Trains roll again over NYMR's Bridge 42 after £520,000 propping scheme

Trains crossed North Yorkshire Moors Railway's Bridge 42 again on 1 June, five months after accelerating deterioration forced the charity-run line to close the Grosmont structure in December 2025. A £520,000 temporary propping scheme installed by CML Civil Engineering and Mabey Hire stabilised the 180-year-old arch in time for the summer season, and the full 24-mile Pickering–Grosmont route reopened with Stanier Black 5 No. 44806 hauling the first train through from Whitby.

The Grade II listed single semicircular arch has carried the railway over the River Murk Esk since 1846, when John Birkenshaw built it for the York and North Midland Railway on the alignment of a horse-drawn tramway crossing. The 18.2 m span — brick arch barrel with sandstone voussoirs, spandrels and parapets — carries every train on the railway, around 10,000 movements a year, including services continuing to Whitby over Network Rail's Eskdale route.

What did the inspection find?

A detailed investigation by GGP Consult found further deterioration in the two years since the previous inspection. Trial holes above the arch revealed significant mortar loss in the extrados and failure of the existing waterproofing, with substantial water penetration. Closer examination exposed ring delamination, water ingress and historic repairs of varying quality. GGP's defect drawings underpinned the capacity assessment and the December decision to suspend traffic.

Repairing the bridge in spring or summer would have cost the heritage railway and the regional economy dearly during the peak tourism period. NYMR chose a two-stage project: under-arch propping to keep trains running this season, followed by permanent repairs next winter.

"Propping Bridge 42 was a carefully considered solution that keeps the bridge fully operational for the upcoming season," said Phil Sash, NYMR's director of civils. "It also gives us the time needed to develop a detailed repair programme, which will be implemented over the winter months to secure the long-term safety and performance of this important structure."

How was the support built?

Works began in mid-April. CML created temporary track access from a level crossing 100 m north, used by a 110-tonne crane lowering plant and materials to river level; personnel reached the site through a scaffold tower suspended from the parapets.

GGP Consult devised timber crib foundations on each riverbank to satisfy Environment Agency concerns over contamination and flow restriction through the bridge opening. Because the arch spans wider than the river channel, even 1-in-100-year flow modelling showed minimal restriction. The northern crib was built on the bank; the southern crib required a temporary dam along the abutment face, with a small excavator lowered in each shift.

The multi-layer cribs used 1,000 reclaimed untreated Ekki sleepers — a dense hardwood resisting water absorption — bedded on SoluForm underwater concrete bagwork that hydrates in situ without releasing cement fines. The timbers will be recovered for reuse at project end.

Mabey Hire designed the steelwork with GGP and NYMR: three pairs of 6.5-tonne MU Truss panels on Superprop beams fastened to the cribs. Crews assembled the trusses on the bridge deck, lowered them by crane and winched them through the arch. Transverse Mass 25 beams, a network of props and bearers, and timber lagging against the intrados completed the load path, with horizontal thrust taken into the abutment face. Inspections ran daily at first, now weekly, with additional checks after floods.

"It was a tight programme on a difficult site: a listed arch over a river, with very little room to work. So how we worked mattered as much as what we built," said Raj Sharma, contracts manager at CML Civil Engineering. "Careful planning with all stakeholders and our supply chain meant trains were back running over Bridge 42 on 1st June, in time for the summer season on one of the UK's busiest heritage railways."

A single-train restriction remains in force on the double-track bridge to limit loading until permanent repairs finish.

What happens this winter?

The NYMR's Bridge 42 Appeal has raised around £400,000 toward the project; the North York Moors National Park contributed £50,000 from its s106 Landscape and Ecology fund under the Restoration of Degraded Heritage Assets scheme.

Permanent repairs run from mid-November 2026 to early March 2027 at a likely cost of around £350,000. GGP Consult has defined a worst-case scope for the Invitation to Tender; the exact extent will be fixed on site by GGP and NYMR, with all works agreed with and monitored by Historic England. The philosophy is minimum intervention, maximum retention of original fabric and reversible strengthening.

Phase one removes track and ballast, repairs the extrados in brick and lime mortar, stitches and pressure-grouts brickwork, applies welded DPM waterproofing and installs French drains to divert water that contributed to the decay. The propping then comes out, leaving trusses as an access platform for breaking out and rebuilding brickwork to the third ring. About 60% of the soffit has delaminated joints; stainless steel HeliBar reinforcement will run through the 700 mm arch, with bar locations fixed on site because Historic England wants to limit insertions. Polyester grouting and invisible ties from the brickwork into the backs of the sandstone voussoirs complete the strengthening — one of NYMR's most significant infrastructure challenges, closing with the structure's long-term future secured.