MARINE ENVIRONMENT AND ECOLOGY Construction Impacts 6

MARINE ENVIRONMENT AND ECOLOGY
Construction Impacts
6.5.1 The main construction impacts will be due, directly and indirectly, to the presence and construction of the Qatalum Port and dredging activities. So far as is possible, the remainder of this Section assesses the significance of the potential impacts associated with the two possible Port locations and addressees the following:
? permanent habitat loss / physical disturbance associated with the construction and presence of the Qatalum Berth / Jetty;
? permanent habitat loss / physical disturbance associated with the construction of the Original Port concept Service Corridor;
? sediment re-suspension and deposition during dredging and dewatering, leading
? to:
– increased turbidity, resulting in inhibition of primary production of flora,
– smothering of sub-tidal marine habitats / communities via sediment deposition xviii; and

xvii
After submission of revision 01 of the EIA report, the Alternative Port concept was chosen. On the other hand the text, relating to both Port concepts, within this updated (revision 02) EIA report has been retained, unchanged.
xviii
The marine impact assessment does not include computer modelling of the potential suspended solids plume that will be produced as a result of dredging. However, a qualitative assessment will be made using existing
– release of sediment-bound contaminants to the water column;
? Impacts of dredging on fish;
? Disturbance to marine species from increased underwater noise activities; and
? Accidental release of hazardous materials to the marine environment, resulting in degradation of seawater and sediment quality.
It is understood that there will be no direct disposal of any dredged material into the marine environment.
Permanent Habitat Loss / Physical Disturbance
6.5.2 The development of the new Port, at either location, will require dredging to depths between -13 m and -15 m CD, in order to construct the necessary access and turning basins for incoming ships. This assessment has been carried out on the basis of the Qatalum preferred common solution (as shown in Figure 3.2). For the purpose of the EIA report, the following three dredging scenarios have been considered for the Alternative Port concept:
? Scenario 1 – minimum dredging for the construction of the alternative Jetty; site fill material mainly sources from onshore materials;
? Scenario 2 – dredging to take place only areas that have been dredged previously, fill material to be supplemented with onshore sourced materials (this would mainly involve dredging in areas A and B on Figure 3.8.
? Scenario 3 – dredging to provide the sole source of fill material; this would involve dredging areas A, B, C and F on Figure 3.8.
6.5.3 A summary of the estimated dredge areas and volumes for the Alternative Port dredging scenarios 1-3 are provided in Table 6.4, below.
Table 6.4 – Alternative Port Dredging Scenarios
Scenario 1 Scenario 2 Scenario 3
Description Jetty, As scenario 1, plus:
Areas A and B As scenario 2, plus:
Areas C and F
Total Dredged Area (km2) ~0.3 up to 0.9 up to 1.8
Total Dredge Volume (m3) 1,000,000 3,000,000 ~ 6,000,000
(~10,000,000 available)
6.5.4 It is anticipated that the main dredging operations would be carried out by cutter suction dredging. For the Original Port concept this would take place over a 6 month period; with a lesser amount of dredging in the 2 to 3 months following this. The duration of the dredging for the Alternative concept would depend on which option was carried forward. For the combined Qatalum Original Port / Gabbro expansion dredge area, approximately 72% of the 1.3 km2 dredge area will comprise areas of ‘Very Dense’ sea grass cover (as indicated in Figure 5.16). The overall extent of sea grass cover across the Qatari coast is not known, although other studies have recorded significant areas of sea grass beds present at Eastern Ras Laffan, Fuwariat (north of Ras Laffan) and Al-Khor/Al-Dhakhira. The area in the vicinity of the proposed Jetty, and the possible dredge areas A and B, will have already been disturbed as a result of previous dredging activities. A significant proportion of possible dredge areas A and C are adjacent to the existing northern approach navigation channel. In addition, the area immediately in front of planned MIC Berth No.7, which is adjacent to the Qatalum Jetty, will be further disturbed due to the construction of Berth No. 7. The desk-top study and video footage review for the Alternative Port location and possible dredge locations showed that these areas are largely barren with, at best, a patchy 1-10% of sea grass coverage (see Section 5.8 for further detail). Macro benthic fauna and flora were found to be present at lower species diversity and abundance compared with other areas around the Qatar coast. No specific mitigation is recommended, however, if dredging scenarios 2 and 3 are taken forward a pre-dredging survey for marine ecology will be undertaken as part of a wider monitoring package (see below). For the Original port concept, a small area of sub-tidal habitat along the eastern edge of the lagoon would be ‘lost’ for use as an access corridor (indicated in Figure 3.3). The area lost is estimated at approximately 435 m2. The loss will be certain and permanent, although limited in its extent and area. However, this small area comprises between only 0 and 1% of sparse sea grass cover (see Figure 5.16), with low numbers and diversity of species observed.
Impacts Associated with Sediment Re-suspension and Deposition
6.5.5 During dredging, sediment, which will include a percentage of finer sediments, is brought back into suspension from which it will re-enter the water column and then disperse with the direction of the current. Sediment plumes may be generated where fines are re suspended in the water column due the following activities:
? Seabed disturbance during dredging;
? Material (sediment) loss during dredging and subsequent transport;
? Re-suspension of losses during pumping and placement of fill; and
? Discharge of de-watering effluent during dredging.
Turbidity
6.5.6 The waters off the MIC coast are generally clear and an increase in turbidity could result in inhibition of primary production of marine flora (e.g. sea grass beds). Increased turbidity causes a reduction in the light available for photosynthesis and in the time available for net photosynthesis, therefore, reducing growth. The percentage cover of sea grass recorded during the 2004 QASCO marine survey37 indicated that the 2002 dredging of main navigation channel had not resulted in a significant impact on sea grass from approximately 100 m eastwards of the navigation channel. In addition, other surveys, carried out since dredging of the main channel occurred in 2002, would suggest that healthy sea grass beds remain in the vicinity of dredging activities. Epifauna and infauna are unlikely to be notably affected by changes in turbidity. Hydrodynamic data, along with the fact that sediments at both Port concept locations contain a large amount of fine material, would suggest that re-suspended sediments will remain in suspension for some time and not be dispersed quickly away from dredging areas. This can cause prolonged periods of high turbidity in proximity to dredging areas. For the Alternative Port location, the impact on sea grass beds in the MIC area, associated with increases in turbidity, is considered to be of minor significance for dredge scenarios 1 and 2 and of minor to moderate significance for scenario 3.
Smothering of Marine Organisms
6.5.7 Depending on the strength of currents at the time of construction, sediments could be mobilized, transported and be deposited elsewhere. Such deposition could lead to the smothering of organisms where sediment settles. Smothering could adversely affect sea grass beds and the feeding and respiratory functions of epifauna, especially of filter feeding organisms, such as corals, molluscs, gorgonians, etc. Sea grass and filter feeding organisms are generally intolerant to smothering. In addition, the redistribution of fine sediments may lead to changes to the make-up of infauna communities in areas affected. Epifaunal and infaunal communities are not considered to be of great ecological value in the proximity to works at either Port locations, or in the dewatering discharge area, and therefore the impact on these species is not considered significant. The significance of the impacts associated with the Alternative Port concept is anticipated to be of minor significance for dredge scenarios 1 and 2, and minor to moderate significance for dredge scenario 3.
Release of Sediment-Bound Contaminants to Water Column during Dredging and Reclamation
6.5.8 Re-suspension of sediment can re-introduce contaminants into the water column in both sediment-bound and dissolved forms. As discussed in Section 5.4, contaminant levels at the Original Port site are low; thus, the release of sediment into the water column during dredging is expected to have no significant adverse effect on water or sediment quality with respect to contaminant levels. Previous surveys33, 34 have indicated that the sediment in the region of the possible dredge areas for the Alternative Port concept could be contaminated with TPH and certain metals. The dispersal and subsequent settlement of sediments could have impacts upon water quality and consequently on marine ecology, through filter feedings, accumulation in flora, ingestion by herbivores and bioaccumulation up the food chain. The potential significance is likely to increases with the scale of dredging, i.e. for scenarios 2 and 3. However, the removal of dredged sediment from the marine environment, for storage and dewatering onshore, will reduce most impacts. In addition, mitigation adopted to reduce the effects of increased turbidity will help to minimize potential effects.
Mitigation and Control to Prevent Sediment Re-suspension and Deposition
6.5.9 Dredging operation and management shall be undertaken in accordance with the principles of BAT and best international practices. Typical measures that would be considered in the EMP include:
• Ensure that production rates do not exceed pumping capacity to avoid the overflow and release of excess material;
• Ensure there is no leakage from the sediment transport pipeline from the dredger to the dewatering / reclamation areas; and
• Use of silt traps, such as weirs, and / or settlement areas to reduce the amount of suspended sediment in the de-watering effluent released to sea.
Prior to dredging, sediment transport modelling should be carried out, for both Port concepts, to determine the potential direction and dispersion of re-suspended sediments.
Sediment and Seawater Quality
6.5.10 No pre-dredge monitoring of sediment or seawater quality is recommended for the Original Port concept. During dredging suspended solids should be monitored at representative locations, agreed with SCENR. No post dredging monitoring of sediment or seawater quality is recommended.
Analysis should be conducted for the following sediment parameters:
? Total Organic Carbon (TOC);
? Total Petroleum Hydrocarbons (TPH);
? Metals (Be, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, V, and Zn);
? PH; and
? Nutrients (total nitrogen and phosphorus).
Seawater samples should be taken from both from surface waters and from waters 0.5 m above the seabed and analyzed for the following:
? Total Suspended Solids (TSS);
? Salinity;
? Total Petroleum Hydrocarbons (TPH);
? Metals (Be, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, V, and Zn);
? Polychlorinated Biphenyls (PCB);
? PH; and
? Nutrients (total nitrogen and phosphorus).
Biological Monitoring
6.5.11 Post dredging biological surveys for both epibenthic organisms (e.g. sea grass communities, gorgonians etc.) and soft sediment infauna should be undertaken at a number of sites to determine the effects of dredging activities for either Port concepts. The focus of the surveys is anticipated to be the health of sea grass beds. For the Alternative Port concept detailed biological pre-dredging monitoring will only be required if dredging scenarios 2 and 3 are selected. A video survey, undertaken along the footprint of the new Jetty and the immediately adjacent area, will suffice if scenario 1 is taken forward. No biological pre-dredging monitoring is required for the Original Port location.
Impacts on Fish
6.5.12 Dredging activities can affect fish directly through increased mortality, whereby fish may be entrained by dredge machinery, through and loss of habitat. Indirectly impacts can also arise due to increased suspended solid loads and/or decreased dissolved oxygen concentrations in the water column. Increased suspended sediment levels can cause physical damage to fish through gill damage and can reduce the ability of fish to locate prey items. However, fish are mobile and can move away from affected areas; in addition, none of the surveys in the vicinity of either Port locations identified significant fish populations or species diversity; thus this impact has been assigned a minor significance.
Underwater Noise
6.5.13 Underwater noise can affect the natural behavior of adult fish; however the Qatalum and
SARC marine surveys have indicated that there is minimal fish interest in proximity to both Port locations and the associated dredging areas. The noise level from dredging activities is therefore highly unlikely to have to have a notable impact on fish and this has been assigned a significance rating of negligible.
Release of Hazardous Materials to Environment
6.5.14 The potential exists for the degradation of seawater and sediment quality to occur as a result of accidental spills, leaks or releases of hazardous materials during construction, and commissioning. Such releases could include those of fuels, lubricants, paints and cleaning products (e.g. solvents). In the absence of any mitigation release of such materials to the marine environment would constitute a potential impact of moderate significance but would be dependent on:
? Physical / chemical properties of the material released;
? The volume of material released; and
? Duration of spillage/discharge event.
Environmental and waste management are discussed further in Chapter 8. Potential impacts arising as a result of emergency events / large scale accidents have been addressed in the environmental risk assessment Section of this Chapter (Section 6.10).

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