Pre-Construction drainage survey at A High School in Bolton
Pre-construction drainage survey carried out at a High School in Bolton on behalf of a renewable energy company planning the installation of heat pumps.
The survey identified extensive structural and operational defects across the drainage network, including one of the worst-condition drainage lines we have encountered during our time carrying out CCTV drainage inspections.
Location: Bolton, Greater Manchester
Service: Pre-Construction drain survey
Overview
We were appointed by a renewable energy company to carry out a pre-construction drainage survey at a High School in Bolton. The survey was required to support the planning of a proposed heat pump installation at the school. Before installation works could move forward, the project team needed to understand the layout, condition and usability of the existing drainage network.
Drainage surveys are an important part of pre-installation and pre-construction planning. They help identify existing drainage defects before works begin, reduce the risk of unexpected issues on site, and provide clear evidence of the condition of the drainage system before new infrastructure is installed.
For this project, our role was to carry out a CCTV drainage survey, assess the condition of the accessible pipework and provide practical recommendations for remedial works where required.
What we did
We carried out a CCTV drainage survey across the accessible drainage network at the High School in the area of the proposed heat pump installation. The survey identified extensive structural and operational defects throughout the system. In total, the drainage report recorded 93 structural defects and 112 service defects, with two survey sections abandoned due to major obstructions.
One of the inspected drainage lines was in extremely poor condition and was, without doubt, one of the worst-condition lines we have seen during our time carrying out drainage surveys. The defects identified included:
Widespread displaced joints across multiple sections
Large displacements creating internal lips within the pipework
Broken pipe sections
Open joints
Longitudinal cracking
Circumferential cracking
Root ingress
Soil visible through structural defects
Settled deposits
Rubble obstruction preventing full inspection
Sections abandoned due to major obstructions
Multiple sections graded 4–5 due to elevated structural risk
Several of the displaced joints were significant, creating internal lips that are likely to trap solids and increase the risk of recurring blockages. A large displacement caused survey abandonment in one section, while rubble obstruction in another section prevented the downstream pipework from being fully inspected.
The survey also identified areas where soil was visible through defects, indicating that the structural integrity of the pipework had been compromised. Where defects of this nature are left unresolved, there is an increased risk of further deterioration, ground movement, service failure or collapse.
The outcome
The pre-construction drainage survey provided the renewable energy company with a clear understanding of the condition of the drainage network at a High School before the proposed heat pump installation progressed.
The findings showed that sections of the drainage system were in very poor condition and would require remedial works before the area could be considered suitable from a drainage perspective. Based on the survey findings, we recommended:
Targeted excavation at the large displacement to replace defective pipework
Excavation to remove the rubble obstruction and inspect the downstream condition
Localised replacement of broken and open-jointed sections near the affected manhole
Full line replacement in sections showing repeated linear defects adjacent to the retaining wall
Further investigation where survey sections had to be abandoned
Post-repair CCTV re-inspection to confirm structural integrity and update condition grading
The recommendation for full line replacement was made where repeated displacements and structural weaknesses suggested progressive movement, particularly near the retaining wall. Without remedial works, the drainage system could be at risk of recurring blockages, ground instability, service failure or structural collapse.
This project is a strong example of why pre-construction CCTV drainage surveys are essential before renewable energy installations and wider infrastructure works. Identifying drainage issues early allows project teams to plan repairs, reduce risk, avoid delays and make informed decisions before installation works begin.
Location
The project was carried out at a High School in Bolton.
We provide pre-construction CCTV drainage surveys for renewable energy companies, contractors, schools and infrastructure teams across the UK, helping identify the layout, condition and serviceability of underground drainage assets ahead of installation or construction works.
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