FLOOD08407

• County: Jefferson
• County: Adams
• Community: Arvada, Westminster
• Stream Name: Little Dry Creek
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 4/1/1979
• Prepared For: Jefferson County / Adams County
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

transition to a 33-foot wide by 6.4-foot high bridge opening at Winona Court, after which

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COMMENTARY - SHEET 13

A concrete-lined channel is proposed for use in conveying the 100-year discharge

event, the continued enforcement of floodplain regulations and an ongoing program of

between West 76th and 75th Avenues. The use of this type of channel will limit the right-

floodplain management will be necessary after the proposed improvements are built to

of-way necessary for improvements to the existing 50 foot wide easement, avoiding the

compensate for larger floods.

costly purchase and/or relocation of structures adjacent to the easement which would be

required by a grass-lined channel.
Improvements to the creek from West 75th to Wolff Street extended are to be

constructed as a condition of the development of the adjacent open area. These

improvements consist principally of a transition section and a 100-year grass-lined channel

paralleled by >m access maintenance road.

Continuing downstream from the grass-lined channel, below station 132 + 00,

TOTAL IMPROVEMENT COSTS - SHEET 13

improvements are to be designed to accommodate the 10-year flood discharge. The

Item
Channel Improvements
Street Improvements
Utility Relocation

Cost
$ 758,800

$ 206,000
$ 42,500

channel section at this point is to have a concrete-walled right bank while the left bank is

to be contoured to a 4 to 1 side slope into the existing park. The channel section is to

the channel is to transition to a concreted-walled section with a natural grass base.

SUB-TOTAL
Contingencies (25% of Sub-Total)

$ 1,007,300
$ 251,800

Two drop structures are to be constructed, one near Wolff Street and the second

allowing the enlarged bridge openings downstream to be constructed without significantly

TOTAL CONSTRUCTION COSTS
Right-of-Way Acquisition
Annual Operation and Maintenance Costs
Present Worth Operation and Maintenance Costs

$ 1,259,100
$ 115,500
$ (7810)

$ 113,100

below 75th Avenue, to reduce channel slopes and to keep flow velocities within

permissible limits. Additional drops at transitions would serve to lower the channel base,

al tering street grades.
The existing floodplain should be regulated and property owners who would be
adversely affected by the 100-year flood should be encouraged to acquire flood insurance.
Residents in the vicinity of the 100-year floodplain should be notified annually of the

TOTAL IMPROVEMENT COSTS

$ 1,487,700

potential flood hazards. Since a portion of the improvements are designed for the 10-year