Delivering Innovation

There are two locations where the culvert passes under the carriageway and one location where it encroaches under the A236. Due to the placement of the culvert, the defects in question presented a significant health and safety risk if left unattended.

The defects included areas where the concrete structure in the crown of the pipe had collapsed, leaving reinforcement bars exposed. Other defects included the ingress of root mass through defective connections, plus a number of the connections were intruding into the main pipe.

The FM Conway team completed an initial survey of the culvert and provided a list of recommendations to the client as how to restore its structural integrity and full flow capacity. Following this the client put the focus on four sections where the culvert passed completely or partially under the carriageway and requested a costed list of options.

The scope of works included:

Section 4 - Manhole 3 – Buried Chamber
A 6m length of Channeline was selected for this 20m length of 900mm x 650mm rectangular pipe. The manhole covers for both manhole chambers were removed to enable the works and were then reinstated post works.

Section 5 – Buried Chamber – Manhole 4
There were eight locations where there were restrictions caused by either intruding connections or roots. These were removed via cutting and then 1-metre long cured-in-place repairs were installed to prevent further root ingress and prevent deterioration of the poorly constructed connections

Section 10 – Manhole 6 – Manhole 7 – Outfall to Main Culvert
The pipe changed diameter three times – from 1m circular to 1.05m x 2m to 730mm x 2m. It joined blind onto a main culvert of 4.7m x 1m. This change took place over a 19m length where there were two connections joining onto the culvert. The solution was to install a 1m diameter UV cured liner into the culvert and the two connections were extended to join into the UV cure liner. A new headwall was formed at the outfall end. The annulus formed between the existing culvert and the newly installed UV liner was then flooded with grout.

Section 11
A fracture was identified to the main culvert. An epoxy mortar was applied manually by a confined space entry crew.

By using UV and Channeline products, these provided innovative solutions to the project that enabled a high-quality delivery of the completed works.

Channeline provided a custom-made solution that provided full structural rehabilitation with the expected service life of over 100 years, whereas using the UV cure liner enabled the team to install a seamless shape/diameter changing pipe retaining the same internal diameter. Then further structural integrity was provided by the flooding of the annulus with grout.

Challenges and Solutions 

One of the main problems facing the project team was dealing with potentially dangerous environmental issues such as risk of pollution to the water course. This meant that an Environmental Agency (EA) permit was required.

The client requested that FM Conway manage this; a process which normally takes two months to obtain a permit. However, following liaison with an EA permitting officer, and strict adherence to the EA guidelines and assistance, this was able to be completed within 17 days.

The team also remained aware to avoid causing further disruption as a result of the project, paying particular attention to the disruption to the water flow and the potential risk of pollution. Therefore, “No-Dig” technology was used in order minimise the carbon footprint, as well as any interruption to traffic in the area.

Utilising No-Dig techniques also gave a boost to the health and safety standards in place across the works, which was monitored by permanent on-site supervision from start to finish.

Outcomes

The Water and Drainage Management team delivered a high-quality culvert repair as all works on the project were completed within a four-week programme with minimal disruption and ahead of the original proposed schedule.

The use of bespoke, innovative solutions ensured that FM Conway delivered a cost-effective approach for the client, matching their budget, whilst also maximizing the extents of the repairs.