Twin Rivers seismic testing prompts county discussion on road-use agreements, escrow and vibration testing

Supervisors on July 21 discussed ongoing seismic testing by Twin Rivers along state and gravel routes and considered possible amendments to road-use agreements to protect county infrastructure.

Board members said Twin Rivers crews have been conducting seismic testing on Highway 3 and adjacent gravel roads and that the company's insurance approach and damage mitigation raised concerns about recoverability. Supervisors discussed requiring an escrow account from the operator, but said the county had not yet determined an appropriate escrow amount. County staff reported outreach with neighboring counties and drainage engineers about methods to calculate monetary risk and the potential to require operators to pay for third-party engineering reviews.

The board also debated vibration impacts from heavy construction equipment. Staff described plans to conduct comparative tests with sensors, including potentially observing an asphalt roller and the company's vibratory compactor at a Hamilton County site to measure peak particle velocity (PPV) and other ground vibration metrics. Supervisors discussed possible numerical limits (examples mentioned included 0.5 PPV) and noted any amendment to the county's road-use agreement would be brought back to the board.

During the discussion, a supervisor also raised the county's interest in early-stage research on hydrogen transportation and a possible severance-tax credit; staff said they were still researching Department of Revenue guidance and whether counties currently receive such funds.