Bob Ortblad says the IBR fraudulently disqualified an immersed tunnel alternative that would require no drilled shafts and could save hundreds of millions of dollars
Editor’s note: Opinions expressed in this letter to the editor are those of the author alone and may not reflect the editorial position of ClarkCountyToday.com
A comparison of the design and contract costs for the SR 520 Portage Bay Bridge reveals that the estimated cost for the current I-5 Bridge design in the Interstate Bridge Replacement Program (IBR), which ranges from $1 billion to $1.5 billion, should be increased by approximately 50%.
The SR 520 Portage Bay Bridge and Lid project was bid in November 2023 at $1.375 billion, which is 70% above the engineers’ estimate. Skanska, the design-build contractor, attributes about 80% of this cost — approximately $1.1 billion — to the new bridge itself. Notably, the Portage Bay Bridge is nearly the same length as the proposed I-5 Bridge design and is supported by identical 10-foot-diameter drilled shafts. Furthermore, this bridge is being constructed in a shallow, weather-protected cove that is only 10 feet deep.
In contrast, the design for the I-5 Bridge is larger and situated in a more challenging location. The I-5 Bridge is approximately twice as wide, featuring bridge spans of 500 feet that are 200 feet longer and nearly four times heavier than those of the Portage Bay Bridge. Its piers must be 80 feet higher, and its 250-foot drilled shafts are 100 feet longer. Additionally, these shafts are likely to encounter cobbles and boulders in the Columbia River’s riverbed, which is deeper and affected by tides, currents, and strong winds.
WSDOT bid documents for the Portage Bay Bridge initially indicated 106 drilled shafts. However, Skanska, the design-build contractor, increased this number to 130. In contrast, the current design for the I-5 Bridge includes only 96 drilled shafts, despite being twice as large and heavy. This discrepancy raises a critical question that WSDOT and the I-5 Bridge team need to address: why does the I-5 Bridge design have significantly fewer drilled shafts compared to the Portage Bay Bridge?
The IBR fraudulently disqualified an immersed tunnel alternative that would require no drilled shafts and could save hundreds of millions of dollars.
Bob Ortblad MSCE, MBA
Seattle
Also read:
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