PIERCE CREEK: Construction Starts, Cofferdam In, Culvert Out, Connection Coming

Pierce Creek Culvert 11.02.2011

Wednesday November 2 we broke ground on the Pierce Creek Reconnection Project.  The 48-inch culvert, one that has over the years turned into a fish barrier, will be removed and a new steel bridge installed.  Here’s a report on the first two days of work.

Photo at right shows the clearing and grubbing on the downstream end of the culvert.  For the first time a clear picture of the stream gradient can be fully appreciated.  And even this did not reveal a surprise (more after the jump). Prior to clearing, willow bushes and aspen trees obscured Pierce Creek between the South Fork Boise road and the South Fork Boise River.

Pierce Creek culvert in 2010 - in the brush

The next step after clearing the site was to install a coffer dam, using a 24-inch pipe to divert the full stream around the bridge site so the construction can work in the dry.  In addition, the road remains open with a short detour or shoe-fly connection.

Building the road crossing caused four separate vehicles to be delayed. The longest delay was 14 minutes.  A trench was dug across the road and the 24-inch pipe buried.  Then the road put back in and compacted.


Bypass pipe in foreground and culvert still under the road. Once the stream was blocked the entire flow fits in the 24-inch pipe.

With the road open again the bypass can be built with a cofferdam across the stream.  To do this the crew brought in fill material from the adjacent dry wash along Joy Lane.  That work was completed on the 2nd and the bypass road was open.

On Thursday the 3rd the culvert came out.  It was also photo opportunity and archeology day. When you are digging up a site like this, on National Forest System lands, there is a need to attend to historical and cultural resources.  In addition, the contractor waited until the Forest Service

Chris Jones stands next to the Pierce Creek culvert.

film crew arrived.  They started around 10:30 on the culvert.   It was out in about two hours.  The culvert was came out in one piece.  The Mountain Home Highway District  said that it was not reusable for them and they will take it back to Mt. Home next week or the week after and haul to scrap.

One surprise: under the big culvert was a  little  18″ culvert that they pulled out also.

The rest of the afternoon the contractor dug the sub grade to the sills and cleared out the stream channel in preparation to stream simulation construction

Digging out the channel and placement for the bridge sills.

tomorrow.  We took several bag samples of the sub grade soil for the geotech to examine.  The fisheries biologist with the Forest Service Mtn. Home office will be on site tomorrow to help with the stream grade control placement.

We are extremely pleased with the contractor and his methods.

Tomorrow the geotechnical engineer will inspect the sill sub grade.  If the sub grade passes, and the sills arrive, they will place them Monday.  The bridge is to be delivered Tuesday.  Hank said that it may end up the bridge arriving Monday and the sills Tuesday.  The guard rail is onsite.  It was delivered Tuesday at the Highway District shop.

We will provide additional pictures and an update next week.

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One Response to PIERCE CREEK: Construction Starts, Cofferdam In, Culvert Out, Connection Coming

  1. Mike Toalson says:

    Way to go TTTU, Pam E, Christ J, Mtn Home HD and USFS for making this happen!!!!