I documented the delivery of Edinburgh Tram on street section from Haymarket to Waverley and compared notes with those reviewing the delivery of contemporary work in Blackpool (the extension to the South & new Squires Gate depot) Plus the steady rolling programme of extensions to Manchester Metrolink, including the Airport extension - delivered ahead of time and on budget
In 1999, working with ORR and based on my experience on pavement construction, with embedded rails I helped to revise the standards from 1870 Tramways Act, to deal with the problems that had plagued the 4 early 2nd generation tram systems in Manchester, Croydon, Sheffield, and Birmingham. All had big problems with rails coming loose plus the notorious Roe vs Supertram case. This saw a much improved system used in Nottingham which has lasted well for over 20 years
Sadly Edinburgh's contractors/project managers failed abysmally in how they built the Phase 1 track between Haymarket and Waverley (South St Andrew Street) with many details that ORR inspectors remarked on as poorly delivered, and I've highlighted to BroughtonSpurtle & Arellcat as we toured this section
Right at the start this project invited problems, by digging out the original road structure which had over 200 years of compaction and stabilsed ground over a deep bed of glacial clays and gravel sitting on a layer of fractured shale, which the plentiful records of core logs drilled long this route, that showed water present along the valley of Princes Street Gardens (the former Nor Loch) and other clues like the original Canal Street Station at the summit of Scotland Street Tunnel, and its water issues
This issue immediately delivered a need to redesign the on street track with a concrete top slab extending around a foot outside the rails when the original design of tarmac just fell away from the rails (Tarmac as almost everyone finds out ! does not stick to steel and being a flexible pavement will just slump, crack and fall apart)
Hence the redesign added the dyed black concrete shoulders extending out from the edge of the rails
This still failed to address the seriously degraded stability of the ground both under the track slabs, but extending across the carriageway pavement on either side leaving a steady trail of steel road plates (a massive hazard for cyclists) with street ironwork requiring continual repairs as valve and access chamber covers come loose, and the carriageway sinks, at one point the Westbound lane at the Scott Monument had sunk 6 inches creating a huge puddle right at the bus stops
In Manchester the Joint Venture team had developed a robust control on project costs by testing the ground underneath the track with standard California Bearing Ratio and Vane Tests for soil strength and cohesion before pouring the concrete, with allowances & daywork rates for remedial work where soil weakness was identified
By contrast almost every load transfer joint between Haymarket and Waverley has cracked, with lumps of concrete becoming detached and patch up repairs
Here's a recent photo of the seriously dangerous 2" step where the concrete of the track slab has broken off and rotated right at the Junction for Castle Street
https://www.flickr.com/photos/h52/55124388436/in/datetaken/
One solution that can cure a raft of problems with the current tram is to complete the work planned 130 years ago by the Caledonian Railway, digging a tunnel under Princes Street, generally easy through easy to dig material from Haymarket Yards to the North Bridge, and removing the conflicting movements of trams, at a high frequency, where all the routes converge between Lothian Road (Queensferry Street) and Leith Street/Regent Road (or North Bridge)
To build this tunnel the side walls would be core piled and the 'umbrella' system used in 1963 to carry out the construction with traffic running over the top as it did for Oxford Circus Station, and the excavated material going out via Scotland Street Tunnel to the Water of Leith for land reclamation
The 2 key stops on Edinburgh Trams would be better located at Lothian Road/Charlotte Square and Waverley Market for the railway station, and a relocated central coach station, extending the underground chamber to the North for coaches (& some buses) - all electric - in a combined interchange with routes coming in from Queen Street or sharing the access with trams
This can deliver a great all weather shopping street along Princes Street with direct access to trams plus Waverley Station plus long distance coaches & bus services using a bus station built under George Street (in a trench dug along the centre where car parking is currently located (and can be closed in stages to build the chamber below, with access from Queen Street which runs at a lower level
Based on the indications for Princes Street George Street is largely a raised beach of weaker soils where digging out between core piled walls can provide these underground facilities with the public space above
To deliver this needs a robust umbrella project that can pull together the diverse interests as a coherent common interest for Edinburgh city development. There's the challenge?
posts
