The replacement is to prevent the bridge which lies beneath the Accra Motorway from collapsing, following the theft of about 1,400 of the 2,000 bolts holding the bridge to the motorway concrete.
The stealing incident was discovered recently following an assessment on the bridge which showed signs of imminent danger.
The assessment found the missing bolts to have also compromised the structural integrity of the bridge, making it susceptible to collapse if not repaired immediately.
The tunnel was closed to traffic last Saturday to allow for the replacement of the bolts.
The Principal Engineer at the Bridge Division of GHA, Aaron Nana Amponsah, told the Daily Graphic yesterday at the tunnel that the missing bolts were essential for holding the bridge together and pointed out that the collapse of the bridge could divide the motorway into two, thereby cutting Accra from Tema.
The tunnel has recently experienced severe vibration due to the heavy axle loads on the motorway.
Officials say the vibration had further weakened the structure of the tunnel.
Similarly, some blocked watercourses have caused floodwaters to form a pool around the bridge, also affecting its basin.
To avoid future theft of the bolts, Mr Amponsah said the new ones were being welded to the corrugated metals, so as to make them firm and hence difficult to remove.
“We have also done concrete works around the bridge basin to prevent water from pooling there; the watercourses have been diverted into a nearby storm drain,” Mr Amponsah said.
A Deputy Minister of Roads and Highways, Stephen Jalulah, who inspected the tunnel last Wednesday prior to the commencement of work, lamented the damage caused to the corrugated metal by the alleged thieves.
Mr Amponsah gave an assurance that the work would be completed by midnight of today to allow for the tunnel to be opened to traffic.