A submission from the Concerned Rangitikei Ratepayers group said the damage to roads from the increase in heavy traffic would be a cost on ratepayers.
The group also held concern about the environmental impact on surrounding businesses.
The Palmerston North City Council supported the consent provided the target of a 75 per cent reduction of waste to the landfill was achieved.
KiwiRail supported the application so long as work was done to improve the level crossings for heavy traffic going to and from the dump.
It acknowledged some of that work was already being done.
Midwest Disposals, the landfill operator, has sought five consents from Horizons Regional Council and one from the Rangitikei District Council to extend its life and size. Submissions closed in June. The landfill is on Wanganui Rd, about 7km west of Marton.
Prehearings are held to clarify issues arising from an application and are only open to submitters and the applicant. All parties involved are invited to talk through the application and effects of the proposed activity.
There are no further prehearings planned at this stage. RDC has appointed independent commissioners to assess its side of the resource consent, while the regional council is co-ordinating the process.
Midwest Disposals is a joint venture between Enviro Waste Services and TPI Waste Management that was set up to buy the Bonny Glen landfill, which was established in 1995.