The Royal Irrigation Department has offered to let the company that won the bid to build a floodway on the western side of the Chao Phraya to use its environmental impact assessment report.
The report is a key requirement that Korea Water resources Cooperation (K-Water) must fulfil before construction of the floodway can begin.
The floodway is one of nine modules under the government's 350 billion baht water management scheme.
K-Water won the bid for construction of the floodway last month, but the Administrative Court ruled that potentially harmful projects under the water management scheme must be subject to public hearings and environmental and health impact assessments before work begins.
Department spokesman Thanar Suwattana said the department started its assessment for the 280km floodway last year before bidding commenced in anticipation of the requirement.
The company could conduct and submit its own report, but Mr Thanar said the department was also offering its findings.
He said the assessment has already involved several public hearings in areas that would be affected by the project.
The report is expected to be completed in October, when it will be forwarded to the Water Management and Flood Prevention Commission.
Mr Thanar said K-Water could submit the department's study to the government or it could choose to add to or amend the report.
However, a new impact report would be required if the company makes any major changes to the existing plan.
Mr Thanar said the floodway would require about 43,000 rai of land in 20 provinces to be reclaimed. The company must take responsibility for the cost of reclaiming the land, while the government will oversee the legal issues involved.
Mr Thanar said the floodway will start in Khanu Woralaksaburi district in Kamphaeng Phet and end at the Mae Klong River in Tha Muang district of Kanchanaburi.
The floodway is aimed at speeding up the flow of water through the Mae Klong River to the Gulf of Thailand.
Mr Thanar said the capacity of the Mae Klong River would increase from 800 cubic metres per second to 1,000 cu/m.
Thai-Water Partnership chairman Hannarong Yaowalers said the company should carry out its own impact assessment, as the project was being carried out by the private firm, not a state agency.
He said he worried that the department's study would not be precise enough and there would be a good chance that it would be rejected by the committee vetting the assessment report.