C150271 Feasibility Study

• Contract/PO #: C150271
• Contractor Name: WRCC, Inc.
• Contract Type: Loan
• Water District: 0
• County: Larimer
• Loan Projects - Doc Type: Feasibility Study

' .. APPENDI% B
STATE OF COLORADO
WATER DIVISION ONE
' OFFICE OF THE STATE ENGINEER
Division of Water Resources oF~co~
;yam„
,
Department of Natural R o
~
esources '
' 810 9'" Street, Suite 200 **
'!8~6'-
Greeley, Colorado 80631
Phone [phone]
Fax [phone] sill Owens
September 28

www. wa to r. s to te. co. u s ,
Governor

Windsor Reservoir & Canal Company
P.O. Box 206
Eaton, CO 80615
Attn: Barry Anderson, President
Dear Barry:

When replying, please refer to:
`v'~'I'iVI)SOR DAM
W. DIV. 1, DAMID: 030335
Russell George
Executive Director
Hal D. Simpson, P.E.
State Engineer
James R. Hall
Division Engineer
On September 23, 2004, you, Bill Johnston, John Andrew, and I had a meeting at the Division 1
office to discuss the Windsor Dam and the low areas along the crest. In re-thinking our discussion and
summarizing the meeting, I propose that there are 3 main alternatives or courses of action available to
Windsor Reservoir and Canak Company to address the issues.
Course of Action # 1 is to bring the dam to the standard that was thought to exist when the
construction, under Plans C-1295A, was completed. This entails filling in the low areas that were
discovered during the 1997 survey. Filling the low areas can be done as maintenance, but under an
engineer's supervision to insure suitable material, proper construction technique, and required compaction
standards. This course of action does not require a new hydrologic study. I believe it corrects some
construction deficiencies that were not caught in the fmal inspection of the construction in approximately
1976. This will allow the present approval of the spillway, based on the grandfather clause, to remain as
long as the SEO does not conduct a hydrology study in the future that unveils some problem with the
hydrology.
Plans C-1295A indicate the maximum flood stage would be GH 40.35 feet. I have not redone the
hydrology to verify this number. It seems believable, and it was approved under those plans. The plans also
indicate a minimum crest height of GH 40.5 feet to safely route the flood. Considering time when the plans
were approved, I also expect that an additional 1.0 feet of residual freeboard was required. So, I would
expect the required crest height would be GH 41.35 feet. Also, the plans at that time indicate the spillway
was at GH 37.15 feet. However, the 1997 survey indicates the spillway is at GH 37.3 ft. So, the maximum
stage should be adjusted upward approximately 0.15 feet. This means the expected high flood stage is to
approximately GH 40.5 feet. So, the minimum crest of the dam should be GH 41.5 feet. Most of the main
dam exceeds this elevation. Some areas. on the main dam need only a few tenths of a foot of fill. However,
the north dike appears to need 1 to 2 feet of fill to come up to GH 41.5 feet.
Course of Action #2 is to conduct a new hydrologic study using current precipitation values and
hydrologic methods. We did not discuss this action in during our meeting. The purpose of this action would
be to see if the dam safely passes the present design storm without any construction. As-built plans showing
the current condition may be required, since the dam existing dam varies from Plans C-1295A.