Same reason taxiways cross runways at most airports. You've got vehicles that need to be on the other side of the approach/departure path, and the only way for

Same reason taxiways cross runways at most airports. You've got vehicles that need to be on the other side of the approach/departure path, and the only way for that to happen is if the paths cross. The airspace in the area is complex, so it's a challenge to provide useful helicopter routes while reducing potential conflict.