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MONITORING REPORT No. 7

DREDGING AND RECLAMATION PROGRAMME IN KINGSTON HARBOUR

 

 

 

 

Prepared for:

The Port Authority of Jamaica

 

 

 

 

 

 

 

 

 

 

 

 

 

Prepared by:

T.E.M.N. Limited

April 4th, 2002

BACKGROUND:

 

Water quality sampling fieldwork was carried out on March 11, 2002, and data from fixed stations at Middle, Angel, and Bustamante beacons was reviewed.

 

The sampling exercise carried out on March 11, was intended to provide measurement of TSS (total suspended solids)/turbidity in the channel (H1 and H2) where dredging was in progress.

 

A monitoring flight took place on 18th March and a selection of the photographs taken are attached.

 

An inspection of the berm at R1 was carried out on March 13th.  The R1 bund preparation continued during the period covered by this report. The first sector was completed and work continued in the extension of the berm by PIHL. Significant plume from this activity was noted in our monitoring flight of March 19. The screen around the berm preparation activity was down at the time of our flight and was being repaired.

 

METHODOLOGY:

 

Monitoring on March 11 was carried out in the channel near Port Royal, where the dredge Cristoforo Colombo was operating.  Other sites monitored included   wake of a small container vessel (Heinrich – Plate 1), a site east of Delbert Sicard beacon, and Angel beacon (Figure 1).  In order to assess the impact of dredging, sampling was carried out in an identified plume (Plate 2) as soon as the dredge departed, and the same site was re-sampled approximately ½hr later. The sampling sites were designated KTP 1 – 6 (Table 1).

 

Table 1: Dredging And Reclamation In Kingston Harbour

Water Quality Sampling Sites March 22, 2002

 

DESCRIPTION

N COORD.

W COORD

STATION NO.

 

Wake of Heinrich (Surface)

18o 00.218'

76o 46.736'

1

Dredge Plume North of Dredge

17o 57.417'

76o 50.999'

2

Area recently dredged

17o 57.147'

76o 51.197'

3

West of Delbert Sicard Beacon

17o 56.894'

76o 51.525'

4

Station 3 Resampled

17o 57.150'

76o 51.201'

5

Angel Beacon

17o 57.180'

76o 49.607'

6

 

 

Samples were generally collected at three depths (sub-stations) at each site sampled using the Van Dorn sampler. These sub-stations were denoted T (surface sample), M (middle depth), and B (bottom depth). The exception was station 6 - Angel beacon where sampling was confined to the surface.   
 

Samples were analysed by Poly-Diagnostic Centre in accordance with Standard Methods for the Analysis of Water and Waste Water. TSS was determined by filtration of a known sample volume through a dried, pre weighed filter. After filtration, the filter was dried and re-weighed. TSS in mg/l is obtained through a determination of the weight difference of the filter before and after filtration. As a precaution against salt-water interference, filters were rinsed with warm distilled water after filtration of the sample. This precaution was employed in analysing samples collected subsequent to February 18. 

 

Relying on the good correlation between turbidity and TSS determined from the February data (Figure 2) the WQ team was able to collect more samples. Most of these samples were analysed to determine turbidity. TSS was then determined from the plot of TSS vs. turbidity (Figure 2).  Turbidity only was determined at Stations 1, 2, and 4, while as a control, turbidity and TSS were measured at stations 3, 5, and 6.

 

 

 

Figure 2:  TSS vs  Turbidity – February 22nd

                       

                    

 

OBSERVATION AND RESULTS

 

During the exercise, sea state was calm, with a light SW wind. There was no visible plume associated with a small container vessel traversing the channel. On approaching sector H1 a plume was observed just north of where the dredge was operating. There was a visible plume remaining after the departure of the dredge.  

 

Laboratory and field data are summarised in Table 2.

 

Laboratory Results:

Laboratory analysis results indicate a range of TSS for all sites monitored of 3.6–76.1mg/l. The highest values were reported for the dredge site (Station 5) where TSS was determined to be 34.0mg/l at the surface, 43.1mg/l at middle depth, and 78.1mg/l at the bottom. At station 2 (fugitive plume) TSS was 12mg/l at the surface, 32.3mg/l at middle depth and 18.2mg/l at the bottom. In the wake of the small container vessel, TSS was 5.5mg/l at the surface, 3.6mg/l at middle depth, and 6.7mg/l at the bottom. At station 5 (dredge site after 30min) TSS was 7.6mg/l at the surface, 14.6mg/l at middle depth, and 69.2mg/l at the bottom. At station 6 TSS was 9.7mg/l at the surface. At station 4 (west of Sicard beacon) TSS was 13.5mg/l at the surface, and 7.8mg/l below the surface.

 

 

Table 2: Kingston Container Terminal Water Quality Data March 11, 2002

 

STATION NO

TIME

DEPTH (M)

LAB. RESULTS

FIELD DATA*

TURBIDITY (NTU)

TSS (mg/l)

TSS (mg/l)

1T

1030

0.5

 

5.5

15

1M

 

6.5

 

3.6

5

1B

 

13.0

 

6.7

20

2T

1050

0.5

 

12.0

20

2M

 

6.0

 

32.3

10

2B

 

12.0

 

18.2

10

3T

1057

0.5

6.0

34.0

50

3M

 

6.0

7.0

43.1

100

3B

 

12.5

19.0

78.1

300

4T

1112

0.5

 

13.5

5

4M

 

5.0

 

7.8

5

4B

 

9.5

 

7.8

10

5T

1129

0.5

1.0

7.6

20

5M

 

6.0

3.0

14.6

10

5B

 

12.5

15.0

69.2

150

6T

1148

0.5

1.0

9.7

5

6M

 

2.0

 

-

10

6B

 

4.0

 

         -

50

 

 

Field Data

 

Field data collected by Jan De Nul on March 11 indicated a range of 5 – 300mg/l for TSS at the sites monitored. The highest values were determined for Station 3, the dredge site. 

 

At the dredge site TSS was 50mg/l at the surface, 100mg/l at middle depth  (6.0M), and  300mg/l at the bottom (12.5M). At this same site approximately thirty minutes later, the values were significantly reduced to 20mg/l at the surface, 10mg/l at middle depth, and 150mg/l at the bottom (Figure 3).

 

 In the wake of the Heinrich, Station 2 TSS was determined to be 15mg/l at the surface, 5mg/l at middle depth (6.5M), and 20mg/l at the bottom (13M).

                     NRCA Standard

 

At Station 3 - the plume north of the dredge site, TSS was determined to be 20mg/l at the surface, and 10mg/l below the surface.

 

At Station 4 (west of Delbert Sicard beacon), TSS was determined to be 5mg/l at surface and middle, and 10mg/l at the bottom.

 

At Angel beacon (Station 6) TSS was 5mg/l at the surface, 10mg/l at middle depth (2.0M) and 50mg/l at the bottom (4.0M).

 

Data from the fixed stations indicated a range of 20 – 200mg/l TSS at Middle ground. For March 4, TSS was around 50mg/l increasing to 200mg/l prior to cleaning on March 5. Subsequent to cleaning TSS reading dropped to around 20mg/l increasing to 160mg/l at around 1100 on March 7. TSS remains high even after cleaning on March 8. After cleaning on March 9 however, TSS drops to 20mg/l through March 10.

 

At Bustamante beacon the range for TSS -was 5 – 40mg/l throughout March 4 to March 10.

 

 

 

CONCLUSION/ENVIRONMENTAL IMPACT

 

Results indicate that effects of the dredging were confined to the channel. The effect was not noticeable at the sampling location to the west of the dredge site or at Angel beacon.

 

The significant fall off in TSS at the dredge site over a 30 minute period indicates that the impact from dredging on water quality is significant for a relatively short period. The fact that the bottom values are also significantly higher than at the surface suggests that much of the disturbed material settled rapidly.

 

Data from the fixed stations suggest that impact from TSS is greater at Middle Ground.

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