After another grilling about traffic and damage to the countryside, Rob Audsley still manages a smile.

“We have been hugely encouraged,” said the project manager for the Lower Thames Crossing, which has seen more than 13,000 people attend public events over nearly nine weeks of consultation on the plans for a new tunnel linking Kent and Essex.

“We have had fantastic engagement with the public, businesses and local politicians. Lots of them recognise how important this infrastructure is and how important it is that people have a say in it.

“Of course there are some challenging views out there but this will generate £7 billion for the economy over our 20-year assessment period.”

There is a favourable consensus among businesses gathered for the final consultation event for the proposals to build a new crossing through countryside to the east of Gravesend.

“This should have been in place a long time ago,” said Graham Mitchell, finance director at Gravesend-based chartered surveyors Caxtons.

“The whole thing has been delayed too long for political reasons and we need to get on and do it. I think Option C is a no brainer and the only logical option. The only real concerns are nimbyism.”

Geoff Miles, co-owner of Maidstone Studios and Kent chairman of South East Local Enterprise Partnership, said: “There is no bigger item than the Lower Thames Crossing.

“We have to get across the importance of this to UK plc. It is all very well talking about a Northern Powerhouse and the engine they want to build up there but if they don’t put oil in the engine down here it will stall.”

Many residents, particularly in the communities of Chalk and Higham, have objected to the plans, which will see the countryside near their homes dominated by the route, which is set to carry 77,000 vehicles a day in its opening year, increasing to 89,000 by 2041.

Highways England said it is expected to relieve 15% of the 135,000 cars a day which use the Dartford Crossing but many businesses are unsure of the wider impact.

“The concept is good but I’m not sure there has been enough research done on the impact that it would have on the surrounding infrastructure,” said Frank Fealey, business development manager at Raymond Brown Construction, which has offices in Strood.

“Every road needs to be considered. We don’t have many main arteries in Kent and they are pretty well congested most of the time. The problem will just move along the roads.”

“The concept is good but I’m not sure there has been enough research done on the impact that it would have on the surrounding infrastructure...” - Frank Fealey, Raymond Brown Construction

Douglas Horner, a director at construction firm Trenport Investments, which has developments across Kent, said: “It is necessary to look further to the east, with the traffic increasing dramatically to Eurotunnel and Dover Port over the next 10 years.

“We also need to look at questions like Brenchley Corner on the A2 and the biovication of traffic from the A249, not the A229. Why are these things not being planned now?”

John Garner, business development manager of BBS Construction, who lives in Chalk, said: “It isn’t a solution to Dartford, which is worrying.

“It will relieve Dartford but only by 15% which doesn’t solve the problem. I’m trying not to be a nimby about it. I would vote for looking at Option A at Dartford again.”

Ministers are expected to make an announcement on which route will be taken later this year, with a crossing not expected to be completed until at least 2025.

However, pressure from environmental campaigners may yet be a stumbling block for the £6 billion scheme.

Highways England admits its preferred eastern route, linking the tunnel to the M2, eats into the largest area of the Kent Downs Area of Outstanding Natural Beauty.

KCC Cllr Martin Whybrow said: “The study pays scant attention to the environmental and human costs. The various options cause destruction to ancient woodland, areas of outstanding natural beauty, pockets of the Green Belt and agricultural land.

“Thurrock and north Kent already experience high levels of air pollution with resulting health issues for local people; a new road will only worsen the living conditions.”

Dr Hilary Newport, director of the Kent branch of the Campaign to Protect Rural England, said: “Most road freight using the Channel crossings has to cross the Thames but very little has its origins or destination in Kent.

“The short crossing across the Channel is quick and cheap for the freight companies but the real costs arising from ever more traffic are borne by the environment and the communities along the rest of the route.

“This traffic brings no real economic advantage to Kent, just pollution, noise and congestion which is potentially now requiring a very expensive ‘fix’.”

Lower Thames Crossing project manager Rob Audsley said: “We have done our work to assess the impact across the whole route. We have been absolutely transparent that the eastern southern link has a great impact in some sectors compared to the western link.

“We also acknowledge it has a great impact on people’s houses. We are working with local authorities and people to minimise these effects.

“I don’t anticipate we will run into problems that we can’t solve but clearly we have to do a lot of work with environmental bodies to make the scheme the best it can be in terms of those effects.”

“The short crossing across the Channel is quick and cheap for the freight companies but the real costs arising from ever more traffic are borne by the environment and the communities along the rest of the route..." - Dr Hilary Newport, Campaign to Protect Rural England

With the consultation over, the findings now go to independent consultancy Ipsos Mori to compile a report and submit it to the government.

Ministers will then reveal their preferred option, which will go out to consultation again.

Work is not expected to start for around five years.

Whatever the result of the consultation on the Lower Thames Crossing, the route will almost certainly be tolled.

Peter Fry, a senior consultant at CJ Associates, which is working on the project for Highways England, said: “Government policy is that estuarial crossings are tolled.

“This crossing has to be tolled because if it isn’t, all the traffic will come from Dartford and use this one and it will be full from day one.

“Both have to have a toll or both have to be toll-free to get the benefits and government policy is that estuarial crossings are tolled.”

Highways England spokesperson Sarah Silk added: “Our operating assumption is that the charge would be set at around the same level as the Dartford Crossing.”