Alleghany, Where?

I don't know what your definition is of cleaner water, but you won't find much of a difference from Kittaning down to the point. The same toxins and the same issues of sewage treatment facilities overflowing during high water events will be found for most of that stretch of river.

I see no issues skiing and fishing down there. It can get busy on that pool for the nice weekends, but if you stay below the Tarentum bridge you will be fine since most of the docks are above the bridge.

I can see how this is going to end.  No action within 20 mins, ahh let's go skiing!  

come further north.  the allegheny reservoir is much cleaner, is a very beautiful ski-ride. and has some big fish.

admittedly fish are few and far between (I have had only a few good experiences fishing wise), but since the main activity is skiing in pristine waters it can't be beat.