FLOOD09313

• County: Denver
• Community: Denver
• Stream Name: Marston Lake North
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 10/1/1979
• Prepared For: Denver
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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13

C. Buried Riprap 247,200
D. Kenyon Avenue Crossing 9,300
E. Grass-lined Channel 225,700
F. Paved Path Crossing 2,200
Total $ 967,600

VII. PHASE B MAJOR DRAINAGEWAY PLANNING

An alternate plan of channelization for the Marston Lake North
drainage basin was recommended in the Phase A report on Major
Drainageway planning for Marston Lake North date February, 1979.

Others

The design criteria used for the improvements were described in
Section V. Master Plan drawings have been prepared showing the loca-
tion and extent of channel improvements and are presented at a reduced
scale. Other infonnation on the drawings include sizes and types of
improvements; capacity of trickle channel; slope of channels,
culverts, conduits and bridges; location of other utilities; channel
bank elevations where appropriate; right-of-way required for
acqui sition; typical channel sections with design fl ow rates and
velocities; and 100-year water surface profiles and floodplain limits
for existing and improved channel conditions. The floodway data is
tabul ated in the "Flood Hazard Area Del ineation Report for Marston
Lake North" dated February 1979.

Most of the existing developments in this watershed occur at the reach
upstream of Colorado State Highway 121. This reach is mostly pri-
vately owned, and contains the most urban developed lands, existing and
potential. The proposed drainage and flood control facil Hies
upstream of Colorado State Highway 121 should be constructed when
developments occur to convey the increasing storm runoff due to urba-
nization.

The channel improvement is not the responsibility of the City since
improvement will mostly serve new development. The sedimentation pond
and the Colorado State Highway 121 crossing must also be constructed
during development.

The prOjected total cost of Master Plan Improvement, based on June,
1979, cost, is $3,748,000, which includes costs for engineering,
contingencies, fiscal, legal and administrative expenses. The present
worth of the annualized operation and maintenance costs (50-year, 6~%)
is estimated at $95,700. A summary of total costs is given in
Table 1. A breakdown of these costs is presented with a commentary on
each of the Plan and Profile drawings at the end of this report.

The estimated capital expenditures including engineering, contingen-
cies, fisc-al, legal and administrative expenses are as follows:

A. 84-inch Rep under Colorado State
Highway 121 $ 306,500
B. Sedimentation Pond 120,000
C. Grass-lined Channel 383,500
Total $ 810,000