US EPA RECORDS CENTER REGION 5

Dover Chemical Superfund Site

Proposed Plan

Dover, Ohio

June 2015

This Proposed Plan provides a description of the Dover Chemical Corporat ion Site ("Site"),

identif ies the Preferred Remedial Alternative ("Preferred Alternative") for the off-site

groundwater plume, and provides the rationale for this preference. In addit ion, the Proposed

Plan includes summaries of other cleanup alternatives evaluated to address the off-site

groundwater plume associated with the Site.

The alternatives discussed in this Proposed Plan relate only to the off-site groundwater

contaminat ion associated with the Site. As part of an Administrat ive Order by Consent issued

in October 2000, Dover Chemical is addressing the contaminated groundwater on-site via a

pump and treat system. This system captures contaminated groundwater on-site so that it

does not migrate off-site, and treats the contaminated water via air stripping before

discharging to a nearby surface water body under an NPDES permit. Dover Chemical has also

instal led soil vapor extraction systems at two locations on-site to address contaminant source

areas. These systems reduce contaminant mass within ongoing sources in the vadose zone.

These on-site activities are reducing contaminant mass in the subsurface, and minimizing

groundwater contaminant migration off-site. The on-site activities are explained later in this

document .

This document is issued by the United States Environmental Protection Agency (EPA), the lead

agency for Site activities, and the Ohio Environmental Protection Agency (OEPA), the support

agency. Following issuance of this Proposed Plan, and after considering any and all public

comments received during the 30 day public comment period, EPA, in consultation with OEPA,

will select a final remedy for the off-site groundwater plume. This final remedy will be

presented in a document called a Record of Decision (ROD). EPA, in consultation with OEPA,

may modi fy the Preferred Alternative or select another response action proposed in this Plan

based on new information or public comments. Therefore, the public is encouraged to review

and comment on all of the alternatives presented in this Proposed Plan.

EPA is issuing this Proposed Plan in accordance with Section 117 of the Comprehensive

Environmental Response, Compensat ion and Liability Act of 1980 (CERCLA), as amended by the

Superfund Amendments and Reauthorization Act 1986 (SARA), which requires the issuance of

decision documents for remedial actions taken pursuant to Sections 104 ,106 ,120 , and 122.

The Proposed Plan is also part of EPA's public participation responsibil it ies under 40 CFR

300.430(f)(2) of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP).

This Proposed Plan summarizes information that can be found in greater detail in the Remedial

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Investigation/ Feasibility Study (RI/FS) report, the Feasibility Study Addendum II (FSA- II), and

other documents contained in the Administrat ive Record file for the Site.

EPA and the State encourage the public to review these documents to gain a more

comprehensive understanding of the Site and the extensive Superfund activities that have been

conducted at the Site to date.

I. SITE HISTORY

The Dover Chemical Corporat ion Site (Site) is an operating chemical manufacturing plant

located in Dover, Ohid. The facility currently produces, alkyl phenols, chlorinated paraffin and

organophosphites. The chlorinated paraffin are used for metal working lubricants, f lame

retardants, and plasticizers for vinyl products; and the organophosphites are additives used in

the polyolef in, rubber and vinyl industries. The first facil it ies at the site were constructed

before Wor ld W a r II, and the plant has continuously manufactured chemicals f rom the 1940's

to the present.

The Site is approximately 60 acres in size and consists of a main plant area east of Interstate 77

(1-77) along with an abandoned canal/ lagoon area, and a wooded low lying area west of 1-77.

Land use surrounding the facility is varied and includes industrial, commercial and residential

areas. Industrial facilities are located to the north and south. Several blocks of residences are

located east of the Site and extend to the north and south. Figure 1 presents a site map.

Operations at the plant have resulted in releases of organic compounds to the ground surface

and ult imately to the groundwater at the Site. The compounds released on-site included

chlorobenzenes; carbon tetrachloride (CCI4); polychlorinated dibenzodioxins and

polychlorinated dibenzofurans ([PCDDs/PCDFs], a group of compounds referred to collectively

as "dioxins"); and other chemicals. Activit ies that caused the releases of compounds to the

environment include disposal of still bottoms f rom a chlorobenzene distillation process in a low

lying area in the southwest part of the plant area known as Area H; temporary storage of

hexachlorocyclohexane (commonly known as benzene hexachloride or BHC) near building 21 in

the area known as Area G, in the center of the plant; and various spills, tank and piping leaks,

and other unintentional discharges during the 1950s, 1960s, and 1970s. Raw materials f rom

the phenol process used to manufacture chlorobenzenes are believed to have contained

dioxins that were concentrated in the still bottoms deposited in Area H (see Figure 2).

II. Clean-up and Investigative activities to date

Since 1981, mult iple environmental investigations have been conducted at the Site to assess

the impact of contaminat ion to the environment. These investigations identif ied high

concentrat ions of hazardous substances in soil on-site and in groundwater both on-site and off-

site. Substances identif ied on-site include: CCL4, chloroform, monochlorobenzene (MCB), 1,2-

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dichlorobenzene (1,2-DCB), 1,3- dichlorobenzene (1,3-DCB), 1,4-dichlorobenzene (1,4-DCB),

1,2,4-trichlorobenzene, dioxins, hexachlorobenzene (HCB), and tr ichioroethene (TCE). Off-Site

groundwater sampling at the t ime found that similar chlorobenzene compounds had migrated

off-site and created an off-site groundwater plume of contaminat ion.

On October 23 ,1981 , EPA issued a 3007 and 3013 Resource Conservation and Recovery Act

order to Dover Chemical Corporat ion (Dover) to study and address soil and groundwater

contaminat ion at the Site. Af ter complet ing the study, Dover removed approximately 6,800

cubic yards (yd 3) of contaminated soil and waste from the site. In 1982, organic compounds

were detected in a water supply well located on the Dover plant property. As a result of this

f inding, Dover initiated addit ional investigations in 1983, to better define the nature and extent

of soil and groundwater contaminat ion associated with the Site.

Between 1983 and 1986, Dover conducted several addit ional voluntary investigations at the

Site. As part of these investigations, Dover installed groundwater monitor ing wells around the

Site. The investigations revealed addit ional locations of groundwater and soil contaminat ion.

These investigations also indicated that contaminated groundwater had migrated southward

beyond the boundary of the plant property.

In 1986, Dover submitted a draft Feasibility Study to EPA and OEPA. After review of this

document , the EPA determined that addit ional investigation would be required to determine

the nature and extent of the contaminat ion associated with releases at the property.

Based on information gathered from all the years of investigative work conducted at this Site,

four areas of concern were identif ied. These areas are identif ied as fol lows:

• Plant area soils

• Lagoon and canal area soils

• Plant area groundwater

• Off-site groundwater plume

Dover entered into a three party Administrat ive Order by Consent (AOC) with EPA and OEPA on

August 24 ,1988. Under this Order, Dover agreed to complete a Remedial Investigation and

Feasibility Study (RI/FS).

During the Rl investigation conducted under the 1988 order, addit ional chemicals of concern

[dioxins and BHC] were discovered in soils on-site. The scope of the 1988 Rl investigation was

expanded to include the characterization of the environmental media at the site for these

addit ional constituents.

Based on the concentrations of the addit ional chemicals found, the EPA requested that Dover

conduct an interim removal action on-site to reduce the mobil ity and potential for contact with

plant area soils containing dioxins. On July 12, 1991, Dover and EPA entered into an

Administrat ive Order of Consent to conduct inter im soil cleanup on-site and at adjacent off-site

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roadways used by Dover Chemical truck traffic. The Interim soil cleanup was taken to mitigate

direct human exposure and included the fol lowing:

• Excavation and removal of off-site soils above the EPA residential area soil cleanup

standards for dioxin (1 part per billion (ppb)) and securing on site soils;

• Capping active plant areas;

• Securing inactive areas with contaminant levels above the soil cleanup standards by

installing snow fencing to prevent access;

• Fencing the entire plant area to maintain security and prevent unauthorized access;

• Reducing the average dioxin soil concentrat ion on the Armory property adjacent to the

Site to below the soil clean up standard by removing the soil in area M and adding 6

inches of clean fill and paving to area AC; and

• Removing soil above the soil cleanup standard for dioxin and installation of a parking lot

and top soil to the east of Building 31 (Area P and part of Area K).

The Armory property and Areas M , AC, P, and K are depicted in Figure 2. The interim action was

completed in late 1994.

In 1993, EPA proposed the Site to the National Priorities List (NPL). The Site has not been

finalized on the list.

In 1994, Dover submitted an expanded RI/FS. EPA did not approve the risk assessment port ion

of the 1994 RI/FS and conducted an independent risk assessment to evaluate risks at the Site.

In August 1999, after reviewing information in the submit ted 1994 RI/FS, the 1995 baseline risk

assessment, the previous removal activities completed at the Site and current site condit ions,

EPA made a determinat ion that a non-t ime critical removal action would be appropriate to

address the plant area soils, lagoon and canal area soils, and the plant area groundwater to

prevent and mitigate further releases of hazardous substances to the environment. On October

20, 2000, Dover and EPA entered into an Administrative Order on Consent to conduct a non-

t ime critical removal actions in the on-site areas identif ied at Dover. The off-site groundwater

plume that has spread south of the facility was evaluated consistent with the 1988 RI/FS AOC.

Soil removal work in the plant area, lagoon area and canal area was completed by Dover in

recent years to address dioxin contaminated soils as wel l as other source areas identif ied as

part of the 2000 AOC. Some of the major areas excavated on-site are identif ied on Figure 3. As

work cont inued to address the on-site environmental issues via the 2000 non-t ime critical

removal act ion, Dover expanded the groundwater monitor ing network and col lected addit ional

data to evaluate the nature and extent of the groundwater plume that extended south of the

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facil ity (off-site groundwater plume) in order to have enough information to determine how to

address it properly.

Il.a. OFF-SITE GROUNDWATER MONITORING

Between 2000 and 2008, Dover Chemical worked with EPA and OEPA to better define the off-

site groundwater p lume. Addit ional groundwater monitor ing wells were installed and a long

term groundwater monitor ing plan to collect groundwater samples quarterly was implemented.

The groundwater investigations identif ied three primary zones within the aquifer. Those zones

are identif ied as fol lows:

Moni tor ing wel l zone

designation

Screening location below the

water table

A-Zone 0-9 feet

B-Zone 35-50 feet

C-Zone 80-90 feet

Early investigations identif ied contaminat ion migrating off-site below A-zone. Off-site B-zone

wells were found to have contaminants associated with on-site contaminat ion above drinking

water standards. Groundwater in the C-zone was below clean-up standards set for on-site

contaminat ion.

Dover has conducted quarterly groundwater monitor ing since 2005. Based on the risk

associated with contaminants in the off-site B-zone groundwater p lume, nine contaminants of

concern (COC) were identif ied. Concentrat ions of these contaminants have shown a general

decrease over t ime. Recent maximum concentrat ions of each contaminant (detected during

quarterly sampling in 2013 and 2014) for each contaminant are shown in the fol lowing table:

Off-Site Groundwater - Max imum Recent Contaminant Concentrat ions (B-Zone)

September 2013 - June 2014

Max imum

Concentrat ion

Off-Site Wel ls We l l # MCL (ug/l)

Benzene 0.36J MW-25B 5

monochlorobenzene 360 M W 2 3 B 100

Chloroform 0.28 M W 2 5 B 100

1,2, dichlorobenzene 1700 M W 3 1 B 600

1,3 dichlorobenzene 300 M W 3 1 B N/A

1,4 dichlorobenzene 1400 M W 3 1 B 75

1,2,4 trichlorobenzene 8.7 M W 3 9 B 70

1,1 dichloroethane 6.1 M W 35B 7

5

trichioroethene 16 M W 3 1 B 5

J= estimated value

li b. 2013 FEASIBLITY STUDY - ADDENDUM II

Dover completed several FS studies as part of the investigative work conducted since 1981. In

1996, an FS was completed as part of the 1983 AOC. The off-site groundwater port ion of this FS

was not approved and EPA requested that an addendum be completed to look at ways to

address this contaminat ion. In 2001, Dover submitted an FS Addendum for the off-site

groundwater p lume, which required addit ional work.

Dover prepared an FSA work plan to gather additional data to fully evaluate monitored natural

attenuation as viable groundwater cleanup option and prepared a second Feasibility Study

Addendum (referred to as the 2013 FSA-II).

Dover installed an extensive network of piezometers which demonstrated an inward

groundwater f low gradient toward the facility. The existing groundwater pumping scheme,

which operates as part of the 2000 NTCRA AOC, effectively prevents contaminated

groundwater f rom leaving the site.

The 2013 FSA-II provided the fol lowing information about the off-site p lume:

• the conceptual mode l ;

• the stabil ity of the aquifer such that the plume is not changing over t ime;

• three dimensional del ineat ion of the plume;

• the geochemical condit ions; and

• microbial populat ion and compound specific isotopes to evaluate whether the in-situ

microbial populat ion is appropriate to biodegrade the plume contaminants.

The work indicates that (1) the off-site groundwater p lume is stable in size and is not

expanding; (2) the groundwater pumping system has maintained capture of contaminated

groundwater on-site and contaminated groundwater is no longer migrating off-site; (3)

geochemical condit ions within the off-site groundwater plume indicate that natural attenuation

including biological processes is naturally occurring in the aquifer; and (4) modif icat ion of the

geochemical condit ions in the off-site plume could accelerate these biological processes and

help reduce contaminant concentrat ions within the plume.

Figure 4 shows the est imated boundaries of the B-zone off-site groundwater plume where total

chlorobenzenes exceed 100 ug/ l , as of March 2014. This is the plume that wil l be addressed by

this action.

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Il.c. ON-SITE ACTIVE REMEDIATION

Soil Vapor Extraction (SVE)

To address contaminant sources located in the plant area on-site, Dover implemented a Soil

Vapor Extraction (SVE) systems in Area G beginning in 2005. Nearly 50,000 pounds of VOCs

have been removed f rom the subsurface to date. In 2014, Dover Chemical added a second SVE

system in Area H to accelerate groundwater cleanup in the plant area (see Figure 2). SVE may

be expanded to other areas of the plant in the future.

Groundwater Pump and Treat System

Dover has used groundwater for non-contact cooling water since the beginning of plant

operat ions. Addit ional product ion wells were installed in 1988 (PW-5) and 1992 (PW-6) to

increase plant cooling water capacity and to keep groundwater contaminat ion f rom moving off-

site. Pumping wells PW-7 and PW-8 were installed in December 2000, and PW-9 was installed

in 2004, to minimize mobil izat ion of dioxins and to further reduce the potential for

contaminants to migrate off-site through groundwater. Figure 2 identif ies the locations of the

current pumping wells. Extracted groundwater is treated by air str ipping to remove VOCs

before discharge to Sugar Creek under a National Pollution Discharge Elimination System

(NPDES) permit.

Dioxins are relatively insoluble, and are believed to have migrated to the aquifer beneath the

Dover facility in organic liquids. Subsequent dissolution of those liquids is believed to have left

the dioxins in the aquifer as small particulates that may be mobi l ized by groundwater pumping.

Wi th the discovery of dioxins in groundwater on-site, the pumping system was reassessed to

help determine an optimal pumping scenario for the product ion/remediat ion wells so that

Dover could continue to recover VOCs without causing migration of dioxins. After a fai led

at tempt in 2005-2007 to optimize the pumping scheme to achieve this goal, Dover is currently

evaluating a revised scheme (pumping scenario 2013A).

III. COMMUNITY INVOLVEMENT ACTIVITIES TO DATE

Various public meetings and availability sessions were held in the Dover, Ohio area when the

various investigation activities, interim actions, and removal actions were being conducted.

EPA has a Site information repository at the Dover Public Library in Dover, Ohio. EPA also

maintains a Site web page located at

h t tp : / /www.epa.gov/R5Super /np l /oh io /OHD004210563.html . The web page and information

repository are regularly updated with current Site information. The public is encouraged to visit

the website and information repository for information regarding Superfund work at the Site.

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IV. SITE CHARACTERISTICS

The Site is located in Tuscarawas County in east central Ohio. The facility is located off of

Interstate 77, and consists of four parcels of land encompassing approximately 60 acres near

the City of Dover city limits. The City of Dover, Ohio has a populat ion of approximately 13,000.

Land use around the Site is varied and includes industrial, commercial , and residential areas.

The Site is located on a meander plain of Sugar Creek that overlies a buried valley fil led with

glaciofluvial sediments comprised primarily of sand and gravel. The buried valley varies

between 0.5 and 2 miles wide and is up to 290 feet deep. In the vicinity of the off-site

groundwater plume, the buried valley is greater than 200 feet deep. The upper foot of soil is

predominant ly fine grained that transit ions to coarse sand and gravel below 10 feet. The

permeable outwash deposits result in a relatively homogenous and isotropic aquifer. These

deposits are underlain by inter-bedded layers of marine sandstone, shale, l imestone, and coal.

Locally these consol idated sedimentary strata appear to be horizontal.

Monitored Natural Attenuation Analysis of Off-Site Groundwater Plume

Moni tored Natural Attenuation (MNA) is the reliance on natural attenuation processes to

achieve site specific remedial objectives within a t imeframe that is reasonable compared to

other remedial actions being considered to address site contaminat ion. The natural processes

that are at work in this approach under favorable condit ions include a variety of physical,

chemical or biological processes such as diffusion, dispersion, adsorpt ion, and degradation, that

act without human intervention to reduce the mass, toxicity mobil ity vo lume or concentrat ions

of contaminants in soil or groundwater. Natural attenuation processes typically occur at all

sites, but to varying degrees of effectiveness depending on the types and concentrat ions of

contaminants present and the physical, chemical and biological characteristics of the

groundwater.

The off-site groundwater plume has been defined in three dimensions by the existing

monitoring wel l and piezometer network. Data has been collected to support the consideration

of natural at tenuat ion including trend analysis, geochemical data, compound specific isotope

analysis, and molecular biological assessment with and without in-situ amendments . Table 1 is

a summary of wel l identif ication numbers, locations in relationship to the off-site plume (i.e.

upgradient, bounding, plume, sentinel), roles of the wel l (i.e. transect, centerl ine), sampling

dates, and f ield and laboratory analysis methods for monitor ing wells screened in the B-zone of

the aquifer.

Groundwater elevation data has been col lected at the off-site groundwater plume quarterly

since 2005. A complete set of groundwater elevation data was collected in June 2012 f rom all

locations, both on-site and off-site, to gain an accurate picture of groundwater f low within the

on-site and off-site B-zone plume. Figure 5 presents contour map of the B-Zone groundwater

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potent iometr ic surface (35-50 feet below the water table) using a 0.5 foot contour intervals for

the off- site plume. The groundwater f low regime is wel l established and well understood.

Trend Analysis

Chlorinated benzene compounds are the predominant contaminants in the off-site

groundwater plume. The heart of the off-site plume is downgradient of the natural f low field

f rom a known source area on-site identif ied as the former fractionation tower area (see Figure

2). Although on-site groundwater is captured by the pumping of non-contact cooling water, it

is likely that desorpt ion f rom soils in the saturated zone off-site continues to contr ibute

chlor inated benzenes to off-site groundwater and on-site groundwater near the extreme

southern boundary of the site at MW-39B .

Since March 2005, Dover Chemical has col lected quarterly groundwater monitor ing data. In

general , contaminant concentrat ions of M C B , 1,2-DCB, and 1,4-DCB have decreased over t ime

and with distance f rom the Site. In May 2013 DCBs and M C B concentrat ion plume maps were

prepared using data col lected from the B-Zone of the aquifer f rom March 2005 and March 2012

to illustrate concentrat ions of MCB and DCBs both on-site and within the off-site plume. Figure

6 of this proposed plan, was prepared using the same data set only using concentrat ions for

total chlorobenzenes (both M C B and DCBs) in the off-site plume, to help illustrate this point.

Both sets of plume maps show that the overall contaminant concentrat ions have decreased and

the area encompassed by the offsite plume has shrunk between 2005 and 2012.

Trend analysis of total DCB and MCB concentrat ions for quarterly events f rom 2005 to 2012,

using data points along the center line of the off-site groundwater plume at MW-39B (0.1 mile

f rom the Site), M W - 2 5 B (0.3 mile f rom the Site), MW-31B (0.5 miles f rom the Site) and MW-38B

(0.9 miles from the Site) are presented in Figures 7 and 8.

The trend analysis for DCB concentrat ions il lustrated in Figure 7 indicates that DCB

concentrat ions decreased .over t ime at M W - 3 9 B (near the southern boundary of the Site) and

M W - 2 5 B (0.3 miles downgradient f rom the Site), increased at M W - 3 1 B (0.5 miles downgradient

f rom the Site), and were not detected at downgradient sentinel wel l location M W - 3 8 B (0.9

miles downgradient f rom the Site). The trend analysis for M C B concentrat ions il lustrated in

Figure 8 indicates that M C B concentrations were below the MCL at MW-39B and trending

slightly down f rom 2005 to 2012. At MW-25B , M C B concentrat ions t rended down toward

levels below the MCL. At MW-31B , MCB concentrat ions were highly variable with no apparent

t rend and were generally above the MCL. At sentinel well MW-38B, M C B concentrat ions

t rended up slightly, but concentrations remained below the MCL. This apparent increase in

M C B downgradient may reflect degradation of DCBs to an MCB intermediate.

Figure 9 presents M C B and total DCB concentrat ions and trend lines f rom March 2005 through

March 2012 for three wells within the most contaminated part of the offsite plume: M W - 2 5 B ,

M W - 3 1 B , and M W - 3 7 B . The figure illustrates concentrat ion trends over t ime, and shows that

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M C B and DCB concentrations in wells M W 25B and M W 37B have decreased over t ime since

2005. At M W - 3 1 B , MCB concentrat ions decreased by about 35% and DCB concentrat ions

decreased by about 45% from 2005 to 2012. At M W - 3 7 B , M C B concentrat ions decreased by

about 35%, and DCB concentrat ions decreased by about 65% f rom 2005 to 2012. M C B and DCB

concentrat ions in well M W - 3 1 B vary irregularly and do not show a clear trend over the t ime

period considered. MCB concentrat ions wells M W - 3 1 B and M W - 3 7 B have trended to below

the MCL f rom 2005 to 2012.

The total mass of the plume was analyzed using the same data set used for evaluation of the

feasibil ity study. The results of this analysis are presented in the FSA-II. In broad terms, the

analysis shows that DCB mass decreases over t ime and MCB mass increases over t ime,

support ing the conclusion that natural attenuation processes are reducing the DCB

concentrat ions and producing M C B along the centerl ine of the off-site plume.

Geochemical conditions

A site specific study was completed for the Site to determine if natural attenuation is ongoing in

the off-site groundwater plume and whether enhancement through the manipulat ion of

groundwater biogeochemistry wou ld be beneficial. Seventeen monitor ing wells located within

the off-site groundwater plume were identif ied for analysis during 4 quarters of sampling (June

2011, September 2011, December 2011 and March 2012). The fol lowing sections of this

proposed plan summarize the geochemical testing conducted.

Dissolved Oxygen (DO) - DO was monitored to assess the current level of oxygen in the B-zone

horizon of the aquifer where contaminat ion has been found. DO data are essential for

understanding the type of bacteria that may be active in the aquifer and how biodegradation of

VOCs of interest could potentially be enhanced. DO levels in the off-site plume indicate that

anaerobic condit ions prevail in the B-Zone groundwater within the area of the off-site plume.

However, previously collected DO data indicate that strongly aerobic condit ions (DO

concentrat ions > 10 mg/L) prevail both upgradient f rom the Site and in the A-Zone directly

above the off-site plume, strongly suggesting that the natural geochemical condit ions of the

aquifer are aerobic. Anaerobic condit ions within the plume may be caused by the presence of

contaminants; the naturally occurring oxygen in the groundwater may be nearly completely

consumed by microorganisms as they metabolize contaminants.

pH - pH was monitored to determine relative groundwater acidity that may inhibit biological

communi ty health and for evidence of pH depression due to format ion of carbon dioxide,

generated as a byproduct during biodegradation of chlorine organic contaminants. Microbial

activity general ly requires a pH range of 6 to 8. Groundwater pH levels were primarily between

7 and 8.

Eh - Eh was monitored to gather information regarding redox condit ions, which indicate

whether the B-Zone horizon of the aquifer at a particular well location is a reducing or oxidizing

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environment. Understanding existing redox condit ions is essential in evaluating how to

manipulate the subsurface to facilitate in-situ biological contaminant destruct ion. Results

indicate a mild to moderately reduced groundwater capable of support ing reductive

dechlorinat ion of chlorinated VOCs.

Carbon Dioxide (CO2), Chloride - CO2 and chloride were moni tored for evidence of natural

degradation of chlorinated organics in the groundwater. The presence of elevated chloride in

conjunction with elevated CO2 can in some instances provide a line of evidence of natural

degradation of chlorinated organic groundwater contaminants. Carbon dioxide is formed

during the metabol ic processes of many biodegradation reactions and is also used as an

electron acceptor during the process of methanogensis. Results of these indicators suggest

intrinsic biodegradation is occurring in the heart of the off-site plume.

Dissolved gases: methane, ethene, ethane - Methane forms under strongly reducing

condit ions while ethene and ethane can be generated from the degradation of chlorinated

aliphatic organic contaminants. Methane can be used as a co-metabol i te in the aerobic

degradation of chlorinated compounds. Methane was not detected in the background well and

both ethene and ethane were not detected at any locations throughout the off-site

groundwater p lume. This suggests that the natural condit ion of the aquifer is not strongly

reducing, and that high concentrat ions of ethene and ethane are not present within the offsite

plume.

Table 2 presents geochemical parameters and VOC concentrat ions within the offsite plume and

boundary wells. A full explanation of these geochemical results can be found in the FSA-II

completed for the site.

Biotrap Sampling

Biotraps (also called in-situ microcosms) were used to collect samples for compound specific

isotope analysis (CSIA) and microbial populat ion monitor ing within the off-site groundwater

plume. Both un-baited biotraps (to determine baseline condit ions within the aquifer) and

baited biotraps (which included amendments to help evaluate potential for biological

enhancement within the aquifer) were deployed and analysed.

Quantitative polymerase chain reaction (qPCR) was used on bacteria collected from the

biotraps to identify specific enzymes present that could only be created by certain bacteria

known to degrade chlorinated aliphatic compounds. The biotrap analyses identif ied populations

of the fol lowing microbes and genes on certain unbaited biotraps:

• Dehalococcoides (DHC);

• Dehalobacter(DHBt) ;

• Methane oxidizing bacteria (MOB);

• tceA reductase (TCE);

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• vinyl chloride reductase (VCR);

• soluble methane monoxygenase (sMMO) ;

• phenol hydroxylase (PHE); and,

• to luene dioxygenases (TOD).

The qPCR baseline analysis identif ied concentrat ions of DHC (produced by reductive

dechlor inat ion of TCE); DHBt (produced by reductive dechlorination of M C B and DCBs); and PHE

and TOD (produced by oxidation of DCBs) without the addit ion of amendments. PHE and TOD

are bacterial oxygenase genes that are involved with the biodegradation of aromatic

compounds such as chlorobenzenes. These functional genes were detected in each of the bio

traps. Numbers of PHE and TOD genes detected were higher in baited bio traps f rom the same

wells indicating that the aquifer could benefit f rom an amendment to accelerate the

attenuat ion of chlorobenzenes in the plume.

Dehalococcoides populations, including TCE reductase gene (tceA), and the vinyl chloride genes

(VCR and BVC), are dechlorinating bacteria that are present in some anaerobic aquifers and are

wel l documented degraders of TCE. Limited populations of cells containing the DHC and the

TCE funct ional genes were detected in the traps.

Compound Specific Isotope Analysis (CSIA)

The recently developed field of CSIA has emerged as a tool that has proven useful in certain

chlor inated organic groundwater contaminat ion situations to assess the occurrence of

biodegradation of certain compounds. CSIA can be used to distinguish contaminant

degradation caused by biological processes f rom physical processes. A number of samples were

col lected and analyzed using CSIA in October 2011 and March 2012. There were some

difficulties with these sample analyses, however, the M C B generally became enriched in

heavier isotopes as it moved downgradient, support ing the overall conclusion that M C B

degradation is occurring within the natural environment and can be bioenhanced. A full

explanation of this CSIA sampling can be found the FSA-II.

V. SCOPE AND ROLE OF THE ACTION

The action proposed in this plan is the remedial act ion for the Off-Site Groundwater Plume.

EPA's strategy is to address areas within the off-site plume identified as hot spots and then

monitor the plume over t ime with additional amendment injection(s) as required.

A hydrostratigraphic interval of groundwater contaminat ion (B-Zone) has been established

below the upper 10 feet of saturated thickness and is monitored in a zone from approximately

35 to 50 feet below the water table by the off-site B-Zone series of monitoring wells. This zone

of groundwater contamination is overlain by a layer of clean groundwater, referred to as the A-

12

Zone. The aquifer below the B-Zone, the C-Zone, is generally free of Site contaminants. As a

result, the off-site plume extends southeast f rom the Site and is bounded in three dimensions.

Monoch lorobenzene (MCB) is intermittently present above the MCL in the A-Zone and the B-

Zone at M W - 5 1 located at the leading edge of the plume along West Third Street.

Tr ichioroethene (TCE) is consistently present above the MCL in the A-Zone and B-Zone at M W -

51, however, there is some debate over whether the TCE at this location is associated with the

Dover Site or if this contaminant is coming from another source in the area. EPA and OEPA

agree that the source of the TCE within the vicinity of West Third Street is undetermined at this

t ime, and may have originated from a source or sources unrelated to the Dover Site (see Figure

10). This area wil l continue to be monitored as part of the long term monitoring program and if

it is determined remedial action is necessary to address this area, EPA, in consultation with

OEPA, will determine a course of act ion.

VI. SUMMARY OF SITE RISKS

In May 1995, a Baseline Risk Assessment was completed for the Dover Site that included both

an on-site and off-site risk evaluation as wel l as an ecological assessment. Potential off-site

residential exposure to groundwater was evaluated as part of the 1995 baseline risk

assessment. This assessment considered potential off-site residential groundwater exposure

via three exposure pathways: (1) ingestion, (2) inhalation of VOCs during showering, and (3)

dermal contact during showering. However the 1995 off-site groundwater evaluation was

based on exposure point concentrat ions (EPC) calculated using analytical results f rom six on-

site monitoring wel ls, a majority of which were screened in the shallow portion of the aquifer

beneath the site. Therefore a risk assessment for the off-site port ion of the plume was recently

conducted.

Superfund Human Health Risk Assessments (HHRAs) are typically prepared fol lowing the

process in EPA's Risk Assessment Guidance for Superfund (RAGS) documents. Because EPA only

updated the HHRA completed in 2005 for the off-site plume, an alternative "rat io" approach

was used to evaluate the current HHRA.

RISK ASSESSMENT METHODOLOGY

A HHRA typically consists of four general components:

1. Data Evaluation and Selection of Chemicals of Potential Concern (COPC)

2. Exposure Assessment

3. Toxicity Assessment

4. Risk Characterization

In a typical Superfund HHRA, medium-specif ic analytical data col lected as part of an Rl are

evaluated and screened using medium-specif ic screening levels to identify contaminants of

13

potential concern. A conceptual site model (CSM) is developed to present the potential sources

of site-related contaminat ion and the release and transport mechanisms by which

contaminat ion moves f rom the sources into and through the environment, resulting in actual or

potential human exposure at various locations via various exposure pathways. Exposure

parameter values are assumed to characterize a reasonable maximum exposure (RME)

condit ion for each of the receptor-specif ic exposure pathways identi f ied. These exposure

assumptions are used to calculate chemical- and pathway-specif ic exposure doses for each

receptor identif ied.

Next, pathway-specif ic cancer and non-cancer-based toxicity factors are identified for each of

the COPCs in accordance with EPA's preferred toxicity factor hierarchy. Finally, the exposure

doses calculated under RME condit ions are combined with the toxicity factors to quantify

chemical , pathway, and receptor-specif ic cancer risk and non-cancer hazards. The risks are

compared with EPA's acceptable risk range (1E-06 to 1E-04) and a target hazard index of 1.

The alterative " rat io" approach used to prepare the off-site HHRA for this action is discussed

below.

SITE-SPECIFIC RATIO APPROACH

The ratio approach used to evaluate off-site risk in this case, involves calculating the ratio

between concentrations in groundwater and EPA tapwater regional screening levels (RSLs) to

evaluate chemical-specif ic risks and hazards. The tapwater RSLs are calculated concentrat ions

in groundwater that incorporate EPA-approved residential exposure assumptions and chemical-

specific toxicity factors. Risks and hazards are calculated for COPCs selected according to RAGS

guidel ines.

Data Evaluation and Selection of COPCs

The off-site B-Zone groundwater contaminat ion was evaluated in the risk assessment. B-Zone

has the highest contaminant concentrations. VOCs are typically either not detected in the A

and C-Zones, or are present at concentrations several orders of magnitude below

concentrat ions in the B-Zone.

COPCs (and EPCs for each of these COPCs) were calculated using the most recent four quarters

of analytical data from the center, most concentrated area of the groundwater plume. The B-

Zone monitor ing wells used for this evaluation include MW-23B , M W - 2 5 B , MW-31B, M W - 3 5 B ,

M W - 3 7 B , and MW-39B (see Figure 4).

Table 3 outl ines the occurrence, distribution and selection of COPCs in the off-site plume.

The 1995 HHRA identif ied chlorinated organics (primarily VOCs), a l imited number of pesticides

(including B-BHC and lindane [gamma-BHC]), 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), and a

single metal (manganese) as Contaminants of Potential Concern (COPCs) in groundwater.

However, non-VOC COPCs were not detected, were detected at levels below their screening

levels, or were detected at concentrat ions below background in the off-site groundwater.

Therefore, off-site VOC groundwater data only was necessary for the risk assessment.

14

EPA reviewed the most recent VOC data f rom September 2013, December 2013, March 2014

and June 2014, collected from the six B-Zone wells identif ied above, and compared the

analytical results with EPA tapwater RSLs (based on a target risk of 1E-06 and a target hazard of

0.1). The fo l lowing 10 VOCs were detected in off-site groundwater at concentrat ions greater

than their EPA tapwater RSLs and represent the off-site ground water COPCs:

• Benzene

• Chloroform

• 1,2-DCB

• 1,3-DCB (screened using 1,2-DCB as a surrogate)

• 1,4-DCB

• 1,1-Dichloroethane

• Monochlorobenzene

• Tetrachloroethene

• 1,2,4-Trichlorobenzene

• TCE

HUMAN HEALTH RISK ASSESSMENT (HHRA) CONCLUSIONS

Only residential receptors were evaluated in the off-site groundwater HHRA. Residential

receptors are considered the reasonable maximum exposure scenario, and a conservative

surrogate for other receptors such as industr ia l /commercial workers and other general

population receptors (such as recreational receptors). Construct ion and utility workers are

unlikely to be exposed to B-Zone groundwater contaminat ion because the B-Zone begins wel l

below the depth of a typical construct ion/ut i l i ty trench or excavation. In addi t ion, the presence

of the over-lying A-Zone groundwater prevents the migration of volati le B-Zone contaminants

into the air wi th in a construction or utility trench.

The 2015 updated HHRA found:

• The total cancer risk is 1E-03, which exceeds EPA's target risk range of 1E-06 to 1E-04.

COPC-specif ic risks are summarized below:

o 1,4-DCB (1E-03) - this risk exceeds EPA's target risk range.

o Benzene (4E-06), chloroform (1E-06), 1,1-dichloroethane (2E-06), 1,2,4-

tr ichlorobenzene (5E-06), and TCE (2E-05) - these risks are within EPA's target

risk range.

o Tetrachloroethene (7E-07) - this risk is less than 1E-06 and considered

insignificant.

15

• The total non-cancer hazard is 10, which exceeds the target hazard of 1. COPC-specif ic

hazards are summarized below:

o 1,2-Dichlorobenzene (2), monochlorobenzene (2), and TCE (3). These hazards

all exceed 1.

o Benzene (0.05), chloroform (0.003), 1,3-DCB (0.4), 1,4-DCB (0.9), 1,1-

dichloroethane (0.003), tetrachloroethene (0.2), and 1,2,4-trichlorobenzene

(1). These hazards are less than or equal to 1 and considered insignificant

individually.

o Collectively, 1,3-DCB, 1,4-DCB, and 1,2,4-trichlorobenzene all affect the same

target organ (liver) with a total hazard of 3.

In summary, there are a total of nine groundwater contaminants of concern (COCs) in the off-

site groundwater plume with risks greater than or equal to 1E-06 or hazards greater than 1

were identif ied (individually or collectively based on target organ):

• Benzene

• Chloroform

• 1,1-Dichloroethane

• 1,2-DCB

• 1,3-DCB

• 1,4-DCB

• Monochlorobenzene

• 1,2,4-Trichlorobenzene

• TCE

Vapor Intrusion

The presence of a lens of uncontaminated groundwater above the contaminated groundwater

in the B-zone of the aquifer limits potential for vapor intrusion in the area above the off-site

p lume. Residential VI exposure would be to VOCs found in the off-site groundwater f rom the A-

zone, rather than the B-zone. Data f rom the A-zone in the off-site plume are l imited to wells

M W 31-A and MW-35A , located in the center of the plume. Review of this l imited data shows

that no samples from A-zone groundwater exceeded the vapor intrusion screening level (VISL)

for any of the VOCs except TCE in Wel l M W 3 1 A , which exceeded the VISL for TCE in 2004, but

did not exceed the VISL in three subsequent samples collected f rom this wel l .

Based on current informat ion, there is no significant VI risk or hazard f rom the off-site

groundwater plume. However, the currently available A-zone wells are located in the main

body of the groundwater plume, which underlies an industrial area, upgradient of the

residential neighborhood where potential VI receptors are located. Future evaluation of the VI

risks to residential receptors is likely as the A-zone plume moves downgradient.

16

VII. REMEDIAL ACTION OBJECTIVES

It is EPA's judgment that the preferred alternative identif ied in this Proposed Plan is necessary

to protect public health, welfare, or the environment f rom actual or threatened releases of

hazardous substances into the environment. Remedial Act ion Objectives (RAOs) are general

descriptions of the goals establ ished for protecting human health and the environment, to be

accomplished through remedial actions. RAOs normally identify the medium of concern, COC,

al lowable risk levels, potential exposure routes, and potential receptors.

The fol lowing RAO has been identif ied for the Dover off-site groundwater p lume: to protect

human health and the environment by preventing residential receptor exposure, via dermal

contact, ingestion, or inhalation of groundwater containing site-related contaminants of

concern exceeding Max imum Contaminant Levels (MCLs). In addit ion, consistent with the NCP

(300.430 (a)(iii)(C)), it is expected that the selected remedial action wil l return the

contaminated off-site groundwater to its beneficial use - drinking water.

The COCs in the off-site groundwater plume and their cleanup standards include:

Groundwater Cleanup Standards

COC MCL (ug/l)

Benzene 5

Monoch lorobenzene 100

Chloroform 80

1,2-Dichlorobenzene 600

1,3-Dichlorobenzene NA

1,4-Dichlorobenzene 75

1,1-Dichloroethane 5

1,2,4-Trichlorobenzene 70

Trichioroethene (TCE) 5

VIII. DESCRIPTION OF ALTERNATIVES

A total of four remedial alternatives were developed to address the off-site groundwater

contaminat ion. The fol lowing cleanup alternatives were evaluated against the nine criteria

identif ied in the National Contingency Plan (NCP). These alternatives are:

• Alternative 1 - No Act ion

• Alternative 2 - Moni tored Natural Attenuation (MNA)

17

• Alternative 3 - Chemical Injection fo l lowed by M N A . Data col lected f rom monitor ing wells

in the off-site plume indicated that certain amendments may accelerate the breakdown of

contaminants within the plume, if appl ied to targeted zones within the aquifer. Each of

the sub Alternative 3 scenarios combines Alternative 2 - M N A with chemical injection in a

gridded area near the Site boundary. Alternative 3B and Alternat ive 3C also include

addit ional amendment injections, down-gradient along the center line of the off-site

plume, as necessary to enhance biological degradation within the plume either aerobically

or anaerobically (see Figure 11). For each of these sub-alternatives EPA anticipates that

Site-specific bench- and / o r pilot test ing will be performed as part of the Remedial Design"

to help determine the optimal implementat ion for this alternative. These sub-alternatives

include:

Alternative 3 A - In-Situ Chemical Oxidation (ISCO) within the injection grid, fo l lowed by

Alternative 2 -MNA in the heart of p lume. This sub-alternative combines ISCO injections

near the origin of the off-site plume wi th an oxidizer to promote in-situ chemical oxidation

of apparent residual source material sorbed to the aquifer, fo l lowed by Alternative 2 -

M N A .

Alternative 3B - ISCO plus aerobic amendments fol lowed by Alternative 2- M N A . This

alternative combines Alternative 3A (ISCO in a grid near the origin of the off-site plume)

and injections of an aerobic amendment in traverses along the center of the off-site

plume as necessary to locally reverse the reducing condit ions of the aquifer to promote

aerobic biodegradation within the offsite plume, fol lowed by Alternative 2 - M N A . This

approach will chemically oxidize the chlorinated benzenes at the origin of the plume and

promote aerobic biodegradation in the center of the plume, as needed.

Alternative 3C - ISCO plus reductive dechlorination fo l lowed by Alternative 2- M N A . This

alternative combines Alternative 3A (ISCO in a grid near the origin of the off-site plume)

and injections of an anaerobic amendment in traverses along the center of the off-site

plume as necessary to enhance reductive dechlorination within the off-site plume. This

approach will chemically oxidize the chlorinated benzenes at the origin of the plume and

promote anaerobic biodegradation in the center of the plume, as needed.

• Alternative 4 - (Also known as Alternative 4B in the FSA II) Groundwater extraction and

treatment by air stripping off- site. This alternative extracts groundwater and treats it at a

location off-site away from the Dover plant area.

Alternative 1: No Action

Estimated Capital Cost: $0

Estimated Total O&M Cost: $0

Estimated Present worth Cost: $0

Estimated Construction Timeframe: none

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Regulations governing the Superfund program require that the "no act ion" alternative be

evaluated to establish a baseline for compar ison. Under this alternative, there would be no

action to address the off-site groundwater plume. The conditions of the off-site plume would

remain unaltered except for changes in condit ions as may occur naturally, without intervention

or other act ion. No groundwater monitoring would occur.

Alternative 2: Monitored Natural Attenuation (MNA)

Estimated Capital Cost: $200,000

Estimated Total O&M: $3,400,000

Estimated Present worth Cost: $1,800,000

Estimated Construction Timeframe: none

This alternative relies on natural attenuation processes to achieve site specific remedial

objectives within a t imeframe that is reasonable compared to other methods. The natural

at tenuat ion processes that are at work in this approach, under favorable condit ions, induce a

variety of physical, chemical or biological processes that act without human intervention to

reduce the mass, toxicity, mobil i ty, volume or concentrat ion of contaminants in soil and

groundwater. Moni tor ing the groundwater plume condit ions until the remedial action

objectives are achieved is part of this remedial alternative.

Alternative 3 A - In-Situ Chemical Oxidation (ISCO) within the injection grid, followed by MNA

in the heart of plume.

Estimated Capital Cost: $2,300,000

Estimated Total O&M: $4,500,000

Estimated Present Worth Cost: $4,800,000

Estimated Construction Timeframe: 1 year

This alternative is a combinat ion of ISCO injections in a gridded area near the origin of the off-

site plume where source material may be sorbed to the aquifer material, fo l lowed by

Alternative 2- M N A . This alternative is designed to reduce the chlorinated benzene levels at the

up-gradient portions of the off-site plume, and ultimately throughout the plume as

groundwater flows down gradient. The injection design consists of a combinat ion of chemical

oxidants such as original Regenesis Oxygen Release Compound (ORC) and RegenOX, injected in

a 54,000 square foot area at the up-gradient portions of the plume. Injecting an amendment to

promote oxidizing condit ions in the up-gradient portions of the off-site plume is intended to

address areas of residual soil contaminat ion below the water table. Re- injections wou ld be

per formed as necessary until contaminat ion in the area of the injection grid is reduced

sufficiently such that cont inued mass loading of the off-site plume has ceased. The remaining

port ion of the off-site plume would be degraded via M N A processes. Site Specific bench-and/or

pilot scale testing would be performed as part of the Remedial Design process. Performance

19

monitor ing would be conducted during the implementat ion of this action to assure the action is

performing as expected.

Alternative 3B - ISCO plus aerobic amendments followed by Alternative 2- MNA.

Estimated Capital Cost: $3,700,000

Estimated Total O&M: $6,000,000

Estimated Total Present worth Cost: $7,400,000

Estimated Construction Timeframe: 3 years

This alternative combines ISCO injections in a grid near the origin of the off-site plume and

injections of an aerobic amendment in traverses along the center of the off-site p lume as

necessary to locally reverse the reducing condit ions of the aquifer to promote aerobic

biodegradation within the offsite plume, fo l lowed by Alternative 2 - M N A . This approach will

chemical ly oxidize the chlorinated benzenes at the origin of the plume and promote aerobic

biodegradation in the center of the plume, as needed.

This alternative wou ld be implemented in a phased approach. The initial phase would include

at least one injection of chemical oxidants in a gridded area near the origin of the off-site

plume, then cont inued groundwater quality and M N A parameter monitoring within the off-site

plume.

After a min imum of four rounds of quarterly monitor ing, condit ions within the off-site plume

would be reviewed and a determinat ion made as to when to inject amendment to stimulate

aerobic bioremediat ion down-gradient off-site in traverses along the center line of the plume.

The amendments would include oxygen and micronutrients to the target zone, such as ORC

Advanced (ORC-A), a Regenesis product. Performance monitor ing would be conducted during

the implementat ion and, based on the monitor ing, the need for addit ional injections wou ld be

evaluated.

Alternative 3C - ISCO plus reductive dechlorination followed by Alternative 2- MNA.

Estimated Capital Cost: $3,300,000

Estimated Total O&M Cost: $6,200,000

Estimated Total Present Worth Cost: $7,200,000

Estimated Construction Timeframe: 3 years

This alternative combines ISCO injections in a grid near the origin of the off-site plume and

injections of an anaerobic amendment in traverses along the center of the off-site plume as

necessary to enhance reductive dechlorination within the off-site plume. This approach will

chemical ly oxidize the chlorinated benzenes at the origin of the plume and promote anaerobic

biodegradation in the center of the plume, as needed.

20

This alternative would be implemented in a phased approach. The initial phase would include

at least one injection of chemical oxidant in a gr idded area near the origin of the off-site plume,

and cont inued groundwater quality and M N A parameters monitoring within the off-site plume.

After a min imum of four rounds of quarterly monitor ing, condit ions within the off-site plume

would be reviewed and a determinat ion made when inject anaerobic amendments in traverses

along the center line of the off-site plume. The injections would include an anaerobic

amendment such as 3-D Micro Emulsion (3-DME), a Regenesis product which stimulates

reductive dechlorination by supplying immediate, midrange and long-term hydrogen to the

target zone within the plume. Performance monitor ing would be conducted during

implementat ion, and based on the monitor ing, the need for addit ional injections would be

evaluated.

Alternative 4 - Pump and Treat by Air Stripping off-Site

Estimated capital Cost: $4,900,000

Estimated Total O&M Cost: $17,600,000

Estimated Present Worth Cost: $12,500,000

Estimated Construction Timeframe: 6 months

This alternative includes the installation of three pumping wells and a treatment building in a

location off-site near the off-site plume, with treated water being discharged to Sugar Creek.

IX. EVALUATION OF ALTERNATIVES

Nine criteria are used to evaluate the different remediat ion alternatives individually and against

each other in order to select a remedy. This section of the Proposed Plan profiles the relative

performance of each alternative against the nine criteria, noting how it compares to the other

options under considerat ion. The nine evaluation criteria are described below. The "Detai led

Analysis of Alternat ives" can be found in the FSA-II.

Overall Protectiveness of Human Health and the Environment determines whether an

alternative el iminates, reduces, or controls threats to public health and the environment

through institutional controls, engineering controls, or t reatment.

Compliance with ARARs evaluates whether the alternative meets federal and state

environmental statutes, regulations, and other requirements that pertain to the site, or

whether a waiver is justif ied.

Long-term Effectiveness and Permanence considers the ability of an alternative to maintain

protection of human health and the environment over t ime.

21

Reduction of Toxicity, Mobility, or Volume of Contaminants through Treatment evaluates an

alternative's use of t reatment to reduce the harmful effects of principal contaminants, their

ability to move in the environment, and the amount of contaminat ion present.

Short-term Effectiveness considers the length of t ime needed to implement an alternative and

the risks the alternative poses to workers, residents, and the environment during

implementat ion.

Implementability considers the technical and administrative feasibility of implement ing the

alternative, including factors such as the relative availability of goods and services.

Cost includes est imated capital and annual operat ion and maintenance costs, as wel l as present

worth cost. Present worth cost is the total cost of an alternative over t ime in terms with today's

dollar value. Cost estimates are expected to be accurate within a range of +50 and -30 percent.

State/Support Agency Acceptance considers whether the State agrees with EPA's analysis and

recommendat ions, as described in the Proposed Plan.

Community Acceptance considers whether the local communi ty agrees with EPA's analysis and

preferred alternative. Comments received on the Proposed P lanare an important indicator of

communi ty acceptance.

IX.A COMPARISON OF ALTERNATIVES TO THE NINE CRITERIA

The comparat ive analysis of the remedial alternatives is presented below,

1. Overall Protection of Human Health and the Environment

This criterion evaluates how an alternative achieves protection over t ime and indicates how

each source of contamination would be minimized, reduced, or control led through treatment,

engineering, or institutional controls. The overall protect ion associated with each alternative is

based largely on the exposure pathways and scenarios set forth in the baseline human health

risk assessment (HHRA).

Alternative 1, No Act ion, would not provide overall protection of human health and the

environment as it would do nothing to treat, remove, or isolate the contaminated groundwater

in the Dover off-site plume. Whi le there are no current exposures to the Dover off-site

contaminated groundwater plume, the No Act ion alternative would al low this contaminated

groundwater to remain, which could result in future exposures.

Alternative 2, M N A , may provide overall protection of human health and the environment.

However, it is uncertain how long it would take Alternative 2 to achieve remedial action

22

objectives, and it is unlikely it would do so in a reasonable t imeframe. The estimated t ime to

achieve RAOs was derived from the earlier 1996 FS. In that document t ime to achieve cleanup

goals was only provided for MCB, estimated at 12 years and p-DCB, est imated at 23 years,

assuming no cont inued mass loading to the plume. Since the plume mass loading would

cont inue without upgradient treatment, Alternative 2 would be expected to take much longer

than 23 years.

Alternatives 3A, 3B, 3C and 4 would provide protect ion of human health and the environment.

Based on site specific data provided to the venders familiar with this type of work, it was

est imated that it would take 2-5 years to reach remediat ion goals for Alternative 3A in the

higher concentrated plume grid area. After that, the t imeframe est imated (an addit ional 23

years) to reach cleanup goals via M N A would apply. This would result in an overall t imeframe to

reach cleanup goals of between 25 to 28 years.

Using published biodegradation half-life values for contaminants found in the off-site

groundwater, it is est imated that Alternative 3B would reach RAOs in 5 to 7 years, and

Alternat ive 3C would reach RAOs in 10 to 12 years. Both of these alternatives address the

higher concentrat ion grid area fol lowed by addit ional t reatment along the heart of the plume

with either an aerobic amendments (Alternative 3B) or anaerobic amendments (Alternative 3C).

In the case that RAOs are not met in the calculated t imelines, both of these alternatives al low

for the use of M N A should that be necessary fol lowing the complet ion of amendment

injections. If M N A is necessary, the full t ime to reach RAOs would be far less than the 23 years

est imated for M N A in Alternative 3A.

It is est imated that Alternative 4 would take 20 - 144 years to reach RAOs.

2. Compliance With ARARs

Alternat ive 1 and Alternative 2 would not provide compl iance with ARARs in the foreseeable

future as the current contaminant concentrat ions in the offsite plume would remain above

applicable criteria for an extended length of t ime.

Alternat ives 3A, 3B and 3C and Alternative 4 wou ld comply with ARARs, however, t ime frames

to meet the ARARs varies as described above.

3. Long-Term Effectiveness and Permanence

Alternat ive 1 would not achieve long term effectiveness.

Alternatives 3A, 3B and 3C would achieve long term effectiveness and permanence through

eventual complete destruction of the COCs within the off-site plume to harmless end products.

23

Alternative 2 and Alternative 4 wou ld eventually achieve long term effectiveness and

permanence; however the t ime frames would be significantly greater than with Alternatives 3A,

3 B a n d 3 C .

4. Reduction of Toxicity, Mobility, or Volume of Contaminants through Treatment

No reduction of contaminant toxicity, mobil i ty or vo lume would be provided by Alternative 1.

The off-site p lume would be al lowed to remain in place at its current location and

concentrations. Alternative 2 wou ld provide for the reduction of the toxicity and volume of

contaminants through natural processes within the aquifer and would be moni tored.

Alternatives 3A, 3B, and 3C would result in the reduction of contaminants within the treated

portions of the off-site contaminated groundwater plume. Evidence shows the plume is

currently in dynamic equil ibrium and therefore contaminant mobil i ty appears not to be a

significant factor for the Dover off-site plume.

Alternative 4 would include reduction in the volume of contaminated groundwater via

extraction f rom the subsurface and transfer of the contaminant mass f rom the extracted

groundwater via air stripping and vapor-phase treatment. Eventual contaminant reduction of

toxicity and vo lume would be achieved during the carbon regeneration t reatment.

Alternative 3A, 3B, 3C, and 4 satisfy EPA's preference for using treatment to cleanup a site.

Although 3A only uses direct t reatment in a portion of the off-site groundwater plume.

5. Short-Term Effectiveness

Alternative 1 wou ld take no t ime to implement and would present no short term risks because '

no action wou ld be taken.

Alternative 2 wou ld requires monitor ing groundwater wells and presents very little short-term

risk.

Alternatives 3A, 3B and 3C would also present very little short term risk. In addit ion to

groundwater monitor ing, injection of substrate presents little risk to the community.

The groundwater extraction and t reatment included in Alternative 4 would present minimal

short-term risk to the local community, however require more construction activity than the

other alternatives.

The est imated t ime for each of the alternative to achieve RAOs is presented above in the

Overall Protection of Human Health and the Environment sect ion.

24

6. Implementability

All of the alternatives are readily implementable.

Alternatives 1 and 2 wou ld be the most implementable. Alternative 3A would be moderately

more difficult to implement as an access agreement would be required beyond the Dover Plant

boundaries.

Alternatives 3B and 3C would be slightly more difficult to implement than Alternative 3A as

numerous access agreements would be required to implement the additional injections

required as part of these alternatives.

Alternat ive 4 presents the greatest degree of difficulty to implement. In addit ion to numerous

long term access agreements, this alternative requires permitt ing and significant construct ion

activit ies.

7. Cost

The est imated present value cost for Alternative 2 is $1.8 mil l ion; Alternative 3A is $4.8 mil l ion;

Alternat ive 3B is $7.4 mi l l ion; Alternative 3C is $7.2 mil l ion; and Alternative 4 is $12.5 mil l ion.

8. State/Support Agency acceptance

The State of Ohio supports the Preferred Alternat ive.

9. Community Acceptance

Communi ty acceptance of the preferred alternative will be evaluated after the public comment

per iod ends and will be described in the Record of Decision (ROD) for the site.

PREFERRED ALTERNATIVE

The selected remedy must be protective of human health and the environment, comply with

ARARs, and be cost-effective. Wi th the exception of Alternative 1, all of the alternatives would

be protective and comply with ARARs.

There is some uncertainty that Alternative 2 wou ld comply with ARARs and meet RAOs in a

reasonable t imeframe. There is potential for cont inued contaminant mass loading to the off-

site plume from residual soil contaminat ion.

Alternatives 3A, 3B, and 3C would protect human health and the environment and achieve

MCLs in a reasonable t ime frame. Alternatives 3B and 3C present greater difficulties in

25

implementat ion due to the need to gain access to propert ies owned by others. Of the three

alternatives, 3A is less likely to impact all areas of concern in a reasonable t ime frame.

Alternative 3A treats only the area near the origin of the off-site plume and does not provide

treatment for the remainder of the plume. Alternatives 3B and 3C treat the area near the

origin of the off-site plume and provide treatment along the center of the off-site plume to help

shrink it faster. Alternative 3B uses an aerobic chemical amendment to address the

chlorobenzenes, while Alternative 3C increases the anaerobic degradation rate within the

plume. It is bel ieved that chlorobenzenes can be degraded both aerobically and anaerobically;

and biodegradation generally proceeds faster aerobically. Therefore, Alternative 3B is expected

to be able to achieve reduction in concentrat ions and meet cleanup standards for

chlorobenzenes in a more t imely fashion.

Alternative 4 can also provide protect ion of human health and the environment and achieve

ARARs. However, the t ime frame associated with this alternative would be expected to be

extensive. This option would also be the most expensive of all the options to implement.

The Preferred Alternative for addressing the off-site groundwater plume is remedial Al ternat ive

3B- ISCO plus aerobic amendments followed by Al ternat ive 2- MNA.

The Preferred Alternative was selected over other alternatives because it is expected to achieve

substantial and long-term risk reduction through treatment, and it is expected to prevent

future exposure to currently contaminated groundwater. The Preferred Alternative also

reduces the risk within a reasonable t ime frame at a reasonable cost when compared to costs

associated wi th the more tradit ional Alternative 4 pump and treat. This alternative also

provides for long-term reliability of the remedy.

It is anticipated that Site-specific bench- and/or pilot- testing will be performed prior to the

remedial design and remedial act ion. This activity helps to determine the opt imal location

within the off-site groundwater plume for ISCO treatment and geochemical amendment in

order to modi fy geochemistry of the aquifer to further stimulate biological degradation of

contaminants.

Based on the information available at this t ime, EPA and OEPA believe the Preferred Alternative

would be protective of human health and the environment, would comply with ARARs, would

be cost-effective, and would utilize permanent solutions and alternative t reatment

technologies to the maximum extent practicable. It would treat the contaminated groundwater

and would meet the statutory preference for the selection of a remedy that involves treatment

as a principal element.

The Preferred Alternative can change in response to public comment or new information.

26

PRINCIPAL THREAT WASTES

The NCP establishes an expectation that EPA will use treatment to address the principal threats

posed by a site whenever practicable (NCP Section 300.430(a)(l)(iii)(A)). The "principal threat"

concept is appl ied to the characterization of "source materials" at a Superfund site. Source

material includes or contains hazardous substances, pollutants, or contaminants that act as a

reservoir for migration of contaminat ion to groundwater, surface water or air; or acts as a

source for direct exposure. Principal threat wastes are those source materials considered to be

highly toxic or highly mobi le that generally cannot be reliably contained, or would present a

significant risk to human health or the environment should exposure occur. The decision to

treat these wastes is made on a site-specific basis through a detailed analysis of the alternatives

using the nine remedy selection criteria. This analysis provides a basis for making a statutory

f inding that the remedy employs treatment as a principal element. Contaminated groundwater

generally is not considered to be a source material.

The heart of the off-site Dover Chemical plume is down gradient of the natural f low field from

the on-site source area known as the former fractionation tower. It is possible there is some

desorpt ion f rom soils at the origin of the off-site plume that continues to contr ibute chlorinated

benzenes to groundwater (see Figure 12). These areas that may continue to desorb chemicals

may be considered "source areas" which would be addressed through the preferred Alternative

3B.

COMMUNITY INVOLVEMENT

EPA and Ohio EPA will provide information regarding the clean-up of the Dover Chemical

Corporat ion Off-Site groundwater plume to the public through a public meet ing, the Site

Administrat ive Record fi le, the Site Information Repository maintained at the Dover Public

Library, and announcements published in the Times Reporter. EPA and the State encourage the

public to gain a more comprehensive understanding of the Site and the Superfund activities

that have been conducted at the Site.

A meeting to present the alternatives to the public will be held on June 25, 2015 at 6:00 pm.

The public comment period for acceptance of wri t ten public comments on this action is

June 22, 2015 to July 22, 2015.

27

Figures

Northeastern Oh io + <-"i.t,j['' ^ "V i-

- - hit- _Z._

115-f[^" 2? '\\ ' k

, r-, '-'* ' -Cleveland ,

" w i l t . + UIj«U* , ^ 1' '

'/-ir.JUILLb L

l*

/ -

4 __

v 7

"lif^roln-'rf

:„. 1,1 . • - • : • 1

6 1 16 _ 29 m£les !. H - | - H - i - H I - l - H ,

1? . Jjr

Dover area Pdtldl

5 -

""•>5!c,

1 mi le I 1 1-

\ - \ Dover

EipiAi Phll.-irtH

Site area

ill'

1 inch = 500 f e e t

500 1J000 i

2,000 Feet

Site boundary

Basemaps source: Esri

DOVER CHEMICAL CORPORATION SITE DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 1 SITE MAP

EPA REGION 5 RAG 2 | REVISION 0 | MARCH 2015

ST SuiTRAC

1 inch = 150 fee t

• 1 C f r y ' l t f t ' l 1 ^ K ^ ^ ^ k

Tewar

see Feet jUEcrnap source: Esri

Pumping well

Interim removal action area

Site boundary

DOVER CHEMICAL CORPORATION SITE

DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 2 1994 INTERIM REMOVAL ACTION A R E A S

EPA REGION 5 RAC 2 | REVISION 0 MAY 2015

ST SuiTRAC

\

I

• Excavation-area C

\

\ A

Former carnal excavation area

\

LA \ \

Excavated 4,403 Square Foci Area

\ \ Excavation area-H"""1

5|W'*'' '^C^-' •'V"<*"v •-'_*<;

\

\

1 inch = 15e f e \ t 1

253 -+-

500 Feet Basemap source: Esri

Approximate limits of non-time-critical removal excavation

Area with post-excavation soil concentrations exceeding action levels

Site boundary

Source: TRC, 2014.

• OVER CHEMICAL CORPORATION SITE

DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 3 N O N - T I M E - G R I T I C A L R E M O V A L

A C T I O N E X C A V A T I O N A R E A S

• \ REGION 5.RAC 2 | REVISION 0 | MARCH 2015

ST SuiTRAC

; i i » p l l l l

500 i • i.eee - 7 , 2 3 3 !=££••: H 1 1 1 1 ! 1 1

+ MSM1B

+

+ MK-29B - ® -

'1:

m-AT-i >-

4 (41-48

4 -

Basemap source; Esri

B-zone monitoring well

Site boundary

> 1000 ug/L

>100 ug/L

Note: March 2014 Total Chlorobenzene Concentrations were taken from "Dover Chemical Corporation Site Quarterly Status Report - December 2014" (TRC, 2015)

•ttJi\CoMf\Pro|>a"i ManPrup«£* Plan -fljun

DOVER CHEMICAL CORPORATION SITE DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 4 OFF-SITE PLUME - TOTAL C H L O R O B E N Z E N E S

IN B-ZONE GROUNDWATER - MARCH 2014

EPA REGION 6 RAC 2 I REVISION 0 | MARCH 2D15

[sf] SuiTRAC

PW-B-

MW-55A

MW-43A MW-53A

MW-43B

MW-58A, MW-56A MW-59A.B

i— MW-57A

/ r— MW-13A / /MW-32A

4 f —MW-14A.B.

MW-33A MW-3C

MW-2AR.2BR.2C MW-1 AR

MW-40A

MW-15A.B

MW-39B

SB.C

MW-17B.C ^ M W - 2 5 B -$MW-41B

&MW-37B

r MW-31 A,B,C

$rMW-23B

•^MW^24B

irlW-ZZB

4 } MW-35A.B.C ^ •^•MW-30BR

Weil ID GW Elev.

(ft)

MW-1 SB 867.01 MW-1 SB 867.66 !.:/. . / ! 3'. .

J vy-.r-j.

MW-24B 866.38 MW-25B 867.31 MW-27B 864.32 MW-28B 864.22 MW-29B 864.20

MW-30BR 864.78

;b MvV-b/b 366.54 MW-38B 864.54 MW-39B 867.62 MW-41B 865.32 MW-43B 868.12 MW-44 863.31 MW-45 863.36 MW-46 863.07 MW-47 862.75 MW-48 862.51 MW-49 862.57 MW-50 862.65 MW-51 862.52

MW-52B 861.64 MW-54B 867.99 MW-56B 867.68 MW-58B 867.88 MW-59A 867.92 MW-59B 867.91 PZ-16B 863.09

PZ-22B 866.98 PZ-42B 867.28 PZ-43B 867.77

$ MW-38B

MW-29B

$ MW-27B

$ MW-28B

$ MW-44

MW-45

MW-50 -A- MW-46 <?1UIW-51 •

"V'MW-47

$MW-48

MW-49 -$-MW-52B

• ~- Approximate Equipotential Groundwater Elevation (0.5 foot Interval;

Site Boundary

MW-1AR Monitoring Well

GW-1 AMKO Well

PW-2 Pumping Well

PZ-1 Piezometer Location 500 1,000 1,500 i Feet

Wannalancit Mills 650 Suffolk Street Lowell, MA 01854 978-970-5600

B-ZONE 0.5-FOOT G R O U N D W A T E R C O N T O U R S

JUNE 2012

DOVER CHEMICAL

PROJECT NO.: 106597

OCTOBER 2012 FIGURE j5

R:\Pmjacts\GIS_2Q0B\106B97_Do\/er\mxMgmp\2Q12\FSA\Fig4 GWContours_BZone_ptSft_2012Jun_20I2-10-22.mxd

fj"

- 1 inrh = 9C0 f>

e 5 0 0 - i j - e e s I , , 1 j — H 1 1

MARCH 2012

MW-37B

MK-22B JL + + +

•is

Note: Chlorobenzene concentrations for March 2005 and March 2012 were taken from "Dover Chemical Corporation Site Quarterly Status Report - December 2014" (TRC 2015)

Basemaps source: Esri

DOVER CHEMICAL CORPORATION SITE DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 6 OFF-SITE PLUMES - TOTAL CHLOROBENZENES

IN B-ZONE GROUNDWATER

EPA REGION 5 RAC 2 | REVISION 0

ST SuiTRAC

Figure "7 Dichlorobenzene Concentrations along the Centerline of Off-site Plume, March 2005- March 2012

Total Dichlorobenzenes in MW-39B (<0.1 mi from on-Site Plume)

5,000

4,500

4,000

_ 3,500 - « v

3 3,000 £

o

'% 2,500

£ g 2,000 c o

U 1,500 1,000 \ -

500

6/1/2005: Start of Modified F3 Pumping Scenario

Total Dichlorobenzenes in MW-25B (0.3 mi from on-Site Plume)

o o o o o o o o o o o o oo o o c o o o c n c n t T i o i

a. CL <-> HI <U

LO Q

Q . (J

at tu Q . cu

L O 01

O

o I

C

o rH

rH rH

Q . O

ai a; C L QJ

LO

rH

Q .

L O

rH rH

5,000

4,500

4,000

_ 3,500

6.0

3. 3,000 c o i i 2,500 * J c g 2,000 C O

U 1,500

1,000

500

0

6/1/200JI Start of Modified F3 Pumping Scenario

A-I \

LO o

CL 01 m

in o

01

LD O

ID O

LO LD r--O c p o

CL U iL 01 OJ to

Q s

o

3

r--o i

CL Ol

LO

o 6

Q

co o

o o o I

c

00 o Q . OJ

IT)

oo o

01 Q

c n o

c n o

2 -

c n c p

o. 0)

o

0) Q

o rH

o rH

U 0)

Q

rH rH

C 3

(N rH

Q . QJ

co

Total Dichlorobenzenes in MW-31B (0.5 mi from on-Site Plume) Total Dichlorobenzenes in MW-38B (0.9 mi from on-Site Plume)

5,000

4,500

4,000

_ 3,500

_i ">«. 3 3,000 £ o

'•g 2,500

c

8 2,000

o u

1,500

1,000

500

0

6/1/2005: Start of Modified F3 Pumping Scenario

A

' V

5,000

4,500

4,000

_ 3,500 - j

3 3,000 £ o

ro 2,500

c g 2,000 £ Q ° 1,500

1,000

500

0 -I

6/1/2005: Start of Modified F3 Pumping Scenario

i n o

LO cp c 3

LO LO LO LD O O cp O o L- SZ CL QJ ru 3 Ol Q 2 LO

LD O

01 D

O o o

a. 01 LO

r̂ o

O) Q

oo o

co o

00 o I

a Ol

oo o

Q

c n o cn

O i SZ zs

c n cp

CL 0)

L O

cn o

QJ Q

o rH C 3

Q . 0J

rH i

rH rH

SZ 3

rH rH

CL 01

rH

QJ Q

sis"-"' _ i .. -„ A , , , . , , * . . . , , . ,....*=_, , : J a A - . i*^ LT) LO LO LO LD LO LD LD r - rv 00 CO 00 00 c n CTi Cn cn o O c p Cp o O o O c p cp o cp o o o cp cp o cp c p cp li­ SZ. CL 6 iL SZ D. 6 i— c D. 6 il- c CL 6 1_ c CL 6 ra 3 01 QJ (13 Zl 0! QJ 3 01 01 fD 3 CU QJ 03 3 m 01 ro

LO Q 5 —t LO Q 5 LO O 2 in Q m Q 5

o rH I

C L QJ

LO

A* T V "' i'* o rH

rH rH

rH rH

rH rH

rH rH rH

Dec

-

Ma

r-

Jun-

Sep

-

Dec

-

Mar

-

Notes Total Dichlorobenzenes —~'--Linear I Trendlihe

* non-detects are expressed as 1/2 laboratory detection limit

Figure 0 Monochlorobenzene Concentrations Along the Centerline of the Off-site Plume

March 2005-March 2012

Monochlorobenzene in MW-39B (<0.1 mi from on-Site Plume) 300

250

200 CUB

3 £ O

1c 1 5 0

£ o

I 100. EPA M C L

50

LD O

LO O

L O O

LD O

LD O

L B O

L D O

r-o

r--o

Q

1̂ -o a. co

o

co o

oo o

0 3 O

C O O

2 -

CO o 0)

Q

01 o

01

o cn o •

Q . CU

L O

Cn O

co Q

o rH

O rH

Q . OJ

LO

rH rH

a. co

Q) Q

Monochlorobenzene in MW-25B (0.3 mi from on-Site Plume)

300

250

200 0J3 5

£ O

150

c 0)

I ioo

50

/ EPA M C L

\ !

\ / % 1 \/ it

i j i 'I t i 1 ! 1 i 1 I i • t t i I I i -' i I I i 1 t»-" 1 1

LO

o LO

o LO

o G . QJ

LO

L O

o 0J

Q

LD O

L D O

LD O

i C L QJ

LO

LD O

CO

o o I

SZ 3

o C L QJ

LO

o

CO Q

CO o

0 0

o 0 0

o I

C L QJ

CO o QJ

Q

cn o o

cn o C L CO

cn o

CO o

rH rH

C L CO

LO CO

a

C L QJ

LO

rH rH

QJ

a

rM rH

Monochlorobenzene in MW-31B (0.5 mi from on-Site Plume) Monochlorobenzene in MW-38B (0.9 mi from on-Site Plume)

300

250

1 6/1/2005: Start of Modified F3 Pumping Scenario^' .

/ \

200 no

c o

ra 1 5 0

£ . QJ (J

3 , 1 0 0

50

\ i

f > I \

> .'-

300

250

1 i r 200

cm

c o

ra 150

EPA M C L

1 /

T T T

c o £

U 1 0 0

50

6/1/2005: Start of Modified F3 Pumping Scenario

EPA MCL

1

LO O

LO O

LD O

C QJ

L D O

SZ 3

LD O

C L QJ

LO

LD O o

1^ o o SZ C L Zj CO

o oo o

co cp SZ 3

CO o

oo o

CD

o cn o

cn o

cn o o o o rH o rH rH rH rH rH L> iL SZ C L U iL CO ro 3 CO CO

o "2. —» LO Q

LO O

LO

o SZ Q . 3 QJ

—i LO QJ

Q

cp Q . QJ

LO

LO O

CO

a

LD O

L D O

LD O

LD O

6 CO

Q

5 cp c 3

rv cp Q . QJ

LO

o

QJ Q

oo o

00

o 0 0

o CO o

cn o

Q S

cn cp C L CO CO

a

a H i C L QJ

H H

QJ Q

(0

5

Notes —4»» Monochlorobenzene Linear Trendline

* non-detects are expressed as 1/2 laboratory detection limit

MW-25B MW-31 B MW-37B

Monochlorobenzene in MW-25B Monochlorobenzene in MW-31 B Monochlorobenzene in MW-37B

Total Dichlorobenzene in MW-25B Total Dichlorobenzene in MW-31 B Total Dichlorobenzene in MW-37B

4,000

„ 3.500

3. 3,000 g

2.C00

, , , . . „ . r , „ . , . „ t .........^ f ^-^V-p f" T j " J f Lri tn JH -ta ia to *ft r-. r-, - ^ ca m as m m CO OT CU Ol- CPl

•5 j» 5 S" aS O S —' v> Q

EPA MCL (Maximum Concentration Limit)

Concentration trend line

Source: Feasibility Study Addendum II, (TRC, 2013).

DOVER CHEMICAL CORPORATION SITE DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 9 CONTAMINANT CONCENTRATION TRENDS

IN HEART OF OFFSITE B-ZONE P L U M E

EPA REGION 5 RAC 2 I REVISION 0

ST SuiTRAC

1 inch = 700 fee

0 50e 1 1 i-

1,000 2,080 Fee

-jj>- B-zone monitoring well

Site boundary

> 5 ug/L

> 10 ug/L

> 100 ug/L

Note:

+ " +

- f

HW-29B I . M-28E

'4- -f

-v

- f •,.-.-o

4-KW-49 '

i f

Basemap source: Esri

March 2014 Total Chlorobenzene Concentrations were taken from "Dover Chemical Corporation Site Quarterly Status Report - December 2014" (TRC, 2015)

DOVER CHEMICAL CORPORATION SITE DOVER,TUSCARAWAS COUNTY, OHIO

FIGURE 10 OFF-SITE PLUME - TRICHLOROETHENE IN

B-ZONE GROUNDWATER - M A R C H 2014

EPA REGION 5 RAC 2 | REVISION 0 |

ST SuiTRAC

N

1 inch = 709 feet

500 1,080

n Injection point

o Grid point

Pumping well

B-zone monitoring well

2^00 .-eet

Chlorobenzene >1000 ug/L

Chlorobenzene >1Q0 ug/L

Site boundary

Note: March 2014 Total Chlorobenzene Concentrations were taken from "Dover Chemical Corporation Site Quarterly Status Report - December 2014" (TRC, 2015)

Basemap source: Esri

DOVER CHEMICAL CORPORATION SITE DOVER, TUSCARAWAS COUNTY, OHIO

FIGURE 11 PROPOSED REMEDIATION ACTION

ALTERNATIVE 3

EPA REGION 5 RAC 2 | REVISIONO: I MAY 2015

ST SuiTRAC

Tables

Table 1:

Well Numbers, Location-Role, Sampling Dates, and Analytical Methods Groundwater Elevations

Dover Chemical Corporation

Sampling Location / / V/ V/ / / y/ MW-14B Upgradient Background 5/24/2011 6/30/2011 6/30/2011 r MW-17B Plume Transect 6/14/2011 6/28/2011 6/28/2011

MW-18B Plume Centerline 6/14/2011 6/28/2011 6/28/2011

MW-22B Bounding Transect 6/14/2011 6/29/2011 6/29/2011

H MW-23B Plume Transect 5/24/2011 6/14/2011 6/27/2011 r-i O CM 0) C

MW-24B Bounding Transect 5/24/2011 6/28/2011 6/28/2011 r-i O CM 0) C

MW-25B Plume Centerline 5/24/2011 6/14/2011 6/27/2011 3 MW-27B Plume Centerline 6/14/2011 6/29/2011 6/29/2011

CD MW-28B ' Bounding Transect 6/14/2011 6/30/2011 6/30/2011

fO MW-30BR Bounding Transect 6/14/2011 6/29/2011 6/29/2011 3

a MW-31B Plume Centerline 5/24/2011 6/14/2011 6/22/2011

MW-35B Plume Centerline 5/24/2011 6/14/2011 6/23/2011 Urn

MW-37B Plume Centerline 5/24/2011 6/14/2011 6/23/2011

MW-38B Plume Centerline 5/24/2011 6/14/2011 6/27/2011

MW-39B Plume Centerline 5/24/2011 6/14/2011 6/22/2011

MW-41B Bounding Transect 5/24/2011 6/28/2011 6/28/2011

MW-51-20 Sentinel Centerline 5/24/2011 6/14/2011 6/22/2011

MW-14B Upgradient Background 8/16/2012 9/6/2011 9/16/2011

MW-17B Plume Transect 8/16/2012 9/13/2011 9/13/2011

MW-1SB Plume Centerline 8/16/2012 9/8/2011 9/8/2011 9/8/2011 10/18/2011 T-f H

MW-22B Bounding Transect 8/16/2012 9/16/2011 9/16/2011 O (M MW-23B Plume Transect 8/16/2012 9/6/2011 9/9/2011 9/9/2011 10/18/2011 CD

XI MW-24B Bounding Transect 8/16/2012 9/13/2011 9/13/2011 E cu

MW-25B Plume Centerline 8/16/2012 9/6/2011 9/9/2011 9/9/2011 10/18/2011 a CL)

MW-27B Plume Centerline 8/16/2012 9/9/2011 9/9/2011 t/> MW-28B Bounding Transect 8/16/2012 9/16/2011 9/16/2011 9/16/2011 10/18/2011 CD

t MW-30BR Bounding Transect 8/16/2012 9/12/2011 9/12/2011

ra MW-31B Plume Centerline 8/16/2012 9/6/2011 9/8/2011 9/8/2011 10/18/2011 Cf TJ MW-35B Plume Centerline 8/16/2012 9/6/2011 9/9/2011 9/9/2011 10/18/2011 C O MW-37B Plume Centerline 8/16/2012 9/6/2011 9/12/2011 CL) V) MW-38B Plume Centerline 8/16/2012 9/6/2001 9/12/2011 9/12/2011 10/18/2011

MW-39B Plume Centerline 8/16/2012 9/6/2011 9/8/2011 9/8/2011 10/18/2011

MW-41B Bounding Transect 8/16/2012 9/6/2011 9/13/2011

MW-51-20 Sentinel Centerline 8/16/2012 9/6/2011 9/13/2011

MW-14B Upgradient Background 11/21/2011 12/13/2011 12/13/2011

MW-17B Plume Transect 11/21/2011 12/12/2011 12/12/2011

MW-18B Plume Centerline 11/21/2011 12/12/2011 12/12/2011

t-H MW-22B Bounding Transect 11/21/2011 12/13/2011 12/13/2011 rH O (Nl

CL)

MW-23B Plume Transect 11/21/2011 12/6/2012 12/13/2012 rH O (Nl

CL) MW-24B Bounding Transect 11/21/2011 12/13/2011 12/13/2011 XI

E MW-25B Plume Centerline 11/21/2011 12/6/2011 12/13/2011 12/13/2011 CU

CL) MW-27B Plume Centerline 11/21/2011 12/14/2011 12/14/2011

a MW-28B Bounding Transect 11/21/2011 12/14/2011 12/14/2011

CL) MW-30BR Bounding Transect 11/21/2011 12/14/2011 12/14/2011

MW-31B Plume Centerline 11/21/2011 12/6/2011 12/12/2011 12/12/2011

MW-35B Plume Centerline 11/21/2011 12/6/2011 12/14/2011

IE MW-37B Plume Centerline 11/21/2011 12/6/2011 12/12/2011 1- MW-38B Plume Centerline 11/21/2011 12/6/2011 12/13/2011 12/13/2011

MW-39B Plume Centerline 11/21/2011 12/6/2011 12/13/2011

MW-41B Bounding Transect 11/21/2011- 12/13/2011 12/13/2011

MW-51-20 Sentinel Centerline 11/21/2011 12/6/2011 12/13/2011

MW-14B Upgradient Background 3/1/2012 3/15/2012 3/23/2012

MW-17B Plume Transect 3/1/2012 3/19/2012 3/19/2012

MW-18B Plume Centerline 3/1/2012 3/15/2012 3/19/2012

MW-22B Bounding Transect 3/1/2012 3/23/2012 3/23/2012 CM rH MW-23B Plume Transect 3/1/2012 3/15/2012 3/26/2012 (M MW-24B Bounding Transect 3/1/2012 3/15/2012 3/26/2012 <J

MW-25B Plume Centerline 3/1/2012 3/15/2012 3/21/2012 3/1/2012

s MW-27B Plume Centerline 3/1/2012 3/15/2012 3/21/2012

0) MW-28B Bounding Transect 3/1/2012 3/23/2012 3/23/2012

ro MW-30BR Bounding Transect 3/1/2012 3/15/2012 3/22/2012 zs a

MW-31B Plume Centerline 3/1/2012 3/15/2012 3/21/2012 3/1/2012

t MW-35B Plume Centerline 3/1/2012 3/15/2012 3/22/2012 3 O MW-37B Plume Centerline 3/1/2012 3/15/2012 3/22/2012

MW-38B Plume Centerline 3/1/2012 3/15/2012 3/21/2012 3/1/2012

MW-39B Plume Centerline 3/1/2012 3/15/2012 3/26/2012

MW-41B Bounding Transect 3/1/2012 3/15/2012 3/20/2012

MW-51-20 Sentinel Centerline 3/1/2012 3/15/2012 3/26/2012

Notes: 1 - DOC Omitted from December 2011 and March 2012 Analyses

2 - temperature, dissolved oxygen, specific conductance, pH, Eh, turbidity, ferrous iron (Fe+ 2)

Abbreviations: As: arsenic B V C : bvcA Reductase

CSIA: Compound Specific Isotope Analysis

DHBt: Dehalobacter spp.

DHC: Dehalococcoides spp.

Diss.: dissolved DOC: dissolved organic carbon Fe: iron HRC: Hydrogen Release Compound M E E : methane, ethane, ethene Mn: manganese

M O B : Methane Oxidizing Bacteria ORC: Oxygen Release Compound

PDB: Passive Diffusion Bag

PHE: Phenol Hydroxylase

sMMO: Soluble Methane Monooxygenase

TCE (Bacteria): tee A Reductase TCE Concentration: trichioroethene TOC: total organic carbon TOD: Toluene Dioxygenase VCR: Vinyl Chloride Reductase VOCs: volatile organic compounds

Laboratory Analytical Methods: As: 200.7 C 0 2 and M E E : RSK-175

Chloride, Sulfate, TOC, DOC: general chemistry

Fe and Mn: 6010B

VOCs: 8260B

Table 2: Geochemical Results Dover Chemical, Dover Ohio

/ £ •i / i f 1 £ 1 3 / 3 / $ I 8 1 # / § 1 <5 I $ 1 £ I <3 I $ ! £ / $ / £ 1 4 / £ 1 £ r $ / * 1 0 / £ 1 1 o / £ E P A M C L A 5 70 2 100 600 N/A 75 70

MW-14B

Upgradient Jun-11 l .OU l . O U l . O U l . O U l . O U l . O U l . O U l . O U Mixed(anoxic) 0.17 691 7.44 112 13.65 9.7 7,440 51,000 J 1 0 U 1 0 U 1,800 200 U 1,800 15U(+) 15U(+) 0.50 U 0.50 U 0.50 U 1,500 U(+) 940 J 140,000

MW-14B Upgradient Sep-11 l . O U l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) 0.22 685 7.54 153.2 13.30 6.5 7,780 46,000 1 0 U 1 0 U 950 200 U 950 4.7 J 1.2 J 3.50 UJ 0.50 UJ 0.50 UJ 570 J 1,100 U(+) 140,000 MW-14B

Upgradient Dec-11 l . O U l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(oxic-anoxic) 0.65 697 7.60 108 12.53 7.8 7,470 46,000 10U 1 0 U 470 200 U 470 15 U(+) 1 5 U 0.50 U 0.50 U 0.50 U 710J N A 130,000 MW-14B

Upgradient Mar-12 l .OU l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) 0.27 534 7.59 131 11.84 2.0 7,590 48,000 10U 10U 290 200 U 290 15U(+) 15 U(+) 0.18J 0.50 U 0.50 U 1,000 U(+) N A 150,000

MW-17B

Plume Jun-11 l .OU 0.20 J l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) 0.38 725 6.86 29 15.23 3.8 6,810 43,000 J 10 U 10U 340 200 U 340 13 J 6.4 J 4.6 0.50 U 0.50 U 1,900 U(+) 1,500 170,000

MW-17B Plume Sep-11 l . O U 1.6 l . O U l . O U 0.44 J 0.32 J 0.87 J l . O U Mixed(anoxic) 0.12 746 7.46 64.3 16.56 2.73 6,990 42,000 10 U 10U 89 J 200 U 89 J 15U(+) 15 U(+) 4.2 0.50 U 0.50 U 2,100 3,500 U(+) 160,000

MW-17B Plume Dec-11 0.19J 1.2 l . O U l .OU 0.19J l . O U l . O U l . O U Mixed(anoxic) 0.09 692 7.63 159 11.91 21.1 6,550 M),000 u(+; 3.5 J 10U 720 200 U 720 15U(+) 15U(+) 23 0.50 U 0.50 U 2,200 N A 180,000

MW-17B

Plume Mar-12 0.19J 1.1 l . O U l .OU l .OU l . O U l . O U l . O U Mixed(anoxic) 0.31 549 7.66 36 14.02 0.3 6,290 41,000 10U 1 0 U 100 U 100 U 100 U 15U(+) 15U(+) 23 0.50 U 0.50 U 1,600 N A 160,000

MW-18B

Plume Jun-11 1.4U 1.8 1.4 U 1.1 J 44 10 23 1.4 U Mixed(anoxic) 0.48 622 7.33 16 13.46 4.7 5,840 32,000 J 10U 1 0 U 210 200 U 210 4.9 J 6.8 J 56 0.50 U 0.50 U 4,200 U(+) 1,900 130,000

MW-18B Plume Sep-11 4.0 U 4.0 U 4.0 U 2.5 J 86 23 47 4.0 U Mixed(anoxic) 0.05 633 7.60 -29 14.18 5.6 5,940 32,000 1 0 U 1 0 U 330 200 U 330 15U(+) 15U(+) 0.50 U 0.50 U 0.50 U 1,600 2,000 U(+) 140,000

MW-18B Plume Dec-11 3.3 U 1.8 J 3.3 U 2.0 J 91 25 51 3.3 U Mixed(oxic-anoxic) 1.78 657 7.60 136 13.20 10.5 6,350 37,000 10U 1 0 U 570 200 U 570 22 15U(+) 8.9 0.50 U 0.50 U 1,900 N A 160,000

MW-18B

Plume Mar-12 2.0 U 2.1 2.0 U 1.4J 63 16 37 2.0 U Mixed(oxic-anoxic) 0.54 505 7.64 92 13.05 3.9 6,740 42,000 10U 10 U 260 200 U 260 15U(+) 15U(+) 5.4 0.50 U 0.50 U 1,700 N A 140,000

MW-22B

Bounding Jun-11 l . O U l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) 0.08 924 7.34 -71 16.70 7.3 9,800 120,000 J 4.4 J 1 0 U 940 200 U 940 110 110 0.10J 0.50 U 0.50 U 2,400 U(+) 2,200 130,000

MW-22B

Bounding Sep-11 1.0 u l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) 0.24 834 7.56 • -60 17.86 11.0 8,770 86,000 10U 1 0 U 570 200 U 570 63 57 0.24 J 0.50 UJ 0.58 J 1,500 1,900 U(+) 140,000

MW-22B Bounding Dec-11 l .OU l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(oxic-anoxic) 0.68 681 7.64 -33 14.01 3.3 7,490 67,000 10 U 1 0 U 170 200 U 170 60 58 0.41 J 0.50 U 0.50 U 1,200 N A 140,000 MW-22B

Bounding

Bounding

Mar-12 l .OU l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) 0.30 568 7.65 -117 13.72 17.0 8,520 54,000 10 U 1 0 U 2,900 200 2,700 71 U(+) 58 U(+) 0.54, 0.50 U 0.50 U 1,700 U(+) N A 150,000

MW-22B

Bounding

Bounding Mar-12 DUP l . O U l . O U l . O U l .OU l . O U l . O U l . O U l . O U Mixed(anoxic) N M N M N M N M N M N M N A N A N A N A N A N M N A N A N A N A N A N A N A N A N A

MW-23B

Plume Jun-11 8.9 5.0 U 5.0 U 39 29 5.0 U 13 5.0 U Mixed(anoxic) 0.38 728 8.02 7.1 14.12 2.7 7,710 65,000 J 3.7 J 10U 710 200 U 710 57 55 2.3 0.50 U 0.50 U 1,600 U(+) 1,800 130,000

MW-23B Plume Sep-11 8.2 J 14U 14 U 40 3! 14U 12 J 14U Mixed(anoxic) 0.27 836 7.48 -103.6 17.17 7.5 8,850 93,000 10U 1 0 U 1,500 400 1,100 61 57 1.1 0.50 U 0.50 U 1,900 1,900 U(+) 130,000

MW-23B Plume Dec-11 7.7 J 14U 14 U 32 32 2.0 J 15 1 4 U Mixed(oxic-anoxic) 1.01 717 7.56 -76.8 13.88 6.4 9,200 79,000 10U 10 u 750 200 U 750 65 60 1.3 0.50 U 0.50 U 1,300 N A 1.30,000

MW-23B

Plume Mar-12 9.7 J 13 U 13 U 39 45 3.6 J 22 13 U Mixed(anoxic) 0.25 627 7.53 -70 10.90 2.9 9,960 97,000 10 U 10 u 610 500 110 67 65 1.1 0.50 U 0.50 U 1,600 U(+) N A 130,000

MW-24B

Bounding Jun-11 l .OU 1.1 l . O U l .OU l .OU l . O U l . O U 1.0 UJ Mixed(oxic-anoxic) 0.55 715 8.12 28 16.84 1.3 5,820 48,000 J 10U 10 u 100 U 100 U 100 U 58 41 0.22 J 0.50 U 0.50 U 1,700 U(+) 5,000 160,000

MW-24B Bounding Sep-11 l .OU 1.3 l . O U l .OU l .OU l . O U l . O U l . O U Mixed(anoxic) 0.20 721 7.60 -14 18.36 4.4 5,060 45,000 10U 1 0 U 100 U 100 U 100 U 68 44 0.42 J 0.50 U 0.50 U 1,500 U(+) 2,800 U(+) 150,000

MW-24B Bounding Dec-11 l .OU 1.1 l . O U l .OU l .OU l . O U l . O U l . O U Mixed(anoxic) 0.24 724 7.67 11 13.58 10.1 5,510 48,000 10U 1 0 U 110 200 U 110 63 51 0.20 J 0.50 U 0.50 U 1,500 N A 170,000

MW-24B

Bounding Mar-12 l . O U 1.5 l . O U 0.25 J l . O U l . O U l . O U l . O U Mixed(anoxic) 0.15 540 7.66 87 12.73 10.0 6,130 42,000 10U 1 0 U 500 200 U 500 67 54 0.31 J 0.50 U 0.50 U 1,600 U(+) N A 200,000

MW-25B

Plume Jun-11 13 U 13 U 13 U 100 680 13 U Mixed(anoxic) 0.48 708 7.63 2.8 16.27 2.4 7,160 40,000 J 10U 1 0 U 270 200 U 270 34 29 2.6 0.50 U 0.50 U 1,600 U(+) 6,300 170,000

MW-25B Plume Sep-11 l .OU l . O U l . O U ( U j 5 ^ ^ 0 _ 0.68 J l . O U Mixed(anoxic) 0.19 741 7.44 -5.7 15.03 2.0 7,280 57,000 10U 1 0 U 160 200 U 160 25 24 1.9 0.50 U 0.50 U 1,800 2,900 U(+) 170,000

MW-25B Plume Dec-11 33 U 33 U 33 U

( U j 5 ^ ^ 0 _

200 K l l 33 U Mixed(anoxic) 0.44 662 7.59 43.3 11.81 1.0 7,200 45,000 10U 1 0 U 100 U 100 U 100 U 24 23 2 0.50 U 0.50 U 1,500 N A 170,000 MW-25B

Plume Mar-12 20 U 20 U 440 B8B 350 20 U Mixed(anoxic) 0.22 610 7.59 18 14.21 0.3 8,030 43,000 10U 10U 100 U 100 U 100 U 26 U(+) 27 U(+) 1.4 0.50 U 0.50 U 1,300 N A 170,000

MW-27B

Plume Jun-11 4.5 3.1 l . O U 25 l . O U l . O U Mixed(anoxic) 0.11 808 7.40 -58 13.36 4.4 9,390 71,000 J 10U 1 0 U 410 200 U 410 120 120 0.82 0.50 U 0.50 U 2,000 U(+) 4,500 180,000

MW-27B Plume Sep-11 0.51 J 0.50 J l . O U 1.6 l . O U l . O U Mixed(anoxic) 0.17 825 7.44 -117 16.92 9.9 9,070 62,000 10U 10 U 770 600 170 120 130 1.0 0.50 U 0.50 U 1,600 3,000 U(+) 190,000

MW-27B Plume Dec-11 3.2 2.2 l . O U 31 l . O U l . O U l . O U l . O U Mixed(oxic-anoxic) 0.80 823 7.53 -82 11.89 19.3 10,100 63,000 10U 10 U 770 200 U 770 120 130 1.9 0.50 U 0.50 U 1,700 N A 180,000

MW-27B

Plume Mar-12 1.4 l . O U l . O U l . O U l . O U l . O U l . O U l . O U Mixed(oxic-anoxic) 0.88 718 7.54 ^14 19.00 4.8 8,330 61,000 1 0 U 1 0 U 370 200 U 370 120 120 1.3 0.50 U 0.50 U 1,600 N A 260,000

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