Widening of a 1.6km length of Galway ring road from single to dual carriageway, with new cycle lanes and footways and overall Road Improvement. Works included four signalised junctions, 5km of new and diverted HV cabling, 40,000m of ducting, new water supplies and drainage, removal/re-planting of trees and various boundary treatments.
The site is located on the R338 Regional Road, extending from the roundabout at the rear of UCHG (Brown Roundabout) westwards to the roundabout at the Western Distributor Road (Deane Roundabout). The contract extends over approximately 1.6km and consists of the construction of a dual-carriageway road with dedicated bus lanes, 2m off-road cycle lanes and 2m footways in both directions. The proposed works also include the provision of 4 no. traffic signals junctions (including 2 no. new junctions) and 1 no. controlled pedestrian crossing.
The scope of works fall under the following headings:
- Traffic Management
- Excavation including excavation of soft ground
- Diversion of services
- Surface water drainage
- Provision of ducting for services
- Provision of retaining walls
- Road kerb construction including combined drainage kerb
- Road widening works
- Road pavement construction
- Provision and installation of 4 sets of Traffic Signals
- Provision and installation of Traffic Signs and Road Markings
- Landscaping works
- Provision and installation of Road Lighting
Earthworks entailed the excavation of both suitable and unsuitable material up to depths of 8m directly adjacent to live traffic in addition to dealing with a substantial number of existing live services. The total volume of excavation was in excess of 60,000 m3. Other earthworks operations include the construction of a capping layer using the imported 6F2 material, the total volume of which will be in excess of 20,000m3.
The surface water drainage consisted of a combined drainage kerb which was then carried to the main surface water pipeline via a large number of gully trap units. Approximately 3,800m of combined drainage kerb was installed with in excess of 2,400m of a carrier network ranging from 150mm Dia. to 750mm Dia. and depths up to 5m.
Existing and new was an important part of the works as this infrastructure supported a number of service providers and careful planning/liaison was essential to avoid unnecessary disruptions. The service providers included Eircom, Bord Gais, E-Net, UPC, ESB, Traffic Signals. A total of approximately 40,000 linear meters of ducting was installed during the course of the works.In addition to new ducting, the majority of existing ducting had to be lowered and protected, often with a concrete surround and at all times in conjunction with the service provider.
One specific element of the project involved the design and construction of an earth retaining structure approximately 170m in length with a maximum height of 4.5m. The solution selected was a combination of soil nailing and shotcrete, with the shotcrete being faced with masonry cladding.
This method of construction was selected both from a practical and economical viewpoint. Its suitability for the site constraints imposed upon us, (i.e. restricted working space) meant the elimination of significant temporary works which would have been necessary for the more traditional method of in-situ or precast concrete structures.