Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Procedure; Human Factors
I was working IADFC combined with IADFE and IADFW. Arrival aircraft CRJ-900 from BARIN in the scratchpad said Runway 19L so I planned for CRJ-900 to be number 1 for 19L. GLF2 was on a right base for Runway 19C. When I cleared CRJ-900 for the visual approach to Runway 19L; the pilot advised me that he was assigned Runway 19C which was conflicting with the scratch pad information. Since he was already on a base turn only about 6 miles out I did not want to change his runway to the runway that was indicated on his scratchpad and that I was vectoring for; so I amended his heading to pass behind GLF2 and turned the aircraft to a 170 degree heading to join the final for Runway 19C. He then saw the airfield and I proceeded to clear him for the approach. CRJ-900 saw GLF2 but I did not say 'maintain visual separation' because I thought I had enough divergence and I was gonna bring him through the localizer and bring CRJ-900 back around to give him plenty of room to follow GLF2. Since I did not say 'maintain visual separation'; I lost separation because I did not quite have 45 degrees opposite course divergence separation. Ensure scratch pad information matches with the runway you assign.  Possibly even restate the runway assignment when the aircraft checks in with the Final Approach Controller.
PCT Controller experienced a loss of separation event when failing to note the incorrect runway assignment scratchpad information in the data block.