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Clearwater Hydrology prepared a restoration and channel daylighting design for a 700 ft. reach of Historic Tulucay Creek as part of a habitat mitigation program associated with College expansion activities. CH conducted a topographic survey to collect detailed stream topography both upstream and downstream of the reach to be restored. The survey data was used to supplement the campus-supplied topographic and pond bathymetric survey that was insufficient for restoration channel design. The collected data was used to develop a HEC-RAS model to assess flow depths and expected bed shear stresses in the restoration reach. Bed shear was important to the design of this project due to concern for sedimentation within the restored channel, and thus cattail growth, that could reduce channel capacity and exacerbate flooding of the nearby sports fields. The project corridor was quite confined, flanked by an existing running track and newly constructed tennis courts. Because of these spatial constraints, the restored channel sinuosity was inordinately low, except for the upstream and downstream ends of the reach.
The dredging plan for the sedimentation pond included the design of a spoils containment area to hold the dredge spoils for drying and a design plan for the finished pond bottom topography, along with a component to guide the removal of a highly invasive aquatic plant, the parrot’s feather. An overflow weir was constructed and reinforced with erosion control fabric to allow for winter runoff from the containment area. The containment area was established for spoils dewatering and was designed to hold the spoils through the first winter season before the area was re-graded in 2007. The College plans to utilize the containment area as an open space/park amenity for the campus. CH is providing post-construction monitoring and maintenance support to the College.
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DATE: December 2006
LOCATION: Napa, CA
CLIENT: Napa Valley College, Campus Planning & Construction
GOALS: Restore open channel; provide wildlife corridor; restore open water habitat; provide mitigation credits for implementation of the campus development plan; provide a campus amenity.
Spoils containment area overflow weir and berm protected with erosion control fabric prior to hydroseed sprouting.
Culverted Historic Tulucay Creek
During restoration construction
Due to less confinement this sub-reach was designed to be more sinuous