Symbolic Mare Island exhaust stack faces final hours

March 04--After defining Vallejo's status as a powerful industrial city for 143 years, the city's iconic exhaust stack on Mare Island is finally coming down.

Lennar Mare Island, the entity that controls the Building 121 power house and its adjoining stack, claims the 6.0 magnitude earthquake that shook the North Bay Area in 2014 caused concrete to break off the tip of the 240 reinforced chimney.

In email correspondence sent July 28, 2016 between private engineering company ZFA Structural Engineers and Lennar Mare Island Representative Brain Nagy, ZFA representatives explained a site visit was performed almost two years after the earthquake to assess the potential danger to surrounding buildings and pedestrians.

In ZFA's official review, senior principal engineer Chris Warner noted extensive rusting of the reinforcing bars in a section of spalled concrete on the upper portion of the tower. More troubling to Warner was that water also appeared to have penetrated the layer of reinforcing for "at least the upper 100 feet of the structure."

In the report's conclusion, ZFA engineers warned that the damage was so significant that another "moderate event" may cause another partial collapse of the stack.

"Given the current condition of the concrete and reinforcing, we do not believe that repair of the stack is feasible," Warner wrote in the email.

The issue of the crumbling exhaust stack was then put before Vallejo's Planning Division's Chief Building Official, Lonell Butler, who determine ZFA's findings were sound.

On Aug. 4, 2016, Butler agreed the dilapidated exhaust stack was a threat and issued a "red tag" for the stack under California Building Code 116, the law that deals with structures determined to be a "public nuisance." Butler gave Lennar Mare Island the option of remedying the situation by either demolition or repair.

As it became clear that Lennar Mare Island intended to tear down the structure rather than try to fix it, representatives from Vallejo's Architectural Heritage and Landmarks Commission (AHLC) pleaded for another opinion by a different structural engineer.

At the request of the City of Vallejo, Interwest Consulting Group was tapped to perform a second assessment.

On Feb. 13, 2017, Interwest Consulting Group structural engineer Roger Peterson delivered his report to the City of Vallejo's Planning Division.

In the report, Peterson notes that he was denied access to the site due to the project owner's insurance and liability concerns and that limited time was allotted for observation. Regardless, Peterson continued with "exterior observations from a distance."

Peterson concluded by describing the exhaust stack as unsafe and unable to be repaired due to the corroded reinforcing steel and delaminated concrete.

A third, privately sought evaluation of the exhaust stack was also offered Feb. 13 by registered professional engineer company Wiss, Janney, Elstner Associates.

In Wiss, Janney, Elstner Associates' remotely-conducted review of the exhaust stack situation, the company noted the lack of in-depth investigative information concerning water penetration in the previous two reports.

The company also drew attention to the fact that there was no indication of any conventional earthquake damage, such as diagonal cracking or crushing of concrete no associated with erosion.

The third report also mentions the fact that exhaust stack has remained standing since the 2014 earthquake, which seems to defy ZFA's initial review that deemed the upper section of the structure in need of immediate removal.

A fourth report submitted March 1 by Vallejo Commissioner Lina Villenas to AHLC Secretary Bill Tuikka appeared supported the third report. Detailed models for structural analysis using specifications taken directly from the exhaust stack seem to proved the structure's ability to withstand any further natural disasters.

Regardless, the demolition of the exhaust stack was in full swing on Friday, with cranes having already removed the top third of the tower.

Avid Mare Island enthusiast Cheryl Martin explained she was disappointed with the city's decision to allow the demolition, calling the situation "horrible."

"It's sad," Martin said. "I come here all the time, every day for the last 10 years. My father was stationed here, and I just hate this is happening. I used to tell people just find that tower and that's where I'm at. I wish they could just fill it with cement rather than tear it down."

Representatives of Lennar Mare Island explained Friday that the demolition will continue until the structure is deemed to no longer be a threat to the public.

Matthew Adkins can be reached at 707-553-6833.

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