Pre-construction drain survey
Pre-construction drainage survey carried out at Lister Hospital in Stevenage ahead of a planned extension over an existing car park.
The survey was undertaken to identify, trace and assess the accessible car park drainage infrastructure, including lifting covers, recording invert levels and carrying out CCTV inspection where practicable.
Location: Lister Hospital, Stevenage
Service: Pre-construction drain survey
Overview
Working alongside UTSS Ltd, we were instructed to carry out a pre-construction drain survey at Lister Hospital in Stevenage to support planning for a proposed extension over a car park area.
Before construction works could progress, the project team needed a clearer understanding of the existing drainage infrastructure beneath and around the proposed build area. This included confirming the location of drainage assets, tracing the routes of accessible drainage runs, recording invert levels and assessing the condition of the pipework where access and equipment allowed.
Pre-construction drainage surveys are an important part of planning works in live healthcare, education and commercial environments, where existing services need to be understood before excavation, foundation design or construction activity begins.
What we did
We carried out a drainage survey across the accessible car park drainage network serving the proposed extension area. All drainage infrastructure that could be safely accessed was surveyed and documented.
A number of manhole covers were found to be rusted and seized. These were not forced open during the survey to avoid causing damage to the surrounding flagging, surfacing or property.
Due to the depth of several manholes, a full visual condition assessment could not be completed using push-rod equipment. In addition, pipework in excess of 225mm diameter could not be adequately surveyed with the equipment available at the time.
The outcome
The pre-construction drain survey successfully mapped the accessible car park drainage network at Lister Hospital and recorded invert levels where chambers could be safely accessed. All accessible drainage runs were traced and plotted, giving the project team valuable drainage layout information ahead of the proposed extension works.
Based on the findings, we recommended:
Deployment of a crawler camera system for pipework exceeding 225mm diameter
Specialist inspection of deeper drainage runs
Mechanical access equipment where seized covers need to be safely opened
Further CCTV inspection once additional access has been achieved
Completion of a full structural condition assessment before construction progresses
This project is a strong example of why pre-construction drainage surveys are valuable before building over or around existing car park drainage infrastructure. Even where some assets cannot be fully inspected during the initial visit, the survey helps identify known drainage routes, access restrictions and the next steps required to reduce risk before construction begins.
Location
The project was carried out at Lister Hospital in Stevenage. We carry out pre- and post- construction drainage surveys across the UK.