Kiwis Against Seabed Mining (KASM) chairman Phil McCabe said a record number of people had voiced their opposition to the proposal.
''Between KASM and Greenpeace, we're confident we will reach a record number of at least 17,000 submissions against this destructive proposal,'' Mr McCabe said in a statement.
In Trans Tasman's first, unsuccessful, bid with the EPA for permission to mine the seafloor, there were 4600 submissions against the proposal.
Both Trans Tasman and would-be seafloor phosphate miner Chatham Rock Phosphate have had their respective applications turned down by the EPA since early 2014.
Submissions on the latest application opened in mid-September but the EPA had to twice extend the submission period, which closed on Monday.
Firstly, it was extended in the face of an objection by local iwi Ngati Ruanui, then KASM, Talley's Fisheries and Ngati Ruanui successfully challenged the EPA in the Environment Court over its redaction of hundreds of pages of Trans Tasman's application.
''Our focus now turns to the expert evidence against this proposal, and the hearing itself,'' Mr McCabe said.
If the proposal was allowed to go ahead, it would create a legal precedent for other mining proposals, not only off the North Island's West Coast but also off Waihi Beach, Mr McCabe said.
Other objectors included recreational fisheries organisations and environmental groups including Greenpeace, Forest & Bird, WWF and the Environment and Conservation Organisations, he said.
