The A627 (M) was built as a 'principal road' motorway linking the towns of Rochdale and Oldham with the Lancashire-Yorkshire Motorway M62, and with each other. As distinct from a 'trunk road' motorway for which the Minister is responsible, a 'principal road' motorway has a Local Authority as the 'highway authority', with the project normally attracting a 75% grant from Central Government. The length between the M62 and Chadderton was, however, considered to be of sufficient importance to warrant a 100% grant, as a 'potential trunk road'.
In December 1958, the Minister of Transport suggested that the local authorities within each of the major conurbations outside London, should investigate and formulate proposals for its long-term highway requirements. This led to the setting-up of a consortium of the authorities in the sub-Region known as SELNEC (South East Lancashire North East Cheshire). It included the Councils of the Counties of Lancashire and Cheshire, together with the County Borough Councils of Manchester, Salford, Rochdale and Oldham, which were highway authorities in their own right.
The need for links to the County Boroughs of Rochdale and Oldham from the motorway system had been envisaged in the 1949 Road Plan for Lancashire. In a Report of a Committee of SELNEC published in December 1962 a Rochdale-Oldham Route was included as a firm proposal to be incorporated in a future 'County' programme.
It was agreed that the Lancashire County Council would design and supervise the construction of the road on behalf of the three highway authorities. The net cost, after the payment of the grants, was to be shared on the basis of the actual measured work carried out within each authority's area.
From Broadway A663 in Chadderton, the proposed route ran north under a roundabout connecting with the local road system, including an all-purpose dual carriageway link into Oldham. Descending into a valley, it then climbed to an interchange at Slattocks, with a motorway link to the A664 in Middleton. After reaching the junction with the M62, where provision was to be made for a future fly-over, the motorway was to descend to a terminal roundabout with links to the A664 and A58 in Rochdale.
Although involving only a comparatively short length of 4 miles of dual two-lane motorway and 7 miles of dual carriageway all-purpose road, the scale of the earthworks was to be considerable. There were to be 8 underbridges, 5 overbridges, 3 pedestrian subways, extensive retaining walls and a railway overbridge designed by British Rail
The statutory procedures began in February 1968 and, although there were several objections to the Compulsory Purchase Order, the procedures were completed, tenders were invited and construction started in March 1970 with a contract period of 25 months.
Situated in the foothills of the Pennine range, the route necessitated sizeable cuttings in extremely variable glacial materials. As a result of the site investigation the Contract envisaged that, of the total requirement of 1.6 million cubic yards of filling material for embankment construction, all but 80,000 cubic yards could be provided from suitable material excavated from the site. 1.1 million cubic yards of material was predicted as being unsuitable for re-use.
The winter prior to the start of the contract had been exceptionally wet. In some of the cuttings there was 'suitable' clay and 'suitable' sand in close proximity. Separately, they could be used as 'fill' but, when mixed in excavation during a period of several months of exceptionally wet weather, they became totally unusable.
The fact that this was a local authority contract enabled the County Surveyor, as the Engineer, to negotiate with the Contractor, the most economic means of dealing with the problem. If the project had been carried out for the Ministry, it would have been necessary to obtain approval for the measures which were adopted and serious delay and disruption would probably have occurred with a consequential excessive increase in cost.
The deficit in suitable material would normally have led to, not only the need to import expensive substitutes, but also the use of land for extra tips, which would have been difficult and expensive in the semi-urban environment. By negotiating new rates, the Contractor was reimbursed for the cost of digging borrow pits for about 200,000 cubic yards of material near to the site, which were subsequently used for the disposal of unusable material.
Additional material was 'created' by lowering the profile of the motorway in locations where it was aesthetically possible and where the underlying material was of good quality.
Agreement was also reached on the use of draglines and wagons rather than rubber tyred scrapers in order to facilitate the separation of different materials.
In all, a deficiency of some ½ million cubic yards, representing one third of the estimated total of suitable excavated material, was made good.
The most dramatic manifestation of the earthworks difficulties occurred at the Slattocks Interchange. The proposed cutting was particularly wide at this point to accommodate the junction roundabout and its attendant slip roads. There were three well-defined strata sloping down from east to west. An upper layer of good sand 30 feet thick covered a layer of good clay of the same thickness. It was intended that the roundabout carriageway should be located in the clay.
Below the clay was a layer of sand and silt of unknown depth which was saturated and, due to the slope was under considerable pressure. With the removal of some 50 feet depth of sand and clay the artesian pressure forced upwards the clay at the bottom of the excavation. This became known as the 'Slattocks Gusher'. A temporary system of well points and pumps linked together around the perimeter of the roundabout, had to be installed to enable the completion of the interchange.
A permanent 'safety valve' consisting of eleven well heads was installed. Three within the roundabout were then incorporated in a landscaped lagoon, which also collects water from other sources - a unique feature in a motorway interchange, which later was designated as a Site of Special Scientific Interest.
There was considerable variety in the design of the bridges. In general, the ground conditions required the use of piled foundations. However, for two bridges over Thornham New Road the bearing capacity was improved by means of the 'Vibroflotation' technique.
The Cripplegate Lane footbridge was of steel box-girder construction. In view of national concern at the possibility of the failure of such structures, the bridge was subjected to design checks but no remedial work was considered to be necessary.
The motorway was opened to traffic in January 1972, three months early, and in view of the difficulties which were experienced, it was a considerable achievement.