PROJ00269

• Contract/PO #: FS0016X
• Contractor Name: Lyons, Town of
• Contract Type: Loan
• Water District: 0
• County: Boulder
• Loan Projects - Doc Type: Feasibility Study

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WATER SUPPLY AND DISTRIBUTION SYSTEM

The Town currently meets its water demands by diverting water from the North St. Vrain Creek through
the Lyons Pipeline to a 1.6 Mgpd Water Treatment Plant. The treated water is pumped to a 1,000,000
gallon storage tank and then distributed through the system to meet water demands. Refer to the Town
of Lyons Long Range Water System Plan by Wright Water Engineers, Inc. included herein in Appendix
E for a detailed description of the Town's existing water supply and distribution system.

LAND OWNERSIDP

A developer currently owns the land at the proposed reservoir location in Stone Canyon. The developer
has agreed to grant 35 acres to the Town of Lyons to be used for the construction of a dam and reservoir.

NEED FOR THE PROJECT

The Town is currently able to store only 300 ac-ft of water for municipal use with storage provided in
Button Rock Reservoir. Stored water is released from Button Rock Reservoir when the demands for
municipal water cannot be metby the direct flow rights in North St. Vrain Creek. During dry periods this
storage can be depleted creating a significant shortage of water for the Town. As demands increase due
to growth of the Town, water shortages become more likely. In order to meet the current and future
demands for water, it is necessary for the Town of Lyons to develop means to store additional raw water
for municipal use. The proposed storage reservoir in Stone Canyon would allow the Town of Lyons to
store 300 ac-ft of C-BT water for municipal use. This additional storage capacity would help meet the
demands for the Town of Lyons, would provide needed storage for a drought period, and would allow
direct utilization of its C-BT water rights.

ALTERNATIVES EVALUATED

During our study we considered three Alternatives. Alternative 1 is to not construct the dam and reservoir
and utilize some other means of storage as evaluated in the long range plan included in Appendix E.
Alternative 2 is to construct the dam and reservoir utilizing the land provided by the developer with the
location as shown on Figure 2. Alternative 3 is to construct the dam and reservoir south of the Alternative
2 location, which has some advantages with regard to the planned development of the site. This location
is shown on Figure 3.

The two dam and reservoir alternatives were planned to meet the following criteria. Figure 4 shows the
typical cross section of the dam to meet this criteria.

· Minimum 300 acre-feet storage capacity to meet the Town's needs.

. 20 foot crest width for access to gate operator and staff gauge.

. 3: 1 upstream and downstream slopes for stability.

. 16,500 cfs peak spillway discharge capacity to pass 100% of PMP storm.

~. 36-inch diameter concrete outlet pipe with sluice gate to meet minimum discharge requirements.

. Maximum high water line of 5375 feet USGS to contain the high water within the property and to
allow for development around the reservoir.

Stone Canyon Dam Feasibility

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