soil, ground water, surface water, and sediments on an d off site from operations at the former disposal area (Route 7 Dump) and the sparkler building area. Samples were collected and submitted for analysis in accordance with the CLP Routine Analytic Services. Samples were analyzed for TAL inorganics and TCL SVOCs and pesticides. Soil samples were additionally sampled for VOCs. Monitoring wells were installed to assess potential contamination (Ref. 97, pp. 16, 17 ).

Ground water sample results showed inorganic contamination in the ground water samples. Ele vated levels of metals were detected at the shallow well (unfiltered sample) on the Route 7 Dump facility, and elevated levels of barium (43,700 μg/L) were detected in the water near the sparkler building (unfiltered sample). Filtering reduced the concent rations; however, barium was still present at levels above the MDE August 2001 Cleanup Standards. Only traces of three SVOC analytes were detected in the ground water samples (bis [2

- ethylhexyl] phthalate, phenol, and chrysene). Perchlorates were detected in the samples collected near the sparkler building and screened against the EPA Drinking Water Equivalent Level (DWEL). Only one sample, near the sparkler building, exceeded the DWEL at 385 μg/L. Perchlorates were detected in four other samples at lev els ranging from 4.79 to 22.6 μg/L (Ref. 97, pp. 21, 22, 23 ).

Surface water sampling was also conducted in August 2004. These samples were collected from Mill Creek, including north and south branches at the Route 7 Dump facility, and an unnamed tributary near the New Jersey Fireworks sparkler building. Low levels of inorganic analytes were detected. Barium was detected at levels greater than three times the background (33.8 to 2

, 590 μg/L). Thallium was detected (8.5 μg/L) at levels above Maryland’s Toxi c Substance Criteria for Ambient Surface Water. One organic compound was detected (di -n- butylphthalate) below the contract

- required detection limit of 10 μg/L. Perchlorate was detected in the samples from the unnamed tributary of Mill Creek, near the spa rkler building. Perchlorate concentrations were detected at greater than three times background (7.52, 7.65, and 8.51 μg/L) (Ref. 97, pp. 23, 24, 25 ).

Sediment samples showed levels of barium, lead, manganese, nickel, and zinc significantly above those in the background sample collected at the Route 7 Dump facility. Barium was the only metal detected near the sparkler building at levels greater than three times the background. Arsenic, chromium, lead, mercury, and zinc were detected in the sparkler building background sample at levels that exceeded the National Oceanic and Atmospheric Administration (NOAA) Threshold Effects Limit (TEL) for freshwater sediments and/or Effects Range Median values. Only five organic compounds were detected at levels exceedin g NOAA TELs: (benzo[a]anthracene, benzo[a]pyrene, chrysene, fluoranthene, and pyrene. Perchlorate was detected in the sediment closest to the sparkler building at 103 micrograms per kilogram (μg/kg), which exceeded three times the background level (Ref. 97, pp.25, 26, 27 ).

Metals contamination was detected throughout the soil samples (surface and subsurface). Most were detected at levels greater than three times their background samples. Arsenic, barium, and mercury were detected in the surface soil at levels exceeding MDE and/or EPA benchmark standards. Arsenic exceeded benchmark levels in subsurface samples. Higher levels of inorganic compounds were detected, especially barium, near the sparkler building area. A total of 14 organic compounds were detected in the soil samples. Only bis(2

- ethylhexyl) phthalate and 4.4’

- dichlorodiphenyldichloroethene (DDE) were detectedGW

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- 38 at levels above their contract

- required quantitation limits (CR Q L) and at levels three times greater than background samples. Perchlorates were detected in soil samples collected from both the Route 7 Dump facility and the sparkler building area. The concentrations of perchlorates (between 6 and 2090 μg/kg) exceeded three times that in the background sample (Ref. 97, pp. 27, 28, 29, 30, 31 ).

Sampling conducted at the facility did not show TCE. New Jersey Fireworks is located southwest of the ground water plume (Dwyer Property) (Ref. 18; Ref. 62 through 64).

Sand, Gravel, and Stone Route 40 Elkton, Maryland

The Sand, Gravel, and Ston e property is an inactive, approximately 200

- acre sand and gravel quarry located approximately 3 miles west of Elkton, Maryland, on U.S. Route 40 (Ref. 40, p. 2). The property is located approximately 2.5 miles east / southeast of the ground water plume (Ref. 7 ; Ref. 18).

The Maryland Sand, Gravel, and Stone Company has owned the property and associated facility since 1962 (Ref. 40, p. 3). Sand and gravel quarrying operations were reportedly conducted in two main areas of the facility, including the western excavated area (WEA) and the eastern excavated area (EEA) (Ref. 40, p. 2). The facility disposed of industrial waste and accepted distillation wastes from a local solvent recycler from the late 1960s to the mid 1970s (Ref. 42, p. 1). A portion of the EE A was reportedly used for the disposal of both liquid and solid wastes including process wastewaters, sludge, still bottoms, and approximately 1,300 drums containing solid and semi

- solid wastes during the period of 1969 to 1974. Three pits were used as su rface impoundments for approximately 700,000 gallons of wastewater. Soil, sediment, and ground water at the property have been contaminated as a result of former disposal activities (Ref. 40, p. 3). The property was listed on the National Priorities List (NPL) on September 8, 1983 (; Ref. 42, p. 2). Approximately 200,000 gallons of liquid waste was removed from the facility in 1974; remaining drums and sludge were buried in excavated pits on the property (Ref. 42, p. 1).

Ground water in the vicinity of the property is contaminated with several VOCs including benzene ; chlorobenzene ; 1,4

- dioxane ; 1,1,1

- trichloroethane ; and vinyl chloride. High concentrations of VOCs are reportedly present within the shallow ground water, and contaminants have migrate d into the underlying aquifer, which is a source of water for local residents. Soil and wastes are contaminated with VOCs, SVOCs, pesticides, PCBs, and heavy metals (Ref. 42, p. 2).

The EPA signed three Records of Decision (ROD) for the facility. The RO Ds mandated the removal of approximately 1,200 drums; installation of a ground water collection and treatment system, which operated for 13 years and treated approximately 145 million gallons of water; excavation of contaminated soil; on

site remediation of soil; expansion of the recovery and treatment system for shallow ground water; continued operation of the ground water recovery and treatment system; and addition of safe substances to the soil and ground water in an effort to break down hazardous substa nces via soil microbes. Effective in June 2005, EPA and 40 potentially responsible parties (PRP) entered a new consent decree to implement the final cleanup plan for the property. Since June 2005, the PRPs have installed an additional shallow ground water collection trench that began operating in 2008. In addition, in 2008 EPA approved the PRPs’ design plans for soil remediation, scheduled to be carried out in spring 2009 (Ref. 42, pp. 2, 3).GW

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- 39 W.L. Gore Trinco Industrial Park Route 279 and 545 Elkton, Maryland

The W.L. Gore property is located within the Trinco Industrial Park in Elkton, Maryland, and consists of approximately 7 acres of land occupied by a warehouse, a paved parking area, lawn areas, and a wooded area. The wooded area on the north ban k of Little Elk Creek, also referred to as the “left bank,” is the location of the former industrial dumpsite that encompasses approximately 2 acres of land within the W.L. Gore property boundaries (Ref. 17, p. 26 ; Ref. 86, p. 1 ). The W.L. Gore property i s located 0.25 to 0.5 mile west of the Dwyer Property ground water plume (Ref. 7).

Since the 1940s, the Trinco Industrial Park has been used for industrial purposes. The property was used, owned, and operated by Triumph Explosives for manufacture of milit ary ordnance through 1947. Following the end of World War II, the old munitions plant was demolished, and the demolition debris from the plant was used as fill in the area along the Little Elk Creek. The property was purchased by the Elkton Company, late r known as the Trinco Industrial Park, in 1947 and used for light industry and warehousing. Historical records indicate that waste from Galaxy Chemical was disposed of at the property in 1968 and 1969, and other waste and construction debris were disposed of in the area of Little Elk Creek. The General Tire and Rubber Company acquired the property in 1972, and W.L. Gore purchased the property in 1983 (Ref. 17, p. 27 ; Ref. 86, p. 1 ).

W.L. Gore conducted a preliminary assessment (PA) of the dump site in 1988. Dark

- stained soils and tar materials were identified as trenches were dug near the waste disposal area, and laboratory analysis of the stained soils indicated elevated levels of VOCs (the VOCs are not listed in reference documentation). Additional inves tigations were conducted at the dumpsite in 1989 and 1990 by MDE. MDE concluded that the dumpsite was a source of ground water contamination in the area (Ref. 17, p. 27 ; Ref. 86, p. 1 ).

Workers uncovered seven 55

- gallon drums during the removal of scrap tires from the property in October 1991. As a result, MDE conducted a limited RA of the drums located on the surface. MDE identified solid and liquid substances emitting solvent odors in the soils beneath the drums. Laboratory analysis of the soil samp les collected from this area indicated high concentrations of volatile hydrocarbons (specific concentrations not listed in reference documentation). In 1997, a RA of the source material was completed at the property. MDE conducted a Brownfields investigation at the property in November 2003. Surface soil, subsurface soil, and ground water samples were collected as part of the Brownfields investigation. VOCs were detected in both soil and ground water, including 1,1,2,2

- tetrachloroethane, PCE, TCE, and 1 ,2

- DCE (concentrations not provided in reference documentation). Chromium, manganese, and nickel were also detected in ground water. Perchlorate was detected at low levels in the ground water. MDE recommended that the property be investigated further and that any potential buyer enter the State Voluntary Cleanup Program (VCP) prior to acquiring the property (Ref. 17, p. 27 ; Ref. 98, pp. 1, 2).GW

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- 40 Vicon Property Route 213 and Dogwood Road Elkton, Cecil County, Maryland

The inactive Vicon property consists of approximately 60 acres of land currently zoned for commercial and industrial purposes (Ref. 17, p. 25 ). The Vicon property is located 0.25 to 0.5 mile east of the ground water plume (Ref. 18).

Victory Sparkler & Specialty Company purchased the Vico n property in 1919. Victory Sparkler & Specialty Company manufactured fireworks and small ordnance products under a U.S. government contract until 1946. In 1953, the property was purchased by Michael Pastuszek under the corporate title of the Sheppard Company. The Sheppard Company manufactured explosives under a U.S. A rmy contract between 1953 and 1980; however, the manufacture of military high explosives, incendiary devices, and military blasting caps ceased in 1955. In the early 1960s, the manufacture of fireworks ended. The estate of Michael Pastuszek acquired the property in 1980 and sold the property to the Vicon Corporation in 1981. The property has been inactive since 1980. On

- site structures were reportedly demolished in 1983. Elkton Village Limited Partnership assumed ownership of the property for a brief period and then sold the property to Michael Davitt and Baldvin & Associates, Inc., in 1987. In 1993, Windsor Pointe acquired the property (Ref. 17, p. 25 ).

An explosives investigation cond ucted at the property in 1978 concluded that no explosive hazard was associated with property soils. MDE conducted a PA of the property in 1990. MDE completed a Focused Site Inspection (FSI) in September 1994, which identified contamination in surface wa ter, sediments, and soil in the settling ponds and in the adjacent Dogwood Run surface water body. Windsor Pointe, Inc.

, submitted a VCP application seeking a No Further Requirements Determination as an inculpable person in March 2002. MDE requested addi tional sampling to further characterize the property. The additional investigation involved installation of eight new ground water monitoring wells, excavation of 53 test pits, collection of surface and/or subsurface soil samples from each pit, and colle ction of ground water samples from 21 new and pre

- existing monitoring wells (Ref. 17, p. 25 ). The soil and ground water samples collected were analyzed for VOCs, SVOCs, priority pollutant metals, explosives, PCBs, total petroleum hydrocarbons gasoline range organics (TPH

- GRO), TPH diesel

- range organics (TPH

- DRO), and perchlorate. Several organic and metal contaminants exceeded the MDE’s ground water cleanup standards, including TCE, PCE, naphthalene, antimony, chromium, nickel, and lead. Arsenic, mercury

, and lead were detected in surface soil samples at concentrations above the MDE’s non

- residential cleanup standards. No contaminants were detected in sediment or surface water samples at levels above MDE cleanup standards (Ref. 17, p. 26 ).

In June 2003, Windsor Pointe, Inc.’s VCP application was approved by MDE. MDE informed Windsor Pointe, Inc., that a response action plan (RAP) needed to be developed and implemented in an effort to address the environmental conditions at the property prior to issuance of a Certificate of Completion by MDE. In March 2004, a proposed RA was submitted to MDE. The plan included capping of localized areas of surface soil, long

- term ground water monitoring, a ground water use prohibition on the property, and additional institutional controls. In November 2004, additional site

- wide ground water sampling was completed in an effort to support finalization of the RAP for the property. A revised RAP was to be issued to the MDE by March 2006 (Ref. 17, p. 26 ; Ref. 41, p. 2 ).

T he presence of DNAPL on the Dwyer Property ground water plume indicates that Vicon may not be the source of the larger TCE plume (Ref. 71, pp.94, 95, 96 ; Ref. 91 ).GW

- Likelihood of Release

GW

- 41 Summary

Several potential source and facilities, both historically and present, are in the vicinity of the TCE plume at the Dwyer Property. While some facilities are eligible as possible sources of contamination to the TCE plume

, further investigation will be necessary to determine the actual sources of TCE contamination at the Dwyer Property Ground Water site (Ref. 18; Refs. 62

- 67 ).

Hazardous Substances Released

Trichloroethylene (TCE)

Ground Water Observed Release Factor Value: 550

### Waste Characteristics

GW

- 42 3.2 WASTE CHARACTERISTICS

3.2.1 TOXICITY/MOBILITY

The toxicity and mobility values for TCE are presente d in Table GW1 0.

TABLE GW1 0 TOXICITY AND MOBILITY

Hazardous Substance Source No. (and/or Observed Release) Toxicity Factor Value Mobility Factor Value Does Haz ardous Substance Meet Observed Release by chemical analysis? (Y/N) Toxicity/ Mobility (Ref. 1, Table 3

- 9) References

Trichloroethylene Observed release 10,000 1 Yes 10,000 2, p. 16

Toxicity/Mobility Factor Value: 10 ,0 00

### Waste Characteristics

GW

- 43 3.2.2 HAZARDOUS WASTE QUANTITY

Source No. Source Type Source Hazardous Waste Quantity

1 Other 260,293

Sum of Values: 260,293 Pathway Hazardous Waste Quantity Factor Value: 10,000 (Ref. 1, Table 2

- 6)

3.2.3 WASTE CHARACTERISTICS FACTOR CATEGORY VALUE

The waste characteristics factor category value is obtained from Reference 1, Table 2

- 7, using the product of the toxicity, mobility, and hazardous waste quantity values.

Toxicity/Mobility Factor Value: 10,000

Hazardous Waste Quantity Factor Value: 10,000

Toxicity/Mobility Factor Value × Hazardous Waste Quantity Factor Value: 1 x 10 8 (subject to a max of 1 x 10 8 )

Waste Characteristics Factor Category Value: 1 00 Ref. 1, Table 2 -7

### GW Targets

GW

- 44 3.3 TARGETS

The ground water targets evaluated for the ground water migration pathway are summarized below.

3.3.1 NEAREST WELL

The nearest known drinking water wells are located on Dogwood Road (Ref. 15, pp. 21, 47, 48, 54, 56, 5 9, 60, 61 ; Ref. 7; Ref. 39). The wells are within the 0.5 to 1

- mile distance category from the ground water plume, measured from the center of the plume, and are assigned a value of 9 for the nearest well factor value (Ref. 1, Section 3.3.1, Table 3

- 11; Ref. 7; Ref. 39).

Nearest Well Factor Value: 9 (Ref. 1, Table 3

- 11)

3.3.2 POPULATION

3.3.2.1 Level of Contamination

No Level I or II concentrations have been documente d in drinking water wells. Potential contamination to drinking water supply wells has been evaluated. The aquifers underlying the ground water plume are considered one aquifer, as documented in Section 3.0.1 of this documentation record. All drinking wa ter wells are within the same aquifer, as documented in Section 3.0.1.

3.3.2.2 Level I Concentrations

No Level I concentrations have been identified.

Sum of Population Served by Level I Wells: 0

Level I Concentrations Factor Value: 0 (Ref. 1, Secti on 3.3.2.2)

3.3.2.3 Level II Concentrations

No Level II concentrations have been identified.

Sum of Population Served by Level II Wells: 0

Level II Concentrations Factor Value: 0 (Ref. 1, Section 3.3.2.3)

3.3.2.4 Potential Contamination

The target s identified within the ground water migration pathway include populations served by the Town of Elkton water supply system, several community water supply systems, and residential wells. The Town of Elkton serves the population within the town limits of Elkton and some outlying areas. Cecil County GIS was used to identify the areas served by the Town of Elkton. The known areas that are provided public water by the Town of Elkton are shown on the 4

- Mile Radius Map, Reference 7, and correspond to fire hydrant locations. The presence of fire hydrants indicates that public water distribution lines are available in that area , along the road (Ref. 22). Areas served by public water are shaded in Reference 7.

### GW Targets

GW

- 45 Community systems were identified by the EPA Safe D rinking Water Information System (Ref. 6). The populations and current use were confirmed by the MDE Public Water Supply Division (Ref. 21). The locations of the community system wells are shown on Reference 7. The populations served by the community sy stem wells are summarized in Table GW1 1

. Areas served by the Town of Elkton and community systems are highlighted on Reference 7. All areas not served by the Town of Elkton or community systems are served by domestic wells (Ref. 22). A summary of the number of domestic wells within 4 miles of the ground water plume is in Table GW1 1 . The approximate number of domestic wells within each target distance category was determined by counting homes not served by public or community water on Reference 7. The population served by each home is the average number of persons per household for Cecil County (2.73 persons) (Ref. 12).

As shown in Reference 7, no drinking water wells are located within the 0 to 0.5

- mile radius of the center of the ground water plume. The 0.5 to 1

- mile radius includes residential wells (homes) along Dogwood Road and roads extending north and south from the center of Dogwood Road, and residential wells along State Route 545, north of the most northern located fire hydrant (Ref. 7).

The Town of Elkton has a complex water supply system that includes (1) a surface water intake supplying 237,600,000 gallons of water per year to the system; (2) Well 1 supplying 64,632,000 gallons per year; and (3) Well 3 supplying 286,344,000 gallons per year. In addition, Elkton purchases 1,500,000 gallons per month (18,000,000 gallons per year) from Artesian Water, a public water supply company. Artesian Water obtains water from wells located in Delaware (Ref. 9; Ref. 10). Wells 1 and 3 are permitted to withdraw 650,000 gallons per day or 237,250,000 gallons per year (Ref. 81, p. 7). The population served by the Town of Elkton is 15,000 persons. The Town of Elkton wells are completed in the Potomac Aquifer (Ref. 9; Ref. 19, p. 1; Ref. 11). Well logs for the Town of Elkton Wells 1 and 3 are provided in Reference 11. PCE has been detected in ground water samples collected from Well 1 (Ref. 19, p. 3).

To assign a population to each of the Town of Elkton’s water source s (wells and other sources), the annu al amount of water supplied by each source in gallons per year is divided by the total amount of water supplied to the system (sum of all the water supplied by each source). The result of this equation gives the percent of water supplied by each source. To determine the number of p erson s served by each source, the percent of water supplied by each source is multiplied by the total population served by the Town of Elkton (Ref. 1, Section 3.3.2). Reference 10 provides a summary of this calculation. The population served by the Town of Elkton is summarized in Table GW1 1

.

### GW Targets

GW

- 46 TABLE GW1 1 DRINKING WATER WELLS WITHIN 4 MILES

Radial Distance from Site

(miles) Residential Well Population (Number of Residential Wells) Population Served by Public Water (Supplier) Total Population Served by

Ground Water Sources Dilution

Weighted Value (Ref. 2, Table 3

- 12) References

0.00 to 0.25 0 0 0 0 0.25 to 0.50 0 0 0 0 0.50 to 1.0 163 (60) 0 163 52 7

1.0 to 2.0 1,056 (387) 1,598 (Elkton Well 1) 60 (Marantha School) 350 (Elkton Christian School) 18 8 (Forest View Trailer Park also known as Sherwood Forest) 3,252 939 6, pp. 2, 3, 4; 7; 10; 21; 24

2.0 to 3.0 1,092 (400) 7,081 (Elkton Well 3) 212 (Forest Green Court Park) 310 (Mt. Aviat

Academy) 8,695 678 6, pp. 2, 4; 7; 10; 20; 21

3.0 to 4.0 2,525 ( 925) 440 (Leeds School) 964 (Kenmore School) 450 (Town and Country Trailer Park) 325 (Whispering Pines Mobile Home Park) 4,704 417 6, pp. 2, 3, 4; 7; 10; 21; 23 ; 110

TOTAL 2,086

Note:

Residential well population is equal to the number of wells multip lied by the average number of persons per household (2.73) for Cecil County (Ref. 12). The potential population value is the sum of the distance

weighed population divided by 10 or 208.6

.

Calculations:

Sum of Distance

- Weighed Population Values: 2,086 S um of Distance

- Weighted Population Values/10: 208.6 Potential Contamination factor Value: 209 ( 208.6 is rounded to 209, per HRS Section 3.3.2.4)GW

- Targets GW

- 47 3.3.3 RESOURCES

Farms located outside the public water distribution systems use ground water to irrigate cr ops on areas greater than 5 acres (Ref. 7; Ref. 28). An aerial photograph of the location of the ground water plume shows numerous crops within 4 miles of the center of the plume (Ref. 28). Reference 7 shows that the location of the crops is not serviced by public water. Therefore, wells used for irrigating crops are located within 4 miles of the center of the ground water plume. According to data published by the Maryland Department of Agriculture's Statistics Service for the year 2000, Cecil County en compasses 222,824 acres. About 37.7% (84,000 acres) is farmland. Much of the agricultural land is devoted to cash grain and dairy farms. Principal crops are corn, soybeans and wheat. Secondary crops include hay, barley, tree fruits (apples, peaches, pears), vegetables, and berries (Ref. 44).

Resources Factor Value: 5 (Ref. 1, Section 3.3.3)

3.3.4 WELLHEAD PROTECTION AREAS

The ground water plume does not lie within a wellhead protection area; however, a wellhead protection area is within the target di stance limit. The wellhead protection areas are shown in Reference 7. The Maryland wellhead protection program was approved by EPA in 1991 (Ref. 25 ; Ref. 43 ). A wellhead protection area factor value of 5 is therefore assigned (Ref. 1, Section 3.3.4, p. 51604).

Wellhead Protection Area Factor Value: 5 (Ref. 1, Section 3.3.4)