AB Lime Landfill Action Group members were devastated consent had been granted, chairwoman Katie Allan said.
"After some pushing, our concerns were listened to, but it seems it had no effect on the outcome whatsoever."
AB Lime will be allowed to operate without any limit on the amount of waste it can take for the next 25 years.
Independent commissioner Allan Cubitt released his decision to grant resource consents on Friday, after a hearing in May.
Submitters have been given 15 days to appeal.
Ms Allan, of nearby Dipton, said the timeframe was unrealistic.
"After all, the commissioner granted himself many more weeks before making his decision."
AB Lime applied for six new consents and to vary a consent for its site at Kings Bend, about 4km east of Winton. There has been a landfill at the site for more than 15 years, as well as a well-established limestone quarry.
Opponents of the landfill proposal promoted a petition, objecting to a plan to make it the premier dump in the lower South Island.
Among their concerns was the potential for air pollution and ground contamination.
Reasons given for Mr Cubitt’s decision included that removing a waste limit for an existing landfill was considered efficient land use and preferable to establishing a new landfill at an alternative location.
The proposal would use landfill gas for energy conversion to power the lime kilns, creating a positive overall effect on air quality.
In January, under a limited notification process, 20 nearby properties were notified about the consent application, as were two others due to potential cultural effects.
Ms Allan said the application should have been subject to a rigorous public notification process.
Advice sought by Environment Southland, which was to refuse the application, had been dismissed, she said.
The landfill’s footprint, overall capacity, final finished profile and overall physical area will not change.
However, when opponents organised a petition against the development, they drew attention to increased truck movements needed to get the rubbish to the mega-tip.
