Background

Severn Trent Water Asset Creation required the construction of a new sewage pumping station (SPS) to replace an existing asset that had reached the end of its working life.

The site presented significant constraints. It was restricted on three sides by residential housing and roads, with maximum available site dimensions of approximately 21.5m x 11m. In addition, the existing pumping station needed to remain operational throughout construction, and acquiring additional land was not an option.

A highly compact, carefully phased solution was required to maintain service continuity while minimising disruption to local residents.

The challenge

The project team faced several overlapping challenges:

  • Extremely restricted site footprint within a residential area
  • A requirement to maintain operation of the existing SPS throughout construction
  • The need to deliver minimum two hours of online storm storage at dry weather flow (62.2m³)
  • Reducing noise, vibration and disruption close to existing properties
  • Avoiding construction methods such as sheet piling that could increase programme risk and environmental impact

The original design template required multiple structures within the limited footprint, creating challenges around access, buildability and programme.

The solution

NMCN worked closely with Marshalls to refine and enhance the original design template into a fully integrated precast solution, suitable for use on this and future schemes.

The adapted solution combined storm storage, wet well and valve chamber within a single precast structure, constructed using 4.0m diameter precast shaft rings. The final configuration included:

  • A 4.0m diameter, 7.0m deep caisson, providing increased storm storage capacity without the need for a separate external tank
  • An integrated wet well and valve chamber within the same structure
  • Air valves, flow meter and Bauer coupling housed within two precast units installed above the wet well
  • Factory designed watertight jointing throughout

By consolidating functions into a single structure, the design significantly reduced the overall footprint and allowed the existing inlet manhole to be retained and used as a temporary pumping station for the duration of the works.

The outcome

The integrated precast solution delivered clear benefits for the client, contractor and local community.

  • Reduced site footprint, enabling construction within severe spatial constraints
  • Retention of existing pumping infrastructure during construction
  • Programme savings of approximately four weeks compared with the original template design
  • Reduced disruption for residents and operational staff
  • Fewer vehicle movements due to reduced excavation and spoil removal
  • Elimination of sheet piling, reducing noise, vibration and environmental impact

Off site manufacture in controlled factory conditions also improved finishing tolerances, ensured consistent quality, and removed weather dependency from critical construction activities.

Following completion, NMCN audited the project and concluded that the use of precast, factory fitted components could deliver similar benefits on other pumping station and wastewater infrastructure schemes, particularly where modern methods of construction are required.