New talks over Merthyr Tydfil £400m waste energy plant
A further meeting is to be held to consider late changes to plans for a controversial £400m energy-from-waste generating station near Merthyr Tydfil.
American firm Covanta Energy wants to open the plant which would burn 750,000 tonnes of residual waste every year.
The UK government's Infrastructure Planning Commission (IPC) will decide on the plans.
At a meeting to discuss the process for examining the scheme, commissioners said the amendments needed more talks.
Covanta Energy says the Brig y Cwm plant will generate enough energy to power homes in the Merthyr and Caerphilly areas.
But the IPC meeting heard the company has changed its planning submission, prompting concern and calls for delays from opponents.
The preliminary meeting of the IPC discussed the implication of the changes, particularly changes to the height of the building.
The company said it also no longer intends to cut three metres into the topsoil and remove the material by lorries from the site.
It is the first Welsh case considered by the IPC, an independent body that examines applications for nationally significant projects ranging from railways to power stations.
Residents and 60 individuals and groups with a registered interest in the plan said they were concerned by the late changes.
Tuesday's meeting was meant to allow views to be expressed about the way the application will be examined, and not the merits of the application itself.
Dai Havard, MP for Merthyr Tydfil and Rhymney, questioned whether there should be a delay in the proceedings due to the change in plans.
Members of the United Valleys Action Group also spoke of their frustration that they could not go through their concerns, time for which had been set aside.
The group's barrister Alex Goodman called for another preliminary meeting after the new application is submitted, which may be by next week.
Officials from Merthyr Tydfil and Caerphilly councils voiced their disappointment about Covanta's late changes to the planning application.
Covanta said the changes were made after they identified a means of reducing the amount of spoil that would need to be removed from site during construction.
"We notified the IPC of these changes in accordance with the proper procedure and within the seven day timescale that was required."
The statement said that, overall, there will be a "significant benefit in reducing the amount of construction traffic".
The plant, which aims to employ 81 people permanently, would take the non-recyclable household and business waste mostly by rail.
It would generate about 70MW of electricity, enough to power up to 180,000 homes.
Covanta has already held consultation days in the Merthyr area, and reduced the size of the proposed site, west of Fochriw and next to the Ffos-y-Fran opencast mine site.
The company was also due to take into account concerns over emissions, smell and dust, traffic and disposal of bottom ash to include in its environmental statement.
It also has plans for a similar plant, Rookery South in Bedfordshire, being looked at by the IPC, and others in the planning stage.
At Tuesday's meeting, chair of the IPC commissioners, Jan Bessell, said a second preliminary meeting will be held because of the planning application changes.
She said the IPC now needs to decide if there have been substantial changes and, if so, the entire process may have to be restarted.
However, the Covanta statement said: "It will not in any way change the mechanics of the facility or the technology that will be used there to effectively and safely treat residual waste."