Contractors working on a major overhaul of Aberdeen's Union Street have revealed the hidden obstructions uncovered during their work so far.

The £17m project's completion date has already been delayed from the autumn of 2025 until the following spring.

Once complete, it will see a new pedestrian-focused look for the 300m (980ft) central section of Union Street as part of Aberdeen City Council's city centre regeneration masterplan.

The main contractor Morrison Construction Infrastructure (MCI) said that among the problems it had encountered were deep hidden manholes, old tram wires, and more than 20 clusters of undocumented utility pipes and cables.

Experts were required to visit the site to determine whether some of the pipework was still in use.

A 46cm (18in) diameter cast iron pipe – thought to be a redundant water main – was also discovered running the length of the construction site and had to be removed.

Workers found a capped-over concrete access shaft, leading to a 10m (33ft) deep underground culvert which could not be safely removed and the new street drainage system had to be redesigned around it.

Councillors were told in March this year that unforeseen problems, as well as lower than expected productivity, were behind delays to the project.

Contractors have since carried out advance excavation work in the western section of the site and deep trench investigations in the central section.

These will help to identify further potential clashes with uncharted utilities before the main construction phase.

MCI construction manager Rod Buchan said: "Despite the challenges presented by these unexpected underground discoveries, the team remains committed to delivering the much-needed upgrades to Union Street Central."