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Union Reservoir Enlargement

Aerial view of Union Reservoir

 

Alternatives Analysis & Feasibility Study

Prepared by:

Tetra Tech RMC

1900 S. Sunset Street

Suite 1-F

Longmont, CO 80501

March, 2007

Due to the large size of this file, it has been divided into several pdf files.

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Table of Contents

1.0 INTRODUCTION (pdf file 486 Kb)

Figure 1.1 Union Reservoir Vicinity Map (pdf file 2113 Kb)

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2.0 SITE DESCRIPTION (pdf file 36 Kb)

2.1 Topographic Mapping and Surveying

2.2 Reservoir Capacity Information

Table 2.1 - Elevation Capacity Data

Figure 2.1 - Elevation Capacity Curves

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3.0 GEOTECHNICAL INVESTIGATION (pdf file 57 Kb)

3.1 Regional Geology

3.2 Geotechnical Field Investigations

3.3 Geotechnical Laboratory Testing

3.4 Site Subsurface Conditions

3.4.1 Eolian Soils

3.4.2 Alluvial Sand and Gravel

3.4.3 Bedrock

3.4.4 Groundwater

Tables 3.1-3.4 Lab Test Results (pdf file 738 Kb)

Figure 3.1 Boring Location Map (pdf file 183 Kb)

Figures 3.2-3.5 Exploratory Borings - South & North Side (pdf file 385 Kb)

Figures 3.6-3.7 Exploratory Borings - East & West Side (pdf file 343 Kb)

Figures 3.11 Summary Logs of Exploratory Borings (pdf file 134 Kb)

Figures 3.12-3.14 Triaxial Stress Path; Geologic Sections (pdf file 508 Kb)

Figures 3.15-3.17 Plasticity; Investigations (pdf file 464 Kb)

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4.0 HYDROLOGY (pdf file 679 Kb)Boats on Union Reservoir

4.1 Dam Hazard Classification

4.2 Precipitation

4.3 Tributary Basin Description

4.4 Unit Hydrograph Development

4.5 Rainfall Losses

4.6 Hydrologic Modeling

Table 4.1 General Storm Depth Duration Values

Table 4.2 Local Storm Depth Duration

Table 4.3 Sub-Basin Physical Parameters

Table 4.4 Sub-Basin Composite Infiltration Rates

Figure 4.1 Tributary Sub-Basins

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5.0 ALTERNATIVE ANALYSIS (pdf file 209 Kb)

5.1 Reservoir Englargements

5.2 Dam Type

5.3 Dam Section

5.3.1 Borrow

5.3.2 Typical Section

5.3.3 Stability Analysis

5.3.4 Seepage Analysis

5.4 Outlet Works

5.5 Union Reservoir Inlet Modifications

5.6 Spillway Design

5.7 Storm Drain Line

5.8 Five-Foot Enlargement Alternative

5.9 Thirteen-Foot Enlargement Alternative

5.10 Nineteen-Foot Enlargement Alternative

5.11 Reservoir Deepening and Filling of Properties West of the Reservoir

5.12 Cost Estimates

Tables 5.1-5.7 Cost Estimates

Figures 5.1-5.4 Borrow Areas; Dam Sections; Slope Stability; Seepage Analysis (pdf file 954 Kb)

Figure 5.5 - 5' Raise Baseline Option (pdf file 1039 Kb)

Figure 5.6 - 5' Raise Shoreline Option (pdf file 1049 Kb)

Figure 5.7 - 13' Raise Baseline Option (pdf file 1106 Kb)

Figure 5.8 - 13' Raise Shoreline Option (pdf file 1179 Kb)

Figure 5.9 - 19' Raise Baseline Option (pdf file 1109 Kb)

Figure 5.10 - 19' Raise Shoreline Option (pdf file 1136 Kb)

Figures 5.11-5.15 - Feasiblity Studies (pdf file 25 Kb)

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6.0 NATURAL RESOURCE REGULATORY COMPLIANCE (pdf file 959 Kb)

6.1 Objectives

6.2 Methods

6.3 Findings

6.3.1 Wetlands

6.3.2 Wildlife

6.3.3 Threatened and Endangered Species

6.4 Discussion and Recommendations

6.4.1 Section 404 of the Clean Water Act

6.4.2 Endangered Species Act

6.4.3 National Environmental Policy Act

6.4.4 Migratory Bird Treaty Act

6.4.5 Summary

Table 6.1 Plant Species

Table 6.2 Wildlife Species

Table 6.3 Threatened and Endangered Species

Figure 6.1 Preliminary Wetlands Mitigation Study Areas

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7.0 UNION RESERVOIR PUMP BACK PIPELINE (pdf file 854 Kb)

7.1 Project Overfiew

7.2 Pipeline and Pump Station Sizing

7.3 Pipeline Phasing

7.4 Pipeline Routing Alternatives

Figure 7.1 Concept Plan

Figure 7.2-7.3 Phasing Plan & Phase I Route Alternatives

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8.0 CONCLUSIONS AND RECOMMENDATIONS (pdf file 15 Kb)

9.0 REFERENCES (pdf file 26 Kb)

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Contact us

Public Works & Natural Resources
Water Resources & Environmental Services
1100 S. Sherman St.
Longmont, CO 80501
Phone (303) 651-8376
Fax (303) 651-8812
Email water@ci.longmont.co.us
Water Resources|Water Utilities|Public Works & Natural Resources|City of Longmont
This site was updated August 27, 2009
City of Longmont Public Works & Natural Resources
Water Resources & Environmental Services