This was looked at once before HERE
but no conclusion was reached.
The only sign of anything is the sewage works which has two spreader/filter tanks and one enclosed tank which I guess is either a biodegrading tank or possibly a UV tank to kill of bacteria.
The sewage works is marked as Storm Water Tanks on some modern detailed maps.
The field to the immediate NW of the sewage works has a raised embankment, but I guess this is just to hide the sewage works, similar in manner to the row of trees by Upton Park Drive.
The 1970's aerials show no trace of anything other than the motorway being built and the two spreader tanks.
Might go for a wander tomorrow and have a look around.