Marine Licence ML 28_12 Islandmagee Gas Storage Project

Date published: 03 April 2020

Last updated: 09 February 2024

The Islandmagee Gas Storage Project; comprises the construction by solution mining of seven underground caverns in the Permian salt strata approximately 1,700m below Larne Lough, off Islandmagee, County Antrim.


The project includes the design and construction of a surface brine pumping facility, a gas compression facility, associated gas pipelines, a brine and seawater pipeline and associated infrastructure.


The components of the Project which are subject of this application are limited to (i) the boreholes and subsurface caverns to be leached (ii) the seawater intake structure and (iii) the brine discharge pipeline.


Proposal Description

Reference: ML 28_12
Project Type: Construction, alteration, improvement
Location: Islandmagee, Larne Lough
Discharge Pipe (Discharge End) D 4507 0347
Intake Pipe (intake End) D 4464 0327
Project Description: The Islandmagee Gas Storage Facility will most likely be constructed as a series of discrete Design and Built contracts, due to the wide range of specialist construction techniques required for such a complex project. The anticipated phasing and scope of the activities affecting the marine environment are outlined below:

The construction of the brine discharge pipe and the seawater intake pipe will commence as soon as possible after the detailed design is complete (anticipated in late 2013). The construction of the two pipelines will run concurrently. The first stage will be the ordering of the materials which are expected to have a lead time of some 12 months. During this time it is anticipated that the contractor would start and complete the civil works on the shoreline and cliff faces in preparation for installation of the pipelines. Once on site, the onshore pipelines are expected to take approximately 2- 4 months to lay across Islandmagee. The directionally drilled section of the outfall extending to a distance of approximately 450m offshore is expected to be installed concurrently with the onshore pipelines.

The solution mining will start with the drilling of the first of seven boreholes to a depth of approx. 1,700 metres. These will each take approximately one month to drill. A single drilling rig will be used on a 24/7 basis, with the rig moved from one completed well to the next. Each completed well will be capped with a well-head and will have concentric leaching strings inserted ready for the introduction of the seawater. The well-heads and well pad will be located onshore although the boreholes will be directionally drilled out under Larne Lough to the positions where the caverns will be constructed.

The solution mining will involve the pumping of sea water into each borehole as it is completed to leach (dissolve) the salt to form the void of each cavern. The returning concentrated brine solution is withdrawn and is pumped along the brine discharge pipeline to an outfall discharge point in the North Channel.

The caverns will be leached in two distinct phases of three caverns each, with a further cavern being leached at a slower rate during both phases. Each phase will last approximately 22 months and the two phases will run consecutively with a minimal interlude between the two.

The drilling will start as soon as the brine pumping facilities are constructed and commissioned and the brine discharge and seawater pipeline (described above) are complete. This is anticipated to be mid-2015.
Applicant: Islandmagee Storage Limited
Date Issued:
Licence Start Date: 05/11/2021
Licence End Date:

The relevant documents for this application can be found on the Environmental Consent Decision webpage Notice of Environmental Consent Decision page.

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