In the south of Hallein towards Kuchl lies a place called Gamp. That's where I found my main running getaway while living there a couple of years ago. I spent most of my time working on my master's thesis, so getting some fresh air and exercise was a very welcome part of my daily routine.
Starting at the old “Pesthaus” we cross the Salzach river and follow it southwards. We pass a newly built sports facility named after Hallein's famous skiing star Thomas Stangassinger and a hydropower plant rebuilt after immense flooding in 2002. Here the paved road ends, but dirt tracks (ideal for interval training) continue along the Salzach before we return towards Hallein on the small and curvy street from Kuchl, hugely popular from spring until autumn bicycle enthusiasts.
It's one of the shorter routes in this series, but options to extend it are plenty. You can continue towards Hallein's old town or a little more challenging up to the top of the Barmstein (through Hallein's old town and then via Kleinkirchentalweg). My favourite one though is continuing in the opposite direction towards Kuchl which allows you to run a 20 or even 30+ km loop.