Civils – Latest Projects Completed – Southern Water – Portswood

This Civil Engineering project was tendered by AFECO in collaboration with Pavenet for Southern Water. This was a upgrade of existing and recently installed plant at the Portswood waste water treatment works in Southampton.

This was a design and build procurement on a two-stage basis starting with feasibility studies (determining OIR, AIR, EIR for PIR including survey of existing assets, ground & ecological investigations etc.) moving to a conceptual design suitable for final development following technical review of civils, mechanical and electrical installations.  The initial concept was developed between June and September 2018 with final submission for stage 1 design together with cost plan in October 2018 detailing proposals for a new sludge treatment plant allowing waste transportation by lorry opposed to barge.

The initial trial holes and investigation uncovered drainage from the existing plant that was not previously identified on existing plans or surveys.  This included a 1200mm diameter concrete outfall pipe that crossed under the River Itchen.  This was further exposed during the initial reduce dig along with redundant washout lines within the pile layout, new foundations, and slab.  Design changes required relocation of piles together with changes to new treatment control pit and relocation of centrifuge, storage sheds, pump housings and waste bin area.

With a limited construction phase (Oct 19 to end March 20), the changes needed to account for M&E equipment delivery.  This required and element of 3D modelling with millimetre precision to ensure no significant changes were made for parts on the production line.

These works were successfully completed on time and within budget.

The works incorporated the following:-

1. Earthworks (2600m3 reduce dig, reprocess, spread, level and grade on site)
2. Piling (135 piles including pile mat and attendances CFA piles with excavated reprocessed and used on site)
3. Slab thickening and concrete construction 490m3 with 42t steel reinforcement including lateral movement joints, expansion joints and contraction joints
4. Deep drainage
5. Basement construction
6. Erection of steel gantry for new centrifuge
7. Service ducting
8. Storm and foul water drainage
9. Pump station (5.6m deep)
10. Road crossing
11. Retrofitting cast iron pipework diameter between 150mm – 450mm
12. Installation of new storage containers
13. Full Mechanical and Electrical Installation, with testing and commissioning