The authority has issued a tender for a contractor to build a 170m quay at the north side of Montrose Harbour, including a 30m concrete hard-standing and heavy lift area.
It is a sequel to an £8.5m project that completed last year to construct a deep water berth on the South Quay, which boosted annual tonnage from 1.4 million to 2 million, mainly by quadrupling its business with oil and gas companies to one million tonnes.
The authority believes the new investment will open the door to further expansion. Montrose is already the country's main port for fertilisers for farming and wood pulp for paper-making.
It has started handling onshore wind-turbine cargoes and is considered well-placed to support offshore wind as that industry develops.
It also benefits from the fact that the ports of Aberdeen and Peterhead to the north are too busy to handle extra traffic.
The port authority's last project received a contribution of £3.25m from the Scottish Government, but this time it has applied to European funds for a sizeable unspecified contribution. With a view to completing the upgrade by September 2014, it needs this grant for the project to go ahead.
John Paterson, chief executive of the port authority, said: "The work will improve the access to the North Quay by providing it with a more modern and suitable structure with deeper water. It will make possible the more efficient use of the quay for imports and exports of fertilisers, wood pulp imports and exports of recycling materials.
"They already use the North Quay but are subject to disruption. The upgrade will mean more trade in and out of the port.
"The new owners of the fertiliser blenders, Koch Industries and Origin Fertilisers, recognise the geographical significance of Montrose as yielding an opportunity to increase their throughput."
On offshore wind he added: "We have had discussions with the potential operators of the north end of the Forth Array and inshore farms like Inch Cape.
"The vessels that are currently transporting the turbines are of a size and shape that they can only get into Nigg, Dundee and Leith, but Montrose has a good opportunity to participate in the operations and maintenance side of the industry."
Nigel Don, Nationalist MSP for Angus North and Mearns, said the harbour was the "jewel in the crown of the constituency".
He added: "I am aware of what they are trying to do in the North Quay and it will be really good to see opportunities for the port increase and benefit that part of Angus."
Other important commodities at the port include sawn timber, barley and wheat. It employs 28 people and is owned by a locally controlled trust.