Monitoring Cruise at the Massachusetts Bay Disposal Site November 1988 - January 1989

Disposal Area Monitoring System DAMOS

Contribution 73 May 1990

us Army Corps of Engineers New England Division

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Monitoring Cruise at the Massachusetts Bay Disposal Site November 1988 - January 1989

6. AUTHORCSI

7. PERFORMING ORGANIZATION .. AMIISI AND AODRESSIUI a. PER'ORMING ORGANIZA nON REPORT NUM.U

Science Applications International Corporation 221 ThiId Street SAIC-89/7558 & C/9 Newport, RI 02840

g. SPONSORINGi MONITORING .. GENa .... M((SI A .. D AODRfSS(£SI 10. SPON50AINGi MONITORING AGINa RIPORT Nu .... a

u.s. Army Corps of Engineers - New England Division 424 Trapelo Road DAMOS Contribution No. 73 Waltham, MA 02254-9149

11. SU'I'UMINTARY HOTES

Available from DAMOS Program Manager, Regulatory Division USACOE-NED, 424 Trapelo Road, Waltham, MA 02254-9149

120. OISTIUIUTlONI"V .. ILAIIUTY STATEMENT 1210. DISTRlaUTION COOl

Approved for public release; distribution unlimited.

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The Massachusetts Bay Disposal Site (MBDS), referred to in previous studies as the Foul Area Disposal Site (FADS), is located at 420 2?7 Nand 7(1' 34.0 W.

Field operations were conducted at MBDS from 28 October to 18 January 1989, and consisted of precision bathymetric and REM~ sediment~piofile bathymetric surveys around the point where the disposal buoy "FDA" was located during the 1987-88 and 1988-89 disposal seasons. At the "FDA" buoy at MBDS, dredged material deposited since the January 1987 bathymetric and REM01'S8 surveys occurred as a circular mound, centered slightly east of the buoy, with gradually sloping sides and a maximum thickness of, 0.3 meters at the apex. Based on changes in bathymetry, the radius of the mound was estimated to be between 50 and 100 meters, while the REM~ results extended the detected radius to 300 to 3SO meters. Based on these combined results, it was estimated that 61,054 m of dredged material had accumulated at the "FDA" buoy since January 1987. The disposal mound was situ~ted well within the disposal site boundaries. The prediction that sediment disposed since the January 1987 surveys would add to the existing mound without increasing the diameter was confirmed.

A REMOTS8 survey was performed at the "A" buoy to assess the benthic community recovery at this former disposal point. Although a minimal amount of dredged material was disposed at the "A" buoy since January 1987, it seemed to have little or no effect on the benthic conditions in this region. The RPD depths and OS] values were similar to those at the reference stations, and a high abundance of Stage III organisms was present. The prediction that the benthic community at the "A" buoy stations would have an abundance of Stage III taxa similar to the reference stations was confirmed. However, given the apparent lack of significant recent disturbance in this area, Stage 1 organisms did not occur in greater abundance compared to the reference stations.

I .. SIltI§6S rUMS 15. NUMIIR O. PAGiS I Precision bathymetric surveys 43 . Massachusetts Bay Disposal Site Dredged material mounds

REMOTS Benthic recolonization stages 16. PIUCI '001 I Sediment profile photography RPD depths

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MONITORING CRUISE AT THE MASSACHUSETTS BAY DISPOSAL SITE

NOVEMBER 1988 - JANUARY 1989

CONTRmUTION #73

May 1990

Report No. SAIC- 89/7558&C79

Submitted to:

Regulatory Branch New England Division

U.S. Army Corps of Engineers 424 Trapelo Road

Waltham, MA 02254-9149

Submitted by:

Science Applications International Corporation Admiral's Gate

221 Third Street Newport, RI 02840

(401) 847-4210

US Anny Corps 1-_____________________ of Engineers -.. ______________________ New England Division _ ..

1.0

2.0 2.1 2.2

3.0 3.1 3.2 3.3

4.0

5.0

6.0

TABLE OP CONTENTS

INTRODUCTION • · . • . · • • •

METHODS . . . . · . • . · • • Bathymetry and Navigation • • REMOTSiit Sediment-Profile Photography • •

RESULTS • • • • • • • • • • • · . . . . . • • 13Cl1:l1)(IREat:~l' • • • • • • • • • • • •• •• REMOTSiit Sediment-Profile Photography • • • • REMOTSiit Sediment-Profile Photography at the "A" Buoy. • •

DISCUSSION • •

CONCLUSIONS • • • •

REFERENCES • • • •

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2 2 2

3 3 4

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Figure 1-1.

Figure 2-1.

Figure .3-1.

Figure 3-2.

Figure 3-3.

Figure 3-4.

Figure 3-5.

Figure 3-6.

Figure 3-7.

Figure 3-8.

Figure 3-9.

Figure 3-10.

Figure 3-11.

LIST OF FIGURES

Map of bathymetric survey lanes used at MBDS, indicating the location of the "FDA" and "A" buoys, as well as the MASTER MBDS survey encompassing the entire area.

Location and designation of REMOTS® stations (triangles) at MBDS, January 1989.

Bathymetric contour chart of the area surrounding the "FDA" buoy at MBDS, November 1988.

Bathymetric contour chart of the area surrounding the "FDA" buoy at MBDS, January 1987.

Depth difference (in meters) contour map based on comparison of the January 1987 and November 1988 precision bathymetric surveys at the "FDA" buoy.

Bathymetric contour chart of the entire MBDS area, November 1988.

3-D contour plot of the entire MBDS area, November 1988.

Map showing the distribution of dredged material based on REMOTS® photography at the "FDA" buoy, January 1989.

REMOTS® photographs from station 500E (A) and 300S (B) showing the presence of apparent relict dredged material on the flanks of the mound.

REMOTS® photographs from station 100E (A) and 200W (B) showing a "chaotic" mixture of silts, fine sands and sands intermixed with clay in the recently deposited dredged material.

REMOTS® photographs from station CTR (A) and 100S (B) showing overconsolidated clay clasts and rubble at the surface and limited camera penetration.

REMOTS® photographs from station 250SW (A) and 200N (B) showing less consolidation and deeper camera penetration with more stratification.

Map of sediment grain size major mode (in phi units) at MBDS, January 1989.

Figure 3-12.

Figure 3-13.

Figure 3-14.

Figure 3-15.

Figure 3-16.

Figure 3-17.

Figure 3-18.

Figure 3-19.

Figure 3-20.

Figure 3-21.

Figure 3-22.

LIST OF FIGURES (CONTINUED)

Frequency distribution of small-scale surface boundary roughness values for all replicates at the reference stations and at the FDA buoy stations where fresh dredged material was present, January. 1989.

Frequency distributions of apparent RPD depths for all replicates at the reference stations and the FDA buoy stations where dredged material was present, January 1989.

ThE! mapped distribution of apparent RPD depths (cm), averaged by station, at the FDA buoy in January 1989.

The mapped distribution of infaunal successional stages at the FDA buoy, January 1989.

A large feeding void at depth indicates the presence of stage III organisms at station 500N (A), while the REMOTS~ photographs from station 300E (B) and 200S (e) show stage I on III organisms at the disposal site,'

The distribution of averaged by station, 1989.

Organism-Sediment Indices, at the FDA buoy in January

Frequency distributions of Organism-Sediment Indices for all replicates at the reference stations and at the disposal site stations where dredged material was present, January 1989.

REMOTS~ photographs from station 200E (A) and 100E (B) showing the presence of dredged material with clay clasts evident at the surface and at depth.

Frequency distributions of small-scale surface boundary roughness values for all replicates at both the "A" buoy and reference site stations at MBDS, January 1989.

Frequency distribution of apparent RPD depths for all replicates at both the "A" buoy and reference site stations at MBDS, January 1989.

The mapped distribution of apparent RPD depths (cm) , averaged by station, at the "A" buoy at MBDS, January 1989.

Fiqure 3-23.

Fiqure 3-24.

Fiqure 3-25.

Fiqure 3-26.

Fiqure 4-1.

LXST OF FXGURES (CONTXNUED)

The mapped distribution of in faunal successional stages at the "A" buoy at MBDS, January 1989.

REMOTSf!> photographs from the vicinity of the "A" buoy showing dense stage III tubes at the surface (photo A) and surface tubes along with a feeding void at depth (photo B).

Frequency distributions of Organism-Sediment Indices for all replicates at both the reference and "A" buoy stations, January 1989.

The distribution of averaged by station, January 1989.

Organism-Sediment at the "A" buoy

Indices, at MBDS,

Depth difference contour chart with the thick contour line indicating the extent of recently­deposited dredged material around the "FDA" buoy as determined by REMOTSf!> photography.

MONITORING CRUISE AT THE MASSACHUSETTS BAY DISPOSAL SITE

NOVEMBER 1988 - JANUARY 1989

1.0 INTRODUCTION

The Massachusetts Bay Disposal site (MBDS), referred to in previous stUdies as the Foul Area Disposal site (FADS), is located approximately 22 nautical miles (nm) east-northeast of the entrance to Boston Harbor and 12 nm south-southeast of Gloucester, Massachusetts. The site consists of a 2 nm diameter circle centered at 42' 25.7 Nand 70' 34.0 W.

Field operations were conducted at MBDS from 28 October 1988 to 18 January 1989. The field operations consisted of precision bathymetric and REMOTS® sediment-profile photographic surveys around the point where the disposal buoy ("FDA") was located during the 1987-88 and 1988-89 disposal seasons (Figure I-1). The last previous surveys occurred at this location in January 1987. The objective of the 1988-89 surveys was to delineate the distribution and thickness of the dredged material deposit resulting from disposal activities which have been on-going since the previous surveys. A second precision bathymetric survey was conducted over the entire MBDS disposal site to provide detailed bathymetric information for the entire area. A REMOTS® sediment­profile photographic survey also was performed at the "A" buoy to assess the benthic community recovery at this former disposal point.

The 1988 sampling plan at the MBDS "FDA" buoy was designed to verify the following predictions:

• sediment disposed during the 1987-88 and the first half of the 1988-89 disposal seasons would add to the existing sediment mound without increasing the size (diameter) of the previously detected mound, and

• the center of this deposit would be detectable with bathymetry

The REMOTS® survey at the "A" buoy was designed to verify the following predictions:

• the benthic community around the buoy would follow expected recolonization patterns with an abundance of Stage III organisms similar to the reference stations, and

• stage I organisms would be present in higher densities than at the reference stations.

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2.0 METHODS

2.1 Bathymetry and Navigation

The precision navigation required for all field operations was provided by the SAIC Integrated Navigation and Data Acquisition System (INDAS). This system uses a Hewlett-Packard 9920 series computer to collect position, depth, and time data for subsequent analysis as well as providing real-time navigation. positions were determined to an accuracy of ±3 meters from ranges provided by a Del Norte Trisponder System. For the present survey, shore stations were established in Massachusetts at known benchmarks at Marblehead Light and Eastern Point Light. A detailed description of the navigation system and its operation can be found in DAMOS contribution #48 (SAIC, 1985).

The depth was determined to a resolution of 3.0 cm (0.1 feet) using an Odom DF3200 Echotrac Survey Recorder with a narrow­beam 208 kHz transducer. The speed of sound was determined from the water temperature and salinity data measured by an Applied Microsystems CTD probe. The speed of sound and the transducer depth were entered into the fathometer to adjust the depth values being transmitted to the computer. During analysis, raw bathymetric data were standardized to Mean Low Water by correcting for changes in tidal height during the survey. A detailed discussion of the bathymetric analysis technique is given in DAMOS Contribution #48 (SAIC, 1985).

The bathymetric survey conducted at the MBDS "FDA" buoy on 4 November 1988 encompassed a 1200 x 1200 m grid with 25 m lane spacing, centered at coo~dinates 42" 25.095 Nand 70" 34.423 W (Figure 1-1). This same grid was used in the previous bathymetric survey of this area in January 1987. Between 5 and 19 November 1988, the master bathymetric survey was conducted over a 4000 x 4000 m grid with 50 m lane spacing, centered at 42" 25.695 Nand 70" 33.999 W (Figure 1-1).

2.2 REMOTS® Sediment-Profile Photography

REMOTS® photography was used to detect the distribution of thin (1 to 20 cm) dredged material layers, map benthic disturbance gradients, and monitor the process of infaunal recolonization on and adjacent to the disposal mounds at the "FDA" and "A" buoys. A detailed description of REMOTS® photograph acquisition, analysis, and interpretative rationale is given in DAMOS contribution #60 (SAIC, 1989).

The REMOTS® stations occupied on 16-18 January 1989 at the "FDA" buoy were the same ones occupied during the last survey in January 1987. Three replicate photographs were obtained at each

2

of 39 stations situated around the disposal buoy in a cross-shaped pattern. stations were spaced 100 m apart and extended 600 m to the north, 800 m to the south, 900 m to the east, and 700 m to the west of center (Figure 2-1). stations were also located in each of the four quadrants at 250 and 500 meters NE, NW, SE, and SW. Additionally, thirteen REMOTS& stations arranged in a cross-shaped pattern and spaced 100 m apart were occupied at each of three reference locations to allow comparisons between ambient and on­site conditions. These reference stations were located at 42· 22.7 N, and 70· 34.6 W (station FG23); 42· 20.0 N, and 70· 28.0 W (station SE-REF); and 42· 24.686 N, and 70· 32.814 W (station 18-17; Figure 2-1).

The REMOTS& stations around the "A" buoy were occupied on 11 and 16 January 1989; the station grid was centered at 42· 25.7 Nand 70· 35.04 W. Three replicate photographs were obtained at each of 39 stations arranged in a cross-shaped pattern, identical to the grid used for the REMOTS& survey at the "FDA" buoy (Figure 2-1).

3.0 RESULTS

3.1 Bathymetry

A comparison of the November 1988 and January 1987 prec1s1on bathymetric surveys (Figures 3-1 and 3-2, respectively) revealed that an acoustically-detectable layer of dredged material had been deposited at the "FDA" buoy in the time between the two surveys. In November 1988, the minimum depth at the disposal point was approximately 88.50 meters (Figure 3-1), compared to a depth of 88.75 meters in January 1987 (Figure 3-2). A depth difference contour chart (Figure 3-3) indicates that the deposit had a maximum thickness of 0.3 meters and was centered slightly east of the buoy. Depth differences on the order of 20 cm (i.e., approaching the limits of detection in this comparison of the 1988 and 1987 surveys) occurred within a 50 to 100 meter radius of the center of the deposit.

For the 1200 x 1200 m survey area, comparison of the depth matrices from the 1987 and 1988 bathymetric surveys resulted in a volume difference calculation of 18,087 m3 of material deposited since the January 1987 survey. Examination of the disposal logs indicated that an estimated 140,000 m3 of material was deposited at this location between the January 1987 and November 1988 surveys.

The second precision bathymetric survey performed at MBDS provided detailed bathymetric data for the entire disposal site and revealed the overall topographical features (Figure 3-4). The disposal site is located in a trough running northwest to southeast, just to the southwest of Stellwagen Bank. Extreme

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changes in depth of up to 20 meters over a 60 meter distance were found on the slopes of the bank (Figure 3-5).

3.2 REMOTS® Sediment-Profile Photography

Dredged material layers presumed to be recently-deposited (i.e., since the January 1987 survey) were evident in the REMOTS® photographs from stations surrounding the disposal buoy (Figure 3-6). The precise boundaries of the "new" mound were difficult to determine due to the presence of relict dredged material at most of these same stations (Figure 3-7). This relict material was the result of disposal operations which have been ongoing at this location since November 1985.

The apparent "fresh" dredged material consisted of a chaotic mixture of silts, fine sands and sands intermixed with clay (Figure 3-8). The REMOTS® photographs from the stations located closest to the point of disposal (CTR, 100S, lOON, out to 200E, and out to 300W) showed over-consolidated clay clasts and occasional rock rubble at the surface which limited camera penetration (Figure 3-9). At other stations, the dredged material appeared to be less consolidated, exhibiting more stratification and allowing deeper camera penetration (Figure 3-10). At these stations, the mixture of silts, fine silts, and sands was less chaotic with only an occasional buried clay clast, reflecting heterogeneity in the composition of the disposed material. Again, the thickness of the recently-deposited layers often could not be measured accurately because of the lack of a clear marker between the "fresh" dredged material and underlying relict material.

The majority of REMOTS® grid and reference stations consisted of silt-clay sediments (~4 phi, Figure 3-11). Many of the stations having either relict or fresh dredged material exhibited grain size major modes from fine sand (4-3 phi) to silt­clay (~4 phi). The majority of small-scale surface boundary roughness values at the stations around the "FDA" buoy where dredged material was present ranged between 0.6 to 1.8 cm, while the majority of values at the reference stations ranged from 0.0 to 0.6 cm (Figure 3-12). Boundary roughness values at the "FDA" buoy stations having dredged material were significantly greater than those at the reference stations (Mann-Whitney u-test, p < 0.001). Not surprisingly, this greater surface boundary roughness reflected the physical bottom disturbance related to disposal operations.

The frequency distribution of mean apparent RPD depths for the "FDA" buoy stations where dredged material was present was right-skewed with a major mode at the 1.0 cm class interval, while the distribution of RPD depths for the reference stations showed a normal distribution with a major mode at the 5.0 cm class interval (Figure 3-13). The reference station RPD values were

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significantly deeper (Mann-Whitney u-test, p < 0.001). RPD depths less than 2.0 cm occurred at stations immediately around the buoy, generally corresponding to that area of the disposal site having recently-deposited dredged material (Figure 3-14).

Only three stations located at or near the point of disposal had evidence of only stage I organisms (lOON, CTR, 100S); stage III taxa were evident at all but five of the reference stations (Figure 3-15). At the remainder of the disposal site stations, there was evidence of stage III taxa (i.e., head-down deposit-feeding infauna) in at least one of the replicate photographs (Figure 3-16). In January 1987, 66% of the replicate photographs (N = 92) at the "FDA" buoy REMOTS® stations showed evidence of stage III taxa, compared to 75% (N = 108) in the present survey. These proportions of stage III taxa present in 1987 and 1989 were not found to be significantly different (Chi­squared Test, p > 0.1). However, at the reference stations, 68% of the 1989 replicates (N = 57) showed evidence of stage III taxa, compared to 94% (N = 32) in January 1987. These proportions of stage III taxa present were found to be significantly different (Chi-squared Test, p < 0.01).

The pooled reference station OSI values were significantly higher than those at the "FDA" buoy stations where dredged material was present (Mann-Whitney u-test, p < 0.001). The mapped distribution of OSI values confirms this statistic: OSI values less than or equal to +6 occurred at stations in the immediate vicinity of the disposal buoy (Figure 3-17). Frequency distributions also showed higher values at the reference stations (Figure 3-18). However, the OSI values for all stations at the disposal site and for the reference stations had not changed significantly since the January 1987 REMOTS® survey (Mann-Whitney u-test, p = .0527 for the disposal site and p = .0608 for the reference stations).

3.3 REMOTS® Sediment-Profile Photography at the "A" BUOY

It was estimated that 6,700 m3 of dredged material were deposited at the "A" buoy since the January 1987 survey at MBDS. In most of the January 1989 REMOTS® photographs, it was difficult to determine whether the observed dredged material was fresh or relict (Figure 3-19). The photographs from eight of the stations showed no evidence of dredged material. Given the small volume of disposed sediment, most of the dredged material evident at the remainder of the stations was assumed to be relict.

All of the REMOTS® stations consisted of silt-clay sediments (~ 4 phi). Boundary roughness values at the "A" buoy stations were significantly greater than those at the reference stations (Mann-Whitney u-test, p < 0.001): more values at the "A"

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buoy stations fell within the higher class intervals (Figure 3-20) •

Mean apparent RPD depths at the "A" buoy stations were not significantly different from the reference stations (Mann­Whitney u-test, p = 0.162; Figure 3-21). Mean RPD depths less than 3.0 cm occurred at stations close to the buoy, corresponding to that area which most likely was affected by disposal operations during the past year (Figure 3-22).

None of the stations within the "A" buoy grid had only stage I taxa present; all showed evidence of stage III taxa in at least one of the replicate photographs (Figures 3-23). The stage III taxa included head-down deposit-feeding infauna, as evidenced by feeding voids at depth, as well as relatively large, tube­dwelling polychaetes visible at the sediment surface (Figure 3-24) • At the "A" buoy stations, 82% of the replicates showed evidence of stage III taxa, compared to 68% at the reference stations.

The frequency distributions of OSI values at the "A" buoy and at the reference stations both had major modes at +11 (Figure 3-25); there was no significant difference between these two groups (Mann-Whitney u-test, p = 0.686). with the exception of station 300W, all the "A" buoy stations had OSI values greater than +6 (Figure 3-26).

4.0 DISCUSSION

The objective of the combined REMOTSe and precl.sl.on bathymetric surveys was to delineate the extent and topography of the dredged material deposit resulting from disposal at the "FDA" buoy since the previous surveys in January 1987. As predicted, the bathymetric survey revealed an accumulation of dredged material within a 50 to 100 meter radius of the disposal buoy (Figure 3-3). The REMOTSe photographs confirmed the existence of dredged material layers beyond the boundaries determined by bathymetry. REMOTSe photography indicated that the roughly circular area around the buoy covered by recently-deposited (i.e., since the January 1987 survey) dredged material had an approximate radius of 300 to 350 meters (Figure 4-1). Some fresh dredged material probably occurred beyond this radius but, as was mentioned earlier, the precise boundaries of the new portion of the mound were difficult to determine due to the difficulties in distinguishing between fresh and "relict" dredged material layers at several of the stations on the mound flank. This coincides with the results found in the last REMOTSe survey in January 1987. In the previous survey, the radius of dredged material was determined to be approximately 350 to 400 meters, with no definitive boundary found to the north. This confirms the prediction that the sediment deposited at the buoy since the 1987 survey would add to the existing mound without increasing the diameter.

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The REMOTS* results showed the new mound had a larger radius than indicated by the bathymetry results mainly because of the camera's ability to detect thin layers on the flanks of the deposit. Such layers were below the limits of detection by precis.ion bathymetry and were therefore unaccounted for in the volume difference calculation. When the area representing the flanks of the mound was digitized and measured, it was found to occupy 306,908 mZ• A reasonable estimate for the average thickness of the fresh dredged material layers in this area was 14 cm, based on the actual thickness of such layers at several flank REMOTS* stations (see Figure 3-6). This results in an estimated volume of 42,967 m3 of material on the mound flanks not accounted for in the bathymetric depth difference calculation. Adding this to the depth difference volume estimate of 18,087 m3 results in a final total of 61,054 m3 of dredged material detected on the bottom using the two techniques.

The final total volume estimate of 61,054 m3 is less than the scow disposal log volume estimate of 140,000 m3 of disposed material. The scow disposal log volume is assumed to be an overestimate due to the significant amount of interstitial water associated with the dredged material in the barges and the self­compaction of the material after it is disposed. Tavolaro (1984) determined an apparent decrease in volume of 40.7% when comparing the scow log volume and the volume estimated by comparing pre- and post-disposal bathymetric surveys in 30 meters of water. However, the Tavolaro study does not include estimates to account for the greater spreading of the material at increased depths, such as those at MBDS (average 88 to 92 meters). During disposal at MBDS, wider distribution of the falling sediment is expected because the greater depth offers more time for entrainment of water. This entrainment facilitates the dispersal of the more flocculent material which may be carried farther away by currents as a result of the increased descent time. Until a comprehensive mass balance study is performed at these greater depths and methods are developed to easily and accurately measure scow disposal volumes, attempts to reconcile the bathymetric volume difference and scow disposal log volume estimates almost certainly will result in a discrepancy. At other DAMOS disposal sites, dredged material volumes calculated from bathymetric data consistently have been less than the scow log volumes (SAIC, 1987 and SAIC, 1989).

Small-scale surface boundary roughness was significantly higher at the "FDA" disposal site stations compared to the reference stations, reflecting the physical bottom disturbance related to past and recent disposal activities. Likewise, RPD depths at the disposal site stations were significantly shallower than those at the reference stations. While Stage III taxa were present at the disposal site stations in a relatively high percentage of the REMOTS* photographs (75%), most of the stage III organisms were also associated with Stage I taxa.

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stage III organisms appeared in a significantly higher percentage of REMOTS® photographs at the reference stations in 1987 than in 1989 (94% in 1987 and 68% in 1989). This most likely was due to a sampling artifact; only one reference area was sampled in 1987, with many replicate photographs from one location, while three reference areas were sampled in 1989 with much greater areal coverage. The 1987 reference data may be somewhat biased because only one reference location was sampled.

Although not significantly different, the percentage of stage III organisms in replicate REMOTS® photos at the "FDA" buoy stations also showed an increase since the January 1987 survey (66% in 1987 compared to 75% in 1989) despite ongoing disposal activity. Likewise, overall site averages for mean RPD and OSI values increased over the same time period. These results suggest a steady recovery in the benthic ecosystem at the disposal site in the time between the two surveys.

The objective of the REMOTS® survey at the "A" buoy was to assess the benthic community recovery at this former disposal point. The REMOTS® survey showed evidence of dredged material at all but eight of the stations. stage III taxa were present at the "A" buoy stations in a high percentage of the REMOTS® photographs (82%) • This was higher than the percentage of stage III taxa present at the reference stations (68%), demonstrating a fairly complete benthic ecosystem recovery at this disposal location. The prediction that stage I organisms would be in greater abundance at the "A" buoy stations than at the reference stations was not confirmed, suggesting that the disposal impacts were not as great as expected. Given the small volume of material deposited, coupled with the healthy rate of recolonization at the "A" buoy since establishment of the "FDA" disposal location, there was not an increased abundance of opportunistic taxa at the "A" buoy.

5.0 CONCLUSIONS

At the "FDA" buoy at MBDS, dredged material deposited since the January 1987 bathymetric and REMOTS® surveys occurred as a circular mound, centered slightly east of the buoy, with gradually sloping sides and a maximum thickness of 0.3 meters at the apex. Based on changes in bathymetry, the radius of the mound was estimated to be between 50 and 100 meters, while the REMOTS® results extended the detected radius to 300 to 350 meters. Based on these combined results, it was estimated that 61,054 m3 of dredged material had accumulated at the "FDA" buoy since Januar~ 1987. This was less than the disposal log estimate of 140,000 m of disposed material, but such discrepancies are expected because of the inaccuracies of scow estimates, the compaction of the dredged material on the bottom following disposal, the significant amount of water associated with the dredged material in the barges,

8

and greater spreading of the material in the deeper waters at MBDS. The disposal mound was situated well within the disposal site boundaries. The prediction that sediment disposed since the January 1987 surveys would add to the existing mound without increasing the diameter was confirmed.

A REMOTS4I survey was performed at the "A" buoy to assess the benthic community recovery at this former disposal point. Although a minimal amount of dredged material was disposed at the "A" buoy since January 1987, it seemed to have little or no effect on the benthic conditions in this region. The RPD depths and OSI values were similar to those at the reference stations, and a high abundance of stage III organisms was present. The prediction that the benthic community at the "A" buoy stations would have an abundance of stage III taxa similar to the reference stations was confirmed. However, given the apparent lack of significant recent disturbance in this area, stage I organisms did not occur in greater abundance compared to the reference stations.

6.0 REFERENCES

SAIC. 1985. Standard operating Procedure Manual for DAMaS Monitoring Activities, Volume 1. us Army Corps of Engineers, New England Division, Waltham, MA. DAMaS Contribution #48 (SAIC Report # SAIC-85/7516&C48).

SAIC. 1987. Seasonal Monitoring Cruise at the Western Long Island Sound Disposal site - August 1986. US Army Corps of Engineers, New England Division, Waltham, MA. DAMaS contribution #61 (SAIC Report # SAIC-87/7500&C61).

SAIC. 1989. Monitoring Surveys at August 1985 - July 1986. US England Division, Waltham, MA. Report # SAIC-86/7540&C60).

the New London Disposal Site, Army Corps of Engineers, New

DAMaS contribution #60 (SAIC

Tavolaro, J.F. 1984. Sediment budget study for clamshell and ocean disposal activities in the New York Bight. Geol. Water Sci. 6 (3): 133-140.

dredging Environ.

9

MBDS 1988

42 26.CJOOU +

422i.000N + .0-

N

070 35.000H 070 34.000H 070 33.000H

+ 42 26.CJOOU

= ii + 42 2i.CJOOU

E BOUNDARY o 2iO ~te:O 1000

Fiqure 1-1.

070 35.000H 070 34.000H 070 33.000H

Map of bathymetric survey lanes used at MBDS, indicating the location of the "FDA" and "A" buoys, as well as the MASTER.MBDS survey encompassing the entire area.

070 36.000W

MBDS 1988 REMOT~STATION LOCATIONS

25.000N + +

24.000N + +

.0-

23.000N N+ + '" I 500 1000 1500 2000

Vet .. s 070 37.000W 070 36.000W

070 .OOOW 070 34.000W

:1 A .. + .. ! .. 'A' BUOY

46 AAAA!~AAAAAA .. A ! A .. .. .. .. .. ..

.. " " "

" ! "'FDA' BUOY AAAAAAA:~AAAAAA

! + " " I> .. .. ..

+ +

+ + FG23 REF

I>

070 35.000W 070 34.0ooM

070 33. OW 070 32.OO0W 070 31.000W

+ + + SITE BOUNDARY

+ + 42 25.0

18-17 REF

+ + + 42 24.0

SE REF 42°20.000N 700 28.000W \

+ + + 42 23.0

070 33.000W 070 32.000W 070 31.0OOW

Fiqure 2-1. Location and designation of REMOTS® stations (triangles) at MBDS, January 1989. Cross-shaped grids with 100 m station spacing were used at the three outlying reference sites (FG23, SE-REF and 18-17).

070 34.750W 070 34.500W 070 34.250W 070 34.000W 070 33.750W

+ + + + + + DEPTH IN METERS

----..... 90.25

+ + 42~N

/\.. 66.15

~~BB~25"-----±~ 42 25.~ft _______ ...,88.00

DISPOSAL SITE BOUNDARY -:=s Q

+ 42 25:1jooN

89.50 ,.,..

+ 69.25 '\ /

0-

N + + nrlmlIIc:::::::::::IF~=ff~ o 100 200 300 400 500

lleters 070 35.000W 070 34.75OW 070 34.500W 070 34.000W 070 33.750W

Fiqure 3-1. Bathymetric contour chart of the area surrounding the "FDA" buoy at MBDS, November 1988. The contour interval is 0.25 meters.

I 1 I I

1/30/87 078 3j"75!l'1 078 31" SOOV 078 3r5!l'l 078 3j"1lOOV

CONTOUR CHART \ /. DEPTH IN METERS ~ ~.=~~

+

+ DISPOSAL SITE BOUNDARY

.0-

N + emmm 8 100 200 300 400 500

H ....... 078 3S. IlIl!lV

I

~ ~7:;;- =lIl.oo-~~oo.~ ------.:--:

/00.58 lIl. 7S <> _ ~'V

~9a2S - .. + c:t ~ '------~ ~~-~~~ ~~~ , lIl.58 lIl.25:

~118.25

078 34.75!l'1 I

•

078 34.5OOlI I

078 34. 25!l'/ 078 34.1lOOV

I 078 -t-75!l'/

+ 4225.

+ 4225.

+ 42 24.

078 33. 75!l'1

Figure 3-2. Bathymetric contour chart of the area surrounding the "FDA" buoy at MBDS, January 1987. The contour interval is 0.25 meters.

II

070 34.7!iOH 070 34.500H

MBDS 1~8 + + DEPTH DIFFERENCE CONTOUR CHART ----rr..-'/ v

-0:1!- -=-

42 25. + + +

FDA ~UOYl~<)

> + + DISPOSAL SITE BOUNDARY

0-4224 .• N + + +

a 100 200 300 400 500 Meters

070 35.oooN 070 34.7!iOH

070 34.250H

+

+ [:;:,

6 +

+

070 34.000lf

+ ~

() I c> .,.,

. +

+

+ 070 34.oooN

070 33.7!iOH

+ +

+

+

+ 070 33.7!iON

Figure 3-3. Depth difference (in meters) contour map based on comparison of the January 1987 and November 1988 precision bathymetric surveys at the "FDA" buoy_

070 35.000W

MASTER MBDS 1988 CONTOUR CH~~T

DEPTH IN METERS

<§.

j

. 42 26.000N +

DISPOSAL SITE DLJ'UI~LJl"\n

42 25.00ON + :1 ~

.0-

N >

0 250 500 750 1000 1250 Meters "-

B8

070 35.000W

070 34.000W 070 33.000W

+ 42 26.000N

B8

Cf~ 90 • 0

-----BB

+ 4225.000N

070 34.000W 070 33.000W

Fiqure 3-4. Bathymetric contour chart of the entire MBDS area, November 1988. Contollr interval is 2.0 meters.

Pigure 3-5.

MBDS 1988

3-D CONTOUR PLOT

'A'

STEllWAGEN BANK

3-D COntour plot of the entire HBDs area, Nov...." 1988_ The vert;cal exaggeration is 25X.

070 .750N 070 3 .500N 070 .250N 070 .000N

MBDS 1989 A

NOM DREDGED MATER'IAL THICKNESS (CM)

4225 •• +

A A

ImM NOM

42 25.00¥t

A A A

NOM RELICT NDft DH>P PATCHY

A

RELICT OR FRESH?

+ A + + A

10.7+ A FRESU

FRESH DH>P nH>p

FDA A BUOY 3.4 FRESH

.6 A .6. I:. A DJRP A A .a. A A A A

RELICT 12.3+ 5.8+ 6.5+ 12.9+ ~SH10.9+ 7.4+ 14.4+ 14.1+ RELICT NDM NDM OR FRESH FRESH OR

'~~\(::., ~~:~:~llr ,,~"' + > A FRESH

DM P RELICT OR DM>P FRESH?

070 .750N

+ 42~

A A

ImM ImM

+

DISPOSAL SITE BOUNDARY A

RELICT OR FRESH?

A

PATCHY RE~ICT OR FRESH.

A

NDM A KEY

IIDM

4224.. + + + # = THICKNESS (CM) OF RELICT

OR FRESH DM LAYER #+ = THICKNESS OF LAYER

EXCEEDS PRISM PENETRATION DEPTH

0-

N o 100 200 300

Meters

Fiqure 3-6.

A

NDM A

400 500 NDM ......

070 35.000N 070 34.750N 070 34.500N 070 34.250N

Map showing the distribution of dredged material based on REMOTS* photography at the "FDA" buoy, January 1989. The contour delimits the extent of dredged material deposited since the January 1987 survey (Le., "fresh" dredged material) .

1 eM

A B

REMOTS· photographs from station 500E (A) and 300S (B) showing the presence of apparent reI ict dredged material on the flanks of the :mound. Scale = O. 5X.

Figure 3-8.

A B

REMOTS(O photographs :from station lOOE (A) and 200W (B) showing a "chaotic" mixture of silts, fine sands and sands intermixed with clay in the recently deposited dredged material. Scale = O.5X

Figure 3-9.

1 eM

A B

REMOTS@ photographs from station CTR (A) and laOS (B) showing overconsolidated clay clasts and rubble at the surface and limited camera penetration. Scale = O.5X.

Figure 3-110.

1 eM A B

REMOTS® photographs froxn station 250SW (A) and 200N (:8) showing less consolidation and deeper camera penetration with more stratification. Scale = O.5X.

070 .750W 070 .5OOH 070 3 .250H 070 .OOOH 070 .750H

MBDS 1989 GRAIN-SIZE MAJOR MODE A

(PHI UNITS) * ONLY THOSE OTHER THAN

A A A

2: 4 PHI (SILT ICLAY) A ARE INDICATED ~4-3

4225.¥ + + +- + + 42~

~ ~4-3 A .. ~4-3

FDA A

. BUOY A

ACE) A A A $ A A A A A .. .. ..

~4-3 ~4-3

-+ • + ~4

~4 • SE REF~ . ~4-3 FG23 R F\

A

~4-3

• ~4-3

A •

4224.+ + + +.o + ~4 422+ .0- A 18-17 F~ N DISPOSAL SITE BOUNDAR

em::mm 0 100 200 JOO 400 500

l'eters 070 35.000W 070 34.750H 070 34.500H 070 .250H

I'iqure 3-11. Map of sediment grain size major mode (in phi units) at FADS, January 1989.

Figure 3-12.

> 0 Z W ::l 0 W a:: LL

40

30

20

10

0 1

40

30

20

10

o

2 3 4

FDA

5

1189 N=46

6 7 8

REF 1/89

N=60

9101112131415

1 2 3 4 5 6 7 8 9 10

CLASS INTERVAL

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

BOUNDARY ROUGHNESS CLASS INTERVAL

RANGE OF VALUES(CM)

0.0· 0.6 0.6· 1.0 1.0· 1.4 1.4· 1.8 1.8·2.2 2.2·2.6 2.6·3.0 3.0·3.4 3.4·3.8 3.8·4.2 4.2·4.6 4.6·5.0 5.0·5.4 5.4·5.8 5.8·6.2

Frequency distribution of small-scale surface boundary roughness values for all replicates at the reference stations and at the FDA buoy stations where fresh dredged material was present, January 1989 (n = number of replicates).

Figure 3-13.

20 FDA 1189

15

10

5

> 0 z w 0

:::l 1 2 3 4 5 6 7 8 9 10 11 12

" REF W 20

a: 1/89

LL N=58

15

10

5

o 1 2 3 4 5 6 7 8 9 10 11 12

MEAN RPD DEPTH (eM)

Frequency distributions of apparent RPD depths for all replicates at the reference stations and the FDA buoy stations where dredged material was present, January 1989.

070 .750H 070 .500W 070 3 .250M 070 .OOOM 070 .750M

MBDS MEAN APPARENT RPD DEPTH (eM) A

0.9

G A A

5.3 5.4

A

5.0

42 25.~ +- +- A +- +- +- 42~ 12.0 A A

3.0 2.0 A

1.5

FDA BUOY t1 A A A A A A $ A A A

AGAQA

A 4.6 4.6 3.4 3.7 0.7 0.7 1.0 INO 1.3 1.8 2.3 ~.3 1.6 0.9 2.1 9.1 7.5

A 4.5 0.0 -I-0~8 ~ +- 5:8

. . 5.3 0.7 .2 4.9 4.7 6.8 INO 3.9 4.2 A A

4.5 A 4.0 4:0 INO

. 4.1 AN = 5.0 SE REF. j 6.7 6.4 3.9 INO INO 7.0 ~ MEAN = 5.3 5.6

3.2

<12 24 •• 2.1

.0-

N "" 0 100 200 300

~ters

Fiqure 3-14.

A

6.3 · 4.5 FG23 EF~ A A A ·

3.7 5.8 4.8 4.4 ·

+- -I-A +- 5.2 <l22~ +s.2 . . . . . A

6.4 6.8 3.6 5.1 3.0 DISPOSAL SITE BOUNDARY 6.2 · 4.7

A 18-17 EF\ 5.0 3.9 400 500

070 35.000H 070 34.750H 070 34.500M 070 34.250M 3.9

The mapped distribution of apparent RPD depths (cm), averaged by station, at the FDA buoy in January 1989. The contours delimit stations having mean apparent RPD depths 5 3 cm.

+ -t- 070 ";G5OW

MBDS 1989 INFAUNAL SUCCESSIONAL STAGES

42 25.~

~ +

o

lND

L::::.iNOiNDlND :

+ -1-

o

o

o

FDA BUOY 6-

o 0 !

0

~

$I

+~ DiSPOSAL SITE BOUNDARY ~

o 100 ~ 300 400 500 ¥£ters

070 35.0OCI'~ 070 34.750)/

o

070 T.250W

000

-t-O

+

070 34.250!ri !

KEY

6. = STAGE 1 ONLY

o = STAGE 1lN COMBINATION o WITH STAGE 1 ON 3 AND/OR STAGE 3 '

= STAGE 3 AND/OR STAGE 1 ON 3

lND = INDETERMINATE

o

• I.. (it (it .. INO. ":1 '

--:--~I: 0

+

i

o .. 0 0 {j. .. OJ 422+-1i " I

I

The mapped distribution of infaunal successional stages at the FDA buoy, January 1989. The contour delimits the disposal site stations where only stage I seres were seen in the replicate REMOTS* photos.

A -B c 1 eM

A large feeding void at depth indicates the presence of stage III organisms at station SOON (A), while the REMOTS8 photographs from station 300E (S) and 2005 (C) show stage I on III organisms at the disposal site. Scale = o.SX.

070 .750N 070 3 .500N 070 .250W 070 .OOON 070 .15ON

MBDS1989 MEAN ORGANISM-SEDIMENT INDEX A

9.7

A A A

7.8 11.0 8.0 A

9.7

42 25.~ + + +6~7 + + + 42~ A A

8.3 A 8.5

5.0 A

FDA BUOy 3.0 A A A A A A A $ A A A A A A A A A 11.0 . 10.0 7.3 10.0 9.3 2.5 4.5 4.3 1.0 5.5 6.3 7.3 8.5 7.7 11.0 8.3 11.0 9.7 11.0 11.0 A

7.0 +

+3.0 + +

11.0 A . . . . . IND 5.3 11.0 ll.O 11.0. ,,\ND 11.0 1 A A

1:0 1i.0 il.O:~ I~D IND 9.7 A 9.0 MEAN=10.7 7.0 11.0 8.7 MEAN=9.7 11.0 7.0 A

11.0 10.3 · SE\ F

10.0 REF \

8.3 11.0 FG A A A ·

11.0 11.0 7.3 8.3 ·

4224.+ + + +1~.0 + 7.0

422~ . . · . . .0 DISPOSAL SITE BOUNDARY A 9.7 11.0 9.0 i'}< 11.0 8.0

N 11.0 MEAN=8.4 1~.7 8.3

1;~ M 8.5 REF\ 0 100 200 300 400 500 18-Meters

070 35.000N 070 34.750N 070 3 .500N 070 34.250N 10.7

piqure 3-17. The distribution of Organism-Sediment Indices, averaged by station, at the FDA buoy in January 1989. The contour delimits stations having mean OSI values 5 +6.

1 0

Figure 3-18.

> 0 Z w ::l a w £t 11.

40

30

20

10

0 -3 -2 -1 0 1 2

40

30

20

10

FDA 1189 N=38

3 4 5 6

REF 1/89

N=58

7891011

o .&...+ _____ --'

-3 -2 - 1 0 1 2 3 4 5 6 7 8 9 10 1 1

ORGANISM-SEDIMENT INDEX VALUES

Frequency distributions of organism-Sediment Indices for all replicates at the reference stations and at the disposal site stations where dredged material was present, January 1989.

Figure 3-19.

-1 eM

A B

REMOTSO photographs from station 200E (A) and IOOE (B) showing the presence of dredged material with clay clasts evident at the surface and at depth. It is difficult to estimate how recently this light-colored, highly­consolidated material was deposited. Scale = O.5X.

Fiqure 3-20.

> o w ~ 0 W a: U-

50

40

30

20

10

o --1

50

40

30

20

10

o

234

BUOY A

5 6

1/89 N=110

7 8 9101112131415

REF 1/89

N=60 CLASS

INTERVAL

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1 2 3 4 5 6 7 8 9 10

BOUNDARY ROUGHNESS CLASS INTERVAL

RANGE OF VALUES(CM)

0.0 - 0.6 0.6 - 1.0 1.0 - 1.4 1.4- 1.8 1.8 - 2.2 2.2 - 2.6 2.6 - 3.0 3.0 - 3.4 3.4 - 3.8 3.8 - 4.2 4.2 - 4.6 4.6 - 5.0 5.0 - 5.4 5.4 - 5.8 5.8 - 6.2

Frequency distributions of small-scale surface boundary roughness values for all replicates at both the "A" buoy and reference site stations at MBDS, January 1989.

Fiqure 3-21.

20

15

10

5

> 0 z 0 W ::)

0 w 20 a: LL

15

10

5

o

1 2 3

BUOY A

4

1189 N=lll

5

REF 1189 N=58

6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

MEAN RPD DEPTH (eM)

Frequency distribution of apparent RPD depths for all replicates at both the "A" buoy and reference site stations at MBDS, January 1989.

070 :Ii.500M 070 :35.25IJM 070 :35.000" 070 34.750" 070 34.500"

MBDS "A" BUOY 1989 MEAN APPARENT RPD DEPTH (eM) A

+ 4.7 + + + -t- 42 26.000N

25.7500 +

25.500N +

.0-

N 200 jo 0 100

Meters 070 :Ii.150M

Fiqure 3-22.

A A A 3.4 5.8 6.6

A 4.3

A

A 5.3 A 5.5 Q 4.7

+ + 'A' BUOy3~2 + + + + 42 25.7500

A A A 8AG~8A A A A A A A 5.6 5.0 4.7 2.8 0.8 3.6 1.8 4.8 2.6 2.5 3.5 3.2 5.9 11.9 6.0 7.4 7.0

A 5.7

A ® A

3.6 A 4.6

+

5.1

+ A+ + + + 42 25.5OON

7.1

A A A 3.3 3.5 4.6

A 5.4

A 5.5

400 500 + + @ + + +

070 35.500" 070 35.25IJ" 070 :35.000" 070 34.750" 070 34.500"

The mapped distribution of apparent RPD depths (cm), averaged by station, at the "A" buoy at MBDS, January 1989. The contours delimit stations having mean apparent RPD depths S 3 cm.

j l l 1 I l ,I ~r 11 070 35. 50CIW 070 35. 25(l:rl 070 35.000W 070 34.750W

MBDS "AII BUOY 1989 KEY

tt--lNFAUNAL SUCCESS'IONAl STAGES 0 :0 = STAGE 1 AND STAGE 3 + + +

* 0 ~ 0 = STAGE 1 IN COMB1NATiON WITH STAGE 1 ON 3 AND/OR STAGE 3

0 e = STAGE 3 AND/OR STAGE ON 3 i 1

tI ~ ~

0

~ Zl.750N -t-- + -+- + 'A' BUOY ~ + + + 42 Zl.75ON-I,

t i ~ 0 ~ @ 0 0 0 ~ @ 0 0 @ 0 ~ 0 ~

01

0 0 ~

~

!:~ Zl.500N + -1- -t- 11+ + + + 42 C5.5OON-

[] ~ $II

~

AC)-t

N 0 I' 0+ :J- rsToo 2C1O ~b ~3 + + + + + 400 500

~ters

II 070 ~.7&\ij 070 i.50CW 070 ~.250H 070 ~.OOOW 0110 ~.750W 070 ~.500W

j

l1iqura 3-23. The mapped distribution of infaunal successional stages at the "A" buoy at MBDS, January 1989.

I

-'

I

I

i

A 1 eM B

REMOTSO photographs from the vicinity of the "A" buoy showing dense stage III tubes at the surface (photo A from station 800S) and surface tubes along with a feeding void at depth (lower right hand corner of photo B from station 250NW). Scale = O.5X.

Figure 3-25.

> 0 Z w ::)

" w a:: LL

60

50

40

30

20

10

0

60

50

40

30

20

10

BUOY A

-3 -2 -1 0 1

1189

N=104

234 5

REF 1189

N=58

67891011

0.1..-........ _____ ........

-3 -2 -1 0 1 2 3 4 5 6 7 8 9 1011

, ,..

ORGANISM-SEDIMENT INDEX VALUES

Frequency distributions of Organism-Sediment Indices for all replicates at both the reference and "A" buoy stations, January 1989_

070 ~ 500K 070 35.25OK 070 35.000K 070 34.750K 070 34.500K

MBDS "A" BUOY 1989 MEAN ORGANISM-SEDIMENT INDEX

A

+ 9.0+ + + + 42 2fi.OOON

2 25.75ON +

25.500N +

.0-

N ttttt"*"'*ti

200 ko 0 100 J.2ters 070 35.750N

Figure 3-26.

. '

A A A

9.3 9.7 10.3 A

8.7

A

A 11.0 10.3 10.7 A

8.3

+ A -1- + + 42 25.75ON 'A' BUOY 9.7

A A A

A@ A

A $ A A A A A A A A A

10.0 8.0 11.0 8.7 4.0 8.3 6.3 10.7 9.0 9.0 8.0 8.7 11.0 9.3 10.3 9.7 11.0

A

11.0 A

7.0 A A

6.5 A 10.0

+ + 11.0+

A + + + 42 25.5OON

10.7 A A A

8.7 9.0 9.3 A

10.5

A

9.7

400 500 + + 7:7+ + + + 070 35.500N 070 35.25OK 070 35.000N 070 34.750K 070 34.500K

The distribution of Organism-Sediment Indices, averaged by station, at the "A" buoy at MBDS, January 1989. The contour delimits the single station (300W) having a mean OSI value 5 +6 .

,

I I I I I 070 34.750H 070 34.500W 070 34.250W 070 34.OOOW 070 33.750H

MBDS 1988 + + + + + + + DEPTH DIFFERENCE CONTOUR CHART .......... U:;r'/ v ~

~ =- () I <>

"'

42 25. + + . + +

FDA ~UOYcJb~ <)

4225 .• + o + + + DISPOSAL SITE BOUNDARY

0 42 24. r.+r N + + + + + + 42 24;~

""""'" :3 0 100 200 300 40Q 500

Heters 070 35.000W 070 34.750H 070 34.500W 070 34.250H 070 34.oooH 070 33.750H

Figure 4-1. Depth difference contour chart with the thick contour line indicating the extent of recently-deposited dredged material around the "FDA" buoy as determined by REMOTS® photography (see Figure 3-6).