Project manager says recent slope slide will require major haul-off and drainage work

Mike Heinzen, project manager in the Public Works Department, briefed the board that an additional landslide occurred on the county road project between July 11 and 14, producing a saturated mass of overburden that must be removed before rock can be placed.

"As of Friday afternoon, we did export 505,012 cubic yards of overburden," Heinzen said, noting that figure represents about 37% of the anticipated haul-off from the site as planned in the project design. He also reported that the presentation materials showed 511 cubic yards of rock fill imported (described in the briefing as about 3% of anticipated placement).

Heinzen described on-site mitigations: the plan calls for armoring much of the failed slope, constructing a 5-foot French drain on the upper side of the road to capture subsurface flow where feasible, and sequencing work from the south end toward higher slopes for accessibility. An HDR engineer was on-site to witness the installation of the tow (rock face reconstruction) and verify the approach, he said.

Board members asked whether groundwater or irrigation flow coming from properties above the slope would continue to feed slides after remediation. Heinzen said the county does not yet know the full depth or source channel for that groundwater and that the trench and armoring are intended to reduce, but not guarantee elimination of, future seepage; he said the county will present additional design and cost options once they are developed.

Heinzen said the county has been communicating with the adjacent private property owner and that crews are taking steps to avoid breaching private property boundaries while removing saturated material. The board thanked him for ongoing landowner coordination. No vote or policy action was taken at the meeting.