Limerick Southern Ring Main – Internal Leak Repairs

Case Studies

Limerick Southern Ring Main - Internal Leak Repairs

October 2015

Background of the Project

Limerick City Council implemented a Water Conservation Project, in line with the Department of the Environment, Community and Local Government (DECLG) Circular L6/07.

One of the elements of their Water Conservation Programme was the commissioning of Southern Ring Main, which has been constructed in sections coinciding with the completion of Phases 1 and 2 of the Limerick Southern Ring Road Project (M7/N18).

The Southern Ring Main is part of a wider Limerick City, Environs and County Area Trunk Water Mains Development Scheme, which when fully complete will integrate the Limerick City and Shannon estuary water supply schemes. Commissioning of the Trunk Main will provide greater security of supply and enhanced fire flows to the Limerick Water Supply Scheme and in particular to the north side of the city.

The Southern Ring Main extends from the Newcastle Reservoir, Monaleen in the east of the city, to the Ennis Rd at Ivan's Cross.

ShareRidge Ltd's Roles and Responsibilites

  • Undertaking all specified and necessary works to allow for the commissioning of the existing Southern Ring Main and specified existing distribution main connections.
  • The investigation, identification and repair of leaks within sections of the southern ring main which have previously failed pressure testing.
  • The provision of new and replacement of existing specified instrumentation and fittings to the southern ring main and specified existing connecting mains, including connections to power supply and monitoring/control kiosks.
  • The actuation of existing butterfly valves, including the provision of specified actuators and connections to power supply and control kiosks.
  • Pressure testing of the existing Southern Ring Main and specified existing connecting mains, including the investigation, identification and repair of any leaks found during testing.
  • Swabbing, sterilisation and commissioning of the Trunk Main and specified existing connecting mains following successful completion of pressure testing.
  • The construction, testing, and commission of specified new watermains to complete connections between the city WSS and the commissioned Southern Ring Main including all fittings, meters, PRV's and chambers.

Preliminary Works

ShareRidge Ltd commenced testing the following sections of existing watermains:

  • Trunk Main - Approx. 13.1KM of 600mm/700mm/1000mm diameter ductile iron and twin 450mm diameter HDPE trunk main.
  • Distribution Main, Old Tipperary Rd - Approx. 1.3km of 400mm Ductile Iron.
  • Distribution Main, Rossbrien Interchange, Childers Rd - Approx. 780m of 400mm/500mm Ductile Iron.

Preliminary Air tests and Hydraulic pressure tests proved unsuccessful and therefore further consultation was required with the Client (Irish Water) and their representatives (RPS Consulting Engineers).

It was agreed to carry out further CCTV and Leak Detection works in order to try and understand the reasons for the failure of the testing. ShareRidge Ltd also carried out man entry works and air tested joint by joint in designated areas where the number of leaks was determined to be at a high level.

Leak Investigation Results

There was deemed to be a high level of leakage failure at the flexible and anchored joints, and minimal leakage at socketed joints all along the pipeline. The main areas for concern were outside existing chamber locations as there were four number flexible joints located at each. ShareRidge Ltd and the client carried out costs estimates for the anticipated level of repair works and it was during this period ShareRidge Ltd submitted an alternative proposal for the repairs.

Alternative Proposal

ShareRidge Ltd proposed an internal leak repair method as opposed to open cut methods. This type of Repair is called AMEX-10 and is carried out by PMP Utilities who come from the UK.

The repair contains the following components:

  • EPDM rubber
  • 316 Stainless Steel

How it works:

  • Provides a new water and air tight seal which spans the leaking joint and surrounding area.
  • Can be used in pipelines of any diameter where safe man access is achievable.
  • A flexible mechanical seal which can provide a "no dig" solution eliminating the need for invasive access.

The following illustration demonstrates the profile of the AMEX-10 within the pipeline (image courtesy of PMP Utilities):
Profile of AMEX 10 within pipeline
Click image for larger view

The following pictures demonstrate steps carried out when using the AMEX-10 repair within the pipeline (images courtesy of PMP Utilities. Click any image to view larger version.):

  • Step 1 - Preparation of the joint
    The internal perimeter of the pipeline is made ready to receive the AMEX-10 repair:
    AMEX 10 repair step 1
  • Step 2 - EPDM rubber is installed:
    AMEX 10 repair step 2
  • Step 3 - Stainless Steel Rings jacked into position and the joint is tested:
    AMEX 10 repair step 3

The benefits with this alternative proposal were as follows:

  • Reduced levels of traffic management as point of entry to carry out the works could be located at a preferred location
  • Little or no impact on traffic or public flow
  • Public Interface greatly reduced as works are internal
  • Can be used on steep gradients and in vertical pipes via rope access
  • Excavation footprint practically non-existent - this was a major factor as locations on the Southern Ring main are very busy areas (Ennis Rd, Monaleen Rd) where the impact on traffic would be at a high level for a considerable amount of time (long diversions, road closures). Sections of the pipeline also run along and through the M6 and M18 motorways where excavation works would be practically impossible. For instance at one location, the pipe is located at 12m deep under the existing slip road and fly over on the motorway. To expose this section of pipeline would mean closing down the motorway for a number of weeks.
  • Programmes accelerated due to minimal excavation and reinstatement works
  • Joint individually tested to ensure there are no leaks after installation
  • Repair will last in excess of 50 years
  • Operationally to 25bar
  • Tested to 50 bar
  • WRAS Approved

Approval of the Proposal

After considerable investigation and in depth consultation with other bodies who have used the AMEX-10 repair method and PMP Utilities the client (Irish Water) accepted ShareRidge Ltd's proposal.

The Works

ShareRidge Ltd carried out advance works prior to PMP Utilities coming to site. This involved the following:

  • Surveyed and determined exact entry points for the leak repair crew
  • Consultation with the land owners and relevant bodies (Direct Route Limerick Tunnel operators)
  • Excavated and exposed the existing watermain at these
  • Cut the existing pipeline and removed the pipe spool which provided access into the watermain
  • Ensured the pipeline was clean and water free by carrying out man entry works and inspections
  • Protected the entry points until the leak repair crew came to site

Once the leak repair crew came to site, ShareRidge Ltd carried out the following attendance works:

  • Inducted the crews
  • Escorted the crews to and from each of the entry points
  • Via man entry identified the joints to be repaired to the foreman of the leak repair crew
  • Provided a continuous air supply via an air trailer during the course of the works
  • Liaised with the relevant bodies to ensure site areas were ok for access (Limerick Council, Irish Water, Direct Route Limerick Tunnel operators, land owners)
  • Completed daily progress reports for the client as the works progressed

Once the leak repair crew had completed their works, ShareRidge Ltd carried out the following works:

  • Replaced the pipe spool
  • Backfilled all excavations
  • Permanent reinstated the works area
  • Provided test results to the client
  • Handed back the sites to the relevant bodies and land owners

Results

Each of the repairs installed were individually pressure tested. All joints passed the tests. ShareRidge Ltd is currently carrying out hydraulic testing on all sections of the pipeline. All of the sections tested to date have passed.

Images from the works
(click any image to view larger version)