The near-α titanium alloy Ti834 is sensitive to reductions in fatigue life when exposed to relatively high constant stress during the loading cycle. The source of failure is usually identified as subsurface crack initiation with a fracture surface containing quasi-cleavage facets near basal orientation regarding the loading direction. The presence of strong textured regions called macrozones has been linked with this dwell fatigue debit where regions of grains share similar crystallographic orientation that become areas for continuous faceted cracking. In this paper quasi-cleavage facet formation and deformation mechanisms in dwell fatigue have been studied on specimens from a Ti834 compressor disc alloy with a bimodal microstructure by ex-situ dwell fatigue testing at temperatures between 80^oC and 200^oC. Ex-situ Electron Backscattered Diffraction acquisition coupled with slip trace analysis used to identify the main operating slip systems at primary alpha grains and secondary alpha colonies at different stages during deformation. Basal<a> slip was observed in grains with their c-axis near parallel the loading direction, while colonies similarly oriented accommodate deformation by tensile twins. This type of slip in basal planes is the most critical damage mode leading to failure during dwell fatigue loading. A Rogue colony-grain combination is presented and a possible criterion for slip transfer in bimodal titanium alloys is introduced. The requirements cited for quasi-cleavage facet formation leading to dwell fatigue failure have been experimentally observed in agreement with the suggested hypothesis in previously presented crystal plasticity models. Temperature, texture and aluminium content are key factors on cold dwell fatigue performance of Ti834 and their influence in defining the deformation modes is discussed.