Attleborough station car park

[trebor79]

So I've been watching with interest the work to expand the car park at Attleborough. So far this has consisted of tree felling, vegetation clearance and demolition of a couple of small derelict buildings associated with the goods yard that disappeared decades ago. Since then they have been digging an enormous hole, over about half of the expanded car park area. It's terrifically deep, to the extent this is now a 360 excavator in the bottom of it passing spoil up to another excavator up top. There's a very large heap of spoil on the other half of the site, and a skip which appears to have been lined with some kind of white plastic.
I can't work out what an earth they are doing. My 7 year old son jokes they are digging for diamonds. I can think only that some contaminated earth is being removed, but it seems a heck of a job and I can't work out why they didn't simply grade and hardcore the site before laying tarmac.
Anyone know what's happening? Must be costing an absolute fortune, whatever it is.

 

[KeithMcC]

If the area of hard surface is being increased then a rainwater storage tank will need to be installed to retain surface water, and they can be big.
Quite likely to be contamination in the ground that will need to be removed if there is any risk of it migrating in to the groundwater or to adjoining land.

 

[trebor79]

I guess that's what it could be. But then where does the water go? Presumably into the sewer, so why not just put a conventional drain in?

 

[Elecman]

It will be an attenuator/interceptor tank. Attenuators store excess water and then slowly release into the surface water drains so they are not overwhelmed by excess water run off from a larger tarmac area rather than soft ground which would absorb the water