This is interesting - I had exactly the same concerns about this pipe. For years it has been there and it has just been water that came out. Since the building work started there were other materials (sand?) coming out, but I thought that it was part and parcel of the temporary land disturbance. The building seems pretty finished, but there is still occasionally some sort of pollution (cement dust? plaster dust?) I took this photo on Thursday and sent it to the park warden voicing my concerns. ( I have seen this sort of cloudiness twice before) If it is either of the above then they could be harmful to wildlife. good idea to send to the site manager though and thank you for the number above