A £50,000 tunnel of love has been hailed a success for the eel population of Essex.
The Environment Agency led the project to help eels and fish navigate over the weir structure on the River Colne.
The scheme was such a success it could be rolled out across Essex to help lonely eels repopulate the declining species.
Vital tools and a JCB were also stolen during the build, but despite this the tunnel was still successfully completed in four weeks.
An Environment Agency spokesman said: "Two eels were found downstream of the structure while the contractors were drying out the work area.
"This is really encouraging as it demonstrates that they can get as far as Earls Colne.
"The new eel pass should now help them further up the catchment."
Because of the unusual shape of the weir, the fish pass was complicated to design, with an added issue of having to dry a section of river out for work to be completed.
The flow of the water was also redirected during the work and eel tiles added while a section of the river was drained.
A dam was built upstream and large pumps were used downstream to bypass the structure as fish and eels were temporarily relocated during the river refurb.
The spokesman added: "We are excited to have completed the project and we are looking forward to the next step where we will be monitoring the flow data and surveying the fish populations to see if it can be rolled out elsewhere."
This weir is one of 22 Essex profile weirs, which means it has an unusual shape.
The fish pass was specifically designed to fit this shape and if it proves to be successful, it can be replicated on other structures.
Numbers of European eels have fallen 95 per cent over the last 30 years and by adding eel tiles to the fish pass, this will help this protected species to continue its fascinating life cycle.
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