Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Last 90 Days 30; Flight Crew Total 13500; Flight Crew Type 6000
Confusion; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
General None Reported / Taken
Environment - Non Weather Related; Procedure
We were flying the GLASR arrival into BFI. Around JAKSN Intersection we were vectored off the arrival on a 180 degree heading for Runway 31L; and given a descent to 6;000 FT. Later ATC cleared us to descend to 4;200 FT. It was daytime and the visibility was at least 20 miles. We could see a hill ahead of us and could tell we would clear it by 1;000 FT or so. I was expecting a turn before we would fly over the hill. Just in case we would not get a turn I double checked the altimeter setting and the HSI map; it showed yellow and red starting 10 miles off to the left but only a few areas of green ahead. When we were directly over the hill at 4;200 FT we received one 'TERRAIN TERRAIN - PULL UP'. We could see that we were clear of the terrain and did not do the CFIT maneuver. We cleared the hill and towers on top by 1;000 FT flying level. Our location was about 10 miles north northeast of the LACKR Intersection.
An Air Carrier being vectored to BFI Runway 31L was given a descent to 4;200 FT and received a TERRAIN TERRAIN - PULL UP warning 10 north northeast of LACKR Intersection but took no evasive action because the conditions were day; VMC.