[brcs-announce] BB Dam Update from Steve Largent

[Norman R. Fred]

Sorry - I can't forward photos but Steve said he will TRY to get some new photos on the GTCD BLOG site soon. 

I can tell you, however, that the site looks amazing and there is no indication whatsoever that there was ever anything there remotely resembling a dam or anything else man made.

Other then the very unfortunate accident in October, the project is a huge success.

Now we wait for the river to clear up so we can get the trash out of it.


Norm


Thursday - December 20, 2012    First off sorry for the delay between updates.  
 
Temporary Dewatering Structure - Since my last update a great deal of work has been completed 
including the reconnection of the river to its historic channel where 
the powerhouse was located.  Once that was done a team of investigators 
were able to inspect the temporary dewatering structure (TDS) to 
determine the cause of the breach.   After inspectors gathered their 
information Molon crews began pulling sheet pile.  As you can see from 
the attached pictures all the sheets have been pulled and the north bank is ready for shaping and grading.   
Temporary Weir - After crews finished dredging the fine organic material (silt) that 
had accumulated in the relic river channel behind the dam a temporary 
weir (approx. 4-foot high) that helped retain some of the silt was 
removed.  The need to remove this organic material was expected from the beginning of the project.  The silt is much lighter than the heavier 
sand and gravel that settled out sooner, upstream in the sand delta 
area.  The silt stays in suspension longer and was the source of the 
high turbidity (cloudiness) of the water while being actively dredged.  
Turbidity – According to Andy Selle from Inter-Fluve, most of the turbidity now is being 
caused by passive cutting into this organic material.  We will most 
likely see this turbidity continue at various levels for another month 
or two.  Once this turbidity subsides to the point where we can see the 
bottom additional elements of the assessment on the extent of the impact of the breach downstream of Brown Bridge will continue.   
Assessment - The Grand Traverse Band and other project partners including the AdamsChapter of Trout Unlimited volunteers, started to survey the river bottom 
(longitudinal profile) beginning at Brown Bridge.  GTB had conducted a 
similar profile last summer.  The two profiles will help assess the 
impact of the breach.  Other assessment work that will begin once the 
river clears includes a fisheries population assessment below the dam at Brown Bridge Road, a habitat survey sponsored by the Adams Chapter, an 
erosion survey, and replication of an aquatic insect survey by the Au 
Sable Institute. Cross-section, velocity, and turbidity data continues 
to be collected on an ongoing basis.  Additional assessments will occur 
as necessary. 
New River Channel – Over 13,500 lineal feet of new river channel has been created with the 
removal of Brown Bridge dam.  Nearly another mile of river upstream of 
the former impoundment is flowing more swiftly and clearing sand that 
had accumulated on the river bottom over the past several decades.  
 Molon crews lead by Inter-Fluve and GTB staff have completed much of 
the shaping of the new river channel and floodplain in the upper end of 
project area.  A beautiful gravel bed is emerging as the sand flushes 
down to the sand traps located closer to the former dam where it’s 
mechanically removed.    
Public Access – Public access continues to be limited during construction.  Last week the 
Brown Bridge Advisory Committee approved keeping the once temporary 
access road at the base of the steep north bank to serve as a permanent 
recreational trail.  Final shaping and stabilization of the access road 
and other steep slopes will occur as weather allows.  As people visit 
the area they are asked to stay off the newly exposed bottomlands for 
several reasons including to allow the native vegetation a chance to 
grow and for their own safety.  Much of the bottomlands remain extremely soft.  Individuals and pets may literally become stuck in the mud.   
 
This is it for now….and, as always, please feel free to contact me anytime if you have questions.
 
All of us here at the Grand Traverse Conservation District wish each and 
every one of you a safe and fun-filled holiday season spent with family 
and friends.     S.
  
 
Steve Largent
Boardman River Program Coordinator
Grand Traverse Conservation District
1450 Cass Rd., Traverse City, MI 49685
231.883.9960
231.941.0960 Ext - 16
www.natureiscalling.org
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