NYANZA CHEMICAL WASTE DUMP SUPERFUND SITE

SITE HISTORY

The Nyanza Chemical Waste Dump Superfund Site (hereafter, Nyanza Site) was

occupied from 1917 through 1978 by several companies that manufactured textile dyes

and dye intermediates. During the period of operation, large volumes of chemical waste

were disposed in burial pits, below ground containment structures, and in various lagoons

scattered throughout the “Megunko Hill” section of the site. Wastes contained in these

disposal areas included partially treated process water, chemical sludge, solid process

wastes (chemical precipitate and filter cakes), solvent recovery distillation residue,

numerous organic and inorganic chemicals (including mercury), and off-specification

products. Process chemicals that could not be reused or recycled, such as phenol,

nitrobenzene, and mercuric sulfate, were also disposed of on-site. Discharges from on-

site structures occurred as overland flow into nearby wetlands and the Sudbury River via

two small streams referred to as Chemical Brook and Trolley Brook.

Mercury and chromium were used as catalysts in the production of textile dyes from 1917

to 1978. Approximately 2.3 metric tons (2,300 kg) of mercury were used per year from

1940 to 1970 (JBF Scientific Corp., 1972), with approximately 45 to 57 metric tons of

mercury released to the Sudbury River during this period (JBF Scientific Corp., 1973).

From 1970 until the facility closed in 1978, wastes were treated on-site and wastewater

was discharged to Ashland’s town sewer system. These revised treatment practices

reduced the quantity of mercury released to the Sudbury River to between 23 and 30 kg

per year or about 0.2 metric tons during that eight-year period.

Nyanza, Inc. was cited for several waste disposal violations by the Massachusetts

regulatory agencies from 1972 to 1977. In 1981, most of the property was acquired by

MCL Development Corporation, which leased a large portion of the site to Nyacol

Products, Inc. In 1982, the Nyanza Site was placed on the National Priorities List (NPL)

by the U.S. EPA. Four other small property owners currently operate or lease facilities to

various light industries and commercial concerns including Ashland Industrial Fuel

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Corporation, Middlesex Equipment, Ashland Excavating Co., A Auto Body, and

Environmental Restoration Engineering Company.

To expedite remediation, the remedial investigation/feasibility study (RI/FS) for the

Nyanza Site was originally divided into the following Operable Units (OUs):

� OU I — addressed on-site surficial soil, sediment and sludges through on-site containment. Lagoon contents addressed as a removal action.

� OU II - “Nyanza II - Groundwater Study” — addresses groundwater contamination from the site, including DNAPL and vapor intrusion issues. The investigation is ongoing.

� OU III - “Nyanza III - Sudbury River” — originally addressed contamination of the Sudbury River by discharges of wastewater and sludge from the site; OU III was altered to focus on addressing mercury contamination in soils and surface water in the continuing source areas, which are the Eastern Wetlands, Trolley Brook, Outfall Creek, and the Lower Raceway. These activities have been completed.

OU IV - “Sudbury River Proper” — As a result of the findings in the 1992 OU III RI,

EPA determined that the potential risk to both human health and ecological receptors

could be attributed principally to mercury contamination of the Sudbury River. To

further evaluate the nature, extent, and potential impacts of mercury contamination in the

river, EPA established an additional operable unit (Operable Unit IV - Sudbury River)

specifically to address mercury contamination within the river proper.

STATUS OF THE REMEDIAL INVESTIGATION/FEASIBILITY STUDY FOR OUIV

The Human Health Risk Assessments have addressed, in various reports, the exposure

scenarios at the site. The Human Health Risk Assessment for the consumption of fish

was just completed based on the collection of a full set of fish data in 2003. The

Ecological Risk Assessment is being drafted. It is expected that a feasibility study (FS)

will be initiated in 2006 and completed in 2007.

SITE DESCRIPTION

The Nyanza Site is located in Ashland, Massachusetts approximately 35 km west of

Boston. The Nyanza Site, which covers approximately 35 acres, is situated in an 2

industrial area 0.4 km south of the Sudbury River. Surface water runoff and groundwater

discharged from the site drains into Trolley Brook, Chemical Brook, and the Eastern

Wetland (Figure 1). Trolley Brook, which drains the Eastern Wetlands, and Chemical

Brook are the primary site drainages. Trolley Brook merges with Chemical Brook and

continues through a culvert that discharges to Outfall Creek, a small man-made channel

approximately 60 m long. Outfall Creek flows to the Lower Raceway, which joins the

Sudbury River 240 m downstream from the site.

EPA is completing a risk assessment for OU IV which consists primarily of the Sudbury

River proper, selected drainage areas that provide input to the Sudbury River, and

reference areas that can provide information regarding background conditions. The study

area consists of an approximately 60 km stretch of river that begins in the river’s

headwaters and extends to where the Sudbury and the Assabet Rivers converge to form

the Concord River (Figure 2).

The Sudbury River is located in the Sudbury-Assabet-Concord (SuAsCo) watershed,

located in the metro-west area of the state, and encompasses a large network of tributaries

that ultimately flow into the Merrimack River. The watershed has a total drainage area of

approximately 377 square miles. The Sudbury River begins in Westborough, flowing

eastward from the Great Cedar Swamp toward Framingham. It then proceeds north

through the towns of Sudbury, Wayland, and Lincoln, and into the town of Concord. The

SuAsCo watershed encompasses all or part of 36 municipalities and supports a

population of 365,000 people.

The Sudbury River flows in a northerly direction through rolling, hilly terrain and

consists of a series of impoundments, flowing reaches, and extensive wetland areas. A

majority of the land surrounding the lower reaches of the study area is suburban

residential, consisting of several closely spaced urban centers connected by arterial

commuting routes. The watershed area of the Sudbury River is approximately 165 square

miles. In the OU III RI (NUS, 1992), the Sudbury River was divided into ten reaches

(i.e., river segments), which were based on changes in river configuration, impounding

structures, roadways and stream junctures (Figure 2). The same geographical convention,

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i.e., reaches, was also used in the more recent investigations conducted specifically to

evaluate potential mercury impacts within the river, OU IV and continues to be used as

part of the current risk assessment.

Sudbury River Reach Descriptions are as follows:

� Reach 1— this reference area extends from the headwaters of the Sudbury River in Cedar Swamp to the Pleasant Street impoundment.

� Reach 2—extends from the Pleasant Street Impoundment to the Union Street Bridge (Route 135) in Ashland. Reach 2 is directly impacted by site discharges in and downstream of Mill Pond, the only impoundment located in this reach. The OU III surface water bodies (i.e., Trolley Brook, Chemical Brook, Outfall Creek, and Lower Raceway) and wetlands (i.e., Eastern Wetlands) discharge into the Sudbury River within Reach 2. In addition, contaminated groundwater underlying the Site discharges to Mill Pond.

� Reach 3—extends from the Union Street Bridge to the Reservoir No. 2 dam. Reach 3 contains Reservoir No. 2 (47 ha, mean depth 3.1 m, maximum depth 4.9 m) and receives discharge from Cold Spring Brook. Reservoir No. 2 is the first major sediment depositional area downstream of the site. This reservoir was developed in 1879 to supply water to Boston.

� Reach 4—extends from the Reservoir No. 2 dam to the Reservoir No. 1 dam. Reach 4 contains Reservoir No. 1 (49 ha, mean depth 2.2 m, maximum depth 4.0 m) which is the second major impoundment downstream from the site. Reservoir No. 1 receives discharge from the Framingham Reservoir No. 3 reference impoundment; in turn, Reservoir No. 3 receives source water from the Sudbury Reservoir. Neither the Sudbury Reservoir nor Reservoir No. 3 receives surface drainage from the site. Reaches 3 and 4 are similar in that they consist primarily of impounded areas with slow moving water.

� Reach 5—extends from the Reservoir No. 1 dam at Winter Street to the Massachusetts Turnpike (Interstate 90) overpass, where the Sudbury River widens. The upper portion of this reach is typically narrow with high stream velocity and only minor depositional areas. In the lower portion of this reach, the river broadens as a result of water retention in Saxonville Reservoir and the water velocity diminishes. Sediment deposition is expected to occur in this portion of the reach.

� Reach 6—extends from the Turnpike overpass to the Saxonville Dam. This reach includes a small section of flowing river and a ponded depositional area behind the Saxonville Dam (Saxonville Reservoir).

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� Reach 7—extends from the Saxonville Dam downstream to the Route 20 overpass in Wayland. Reach 7 has a low stream gradient (<1 foot drop per mile) resulting in a slow, meandering river with increased potential for deposition. This reach also includes Heard Pond, which, although not an impoundment of the Sudbury River, lies within the Sudbury’s floodplain and at times of high water receives overflow from the river.

� Reach 8—extends from the Route 20 overpass to the Route 117 overpass, before the Fairhaven Bay inlet. This reach includes the Great Meadows National Wildlife Refuge (GMNWR). The river channel within Reach 8 meanders through an extensive wooded and emergent wetland complex that has a high depositional potential.

� Reach 9—extends from the inlet area to Fairhaven Bay to the Fairhaven Bay outlet. Fairhaven Bay is a large pond-like feature in the Sudbury River (27 ha, mean depth 1.5 m, maximum depth 3.4 m) that is the last major depositional area before the Sudbury/Assabet River confluence.

� Reach 10—extends from the Fairhaven Bay outlet to the Sudbury/Assabet River confluence. This portion of the Sudbury River has a flow regime similar to that of Reach 8, with slightly less meander.

These reach designations are still used in evaluating site data and human health risks,

however the ecological risk assessment grouped some reaches together to focus on

primary and secondary target areas. The primary focus areas are the two reservoirs and

the Great Meadows National Wildlife Refuge and the secondary areas are the remaining

slow and fast flowing portions of the river.

Reference Area Descriptions

Portions of the Sudbury River lie within the Boston-Sudbury Lowland and Eastern

Plateau hydrologic provinces of eastern Massachusetts. Reference areas located within

these provinces were used to provide data on background levels of mercury for the field

investigations. The primary reference areas include Reach 1 (headwaters of the Sudbury

River), the Charles River in the vicinity of Millis, and the Sudbury Reservoir west of

Framingham.

Reach 1 – Headwaters of the Sudbury River

Reach 1 extends from the headwaters of the Sudbury River in Cedar Swamp to a small

dam (referred to as the Pleasant Street Impoundment), just upstream of Mill Pond in

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Ashland. Reach 1 contains several sampling locations, including Whitehall Reservoir

(233 ha, mean depth 2.0 m, maximum depth 9.8 m). The flowing portion of Reach 1

serves as a reference area for Reaches 2, 5, 7, and 10.

Charles River

The Charles River reference area lies within the Boston-Sudbury Lowland hydrologic

province. This province represents a small irregularly-shaped area of low relief in eastern

Massachusetts. It consists mainly of broad plains interrupted by numerous low hills and

ridges. The lowland in the vicinity of the site and reference areas is drained by the

Charles and Sudbury Rivers. The surficial geology of the region consists mostly of

stratified drift surrounding drumlins and isolated till-covered bedrock hills.

Glaciolacustrine sediments occupy much of the lowland around the Sudbury River. The

habitat of the Charles River near Millis is similar to that of the Sudbury River especially

in the vicinity of the GMNWR. Flow characteristics, open water, emergent wetlands and

adjacent scrub-shrub areas are similar and are expected to support fish and wildlife

species that have been observed in the Great Meadows and other meandering portions of

the Sudbury River watershed. The Charles River was selected to serve as a reference for

portions of the slower flowing areas of the Sudbury River, including GMNWR (Reach 8)

and Reach 9.

Sudbury Reservoir

The Sudbury Reservoir is a man-made impoundment located with the Eastern Plateau

province. This province is characterized as low-lying region, sloping gently seaward.

Elevations in this province are generally less than 500 ft above sea level. In addition to

the Sudbury River, this region is drained by the Concord, Charles, and Assabet Rivers,

among others. Surface waters reflect poorly-integrated drainage due to disruption by

glaciation. Surface topography in the province reflects stratified drift of sand and gravel

deposits. The Sudbury Reservoir was selected to serve as a reference for the impounded

areas of the Sudbury River, including Mill Pond (Reach 2), Reservoirs 1 and 2 (Reaches

4 and 3, respectively), and the Saxonville Reservoir (Reach 6). Although lacking the

substantial industrial, commercial and residential development surrounding many of the

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Sudbury River reservoirs, it is, nevertheless, expected to provide a suitable reference area

for ambient mercury levels in fish.

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RISK MANAGEMENT PRICIPLES FOR MANAGING CONTAMINATED SEDIMENT RISK AT

THE NYANZA CHEMICAL WASTE DUMP SITE - SUDBURY RIVER

1. CONTROL SOURCES EARLY

Early removal actions addressed the on-site immediate health threats posed by the on-site

storage of wastes. There are four operable units at this site which address soils, sediment,

groundwater and the mercury contamination in the Sudbury River.

In 1987 and 1988, EPA excavated an underground storage vault containing 12,025 tons

of material; 300 tons of contaminated soils were incinerated, and an additional 356 tons

of soils were excavated and disposed of at an approved off-site facility.

OPERABLE UNIT 1: EPA's source control remedy included excavating all outlying

sludge deposits and contaminated soils and sediments associated with these deposits,

consolidating this material with the on-site Hill sludge deposits, capping the Hill section

to prevent water from entering it and spreading contaminants, constructing a groundwater

and surface water diversion system on the upgradient side of the Hill area, backfilling the

excavated areas to original grade, establishing a vegetative cover in the wetland areas,

and constructing a more extensive groundwater monitoring system to allow for future

evaluation of the cap. Approximately 60 percent of the 13-acre cap is in an area of

existing lagoons, sludge pits, and buried building debris and was covered with earth from

on-site excavations in clean areas. The remaining portion of the area that was capped was

excavated to bedrock to create a cell for the disposal of contaminated soils and solidified

sludges from the on- and off-site cleanup areas. The site is fenced. More than 65,000

cubic yards of contaminated soil were excavated and placed in the landfill in 1990. Final

construction of the site cap was completed in 1991. All cleanup actions were completed

in late 1992. The Massachusetts Department of Environmental Protection (DEP) is

currently responsible for conducting operation and maintenance activities.

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OPERABLE UNIT II: EPA selected an interim remedy to clean up the off-site

groundwater contamination in 1991. The selected remedy was to pump and treat the

contaminated groundwater from the most contaminated portions of the plume for five

years. However, due to the discovery of additional contamination (dense non-aqueous

phase liquid [DNAPL] during a 1995 pump test), this remedy is being re-evaluated to

determine whether it is still likely to be effective. Additional data collection and risk

assessment activities are ongoing. Indoor Air sampling was conducted in 2004 on several

homes due to the potential exposure from vapor intrusion as a result of the high levels of

contamination found in the groundwater at the site. EPA plans to make a remedy decision

in early 2006 for installation of sub slab ventilation systems and DNAPL recovery.

OPERABLE UNIT III: Preliminary sampling showed that sediment and surface water of

the wetlands and drainage-ways between the site and the Sudbury River were

contaminated with heavy metals. A decision was reached in 1993 to excavate and

landfill contaminated sediments from these wetlands (mercury cleanup level = 1 ppm).

The design of the remedy was completed in 1998 and cleanup activities began in March

1999. Over 45,000 cubic yards of mercury-contaminated sediments were excavated from

four areas (Eastern Wetland, Trolley Brook, Outfall Creek, and Lower Raceway) and

disposed of in the on-site landfill. EPA completed all remedial and restoration activities

by August 2001. The MA DEP is currently responsible for conducting operation and

maintenance activities.

2. INVOLVE THE COMMUNITY EARLY AND OFTEN

A. Briefly describe the role of the community in the RI/FS or EE/CA and the mechanisms that were used to solicit effective involvement of a variety of community members in sediment-related issues.

The Town of Ashland has been the most involved community to date on the river,

primarily since the Nyanza Site is located behind the downtown area. The Ashland

community has actively participated in all phases of the cleanup remedy for OU I– the

landfill, OU II the 1991 selection of a groundwater remedy, and for OU III the cleanup of

the continuing source areas (Eastern Wetlands, Chemical Brook, Trolley Brook, Outfall

Creek, and the Lower Raceway). EPA communicates often with the Town Manager and

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Health Agent related to ongoing activities at Nyanza, as the site has had some form of

continuous action since its listing on the NPL. These communications will continue in

light of the recently released MA Department of Public Health (DPH) finding that the

Nyanza Site is linked to incidences of cancer in Ashland.

A multi-town tour was conducted in 1997 to present the findings of the Task Force

Studies on the River. In 2003, EPA issued a multi-town fact sheet on the river indicating

the objectives of the on-going RI studies and data collection efforts. Fish consumption

advisory signs are posted in all reaches the river.

Local groups consulted during the early RI actions included the Framingham Advocates

for the Sudbury River (FASR), which also held a Technical Assistance Grant (TAG) on

the site for the river. SuAsCo is another organization with interests in the Sudbury

River. SuAsCo brings together many of the other grass root organizations as well as

local communities for a partnering of interests in the SuAsCo watershed. EPA will be

presenting an update of the RI data at the annual meeting on June 19th.

Other organizations that EPA communicated with regarding our studies on the river

include the Department of Conservation and Recreation (DCR), which controls the

reservoirs and the Fish and Wildlife (F&WL) regarding Great Meadows.

A multi town presentation will again be conducted at the conclusion of the RI. Interest in

potential remedial actions related to the contaminated sediment is high in all the

communities involved.

B. Briefly describe how local societal and cultural practices were considered in (1) the human health risk assessment (e.g., local recreational use of the water body, local fishing practices) and (2) the selection or development of the proposed remedy (e.g., current and future uses of the water body).

Local societal and cultural practices have been considered in the development of the

scopes for the human health and ecological risk assessments, in data collection activities,

and in drafting the reports for the Sudbury River.

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Current and foreseeable future uses of the river are reflected in the exposure scenarios

evaluated in the risk assessment including direct contact and incidental ingestion from

swimming and wading and use of the water as a potable drinking water supply. Fish

consumption scenarios included subsistence, ethnic and recreational fishing, even though

evidence of subsistence fishing is anecdotal. Recreational fishing is seen often and

occurs along all reaches of the river.

The DCR regulates Boston’s back-up drinking water reservoir system and the uses of

these systems in its Public Access Plans. The Sudbury Reservoir (reference area) and

Reservoir No. 3 are back-up drinking water supplies for the Massachusetts Water

Resources Authority (MWRA) water supply system. Reservoirs No. 1 (Reach 4) and No.

2 (Reach 3) are no longer considered water supply reservoirs, however a potable use

scenario was evaluated in EPA’s risk assessment.

C. Briefly describe the major ways the proposed sediment remedy is expected to affect the local community during remedy implementation.

There is no sediment remedy currently proposed for the Sudbury River. Any invasive

remedy would require the extensive use of private, local and State property for access

roads, staging areas, dewatering equipment, piping, etc. There would also be increased

truck traffic on public roads and some noise associated with a construction project of this

magnitude. The landfill on Nyanza was constructed to contain the on-site soil and

sludges as part of OU 1 and reopened (as was planned) to also contain the OU III

sediments. This landfill is only 13 acres and the land surrounding this landfill is being

prepared for development. Large volumes of excavated sediments from the River would

not be able to be re-located to the Nyanza Site.

The Reservoirs are surrounded by residential neighborhoods, as is the flowing river

portions in Framingham up to the Saxonville impoundment. Access, staging, noise, etc

could impact these residents. The river also winds its way through commercial areas of

Framingham which sees a high traffic volume and where the river is not easily accessible.

Eight miles of the river flows through the GMNWR, the largest remaining wetland in

Massachusetts. Any invasive action along this stretch of the river would have large

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implications to the habitat and wildlife that are located in the refuge. These stretches of

the river are boarded by extensive wetlands, low lying scrub-shrub and forested lands as

well as several golf courses. Fairhaven Bay is a fairly isolated impoundment at the

Lincoln/Concord town lines.

D. What is the expected level of community support for the proposed sediment remedy? Briefly identify any aspects that are expected to be of great concern and how the expected concerns have been addressed or considered.

No remedy has yet been proposed for the Sudbury River. Support is likely to be mixed in

that many will expressed a desire for removal of mercury from the sediment, while others

will be concerned about the about habitat destruction, particularly in Great Meadows

National Wildlife Refuge. The reservoirs, being by far the largest depositional areas for

the mercury in the sediments, would likely also receive mixed support for removal

actions due to the invasiveness of any large physical effort, but may garner support in that

these reservoirs are currently not used and a cleanup could potentially facilitate a

recreational future use of these waters, thereby benefiting the local residents. EPA will

develop a range of cleanup remedies to address the risks posed by the site and convey the

potential impacts of remedial activities to the public. The two primary areas (reservoirs

and GMNWR) will gain the most public interest in the review of potential remedies for

the river.

EPA has had great support from the local community with respect to the implementation

of the remedies for OU I and OU III. These remedies however did not significantly

impact residential areas, other than a portion of OU III in the cleanup of Outfall Creek

and the Lower Raceway. The remedies considered for the river could have major

impacts to the property owners adjacent to the river. Extensive public outreach would be

required for any invasive remedial action deemed necessary on any portion of the river.

EPA could minimize the impact to the surrounding residential areas by limiting work

hours, minimizing the use of secondary public roads, soundproofing pumps and

generators and implementing other engineering controls. In addition, for property owners

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whose land is needed to conduct the remedial action, EPA could provide monetary

compensation via compensated easements and/or leases.

3. COORDINATE WITH STATES, LOCAL GOVERNMENTS, TRIBES, AND NATURAL RESOURCE TRUSTEES

A. Briefly describe the major sediment-related issues in which State and local governments have been involved at the site. Briefly identify any aspects that are expected to be of great concern and how the expected concern has been addressed or considered.

Massachusetts has been involved in review of river-related work plans and reports. The

DCR has been contacted regarding RI work on or near the reservoirs and dams. There

are many local governments situated along the study area of the Sudbury River. The last

touring, multi-town meeting presentation was in 1997 with the presentation of the results

of the Task Force Studies. Discussions since then have been mainly with the Town of

Ashland, in conjunction with the other operable unit activities. Communication during

the 2002-2005 supplemental RI work focused on the Town of Ashland, the DCR, since

they control the use of the reservoirs and with the F&WL at Great Meadows, for the 8­

mile portion of the river which flows through the refuge, and the Trustees.

While EPA has the lead for the work at the River, the state remains very involved in all

aspects of the site, and are the lead for the operation and maintenance (O&M) for both

the on-site landfill and the restored wetlands.

There are many “grass-root” organizations which have interests in the

Sudbury/Assabet/Concord River Watershed. Many of these organizations are focused on

actions outside of the river that may affect land development and land conservation as

well as river use and storm water discharges. We would expect Ashland and all

downstream towns to become more involved as we finalize the risk assessments and

move closer to a remedy decision. Any proposal by the EPA for an invasive action

related to the cleanup of mercury contaminated sediments would be expected to be a

major issue.

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As of April 9, 1999, seventeen miles of the Sudbury River were designated as “wild and

scenic” based on its free flowing condition and outstanding scenic, recreational, wildlife,

cultural, literary, and historic value.

B. For sites that include water bodies where Total Maximum Daily Loads (TMDLs) are being or have been developed, briefly describe the coordination efforts with the State and with EPA’s water program. Identify any aspects of the TMDL that were considered in selection of the proposed remedy.

The State of MA has not proposed TMDLs on the Sudbury River, but is working towards

that goal for sections of the river. EPA has met on occasion with members of the State

which worked toward the proposal of 14 TMDLs for the Assabet River, located in the

same watershed.

On a related matter, MA has designated portions of the Sudbury River as impaired.

There are no known intentions for the MA DEP to propose a TMDL for mercury

contamination in the Sudbury River. The impaired segments from its impaired waters

list, do however list mercury contamination as one reason for impairment.

C. If there are Tribal interests at the site, briefly identify any aspects of the proposed sediment remedy that are expected to be of great concern and how the expected concern has been addressed or considered.

There are no known tribes with interests at the Sudbury River. EPA did consider several

human health exposure scenarios including subsistence, ethnic minority, and recreational

angler consumption of fish in the human health risk assessment.

D. If there are Natural Resource Trustee interests at the site, briefly identify the major areas of coordination related to the sediment response action. Are Trustee restoration activities expected concurrent with or following the Superfund action?

The Natural Resource Trustees (National Oceanic and Atmospheric Administration

[NOAA], Department of the Interior [DOI], and MA Executive Office of Environmental

Affairs [EOEA]) settled their Natural Resource Damage claims in a cash-out settlement

of approximately $3,000,000. Negotiated settlements for natural resource damages were

covered and are governed by the terms of a Memorandum of Agreement (MOA) amongst

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the Trustees and EPA. The Trustees are being consulted and participate in discussions

regarding the ecological risk assessment, and will continue to be consulted as the

ecological risk assessment and the remedial alternatives are being discussed, developed,

and implemented.

4. DEVELOP AND REFINE A CONCEPTUAL SITE MODEL THAT CONSIDERS SEDIMENT STABILITY

A. Attach a copy of the conceptual site model (e.g., one or more diagrams or charts not Numerical Models) for sediment which identifies contaminant sources, contaminants of concern, affected media, existing and potential exposure pathways, and human ahd ecological recpetors that may be threatened.

Operable Unit IV – Sudbury River, was delineated specifically to characterize the nature

and extent of contamination, as well as human health and ecological risks from exposure

to mercury contamination in the Sudbury River proper.

4.1.1 All Known and Suspected Sources of Contamination

An overview of the known and suspected sources of mercury contamination in the

Sudbury River resulting from the historical activities was presented in the “Site History”

section. Reiterating briefly, wastes from the manufacture of textile dyes and dye

intermediates (including mercury) were disposed of on-site in burial pits, below ground

containment structures, and lagoons. In addition, process chemicals (e.g., phenol,

nitrobenzene, and mercuric sulfate) were disposed of on-site or discharged into the

Sudbury River via Chemical Brook.

Surface water runoff and groundwater discharged from the site drains into Trolley Brook,

Chemical Brook, and the Eastern Wetland. Trolley Brook, which drains the Eastern

Wetlands, and Chemical Brook are the primary Nyanza property drainages. Trolley

Brook merges with Chemical Brook and continues through a culvert that discharges to

Outfall Creek, a small man-made channel approximately 60 m long. Outfall Creek flows

to the Lower Raceway, which joins the Sudbury River 240 m downstream from the

property. The Sudbury River flows in a northerly direction through rolling, hilly terrain

and consists of a series of impoundments, flowing reaches, and extensive wetland areas,

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until it converges with the Assabet River to form the Concord River (~ 50 km)

downstream from the Lower Raceway Outfall).

The closing of the plant eliminated procedural discharges while capping the landfill and

wetland restoration eliminated the major sources of contaminated surface soil runoff and

surface water discharges. It is estimated that a total of 45 to 57 metric tons of mercury

was released to the Sudbury River and continues to cycle through the aquatic

environments associated with the Sudbury River.

4.1.2 Affected Area

In an effort to refine the extent of contamination and the associated risk potential to both

human and ecological receptors, the Sudbury River was divided into ten reaches (i.e.,

river segments), which were based on changes in river configuration, impounding

structures, and stream junctures.

In addition to reaches affected by mercury contamination, reference areas were selected

to provide data on background levels of mercury. Different guidelines were used to

determine reference areas for different iterations of the river study, but ultimately, the

following criteria were used. References areas selected, like the site, lie within the

Boston-Sudbury Lowland and Eastern Plateau hydrologic provinces of eastern

Massachusetts. Areas selected as reference locations are within these provinces and

represent three types of riverine characteristics:

1) a lotic environment characterized by shallow water (i.e., < 3 ft) segments of moderate to fast flowing water;

2) a lotic environment characterized by somewhat deeper water segments (i.e., > 3 ft) of relatively slow flowing water, bordered by wide floodplain wetlands; and

3) a lacustrine environment characterized by a reservoir.

As such, the primary reference areas included Reach 1 (headwaters of the Sudbury River;

shallow lotic), the Charles River in the vicinity of Millis (deeper lotic), and the Sudbury

Reservoir west of Framingham (lacustrine). Other reference areas included Whitehall

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Reservoir (also in the headwaters of the Sudbury River; lacustrine) and Delaney National

Wildlife Refuge (lacustrine).

4.1.3 Affected Media

As noted previously, mercury is the contaminant of concern for this Operable Unit of the

Sudbury River. As such, the following discussion presents information regarding the

cycling of mercury in the Sudbury River.

Sediments can function as a sink for mercury in aquatic ecosystems if they are isolated

from active biogeochemical cycling. Conversely, the sediments can serve as a source of

potentially available mercury, given that some of the inorganic mercury can be

methylated and/or resuspended. Within the Sudbury River system, inorganic mercury

binds tightly to organic particles and shows little tendency to diffuse within the sediment

profile once buried (Frazier et al. 2000). Reaches with high potential to act as

depositional areas include Reaches 3 (Reservoir 2), 4 (Reservoir 1), 6 (Saxonville Pond),

and 9 (Fairhaven Bay).

Waldron et al. (2000) have shown that the reservoirs (i.e., Reaches 3 and 4, which were

the only potential depositional areas studied) are sinks for total mercury. Mass-balance

studies (Colman and Breault, 2000; Waldron et al., 2000) and bioaccumulation

experiments (Naimo et al., 2000) have shown that methylmercury is actively produced in

the contaminated palustrine wetlands adjoining the Sudbury River in the upper extent of

Reach 7. The concept of methylation in the wetlands is supported by the data collected

during the 2003-2005 Supplemental Investigation. The average ratio of methylmercury

to total mercury in surficial soil (0-5 cm) samples from the wetlands in the lower extent

of Reach 8 is 0.9% versus averages from Reaches 2 through 10 ranging from 0.05% to

0.7% (the maximum average of which is less than the median for Reach 8 wetlands).

The export of methylmercury from the contaminated wetlands exceeds that from the

reservoirs. Production of methylmercury in wetlands increases during flooding, which is

a frequent event in the wetlands adjoining the Sudbury (Weiner and Shields, 2000).

Active methylation and subsequent releases to adjacent surface waters is consistent with

17

current literature on the cycling of mercury in riverine systems (Dennis et al., 2005; St.

Louis et al., 1994).

Mercury contamination has also been found in surface water (USGS, unpublished report)

and in various biota (e.g., fish and birds) inhabiting or foraging in the Sudbury River

(BRI, in progress).

4.1.4 Existing and Potential Exposure Pathways

The Nyanza Site, which covers approximately 35 acres, is situated in an industrial area

0.4 km south of the Sudbury River. As noted previously, surface water runoff and

groundwater discharged from the property drains through a series of waterways and

wetlands until releasing into the Sudbury River. A majority of the land surrounding the

Sudbury River is suburban residential, consisting of several closely spaced urban centers

connected by arterial commuting routes.

The Sudbury River from its source to its confluence with the Assabet and Concord Rivers

is designated by the Massachusetts Department of Environmental Protection as a Class B

Inland Water (MADEP, 2000). As such, the waters of the Sudbury are designated as

habitat for fish, other aquatic life and wildlife, and for primary (e.g., wading and

swimming) and secondary recreation (e.g., fishing and boating). In addition, they are

designated as a suitable source of irrigation and other agricultural uses water, industrial

cooling and process uses, and public water supply with appropriate treatment. Seventeen

miles of the Sudbury River were designated “wild and scenic” in April, 1999.

4.1.5 Conceptual Model Presentation

Based on a review of the extent and transport of mercury within the Sudbury River

drainage, and as a result of a thorough evaluation of potential human health and

ecological exposures, graphical depictions of the site conceptual model are presented.

The human health site conceptual model, incorporating all exposure scenarios evaluated

among the three risk assessments performed to date (i.e., 1992, 1999, and 2006) is

presented in Figure 3. The ecological site conceptual model is presented in Figure 4.

18

B. Identify the natural and man-made disruptive forces that were considered and how they were considered when evaluating sediment alternatives. Where appropriate, identify the intensities or recurrence intervals of the fources, e.g., hurricane rating, flood recurrence interval and briefly expliain why these intensities or recurrence intervals were chosen.

Although the remedial alternatives have not been selected yet, what is known about the

transport of contaminated sediment and forces potentially disruptive to sediment is

presented below.

4.1.6 Sediment Transport

Concentrations of mercury in the most recently deposited sediments (<1 cm) far exceed

the natural abundance of mercury in fine-grained sediments from the river basin. These

concentrations are presumably not derived from upward movement of mercury given the

high organic content of the sediments (Frazier et al., 2000).

Since substantial vertical mixing was not evident from the 210Pb profiles, the surficial

concentrations higher than attributable to atmospheric deposition indicate that mercury is

entering or recycling within the ecosystem. For Reaches 3 and 4, where the highest

mercury sediment concentrations are found, the increased mercury concentrations are

suggested to be from inputs from site, based on findings in Frazier et al. (2000) and the

mass-balance analysis of Waldron et al. (2000). In contrast with the recent decreases in

sediment accumulation seen in the reservoir cores, in cores collected from the wetlands

associated with Reach 7 and Reach 9 itself, mercury accumulation and flux ratios in

surface sediments were more than ¾ of the historical maximal values. This is likely

attributable to increased rates of sedimentation in these areas or from other, unidentified

point sources downstream of Nyanza site (Frazier et al., 2000). Based on the high (i.e.,

approximately an order of magnitude higher) surficial sediment mercury concentrations

found in samples collected in the Reach 7 floodplain wetland complex during 2005, the

Reach 7 wetland area it is a likely downstream source of mercury contamination.

4.1.7 Potential Catastrophic Events

Wiener and Shields (2000) noted that the “probability of substantial hydrologic

resuspension and transport of bottom sediments in the most contaminated reservoirs

19

seems to be small under prevailing conditions.” Results from modeling conducted by the

Army Corps of Engineers, Waterways Experiment Station are presented in: Report on

Sediment Transport Modeling of the Sudbury River (Nail and Abraham., 1997). The

purpose of this report was determine the potential for resuspension and transport of

mercury contaminated sediments within Reservoirs 2 and 1 (Reaches 3 and 4,

respectively) on the Sudbury River. The models run were the RMA-2 and SED2D

models from the TABS-MD system (Thomas and McAnally, 1990). Five different

scenarios were considered: 1) 3-year flood (as in 1991); 2) 14-year flood (as in 1987), 3)

100-year flood (as in 1955); 4) 1000-year flood; and 5) dam breakage.

The modeling indicated that, under 100-year flood conditions there are no extended areas

where scour depth is deep enough to reach the most highly contaminated sediments. The

maximum depth of scour predicted is locally at the constriction marking the uppermost

extreme reach of each reservoir. Although the predicted maximum scour at these two

locations is sufficient to reach contaminated sediments; these locations are isolated and

are not co-located with the highest contamination. The 1000-year flood modeling results

show limited (albeit deeper) localized areas of scour. The results of the dam break

scenario indicated three areas (just downstream of the Conrail Bridge, the bend above the

Fountain Street Bridge, and near Dam 2) in which the maximum scour in Reach 3 would

exceed 45.7 cm, with the maximum scour being 53.3 cm in the bend above the Fountain

Street Bridge. Maximum concentrations in Reach 3 were found at 26 cm or less.

Several dams are located along the Sudbury River. Of these, at least 4 are listed as “high

hazard” i.e., “Dams located where failure or misoperation will likely cause loss of life

and serious damage to home(s), industrial or commercial facilities, important public

utilities, main highway(s) or railroad(s)” (310 CMR 10.00. Section 10.06 (3)). The dams

associated with the reservoirs are considered high hazard and are owned and operated by

the Massachusetts Department of Conservation and Recreation (DCR). All “high hazard”

dams must be inspected every 1-2 years. Middlesex County has experienced additional

flooding since the Nail and Abraham (1997) report was issued, including one flood in

2001 in which the county was declared a federal disaster area.

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Predictions from sediment transport modeling are supported by results from 210Pb dating

of sediment cores from the reservoirs (Frazier et al. 2000). Substantial vertical mixing

was not evident from the 210Pb profiles, and cores from the reservoirs showed little

evidence of bioturbation or past physical disturbance. Barring human disturbance or dam

failure, the probability of substantial resuspension in or transport of contaminated

sediments from the reservoirs would seem to be small (Frazier et al., 2000).

Additional information that will be considered when weighing remedial alternatives

includes that of the safety rating of the dams, likelihood of dam failure, and probability of

natural disasters (e.g., earthquakes, hurricanes) that could cause or contribute to major

flooding.

4.1.8 Sediment Core Concentrations

During the remedial alternative selection phase, it will be important to overlay the

scour/deposition modeling results with the most current sediment concentrations to

determine the potential for disturbing contaminated sediment. Figure 5 presents the

Reach 3 sediment core concentrations to show the vertical distribution of contamination.

5. USE AN ITERATIVE APPROACH IN A RISK-BASED FRAMEWORK

A. Briefly describe the major ways in which an iterative approach was used at the site. (We define “iterative approach” broadly it include approaches that incorporate testing of hypotheses and conclusions and foster re­evaluation as new information is gathered.)

As presented in the Conceptual Model discussion (see Risk management Principle #4),

Nyanza OU IV is a structurally a diverse and complex site (e.g., flowing reaches,

impoundments, bordering wetlands). An additional complication associated with the

understanding and management of risk at this site is the complex chemical cycle of

mercury in aquatic environments that is closely tied to site-specific conditions like pH,

redox conditions, nutrient content, microbial activity, sedimentation rates, etc. Therefore

an iterative approach was used to characterize the nature and extent of mercury

contamination within this Sudbury River and to clarify and reduce the uncertainty

associated with the assessment of human health and ecological risks. Figure 6 highlights

21

the primary components of the iterative process used for OU IV (Sudbury River). The

following discussion provides a brief overview of the objectives, results and limitations

of each of the major components identified in Figure 6.

5.1.1 Nyanza OU III Remedial Investigation Report (NUS 1992)

The primary objectives of this report were to characterize the nature end extent of

contamination in the Sudbury River, identify potential human health and environmental

risks and support the evaluation of remedial alternatives. Characterization included 2

Phases of surface water, sediment, and biota (fish and invertebrate) collection. The first

phase looked at a full CLP suite whenever possible, by phase 2 the emphasis was focused

on mercury, chromium, chlorobenzene, 1-2 dichlorobenzene and TCE, with mercury

being the only contaminant unique to the Nyanza Site. In general, the highest levels of

mercury were identified in Reach 3 (Reservoir 2), the first major depositional area

downstream from the site. Both the HHRA and ERA identified mercury (or

methylmercury) as the risk drivers. The fish ingestion pathway was the major contributor

to observed risk. Major report limitations included: no fish data for several reaches, no

whole body fish samples, data quality concern for some biota samples, high degree of

uncertainty with exposure modeling, and limited knowledge regarding the bioavailability

of sedimentary mercury in the ecosystem.

5.1.2 Task Force Studies (1994-1996)

As a result of information gaps identified with the submission of the OU III RI, a

multidisciplinary team was assembled to critically examine the environmental fate,

physical transport, bioavailability and bioaccumulation of mercury within the Sudbury

River system. The investigations included contaminated and reference impoundments,

flowing reaches and palustrine wetlands in the river floodplain and employed both

mensurative studies and manipulative experiments. The following is a list of the studies

conducted and a brief summary of the associated results:

1) Stratigraphy and historic accumulation of mercury in recent depositional sediments in the Sudbury River (Frazier et al. 2000) – mercury accumulation in sediments peaked from 1976-1982. Mercury accumulation rates generally decrease with increasing distance from the site, upward

22

movement of mercury from deeper strata seems unlikely, remobilization and recycling of mercury may be occurring in wetland areas associated with the Great Meadows National Wildlife Refuge.

2) Sampling for mercury at subnanogram per litre concentration for load estimation in rivers (Colman and Breault 2000) – ultra-clean sampling methodologies were integrated with isokinetic vertical composites sampling procedures to provide high quality data subsequently used to estimate mercury loads (see Waldron et al. 2000).

3) Distribution, hydrologic transport and cycling of total mercury in a contaminated river-reservoir-wetland system (Waldron et al. 2000) – mercury loading calculations indicate mean ∑Hg loads increased six-fold as the Sudbury River passes the Nyanza Site, mean ∑Hg loads continue to decrease through Reaches 3, 4, 5, and 6, with 23% of the load removed by sedimentation at Reach 3 (Reservoir 2); mean ∑Hg and MeHg levels increased as they passed through the wetland complex in Reaches 7 and 8, highest MeHg loads were associated with low flows and increased temperature.

4) Sediment transport modeling of the Sudbury River (Nail and Abraham 1997) – study looked at the potential for resuspension and transport of mercury contaminated sediments within Reservoirs 1 and 2; 1000 yr flood event would result in up to 1 ft of scouring between Conrail Bridge and Fountain Street in Reservoir 2; no flooding scenarios resulted in enough scour to reach highly contaminated sediments in Reservoir 1; dam break scenario at Reservoirs 2 and 1 would result in approximately 1.75 ft of scour in Reservoir 2 near the dam and at locations identified in 1000 yr flood scenario.

5) Bioavailability of sediment-associated mercury to Hexagenia mayflies in a contaminated floodplain river (Naimo et al. 2000) – no toxic effects were observed in mayflies exposed to surface sediments, mayfly growth and MeHg burdens were unrelated to ∑Hg content in surficial sediments, MeHg concentrations in mayflies were highest in individuals exposed to sediments collected from Reservoir 2 and the wetlands in Reaches 7 and 8 – this parallels the spatial trend in MeHg abundance in river water observed Waldron et al.

6) An in situ assessment of mercury contamination in the Sudbury River, Massachusetts, using transplanted freshwater mussels (Elliptio complanta) (Beckvar et al. 2000) – survival rates were not significantly different between stations (except station with low DO); reference stations had mussels in poor condition at study end, mean ∑ Hg and MeHg decreased with distance from the site; greatest growth occurred in Reach 9 and 10 mussels (not statistically significant), MeHg concentrations significantly increased at all stations except the reference location in Whitehall Reservoir, factors other than Hg in sediments appear to be influencing mussels growth.

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7) Factors affecting food chain transfer of mercury in the vicinity of the Nyanza Site, Sudbury River, Massachusetts (Haines et al. 2003) – larger predatory fish have higher Hg concentrations than smaller fish of the same species; fillet and whole-body Hg concentrations in largemouth bass are higher in site impacted areas than reference locations, prey item Hg concentrations are highest in Reservoir 2, prey item ∑Hg and MeHg concentrations are significantly related to largemouth bass ∑Hg concentrations.

5.1.3 Supplemental Baseline Human Health and Ecological Risk Assessments (Weston 1999)

The supplemental human health and ecological risk assessments incorporated data

collected by the Task Force and surface water and sediment data collected by NUS as

part of the OU III Remedial Investigation Report (NUS, 1992). The primary objectives

of these assessments were to evaluate the potential for adverse effects to susceptible

human populations and target ecological communities and receptors that could result

from exposure to mercury present in Sudbury River surface water, sediment, and biota.

The 1999 HHRA concluded that potential human exposure to mercury in surface water

and sediment in the Sudbury River was well below any level of concern. Exposure

through the catch and consumption of fish from Reach 3 (Reservoir 2) and Reach 8

(Great Meadows National Wildlife Refuge) posed an unacceptable level of risk (HQs >

10) to subsistence anglers, i.e., individuals who obtain all of their dietary protein from

fish caught from theses segments of the river. Hazard quotients for ethnic and

recreational anglers also exceeded unity in Reaches 2 and 8. However it is important to

recognize that fish data for this assessment were only available for Reaches 1 (reference),

3 and 8, and that the Reach 1 HQs for the ethnic and subsistence angler were slightly

greater that unity.

The 1999 SBERA incorporated the findings reported in the Task Force ecological studies

presented in the Section 5.1; compared surface water, sediment and biota mercury

concentrations to appropriate criteria and benchmarks; and modeled potential exposure

and effects for the belted kingfisher, great blue heron, raccoon, and river otter. Chronic

ambient water quality criteria (using NUS, 1992 data) was exceeded for several samples

24

in Reaches 3 and 4, and one sample in Reaches 1 (reference) and 6. Surface water

samples taken as part of the Task Force studies did not exceed water criteria. OMEE

severe effect level (SEL) for mercury in sediments, compared with both the NUS 1992

and Task Force datasets, was exceeded by multiple samples in Reaches 2,3,4,6,7,8 and 9

with the greatest exceedances in Reaches 3 (Reservoir 2) and 4 (Reservoir 1).

Comparisons of Task Force fish tissue data to literature-based effect levels resulted in

HQs less than unity. The modeled exposure and effects analysis for avian receptors

indicated the potential for reproductive effects to belted kingfisher foraging in Reaches 3

and 8, in tributaries to Reach 7 and 1. The mammalian modeling results indicate a slight

potential for nephrotoxic effects to river otters foraging in Reaches 7, 8, and the Reach 1

tributary. The ingestion of fish and crayfish were the dominant exposure pathways that

resulted in risk to these two target species.

While the Task Force study results help elucidate mercury transport and availability

within the Sudbury River system, several information gaps identified after the completion

of the 1999 human health and ecological risk assessment they include, but are not limited

to the following: there is limited sediment contamination information in the original RI

data (which 10 years old and has data quality issues); because the mercury concentration

data for fish tissue from the RI did not meet quality specifications required for risk

assessments it was not included in the 1999 HHRA and SBERA, therefore fish tissue data

were not available or limited for several reaches; fish tissue benchmark comparisons and

trophic level exposure models have a high degree of uncertainty as a result of the fish

tissue chemistry data gaps; there are no direct measures of mercury exposure and

potential effects to upper trophic level organisms.

5.1.4 2003-2005 Supplemental Investigation

As a result of data gaps identified in the 1999 risks assessments and a better

understanding of potential risks associated with mercury bioaccumulation and

biomagnification within an aquatic food chain like the Sudbury River, additional data

collection activities were initiated in the spring of 2003. The primary objectives for this

new scope of work were to collect sufficient quality data so that the HHRA could be

updated and the ERA revised and finalized; at the same time, provide sufficient

25

information so that remediation alternatives could be evaluated to support a record of

decision (ROD). Major data collection activities included: 1) surface water, sediment,

and fish tissue collection as following a data gaps analysis; 2) collect tissue samples

(blood, feathers, and/or eggs) from different avian feeding guilds to better quantify

mercury bioavailability and potential effects; 3) collect crayfish tissue samples to

elucidate mercury food chain transfer; 4) collect piscivorous mammal tissues to quantify

mercury bioavailabilty and potential effects; and 5) conduct mercury transfer modeling

studies to help quantify the movement of mercury through the diverse and complex

environments present within the Sudbury River ecosystem (Bart needs to confirm).

5.1.5 Baseline Human Health and Ecological Risk Assessments (Avatar 2006)

This section presents a brief summary of the completed HHRA and some preliminary

results form the SBERA that will be completed later this year.

5.1.5.1 2006 HHRA Results

Exposure to mercury levels in fish caught and consumed from Reaches 2, 3, and 9

represented a potential risk to individuals for all fish consumption scenarios evaluated.

For Reaches 4, 6, 8, and 10, exposure to mercury levels in fish caught and consumed

from each reach represented a potential risk to individuals for all fish consumption

scenarios evaluated except for the adult recreational angler scenario. For Reaches 5 and

7 (excluding Heard Pond), exposure to mercury levels in fish caught and consumed from

each reach represented a potential risk to individuals for all fish consumption scenarios

evaluated except for the adult and child recreational angler scenarios. As for Heard Pond,

the exposure to mercury levels in fish caught and consumed from Heard Pond

represented a potential risk only to the child of the ethnic angler and the subsistence

angler. Table 1 presents a summary of these results.

5.1.5.2 2006 SBERA Preliminary Results

The SBERA is not yet complete, but preliminary results are available for surface water

and sediment hazards based on comparisons to benchmarks, as well as potential risks to

wildlife based on critical body residue and modeled dose comparisons. These

26

preliminary results, as well as the final results from the mayfly (Naimo et al., 1997) and

mussel (Salazar et al. 1996) studies are summarized below. Note that modeling results

are available for reasonable maximum exposure (RME) and central tendency (CTE)

scenarios combined with both no-effect and effect level toxicity values. Only the no-

effect RME-based ecological effects quotients (EEQs) are used for discussion purposes

herein.

5.1.5.2.1 Aquatic Life

Comparisons with Surface Water Benchmarks

Potential direct effects associated with surface water contamination in the Sudbury River

were evaluated by comparing COPC concentrations in surface water to federal AWQCs.

The surface water data set had no concentrations exceeding either the acute or chronic

AWQCs (i.e., all EEQs < 1).

Comparisons with Sediment Benchmarks

Sediment effects were estimated by comparing sediment chemical concentrations with

sediment quality guidelines developed by MacDonald et al. (2000). Approximately 81%

of the surficial sediment samples from Reaches 2 through 10 (including Heard Pond)

exceeded the threshold effect concentration (TEC). All of the sediment samples

exceeded the TEC in Reaches 3, 4, 7 – Heard Pond, and 9. The frequency of exceeding

the TEC was lowest in Reach 7 proper – 38%. As far the magnitude by which the TEC

was exceeded, approximately 50 exceeded by <10-fold, approximately 50 more exceeded

by 10- to 100-fold, and 16 (all from Reach 3) exceeded the TEC by >1000-fold. The

probably effects concentration (PEC) was exceeded by approximately 60% of the same

samples. Of the samples exceeding the PEC, approximately two-thirds did so by <10­

fold. The remainder exceed the PEC by less than > 10 but <100.

Mayfly Study

When data from both years of the study were combined, there was a significant, positive

correlation between the concentration of total mercury in mayflies and test sediment.

27

However, total mercury concentrations in test sediments were not a good predictor of

methylmercury concentrations in mayflies.

The growth of mayflies evaluated in 1994 varied significantly among sediment

treatments, but was unrelated to the total mercury concentrations in test sediment.

Average mayfly growth in the Whitehall Reservoir reference area, 2.2 mm (test 1) and

2.3 mm (test 2) was significantly less than a majority of the other treatments, 5.1 mm

(test 1) and 6.1 mm (test 2). Slower growth in mayflies exposed to sediments from

Whitehall Reservoir may have resulted from physical characteristics of the test sediment

such as high organic content.

The growth of mayflies evaluated in 1995 varied among treatments, but was also

unrelated to the total mercury concentrations in test sediment. Average mayfly growth in

the Northern Contaminated Wetland (in Reach 8) was significantly lower than that in the

Hop Brook reference-wetland during both tests 3 and 4. The overall mean growth of

mayflies was greater in test 3 (5.8 mm) than in test 4 (3.5 mm), which may be related to

water levels in the study area when sediments were sampled.

Variation in mayfly growth seems unrelated to mercury exposure. The growth of

mayflies (all data combined) did not decrease with (1) increasing concentrations of

methylmercury in water, (2) total mercury in sediment, (3) total mercury in mayflies, and

(4) methylmercury in mayflies.

Survival of mayflies in all tests was unrelated to the concentrations of total mercury in

test sediment. Overall mayfly survival ranged from 90% in test 3 to 96% in test 2. Mean

mayfly survival did not vary among treatment in any test.

Mussel Study

The use of concentration data alone suggests the preferential accumulation of total

mercury by mussels closest to the Nyanza site and depuration by those mussels in the

wetlands in the lower reach (Reach 10) of the Sudbury River study area. However, the

use of content data, which normalizes the mercury data for growth, indicates that the total

mercury content data showed no statistical difference in uptake among stations.

28

Similarly, the concentration data also suggests that methylmercury was not significantly

bioaccumulated by mussels placed at the two farthest downriver stations (Fairhaven Bay

– Reach 9 and Thoreau Street Bridge – Reach 10). However, when data are normalized

for growth, the methylmercury content data strongly suggests that mussels at all stations,

including these two stations, increased their body burden of methylmercury.

Mussel growth rates exhibited a downriver trend with growth rates lowest near the

Nyanza site and highest farther away from the site. The effects on mussel growth are

correlated to, and are likely associated with exposure to methylmercury. However,

without supporting sediment and surface water chemistry data, it cannot be definitely

concluded that the measured effects are due only to mercury exposure. The presence of

other unmeasured chemicals or environmental factors, such as food availability, may

have influenced mussel growth. It should also be noted that the source of methylmercury

that was accumulated by mussels throughout the study area is uncertain.

Crayfish CBRs

The crayfish data set had no concentrations exceeding either the no-effect or the effect-

based CBRs (i.e., all EEQs < 1).

Fish CBRs

On a per-reach basis, at least 85% of the concentrations in the fish data sets were below

the no-effect level (NEL). Except for one fish each from Reaches 8 and 9 and two fish

from Reach 10, all of the fish tissue concentrations were below the lowest effect level

(LEL).

5.1.5.2.2 Avian Wildlife

Tree Swallow

Trees swallow tissue (blood, feathers, and eggs) was collected in 2003 and 2004.

Between the two efforts, data are available for Reaches 3, 4, 7, 7 – Heard Pond, and 8.

Results from CBR comparisons with tissue associated with tree swallows are ambiguous.

Comparisons with blood and feathers (collected 2003 and 2004) show that concentrations

29

in tissue from tree swallows are below effect levels. However, these effect levels are

unbounded as no-effect level CBRs are not available for these tissues.

For eggs, both a no-effect level and effect level were available. Approximately 80-85%

of the concentrations in Reaches 3 and 4 (2004 collections) were below the no-effect

level but maximum concentrations exceeded the effect level. Reach 7 (2003 collection)

had egg concentrations falling between the no-effect and effect levels. Reach 7 – Heard

Pond (2004 collection) had approximately 15% of the egg concentrations falling below

the no-effect level, approximately 45% between the no-effect and effect levels, and 40%

above the effect levels. Eggs were collected in Reach 8 during both 2003 and 2004. In

2003, approximately 20% of the egg concentrations fell below the no-effect level, with

approximately 50% falling in between the no-effect and effect levels, and 30% above

effect levels. From the 2004 sampling, 10% fell below the no-effect level, with the

remaining 90% greater than the effect level.

In addition, eggs collected from reference areas (Charles River 2003 and 2004; Sudbury

Reservoir – 2003) had some mercury concentrations exceeding CBRs. Approximately

30% of the samples collected from the Charles River in 2003 fell between the no-effect

and effect levels, with approximately 25% of the concentrations being greater than the

effect level. For the 2004 data, 70% of the concentrations were between the no-effect

and effect levels. Sudbury Reservoir eggs were less contaminated, with approximately

80% of the concentrations falling below the no-effect level and the other 30% falling

between the no-effect and effect levels.

Based on comparisons of modeled doses to TRVs, EEQ values for total mercury exceed 1

for the tree swallow in all Sudbury River reaches, including Heard Pond. Doses are

marginally above the TRV (i.e., EEQ <2) in Reaches 7, 8, and 10. EEQs are range from

2 to 10 for Reaches 2, 5, 6, 7 – Heard Pond, 9 and are above 10 for Reaches 3 and 4.

Marsh Birds

Tissue samples were collected from several species of marsh birds. The general

collection included song and swamp sparrows, common yellowthroat, northern

30

waterthrush, and yellow warbler. Focused sampling was done for eastern kingbird (eggs

only) and red-winged blackbird (blood only). Each is discussed below.

Marsh bird tissue collected from Reach 7 (2003 and 2004 blood; 2003 feathers) had

concentrations below the effect levels. Blood and feathers collected from Reach 8 in

2003 had approximately 90% of the concentrations falling below the effect level; whereas

blood samples collected in 2004 all had concentrations below the effect level. In

addition, blood collected from the Charles River reference area (2003 and 2004) had

concentrations well below the effect level; whereas approximately 10% of the feather

samples (2003) had concentrations greater than the effect level. Note that these effect

levels are unbounded as no-effect level CBRs are not available for these tissues.

Eastern kingbird egg concentrations exceeded no effect levels in Reaches 7, 8, 9, 10, and

the Charles River. Reach 8 and the Charles River had some egg concentrations greater

than the effect level. For red-winged blackbirds, samples were available from Reach 8

for blood only. The potential for adverse effects are higher as all but 1 of 10 samples had

concentrations greater than the effect level.

Waterfowl

Hooded merganser and wood duck tissue samples (blood, feathers, and eggs) were

collected.

Hooded merganser tissue was collected in 2003, 2004, and 2005. The 2003 collection

year only yielded samples from reference areas (Delaney Wildlife Management Area and

Whitehall Reservoir). Concentrations in blood were below effect level, one of the two

available feather concentrations had a concentration above the effect level, and almost all

of the egg concentrations were above the effect level. For the 2004 sampling season, one

blood and one feather sample from Reach 8 were taken. Neither of these had

concentrations above the effect level. In 2005, samples were available from Reaches 4,

8, and reference areas (Charles River and Sudbury Reservoir). For Reach 4, only two egg

samples were collected. Both of the concentrations were greater than the effect level.

For Reach 8, 1 of 8 blood samples had a concentration greater than the effect level,

feather concentrations (n = 5) were below the effect level, and egg concentrations (n =

31

21) were all greater than the effect level. One of the two concentrations available from

the reference area were also above the effect level, feather concentrations were below the

effect level, and egg concentrations were above the effect level.

Wood duck tissue was collected in 2003 and 2004. Blood concentrations from Reach 7

(2004 n = 1) and Reach 8 (2003 n = 4; 2004 n= 1) and feather concentrations (2004 n= 1

each) were well below the effect levels. Only 1 of 4 egg concentrations from Reach 8

(2003 only) was above the effect level. Tissue concentrations from the reference areas

(Delaney Wildlife Management Area and Sudbury Reservoir) were below effect levels.

Kingfisher

Results from CBR comparisons with kingfisher levels (blood, feathers, egg, and prey

items) are ambiguous. In general, comparisons with egg and blood concentrations show

that adverse effects are unlikely; whereas comparisons with feather and prey

concentrations indicate the potential for adverse effects (i.e., Sudbury River-related

concentrations higher than lowest effect concentrations). Note that kingfisher

concentrations are only available from Reaches 7 and 8.

Based on comparisons of modeled doses to TRVs, EEQ values for methylmercury exceed

1 for the kingfisher in all Sudbury River reaches, except for Heard Pond. All EEQs,

however, are less than 3.

Great Blue Heron

Based on comparisons of modeled doses to TRVs, EEQ values for methylmercury

marginally exceed 1 for the great blue heron in Reaches 3, 9, and 10. The highest EEQ is

1.21 (Reach 3 and 10).

5.1.5.2.3 Mammalian Wildlife

Comparisons of mink blood, fur, brain, and liver concentrations to CBRs indicate some

individuals have the potential for reproductive changes or reduced survivorship.

However, concentrations in liver were well below concentrations associated with lethality

in mink and concentrations in the brain were well below concentrations associated with

neurochemical changes in mink.

32

Based on comparisons of modeled doses to TRVs, EEQ values for methylmercury exceed

1 for the mink in all Sudbury River reaches, except for Reach 7 – Heard Pond. Doses are

marginally above the TRV (i.e., EEQ <2) in Reaches 2, 3, 4, 5, 6, and 7. The maximum

EEQ is 4.6 from Reach 10.

B. Briefly describe any early or interim actions planned or implemented at the site that address threats from contaminated sediment.

No interim actions have been undertaken or planned for OU IV. Remedial Actions have

been completed on OU III which addressed the continuing source areas of the site

including the Eastern Wetlands, Trolley Brook, Chemical Brook, Outfall Creek and the

Lower Raceway. These sediments were cleaned up to a mercury concentration of 1 ppm.

C. If the proposed sediment remedy will be implemented in phases or is part of a larger phased approach to the site as a whole, briefly describe the phases.

The four operable units of the site have been described previously. OU I, the landfill and

OU III, the continuing source areas have been cleaned up and long term monitoring is

being conducted by the MA DEP. While phasing is not expected on OU IV, it is possible

that the river could end up with two distinct recommended actions for the reservoir and

Great Meadows.

6. CAREFULLY EVALUATE THE ASSUMPTIONS AND UNCERTAINTIES ASSOCIATED WITH SITE CHARACTERIZATION DATA AND SITE MODELS

A. Briefly identify the most important continuing uncertainties associated with site characterization data and, where applicable, with qualitative or quantitative models, including input parameters, which were important (1) to the human health and ecological risk assessments and (2) to the evaluation of potential sediment remedies. Briefly explain how those uncertainties were accounted for (e.g., use of sensitivity analyses or reasonable conservative assumptions.)

The primary sources of uncertainty regarding the estimation of risk and subsequent clean­

up decisions lie with the site characterization data, field studies, and modeling exercises.

The following subsections highlight the key sources of uncertainty as they pertain to the

risk assessment process for OU IV.

33

6.1.1 Site Characterization

Data were collected for chemical analysis from the Sudbury River in support of the OU

III RI (NUS, 1992), Task Force studies, and during 2003-2005 Supplemental

Investigation field efforts. Limitations with the OU III RI data were discussed in Risk

Management Principle #5. Since this data was not deemed appropriate for use in the

2006 risk assessments, uncertainties with OU III RI will not be presented in this section.

Uncertainties and limitations associated with the data used in support of the 2006 risk

assessments (i.e., Task Force and 2003-2005 Supplemental Investigations) is the focus of

the discussion below.

6.1.1.1 Task Force Studies Data Sets

As noted under Risk Management Principle #5, the Task Force was directed to develop

information necessary to produce a scientifically defensible ecological risk assessment

associated with mercury contamination in the Sudbury River. Numerous studies were

undertaken from 1993 to 1995, resulting in the collection of mercury data for surface

water, sediment, and tissue (mussel, mayfly, dragonfly, crayfish, and fish) in addition to

direct measurements of effects to mayflies and freshwater mussels. Because of the data

overlap and temporal differences (8-10 years) between the Task Force and Supplemental

Investigation data, the only Task Force data directly incorporated in the 2006 risk

assessments were the mussel study (Salazar et al., 1996) and mayfly study (Naimo et al.,

1997), which were used in the 2006 SBERA. There were numerous spatial gaps in data

coverage in the Task Force data, as these data were to supplement the OU III RI data,

which was later found to be of insufficient quality.

6.1.1.2 2003-2005 Supplemental Investigation Data Set

As noted under Risk Management Principle #5, several rounds of sampling have been

conducted as part of the 2003-2005 Supplemental Investigation. Sediment, surface water,

and several different biological tissues were analyzed to support the HHRA and SBERA.

Tissue chemistry data collected included: crayfish, fish of various size and age classes,

waterfowl (eggs, blood, and feathers), tree swallows (eggs, blood, and feathers), eastern

kingbird (eggs), belted kingfisher (blood and eggs), marsh bird (eggs, blood, and

feathers), and mink (blood, fur, liver, and brain). Fish tissue and sediment were collected 34

from all reaches of the river. Crayfish were collected from those reaches where they were

found. Tissue samples from higher trophic-level organisms (birds and mammals) were

measured only in the primary target areas (i.e., areas that indicated the greatest risk

potential based on the 1999 RAs). All tissue collection efforts included the collection of

samples from reference locations. Biological tissue was collected to reduce the

uncertainty associated with estimating the bioavailability and bioaccumulation of

mercury within the Sudbury River. Figures 7 through 13 present the sampling locations

for sediment, surface water, and crayfish; and Figures 14 through 19 present the sampling

locations for birds and mammals.

Over 200 sediments samples were collected during the 2003-2005 Supplemental

Investigation. Although sediment samples were collected from each reach, the samples

collected were not evenly distributed throughout the reaches as the results from historic

sampling and previous risk assessments allowed for targeting areas that were data-poor as

well as targeting areas of potentially higher concentrations and/or exposure.

Uncertainties regarding mercury sediment concentrations in the river are fairly low,

particularly in the primary target areas.

Surface water mercury and methylmercury concentrations are available for each reach

except for Reach 6 (Saxonville Reservoir); and for Reaches 9 (Fairhaven Bay) and 10

(Fairhaven Bay outlet to the Assabet River). Not having surface water data for these

reaches is a data gap, but likely does not significantly affect the risk assessments for the

reasons below (among others).

� Historic surface water concentrations were available from these reaches with

which to calculate risk from mercury. Resultant risks were below levels of

concern.

� Surface water concentrations for total mercury and methylmercury collected

during the Supplemental Investigation did not exceed AWQC in reaches

where historical data indicate the highest concentration were typically

detected (i.e., Reaches 2, 7, and 8). Note that this surface water data used in

35

the ERA were collected in October 2003; therefore, mercury concentrations

associated with varying flow conditions was not accounted for.

� Since mercury is a bioaccumulative, effects on higher trophic level organisms

from the ingestion of contaminated prey is of most concern. Mercury data are

available for prey items; therefore, surface water data are not needed to

estimate prey concentrations.

Both whole body (for the most part individual whole body, but some composited whole

body) crayfish and crayfish tails were submitted for chemical analyses. Crayfish data are

only available for Reaches 1 through 7. Although crayfish collection was attempted in

the lower reaches (Reaches 8 through 10), the collection effort from the GMNWR (Reach

8) to the confluence with the Assabet River was not successful. While the absence of

crayfish data from the lower reaches is a data gap, in the ecological risk assessment,

higher dietary proportions of fish were used in place of crayfish concentrations for

modeling purposes. Since fish are higher trophic level organisms, and; therefore,

expected to have higher concentrations than crayfish, this substitution is conservative.

Table 2 presents the number of fish samples analyzed per reach. Well over 1,000 fish

samples from various species and size classes were analyzed. Figures 20 through 28 are

graphical depictions of the mercury and methylmercury concentrations per species per

reach. The confidence in the fish characterization data is high.

Blood, feather, and egg samples were collected from various avian species (hooded

mergansers, wood ducks, belted kingfisher, tree swallows, eastern kingbird, red-winged

blackbird, and marsh birds) in support of the field investigations. In addition to reference

locations, the reaches from which avian tissue were collected is as follows:

� Hooded mergansers and wood ducks – Reaches 4, 7, and 8;

� Belted kingfisher – Reaches 7 and 8;

� Tree swallow – Reaches 3, 4, 7, 7 – Heard Pond, and 8;

� Eastern kingbird – Reaches 7, 8, 9, and 10;

36

� Red-winged blackbird – Reach 8

� Marsh birds – Reaches 7, 7 – Heard Pond, and 8.

Blood, fur, liver, and brain samples were submitted for 5 mink trapped from 3 locations –

Reservoir 2 (Reach 3), Reservoir 1 (Reach 4), and Reach 7. Uncertainties associated

with the avian and mammalian data will be discussed in more detail in the “Laboratory

and Field Investigations” subsection below.

Aside from potential issues with coverage, there are uncertainties associated with the

mercury analyses performed. For sediment and surface water, total and methylmercury

were analyzed for in each sample, reducing the uncertainties associated with the

speciation split. For biota total mercury was always analyzed for, with a subset of

samples analyzed for methylmercury (as for crayfish and fish) or methylmercury was not

a requested analysis (as for all bird and mammal tissue). Literature reports that the

majority of mercury found in fish, bird, and mammal tissue (i.e., approximately 90% or

greater) is in the methylated form; and comparisons of site-specific paired crayfish and

fish samples bears this out. However, since methylmercury was not analyzed for in avian

and mammalian tissue there are uncertainties as to what the site-specific speciation ratio

is.

6.1.2 Laboratory and Field Investigations

Numerous field investigations have been undertaken for assessment of mercury

contamination in the Sudbury River. In addition to the avian and mammalian studies

undertaken during the 2003-2005 Supplemental Investigation, biological accumulation

and effects studies were conducted by Task Force members (Naimo et al., 1997; and

Salazar et al., 1996), which looked at mayflies and freshwater mussels, respectively. The

mayfly study was a laboratory-based study that used the sediments collected in the field.

The mussel study was conducted in situ thereby eliminating the typical uncertainties

associated with laboratory to field extrapolation. General uncertainties applying to both

laboratory and field investigations are noted below.

While advances in the standardization and methodologies associated with laboratory-

based sediment bioaccumulation and toxicity tests and in situ studies continue,

37

uncertainties still exist when trying to extrapolate the results of these tests from a few

species to an enormously complex ecosystem (Cairns and Mount, 1990, Chapman, 1995).

A reduction of these uncertainties can be achieved only by understanding the basic

processes that affect chemical accumulation and toxicity, such as speciation, partitioning,

solubility, thermodynamics, and microbial metabolism (Burgess and Scott, 1992). These

factors are location-specific and subject to the unique biological and abiotic conditions

present within each sample or sample location (Suter et al., 2000) and as such, cannot be

simultaneously accounted for in sediment toxicity.

As for Supplemental Investigation field studies (i.e., tissue residue studies), additional

uncertainties apply. For migratory species, the initial contaminant body burden of the

contaminant is unknown, confounding the ability to tie potential toxicological effects on

adults the site. However, when possible the field studies included a range of measures

(e.g., blood, feather, and egg concentrations) for various life stages. Other general

uncertainties are as follows:

� Various environmental conditions such as water temperature could affect food

availability and other factors that could affect the biological indicators of

concern.

� Studies did not evaluate potential behavioral effects and did not monitor

fledgling success and survival.

� It was assumed that exposure during the reproductive period was all site-

related.

6.1.3 Modeling

The hazard quotient (HQ) approach was used to characterize potential risks when

evaluating mercury concentrations in surface water, sediment, biological tissue and when

comparing exposure modeling results to reference doses (RfDs; human health) and

toxicity reference values (TRVs; ecological). The HQ approach, which is typically

conservative (e.g., TRVs are typically NOAEL-based, RfD incorporates safety factors),

38

does not quantify associated uncertainty and variability and simply provides a relative

measure of the potential for adverse effects.

Another general uncertainty associated with calculating HQs on a chemical-specific basis

is that this does not account for additivity, synergism, or antagonism as well as

interactions with other chemicals present, and may result in an over- or underestimation

of total potential risk. This may be particularly important as mercury was the only

chemical of concern for this operable unit (OU IV), although not the only contaminant

present in the Sudbury River.

In general, worst-case assumptions were used to develop risk estimates in both the

HHRA and ERA; therefore, it is usually safe to assume the HQs or EEQs near or below

unity are indicative of scenarios where adverse effects are unlikely.

The major uncertainties associated with the exposure modeling exercises are presented

for the HHRA and SBERA below.

6.1.3.1 Human Health

The equation and discussion below presents the exposure model and uncertainties

associated with assessing risk to human health receptors

General HHRA Fish Ingestion Dose Model

AT 1 x

BW 1IR - F x FI x CF x EF x ED xCTDI fish ×=

Where:

TDI = Total daily intake (mg/kg-day) Cfish = Chemical concentration in fish (mg/kg) IR-F = Fish ingestion rate (g/day) FI = Fraction of fish ingested from contaminated source (unitless)

CF = Conversion factor (kg/g) EF = Exposure frequency (days/year) ED = Exposure duration (years) BW = Body weight (kg) AT = Averaging time (days)

39

There are a few general uncertainties relating to the overall human health evaluation that

pertain to exposure routes, receptors, and toxicity. Also, although the existence of

subsistence and ethnic fishing is unsubstantiated, the 2006 HHRA evaluated the potential

for health effects associated with subsistence and ethnic fishing. Lastly, the chronic oral

reference dose developed by the EPA for mercury was derived to be protective of adverse

neurological effects in infants and young children based on maternal exposure. As such,

the application of the chronic oral RfD used in this assessment most probably

overestimates the risk of mercury exposure to adults.

In addition to the general uncertainties discussed above, the following is a list of more

detailed uncertainties related to the above exposure parameters:

� Aggregate fish species EPCs were used instead of individual species EPCs due to the lack of site-specific information and may underestimate or overestimate concentrations depending on the species.

� The use of fillet data to approximate the concentrations in whole body fish when corresponding offal data were not available is conservative and likely to overestimate the potential for adverse health effects to the ethnic angler receptors.

� Recreational Angler Ingestion Rates –Fish ingestion rates were specific to the types of water body (e.g., flowing or standing) applicable to the reach. Therefore, if an individual fishes only the flowing or standing waters, the potential for health effects may be overestimated.

� Recreational and Ethnic Angler – The “all household consumers share” values were used as the child fish ingestion rates. This assumption requires that all household members ingest the same amount and therefore the child ingestion rate is likely overestimated. The same applies to the ethnic child receptor as well.

� Fraction Ingested – The fraction ingested is assumed to be 0.5 based on the assumption that 80% of anglers fish at least two areas. Since this risk assessment was done on a per-reach basis, it is not known if this assumption would under- or overestimate risk.

� Exposure Frequency – The ingestion rates used in this risk assessment are average daily ingestion rates. Using an exposure frequency of 350 days/year may slightly underestimate the overall consumption of fish; and therefore, the potential for health effects.

40

� Body Weight – A child body weight of 15 kg (~33 lb) and an adult body weight of 70 kg (~154 lb) were used. Depending upon a child’s age, the 15 kg value could lead to an under- or overestimate of exposure. Also, the 70 kg value likely underestimates exposure for receptors aged 7 through late adolescence and women.

6.1.3.2 Ecological

Major uncertainties for ecological risk modeling fall into two categories: uncertainty in

the dose estimate (i.e., exposure modeling) and uncertainty with the effects estimate.

Both are discussed below.

6.1.3.2.1 Exposure Dose Modeling Uncertainties

The general form of the ecological exposure model and discussion of exposure modeling

uncertainties for ecological receptors is discussed below.

General Ecological Ingestion-based Dose Model

n⎡⎛ ⎞ ⎤TDI = FT × ⎢⎜ FIR ×∑Ci × Pi ⎟ + SIR × Csed + WIR × Cw ⎥

⎣⎝ i=1 ⎠ ⎦

Where:

TDI = Total daily intake (mg/kg BW-day) FT = Foraging time in the exposure area (unitless) FIR = Body weight normalized food intake rate (kg ww/kg BW-day) Ci = Concentration in the ith prey item (mg/kg ww) Pi = Proportion of the ith prey item in the diet (unitless) SIR = Sediment ingestion rate (kg dw/kg BW-day) Csed = Concentration in sediment (mg/kg dw) WIR = Water ingestion rate (L/kg BW-day) Cw = Concentration in water (mg/L)

The ingestion route was the only exposure route evaluated in the SBERA because there is

limited information to assess other potential exposure routes such as dermal absorption

41

and inhalation. However, the ingestion route is expected to be of greatest concern for a

bioaccumulative chemical like mercury.

There are several uncertainties associated with assumptions regarding foraging and

dietary habits of the ecological receptors. It was assumed that avian and mammalian

target receptors forage exclusively within a given reach.

There are also several uncertainties associated with the exposure model input parameters

such as body weight and dietary components. The use of average body weights may

under- or overestimate daily intake for individuals depending upon their sex, age,

breeding status, and time of year. It was also assumed that any sediment ingestion intake

was in addition to 100% of the dietary (food) intake, and not part of the total diet, which

may overestimate the intake of contaminants. Tree swallow prey concentrations were

estimated using the regression relationship developed by Naimo et al. (1997). It was also

assumed that for the kingfisher, great blue heron, and mink, the concentrations in crayfish

and/or fish were representative of concentrations in other dietary items since they were

the only potential prey items for which site-specific tissue concentrations were available

and the other potential dietary items likely have a relatively small contribution to total

diet. However, because mercury does bioaccumulate and biomagnifiy within the aquatic

food chain, prey items like fish are expected to be primary contributors to mercury

exposure in upper trophic level organisms. Since the fish data set developed for this ERA

is comprehensive, the uncertainty associated with this exposure pathway is considered

minimal.

6.1.3.2.2 Effects Uncertainties

In the 2006 SBERA, three types of effects values were employed: 1) abiotic medium

concentrations (e.g., federal ambient water quality criteria [AWQCs], sediment threshold

effect concentrations [TECs]); 2) critical body residues (CBRs); and 3) per-body weight

dose levels (i.e., toxicity reference values; TRVs).

In the case of abiotic media (i.e., surface water and sediment), site-specific toxicity

values were not available. However, the studies used in the development in the

benchmarks had to meet rigorous criteria and represented a wide-variety of species.

42

A major uncertainty with using CBRs is that there are few studies that have been

designed to link residues and biological effects. That is, there is not a strong a cause-

effect relationship between the tissue level and the observed toxicological effect in all

cases. However, advantages to using this approach over dose estimation methods is that

it implicitly considers system-specific differences in contaminant bioavailability,

assimilation, and metabolism differences among species or life stages, and multiple

routes of exposure, thereby resulting in less uncertainty from extrapolation approaches.

CBRs used in the 2006 SBERA are not species-specific (with the exception of tree

swallow eggs and mink fur), but were developed from the most sensitive endpoints

found.

The causal relationship between contaminant and effects, unlike CBRs, is implicit when

TRVs are used. However, perhaps the biggest uncertainty with the estimation of effects

is in the extrapolation of effect levels between species. Since extensive literature reviews

were conducted, good data are available on the potential range of effect levels. Although

data were available for the mammalian target species for use in the 2006 SBERA, avian

TRV values are not species-specific. Unlike most ERAs, there was no use of

uncertainty/safety factors in the development of TRVs incorporated in this assessment.

B. Identify any computer models used in the assessment of the site or evaluation of sediment alternatives. For each model or model group, indicate whether the model or model application was peer-reviewed and if so, briefly indicate whether that reivew was internal or external to EPA.

The Sudbury River in Massachusetts has increased levels of mercury concentrations in

the sediments due to historical releases at the Nyanza site. A screening-level mercury

cycling modeling analysis is proposed to evaluate the feasible effectiveness of sediment

remediation strategies. The EPA model SERAFM (Spreadsheet-based Ecological Risk

Assessment for the Fate of Mercury) is a process-based, steady state modeling framework

based on the Indirect Exposure Model, Version 2 (IEM-2M) used in the Mercury Study

Report to Congress. SERAFM is currently being reviewed for publication as an EPA

report and will be posted publicly on the Office of Research and Development’s (ORD’s)

Center for Exposure Assessment Modeling (CEAM) website. SERAFM incorporates a

series of modules linked to simulate mercury concentrations in the water column, the

43

sediments, and fish and to calculate wildlife and human exposure risk factors (hazard

indices). The modules within SERAFM include atmospheric deposition, solids cycling

(soil particles, plankton, and detritus), mercury cycling (oxidation, reduction,

methylation, reduction), and watershed transport (mercury transport within watersheds

via delivery coefficients, soil erosion, and runoff). Mercury modeling at superfund sites

is complicated by the fact that there are background sources of mercury from atmospheric

deposition and watershed loading and the mercury transformation and transport

processes. Therefore, to fully evaluate reductions in mercury concentrations, background

sources as well as mercury transformation and bioaccumulation must be considered.

SERAFM is structured to calculate mercury concentrations for a contaminated sediment

scenario as well as for the condition where Nyanza never had released mercury to the

system. Using the indicated sensitive wildlife species, the model then back-calculates a

proposed remediation level in the sediments to protect this most sensitive species. Due to

background loading, it is possible that no level of remediation would protect this species.

SERAFM can be used to calculate the possible reduction in exposure risk to humans and

wildlife given different levels of sediment mercury concentrations. The model system for

this SERAFM application will consist of Reservoir 1 and 2, modeling SERAFM in series

for the two reservoirs. To perform a screening-level analysis of this site, SERAFM will

run in its designed steady-state mode, calibrated to current site conditions, and then used

to forecast feasible risk reductions with associated remedial initiatives.

7. SELECT SITE-SPECIFIC, PROJECT-SPECIFIC, AND SEDIMENT-SPECIFIC RISK MANAGEMENT APPROACHES THAT WILL ACHIEVE RISK-BASED GOALS.

Evaluation of remedial alternatives has not yet been done for the Sudbury River. It is

expected that the alternatives that will be evaluated in the FS will be similar to those

considered for other similar sites such as no action, long-term monitoring (MNA), in-situ

capping, excavation and disposal and any innovative technology with the potential to

address mercury contamination in sediments. All remedies that will be considered in the

FS, would be designed to meet the remedial action objectives set for the river taking into

consideration the site specific risks presented by the site in the establishment of site­

44

specific risk-based goals. This evaluation would consider the overall risk reduction that

could potentially be achieved by each alternative.

8. ENSURE THAT SEDIMENT CLEANUP LEVELS ARE CLEARLY TIED TO RISK MANAGEMENT GOALS

The ecological risks from contaminated sediment for the Sudbury River have not yet

been established. The Human Health Risk Assessment has just been finalized. These

risks were presented in Table 1 Sediment cleanup levels will be clearly tied to the risk

management goals set for the river. Site monitoring data and new information will also

be considered in future reviews of the site (e.g., the Superfund five-year review) to ensure

that the remedy remains protective of human health and the environment.

9. MAXIMIZE THE EFFECTIVENESS OF INSTITUTIONAL CONTROLS AND RECOGNIZE THEIR LIMITATIONS DESIGN REMEDIES TO MINIMIZE SHORT-TERM RISKS WHILE ACHIEVEING LONG-TERM PROTECTION

A. Briefly list any institutional controls that are part of the proposed sediment remedy. Describe any plans to maximize their effectiveness (e.g., public education regarding fish consumption advisories).

The remedy for Sudbury River has not yet been selected. Current institutional controls

include consumption advisories for fish. Signs indicating the advisory are posted along

the river. Institutional controls would be a necessary part of any remedy, other than no

action. If monitoring data or other site information indicates that institutional controls are

not effective, additional actions may be necessary. The MA DPH has already issued “no

consumption” fish advisories due to mercury contamination for all of Massachusetts.

Long-term state and local government coordination would be anticipated.

Framingham hands out pamphlets on mercury in fish when it issues fishing licenses. If a

long term monitoring remedy is selected for any portion of the river, public

education/outreach would also need to be included.

B. Briefly describe any plans for on-going monitoring and gathering of information at the site which may indicate the effectiveness of institutional controls.

45

The remedy for Sudbury River has not been selected. Current institutional controls

include consumption advisories for fish. Local communities contact the EPA if signs are

unreadable or missing.

10. DESIGN REMEDIES TO MINIMIZE SHORT-TERM RISKS WHILE ACHIEVING LONG-TERM PROTECTION.

The proposed remedy for the Sudbury River will be selected after an evaluation of all

potential remedies against the nine criteria. The proposed alternative will be developed

which will minimize short-term impacts to the extent practicable, and achieve long-term

protection. Increases in short term risks may be necessary for any sediment remedial

action selected and implemented in order to achieve a long-term solution that is

protective.

11. MONITOR DURING AND AFTER SEDIMENT REMEDIATION TO ASSESS AND DOCUMENT REMEDY EFFECTIVENESS

The remedy for the Sudbury River has not yet been proposed. A comprehensive

monitoring program would need to be part of any action proposed (other than no action)

to determine if short- and long-term human health and ecological risks are being

adequately mitigated at the site. Monitoring would be required to evaluate remedy

effectiveness of any proposed sediment remediation as well as to evaluate if remedial

action objectives are being met. Monitoring would be conducted during remedy

implementation and as long as necessary thereafter to ensure that all sediment risks have

been adequately managed. Baseline data that have been collected to evaluate the

effectiveness of the remedy was collected during the RI, the Task Force Studies, and

during the Supplemental Investigation.

46

REFERENCES

Avatar Environmental. 2006. Supplemental Baseline Human Health Risk Assessment, Nyanza Superfund Site, Operable Unit IV, Sudbury River Mercury Contamination.

Beckvar, N., Salazar, S., Salazar, M., and Finkelstein, K. 2000. An in-situ assessment of mercury contamination in the Sudbury River, Massachusetts, using transplanted freshwater mussels (Elliptio complanata). Can. J. Fish. Aquat. Sci. 57(5): 1103­1112.

Burgess, R.M. and K.J. Scott. 1992. "The Significance of In-Place Contaminated Marine Sediments on the Water Column: Processes and Effects." In: Sediment Toxicity Assessment. G.A.Burton, Jr. (Editor). Lewis Publishers, Inc., Chelsea, MI. pp. 129­165.

Cairns, J., Jr. and D.I. Mount. 1990. Aquatic toxicology. Environ. Sci. Technol. 24:154­161.

Chapman, P.M. 1995. Extrapolating laboratory toxicity results to the field. Environ. Toxicol. Chem. 14:927-930.

Colman, J.A. and R.F Breault. 2000. Sampling for mercury at subnanogram per litre concentrations for load estimation in rivers. Can. J. Fish. Aquat. Sci. 57: 1073­1079.

Dennis, I.F., T.A. Clair, C.T. Driscoll, N. Kamman, A. Chalmers, J. Shanley, S.A. Norton and S. Kahl. 2005. Distribution Patterns of Mercury in Lakes and Rivers of Northeastern North America. Ecotoxicology. 14: 113-123.

Frazier, B.E., J.G. Wiener, R.G. Rada, and D.R. Engstrom. 2000. Stratigraphy and Historic Accumulation of Mercury in Recent Depositional Sediments in the Sudbury River. Can. J. Fish. Aquat. Sci. 57(5): 1062-1072.

Haines, T.A., May, T.W., Finalyson, R.T., and Mierzykowski, S.E. 2003. Factors Affecting Food Chain Transfer of Mercury in the Vicinity of the Nyanza Site, Sudbury River, Massachusetts. Environmental Monitoring and Assessment 86: 211-232.

JBF (JBF Scientific Corporation). 1973. An Investigation of Mercury Problems in Massachusetts. Boston Massachusetts Water Resources Commission, Division of Water Pollution Control.

JBF (JBF Scientific Corporation). 1972. Control of Mercury Contamination in Freshwater Sediments. EPA-R2-72-077. Washington, D.C., U.S. Environmental Protection Agency, Office of Research and Monitoring.

MacDonald, D.D., C.G. Ingersoll, T.A. Berger. 2000. Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Arch. Environ. Contam. Toxicol. 39: 20-31.

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MADEP (Massachusetts Department of Environmental Protection). 2000. Massachusetts Surface Water Quality Standards. 314 CMR 4.00. May 12, 2000.

Nail, G.H. and D.D. Abraham. 1997. Sudbury River Sediment Transport Model: Draft Final Report. New England Division, Corps of Engineers.

Naimo, T.J., J.G. Wiener, W.G. Cope, and N.S. Bloom. 2000. Bioavailability of sediment-associated mercury to Hexagenia mayflies in a contaminated floodplain river. Can. J. Fish. Aquat. Sci. 57:1092-1102.

Naimo, T.J., J.G. Wiener, W.G. Cope and N.S. Bloom. 1997. Bioavailability of Sediment-Associated Mercury to Hexagenia Mayflies in a Contaminated Floodplain River. Draft Final Report-submitted to U.S. EPA, Region 1.

NUS (NUS Corporation). 1992. Final Remedial Investigation Report (Volumes I to IV): Nyanza Operable Unit III-Sudbury River Study, Middlesex County, Massachusetts.

Salazar, S.M., N. Beckvar, M.H. Salazar, and K. Finkelstein. 1996. An In-situ Assessment of Mercury Contamination in the Sudbury River, Massachusetts, Using Bioaccumulation and Growth in Transplanted Freshwater Mussels (Elliptio complanata). NOAA Tech.Memo NOS ORCA 89.

St. Louis, V.L., Rudd, J.W.M., Kelly, C.A., Beaty, K.G., Bloom, N.S., and Flett, R.J. 1994. Importance of wetlands as sources of methyl mercury to boreal forest ecosystems. Can. J. Fish. Aquat. Sci. 51:1065–1076.

Suter, G. W. II, R. A. Efroymson, B. E. Sample, and D. S. Jones. 2000. Ecological Risk Assessment for Contaminated Sites. CRC/Lewis Press. Boca Raton, FL.

Thomas, W. A., and McAnally, W. H. 1990. Open-Channel Flow and Sedimentation, TABS-MD. IR-HL-85-1, Revised, USAE Waterways Experiment Station, Vicksburg, MS.

Waldron, M.C., J.A. Colman, and R.F. Breault. 2000. Distribution, hydrologic transport, and cycling of total mercury and methyl mercury in a contaminated river-reservoir­wetland system (Sudbury River, eastern Massachusetts). Can. J. Fish. Aquat. Sci. 57: 1080-1091.

Wiener, J. G., and P. J. Shields. 2000. Mercury in the Sudbury River (Massachusetts, USA): Pollution History and a Synthesis of Recent Research. Can. J. Fish. Aquat. Sci. 57(5): 1053-1061.

Weston (Roy F. Weston, Inc.). 1999a. Draft: Nyanza Chemical Waste Dump Superfund Site, Supplemental Baseline Human Health Risk Assessment.

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FIGURES

Legend:

Brooks/Streams Wetlands Scale: 1” ≅ 700’

Nyanza Chemical Dump Superfund Site Middlesex County, Massachusetts

FIGURE 1 NYANZA FACILITY MAP

F:\Projects\Nyanza\Reports & Documents\HHRA Synthesis\Figure 1-1.ppt

M �

S

W R H

S R

Sudbury River

Hop roo

Sudbury

Riv e r

Indian r

Sudbury River

abet Riv

er

Concord

River

Charl

e R

iver

Sudbury River Water hed

N

20 0 20 40

Scale in Miles 50 0 50 100

Scale in Kilometers

DELANEY WMA 2

REACH Walden Pond10

CONCORD Fairhaven

REACH 9 117

Farrar Pond

ay

LINCOLN

REFERENCE AREAS

Willi a e

REACH �

126

SUD UR:

27Cardin Mill Pond 20MARL OROUGH

�ri t Heard PondMillHa er WA:LANDPond REACHPond

� Sudbury Re ervoir

DudleyPond

4 5 REACHFRAMINGHAM :Saxonville

85 Pond

0NORTH OROUGH

a eREACH Cochituate30 5

Re 27SOUTH OROUGH REACH NATICK � Re �

Fi Pond135WEST OROUGH Cedar Re

ASHLANDSwamp REACH 3 Wau hacumPond Mill REACHPond 2 PondREACH

1

SHER ORN 0 NYANZAHop inton SUPERFUND 126Re ervoir S TEWe tborou h hland Re ervoir Re ervoirWhitehall

Re ervoir

135 HO KINTON REFERENCE AREAS

4 5

LEGEND: ownship Boundary River Reaches

Nyanza Superfund Site OU IV 1 0 1 2 N Sudbury River Mercury Contamination1 6 Reference Area Scale in Miles ounty Boundary

1 0 1 22 7 Figure 2Scale in KilometersWatershed Boundary 3 Sudbury River Watershed8 River Reaches and Reference Area Locations 4

Hydrography5 10

I C:\NYANZA\APRs\ ocation.apr I CSTAG I c:\nyanza\exports\out\cstag_figure2_051206.eps I 1:05 PM, 5/12/2006 I

SOURCE

PRIMARY RELEASE/

TRANSPORT MECHANISMS

PRIMARY RECEIVING

MEDIA

PRIMARY EXPOSURE

MEDIA

SECONDARY EXPOSURE

MEDIA

EXPOSURE ROUTES

Residential (Direct Contact)

Recreational (Direct Contact)

EXPOSURE SCENARIOS

Surface Runoff

Nyanza Site

Facility Fish Sudbury

River

SECONDARY RELEASE/

TRANSPORT MECHANISMS

• Surface water flow downstream

• Flooding and runoff • Sediment re-suspension and downstream transport

Surface Water

Sediment

Ingestion Riverbank Soil Erosion

••

Ingestion

•• •

•• •

Dermal Contact

•• •

•• •Ingestion

Dermal Contact

Discharge of Wastes into Chemical

Brook

Fish Consumption

Child Adult

••

Child Adult

••

Child Adult Recreational Subsistence Ethnic

Adult Child Child Teen Teen Adult

= Incomplete exposure pathway.

= Pathway/receptor was only evaluated in the 1992 HHRA. •

= Pathway/receptor was evaluated quantitatively in the 1992 HHRA and qualitatively in the 1999 HHRA. •

= Pathway/receptor was only evaluated in the 1999 and 2006 HHRAs. •

= Pathway/receptor was evaluated in all three HHRAs. •

= Pathway/receptor was evaluated qualitatively in the 2006 HHRA. •

= Pathway/receptor was evaluated quantitatively in the 2006 HHRA. •

Note: Pertains to exposures in Sudbury River proper only.

Nyanza Superfund Site Sudbury River Mercury Contamination

Figure 3 Conceptual Site Model

Nyanza Superfund Site Sudbury River Mercury Contamination

FIGURE 4 CONCEPTUAL DIAGRAM OF POTENTIAL TRANSPORT AND EXPOSURE PATHWAYS OF CONTAMINANTS OF CONCERN

FROM THE SITE THROUGH THE AQUATIC ECOSYSTEM

PRIMARY SOURCE

SECONDARY SOURCE

AQUATIC INVERTEBRATES hCrayfish hHexagenia

- Accumulation - Reproduction and

Survival

WETLAND AND SURFACE WATER

DISCHARGE

SURFACE SOIL RUNOFF

GROUNDWATER DISCHARGE

AQUATIC VERTEBRATES

h Fish - Accumulation

- Reproduction and Survival

SURFACE WATER AND SEDIMENTS

INSECTIVOROUS BIRDS

hTree Swallow h Eastern Kingbird h Marsh Birds -Accumulation -Reproduction,

Survival, and Neurological Effects

PISCIVOROUS BIRDS

hKingfisher h Great Blue Heron h Common Merganser

-Accumulation -Reproduction,

Survival, and Neurological Effects

LEGEND

Prime Areas of Consideration

Target Species h

RECEPTORS AND

TROPHIC TRANSFER

PISCIVOROUS MAMMALS hMink

-Accumulation - Reproduction,

Survival, and Neurological Effects

VEGETATION Submergent

Emergent

Pathway Evaluated

Pathway not evaluated

Uptake

Consumption

Uptake/Ingestion

Ingestion (evaluating surface water only)

Ingestion

Ingestion

Consumption

Consumption

Consumption Consumption

Consumption

0.E+00

1.E+04

2.E+04

3.E+04

4.E+04

5.E+04

6.E+04 To

tal M

ercu

ry C

once

ntra

tion

(µg/

kg d

ry w

eigh

t)

0 - 3 0 - 5 3 - 6 5 - 10 9 - 12 10 - 15 15 - 20

Depth (cm)

6 - 90

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 5 Total Mercury Concentrations in Reach 3 Sediment Cores

2003-2005 Supplemental Investigation Data

Legend:

- Sediment core sample

1992 OU III RI/FS

Formation of OU IV and Task Force

1994-1995 Task Force Studies

1999 HHRA and ERA

2003-2005 Supplemental Investigation

2006 HHRA and ERA

Figure 6 Chronology of Investigations

C�ar�e� Rive

� Sudbury River� 0 � 2 �ater��ed Inset Scale in Miles

�� �

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9 66 O O

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O

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0 9 O

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8 O

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LEGEND: Wetland Habitat 3000 0 3000 6000 Nyanza Superfund Site OU IV Sudbury River Mercury ContaminationScale in Feet

900 0 900 800 FIGURE 7 SURFACE SEDIMENT, SURFACE WATER 1 Scale in Meters AND CRAYFISH SAMPLE RESULTS

O Sediment sample - 2003 Open WaterO Sediment core sample - 2003Deep Marsh Surface water sample - 2003 Shallow Marsh Crayfish sample(s) - composite

Crayfish sample - Shrub Swamp wholebody or tailDeciduous Wood Swamp

Mixed Wood Swamp Source: CHARLES RIVER - REFERENCE AREASediment and crayfish results are in units of uglkg Hg. Surface water results are in units of nglL Hg. Commonwealth of Massachusetts Executive Office of Environmental Affairs.

I C:\NYANZA\APRs\era aquatic maps 2005.apr I Charles River I c:\nyanza\exports\out\cstaa _iaure7 051206.eps I 1:08 PM, 5/12/2006 I

Office of Geographic and Environmental Information (MassGIS),

Sudbury River �aters�ed

����

�������������������� ��������������

1 0 1 2

Inset Scale in Miles

���� ����

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Nyanza Superfund Site OU IVLEGEND: Wetland Habitat 1000 0 1000 2000 Open Water O Sediment sample - 2003 Sudbury River Mercury Contamination

. Deep Marsht Surface water sample - 2003 Scale in Feet • Crayfish sample(s) - composite Shallow Marsh FIGURE S400 0 400 800 Crayfish sample(s) - Shrub Swamp• SURFACE SEDIMENT, SURFACE WATER wholebody or tail

Deciduous Wood Swamp 1 AND CRAYFISH SAMPLE RESULTS Mixed Wood Swamp Source:

Scale in Meters Note: Sediment and crayfish results are in units of uglkg Hg. Office of Geographic and Environmental Information (MassGIS), SUDBURY RESERVOIR - REFERENCE AREA Surface water results are in units of nglL Hg. Commonwealth of Massachusetts Executive Office of Environmental Affairs.

I C:\NYANZA\APRs\era aquatic maps 2005.apr I Sudbury Reservoir I c:\nyanza\exports\out\cstag figure8 051206.eps I 1:11 PM, 5/12/2006 I

Sudbury River O �ater��ed O

O O O OO

R������

1 0 1 2 �

Inset Scale in Miles ��

����

SOUTHBOROUGH

,9 0

.tO

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O OO .t

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LEGEND: Wetland Habitat Open Water

1000 0 1000 2000 Nyanza Superfund Site OU IVReach O Sediment sample - 2003Reach 1 Sudbury River Mercury Contamination. Deep Marsht Surface water sample - 2003 Scale in FeetReach 2• Crayfish sample(s) - composite Shallow Marsh FIGURE 9400 0 400 800 Crayfish sample - Shrub Swamp• SURFACE SEDIMENT, SURFACE WATER wholebody or tail

Deciduous Wood Swamp 1 Scale in Meters AND CRAYFISH SAMPLE RESULTSMixed Wood Swamp Source: Note: Sediment and crayfish results are in units of uglkg Hg. Office of Geographic and Environmental Information (MassGIS), REACH 1 - REFERENCE AREA Surface water results are in units of nglL Hg. Commonwealth of Massachusetts Executive Office of Environmental Affairs.

I C:\NYANZA\APRs\era aquatic maps 2005.apr I Reach 1 I c:\nyanza\exports\out\cstag figure9 051206.eps I 1:12 PM, 511212006 I

�

Sudbury River

�aters�ed

�������� �����������

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1 0 1 2 Inset Scale in Miles

Reservoir No

��� �

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��� ��

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Focus Area Inset LEGEND: Wetland Habitat 500 0 500 1000 1500 Nyanza Superfund Site OU IVReach Sediment sample - 2003 Open Water Sudbury River Mercury Contamination Sediment core sample - 2003 Reach 2Deep Marsh Sediment sample - 2005 Scale in FeetReach 3 Sediment core sample - 2005 Shallow Marsh 400 0 400 FIGURE lO Surface water sample - 2003 Reach 4Shrub Swamp Crayfish sample(s) - composite Reach 5 SURFACE SEDIMENT, SURFACE WATER

Deciduous Wood Swamp Crayfish sample(s) - 1 Scale in Meters AND CRAYFISH SAMPLE RESULTSwholebody or tail Mixed Wood Swamp Source: Office of Geographic and Environmental Information (MassGIS), REACHES 2, 3, AND 4Note: Sediment and crayfish results are in units of ug/kg Hg. Commonwealth of Massachusetts Executive Office of Environmental Affairs.Surface water results are in units of ng/ Hg.

I C:\NYANZA\APRs\era aquatic maps 2005.apr I Reach 2 3 4 I c:\nyanza\exports\out\cstag figure10 051206.eps I 1:13 PM, 5/12/2006 I

98

Sudbury River 8 �ater �ed

eaches 17 08 2 and

See Crayfish Summary Table 1 9 1 2

Inset: 7(b)

17 8 6 6 217 2 68 ( )

�op �roo� 2 6 2998

�eard 1 1

ond 2 71 7 2

See Crayfish 1068 1 0 1 2 Summary Table

2 8 Inset Scale in Miles Inset: 7(b) 1 1127

2 1 62 2

06 92 ( ) 2

7 80 170 99 Subrea h 7 279 ( )

� �

Subrea h 7 1

1 1 2 0 7

217 0 86 1 62

l L See Crayfish Summary Table Number of Number of om oslte 1 2 Inset: 7(a) each Locatlons lndlvlduals esult

2 7 2 (a) 8 6 7 97 7 2 (b) 2 7 88 6 1

7 (a) 2 1 6 20 0 7 (b) 7 2 17 9

Sa onvi e 1 60

1

ond 177 2 2

9

2 ( ) 62

22 181 12 09 29 7 198

1170 1670

� ��

9 1 72 10 � � 172

1 9 18 0 Subrea h � 200 ( )

Subrea h 1 � 1110 82

90 0 72 6 188

See Crayfish 66

Summary Table 11 0 7 2 68

Inset: 2(b) 10 0 8 188 See us

72 1 1 rea Inset Subrea h 2 100 8

1990 See Crayfish Summary Table 1 0

98 8 66 9 Inset: 2(a) 192 0 800 7 01 2116 0 87 7 98 122 0 77 87 ( ) 89 6 1 0 0

Focus Area Inset

Re ervoir

LEGEND: Wetland Habitat Open Water Reach 1000 0 1000 2000 Nyanza Superfund Site OU IV

Sediment sample - 2003 Reach 5 Sudbury River Mercury Contamination Sediment sample - 2005 Deep Marsh Scale in FeetReach 6 Sediment core sample - 2005 Shallow Marsh Reach ? 400 0 400 800 FIGURE 11 Surface water sample - 2003 Shrub Swamp

Crayfish sample(s) - composite SURFACE SEDIMENT, SURFACE WATER Reach 8Deciduous Wood Swamp Crayfish sample(s) -

Mixed Wood Swamp Source: Scale in Meters AND CRAYFISH SAMPLE RESULTSwholebody or tail

Note: Sediment and crayfish results are in units of uglkg Hg. Office of Geographic and Environmental Information (MassGIS), REACHES 5, 6, AND 7Surface water results are in units of nglL Hg. Commonwealth of Massachusetts Executive Office of Environmental Affairs.

I C:\NYANZA\APRs\era aquatic maps 2005.apr I Reach 5 6 7 I c:\nyanza\exports\out\cstag figure11 051206.eps I 1:15 PM, 5/12/2006 I

O

O O

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� 0 � 2 �

Inset Scale in Miles

Source: Office of Geographic and Environmental Information (MassGIS), Commonwealth of Massachusetts Executive Office of Environmental Affairs.

Scale in Feet 1000 0 1000 2000

Scale in Meters 500 0 500

FIGURE 12 SURFACE SEDIMENT, SURFACE WATER

AND CRAYFISH SAMPLE RESULTS REACH 8 - GREAT MEADOWS NATIONAL

WILDLIFE REFUGE

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination1LEGEND: Wetland Habitat

Deep Marsh

Shallow Marsh

Open Water

Shrub Swamp

Deciduous Wood Swamp

Mixed Wood Swamp

• Crayfish sample -wholebody or tail

• Crayfish sample - composite

.t Surface water sample - 2003

Sediment sample - 2003O

Note: Sediment and crayfish results are in units of uglkg Hg. Surface water results are in units of nglL Hg.

Reach 8

Reach

Reach 9

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3

_

54 JEB 54 JEB (DUP)

435 J 498 J (DUP)

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4 3 U

4 9 U

4 U

5

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5 88 U

5 U

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������� �����Sudbury River

�ater�hed

1 0 1 2 �

Inset Scale in Miles

������� ��������

Scale in Meters

Scale in Feet 500 0 500 1000 1500

400 0 400

Source: Office of Geographic and Environmental Information (MassGIS), Commonwealth of Massachusetts Executive Office of Environmental Affairs.

FIGURE 13 SURFACE SEDIMENT, SURFACE WATER

AND CRAYFISH SAMPLE RESULTS REACHES 9 AND 10

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

LEGEND: Wetland Habitat

Deep Marsh

Shallow Marsh

Open Water

Shrub Swamp

Deciduous Wood Swamp

Mixed Wood Swamp

• Crayfish sample -wholebody or tail

• Crayfish sample - composite Surface water sample - 2003

Sediment sample - 2003

Note: Sediment and crayfish results are in units of uglkg Hg. Surface water results are in units of nglL Hg.

Reach 9

Reach 10

Reach 8 Reach

I C:\NYANZA\APRs\era aquat,c maps 2005.apr I Reach 9 10 I c:\nyanza\exports\out\cstaa f,aure13 051206.eps I 1:17 PM, 511212006 I

______ _

�������������

� 1 0 1 2

Inset Scale in Miles

Sudbury River �ater��ed

����

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CR�2SB � eeeee eee CR��SB����

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e e ee CR���� ��� � �CR���� ee �������CR�� CR����

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eeeeee CR��SB����CR�� �

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LEGEND: 1000 0 1000 2000 Nyanza Superfund Site OU IVSample Location Wetland Habitat e Tree Swallow Nest Box Open Water Scale in Feet Sudbury River Mercury Contamination

Deep Marshe Waterfowl Nest Box 400 0 400 800 FIGURE 14Shallow Marshe Eastern Kingbird Egg Sample Shrub Swamp 1 Scale in Meters AVIAN SAMPLE LOCATIONSe Marsh Bird Sampling Area Deciduous Wood Swamp Source:e Belted Kingfisher Nest CHARLES RIVER - REFERENCE AREAOffice of Geographic and Environmental Information (MassGIS), Mixed Wood Swamp Commonwealth of Massachusetts Executive Office of Environmental Affairs.

Sudbury River aters ed

����� � � ��� �

1 0 1 2

Inset Scale in Miles

����

���

������ ���

eee eee

������ ���

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Sudbury Reservoir

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eeeeee �������� eeeeee ���� ���

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LEGEND: 1000 0 1000 2000 Nyanza Superfund Site OU IVSample Location Wetland Habitat e Tree Swallow Nest Box Open Water Scale in Feet Sudbury River Mercury Contamination

Deep Marshe Waterfowl Nest Box 400 0 400 800Shallow Marshe Eastern Kingbird Egg Sample FIGURE 15Shrub Swamp 1e Marsh Bird Sampling Area Deciduous Wood Swamp Source:

Scale in Meters AVIAN SAMPLE LOCATIONS Belted Kingfisher NesteOffice of Geographic and Environmental Information (MassGIS), SUDBURY RESERVOIR - REFERENCE AREAMixed Wood Swamp Commonwealth of Massachusetts Executive Office of Environmental Affairs.

_ ______ __ _

B�ST� T

��

Sudbury River �ater��ed �

Re�ervoir No� �

������� �����������

RES116

Res1-06SB Re�ervoir

No� �

R 0 11

1 0 1 2 R 0 10Inset Scale in Miles 2-0 R 0 13

R 0 05 RES113

R 0 02Ear Tag ID 85 Res2-05SB

R30 2 R 0 0

R30 31R 0 06

R 0 01 R30 23

Re�ervoir No� �

R30 1

R30 20 R30 1

R30 13

R30 15 R30 16

Res2-01DB

R30 0

Res2-0 DBR30 0

R30 06 Mi�� R30 05

�ond Res2-05DB R30 0

� R30 01

AJanza Superfund Ear Tag ID 8556

Site

LEGEND: 500 0 500 1000 1500 Nyanza Superfund Site OU IVSample Location Wetland Habitat Reach Tree Swallow Nest Box Open Water Reach 2 Scale in Feet Sudbury River Mercury Contamination

Deep Marsh Waterfowl Nest Box Reach 3 400 0 400 Shallow Marsh Eastern Kingbird Egg Sample Reach 4 FIGURE 16 Shrub Swamp Marsh Bird Sampling Area Reach 5 1 Scale in Meters AVIAN AND MINK SAMPLE LOCATIONS Deciduous Wood Swamp Source: Belted Kingfisher Nest

Office of Geographic and Environmental Information (MassGIS), REACHES 2, 3, AND 4Mixed Wood Swamp Mink Commonwealth of Massachusetts Executive Office of Environmental Affairs.

I C:\NYANZA\APRs\era avian maps 2005.apr I Reach 2 3 4 I Full Name of Plot File I 8:18 AM, 5/2/2000 I

Sudbury River �ater �ed

23

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@

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@

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ear Pon Tree �a��o�s EA I EPA 6@�op �roo� 0 5

1 0 1 2 N

Inset Scale in Miles

25

u ury iver ear Pon ocation

Ear Tag I . 85 8

0� 05 06 08 0 0 2 3 �

6 7 8 20 22 23 2� 26

33

32

@

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@

@@

3

30 28

@

26

@

@

@

@ @

u ury iver ear Pon ocations

@

27

@

EA I

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26

03

02

0�

EPA 7

Saxonville Pond

@

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Ear Tag I . 8532

Re ervoir No

LEGEND: 1000 0 1000 2000 Nyanza Superfund Site OU IVSample Location Wetland Habitat Reach Tree Swallow Nest Box Open Water Reach 5 Scale in Feet Sudbury River Mercury Contamination

Deep Marsh Waterfowl Nest Box Reach 6 400 0 400 800Shallow Marsh FIGURE 17 Eastern Kingbird Egg Sample Reach 7 Shrub Swamp Marsh Bird Sampling Area Reach 8 1 Scale in Meters AVIAN SAMPLE LOCATIONS Deciduous Wood Swamp Source: Belted Kingfisher Nest REACHES 5, 6, AND 7Office of Geographic and Environmental Information (MassGIS), Mixed Wood Swamp@ Mink Commonwealth of Massachusetts Executive Office of Environmental Affairs.

I C:\NYANZA\AP s\era avian maps 2005.apr I each 5 6 7 I c:\nyanza\exports\out\cstag figure 7 052306.eps I 8:57 AM, 5/23/2006 I

��12�

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SUDR07S

SUDR1�D

SUDR17D

SUDR1 S

SUDR1 S

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��2-0�S

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EAKISUDREPA02

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Sudbury -Route 117 Pit Location

Sudbury - Transfer Station Pit Location

Sudbury Ri�er -�idd�e Location�s�

Sudbury Ri�er -�acone�s Pi�e Location

Sudbury Ri�er -�acone�s Pi�e Location

��1-11S

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SUDRV-12

SUDRV-0�

SUDRV-07

SUDRV-01

SUDRV-0 SUDRV-05

SUDRV-02

SUDRV-22

SUDRV-2

SUDRV-17

SUDRV-25

SUDRV-1�

SUDR20D

SUDR05D

Sudbury River �ater��ed

� � � � �

Inset Scale in Miles

LEGEND:

Belted Kingfisher Nest Marsh Bird Sampling Area Eastern Kingbird Egg Sample Waterfowl Nest Box Tree Swallow Nest Box Sample Location Wetland Habitat

Deep Marsh Shallow Marsh

Open Water

Shrub Swamp Deciduous Wood Swamp Mixed Wood Swamp

Reach Reach 8 Reach 9

Scale in Meters 500 0 500

Scale in Feet 1000 0 1000 2000

Source: Office of Geographic and Environmental Information (MassGIS), Commonwealth of Massachusetts Executive Office of Environmental Affairs.

1 Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

FIGURE 18 AVIAN SAMPLE LOCATIONS

REACH 8 - GREAT MEADOWS NATIONAL WILDLIFE REFUGE

I C:\NYANZA\APRs\era avian maps 2005.apr I Reach 8 I c:\nyanza\exports\out\cstag figure18 052306.eps I 8:58 AM, 512312006 I

117

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SUDR20D�

SUDR0�D�

Assabet River Sudbury River

�ater��ed

1 0 1 � �

Inset Scale in Miles

������� ��������

LEGEND:

• Belted Kingfisher Nest • Marsh Bird Sampling Area • Eastern Kingbird Egg Sample • Waterfowl Nest Box

Tree Swallow Nest Box• Sample Location Reach

Reach 9 Reach 10

Reach 8

Mixed Wood Swamp Deciduous Wood Swamp Shrub Swamp

Open Water

Shallow Marsh Deep Marsh

Wetland Habitat 1 Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

FIGURE 19 AVIAN SAMPLE LOCATIONS

REACHES 9 AND 10Source: Office of Geographic and Environmental Information (MassGIS), Commonwealth of Massachusetts Executive Office of Environmental Affairs.

Scale in Meters

Scale in Feet 500 0 500 1000 1500

400 0 400

_ ______ __ _ _ _

0.00E+00

1.00E+02

2.00E+02

3.00E+02

4.00E+02

5.00E+02

6.00E+02

Tota

l Hg

Con

cent

ratio

n (µ

g/kg

wet

wei

ght)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

n = 3

n = 3

n = 4

n = 3

n = 4

n = 4

n = 6

n = 3

n = 3

n = 6

n = 3

n = 3

Reach 7

Heard Pond

n = 3

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 20 Total Mercury Concentrations in

Bullhead Samples

Legend:

- Fish sample

0.00E+00

1.00E+02

2.00E+02

3.00E+02

4.00E+02

5.00E+02

Met

hyl H

g C

once

ntra

tion

(µg/

kg w

et w

eigh

t)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

n = 3 n = 3

n = 2

n = 3

n = 3

n = 3

n = 3

n = 3

n = 3

n = 3 n = 3

n = 3 R

each 7H

eard Pond

n = 3

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 21 Methyl Mercury Concentrations in

Bullhead Samples

Legend:

- Fish sample

0.00E+00

2.50E+02

5.00E+02

7.50E+02

1.00E+03

1.25E+03

1.50E+03

Tota

l Hg

Con

cent

ratio

n (µ

g/kg

wet

wei

ght)

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reference Areas

3 samples taken – 240, 245 and 252 µg/kg

n = 3

n = 2 n = 3

n = 6

n = 4

n = 3

n =4

n = 3 n = 4

Reach 8

n = 6 R

each 9

n = 3 R

each 10n = 3

Reach 7

Heard Pond

n = 3

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 22 Total Mercury Concentrations in

Largemouth Bass Samples

Legend:

- Fish sample

0.00E+00

2.50E+02

5.00E+02

7.50E+02

1.00E+03

1.25E+03

1.50E+03

Met

hyl H

g C

once

ntra

tion

(µg/

kg w

et w

eigh

t)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reference Areas

2 samples taken – 274 and 277 µg/kg

n = 3

n = 2 n = 3

n = 3

n = 3

n = 3

n = 3 n = 3

n = 3

n = 3

n = 3

Reach 10

n = 3

Reach 7

Heard Pond

n = 3

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 23 Methyl Mercury Concentrations in

Largemouth Bass Samples

Legend:

- Fish sample

0.00E+00

5.00E+01

1.00E+02

1.50E+02

2.00E+02

2.50E+02

3.00E+02

3.50E+02

4.00E+02

4.50E+02

5.00E+02

Tota

l Hg

Con

cent

ratio

n (µ

g/kg

wet

wei

ght)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

Reach 7

Heard Pond

n = 12

n = 13

n = 11

n = 11

n = 13

n = 13

n = 13

n = 13

n = 10

n = 37

n = 7

n = 13

n = 13

Legend: Maximum concentration

Minimum concentration

75th Percentile concentration

25th Percentile concentration 50th Percentile concentration

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 24 Total Mercury Concentrations in

Class A (5-10 cm) Perch/Sunfish Samples

0.00E+00

5.00E+01

1.00E+02

1.50E+02

2.00E+02

2.50E+02

3.00E+02

3.50E+02

4.00E+02

4.50E+02

5.00E+02

Tota

l Hg

Con

cent

ratio

n (µ

g/kg

wet

wei

ght)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

n = 13

n = 13

n = 10

n = 13

n = 13

n = 13

n = 11

n = 10

n = 13

n = 56

n = 11 n = 13

Reach 7

Heard Pond

n = 13

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 25 Total Mercury Concentrations in

Class B (10-15 cm) Perch/Sunfish Samples

Legend: Maximum concentration

Minimum concentration

75th Percentile concentration

25th Percentile concentration 50th Percentile concentration

0.00E+00

5.00E+01

1.00E+02

1.50E+02

2.00E+02

2.50E+02

3.00E+02

3.50E+02

4.00E+02

4.50E+02

5.00E+02

Tota

l Hg

Con

cent

ratio

n (µ

g/kg

wet

wei

ght)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

n = 13 n = 13 n = 5

n = 13

n = 13

n = 13

n = 3

n = 13 n = 13

n = 35

n = 13

n = 13

Reach 7

Heard Pond

n = 13

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 26 Total Mercury Concentrations in

Class C (15-20) Perch/Sunfish Samples

Legend: Maximum concentration

Minimum concentration

75th Percentile concentration

25th Percentile concentration 50th Percentile concentration

- Fish sample

0.00E+00

1.00E+02

2.00E+02

3.00E+02

4.00E+02

5.00E+02

6.00E+02

7.00E+02

Tota

l Hg

Con

cent

ratio

n (µ

g/kg

wet

wei

ght)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

n = 3

n = 3

n = 3

n = 6 n = 3

n = 4 n = 3

n = 3 n = 4

n = 10

n = 3

n = 3

Reach 7

Heard Pond

n = 3

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 27 Total Mercury Concentrations in

Class D (>20 cm) Perch/Sunfish Samples

Legend:

- Fish sample

0.00E+00

1.00E+02

2.00E+02

3.00E+02

4.00E+02

5.00E+02

6.00E+02

7.00E+02

8.00E+02

Met

hyl H

g C

once

ntra

tion

(µg/

kg w

et w

eigh

t)

Reach 8

Sudbury R

eservoir

Charles

River

Reach 1

Reach 2

Reach 3

Reach 4

Reach 5

Reach 6

Reach 7

Reach 9

Reach 10

Reference Areas

n = 3

n = 3 n = 3

n = 3

n = 3 n = 3

n = 2

n = 3 n = 3

n = 5 n = 3

n = 3 R

each 7H

eard Pond

n = 3

Nyanza Superfund Site OU IV Sudbury River Mercury Contamination

Figure 28 Methyl Mercury Concentrations in

Class D (>20 cm) Perch/Sunfish Samples

Legend:

- Fish sample

TABLES

Table 1

2006 HHRA Hazard Quotient Summary*

Operable Unit IV - Nyanza Chemical Dump Superfund Site - Middlesex County, Massachusetts

Reach

Site Impacted RME Hazard Quotient

Recreational Angler Subsistence Angler Ethnic Angler

Child Adult Adult Child Adult

Reach 2 3.5 1.8 8.1 7.5 4.0

Reach 3 2.1 1.2 9.1 15 8.0

Reach 4 1.3 0.7 5.6 8.9 4.8

Reach 5 0.9 0.4 4.5 7.2 3.9

Reach 6 1.3 0.7 5.9 9.3 5.0

Reach 7 1.0 0.5 4.9 8.3 4.5

Reach 7 - Heard Pond 0.3 0.1 1.2 1.8 1.0

Reach 8 1.3 0.7 6.7 8.6 4.6

Reach 9 2.8 1.5 6.7 10 5.4

Reach 10 1.4 0.7 7.0 11 6.1

*Mercury was the only COPC.

Excel Tables1 5/23/2006

Table 2 Nyanza OU IV Fish Summary

Operable Unit IV - Nyanza Chemical Dump Superfund Site - Middlesex County, Massachusetts

Reach Subreach Species Size Class

# Samples Analyzed

Fillet Offal Whole Body

1 0 Bluegill A - - 5 B - - 5

Largemouth Bass - 11 3 -Pumpkinseed A - - 6

B - - 5 White Sucker - - - 8

Yellow Bullhead - 2 2 2 Yellow Perch C - - 5

D 14 3 -2 0 Bluegill A - - 2

B - - 1 Largemouth Bass - 3 2 -

Pumpkinseed A - - 2 B - - 1

White Sucker - - - 2 Yellow Perch B - - 4

C - - 6 D 7 3 -

1 Bluegill A - - 5 Brown Bullhead - - - 3

Largemouth Bass - 3 2 -Pumpkinseed A - - 2 Yellow Perch B - - 2

C - - 2 D 1 1 -

2 Largemouth Bass - 4 2 -White Sucker - - - 2 Yellow Perch B - - 5

C - - 5 D 5 2 -

3 0 Bluegill A - - 3 Pumpkinseed A - - 3

1 Bluegill A - - 3 Brown Bullhead - 3 1 -

Largemouth Bass - 3 1 -Yellow Perch B - - 6

C - - 6 D 6 1 -

2 Bluegill B - - 1 Brown Bullhead - 1 1 -

Largemouth Bass - 3 1 -Yellow Bullhead - 2 - -

Yellow Perch B - - 1 D 5 1 -

3 Bluegill A - - 3 Brown Bullhead - 3 1 -

Largemouth Bass - 4 2 -Yellow Bullhead - 1 1 -

Yellow Perch B - - 6 C - - 7 D 2 1 -

4 0 Bluegill A - - 13 1 Largemouth Bass - 5 2 -

Yellow Bullhead - 1 1 -Yellow Perch B - - 4

C - - 5 D 6 2 -

2 Brown Bullhead - 5 1 -Largemouth Bass - 5 1 -Yellow Bullhead - 4 2 -

Yellow Perch B - - 9 C - - 8 D 9 2 -

5 0 Bluegill A - - 2 1 Bluegill A - - 8

B - - 2 Pumpkinseed A - - 3

B - - 1 Yellow Bullhead - - - 3

2 Largemouth Bass - 6 2 -Yellow Bullhead - 1 1 -

Yellow Perch C - - 2 D 6 1 -

3 Bluegill B - - 8 Brown Bullhead - 10 2 -

Largemouth Bass - 5 2 -Yellow Perch C - - 1

D 8 2 -

Excel Tables 2

Table 2 Nyanza OU IV Fish Summary

Operable Unit IV - Nyanza Chemical Dump Superfund Site - Middlesex County, Massachusetts

Reach Subreach Species Size Class

# Samples Analyzed

Fillet Offal Whole Body

6 0 Bluegill A - - 8 B - - 7

Brown Bullhead - 1 1 -Largemouth Bass - 11 3 -

Pumpkinseed A - - 4 B - - 1

Yellow Bullhead - 9 2 -Yellow Perch A - - 1

B - - 2 C - - 13 D 14 3 -

7 1 Brown Bullhead - 2 1 -Largemouth Bass - 6 2 -Yellow Bullhead - 2 1 -

Yellow Perch A - - 2 B - - 7 C - - 6 D 9 2 -

2 Bluegill A - - 6 Brown Bullhead - 2 1 -

Largemouth Bass - 7 2 -Pumpkinseed A - - 1

Yellow Bullhead - 4 - -Yellow Perch A - - 1

B - - 6 C - - 7 D 5 2 -

3 Largemouth Bass - 10 3 -Yellow Bullhead - 10 3 -

Yellow Perch A - - 13 B - - 13 C - - 13 D 10 3 -

X Bluegill A - - 1 Brown Bullhead - - - -Golden Shiner A - - 1

B - - 1 Largemouth Bass - - - -

White Crappie B - - 1 Yellow Bullhead - - - -

Yellow Perch A - - -B - - -C - - -D - - -

8 1 Bluegill A - - 11 Largemouth Bass - 4 2 -Yellow Bullhead - 3 2 -

Yellow Perch A - - 2 B - - 20 C - - 10 D 6 3 -

2 Bluegill A - - 21 B - - 3 C - - 5

Brown Bullhead - 2 2 -Largemouth Bass - 4 2 -

Pumpkinseed A - - 2 B - - 3

Yellow Bullhead - 4 - -Yellow Perch A - - 1

B - - 18 C 1 - 10 D 10 4 -

3 Brown Bullhead - 5 2 -Largemouth Bass - 3 2 -

Yellow Perch B - - 12 C - - 10 D 6 3 -

X Bluegill A - - 1 Brown Bullhead - - - -Chain Pickerel A - - 2 Golden Shiner A - - 1

B - - 1 Largemouth Bass - - - -Yellow Bullhead - - - -

Yellow Perch A - - -B - - -C - - -D - - -

Excel Tables 2

Table 2 Nyanza OU IV Fish Summary

Operable Unit IV - Nyanza Chemical Dump Superfund Site - Middlesex County, Massachusetts

Reach Subreach Species Size Class

# Samples Analyzed

Fillet Offal Whole Body

9 0 Bluegill A - - 7 B - - 7

Brown Bullhead - 10 3 -Largemouth Bass - 11 3 -

Yellow Perch B - - 4 C - - 13 D 14 3 -

10 0 Bluegill A - - 12 Brown Bullhead - 7 1 -

Largemouth Bass - 11 3 -Yellow Bullhead - 4 2 -

Yellow Perch A - - 1 B - - 13 C 1 - 13 D 13 3 -

Charles River 0 Bluegill A - - 3 Brown Bullhead - 2 2 -

Largemouth Bass - 10 3 -Pumpkinseed A - - 9

Yellow Bullhead - 8 1 -Yellow Perch B - - 13

C - - 13 D 13 3 -

Sudbury Reservoir 0 Bluegill A - - 6 Brown Bullhead - 2 1 -

Largemouth Bass - 9 2 -Pumpkinseed A - - 1

Yellow Bullhead - 7 2 -Yellow Perch A - - 6

B - - 13 C 1 - 13 D 13 3 -

Note - Fish from subreaches noted "X" are kingfisher prey.

Excel Tables 2