A controversial new gas pipeline that will span the breadth of Wales will attract new business and industry, says the National Grid.
The pipe will link two liquefied natural gas (LNG) terminals at Milford Haven with the national network.
Critics claim the project has been surrounded in secrecy and have questioned the need for it.
But the company said it would be
vital for the energy needs of the UK for many years.
Phase one, which runs 120km (75 miles) from Milford Haven to the Neath Valley, is set to be completed in a year.
Phase two - for which planning permission is yet to be granted by the Department of Trade and Industry - would extend further east to Gloucestershire, cutting a corner of the Brecon Beacons National Park.
The National Grid has come in for criticism from some people living near the pipeline, and last week representatives of communities affected along the length of the route met in Cross Hands.
Some residents in the Swansea Valley village of Trebanos are concerned about blasting needed to run the pipe under an old quarry.
There is opposition in Cilfrew where a pressure station is due to be built, and there are others fighting the route through the Beacons.
The Safe Haven Network, set up to promote their interests, wants the whole project called in by the Welsh Assembly Government.
But the National Grid's senior project manager David Mercer told BBC Wales that although the project was the largest single link the company had built, it was similar to those 30 years ago when the UK's main network was put in place.
Will supply 20% of the UK's gas needs
Crosses 16 roads, 40 rivers and streams and nine railway lines
1,300 people working on it, over half from south Wales
23,000 sections of pipe between 12 - 18m long
Uses 242,000 tonnes of steel
"The high pressure national transmission system in the UK has been in operation in the UK for over 35 years and we have never had a serious incident on our system.
"It's a very safe system built to the highest internationally recognised standards.
"This pipeline is needed to connect the two LNG terminals at Milford Haven with our existing gas network.
"Some of that gas will supply south Wales and some of that gas will go into England.
"What is vital to say is that new gas infrastructure in west Wales will aid development and it will give opportunities for industry and users of gas to create business opportunities.
"A key part of the government's policy is to have diversity of supply and a secure gas supply both for electricity generation and for home and industry is a vital component for that and will continue to be for many years in the future.
"I'm disappointed if people feel we have not communicated as well as we have done.
"We have a large communications team on this project and we worked very hard to inform communities before construction started."