HomeMy WebLinkAboutSourdough Dam Reservoir Project.pdf Commission Memorandum
REPORT TO: Honorable Mayor and City Commission
FROM: Brian Heaston, Project Engineer
Richard Hixson, City Engineer
Debbie Arkell, Director of Public Services
Chuck Winn, Assistant City Manager
SUBJECT: Sourdough Dam/Reservoir Project
MEETING DATE: May 24, 2010
AGENDA ITEM TYPE: Special Presentation
RECOMMENDATION: No formal action needed from the City Commission; memo and
presentation are primarily informational. Staff welcomes discussion and suggestion regarding
the contents of the presentation.
BACKGROUND: The city is diligent and active in providing a dependable, high-quality source
of water supply to Bozeman, both now, and into the future. A new source of raw water supply is
required to meet the city’s projected water demand, as analyzed and documented in our current
water facility plan (2005 by Allied Engineering). This facility plan indicates -- that within the
20-year planning horizon of the document -- that water demand will outstrip the city’s present
reliable water supply. To address this supply deficiency, the plan recommends a multi-faceted
planning and implementation approach for the city to continuously meet its ongoing demand for
water. Many of the recommended actions in the plan are already complete. For instance, water
conservation and supply-side transmission and treatment plant efficiencies allow our current
water supply to satisfy a broader demand.
An integral component of the future water supply picture is re-utilization of the city’s existing
water storage rights in the Sourdough municipal watershed. The city holds existing water rights
for ~6,600 acre-feet of reservoir water in Sourdough, which can only be realized if a replacement
reservoir is constructed – a reservoir to replace the old Mystic Lake storage which was lost when
Mystic Dam was breached in 1985.
The city completed a Sourdough Dam feasibility study in 1999 that analyzed, at a reconnaissance
level, several new dam/reservoir sites to replace the lost Mystic Lake storage. This feasibility
study ultimately recommended two sites for future in-depth analysis and consideration. Both are
located in the lower reaches of the Sourdough municipal watershed. Reconstructing Mystic Lake
Dam was analyzed in a 1982 study (Report of Engineering Feasibility for Repair and/or
Rehabilitation of Mystic Lake Dam; February 1982) and was again screened in the 1999
feasibility. Geologic instability principally from a large landslide at the Mystic site proved a
fatal flaw and has dropped it from further consideration.
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In June 2009, the City Commission approved a Professional Services Agreement with a project
team lead by Great West Engineering to prepare a development plan for the Sourdough Dam
project. The development plan, in essence and once complete, will be a due diligence
compilation aimed at addressing the myriad issues of planning, permitting, designing, funding,
and constructing a replacement dam/reservoir in Sourdough. This “big picture” approach is
intended to lay the foundation for subsequent staff recommendations and future City
Commission decisions regarding the project.
Public outreach and involvement is a critical and integral component used to prepare the
Sourdough development plan. The community in general, along with niche conservation,
environmental, and recreational user groups – each with their respective concerns -- are inherent
pieces of the project’s overall planning picture. These constituents, along with the city’s political
leadership and applicable federal/state agencies form the project stakeholders and consensus
body.
City staff and its consultant team are poised with moving forward into the public outreach and
involvement portion of the development plan. We felt it important to approach the City
Commission, as an interim step, to inform you of the processes employed to date in preparing the
development plan, as well as steps remaining to complete the plan and how public outreach will
be used to finalize the plan. Details will presented by our team project manager, Mr. Dave Aune,
P.E. of Great West Engineering.
UNRESOLVED ISSUES: There are no unresolved issues with respect to this Special
Presentation. However, once the development plan is finalized and subsequently presented to
the City Commission, a myriad of unresolved issues are presumably envisioned.
ALTERNATIVES: Not applicable to this Special Presentation.
FISCAL EFFECTS: Not applicable to this Special Presentation.
Attachments: None
Report compiled on: May 19, 2010
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