Caltrans has been granted permission to remove two piers of the old eastern span of the Bay Bridge using the same implosion technique that safely demolished the span’s largest pier in a matter of seconds last November, the transportation agency said.
The San Francisco Bay Conservation and Development Commission signed off on the implosion technique for Piers E4 and E5 at a meeting on Thursday and the implosions could take place as early as October, Caltrans said.
The BCDC also granted approval for Caltrans to remove 13 additional remaining piers over the next two years, some by implosion and some by mechanical means.
Caltrans said the approvals will allow it to continue the innovative demolition that began with the successful demonstration removal of pier E3 in about six seconds last Nov. 14.
Caltrans said the implosion of Pier E3 proved that the implosion demolition was not only the most cost-effective option but had even less of an environmental impact than had been expected.
It said there were no visible signs of changes in turbidity after the blast and increases in pH levels were less than expected and the water was affected for a shorter period than expected.
Analysis also indicated that a “bubble curtain” of air blown around the pier was effective in protecting fish and birds and wildlife were unharmed, Caltrans said.
The agency said it will remove Piers E4 and E5 during the upcoming window months of October and November, during slack tide to minimize the transfer of energy and debris downstream.
Another factor is that period is when there’s the least impact on fish and mammals because many species such as salmon, herring and nesting birds aren’t around then.
Caltrans said the process for demolishing Piers E4 and E5 will be a bit different from that of Pier E3 in that E4 and E5 will be imploded within two weeks of each other.
The agency said that although the two piers are similar to Pier E3, they aren’t as extensive and will therefore require fewer explosives for each implosion.
The two piers are east of E3.
Caltrans said the controlled charges will happen underwater and are unlikely to be heard or seen by nearby motorists.
The agency said it will also provide a temporary rolling traffic stop strictly for sound to ensure that motorists aren’t distracted.
Caltrans began demolishing the old eastern span in September 2013 after the new eastern span was opened to traffic and is expected to complete the demolition process in 2018.
It will remove seven underwater piers in the fall of 2017 and six underwater piers in the fall of 2018.