Skookum Creek Bridge Replacement*

The existing bridge crossed a salmon-bearing creek with an in-water work window that closed on September 15. The permit allowed no more than 14 weeks of work below the ordinary high-water mark, and the geotechnical report identified a boulder layer at 60 feet that had stopped two earlier shaft attempts on a neighboring structure.

The corridor also carried school bus routes and log trucks. The owner required a signed detour and no closure longer than 45 minutes during school hours.

We built a 620-foot temporary work trestle in the first three weeks so that shaft rigs, cranes and concrete trucks never entered the channel. Two shaft rigs worked in parallel, one fitted with a rock auger and core barrel for the boulder layer, and crosshole sonic logging was run within 48 hours of every pour so that the engineer could accept shafts without delay.

Girders were set in a single 11-day campaign using a 330-ton crawler crane. We placed the deck in three pours at night with a retarded mix to keep surface temperature inside the specified window, then installed the barrier and approach slabs from a fixed schedule of 45-minute lane closures.

The bridge opened to traffic 47 days ahead of the contract completion date and $412,000 under the original contract value. Every in-water activity finished eight days before the fish window closed, and turbidity monitoring recorded no exceedances.

The project logged 0 lost-time incidents over 186,000 hours. The owner scored the final ride quality at 38 inches per mile on the international roughness index, earning the full smoothness incentive.