T0483 AD10 M60 Barton High Level Bridge Steady State Assessment and Category 3 Check 23/25

The Area 10, Asset Support Contract completed on 31st March 2019. Since the start of the AD 10 contract on 1st April, NH has enjoyed support from SPATs framework consultants in the management of existing asset risks that traversed both contracts following the uncertainty of ASC, BBMM expertise not transferring either into NH or the DSC under TUPE legislation for the AD contract. That support has come via recent SPATs2 Framework (TO311).

A range of structures asset risks currently occupy the Area 10 Risk Register, some with enhanced inspections and live website monitoring equipment in place. These processes, procedures and interpretation of monitoring equipment and the data produced are vital to maintaining the continued safe and operation of the network where these structures are located. M60 Barton High Level Bridge currently sits within National Highways top 20, "Structures Requiring Most Consideration".

This task seeks to ensure the continuing use of expertise through this SPATs2 task to successfully manage the ongoing risks posed by the management of substandard bridges in AD 10, including the provision of essential bridge assessment and design expertise on BHLB.

In 1989 BHLB was widened. The design allowed for differential vertical movement between the piers that were constructed as part of the original bridge in 1960 and those added in the 1989 widening scheme. The resulting bridge maintenance manual from the 1989 widening scheme required the then Highways Agency, then Highways England, and now National Highways) to monitor the relative movement of the piers and their impact on the bridge deck and running lanes above. The existing piers were also thought to be suffering from Alkali Silica Reaction

A tolerance of -3mm was a condition placed in the manual that if exceeded, National Highways would need to implement a jacking scheme that would lift the bridge deck and reintroduce tolerances back into the bridge. Recent monitoring of these tolerances is indicating that they are at or beyond their limit triggering the need for a possible jacking scheme, the first of which has been implemented at Pier D, with further locations done at Piers P and Q. The pier locations over the Manchester Ship Canal are to be jacked in 2023/24 with design and check in advance of works on site.

This main risk posed is the possibility of lane restrictions on the M60 at short notice at this key location where 3 motorways converge. Part of this task seeks to further address those needs that do not warrant capital works with disproportionate costs, aimed at safety critical monitoring while limiting disruption of the M60. Interpretation of monitoring information, provided by NH 3rd party monitoring contractor suppliers, remains a key function of the appointment in further assessment of the bridge deck, which is at it limit for normal traffic loading of 40tonnes and no heavier loads above this.