Geotechnical investigations are now underway along the Werribee corridor, with crucial information below the surface essential to determining the best outcome for faster services on the Geelong Line.

Drilling of up to 40 boreholes - each between 3m and 25m deep - is expected to take place by the end of the year as part of an extensive site investigations programme which includes site inspections, surveys, geotechnical drilling and sampling.

The information gathered will help to inform ongoing planning and design work to refine the scope, cost and timing of the first stage of Geelong Fast Rail, which will cut travel times.

Site investigations will take place primarily within or near the rail corridor at locations from Newport to Werribee, with around 300 individual locations earmarked for a combination of boreholes or cone penetration tests, all of which are carefully controlled geotechnical investigations and minimally disruptive.

This upgrade will complement works already underway further down the state's busiest regional rail line to increase frequency and reliability including the Waurn Ponds Station upgrade, Waurn Ponds stabling and the South Geelong to Waurn Ponds Duplication.