FLOOD10390

• County: Boulder
• Community: Boulder
• Stream Name: Fourmile Canyon
• Basin: South Platte
• Title: Fourmile Canyon Creek - Major Drainageway Planning - Phase A Report - Alternatives Analysis
• Date: 6/1/2000
• Prepared For: UDFCD, Boulder
• Prepared By: Love & Associates
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

Remove & replace the existing pedestrian crossing immediately downstream of Broadway.
Construct pedestrian/maintenance trail along north overbank.

~edestrian Trail
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BOW /Property A, uisition or Easements
. 13S-foot minimum channel top width is required for the proposed channel improvements
. Channel improvements will require the acquisition of an additional 7S-foot minimum right-of-
way or drainage easement. The City of Boulder has identified a 60-foot drainage easement along
the north bank that will be dedicated as a part of the development of the library site.

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Excavate north overbank to increase channel capacity. This will require the remova of
Rosewood Avenue located on the north bank of the creek between Broadway and the Self-Storage
facility.
No modifications to the channel invert or south overbank.
Modify existing drop structures to match the proposed channel geometry.
Revegetate, landscape and mitigate wetland damage of all disturbed areas.

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~edestrian Trail
. No modifications to the pedestrian trail on the south overbank.
. Modify existing pedestrian crossing to match the proposed channel

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geometry.

Miscellaneous
. Coordinate development of the channel improvements with the development of the City of
Boulder Library site on the north bank and redevelopment of the property on the south bank.

Structures
Enlarge the Broadway Box culvert.
Bridge or box culvert at the proposed 9th Street crossing of Fourmile Canyon Creek.

B.oad Crossin
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Channel Work
. Channel design capacity 3,300 cfs. Allow discharges in excess of 3,300 cfs to overtop the south
bank and spill to the south. See typical channel cross section Figure 8-3.
. Excavate south overbank to increase channel capacity.
. No modifications to the channel invert or north overbank.
. Repair failed drop structure and stabilize erosion at east end of this reach.
. Revegetate, landscape and mitigate wetland damage of all disturbed areas.
. Construct a sediment capture and wetland mitigation facility at the east end of this reach.

Reach 5A

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B.OW/Property A,
. lOa-foot minimum channel top width required for the proposed channel improvements
. City of Boulder currently has a drainage right-of-way width of approximate 50 feet.
. Expand the channel into the existing Rosewood Avenue right-of-way located on the north bank of
the creek between Broadway and the Self-Storage units.
ROWand property acquisitions, associated with the roadway

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Miscellaneous
. Modify the Silver Lake Ditch crossing to match proposed channel geometry.
Obtain off site right-of way or easements and construct off site transportation improvements and
related utility relocations necessitated by the removal of Rosewood Ave. Off site roadway
improvements, identified by the City of Boulder, include an extension of 9th Street from Cheery
Street north to 10th Street, a westerly extension of Yarmouth Avenue from Broadway to the new
9th Street extension, relocation of Rosewood and the creation of 11th Street between the relocated
Rosewood Avenue and the Yarmouth Avenue extension.
Coordinate development of the channel improvements with the
Boulder Housing Authority's site located on the south bank.

Construct pedestrian/maintenance trail along the south overbank.
Construct pedestrian/maintenance access crossing structure
Construct a multi-use underpass at Violet Avenue.

~edestrian Trail
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are discussed below

improvements,

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B.oad Crossing Structures
. Remove and replace the Violet Avenue bridge structure and incorporate a multi-use underpass

City of

the

of

development

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uisition

B.OW/Pro
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Reach 5B

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improvements

top width is required for the proposed channel
This reach located on City of Boulder property.

the City of

the development of

with

Coordinate development of the channel improvements
Boulder Violet Park site located on the south bank.

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Miscellaneous
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and continue to allow a

riparian habitat

This mitigation approach will preserve the existing creek
developed and level park use of this site.

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Work
Channel design capacity 3,300 cfs. Allow discharges in excess of 3,300 cfs to overtop
bank and spill to the south. See typical channel cross section Figure 8-3.
Excavate north and south overbanks to increase channel capacity.
No modifications to the channel invert.
Construct 5 grade control structures to stabilize existing head cuts.
Remove debris and concrete slabs from the north bank.
Revegetation, landscaping and wetland mitigation of disturbed areas

the south

Channel
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8-3

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