u/filbertnonsuch

Does anyone know the purpose of the 8 metre high gravel mountain on bare land between grassmere and cranford st? I had thought it was going to be for housing, with water retention etc, but the purpose of this compacted gravel mountain is lost on me. I can’t see it being built on because it’s about 8 metres high, large and rectangular. About two football fields in size - so enormous. Rollers compact each layer so it can’t be just a pile of gravel for using go elsewhere - it may be something to do with the water retention / filtering, but how?
Any ideas?