C153804 Feasibility Study

• Contract/PO #: C153804
• Contractor Name: Left Hand Ditch Company
• Contract Type: Loan
• Water District: 5
• County: Boulder
• Bill Number: HB 95-1155
• Loan Projects - Doc Type: Feasibility Study

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Table of Contents

Certification. ..........................................................
Acknowledgements ........................................................
Executive Summary ....................................................... 11
Table of Contents ..................... _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Chapter I

Chapter II

Chapter m
A.
B.
C.
D.
E.
F.

Chapter IV
A.
B.
C.
D.

Chapter V
A.
B.
C.

D.

Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

Description of Sponsoring Entity

..........2

Background Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Study Area Description ........................................... 8
Water Demands .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Project Lands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Hydrology and Water Rights ...................................... 10
Water Quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Field Investigations ............................................. 12

Formulation of Alternatives ..................................... 13
Plan A - No Action ............................................. 13
Plan B - Widening the Existing Spillway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Plan C - Constructing a New Spillway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Plan D - Overtopping Protection for the North Dam . . . . . . . . . . . . . . . . . . . . . 20

Evaluation of Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Plan A - No Action ............................................. 25
Plan B - Widening the Existing Spillway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Plan C - Constructing a New Spillway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
C.I General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
C.2 Formed Concrete vs. Roller Compacted Concrete. . . . . . . . . . . . . . . . . 28
C.3 Raising the Dams ..................... . . . . . . . . . . . . . . . . . . . . 30
CA Fuse Plug Spillway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
C.5 Plan C-I, 200 ft RCC Spillway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
C.6 Plan C-2, 140 ft RCC Spillway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
C.7 Plan C-3b, 95 ft RCC Spillway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
C.8 Plan C-4, 65 ft RCC Spillway. . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Plan D - Overtopping Protection for the North Dam . . . . . . . . . . . . . . . . . . . . . 36
D.I Plan D-I, 400 ft RCC Overtopping Section
with Raise of the South Dam ...........................36
D.2 Plan D-2, 400 ft RCC Overtopping Section with Fuse Plug ......... 39

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