3.0       METHODOLOGY

3.1       Water Quality

The environmental chemistry component was carried out based on the assumption that the area of influence of the project includes, the heavily impacted Hunts Bay/Kingston Harbour system, as well as the relatively unpolluted Port Royal cays and reefs within the Palisadoes/Port Royal Protected Area.

The environmental chemistry assessment aims to provide critical information to the planning process to ensure that conflicts that arise during dredging and dredged material disposal can be reduced, thus resulting in economic growth and environmental protection.

The main objectives in Stage 1 of the environmental chemistry component of the assessment were as follows:

·        Characterise water resources within the zone of influence of the project including potential marine disposal sites

·        Characterise sediment to be dredged

·        Project environmental impact of proposed development on water chemistry within the zone of influence

·        Develop a plan to mitigate negative environmental impacts of the dredging and disposal of dredged material (spoil) on water quality. 

The assessment was based on a review of existing information, the collection and analysis of sediment and water samples, and the conducting of leaching experiments in the laboratory. The programme of work was also designed to provide additional information in order to inform Phase 2 of the project i.e. the development of Fort Augusta.

Through literature review, typical values of indicator parameters have been established for the study area. A review of relevant local and international standards, and criteria has also been carried out to assist in the assessment of the material to be dredged and contribute to guiding the selection of an appropriate disposal option.  Information sources for the literature review included UWI, NRCA, USEPA, and TEMN, and various web-sites.

Five sampling stations were established (See Figure 3) to obtain background information on the following:

      Offshore background conditions                        -           Station 1

      The channel (near Port Royal)               -           Station 2

      The channel (near Fort Augusta)                       -           Station 3

      The turning basin (Gordon Cay)                        -           Station 4

      Hunts Bay (near Causeway)                              -           Station 5 

Surface and sub-surface water samples were collected at all sites established using a Van Dorn sampler. Samples of sediment were collected by the biology team at the sites to be dredged (channel, and turning basin) using a core sampler. 

Laboratory analyses were carried out by the Bureau of Standards, and Environmental Focus Ltd. in accordance with Standard Methods for the Analysis of water and wastewater (17) to determine the following: total suspended solids (TSS), nitrate (NO₃), available phosphate (o-PO₄), hydrogen sulphide, heavy metals (Pb, Cr, Cu, Cd), chemical oxygen demand (COD), biochemical oxygen demand (BOD), coliform. Organic residues were determined using Gas chromatography-mass spectrometry (GCMS). Dissolved oxygen (DO) was determined in situ using portable instrumentation.

Rationale for Selection of Water Quality Indicators:

Water quality parameters have been selected based on the known potential impacts associated with dredging, as well as an understanding of the issues affecting the quality of surface run-off and effluent quality entering the area to be dredged. Dredging, and the disposal of dredged material (spoil) can impact water quality in the following ways:

·        Temporary increase in turbidity (suspended matter) at the site(s) being dredged and adjoining areas,

·        Temporary increase in turbidity at the disposal site (for marine disposal),

·        Trailing of spoil by barges conveying dredged material to disposal sites,

·        Leaching of sediment during descent at disposal site,

·        Shifting of  dumped spoil from disposal site

The indicator parameters considered relevant to the assessment are as follows: total suspended solids (TSS), nitrate (NO₃), available phosphate (o-PO₄), heavy metals (Pb, Cr, Cu, Cd), chemical oxygen demand (COD), biochemical oxygen demand (BOD), dissolved oxygen (DO), hydrogen sulphide, coliform, and pesticides.

Total Suspended Solids was determined by filtration and gravimetry.

Nitrate was determined using the salt tolerant copper/cadmium reduction method. 

Available Phosphate (o-PO₄) was determined by the molybdenum colorimetric method.

The heavy metals Lead (Pb), chromium (Cr), Copper (Cu), and Cadmium (Cd), were determined by atomic absorption spectrophotometry using a Thermo Jarrel Ashe Video 11 spectrophotometer which features background correction for matrix interference.

Chemical oxygen demand (COD) was determined using colorimetry.

Biochemical oxygen demand (BOD) was determined by the bottle dilution method.

Dissolved oxygen (DO) was determined using the YSI Model 51B Oxygen meter, and Model 5739 Field Probe. The probe uses a Clark-type gas permeable membrane that covers polarographic electrode sensors. The system has a built in thermistor for temperature compensation, and temperature measurement. Measurement range of the instrument is 0 -15mg/l, and accuracy is better than 0.2mg/l when calibrated within + or -5^oC of actual sample temperature. Readability is better than 0.1mg/l.

Coliform was determined by the membrane filter method.

Organic residues (pesticides etc.) were determined using gas chromatography - mass spectrometry (GCMS).

Hydrogen Sulphide was determined in sediment and water samples using Standard Methods 450052-C, 450052-E. The method involves pre-treatment of samples with zinc acetate, sodium hydroxide, and iodine. Titrimetric determination of excess iodine provided the basis for calculation of hydrogen sulphide concentration.

Leaching experiments were performed on sediment taken from the channel, the turning basin (near Gordon Cay), and Hunts Bay. This involved 10 g sediment (collected from proposed dredge sites close to Gordon Cay) being leached with 250 mls water collected from Station 1 for 0.5 hrs (offshore site being considered for spoil disposal). In all cases, the filtered leachate was analysed to determine levels of all indicator parameters with the exception of dissolved oxygen.

In addition, wet sediment samples from near Gordon Cay were allowed to settle, and the supernatant decanted and analysed. These samples were assumed to represent pore-water/worst-case-leachate associated with the sediment from the more polluted section of the harbour to be dredged (the turning basin downstream of the Greenwich sewage treatment plant discharge near Gordon Cay). 

3.2       Ecology

A survey of the existing literature relating to work carried out on Kingston Harbour, Hunts Bay and the Port Royal Cays area was carried out with a view to determining the present ecological status of the area. The review also helped to facilitate the identification of environmental parameters that justified further investigation in the context of the proposed dredge and fill activities.

Information from the literature review, available maps, marine charts and aerial photographs was used to establish the locations of sampling stations and of swim-line transects at each station. Transects were then examined with a view to obtaining a detailed assessment of floral/faunal composition and status of sublittoral areas at each station.

Along with existing data from previous reports, six locations generating twelve different sampling transects were established (Figure 3) to generate information that would serve to add to the database for the purpose of comprehensively evaluating the ecosystems involved:

Hunts Bay (marine - north, middle, south & terrestrial east/west)      -     Transects 1, 2 , 3 & 4

Gordon Cay (west & east)                                                  -           Transects  5  & 6

                  Ship Channel (east of Fort Augusta & west of Port Royal)                     -           Transects 7 &8

                  Rackhams Cay (north to south & east to west)                          -           Transects 9 & 10

                  Gun Cay (east to west)                                                 -           Transect  11 

Farewell / Sea Buoy                                                                              -             Transect 12

Data on the substrate was obtained by a visual examination of the substrate at the various stations.  The visual technique was based on an immediate estimation of a 0.2 m² quadrat placed on the substrate at randomly chosen locations along the swim-line transects. Videotapes were also taken of the substrate along the transect lines chosen. Substrate composition data was extracted from these videotapes by selecting random stills from the video tape and using the random point intercept method to analyze the content of the photographs.

The results of this assessment of the marine environment were recorded under the following headings:- SEAGRASS - `r' species or climax communities; ALGAE  -  turf or macrophytic;  CORAL  -  branching, boulder or encrusting;  MACRO FAUNA - other cnidarians e.g. gorgonians, anemones or zoanthids;  SPONGES  -  fleshy, boring or encrusting; BARE SUBSTRATE    -  bare rock, rubble, sand or mud.

Examination of the terrestrial habitat in the vicinity of the proposed Hunts Bay reclamation site was carried out by sampling the vegetation along 20m transects within each sample site. Along these transects the vegetation occurring within 1.5m of either side was noted and recorded under the following headings:-

·         species  - recorded as TREES; SHRUBS;  HERBS;  FERNS;  GRASSES;  WEEDS; EPIPHYTES;  VINES; CACTI; and ranked using the DAFOR (dominant, abundant, frequent, occasional, rare) scale.

·         tree diameter at a height of 1m above ground level

·         average canopy height

·         percent of ground covered by shrubs, herbs or grasses.

Trees were considered to be species with a trunk diameter greater than or equal to 4cm at 1m above ground level. Shrubs were considered to be species with a trunk diameter less than 4cm at 1m above ground. Herbs were considered to be species less than 1m tall.  Identification of as much as possible of the existing species of flora was carried out on site.  Photographs were taken and samples collected of the more obscure species for later identification in the Lab.

The following general terrestrial features were noted along each transect:

C             Soil Type & Structure

·                     Leaf Litter depth

C                    Topography in vicinity of transect

The general land use within the area of the sampling stations was also noted.

Faunal community composition was recorded under the following headings: AVIFAUNA; MACROFAUNA; INSECTS.

Avifauna were sought by direct observation or by searching for indicators such as nests. Physical descriptions and vocal peculiarities of any bird that could not be immediately identified were noted and later verified with field guides. This method is only capable of identifying the most common birds found in an area. Rare, migratory or cryptic species can be under represented by this technique. The Point Count Method (without distance estimates) was used to sample the bird population. This method produced data that revealed the bird species present, their abundance and habitat preferences. It does not permit estimates of the total population size in the area.

Avifauna identified were ranked according to the following criteria:

R  = resident                        1 = common in suitable habitat

E  = endemic                       2 = uncommon

I   = introduced                    3 = rare

W = winter migrant             4 = vagrant/unexpected/accidental

S  = summer migrant

Insects and other macrofauna utilising the site were recorded as encountered. No special searches were carried out.

Special note was made of ecologically or commercially important species of flora or fauna. Any  other physical and/or ecological characteristics of interest were noted. 

The methodology outlined above resulted in a stratified sampling routine in which the transects  were not evenly spaced over the entire study area but were grouped to create sample sites in certain predetermined areas. The result of this approach was coverage of the area by points representing the major land use types distinguishable.

3.3          Coastal Dynamics

In order to predict the nature and movement of the disposed sediment, a U.S. Army Corps of Engineers computer model (STFATE) (Johnson, 1990, 1995) was used to examine the parameters of spoil released from a Hopper barge.

3.3.1    Model Setup for Hopper Barge Discharge

3.3.1.1             Modelling of Disposal of Dredged Material

The STFATE model incorporates state‑of‑the‑art techniques for simulating short‑ and long‑term fate of dredged material due to dredging disposal operations and environmental processes. The model was developed by the US Army Corps of Engineers, Waterways Experiment Station. The model predicts the distribution of dredged material through the water column and bathymetric distribution of dredged material on the seabed on the basis of individual disposal loads. The model accounts for various parameters including the type of disposal vessel, physical properties of the water column, and material properties.

STFATE estimates the behavior of dredged material as it is released in open water, passes through the water column, and encounters the seabed. Through its 25‑year period of development, the model has been calibrated and successfully applied at numerous locations.  The following studies have used the STFATE model: Koh and Chang (1973), Brandsma and Divoky (1976), Bokuniewicz at al (1978), Bowers and Goldenblatt (1978), Johnson and Holliday (1978), Thevenot and Johnson (1994), Moritz and Randall (1995), Lillycrop and Clausner (1997), and Johnson et al 1998).  It must be noted that STFATE is a tool that provide estimates of sediment behavior and related processes. The accuracy of STFATE model‑generated results is highly dependent upon the parameters input to the model. Controlling parameters which must be properly specified within the STFATE model are physical characteristics of the dredged material, disposal operation sequencing, and forcing environmental conditions within the water column (waves, currents, density structure).

The objectives of this short‑term fate assessment were:

‑ Evaluate the overall size of the mixing zone for discrete discharges from the disposal vessel.

‑ Determine the concentration of the pollutant of most concern (lead) at various points in the water column and on the seabed.

‑ Estimate the distance that the disposed dredged material is displaced away from the point of release.

‑ Estimate the fall speed, density, and detailed aerial extent of dredged material as it encounters the seabed during disposal.

‑ Estimate the disposal mound geometry in terms of thickness and aerial extent after the placed material comes to rest on the seabed.

3.3.1.2             The Fate of Dredged Sediment Placed in Open Water

The operation of hopper dredges result in a mixture of water and solids stored in the hopper for transport to the disposal site.  At the disposal site, the hopper doors in the bottom the vessel's hull are opened, and the entire hopper contents are released within a time‑frame of tens of seconds to minutes.

When dredged material is released in open water by a disposal vessel, the material falls through the water column, mixing with ambient water, and forming a high‑density plume which may contain blocks of solid material.  This process is called convective descent.  As the convecting plume descends in a hemispherical shape, it grows as a result of ambient water entrainment, and a fraction of material (typically 1 to 5 percent) and fluid with dissolved contaminants may be stripped away.  When the diluted dredged material plume encounters the seabed (or arrives at neutral buoyancy), the plume spreads laterally along the seabed.  This process is called dynamic collapse.  Fine material may be lost to the water column at the top of the collapsing plume.  After the plume has expended all of its momentum along the seabed, the dredged material slowly settles under the influences of gravity and the ambient current environment.  This process is called passive transport and dispersion.

The fate of dredged material placed in open water is primarily governed by gravity, surface waves and currents.   Dredged material falls from the release point of the disposal vessel through the water column, convects and diffuses laterally, and eventually comes to rest on the sea floor.

Within minutes to hours following disposal, dredged material can be spread out on the seabed to varying degrees, depending upon the speed of the disposal vessel upon release, water depth, water column currents, ambient bathymetry, and other variables.

Once dredged material has come to rest on the seabed it can be transported by waves and currents to varying degrees, depending on sediment grain size, bathymetry, and physical forcing, which, for surface gravity waves, decreases with depth.  If the dredged material is cohesive, it can self‑consolidate due to gravity.  If many loads of dredged material are placed one on top of another to develop a mound on the seabed, the mound will tend to avalanche and material will be transported downslope.  The combination of these processes determine the long‑term fate of dredged material placed in open water.  The time‑frame for processes affecting the long‑term fate of placed dredged material is days to years.

Several aspects influence the dispersion, accumulation quantity and shape of the disposal mound on the seabed:

‑ Speed of hopper dredge while dumping

‑ Current speed and direction in the water column

‑ Water depth and bathymetry at disposal location

The mound length and thickness is a function of vessel speed.  Increasing current speed reduces mound height.  Split‑hull hopper dredges produce a thicker (higher) resultant mound than the multiple bottom‑door hopper dredges.  The most significant parameter affecting mound geometry (width and height) is water depth.  As a general rule of the practice in shallow water, increasing the water depth by a factor of 3 will decrease disposal mound height for a single dump by a factor of 2.  Increasing the water depth by a factor of 3 will increase disposal mound width for a single dump by a factor of 2.5.

3.3.2       Hopper Barge Spoil Disposal Logistics used as data input for model, as supplied by the dredging consultants

An 8,000 cubic metre capacity trailer will bottom dump its whole load in a minute or so and then spend a few more minutes cleaning out the hopper.

The total load carried can be estimated by assuming that the average hopper density is 1.35  t/cu.m. Past experience indicates that this material descends to the seabed in a large density current and that the amount stripped off during descent is about 5% of the dry solids distributed over the full water column.

The trailer proposed to be used has a hopper with dimensions 43m x 19m and the draft of the vessel would be 2.8 metres light and 7.5 metres laden.

The proposed disposal site marked on the maps drawn by Mott MacDonald is 1,200m x 3,000m.   The model grid for the STFATE runs used is 1,829 x 2,438 m (6,000 x 8,000 ft); that is, it was necessary to use a grid height (x‑direction) of about 400m greater in order to display the entire     bottom dump within the grid. Therefore we can assume that the bottom material will extend past the boundaries of the disposal site in the northwest ‑ southeast direction. An average depth of 350m (1148 ft) was used for the grid since the site is bounded by the 200m and 500m bathymetric contours.

** Note: Due to the varying nature of the ocean currents and the tendency of the tides to cause a rotation in the direction vector of the currents, it is prudent to assume the current may travel in all directions from the dump site at varying stages of the tide.

Note that a 0.7 fps (0.21 m/s) velocity for the water column flowing from the east (with a velocity within the bottom 30 m at 0.15 m/s) was used based on the field data recorded during the 1994 TEMN study, with a 0.1 fps downslope velocity component from the north.  The barge was assumed to be stationary during disposal that takes 1 minute so as to minimize        directional spreading of the material.

To set up the model as a realistic case, we assume the dredged material in the barge has two major layers, due to settling in the barge during transport to the dump site.  The bottom layer of 5,352 cu meters (7,000 cu yds) has a higher volumetric concentration of sand, and a top layer of 2,648 cu meters (3,464 cu yds) has a lower concentration of sand and slightly higher concentrations of silts and clays.  The bulk density for both layers is about 1.33 g/cc (close to 1.35 t/cu m).

The concentration of sand, 0.09 and 0.06 (in the two layers respectively) was used due to the fact that this project is excavating deeper, past the top layer in the channel that contains relatively less sand and more silt and clay; i.e. the deeper the dredging, the higher concentration of sand would be expected.

The model output (Appendix 3) gives "plots" for the surface water concentration of suspended material (relatively small) and sea floor accumulation of the settled material.  See the last pages of the plots for total bottom accumulation.  Other tables describe the dimensions and position of the plume in the water column.

Note that the suspended material values should be considered at radial distances from the disposal site, once again due to the varying direction of the currents.

Sediment #5 has the lowest total solids and highest concentration of lead at 96.89 ppm, which is equivalent to 156.7 mg/l. This is nearly identical to the Chromium values in the same sample.  All the other sediment samples have lower concentrations.

Regulatory levels for both lead and chromium are 5.0 mg/l.  These are the toxicity levels in Table 3.  But in Table 2, the standards are different for lead and chromium; lead has a much lower allowable concentration.  Therefore, lead is considered to be the "conservative" tracer.  For the original disposal site using 350 m of water, and using the 156.7 mg/l concentration for lead, the maximum concentration of lead in the accumulation on the bottom is 8.9 mg/l.

3.3.3    Pipeline Discharge Modelling - Cutter Suction Dredge

The algorithms for modelling a continuous pipeline discharge were developed in the late 1970's and early 1980's, and are still evolving as a result of technological advances. A new model, D‑CORMIX, is currently under evaluation for this application, but has not yet been sanctioned for use.  The model used for this work, CDFATE, is part of the ADDAMS suite of environmental models recommended by the US Corps of Engineers, Waterways Experiment Station.  It is based on a widely‑used point source model, CORMIX, which assumes a Gaussian distribution for the plume shape.  The model results presented in Section 6.3.4 are to be used as a rough estimate, and field experiments should ultimately determine the best dredging operation practices to use in this situation.

3.3.4    Cutter Suction Dredge Discharge

The input parameters used for CDFATE are as follows:

Mean depth of receiving water              20 m (Modelled as a straight, uniform  channel)

Bottom roughness, Mannings coefficient            0.035

Mean velocity of receiving water                       0.15 m/s

Water density profile                             Uniform

Density of receiving water at 20m                      1020 kg/m3

Density of dredged material                               1250 kg/m3

Distance from nearest bank                               260 m

Depth of discharge                                6  m (***The model not allow a discharge depth greater than 1/3 the total depth)

Discharge rate                                      0.24 m3/sec

Pipe diameter                                                   0.75 m

Vertical angle of pipe with water surface       90 degrees

Angle pipe makes with the current                     0 degrees

Solids in effluent                                                30%

The output for CDFATE is presented in Table 1 below.  The x ‑axis is aligned from north to south, and the y‑axis from east to west.  The point of origin (0,0) is the point of discharge assumed to be at the north end of the channel basin, 260 m from the east bank.  The channel basin is approximated in the model to represent the area between Rackham’s Cay (east bank) and the West Middle Shoal (west bank) that is 20 m deep.  The parameter BH is defined as the half width of the Gaussian plume measured horizontally.  The ZLTMZUB parameter is interpreted to be the upper plume boundary minus the lower plume boundary in the vertical direction.

Table 1:  CDFATE Model output

3.4       Socio-economics

The socioeconomic impacts assessment (SIA) study area of this project was the area including the proposed port expansion and surrounding areas within a 2 km boundary. It included areas surrounding the Harbour that might be impacted by the proposed expansion activities as well as direct and indirect users of the port (and water) area and other stakeholders. In some instances, for ease of description and discussion, the study area may be specifically divided into three distinct regions of Port Royal, Kingston, and Portmore/Causeway, but, should be viewed as part of the whole SIA area. Socioeconomic impacts may be both micro (local) and macro (regional and national) in extent.  The local impacts were usually those perceived within the SIA area while macro impacts were those perceived nationally.

Information on the existing socioeconomic and cultural environment was obtained by desktop research and interviews with the Statistical Institute of Jamaica (STATIN), the Town Planning Department (TPD), Kingston and St. Andrew Corporation (KSAC) and the Port Authority of Jamaica (PAJ). The socioeconomic profile draws heavily from existing information contained in The Portmore Causeway Project (1996-7), The Strategic EIA - Port Royal Heritage Tourism Project (1998), and the Kingston Foreshore Road (1999). In the above mentioned Portmore Causeway Project (1996-7), a stratified random socioeconomic survey was administered and analyzed using SPSS.

Combined, these studies and other relevant reports such as the Kingston Harbour Rehabilitation Plan provided substantial information. To every extent possible, the information was then updated through projections, field investigations, and further research. Information was also obtained from the Public Forum on this porject held on 3 August 2000 by the PAJ.  As a follow-up to the Public Forum, public interviews/ consultations were also held with representatives of the key fishing communities of Hunts Bay at the Causeway, Greenwich Town, Rae Town and Port Royal during 21 August to 15 September 2000. A land use survey was also conducted within the larger Hunts Bay - Causeway area - proposed site for land reclamation during May 21-22, 2000.