5. POTENTIAL IMPACTS
5.2 Offshore operation
For operation offshore, the potential impacts are listed in Table 5-13.
Table 5-13 Potential impacts for operation offshore and identification of potential receptor interaction.
Potential impact Receptor*
Presence of pipeline
Bathymetry; hydrography and water quality; surface sediments and contaminants; bathymetry; benthic habitats, flora and fauna; fish; seabirds and migrating birds; biodiversity;
protected areas; shipping and shipping lanes; commercial fisheries; raw material extraction sites and dumping sites military practise areas; cables, pipelines and wind farms Restriction zone
Commercial fisheries; raw material extraction sites and dumping sites; military practice areas; shipping and shipping lanes
5 Order on discharges of substances and materials for the sea5 no 394 of 17/07/1984 (Bekendtgørelse om udledning i havet af stoffer og materialer fra visse havanlæg).
BOX 5-4: Summary of discharges to sea from hydrotesting FLOODING, CLEANING, GAUGING AND DEWATERING
Maximum total discharge volume: 374,000 m3 (220% of pipeline volume, contingency for re-flooding if first re-flooding is unsuccessful)
Duration of discharge: 2 weeks
ADDITIVE FOR PREVENTING CORROSION OF PIPELINE (OXYGEN SCAVENGER)
Chemical usage: 20 tonnes of NaHSO3 per flooding, based on assumed oxygen content of 8 mg/l
Discharge water is assumed to be oxygen-free, as almost all NaHSO3 will have reacted with O2 before discharge
ADDITIVE FOR PREVENTING HYDRATES FORMATION
Chemical use: 240 m3 Mono Ethylene Glycol (MEG) used for drying pipeline / avoiding hydrate formation during gas filling
The water slugs with MEG (between the pigs) will be recovered to storage tanks in Poland The discharge of water from pressure testing requires a permit from Danish Envoronmental Protection Agency and the discharge permit is granted on the basis of the Order on discharges of substances and materials for the sea5. This order is attached to the consolidated Danish Marine Environmental Act (Section 7.8)
Document ID: PL1-RAM-12-Z02-RA-00003-EN 90/433
Potential impact Receptor*
Heat from pipeline Hydrography and water quality; benthic habitats, flora and fauna; fish
Underwater noise from gas flow in
the pipeline Marine mammals
Release of contaminants from anodes
Hydrography and water quality; surface sediments and
contaminants; benthic habitats, flora and fauna; fish; protected areas
Physical disturbance above water Birds; biodiversity; commercial fisheries; tourism and
recreational areas; protected areas; shipping and shipping lanes Emissions to air Climate and air quality; population and human health
Safety zones
Shipping and shipping lanes; commercial fisheries, raw material extraction sites and dumping sites; military practise areas;
environmental monitoring stations; tourism and recreational areas
* Assessments of potential impacts on Natura 2000 sites and Annex IV species follow the methodology of Sections 8.3 and 8.4.
Employment generation will be very limited during operation of the pipeline and will not be dealt with further.
5.2.1 Presence of pipeline
The presence of the pipeline may change the seabed conditions and hydrodynamics, resulting in temporary disturbance or permanent loss of habitats for benthic flora and fauna; another potential impact is the introduction of a new substrate i.e. artificial reef.
The pipeline length in Danish waters is 137.6 km, of which a large proportion is laid directly on the seabed and not trenched or supported by rock installations. Rocks are installed as support for the pipeline and/or to cover and protect the pipeline at cable crossings and potentially at shipping lanes. Rock installations placed at numerous locations create new substrate at the seabed.
BOX 5-5: Summary of offshore operation in Denmark
OPERATIONopeopeationoperopeoperationsasasasasasasasasasasasasasassasasas OPERATION TIME: Approx. 50 years
DIMENSIONS:
• Pipeline width: Approximately 1 m
• Pipeline length in Danish waters and disputed area: 137.6 km
• Trenched pipeline length (expected): 63.5 km
• Rock installation: Approximately 13 locations RESTRICTION ZONE: 200 m / each side of pipeline HEAT FROM PIPELINE: max 0.5 °C, 0.5-1 m from pipeline
MAINTENANCE AND SURVEY TRAFFIC: 1 time/year
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5.2.2 Restriction zone
Under the administrative order on protection of submarine cables and submarine pipelines6, cable or pipeline fields are given a 200 m wide restriction zone along and on each side of the
infrastructure. Ships may not, without urgent necessity, anchor in the cable and pipeline fields established for such infrastructure (e.g. pipelines for the transport of hydrocarbons, etc.), which cover the associated restriction zones. In the restriction zones, suction dredging, fishing for stones as well as any use of tools or other gear that is dragged on the seabed is prohibited.
This environmental impact assessment for the Baltic Pipe project is based on the scenario in which the pipeline has a restriction zone as described above. The restriction zone is assessed to have a potential impact on ships and activities in the Baltic Sea (commercial fisheries; raw material extraction sites; military practice areas; shipping and shipping lanes). However, as a part of the further development of the project, it will be clarified if it is possible to eliminate the restriction zone. A scenario with no restriction zone is assessed to have a potential impact on trawling by commercial fisheries.
5.2.3 Heat from pipeline
The temperature of the gas in the pipeline varies, depending on the flow conditions and the temperature of the surrounding seawater and sediments. Figure 5-11 shows the simulated temperature of the gas in the pipeline along the route, for the normal flow situation from Denmark to Poland. The temperature profile for the flow situation from Poland to Denmark is shown in Figure 5-12.
For the situation with gas flow from Denmark to Poland (Figure 5-11), the temperature of the gas at the Danish landfall will be approximately 50°C. The temperature thereafter drops towards the temperature of the surrounding seawater at a rate determined by the flow conditions and the temperature difference between the gas and the surrounding seawater and seabed surface sediments. The temperature analysis, which includes the cooling caused by the pressure drop (the Joule-Thompson effect), has been used when designing seabed interventions etc. for ensuring that no ice formation takes place at the pipeline surface.
6Administrative order no. 939 of 27/11/1992 on protection of submarine cables and submarine pipelines (bekendtgørelse om beskyttelse af søkabler og undersøiske rørledninger).
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Document ID: PL1-RAM-12-Z02-RA-00003-EN 92/433 Figure 5-11 Simulated temperature profiles of the gas along the Baltic Pipe pipeline – flow from
Denmark to Poland (Rambøll, 2018l).
For the situation with gas flow from Poland to Denmark (Figure 5-12), the temperature along the pipeline is very close to the temperature of the surrounding seawater and seabed surface
sediments.
Figure 5-12 Simulated temperature profiles of the gas along the Baltic Pipe pipeline – flow from Poland to Denmark. (Rambøll, 2018l).
The largest temperature difference between the gas in the pipeline and the surrounding seawater and sediments is hence approximately 50°C, which will occur in winter near the Danish landfall.
The temperature difference will cause heat transport from the gas to the surrounding seawater and sediments, which is proportional with the difference in temperature, i.e. largest near the Danish landfall.
Analysis and monitoring from comparable offshore pipeline projects have shown that the temperature impact is small and local. For the Nord Stream pipelines, in the area where the pipelines are exposed with the largest temperature difference (gas temperature: approximately 40°C), there was a small temperature increase (maximum 0.5°C) in the water near the seabed and in the water on the downstream side of the pipeline. The temperature change was only detectable at a maximum distance of approximately 0.5-1.0 m from the pipelines. When there was no current, the increase in water temperature was up to 0.1°C, 5 m vertically above the pipeline (Rambøll / Nord Stream 2 AG, 2017a).
A temperature impact of the same order of magnitude or less is expected from the Baltic Pipe pipeline near the Danish landfall, where the temperature difference between the gas and the surroundings will be the greatest.
5.2.4 Underwater noise from gas flow in the pipeline
Along the alignment through Danish waters, the pipeline will partly be trenched into the seabed and partly be exposed directly on the seabed. At stretches where the pipeline is trenched into the seabed, no underwater noise is expected to be emitted from the operating pipeline to the water above.
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During the operational phase, the gas flow will generate low levels of noise at low frequencies. In the literature it is acknowledged that underwater noise from subsea pipeline operation or
installation may occur, but the impacts are most likely to be much lower than the noise from commercial ships and will therefore be masked (IISD, 2018). Calculations carried out for a comparable submarine gas pipeline project in the Baltic Sea have shown that noise emitted from the pipeline itself due to the gas flow inside of it is of a very low intensity and only audible to marine mammals very close to the pipeline (Sveegaard et al., 2016).
5.2.5 Release of contaminants from anodes
As outlined in Section 3.3, sacrificial anodes mainly consisting of aluminium will be used as a back-up corrosion protection system in case of damage to the coating of the pipeline. Beyond the immediate vicinity of the anode (i.e. <5 m), the concentrations of metal ions within the water column because of anode degradation during the operational phase will generally be
indistinguishable from background concentrations.
Monitoring around the Nord Stream pipeline in the Baltic Sea has shown that concentrations of heavy metals in the water were below the detection limit approximately 1-2 m from the pipelines (Rambøll / Nord Stream 2 AG, 2017a). The same is expected to apply to the sacrificial anodes to be installed on the Baltic Pipe pipeline.
5.2.6 Physical disturbance above water
The physical disturbance above water during operation is mainly related to the presence and activity of survey and maintenance vessels. The physical disturbance is of the same nature as during the construction period (see Section 5.1.6), but with a much lower frequency. The expected frequency of surveys and maintenance is once per year.
5.2.7 Emissions to air
Survey and maintenance vessels will emit emissions to air during operation of the Baltic Pipe Pipeline. The delimitation and basis for air emissions calculations presented in Section 5.1.8 also apply to the offshore air emissions during operation.
Air emissions from offshore operation
The results of the air emissions calculations for operation of the offshore part of the project are presented in Table 5-14. The air emissions are presented as average emissions per year during an estimated operation time of 50 years.
Table 5-14 Air emissions from offshore operation, per year on average during the estimated operation time (50 years).
For the vessels carrying out survey and maintenance, exclusion zones will be defined around vessels carrying out the work, corresponding to the safety zone for “other” vessels during operation (500 m radius around the vessels).
The establishment of safety zones results in all ship traffic being requested to avoid these exclusive zones, thus potentially having an impact on both commercial and leisure shipping as well as fishery. The frequency of the survey and maintenance activities are, however, low, i.e.
approximately once per year.
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