The first “heavy construction” contract for the $16 billion Gateway rail tunnel under the Hudson River between New York and New Jersey was approved Friday by the Gateway Development Commission.

The Hudson River Ground Stabilization Project, was awarded to Weeks Marine, Inc. of Cranford, for $100 million for the first phase. The company had the highest qualified proposal out of three and was selected by an evaluation panel.

“The construction is the start of our first heavy construction in water,” said Kris Kolluri, the commission’s CEO. “Our commitment is to make sure the project enters the point of no return and that is where we are today.”

The project will build the infrastructure and stabilizes 1,200 feet of shallow riverbed on the Manhattan side to allow the massive tunnel boring machine to start excavating the new tunnel and protect the riverbed. The entire project has a $284 million price tag and awards of contracts to do phase 2 of the work is expected in late summer or early fall, officials said.

Phase one will be performed between March and September and includes surveying, design, and construction of the test cofferdam. Phase two includes the design and construction of remaining design and construction work.

“The year is starting off the same way last year ended, with GDC hitting our milestones to make sure the most urgent infrastructure project in the nation is built,” Kolluri said. “Progress on the Hudson Tunnel Project is an ongoing testament to American infrastructure at its best.”

The project addresses conditions where the riverbed off the Manhattan shoreline is made up of silt that is too soft to support a tunnel.

Work includes injecting grout into the silt, and using columns of soil mixed with cement and water to stabilize the ground above the future tunnel. Temporary sheet pile cofferdams will enclose the work area. Work will begin in the section of the river closest to Manhattan and move westward toward the Hudson River’s navigation channel, officials said.

Silt affected the original Hudson River tunnels, which sit in 20 feet of silt under the river bottom. Engineers discovered after they were built that the tunnels moved with the high and low tides, prompting Pennsylvania Railroad officials to increase the weight of steel casings that made up the tunnels. But the added weight didn’t help the tunnels to settle.

Gauges were attached in 1907 and measurements showed the tunnels movement corresponded to high and low tides. Engineers considered chaining the tunnel to bed rock, but rejected it over concerns the tunnel would crack, according to a PBS documentary. Gateway’s tunnel will be built deeper in the river.

Officials also said the federal government’s share of the cost of project will be 73% while New Jersey and New York’s share of the cost has been reduced to roughly 27%. New Jersey’s share will be $308 million and New York’s will be $1.335 billion, according to the final financial plan the commission filed with the Federal Transit administration last month.

The difference between the two state reflects credit for New Jersey’s funding of the new Portal Bridge North that carries the Northeast Corridor line over Hackensack River in Kearny, Kolluri said.

Official anticipate the Federal Transit Administration could make a decision on a $6 billion full funding grant agreement for the tunnel in June.