Diablo Road trail nears creek‑area finish; soldier‑pile walls complete

Transportation Manager Soren Fajot updated the commission on construction progress for the Diablo Road multi‑use trail on Sept. 28, describing heavy structural work in the creek area, permitting constraints and remaining finishing tasks.

Fajot said the project is about 0.9 miles long and that three soldier‑pile retaining walls accounted for the most complex work, representing "about 45% of the total project cost." He gave counts and measurements used for scheduling and contractor sequencing: the walls total roughly 414 linear feet, with about 72 vertical beams placed across the project; Wall 3 had 25 beams and a 144‑foot length, Wall 2 had 35 piles and just over 200 linear feet, and Wall 1 was the shortest at 12 piles and about 70 feet.

Staff described unexpected technical challenges encountered during construction—unanticipated shallow PG&E underground lines, AT&T guy wires, buried survey discrepancies and a buried tree stump discovered in the creek that required an emergency CDFW notification. The creek‑area work was governed by a California Department of Fish and Wildlife stream‑bed alteration agreement with two key permit dates: Sept. 15 (deadline for wet‑concrete work) and Oct. 15 (final creek‑area work). Fajot said, "All that work got completed prior to that date," referring to the Sept. 15 requirement.

Remaining tasks include slope stabilization and restoration in the creek, placement of outfalls and drainage connections, backfill and rough grading, underground drainage systems uphill, bioretention work, guardrail and handrail installation, and a new HAWK signal at Fairview Avenue scheduled toward the end of the project. Staff said once drainage and rough grading are completed the contractor will move to structural trail paving (8‑foot paved section, aggregate base with 3 inches of paving).