NorthConnex Tunnel Stacks

There's an interesting and informative article on page 4 of the Northern District Times today, about the proposed ventilation stacks at the southern end of the NorthConnex tunnels.  The article quotes one of the local residents making the point that at present Pennant Hills Road is mostly occupied by stationary or very slow moving trucks and other vehicles belching fumes out at ground level, and if those vehicles can enter and exit the tunnels at 70kph they will generate far less atmospheric polution.  The proposed ventilation stacks will be 23m tall (a typical mature Sydney redgum tree is about 21m tall) and located just west of Pennant Hills Road and north of the M2.  Transurban studies show air quality at road level will improve by 38%.