'With this recent hiring the white and red box presidency reiterates its commitment to have a highly competitive payroll for national and international championships this year.
In the press release, Pastrana did not confirm or deny reports of a purchase option being included as part of the deal.
Valdes' departure from the Union, either temporarily or permanently, stemmed from both personal ambition and also a push by his international coach. The 27-year-old Valdes moved to Bogota in order to further his career, both at the club level and internationally, according to the player himself last week.
Colombian National Team manager Jose Pekerman had stated his desire for Valdes to play in South America, especially in Copa Libertadores, prior to the 2014 World Cup. Valdes also believed that his best option for reaching his personal goal of playing in Europe was to move back to Colombia.
The center back reportedly turned down offers from Boca Juniors (Argentina), Nacional (Uruguay) and Deportivo Cali (Colombia), which Faryd Mondragon has played for since leaving the Union himself in 2011.
Valdes previously played for Santa Fe until 2011, while previously doing so as well for America de Cali and Real Cartagena. He came to the Union on loan and his rights were purchased by the Union in August of 2011.