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

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

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INDEX

APPENDIX

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LIST OF TABLES

History of Dredged Material Disposal Activity at the Bridgeport Disposal Site

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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

4

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

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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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Reconnaissance Survey of the Historical Bridgeport Disposal Site, August 1992

12

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

15

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

18

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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

ee ee eee 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

21

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

24

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

ae

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

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