The contract notice has been published in the Official Journal of the EU today (18th September 2015).
The corporation has set aside £5m for the work but appears to have little idea what the project will actually cost. The contract notice states that the estimated value, excluding VAT, is the range between £1m and £5m.
The timetable envisages work starting in mid November, with completion by the end of April 2016.
The 178-metre slide will take approximately 40 seconds to descend as riders travel at speeds of up to 15mph. It is being billed as the world's 'longest and tallest tunnel slide'.
The 114.5-metre high ArcelorMittal Orbit was designed by sculptor Anish Kapoor for the 2012 Olympics and built with sponsorship funding from steel firm ArcelorMittal. It remains a landmark of what is now called the Queen Elizabeth Olympic Park.