WSP03245

• File Number: 8220.101.16
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 10/1/1991
• Author: BOR
• Title: Glen Canyon Dam Interim Operating Criteria: Finding of No Significant Impact & Environmental Assessment
• Water Supply Pro - Doc Type: EIS

GLEN CANYON DAM INTERIM FLOWS
ENVIRONMENTAL ASSESSMENT

CONTENTS

Page
Finding of No Significant Impact. . . . . . . . . . . . . . . . . . . . . . . . . iii

Table of Contents .................................... vii
Tables ........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
Figures ............................................ x

CHAPTER! Purpose and Need. . . . . . . . . . . . . . . . . . . . . . . . . I-I

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-I
Background ................... . . . . . . . . . . . . . . . . . . . I-I
Development of Alternatives ......................... I-I
Other Related Actions .............................. 1-4
Glen Canyon Dam EIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Glen Canyon Environmental Studies . . . . . . . . . . . . . . . . . 1.4

Western's EIS .................................. 1.4

CHAPTER 2 Proposed Action and Alternatives. . . . . . . . . . . . . II.l

No Action. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-I
Low Fluctuating Flow Alternative
(Proposed Action) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-2
Exception Criteria .............................. II-2
Operational Exception Criteria. . . . . . . . . . . . . . . . . . . . II.2
Financial Exception Criteria Element. . . . . . . . . . . . . . . II-3
Monitoring Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-4
Alternatives Considered but Eliminated. . . . . . . . . . . . . . . . . II-4
Intermediate Fluctuating Flow Alternative ............ II-4
Sustained Fluctuating Flow Alternative. . . . . . . . . . . . . . . II.5
Environmental Impacts ............................. II-5

CHAPTER 3 Affected Environment and
Environmental Consequences .......................... III-!

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III. 1
Assumptions ................................... III. 1
Location. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III.3
Immediate Area .............................. III.3
Area of General Influence . . . . . . . . . . . . . . . . . . . . . . . III.3
Colorado River Flows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . III.3

Resources ..................................... 111.3
Sediment ..................................... . . . 1II-5
Affected EnvironmentINo Action
Alternative Consequences ........................ III.5
Erosion of Sand Bars .......................... III.5
Replenishment of Sand Bar Deposits .............. III.7
Low Fluctuating Flow Alternativen
Consequences ................................. III.S
Erosion of Sand Bars .......................... III-S
Replenishment of Sand Bar Deposits .............. III-S
Financial Exception Criteria Element . . . . . . . . . . . . . . III.9