The June and July update on progress towards the A46 Stoneleigh Junction Improvement Scheme.
Overview
As the year progressed into the summer months, work on site has been progressing on the new Westley Bridge structure along with highways work to the new Dalehouse Lane Roundabout, the Northbound off slip, and Stoneleigh Road East and West.
There is still a 50mph speed limit on the A46 mainline to allow safe working for the new A46 bridge construction and will remain in place for the foreseeable future. There is also a 30mph speed limit in effect on Stoneleigh Rd from one of the works to the other.
Progress to date
Northbound Off Slip Realignment Works
Throughout May, kerb drains were installed on the Northbound off slip on the side nearest the mainline A46. The kerb drains that are being installed are again the recycled plastic kerbs previously used elsewhere on the site. These kerbs will form the new realignment of the off slip leading to the eventual roundabout gyratory upon completion.
At the same time, capping and subbase for the new road construction was installed for the new area over part of the slip road. This forms the foundation of the road and has only been installed over half the width of the eventual final slip road. This subbase has been transported to the newly aligned slip road and rolled to be compacted.
New ducting and chambers for the future traffic signals were also installed at this time and works to topsoil the embankment and verge were completed to this side.
In June, the road surfacing was installed in various layers in this section, eventually culminating in an overnight works taking place on Tuesday 28 June to finalise the road surfacing. Temporary road studs and white lining have been applied and the temporary safety barrier moved to enable the switch of traffic onto this newly constructed section of slip road. With this done, this enables the area of the old slip road to be accessible to works traffic to be able to finish the second half of the slip road realignment.
Figures 1 and 2 show the progress of the works through May and June.
Figure 1 – Progress of the northbound off slip realignment – placing and compacting of road subbase
Figure 2 – Northbound off slip realignment – showing the kerbing and first layers of tarmac road surfacing
Westley Bridge
In May/June, the concrete abutments on both sides of the bridge were waterproofed. This was done by applying three layers of a waterproofing liquid which is applied to the abutment like paint. This is conducted in areas where the ground will be placed against the concrete abutment and is done to eliminate moisture ingress into the concrete and thereby damage it over time. This is particularly important with the bridge being next to Finham Brook.
The otter shelf was also finished to the north abutment. This is a concrete shelf that allows safe passage for otters under the bridge at times when Finham Brook suffers high flooding and is an important ecological feature.
In the middle of May, a major milestone was achieved when 21 prestressed concrete beams for the new bridge deck were delivered to site and installed. Each beam was individually lifted into place onto the abutments with a crane and positioned correctly so they spanned across Finham Brook. All 21 beams were installed over a 3-day period. The installation can be seen in Figures 3 and 4.
Figure 3 – Westley Bridge – lifting the concrete beams onto the abutments with a crane
Figure 4 – Westley Bridge – concrete beams now in place
Following the installation of the beams, work commenced in June to erect temporary working platforms around the bridge to enable work to construct the permanent formwork to begin.
Stoneleigh Road East
The first stage of surfacing has now been completed for Stoneleigh Road East heading away from the Southbound off slip road heading towards Stoneleigh. The surfacing has been carried out all the way up to the tie in point to the existing Stoneleigh Road and comprises of the lower road layers only at present. At some point in the future, the final tie in will be built and the road surfaced to enable traffic to be switched across to the new road and the old Stoneleigh Road closed up to the southbound on slip.
The new footway/cycleway that runs alongside the new Stoneleigh Road East, has also been surfaced although the final layer of surfacing is still to be installed. Specialist tactile paving is now being installed in the footway and crossing points to help blind and partially sighted people use the new facility.
Southbound off slip road
With this area largely complete, landscaping works have taken place over the last few months. This involves carrying out topsoil cultivation to remove debris and large stones and then seed the area with a special wildflower seed mix to help promote biodiversity. Figure 5 shows an example of the topsoil cultivated and seeded area.
Figure 5 – Southbound off slip road – topsoil and seeded verge
Stoneleigh Road West and dual carriageway link
The remainder of the impermeable geotextile layers for the two ponds parallel to Stoneleigh Road West, were installed and covered with topsoil. This can be seen in Figure 6. Following this, a second layer of geotextile has started to be installed to help control soil erosion in the pond until such time as the planting that will go in the pond establishes itself and helps maintain the shape of the slope.
The first layer of surfacing has been installed on both sides of the dual link road. This has been installed from the previously surfaced western gyratory, which is currently open to live traffic, to where the new kerbs have been installed at the new Stoneleigh Road roundabout location. Much of the shared use footway/cycleway which will run next to the dual-link road, has also been surfaced during this period.
Figure 6 - Geotextile being installed in retention pond
New Dalehouse Lane Roundabout
Work has begun to construct the new Dalehouse Lane roundabout. This has begun by filling the ground on the approach to the new Westley Bridge and then marking out the new roundabout central island. As part of the scheme’s strategy of dealing with Himalayan Balsam, it is intended to bury some soil contaminated with Himalayan Balsam within a mound in the centre of the roundabout. This will be topsoiled over and seeded.
The first part of this central island construction has commenced and has been excavated. Work has also been conducted to build up layers of material surrounding the roundabout, to form the correct levels and profile of the new carriageway. This can be seen in Figure 7.
Figure 7 – New Dalehouse Lane roundabout – excavation for the roundabout central island
New Dalehouse Lane link
In June, work has begun to construct the new alignment for Dalehouse Lane leading up to the location of the new roundabout. The excavation for the area was conducted some months ago, but now drainage works have been carried out. These involves the installation of multiple new catchpits and pipe runs that will ultimately tie into the scheme’s attenuation ponds.
The road “box cut” has also commenced, which is the extent of the excavation that will make up the new road construction. After this, capping (the first part of the road foundation) has been installed and compacted. Work has also been taking place carefully to ensure no further damage to the mature oak trees in the area. Figure 8 shows the work taking place to install the capping.
Figure 8 – New Dalehouse Lane link – excavation and capping installation
New A46 Bridge
In this period, the steel reinforcement for the West abutment was completed and a concrete pour took place complete the construction. The formwork used for the concrete pour and the concrete exposed and the finished abutment can now be seen from the mainline A46. The abutment has now also been waterproofed at its base and lower area of the abutment, similar to previously done on Westley Bridge mentioned previously. Figures 9 and 10 shows the abutment and the waterproofing at the base.
Figure 9 – Current status of west abutment
Figure 10 – Current west abutment with the waterproofing (in black) applied at the base
On the east side of the A46 bridge, the formwork for the East abutment has been erected and the abutment is ready for the concrete pour at a later date. This will be undertaken through the use of a pump lifting the concrete into the top of the abutment formwork which is then compacted using a poker vibrator which is a vibrating “wand” which is inserted into the wet concrete to ensure no air remains in the concrete which could form a structural weakness.
Further information
Over the coming weeks, there will be works on Westley Bridge to complete the permanent formwork panels on the beams and installing reinforcement for the bridge deck. Works will also continue on the construction of the new Dalehouse Lane roundabout and link road.
Finally, it is intended to conduct the concrete pour to the east abutment for the new A46 Bridge swiftly be followed by the waterproofing of the base of the abutment, similarly to the work done to the west abutment during June. Once the abutments are completed, focus will then turn to finalising the bridge deck in preparation for the bridge deck to be moved in the future.
In addition, some temporary works to the existing A46 bridge to realign the northern kerb line will take place. This is intended to create a temporary road on which the traffic will be moved to create a working area on the south verge to conduct some strengthening works to the bridge structure.