Ahtna Environmental, Inc. (Ahtna) was challenged during renovations to a fish passage located underneath the Yakutat Highway, Alaska. Rain events, maintaining open fish passage, controlling traffic flow, and avoiding impact to fish in the creek were the most complicating factors.
Rainfall caused rapid surges in the creek during construction work, dismantling fish fences and pumps and affecting excavation areas. To maintain traffic flow in at least one highway lane, Ahtna had to build a bypass road and place flagger to ensure traffic safety through the work zone.
The Ahtna team diverted the creek with two 6-inch pumps and left one lane open to traffic. By the time we excavated the roadway to install the new culvert, we needed to build a bypass road offset approximately 40 feet from existing road embankment.
Typical of mountainous streams, the creek flows vary greatly depending on rainfall. Generally, the flows were low but during heavy rain events, the creek would turn into a river. On most projects, streambed material is manufactured per specification. Ahtna was able to salvage streambed material instead of importing the stream substrate. This saved the project both time and money.
The team worked 12-hour days to stay within fast-track schedule and completed the project three weeks ahead of schedule.