SMR Applications: Hand-Mix for Reinstatement
Where: Devon
Background
Devon boasts the UK’s largest road network (some 12900 km) and is reputed to have one of the strictest Street Works regimes in England.
Problem
Utility companies and the County Council across Devon need to reinstate hundreds of major and minor repairs (each typically just one or two metres square) to footpaths, carriageways and other areas on a weekly basis. Traditional methods not only required reinstatements materials that comply with Type 1 GSB standards being brought in, but the excavated spoil had to be appropriately disposed of, typically to landfill, both of which are becoming increasingly expensive. An cost effective alternative was therefore needed.
Solution
Initial trials in 1999 were carried out by John Kennedy (Civil Eng) Ltd (now Balfour Beatty Utility Solutions Ltd) on behalf of South West Water and under strict monitoring by Devon County Materials Laboratory. The trials encompassed numerous laboratory and field tests including CBR and compressive strength testing, frost heave susceptibility tests and air void testing of wearing course applied onto SMR reinstatements. In all tests, the SMR reinstatements solution was proven to outperform control reinstatements using Type 1 GSB.
Following the trials, permission was granted to South West Water to use SMR in footway reinstatements under clause S1.5 of the SROH, New Roads and Street Works Act 1991, (more commonly referred to as the HAUC spec). Ongoing success subsequently resulted in SMR also being trialled for carriageway reinstatement and approval was extended in December 2000 to South West Water to include reinstatements in Type 3&4 carriageway.
The approvals permit SMR treated spoil (which typically outperforms the prescribed minimum stability requirements) to be used as a replacement for traditional materials up to and including road base levels. Under the revised SROH introduced in June 2002, performance criteria set down for alternative materials in Appendix A9 to be used at these levels deem the material to be classified as an NFSMR (non-flowable structural material for reinstatement).
SMR has subsequently been used by South West Water on hundreds of thousands of reinstatements across Devon’s footways and carriageways. SMR is hand mixed in small quantities with excavated spoil as this both eliminates the need for imported backfill material and the need to remove spoil to landfill.
Benefits
Having tried and tested SMR and been happy with its ongoing performance this methodology delivers a number of substantial environmental, operational and financial benefits:
Ongoing financial benefits: A typically saving of £40.00 per cubic metre is enjoyed by Utility Companies using SMR when compared to traditional methods. These savings can be further increased should the Utility Company adopt a first time / single visit – permanent reinstatement policy.
Zero failure means zero remedial works: Both South West Water and Devon County Council are delighted with the ongoing performance of the SMR reinstatements, with hundreds of thousands of completed reinstatements and not a single reported failure which equates to no further disruption.
Convenience: Because SMR is supplied in convenient sized tubs and sacks it can be part of a road crew’s standard equipment and therefore be immediately available when and where required.
Reduced transportation: Many thousands of material and vehicle movements have been avoided through the use of SMR, reducing pollution and disruption to the road going public.
Environmental and manpower savings: With literally hundreds of thousands of tonnes of material being diverted from landfill and new reinstatement materials not being needed this has significantly reduced the environmental impact as well as significantly improving the speed and efficiency of the work crews undertaking the reinstatement tasks.
Wider appeal: SMR has been approved for use by over 130 Local Highway Authorities nationally and has been used on over a 900,000 reinstatements, saving over a million tonnes of landfill capacity and a similar quantity of primary aggregate.
Increasingly Utility Companies, Contractors, and Highway Authorities are adopting SMR as their first option for footway, carriageway and other project reinstatements because it is highly sustainable, environmentally ideal and a financially sound alternative to ‘traditional’ methods.