A reduced service ran between Chester and Llandudno Junction with buses supplementing services.
Buses replaced trains between Llandudno Junction and Blaenau Ffestiniog.
There was also a warning that services between Llandudno Junction and Holyhead could have been affected by the work.

The Crues face a testing away trip to third-placed Coleraine on Saturday as they aim to protect a seven-point lead.
"If you are going to try and win a title, you have to go and win games. We are only thinking of collecting the three points," said Baxter.
"There is no point going there, sitting back and accepting pressure."
The Crues boss believes the outstanding recent form of the Bannsiders has made them "the big surprise package" of the campaign, but concedes that their progress does not come as a total surprise to him.
"I always knew Coleraine were developing something very strong - they have very good young players in their team with a lot of quality.
"They have really come to the fore in the last two months and hats off to Oran (Kearney) because he has worked tirelessly behind the scenes.
"He's a good manager and it will be a big test for us."
Kearney's charges have hit form at just the right time and are now unbeaten in 13 matches in all competitions.
"This is the business end of the season and it's full of big games. Crusaders had another emphatic win over Ballinamallard so we have a tough task ahead of us," observed the Coleraine manager.
Meanwhile Ballymena United boss David Jeffrey expects Cliftonville to pose a major threat to their ambition to get back to winning ways after picking up just one point from two home fixtures in the last week.
"It's going to be difficult at Solitude. They are a class act and are coming off the back of a few disappointing results. They will want to make amends on Saturday," argued the Sky Blues' boss.
Linfield will be out to keep up their pursuit of Crusaders at the top when they travel to Ferney Park to take on Ballinamallard United.
David Healy's outfit are on an impressive run of form, winning 11 and drawing one on of their last 12 outings.
"We are going to be playing the second best team in the country and they gave us a lesson the last time we played them at Windsor Park," said Mallards manager Gavin Dykes.
"Having said that, when we're at it, we can give anyone a game at Ferney Park."
Dungannon boss Rodney McAree has seen his side drop to eighth spot after Glentoran's 1-0 win over Carrick Rangers on Friday night as the Swifts head to Shamrock Park to face basement club Portadown.
"We don't want to finish any lower than seventh and we have to fight tooth and nail to try and achieve that," said McAree.
Glenavon manager Gary Hamilton is expected to make wholesale changes to his starting line-up for the Premiership game at Ards, with the Irish Cup semi-final against Coleraine a week later in mind.
Services have resumed on the north Wales coast main line and Blaenau Ffestiniog branch line after earlier disruption on Monday when engineering work overran.
[NEXT_CONCEPT]
Crusaders manager Stephen Baxter has urged his players to keep chasing wins in every game as they close in on a third consecutive Premiership title.