Checking the Boulder description page and trail map posted, I do not see any "direction of travel" stated; however I have always ridden the trail in a clockwise direction...to be truthful, It's been quite a while since I have ridden Boulder and I think I remember seeing clockwise directional arrows posted. If it were me running I would go in a counterclockwise direction. I know that this is a "hot button" for some and a personal decision for others...and that some trails actually desire and mark their "direction of travel" for all trail users in the same direction, e.g. NorthShore.
You may want the ping the Boulder TS...I believe his DORBA forum handle is "WhiskyCreek5" (and can be found on threads in the "Individual Trails" forum for Boulder or Nick, our DORBA VP of Trails.
Enjoy the run at Boulder, it's a great trail AND will provide you lots more elevation changes than you find at RCP.
Rowlett Creek Preserve