Client:
Highways
Agency
Principal
Contractor: Balfour Beatty Civil Engineering
Ltd.
Designer:
URS Infrastructure & Environment UK
Ltd.
URS were appointed as Contractor's Designer by Balfour
Beatty on their £265M Early Contractor Involvement contract to
improve the A46 between Widmerpool and Newark. The project spanned
a 28 km stretch of the A46 between the A606 two level junction at
Widmerpool to an improved roundabout at Farndon, just south of
Newark in Nottinghamshire. The aim of the scheme was to widen the
existing A46, from a single carriageway to a dual carriageway to
reduce congestion, improve safety and provide a bypass for East
Stoke and Farndon including new junctions at Roehoe, Owthorpe,
Stragglethorpe, Saxondale, Margidunum, Red Lodge, Flintham and
Lodge Lane. As part of their Sustainability Vision, Balfour Beatty
introduced "zero waste to landfill" targets and therefore expressed
a desire to reuse all material generated from the improvement
works.
With this "zero waste to landfill" goal in mind URS was
commissioned by Balfour Beatty to prepare a Materials Management
Plan ("MMP") in accordance with the 'Definition of Waste:
Development Industry Code of Practice' ("CL:AIRE CoP") (CL:AIRE,
2008) which would include the reuse of the former A46 pavement
materials.
URS produced the MMP which detailed the procedures and measures
that should be taken to classify, track, store, and re-use all
materials excavated including the former road planings. In
particular the report detailed the procedures to deal with any of
the former road planings that may be affected by elevated
polycyclic aromatic hydrocarbons (PAHs) derived from coal tar
products. Any material with elevated PAH which could not be used in
unbound applications was suggested to be reused within the road
sub-base as part of the hydraulic bound mixture (HBM).
URS produced a series of designs which allowed the PAH affected
planings to be blended with imported clean granular material and
cement to form the HBM pavement foundation. Three alternative HBM
mixes based on the level of PAH contamination were presented;
50/50, 40/60 and 30/70 ratios of planings and scalpings. The scheme
and mixes were based on detailed pre-works laboratory testing and
analysis undertaken by both Balfour Beatty and URS within their own
laboratories. The results of these findings were presented within a
secondary Laboratory Testing Report and the conclusions used to
support the scheme suggested in the MMP.
As part of these pre-works tests by URS, Ultraviolet
Fluorescence (UVF) spectrometry was selected to trial as an
analytical technique for onsite verification based on previous
experience of successfully applying this technique on PAH affected
soils. The UVF method was shown to reliably determine total PAH
concentrations within the laboratory report and later in samples of
planings from the site.
During the works samples were taken onsite for UVF testing at an
approximate rate of 1 sample per 25m3. The use of UVF
testing allowed the majority of the testing to be undertaken within
an onsite laboratory, with only a number being tested by accredited
laboratory for verification. This quick on-site test allowed
Balfour Beatty to classify the planings and ensure they were
directed to the right location for re-use in the pavement
foundation.
To confirm that the reuse of the pavement planings within the
HBM was acceptable, HBM cube samples were taken at 500m intervals
where pavement planings were reused within the HBM material. These
cube samples were subject to 4 day tank tests to determine leaching
characteristics. Once the tank tests were completed the cubes were
crushed and tested for PAH concentrations. The testing confirmed
that the material re-used in the HBM mix met the environmental
specifications outlined in the URS Laboratory Report and MMP.
URS produced a verification report for the works proving that
the overall testing carried out for the reuse of materials within
HBM mixes onsite met the environmental and geotechnical
requirements for HBM within the A46 project. The report confirmed
that the properties determined within the URS Laboratory Report
were replicated onsite and that the materials operated as
identified within the pre-works laboratory testing.
Project Example compiled by:
Robert Eaton
Campbell Ogilvie
Danny Hope
URS Infrastructure & Environment UK Ltd
