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 MASTER DRAINAGE STUDY

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meets the face of the improved inlet. Depending on survey for
final design, there may be an opportunity to install a drop and
tapered inlet which may provide additional hydraulic benefits.

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4.4

Other Eureka Gulch Locations

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4.4.1

Gregory Gulch/Lawrence Street Cribbing

Existing cribbing supporting channel banks east of downtown is
failing (Figure 4.1.4). Flood flows will further damage the
cribbing resulting in damage to surrounding property and Lawrence
Street. Standard Colorado Department of Highways steel cribbing
is recommended at this location.

4.4.2

MacFarlane Foundry Flume

The capacity of the existing flume underneath the MacFarlane
Foundry (Figure 4.1.2) is insignificant compared to flood
discharges on Eureka Gulch. Street flows at MacFarlane Foundry
resul t in damage to property as water returns to the channel.
Capacity of the Opera House flume improved inlet was used as
design capacity of the culvert under MacFarlane Foundry.

The existing flume may be classified as a historical structure.
It bccupies the "better" hydraulic alignment for a drainage
structure beneath the foundry. The new culvert can be installed
parallel to the existing flume to preserve it. The new culvert
will be either jacked under the foundry or the foundry will be
supported and a culvert placed underneath.

4.4.3

Prosser Loop pipes

Both the upper and lower Prosser Loops crossings (Figures 4.1.1
and 4.1.2) have less than 10-year flood capacity. When
overtopping occurs, local flooding and debris and sediment
deposition occurs. Increasing pipe size and improving inlet
conditions will decrease the frequency of these problems.

4,.4.4

Rehabilitate Opera House Flume

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The Opera House flume (Figures 4.1.2 and 4.1.3) consists of a
series of metal pipes, masonry tunnels and concrete pipe. It is
also has historical significance being primarily constructed in
the 1870's. Increasing the capacity of the flume inlet will
cause additional stress to the flume lining. Masonry tuck
pointing, reinforcing joints and installing flash boards at
potential overflow locations will improve'the hydraulic capacity
as well as the historical integrity of the flume.

4.4.5

Tree and Debris Removal

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Eureka Gulch channel upstrea~'of
overgrown with phreatophytic growth.
channel reduce channel capacity and
debris clogging of flume and culvert

the Opera House flume is
Willows and aspen in the
raise the potential for
inlets. Selective tree

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HydroDynamics Incorporated