COVER SHEET
Name of Site: Milford Contaminated Aquifer EPA ID No.: OHSFN0507973



### United States Environmental Protection Agency (EPA), Region V: Contact Person



### Patrick Hamblin 77 West Jackson Boulevard, Mail Code: SR-6J Chicago, Illinois 60604 312-886-6312 Site Investigation: Jon R. Watterworth Ohio Environmental Protection Agency Division of Emergency and Remedial Response 401 East Fifth Street Dayton, Ohio 45402-2911 (937) 285-6062 (direct)

The surface water, soil exposure and air migration pathways are not scored as part of this Hazard Ranking System (HRS) evaluation. The surface water migration , soil exposure, and air migration pathways were not included because a release or potential rel ease to these media doe s not significantly affect the overall site score and because the ground water migration pathway produces an overall site score above the minimum required for the site to qualify for inclusion on the National Priorities List (NPL). Pathways, Components or Threat Not Scored1 HRS DOCUMENTATION RECORD
Name of Site: Milford Contaminated Aquifer Date Prepared: October 2010
E PA Region: V
Street Address*: 101 Race Street City, County, State, Zip Code: Milford, Clermont, Ohio, 45150 (Figure 1) (Ref. 3, p. 1)
General Location in State: Southwe stern corner of Ohio in the City of Milford along the eastern bank of the Little Miami River (Ref. 3, p. 1) Topographic Map: U.S. Geological Survey 7.5

- Minute Series Topographic Map of Madeira, Ohio, Quadrangle , 1996 (Ref. 3, p. 1)
Latitude: 39 ○ 10’ 40.13” North (Ref. 3, p. 1; Ref. 4, p. 1) Longitude: 84 ○ 17’ 37.63” West (Ref. 3, p. 1; Ref. 4, p. 1) The latitude and longitude listed above mark the approximate location of the Milford Contaminated Aquifer s ite, specifically the City of Milford we ll field (Ref. 4, pp. 1, 2).
* The street address, coordinates, and contaminant locations presented in this HRS documentation record identify the general area the site is located. They represent one or more locations EPA considers to be part of the site b ased 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 boundarie s. A site is defined as where a hazardous substance has been “deposited, stored, placed, or otherwise come to be located.” Generally, HRS scoring and the subsequent listing of a release merely represent the initial determination that a certain area may

n eed to be addressed under the Comprehensive Environmental Response , Compensation, and Liability Act (CERCLA). Accordingly, EPA contemplates that the preliminary 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.

Scores Ground Water Migration Pathway - 100.00 Surface Water Migration Pathway - Not S cored Soil Exposure Pathway - Not S cored Air Pathway - Not S cored HRS SITE SCORE 50.002 WORKSHEET FOR COMPUTING HRS SITE SCORE
S S 2 1. Ground Water Migration Pathway Score (S gw ) (from Table 3-1, line 13) 100 10,000 2a. Surface Water Overland/Flood Migration Component (from Table 4-1, line 30) NS

--- 2b Ground Water to Surface Water Migration Component (from Table 4- 25, line 28) NS

--- 2c. Surface Water Migration Pathway Score (S sw ) (enter the larger of lines 2a and 2b as the pathway score) NS

--- 3. Soil Exposure Pathway Score (S s ) (from Table 5-1, line 22) NS

--- 4. Air Migration Pathway Score (S a ) (from Table 6-1, line 12) NS

--- 5. Total of S gw 2 + S sw 2 + S s 2 + S a 2 10,000
6. HRS Site Score

NS – Not Scored 50.00 Divide the value on line 5 by 4 and take the square root.
Note:3 HRS TABLE 3 -1 – GROUND WATER MIGRATION PATHWAY SCORESHEET MILFORD CONTAMINATED AQUIFER

Maximum Factor Categories and Factors Value Value Assigned

Likelihood of Release to an Aquifer: 1. Observed Release 550 550 2. Potential to Rele ase: 2a. Containment 10 NS 2b

. Net Precipitation 10 NS 2c. Depth to Aquifer 5 NS 2d. Travel Time 35 NS 2e. Potential to Release (lines 2a x (2b+ 2c+2d)) 500 NS 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) 100 6. Waste Characteristics 100 32 Targets : 7. Nearest Well 50 5 0 8. Population: 8a

. Level I Concentrations (b) 8 , 870 8b

. Level II Concentrations (b) 

### 4 , 404 8c

. Potential Contamination (b) NS 8d

. Population (lines 8a+8b+8c) (b) 13,274 9. Resources 5 0 10. Wellhead Protection Area 20 0 11. Targets (lines 7+8d+9+10) (b) 

### 1 3,324 Ground Water Migration Score for a n Aquifer 12. Aquifer Score [(lines 3X6X11)/82,500] 100 c 100 Ground Water Migration Pathway Score: 13. Pathway Score (S gw ) (highest value from line 12 for all aquifers e valuated) 100
c 100

Notes: a. Maximum value applies to waste characteristics category b. Maximum value not applicable c. Do not round to nearest integer NS - Not Scored> 

## "

Not e s ' Co ncen t rations In ugl l Ch l or i nated sowents w e re n o t detected in l oca t i ons without r e5 u l t s

LEGEND

TCE TRICHLOROETHENE PCE

- TETRACHLOROETHENE TCA

- TRICHLOROETHANE t. P h ase 1**oca~on5**

... Phase II l oca t i o n , 

### o 25 50 150 200



## ---



# -- - - Met ers
SOURCE: REFERENCE B, PAGE 1 B. Figure

DCE

- DICHLOROETHENE EPA. REGION V EP-S5-06-1l4 

# WWj;IJ 

# """""'by.
WESTON SOLUTIONS, INC. 750 E. Bunker Ct. SoD Boring Locations Milford Contaminated Aquifer

5 2m n

0'
u o 

### '" :;;:

o /' o o o /' n m o « u /.
-0 LEGEND TCE

- TRICHLO TCA

- TRICHLO ND

- NOT NA

- NOT ANA MTBE

- METHY BUTYL UNITS; ug/L

SOURCE: REFERENCE 7. PAGE

NOT TO SCALE OETHENE OETHANE DET CTED ZED TERTIARY ETHER GP56

# O**~TCA=3~**
GP54 TCA = 4J ® 

# aPO GP44 ® NA

GP53 TCA:? ®
® GP42 TCA=8

GP43 PCE 

### = 14 GP49

GP50 TCA '" 3J

GP51 TCA = 3J ® ® NO

10; REFERENCE 9B. PAGE 10.

6

# ~~ Prepared by: WESTON SOLUTIONS, INC. 750 E. Bunker Ct. Vernon Hills IL 60061 Figure Additional Soil Boring Locations

Milford Contaminated Aquifer Milford, Clermont Coun ,Ohio 3Co n cen t rat i ons i n u gll 

# .. ,**.~** 

# .**:~**

, 

## .,

, 

# ,,"

..**~ O** **-= 50**  ..**1~ OO** **=== 'g**  .... oj 200 • M eters 

# .' •

• M o nit ori n g w e ll

SOURCE: REFERENCE 8, PAGE 19. Figure 

### LEGEND

. ... '

... ....:. Prepared for: Moaitor:la.g Well Locations

TeE TRICHLOROETHENE 

# l .iz) u.S. EPA. REGION V peE

- TETRACHLOROETHENE 

# WWj;IJ 

# """"'by:**t>._~** ContractNo: EP-S5-06-04 Milfonl Contaminated Aquifer TCA

- TRICHLOROETHANE WESTON SOLUTIONS, INC. DeE

- DICHLOROETHENE IDD: S05-1>008-OOO8-021 7S0 E. Bunkec Ct. Milfonl, Clennont Co ,Ohio VemonHills IL 60061 DCN: 762-2A-AIDL 7 4

# .... •

04 

# • 

# •
50'



# o ,**gend** Environmental

_ .. ,... . ..... voc Protection Agency G"' u nd_

.. C

...... ..... ""

. . .... .. W

... 

### ..... '"".'I""',

.. ""y 

# ,.**""'M_"~** 

### •• ,"",,,**~** 

### -"

. , "';



## .... .. Tw l>'l..,.V'.

_ . .. ,
___ .......... ",00' , 1

... -.. ... _ M a y 17 , 2010



### .... _ , ... . "" '"_ ' Io>n

.. I

_ ....... . ... . JRW C""'

..... , .,.. ..... .- .. uoIng .""

... ""

... ........
__ .. l gIooj

.

Figure SOURCE: REFERENCE 10, PAGE 24. PubHe Supply Well Location. EPA. REGION V EP-S5-06-1l4 Milford Contaminated Aquifer**7~O** E. BIlIIkcr Ct. Ohio WESTON SOLUTIONS, INC.

B> 

## " N 

# " rn 0 Sou"", lI.p: USCS 1.5 IUnute Quadranr'. 

# -

.. 

# ­ . - ­ .. ­ 

## .... 

# ­ v

### ~w**~~** Fiel d



# h**~** 

# . . ,

0



# , 0



# , , • N

rn 

# , " a 

## " 0 -:: 0 

### 8 -:: 

## " e l, ",o,IL.c\lol1 0 , 1 

## "" -1 0 "

- 1 6 0

_ _ (n'IIj W , I 1OCd'"
SI

- ll $ Sol 8or'""i LocGIOn 

### (;q,,* 1.0:0 1 1001**~p'tled** "'" of tQUOI <00<", 1'01100 

# £ SOURCE: REFERENCE B, PAGE 47. Figure 

# •**h~I"'9** moAA"'''''l

. .. 

### t.J CIOSS·\EC TnI l ot<!01

,:.""''''1:. Prepared for: Ground Water Plume Map
- TetraehJ.oroethene 

## i .iz l u.s. EPA. REGION V T

# q.~ 

# .,..,""""'"**_~** Contract No: EP-S5-06-04 

# I

--
, l, Milford Contaminated Aquifer WESTON SOLUTIONS, INC. rnD: SOS-0008-0908-021 150 E. BunkcI' Ct Milfi Clermont Ohio DCN: 762-2A-AHJL VemonHilla IT. 60061
rn 

## " 0 9 u 

### -:: " 610 REFERENCES
1. U.S. Environmental Protection Agency (EPA). Hazard Ranking System , Final Rule , Title 40 Code of Federal Regulations (CFR), Part 300, 55 Federal Register (FR) 51532. December 14, 1990. 138 p ages. A complete copy of the H azard R anking S ystem can be obtained at the Regional docket upon request.
2. EPA. Superfund Chemical Data Matrix (SCDM), SCDM Data Versions: January 28, 2004 and October 23, 2006. Excerpt. 8 pages. 

### A complete copy of SCDM is available at http://www.epa.gov/superfund/sites/npl/hrsres/tools/scdm.htm

. 3. U.S. Geological Survey (USGS). 7.5

- Minute Series Topographic Map: Madeira, Ohio. Scale 1:24,000. 1996. 1 page. 4. Weston Solutions Inc. (WESTON). Latitude and Longitude Calculations for Milford Contaminated Aquifer Site by Brian Coninx, October 19 , 2009, 2 pages.
5. Ohio Environmental Protection Agency (OEPA). Integrated Assessment, Milford Contaminated Aquifer. November 14, 2000. 40 pages.
6. OEPA. Combined P reliminary A ssessment /S ite I nvestigation Report, Milford Contaminated Aquifer. September 15, 2001. 144 pages.
7. Tetra Tech EM Inc. Final Report Hydrogeologic Investigation

— Milford Wellfield

. June 30, 2003. 95 pages. 8. OEPA. Expanded Site Inspection Report, Milford Contaminated Aquifer, September 19, 2002. 240 pages. 8A. OEPA. Report On Investigation s , Milford Well Field, Clermont County, Ohio, April 26, 1999. 170 pages. 9. OEPA. Laboratory Data and Field Log Sheets, 2001 PA/SI, Milford Wellfield. July 26, 2010. 167 pages. 9A. OEPA

. Exp anded Site Inspection Report, Milford Contaminated Aquifer. September 19, 2002. 61 pages.
9B. Reference reserved.
10. OEPA . Supplemental Expanded Site Inspection Report. Marc h 30, 2010. 450 pages. 10A. OEPA. Soil Gas Survey Information. March 27, 2007. 13 pages. 10B. Ohio Department of Natural Resources and Center for Ground Water Management , Wright State University

. Ground Water Pollution Potential of Clermont County, Ohio, Report Number 18. October 1994. 44 p ages
. 11. OEPA. Geographic Initiative Report, Milford Wellfield. June 16, 2000. 125 pages.
11A. Tetra Tech EM, Inc. Hydrogeologic Investigation, Milford Wellfield Site, Milford, Ohio

. June 29, 2006. 263 pages.
11B. OEPA

. Milford Well Field, Sub -Slab Sample Investigation Information. September 28, 2006. 374 pages

. 12. Groundwater Management, Incorporated. City of Milford, Ohio, Hydrogeologic Investigation, November 4, 1987. 114 pages.11 12A. WESTON, Ground Water Contour Maps based on July 10 and July 25 , 2002 Ground Water Elevation Measurements Performed by M.S. Belfi n and Associates, August 2002. 4 pages. 12B. OEPA, Soil Gas Sampling Information. March 27, 2007. 179 pages.
13. OEPA . Milford Contaminated Aquifer – Public Well Inf ormation

. February 8, 2010. 9 pages. 13A. Vadose Research Inc. Preliminary Report : Volume I , Soil Gas Contaminant Determination and Associated Monitoring Well Sampling , Milford Well Field Area. October 6, 1993 . Excerpt. 62 pages. 13B. OEPA. Report on Inv estigations, Milford Well Field . April 26, 1999. 24 pages. 13C. University of Idaho

. Principles of Environmental Toxicology, Perchloroethylene (PCE) in Dry Cleaning Establishments. December 2000. 17 pages.
14. WESTON. Telephone Conversation Record. Between Lauren Cook, WESTON, and Matthew Newman, City of Milford Water Department. November 30, 2009. 3 pages.
14A. U.S. EPA, Superfund Analytical Services/Contract Laboratory Program (CLP)

. SOM01.2 Volatile Target Compound List and Corresponding CRQLS. Accessed June 29, 2010. 2 pages. Accessed Online at http://www.epa.gov/oerrpage/superfund/programs/clp/som- vtarget.htm. 14B. WESTON. Telephone Conversation Record. Between Omprakash Patel , WESTON, and Matthew Newman, City of Milford Water De partment. July 2 , 2010. 1 page. 15. WESTON. Telephone Conversation Record. Between Lauren Cook, WESTON, and Mark Day, Clermont County Water Works Division. December 7, 2009. 2 pages.
16. WESTON. Telephone Conversation Record. Between Lauren Cook, WESTON, and Customer Service of Greater Cincinnati Water Works, Cincinnati, Ohio. December 30, 2009. 2 pages.
17. U.S. Census Bureau. 2006 through 2008 American Community Survey 3

- Year Estimate s for Clermont County, Ohio, Data Profile Highlights. Accessed February 12, 2010. 2 pages

. 

### http://factfinder.census.gov/servlet/ACSSAFFFacts?_event=Search&geo_id=&_geoContext=&_s treet=&_county=clermont+county&_cityTown=clermont+county&_state=04000US39&_zip=&_l ang=en&_sse=on&pctxt=fph&pgsl=010
18. OEPA. So uthwest District Office, Milford Well Field. Updated March 2008. Accessed on October 26, 2009. 1 page. Accessed On

- line at 

### http://www.epa.state.oh.us/swdo/To_be_Deleted/derr_sites/milford_well_field.aspx.
19. OEPA. Drinking Water State Revolving Fund Wel lhead Protection Set

- Aside Annual Report, Program Year 2008, August 2008. 10 pages.
20. WESTON. Map Depicting 4

- Mile Radius Target Distance Limit. Source of Map: USGS 7.5-Minute Series Topographic Quadrangles, Ohio : Made i ra, 1996; Withamsville, 1996; Goshe n, 1965, Photorevised 1986. October 16, 2009. 1 page.12 1.0 SITE DESCRIPTION The City of Milford is located in western Clermont County, Ohio, approximately 15 miles northeast of Cincinnati, Ohio (Refs

. 5, p. 3; 6, p. 7). The city obtains its drinking wat er from a well field consisting of four wells drilled in alluvium in the Little Miami River valley (Ref s. 10, p. 6;18, p. 1 ). The well field contains three wells contaminated with volatile organic compounds (VOCs ) (Ref s. 7, p. 6; 10, p. 15, 16 ).

The Milfo rd Contaminated Aquifer s ite is a ground water plume of chlorinated solvents in the vicinity of Main Street and Lila Avenue in the City of Milford, Clermont County, Ohio (Figure 6 ) (Ref. 8, p. 12). Chlorinated solvents detected in ground water at the site include tetrachloroethene (PCE); trichloroethene (TCE); cis -1,2- dichloroethene (DCE); and 1,1,1

- trichloroethane (TCA) (Ref. 8, pp. 9, 10). The area of the ground water plume was defined based on ground water samples collected from public wells, monitorin g wells , and direct

push sampling devices from the unconfined aquifer (Ref. 8, pp. 9, 10, 11, 13, 44, 47 ). The precise extent of the ground water plume and source(s) of ground water contamination have not yet been identified.
The Ohio Environmental Protection Agency (OEPA) has been the primary agency involved in the investigation of this ground water plume. Halogenated solvents were first detected in City of Milford public wells (PW)

- 1 and PW

- 3 in 1986 (Ref. 8, p. 6). Since then, 1,1,1

- TCA and TCE have b een detected in PW

- 3 at levels exceeding the maximum contaminant levels (MCL) established under the Safe Drinking Water Act (Ref. 8, p. 6). TCE concentrations in PW

- 1 also have exceeded the MCL (Ref. 8, p. 6). In 1987, 1990, and 1991, 1,1,1- TCA and TCE w ere detected in PW -2 but at concentrations less than the MCLs (Ref. 8, p. 6).
OEPA began searching for a source of the VOC contamination in 1991 (Ref s . 8, p. 6). OEPA’s contractor, Vadose Research, conducted a soil gas survey of the well field area in 1 992 (Ref. 8, p. 6). VOCs including 1,1,1- TCA, 1,1

- dichloroethane (1,1

- DCA), 1,2

- DCE, and 1,1,2

- TCA were detected at nine locations (Ref. 8A, p. 15). The soil gas survey revealed three potential contaminant source areas, but the results were judged to be unreliable because of poor quality assurance (QA)/quality control (QC) results (Ref s . 8, p. 6; 8A, p. 23 ). OEPA collected soil samples in 1994 from the potential source areas revealed by the soil gas survey, but no VOCs were detected (Ref s. 8, p. 6; 8A, p. 18)

. OEPA collected 21 ground water samples in the vicinity of the well field using a direct

- push sampling device on April 23 through 25 and June 18 and 19, 1996 (Ref s . 8, p. 6; 8A, pp. 14, 30). The ground water samples were collected from approximately 25 to 50 feet below ground surface (bgs) using plastic tubing with a ball check valve (Ref s. 8, p. 6 ; 8A , p.14 ). Ground water samples could not be collected at many locations because of the inability of the direct

- push equipment to penetrate the subsurfa ce (Ref. 8A, p.14) . Although VOCs were detected in samples collected from several areas, a source area was not identified (Ref s . 8, p. 7; 8A, p. 23 ).13 In April and May, 2000, OEPA conducted a geographic initiative of the Milford well field and OEPA’s
contr actor, PSARA Technology Inc., installed nine wells at five locations in the well field in a semicircle starting east and continuing around the south side of the well field (Ref. 11, pp. 7, 13, 22) . The new wells were installed in pairs, with one well scre ened at the water table and the other at the bottom of the aquifer (Ref. 8, p. 7). OEPA collected ground water samples from both the new and existing wells, and results confirmed that the aquifer and the well field were contaminated with VOCs (Ref. 8, p. 7). The samples were analyzed for VOCs using SW 846 Method 8260B (Ref. 11, p.13). In general, VOC concentrations were higher in the deep wells than in the shallow wells (Ref s . 8, p. 7; 11, pp. 14, 16 ). The pattern of detections suggested a possible sour ce of 1,1,1- TCA (one of the VOCs detected in the wells) east of the well field (Ref s. 8, p. 7 ; 11, p.18 ).
OEPA conducted a combined preliminary assessment (PA)/site inspection (SI) in 2001 consisting of the installation of three wells east of the well fiel d and the collection of ground water samples from both new and existing wells (Ref s. 6, pp. 6 , 7, 14; 8, p. 7). The samples collected in May 2001 were sent to a CLP laboratory for Target Compound List (TCL) VOC analysis (Ref. 6, p.12). The samples collected in August 2001 were analyzed for VOCs by mobile laboratory using Method 8260 (Ref. 6, p. 12). The PA/SI confirmed that the aquifer and well field were contaminated with VOCs originating from sources east of the well field (Refs. 8, p.7; 6, p.21) . Th e pattern of detections suggested that the 1,1,1

- TCA source was north of the PCE and TCE source (Ref. 8, p. 7; 6, p. 21 ).
OEPA prepared an expanded site inspection (ESI) work plan dated December 12, 2001 (Ref. 8, p. 5). ESI field work was conducted in fou r phases on March 18 through 22, May 13 through 17, June 6, and July 9, 2002 (Ref s . 8, p. 5; 9A, p. 7). OEPA advanced 36 soil borings, collected 27 ground water samples from the direct

push boreholes, and installed and sampled 3 monitoring wells (Ref s . 8, p. 5; 9A, pp. 7, 20, 21). The ground water samples were submitted to DataChem Laboratories in Cincinnati, Ohio, for rush analysis using U.S. Environmental Protection Agency (EPA) Method 8260 (Refs. 8, p.5; 9A, p. 7)

. PCE was detected in ground water samples at concentrations up to 730 μg/L ; 1,1,1- TCA was detected at concentrations up to 19 μg/L; TCE was detected at concentrations up to 40 μg/L; and cis -1,2- DCE was detected at concentrations up to 40 μg/L (Ref. 9A, pp. 11, 12 ; Figure 2 of this HRS docume ntation record ). The monitoring well samples were analyzed for target compound list VOCs by an EPA contract laboratory (Ref s . 8, p. 5; 9A, p. 7 ). The ESI confirmed that the aquifer is contaminated with VOCs from sources east of the well field. The patt ern of detections suggests that a release of PCE has occurred in the vicinity of a shopping center located approximately 3,300 feet east of the well field (Ref. 8, p. 13).
Ohio EPA conducted a second direct push investigation in 2003 to determine whether VOC contamination exists in the vicinity of a Kroger Store located in the area of Service Road, Main Street, and Lila Avenue (Ref. 7 , p p . 8, 9). The Ohio EPA contractor, Tetra Tech EM Inc. completed 18 borings east of Baker Drive between Main Street and L ila Avenue (Refs. 7 , pp. 9, 10, 16; 10, p. 9). A photoionization detector (PID) was used to14 evaluate potential presence of VOCs in soil samples (Ref. 7 , p.11). Soil samples were not collected for VOC analysis because no elevated PID readings were observed (Ref. 7 , p. 11). Ground water samples collected were submitted to DataChem Laboratory for VOC analysis by EPA Method 8260b (Ref. 7 , p. 12). Low concentrations of 1,1,1

- TCA and/or PCE were detected in six samples collected from the borings located near Lila Avenue and northward to the approximate center of the study area (Ref. 7, p. 16). Results suggested that a source of PCE was near Baker Drive (Ref. 10, p. 9 ). Ground water samples east of Baker Feeds property were clean while those on Baker Feed pro perty contained VOCs (Ref. 10, p. 9).
In April and May 2006, Tetra Tech EM Inc. completed ten soil borings and installed four monitoring wells in the Baker Feeds /Baker Party Supply area to further define the suspected source area (Ref s . 10, p. 10; 11A, p p. 10, 11). Monitoring wells MW

- 17, MW

- 18, MW

- 19 and MW

- 20 were installed during this mobilization (Ref s . 10, p. 10; 11A, pp. 10, 12 ). Nine ground water samples and one soil sample were collected from borings installed in the study area (Ref. 11A, p. 17) . The samples were analyzed for VOCs by Kemron Environmental Services using Method 8260A and 8260B (Ref. 11A, p. 17). The direct

- push ground water sampling revealed levels of PCE in the vicinity of the Baker Feeds store (Ref. 11A, p. 23, Figure 5-1).

Oh io EPA conducted a State Site Assessment Investigation in 2006 collecting sub

- slab soil gas sampling in buildings surrounding the suspected source property (Ref s . 10, p. 10; 11B, pp. 2 -98, 104-109 ). PCE was detected in the sub

- slab sample at the Baker Party Store at a concentration of 3 5 0 parts per billion volume (ppbv) (Refs. 10, p. 10;11B, p. 102 ).
An exterior soil gas investigation was conducted by Ohio EPA between the suspected source area and the well field in March 2007 (Ref s . 10, p. 10; 12B, pp. 2 , 12 ). The soil gas samples were analyzed for VOCs by DataChem using Method 8260B (Ref. 12B, pp. 2, 11). PCE was detected at low levels in 4 of 13 soil gas samples (Ref. 10A, pp. 2, 3, 5, 9). Additionally, ground water samples were collected from the mo nitoring wells (Ref. 12B, pp. 24-83, 165, 166).
OEPA prepared a supplemental expanded site inspection (SESI) work plan that was approved by U.S. EPA on July 9, 2009 (Ref. 10, p. 6 ). SESI field work included sampling of 15 monitoring wells; public supply wells; and 5 soil samples (including 1 duplicate) for a potential source area identification (Ref. 10, pp. 6, 12 , 1 3 , 14, 15 ; 23 -25 ). The samples were analyzed for target compound list VOCs by an EPA contract laboratory (Ref. 10, p. 6 ). The soil and gro und water samples were submitted to Mitkem Laboratories Inc. in Warwick, Rhode Island for analysis using CLP SOW SOM01.2 (Ref. 10, pp. 2 7 , 2 8 ). The SESI confirmed that the aquifer is contaminated with VOCs (Ref.10, p. 6 ). The soil sampling was not able t o identify the source (Ref. 10 , p. 1 8).

2.2 SOURCE CHARACTERIZATION
2.2.1 Source Identification15 Source Number : 1 Source Type : Other – Ground water plume with no identified source Description and Location of Source (with reference to a map of the site): Source 1 is a contaminated ground water plume containing the chlorinated solvents PCE; TCE; 1,1,1

- TCA; and cis -1,2- DCE with no identified source. In accordance with the HRS, the plume itself is considered the source (Ref. 1, Sec. 1.1, p. 51587). As curr ently delineated, the S ource 1 ground water plume continues east from the City of Milford municipal well field (Figure 6) . Despite all the investigations performed to date, the ground water contamination cannot be attributed to any source with confidence (Ref. 10, p. 6) . The extent of this plume has not yet been completely delineated but it has been characterized based on data from soil borings (Figures 2 and 3), monitoring wells (Figure 4), and public supply wells and S ESI sampling locations (Figure 5) gathered during various investigations.
During the 200 2 ESI, in order to identify the ground water contamination source(s), OEPA advanced 36 soil borings, collected 27 ground water samples from the direct

- push boreholes, installed 3 monitoring wells, and collected 3 ground water samples from 3 monitoring wells (Refs. 8, p. 5; 9A, pp. 20, 21).
A possible source of PCE and its degradation products (TCE and cis -1,2- DCE) is located east of the City of Milford well field in the commercial business area between Lila Avenue and Main Street (Ref. 8, p. 12). Land use in the area primarily consists of mixed residential and commercial uses, with some industrial activity interspersed throughout the area (Ref. 7, p. 5).
During the 2002 ESI, OEPA contractor PSARA Techn ologies collected ground water samples from direct

push borings from March 18 through 22, May 13 through 17, and June 6, 2002 (Refs. 8, p.5 , 9; 9A, p.7)

. Results indicated the presence of chlorinated solvents including PCE (maximum concentration of 730 mi crograms per liter [μg/L]); TCE (maximum concentration of 40 μg/L); cis -1,2- DCE (maximum concentration of 40 μg/L); and 1,1,1

- TCA (maximum concentration of 19 μg/L) (Ref. 8, pp. 9, 10). Ground water samples collected by the OEPA contractor from monitoring well MW

- 14 contained PCE (120 μg/L); TCE (7 μg/L); and cis -1,2- DCE (4 μg/L) (Ref s , 8, p. 11 ; 9A, p. 13 ).
EnviroCore advanced soil borings MGP40 through MGP57 between June 16 and 23, 2003 (Ref s . 7, p. 9 , 10, 16; 10, p. 9 ). Tetra Tech EM Inc. collected g round water samples from each boring location using dedicated polyvinyl chloride (PVC) tubing (Ref s. 7 , p. 11 , 12 ). The ground water samples were analyzed for VOCs by DataChem Laboratories using EPA Method 8260B (Ref s . 7, p. 12). Ten of the ground water samples near Baker Drive contained low levels of TCA and/or PCE (Ref. 7, pp. 10, 15).16 Ground water samples also were collected on May 23, 2001, from PW-1, PW-2, and PW-3 (Ref. 9, p. 41 ). The ground water samples were analyzed for VOCs by American Analytic al and Technical Services Inc. using the CLP Statement of Work (SOW) OLM04.2 (Ref. 9, pp. 61, 62). PW

- 3 was found to contain 1,1,1

- TCA, DCE, and PCE (Ref. 9, pp. 94-98 ).
OEPA conducted a State Site Assessment Investigation in September 2006 collecting sub

- slab soil gas samples in buildings surrounding the suspected source property (Ref s . 10, p. 10; 11B, pp. 2- 21, 94 -109 ). PCE was detected in the sub

- slab sample at the Baker Party Store at a concentration of 350 parts per billion volume (ppbv) (Ref. 10, p. 10 ; 11B, p. 102 ). An exterior soil gas investigation was conducted by Ohio EPA between the suspected source area and the well field in March 2007 (Ref. 10, p. 10; 12B, pp. 1, 2 ). The figure in Ref. 10A on page 3 illustrates the sample locations with respect to the plume axis. PCE was detected at low levels in 4 soil gas samples (Ref. 10 A, p p. 2 , 3, 5, 9 ). The investigations completed to date have not been able to determine the full extent of the ground water plume or sources contributing to the groun d water contamination.

2.2.2 Hazardous Substances Associated with the Source The following ground water data are presented to illustrate the haz a rdous substances associated with Source 1. As part of the SESI conducted by OEPA, g round water samples were co llected from 15 monitoring wells on August 4 and 5, 2009 (Ref. 10, pp. 6, 13). Three of four Milford public wells (PW

- 1, PW

- 2 and PW

- 4) were sampled on August 5, 2009, and again on September 14, 2009 (Ref. 10, p. 6 ). All four public wells (PW

- 1 through PW

- 4) were re

- sampled on February 2, 2010 (Ref. 10, p. 6 ). The ground water samples were analyzed for VOCs by Mitkem Laboratories Inc. and DataChem Laboratories using the CLP SOW SOM01.2 (6/2007) (Ref. 10, pp. 5, 26, 27 ).

The hazardous substances associa ted with Source 1 are PCE; TCE; cis -1,2- DCE; and 1,1,1

- TCA. Figure 6 shows the location of Source 1.
Background Levels

- Background Level at Source 1 – Other

-- Contaminant Plume :

The water elevations recorded in the Baker Drive wells were compared to the water elevations measured in wells installed during the geographic initiative and the combined PA/SI (Ref. 8, p. 12). The water table is approximately 20 feet shallower at Baker Drive than near the well field, which indicates that ground water flows west f rom Baker Drive to the well field (Ref. 8, p. 12). Based on this ground water flow direction, monitoring well locations MW

- 3 and MW -16 are considered upgradient or sidegradient (or background) locations (Refs.10, p. 13, 24; 12A, pp. 1 -4). Municipal well PW

- 4 is also considered to be a background well because concentrations of chlorinated solvents detected in this well are either non

- detect or at estimated17 concentrations below Contract

- Required Qua n titation Limit s (CRQL s ) (Ref. 10, pp. 14, 15). The backg round well sample locations are shown in Figure 5 of this HRS documentation record.
Table 1 below summarizes background monitoring well and public well location information and the concentrations of contaminants of concern for the site detected in ground w ater samples collected from each location. The contaminants of concern for the Milford Contaminated Aquifer s ite (PCE; TCE; cis -1,2- DCE; and 1,1,1

- TCA) were not detected in ground water samples collected from the background locations , demonstrating that t he background locations have not been impacted by the site

- related hazardous substances. (See Table 1 of this HRS documentation record).

Furthermore , ground water samples were collected from direct -push locations GP7, GP11, GP12, GP13, GP21, and GP32. Based on the ground water flow direction described above, these locations are also considered to be upgradient or sidegradient (or background) locations. The ground water samples from direct push locations were collected from a depth of 39 to 64 feet below ground surface (bgs) (Refs. 8, pp. 18, 36, 37, 44). The contaminants of concern for the Milford Contaminated Aquif er s ite (PCE; TCE; cis -1,2- DCE and 1,1,1- TCA) were not detected in ground water samples collected from the direct -push background locations (Ref. 8 , pp. 36, 37, 103, 110, 112, 113, 119, 121, 122, 128, 136, 137, 143, 169, 170, 176). Absence of contaminants of concern in the direct-push ground water samples suggests that the background locations to the depth of approximately 64 feet bgs lie ou tside the area of contamination. Based on the description provided in the PSARA Technology Inc. June 2002 Report the direct

- push samples appear to have been collected from the unconfined aquifer (Ref. 8 , pp. 28, 44, 58, 59, 66, 67 ). Figure 4 of the ESI report show s these direct -push background locations (Ref. 8, p. 18 ).

TABLE 1 BACKGROUND LOCATION INFORMATION

Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

PW

- 4 UC 25

- 51 36

- 51 E2467 2/2/2010 PCE 0. 5 U 0. 5 Refs. 10, pp. 15, 16, 338

- 343, 346,347, 350, 372, 373, 381

- 386;13, p. 8 ; 14A, pp.1, 2 TCE 0. 5 U 0. 5 Cis

- 1,2

- DCE 0. 5 U 0. 5 1,1,1

- TCA 0. 5 U 0.5

MW

- 3 UC 28.45

- 38.45 30

- 40 E2341 8/6/09 PCE 5 .0 U 5 .0 Ref s . 10, pp. 13, 14 , 22, 23, 24 , 27- 33 , 4 3, 44, 47, 48, 51 , 12 5 , 12 6, 127 , 12 8- 1 42, 408 ; 14 A, pp. 1, 2; .12, p. 60 TCE 5 .0 U 5 .0 Cis

- 1,2

- DCE 5 .0 U 5 .0 1,1,1

- TCA 5 .0 U 5 .018 Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

MW

- 1 6 UC 30.4

- 40.4 30

- 40 E2332 8/5/09 PCE 5 .0 U 5 .0 Refs. 10, pp. 13, 14, 22, 23, 24 , 27- 33 , 3 7 , 38, 47, 48, 50 , 8 8 , 89, 90, 12 8-1 42 , 418; 14 A, pp. 1, 2 TCE 5 .0 U 5 .0 Cis

- 1,2

- DCE 5 .0 U 5 .0 1,1,1

- TCA 5 .0 U 5 .0

Notes: μg/L – Microgram per liter bgs – Below ground surface DCE

- Dichloroethene PCE – Tetrachloroethene CRQL – Contract

- Required Quantitation L imit (Ref. 14A, pp. 1, 2) TCA

- Trichloroethane TCE - Trichloroethene U C – Uncon fined aquifer U – Analyte was analyzed for, but was not detected above the reported sample quantitation limit (Ref. 10, pp. 33, 343).

Contaminated Samples

- Contaminated Samples at Source 1 – Contaminated Plume :

The results for contaminated ground water samples collected from monitoring wells and public wells at the Milford Contaminated Aquifer s ite are summarized in Table 2 below. The sample locations are shown in Figure 5 of this HRS documentation record package.

TABLE 2 CONTAMINATED SAMPLE INFORMATION

Location No. Aquifer Well or Sampling

Depth (f

eet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

MW

- 10D UC 50 .41 40

- 50 E2325 8/4/09 PCE 9.6 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 6 , 47, 48 , 49, 68 , 12 8-1 42 , 4 12; 14A, p. 2 MW

- 15 UC 55 45

- 55 E2331 8/5/09 16 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 8 , 47, 48, 50 , 8 6 , 12 8-1 42 , 41 7; 14A, p. 2 MW

- 18 UC 54 .4 44

- 54 E2334 8/5/09 40 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 8 , 47, 48, 50 , 9 5 , 12 8-1 42 , 4 20; 14A, p. 219 Location No. Aquifer Well or Sampling

Depth (f

eet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

MW

- 19 UC 49.91 40

- 50 E2335 8/5/09 31 5 Ref. 10, pp. 13, 14 , 24 - 33 , 40 , 47, 48, 50 , 9 8 , 12 8-1 42 , 421 ; 14A, p. 2 MW

- 14 UC 57.9 47

- 57 E2330 8/4/09 1100 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 8 , 47, 48, 50 , 8 3 , 12 8-1 42 , 41 6; 14A, p. 2 MW

- 17 UC 54.45 45

- 55 E2333 8/5/09 530 5 Ref. 10, pp. 13, 14 , 24 - 33 , 38 , 47, 48, 50 , 9 2 , 12 8-1 42 , 41 9; 14A, p. 2 MW

- 20 UC 54.35 45

- 55 E2336 DL 8/5/09 1100 D 50* Ref. 10, pp. 13, 14 , 24 - 33, 40 , 47, 48, 50 , 10 8 , 12 8-1 42 , 4 22; 14A, p. 2 PW

- 1 UC 59. 83 39 .83

- 59.83 E2464 1 2/2/10 1.2 0.5 Ref. 10, pp. 1 5 , 16, 33 8- 34 3 , 34 5 , 348 -3 50 , 36 0 , 38 1- 38 6 ; 13, p p
. 2, 9 ; 14A, p. 2 PW

- 3 UC 63 43

- 63 E2 466 1 2/2/10 9.9 0.5 Ref. 10, pp. 15, 16 , 33 8- 34 3 , 345, 348

- 350, 370, 381

- 386 ; 13, p p
. 7, 9 ; 14A, p. 2 ; 14B MW

- 14 UC 57.9 47

- 57 E2330 8/4/09 TCE 78 5 Ref. 10, pp. 13, 14 , 24 - 33 , 37 , 47, 48, 50 , 8 3 , 128

- 142, 41 6; 14A, p. 1 MW

- 17 UC 54.45 45

- 55 E2333 8/5/09 39 5 Ref. 10, pp. 13, 14 , 24 - 33 , 37 , 47, 48, 50 , 9 2 , 12 8-1 42 , 41 9; 14A, p. 1 MW

- 20 UC 54.35 45

- 55 E2336 8/5/09 57 5 Ref. 10, pp. 13, 14 , 24 - 33 , 39 , 47, 48, 50 , 10 5 , 12 8-1 42 , 4 22; 14A, p. 1 MW

- 20 UC 54.35 45

- 55 E2336 8/5/09 Cis

- 1,2

- DCE 9. 5 5 Ref. 10, pp. 13, 14 , 24 - 33 , 39 , 47, 48, 50 , 10 4 , 12 8-1 42 , 4 22; 14A, p. 120 Location No. Aquifer Well or Sampling

Depth (f

eet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

PW

- 1 UC 59. 83 39. 83

- 59.83 E2464 1 2/2/10 1,1,1

- TCA 9.6 0.5 Ref. 10, pp. 15, 16, 24

- 33, 33 8- 34 3 , 344 , 348

- 350 , 3 59 , 38 1- 38 6 ; 13, p p
. 2, 9 ; 14A, p. 1 PW

- 2 UC 6 1 41

- 61 E2320 1 8/5/09 3.6 0.5 Ref. 10, pp. 15, 16 , 24

- 33, 15 3- 15 7 , 15 9 , 163

- 16 5 , 18 1 , 19 3- 195 ; 13, p p
. 3, 5, 9 ; 14A, p. 1 MW

- 5S UC 34.65 25

- 35 E2340 8/4/09 17 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 41 , 47, 48, 51 , 1 22 , 12 8-1 42 , 40 9; 14A, p. 1 MW

- 5D UC 6 4.41 55

- 65 E2339 8/ 4/09 45 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 41 , 47, 48, 51 , 11 9 , 12 8-1 42 , 410 ; 14A, p. 1 MW

- 10S UC 29.28 19

- 29 E2326 8/4/09 13 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 3 5 , 47, 48, 49 , 7 0 , 12 8- 142, 4 11; 14A, p. 1 MW

- 11 UC 69.2 60

- 70 E2327 8/6/09 10 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 3 5 , 47, 48, 49 , 7 3 , 128

- 142, 41 3; 14A, p. 1 Notes: 1

The monitoring well samples were collected within the same time frame ( between August 4 and 6 , 2009 ) (Ref. 10, pp. 49 -51) . The samples were collected using bladder pump using low

- flow sampling te chnique (Ref. 10, pp. 13, 408-422) . The ground water s amples were collected after the field parameters (pH, conductivity, dissolved oxygen (DO), temperature, oxidation reduction potential and turbidity) had stabilized (Ref. 10, pp.

-- The screen interval was estimated based on the well depth and screen length provided in Reference 13, page 9. μg/L – Microgram per liter bgs – Below ground surface DCE – Dichlo roethene D - Analysis was performed at a secondary dilution factor NA – Not available PCE – Tetrachloroethene CRQ L – Contract

- Required Quantitation Limit (Ref. 14A, pp. 1, 2) TCA

– Trichloroethane TCE – Trichloroethene UC – Uncon fined aquifer * - Dilution of 10 was performed on this sample (Ref. 10, pp. 39, 108).21 13, 408-422) . The samp les were analyzed by the U.S. EPA (CLP) for VOCs (R ef. 10, pp. 49 -51 ; Tables 1 and 2).
The background and downgradient ground water samples were c ollected using bladder pump and the low

- flow sampling procedures (Ref. 10, pp. 408-422) ; were collected within the same time frame ( between 4th August 2009 and 6 th A ugust 2009) and therefore, the same weather conditions (Ref. 10 , pp. 408-422) ; were collected within the same aquifer (glacial deposits , Little Miami River Aquifer ) (Ref. 8, pp

. 44, 47, 80, 81; 10, pp. 408

- 422; 11A, pp. 37-40 ); and were analyzed using the same methods ( Ref . 10, pp. 49 -51 ; Tables 1 and 2 ).
The ground water samples from drinking water wells (public supply wells) were collected three times between August 2009 and February 2010 (Ref. 10, pp. 404

- 407, 447

- 450). The samples collected in August 2009 were collected on the same day by the same sampler (Ref. 10, pp. 404

- 407); and samples collected in February 2010 were collected on the same day by the same sampler (Ref. 10, pp. 447

- 450). The samples were analyzed by the U.S. EPA CLP for VOCs (Ref. 10, pp. 49-51, 217, 350 ; Tables 1 and 2 ).

**•** TCE List of Hazardous Substances Associated with Source:
The following hazardous substances are associated with the source:

**•** Cis -1,2- DCE

**•** 1,1,1- TCA

**•** PCE

2.2.3 Hazardous Substances Available to a Pathway
The soil boring investigations at the site have shown that the site has no liner, maintained engineered cover, functioning and maintained run

- on control system, runoff management system, or functioning leachate coll ection and removal system (Refs. 6, pp. 42

- 57; 7, pp. 20

- 37; 8, pp. 49

- 77; 10, pp. 427 -446). Furthermore, a ground water release of hazardous constituents from unknown sources is documented based on analytical results for ground water samples collected f rom the site. Therefore, the Containment Factor Value (CFV) for the ground water migration pathway was assigned a maximum value of 10 (Ref. 1, Section 3.1.2.1, Table 3 -2 , p. 51596 ). The maximum CFV reflects the minimum level of containment. A source is assigned the maximum CFV if there is evidence that hazardous substances have migrated from the source area or that there is no liner, maintained engineered cover, functioning leachate collection and removal system, or functioning and maintained run

- on cont rol system and runoff management system (Ref. 1, Section 3.1.2.1, Table 3

- 2, p. 51596).22 Because the CFV for Source 1 is greater than zero, the following substances are identified as having been released to the ground water migration pathway: TCE; PCE; ci s-1,2- DCE; and 1,1,1

- TCA. Table 3 below summarizes the CFVs for each pathway.

TABLE 3 CONTAINMENT FACTOR VALUE SUMMARY Release Description CFV Reference Gas Release to Air Not Scored NA Particulate Release to Air Not Scored NA Release to Ground Water: Because there is an observed release of hazardous substances to ground water, a CFV of 10 was assigned (see Sections 2.2.2 and 3.1.1 of this HRS documentation record package)

. 10 Ref. 1, Section 3.1.2.1, Table 3 -2, p. 51596

Release through Overland Migra tion and/or Flood Not Scored NA Notes: CFV

- Containment Factor Value HRS

- Hazard Ranking System NA

- Not applicable

2.4.2 HAZARDOUS WASTE QUANTITY

2.4.2.1 Source Hazardous Waste Quantity 2.4.2.1.1 Hazardous Constituent Quantity (Tier A)
The available i nformation is not sufficient to adequately evaluate Tier A as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to the evaluation of Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1, pp. 51590-51591).

2.4.2.1.2 Hazardous Waste s tream Quantity (Tier B) The available information is not sufficient to adequately evaluate Tier B as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds t o the evaluation of Tier C, volume (Ref. 1, Section 2.4.2.1.2, p. 51591).

2.4.2.1.3 Volume (Tier C)
Because the lateral and vertical extent of the ground water plume have not been adequately characterized, the volume for the ground water plume is designated as unknown but greater than zero (Tier C) (Ref. 1, Section 2.4.2.1.3, Table 2 -6, p. 51591).

2.4.2.1.4 Area (Tier D) The area (Tier D) is not evaluated for source type “other” (Ref. 1, Table 2 -5, p. 51591).23 2.4.2.2 Calculation of Hazardous Waste Quantity Factor Value As described in the HRS, the highest value assigned to a source from among the four tiers of hazardous constituent quantity (Tier A), hazardous wastestream quantity (Tier B), volume (Tier C), or area (Tier D) shall be selected as the source h azardous waste quantity value (Ref. 1, Section 2.4.2.1.5, p. 51591). Table 4 below summarizes the hazardous waste quantity values.

TABLE 4 HAZARDOUS WASTE QUANTITY VALUES

Tier Measure Source Value Tier A, Hazardous Constituent Quantity Not Evaluated Tie r B, Hazardous Waste s tream Quantity Not Evaluated Tier C, Volume >0 Tier D, Area Not Applicable Table 5 below summarizes the source description.

TABLE 5 SOURCE DESCRIPTION SUMMARY

Source

No. Source Hazardous Waste Quantity

Value Source Hazardous Cons tituent

Quantity Complete? CFV by Pathway Ground Water Surface Water Air (Ref. 1, Table 3 -2) Overland/ Flood (Ref. 1, Table 4
- 2) Ground Water to Surface Water (Ref. 1, Table 3
- 2) Gas (Ref. 1, Table 6
- 3) Particulate (Table 6
- 9)

1 Unknown, but >0 No 10 Not scored Not scored Not scored Not scored
Note: CFV

- Containment Factor Value
Description of Other Possible Sources : Historical Releases of Chlorinated Solvents from Other Possible Operations
Baker Feed Property and Nearby Area : Based on previous ground water investigations, the area at or near Baker Feeds, 527 Baker Drive is believed to be one possible historic contributor to the ground water contamination (Ref. 10, p. 7 ). Baker Feeds consists of several buildings including the feed store (th e oldest structure), the Baker Party Store and two storage buildings (Figure 5, Source Area Investigation Map) (Ref. 10, p. 7 ). The party store is divided into three sections (Ref. 10, p. 7 ). Currently the southern two sections closest to the feed store are used as the Baker Party Store (Ref. 10, p. 7 ). The northern

- most section is currently unoccupied but was used for dry cleaning in the past according to the current owner (Ref. 10, p. 7 ). Historical research conducted by Ohio EPA using Polk Directorie s indicates that Bernges 1

- Hour Martinizing operated at24 527 Baker Drive at least between 1957 and 1967 (Ref. 10, p p. 7, 8). Additional evidence includes a large circular fan housing in the north wall of the building (Ref. 10, p. 8 ). This is believed to be the vent for the dry cleaning operation (Ref. 10, p. 8 ). The former dry cleaning operation in the party store building is the only link to PCE use that Ohio EPA was able to find. In September, 2002, Ohio EPA conducted an Expanded Site Inspection (ESI). ESI field work was conducted in four phases on March 18 through 22, May 13 through 17, June 6, and July 9, 2002 (Ref s . 8, p. 5; 9A, p. 7). OEPA collected ground water samples from both Direct Push and rotosonic boreholes (Ref. 10, p. 9 ). Monitoring wel ls were installed and sampled to look for contaminant source areas and to delineate the pathways by which VOCs were entering the well field (Ref. 10, p. 9). OEPA advanced 36 soil borings, collected 27 ground water samples from the direct

- push boreholes, a nd installed and sampled 3 monitoring wells (Ref s . 8, p. 5; 9A, pp . 7, 20, 21 ). The ground water samples were submitted to DataChem Laboratories in Cincinnati, Ohio, for rush analysis using U.S. Environmental Protection Agency (EPA) Method 8260 (Refs. 8, p.5; 9A, p. 7)

. PCE was detected in direct -push ground water samples at concentrations of up to 730 J μg/L ; 1,1,1- TCA was detected at concentrations of up to 19 μg/L; TCE was detected at concentrations of up to 40 μg/L; and cis -1,2- DCE was detected at concentrations of up to 40 μg/L (Ref. 9A, pp. 11, 12). Based on screening results from borehole sampling, monitoring wells MW -14, MW

- 15 and MW

- 16 were installed and sampled during the ESI (Ref. 10, p. 9 ). MW

- 14 and MW

- 15 were installed along Baker Drive; M W- 16 was installed at the COMCO facility (Ref. 8, p. 8). The analytical results indicated that the aquifer was contaminated with VOCs which could be emanating from more than one source (Ref. 10, p. 9 ). The pattern of detections indicated that a release of PCE occurred in the vicinity of the Milford Shopping Center located approximately 3300 feet east of the well field (Ref s . 8, p. 13 ; 10, p. 9 ). ESI sampling also documented low concentrations of residual VOCs in ground water at the COMCO facility (Ref. 10 , p. 9 ). Ohio EPA conducted a Direct

- Push investigation in 2003 to further define a source of PCE found in MW -14 along Baker Drive (Ref. 10, p. 9 ). The Ohio EPA contractor, Tetra Tech EM Inc. completed 18 borings in the Milford Shopping Center parking lot, east of Baker Drive and in the Big Lots parking lot, on the north side of Main Street (Ref s. 7 , pp. 9, 10, 11, 16; 10, p. 9 ). Figure 3 of this HRS documentation record illustrates the results of the direct

- push ground water samples collected from these borings. In April and May 2006, Tetra Tech EM Inc. completed ten soil borings and installed four monitoring wells in the Baker Feeds area to further define the suspected source area (Ref. 10, p. 10; 11A, pp. 5, 6, 7 ). Nine ground water samples and one soil sample were collected from borings installed in the study area (Ref. 11A, p. 12 ). The samples were analyzed for VOCs by Kemron Environmental Services using Method 8260A (Ref. 11A, p. 17). The direct -push ground water samples revealed levels of PCE i n the vicinity of the Baker Feed Store (Ref. 11A, p. 18, Fig. 5-1 ).
Ohio EPA conducted a State Site Assessment Investigation in September 2006 collecting sub

- slab soil gas sampling in buildings surrounding a suspected source property (Ref s . 10, p. 10; 11B, pp. 2 -21, 94-109 ). PCE was detected in the sub

- slab sample at the Baker Party Store at a concentration of 350 parts per billion volume (ppbv) (Ref. 10, pp. 10; 11B, p. 102 ). An exterior soil gas investigation was conducted by Ohio EPA between25 a suspect ed source area and the well field in March 2007 (Ref. 10, p. 10; 12B, pp. 1, 2). The soil gas samples were analyzed for VOCs by DataChem using Method TO

- 14 (Ref. 12B, pp. 2, 11

- 22). PCE was detected at low levels in 4 of 13 soil gas samples (Ref. 10A, pp. 2, 3, 5, 9). Additionally, ground water samples were collected from the monitoring wells (Ref. 12B, pp. 24

- 76, 165). Based on ground water data, OEPA concluded that a source of contamination still appear ed to be at or near the Baker Feeds property (Ref. 10, p. 18).
OEPA prepared a SESI work plan that was approved by U.S. EPA on July 9, 2009 (Ref. 10, p. 6 ). SESI field work included sampling of 15 monitoring wells; public supply wells; and 5 soil samples (including 1 duplicate) for a potential source ar ea identification (Ref. 10, pp. 6, 12 , 1 3, 23 -25 ). The samples were analyzed for target compound list VOCs by an EPA contract laboratory (Ref. 10, p. 6 ). The soil and ground water samples were submitted to Mitkem Laboratories Inc. in Warwick, Rhode Islan d , and DataChem Laboratories in Salt Lake City, Utah for analysis using CLP SOW SOM01.2 (Ref. 10, pp. 2 7 , 2 8, 202 ). The SESI ground water samples confirmed that the aquifer is contaminated with VOCs (Ref.10, p. 6 ). Of the 5 soil samples collected, one sa mple contained concentrations of site

- related contaminants: estimated concentrations of PCE and DCE at levels below the CRQL. Thus, the soil sampling was not able to identify a source (Ref. 10 , p p. 13, 16, 18 ).

Mosler Inc: On June 9, 1986, the former Mo sler Inc. (Mosler) facility located approximately 1 mile east of the well field filed a Notification of Hazardous Waste Activity form (Ref. 8, p. 7). The form indicates that the facility handled F001 listed wastes (Ref. 8, p. 7). F001 listed wastes are defined as spent halogenated solvents used for degreasing, including PCE, TCE, and 1,1,1

- TCA, all of which have been detected in ground water samples collected from the City of Milford well field (Ref. 8, p. 7). Mosler operated a solvent vapor degreaser th at used 1,1,1

- TCA for parts cleaning (Ref. 8, p. 7). The Mosler facility ceased operations in 1991 (Ref. 8 , p. 7). Site investigations conducted in the early 1990s revealed that 1,1,1

- TCA and other solvents had been released to soil and ground water at t he Mosler facility (Ref. 8, p. 7). Contaminated soils were removed from the Mosler facility in 1992 and 1993, and a soil vapor extraction system was installed in 1995 (Ref. 8, p. 7). Soil and ground water sampling performed in 1996 indicated that most of the contamination had been removed (Ref. 8, p. 7). The Mosler facility is currently occupied by COMCO Machinery (COMCO), a division of MARKANDY (Ref. 8, p. 7). The figure on Reference 8, page 19 illustrates that MW

- 16 is located on the former Mosler (no w COMCO) property, and during the 2002 ESI was found to contain levels of PCE and 1,1,1- TCA. At present, it is not known if the ground water contamination at the former Mosler property is or

was com m ingled with the Milford Contaminated Aquifer plume.26 3.0 GROUND WATER MIGRATION PATHWAY

A nalysis of the several field investigations near the Milford Treatment Plant and installed wells indicate the bedrock surface is generally encountered at a depth from ground surface ranging from 38 feet in the southern part of the Indian Hill wellfield to greater than 60 feet around the production wells in Milford's wellfield (Ref. 10, p p. 10, 11 ). The Little Miami River Aquifer is unconfined and thus it receives direct recharge from precipitation (Ref. 10, p. 11). Geology and Hydrogeology:
The Milford well field is located in the north

- south trending valley of the Little Miami River (Ref. 8, p. 12). The East Fork of the Little Miami River flows into the Little Miami River just sou th of Milford (Ref. 8, p. 12). Below the junction, the Little Miami River valley is broader (approximately 11⁄2 miles wide) than at Milford, where the valley is approximately 1⁄2 mile wide (Ref. 8, p. 12). The broad valley continues upstream along the East Fork. The narrowness of the valley at Milford suggests a recent origin (Ref. 8, p. 12). The valley between Milford and Foster was formed when a glacier blocked the westward flow of Todd’s Fork, forming a lake that overflowed the divide at Foster and carved the present valley (Ref. 8, p. 12). A pumping test of PW- 3 conducted in 1987 revealed that the hydraulic conductivity of the sand and gravel aquifer was 7,900 gallons per day (gpd) per square foot (Ref. 8, p. 12).
During the 2002 ESI, the depth to the w ater table was shallower at the COMCO property well (MW16) than in the Baker Drive wells (MW14 and MW15) (Ref. 8, p. 12), suggesting that ground water flows north from the COMCO property toward Baker Drive (Ref. 8, p. 12). The water elevations recorded in the Baker Drive wells were compared to the water elevations measured in wells installed during the geographic initiative and the combined PA/SI (Ref. 8, p. 12). The water table is approximately 20 feet shallower at Baker Drive than near the well field, w hich indicates that ground water flows west from Baker Drive to ward the well field and the Little Miami River (Ref s. 8, p. 12; 12A, pp. 1-3 ).
Clermont County is within the Till Plains section of the Central Lowland physiographic province. Uppermost subsurf ace materials in the area typically consist of Pleistocene glacial deposits which are predominately clay

rich glacial till, with sand or gravel in places (Ref. 10, p. 10 ). The glacial cover ranges in thickness from 20 to more than 50 feet in areas near th e Little Miami River and overlies interbedded shale and thin, hard, blue

- gray limestone of Ordovician age (Ref. 10, p. 10).
The Milford Well Field is located in the flood plain of the Little Miami River, which consists of permeable sand and gravel deposits “comprised of both pre - and post

- glacial alluvium " (Ref. 10, p. 10 ). The Little Miami River Aquifer near Milford is typified by layers of coarse, unconsolidated, permeable sand and gravel with minimal occurrences of clay sediments (Ref. 10, p. 10).27 With respect to water production, the ar ea along the Little Miami River is particularly favorable because of induced stream infiltration (Ref. 10, p. 1 1 ). Much of a well's yield is likely derived from the induced infiltration from the Little Miami River (Ref. 10, p. 1 1 ). The annual average of pr ecipitation in the Milford area is 37.7 inches of which approximately one

- third infiltrates and recharges the ground water (Ref. 10, p. 11 ). Additional recharge to the aquifer occurs through the fractures in the bedrock and the valley walls (Ref. 10, p. 1 1 ). However, this amount of recharge is negligible compared to the areal recharge component (Ref. 10, p. 11 ).
The City of Milford lies on the northeastern edge of a very large buried valley system (Ref. 12, p. 22). The aquifer in the vicinity of the Milford water treatment plant is a buried channel containing sand and gravel deposits (Ref. 12, p. 46). The composition of the surficial deposits is highly variable (Ref. 12, p. 22). Geologic samples collected in Milford indicate that the soil is a mixture of ancient buried channel deposits and recent alluvial deposits (Ref. 12, p. 22). In general, approximately 50 feet of unconsolidated materials were present in borings drilled during the geological investigations and the upper 10 feet was composed of silt, loam, clay, and fill, while the remainder was composed of sand and gravel (Ref. 11, p p . 14 , 38 -57 ). Although the sand and gravel contained silt and clay, no clay or other low

- permeability material layers were encountered in the geological investigation borings that could impede the movement of water (Ref. 11, p. 14). The absence of thick laterally extensive clay layers indicates that the aquifer in the vicinity of the Milford water treatment plant is unconfined (Ref. 12, pp. 24, 25, 46).

Based on the inv estigations conducted at the site and a geologic cross section developed for the site , the contaminated ground water plume is located in the Pleistocene glacial deposits overlying the interbedded shale and thin, hard, blue

- gray limestone of Ordovician age (Ref s . 8, pp. 44, 47; 10, p. 10; 12, p. 60). The public supply wells are located in the Pleistocene glacial deposits (also known as t he Little Miami River Aquifer) (Ref. 14, p. 1).
Aquifer Interconnection /Discontinuity
The hydrogeologic setting across the study area is characterized as a buried valley, with one smaller area of glacial till directly overlying bedrock (Ref. 10 B, pp. 34, 44; 12, pp. 22, 46 ). The geology of this buried valley consists of thick deposits of sand and gravel deposited by gla cial meltwaters in former river valleys (Ref. 10 B, p. 40 ). The cross section developed for the site indicates that abundant sand and gravel deposits are present throughout the study area and shows that no discontinuities between the eastern and western p ortions of the study area are likely (Ref. 8, pp. 44, 46, 47). The glacial till identified in this cross section appears to be localized and is not likely to hinder ground water flow from east to west (Ref. 8, p p. 44 , 46 ; 10 B, 44). Based on the similar hydrogeologic conditions across the study area, it is expected that the sand and gravel deposits are continuous throughout the study area. :28 The sand and gravel aquifer at the Milford Contaminated Aquifer s ite is an unconfined water table aquifer. The absen ce of thick laterally extensive clay layers in the sediment indicates that the aquifer in the vicinity of the Milford water treatment plant is unconfined (Ref. 5, p. 42; Ref. 10, pp. 24, 25). Because the aquifer is unconfined and contains no continuous layer of low hydraulic conductivity material, there is no need to demonstrate aquifer interconnection. Table 6 below summarizes the aquifer characteristics.

TABLE 6 AQUIFER CHARACTERISTICS SUMMARY

Source No. Aquifer Type Is Aquifer Continuous Within -4- Mi le Target Distance Limit? Is Aquifer Karst? 1 Unconsolidated Yes No

3.1 LIKELIHOOD OF RELEASE
3.1.1 Observed Release Aquifer Being Evaluated: Little Miami River Aquifer (Unconfined Aquifer).

Direct Observation : An observed release by direct observatio n to the ground water migration pathway from the unconsolidated aquifer has not been established at the Milford Contaminated Aquifer s ite.
Chemical Analysis: Establishing an observed release through chemical analysis requires analytical evidence of a haz ardous substance in a medium at a concentration significantly exceeding the background concentration. If the background concentration of a chemical is not detected (or is less than the detection limit), an observed release is established when a sample mea surement equals or exceeds its own sample quantitation limit (SQL) and the background sample concentration. If the SQL cannot be established, the EPA contract

- required quantitation limit (CRQL) should be used instead of the SQL (Ref. 1, Section 2.3, p. 51589).

The water elevations recorded in the Baker Drive wells were compared to the water elevations measured in wells installed during the geographic initiative and the combined PA/SI (Ref. 8, p. 12). The water table is approximately 20 feet shallower at Baker Drive than near the well field, which indicates that ground water flows west from Baker Drive to the well field (Ref. 8, p. 12). Based on this ground water flow direction, monitoring well locations MW

- 3 and MW -16 are considered upg radient or sidegradient (or background ) locations (Refs.10, pp. 13, 24; 12A, pp. 1 -4). Municipal well PW

- 4 is also considered to be a background well because concentrations of chlorinated solvents detected in this well are either non

- detect or at estimate d Background Level:29 concentrations below Contract Required Qua n titation Limit s (CRQL s ) (Ref. 10, pp. 14, 15). The background well sample locations are shown in Figure 5 of this HRS documentation record.

Table 7 below summarizes background monitoring well and public well l ocation information and the concentrations of contaminants of concern for the site detected in ground water samples collected from each location. The contaminants of concern for the Milford Contaminated Aquifer s ite (PCE; TCE; cis -1,2- DCE; and 1,1,1

- TCA) were not detected in ground water samples collected from the background locations , demonstrating that the background locations have not been impacted by the site

- related hazardous substances. ( See Table 7 of this HRS documentation record ).

Furthermore , g round water samples were collected from direct -push locations GP7, GP11, GP12, GP13, GP21, and GP32. Based on the ground water flow direction described above , these locations are also considered to be upgradient (or background) location s . The ground wate r samples from direct push locations were collected from a depth of 39 to 64 feet below ground surface (bgs) (Refs. 8, pp. 18, 36, 37, 44). The contaminants of concern for the Milford Contaminated Aquifer s ite (PCE; TCE; cis -1,2-DCE and 1,1,1- TCA) were no t detected in ground water samples collected from the direct

- push background locations (Ref. 8, pp. 36, 37, 103, 110, 112, 113, 119, 121, 122, 128, 136, 137, 143, 169, 170, 176). Absence of contaminants of concern in the direct

push ground water samples s uggest s that the background locations to the depth of approximately 64 feet bgs lie outside the area of contamination. Based on the description provided in the PSARA Technology Inc. June 2002 Report, the direct

- push samples appear to have been collected from the unconfined aquifer (Ref. 8 , pp. 28, 44, 58, 59, 66, 67 ). Figure 4 of the ESI report show s these direct

- push background locations (Ref. 8, p. 18 ).

TABLE 7 BACKGROUND WELL INFORMATION

Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Sc reen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

PW

- 4 UC 25

- 51 36

- 51 E2467 2/2/2010 PCE 0. 5 U 0. 5 Refs. 10, pp. 15, 16, 338

- 343, 346, 347, 350, 372, 373, 381

- 386; 13, p. 8 ; 14A, pp.1, 2 TCE 0. 5 U 0. 5 Cis

- 1,2

- DCE 0. 5 U 0. 5 1,1,1

- TCA 0. 5 U 0.5

MW

- 3 UC 28.45

- 38.45 30

- 40 E2341 8/6/09 PCE 5.0 U 5 .0 Ref s . 10, pp. 13, 14 , 22, 23, 24 , 27- 33 , 4 3, 44, TCE 5.0 U 5.0 Cis

- 1,2

- DCE 5.0 U 5.030 Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Sc reen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

1,1,1

- TCA 5.0 U 5.0 47, 48, 51 , 12 5 , 12 6, 127 , 12 8- 1 42, 408 ; 14 A, pp. 1, 2; . 12, p. 60 MW

- 16 UC 30.4

- 40.4 30

- 40 E2332 8/5/09 PCE 5.0 U 5.0 Refs. 10, pp. 13, 14, 22, 23, 24 , 27- 33 , 3 7 , 38, 47, 48, 50 , 8 8 , 89, 90, 12 8-1 42 , 418; 14 A, pp. 1, 2 TCE 5.0 U 5.0 Cis

- 1,2

- DCE 5.0 U 5.0 1,1,1

- TCA 5.0 U 5.0

Notes: μg/L – Microgram per liter bgs – Below ground surface DCE

- Dichloroethene PCE – Tetrachloroethene CRQL – Contract

- Required Quantitation L imit (Ref. 14A, pp. 1, 2) TCA

- Trichlo roethane TCE – Trichloroethene UC – Unconfined aquifer U – Analyte was analyzed for, but was not detected above the reported sample quantitation limit (Ref. 10, pp. 33, 343).

- Contaminated Samples
The results for contaminated ground water samples colle cted from monitoring wells and public wells at the Milford Contaminated Aquifer s ite are summarized in Table 8 below. The sample locations are shown in Figure 5 of this HRS documentation record.

TABLE 8

CONTAMINATED WELL INFORMATION

Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

MW

- 10D UC 50 .41 40

- 50 E2325 8/4/09 PCE 9.6 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 6 , 47, 48 , 49, 68 , 12 8-1 42, 4 12; 14A, p. 2 MW

- 15 UC 55 45

- 55 E2331 8/5/09 16 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 8 , 47, 48, 50 , 8 6 , 12 8-1 42, 41 7; 14A, p. 231 Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

MW

- 18 UC 54 .4 44

- 54 E2334 8/5/09 40 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 8 , 47, 48, 50 , 9 5 , 12 8-1 42 , 4 20; 14A, p. 2 MW

- 19 UC 49.91 40

- 50 E2335 8/5/09 31 5 Ref. 10, pp. 13, 14 , 24 - 33 , 40 , 47, 48, 50 , 9 8 , 12 8-1 42, 421; 14A, p. 2 MW

- 14 UC 57.9 47

- 57 E2330 8/4/09 1100 5 Ref. 10, pp. 13, 14 , 24 - 33 , 3 8 , 47, 48, 50 , 8 3 , 12 8-1 42, 41 6; 14A, p. 2 MW

- 17 UC 54.45 45

- 55 E2333 8/5/09 530 5 Ref. 10, pp. 13, 14 , 24 - 33 , 38 , 47, 48, 50 , 9 2 , 12 8-1 42, 41 9; 14A, p. 2 MW

- 20 UC 54.3 5 45

- 55 E2336 DL 8/5/09 1100 D 50* Ref. 10, pp. 13, 14 , 24 - 33 , 40 , 47, 48, 50 , 10 8 , 12 8-1 42, 4 22; 14A, p. 2 PW

- 1 UC 59.83 39. 83

- 59.83 E2464 1 2/2/10 1.2 0.5 Ref. 10, pp. 1 5, 16, 33 8- 34 3 , 34 5 , 348 -3 50 , 36 0 , 38 1- 38 6 ; 13, p p
. 2 , 9 ; 14A, p. 2 PW

- 3 UC 63 43

- 63 E2466 1 2/2/10 9.9 0.5 Ref. 10, pp. 15, 16 , 33 8- 34 3 , 345, 348

- 350, 370, 381

- 386 ; 13, p p
. 7 , 9 ; 14A, p. 2 ; 14B MW

- 14 UC 57.9 47

- 57 E2330 8/4/09 TCE 78 5 Ref. 10, pp. 13, 14 , 24 - 33 , 37 , 47, 48, 50 , 8 3 , 128

- 142, 41 6; 14A, p. 1 MW

- 17 UC 54.45 45

- 55 E2333 8/5/09 39 5 Ref. 10, pp. 13, 14 , 24 - 33 , 37, 47, 48, 50 , 9 2 , 12 8-1 42, 41 9; 14A, p. 1 MW

- 20 UC 54.35 45

- 55 E2336 8/5/09 57 5 Ref. 10, pp. 13, 14 , 24 - 33 , 39 , 47, 48, 50 , 10 5 , 12 8-1 42, 4 22; 14A, p. 1 MW

- 20 UC 54.35 45

- 55 E2336 8/5/09 C is

- 1,2

- DCE 9.5 5 Ref. 10, pp. 13,32 Location No. Aquifer Well or Sampling

Depth (feet bgs) Well Screen Interval

(feet) Sample No. Sampling Date Hazardous Substance Concentration Detected (μg/L) CRQL (μg/L) References

1 4 , 24

- 3 3 , 39 , 47, 48, 50 , 10 4 , 12 8-1 42, 4 22; 14A, p. 1 PW

- 1 UC 59. 83 39. 83

- 59.83 E2464 1 2/2/10 1,1,1

- TCA 9.6 0.5 Ref. 10, pp. 15, 16, 24

- 33, 33 8- 34 3 , 344 , 348

- 350 , 3 59 , 38 1- 38 6 ; 13, p p. 2 , 9 ; 14A, p. 1 PW

- 2 UC 6 1 4 1

- 61 E2320 1 8/5/09 3.6 0.5 Ref. 10, pp. 15, 16 , 24

- 33, 15 3- 15 7 , 15 9 , 163

- 16 5 , 18 1 , 19 3- 195 ; 13, p. 3 , 5, 9 ; 14A, p. 1 MW

- 5S UC 34.65 25

- 35 E2340 8/4/09 17 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 41 , 47, 48, 51 , 1 22 , 12 8-1 42, 40 9; 14A, p. 1 MW

- 5D UC 6 4.41 55

- 65 E2339 8/4/09 45 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 41 , 47, 48, 51 , 11 9 , 12 8-1 42, 410 ; 14A, p. 1 MW

- 10S UC 29.28 19

- 29 E2326 8/4/09 13 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 3 5 , 47, 48, 49 , 7 0 , 12 8- 142, 4 11; 14A, p. 1 MW

- 11 UC 69.2 60

- 70 E2327 8/6/09 10 5 Ref. 10, pp

. 13, 14 , 24 - 33 , 3 5 , 47, 48, 49 , 7 3 , 128

- 142, 41 3; 14A, p. 1 Notes:

1

-- The screen interval was estimated based on the well depth and screen length provided in Reference 13, page 9. μg/L – Microgram per liter bgs – Below ground surface DCE – Dichloroethene D - Analysis was performed at a secondary dilution factor PCE – Tetrachloroethene CRQ L – Contract

- Required Quantitation Limit (Ref. 14A, pp. 1, 2) TCA

– Trichloroethane TCE – Trichloroethene UC – Uncon fined aquifer * - Dilution of 10 was performed on this sample (Ref. 10, pp. 39, 108).33 The monitoring well samples were collected within the same time frame ( between August 4 and 6 , 2009 ) (Ref. 10, pp. 49 -51) . The samples were collected using bladder pump using low

- flow sampling techniqu e (Ref. 10, pp. 13, 408-422) . The ground water s amples were collected after the field parameters (pH, conductivity, dissolved oxygen (DO), t emperature, oxidation- reduction potential and turbidity) had stabilized (Ref. 10, pp. 13, 408-422) . The samples we re analyzed by the U.S. EPA (CLP) for VOCs (R ef. 10, pp. 49 -51 ; Tables 1 and 2).
The background and downgradient ground water samples were c ollected using bladder pump and the low

- flow sampling procedures (Ref. 10, pp. 408-422) ; were collected within th e same time frame ( between 4th August 2009 and 6 th A ugust 2009) and therefore, the same weather conditions (Ref. 10 , pp. 408-422) ; were collected within the same aquifer (glacial deposits, Little Miami River Aquifer) (Ref. 8, pp, 44, 47, 80, 81; 10, pp. 40 8- 422; 11A, pp. 37-40 ); and were analyzed using the same methods ( Ref . 10 pp. 49-51; Tables 1 and 2).
The ground water samples from drinking water wells (public supply wells) were collected three times between August 2009 and February 2010 (Ref. 10, pp. 40 4- 407, 447

- 450). The samples collected in August 2009 were collected on the same day by the same sampler (Ref. 10, pp. 404

- 407); and samples collected in February 2010 were collected on the same day by the same sampler (Ref. 10, pp. 447

- 450). The samples were analyzed by the U.S. EPA CLP for VOCs (Ref. 10, pp. 49-51, 217, 350; Tables 1 and 2).
Milford Contaminated Aquifer Plume Releases (Contaminated Plume):
The Milford Contaminated Aquifer plume has received releases from unidentified source(s). Relea ses associated with the plume area were detected through chemical analysis of ground water samples collected from numerous direct

- push soil borings, monitoring wells, and municipal wells. Analytical results for ground water samples collected from the plume area document observed releases to ground water, primarily of PCE; TCE; cis -1,2- DCE; and 1,1,1

- TCA (see Table 8 above, Contaminated Sample Information). As discussed in Section 3.1.1 above, if the background concentration of a chemical is not detected ( or is less than the detection limit), an observed release is established when a sample measurement equals or exceeds its own SQL and the background sample concentration. If the SQL cannot be established, the EPA CRQL should be used instead of the SQL (Ref . 1, Section 2.3, p. 51589). VOCs were not detected in background wells, so all detected VOC concentrations exceeding the detection limit qualify as observed release

.
Attribution The Milford Contaminated Aquifer s ite plume has received releases of PCE an d 1,1,1

- TCA from unidentified source(s). The plume also contains TCE and cis -1,2- DCE, which are biodegradation products of PCE and TCE. PCE; cis -1,2- DCE; 1,1,1

- TCA; and TCE do not exist naturally and are manmade chemicals (Ref. 13 C, pp. 2, 5) . Signific ant ground water sampling has been performed to identify sources of the PCE and 1,1,1

- :34 TCA contamination, but no sources have yet been identified. Vadose Research, Inc. (VRI), conducted soil gas survey and monitoring well sampling to identify the potential source(s) of ground water contamination in the vicinity of the City of Milford Well Field (Ref. 13 A, p. 5). The potential sources identified for investigation in the vicinity of the City of Milford Well field include a U- Haul dealer on a site formerly o ccupied by a Ford automobile dealership; Victor Tire dealer, on a site formerly occupied by a retail gasoline station and fuels distributorship; Clermont Savings, on a site formerly occupied by a historical gasoline station; Milford City Garage, near city well # 3; Milford City shop/storage buildings, near city well # 3; a site formerly occupied by a dry cleaner, now a vacant lot; and dry wells, integral with the city storm water system, located immediately east of the new garage and behind the U

- Haul deale r at the north end of their back lot (Ref. 13 A, p.10). As part of this investigation soil gas samples were collected from 115 locations and ground water samples were collected from 7 locations (Ref. 13 A, pp. 5, 18). Based on the VRI investigation 3 pri mary source areas were identified (Refs. 13A, pp. 42, 43; 13B , p . 19). The 3 primary source areas that were identified during VRI investigations include the U- Haul dealer on a site formerly occupied by a Ford automobile dealership; the Victor Tire dealer, and a site formerly occupied by a dry cleaner, now a vacant lot (Ref. 13A, pp. 42, 43, 48). Ohio EPA collected approximately 12 soil samples to confirm contamination in areas indicated to be contaminated by the soil

- gas survey (Ref. 13B, pp.12, 17, 18, 21). The only VOCs detected by the laboratory were methylene chloride and acetone (Ref. 13B, p. 17 ). These are common laboratory contaminants and are not believed to occur at the site (Ref. 13B, p. 17 ). Neither chemical has been listed as a contaminant in the well field (Ref. 13B, p. 17 ). No semivolatile organic compounds were detected (Ref. 13B, p. 17 ). Even though the soil gas sampling identified 3 potential sources, the follow

- up soil confirmatory sampling by OEPA was not able to confirm these sources. Based on this information it appears that the above listed locations have not been identified as potential sources for the plume.
Based on the investigation s performed on several potential source areas , the ground water contamination
source cannot be identified or reasonably attributed with confidence. Because the source is a contaminated ground water plume with no positively identified source of contamination, no separate attribution is required (Ref. 1, Section 3.1.1, p. 51595).

**•** TCE Hazardous Substances Released:
The following hazardous substances have been released from the source:

**•** Cis -1,2- DCE

**•** 1,1,1- TCA

**•** PCE

Ground Water Observed Release Factor Value: 55035 3.1.2 Potential to Release As specified in the HRS, because an observed release has been established for the aquifer, the potential to release was not scored (Ref. 1, Section 3.1.2, p. 51595).

3.2 WASTE CHARACTERISTICS The ground water plume at Milford primarily is composed of PCE; TCE; cis -1,2- DCE; and 1,1,1

- TCA. The contamination is desc ribed as a ground water plume with no identified source. PCE; TCE; cis -1,2- DCE; and 1,1,1- TCA were detected in several wells at concentrations exceeding the background levels . Ground water samples collected from municipal wells PW

- 1 and PW

- 3 have been sh own to be impacted by 1,1,1

- TCA and PCE (Ref. 10, pp. 15, 16) . TCE and cis -1,2- DCE were detected in estimated quantity in the ground water sample obtained from the municipal well PW

- 1 (Ref. 10 , pp. 15, 16). 1,1,1- TCA was detected in the ground
water sam ple obtained from the municipal well PW -2 (Ref. 10 , pp. 15, 16). PCE was in estimated quantity in the ground water sample obtained from the municipal well PW -2 (Ref. 10 , pp. 15, 16 ). PCE, TCE , 1,1,1 TCA and cis -1,2- DCE were detected in the ground water sample obtained from the municipal well PW

- 3 (Ref. 10 , p. 16 ). 1,1,1 TC A was detected in estimated quantity in the ground water sample obtained from the municipal well PW -4 (Ref. 10 , p. 15 ). The released substances are believed to be from an unknown source or sources east of the municipal wells.

3.2.1 Toxicity/Mobility
All hazardous substances listed in Table 9 below are documented in ground water samples collected from the Milford Contaminated Aquifer plume. These hazardous substances were detected a t concentrations significantly exceeding background levels.36 TABLE 9 OBSERVED RELEASE AND TOXICITY/MOBILITY SUMMARY

Hazardous Substance Toxicity Factor Value Mobility Factor Value Does Hazardous Substance Meet Observed Release Criteria? Toxicity/ Mobility Reference

PCE 100 1 Yes 100 Ref. 1, Sections 3.2.1.1, 3.2.1.2, and 3.2.1.3, pp.51601, 51602; Ref. 2, p. A336 TCE 10,000 1 Yes 10,000 Ref. 1, Sections 3.2.1.1, 3.2.1.2, and 3.2.1.3, pp. 51601, 51602; Ref. 2, p. A-2 Cis

- 1,2

- DCE 100 1 Yes 100 Ref. 1, Se ctions 3.2.1.1, 3.2.1.2, and 3.2.1.3, pp.51601, 51602; Ref. 2, p. A134 1,1,1

- TCA 1 1 Yes 1 Ref. 1, Sections 3.2.1.1, 3.2.1.2, and 3.2.1.3, pp.51601, 51602; Ref. 2, p. A362 Notes: DCE

- Dichloroethene PCE – Tetrachloroethene TCA

- Trichloroethane TCE – Trichloroethene Because an observed release to the ground water migration pathway has been established, a mobility factor of 1 was applied to the hazardous substances released (Ref. 1, Section 3.2.1.2, p. 51601). As shown in Table 9 above, the toxicity/mobility factor value for TCE is 10,000. The Toxicity/Mobility Factor Value of 10,000 was assigned based on Table 3 -9 of the HRS (Ref. 1, Section 3.2.1.3, p. 51602).
Toxicity/Mobility Factor Value: 10,000

3.2.2 Hazardous Waste Quantity Table 10 below summarizes the hazardous waste quantity information for the Milford Contaminated Aquifer.

TABLE 10 HAZARDOUS WASTE QUANTITY SUMMARY

Source No. Source Name Source Type Source Hazardous Waste Quantity 1 Other Ground Water Plume Unknown but > 0

The Milford Contaminated Aquifer s ite has been scored as a contaminated ground water plume with no identified source. According to Section 2.4.2.2 in the HRS (Ref. 1, p. 51592), if any target for the migration37 pathway is subject to Level I or Level II concentrations, an d the hazardous constituent quantity is not adequately determined, the Hazardous Waste Quantity Factor Value for that pathway should either be assigned the value from Table 2

- 6 (Ref. 1, p. 51591) or a value of 100, whichever is greater. Because Level I

co ncentrations were detected in samples from a drinking water well (see Section 3.3.2.2 of this HRS documentation record package), a Hazardous Waste Quantity Factor Value of 100 was assigned to the ground water pathway.
Hazardous Waste Quantity Factor Value : 100 (Ref. 1, Section 2.4.2.2, p. 51592)

3.2.3 Calculation of Waste Characteristics Factor Category Value As specified in the HRS (Ref. 1, Section 3.2.3, p. 51602), the Hazardous Waste Quantity Factor Value of 100 was multiplied by the highest Toxicity/Mo bility Factor Value of 10,000, resulting in a product of 1,000,000 (1.0E+06). Based on this product, a Waste Characteristics Factor Category Value of 32 was assigned from Table 2

- 7 of the HRS (Ref. 1, Section 2.4.3.1, p. 51592). The highest Toxicity/Mobi lity Factor Value of the substances listed in Section 3.2.1 of this HRS documentation record package was for TCE.
Toxicity/Mobility Factor Value: 10,000 Hazardous Waste Quantity Factor Value: 100 Toxicity/Mobility Factor Value (10,000) X Hazardous Waste Quantity Factor Value (100): 1,000,000 = 1X10 6 Waste Characteristics Factor Category Value: 32 (Ref. 1, Table 2 -7, p. 51592)

3.3 TARGETS
A total of 18 municipal wells are located within the 4 - mile radius Target Distance Limit (TDL) from the site (Ref. 1 4, p. 1; Ref. 15, p. 1; Ref. 16, p. 1). The 4

- mile target distance limit (TDL) is shown in Reference 20. The primary municipal wells of concern are operated by the City of Milford municipal water system (Ref. 6, p. 10 ). T hree municipal wells (PW -1 , PW -2 and PW

- 3) operated by the City of Milford are within the ground water contamination plume and are impacted by the chemicals of concern (Tables 11 and 12). Approximately 24 private wells within the TDL could potentially be exposed to contaminated drinking water. An estimated 63 people are served by private wells within the TDL (Ref. 17, pp. 2 -5). The targets evaluated for the ground water migration pathway are summarized below

.
Level I Concentrations38 Level I concentrations have been documented in one City of Milford public supply well (PW

- 3) that draws from the Little Miami River Aquifer as shown in Table 11 below.

TABLE 11 LEVEL I CONCENTRATIONS

Sample ID Hazardous Substance Hazardous Substance Concentration ( μg/L ) Benchmark Concentration ( μ g/L) Bench mark References for Benchmark E2466 (PW -3) PCE 9.9 1.6 Cancer Risk Screening Concentration 2, p. A

- 336

Notes: See Table 8 for the concentrations detected in the drinking water well samples. μg/L Micrograms per liter ID Identification

Level I I Concentrations
Level II concentrations have been documented in two of the City of Milford public water supply wells (PW

- 1 and PW-2) that draw from the Little Miami River Aquifer and are summarized in Table 12 below.

TABLE 12 LEVEL I I CONCENTRATIONS

Hazardous Substance Hazardous Substance Concentration ( μg/L ) Benchmark Concentration ( μ g/L) Benchmark References for Benchmark E2 Sample I D

464 (PW -1) PCE 1.2 1.6 Cancer Risk Screening Concentration 2, p. A

- 336

E2464 (PW -1) 1,1,1

- TCA 9.6 200 MCL 2, p. A

- 362
E2 320 (PW -2) 1,1,1

- TCA 3.6 200 MCL 2, p. A

- 362

Notes: See Table 8 for the concentrations detected in the drinking water well samples. μg/L Micrograms per liter ID Identification MCL Maximum contaminant level39 3.3.1 Nearest Well
Because actual contamination at Level I concentrations has been documented, a nearest well factor value of 50 is assigned (Ref. 1, Section 3.3.1, Table 3-11, p. 51603).

Well ID: PW -3
Level of Contamination (I, II, or potential): I

Nearest Well Factor Value: 50
(Ref. 1, Table 3 -11, p. 51603)

3.3.2 Population
3.3.2.1 Level of Contamination The City of Milford municipal system has approximately 2,077 service connections (Ref. 14, p. 2). According to the U.S. Census Bureau, there are approximately 2.67 persons per household in Clermont Cou nty (Ref. 17, p. 1). Therefore, the total estimated population served by the City of Milford water system is 5,546 (2,077 total service connections x 2.67 persons per household for Clermont county). The City of Milford water system has four municipal wel ls (PW

- 1 through PW

- 4) (Ref. 14, p. 1). The water pumped from these wells is blended (Ref. 14, pp. 1, 2). Water from PW-1 and PW-3 is treated by an air stripper prior to distribution due to chlorinated solvents contamination (Ref. 14, p. 1, 2).
The annual pumping rate for each municipal well was provided by the City of Milford Water Department for 2006, 2007, and 2008 (Ref. 14, pp. 2, 3). For population allocation, the data from 2007 were used because in 2006 municipal well PW

- 4 was being designed and because in 2008, municipal wells PW

- 1 and PW

- 3 were not used because the air stripper was being repaired (Ref. 14, pp. 2, 3). According to 2007 data, the annual pumping rates were as follows: for PW

- 1, 0 gallons (0 percent); for PW -2, 219 .07 million gallon s (79.4 percent of total pumping volume); for PW -3, 44.02 million gallons (16 percent of the total pumping volume); and for PW

- 4, 12.74 million gallons (4.6 percent of total pumping volume) (Ref. 14, p. 2). Based on the annual pumping rates for 2007, municipal well PW

- 2 supplied more than 40 percent of the system’s total water. Therefore, the population was apportioned to each municipal well in accordance with the annual pumping rates (Ref. 1, Section 3.3.2, p. 51603; Ref. 14, pp. 1-2).40 3.3.2.2 Level I Concentrations

Level I Well Level I Population Targets

For munic ipal well PW

- 3, the population allocated was 88 7 individuals (16 percent of 5,546 individuals). The Level I well is documented in Tables 8 and 11. Table 13 summarizes the Level I population affected by PW-3, which is completed in the Little Miami River a quifer.

TABLE 13 LEVEL I POPULATION Aquifer Population Reference PW

- 3 Unconfined or Little Miami River Aquifer 887 14

Sum of Population Served by Level I Wells: 887
Sum of Population Served by Level I Wells x 10: 8,870 (Ref. 1, Section 3.3.2.2, p. 51603).

Level I Concentrations Factor Value: 8,870

3.3.2.3 Level II Concentrations

Level I I Well Level I I Population Targets
For municipal well PW -1 , the population allocated was 0 individuals ( PW

- 1 provided 0 gallons in 2007). For municipal well PW

- 2, the population allocated was 4,404 individuals (79.4 percent of 5,546 individuals). The Level II wells are documented in Tables 8 and 12. Table 14 summarizes the Level II population affected by PW -1 and PW-2, which are completed in the Little Miami River aquifer.

TABLE 14 LEVEL I I POPULATION Aquifer Population Reference PW

- 1 Unconfined or Little Miami River Aquifer 0 14

PW

- 2 Unconfined or Little Miami River Aquifer 4,404 1441 Sum of Population Served by Level I I Wells: 4,404 (Ref. 1, Sectio n 3.3.2.3, p. 51603).

Level I I Concentrations Factor Value: 4,404

3.3.2.4 Potential Contamination
Because Level I and II concentrations provide the maximum score for the ground water migration pathway, the potential contamination factor was not scored for this HRS documentation record package. Although potential contamination was not scored, there is a concern about populations that could be exposed to contaminated drinking water.

Potential Contamination Factor Value: Not Scored

3.3.3 RESOURCES
Ground water within the 4

- mile radius TDL is not used as a resource (Ref. 14, p. 3 ; Ref. 15, p. 2). Therefore, the Resources Factor was assigned a value of 0 (Ref. 1, Section 3.3.3, p. 51604).

Resources Factor Value: 0

3.3.4 WELLHEAD PROTECTION AREA
There is no Wellhead Protection Area in the area of contaminated ground water (Ref. 1, Section 3.3.4, page 51604; Ref. 14, p. 1; and Ref. 19, p. 10). The Milford Water Department is currently working under the direction of OEPA to formulate a Wellhead Protection Program (Ref. 14, p. 1; Ref. 19, p. 10). Therefore, the Wellhead Protection Area Factor was assigned a value of 0 (Ref. 1, Section 3.3.4, p. 51604).

Wellhead Protection Area Factor Value: 0

3.3.5 CALCULATION OF TARGET S FACTOR CATEGORY VALUE The total target factor category value is the sum of the nearest well, population, resources, and wellhead protection area values (Ref. 1, Section 3.3.5, p. 51604). The total target factor category value for the site is 50 (nearest well) + 1 3,274 (population) + 0 (resources) + 0 (wellhead protection area) = 13,324.