Start
January 2020
End
December 2020
Client
Skanska
Location
Hertfordshire
VGC contract value
£3.5 million
M25 ERA completed

Our team is delivering additional emergency refuge areas (ERA) on the M25 between junctions 24 and 25.

The new refuge areas will give extra safe places for drivers to pull over in case of an emergency on the M25 smart motorway.

The M25 bays show VGC’s expertise in safe, efficient working in high risk environments.

Total quantities for all five bays:

  • 18,000 m3 of imported fill
  • 14,500 m3 of waste material removed
  • 700 m of drainage pipe
  • 260 m new slot drains
  • 415 m2 of new layby

Bay 02 (Jan – Jun 2020)

RediRock on the M25 ERA bay 02
RediRock on the M25 ERA bay 02

Scope:

  • site clearance
  • lay, level and compact sub-base
  • level and prepare the formation
  • drainage: bespoke oil separation chamber, attenuation pipes, combined kerb drainage, filter and slot drains
  • construct ‘RediRock’ modular block retaining wall 2m high, 70m long. We installed the blocks onto a mass concrete foundation. We placed 10mm shingle between the blocks and back of wall fill, separated by geotextile, to facilitate back of wall drainage.
  • ducting and infrastructure for NRTS emergency telephones and vehicle detection hardware. This indicates to the control centre if a vehicle stops in the area, so the emergency services can assist them if necessary.
  • topsoil and landscaping
  • asphalt surfacing
  • orange high-friction surfacing. This helps drivers reduce speed safely, and makes the ERA easy for motorists to spot.

Bay 03 (Jan – Jun 2020)

The scope for bay 03 was similar to that for bay 02.

Earthworks required the embankment to be built out with a stepped formation detail. We used 1700t of imported aggregate to raise the ground level by 4m.

We made a drainage connection onto existing 900mm concrete pipe, 5.5m below existing ground level, using ‘titan’ excavation support boxes weighing 6.5 tonnes.

M25 ERA bay 3
M25 ERA bay 03

We installed pavement-quality concrete carriageway with steel reinforcement. After paving, the final bright high-friction orange surface coating was applied.

We finished each bay with white-lining, soft landscaping and fencing works. We also installed new driver information signs in the area.

Bay 01 (Jun – Oct 2020)

For this bay, the earthworks solution is a sheet-piled retaining structure. This supports the new bay where the adjoining embankment slopes away sharply.

Site space is restricted in order not to disturb nesting birds.

  • Temporary works design
  • Vegetation clearance and tree stump removal
  • Instal piling platforms
  • Pre-augur 170m length to prepare for the sheet piles.

We installed 120 individual sheet piles to between 6.5m and 13.5m in depth. Initially using vibratory methods until refusal, with impact hammering the piles a further 1-8 metres.

We installed drainage, NRTS communications ducting and infrastructure, electrical lighting infrastructure, and will shortly lay the sub-base of the carriageway.

Surface drainage installation of combined kerb and drainage units and pre-cast concrete slot drainage.

The orange surface will be done separately after completion.

Bay 12 (Aug – Dec 2020)

Bay 12 is the largest single EA bay project to date. The design includes a 130m long pre-cast concrete L-shaped retaining structure up to 2.5m high at the base of the embankment.

The foundation was constructed of 400mm thick reinforced concrete of varying width and level. 150m3 of concrete is being pumped 160m from the carriageway to the foundation.

The L-shaped wall was installed using two large excavators in a two-part lift to be as efficient as possible. The sections are lifted from the road to the middle of the stepped embankment, then an excavator 6m below the carriageway at the foundation level can continuously install wall sections unimpeded.

Once the structure is installed, we proposed the use of ’deckdrain’ back-of-wall drainage system to save time on installation. The embankment will be filled with over 5,500 tonnes of structural fill.

This bay is due to complete before the Christmas embargo in December.

Bay 08a (Aug – Dec 2020)

This bay is similar to bay 03: the carriageway is being built out with a stepped formation detail, and 1,600t of imported aggregate to widen the embankment.

Some of the fill is being reused from the bay 02 piling platform. We minimised vehicle movements by using the same vehicle to bring in the structural fill and to remove muck from site, thus reducing the carbon footprint of the project.

We manage material movements on each site with a cloud-based platform for real-time live data.

Drainage

We have installed surface water drainage solutions to capture surface run-off. These are connected to the deep drainage.

The deep drainage removes the water to areas where it is appropriately filtered to remove pollutants and ensure they do not enter the environment, before the outfall returns the water to nearby water courses.

The drainage connections required excavations up to 5.5m deep, for which we used large excavation supports. The excavated London clay was removed from site, with some clay being dried out in windrows for reuse as backfill.

Mihai Gligor
Key influencer Mihai Gligor carefully cleaning surfaces on the welfare unit

Coronavirus

Works on site have continued throughout the coronavirus outbreak. Safety measures include:

  • Reminder signs outside and inside the offices
  • Allowing just one person at a time into welfare facilities
  • Regular careful cleaning of all touch surfaces
  • Restrictions on the use of facilities by Highways England and Highways Agency traffic officers to reduce risks
  • People are carefully spaced in the offices to maintain adequate social distancing.

After a site inspection in early June 2020, Skanska’s operations director said:

The measures put in place by the teams for M25 COFA and renewals relating to the Covid risk are good. Quality of workmanship on site very good.

“The continuation of the works throughout the restrictions has been managed very well by the teams, and the measures put in place seem to be well managed and sustainable.

Other compliments

Skanska’s works manager commended our teams:

Your site teams are producing an excellent job despite current conditions and restrictions. The sites were in excellent condition and all H&S measures were being employed. The gate operative was courteous and informative. I felt the team was creating a positive impression with the travelling public.

Skanska’s senior engineer emailed to say their health and safety adviser was

impressed with how the site is set up, measures in place, PPE compliance and generally how it presents itself.

The engineer asked us to relay these positive comments to the site team,

and thank them for the hard work in this very difficult time.

The works are part of an M25 call off framework agreement (COFA) with client Skanska for client Highways England. The contract is being managed by project manager Seb Borgers, supported by works manager Declan McComb and foreman Saulius Vaitkevicius, plus Ron Turnage and Eamon Gallagher.