Commissioned by Northumbrian Water, the Johnson Street Storm Overflow Screening Project in Gateshead aimed to improve water quality in the River Tyne by reducing unscreened storm discharges from a 22,500-population catchment. Delivered by the Esh-Stantec JV, with shaft and tunnelling works by Active Tunnelling, the project involved constructing a 10.5m diameter, 8m deep shaft over the live Tyneside Interceptor Sewer, installing two high-capacity mechanical self-cleansing screens, and constructing 1800mm diameter overflow sewers using tunnelling techniques.

To maintain flow during works, a temporary pumping station was installed, allowing live sewer operations to continue with minimal disruption. The design met Environment Agency requirements to screen flows up to 6mm during a 1-in-5-year storm and repurposed the existing overflow as a secondary relief point. Despite the challenges of the COVID-19 pandemic, the project was completed in January 2022, ahead of the March regulatory deadline, and came in under budget at £6.95 million.

The 1500dia concrete sleeve was to allow 2 x 710mm dia plastic pipes to pass through (also as sleeves), with ultimately 2 x 500mm water mains then being housed within the sleeves. The 1500dia tunnel x 75m long will be installed as a pipe jack using a full faced TBM.

ATL own a large fleet of shoring equipment including sheets & frames, some of which was used to construct the drive & reception pits on this scheme.

The drive pit was 6m x 4m in plan x 7m deep, with reception pit being 7.5m x 3.5m in plan x 5m deep. ATL installed these cofferdams with the aid of their own 36ton zero swing excavator, which was also used to lift the TBM in/out of cofferdam during the tunnelling works.

ATL’s own TBM with rock head was used to dig through the Phyllite ground, which it chewed through with ease, nearly doubling forecast production & saving 2 weeks on the tunnel operation alone.

Installing plastic sleeves

ATL proposed to cast timber rails, set in concrete to gradient within the 1500 tunnel, to allow the twin 710mm plastic pipes to be slid along into position. ATL also proposed to install steel restraining bars (fabricated by ATL) within the tunnel to prevent the 710mm plastic pipes from floating when the tunnel void was pumped full of grout later. Both details worked very well & the pipes were installed successfully with no issues.

The client was extremely pleased with all the work carried out on this site with the contract programme being reduced by a total of 3 weeks.

Client Feedback:

“Pre-Construction, Active Tunnelling were engaged early to assist with the detailing of the water main / grouting details within the tunnel and provide technical submissions for Highways England approval.

During the Construction phase Active Tunnelling successfully completed installation on site in 10 weeks, 3 weeks ahead of programme with zero safety incidents.

Kier were pleased with Active’s performance and would be happy to engage with them again on future schemes”.

The aim of the project was to prevent over land flooding in the Anlaby and East Ella area. ATL constructed 1350m of 1800mm diameter tunnel with associated shafts and cover slabs, including internal backdrop pipework and steel access ladders and platforms under a design and build contract.1350m of tunnelling comprised of one drive of over 600m and two shorter drives, one of which crossed under B1231 Tranby Lane. x1 6m dia segmental drive shaft x2 sheeted pits x1 4m dia segmental intermediate shaft.

Challenges and Solutions…

The Anlaby and East Ella Flood Alleviation Scheme Phase 3 works comprised of flood water collection structures in 2 locations that deliver flood waters into a 1.8m dia culvert to carry them through the high points of the catchment area before discharging them into an open watercourse that carries the flood water to Beverley Road and into the works created as phase 2 of the project. The flood water collection structure on the Easenby Drain, a flood water transfer unit in Kerry Pit and a series of open watercourses collect overland flood flows.  A flood water collection agreement at Tranby Lane collects further waters and directs these into the culvert. The accumulated waters in the culvert discharge into an energy dissipation structure at the start of the watercourse and the outfall watercourse includes energy dissipation measures too.