The deal will also see Croatia global Mateo Kovacic join Chelsea on loan for the duration of the 2018-19 season.
He is believed to have a release clause of 80m euros (£71m) in his Athletic contract, which the Premier League club are apparently willing to meet.
Thibaut Courtois is set to leave Chelsea for Real Madrid
The Blues broke the world record fee for a goalkeeper to bring the 23-year-old in from Athletic Bilbao in a deal worth £72m.
Report after report has surfaced over Courtois' exit, with stories going as far to say that a fee had been agreed between Chelsea and Real Madrid for the Belgian.
New York City has hit Uber with a cap on new cars
Drivers previously pushed for a cap on new competition in 2015, but were beaten back by ride-hailing companies. The legislation also allows the city to set a minimum pay rate for drivers and minimum fares for the industry.
"It's a very important decision for me, for my career, and also for my personal life", Kepa told Chelsea's website.
Courtois spent three years on loan at Atlético Madrid from Chelsea, before becoming Chelsea's No 1 in 2014-15.
I fulfilled a childhood dream playing in the Premier League, therefore I am really proud that we were able to win two Premier League titles, a League Cup and an FA cup!
Snap revenue tops estimates due to mobile ad demand
Snap disclosed Tuesday that the app lost 3 million of its daily active users due in large part to its controversial redesign . Snap's second-quarter sales climbed 44 per cent from a year earlier to US$262.3 million, Snap said Tuesday in a statement.
"It's an accumulation of things, and I am very glad Chelsea has chose to trust me and to take me in as well".
Meanwhile, midfielder Willian continues to be linked with a move to Manchester United and Barcelona, even though Chelsea are reluctant to sell the 29-year-old Brazilian.
Chelsea have wasted no time in showing off their latest addition, with Kovacic snapped around Stamford Bridge with the new home kit for 2018/19. As part of the deal Mateo Kovacic will join on a season-long loan'.
Buildings collapse as strong new quake rocks Lombok island
He said: "People are always saying they need water and tarps". "I don't think people will choose Lombok anymore this summer". Many farmers were reluctant to move far from their damaged homes and leave precious livestock behind, he added.