IAS37 Provisions

Hi tutors,

I have some problems with this question:

On 1 October 20X3 Xplorer Co commenced drilling for oil from an undersea oilfield. The extraction of oil causes damage to the seabed which has a restorative cost (ignore discounting) of $10,000 per million barrels of oil extracted. Xplorer Co extracted 250 million barrels in the year ended 30 September 20X4.
Xplorer Co is also required to dismantle the drilling equipment at the end of its five-year licence. This has an estimated cost of $30 million on 30 September 20X8. Xplorer Co’s cost of capital is 8% per annum and $1 has a present value of 68 cents in five years’ time.
What is the total provision (extraction plus dismantling) which Xplorer Co would report in its statement of financial position as at 30 September 20X4 in respect of its oil operations?

Here’s the answer from BPP book:
$24,532,000
$’000
Restoration of seabed (10,000 × 250) 2,500
Dismantling of equipment (30m × 0.68) 20,400
Unwinding of discount (20,400 × 8%) 1,632

Why can’t we capitalise the dismantling of equipment and depreciate it over the year?

Thank you for helping me out.