Landscape Frequently Asked Questions
Q. Who is responsible for maintaining the planting along the tramway infrastructure?
A. The Infrastructure Maintenance Contract (IMC) covers the maintenance of the entire infrastructure, including the tram stops and furniture, rails and track-bed and adjacent areas, both hard and soft. The IMC main Contractor may sub-contract the maintenance of the soft landscape section of the tender, which includes a set number of tasks to carry out on a weekly, monthly & yearly basis. Soft landscape maintenance tasks encompass weeding, strimming, pruning trees and shrubs, litter picking, replacement planting, grass cutting etc. This is under the remit of RPA Operations, please click here to view RPA Operations pages.
Q. How closely to the tramway can you plant trees and shrubs?
A. Depending on the type of plant and its potential growth, the final spread of a shrub should have a minimum clearance of 600mm from the swept path. (The swept path is determined from the Developed Kinetic Envelope (DKE) of the moving tram and is generally 300mm from the outer rails running parallel with the tracks, increasing in width on bends). Tree trunks should be a minimum 600mm back from the swept path and the tree crown should be a minimum of 3,050mm back from the Overhead Contact System (OCS) lines. Due care should be taken in deciding the variety of trees planted near Luas lines. Trees with upright (fastigiated) habits are preferable, and leaf litter should be minimised through species selection. The planting of trees 600mm from the swept path usually needs to be extended because of the potential growing spread of their crowns. A tree requires an absolute minimum planting pit of 2,000 X 2000 X 900 mm (w x w x d) in order to grow healthily. For this reason it is sometimes difficult to find enough space to plant trees close to the Luas lines.
Q. How do you deal with slope stabilisation on new and existing lines?
A. Depending on geotechnical survey, an analysis of a number of methods can be used in stabilising embankments. Once the slump angle is determined the method of reinforcement can be determined. Slope stabilisation can be separated into cut and fill. Most of the following reinforcement solutions have been utilised in stabilising slopes and embankments on the existing infrastructure.
Cut stabilisation:
· Retaining walls
· Geo-grids
· Geo-nets
· Geo-membranes
· Geo-composites
· Geo-synthetic clay liners
· Geo-cells
· Bio-mats
· Rock armour
· Hydro seeding
· Rock bolts and wire mesh
· Planting
Fill stabilisation
· Gabion baskets
· Terratrel system & stone infill
· Retaining walls
· Rock armour
Q. How are tasks for landscape architects managed by RPA for the Luas and Metro projects?
A. A core team of four Landscape Architects form part of RPA’s Architects’ department. The Landscape Architects liaise with other RPA departments, including the Drawing Control Team, Operations Department, Safety Department and Environment Department to ensure continued success in the running of the existing Luas lines. RPA Landscape Architects also from part of the design team for future RPA projects, getting involved at the planning stages of large projects and following through to construction and completion of the tramway on the ground. There is also a requirement to liaise with external Landscape Architect consultants through the Environment Department for the duration of the EIA process of each project. Occassionally consultants are embedded within the RPA teams, and work within our offices.
Q. What are the five most important tasks a landscape Architect must perform in order to, design, construct and operate either a tramway or Metro line?
A. It is difficult to summarise the Landscape Architects’ role in five tasks as there are so many; however, in no particular order of importance the following five tasks play a major role in the design, construction and operation of Metro and Luas.
· Optioneering - Route corridor selection at preliminary design stage
· Liaising with project Environmental Impact Accessment (EIA) teams
· Designing soft and hard landscape plans for the infrastructure
· Monitoring on site construction and fulfilling EIS commitments
· Communication with IMC’s maintenance contract managers
Q. Do you find it difficult to find space to plant trees in the city landscape seeing that you are constantly competing for space with pedestrians, traffic and underground and overground services? If so how do you deal with this?
A. Yes. With the growing increase and demand of under ground & over ground services such as water, drainage, sewage, electricity, gas and telecommunications finding space to plant trees can be very hard and sometimes impossible. The increasing demand of new service such as broadband and the proliferation of service providers will make the task even more challenging. The best way to deal with this is in the planning stage by liaising with RPA’s Utility Department and with other designers.
Q. How do RPA Landscape Architects envisage Dublin city’s development progressing over the coming decades?
A. We would like to see Dublin as a unique city that holds its own specific identity. To improve on this the city should integrate well with its surrounding environment by providing a transport system that works, hence relieving the city from constant traffic problems.