Transport Scotland appointed Norwest Holst and Ritchies to carry out ground investigations for the project, and Blom Aerofilms for topographical surveys. The three separate contracts have a combined value of £1.7M.
Findings from the surveys will provide information on the contours of the land and ground conditions in the area to inform the proposed bridge and connecting road network designs.
Forth Replacement Crossing project manager Lawrence Shackman said: "Following the government's announcement in December to build a multi-modal, cable-stay bridge across the Forth, work has been progressing rapidly and these surveys are the next key milestones in the project.
"A team of about 40 geotechnical engineers, geologists and drillers are undertaking ground investigations on the northern and southern banks of the Firth [a narrow sea inlet] of Forth. The findings will be used by our engineers to progress the preliminary designs for the bridge and connecting roads."
Ritchies, whose 12-week contract is worth £800,000, is working on the south side of the Forth. It has deployed four cable percussive rigs and five rotary rigs to the site from its Scottish Kilsyth base. Boreholes are being drilled to a maximum 80m using a combination of cable percussion boring followed by rotary drilling, with extensive use of rotary wireline drilling.
Norwest Holst won the ground investigation contract for the area north of the Forth. The works, which are expected to last about nine weeks, involve excavating trial pits and boreholes in the vicinity of the M90/A90 road corridor.
Ecologists and archaeologists have accompanied the teams on site.
Somerset-based Blom Aerofilms began aerial photography for the topographical surveys at the end of March.
The engineer is a Jacobs-Arup consortium. Construction of the £3.2bn to £4.2bn project (at 2016 out-turn prices) is expected to start in 2011 and take five and a half years to complete.