INJURY TO WETLANDS RESULTING FROM THE CHALK POINT OIL SPILL 

8 MARCH 2002 

Prepared by: 

Wetlands Assessment Team: 

Jacqueline Michel, Jim Hoff, Kevin Smith, Mitch Keiler, 

Al Rizzo, and Rick Ayella1

 1

 Michel: Research Planning, Inc.; Hoff: National Oceanic and Atmospheric 

Administration; Smith and Keiler: Maryland Department of Natural Resources; Rizzo: U.S. Fish 

and Wildlife Service; Ayella: Maryland Department of Environment. 
8 March 2002 

1 

Introduction..................................................................................................................................... 2 

Methodology................................................................................................................................... 3 

Wetland Categories....................................................................................................................................................3 

Data Collection..........................................................................................................................................................4 

Field Data Summaries..................................................................................................................... 5 

Vegetation..................................................................................................................................................................5 

Benthic community....................................................................................................................................................6 

Chemistry ..................................................................................................................................................................6 

Injury Assessment......................................................................................................................... 11 

Finalization of Wetland Categories for Injury Determination .................................................................................11 

Service Losses and Recovery Rates.........................................................................................................................12 

Injury by Category...................................................................................................................................................14 

Lightly Oiled Wetlands........................................................................................................................................14 

Moderately Oiled Spartina spp............................................................................................................................15 

Heavily Oiled Typha spp. (Shoreline and Interior)..............................................................................................17 

Heavily Oiled S. alterniflora (Shoreline and Interior).........................................................................................18 

Heavily Oiled S. cynosuroides (Shoreline and Interior) ......................................................................................20 

Wetlands Immediately East of Pipeline Break ("W1A" Less Impacted and More Impacted).............................21 

Restricted Access Wetlands.................................................................................................................................22 

Restoration Scaling ....................................................................................................................... 23 

Habitat Equivalency Analysis..................................................................................................................................23 

Injury to Wetlands ...................................................................................................................................................24 

Injury to Other Resources........................................................................................................................................25 

Acknowledgements....................................................................................................................... 26 

References..................................................................................................................................... 26 

Appendix A - Location Maps 

Appendix B - Benthic Community Data Sheets 

Appendix C - Wetland Category Recovery Curves 

Appendix D – Injury to Muskrats 

Appendix E – Injury to Beaches 
8 March 2002 

2 

INTRODUCTION 

On 7 April 2000, an estimated 126,000 gallons of a mixture of No. 6 and No. 2 fuel oils 

spilled from a ruptured subsurface pipeline that supplies oil to the PEPCO Chalk Point Facility 

on the Patuxent River. The spill affected a variety of natural resources, including approximately 

80 acres of brackish marsh habitat (i.e., wetlands). As part of natural resource damage 

assessment activities associated with the spill, the designated natural resource Trustees 

(Maryland Department of Natural Resources, Maryland Department of the Environment, U.S. 

Fish and Wildlife Service, and National Oceanic and Atmospheric Administration) and 

representatives of the Responsible Parties (PEPCO, the pipeline owner and ST Services, the 

pipeline operator) collected and analyzed data to determine the nature and extent of wetland 

"injuries" caused by the spill.2

 This report presents the Trustees’ assessment and analysis of the 

available data to generate a quantitative measure of wetland injury due to the Chalk Point spill. 

Wetlands provide a variety of ecosystem services that generate beneficial outcomes, such 

as better fishing and hunting, cleaner water, better views, and reduced human health and 

ecological risks (King et al., 2000). Exhibit 1 presents several categories of services and 

examples of many specific services provided by wetlands. Injury, for purposes of this injury 

assessment, is measured in terms of the area of wetlands affected and the time during which the 

wetland is unable to function at less than 100 percent of its baseline condition. 

This report consists of four major sections. First, the Trustees present their methodology 

for data collection and interpretation. The second section contains a summary of data collected 

as part of wetlands injury assessment activities. The third and largest section of the report 

presents the Trustees' findings, including the quantification of the spatial and temporal extent of 

wetland injury, based on assessment data, information from the literature, and professional 

judgment of Trustee experts. The fourth and final section describes the Trustees' preliminary 

efforts at scaling a restoration project to compensate for the quantified wetland loss, as well as 

losses to muskrats and beaches. 

Five appendices present additional data and findings relevant to the wetlands injury 

assessment. Appendix A contains maps showing the location of all wetland survey stations and 

the location of the pipeline break, Appendix B presents the raw benthic community data, and 

Appendix C provides graphical representations of the recovery curves described in the injury 

assessment section and summarized in Exhibit 6. Appendix D provides an assessment of the 

injuries to muskrats in the oiled marshes, including calculations to ensure that the scale of 

restoration needed to restore wetlands losses will also be sufficient to restore muskrat losses. 

Appendix E provides the total area of oiled sand beaches oiled by the spill, along with an 

estimate of needed restoration. 

 2

 As defined by the Oil Pollution Act of 1990 regulations, injury is defined as "an 

observable or measurable adverse change in a natural resource or impairment of a natural 

resource service." 
8 March 2002 

3 

Exhibit 1. Examples of Wetland Services (King et al., 2000)

Active Passive 

Commercial Uses 

• Agriculture 

• Trapping 

• Mining 

• Forestry 

• Fisheries 

Recreational Uses 

• Fishing 

• Swimming 

• Hiking 

• Nature Viewing 

• Hunting 

• Birding 

• Boating 

Municipal Uses 

• Groundwater Recharge/Discharge 

• Drinking Water Purification 

• Pollution Prevention 

Other Active Uses 

• Aesthetics - visibility, odor, noise 

• Education/Learning Opportunities 

• Research/Scientific Opportunities 

• Cultural/Spiritual Enrichment 

Property Damage Avoided 

• Flooding 

• Storm/Waves/Surge 

• Siltation/Sedimentation 

• Overnutrification 

• Noxious Weed Infestations 

Human Health Risks/Costs Avoided 

• Nutrient Cycling 

• Carbon Cycling 

• Chemical Cycling 

• Oxygen Cycling 

Ecosystem Health Risks Avoided 

• Biodiversity Support 

• Endangered Species Protection 

• Protection of Ecological Infrastructure 

Climate Regulation 

• Global Climate Effects/Attenuation 

• Microclimate Effects/Attenuation 

General Nonuse 

• Existence Values 

• Options Values 

• Bequest Values 

METHODOLOGY 

Wetland Categories

Immediately following the spill, the Trustees and Responsible Parties conducted several 

initial field surveys to assess the extent of oiling. During these surveys, the Trustees identified 

several "categories" of marsh habitat reflecting both different species of marsh vegetation and 

different degrees of oiling. The categories were as follows: 

• Lightly oiled wetlands: Light oiling was defined as less than 10 percent oil 

distribution and oil thickness less than 0.01 cm based on Shoreline 

Comprehensive Assessment Team (SCAT) data from 12-24 April 2000 

(Entrix, 2001c). This category included all plant species, throughout the 

entire spill zone. 

• Moderately oiled wetlands: All areas located outside of Swanson Creek 

that did not meet the definition lightly oiled were considered to be 

moderately oiled. Several species of vegetation were found in moderately 
8 March 2002 

4 

oiled wetlands, including Spartina alterniflora, S. cynosuroides, and Iva 

spp. Separate categories were established for each of these species. 

• Heavily oiled wetlands: All areas within Swanson Creek that did not meet 

the definition lightly oiled were considered to be heavily oiled. Separate 

categories were established for each of the predominant vegetation types: 

Typha spp., S. alterniflora, or S. cynosuroides. Each of these marsh types 

were further segregated into shoreline and interior areas, resulting in six 

heavily oiled categories. 

• W1A wetlands: The area of wetlands in the immediate vicinity of the 

pipeline break that were the most heavily oiled (fresh oil pooled on the 

surface for long periods, etc.) and where the degree of cleanup activities 

was most aggressive (flooding, flushing, trenching, construction of 

boardwalks, nutrient augmentation, replanting, etc.) was treated 

separately. For purposes of establishing survey quadrats (see below), this 

category was divided into three subcategories: areas where vegetation was 

replanted; areas where ditches had been dug in the marsh interior to assist 

with oil recovery, backfilled with clean sand, and replanted; and areas of 

natural revegetation. In areas of natural revegetation, the survey efforts 

focused on areas of Scirpus spp. vegetation, because the Trustees felt that 

Spartina spp. and Typha spp. in this area were similarly affected as those 

in other heavily oiled areas. 

Data Collection

Three permanent one square meter quadrats were established in marsh habitat 

representing each wetland category, with the exception of lightly oiled areas. Quadrats for Iva 

spp. were circles of 2 meter radius. No quadrats were established for lightly oiled areas because 

it has been shown that vegetation impacts from such light oiling are undetectable (Michel et al., 

1998). Quadrats were also established at unoiled "reference" areas that were otherwise similar to 

impacted marsh areas. Exhibit 2 lists each study quadrat, along with designated habitat code; 

Exhibits A1-A4 in Appendix A show the location of the quadrats, also identified by habitat 

code.3

Field surveys were conducted by technical representatives for the Trustees and 

Responsible Parties (the Wetlands Assessment Team (WAT)) in July and September 2000 and 

July 2001. The initial July 2000 survey did not include W1A sites, because cleanup operations 

were still underway in that area. The WAT surveyed the W1A sites in September 2000 and 

visited all other sites to collect fruit, flower, and oiling information. The July 2001 survey 

included all of the established sites, both within and outside the W1A area. 

Parameters measured at each quadrat included stem density by species, stem height, 

percent cover, oiling descriptors, flowering and seed condition, and chlorosis. Each quadrat was 

 3

 Fewer than three reference quadrats were established for some categories. 
8 March 2002 

5 

photographed, and sediment samples were collected for chemical analysis and benthic 

community assessment.4

 

Exhibit 2. Wetland Survey Locations 

Survey Location ID Wetland Category 

AH1S, AH2S, AH3S S. alterniflora heavy shoreline 

AH1I, AH2I, AH3I S. alterniflora heavy interior 

AMI2S, AMI3S S. alterniflora moderate shoreline Indian Creek 

AMT1S S. alterniflora moderate shoreline Trent Hall Creek 

CH1S, CH2S, CH3S S. cynosuroides heavy interior 

CH1I, CH2I, CH3I S. cynosuroides heavy shoreline 

CMI1S CMI3S S. cynosuroides moderate shoreline Indian Creek 

CMT1S S. cynosuroides moderate shoreline Trent Hall Creek 

TH1I, TH2I, TH3I Typha spp heavy interior 

TH1S, TH2S, TH3S Typha spp heavy shoreline 

IH1S Iva spp heavy shoreline 

IMI1S Iva spp moderate shoreline Indian Creek 

IMT2 Iva spp moderate Trent Hall Creek 

IMT2I Iva spp moderate interior Trent Hall Creek 

DH1I, DH2I, DH3I Ditched heavy interior 

PH1I, PH2I, PH3I Planted heavy interior 

SH1I, SH2I, SH3I Scirpus spp. heavy interior 

Reference Location ID 

ARH3S S. alterniflora shoreline Hunting Creek

ARP1S, ARP2S S. alterniflora planted shoreline 

ARH1I, ARH2I, ARH3I S. alterniflora interior Hunting Creek 

CRH1I, CRH3I S. cynosuroides interior Hunting Creek 

CRH1S, CRH2S, CRH3S S. cynosuroides shoreline Hunting Creek 

CRT2I S. cynosuroides interior Trent Hall Creek 

IRR2I, IRH3I Iva spp interior Hunting Creek 

IRT4 Iva spp Trent Hall Creek 

SRI1I, SRI2I Scirpus spp. interior Indian Creek 

SRT3I Scirpus spp. interior Trent Hall Creek 

TRI3I Typha spp interior Indian Creek 

TRT1I, TRT2I Typha spp interior Trent Hall Creek 

TR1S, TR2S, TR3S Typha spp shoreline 

FIELD DATA SUMMARIES 

This section presents brief summaries of the data collected during field surveys in July 

and September 2000 and July 2001. Detailed information from these surveys is provided in data 

reports prepared by Entrix (2000; 2001a; 2001b). 

Vegetation

Exhibit 3 provides a summary of the vegetative parameters measured in July 2000 (or 

September 2000 in the case of the W1A wetlands) and July 2001. For each parameter (i.e., 

 4

 Sediment cores measured 12 inches (length) by 4 inches (diameter). 
8 March 2002 

6 

percent cover, stem count, and stem height), observed values from the three quadrats for each 

wetland category in heavily and moderately oiled areas are averaged. The average values from 

the reference areas also are presented. 

Benthic community

The benthic community was sampled using a 4-inch diameter PVC core tube driven to a 

depth of 1 foot. The cores were sieved in the field through a 500 micron sieve and preserved in 

formalin. Cores collected at heavily oiled wetland quadrat sites and reference areas were 

analyzed for benthic community composition. Species were identified to species or taxa as 

appropriate and counted. Exhibit 4 presents a summary of the data; the original data are included 

in Appendix B. The data for S. cynosuroides are summarized with and without station CH-2S, 

which had relatively low oiling relative to the other sites, thus raising questions about its 

comparability to other samples. 

Chemistry

The field survey teams collected sediment samples using a pre-cleaned 4-inch diameter 

Lexan core tube driven to a depth of 1 foot. The cores were stored upright on ice in the field, 

frozen each night, and sent to a laboratory frozen in the core tubes at the end of the field survey. 

The laboratory extruded and sub-sectioned the cores into the requested sediment intervals. There 

was variable compaction of the sediment core during collection; as a result, reported intervals 

may vary slightly from actual depths. Exhibit 5 summarizes the results of chemical analyses 

conducted on sample cores collected by the Wetlands Assessment Team. Data are not averaged 

among quadrats for each category. Exhibit 5 includes total petroleum hydrocarbon (TPH) and 

total polynuclear aromatic hydrocarbon (PAH) concentrations for each sample.5

 Also presented 

is a qualitative assessment of the degree of weathering of the residual oil in the samples based on 

concentrations of saturated hydrocarbons (SHC, primarily n-alkanes), which are known to 

degrade relatively rapidly, and PAHs, which are known to be more resistant to weathering. 

 5

 TPH was measured by summing the total resolved hydrocarbons and the unresolved 

complex mixture using GC-FID. Total PAH was measured by summing 41 individual target 

PAHs, using GC/MS. 
8 March 2002 

7 

Exhibit 3. Summary of Vegetative Parameters, Reported as the Three-quadrat Average for Each Survey

July, 2000 

Percent cover1 Stem Count (/m2)2 Stem He

Heavy Moderate Reference Heavy Moderate Reference Heavy Modera

S. alterniflora shoreline 36.67 63.33 75 88 324 421.3 1.09 0.88 S. alterniflora interior 90 N/A 88.33 261 N/A 150 1.3 N/A S. cynosuroidesshoreline 

85 93.33 93.33 181.3 216 237.3 1.50 1.7 

S. cynosuroides interior 63.33 N/A 67.5 45 N/A 141.3 1.56 N/A Typha spp. shoreline 40 N/A 56.67 44 N/A 120.7 2.1 N/A Typha spp. interior 66.67 N/A 66.67 111.6 N/A 55.6 2.26 N/A Iva spp. 75 85 7.753 83 1.61 

September, 2000 

Percent cover1 Stem Count (/m2)2 Stem He

Heavy Moderate Reference Heavy Moderate Reference Heavy Modera

W1A S. alterniflora ditched 20 N/A 88.33 45.67 N/A 150 1.11 N/A S. alterniflora planted 6.67 N/A 88.33 19.33 N/A 150 0.71 N/A Scirpus spp. Interior 91.67 N/A 80 701 N/A 500 1.35 N/A 

July, 2001 

Percent cover1 Stem Count (/m2)2 Stem He

Heavy Moderate Reference Heavy Moderate Reference Heavy Modera

S. alterniflora shoreline 66.67 46.7 73.3 187 85 260 1.30 0.89 S. alterniflora interior 73.3 N/A 96 95 N/A 233 1.02 N/A S. cynosuroidesshoreline 

73.3 63.3 68.3 139 111 89 1.37 1.58 

S. cynosuroides interior 61.7 N/A 85 77 N/A 94 1.35 N/A Typha spp. shoreline 75 N/A 75 61 N/A 93 2.21 N/A Typha spp. interior 46.7 N/A 52 93 N/A 55 2.24 N/A Iva spp. 60 65 43 5.33 1.4 W1A S. alterniflora ditched 35.7 N/A 96 47.3 N/A 233 0.92 N/A S. alterniflora planted 27.3 N/A 96 61 N/A 233 0.86 N/A Scirpus spp. Interior 44 N/A 47 258 N/A 148 1.12 N/A 

N/A indicates that no habitat of that type was considered to be moderately oiled. 1 Average percent coverage by all live vegetation. 2 Stem count for predominant species only. 3 Stem density for Iva spp. was measured as the number of shrubs/trees per 2-m radius circle. 
8 March 2002 

8 

Exhibit 4. Summary of the Benthic Data from 44 Cores Collected from Heavily Oiled and Reference Sites 

July 2000 Sept 2000 July 2001 

 Heavy 

Oil Ref 

Heavy 

Oil Ref 

Heavy 

Oil Ref 

S. alterniflora habitat 

Avg. number of species 6.3 13.0 10.0 8.0 11.0 11.7

Avg. density of tubificids w/o hair 193.7 99.7 51.0 55.7 219.7 50.0

Avg. amphipod density 0.3 6.3 0.3 0.7 5.0 1.3

Avg. amphipods plus isopods 1.3 12.0 1.3 2.3 8.0 4.3

 (n=3) (n=3) (n=3) (n=3) (n=3) (n=3)

 

S. cynosuroides habitat 

Avg. number of species 8.0 14.0 [8.5] 11.7 10.3 6.3 9.0

Avg. density of tubificids w/o hair 132.7 25.0 [38.0] 35.3 47.3 32.3 3.7

Avg. amphipod density 0.0 4.0 [1.0] 4.3 1.7 0.0 1.7

Avg. amphipods plus isopods 0.3 8.5 [3.5] 9.3 4.0 0.0 1.7

 (n=3) (n=2) (n=2) (n=3) (n=3) (n=3) (n=3)

 

Typha habitat 

Avg. number of species no data 10.3 no data 11.0 no 

data 

Avg. density of tubificids w/o hair no data 42.3 no data 32.0 no 

data 

Avg. amphipod density no data 1.0 no data 2.3 no 

data 

Avg. amphipods plus isopods no data 3.8 no data 5.3 no 

data 

 (n=4) (n=3) 

[ ] - without site CH2S, which had low oiling 

The degree of weathering (Wx) is estimated on a scale of 1 to 4, as defined below: 

1 = Evidence of evaporative weathering only; significant amount of C10-12 n-alkanes still 

present; naphthalenes more abundant than phenanthrenes/anthracenes, with parent 

naphthalene still present. 

2 = Evidence of some microbial degradation, with a reduction in the 2-ringed PAH 

relative to the 3+ ringed PAHs, and reduction in the low to middle weight SHCs. 

3 = Moderately weathered, with near complete removal of 2-ringed PAHs and a reduction 

in the 3-ringed PAHs, and for the SHCs, complete removal of the low and middle-weight 

SHCs. 

4 = Near complete removal of all 2- and 3-ringed PAHs; all SHCs are at "background." 

To facilitate comparison of the weathering state of the oil over time, Exhibit 5 provides 

the mean weathering value for each category of wetland. Means are calculated across all 

available data in a category, regardless of depth interval. 
8 March 2002 

9 

Exhibit 5. Soil Analytic Chemistry Results for Heavily Oiled Wetland Categories, 

Including Mean Degree of Weathering

Station Interval 

(cm) 

TPH 

(ppm) 

2000 

TPH 

(ppm) 

2001 

SHC Wx 

2000 

SHC Wx 

2001 

PAH 

(ppm) 

2000 

PAH 

(ppm) 

2001 

PAH Wx

2000 

PAH Wx 

2001 

Typha spp. 

Interior 

 

TH1I 0-5 286 2.5 

 5-10 577 

TH2I 0-5 653 

TH2I 10-15 510 

 

TH3I 0-5 7,567 1.5 540 1.5 

Typha spp. 

Interior Mean 

 2.0 1.5 

 

Typha spp. 

Shoreline 

 

TH1S 0-5 839 739 3.0 3.0 5 9 2.5 2.5

TH1S 10-15 545 6 2.5

 

TH3S 0-5 36,839 27,773 1.5 2.5 1,472 2.0

TH3S 5-10 669 2.5 

TH3S 11-15 454 3.0 3 2.0

Typha spp. 

Shoreline Mean 

 2.3 2.5 2.3

 

S. alterniflora

Interior

 

AH1I 0-5 383 516 4 2 3 2.5 

 

AH2I 0-5 3,728 1,853 2.5 3.0 205 54 2.5 2.5

AH2I 8-10 2,890 662 2.5 3.0* 194 8 2.5 2.0*

AH2I 20-25 756 3.0 14 2.5

AH3I 0-5 15,347 583 1.5 3.0 887 1 1.5*

AH3I 5-10 897 2.5 

AH3I 11-15 442 3.0 1 2*

AH3I 15-20 381 3.0 

S. alterniflora

Interior Mean 

 2.4 3.2 2.5 2.1

 

S. alterniflora

Shoreline

 

AH2S 0-5 734 3.0 

 

AH3S 0-5 3,376 157 2.0 

S. alterniflora

Shoreline Mean 

 3.0 2.0 
8 March 2002 

10 

Station Interval 

(cm) 

TPH 

(ppm) 

2000 

TPH 

(ppm) 

2001 

SHC Wx 

2000 

SHC Wx 

2001 

PAH 

(ppm) 

2000 

PAH 

(ppm) 

2001 

PAH Wx

2000 

PAH Wx 

2001 

S. cynosuroides

Interior 

 

CH1I 0-5 6,417 40,205 1.0 473 2,160 

CH1I 5-10 11,740 22,142 1.0 1.0 722 1,216 1.0

CH1I 10-15 2,652 1.5 189 

CH1I 18-20 318 6,391 3.0 1.0 6 372 1.0

 

CH2I 0-5 40,580 51,867 1.5 3.0 2,600 4,326 1.5 

CH2I 13-15 35,948 1.0 2,186 1.0

 

CH3I 0-5 11,698 2,064 1.0 3.0 760 110 1.5

CH3I 10-15 4,585 1.5 

CH3I 18-20 3,391 1.5 173 2.0 

CH3I 16-19 892 3.0 28 2.0

CH3I 22-25 1,658 

S. cynosuroides

Interior Mean 

 1.5 2.2 1.8 1.3

 

S. cynosuroides

Shoreline 

CH1S 0-5 39,267 2,610 1.0 

 

CH2S 0-5 1,329 2.5 

 

CH3S 0-5 13,919 1.5 

CH3S 10-15 10,209 1.5 

S. cynosuroides

Shoreline Mean 

 1.8 1.0 

 

Scirpus spp. 

Interior 

SH1I 0-5 46,861 1.5 3,192 

SH1I 12-17 3,353 2.0 

SH1I 21-25 2,884 2.0 183 

 

SH2I 0-5 17,554 3,772 1.5 2.0 901 147 2.0

SH2I 12-17 6,318 1.5 

SH2I 25-28 10,290 4,116 1.0 1.5 292 1.5

SH2I 30-32 2,341 1.5 167 2.0 

Scirpus spp. 

Interior Mean 

 1.6 1.8 2.0 1.8
8 March 2002 

11 

Station Interval 

(cm) 

TPH 

(ppm) 

2000 

TPH 

(ppm) 

2001 

SHC Wx 

2000 

SHC Wx 

2001 

PAH 

(ppm) 

2000 

PAH 

(ppm) 

2001 

PAH Wx

2000 

PAH Wx 

2001 

Planted Interior 

PH1I 0-5 77,758 41,238 1.5 2.0 7,020 2,522 2.0 2.0

PH1I 18-20 6,298 12,540 2.0 1.5 408 847 2.0 1.5

PH1I 

 

PH2I 0-5 8,121 14,794 3.0 3.0 486 999 

PH2I 10-15 759 

Planted Interior 

Mean 

 2.2 2.2 1.8

 

Ditched Interior 

DH1I 0-5 3,923 2.5 

DH1I 5-10 5,640 1.0 

DH1I 20-25 2,410 2.5 

 

DH2I 0-5 1,328 2.0 

DH2I 

DH3I 10-15 195 3.0 

Ditched Interior 

Mean 

 2.2 

* Concentration of SHCs or PAHs was near background. 

Blank cell indicates no data. 

TPH= total petroleum hydrocarbons; PAH = polynuclear aromatic hydrocarbons; SHC = saturated hydrocarbons. 

See text for explanation of the weathering (Wx) scale 

INJURY ASSESSMENT 

The Trustees assess injury to the wetlands impacted by the spill using the data described 

above, information from the scientific literature, and professional judgement. The first step is to 

develop a final list of injured wetland categories. Next, the area of each of these categories is 

estimated using a combination of remotely-sensed and field-collected data. Finally, recovery 

curves describing both the magnitude of service loss and the time to recovery for each category 

of wetland are developed. The following sections describe these steps in more detail. 

Finalization of Wetland Categories for Injury Determination

The Wetlands Assessment Team (WAT) is responsible for the assessment and 

quantification of injury. Based on the field surveys, the final list of wetland categories for which 

injury will be assessed and quantified is as follows: 

• All lightly oiled wetlands are grouped into a single category. 
8 March 2002 

12 

• All moderately oiled wetlands are grouped into a single category. 

Although separate quadrats were established for Spartina alterniflora and 

S. cynosuroides, few differences were noted between them, and they often 

formed mixed stands. In addition, Iva spp. (a woody shrub or tree) were 

found among the Spartina spp., rather than as isolated stands. Therefore, 

the WAT combines all moderately oiled areas into one injury category. 

• Heavily oiled wetlands are divided into shoreline and interior areas for 

each of the predominant vegetation types (Typha spp., S. alterniflora, or S. 

cynosuroides), resulting in six heavily oiled categories. 

• As described above, quadrats were established in the W1A area for three 

different categories: planted areas, ditched and planted areas, and Scirpus 

spp. Based on field observations of the W1A area during the July 2001 

survey, the WAT determines that impact and recovery are most 

appropriately assessed for two different categories: "less-impacted areas" 

and "more-impacted areas." These areas are shown on Exhibit A5 in 

Appendix A. The red line delineates the "more-impacted" area, 

representing approximately half of the W1A. The remainder of W1A, 

where the vegetation showed better recovery, is considered "lessimpacted." 

• Areas of un-oiled wetlands that were surrounded or nearly surrounded by 

oiled wetlands compose the final category of injured wetland, because 

access to these areas would be restricted to wildlife during the time oil 

persisted in adjacent areas. 

The WAT estimates the area of each category of wetland using methods described in a 

report by Entrix (2001c), which includes maps showing the distribution of each category. 

Briefly, areas are determined using one of two methods. Interior areas of oiled wetlands are 

based on interpretation of April 2000 aerial photography and McCormick vegetation maps 

(McCormick and Somes 1982), with a major effort by the WAT to ground-truth the vegetation 

maps. Fringing areas of oiled vegetation are based on vegetation type and the length and width 

of oiling as reported by the WAT during the field surveys. The second column of Exhibit 7 

presents the estimated area for each category. 

Service Losses and Recovery Rates

Determining the degree of initial injury and rate of recovery curves for wetlands is a 

complex process. Several factors are known to influence the severity of impact to wetland 

vegetation from oiling, including vegetation coverage, substrate oiling, and exposure to natural 

removal processes. There have been very few long-term studies of oiled wetlands recovery rates. 

Most studies have focused on qualitative monitoring of vegetative recovery. For example, 

Alexander and Webb (1983) showed a reduction in biomass for plants where No. 6 fuel oil was 

applied to the entire plant surface. Baca et al. (1985) found reduced stem density two years after 
8 March 2002 

13 

a spill in brackish wetlands along the Cape Fear River in North Carolina where the plants had 

been completely coated with oil, but not where oiling was limited mainly to the plant stems. 

Studies on the effects of oil on benthic communities are similarly lacking, and there are 

no long-term studies on recovery of biological communities. The available quantitative measures 

of benthic community impact (e.g., total abundance, species richness, diversity indices) each 

suffer from one or more disadvantages when applied to the task of projecting recovery for a 

specific wetland. For these reasons, the vegetation and benthic community data are most 

appropriately used to determine large-scale differences between oiled and reference sites, and 

cannot be used alone to determine the shape of recovery curves for wetland services provided by 

soil and vegetation. The field data were used as relative indicators of the degree of injury, and to 

guide development of the recovery curves for each injury category. Given natural variability and 

the complex set of factors that can affect marsh structure, health, and productivity, it is extremely 

difficult to extract simple relationships between oiling, injury, and recovery. 

Determining service losses and recovery rates for the areas affected by the Chalk Point 

spill therefore requires integration of available site data (summarized in the previous section of 

this document), knowledge of the published literature on oil spill impacts to wetlands (see 

reference list at the end of this document), and use of professional judgment. Care has been 

taken to make sure that the recovery curves are consistent with the WAT's understanding of the 

relative rates of weathering and removal expected for the different wetland categories. The 

scientific literature provides support for this approach of using multiple sources of data to 

estimate loss of ecological services. In a review article, Strange et al. (2001) concluded that 

“While structural metrics such as vegetative cover may indicate full recovery 

within a relatively short time, functional metrics may reveal a significant lag in 

the recovery of ecological processes such as nutrient cycling that are necessary for 

a fully functioning salt marsh. As a result, 100 percent recovery of some 

ecological services may represent only partial recovery of the system as a whole.” 

Two metrics were selected to represent the lost services and functions of the wetlands as 

a result of the oil spill: above-ground vegetation and soils. Above-ground vegetation represents a 

broad range of services related to primary production, habitat structure, recreational and aesthetic 

value, food chain support, and fish and shellfish production. It is an appropriate metric because it 

can be readily used for both injury quantification and restoration scaling. Use of a soil-related 

metric is particularly important for this spill site because of the nature of oiling and the 

importance of soil development and biogeochemical cycling to the overall ecological services of 

wetlands. 

Exhibit 6 summarizes the WAT's estimates of the extent and duration of service loss for 

each wetland category. Service loss is expressed as the level of services in the oiled area after 

the spill as a percentage of the pre-spill level of services. For example, the WAT estimates an 

initial 75 percent loss of soil-related services in heavily oiled S. alterniflora wetlands. This is 

shown on Exhibit 6 as post-spill services of 25 percent. Services are assumed to recover linearly 

(i.e., at a constant rate) over the period of time noted. In some cases, the WAT estimates a "two 

phase" recovery period, reflecting an expected change in recovery rates between initial and later 
8 March 2002 

14 

years of the recovery period. In these cases, recovery rates are assumed to be linear within each 

"phase." Appendix C presents graphical representations of all recovery curves. 

Exhibit 6. Estimated impacts to ecological service flows and recovery rates for wetland vegetation oiled 

during the Chalk Point oil spill 

VEGETATION SOILS 

Category 

Services Post 

Spill (% of 

Pre-Spill) 

Recovery 

Phase 1 

%/years 

Recovery 

Phase 2 

%/years 

Services Post 

Spill (% of 

Pre-Spill) 

Recovery 

Phase 1 

%/years 

Recovery 

Phase 2 

%/years 

All Light 90 100/0.5 90 100/0.5 

Spartina spp. Moderate 50 100/1 50 100/3 

Typha spp.

Heavy Shoreline 

0 100/1 25 60/3 100/10 

Typha spp.

Heavy Interior

0 100/1 50 80/5 100/10 

S. alterniflora

Heavy Shoreline 

0 50/1 100/5 25 80/3 100/5 

S. alterniflora

Heavy Interior

0 50/1 100/5 25 75/5 100/10 

S. cynosuroides

Heavy Shoreline 

0 50/1 100/10 25 60/3 100/10 

S. cynosuroides

Heavy Interior

0 50/1 100/10 25 50/5 100/20 

W1A-Less Impacted 0 50/1 100/10 0 35/1 100/20 

W1A-More Impacted 0 20/1 100/10 0 20/1 100/20 

Restricted Access Areas 0 100/1 N/A 

Injury by Category

Lightly Oiled Wetlands 

All wetlands with less than 10 percent oil distribution and oil thickness less than 0.01 cm 

based on April 2000 SCAT data (Entrix, 2001c) and "transitional area" (defined as a five-meter 

band on the landward side of moderately and heavily oiled marsh shorelines) are defined as 

"lightly oiled." As described below, impacts to lightly oiled wetlands are expected to be minimal. 

No investigative quadrats were established for lightly oiled wetlands, and no quantitative 

vegetative data or soil samples for chemical analysis were collected. As a result, the WAT 

combines all lightly oiled wetlands into one category, without distinction among vegetation 

types. 

Oiling exposure and impacts for the lightly oiled wetlands can be summarized as follows: 

• Initial oil distribution on a segment was no more than 10 percent, with an 

average distribution of eight percent for all lightly oiled areas (Entrix, 

2001c). 

• There was one major oiling event, in April. 
8 March 2002 

15 

• Oil was mostly on the stems and lower leaves of vegetation and on surface 

soils.

• The oiled stems sloughed off when the new shoots appeared. New 

vegetation was not oiled.

• Oil on vegetation and soils was 0.01 cm thick or less, and complete oil 

degradation likely occurred within 6 months of the spill. 

Numerous studies (primarily related to S. alterniflora) document the rapid recovery of 

lightly oiled salt marsh vegetation. For example, S. alterniflora lightly oiled with IFO 180 from 

the Julie N spill had the same stem density and stem height as unoiled controls one year later 

(Michel et al. 1998). Sediments and lower plants sprayed with No. 6 fuel oil had the same 

biomass, new stems, seedlings and decomposition rates as unoiled controls after five months 

(Alexander and Webb 1983). In another study, brackish wetlands exhibiting oil banding showed 

no impacts from oil exposure (Levine et al. 1995). 

Although no acute or chronic vegetative impacts are expected for lightly oiled areas, 

impacts may have occurred to epiphytic communities on the oiled vegetation. Given the 

literature cited above, the WAT technical experts estimate that the oil spill resulted in a 10 

percent reduction in overall service flows for both soils and vegetation. Using similar available 

information and expertise, the WAT estimates that recovery was complete in one-half year, 

following the first growing season. Recovery curves for lightly oiled wetlands are shown in 

Exhibit C1. 

Moderately Oiled Spartina spp. 

Wetlands outside of Swanson Creek with more than 10 percent oil distribution or oil 

thickness greater than 0.01 cm, based on SCAT data (Entrix, 2001c), are categorized as 

moderately oiled. Although separate quadrats were established for Spartina alterniflora and S. 

cynosuroides, few differences were noted between them, and these species often formed mixed 

stands. Therefore, both species (when moderately oiled) are combined into one injury category. 

Oiling exposure and impacts for the moderately oiled Spartina spp. wetlands can be 

summarized as follows: 

• Initial oil distribution was greater than 10 percent, and averaged 60 

percent. 

• There was one major oiling event, in April. 

• Oil was initially on the stems and lower leaves of vegetation and on 

surface soils. 

• The oiled stems sloughed off when the new shoots appeared. New 

vegetation was not oiled; during the July survey, there was little or no 

visible oil on the vegetation. 
8 March 2002 

16 

• The July 2000 survey found no visible oil or only a light film of oil on the 

soil surface. 

• At most sites, when the soils were disturbed underwater in 2000, they 

released sheens. By 2001, slight sheening was observed after soil 

disturbance at just two quadrat sites. 

• At one site in 2001, disturbed soils released black oil droplets. Based on 

field observations in July and September 2000, an estimated 25 percent of 

the soils in moderately oiled Spartina spp. wetlands would release black 

oil droplets when disturbed. 

• One of the three S. alterniflora quadrats, located in an area that received 

intensive cleanup, showed reduced cover and stem count in 2000 and 

2001. 

• Total petroleum hydrocarbon (TPH) concentrations in soils from two 

quadrats in 2000 were 3,270 and 4,230 parts per million (ppm); 

concentrations of polynuclear aromatic hydrocarbons (PAH) in soils from 

these sites were 90 and 330 ppm, and the oil was characterized as 

weathered to significantly weathered. The Trustees did not collect any 

soil samples from moderately oiled habitats in 2001. 

Krebs and Tanner (1981) reported no impacts to S. alterniflora vegetation when soil 

concentrations were below 2,000 ppm oil at a No. 6 fuel oil spill in the Potomac River. Above 

2,000 ppm, they reported decreased stem height, density, and aboveground biomass; above 

10,000 ppm, most of the underground rhizomes were killed (Krebs and Tanner, 1981). For a spill 

of crude oil in Louisiana, Alexander and Webb (1987) reported no impacts to vegetative growth 

for marshes with soil oiling levels less than 5,000 ppm TPH. 

With respect to natural removal processes, the outer fringe of a marsh is often exposed to 

tidal flushing and wave action. Hershner and Moore (1977) studied a No. 6 fuel oil spill on the 

lower Chesapeake Bay and reported an increase in net productivity of oiled marshes after one 

growing season. They attributed the lack of long-term impact to the relatively exposed setting. In 

contrast, Bender et al. (1977, 1980) conducted a field oiling experiment with fresh and weathered 

South Louisiana crude oil in an isolated mesohaline marsh off the York River, Virginia. In these 

studies, oiling of the S. alterniflora vegetation resulted in a 50 percent reduction in biomass one 

year post-oiling.6

 Nearly all of the areas classified as moderately oiled Spartina spp. are marsh 

fringes. 

Based on the literature referenced above, field observations in 2000 and 2001, and 

experience at previous spills, technical representatives on the WAT estimate that there was an 

 6

 The correlation of recovery with degree of exposure to natural removal processes has 

been observed at many spills, and was the basis for establishing quadrats in both shoreline and 

interior sites for this spill. 
8 March 2002 

17 

initial vegetative service loss in the moderately oiled wetlands of 50 percent, with full recovery 

in one year. This recovery curve is applied to all species of vegetation found in moderately oiled 

areas. 

Impacts associated with contaminated marsh soils are more difficult to assess because 

few studies have addressed this issue. Oil degradation rates have been correlated with oil loading 

and depth of penetration into sediments (Michel and Hayes, 1999). Hoff et al. (1993) studied a 

spill of Alaska crude oil in a Salicornia virginica wetland in Puget Sound and found extensive 

weathering in lightly oiled soils after one summer and slower weathering (as determined by 

elevated PAH levels in the soils 16 months post-spill) in soils with thicker layers of oil. 

Considering that most of the oil in the moderately oiled areas was along the outer marsh fringe 

and did not penetrate very deep into the sediments, oiled soils in these areas are expected to 

recover in three years. Exhibit C2 shows the recovery curves for moderately oiled areas.

Heavily Oiled Typha spp. (Shoreline and Interior) 

Typha spp. wetlands inside Swanson Creek with more than 10 percent oil distribution and 

oil thickness greater than 0.01 cm are categorized as heavily oiled (Entrix, 2001c). Quadrats 

were established at both shoreline and interior locations. 

Oiling exposure and impacts for heavily oiled Typha spp. can be summarized as follows: 

• Initial oil distribution occurred as a band of heavy oil on the substrate and 

lower vegetation (stems and lower leaves). 

• There were multiple oiling events throughout the summer of 2000, as 

pooled oil was released from adjacent heavily oiled marshes. 

• In July 2000, stain and coating on stems were visible. By July 2001, no 

oil was visible on any vegetation. 

• Percent cover, stem density, and stem height were highly variable, but 

generally comparable with controls in July 2000 and 2001. 

• At all quadrats, the soils released black oil droplets when disturbed 

underwater in 2000. By 2001, only sheens were released after 

disturbance. 

• The soils were highly organic (15 percent total organic carbon, TOC). 

• Analysis of two shoreline samples (0-5 cm depth) collected in 2000 

revealed widely different degrees of soil contamination, with one site 

having 40 times more TPH (37,000 ppm) than the other (840 ppm). Only 

slight decreases were observed by 2001. PAH levels in surface soils in 

2001 were 9 and 1,500 ppm and moderately weathered, indicating highly 

variable but very high and toxic levels. Some of these habitats had high 
8 March 2002 

18 

initial loadings and apparently relatively low natural removal and 

weathering rates. 

• Concentrations of TPH for all three interior sites from 2000 were typically 

lower than those on the shoreline, and ranged from background to 7,600 

ppm. Only one PAH analysis was performed in 2000, with a result of 540 

ppm and slight weathering. 

• The WAT did not conduct benthic community analysis on heavily oiled 

Typha spp, although analysis was completed on reference sites. 

The available literature on heavily oiled salt marshes indicates a moderate recovery 

trajectory. In a study of the rate of recovery of twenty heavily oiled salt marshes, the majority of 

marshes recovered within five years (Sell et al. 1995). Exceptions were the result of extensive 

mechanical cleanup, thick oil residues that smothered the vegetation, and/or deep penetration of 

a highly toxic oil (No. 2 fuel oil). There are very few studies on the effects of oil specifically on 

Typha spp. wetlands. The notable exception is a study of a No. 6 fuel oil spill in the St. Lawrence 

River where most of the oiled vegetation was cut (Alexander et al., 1981). Studies of the cut 

versus uncut areas showed normal or enhanced vegetation growth for the oiled areas after one 

year. The only impact observed was that the cut vegetation did not produce flowers. 

Based on field data at both shoreline and interior sites, and observations at other spills, 

the WAT assumes that Typha spp. vegetation recovered completely within one year of the spill.

Because the soils were highly organic and contained black oil droplets in 2000 and continued to 

release sheens in 2001, the WAT estimates that the effect on soils in the interior was a 50 percent 

initial reduction of services, with a return to 80 percent services in 5 years and 100 percent 

services in 10 years. For the shoreline fringe, where the soils were initially more heavily oiled 

yet are more exposed to natural removal processes, the WAT estimates an initial 75 percent 

reduction in services, with a return to 60 percent services in 3 years, and 100 percent services in 

10 years. Recovery curves for heavily oiled Typha spp. wetlands are shown in Exhibits C3 and 

C4. 

Heavily Oiled S. alterniflora (Shoreline and Interior) 

Oiled S. alterniflora wetlands in Swanson Creek with more than 10 percent oil 

distribution and oil thickness greater than 0.01 cm are categorized as heavily oiled (Entrix, 

2001c). Quadrats were established at both shoreline and interior settings. 

Oiling exposure and impacts for the heavily oiled S. alterniflora wetlands can be 

summarized as follows: 

• Initial oil distribution occurred as a band of heavy oil. 

• Multiple oiling events occurred throughout the summer of 2000, as pooled oil was 

released from adjacent heavily oiled marshes. 
8 March 2002 

19 

• Vegetation showed oiling mainly on stems and lower leaves. By July 2000, stain 

and coating on stems were still visible, mostly in trace amounts. 

• Shortly after the spill, the WAT observed reduced percent cover and stem 

densities at shoreline vegetation quadrats as compared to reference sites. 

Although values were still lower than reference sites in 2001, percent cover and 

stem density had increased by about a factor of two. 

• Black oil had penetrated into the substrate, along stem cavities and roots. 

• In July 2000, sediments in four of six quadrats released black oil droplets when 

disturbed underwater. By July 2001, these sediments released only sheens. 

• TPH levels in interior surficial soils in 2000 were highly variable, ranging from 

background to over 15,000 ppm, with evidence of penetration to greater than 

10 cm. Levels of SHCs and TPHs indicated intermediate and moderate amounts 

of weathering, respectively. By 2001, TPH levels had decreased (maximum 

1,850 ppm), and all saturated hydrocarbons had weathered significantly. 

• PAH levels in interior soils in 2000 ranged from 2-200 ppm; levels in 2001 were 

1-54 ppm and characterized as moderately weathered. 

• The Trustees found reduced overall species numbers and numbers of oil-sensitive 

species (amphipods and isopods) as compared to reference sites in samples 

collected in July 2000. Species numbers were similar to reference sites by 

September 2000. 

The available literature on heavily oiled salt marshes indicates a moderate recovery 

trajectory. In a study of the rate of recovery of twenty heavily oiled salt marshes, the majority of 

marshes recovered within five years (Sell et al. 1995). Exceptions were the result of extensive 

mechanical cleanup, thick oil residues that smothered the vegetation, and/or deep penetration of 

a highly toxic oil (No. 2 fuel oil). The impacts to Spartina spp. vegetation and the degree of soil 

contamination at Chalk Point are similar to that reported by Krebs and Tanner (1981) for a No. 6 

fuel oil spill in the Potomac River, where significant impacts to vegetation occurred and marsh 

sediments showed no decreasing trend in oil concentration in the first year after the spill. These 

authors also observed a delay in vegetation mortality in oiled but not replanted areas. 

Based on these studies, the WAT expects the heavily oiled S. alterniflora vegetation in 

both shoreline and interior habitats to recover in five years. Because field data indicate 

significant vegetative recovery, the WAT assumes first year recovery to 50 percent. Soil-related 

service recovery is expected to be slower than for vegetation-related services. Based on results 

of sediment chemistry and professional judgment, the WAT assumes an initial reduction in soilrelated services of 75 percent. Along the shoreline fringe, the WAT expects 80 percent recovery 

within 3 years and 100 percent within 5 years. As interior soils experience higher initial oil levels 

and are subject to lower natural removal rates, the WAT estimates 75 percent recovery within 5 

years and 100 percent recovery within 10 years. Exhibits C5 and C6 present these recovery 

curves graphically. 
8 March 2002 

20 

Heavily Oiled S. cynosuroides (Shoreline and Interior) 

Oiled S. cynosuroides wetlands in Swanson Creek with more than 10 percent oil 

distribution and oil thickness greater than 0.01 cm are categorized as heavily oiled (Entrix, 

2001c). Quadrats were established at both shoreline and interior settings. 

Oiling exposure and impacts for heavily oiled S. cynosuroides wetlands can be 

summarized as follows: 

• Initial oil distribution occurred as a band of heavy oil. 

• Multiple oiling events occurred throughout the summer of 2000, as pooled oil was 

released from adjacent heavily oiled marshes. 

• Vegetation showed oiling mainly on stems and lower leaves. Stain and coating on 

stems remained visible in July 2000. 

• Impacts to vegetation varied widely. Some interior areas were completely devoid 

of vegetation while others had reduced stem densities or appeared normal. By 

2001, two interior sites showed good recovery (similar to reference sites) while a 

third showed very little re-growth. Shoreline vegetation showed good recovery by 

2001. 

• Black oil penetrated deeply into root clumps, along stem cavities, roots, and 

burrows, to a greater extent than in S. alterniflora marshes. Visual observation of 

subsurface oil at the interior sites described oil-filled pores and partially filled 

pores (2000-2001). In July 2000, disturbed sediments released black oil droplets 

at all quadrats. In July 2001, one shoreline site had oil-filled pores and one site 

had no visible oil. 

• Sediments were highly organic (20 percent TOC) and the marsh surface was 

hummocky with root mats forming higher clumps. 

• S. cynosuroides wetlands had the highest degree of oil contamination of any 

shoreline habitat, with a July 2000 surface soil sample containing 39,300 ppm 

TPH and 2,610 ppm PAH; the oil was characterized as slightly weathered. The 

Trustees did not analyze any shoreline samples collected in 2001. 

• S. cynosuroides wetlands also had the highest degree of oil contamination of any 

interior habitat except the wetlands immediately adjacent to the pipeline break. 

Surface samples collected in both 2000 and 2001 contained over 40,000 ppm 

TPH. The WAT found evidence of alkane weathering in the surficial soils 

between 2000 and 2001, but little to no weathering of the PAHs. 

• Oil penetrated to 20+ cm in some cores, and this deeper oil showed much slower 

weathering. 

• Benthic communities showed partial recovery by September 2000, but poor 

recruitment of oil-sensitive species in July 2001. 

Overall, the field data demonstrate that heavily oiled S. cynosuroides wetlands displayed 

the highest degree of impact of all habitat types. The highly organic soils contained the highest 
8 March 2002 

21 

levels of oil contamination (outside of W1A), both on the surface and with depth, and exhibited 

the slowest rate of oil weathering. PAHs were only slightly weathered and showed little change 

in weathering by 2001. Oil entered these sheltered interior habitats via many “micro-channels” 

and muskrat runs, where tidal flushing rates are almost zero. An important consideration in the 

analysis for this category of wetland is the available evidence from a marsh in Buzzards Bay, 

Massachusetts oiled with No. 2 fuel oil. There, concentrations in soil 30 years after the spill 

were similar to those observed immediately after the spill (Reddy et al., 2001). As a result, the 

WAT expects long-term impacts to heavily oiled S. cynosuroides wetlands. 

The WAT estimates recovery rates for this category to be twice as long as those of other 

heavily oiled wetlands. Based on field observations, vegetation-related services for both 

shoreline and interior habitats are assumed to have returned to 50 percent after one year, but full 

recovery may take up to 10 years because of the degree of substrate oiling and slow recovery of 

vegetation. Soil-related services are estimated to have been reduced by 75 percent initially, with 

shoreline habitats returning to 60 percent services in 3 years and 100 percent in 10 years. Soil 

services for interior habitats will recover even slower, to 50 percent in 5 years and 100 percent in 

20 years. Please refer to Exhibits C7 and C8 for graphical depictions of these curves. 

Wetlands Immediately East of Pipeline Break ("W1A" Less Impacted and More Impacted) 

The wetlands adjacent to the pipeline break are treated as a separate category because the 

heavily oiling (fresh oil pooled on the surface for long periods, etc.) and the aggressive cleanup 

activities conducted in the area (flooding, flushing, trenching, construction of boardwalks, 

nutrient augmentation, replanting, etc.) distinguish them from other wetlands oiled by the spill. 

In addition, these areas were not accessible until September 2000 because of ongoing cleanup 

activities. Within this category, the WAT established quadrats in areas where vegetation 

appeared to have completely died and thus was replanted; areas where ditches had been dug in 

the marsh interior to assist in oil recovery, backfilled with clean sand, and replanted; and areas of 

interior (rather than shoreline) Scirpus spp. vegetation that appeared to be heavily oiled. 

Oiling exposure and impacts for W1A wetlands can be summarized as follows: 

• Initial oiling occurred as thick slicks of fresh oil (mixture of No. 2 and No. 

6 fuel oils) pooled on the marsh surface that persisted for several weeks as 

the cleanup progressed. 

• Chronic re-oiling occurred through 2001, as residual oil was re-mobilized 

from oiled areas within W1A. 

• Soils at most quadrats released black oil droplets when disturbed during 

the July 2001 surveys. 

• Black oil penetrated deeply into the root clumps, along stem cavities, 

roots, burrows, etc. In September 2000, one replanted site contained 

77,800 ppm TPH and 7,140 ppm PAH in the top 5 cm, with 6,300 ppm 

TPH and 420 ppm PAH at the interval 18-20 cm. At this same site in 

8 March 2002 

22 

2001, the surficial oiling decreased by about half, but the subsurface oiling 

increased by about a factor of two, with no evidence of further weathering. 

• Ditched areas, although backfilled with clean sand, contained 1,300 and 

3,900 ppm TPH in September 2000, indicating a substantial amount of reoiling.

• Scirpus spp. habitat also showed extensive oil contamination on the 

surface and the deepest penetration observed anywhere (2,340 ppm TPH 

and 167 ppm PAH at depths of 30-32 cm in September 2000). Data from 

this same quadrat in 2001 showed reductions both at the surface and with 

depth. 

• Vegetation in the replanted areas (whether ditched or not) showed large 

reductions in cover and stem density. 

Exhibit A5 in Appendix A shows an aerial photograph of W1A obtained in July 2001. 

Based on corresponding field observations during the July 2001 survey, the WAT designates two 

sub-areas in W1A. The red line on Exhibit A5 delineates a "more-impacted" area representing 

approximately half of the W1A. These "more-impacted" areas include those that were planted 

and ditched and planted, as well as areas of extensive physical disturbance during pipeline repair 

activities. The remainder of W1A, where the vegetation showed significant recovery, is 

considered "less-impacted," and includes areas represented by Scirpus habitat. 

The most applicable case study of the likely recovery rate for W1A is of the T/V Amoco 

Cadiz spill of crude oil in Brittany, France in March 1978. Heavy oiling of a coastal marsh was 

followed by intensive cleanup using high-pressure flushing, extensive vehicular and foot traffic, 

channelization, and sediment removal. Replanting efforts were conducted one and three years 

later. Baca et al. (1987) reported that restoration was "complete" within eight years, although 

only vegetative parameters were measured. 

Based on the similarity of the Amoco Cadiz site to the "more-impacted" areas in W1A, 

the WAT estimates a ten-year recovery curve for vegetation. For the less-impacted areas, the 

vegetation is estimated to have recovered to 50 percent services within one year, similar to the 

other interior habitats discussed above. For the more-impacted areas, the WAT estimates first 

year recovery of only 20 percent services. For soil-related services, the initial injury is assumed 

to be 100 percent loss of services, with complete recovery in 20 years. The WAT estimates first 

year recovery of 35 percent for less-impacted areas and 20 percent for more-impacted areas. 

Recovery curves for the W1A wetlands can be found in Exhibits C9 and C10. 

Restricted Access Wetlands 

After the spill, there were areas of unoiled wetlands in Swanson Creek that were nearly 

surrounded by oiled wetlands. These areas are clearly visible on the aerial photographs and 

computer maps delineating the oiled habitats. Access to these areas would be restricted to 

wildlife during the time that oil persisted in adjacent areas. The Wetlands Assessment Team 
8 March 2002 

23 

believes that access to these areas would return to normal within one year of the spill, when the 

oiled vegetation would no longer be a deterrent. Therefore, vegetation services were completely 

lost immediately following the spill, but recovered fully in one year; there were no reductions in 

soil-related services for this injury category. This recovery curve is presented in Exhibit C11. 

RESTORATION SCALING 

Habitat Equivalency Analysis

The process of scaling a restoration project involves adjusting the size of a restoration 

action to ensure that the present discounted value of project gains equals the present discounted 

value of interim losses. There are two major scaling approaches: the valuation approach and the 

simplified service-to-service approach. Habitat Equivalency Analysis (HEA) is an example of 

the service-to-service approach, and the approach implemented by the Trustees in this case. The 

principal concept underlying the method is that the public can be compensated for past losses of 

habitat resources through habitat replacement projects providing additional resources of the same 

type. The implicit assumption of HEA is that the public is willing to accept a one-to-one tradeoff between a unit of lost habitat services and a unit of restoration project services.7

 That is, the 

public equally values a unit of services at the injury site and the restoration site. HEA does not 

necessarily assume a one-to-one trade-off in resources, but instead in the services they provide. 

The basic steps for implementation of HEA are: 

• Document and estimate the duration and extent of injury, from the time of 

injury until the resource recovers to baseline (or possibly to a maximum 

level below baseline); 

• Document and estimate the services provided by the replacement project, 

over the full life of the habitat; 

• Calculate the size of the replacement project for which the total increase in 

services provided by the replacement project equals the total interim loss 

of services due to the injury; and 

• Calculate the costs of the replacement project, or specify the performance 

standards in cases where the responsible party will be implementing the 

project. 

 7

 The concept of services refers to functions a resource serves for other resources and for 

humans. For example, a wetland habitat may provide on-site ecological services such as faunal 

food and shelter, sediment stabilization, nutrient cycling, and primary production. Off-site 

services may include commercial and/or recreational fishing, bird watching, water quality 

improvements due to on-site water filtration, and storm protection for on-shore properties due to 

the creation of wave breaks. Human services include both use and non-use services, so the HEA 

approach measures and accounts for non-use services in the damage claim. 
Addendum 

---------------- 

The Extent of Oiling Report and the Wetland Injury Report differ in the number of acres 

that were reported as oiled. This difference is not an error but results from differences in 

the treatment of heavily oiled interior marsh and interior transitional areas in the two 

reports. The area of heavily oiled marsh was determined from aerial photographs taken of 

the spill site. During the damage assessment, the marsh assessment group agreed that a 5-

meter wide band adjacent to the heavily oiled marsh would be added to account for areas 

that were oiled but were not visible on the aerial photographs. This 5 meter wide band 

was designated as the interior transitional area in Table 4-2 of the Extent of Oiling Report 

and treated as a separate oiling category. 

In the estimating the wetland injury, the marsh assessment group agreed that the interior 

transitional areas suffered half the injury of the heavily oiled interior marsh. To facilitate 

the calculation of injury in the Wetland Injury Report, the acreage of the interior 

transition area associated with each species was divided by two and added to the area of 

heavy interior oiling. For any heavily oiled interior injury category, the acreage from the 

Wetland Injury Report can be calculated by adding one half the acreage from the interior 

transition area to the acreage from the injury category in Extent of Oiling Report. For 

example, Exhibit 7 of the Wetland Injury Report shows 2.3 acres of heavily oiled interior 

Typha angustifolia which includes 1.49 acres of heavily oiled marsh that was visible on 

the aerial photographs plus one half of the 1.63 acres of T. angustifolia from the adjacent 

interior transitional area. The 1.49 acres of heavily oiled interior T. angustifolia marsh 

and the 1.63 acres if interior transitional T. angustifolia marsh are reported separately in 

Table 4.2 of the Extent of Oiling Report. The same method of calculation can be used to 

reconcile the acreage of Spartina injury, W1A injury, and the total acres impacted in the 

two reports. 
8 March 2002 

24 

Injury to Wetlands

This report presents the Trustees' efforts to complete the first three steps of the HEA 

process for injury to wetlands. The measure of injury combines the level of services lost and the 

time over which this loss occurred. In this case the Trustees express injury in discounted acreyears of wetland services. For each category of injured wetland, the fraction of wetland services 

lost in each year from the time of the spill to full recovery (as described by the recovery curves 

in Exhibit 6 and Appendix C) is discounted at three percent per year to the year of the spill 

(2000) and summed. Total injury is the product of this total discounted loss and the area of 

wetlands in that category.8

 Exhibit 7 shows the final estimated area for each of the 11 oiled 

wetland categories and the associated lost services for both vegetation and soils. 

Exhibit 7. Summary of Wetland Injury by Category 

Wetland Total Area 

(Acres) 

Vegetation Injury 

(Acre-years) 

Soil Injury 

(Acre-years) 

All Lightly Oiled Wetlands 40.46 1.012 1.012 

Spartina spp. Moderate 12.02 3.005 8.870 

Typha spp. Heavy Shoreline 0.16 0.080 0.463 

Typha spp. Heavy Interior 2.3 1.150 4.794 

S. alterniflora Heavy Shoreline 1.52 2.579 2.396 

S. alterniflora Heavy Interior 3.8 6.446 11.047 

S. cynosuroides Heavy Shoreline 1.66 4.618 4.808 

S. cynosuroides Heavy Interior 7.6 21.141 44.143 

W1A: Less Impact 3.2125 8.936 18.994 

W1A: More Impact 3.2125 13.334 23.006 

Restricted Access Areas 4.11 2.055 N/A 

Total 80.055 64.355 119.532 

Injury to wetlands totals approximately 64 acre-years for vegetation-related services and 

approximately 120 acre-years for soil-related services. Assuming that the contributions of 

vegetation and soils to overall wetland services are equal, the total injury is approximately 92 

wetland acre-years.9

The Trustees and RP are working to identify potential wetland restoration options. One 

preferred option is the creation of new wetlands from an upland site in the immediate vicinity of 

the spill impact area. The Wetlands Assessment Team bases its predicted recovery trajectory for 

created wetlands at this site on the professional knowledge of its members; input from a wetlands 

 8

 For example, vegetation in moderately oiled Spartina spp. wetlands suffered an initial 

50 percent service loss. This loss decreased over time, until full services were restored one year 

after the spill. Assuming a linear recovery, 25 percent of the total services provided by those 

wetlands over the course of the year were lost. Multiplying this loss by the total acreage of 12.02 

gives the vegetation injury for this category of wetland, 3.005 acre-years. 

9

 If we assume that soil and vegetation provide the entirety of wetland services and 

further assume that each makes an equal contribution to these services, each acre-year of soil- or 

vegetation-related services is equal to one-half acre-year of total wetland services. 
8 March 2002 

25 

restoration specialist (Ed Garbish, pers. comm., 2001)10; the recent National Research Council 

publication on Compensating for Wetland Losses Under the Clean Water Act (NRC, 2001); and 

a synthesis of studies of created wetlands (Strange et al., 2001). Strange et al reported that 

metrics such as above-ground biomass and stem density recovered to 100% of natural wetlands 

within 2-6 years of an oil spill. On the other hand, they also reported that services related to soil 

development and biogeochemical cycling often took decades to recover and seldom reached the 

equivalent of natural wetlands by the end of the study. 

The input parameters for the restoration credit, based on the preferred site, are: 

• Project completion in 2003; 

• 50 percent services in 5 years; 

• 75 percent services in 10 years; 

• 80 percent services in 20 years and beyond11; and 

• Project life-span of 50 years. 

Based on these inputs and assuming a three percent discount rate, each restored acre 

provides a credit of 16.23 acre-years. Therefore, an area of 5.66 acres at the preferred restoration 

site will compensate for the 92 acre-year wetland injury determined above. 

Injury to Other Resources

The Trustees also assessed spill-related injury to a variety of other resources. The 

Trustees believe it is feasible to restore two of these, injury to muskrats and injury to beach 

areas, in conjunction with a wetlands restoration project. 

Appendix D describes the Trustees' estimate of injury to muskrats and the area of wetland 

required to restore this loss. Based on an estimate of 373 muskrat-years lost due to the spill, 

approximately 5.48 acres of wetland are required as compensation. Because this area is less than 

that needed for restoration of injury to wetlands (i.e., 5.66 acres), the wetland restoration is 

expected to fully compensate for the muskrat injury. The area required for muskrat restoration is 

not additive to that for wetland restoration, because these services are one part of the overall set 

of services provided by the restored wetlands. 

Appendix E describes the Trustees' estimate of injury to beaches oiled by the Chalk Point 

spill. Based on an estimated 4.7 acre-year loss, approximately 0.06 acres of wetland are required 

as compensation. Restoring beach injury with wetlands assumes that wetland services can be 

 10 Ed Garbisch. Environmental Concern, Inc., St. Michaels, MD. 

11 That is, the created wetland will never provide the equivalent level of services as an 

otherwise-comparable natural wetland. 
8 March 2002 

26 

traded for beach services.12 In contrast with the muskrat injury, this area is additive to the 

wetland injury restoration area. Compensation for injured beach habitat is in addition to habitat 

needed to address wetland losses. The services provided by the 0.06 acres of wetland are 

required to compensate for the beach injury, and therefore must be in addition to the area 

provided as compensation for wetland injury. The Trustees also estimated the scale of a beach 

restoration project. Please refer to Appendix E for details of this calculation. 

ACKNOWLEDGEMENTS 

This report was prepared for the Chalk Point NRDA Council by the Wetlands 

Assessment Team, consisting of representatives from the USF&WS, NOAA, Maryland 

Department of the Environment, Maryland Department of Natural Resources, PEPCO, and ST 

Services. James Hoff of NOAA and Ralph Markarian and Wayne Kicklighter of Entrix, Inc. are 

acknowledged for their review and comments on the draft report. 

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 12 As described in Appendix E, the Trustees assume that wetlands are five times as 

productive as beaches. Therefore, one acre-year of wetland services is equivalent to five acreyears of beach services. 
8 March 2002 

27 

Baca, B.J., Getter, C.D. and Lindstedt-Siva, J. 1985. Freshwater oil spill considerations: 

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28 

Entrix, 2001c. Swanson Creek incident extent of oiling report. Report prepared by Entrix for the 

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Krebs, C.T. and C.E. Turner, 1981. Restoration of oiled marshes through sediment stripping and 

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221-238. 

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experimentally dispersed crude oil on vegetation in a northwestern Atlantic salt marsh: 

preliminary observations: Proc. 1987 Oil Spill Conference, API Publ. 4452, 6-9 April 

1987, Baltimore, Maryland, Am. Petroleum Institute, Washington, D.C. pp. 509-514. 

Levine, E.A., Pinckney, J. and Montello, T., 1995. Follow-up study on oiled vegetation cutting 

along the Delaware River. Proc. 1995 International Oil Spill Conference, American 

Petroleum Institute, Washington, D.C., pp. 465-472. 

Leendertse, P. and M. Scholten, 1987. The effects of oil on interacting salt marsh plants, An 

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Maryland, Am. Petroleum Institute, Washington, D.C. p. 626. 
8 March 2002 

29 

Lin, Q. and I.A. Mendelssohn, 1996. A comparative investigation of the effects of South 

Louisiana crude oil on the vegetation of fresh, brackish, and salt marshes: Marine 

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Lytle, J.S. and T.F. Lytle, 1987. The role of Juncus roemerianus in cleanup of oil-polluted 

sediments: Proc. 1987 Oil Spill Conference, API Publ. 4452, 6-9 April 1987, Baltimore, 

Maryland, Am. Petroleum Institute, Washington, D.C. pp. 495-502. 

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cutting oil-soaked marsh grass as an innovative damage control technique. Proc. 1977 

International Oil Spill Conference, American Petroleum Institute, Washington, D.C., pp. 

243-246. 

McCauley, C.A. and R.C. Harrel, 1981. Effects of the oil spill cleanup techniques on a salt 

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Seminar, Environment Canada, pp. 841-856. 

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468. 

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8 March 2002 

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functional indices. U.S. Army Engineer Waterways Experiment Station, Vicksburg, MA, 

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ecological equivalence in Service to Service Scaling of Salt Marsh Restoration. Report 

prepared for NOAA Damage Assessment Center, Silver Spring, MD. 

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Marine Pollution Bulletin, Vol. 32, No. 12, pp. 876-885. 
Appendix A 

Location Maps 
2 

Exhibit A1 - Chalk Point Oil Spill Wetland Survey Index Map 
3 

Exhibit A2 - Chalk Point Oil Spill Wetland Survey - Reference Areas 
4 

Exhibit A3 - Chalk Point Oil Spill Wetland Survey - Swanson's Creek 

x

Location of pipeline break 
5 

Exhibit A4 - Chalk Point Oil Spill Wetland Survey - Trent Hall and Indian Creeks 
6 

Exhibit A5 - Aerial Photograph of the W1A Area 

Red line delineates "more impacted" area of W1A. 
11 February 2002 

Appendix B 

Benthic Community Data Sheets 
11 February 2002 

B-2 

Chalk Point Marsh reference samples for EntrixBatch 1 Total number of samples:12Completed by Versar Inc.Taxonomist: Lisa ScottGroup Species or taxa Station/Date

ARH2I/July CRH1I/July TR2S/July ARH3S/Sept ARP1S/Sept CRH1S/Sept CRH2S/Sept 

Annelida/Polychaeta

Boccardiella ligerica 3 1 36 

Hobsonia florida 61 Laeonereis culveri 1Manayunkia speciosa 94 6 8 29 717 Neanthes succinea 4 1

Annelida/Oligochaeta

Enchytracidae 66 8 9 9 Immature Tubificidae without hair chaetae 188 20 15 116 11 23 75 Immature Tubificidae with hair chaetae 9 24 Nais variablilisParanais litoralis 3 4 60 69 

Mollusca/Gastropoda

Littoridinops tenuipes 9 1 

Lymnaeidae 74

Mollusca/Bivalvia

Pisidium spp. 16

Crustacea/Amphipoda

Orchestia uhleri 5 1 Gammarus daiberi 2Gammarus spp. (juvenile) 1 4 2 Leptocheirus plumulosus

Crustacea/Isopoda

Cassidinidea ovalis 1 Cyathura polita 5 315

Crustacea/Tanaidacea

Leptochelia dubia 2 48

Crustacea/Decapoda

Rhithropanopeus harrisi 1

Hydrachnidia

Acari 46 9 

Insecta/Coleoptera

Coleoptera terrestrial adult 1Coleoptera terrestrial larva 1

Insecta/Diptera

Bezzia/Palpomyia spp. group 1 1 

Culicoides spp. 1 Dashyhelea spp. 58Dolichopodidae 21 2 2 2 

Insecta/Chironomidae

Dicrotendipes modestus 5 2 Goelidichironomus devineyae 14Pseudosmittia spp. 3Tanypus neopunctipennis 2

Total Benthos 200 407 44 135 32 125 999 
11 February 2002 

B-3 

C halk Point M arsh reference sam ples for EntrixBatch 2 Total num ber of sam ples:12C om pleted by Versar Inc. 3/30/01Taxonom ist: Lisa ScottG roup Species or taxa Station/D ate

AR H 1I/July AR H 3I/July C T R 2I/July IR H 3I/July IR R 1I/July IR T 4/July T R T 1I/July T 

Annelida/Polychaeta

Boccardiella ligerica 3 1 25 H eterom astus filiform is 

H obsonia florida 1 4 1 Laeonereis culveri M anayunkia speciosa 231 76 2 2 259 1 N eanthes succinea 4 1 

Streblospio benedicti 6 

Annelida/O ligochaeta

Enchytracidae 9 60 32 60 60 Im m ature T ubificidae w ithout hair chaetae 102 9 30 84 299 20 20 Im m ature T ubificidae w ith hair chaetae 3 39 6 Paranais litoralis 6 2 6 71 2 Tubificoides spp. 24 299 

M ollusca/G astropoda

G astropoda (unidentified) 4 1 Littoridinops tenuipes 1 1

M ollusca/B ivalvia

Pisidium spp. 1 7 

C rustacea/Am phipoda

Apocorophium lacustre 5O rchestia uhleri 4 4 1G am m arus daiberi 5 1G am m arus spp. (juvenile) 1 3 2

Crustacea/Isopoda

C assidinidea ovalis 1 1

C yathura polita 14 3 9 1 9 1 

C rustacea/T anaidacea

Leptochelia dubia 9 11 1 

Crustacea/Decapoda

R hithropanopeus harrisi 2

C rustacea/M ysidacea

N eom ysis am ericana 1

H ydrachnidia

Acari 11 2

Insecta/D iptera

Atrichopogon spp. 1

Bezzia/Palpom yia spp. group 3 C eratopogonidae (unidentified) 25 5 4 2 2 3 Chrysops spp. 1 1D ashyhelea spp. 27 4D olichopodidae 4 3 1 1 2Ephydridae 4Pilaria spp. 1 1T ipula spp. 

Insecta/C hironom idae

C hironom us spp.D icrotendipes spp. 10 2G oelidichironom us devineyae 42 2 2 22 68 Pseudosm ittia spp. 1Tanytarsus spp. 22 

Total Benthos 465 167 83 127 1034 104 92 
11 February 2002 

B-4 

C halk Point M arsh sam ples for EntrixBatch 3 T otal num ber of sam ples:12C om pleted by Versar Inc. 7/01/01T axonom ist: Lisa Scott

Sam pling D ate and Station

G roup Species or taxa 7/20/00 7/18/00 7/27/00 9/19/00 9/18/00 9/19/00 7/20/00 

AH-1I AH-2I AH-3I AH-1S AH-2S AH-3S CH-1I 

Annelida/Polychaeta

H eterom astus filiform isH obsonia floridaLaeonereis culveri 2 25 5

M anayunkia speciosa 122 2 7 

N eanthes succinea 252

Polydora cornuta 5 157Streblospio benedicti 1 1

Annelida/O ligochaeta

Enchytracidae 7 15 1 Im m ature Tubificidae without hair chaetae 10 189 382 14 1 138 2 Im m ature T ubificidae with hair chaetae 15 

Lim nodrilus hoffm eisteri 1N ais pardalis 1N ais sim plex 1Paranais litoralis 1 12 T ubificoides spp.

M ollusca/G astropoda

Littoridinops tenuipes 1 

M ollusca/Bivalvia

U nidentified bivalvia 7

M acom a m itchelli 1

C rustacea/Am phipoda

Apocorophium lacustre 1O rchestia uhleri 1G am m arus daiberi

Crustacea/Isopoda

C assidinidea ovalisC yathura polita 3 2 1 1

Crustacea/Decapoda

R hithropanopeus harrisi 3

H ydrachnidia

Acari

Insecta/D iptera

C ulicoides spp. 1D ashyhelea spp. 1 11 2 D olichopodidae 4 Ephydridae 1

Insecta/C hironom idae

C hironom us spp. 1 

C ricotopus/O rthocladius spp. 11 D icrotendipes spp. 3 1 G oelidichironom us devineyae 4 12 1 Larsia spp. 4Polypedilus illinoense 1Tanypus spp. 1 U nidentified C hironom ini U nidentified O rthocladini 1 U nidentified T anypodinae 

T otal Benthos T otal organism s 35 204 407 166 36 341 9 
11 February 2002 

B-5 

C halk P oint M arsh 2001 benthic sam ples for E ntrixBatch 4 T otal num ber of sam ples:12C om pleted by Versar Inc. 9/04/01T axonom ist: Lisa Scott

S am pling D ate and Station

G roup Species or taxa 7/16/01 7/16/01 7/18/01 7/10/01 7/18/01 7/17/01 7/16/01 7/16/01 7

AH-1I AH-2I AH-3I ARH-1I ARH-2I ARH-3I CH-1I CH-2I* 

T urbellaria T urbellaria 4A nnelida/Polychaeta

H obsonia florida 34 7 21Laeonereis culveri 2M anayunkia speciosa 7 4 79 39 1 4 P olydora cornuta 3

A nnelida/O ligochaeta

Enchytracidae 28 36 18 6 156 8 12 3 Im m ature T ubificidae without hair chaeta 392 129 138 26 108 16 26 5 

Im m ature T ubificidae with hair chaetae 6 9 6 6 10 Lim nodrilus hoffm eisteri 42 1 

T ubificoides spp. 10

M ollusca/G astropoda

Littoridinops tenuipes 36 1 29 10 7 Littorina spp. 1 

M ollusca/B ivalvia

Sphaeridae 19 1

C rustacea/Am phipoda

Leptochelia rapax 3O rchestia uhleri 1 Gam m arus spp. 6 1 8 

Crustacea/Isopoda

C assidinidea ovalis 2C yathura polita 9 7

H ydrachnidia

Acari 2

Insecta/D iptera

Bezzia/Palpom yia 2 1 4 C haoborus punctipennis 1C ulicoides spp. 2 D olichopodidae 1 4 2 E phydridae 5 1 1 P ilaria spp. T abanidae 1T ipula spp. 1 2 

Insecta/C hironom idae

A blabesm yia spp. 3C hironom idae pupae 1C ricotopus/O rthocladius spp. 2 12 2 D icrotendipes spp. 1 52 12 2 

Insecta/Lepidoptera

P yralidae 1

Insecta/C oleoptera

C urculionidae 2 E lm idae adult 1H ydrophilidae larvae 1

Total Benthos T otal organism s 487 214 388 126 318 49 67 16 
11 February 2002 

B-6 

Chalk Point Marsh 2001 benthic samples for EntrixBatch 5 Total number of samples:6Completed by Versar Inc. 10/05/01Taxonomist: Lisa Scott

Sampling Date and Station

Group Species or taxa 7/16/01 7/16/01 7/17/01 7/17

SH-2I SH-3I SRI-1I SRT

Annelida/Polychaeta

Manayunkia speciosa 6

Annelida/Oligochaeta

Enchytracidae 7 16 165 Immature Tubificidae without hair chaetae 142 81 Immature Tubificidae with hair chaetae 42 

Mollusca/Gastropoda

Littoridinops tenuipes Physella spp. 1

Crustacea/Amphipoda

Orchestia uhleri 2Gammarus spp. 

Insecta/Diptera

Bezzia/Palpomyia 1 16 Ceratopogonidae pupa 12 Culicoides spp. 1 94 2 Dolichopodidae 2 Limnophila spp 3 15Tipula spp. 1

Insecta/Chironomidae

Cricotopus/Orthocladius spp. 1 Dicrotendipes spp. 3 Tanytarsus spp. 24Tanypus spp. 

Insecta/Trichoptera

Hydropsychidae 1

Insecta/Coleoptera

Hydrophilidae larvae 1

Total Benthos Total organisms 13 268 358 
Appendix C 

WETLAND CATEGORY RECOVERY CURVES 
2 

Exhibit C2. Spartina spp. Moderate Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils

Exhibit C1. All Light Recovery Curves

0

50

100

0 0.5 1 1.5 2

Years

Percent Services 

Vegetation Soils
3 

Exhibit C3. Typha spp.- Heavy Shoreline Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils

Exhibit C4. Typha spp.- Heavy Interior Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils
4 

Exhibit C5. S. alterniflora - Heavy Shoreline

Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils

Exhibit C6. S. alterniflora - Heavy Interior

Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils
5 

Exhibit C7. S. cynosuroides- Heavy Shoreline

Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils

Exhibit C8. S. cynosuroides- Heavy Interior

Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils
6 

Exhibit C9. W1A- Less Impacted Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils

Exhibit C10. W1A- More Impacted Recovery Curves

0

50

100

0 5 10 15 20

Years

Percent Services

Vegetation Soils
7 

Exhibit C11. Restricted Access Areas Recovery Curve

0

50

100

0 0.5 1 1.5 2

Years

Percent Services

Vegetation
APPENDIX D 

ESTIMATE OF TOTAL MORTALITY 

TO MUSKRATS RESULTING FROM THE 

CHALK POINT OIL SPILL 

A Report Prepared by the Wildlife Injury Workgroup 

For the Chalk Point Natural Resource Damage 

Assessment Trustee Council 

February 13, 2002 
1

I. INTRODUCTION 

As part of the natural resource damage assessment for the Chalk Point oil spill, natural resource 

trustees are assessing injuries to marsh habitats and the compensation required for these injuries. 

That assessment identifies all the marsh services lost due to the spill in marsh years and 

computes the acreage of created marsh that will produce sufficient marsh years to compensate 

for the injuries.1

 One of the many important services provided by marshes is habitat for wildlife, 

including muskrats. In order to corroborate the marsh services assessment, an independent 

analysis of injuries to muskrats and the marsh acres needed to compensate for these injuries has 

been undertaken. This document reports the methods and results used in that analysis. 

Wildlife rescue efforts began immediately after the spill, and resulted in the collection of 63 dead 

and 8 live muskrats. Seven of the captured live muskrats died in rehabilitation and one was 

released, for a total of 70 dead muskrats (USFWS, 2000b). One muskrat died in rehabilitation 

with no visible oil, and three were collected dead with no visible oil. 

The number of oiled muskrats retrieved after a spill represents a fraction of the actual number 

adversely affected. Oiled and/or dead muskrats may not be recovered because they can sink, 

become scavenged, can be overlooked by search teams, or hide. The adverse effects of oil on 

muskrats have been investigated. McEwan, Aitchison, and Whitehead (1974) evaluated the 

energy metabolism of oiled muskrats. They demonstrated that fur treated with 25.6-42.3 g of oil 

became wet, resulting in loss of buoyancy. Behavior manifested by muskrats placed in oily 

water consisted of trying to escape, preening, and shivering. They found that heavy crude oil 

increased the thermal conductivity of muskrats by as much as 122 percent. To compensate for 

the loss of thermal insulation, oiled muskrats increased their dry-matter intake 2.5 fold. The 

investigators doubted that muskrats exposed to moderate quantities of oil could survive under 

natural conditions. Similarly, Wragg (1954) found that oil had a persistent and cumulative 

wetting effect on muskrats. He showed that muskrats exposed to 4 ml of fuel oil were almost 

completely submerged in 40 minutes. 

Literature regarding the impacts of oil spills on muskrat populations is scarce. Fifteen dead oiled 

muskrats were found following an oil spill in the Gasconade River, Missouri in 1988 (Heatherly, 

1993), and 28 were collected following a spill in the Arthur Kill, Staten Island in 1990 (Burger, 

1997). In neither case was total oil-related mortality estimated. 

II. INJURY ASSESSMENT 

Data and Assumptions 

From the total of 70 dead muskrats that were found, 66 were collected from the Swanson Creek 

area, and one each was collected from Indian Creek, Trent Hall Creek, the Benedict Bridge area, 

and Ramsey Creek. 

 

1 For more information about the Chalk Point oil spill natural resource damage assessment, please go to the 

following web site: www.darp.noaa.gov/neregion/chalkpt.htm . 
2

Muskrat habitat acreage within Swanson Creek was delineated by manually circumscribing the 

marsh habitat type on 1:300 true color aerial photographs of the area, as shown on Figure 1. 

Total habitat acreage was quantified by digitizing the marsh boundaries, and calculating the area 

enclosed using GIS (ArcView). Total marsh habitat within Swanson Creek was determined to be 

189.37 acres. 

Muskrat density in Swanson Creek was estimated by two methods: 1) local expert knowledge; 

and 2) extrapolation from densities reported for Blackwater National Wildlife Refuge on the 

Eastern Shore of Maryland. No population studies or trapping records were available for 

Swanson Creek or any other creek in the spill area. The yearly trapping harvest of muskrats 

from Swanson Creek was estimated to be 150-300 individuals, with a local population of 2-3 

times the harvest (Mask, 2000-2001). Based on these ranges, the population abundance of 

muskrats in Swanson Creek prior to the spill was estimated to be 300 to 900 individuals. At the 

Blackwater National Wildlife Refuge, the 16-year (1984-2000) mean density of muskrats was 

4.2 muskrats/acre (USFWS, 2000a). The acreage of marsh habitat in Swanson Creek was 

estimated to be 189.37 acres, as shown above. Thus, the population abundance of muskrats in 

Swanson Creek was estimated to be 795 individuals (4.2 muskrats/acre x 189.37 acres). This 

population estimate (795 individuals) lies within the bounds of the range estimated by Mask 

(2000-2001). The estimate of 4.2 muskrats per acre was also used in calculations to determine 

total mortality for injury assessment purposes. 

Acreage of oiled marsh habitat within the three creeks was estimated by manually 

circumscribing the extent of oiling on 1:300 scale true color aerial photographs of each creek. 

Along the marsh shorelines, individual segment lengths and widths were determined using 

Shoreline Clean-up Assessment Team (SCAT) data (ENTRIX, 2000) and interpretation by the 

NRDA Wetlands Subgroup. 

Restricted Access areas (marsh areas essentially enclosed within oiled polygons that would be 

unavailable as habitat) were included in the oiled acreage. Finally, a 5-m transitional zone buffer 

was delineated around all oiled acreage, including the shorelines. This transitional zone was 

added to the oiled acreage to consider total area of habitat that could present oiling risk to 

muskrats. Figures 2 through 4 show the total oiled areas in Swanson, Indian, and Trent Hall 

Creeks in red. 

These oil exposed marsh areas (including oiled polygons, shorelines, restricted access areas, and 

5-m transition zones) were digitized. Using GIS (ArcView), total areas of oil exposed marsh 

habitat in Swanson, Indian, and Trent Hall Creeks were calculated to be 34.87 acres, 3.83 acres, 

and 1.57 acres, respectively. 

In addition to the oiling of muskrats within the spill zone, oiling was also likely to have occurred 

to muskrats living outside the immediate spill area whose home ranges included oiled marsh. 

The area occupied by a muskrat depends upon the size, configuration, and diversity of aquatic 

habitat; social pressures; sex; age; season; and environmental conditions. After a muskrat 

becomes established in an area in the early spring, under normal conditions the area is occupied 

until the following spring (Perry 1982). 

Muskrats have a relatively small home range that varies in configuration depending on aquatic 

habitat (Perry 1982), and is normally within 7 to 30 meters of its main dwelling (McConnell and 

Powers, 1995). For a marsh in Maine, Takos (1944) reported that about 50 percent of the 
3

recaptures were within a 7.6-meter radius of the original tagging site, and less than 30 percent 

were beyond 30.5 meters. For Iowa populations, Errington (1963) estimated that the radius of 

summer home range averaged approximately 30.5 meters. Caley (1986) showed an average 

intercapture distance of 25.3 meters, with an upper 95% confidence interval of 101 meters. 

MacArthur (1978) found muskrats within 15-meter of their primary dwelling lodge during 50 

percent or more of the position determinations. Most foraging occurred within 5- to 10-meter 

radius of the lodge or pushup, and few muskrats movements exceeded 150 meter. Similarly, 

Coon (1965) found the majority of movements of muskrats in an Illinois lake within 15 meters of 

the home den. 

For purposes of this assessment, Trustees assumed a muskrat home range radius of 30 meters 

from their huts (and into potentially oiled habitat). Thus, all muskrats within 30 meters of oil 

exposed habitat (exposure zone) would potentially be at-risk of becoming oiled. Muskrats 

beyond 30 meters of oil exposed habitat would not be considered at-risk of becoming oiled. 

To determine the muskrat home range acreages beyond the oil exposed marsh area (including 

oiled polygons and shorelines, the restricted access areas, and 5-meter transition zone), a 30-

meter boundary was defined along the border of the oil exposed areas for each of the three 

creeks. This boundary area is shown on Figures 2 through 4 in yellow. The areas within these 

30-meter boundary zones for Swanson, Indian, and Trent Hall Creeks were quantified using GIS 

(ArcView) to be 40.15 acres, 15.72 acres, and 7.55 acres, respectively. 

The exposure zone acreage for muskrats was determined by summing the 30-meter boundary 

areas and oil exposed marsh areas for each of the three creeks. Thus, total acreage of the 

exposure zones is: 75.02 acres (40.15 + 34.87) for Swanson Creek, 19.55 acres (15.72 + 3.83) for 

Indian Creek, and 9.12 acres (7.55 + 1.57) for Trent Hall Creek. 

Estimated Exposure and Mortality 

Exposure of the muskrat population within Swanson Creek was estimated by multiplying the 

exposure zone acreage (75.02 acres) by the density of muskrats (4.2 per acre). Thus, the 

potentially exposed population in Swanson Creek was 315 individuals. 

Of the 70 muskrats collected, one each was collected from the Indian and Trent Hall Creek areas. 

Although clean-up workers collected the majority of muskrats from Swanson Creek, equivalent 

recovery efforts were not undertaken at Indian and Trent Hall Creeks. Thus, muskrat mortality 

was also estimated for these two creeks. 

Muskrat abundance in Indian and Trent Hall Creeks is not known, but would be expected to be 

lower than Swanson Creek because of lower habitat suitability (i.e., less marsh acreage, 

relatively more forested habitat bordering the creeks rather than marsh (Mask, 2000-2001). An 

index of the muskrat population size in these creeks was developed using hut counts (Best 1982, 

Proulx and Gilbert 1984). On aerial photographs, houses are defined as light dots, often 

surrounded by a circle of dark open water where the vegetation has been cleared for food and 

construction (Best 1982). These houses, along with feeding huts, were evident on the 9-in. by 9-

in. true color aerial photographs of the spill area that were taken in April 2000 at 1:300 scale. 

Active houses, inactive houses, and feeding huts could not be distinguished on these 

photographs, and all were counted for the hut index. Hereafter all houses and huts appearing as 

light dots on the photographs will be designated as “huts”. 
4

In order to estimate the muskrat population sizes for Indian and Trent Hall Creeks, we developed 

hut indices to compare to the hut index and population density estimate for Swanson Creek. For 

each of the three creeks, all huts were counted within the exposure zones (oiled area, 5 m buffer, 

and 30 meter home range) and compared to the count from Swanson Creek. Hut counts for 

Swanson, Indian, and Trent Hall Creeks were 239, 24, and 22 respectively. The hut count per 

acre for Swanson Creek was 3.19 (239/75.02), for Indian Creek was 1.23 (24/19.55), and for 

Trent Hall Creek was 2.41 (22/9.12). The percentages of huts per acre in Indian and Trent Hall 

Creeks compared to Swanson Creek were 0.39 (1.23/3.19), and 0.76 (2.41/3.19), respectively. 

Applying these percentages to the density in Swanson Creek (4.2 muskrats per acre, as shown 

above) yields muskrat densities in Indian and Trent Hall Creeks of 1.64 (0.39 x 4.2), and 3.19 

(0.76 x 4.2) muskrats per acre, respectively. 

Muskrat exposures in Indian and Trent Hall Creeks were determined by multiplying the 

estimated muskrat density in each creek by the exposure zone acreage in each creek. The 

exposed population was therefore calculated to be 32 muskrats (1.64 per acre x 19.55 acres) for 

Indian Creek, and 29 muskrats (3.19 per acre x 9.12 acres) for Trent Hall Creek. 

Swanson Creek supported the largest muskrat population, and was much more heavily oiled than 

the other two creeks. Assuming 100% mortality for muskrats potentially exposed to oiled marsh 

habitat, the total acute mortality was estimated to be 376 individuals (i.e. 315 in Swanson Creek, 

32 in Indian Creek, and 29 in Trent Hall Creek). Note: this estimate assumes all muskrats within 

30 meters of oiled marsh habitat would be killed independent of actual exposure or oiling level. 

Total Muskrat Years Lost

Muskrats are prolific breeders with high levels of reproductive success. For purposes of this 

study, based on McCabe (2001) we assume that the muskrat population in the exposure zone was 

in equilibrium at the time of the spill. Muskrats are highly successful breeders and they will 

likely rapidly return to prespill population levels following a loss of a fraction of the individuals 

located in the vicinity (see, for example, Krolls, et al., 1985; and Heatherly, 1993). Therefore, it 

is assumed that the equilibrium population level was restored, linearly, over a period of two 

years following the spill. 

Because muskrats are prolific breeders, many pups born to adults in populations that have 

reached density dependent equilibrium, as in the area in question in the Patuxent River prior to 

the spill, are redundant and suffer high mortality rates (McCabe, 2001). Those mortality rates 

appear to go down when population levels are reduced below equilibrium and return to normal 

levels once population equilibrium is restored (Krolls, et al., 1985 and Heatherly, 1993). Thus, 

for purposes of this analysis, it is assumed that the spill did not have an adverse effect on the 

number of young produced by the affected Patuxent River muskrat population. 

Our analysis is, therefore, confined to quantifying the total number of muskrat years lost due to 

acute mortality alone. Since recovery of the loss is linear and continuous over a two year period, 

approximately half, i.e. 188, of the dead muskrats are returned to the population after the first 

year (April, 2000 to April, 2001), with the remainder returning in year two (April 2001 to April 

2002). The estimated muskrat years lost are discounted at the standard 3% discount rate, 

resulting in a total estimated loss of 373 muskrat years. The total muskrat years lost (373) is less 

than the total estimated to have been killed (376) primarily because a linear two-year recovery 

process beginning immediately after the spill implicitly assumes that half of the dead muskrats 
5

are replaced in one year or less. Discounting further reduces the total number of muskrat years 

lost in the second year of recovery (discounting is not applied to the first year of losses as a 

matter of standard trustee policy). 

Using habitat equivalency analysis (U.S. Department of Commerce, 2000), based on the 

assumption that an acre of restored marsh can support 4.2 muskrats per year for 50 years, it will 

take 5.48 acres (discounted at 3% per annum) to restore the estimated 373 acre years lost 

III. LITERATURE CITED

Best, R.G. 1982. Handbook of Remote Sensing in Fish and Wildlife Management. Remote 

Sensing Institute. South Dakota State University, Brookings, SD. 

Burger, J. 1997. Oil spills. Rutgers University Press, New Brunswick, NJ. 

Caley, M.J. 1986. Kinship-mediated spacing patterns in muskrats. M.S. Thesis. Univ. Guelph, 

Ont. 67 pp. 

Coon, R.A. 1965. Daily movements and home range of the muskrat (Ondatra zibethicus). M.S. 

Thesis. Western Illinois Univ., Macomb, 75 pp. 

ENTRIX, Inc. 2000. Summary of SCAT Activities and Data Management, Swanson Creek 

Incident. October 16, 2000. Report prepared by ENTRIX, Inc., Walnut Creek, CA. 

Errington, P.L. 1963. Muskrat populations. Iowa State University Press, Ames. 

Heatherly, W.G. 1993. Demographic characteristics of riverine muskrats after an oil spill. 

Unpublished Masters Thesis. University of Missouri, Columbia, MO. 

Krolls, R.W. and R.L. Meeks. 1985. Muskrat population recovery following habitat reestablishment near southwestern Lake Erie. Wildlife Society Bulletin 13: 483-486. 

MacArthur, R.A. 1978. Winter movements and home range of the muskrat. Can. Field Nat. 

92:345-349. 

Mask, C., personal communication, 2000 and 2001. Multiple conversations with a member of the 

Maryland Fur Trappers Association regarding muskrat habitat, population levels and trapping in 

the spill area. 

McCabe, T., personal communication, 2001. Multiple conversations with a U.S. Fish and 

Wildlife Service biologist from the Chesapeake Bay Field Office with expert knowledge of 

muskrat life history and habitats. 

McConnell, P.A. and J.L. Powers. 1995. Muskrat. pp. 507-513 in Living Resources of the 

Delaware Estuary (L. Dove and R.M. Nyman, eds.). The Delaware Bay Estuary Program. 

McEwan, E.H., N. Aitchison, and P.E. Whitehead. 1974. Canadian Journal of Zoology. 52:1057-

1062. 

Terry, H.R., Jr. 1982. Muskrats. pp. 282-324 in Wild Mammals of North America, Biology, 

Management, and Economics (J.A. Chapman and G.A. Feldhamer, eds.). The John Hopkins 

University Press, Baltimore, MD. 
6

Proulx, G. and F.F. Gilbert. 1984. Estimating muskrat population trends by house counts. Journal 

of Wildlife Management. 48(3): 917-922. 

Takos, M.J. 1944. Summer movements of banded muskrats. J. Wildlife Management. 8:307-311. 

United States Department of Commerce, NOAA, Damage Assessment and Restoration Program. 

2000. Habitat Equivalency Analysis: An Overview. (for a PDF version, please go to: 

http://www.darp.noaa.gov/pdf/heaoverv.pdf ). 

United States Fish and Wildlife Service (USFWS), 2000a. Muskrat Populations and Harvests. 

Unpublished data from Blackwater National Wildlife Refuge, Cambridge, MD. 

United States Fish and Wildlife Service (USFWS), 2000b. Draft Report. USFWS Response 

During the Chalk Point Oil Spill. October 5, 2000. Chesapeake Bay Field Office, Annapolis, 

MD. 

Wragg, L.E. 1954. The effect of DDT and oil on muskrats. Canadian Field Nat. 68:11-13. 
7

Figure 1. Marsh habitat area delineated for Swanson Creek. 
8

Figure 2. Oil exposed marsh area delineated for Swanson Creek in red. This area includpolygons and shorelines, restricted access areas, and the 5-meter transition zone. The 30-me

range area for muskrats is shown in yellow. 
9

Figure 3. Oil exposed marsh area delineated for Indian Creek in red. This area includes oi

and the 5-meter transition zone. The 30-meter home range area for muskrats is shown in yello
10

Figure 4. Oil exposed marsh area delineated for Trent Hall Creek in red. This area ishorelines and the 5-meter transition zone. The 30-meter home range area for muskrats is sho
 

Appendix E 

QUANTIFICATION AND SCALING OF BEACH INJURY 
ERRATA SHEET 

INJURY TO WETLANDS RESULTING FROM THE CHALK POINT OIL SPILL 

3 May 2002 

Appendix E: Quantification and Scaling of Beach Injury

To quantify injury to beach habitat, each subdivision of oiled beach area was assigned to 

one of three categories (A, B or C), based on if/when it met Phase I and Phase II SCAT cleanup 

criteria. Category C was defined as those areas that met Phase I criteria within approximately 

fourteen months of the spill, but have not yet met Phase II criteria. 

Although Appendix E of the Injury to Wetlands report dated 8 March 2002 states that all 

Category C areas have met Phase I criteria, the Trustees inadvertently included area W1 in 

Category C even though this area has not yet met Phase I criteria. Area W1, the area immediately 

surrounding the pipeline break, contains a total of 0.144 acres of oiled beach, representing 4.5 

percent of the total area of Category C (3.19 acres). 

A new category (i.e., Category D) would be necessary to estimate the injury from the W1 

area. However, based on initial calculations, the resulting change in total beach injury would be 

too small to affect the beach restoration requirement of 0.06 wetland acres as estimated in the 8 

March 2002 Injury to Wetlands Report. Therefore, no such change has been made to the beach 

injury or beach restoration calculations. 
 

This appendix describes our quantification and scaling efforts for injury to beach habitat. 

Specifically, this analysis addresses potential productivity-related injuries to beach habitat not 

accounted for in the human use or terrapin analyses already completed by the Trustees. 

Methodology

Existing SCAT data were used to develop reasoned judgements about the duration and 

extent of beach habitat productivity loss caused by oiling associated with the Chalk Point oil 

spill.1

 While SCAT data provide qualitative information about the degree and extent of oiling on 

beach habitat, no spill-specific quantitative data were collected to document associated impacts 

to invertebrates or other biota that utilize beach habitat (other than terrapins, which are addressed 

in other spill assessment efforts). Nevertheless, based on the degree of oiling, potential impacts 

associated with cleaning operations and other documented injuries caused by the spill, it is 

reasonable to expect some impacts. 

 For restoration, we propose two options for restoring quantified beach injuries: (1) 

restoring an equivalent area of beach; and (2) restoring wetlands, using an appropriate 

conversion between beaches and wetlands based on their relative productivity. In this way, 

equivalencies between beach acre years lost and wetland acre years gained can be estimated. Our 

proposed translation factor reflects the reasonable expectation that wetland habitat is more 

productive than beach habitat. 

Injury Quantification

The "Swanson Creek Incident Extent of Oiling Report" (July 6, 2001) indicates that 

10.11 acres of beach shoreline were oiled by the Chalk Point spill. In the first step of the injury 

quantification analysis, each subdivision of oiled beach area was assigned to one of three 

categories (A, B or C), based on if/when it met Phase I and Phase II SCAT cleanup criteria.2

These categories are defined in Exhibit 1. 

 1 Dr. Jacqui Michel of Research Planning, Inc. provided input used in the development of these judgments. 

2

 Consistent with the "Swanson Creek Incident Extent of Oiling Report" we assume that subdivisions 

identified as "area unvegetated" are beach habitat. Furthermore, because Phase I/II status is only tracked at the 

segment level, we categorize each subdivision based on the status of parent segment. Because of the possibility that 

one or more subdivisions within the segment were "clean" enough to meet the Phase I/II criteria sooner than the 

overall segment, this approach may overstate recovery time for some subdivisions. The area of each subdivision 

(measured in square meters) was obtained from Appendix 1 of the same report. 
 

Exhibit 1 

BEACH AREA CATEGORIES 

Beach Area 

Categories 

Phase I met in 

Spring 2000 

Phase I met in 

Spring 2001 

Phase II met in 

Fall 2000 

Phase II not yet 

met 

A X X 

B X X 

C X X 

Exhibit 2 provides an annotated matrix of recovery curves and associated service levels 

for each category (A, B or C) of oiled beach habitat. As shown in the exhibit, beach areas in each 

category (A, B or C) were further subdivided into "light", "moderate" or "heavy" oiling based on 

their "NRDA Oiling Category" classification in the "Swanson Creek Incident Extent of Oiling 

Report" (July 6, 2001). 

The estimates of recovery curves and associated service levels are based on SCAT data 

and professional judgement. Key assumptions underlying the matrix are identified below: 

• Immediately following the spill, we assume service levels (i.e., the 

productivity of beach habitat) dropped to 75 percent of baseline levels for 

areas classified as lightly oiled. We assume service levels dropped to 25 

percent and 0 percent for moderately and heavily oiled areas, respectively. 

• The choice of June 1st and October 1st in each year as the "transition" 

points for the recovery curves is based on the assumed start and end dates 

of the yearly benthic recruitment and production cycle. 
Exhibit 2

ESTIMATE OF BEACH HABITAT RECOVERY AND ASSOCIATED SERVICE LEVELS

Percent Service (100% = Baseline Productivity Level)

Beach 

Category Acreage 04/06/00 04/07/00 06/01/00 10/01/00 06/01/01 10/01/01 10/01

A light 0.97 100% 75% 75% 100% 100% 100% 100%A moderate 0.42 100% 25% 25% 100% 100% 100% 100%A heavy 0.00 100% 0% 0% 100% 100% 100% 100%Sub-Total A 1.39B light 1.75 100% 75% 75% 85% 85% 95% 100%B moderate 3.78 100% 25% 25% 85% 85% 95% 100%B heavy 0.00 100% 0% 0% 85% 85% 95% 100%Sub-Total B 5.53C light 0.52 100% 75% 75% 75% 75% 95% 100%C moderate 2.20 100% 25% 25% 50% 50% 85% 100%C heavy 0.47 100% 0% 0% 50% 50% 85% 100%Sub-Total C 3.19

Total 10.11

The different categories within A, 

B, and C refer to an area's initial designation of light, moderate, or 

heavy oiling, based on the "NRDA 

oiling category" identified in the Extent of Oiling Report.

Beach habitat at baseline service levels.

Spill occured. Beach productivity reduced to specified service level.

Phase I met for A and B; recovery of biota is assumed to begin after 

this date. Recovery also assumed to begin after this date for C areas, although at a slower rate because these areas have not yet met Phase I criteria.

For A, Phase II met. Recovery is assumed to be complete; productivity restored to baseline.For B, Phase II has not been met, but we assume majority of productivity is restored.For C, Phase I has not been met, but we assume partial recovery of productivity has occurred.

Service recovery unchanged between 10/01/00 and 06/01/01, reflecting low natural productivity during these months. Phase I is met for C; recovery for C areas begins to accelerate.

B and C have not met Phase II, but we assume productivity is approaching baseline levels.

We assume Phase II will be met for B and C; all areas returned to baseline productivity levels.
 

• SCAT data indicate that all Category A areas met Phase I and II criteria 

within approximately six months of the spill. Therefore, we assume 

complete recovery of these areas by the end of this period. 

• SCAT data indicate that all Category B areas met Phase I criteria within 

approximately two months of the spill, but have not yet met Phase II 

criteria. We assume Category B areas recovered to 85 percent of baseline 

service levels within six months of the spill, 95 percent of baseline levels 

18 months after the spill, and complete recovery 30 months after the spill. 

• SCAT data indicate that all Category C areas met Phase I criteria within 

approximately fourteen months of the spill, but have not yet met Phase II 

criteria. Similar to Category B, we assume Category C areas recover 

completely 30 months after the spill. However, because Category C areas 

took longer to meet Phase I criteria, we assume a slower rate of recovery 

during the beginning and middle of the injury period (see Exhibit 2). 

The recovery curves and associated service loss estimates identified in Exhibit 2 are 

simplified representations of complex ecological processes and detailed SCAT data. While 

alternative estimates could be made and defended, reasonable variation in these parameters is 

unlikely to have a substantial impact on injury quantification. Approximately 70 percent of the 

oiled beach acreage (approximately 7 out of 10 acres; see Category A and B in our analysis) met 

the relatively rigorous Phase I criteria within several months of the spill, suggesting that recovery 

of any lost productivity was well underway relatively quickly. The remaining oiled acreage met 

Phase I criteria within approximately a year (or less). Overall, these data are indicative of a 

modest impact to beach productivity, particularly given the limited extent of oiling (roughly 10 

acres). 

Application of the recovery curves and service loss estimates specified in Exhibit 2 to 

relevant beach acreage results in a total injury of approximately 4.7 beach acre years of lost 

productivity. Although a portion of this injury occurs more than a year after the spill, we do not 

incorporate discounting in our analysis because its impact will be negligible.3

Restoration Scaling

We propose two options for restoring quantified beach injuries: (1) restoring an 

equivalent area of beach, and (2) restoring wetlands, using an appropriate conversion between 

beaches and wetlands based on their relative productivity. 

 3 Based on the methodology described in this analysis, approximately 77 percent of estimated service 

losses are restored within 14 months of the spill. After 18 months, service losses are 93 percent restored. Recovery is 

assumed to be complete within 30 months. 
For restoring an equivalent area of beach, we use the following assumptions: 

• Project implementation in 2003; 

• Linear recovery of services from zero percent at implementation to 100 

percent after five years (i.e., in 2008); and 

• Project life-span of 25 years. 

Using these parameters, each acre of restored beach provides approximately 14.5 beach 

acre years of services. Therefore, to restore the 4.7 beach acre year loss, approximately 0.32 

acres of beach are required.4

To calculate the acreage of restored wetland needed to address the injury to beach habitat, 

a translation factor must be determined that reflects the relative productivity of these habitats. 

For the purposes of this analysis, we assume a ratio of 5:1 (i.e., wetland habitat is five times 

more productive than beach habitat). While this ratio is consistent with the notion that wetlands 

are more productive than beaches, other ratios could be selected. As noted below, given the 

magnitude of injury, the required restoration will be small over a relatively wide range of 

translation factors. 

Based on a 5:1 translation factor, 4.7 acre years of lost beach productivity converts to 

approximately 0.94 acre years of lost wetland productivity.5

 Based on the scaling analysis 

performed for wetland injury, one acre of restored wetland will compensate for approximately 

16 acre years of lost wetland productivity (see main text of wetland injury report, page 25). 

Given this figure, approximately 0.06 acres of restored wetland would be sufficient to 

compensate for the quantified injury to beach productivity.6

Based these results, we do not believe the assumptions used in the injury quantification 

and scaling analyses warrant further refinement. Additional time and effort is unlikely to result in 

substantial changes to the results presented in this analysis. Even if analytic assumptions 

understate injury by a factor of five (which we do not believe to be the case), less than 0.5 acres 

of wetland (or less than one acre of beach habitat) would be required to compensate for the beach 

injury. Potential variation in translation factors (e.g., between 2:1 and 20:1) also would result in a 

restoration requirement of less than 0.5 acres of wetland. 

 4 0.32 acres of restored beach = 4.7 beach acre years of loss / 14.5 compensatory years per beach acre.

5

 0.94 wetland acre years of loss = 4.7 beach acre years of loss / 5. 

6

 0.06 acres of restored wetland = 0.94 wetland acre years of loss / 16 compensatory years per wetlands 

acre.
To: The Trustees and Responsible Parties 

From: Carl Hershner 

Date: 16 February 2002 

Re: Review of draft report 

“Injury to wetlands resulting from the Chalk Point Oil Spill” 

I have reviewed the subject report and the supporting materials provided me. In my 

opinion, the basic assumptions used in development of the injury assessment and the 

habitat equivalency analysis are appropriate and well within the bounds of general 

technical understandings. I believe the Trustees’ conclusions regarding both the degree 

of impact and appropriate restoration are reasonable and consistent with accepted 

practices in this type of event. 

The strengths of the report lie in the thoroughness of the field surveys, the specificity of 

injury class identification, and the use of best professional judgment. As a result of these 

elements, the derived assessment of wetland injury is clearly explained and easy to 

follow. The conclusions, estimating acre-years of both injuries sustained and potential 

for created wetland compensation, are straightforward and simple to understand. 

It is clear that a lot of work was undertaken to document and quantify the wetland 

impacts associated with this spill. The detailed reports of conditions immediately 

following the spill and during the subsequent cleanup and recovery phases are useful and 

provide an informative record for evaluation of the injury characterization. 

It is noteworthy, that most of the conclusions, and particularly the critical recovery 

curves, are primarily products of the professional judgment of the Wetland Assessment 

Team (WAT). A quick review of the quantitative data included in the report makes it 

clear that this data alone would not be not sufficient to lead precisely to the final 

conclusions regarding recovery curve forms. Best professional judgement was a critical 

element in developing the guidance necessary to conclude the study within the reported 

timeframe. This is true for a number of reasons. 

The types of intertidal wetlands impacted by the Chalk Point oil spill are quite common 

in the mid-Atlantic region. There are decades of research documenting characteristics of 

these systems, and one common finding is that at the square meter scale they can be 

exceptionally variable. For example, comparison studies using plant morphometrics 

typically require many sample replicates (often about 20/strata in meso/oligohaline 

wetlands) to produce means with useful variances. In the follow-up study of this spill it 

was clearly impractical to mount the sampling effort necessary to develop statistically 

significant comparisons or trends. 

In my opinion this is not a critical flaw in the report. It is a fact that it would require an 

enormous sampling program to be able to quantify responses in 11 different categories of 
oiled wetlands along with the necessary reference set. The only problem is that anyone 

reviewing the report and expecting the quantitative data to be a principal determinant of 

the conclusions, will be struck by several observations: 

1. The sampling program does not address all categories of modeled responses. There 

was no sampling in lightly oiled areas, and it is not clear what sampling is pertinent to 

the W1A sub-categories. 

2. Among categories sampled, many had no time series information. Not all categories 

were sampled both in 2000 and 2001, preventing any observation about trends. 

3. When time series information is present in the quantitative data, indicated changes do 

not (and generally can not because of sample number) provide strong evidence to 

support the final recovery models. For example, much of the reported morphometric 

data (i.e. %cover, stem counts, stem heights) appears counter to the expected trends in 

a recovery model, and the chemical analyses provide either no trend data or equivocal 

indications. (This is most probably due to the inherent variability of these systems, 

the variable nature of short-term recovery, and the limited sample/replication number. 

All of these factors combine to keep this information from being really useful in 

developing the slopes of recovery curves.) 

The fact of the matter is that the qualitative observational data was far more important to 

the final WAT conclusions. That information, combined with evidence from previous oil 

spill recovery studies and appropriate judgment, form the basis for the recovery model 

development. 

This is appropriate. This spill covered 80 acres of wetlands, less than half with “heavy” 

amounts, and most of that in long narrow bands. Previous studies have shown tidal 

wetlands to be fairly resilient to spilled oil except in extreme amounts. These studies 

provide the background necessary to estimate recovery curves. Based on that record, the 

assumptions used for models in this study seem very appropriate. (Developing recovery 

curves de novo would have required extensive sampling, potentially involving sampling 

impacts on approximately 1 acre of wetlands each year for 3 or more years). 

For this reason, I believe the report might benefit from being a little more direct about the 

utility and/or use of the quantitative data. It is useful as relative indicators of the degree 

of impact. It is of limited utility in recovery curve development. 

A second area I believe might benefit from a bit more explicit treatment is the rationale 

for assessment of wetland injury. The table from King et al. provides a generally 

accepted list of potential wetland services. The report, however, requires the reader to 

make some significant independent assumptions to get from that comprehensive list to a 

conceptual model explaining the WAT simplification to ecological service flows from 

“vegetation” and “soils.” 

I believe the simplification is appropriate. My point is that the report leaves some 

significant logic gaps in reducing all of the potential injuries suffered by the oiled 

wetlands and their potential users in the Chalk Point area, to an aerial vegetation metric 

and a soil contamination metric. I believe a concise description of which wetland 
services the WAT believes are most pertinent in the Chalk Point area, and how those 

services are potentially indexed by vegetation and soil contamination would be very 

useful. 

A second reason for suggesting some attention to the logic underlying the injury 

assessment is that the wetland replacement evaluation should be driven by a consistent 

application of the same conceptual model. In other words, assume the WAT determines 

that habitat services (nee “protection of ecological infrastructure”) is important. It would 

seem that there should be some thought given to the process by which a fringing tidal 

marsh provides this service, and how above ground vegetation and soil contamination 

affect that service. Those same assumptions should then be used to assess the capacity of 

replacement wetlands to provide the same service. 

I mention this, not because I believe the two metrics selected are inappropriate. Actually, 

I believe they are excellent choices, consistent with generally accepted procedures in this 

type of incident. The issue, I believe, is whether the wetland replacement evaluation will 

actually reflect the state of the science. The entire Habitat Equivalency Analysis is based 

on a concern for functional replacement rather than simple area considerations. So, the 

pertinent question in the Chalk Point case is whether the habitat services provided by 

oiled fringe and interior wetlands, are equivalent to the habitat services provided by a 

wetland excavated from uplands. This amounts to a landscape analysis. The state of the 

science is to recognize that wetlands vary in performance of functions, and that much of 

the variance is based on landscape setting. 

In short, I believe the report, and the conclusions, would be stronger if they were based 

on an explicit conceptual model of the wetland functions (services) injured and replaced. 

I do not believe this needs to be a highly sophisticated effort. It can be as simple as 

inclusion of a landscape position modifier in evaluation (e.g. level of habitat services/acre 

= % recovery of vegetation X factor for shape and position of wetland). 

Finally, I found it interesting that no where in the report is the type or amount of oil 

spilled identified. There is also nothing (that I could find) in the various supporting 

documents that actually indicate exactly where the pipeline leak occurred. It can be fairly 

easily deduced from the damage maps, but there is no specific designation of the point of 

origin. Perhaps these are not really pertinent in the injury assessment report. 

At your request I have also reviewed the appendices documenting the injury assessment 

and compensation calculations for the muskrat mortality and the beach injury. Based on 

the material presented and my experience, I believe the conclusions are appropriate. 

The calculations of muskrat densities are founded on both available site specific 

information and appropriate reference to the extant literature. The method used to derive 

the final acute mortality estimation is well explained and results in numbers that seem 

reasonable for the type of setting. I believe the decision to limit the injury assessment to 

acute mortality is defensible, and the underlying assumptions are all adequately 

conservative to minimize the potential for either significant over or under estimation. 
As with the marsh compensation planning, I believe the landscape position of the 

replacement wetlands will have some significant impact of the likelihood that 

compensation for lost muskrat habitat will in fact be accomplished. Evidence gathered in 

the injury assessment regarding the distribution of local muskrat populations would seem 

to provide some basis for addressing this issue (i.e. the difference in densities between 

Swanson Creek, Indian Creek and Trent Hall Creek). 

The beach injury assessment is somewhat more difficult to evaluate. I believe the 

conclusion that recovery will be relatively rapid, with comparatively minor cumulative 

impacts is reasonable based on the setting and available information from other studies. 

The method used to develop the service recovery estimate is well documented. I believe 

the assumptions are defensible and/or explicit. The proposal to use marsh replacement as 

compensation for service loss is interesting, and not unprecedented. There are a number 

of technical reasons for preferring this option to intertidal beach creation (e.g. conversion 

of existing intertidal habitats, and long term maintenance issues). In the absence of 

compelling rationales for alternative approaches, I believe the conclusions and proposed 

resolution are adequate. 

As a very minor point, I think the reader might be assisted in following all of the 

calculations if the units of some of the numbers reported in the text and footnotes were a 

bit more explicit. The calculations all appear to be correct, but it is easy to lose track in 

the welter of beach acre-years, marsh acre years, and acre-years per acre. Not all of these 

terms are as fully labeled as they might be. (In particular, see the final section of the 

beach appendix and the accompanying footnotes.) 

 

In conclusion, I believe the draft report and appendices represent an effective and 

appropriate assessment of the Chalk Point oil spill impacts and compensation needs. It 

appears to me that the Trustees have used available information and professional 

judgement in judicious combination. The approach and findings are consistent with 

accepted practices, and within reasonable bounds for the type and extent of the incident. 
 1 19 February 2002 

Trustees' Responses to Comments 

Chalk Point Wetlands Injury Report 

This note documents the Trustees' responses to the peer review comments on the wetlands injury 

report submitted by Dr. Carl Hershner on 16 February 2002. Excerpts of comments requiring a 

response are found below, italicized, followed by the action taken by the Trustees, if any. 

The sampling program does not address all categories of modeled responses. There was no 

sampling in lightly oiled areas, and it is not clear what sampling is pertinent to the W1A subcategories. 

The discussion of each injury category explains the need (or lack thereof) for field data to 

support the injury quantification (e.g., field data would not detect the injury expected for lightly 

oiled wetlands). The description of W1A on page 4 indicates the subdivision of this area into 

planted, ditched and planted, and areas of Scirpus spp. The corresponding sampling stations are 

shown on Exhibit 2 as "ditched heavy interior," "planted heavy interior," and "Scirpus spp. heavy 

interior."

Among categories sampled, many had no time series information. Not all categories were 

sampled both in 2000 and 2001, preventing any observation about trends. 

The reviewer is correct in noting that chemical analyses for some categories were not 

performed, particularly from the 2001 sampling event. The Trustees selected samples for 

chemical analysis based on their assessment of which samples would provide the most useful 

information for establishing soil recovery curves. 

Vegetation and benthic community sampling for all the injury categories were conducted 

in both 2000 and 2001. Note that the designation "N/A" in Exhibit 3 (vegetation data) indicates 

that the injury category did not exist. For example, there was no moderately oiled Typha 

shoreline category. 

When time series information is present in the quantitative data, indicated changes do not (and 

generally can not because of sample number) provide strong evidence to support the final 

recovery models. For example, much of the reported morphometric data (i.e. %cover, stem 

counts, stem heights) appears counter to the expected trends in a recovery model, and the 

chemical analyses provide either no trend data or equivocal indications. 

 During a teleconference on 1 February 2002, Dr. Hershner clarified that he did not mean 

to imply that the morphometric data conclusively demonstrates a lack of recovery, but rather that 

it does not provide positive evidence of recovery. Instead, the Trustees relied primarily on their 

collective experience and judgement regarding wetland recovery. This approach was deemed 

appropriate by the reviewer. 
 2 19 February 2002 

For this reason, I believe the report might benefit from being a little more direct about the utility 

and/or use of the quantitative data. It is useful as relative indicators of the degree of impact. It 

is of limited utility in recovery curve development.

 The following text was added to the first full paragraph on page 13: "The field data were 

used as relative indicators of the degree of injury, and to guide development of the recovery 

curves for each injury category." 

A second area I believe might benefit from a bit more explicit treatment is the rationale for 

assessment of wetland injury...I believe a concise description of which wetland services the WAT 

believes are most pertinent in the Chalk Point area, and how those services are potentially 

indexed by vegetation and soil contamination would be very useful. 

 A paragraph describing the choice of wetland services used in the injury assessment was 

added to page 13, immediately following the quotation from Strange et al. (2001). It begins: 

"Two metrics were selected to represent the lost services and functions of the wetlands..." 

It would seem that there should be some thought given to the process by which a fringing tidal 

marsh provides this service, and how above ground vegetation and soil contamination affect that 

service. Those same assumptions should then be used to assess the capacity of replacement 

wetlands to provide the same service...So, the pertinent question in the Chalk Point case is 

whether the habitat services provided by oiled fringe and interior wetlands, are equivalent to the 

habitat services provided by a wetland excavated from uplands...In short, I believe the report, 

and the conclusions, would be stronger if they were based on an explicit conceptual model of the 

wetland functions (services) injured and replaced. I do not believe this needs to be a highly 

sophisticated effort. It can be as simple as inclusion of a landscape position modifier in 

evaluation (e.g. level of habitat services/acre = % recovery of vegetation X factor for shape and 

position of wetland). 

 The Trustees agree that an adjustment for differences in services provided by the injured 

and restored wetlands is appropriate. As described on page 25 of the injury report, the Trustees 

assume that the restored wetlands will provide a maximum of 80 percent of the services of the 

injured wetlands. The Trustees believe this is a conservative value, and will monitor the 

restoration project to verify this assumption. Appropriate action will be taken if significant 

differences are found. 

Finally, I found it interesting that no where[sic] in the report is the type or amount of oil spilled 

identified. 

 This information has been added to the opening paragraph of the report. 
 3 19 February 2002 

There is also nothing (that I could find) in the various supporting documents that actually 

indicate exactly where the pipeline leak occurred. 

 The location of the pipeline break is now marked on Exhibit A3 in Appendix A. 

As a very minor point, I think the reader might be assisted in following all of the calculations [in 

Appendix E] if the units of some of the numbers reported in the text and footnotes were a bit 

more explicit. The calculations all appear to be correct, but it is easy to lose track in the welter 

of beach acre-years, marsh acre years, and acre-years per acre. Not all of these terms are as 

fully labeled as they might be. (In particular, see the final section of the beach appendix and the 

accompanying footnotes.) 

 

 Additional unit descriptors have been added to Appendix E, particularly in footnotes 4 

through 6.