A47 Improvements Programme – Wansford to Sutton Dualling Scheme

Upgrading the A47 single carriageway to a dual carriageway standard including access routes and a new bridge

Client (s): Interserve (Principal Contractor) | Mott MacDonald ( Investigation Supervisor and Principal Designers) | Highways England (Client)

Site Investigation Value: £415,000.00

Project Overview:

The site stretched 2.5km along the existing A47 and was located west of Peterborough between the interchange with the A1 (to the west) and the existing roundabout at Sutton (to the east).

The improvement programme involved an on-and-off carriageway intrusive ground investigation to assist in the redesign, modification and widening of the existing carriageway.

The works were designed to enable the existing A47 single carriageway to be upgraded to dual carriageway standard and included access routes and a new bridge. It was understood that from the western end the new road will be constructed slightly to the north of the existing, before crossing the existing A47 to the south of the existing alignment, the new road system will then merge into the existing dual carriageway at the Sutton Roundabout at the eastern extent.

Site Investigation Overview:

The proposed and the purpose of the contract was to undertake an intrusive ground investigation of the site and to establish the ground conditions and the suitability of the natural geological strata as a founding stratum.

What Soils Limited Brought To The Table:

Using our extensive experience in large road widening/alteration schemes, Soils Limited successfully supervised the site works which involved ninety-three (93) trial holes being undertaken within traffic management on busy ‘A’ roads, within adjacent soft landscape and within rural field settings. Site works comprised:

· 15No. Cable Percussive boreholes

· 2No. Windowless Sampler boreholes

· 5No. Cable Percussive boreholes with Rotary Core follow on

· 24No. Rotary Cored boreholes, commencing with dynamic sampling boreholes

· 5No. Cone Penetration Tests (CPTUs)

· 30No. Machine Excavated Trial Pits

· 12No. Dynamic Cone Penetrometer Tests

· 51No. Hand excavated inspection pits at all exploratory hole locations to a maximum depth of 1.20m below ground level

· 5No. infiltration tests to BRE 365 DG:2016

· 19No. Installations for groundwater and gas monitoring

· Geotechnical laboratory testing on soils and rock

· Chemical laboratory testing on soils and groundwater

· Establishing ground levels and locations of exploratory holes

· Groundwater and gas monitoring comprising eight visits over a period of three months following the completion of initial fieldwork

· Logging of windowless sampler boreholes in accordance with BS5930:2015,

· Onsite PAH testing

· Factual Reporting

Works were undertaken in accordance with the precise requirements of the Investigation Supervisor and in accordance with a demanding specification.

Challenges

The natural geology onsite proved to be one of the most difficult aspects of this project, The 1:50,000 BGS map showed the site to be located directly upon eight bedrock formations with three overlying superficial deposits, furthermore, slip surfaces were recorded in the east of the site and a fault was noted 250m north of the proposed route boundary. The fault is orientated northeast-southwest but is not shown to extend across the scheme.

 

Health and Safety

Health and safety formed an integral part of the project and was planned into the works from the outset in conjunction with our partners on the project. Full Risk Assessments and Method Statements (RAMS) were prepared and refined in conjunction with our partners in good advance of the intrusive works. This included reference to the Highways England HSG47 document – ‘Avoiding Danger from Underground Services’

All site personnel received comprehensive instruction ahead of the site works, including full discussion of associated RAMS, documents which remained ‘live’ and open to alteration in light of any additional observations/changes to working conditions as works proceeded.

Full training of the CITB – ‘Health & Safety Awareness Site Safety Plus Level 1 Award’ course was provided by Soils Limited to all site crews (including contracted staff) in order to abide by Interserve’s Health and Safety requirements.

Soils Limited site teams all signed on to a Permit to Dig prepared by Interserve and a daily briefing sheet was prepared so that personnel were fully appraised of the task at hand at regular intervals on a long-term project.

Soils Limited operates a comprehensive incident reporting system, including near-misses, in an effort to provide continual learning and improvement with regard to Health and Safety issues. During the works, Soils Limited crews underwent Health and Safety audits internally, by SM Associates and Interserve Construction Limited.