Narrative:

A cessna was on a left base for runway xxl. [I] advised [the cessna] of landing traffic for runway xxr; a B737 on final and a B737 on wide left base for runway xxr. When closer in [the cessna] was also advised of departing traffic off runway xxr; air carrier Y; and was also told to keep their base in tight to avoid conflict with the second B737. The cessna was also given wake turbulence advisories for all aircraft. After the first B737 landed on runway xxr; air carrier Y was given; 'runway xxr; line up and wait;' and was also given traffic information on both airborne aircraft. When the B737 exited the runway; air carrier Y was not yet on the runway; but was cleared for takeoff. As air carrier Y lined up on center line; they asked if they were cleared for takeoff. At this point I observed the cessna making a short approach and just crossing over runway xxr about 1;000 ft down the runway from the approach end at about 500 ft AGL. I waited for 2 or 3 seconds to ensure that the cessna was clear and told air carrier Y; 'cleared for takeoff.' I did not ensure that the cessna would remain clear of runway xxr by instructing them to their base outside runway xxr. I believe that the pilot wanted to stay clear of the wake turbulence from the B737. My problem was that I was impatient and trying to keep the traffic moving so that the next aircraft in line after air carrier Y could depart before the next B737 arrival on runway xxr. My recommendation would be to take care to get everything done correctly and not feel hurried to get the planes moving when the situation becomes more hectic.

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Original NASA ASRS Text

Title: Tower Controller described an unsafe condition when failing to insure an arrival remained clear of a departure runway; noting the 'hurried' approach to the increased traffic lead to the event.

Narrative: A Cessna was on a left base for Runway XXL. [I] advised [the Cessna] of landing traffic for Runway XXR; a B737 on final and a B737 on wide left base for Runway XXR. When closer in [the Cessna] was also advised of departing traffic off Runway XXR; Air Carrier Y; and was also told to keep their base in tight to avoid conflict with the second B737. The Cessna was also given wake turbulence advisories for all aircraft. After the first B737 landed on Runway XXR; Air Carrier Y was given; 'Runway XXR; line up and wait;' and was also given traffic information on both airborne aircraft. When the B737 exited the runway; Air Carrier Y was not yet on the runway; but was cleared for takeoff. As Air Carrier Y lined up on center line; they asked if they were cleared for takeoff. At this point I observed the Cessna making a short approach and just crossing over Runway XXR about 1;000 FT down the runway from the approach end at about 500 FT AGL. I waited for 2 or 3 seconds to ensure that the Cessna was clear and told Air Carrier Y; 'Cleared for takeoff.' I did not ensure that the Cessna would remain clear of Runway XXR by instructing them to their base outside Runway XXR. I believe that the pilot wanted to stay clear of the wake turbulence from the B737. My problem was that I was impatient and trying to keep the traffic moving so that the next aircraft in line after Air Carrier Y could depart before the next B737 arrival on Runway XXR. My recommendation would be to take care to get everything done correctly and not feel hurried to get the planes moving when the situation becomes more hectic.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.