Mr Gadkari's predecessor in the ministry, Ms Uma Bharti, had earlier stated that the government had resolved to make Ganga a clean river by October 2018 by completing the first phase of its Namami Gange initiative.
Addressing an event in New Delhi, Mr Gadkari said efforts are being made to float tenders for all the works relating to Namami Gange by December-end this year and issue work orders by March next year. He also said that the government will ensure transparent and corruption-free work.
"It (cleaning Ganga) is a difficult task. It is not an easy task. Our effort is to see that, when you will calculate the COD and BOD levels of Ganga waters in March (2019), you will see lot of change (improvement) in it," Mr Gadkari said.
The chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are valuable tests for assessing pollution levels.
The minister said, "Let's try for it, think for the best. And it is a difficult task, this is not my commitment and I am not saying I will accomplish it. (but) I am saying I will try to accomplish it."
Mr Gadkari made the remarks during signing of a tripartite agreement with private sector concessionaires for two hybrid annuity-based public private partnership mode projects in two Ganga cities: Varanasi (Uttar Pradesh) and Haridwar Uttarakhand).
The minister said that the government has resolved to complete the works and the chief ministers of all Ganga basin states were co-operating on the issue.
On the tanneries in Uttar Pradesh's Kanpur polluting Ganga waters, Mr Gadkari said the ministry has discussed a new technology to curb pollution with the tanneries association there.
He said the association has responded positively to the proposal, which will be discussed with the Uttar Pradesh government too before a tender is floated.
Mr Gadkari also said that the ministry has convened a meeting of top officials from six Ganga basin states on October 30 to review "each water recycling/purifying project" there.
Minister of State for Water Resources Satyapal Singh will also be attending the meeting, he said.
Mr Gadkari also said that ensuring a 'nirmal Ganga' (Clean Ganga) was the government's priority. He said an "unfettered flow" in the river will be ensured automatically once the river is clean.
He also urged the media to spread awareness about social- cultural programmes relating to the Ganga for ensuring that the campaign becomes a social movement.
"This is not just a government programme, but of all those who love the river," he added.
At one point, Mr Gadkari said officials will have to work in a "do or die" mode and also said that contractors will be dealt with sternly if they put up a poor show.
According to an official statement, the tripartite agreement for Varanasi was signed among National Mission for Clean Ganga (NMCG), Uttar Pradesh Jal Nigam and Essel Infra Projects Limited.
The contract for Haridwar was signed among NMCG, Uttarakhand Peyjal Nigam and HNB Engineers Private Limited.
The work for setting up 50 million litres daily capacity sewage treatment plant in Varanasi will be carried out at an estimated cost of Rs 153.16 crore.
In Haridwar, two STPs of 68 MLD and 14 MLD will be developed, spending around Rs 171.53 crore, the statement said. Both the projects are 100 per cent centrally-funded.
After the signing ceremony, the minister also launched a website to enable corporates undertake social responsibility activities.
The first quarterly newsletter titled Namami Gange was also released by Mr Gadkari.