FLOOD01607

• County: Gilpin
• Community: Central City
• Stream Name: Eureka and Nevada Gulches
• Title: Master Drainage Study
• Date: 2/12/1988
• Prepared For: Central City
• Prepared By: HydroDynamics
• Floodplain - Doc Type: Floodplain Report/Masterplan

CENTRAL CITY KASTER DRAINAGE STUDY

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embankment can provide sufficient storage capacity to
significantly reduce peak flows.

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An improved inlet on the Opera House flume can significantly
reduce or prevent street flooding for given discharges. The
Opera House flume capacity is over 400 cfs. (see Figures 4.1.2
and 4.1.3). The present inlet configuration, according to CWCB,
allows only 150 cfs to enter before water overtops the headwall.
The improved inlet will properly align flows and hydraulically
smooth the inlet to increase capacity to 250 cfs.

Major drainage facility recommendations for Eureka Gulch are:

1. Dorothy Lee Placer detention pond (Figure 1.1.1)

2. Opera House flume inlet improvements (Figure 4.1.2)

3. Gregory Gulch/Lawrence Street cribbing (Figure 4.1.4)

4. MacFarlane Foundry flume replacement (Figure 4.1.2)

5. Prosser Loop pipe replacements (Figures 4.1.1. and
4.1. 2)

6. Rehabilitate Opera House flume (Figures 4.1.2 and
4.1.3, Miscellaneus Construction in Section 6)

7, Remove trees and debris from Eureka Gulch west of the
Opera House (Miscellaneus Construction in Section 6)

8. Rehabilitate Prosser Loop (Lion's Park) Pond (Figure
4.1.1, Miscellaneus Construction in Section 6)

Each of these are discussed in more detail below.

4..1.2

Local Drainage

All existing local drainage is overland in the residential areas
above downtown. Freeze/thaw damage, rutted roads and erosion of
road base result. T~e problem is especially damaging on southern
aspect slopes which experience larger temperature changes during
winter.

Water conveyed overland during winter thaws collects in shadows
forming ice floes behind buildings resulting in hazards to both
the residents and structures themselves. Summer rains wash road
base from City streets (some of which have slopes greater than 25
percent) into the downtown area.

A remedy for these problems is to collect drainage and convey it
to Gregory Gulch before it causes damage. A second part of the
effort is to re-train City maintenance crews to grade streets to
make the best use of the local drainage system.

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HydroDynamics Incorporated