Thanks man. Yes, no more sludge! Can't remember exactly where the sludge started but probably where there is a very obvious 2ft step about 20m up the pipe in the first pic (not visible in my pic). And nope it is no longer affected by high tideGreat stuff! Have they cleared the sludge out of the original outfall chamber then? Or any other changes ahead of connecting it up? I guess it won't be subject to backfilling from high tide anymore