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

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EXECUTIVE SUMMARY

This report was prepared to provide Central City with specific
recommendations regarding feasible drainage structures and
reconstruction of existing drainage facilities to reduce
potential flood and sediment damage. Th2 report presents
designs and cost estimates for a program necessary to relieve the
health and safety hazard existing in Central City. The Colorado
Water Conservation Board's 1987 Flood Hazard Identification
Report for Central City provided basic information for this
report.

Central City has experienced flooding, sediment and debris
damage, and loss of life due to severe summer thunderstorm that
have plagued the Colorado Front Range. Much of the potential
flood damage is to historical structures and the commercial area
of downtown Central City.

Central City has planned for, constructed and maintained flood
control facilities for many years. Recommended designs in this
report will be constructed at sites previously obtained and
will upgrade existing structures in addition to new construction.

Existing major and local drainage systems are inadequate.
Proposed improvements wi 11 maximize use of existing structures
and ,build additional structures to increase overall system
efficiency. Additionally, Eureka Gulch peak flood flows will be
reduced to a less damaging level by construction of a minor dam
on City-owned land.

The net result of the major drainage system improvements is a
signif icant reduction in frequency of damaging storms. Through
detention storage and improvement of storm flow conveyance, the
"overtopping" flood (i.e., the damaging storm) that presently is
a two to three-year storm will become a 13 to IS-year storm.

Sedimentation and debris problems are particularly severe on
Nevada Gulch due to mine tailings piles and the Free Parking lot
which is built on mine tailings. Construction to correct these
problems may benefit from inter-agency cooperation with the U.S.
Environmental Protection Agency Superfund Program.

There are many benefits derived this program. Much of Central
City's economy is built upon the tourist trade and interest in
Colordo's mining history. Unlike other mountain towns that
thrive during the winter months, Central City's important season
is during the summer, when the flood risk is greatest.

Therefore, in addition to reducing the risk to lives and historic
structures, Central City's livelihood will be protected, Under
existing conditions, relatively frequent floods cause water and
debris damage to downtown streets, buildings and merchandise
that takes weeks to clean up and'repair. During the clean up,
beside destroyed merchandise, there are lost revenues tha t
provide (through sales tax) much of the City's operating funds.

HydroDynamics Incorporated