4. Potential Spill Sources and Control Measures

4.1. Potential Spill Sources and Control Measures

  1. Construction and operation and maintenance works will be undertaken in such a manner as to minimise the risk of spills and accidental pollution events.
  2. Spills are considered most likely to occur during transfer of hydrocarbons and chemicals offshore (e.g. during refuelling operations, or in the event of a leak within equipment within the Array). However, due to measures adopted such as operating procedures, toolbox talks and experience working in the marine environment, the majority of spills associated with the Array are considered likely to be small (Tier 1).
  3. The Contractor/Subcontractor MPCP will be requested to include the following information:
  • an inventory of the types of pollutants (particularly hydrocarbons) to be used during the construction and/or operation of the Array. These should include volumes, type and source for each of the pollutants identified (e.g. hydraulic oils, lubricants etc); and
  • preventative measures relevant to the activities to be undertaken at the Array.
  1. A register of all the vessels involved in construction and operation activities at the Array shall be developed and updated by the Marine Coordinator. This register will list the types and volumes of hydrocarbons carried on board vessels associated with the Array.
  2. The risk of spillage and pollution will be minimised by using correct procedures during the construction and operation and maintenance phases. Potential spill risks and control measures will be identified using planning tools such as:
  • programme review meetings (involving relevant Contractors);
  • pre-commencement meetings to review the final work programme(s); and
  • preparation of Risk Assessment Method Statements (RAMS) for all operations including hazard and risk identification. This will test the work programme for likelihood and severity of all potential risks and to identify appropriate control measures.
  1. Section 4.2 contains information regarding pollution sources and risk assessment, together with proposed control measures.

4.2. Pollution Sources and Risk Assessment

4.2.1. Tier Classification

  1. Potential spill scenarios will be dictated by the chemical inventories (including hydrocarbons) associated with activities associated with the Array.
  2. Levels of response for oil spill are generally divided into three tiers, depending on the severity of the spill, the resources required to deal with the spill, and the potential impact on environmental and human receptors. Applying a tiered approach ensures the appropriate resource can be made available for potential pollution incidents. These tiers are commonly described as follows and are illustrated in Figure 4.1   Open ▸ :
  • Tier 1 response is that which is immediately available on site, geared for the most likely and low risk spill. Generally, Tier 1 responses will be managed by the Contractor/Subcontractor;
  • Tier 2 response is for less frequently anticipated spills of larger size and for which external resources at a regional level will be required to assist in monitoring and clean-up; and
  • Tier 3 response is in place for the very rarely anticipated spill of major proportions and which will possibly require national and international resources to assist in protecting vulnerable areas and in the clean-up.

Figure 4.1:
Tier Definition (based on MMO, 2020)

Figure 4.1: Tier Definition (based on MMO, 2020)

 

  1. Tier 3 scenario usually covers an exceptionally large volume of spilled oil, usually a rare but highly significant event, such an oil well blowout or major spill from a ship. However, a Tier 3 response may also be required for smaller spills which would usually fall under Tier 2, but if located in highly sensitive areas (e.g. near to designated sites with features vulnerable to the impact of accidental pollution), or when highly specialised strategies to deal with the spill may be needed and are not available locally.

4.2.2. Array Potential Spill Scenarios and Control Measures

  1. Table 4.1   Open ▸ describes the potential spill scenarios and control measures identified for the Array. This table will be refined prior to commencement of construction and adapted accordingly for the relevant Contractor MPCP and as much is subject to change once further detail is available. Furthermore, the risk assessment will be reviewed and updated annually or after significant legislative or procedural changes as necessary after completion of the construction phase to verify its relevance before the operation and maintenance phase of the Array commences.
  2. The main source of hydrocarbons associated with the Array will include the following:
  • wind turbines: synthetic oil, hydraulic oil, gear oil and diesel fuel; and
  • OSPs: diesel fuel, transformer coolant oil, HVAC coolant.
  1. The volumes of these will be limited to the bunkering capabilities of the vessels. The realistic maximum adverse scenario would be a complete loss of fuel inventory from two large vessels (either as a result of a two vessel collision or a vessel to wind farm allision).
Table 4.1:
Potential Spill Scenarios and Control Measures for the Array