FLOOD06791

• County: Hinsdale
• Community: Lake City
• Stream Name: Henson Creek
• Basin: Gunnison
• Title: Henson Creek Flood Control Improvements
• Date: 12/1/1985
• Prepared For: Lake City
• Prepared By: Westwater Engineering
• Floodplain - Doc Type: Project

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PART IV - PRELIMINARY DESIGN

A. Basls for Cas: ES:lmcles.

It is assumed that (1) the flood control berm will be constructed by
crews frOll Hinsdale County and will not be put out to bid (2) riprap for
construction of the flood control berm can be obtained from local sources
without the need for blasting and (3) most of the embankment material will
be rockfi II (rock fragments with some fines). All construction should be
done during the lOtI water period on Henson Creek.

B. Technical Specifications.
1. The General Standard Specifications, Sections 4, 7, 8, 9,
and 10 which are included in Part V, will apply for this
proj ect.
2. Site preparation: all surface debris and unstable material should
be removed fran the foundation of the embankment. Trees and brush
should be cut off to ground level.
3. If the embankment material fits the category of "rockfill
embankment" (see Section 7) it should be graded in place and
canpacted with a crawler tractor. If the embankment material
fits the category of" earth fi 11 embankment" , it should be
canpacted to 90% of optimlJll density as determined by ASTM 0-698.
4. All riprap should be angular granite rock of Class II size and
gradations (see Section 10). A filter under the riprap is not
needed. All riprap should be dumped in place using a backhoe
(it should not be allowed to slide down the embankment from the
back of a truck). (See Standard Drawings.)
5. Topsoil should be placed on the top and back of the embankment
and embankment should be reseeded with a native grass material.
6. Restoration work will be in accordance with Section 9. If any
gravel surfaces are disturbed by construction, they should
reconstructed in accordance with Section 4.

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