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ARMY . NE DAM OS
Cont, \0'7

Reconnaissance Survey of the
Historical Bridgeport Disposal Site

August 1992

Disposal Area
Monitoring System
DAMOS

D A|M O §$

Contribution 107
January 1996

US Army Corps
of Engineers
New England Division

REPORT DOCUMENTATION PAGE
OMB No. 0704-0188

Public reporting concern for the collection of information Is estimated to average 1 hour per response Including the time for reviewing instructions, searching existing
data sources, gathering and measuring the data needed and correcting and reviewing the collection of information. Send comments regarding this burden estimate or
any other aspect of this collection of information including suggestions for reducing this burden to Washington Headquarters Services, Directorate for information
Observations and Records, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302 and to the Office of Management and Support, Paperwork Reduction
Project (0704-0188), Washington, D.C. 20503.

1. AGENCY USE ONLY (LEAVE BLANK) B. REPORT DATE B. REPORT TYPE AND DATES COVERED
January 1996 Final report

. TITLE AND SUBTITLE 6. FUNDING NUMBERS
Reconnassiance Survey of the Historical Bridgeport Disposal Site, August 1992

6. AUTHOR(S)
Eliabeth Caporelli, Sandy Browning

8. PERFORMING ORGANIZATION REPORT
NUMBER

SAIC- C109

. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
Science Applications International Corporation
221 Thrid Street

Newport, RI 02840

0. SPONSORING/ MONITORING AGENCY
REPORT NUMBER

DAMOS Contribution
Number 107

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
US Army Corps of Engineers-New England Division
424 Trapelo Road

Waltham, MA 02254-9149

11. SUPPLEMENTARY NOTES
Available from DAMOS Program Manager, Regulatory Division
USACE-NED, 424 Trapelo Road, Waltham, MA 02254-9149

12a. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release; distribution unlimited

2b. DISTRIBUTION CODE

13. ABSTRACT

A reconnaissance survey of the historical Bridgeport Disposal Site was performed on August 4, 1992 to document on-site
physical and biological conditions. The site was closed in 1977 after receiving about 4.2 million m3 of dredged material over a twenty-five
year period. Until this survey, the Bridgeport Disposal Site had never been monitored under the Disposal Area Monitoring System
DAMOS) Program. This report presents the results of the one-day field effort involving side-scan sonar and Remote Ecological
Monitoring of the Seafloor (REMOTS) surveys.

—

The distribution of relic dredged material at the site was mapped using side-scan sonar. Thirteen REMOTS stations then
situated in areas where the side-scan sonar records indicated the presence or absence of dredged material disposal mounds, to assess
he areal extent and state of reworking of existing dredged material, to examine present benthic biological conditions at the site, and to
incorporate these results into future management plans for other disposal sites.

Results of the side-scan survey indicated that well-defined mounds of dredged material do not exist at the historical Bridgeport
Disposal Site; however, relic dredged material is present throughout the site in low relief. Analysis of the REMOTS photographs revealed
hat the site has experienced some physical and biological disturbances yet, overall, supports a relatively healthy benthic community.
his result suggests that the Long Island Sound disposal sites currently in use have encouraging future biologically. Because of the large
areal extent of historical dredged material present at the site, however, any future assessment of the biological and chemical state of the
historical dredged material should include additional REMOTS photography and sediment sampling for chemical analyses.

14. SUBJECT TERMS
side scansonar REMOTS DAMOS Bridgeport Disposal Site

15. NUMBER OF PAGES
16. PRICE CODE

17. SECURITY CLASSIFICATION OF REPORT 18. SECURITY CLASSIFICATION OF THIS 9. SECURITY CLASSIFICATION OF 20. LIMITATION OF ABSTRACT
Unclassified PAGE ABSTRACT

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RECONNASSIANCE SURVEY OF THE
HISTORICAL BRIDGEPORT
DISPOSAL SITE
AUGUST 1992

CONTRIBUTION #107

January 1996

Report No.
SAIC-C109

Submitted to:

Regulatory Branch
New England Division
U.S. Army Corps of Engineers
424 Trapelo Road
Waltham, MA 02254-9149

Prepared by:
Elizabeth Caporelli
Sandy Browning

Submitted by:
Science Applications International Corporation
Admiral's Gate
221 Third Street
Newport, RI 02840

(401) 847-4210

US Army Corps
of Engineers
New England Division

TABLE OF CONTENTS

Page

NET SIM @ REVAIB IEE Spee apes ees Fetes Urner ala bis Vise: ae iaiae DU eee Oa eg ill

PISIBO@ORFEIGWRIES wae Mgr ss tt aie or Ge Bg Sas) aya lee Meena ee ee al ae IV

EUG CUD VE TSW NINUARY iy es pas So ee ees sk ke Se i es eee ae nee a Vv

1 Oe IN ROD WETION as ee ees 8 renee ed io VS Ee ee rg ieee 1

1.1 History of Disposal Activity at the Historical Bridgeport Disposal Site .. 1

25 Oe VEEL OD) Sycreate se atest AUN, cate an Es sa cn Mee Mg OE Ay eo Re 5

DEM MIN AVIS ALLO Mepatere eae nti tu) Ga Bars aint, Ch ce case May By a ael sumer ued rks ter ae 5

DED ee A SIGE-SCAnle SONAL SURVEV iii. 25 GusHAGL Ge @ Sodio TeS Gesen Bia teags eae ee 5

2.3 REMOTS® Sediment-Profile Photography .................... B)

Si(0). | RUSS) G0 bed RGSS. Mi ot 2h ce Reece ONE A re RD aE ER A ORE ote Sete Nigar 9

SP MME SIGE SCAM SONAT ta oh x een ig beat istics Ss ses eu yh Rnd eee eee ON 9

3:2) REMODS2 Sediment-Profile Photopraphy) 2). 450-50 0000000 00 9

Sad si SCdimentyheatures: iis cae ane ae ons Np 12

522-2) Suttaceyboundary, Roughness) 9444-504 see eee 12

3.2.3 Apparent Redox Potential Discontinuity Depth ............. 15

82-4. sintaunalySuccessionalistagersgnis oie eae ne eee 15

3 2-5 OFZ anism-SeGiment INGexaa ssc eee ioe iy nee Wey (6)

3.2.6 Apparent Relic Dredged Material ................... beel6

3.2 GeneralObservations: acs ate 2 aie Ske ee ee 20

a0 Mee DES CUSSION 5.32 ein Se hue & Bis ees etd MOE Se ne ce Saale Cah ah Sua One 21

3.0 CONCLUSIONS AND RECOMMENDATIONS .................... 23

Gr Oma ERIEN GES mPa rmeiy aibs 5 teaes acs Se are eink Se eer ea ee 24

INDEX

APPENDIX

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Table 1-1.

LIST OF TABLES

History of Dredged Material Disposal Activity at the Bridgeport
Disposal Site

LIST OF FIGURES

Figure 1-1.

Figure 2-1.
Figure 2-2.
Figure 3-1.

Figure 3-2.

Figure 3-3.
Figure 3-4.
Figure 3-5.

Figure 3-6.

Figure 3-7.

Figure 4-1.

Page
Long Island Sound and the historical Bridgeport Disposal Site......... 2
Vessel track of the side-scan sonar survey and locations of the selected
FOE MOMS SiStatiOms cc sy ee s. 20 5) figse sue cas hese, ed © a ad Ea eee 6
Bridgeport Disposal Site side-scan sonar survey mosaic ............. 7
Example of a side-scan sonar record from the western portion of
lane 2 showing the smooth, featureless image produced by the ambient
SilCDOLOMIE re eRe en ate he ton cole 5 race es rans gene: PER er 10

Example of a side-scan record from the eastern portion of lane 7 exhibiting
mottled texture and low-relief patches of high-reflectance areas on low-
reflectancesambientbomome syria i ese eee 11

Bridgeport Disposal Site REMOTS® photograph from Station B21/C
showing surface shell fragments and mud clasts................. 13

Example of a side-scan record (lane 9) showing evidence of bottom
(rawlingeen ence ee ee Sonnet Noa tke ee rere ene oe ae 14

Bridgeport Disposal Site REMOTS® photograph from Station B28/B
exhibiting Stage I on einfaunae ere oe tr Ce cae ee eee 17

Relic dredged material distribution at the Bridgeport Disposal Site mae 18

Bridgeport Disposal Site REMOTS® photographs from the ambient
bottom, Station B22/A, and on dredged material, Station B25/B ...... 19

Median OSI values at Bridgeport Disposal Site REMOTS® stations... . . 22

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EXECUTIVE SUMMARY

A reconnaissance survey of the historical Bridgeport Disposal Site was performed on 4
August 1992 to document on-site physical and biological conditions. The site was closed in
1977 after receiving about 4.2 million m° of dredged material over a twenty-five-year period.
Until this survey, the Bridgeport Disposal Site had never been monitored under the Disposal
Area Monitoring System (DAMOS) Program. This report presents the results of the one-day
field effort involving side-scan sonar and Remote Ecological Monitoring Of The Seafloor
(REMOTS®) surveys.

The distribution of relic dredged material at the site was mapped using side-scan sonar.
Thirteen REMOTS® stations were then situated in areas where the side-scan sonar records
indicated the presence of dredged material. These data were used to identify the presence or
absence of dredged material disposal mounds, to assess the areal extent and state of reworking
of existing dredged material, to examine present benthic biological conditions at the site, and
to incorporate these results into future management plans for other disposal sites.

Results of the side-scan survey indicated that well-defined mounds of dredged material
do not exist at the historical Bridgeport Disposal Site; however, relic dredged material is
present throughout the site in low relief. Analysis of the REMOTS® photographs revealed that
the site has experienced some physical and biological disturbances yet, overall, supports a
relatively healthy benthic community. This result suggests that the Long Island Sound disposal
sites Currently in use have an encouraging future biologically. Because of the large areal
extent of historical dredged material present at the site, however, any future assessment of the
biological and chemical state of the historical dredged material should include additional
REMOTS® photography and sediment sampling for chemical analyses.

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10 INTRODUCTION

The Bridgeport Disposal Site is an inactive disposal site in Long Island Sound (Figure 1-
1). It is located approximately 5 nmi south-southwest of the entrance to Bridgeport Harbor,
Connecticut. The disposal site is 2 nmi long and 1 nmi wide (the long axis of which runs east-
west) and is centered about 41°04.4’ N latitude and 73°12.6’ W longitude. The site was used
frequently for dredged material disposal over a period of twenty-five years from 1953 to 1977.
Until now, the site was never monitored under the DAMOS Program. The DAMOS Program
began in 1977 around the time that site use was discontinued.

On 4 August 1992, Science Applications International Corporation (SAIC) conducted
side-scan sonar and REMOTS® reconnaissance surveys at this historical site to document
existing site conditions. The surveys were performed in one day to obtain information
concerning onsite physical and biological conditions. The goals of the 1992 survey were

° to search for the existence of relic disposal mounds;

e to assess the current status (i.e., areal extent, topography, amount of reworking, etc.) of
relic dredged material;

e to examine present benthic biological conditions at the site; and

e to predict future site conditions at DAMOS disposal sites currently in use.

The side-scan sonar survey was performed first, to identify potential relic disposal
mounds 1 to 5 m in elevation. The identification of relic dredged material using side-scan sonar
was used to guide the placement of REMOTS® sampling locations. Following field operations,
the REMOTS® sediment-profile photographs were analyzed for physical and biological
parameters to assess onsite conditions. These data may provide a better understanding of the
long-term behavior of dredged material and may be used to predict the future of Long Island
Sound disposal sites that are presently in use.

1.1 History of Disposal Activity at the Bridgeport Disposal Site

The Bridgeport Disposal Site was active from 1953 to 1977. In this twenty-five-year
period, the disposal site received more than 4.1 million m? of material dredged from multiple
locations (Table 1-1). The dredged material source areas extended over a 70 mi stretch of
coastline from Newall Harbor to the Thames River in New London. The majority of the
material, 1,987,960 m*, was dredged from Bridgeport Harbor and Black Rock Harbor and
deposited at the disposal site between 1960 and 1963.

Before the mid 1970s, harbor sediments underwent minimal testing prior to dredging and

disposal. Moreover, while the Bridgeport Disposal Site was in use, the majority of disposal
records do not list the sources of dredged material released at the site. The records do

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

Table 1-1

History of Dredged Material Disposal Activity at the Bridgeport Disposal Site

Year Volume Disposed (m?

42,053
44,500
663,565
246,965
9,098
451
301,252
823,914
1,250,121
116,984
18,350
3,303
464,303
24,850
5,505
765
19,650
1,529
0
11,469
24,391

4,404.
84,575
23,882

Total 4,185,879

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

indicate that samples for geophysical testing were taken from various points in Bridgeport
Harbor to delineate areas that would require blasting and those that would require dredging.
The materials found suitable for dredging were characterized as fine sand.

In the late 1970s, an effort was made to condense the number of disposal sites within
Long Island Sound. During this process, the Bridgeport Disposal Site was closed in 1977.
The remaining twenty-seven disposal sites were reduced to four regional disposal sites. The
current regional sites are the Western Long Island Sound Disposal Site (WLIS), the Central
Long Island Sound Disposal Site (CLIS), the New London Disposal Site (NLON), and the
Cornfield Shoals Disposal Site (CSDS).

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

2.0 METHODS
2.1 Navigation

The 4 August 1992 survey was performed onboard the research vessel R/V UCONN
owned and operated by the University of Connecticut. Positioning and navigation were
accomplished using Northstar 800 LORAN-C and Differential Global Positioning System
(DGPS) MX4200 receivers interfaced to an integrated navigation system. Positional data were
serially routed from the receivers to SAIC's Portable Integrated Navigation and Survey System
(PINSS). PINSS consists of an IBM-compatible 386 computer capable of processing data
from multiple sensors. A video display of the vessel's position aids the helmsman in
navigating to a particular station location or maintaining a specific course. Positional data are
recorded on diskette and may be redundantly charted on a plotter. Navigational procedures are
discussed in greater detail in SAIC's QA/QC Manual (SAIC 1990a).

2.2 Side-scan Sonar Survey

Side-scan sonar data were acquired using a Klein Model 400 Graphic Sonar Recorder
and a Model 422 dual frequency towfish capable of detecting bottom features to a resolution of
less than 1 m. The survey was performed using a single 100 kHz frequency transducer. The
side-scan recorder was configured to produce an 85 m instrument sweep to optimize the
resolution. A 1600 m by 3800 m survey grid centered about the midpoint of the disposal site
was established to characterize the entire disposal site. Eight tracklines 200 m apart were
situated in an east-west trend to parallel the depth contours in the vicinity of the disposal site.

The speed of the vessel was maintained at 3 knots while the sonar (i.e., towfish) was
towed approximately 11 m from the seafloor. During the survey, the navigation system
generated a plot of the ship's position with respect to the target survey lanes (Figure 2-1).
Time was automatically annotated on the plot every 5 minutes. At the same time, the sonar
record was annotated with time so that targets present on the sonar record could be transferred
(compensating for cable layback) to the real-time navigation plots following the survey. The
resulting mosaic of acoustic targets was used to establish the locations of the REMOTS®
stations (Figure 2-2).

2.3 REMOTS® Sediment-Profile Photography

Thirteen REMOTS® stations were visited during the 4 August 1992 survey (Figure 2-
1). Twelve of the thirteen stations were clustered in the northeast quadrant of the site where
the presence of dredged material was suspected. Two other stations were situated in the
western half of the site to characterize areas of suspected dredged material deposits there.
Film from the REMOTS® camera was developed on the research vessel to verify that the
photographs collected during the one-day sampling effort were usable. Three replicate

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1 992

photographs were collected at each of twelve stations, while six replicate photographs were
taken at Station B34.

Following field operations, REMOTS® biological and physical parameters were
measured directly from color transparencies using a video digitizer and computer image
analysis system. Sediment-profile analysis and interpretation are formal and standardized
techniques (Rhoads and Germano 1982, 1986). Customized software allows the measurement
and storage of data from as many as 21 different variables for each REMOTS® photograph.
All data were edited and verified by a senior-level scientist before being approved for final
interpretation. REMOTS® parameters measured in this survey included sediment type, prism
penetration depth, surface boundary roughness, presence of mud clasts, apparent redox
potential discontinuity (RPD) depth, infaunal successional stage, presence of sedimentary
methane, organism-sediment index (OSI), and bedforms. REMOTS® data for each photograph
are included in the Appendix. A more detailed description of these parameters and the image
analysis methods are available in SAIC Report No. 240 (SAIC 1990b).

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

3.0 RESULTS
3.1 Side-scan Sonar

The historical Bridgeport Disposal Site, based on the results of the side-scan survey, is
mottled with relic, low-relief dredged material deposits. The natural or ambient bottom in
the western portion of the site exhibits a predominantly smooth, low-reflectance, silty texture
(Figure 3-1). Numerous low-relief, high-reflectance features, inferred to be dredged
material, are present throughout the disposal area but are concentrated in the central portion
of the site (Figure 3-2). The mottled, patchy appearance of these strong acoustic reflectors,
or targets, is characteristic of dredged material deposits and is due to alternating patches of
high- and low-reflectance materials. Strong reflectance of dredged material deposits relative
to the ambient, smooth bottom is a function of increased acoustic backscattering at the surface
of the deposit. This backscattering is likely related to increased microtopography and surface
roughness (i.e., coarse-grained texture) of dredged material in comparison to smooth,
ambient sediments. While storm activity may reduce the topographic relief of credged
material mounds, net deposition in Long Island Sound is slow, approximately 1 mm/yr.
Coarse-grained dredged t..aterial covered by a thin surface deposit may bc so1ie- 117 1etected
with side-scan sonar wli~: nas a small degree of bottom penetration. !

The mottled textire has been observed in other side-scan sonar surveys of «‘:-dged
material disposal sites on the West Coast and is caused by one or more of the follow‘ng
processes or events (SAIC 1990c, 1990d):

e physical and/or biological reworking of the deposit, produeiue a sinooth, low-
reflectance signature;

e disposal of sandy material with some cohesive silts;

e random spacing of individual disposal operations of cohesive silty material; or

e transport and deposition of sediments over the dredged material.

Recently deposited dredged material will typically form a localized, circular high-reflectance
pattern in side-scan sonar traces (SAIC 1987, 1990c). The mottled appearance and low relief
of dredged material in this survey suggest that the acoustic reflectivity of the material has
decayed due to physical or biological reworking of the deposit or that natural deposition over
the last fifteen years has covered portions of the relic dredged material.

3.2 REMOTS® Sediment-Profile Photography
The physical and biological parameters discussed in this section pertain to those areas

sampled using REMOTS® sediment-vertical profiling. These areas are restricted to the
northeastern and southwestern quadrants of the site. For purposes of discussion, the data

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Figure 3-1. Example of a side-scan sonar record from the western portion of lane 2
showing the smooth, featureless image produced by the ambient silt bottom

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Figure 3-2. Example of a side-scan record from the eastern portion of lane 7 exhibiting
mottled texture and low-relief patches of high-reflectance areas on low-
reflectance ambient bottom

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

obtained from the REMOTS® photographs will be applied to the site in general based on the
assumed presence of relic dredged material throughout the site (see above). The results of
the REMOTS® image analysis are presented in the Appendix.

3.2.1 Sediment Features

Grain size ranges are estimated visually by comparing the sediment image to the
Udden-Wentworth size classes. The Udden-Wentworth size class system is a standard grain
size measurement ranging from greater than 4 phi (silt/clay) to less than -1 phi (gravel). A
major mode (the most common grain size) and the range of grain sizes are estimated.

The Bridgeport Disposal Site is dominated by sediments with a major mode of 1 to
>4 phi, i.e., medium sand or finer. Thin surface layers of coarse sand were also observed
among three stations: B27, B30, and B32.

Some stations suiting relatively high modal grain sizes (1 or less) also contained
shell fragments and mudclasts. Shell fragments were present in 25 percent of the Bridgeport
photographs, and mudclasts were present in 50 percent of .he REMOTS® photographs
(Figure 3-3). Mud clasts are typically associated with the reduction of topographic relief due
to physical and biological processes. While fine-grained sediment is reworked into ball
structures and concentrated in topographic lows, coarse-grained materials, including shell
fragments, are concentrated at the crest of the gradually decaying mound (SAIC 1984).
Localized disturbances, such as trawling activities, may also disturb relic dredged material
and initiate the formation of small mud clasts. Evidence of trawling was noted on the side-
scan records (Figure 3-4).

Both oxidized and reduced mudclasts were observed at the Bridgeport Disposal Site.
While the presence of reduced mud clasts in an aerobic setting is sometimes indicative of
recent origin (Germano 1983), the mud clasts in this survey were well rounded, suggesting
the clasts were not recently formed. The clasts may have been generated from underlying
reduced sediments that were brought to the surface by relatively recent disturbances.
Disturbances could have been physically or biogenically induced.

3.2.2 Surface Boundary Roughness

Boundary roughness is the vertical distance between the highest and lowest points of
the sediment-water interface. Boundary roughness values at Bridgeport ranged from 0.17 to
5.46 cm with a mean boundary roughness value of 1.4 cm. The surface relief is both
physically induced, reflecting either bottom disturbance (scour depressions, mud clasts) or
natural bedforms (sand ripples), and biogenically created, including infaunal burrows: or
mounds. Physical processes accounted for most of the relief at the historical Bridgeport
Disposal Site.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

Figure 3-3. Bridgeport Disposal Site REMOTS® photograph from Station B21/C showing
surface shell fragments and mud clasts. The large burrow may be that of a
lobster. Scale = 1.0.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

Mud clasts were observed at ten stations, and ripples were noted at six stations.
Biological processes accounted for relief measured at only two stations. The majority of
replicate photographs, however, demonstrated low surface relief, pointing to the absence of
recent disposal activity.

3.2.3 Apparent Redox Potential Discontinuity Depth

The Apparent Redox Potential Discontinuity (RPD) depth is the depth of the upper
oxygenated sediment layer. This depth is related to the rate of supply of molecular oxygen
into the bottom and the consumption of that oxygen by the sediment and associated
microfauna. The boundary between high-reflectance, aerobic sediment and underlying gray to
black sediment is termed the apparent RPD.

Mean apparent RPD values ranged from 1.26 to 3.13 cm and were evenly distributed
above and below 2.0 cm. There was no obvious spatial pattern in the distribution of RPD
values among stations. Shallow RPD depths have been documented under the DAMOS
Program in areas affected by past dredged material disposal (e.g., SAIC 1984). RPD values
measured at the Mill-Quinnipiac River (MQR) disposal mound located in the Central Long
Island Sound Disposal Site ranged from 0.54 to 2.00 cm in August of 1992. Although
disposal operations at the MQR mound ceased in 1983, recolonization of the mound by
ambient benthos has been relatively slow compared to other disposal mounds within CLIS.
The wide range of RPD values measured among stations showing dredged material at the
Bridgeport Disposal Site suggests that bioturbation in the area surveyed may have been
disrupted by surface disturbance (i.e., trawling).

In addition, the reflectance contrasts across the RPD boundary were typically not
distinct and were similar for both ambient sediments and relic dredged material. Low RPD
contrasts indicate the lack of relatively tel inputs of organic-rich material, such as recently
deposited dredged material.

3.2.4 Infaunal Successional Stage

Infaunal successional stages refer to the sequential appearances of benthic infauna
assemblages following seafloor disturbances, such as dredged material disposal or a major
storm event (Rhoads and Germano 1982, Revelas et al. 1987). The sequence proceeds from
the colonization of disturbed areas by Stage I pioneering assemblages (i.e., near-surface, tube-
dwelling polychaetes). Stage I organisms are eventually replaced by Stage II infaunal deposit
feeders (i.e., shallow-dwelling bivalves or tubicolous amphipods), followed by Stage III head-
down deposit feeders. The recolonization sequence generally proceeds to Stage III
assemblages as long as the bottom is not redisturbed.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

Both Stage I and Stage III infaunal successional stages were observed at the Bridgeport
Disposal Site. Stage I infauna were frequently observed in the same photograph as Stage III
head-down deposit feeders (as evidenced by feeding voids) (Figure 3-5). At three stations,
Stage I benthos were observed exclusively, and two of these stations were interpreted to be
ambient. The area, overall, was apparently occupied by Stage III infaunal benthos which
typically inhabit low disturbance regimes.

3.2.5 Organism-Sediment Index

The Organism-Sediment Index (OSI) values reflect both the apparent RPD depths and
the infaunal successional status of a REMOTS® photograph. OSI values can range from -10
(no apparent macrofaunal life and methane gas present) to 11 (deep apparent RPD, evidence of
mature macrofaunal assemblages, and no apparent methane). Based on other studies, SAIC
has determined that OSI values less than or equal to +6 are indicative of a “disturbed”’ benthic
environment (i.e., erosion, dredged material disposal, hypoxia, etc.; Rhoads and Germano
1986). OSI values ranged from +2 to +11 for all replicates with a mean value of +7 for all
stations. Among stations, there was no apparent pattern of OSI values. Those stations where
dredged material was observed displayed mean OSI values ranging from +3.3 to +10. Mean
OSI values for apparent ambient sediments ranged from +3.3 to +9.7. In comparison to
mean OSI indices measured in the MQR mound in 1992 (+3.to +7), the range of mean OSI
values observed in the Bridgeport Disposal Site fell within and slightly above those measured
in the MQR mound. These data suggest disturbances within the Bridgeport Disposal Site were
heterogeneous in their distribution.

3.2.6 Apparent Relic Dredged Material

Relic dredged material was detected in nine (B21, B28, B32, B33, B27, B29, B30,
B34, and B25) of the 13 stations occupied (Figure 3-6). Dredged material was recognized by
its coarse-grained, slightly reduced texture (Figure 3-7). Shell fragments were also observed.
Relic dredged material did not contrast sharply with ambient sediments in terms of sediment
color, reflectance, apparent RPD depth, or infaunal successional stage. Dredged material
layers ranged in thickness from 12 to 18 cm and frequently exceeded the camera prism
penetration depth. This indicates either that dredged material has remained in layers of this
thickness in the area surveyed or that relatively thin dredged material layers have been buried
with time by natural sedimentation. Two stations, B22 and B23, were characterized by
ambient sediment (Figure 3-6). Both possible relic dredged material and ambient sediment
were observed in some, but not all, of the replicate photos collected at the two westernmost
stations, B26 and B24.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

Figure 3-5. Bridgeport Disposal Site REMOTS® photograph from Station B28/B exhibiting
Stage I on III infauna. In this photograph, dredged material is greater than the

camera prism penetration depth. Note the backfilled infaunal burrow.
Scale = 1.0.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

a eee
20

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3.2.7 General Observations

Neither the presence of methane nor apparent low dissolved oxygen was observed in
the REMOTS® photographs. The lack of methane suggests the area surveyed was not
affected by organic loading.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

4.0 DISCUSSION

Despite the large amount of material (approximately 4.2 million m*) disposed at the
historical Bridgeport Disposal Site prior to 1977, side-scan sonar used during the 1992 survey
revealed no dredged material mounds. Rather, numerous low-relief, high-reflectance
features, inferred to be dredged material, were present throughout the disposal area. The
most plausible cause for the wide distribution of dredged material was the fact that, over a
twenty-five-year disposal period, a target disposal buoy was never deployed. .

The habitat quality of infaunal benthos within the disposal site was, in general, stable.
The average OSI for all stations was +7, and the presence of Stage III deposit-feeding
assemblages indicated the benthic environment was relatively healthy. Among the 13 stations
analyzed using REMOTS®, however, OSI values were not consistently high, nor were Stage
III fauna present at every station. The OSI values at Stations B22, B23, B29, and B30 were
less than +6 due to the presence of Stage I fauna only and the relatively low RPD depths
(Figure 4-1). Two of these stations (B22 and B23) were stations where no dredged material
was present (Figure 3-6), indicating no correlation between the presence of dredged material
and OSI. In the remaining stations, the OSI values were high, ranging from +7 to +11,
because Stage III organisms were present. High OSI values occurred even though the RPDs
for these stations were relatively shallow. Although REMOTS® data indicated a healthy
benthic community overall, recolonization was somewhat patchy in the area surveyed. The
patchy distribution of Stage III assemblages may be caused by bottom trawling activities that
-disrupt the sequence of infaunal recolonization, or by long-term impact from contaminated
dredged material. Both the scattered pattern of trawl marks and dredged material deposits
are evident in the side-scan record at Bridgeport (Figure 2-2).

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

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5.0 CONCLUSIONS AND RECOMMENDATIONS

One important goal of the survey was to use the results to predict future site
conditions of existing disposal sites within Long Island Sound. The historical Bridgeport
Disposal Site is a suitable model for comparison. Like the present sites in Long Island
Sound, the Bridgeport Disposal Site received a large amount of dredged material from many
sources over a period of two decades and is subjected to the same biological and physical
processes experienced by other Long Island Sound disposal sites. Some of the dredged
material disposed at the Bridgeport Disposal Site, however, would probably have been
deemed unsuitable for unconfined open-water disposal using current standards.

The August 1992 survey of the historical Bridgeport Disposal Site indicated that relic
dredged material was distributed throughout the site in low relief. The benthic habitat
quality was relatively high despite the fact that materials disposed at the site between 1953
and 1977 were not rigorously screened (and were potentially contaminated) prior to open-
water disposal. Currently, active Long Island Sound disposal sites are subject to dredged
material characterization screening procedures which are intended to be environmentally
protective. Because of these management practices, the future biological health of these
sites is likely to be maintained.

The August 1992 reconnaissance survey at the Bridgeport Disposal Site succeeded in
providing a cursory look at the physical nature of relic dredged material and the overall
quality of the biological conditions at a historical disposal site. While the need for further
surveys seems unwarranted, additional surveying would provide a much better assessment
of the area's biological status and the location and characteristics of the relic dredged
material. Since the dredged material appears to occur over the entire site, a REMOTS®
survey using a systematic sampling design (i.e., orthogonal grid or radiating transects) is
recommended to provide the needed coverage for a comprehensive site evaluation. In
addition, because the distinction between ambient sediment and dredged material was
sometimes not clear in the REMOTS® photographs, any future survey should include an off-
site reference station for purposes of comparison. Finally, sediment sampling for chemistry
analyses would help to better understand the long-term biological response to any existing
chemical contamination at the site.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

6.0 REFERENCES

Germano, J. D. 1983. Infaunal succession in Long Island Sound: animal-sediment
interactions and the effects of predation. Ph.D. dissertation, Yale University, New
Haven, CT.

Revelas, E. C.; Germano, J. D.; Rhoads, D. C. 1987. REMOTS® reconnaissance of benthic
environments. Coastal Zone '87: Proceedings of Conference, WW Div/ASCE/May
26-29, Seattle, WA, pp. 2069-2083.

Rhoads, D.C.; Germano, J. D. 1982. Characterization of organism-sediment relations using
sediment-profile imaging: an effective method of Remote Ecological Monitoring of
the Seafloor (REMOTS™ System). Mar. Ecol. Prog. Ser. 8: 115-128.

Rhoads, D.C.; Germano, J. D. 1986. Interpreting long-term changes in benthic community
structure: a new protocol. Hydrobiologia 142: 291 - 308.

SAIC. 1984. Results of monitoring studies at cap sites #1, #2, and the FVP Site in Central
Long Island Sound and classification scheme for the management of capping
procedures. DAMOS Contribution No. 38. US Army Corps of Engineers, Waltham,
MA.

SAIC. 1987. Environmental information in support of site designation documents for the Foul
Area Disposal Site - Volume I: Technical Report No. 93. Submitted to US Army
Corps of Engineers, New England Division, Waltham, MA. --

SAIC. 1990a. QA/QC plan for the DAMOS Program. SAIC Report No. SAIC-90/7573&232.
: Submitted to US Army Corps of Engineers, New England Division, Waltham, MA.

SAIC. 1990b. Canaveral Harbor Dredged Material Disposal Site Resurvey. SAIC Report
No. 240. US EPA contract No. 68-C8-0061. US Environmental Protection Agency,
Athens, GA.

SAIC. 1990c. Survey of the ocean dredged material disposal site (LA-5) off San Diego,
California. Final Report submitted to US Environmental Protection Agency, Region
IX, under Contract No. 68-C8-0061.

SAIC. 1990d. Survey of the ocean dredged material disposal site (LA-2) off Los Angeles,

California. Final Report submitted to US Environmental Protection Agency, Region
IX, under Contract No. 68-C8-0061.

Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

aerobic 12, 15
benthos iv, v, 8, 12, 15-17, 20,
2p 228)
amphipod 15
bivalve 15
deposit feeder 15, 17
macro- 17
polychaete 15
bioturbation 15
feeding void 17
Black Rock Harbor 1
boundary roughness 8, 12
buoy 20
disposal 20
capping 23
Central Long Island Sound (CLIS)
4, 15, 23
FVP 23
MQR 15, 17
Norwalk (NOR) 1
colonization 15
deposition 9
‘dispersive site
Cornfield Shoals 4
disposal site
Central Long Island Sound
(CLIS) 4, 15, 23
Cornfield Shoals 4
New London 1, 4
Western Long Island Sound
(WLIS) 4
dissolved oxygen 17
erosion 17
feeding void 17
grain size 12
habitat 20, 22
hypoxia 17
methane 8, 17
mud clast iv, 8, 12, 13
recolonization 15, 20
REMOTS®
boundary roughness 8, 12

INDEX

Organism-Sediment Index
(OSD iv, 8, 17, 20,
21
redox potential discontinuity
(RPD) 8, 15, 20
REMOTS® ii, iv, v, 1, 5, 6, 8, 9,
W235 IO, 37,
19-23, 25
camera 5
RPD
REMOTS®;redox potential
discontinuity (RPD)
Si, 1S), i7/, 240
RPDs
REMOTS®;redox potential
discontinuity (RPD)
20
sandy 1, 9
sediment
clay 12
gravel 12
sand 4, 12
silt iv, 9, 10, 12
sediment sampling v, 22
side-scan sonar iv, v, 1, 5-7, 9-12,
14, 20
succession 23
pioneer stage 15
successional stage 8, 15, 17

survey

REMOTS® v, 22
side-scan v, 9
topography 1, 9, 12
micro- 9
trawling iv, 12, 14, 15, 20

APPENDIX

Historical Bridgeport Disposal Site
REMOTS® Data, August 1992

eee Boundary Boundary Grain Size | Grain Size
Loc.| Sta. /Rep. Roughness} Roughness type ‘ete vee Range

B21 /A = 7a 2.07 Physical enlntorss<40

2 B21 He 14.47 2.03 |Physical > oe 1to>4

B21 11.02 4.02 {Biological >4 1to>4

B22 ~ 12.71 0.21 Indeterminate >4 1to>4

B22 /B 12.78 0.76 |Physical >4 2to>4

B22 /C 15.53 2.2 Physical >4 1jto>4

it 13.71 1.18 |Physical >4 1to>4

B23 /B 14.89 0.68 |Physical >4 1to>4

BP |B23 /C 15.23 0.76 Physical >4 1to>4

B24 /A 12.44 1.18 |Physical >4 1to>4

B24 /B 16.63 0.34 |Physical >4 1to>4

| B24 /C 13.79 2.28 Physical >4 1to>4

B25 /A 15.34 0.55 {Physical >4 1to>4

a B25 /B 18.36 0.85 |Physical >4 1to>4

BP |B25 /C 15.02 1.78 Physical >4 ito>4

BP |B26 /A 15.49 1.44 {Physical >4 1to>4

BP |B26 /B 15.27 0.17 |Physical > 4 1to>4

BP |B26 /C 16.65 1.9 Physical >4 1to>4

B27 /A 13.05 5.46 |Physical >4 Oto>4

B27 /B 17.45 0.21 |Physical >4 Oto>4

BP |B27 /C 15.34 0.8 Physical >4 2to>4

BP |B28 /A 16.48 0.63 |Physical >4 1to>4
BP |B28 /B 17.07 0.97 | Physical >4

BP |B28 /C 14.45 S77 Physical >4

14.7 0.21 Physical —>4

10.3 4.78 |Physical >4

12.54 1.23 Physical >4
el B30 /A 14.22 0.68 |Physical >4 1to>4
B30 /B 16.33 0.42 |Physical >4 Oto>4
B30 /C 14.39 0.51 Physical >4 Oto >4
B32 /A 17.09 1.27. |Physical >4 Oto >4
B32 /B 13.33 0.68 {Physical >4 1to>4
B32 /C 15.57 0.93 | Physical >4 1to>4

= B33 /A 13.31 1.06 Physical >4 1to>4
B33 /B 15.59 1.14 |Physical > 4 1to>4
er B33 x 11.59 0.59 Physical >4 1to>4

ioc | RPD et Mud Clast Mud Clast | Mud Clast
[B21 - Fe areOkay

eet ere (Els Ge

._ {BP {B21 0.34 Oxidized

eles [s(2 (2 [i bm

BP |B22 /B ts 034 a i

BP |B22 /C

BP B23 /A 1.16
tle l: Tee
B23 /C 1.12 Reduced

B25 /A
HiHHEisia
B25 /C 1.04

B26 /A 2.28

B26 /B ae

B26 /C
efesle(:(:[* P=

B27 /B 127
BP |B27 /C 3.05
BP |B28 /A
Perel ita
BP |B28 /C 3.24 0.89 |Reduced
BP |B29 /A 1.88 0.42 {Oxidized
BP |B29 /B oe 0.42 |Reduced
BP |B29 /C 0.17 Reduced
BP |B30 /A me ae
BP |B30 /B 281
BP {B30 /C ae oe
B B32 /A 2.01
ceelelili lee
BP |B32 /C 3.36
BP |B33 /B 3.45

B33 /C 3.17 028 Bot

ener
Oxidized

Reduced

—— Sta. ee Penetration Successional Stage \SI_| > Pen.

B24 /A Stage | ON Stage Ill 9
B24 /B Stage | ON Stage Ill 10
B24 /C Stage Ill 10
B25 /A Stage | ON Stage Ill 9

B25 /B 8 79 Stage | ON Stage Ill _— 6

B25 /C Stage Ill 7

B26 /A Stage | ON Stage Ill 9
B26 /B Stage | ON Stage Ill 11
B26 /C Stage | ON Stage Ill 9

P |B27 /A 15.78 Stage i ON Stage Ill
P |B27 /B 17.56 Stage |
P {B27 /C 15.74 Stage |

BP |B28 /A 16.8 Stage | ON Stage Ill 11

BP |B28 /B 17.56 Stage | ON Stage Ill 9

BP |B28 /C 16.33 Stage | ON Stage Ill 10

=e B29 /A 14.81 Stage !
B29 /B 12.69 Stage |
B29 /C 13.16 Stage |

sr B30 /A 14.55 Stage |
B30 /B 16.54 Stage |
B30 /C 14.64 Stage | ON Stage Ill

4 /A 17.73 Stage | ON Stage Ill Bae
B32 /B 13.67 Stage | 4
B32 /C 16.04 Stage | ON Stage Ill 10
B33 /A 13.84 Stage |
Hi
BP
BP

B33 /B 16.16 Stage Ill

B33 /C 11.89 Stage |

Stage | ON Stage Ill

— DM and/ a Fresh
hoe

Bot A [DM > Pet ‘Sand/Mud Bed a KD

B21 DM > Pe Sand/Mud Bed ara

B22 2 Sand/Mud
; Re Sera

B22 /C Sand/Mud Bed Form

B23 /A Sand/Mud Bed Form

B23 /B sed 0

B23 /C Sand/Mud (0)

B24 /A 0 Bed Form
per erly
B24 /C Sand/Mud
-|B25 /A Sand/Mud
2 ee
“4 Sand/Muc

Lae ie

Sand/Mud
Sand/Mucd
Sand/Mud
DM > Pe Sand/Mud
DM > Pe pees
DM > Pe
DM > Pe Sai
DM > Pe
DM > Pe el
DM > Pe Sand/Mucd
DM > Pe Sand/Mud ;
B3sO /C DM > Pe Sand/Mud 0
B32 /A DM > Pe Sand/Mud
B32 /B DM > Pe Sand/Mud
B32 /C DM > Pe Sand/Mud
B33 /A DM > Pe Sand/Mud
B33 /B DM > Pe ae
ae B33 /C DM > Pe

Bed Form| 0O
Bed Form| 0O

Satake
0
Sand/Mud
0

B24 /A
B24 /B

Shell Lag
0
0

0
stim te tite
B29 /C 0
B30 /A Poor Sort
inn
B30 /C 0
B32 /A
B32 /B

wz [six on|tyaoes| _—onaatconmens

cut through ox mudclasts_ relic dm
soft sed small mc shell fragment lobster burrow?
numerous small mc on surface looks ambient

looks ambient
ambient sand and shell fragments over silt clay
ambient some slope

rippled ambient? sand shell fragments over silt cla

shell fragments rippled

looks ambient

rippled sand and shell fragments over >4 relic dm?

small voids on right

patchy rpd layer darker mud on top shell fragments

rippled burrowing anemone

ambient

possible relicdm somesiope shell frag

relic dm sloped surface

relic dm

relic dm or possibly ambient

relic dm

relic dm large burrow

Stage Ill relic? some slope

relic dm _ relic Stage III? numerous small mc

relic dm sloped surface patchy rpd

some slope numerous small mc

relic dm _ rippled

relic dm relic Stage Ill shell frags

shell fragments on surface burrowing

rippled shell fragments on surface

sloped surface relicdm

some slope

relic dm and relic Stage Ill some sire

rippled relic DM?

relicdm rippled surface some shell fraq Ss

layer of surface organic matter relicdm

relic dm

relic dm?

organic matter layer on surface due to burrowing excavation}

some slope polychaete visible

some slope

Ow
vilv0 U

uv Uv

B
B
B
B
BP
B
B
B

oO oO;w
uv Ul U

ee «

N a (ae ep —
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we
pee
ai J
cf » —_ = e
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oir a ’ os a vd ua

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exo Dees

Ce geet Ey,

ral

if
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7 mn eee

;

pit
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ar nem arn

A's st - dyn
yirgo,

% »

ad 6 liege {
i

——_

Shiller

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> ee

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