PROJ00156

• Contract/PO #: C153721
• Contractor Name: Lyons, Town of
• Contract Type: Loan
• Water District: 5
• County: Boulder
• Loan Projects - Doc Type: Feasibility Study

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3. WATER SUPPLY

3.1 Raw Water Supply and Water Rights

The water supply and treatment facilities for the Town of Lyons are principally located in
Sections 1 and 12, Township 3 North, Range 71 West, Boulder County, Colorado, A vicinity
map is shown in Figure 1. At present, the water supply consists of diversions from North St.
Vrain Creek, the northern branch of the St. Vrain River. The Town also owns shares in the
Colorado-Big Thompson (C-BT) Project. These shares are administered by the Northern
Colorado Water Conservancy District and delivered to the Town, via the St, Vrain Canal, during
the growing season each year. This period is generally May 15 to September 15, but can vary
from year to year. The Town utilizes its C-BT shares by exchange in the high demand months
of summer, diverting additional water out of priority at its intake structure and releasing its C-BT
shares to the St. Vrain River to protect senior water rights,

The annexation policy of the Town requires new developers to tender C-BT shares for the water
supply for properties to be served by the Town's water system, Additionally, subdivision
agreements cover shared cost and scope of any system expansions or improvements on a case-by-
case basis, Providing that the appropriate engineering analysis is performed to assure that the
additional water shares can be delivered to the treatment facility, water supply assets should
increase at the same pace as the additional demand,

In brief, the Town has the following water supply assets: a 1.0 cfs direct diversion water right
at the intake pipeline, 523 shares of C-BT, 300 acre-feet (at) of storage in Button Rock Reservoir,
and minor irrigation ditch rights, Refer to Figure 1 for the location of the intake structure, about
one-half mile upstream of the water treatment plant (WTP) , These water supply assets are
managed by the Town water utility personnel on a day-to-day and seasonal basis to meet the
inflow requirements at the WTP intake structure, Natural stream flows (direct diversion) is
available in the spring and early summer. C-BT shares are used in mid and late summer.
Releases from the Button Rock Reservoir storage account are used in winter months, This pattern
can be seen in Table 1.

Taking the WY1993 data from Table 1, use of these water rights is illustrated in Figure 2, Table
1 contains data compiled by the Water Commissioner, Division of Water Resources, State of
Colorado, Flow data is recorded by the state in second-feet (st) which is identical to cubic feet
per second (cfs), Volume data is recorded in second-feet-days, or the equivalent of 1.0 cfs for

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