**Appendix A. Screening-Level Ecological Risk Assessment**

# Introduction 

This section describes the screening-level ecological risk evaluation
that was performed for Maurepas Swamp using available chemical data from
the study area. Ecological risk was evaluated in support of EPA's
Environmental Impact Statement (EIS) for the Maurepas Swamp freshwater
diversion project, which proposes to divert an estimated 1500 cubic feet
per second (cfs) of freshwater from the Mississippi River into Maurepas
Swamp (Day *et al.,* 2004). This screening-level ecological risk
assessment is designed to assess if, upon completion of the project,
chemicals carried in Mississippi River water and sediments could
adversely affect wildlife species in Maurepas Swamp and Lake Maurepas.
This assessment follows EPA's ecological risk assessment guidance (EPA,
1997) and includes the following components:

-   Overview of the biological resources;

-   Conceptual site model (CSM);

-   Identification of contaminants of concern;

-   Selection of receptors of concern;

-   Assessment and measurement endpoints;

-   Ecological effects assessment;

-   Risk characterization; and,

-   Uncertainties.

**A.1.1 Biological Evaluation**

Maurepas Swamp (Figure A-1) lies partly within the 62,500 acres
encompassing the Maurepas Swamp Wildlife Management Area, which is owned
by the State of Louisiana. This management area is located 25 miles west
of New Orleans and along the south shore of Lake Maurepas to near
Sorrento (LDWF, 2003). Much of the flood control on the Mississippi
River has eliminated the natural inputs of freshwater, nutrients, and
sediment to the area that historically built and maintained the wetlands
(Lee Wilson & Associates, 2001). Thus, permanent flooding, as well as
nutrient and sediment starvation has injured much of the swamp. Major
plant species in the area include stressed and dying cypress-tupelo
trees, cattails, swamp maple, and submerged aquatics. The area is also
home to various game species such as whitetail deer, squirrels,
bullfrogs, rabbits, and raccoons. Freshwater fishing for largemouth
bass, perch, and crappie is common in the area. Bald eagles nest in and
around the area along with many other species of birds including
warblers, ducks, woodpeckers, swallows, and various wading birds and
birds of prey (Table A-1).

![](media/image1.jpeg){width="5.979166666666667in"
height="4.854166666666667in"}

Figure A-1. Maurepas Study Area. *Source: Day et al. (2004)*.

Adjacent to the Maurepas Wildlife Management Area lays the Manchac Swamp
Wildlife Management Area. This area, between Lake Maurepas and Lake
Pontchartrain, consists of approximately 8,300 acres of second growth
cypress-tupelo swamp. Bird sightings in the Manchac Swamp in 2004
included pelicans, cormorants, wading birds, bald eagles, shorebirds,
gulls, and various other insectivores and song birds (BirdFest, 2004).

Table A-1. Wildlife Species Commonly Found in and around Lake Maurepas,
Pass Manchac, and Lake Pontchartrain. Source: *Handley et al., 2002.*

  -----------------------------------------------------------------------
  **Common Names**                    
  ----------------------------------- -----------------------------------
  **Wading Birds**                    **Shorebirds**

  Great Blue Heron                    Wilson's Phalarope

  Little Blue Heron                   Spotted Sandpiper

  Great Egret                         Pectoral Sandpiper

  Snowy Egret                         Least Sandpiper

  Black-crowned Night-heron           Short-billed Dowitcher

  Tricolored Heron                    Western Sandpiper

  White Ibis                          Common Snipe

  Clapper Rail                        Solitary Sandpiper

  White-faced Ibis                    **Reptiles**

  Least Bittern                       American Alligator

  American Bittern                    **Mammals**

  Virginia Rail                       River Otter

  Sora Rail                           Muskrat

  Common Moorhen                      Mink

  **Waterfowl**                       Nutria

  Canvasback                          Northern Raccoon

  Canada Goose                        **Shellfish**

  Snow Goose                          Brackish Water Clam

  Mallard                             River Crayfish

  Northern Pintail                    Red Swamp Crayfish

  Northern Shoveler                   Blue Crab

  Greater Scaup                       White Shrimp

  Lesser Scaup                        Brown Shrimp

  Bufflehead                          **Marine and Freshwater Fish**

  Red-breasted Merganser              Spotted Seatrout

  Redhead                             Red Drum

  Ruddy Duck\*                        Southern Flounder

  Gadwall                             Bay Anchovy

  American Wigeon                     Spot

  Blue-winged Teal                    Black Drum

  Hooded Merganser                    Atlantic Croaker

  Mottled Duck                        Southern Kingfish

  **Diving Birds**                    Sheepshead

  Common Loon                         Gizzard Shad

  Horned Grebe                        Largemouth Bass

  Eared Grebe                         Black Crappie

  Double-created Cormorant            Bluegill

  Anhinga                             Blue Catfish

  Pied-billed Grebe                   Channel Catfish

  **Raptors**                         White Crappie

  Bald Eagle\*                        Warmouth

  Osprey\*                            Redear Sunfish

  Peregrine Falcon\*                  Freshwater Drum

  American Kestrel\*                  Spotted Sunfish

                                      Gulf Menhaden

                                      Gulf Kingfish
  -----------------------------------------------------------------------

\* indicates threatened or endangered status

# Conceptual Site Model and Exposure Pathway Analysis

The first step in the ecological risk assessment process is to define a
conceptual site model (EPA, 1997). The CSM is a framework for relating
ecological wildlife receptors to contaminated media (*i.e.,* water
and/or sediment) and determining the degree of completion and
significance of exposure pathways. An exposure pathway describes the
route(s) a chemical takes from its source to a receptor of concern
(ROC). An exposure pathway analysis links the source, location, and type
of contaminants with a wildlife population, location, and activity
patterns to determine the primary means of potential exposure. If
potentially complete and significant exposure pathways exist between
contaminants and ROCs, an assessment of potential effects and exposure
is conducted.

An exposure pathway is considered complete if all four of the following
elements are present:

-   A source and mechanism of chemical release to the environment;

-   An environmental retention or transport medium (*e.g.,* water or
    sediment) for the released chemical;

-   A point of potential physical contact to a receptor with the
    contaminated medium (exposure point); and,

-   An exposure route (*e.g.,* ingestion of contaminated prey,
    incidental ingestion of sediment).

In the absence of any one of these components, a complete exposure
pathway does not exist, and risk to ecological receptors is not
plausible.

As discussed in Section 2.2.3, discharges of contaminants to the
Mississippi River, in general, include industrial point sources and
non-point source agricultural runoff. Following discharge to the river,
contaminants can partition from water into sediments, and bioavailable
contaminants can make their way through the food chain. After completion
of the freshwater diversion, approximately 1500 cfs of water (and
suspended sediment) will be diverted to Maurepas Swamp and subsequently
into Lake Maurepas (Day *et al.,* 2004). In addition, there are several
oil production sites within Maurepas Swamp. Potential exposure to
contaminants, therefore, may occur to wildlife in the study area through
direct exposure of contaminants in the water column, in sediments,
and/or in the tissues of prey items. Upper-trophic level receptors may
also be exposed through consumption of contaminated prey. The CSM for
this screening-level risk evaluation is illustrated in Figure A-2.

![](media/image2.wmf)

**Figure A-2. Conceptual Site Model for Screening-Level Risk Evaluation
of Maurepas Swamp Diversion Project.**

**A.2.1 Exposure Pathways**

The identified media of concern are surface water, sediment, and the
tissues of prey items. Correspondingly, a wide range of ecological
receptors are potentially at risk, including benthic invertebrates,
fish, and a variety of piscivorous or aquatic avian predator species.

The contaminants of concern represent a range of chemical classes and
possess different physicochemical properties that affect their behavior
(*i.e.,* partitioning, bioaccumulation) in the environment. These
properties are important considerations in an exposure pathway analysis
because they are a primary determinant of whether a detected chemical is
likely to possess a risk to ROCs. For example, the physicochemical
properties of polychlorinated biphenyls (PCBs), polycyclic aromatic
hydrocarbons (PAHs), and most metals suggest that if these chemicals are
detected in sediments at the study area, receptors exposed to this
medium will likely be exposed to the chemical (*i.e.*, the exposure
pathway is complete).

Ecological receptors may be exposed to chemical contaminants through
three major pathways: ingestion, dermal contact, and inhalation. Dermal
exposure to sediment contaminants for birds and mammals, although likely
to occur, is considered to be *de minimus*. Dermal contact with sediment
is typically incidental when foraging for food. Although established
methods are available to assess dermal exposure to humans, limited data
are available to quantitatively assess dermal exposure of wildlife to
sediments. In addition, the presence of scales, fur, and feathers, along
with grooming and preening activities, reduces contaminant contact with
skin.

Organic compounds and metal contaminants typically adsorb to sediments,
as such, risk evaluations are frequently based on sediment
concentrations of contaminants, which flux into and out of the water
column by various chemical and physical process. Many of these
contaminants become bioavailable to benthic organisms, which are then
consumed by fish, and subsequently make their way up the food chain to
upper-trophic level consumers.

Exposure via inhalation can occur to upper-trophic receptors in
terrestrial environments from exposure to contaminants in soil. It is
considered, however, *de minimus* in Maurepas Swamp due to the high
moisture content in the sediments and lack of direct exposure to air due
to water cover.

Based on a review of major exposure pathways, the significant complete
exposure routes for higher-trophic level organisms are associated with
the ingestion of contaminated prey and to a lesser extent, the
direct/incidental ingestion of sediment and surface water.

**A.2.2 Contaminants of Concern**

Available data that could represent future conditions (*i.e.,*
contaminant data from the Mississippi River for surface water, sediment,
and prey items) was compiled and the maximum concentrations were used to
conservatively estimate potential risk to wildlife receptors in the
Maurepas Swamp study area. The following sections describe the available
data used for this screening-level risk evaluation.

*Surface Water*

The most recent surface water contaminant data were collected by
Louisiana Department of Environmental Quality (LDEQ) from 1995 to 2001
from six stations that were determined to be in the vicinity of the
Maurepas Swamp study area: Amite River Diversion Canal north of
Gramercy, Blind River near confluence with Lake Maurepas, Blind River
near Gramercy, Lake Maurepas, Mississippi Bayou north of Reserve, and
Mississippi River south of Lutcher. Between the time periods of 1995 to
2001 these sites were monitored for metals such as arsenic, cadmium,
chromium, copper, lead, mercury, nickel, and zinc (Table A-2).

Table A-2. Summary of Metals in Surface Water from\
the Maurepas Swamp Study Area (µg/L).

  ----------------------------------------------------------------------------------
  **Date**   **As**   **Cd**   **Cr**   **Cu**   **Hg**   **Ni**   **Pb**   **Zn**
  ---------- -------- -------- -------- -------- -------- -------- -------- --------
  1995       ND       0.2      0.4      3.1      0.1      1.7      ND       \-

  1995       2.0      0.3      ND       4.9      ND       2.5      1.2      \-

  1995       2.8      0.3      ND       8.5      ND       1.9      1.3      \-

  1995       ND       0.2      ND       3.7      ND       0.9      0.5      \-

  1995       ND       0.1      0.2      6.2      ND       2.2      ND       \-

  1995       2.0      ND       0.3      2.6      ND       ND       ND       \-

  1995       2.6      ND       0.5      5.4      ND       ND       ND       \-

  1995       3.7      ND       0.7      ND       ND       1.8      ND       \-

  1995       ND       0.2      0.3      5.4      ND       2.4      0.4      \-

  1995       2.0      0.4      0.3      3.5      ND       1.2      0.4      \-

  1995       3.3      0.3      0.3      2.1      ND       2.2      0.8      \-

  1995       1.2      0.1      0.7      2.2      ND       2.8      0.2      \-

  1995       1.5      0.1      0.3      3.7      0.1      1.0      0.4      \-

  1995       0.8      0.1      0.5      2.7      ND       1.9      0.5      \-

  1995       1.1      ND       0.5      2.8      ND       1.4      0.5      \-

  1995       2.1      ND       ND       1.6      ND       2.8      ND       \-

  1995       ND       ND       ND       1.7      ND       2.5      0.2      \-

  1996       0.8      ND       0.2      0.7      ND       1.3      ND       \-

  1996       1.4      ND       0.4      3.6      ND       2.3      ND       \-

  1996       1.5      0.4      0.4      3.9      ND       1.8      0.2      \-

  1996       ND       0.3      0.3      1.9      ND       3.0      0.5      \-

  1996       1.3      0.2      ND       3.7      ND       5.1      1.0      \-

  1996       ND       0.1      ND       1.7      ND       7.1      0.4      \-

  1996       3.1      0.1      ND       2.2      ND       1.5      0.2      \-

  1996       3.7      0.1      0.6      3.2      ND       4.0      ND       \-

  1996       0.8      0.3      0.3      0.7      ND       2.5      ND       \-

  1996       0.9      0.3      0.3      3.1      ND       1.5      0.6      \-

  1996       1.0      ND       0.4      1.6      ND       2.8      0.4      \-

  1996       ND       0.1      0.5      1.8      ND       2.4      ND       \-

  1997       ND       0.1      0.5      2.4      ND       2.7      ND       \-

  1997       ND       0.2      0.4      6.9      ND       ND       ND       \-

  1997       ND       0.5      0.4      0.9      ND       ND       ND       \-

  1997       ND       ND       0.4      0.8      ND       ND       ND       \-

  1997       5.0      ND       ND       2.8      ND       ND       ND       \-

  1997       ND       ND       ND       ND       ND       ND       ND       \-

  1997       ND       ND       ND       5.7      ND       ND       ND       \-

  1997       ND       ND       ND       3.0      ND       ND       ND       \-

  1997       ND       ND       ND       ND       0.1      ND       ND       \-

  1997       ND       ND       ND       ND       0.1      ND       ND       \-

  1997       ND       1.4      ND       11.9     0.1      ND       ND       \-

  1997       ND       6.5      ND       24.1     ND       ND       ND       \-
  ----------------------------------------------------------------------------------

Table A-2. Summary of Metals in Surface Water from\
the Maurepas Swamp Study Area (µg/L).

  ---------- -------- -------- -------- -------- -------- -------- -------- --------
  **Date**   **As**   **Cd**   **Cr**   **Cu**   **Hg**   **Ni**   **Pb**   **Zn**

  1998       ND       ND       ND       ND       ND       ND       ND       \-

  1998       ND       ND       ND       ND       0.1      ND       ND       \-

  1998       ND       ND       ND       ND       0.2      ND       ND       \-

  1998       ND       ND       ND       3.1      0.1      ND       ND       \-

  2001       0.3      0.01     0.1      1.4      0.001    1.1      ND       ND

  2001       1.3      0.01     0.03     1.1      0.001    91.0     0.4      1.2

  2001       1.4      \-       ND       1.1      0.001    1.2      0.3      0.5

  2001       1.5      0.02     ND       0.8      0.001    1.2      0.02     ND

  2001       2.0      0.01     0.2      2.2      0.006    1.2      0.4      2.3

  2001       1.5      0.01     0.16     1.6      0.004    1.3      0.3      1.6

  2001       1.8      0.0      0.1      1.9      \-       1.2      0.3      1.7

  2001       0.7      0.3      0.4      2.1      0.001    1.3      4.0      ND

  2001       0.9      \-       0.1      1.4      0.001    0.8      0.03     0.6

  2001       0.9      \-       0.03     0.6      0.002    0.5      0.2      0.9

  2001       1.3      0.01     0.1      0.9      0.002    0.5      0.1      2.1
  ---------- -------- -------- -------- -------- -------- -------- -------- --------

ND = not detected

-   = no data available

*Sediment*

Available data for many chemical contaminants in sediment are lacking
for the Maurepas Swamp study area. As a result, available data from
Mississippi River sediments were compiled from a study reported by
Macauley and Summers (1998). Surface sediments were sampled during EPA's
Environmental Monitoring and Assessment Program (EMAP) from 1991 to 1994
for chemical contaminants including metals, several PAHs, two PCB
congeners, and several pesticides (Table A-3).

Table A-3. Contaminant Concentrations in Sediment from the Mississippi
River.

  -----------------------------------------------------------------------
  **Chemical Parameters**           **Minimum          **Maximum
                                    Concentration**    Concentration**
  --------------------------------- ------------------ ------------------
  **Metals (ppm)**                                     

  Arsenic                           2.2                15.9

  Cadmium                           0.03               0.86

  Chromium                          6.7                84

  Copper                            1.5                33.7

  Lead                              7.4                35.7

  Mercury                           0.002              0.15

  Nickel                            9                  45.5

  Selenium                          0.02               0.82

  Silver                            0.04               0.46

  Zinc                              12.4               165

  **PAHs (ppb)**                                       

  1-Methylphenanthrene              0.25               65.45

  2,3,5-Trimethylnaphthalene        NA                 NA

  2,6-Dimethylnaphthalene           NA                 NA

  2-Methylnaphthalene               NA                 NA

  Acenaphthene                      NA                 NA

  Acenaphthylene                    NA                 NA

  Anthracene                        0.1                34.6

  Fluorene                          0.25               76.29

  Naphthalene                       1.08               218.7

  Phenanthrene                      0.94               164.19

  Benzo\[a\]anthracene              0.29               224.21

  Benzo\[a\]pyrene                  0.13               307.84

  Benzo\[b\]fluoranthene            0.3                89

  Benzo\[e\]pyrene                  0.19               260.36

  Benzo\[g,h,i\]perylene            0.11               252.28

  Benzo\[k\]fluoranthene            0.09               94.74

  Chrysene                          0.44               294.73

  Dibenz\[a,h\]anthracene           0.04               105.68

  Dibenzothiophene                  0.15               54.66

  Fluoranthene                      0.73               95.9

  Indeno\[1,2,3-c,d\]-pyrene        0.15               66.31

  Perylene                          4.52               263.66

  Pyrene                            1.02               185.28

  PAHs, Total                       NA                 NA

  PCB 44                            0.03               3.89

  PCB 209                           0.04               0.45

  **PCBs, Total**                   NA                 NA
  -----------------------------------------------------------------------

Table A-3. Contaminant Concentrations in Sediment from the Mississippi
River.

  -----------------------------------------------------------------------
  **Chemical Parameters**           **Minimum          **Maximum
                                    Concentration**    Concentration**
  --------------------------------- ------------------ ------------------
  **Pesticides (ppb)**                                 

  4,4\'-DDD                         0.09               5.39

  4,4\'-DDE                         0.03               2.89

  4,4\'-DDT                         0.02               18.44

  Total DDx compounds (sum of       ND                 23.24
  4,4\'- and 2,4\'-isomers)                            

  Aldrin                            0.028              0.09

  cis-Nonachlor                     0.01               0.29

  trans-Nonachlor                   0.04               0.55

  Atrazine                          NA                 NA

  BHC (alpha)                       0.0071             1.67

  Chlordane                         NA                 NA

  Dieldrin                          0.15               0.68

  Endosulfan                        NA                 NA

  Endrin                            0.04               0.31

  Heptachlor                        NA                 NA

  Heptachlor epoxide                0.03               0.48

  Methoxychlor                      NA                 NA

  **Herbicides (ppb)**                                 

  Acetochlor                        NA                 NA

  Alachlor                          NA                 NA

  Carbonate                         NA                 NA

  Triazine                          NA                 NA

  2-4-dichlorophenoxy acetic acid   NA                 NA
  (2,4-D)                                              

  2, 4, 5-trichlorophenoxy acetic   NA                 NA
  acid (2,4,5-T)                                       

  4-(2,4-dichlorophenoxy)butyric    NA                 NA
  acid (2,4-DB)                                        

  2-(2,4,5-Trichlorophenoxy)        NA                 NA
  propionic acid (2,4,5-TP)                            

  **Volatile Organic Compounds                         
  (ppb)**                                              

  1,1,1-Trichloroethane             NA                 NA

  1,1,2,2-Tetrachloroethane         NA                 NA

  1,1,2-Trichloroethane             NA                 NA

  1,1-Dichloroethane                NA                 NA

  1,1-Dichloroethene                NA                 NA

  2-Hexanone                        NA                 NA
  -----------------------------------------------------------------------

Table A-3. Contaminant Concentrations in Sediment from the Mississippi
River.

  -----------------------------------------------------------------------
  **Chemical Parameters**           **Minimum          **Maximum
                                    Concentration**    Concentration**
  --------------------------------- ------------------ ------------------
  4-Methyl-2-Pentanone              NA                 NA

  Benzene                           NA                 NA

  Carbon Disulfide                  NA                 NA

  Carbon Tetrachloride              NA                 NA

  Chlorobenzene                     NA                 NA

  Chloroform                        NA                 NA

  cis-1,3-Dichloropropene           NA                 NA

  Ethylbenzene                      NA                 NA

  Methylene chloride                NA                 NA

  Toluene                           NA                 NA

  Total Xylenes                     NA                 NA

  Trans-1,3-dichloropropene         NA                 NA
  -----------------------------------------------------------------------

NA = not available

*Fish*

To assess potential exposures to upper-trophic level receptors, such as
the bald eagle, it is necessary to estimate chemical contaminant levels
in prey items, such as fish tissue. These concentrations are used in a
dose-assessment model (Section A2.4) to evaluate exposures. For this
screening-level ecological risk evaluation, available fish tissue data
were obtained from USGS (2002) and LDEQ (1997-2004). Mercury-in-fish
tissue data, collected by LDEQ, were grouped according to three distinct
areas: Mississippi River, Lake Maurepas, and Lake Pontchartrain. Mercury
concentrations in fish tissue ranged from 0.14 to 0.73 ppm in Lake
Maurepas, \<0.0001 to 1.11 ppm in Lake Pontchartrain, and 0.008 to 0.53
ppm in the Mississippi River (Attachment 2). Fish samples collected in
1995 by USGS at Luling, LA revealed moderately high concentrations of
PCBs and TCDD in carp and white bass (USGS, 2002) as well as DDx
compounds, chlordane, dieldrin, and nonachlor (USGS, 2002) (Table A-4).

Table A-4. Contaminant Data (µg/g wet weight) in Fish Tissue Samples
from Luling, LA (1995). *Source: USGS, 2002.*

<table style="width:100%;">
<colgroup>
<col style="width: 11%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 6%" />
</colgroup>
<tbody>
<tr class="odd">
<td><strong>Species</strong></td>
<td><blockquote>
<p><strong>Percent Lipid</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>Percent Moisture</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>p,p'-DDD</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>p,p'-DDE</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>p,p'-DDT</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>Total DDx</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>a-Chlordane</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>g-Chlordane</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>trans-Nonachlor</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>Dieldrin</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>PCB-Total</strong></p>
</blockquote></td>
<td><blockquote>
<p><strong>Nickel</strong></p>
</blockquote></td>
</tr>
<tr class="even">
<td>Carp</td>
<td>12.1</td>
<td>69.2</td>
<td>0.062</td>
<td>0.098</td>
<td>&lt;0.01</td>
<td>0.16</td>
<td>0.015</td>
<td>0.012</td>
<td>0.017</td>
<td>0.023</td>
<td>0.48</td>
<td>0.34</td>
</tr>
<tr class="odd">
<td>Carp</td>
<td>13.4</td>
<td>64.7</td>
<td>0.054</td>
<td>0.074</td>
<td>&lt;0.01</td>
<td>0.13</td>
<td>0.016</td>
<td>0.014</td>
<td>0.015</td>
<td>0.028</td>
<td>0.35</td>
<td>0.41</td>
</tr>
<tr class="even">
<td><p>Largemouth</p>
<p>Bass</p></td>
<td>4.69</td>
<td>72.4</td>
<td>0.021</td>
<td>0.041</td>
<td>&lt;0.01</td>
<td>0.06</td>
<td>&lt;0.01</td>
<td>&lt;0.01</td>
<td>&lt;0.01</td>
<td>0.021</td>
<td>0.22</td>
<td>0.53</td>
</tr>
<tr class="odd">
<td>White Bass</td>
<td>7.38</td>
<td>71.6</td>
<td>0.031</td>
<td>0.064</td>
<td>0.018</td>
<td>0.11</td>
<td>&lt;0.01</td>
<td>&lt;0.01</td>
<td>&lt;0.01</td>
<td>0.028</td>
<td>0.31</td>
<td>0.56</td>
</tr>
<tr class="even">
<td>White Bass</td>
<td>7.84</td>
<td>71.4</td>
<td>0.043</td>
<td>0.11</td>
<td>0.015</td>
<td>0.17</td>
<td>0.014</td>
<td>&lt;0.01</td>
<td>0.014</td>
<td>0.025</td>
<td>0.53</td>
<td>0.44</td>
</tr>
</tbody>
</table>

**A.2.3 Selection of Receptors of Concern (ROCs)**

The selection of ROCs takes into account a variety of factors which
include federally listed threatened and endangered (T&E) species;
species of special concern within the State of Louisiana; the likelihood
of the species expected to occur based on existing conditions in the
swamp; significance of the species to ecosystem function; availability
of toxicity and life history data; and species sensitivity to expected
contaminants.

Because it is impractical to assess exposure to all potentially exposed
species within a trophic group, representative species were selected as
conservative surrogates for exposure to a group of taxonomically related
and ecologically similar receptors.

For this risk evaluation, biological information was gathered to
determine the species that are most abundant in the Maurepas Swamp study
area (Table A-5). Benthic invertebrates may be exposed to contaminants
from the sediment, from surface water, and from food items (i.e,
plankton and small fish). Blue crabs are an example of a large
macroinvertebrate that comes into direct contact with potentially
contaminated sediments throughout their entire lifespan. Other
invertebrates include shrimp, crayfish, and clams. These all have the
potential to accumulate contaminants in their tissues and transfer them
up the food chain when preyed upon by other organisms (Figure A-2).

Available fish species in the Maurepas Swamp study area include the Gulf
Sturgeon which is listed on both the State and Federal threatened and
endangered species lists. It is a demersal fish that spends most of its
time in close proximity to the benthos, where it may consume
contaminated sediments and food items. Channel catfish are another
demersal fish species that are prevalent in the area, foraging on
potentially contaminated sediments, invertebrates, and detritus.

A variety of avian species have been observed in and around the Maurepas
Swamp study area. These include wading birds, diving birds, raptors, and
song birds. The bald eagle was selected as a ROC for the Maurepas Swamp
freshwater diversion project because it is listed as both a State and
Federal threatened and endangered species and is a diurnal opportunistic
raptor. It primarily feeds on carrion and dead and dying fish. Bald
eagles will generally consume whatever food source is most plentiful and
easy to scavenge or capture (EPA, 1993). They will however, actively
hunt and prey on fish, waterfowl, and muskrats. Because bald eagles
scavenge for dead or dying prey, they are particularly vulnerable to
environmental contaminants and pesticides (e.g*.*, from feeding on birds
that died from pesticide toxicity). To be conservative, the
screening-level risk assessment assumes the bald eagle's diet is
comprised completely of contaminated fish from the Maurepas Swamp study
area.

**Table A-5. Potential Receptors of Concern for the Maurepas Swamp**

**Ecological Risk Evaluation.**

  -----------------------------------------------------------------------
  **Receptor**         **Exposure Media**         **Rationale for
                                                  Selection of Receptor
                                                  and Pathway**
  -------------------- -------------------------- -----------------------
  **Benthic                                       
  Invertebrates**                                 

  Blue crab            Sediment/surface           Epibenthic omnivorous
                       water/biota                invertebrate that
                                                  consumes plankton and
                                                  small fish and comes
                                                  into direct contact
                                                  with contaminated
                                                  sediments

  Benthic              Sediment/surface           Various benthic
  macroinvertebrate    water/biota                invertebrate
  community                                       populations
                                                  representing different
                                                  trophic levels which
                                                  are in intimate contact
                                                  with contaminated
                                                  sediments

  **Fish**                                        

  Gulf sturgeon        Sediment/surface           Listed as a threatened
                       water/biota                anadromous species on
                                                  both the State and
                                                  Federal T&E list and
                                                  feeds on benthic
                                                  invertebrates and small
                                                  fish

  Largemouth bass      Surface water/biota        Dominant predatory
                                                  species that has
                                                  sensitive early-life
                                                  stages

  Channel catfish      Sediment/surface           Freshwater demersal
                       water/biota                species that comes in
                                                  direct contact with
                                                  contaminated sediment
                                                  as a result of foraging
                                                  on benthic and
                                                  epibenthic organisms
                                                  and detritus

  **Birds**                                       

  Bald eagle           Sediment/surface           Listed as a threatened
                       water/biota                species on the Federal
                                                  T&E list and endangered
                                                  on the State list;
                                                  observed nesting in the
                                                  area and feeds on fish,
                                                  waterfowl, and muskrats

  Great blue heron     Sediment/surface           Wading bird that
                       water/biota                potentially consumes
                                                  large amounts of
                                                  sediment while feeding
                                                  on benthic aquatic life

  Double-crested       Sediment/surface           Piscivorous bird that
  cormorant            water/biota                has been observed
                                                  foraging in the area
  -----------------------------------------------------------------------

**A.2.4 Assessment and Measurement Endpoints**

As defined by EPA (1997), assessment endpoints (AEs) are formal
expressions of the actual environmental values that are to be protected
at a site. AEs are defined based on technical considerations including
the significance of exposure pathways, the presence of receptors, and a
chemical's biotic transfer pathway. Selection of AEs must consider the
ecosystem, communities, and species relevant to a particular site. The
selection of AEs depends on:

-   The chemicals present and their concentration;

-   Mechanisms of toxicity of the chemicals to different groups of
    organisms;

-   Ecologically relevant receptor groups that are potentially sensitive
    or highly exposed to the chemicals; and,

-   Potentially complete exposure pathways.

The AEs proposed for quantitative evaluation at the Maurepas Swamp are
based on protection of the most sensitive environmental resources
identified at the site. For this screening-level ecological the
following three AEs and subsequent measurement endpoints (MEs) are
proposed to represent the resources to be protected in Maurepas Swamp:

-   AE(1): Protection and maintenance (*i.e.,* survival, growth, and
    reproduction) of benthic invertebrate communities that serve as a
    forage base for fish and wildlife populations.

> ME(1): This will be evaluated by comparing concentrations of
> contaminants in sediments to available freshwater sediment benchmarks
> from the National Oceanic and Atmospheric Administration (NOAA)
> (*e.g.,* PELs and TELs) which are protective of benthic organisms.

-   AE(2): Protection and maintenance (*i.e.,* survival, growth, and
    reproduction) of benthic and pelagic fish populations that serve as
    a forage base for other fish and wildlife populations.

> ME(2): This will be evaluated by comparing concentrations of surface
> water contaminants to the National Recommended Ambient Water Quality
> Criteria (NRAWQC) developed by EPA (and Canadian standards where U.S.
> criteria are not available).

-   AE(3): Protection and maintenance (*i.e.,* survival, growth, and
    reproduction) of the bald eagle.

ME(3): This will be evaluated by modeling the daily dose of chemicals to
the bald eagle from the ingestion of contaminated surface water,
sediment, and prey items. Potential risk will be characterized by
comparing the modeled dose estimate to toxicity reference values (TRVs).

**A.2.5 Exposure Assessment**

For the first measurement endpoint, sediment concentrations collected by
Macauley and Summers (1998) were compared to available sediment quality
guidelines for freshwater. These guidelines were developed by NOAA and
represent a low value, Threshold Effects Level (TEL) and a high value,
Probable Effects Level (PEL). The TEL represents the concentration below
which adverse effects are expected to occur only rarely. The PEL is the
level above which adverse effects are frequently expected to occur
(Table A-6).

Table A-6. Comparison of Available Surface Sediment Concentrations from
the Mississippi River (1991-1994) to Applicable Benchmarks.

  ------------------------------------------------------------------------------------------
  **Chemical Parameters**      **Sediment   **Sediment   **Minimum         **Maximum
                               Quality      Quality      Concentration**   Concentration**
                               Guidelines   Guidelines                     
                               (TEL)**      (PEL)**                        
  ---------------------------- ------------ ------------ ----------------- -----------------
  **Metals (ppm)**                                                         

  Arsenic                      5.9          17           2.2               15.9

  Cadmium                      0.596        3.53         0.03              0.86

  Chromium                     37.3         90           6.7               84

  Copper                       35.7         197          1.5               33.7

  Lead                         35           91.3         7.4               35.7

  Mercury                      0.174        0.486        0.002             0.15

  Nickel                       18           35.9         9                 45.5

  Selenium                     NVA          NVA          0.02              0.82

  Silver                       NVA          NVA          0.04              0.46

  Zinc                         123.1        315          12.4              165

  **PAHs (ppb)**                                                           

  1-Methylphenanthrene         NVA          NVA          0.25              65.45

  2,3,5-Trimethylnaphthalene   NVA          NVA          NA                NA

  2,6-Dimethylnaphthalene      NVA          NVA          NA                NA

  2-Methylnaphthalene          NVA          NVA          NA                NA

  Acenaphthene                 NVA          NVA          NA                NA

  Acenaphthylene               NVA          NVA          NA                NA

  Anthracene                   NVA          NVA          0.1               34.6

  Fluorene                     NVA          NVA          0.25              76.29
  ------------------------------------------------------------------------------------------

Table A-6. Comparison of Available Surface Sediment Concentrations from
the Mississippi River (1991-1994) to Applicable Benchmarks.

  ---------------------------- ------------ ------------ ----------------- -----------------
  **Chemical Parameters**      **Sediment   **Sediment   **Minimum         **Maximum
                               Quality      Quality      Concentration**   Concentration**
                               Guidelines   Guidelines                     
                               (TEL)**      (PEL)**                        

  Naphthalene                  NVA          NVA          1.08              218.7

  Phenanthrene                 NVA          NVA          0.94              164.19

  Benzo\[a\]anthracene         31.7         385          0.29              224.21

  Benzo\[a\]pyrene             31.9         782          0.13              307.84

  Benzo\[b\]fluoranthene       NVA          NVA          0.3               89

  Benzo\[e\]pyrene             NVA          NVA          0.19              260.36

  Benzo\[g,h,i\]perylene       NVA          NVA          0.11              252.28

  Benzo\[k\]fluoranthene       NVA          NVA          0.09              94.74

  Chrysene                     57.1         862          0.44              294.73

  Dibenz\[a,h\]anthracene      NVA          NVA          NA                NA

  Dibenzothiophene             NVA          NVA          0.15              54.66

  Fluoranthene                 111          2355         0.73              95.9

  Indeno\[1,2,3-c,d\]-pyrene   NVA          NVA          0.15              66.31

  Perylene                     NVA          NVA          4.52              263.66

  Pyrene                       53           875          1.02              185.28

  PAHs, Total                  34.1         277          NA                NA

  PCB 44                       NVA          NVA          0.03              3.89

  PCB 209                      NVA          NVA          0.04              0.45

  **PCBs, Total**              NVA          NVA          NA                NA

  **Pesticides (ppb)**                                                     

  4,4\'-DDD                    3.54         8.51         0.09              5.39

  4,4\'-DDE                    1.42         6.75         0.03              2.89

  4,4\'-DDT                    NVA          NVA          0.02              18.44

  Total DDx compounds (sum of  6.98         4450         ND                23.24
  4,4\'- and 2,4\'-isomers)                                                

  Aldrin                       NVA          NVA          0.028             0.09

  BHC (alpha)                  NVA          NVA          0.0071            1.67

  Chlordane                    4.5          8.9          NA                NA

  Dieldrin                     2.85         6.67         0.15              0.68

  Endosulfan                   NVA          NVA          NA                NA

  Endrin                       2.67         62.4         0.04              0.31

  Heptachlor                   NVA          NVA          NA                NA

  Heptachlor epoxide           0.6          2.74         0.03              0.48

  Methoxychlor                 NVA          NVA          NA                NA
  ---------------------------- ------------ ------------ ----------------- -----------------

Table A-6. Comparison of Available Surface Sediment Concentrations from
the Mississippi River (1991-1994) to Applicable Benchmarks.

  ----------------------------------------------------------------------------------------------
  **Chemical Parameters**          **Sediment   **Sediment   **Minimum         **Maximum
                                   Quality      Quality      Concentration**   Concentration**
                                   Guidelines   Guidelines                     
                                   (TEL)**      (PEL)**                        
  -------------------------------- ------------ ------------ ----------------- -----------------
  **Herbicides (ppb)**                                                         

  Acetochlor                       NVA          NVA          NA                NA

  Alachlor                         NVA          NVA          NA                NA

  Atrazine                         NVA          NVA          NA                NA

  Carbonate                        NVA          NVA          NA                NA

  Triazine                         NVA          NVA          NA                NA

  2-4-dichlorophenoxy acetic acid  NVA          NVA          NA                NA
  (2,4-D)                                                                      

  2, 4, 5-trichlorophenoxy acetic  NVA          NVA          NA                NA
  acid (2,4,5-T)                                                               

  4-(2,4-dichlorophenoxy)butyric   NVA          NVA          NA                NA
  acid (2,4-DB)                                                                

  2-(2,4,5-Trichlorophenoxy)       NVA          NVA          NA                NA
  propionic acid (2,4,5-TP)                                                    

  **Volatile Organic Compounds                                                 
  (ppb)**                                                                      

  1,1,1-Trichloroethane            NVA          NVA          NA                NA

  1,1,2,2-Tetrachloroethane        NVA          NVA          NA                NA

  1,1,2-Trichloroethane            NVA          NVA          NA                NA

  1,1-Dichloroethane               NVA          NVA          NA                NA

  1,1-Dichloroethene               NVA          NVA          NA                NA

  2-Hexanone                       NVA          NVA          NA                NA

  4-Methyl-2-Pentanone             NVA          NVA          NA                NA

  Benzene                          NVA          NVA          NA                NA

  Carbon Disulfide                 NVA          NVA          NA                NA

  Carbon Tetrachloride             NVA          NVA          NA                NA

  Chlorobenzene                    NVA          NVA          NA                NA

  Chloroform                       NVA          NVA          NA                NA

  cis-1,3-Dichloropropene          NVA          NVA          NA                NA

  Ethylbenzene                     NVA          NVA          NA                NA

  Methylene chloride               NVA          NVA          NA                NA

  Toluene                          NVA          NVA          NA                NA

  Total Xylenes                    NVA          NVA          NA                NA

  Trans-1,3-dichloropropene        NVA          NVA          NA                NA
  ----------------------------------------------------------------------------------------------

NVA= no (criteria) value available

NA = not available

For the second measurement endpoint, surface water data were compared to
chronic aquatic life standards from EPA's National Ambient Water Quality
Criteria (NAWQC) (EPA, 2004) (Table A-7). Because U.S. guidelines or
criteria for aquatic life do not presently exist for most pesticides in
current use, the Canadian pesticide water-quality guidelines, where
available, are used as a point of reference for pesticide concentrations
(Table A-8).

Table A-7. National Ambient Water Quality Criteria (NAWQC) for Metals.

+-----------------------------+----------------------------------------+
| **Metals**                  | **NAWQC**                              |
|                             |                                        |
|                             | **(ppb)**                              |
+-----------------------------+----------------------------------------+
| Arsenic                     | 150                                    |
+-----------------------------+----------------------------------------+
| Cadmium                     | 0.25                                   |
+-----------------------------+----------------------------------------+
| Chromium                    | 11 (Cr VI)                             |
+-----------------------------+----------------------------------------+
| Copper                      | 9                                      |
+-----------------------------+----------------------------------------+
| Lead                        | 2.5                                    |
+-----------------------------+----------------------------------------+
| Mercury                     | 0.77                                   |
+-----------------------------+----------------------------------------+
| Nickel                      | 52                                     |
+-----------------------------+----------------------------------------+
| Selenium                    | 5                                      |
+-----------------------------+----------------------------------------+
| Silver                      | 0.12                                   |
+-----------------------------+----------------------------------------+
| Zinc                        | 120                                    |
+-----------------------------+----------------------------------------+

For the third measurement endpoint, the exposure assessment
quantitatively estimates potential exposure of the bald eagle to
chemicals identified at the site. An exposure (dose) model incorporating
the receptor's natural history information and characteristics
(including diet composition, ingestion rates, body weights, and foraging
ranges) was developed to evaluate its exposure to contaminants. It was
assumed that the bald eagle is exposed to site contaminants through
consumption of contaminated prey, including fish and benthic
invertebrates, as well as from the incidental ingestion of sediment.
This screening-level risk evaluation conservatively assumes that the
bald eagle will forage only on the most contaminated fish (maximum
concentrations) within the Maurepas Swamp study area (*i.e.,* site use
factor = 1).

Table A-8. Aquatic Life Criteria for Selected Major Pesticides in the
Mississippi River Basin. *Source: Meade, 1995.*

+--------------------+----------------+-------------------------------+
| **Pesticide**      | **Aquatic Life | **Source**                    |
|                    | Criteria       |                               |
|                    | (µg/L)**       |                               |
+--------------------+----------------+-------------------------------+
| Alachlor           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Atrazine           | 2              | Trotter et al. 1990 (Canada)  |
+--------------------+----------------+-------------------------------+
| Bentazon           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Butylate           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Cyanazine          | 2              | Pauli et al. 1991b (Canada)   |
+--------------------+----------------+-------------------------------+
| 2                  | 4              | Task Force on Water Quality   |
| -4-dichlorophenoxy |                | Guidelines (Canada)           |
| acetic acid        |                |                               |
|                    |                |                               |
| (2,4-D)            |                |                               |
+--------------------+----------------+-------------------------------+
| EPTC               | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Metolachlor        | 8              | Kent et al. 1991 (Canada)     |
+--------------------+----------------+-------------------------------+
| Metribuzin         | 1              | Pauli et al. 1990 (Canada)    |
+--------------------+----------------+-------------------------------+
| Molinate           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Propachlor         | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Propanil           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Propazine          | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Simazine           | 10             | Pauli et al. 1991b (Canada)   |
+--------------------+----------------+-------------------------------+
| Triflualin         | 0.2            | Kent et al. 1992 (Canada)     |
+--------------------+----------------+-------------------------------+
| Carbaryl           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+
| Carbofuran         | 1.75           | Trotter et al. 1989 (Canada)  |
+--------------------+----------------+-------------------------------+
| Chlorpyrifos       | 0.041          | EPA, 2004 (US)                |
+--------------------+----------------+-------------------------------+
| Diazinon           | NVA            | \-                            |
+--------------------+----------------+-------------------------------+

NVA = no value available

The following dose model was used to assess daily exposures of
contaminants to the bald eagle and to characterize exposure:

Dose *=* [(C~sed~ \* IR~sed~)+ (C~food~ \* IR~food~) \* SUF]{.underline}
(Equation 1)

BW

> Where:
>
> Dose = daily dose resulting from ingestion (mg/kg)
>
> C~sed~ = concentration of contaminant in surface sediment (mg/kg)
>
> IR~sed~ = estimate of receptor's daily ingestion rate of surface
> sediment (kg/d)
>
> C~food~ = concentration of contaminant in food tissue (mg/kg)
>
> IR~food~ = estimate of daily ingestion rate of food tissue (kg/d)
>
> SUF = site use factor (unitless)
>
> BW = body weight (kg)

The exposure parameters for the bald eagle that are summarized in Table
A-9 and the maximum sediment contaminant data provided in Table A-3 were
used to evaluate potential chemical doses to the bald eagle using
Equation 1. Due to the limited amount of available toxicity information
on many contaminants, only a select few contaminants (*i.e.,* those that
are generally considered the most toxic) were modeled to obtain the most
conservative level of risk. These include mercury, due to its high
potential for bioavailability, especially in its methylated form; nickel
because it exceeded the screening level benchmark; and total DDx because
of its known toxicity to bald eagles (EPA, 1993). Fish tissue data for
mercury were acquired by LDEQ from various stations along the
Mississippi River (Attachment 2). Fish tissue data for total DDx and
nickel were acquired by USGS from the Mississippi River at Luling,
Lousiana (USGS, 2002) (Table A-4). These tissue concentrations were
converted to mg/kg dry weight and used in the dose models to represent
the concentration of food (C~fish~) for these contaminants.

Table A-9. Exposure Parameters for the Bald Eagle.

  ---------------------- ------------------ ------------ ------------ --------------
  **Exposure Parameter** **Abbreviation**   **Unit**     **Value**    **Source**

  Body weight            BW                 kg           4.5          EPA, 1993

  Daily ingestion rate   IR~fish~           kg/day       0.451        EPA, 1993
  of food^a^                                                          

  Daily ingestion rate   IR~sed~            kg/day       0.004        Beyer et al.
  of sediment^b^                                                      1994

  Site Use Factor (max   SUF                unitless     1            Most
  of 1)^c^                                                            conservative
  ---------------------- ------------------ ------------ ------------ --------------

> ^a^ Conservatively assumed to be comprised of 100% fish. The food
> ingestion rate (g/g/day) from EPA (1993) was multiplied by the body
> weight to obtain a daily ingestion rate (kg/day).
>
> ^b^ Sediment uptake was assumed to be 1% of the daily ingestion rate.
>
> ^c^ A site use factor describes the percentage of the study area the
> receptor is expected to use for foraging. In a screening-level
> evaluation, it is typically set at 1 to be the most conservative
> (*i.e.,* the eagle spends all of its time foraging within the study
> area).

# Ecological Effects Assessment 

For the purpose of evaluating the ecological effects on benthic
organisms, sediment contaminant data were compared to appropriate
benchmarks. It is important to note that the sediment sampling stations
(Macauley and Summers, 1998) were all located south of the Maurepas
Swamp study area, downstream of New Orleans and a highly industrialized
corridor in Louisiana. Because of the downward flow of Mississippi River
water, one might expect the sediments at these stations to contain
relatively high levels of contaminants from industrial point sources.
However, concentrations were compared to available benchmarks (NOAA,
1999) revealing that the majority of all maximum surface sediment
concentrations were lower than the appropriate PEL, but higher than the
TEL. Only nickel exceeded its PEL with a maximum concentration of 45.5
ppm (compared to a PEL of 35.9) (Table A-6).

[]{.mark}

To evaluate the potential ecological effects to fish, surface water
quality criteria for aquatic life were compared to available data. In
general, metal concentrations in surface water were either not detected
or were below water quality criteria. The majority of concentrations of
metals in surface water over a six-year time span either fell below
EPA's standards or were not detected. Exceedances were noted for cadmium
and copper, and one exceedance occurred for nickel (Table A-10). Total
herbicide loads in the Mississippi River at Baton Rouge did not exceed
10 µg/L during 1991-1997 (USGS, 1999). No herbicide or metabolite was
detected at a concentration exceeding 5 µg/L. Although concentrations of
atrazine, cyanazine, and metolachlor peak simultaneously in late May and
early June, none of the average annual concentrations of herbicides
exceeded maximum contaminant levels (MCLs) or Health Advisories (HA) for
drinking water (USGS, 1999).

**Table A-10. Number of Exceedances of National Ambient Water Quality
Criteria (NAWQC) for Metals in the Maurepas Swamp Study Area.**

+---------------------+-----------------------+-----------------------+
| **Metals**          | **NAWQC**             | **Number**            |
|                     |                       |                       |
|                     | **(ppb)**             | **Exceedances**       |
+---------------------+-----------------------+-----------------------+
| Arsenic             | 150                   | 0                     |
+---------------------+-----------------------+-----------------------+
| Cadmium             | 0.25                  | 11                    |
+---------------------+-----------------------+-----------------------+
| Chromium            | 11 (Cr VI)            | 0                     |
+---------------------+-----------------------+-----------------------+
| Copper              | 9                     | 2                     |
+---------------------+-----------------------+-----------------------+
| Lead                | 2.5                   | 0                     |
+---------------------+-----------------------+-----------------------+
| Mercury             | 0.77                  | 0                     |
+---------------------+-----------------------+-----------------------+
| Nickel              | 52                    | 1                     |
+---------------------+-----------------------+-----------------------+
| Selenium            | 5                     | NA                    |
+---------------------+-----------------------+-----------------------+
| Silver              | 0.12                  | NA                    |
+---------------------+-----------------------+-----------------------+
| Zinc                | 120                   | 0                     |
+---------------------+-----------------------+-----------------------+

NA = not available

For the purpose of evaluating the potential effects associated with
wildlife exposure to contaminants, chemical- and receptor-specific
toxicity reference values (TRVs) were compared to the calculated doses.
A TRV is defined as a dose level at which a particular biological effect
may be expected to occur in an organism, based on laboratory
toxicological investigations. The calculation of TRVs commonly
incorporates both toxicity-based reference doses as well as uncertainty
factors to account for a wide range of limitations, including
differential interspecies sensitivities.

The EPA Region IX Biological Technical Assistance Group (BTAG), in
conjunction with the Navy, has developed effects-based TRVs (DTSC,
2002). Each of these values represents a critical exposure level from a
toxicological study and is supported by a published dataset of
toxicological exposures and effects. Rather than derive a single point
estimate associated with specific adverse biological effects, high- and
low-TRVs were derived for each receptor and contaminant to reflect the
variability of parameters within an ecological risk context. The low TRV
is a conservative value consistent with a chronic, no observed adverse
effects level (NOAEL). It represents a level at which adverse effects
are unlikely to occur, and is used to identify areas posing little or no
risk. Conversely, the high TRV is a less conservative estimator of
potential adverse effects and is consistent with a low observed adverse
effect level (LOAEL), falling approximately mid-range of all of the
reported adverse effects. The high TRV represents a level at which there
is a higher potential for adverse effects to occur. Available TRVs for
birds are listed in Table A-11.

Table A-11. Available TRVs for Birds from EPA Region IX.

  ----------------------------- ------------------- ----------------------
  **Chemical**                  **Low TRV           **High TRV
                                (mg/kg-day)**       (mg/kg-day)**

  Arsenic                       5.5                 22

  Cadmium                       0.08                10.4

  Copper                        2.3                 52.3

  DDT and metabolites           0.009               1.5

  Lead                          0.014               8.75

  Manganese                     77.6                776

  Mercury                       0.039               0.18

  Nickel                        1.38                56.3

  PCBs                          0.09                1.27

  Selenium                      0.23                0.93

  Zinc                          17.2                172
  ----------------------------- ------------------- ----------------------

## A.3.1 Risk Characterization  {#a.3.1-risk-characterization .unnumbered}

The risk characterization combines the exposure and effects assessments
to provide an estimate of the potential risks to receptors. Each
receptor group is discussed in the following sections.

> *Protection and Maintenance of Benthic Invertebrate Communities*
>
> To assess the potential risks to benthic invertebrate communities in
> this screening-level risk evaluation, maximum chemical concentrations
> in sediment were compared to available freshwater sediment benchmarks
> compiled by NOAA (e.g*.*, PELs and TELs) which are protective of
> benthic organisms. With the exception of nickel, maximum
> concentrations of contaminants in sediment were all below PEL
> guidelines. However, some metals (arsenic, cadmium, chromium, lead,
> and zinc) had maximum concentrations that were above the TEL
> guidelines. Similarly, three PAHs (benz\[a\]pyrene, chrysene, and
> pyrene), DDT isomers (4,4'-DDD, 4-4'-DDE) and total DDx had maximum
> concentrations which were also above TEL guidelines. In general, the
> maximum concentrations of these compounds are above levels which are
> considered to be "safe" (*i.e.,* will not likely cause adverse
> effects); and are well below probable effect levels (PELs) which are
> consistent with adverse effects. These results would indicate a low
> magnitude level of risk to the benthic invertebrate community. In the
> absence of any site-specific sediment data, quantitative comparisons
> to existing conditions are not possible. However, qualitatively, these
> compounds, in particular the organic ones, are relatively ubiquitous
> in industrialized environments. The concentrations likely reflect
> regional level of contamination and would be consistent with current
> levels in Maurepas Swamp and Lake Maurepas.

*Protection and Maintenance of Benthic and Pelagic Fish Populations*

In the screening-level risk evaluation, fish populations were assessed
using EPA's NAWQC for the protection of aquatic life and Canadian water
quality standards where U.S. criteria were not available. These surface
water quality criteria were compared to available data. The majority of
concentrations of metals in surface water over a six-year time span
either fall below EPA's standards or were not detected. Exceedances were
noted for cadmium (eleven exceedances), copper (two exceedances), and
one exceedance occurred for nickel (Table A-10). The low frequency of
exceedances for nickel and copper would indicate that these compounds
pose a low magnitude level of risk to fish and that cadmium may pose a
high magnitude level of risk to fish.

Total herbicide loads in the Mississippi River at Baton Rouge did not
exceed 10 µg/L during 1991-1997 (USGS, 1999). No herbicide or metabolite
was detected at a concentration exceeding 5 µg/L. Although
concentrations of atrazine, cyanazine, and metolachlor peak
simultaneously in late May and early June, none of the average annual
concentrations of herbicides exceeded MCLs or HAs for drinking water.

> *Protection and Maintenance of Bald Eagles*
>
> To assess exposure to bald eagles, a dose assessment model was
> developed to estimate the daily dose of chemicals to the bald eagle
> from the ingestion of contaminated surface water, sediment, and prey
> items. Potential risk was then characterized by comparing the modeled
> dose estimate to chemical specific TRVs.

The estimated daily doses were calculated (Equation 1) for potential
contaminants, using the available maximum concentrations, which were
then compared to the high and low TRVs according to the following
equation:

HQ = dose/TRV (Equation 2)

The dose estimates were used to derive two hazard quotients (HQs), an
HQ~low~ using the low TRV, based on NOAEL, and an HQ~high~ using the
high TRV, based on a LOAEL, for each contaminant. When the dose is lower
than the low TRV (*i.e.,* HQ~low~ \<1), it is likely that no risk is
present from the contaminant. When the dose exceeds the low TRV (*i.e.,*
HQ~low~ \>1), it indicates that further evaluation may be warranted.
Following EPA's 8-step Ecological Risk Assessment process, there are
three possible outcomes: (1) it is adequate to conclude that the site
poses no unacceptable risks to ecological receptors; (2) the conclusions
are inconclusive and the ecological risk evaluation should continue; and
(3) a potential for adverse ecological effects is indicated and a more
thorough analysis is warranted (EPA, 1997).

The screening-level risk assessment evaluated exposures to the bald
eagle from mercury, nickel, and DDT. The results are summarized in Table
A-12. Bald eagle exposures to all three chemicals were below the
HQ~high~. However, the HQ~low~ for mercury and total DDx exceeded 1.0,
indicating low magnitude risk. These exposures are primarily driven by
the contaminant levels in fish tissue, as the main source of exposure.
Mercury levels in fish collected from Lake Maurepas and Lake
Pontchartrain have generally higher tissue concentrations of mercury
than fish sampled from the Mississippi River. Therefore, the potential
risk from an increase of mercury-contaminated fish entering Lake
Maurepas from the Mississippi River is considered to be equal to or
lower than the risk currently at the lake. Based on available maximum
concentrations, there is a low magnitude risk associated with exposure
from the river; however, these risks, at least for mercury, are likely
lower than present risk levels in the study area.

Table A-12. Results of the Screening-Level Risk Evaluation to the Bald
Eagle.

<table>
<colgroup>
<col style="width: 11%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 6%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 7%" />
</colgroup>
<tbody>
<tr class="odd">
<td><blockquote>
<p><strong>Chemical</strong></p>
</blockquote></td>
<td><strong>C<sub>sed</sub> (mg/kg)</strong></td>
<td><strong>BW (kg)</strong></td>
<td><strong>IR<sub>sed</sub> (kg/day)</strong></td>
<td><strong>C<sub>fish</sub> (mg/kg)</strong></td>
<td><strong>IR<sub>fish</sub> (kg/day)</strong></td>
<td><strong>SUF</strong></td>
<td><strong>Dose (mg/kg-day)</strong></td>
<td><strong>TRV<sub>low</sub> (mg/kg-day)</strong></td>
<td><strong>TRV<sub>high</sub> (mg/kg-day)</strong></td>
<td><strong>HQ<sub>low</sub></strong></td>
<td><strong>HQ<sub>high</sub></strong></td>
</tr>
<tr class="even">
<td>Mercury</td>
<td>0.15</td>
<td>4.5</td>
<td>0.004</td>
<td>0.53</td>
<td>0.451</td>
<td>1</td>
<td>0.053</td>
<td>0.039</td>
<td>0.18</td>
<td>1.37</td>
<td>0.295</td>
</tr>
<tr class="odd">
<td>Nickel</td>
<td>45.5</td>
<td>4.5</td>
<td>0.004</td>
<td>2</td>
<td>0.451</td>
<td>1</td>
<td>0.241</td>
<td>1.38</td>
<td>56.3</td>
<td>0.17</td>
<td>0.004</td>
</tr>
<tr class="even">
<td>Total DDx</td>
<td>0.023</td>
<td>4.5</td>
<td>0.004</td>
<td>0.59</td>
<td>0.451</td>
<td>1</td>
<td>0.059</td>
<td>0.009</td>
<td>1.5</td>
<td>6.57</td>
<td>0.039</td>
</tr>
</tbody>
</table>

# Conclusion

The results of this screening-level risk evaluation support the
conclusions of the Mississippi River Sediment, Nutrient, and Freshwater
Redistribution Study (MRSNR) (as cited in Lee Wilson & Associates,
2001). In the MRSNR study, only a few compounds, mainly mercury and some
organopesticides were found to occasionally exceed water or sediment
benchmarks. In this risk evaluation maximum concentrations in sediment
for five metals (arsenic, cadmium, chromium, lead, and zinc), three PAHs
(benz\[a\]pyrene, chrysene, and pyrene), DDT isomers (4,4'-DDD and
4-4'-DDE) and total DDx exceeded the lower sediment quality benchmark
(*i.e.,* TEL). Concentrations of cadmium, copper, and nickel have
occasionally exceeded water quality criteria. Both mercury and DDx
compounds were below available ecological benchmarks for surface water,
and mercury concentrations were below sediment benchmarks. However, both
mercury and DDx compounds are bioaccumulative and slow to decompose and
are, therefore, persistent in the environment. In addition, the maximum
nickel concentration in sediments exceeded the PEL guidance value.
Nickel, mercury, and DDx compounds, therefore, were assessed through a
dose assessment model for the bald eagle and were found to present a
potential low magnitude risk.

For the benthic invertebrate communities, exposure to the maximum
concentration reported for nickel may pose a potential risk. In
addition, the maximum concentration of five metals (arsenic, cadmium,
chromium, lead, and zinc), three PAHs (benz\[a\]pyrene, chrysene, and
pyrene), DDT isomers (4,4'-DDD and 4-4'-DDE) and total DDx reported in
sediment were slightly elevated and would be classified as presenting a
low magnitude risk to benthic invertebrates.

The benthic and pelagic fish populations may be at risk from exposures
to cadmium, and to a lesser extent copper and nickel which all exceeded
water quality criteria on at least one occasion between 1995 and 2001.

Exposures to maximum concentrations of mercury and total DDx reported in
sediment and prey items pose a low magnitude level of risk to bald
eagles.

*Atrazine*

Although atrazine concentrations in the Mississippi River are of public
concern due to the widespread use of this pesticide in the river basin,
there is limited data for atrazine in sediments or fish tissue in the
Maurepas Swamp Study Area. Furthermore, there are no relevant literature
TRVs or screening values for effects of atrazine on wildlife and/or
aquatic organisms. In addition, a study conducted by EPA (2005)
concluded that atrazine is not expected to bioaccumulate into fish
tissue. Thus, effects of atrazine on wildlife in the study area could
not be modeled. However, atrazine concentrations were monitored in the
water column by LDEQ from the Mississippi River in March through August
1999 at the St. Francisville station. Results ranged from 0.11 µg/L to
1.31 µg/L, which were well below the 3 µg/L Maximum Contaminant Level
(MCL) for human health effects from atrazine in drinking water (USGS,
2003). In addition, the concentrations of atrazine from three stations
in the Barataria Basin, located just south of Maurepas Swamp, were also
relatively low (0.01 to 0.84 µg/L).

LDEQ has identified the Bayou Grosse Tete, a tributary in the Terrebonne
Basin, as a stream of concern due to elevated atrazine concentrations.
Because of this stream's location in the Basin, the waterway is
hydrologically isolated from the Mississippi River, and concentrations
of atrazine are believed to be the result of local inputs to the stream
which is located in a corn and sugarcane-producing area (USGS, 2003). As
discussed above, atrazine is not expected to significantly bioaccumulate
into fish tissue (EPA, 2005). Therefore, it can be concluded that,
although concentrations of atrazine may peak at times over the entire
Mississippi River, concentrations in the river just north of the
Maurepas Swamp study area in Louisiana are not likely to cause adverse
effects to wildlife in the Maurepas Swamp. High concentrations of
atrazine in the Terrebonne Basin of Louisiana are the result of local
atrazine inputs and do not likely originate in the Mississippi River.

In the absence of surface water and sediment data from the study area,
it is difficult to quantitatively determine the increase or decrease in
potential risks that the diversion project may have on ecological
exposures to chemical contaminants. Qualitatively, the contaminants that
exceeded relevant ecological benchmarks are generally consistent with
low magnitude levels of risk. These levels of risk are consistent with
an industrialized area, and are likely consistent with regional
conditions. As such, the diversion project may not result in any
significant changes from regional conditions and risks to wildlife would
not likely change. Additional investigations would be necessary to
validate these assumptions.

# Uncertainty and Recommendations

This screening-level risk evaluation was performed on maximum
concentrations of available surface sediment and fish tissue data from
the Mississippi River which is assumed to be the source of surface water
and suspended sediments for the diversion project. The existing data set
used in this evaluation is not temporally or spatially robust enough to
draw any definitive conclusions. There are six major sources of
uncertainty in the data:

1.  Sediment and fish tissue data were obtained from different areas of
    the Mississippi River; some were located south of the Maurepas Swamp
    study area. Although these data represent the closest sampling
    location to the proposed project, they may not accurately reflect
    the contaminant load that may be introduced through the diversion,
    into Maurepas Swamp.

2.  Fish tissue data for nickel and DDx concentrations were collected
    from Luling, LA. This sampling station is located south of the study
    area and may not adequately reflect contaminant levels in fish
    tissue in Maurepas Swamp after completion of the diversion project.

3.  Sediment and fish tissue sampling stations were not co-located,
    meaning they were not collected from the same station or even during
    the same time period. This has significant implications in the dose
    model for the bald eagle which assumes the sediment and fish tissue
    concentrations are related. Using different concentrations from
    different stations over different years introduces greater
    uncertainty in the exposure to contaminants.

4.  Available surface sediment data used in this assessment are from
    1998 and are now seven years old. These data are not likely to
    represent current environmental conditions. Depositional and
    erosional events over the last seven years have likely changed
    current surface sediment contaminant concentrations.

5.  Data for only a limited number of potential contaminants of concern
    were available for surface water, sediment, and fish tissue
    concentrations.

6.  There is limited toxicity information for many contaminants.
    Sediment quality benchmarks, water quality criteria, and TRVs were
    not available for some of the PAH compounds and
    pesticides/herbicides, including atrazine.

The following recommendations are provided to fill in data gaps and
reduce areas of uncertainty:

1.  Additional sediment and surface water samples should be collected in
    the Mississippi River to validate the chemical exposure data
    compiled for this screening-level risk evaluation. These samples
    should be collected from areas near the proposed diversion such that
    it represents a source of inputs to the Maurepas Swamp study area.
    These data would reduce the temporal and spatial uncertainty in the
    current data set.

2.  Additional data collection should be considered within the study
    area; even a limited number of sediment and surface water samples
    would allow for comparative risks/benefits to be assessed
    quantitatively.

3.  Available criteria for atrazine toxicity are based on values
    protective of aquatic organisms. Additional information on the
    toxicity of atrazine effects to upper-trophic level organisms should
    be evaluated to address potential public concern and the seasonal
    spikes of this contaminant.

4.  This screening-level risk evaluation assumed that the maximum
    concentration of contaminants in sediment and surface water samples
    in the Mississippi River will be present in the Maurepas Swamp,
    following the diversion. This is a highly conservative assumption
    and does not take into account any fate and transport processes. To
    resolve this uncertainty, a fate and transport model should be
    considered, in conjunction with the hydrologic model currently being
    developed for this project.

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