Costain, Edmund Nuttall, Kier and Laing ORourke are pricing the civils package for the £200 million, 5.93-hectare plant in the London borough of Bexley. This will include preparing the ground and building the plant with a wharf and jetty.
The Government gave project promoter Cory Environmental the green light for construction last year, to much protest from Mayor Ken Livingstone.
A Cory spokesman said the financial close for the deal would come in December, so work could start in 2008.
A 30-year contract worth £700 million will see 585,000 tonnes of non-recyclable waste processed annually, which will come from the London boroughs of Kensington & Chelsea, Hammersmith & Fulham, Lambeth and Wandsworth.
Corys subsidiary Riverside Resource Recovery will run the operation, transporting waste along the River Thames via the Western Riverside Waste Authority and generating up to 66MW of electricity annually.