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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CENTRAL CITY MASTER DRAINAGE STUDY

6

SECTION 2. DRAINAGE HISTORY

Central City is like several mining towns throughout Colorado
that were built in a mining valley with little attention paid to
drainage. When drainage structures were constructed, they were
typically improperly designed for the hydrologic conditions,
Good fortune (in that major damage has not recently occurred) and
application of modern engineering techniques has provided Central
CIty an opportunity to meld the existing drainage structures into
a much more efficient drainage system. This system would benefit
all the residents of Central City and provide a much higher level
of protection for life, commerce (primarily the tourism industry)
and valuable historical structures.

Drainage problems are compounded with the mine tail ings strewn
throughout the valleys above downtown which erode during intense
rainstorms. Mine tailings dislodged by raindrops are carried to
the stream where they eventually flow through Central City. As
a consequence, there is significant flood and debris danger to
several historical structures, including the Opera House, the
Teller House, City Hall, the Masonic Lodge, and many of the
,stores and buildings in the remainder of downtown.

Central City has a history of floods and drainage destruction.
CWCB (1987) cites five storms dating back to 1863 that caused
various levels of damage and loss of life. That list is repeated
below (Table 2.1). Central City has dealt with these drainage
problems throughout the years and has taken several steps to
protect the city from water damage. These steps include
construction of culverts, bridges and flumes to pass water
through town and beneath the existing buildings. The purpose of
this report is to study the existing structures and determine how
they can be combined into a properly working drainage system.

In recent years, Central City has concentrated on rehabilitating
nheir water system. This effort started in 1973 when the water
distribution system froze. Since that time, pipes, improvements
to raw water storage and treatment have been the priority.
Through 1987 with the reconstruction of the drain system on the
Hole-in-the-Ground Reservoir as required by the State Engineer's
Office, the water system has received most of the attention and
construction money.

However, the City's priorities have now returned to drainage to
continue the effort that started in 1975. In 1975, a series of
severe storms over Spring Gulch caused flooding and sediment
damage to the downtown area (see Appendix A). Recent efforts to
enhance the drainage system include obtaining the Dorothy Lee
placer site from the Bureau of Land Management where a park was
built along with a temporary embankment to impound water for
recreational purposes. Lion's, Park in the Prosser Loop was
constructed with a pond which provided debris protection in 1984
when the Boodle Mill Dam failed (filling the pond with debris and
sediment). In 1985, Central City applied for a block grant which
was turned down due to the lack of a flood hazard study. In

HydrODynamics Incorporated