The eucalyptus must go.

That was the conclusion drawn by a professional arborist hired by the county to determine if there is a viable way to mitigate the risks of the 219 eucalyptus trees on the U.S. Highway 101 corridor north of the former California Redwood Company mill while making way for the last leg of the Humboldt Bay Trail, a 4-mile stretch that would connect the trail to already constructed segments south of Arcata and north from Eureka.

Citing liability concerns related to falling trees and tree limbs, county staff recommended back in July that the county remove all the trees north of the mill as part of the trail plan. On July 31, the board voted unanimously, with First District Supervisor Rex Bohn absent, to approve an environmental impact report for the trail that included the trees’ removal. But the board also asked county staff to hire a certified arborist, or two, to conduct a risk assessment of the trees to determine if county staff was being overly cautious and if there is a way to keep the trees and build the trail without dramatically increasing maintenance costs or county liability.

In a 17-page letter that will come before the board tomorrow, certified arborist Torrey Young writes that “the trees as a whole are in an advanced state of physiological decline.” They have gone prolonged and heavy trimming, Young writes, and are growing in an inhospitable environment with high concentrations of salts in the soil. Additionally, he writes, there is some documented decay.

“In my opinion, there is no reasonable method for mitigating these risks through pruning, cabling and bracing or the moving of targets,” Young writes. “If allowed to remain, the risk of failures will increase over time. The health of these trees will continue to decline. … I recommend removing the entire stand to grade. The physiological and structural conditions that render these trees a risk will worsen over time and cannot be effectively mitigated except via removal.”

The board is slated to receive Young’s report tomorrow and then to decide whether to seek a second expert opinion. Back in July, the board had directed staff to get risk assessments performed by two certified arborists based on staff’s estimate that they could be done for approximately $10,000 apiece. But county staff apparently underestimated the cost of finding certified arborists and getting them here to perform the assessments, noting in its report that travel costs were “substantial” and “unavoidable.”

The county wound up paying Dryad LLC $12,000 for Young’s report and staff is now seeking the board’s direction on whether it should spend another estimated $12,000 to $15,000 on an additional assessment. The cost, county staff writes, is potentially reimbursable by the state as part of the engineering phase of the Humboldt Bay Trail project.

See the full agenda for tomorrow’s meeting here.