MIAMI (CBSMiami) – Construction of the new $1 billion Port of Miami tunnel will take a giant leap forward Thursday when boring finally gets underway.

The start of drilling was held up by a Key Biscayne councilman who sent the state a letter erroneously suggesting the village was considering a legal challenge to the project due to environmental concerns. The legal letter, sent to the Florida Department of Environmental Protection, was later withdrawn.

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The Port of Miami tunnel concessionaire received the final environmental permit from state environmental regulators on Monday. Now, officials with the DEP say drilling can begin. 

Crews have been bringing in parts of the tunnel this week in preparation for boring to begin Thursday. 

The boring machine, nicknamed Harriet, is four stories tall and as long as a football field. It will bore through ground under water to create the Port of Miami Tunnel. The boring machine will dig about four feet an hour which should take it about 6 months to re-emerge at the port on Dodge Island. It will then be partly disassembled, turned around and re-assembled before boring out the separate return tunnel to Watson Island. The tunnel will consist of two tubes featuring two lanes each.

Tons of soil is expected to be excavated for the tunnel. More than 400,000 cubic yards of limestone rock and dirt was supposed to be hauled to a former landfill on Virginia Key. However, tunnel concessionaire Miami Access Tunnel (MAT), and the Florida Department of Transportation removed the Virginia Key Landfill site as one of the four authorized disposal sites and replaced it with the Medley Landfill.

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There, the soil will be tested to ensure it is sufficiently free of contaminants to meet standards for use in residential development, city of Miami officials said. If it passes the test, MAT will then reapply to the state for a permit to deposit fill from the dig on Virginia Key, where the city wants to use it to cap an old landfill as a part of an environmental-restoration project.

The tunnel project is also fighting another legal challenge. According to CBS4 News partner The Miami Herald, the operator of Chalk’s Airlines on Watson Island has sued the multinational group, alleging project contractors are routinely trespassing on the seaplane company’s base. The suit, filed Friday in Miami-Dade Circuit Court, alleges MAT is using Chalk’s base, which the company leases from the city of Miami, to move and store machinery and heavy equipment without authorization, interfering with the airline’s operation. Chalk’s, which contends MAT has ignored “multiple” requests to stop trespassing, is seeking a court order barring MAT from entering the seaplane base. MAT officials said they are using the property with city of Miami authorization.

The tunnel project is supposed to ease traffic congestion from cargo trucks heading to the Port of Miami.

Construction is expected to be complete by May of 2014.

When the twin-tube tunnel is completed, the Tunnel Boring Machine will be dismantled and removed from the site.

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