Project: Manchester University Build Over
Client: United Utilities Total Solutions Ltd:
End Customer: Manchester University
Location: Materials Science Centre Upper Brook Street, Manchester
Manchester University want to construct a new building over a deep United Utilities combined major trunk sewer.
The sewer is a 3.8 diameter Trunk Main located directly beneath the build over site, the precise location needed to be determined prior to any piling and construction works and to ensure the asset was safe from the construction activities. The sewer is constructed in rock with a brick lining and is up to 18 metres below ground level. To assist with the build over design a pre-condition survey was required so that UU could approve the design and sanction the construction. On completion of the build a post construction survey is also required.
Access to the sewer was problematic due to limited access points, depth, multi landings, high flows and side entries. The sheer size and flow levels also meant conventional crawler mounted CCTV and Man Entry surveys were ruled out.
A recce of all located chambers was undertaken to determine equipment access issues, rescue techniques and the survey method. Detailed surveys were undertaken of all manholes and landings supported by diagrams and photographs which enabled the RAMS to be prepared and access permits granted.
Following several site meetings with representatives from the University, the construction Design Consultants, United Utilities operational and management staff and IWJS Managers and Supervisors an acceptable method was proposed and eventually accepted once it was vigorously checked by the relevant health and safety departments of all concerned .
Using a high volume combination unit as a winch device we towed an inflatable raft complete with a CCTV platform and location probe from a number of limited access points over a period of three night shifts. A four man, high risk confined space entry team were required to position the equipment and inflate the raft below ground using protective sheets to avoid puncturing the floatation device when installing and retrieving it. The whole project was supported by a six man IWJS Rescue Team complete with BA equipment in case of safety alerts or in sewer incident.
During the survey an above ground mapping team was engaged to locate the sewer using a transmitting sond attached to the raft which was picked up on the surface with an RD7000 radio detection device. All points marked on the surface were then surveyed using a GPS unit which accurately pin pointed all signals received to enable the sewer route to be created on a CAD drawing.
All works were in accordance with:
- Confined Spaces Regulations 1997
- The Management of Health and Safety at work regulations 1999
- Water Industry act 1991
- Water Act 2003
- Flood and Water Act 2010.
Provision of survey report including:
- Summary of findings
- Details of all points of interest
- CCTV recording on DVD
CAD drawing of survey results showing:
- Points of damage and extent (if known)
- Points of erosion and extent (if known)
- Other areas of interest
- Depth and level recordings