EMB ERJ 135 ER/LR
Air Traffic Control Developmental
Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
The E135 was ready for departure and I made a plan to depart the aircraft after the MU2 had landed. The aircraft would offset to the right after departure to pass off the left of the Cessna Citation X on final. I did not control the turn for the MU2. I said when able turn left; join Alpha and contact Ground. I anticipated the aircraft exiting at Alpha 6 and not taxiing to A7. I had cleared the E135 for takeoff. My opposite direction cut off of 7 miles was decreasing. I tried to have the E135 hold short. I did not say cancel takeoff clearance; and yes; I do realize that was definately wrong. The E135 called and said he was past the hold short line. I think I had a little panic of getting in trouble; because someone just had a similar situation. I decided to clear the aircraft; because I should still make the cut off and the MU2 had exited. I gave the traffic to both aircraft and prompted the E135 to offset to the right per the SID. It was closer than I am used to for that similar situation. I had previously told the aircraft about each other. I continued to make the E135 turn in front of and underneath the traffic. In hindsight I wish I would've made the E135 continue on the 343 heading on the SID and turn behind the CRJ-700.  I made the situation worse than it had to be.  The CRJ-700 reported traffic in sight and said they would maintain visual seperation. I have controlled the E135 once before at this airport and am not familiar with their climb performance. I also felt like the MU2 was at a slow enough taxi speed to make A6. I should have controlled the turn. I am not used to the way the aircraft had exited so slowly; but I could have also controlled that. I could have taken much better steps.
Tower Controller described an unsafe event when trying to complete an opposite direction operation; the reporter acknowledging more specific instructions should have been issued.