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Technical Memorandum

Limitations:

This document was prepared solely for CEMEX Construction Materials, Inc. in accordance with professional standards at the time the services were

performed and in accordance with the contract between CEMEX Construction Materials, Inc. and Brown and Caldwell dated September 13, 2013.

This document is governed by the specific scope of work authorized by CEMEX Construction Materials, Inc.; it is not intended to be relied upon by any

other party except for regulatory authorities contemplated by the scope of work. We have relied on information or instructions provided by CEMEX

Construction Materials, Inc. and other parties and, unless otherwise expressly indicated, have made no independent investigation as to the validity,

completeness, or accuracy of such information.

701 Pike Street, Suite 1200 Seattle, WA 98101 Phone: 206-624-0100 Fax: 206-749-2200

Prepared for: CEMEX Construction Materials, Inc.

Project Title: Eliot Facility Reclamation Plan Amendment, Surface Mining Permit 23, CA Mine 91-01-0009

Project No.: 144718

Technical Memorandum 2

Subject: Arroyo del Valle Diversion and Conveyance Feasibility

Date: March 7, 2014

To: Ronald D. Wilson, Manager, Land Use Permits: Pacific Region

From: Nathan Foged, Supervising Engineer

Copy to: Andrew Kopania, EMKO Environmental Karen Spinardi, Spinardi and Associates

Prepared by: Nathan Foged, Supervising Engineer California Civil Engineer C66395, Exp. June 2014

Prepared by: Aren Hansen, Principal Engineer California Civil Engineer C78259, Exp. June 2014

Reviewed by: William K. Faisst, Vice President California Civil Engineer C29146, Exp. March 2015

Eliot Facility Reclamation Plan Amendment Arroyo del Valle Diversion and Conveyance Feasibility

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Use of contents on this sheet is subject to the limitations specified at the beginning of this document. CEMEX AdVHS TM02 20140307.docx

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Table of Contents

List of Figures ........................................................................................................................................................... iv

List of Tables .............................................................................................................................................................. v

List of Abbreviations ................................................................................................................................................. vi

Section 1: Introduction ............................................................................................................................................. 1

Section 2: Background ............................................................................................................................................. 2

2.1 Site Description ........................................................................................................................................ 2

2.1.1 Livermore-Amador Valley ............................................................................................................ 2

2.1.2 Arroyo del Valle ............................................................................................................................ 3

2.2 Reclamation Planning .............................................................................................................................. 4

Section 3: Design Requirements ............................................................................................................................. 5

3.1 Diversion Criteria ...................................................................................................................................... 5

3.2 Fish Passage and Exclusion .................................................................................................................... 6

3.3 Diversion Location .................................................................................................................................... 7

3.4 Additional Design Considerations ........................................................................................................... 8

Section 4: Options Investigation .............................................................................................................................. 9

4.1 Intake and Fish Exclusion Devices .......................................................................................................... 9

4.1.1 Fish Screening ........................................................................................................................... 10

4.1.2 Infiltration and Seepage ........................................................................................................... 16

4.1.3 Selection of Options for Further Evaluation ............................................................................ 18

4.2 Hydraulic Grade Control Structure ........................................................................................................ 18

4.2.1 Design Options .......................................................................................................................... 18

4.2.2 Options Screening ..................................................................................................................... 21

4.3 Fish Passage or Bypass Structures ....................................................................................................... 23

4.3.1 Design Options .......................................................................................................................... 23

4.3.2 Options Screening ..................................................................................................................... 25

4.3.3 Provision for Controlled Bypass Flows ..................................................................................... 26

Section 5: Evaluation of Conceptual Design Alternatives .................................................................................... 27

5.1 Formulation of Alternatives ................................................................................................................... 27

5.1.1 Alternative 1: Infiltration Bed.................................................................................................... 28

5.1.2 Alternative 2: Linear Screen ..................................................................................................... 29

5.1.3 Alternative 3: Two Cone Screens ............................................................................................. 30

5.1.4 Alternative 4: Nine Cone Screens ............................................................................................ 31

5.2 Evaluation of Alternatives ...................................................................................................................... 32

Section 6: Recommendations for Preferred Alternative ...................................................................................... 36

6.1 Conceptual Layout and Conveyance into Lake A ................................................................................. 37

6.2 Concept-Level Plans and Cost Estimate ............................................................................................... 37

6.3 Potential Downstream Location ............................................................................................................ 38


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6.4 Recommendations for Further Study .................................................................................................... 40

References .............................................................................................................................................................. 41

Attachment A: Conceptual Design Figures ........................................................................................................... A-1

Attachment B: Construction Cost Estimate .......................................................................................................... B-1

List of Figures

Figure 1. Location of CEMEX’s Eliot Facility ............................................................................................................ 2

Figure 2. Surface flows related to Arroyo del Valle and the Chain of Lakes ......................................................... 5

Figure 3. Schematic representation of diversion system ...................................................................................... 9

Figure 4. Decision flow chart for selecting fish screen options ........................................................................... 10

Figure 5. Example of an on-stream fish screen (USBR, 2006) ............................................................................ 11

Figure 6. Examples of an in-canal fish screen (USBR, 2006) .............................................................................. 11

Figure 7. Example of inclined linear fish screens (USBR, 2009) ........................................................................ 12

Figure 8. Example of cylindrical fish screens ........................................................................................................ 12

Figure 9. Example of conical screens.................................................................................................................... 13

Figure 10. Hydraulic depth relationships in Arroyo del Valle near east end of Lake A ...................................... 14

Figure 11. Existing Arroyo del Valle channel geometry near east end of Lake A ............................................... 14

Figure 12. Example of a 500 cfs diversion using conical screens ...................................................................... 15

Figure 13. Conceptual sketch of a lateral infiltration gallery ............................................................................... 16

Figure 14. Conceptual sketch of a permeable berm ........................................................................................... 17

Figure 15. Definition sketch for calculating berm seepage (USACE, 1986) ....................................................... 17

Figure 16. Examples of in-channel rock structures that could pool water upstream ........................................ 19

Figure 17. Example of a flashboard weir used to impound water on a stream ................................................. 19

Figure 18. Example of an inflatable rubber dam .................................................................................................. 20

Figure 19. Examples of pneumatically actuated (Obermeyer) gates .................................................................. 20

Figure 20. Examples of low-head concrete diversion dams ................................................................................ 21

Figure 21. Examples of fish bypass channels ...................................................................................................... 23

Figure 22. Conceptual layout of a partial-width rock ramp fishway .................................................................... 24

Figure 23. Sketch of a vertical-slot fish ladder (NMFS, 2011) ............................................................................ 24

Figure 24. Example of vertical-slot fish ladder ..................................................................................................... 25

Figure 25. Dimensions of a cutthroat flume ......................................................................................................... 26

Figure 26. Schematic sketch of Alternative 1 (plan view) ................................................................................... 28



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Figure 30. Overall ratings based on weighted evaluation criteria ....................................................................... 36

Figure 31. Dimensional sketch of Parshall flume (FOA, 1993) ....................................................................... 37

Figure 32. Comparison of required diversion head differential with Lake A water surface .............................. 39

List of Tables

Table 1. Water Agencies Served by the South Bay Aqueduct ................................................................................ 3

Table 2. Preliminary Sizing for On-Stream Fish Screen Options .......................................................................... 15

Table 3. Comparison of Hydraulic Grade Control Options ................................................................................... 21

Table 4. Comparison of Fish Passage and Bypass Options ................................................................................. 25

Table 5. Ratings for Evaluation of Design Criteria ................................................................................................ 33

Table 6. Evaluation of Design Alternatives based on Design Criteria ................................................................. 34

Table 7. Summary of Pipe Sizing ........................................................................................................................... 38


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List of Abbreviations

ACCDA Alameda County Community Development Agency

Amendment SMP-23 Reclamation Plan Amendment

BC Brown and Caldwell

CDFW California Department of Fish and Wildlife

CEMEX CEMEX Construction Materials, Inc.

cfs cubic foot/feet per second

County Alameda County, California

ft foot/feet

ft2 square foot/feet

ft/s foot/feet per second

gpd/ft2 gallon(s) per day per square foot

LAVQAR Livermore-Amador Valley Quarry Area Reclamation

NMFS National Marine Fisheries Service

NOAA National Oceanic and Atmospheric Administration

O&M operations and maintenance

PVC polyvinyl chloride

Q-1 Alameda County Quarry Permit 1

Q-76 Alameda County Quarry Permit 76

RCP reinforced concrete pipe

SFEI San Francisco Estuary Institute

SFHA Special Flood Hazard Area

SFPUC San Francisco Public Utilities Commission

Site authorized mining area

SMP-23 Surface Mining Permit 23

Specific Plan LAVQAR Specific Plan

Spinardi Spinardi Associates

Study analysis of hydraulic impacts and evaluation of design options for the Arroyo del Valle diversion to Lake A

USACE U.S. Army Corps of Engineers

USBR U.S. Bureau of Reclamation

Valley Livermore-Amador Valley

Zone 7 Zone 7 of the Alameda County Flood Control and Water Conservation District


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Section 1: Introduction CEMEX Construction Materials, Inc. (CEMEX) owns and operates the Eliot Facility, a sand-and-gravel mining

operation located between the cities of Pleasanton and Livermore within the unincorporated area of

Alameda County (County), California. CEMEX is seeking the approval of an amendment to its existing

Reclamation Plan, which was originally approved in 1987 under Surface Mining Permit 23 (SMP-23).

In June 2013, Spinardi Associates (Spinardi) prepared the SMP-23 Reclamation Plan Amendment

(Amendment) and submitted it to the Alameda County Community Development Agency (ACCDA). ACCDA

provided comments on the Amendment in a July 8, 2013, letter from James Gilford to Ron Wilson, titled

“Completeness Review of Application to Amend Surface Mining Permit and Reclamation Plan No. 23.” The

letter requested additional technical evaluations, including the following two comments (summarized here):

• Hydraulic impacts: Conduct technical analyses (e.g., hydraulic modeling) to demonstrate that the

restored channel will remain stable, and that neither the channel modifications nor the diversion struc-

ture will increase flood risk to neighboring properties and infrastructure.

• Design feasibility: Present a complete design concept (e.g., schematic plans) and demonstrate that the

elements of the reclamation plan designed to address diversion and conveyance into the Chain of

Lakes1 can be feasibly constructed in compliance with known regulatory requirements.

In response to these comments, CEMEX retained Brown and Caldwell (BC) to analyze hydraulic impacts

along affected reaches of Arroyo del Valle to evaluate design alternatives for the Chain of Lakes diversion

(Study). This document, Technical Memorandum 2, addresses design feasibility as described in the above

comment. A separate document, Technical Memorandum 1, addresses hydraulic impacts.

This document addresses the following Study objectives assigned to BC:

• Investigate design requirements and performance criteria for diversion and conveyance facilities,

including pertinent design criteria requested by the Alameda County Flood Control and Water Conserva-

tion District Zone 7, also known as the Zone 7 Water Agency (“Zone 7”).

• Investigate options for key project components (e.g., fish exclusion, hydraulic grade controls, and fish

passage), perform an initial screening of options, and then formulate up to four conceptual design alter-

natives.

• Evaluate each alternative with respect to key design criteria and identify a preferred alternative.

• Develop conceptual design sketches and prepare a preliminary construction cost estimate for the

preferred alternative.

Technical Memorandum 2 includes the following six sections:

1. Introduction: This section provides a brief introduction to the Reclamation Plan Amendment, describes

the purpose of the Study, and lists specific objectives addressed by this document.

2. Background: This section provides background information regarding the project site, Arroyo del Valle,

and the development of the Amendment.

3. Design Requirements: This section discusses diversion criteria and key design considerations, as well as

regulatory requirements that are likely to influence design options and project feasibility.

1 The original SMP-23 Reclamation Plan was developed in accordance with the Specific Plan for Livermore-Amador Valley Quarry

Area Reclamation (LAVQAR Specific Plan), adopted by the County in November 1981. The LAVQAR Specific Plan describes a “Chain of Lakes” reclamation concept that calls for the creation of a series of excavated lakes to be used for storage and groundwater recharge. See Section 2.2 for more information.


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4. Options Investigation: This section provides information on design options for key project components

including an initial screening of hydraulic grade control and fish bypass options.

5. Evaluation of Conceptual Design Alternatives: This section describes each of the conceptual design

alternatives and evaluates those alternatives with respect to the specified design criteria.

6. Recommendations: This section draws conclusions from the alternatives evaluation and provides

specific recommendations for a preferred conceptual design alternative.

Section 2: Background This section provides background information regarding the project site (Section 2.1) and the development

of the Amendment (Section 2.2).

2.1 Site Description

The CEMEX Eliot Facility is located in the

Livermore-Amador Valley (Valley) between

the cities of Pleasanton and Livermore,

California (see Figure 1). Mining

operations at the Eliot Facility are vested

under Alameda County Quarry Permit 1 (Q-

1) and Quarry Permit 76 (Q-76) granted in

1957 and 1969, respectively. The

authorized mining area (Site) covers

approximately 975 acres of land between

Stanley Boulevard and Vineyard Avenue.

The Shadow Cliffs Regional Recreation

Area is located directly west of the Site,

Vulcan’s sand and gravel operation is

located to the north and east, and the

Ruby Hill subdivision is located across

Vineyard Avenue to the south. The

evaluations presented in this technical

memorandum address the diversion of

water from Arroyo del Valle into Lake A,

near the east end of the Eliot Facility.

2.1.1 Livermore-Amador Valley

The Valley is a wide depression in the

Diablo Range, bounded by the East Bay

Hills to the west and the Altamont Hills to

the east. The Valley’s western portion is the Amador Valley; it includes the city of Pleasanton. The Valley’s

eastern portion is the Livermore Valley; it includes the city of Livermore. The two valleys together form the

Valley. According to the San Francisco Estuary Institute (SFEI, 2013), the Valley was formed by geological

processes and provides a wide space for streams to spread and sink.

Numerous streams that drain out of the surrounding hills have deposited sediments over thousands of years

and filled the Valley (SFEI, 2013). Arroyo Mocho and Arroyo del Valle are two major streams draining into the

Figure 1. Location of CEMEX’s Eliot Facility


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southern portion of the Valley. Historically, these were wide and braided streams that deposited large

amounts of coarse sediment transported from their headwaters in the Diablo Range (SFEI, 2013).

Sand and gravel mining has occurred along the Arroyo Mocho and Arroyo del Valle alluvial formations since

the late 1800s, including the areas around the Eliot Facility. Over the years, mining and development

activities have rerouted and channelized much of the lower reaches of Arroyo Mocho and Arroyo del Valle.

Arroyo del Valle’s existing channel flows along the southern portion of the Site. Section 2.2 discusses

proposed mining and reclamation activities and potential impacts to Arroyo del Valle. Section 2.1.2 provides

an overview of the Arroyo del Valle hydrology and geomorphology.

2.1.2 Arroyo del Valle

Arroyo del Valle is located in the upper Alameda Creek watershed. The arroyo drains an area of

approximately 172 square miles before it discharges to Arroyo de la Laguna, west of Pleasanton. Arroyo de

la Laguna flows south and discharges into Alameda Creek, near the town of Sunol. Alameda Creek then

flows west through the East Bay Hills before discharging into San Francisco Bay.

Approximately 85 percent (146 square miles) of the Arroyo

del Valle basin is located upstream of Del Valle Reservoir,

constructed in 1968 to serve as off-channel storage for

water delivered through the South Bay Aqueduct (part of

the California State Water project) and for flood control.

Zone 7 is one of three water agencies served by the South

Bay Aqueduct; Table 1 shows the annual entitlements for

each agency. Zone 7 also uses a small portion of Del Valle

Reservoir capacity to store runoff from the local

watershed2. Although Del Valle Reservoir serves primarily

as water supply storage, a portion of its 77,100-acre-foot

capacity is normally reserved for flood control.

Del Valle Reservoir has altered the hydrologic flow regime in the lower reaches of Arroyo del Valle (Kamman,

2009). Peak flows have decreased and large-magnitude flood flows have been virtually eliminated. Managed

releases during the dry season have resulted in perennial flow conditions along the valley floor rather than

the historical intermittent flow conditions when the arroyo would become dry in the summertime (Kamman,

2009; LSA, 2013). Altered flows have also contributed to changes in Arroyo del Valle channel; the once

actively braided channel network along the valley floor now has shifted to a more defined central channel

system (Kamman, 2009).

Directly downstream of the dam, Arroyo del Valle flows through a narrow, sinuous canyon until it reaches the

valley floor about 1 mile downstream, near the Veterans Administration hospital. At this point, the channel

and floodplain become wider and, in the past, became more active and braided. Sycamore Grove Park is an

important community park that preserves mature Western Sycamore trees along this reach of the historical

Arroyo del Valle floodplain. This park stretches approximately 2 miles from the hospital to Vallecitos Road.

The Eliot Facility Site is located just downstream of Sycamore Grove Park. Arroyo del Valle flows along the

southern portion of the Site adjacent to Lakes A and B (see Section 2.2, Reclamation Planning). The arroyo

flows through two small lakes along the south side of the Shadow Cliffs Regional Recreation Area and then

continues west through the city of Pleasanton. Several small streams drain into Arroyo del Valle between the

dam and its confluence with Arroyo de la Laguna ).

2 Del Valle Reservoir data are available on the Zone 7 Web site: http://www.zone7water.com/water-supply/48-del-valle-reservoir.

Table 1. Water Agencies Served by the South Bay

Aqueduct

Water agency Annual entitlement

(acre-feet)

Zone 7 46,000

Alameda County Water District 42,000

Santa Clara Valley Water District 100,000

Total 188,000

Source: California Department of Water Resources (1968,

2001).


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2.2 Reclamation Planning

The SMP-23 Reclamation Plan (1987) was developed in accordance with the Specific Plan for Livermore-

Amador Valley Quarry Area Reclamation (LAVQAR Specific Plan, or Specific Plan), adopted by the County in

November 1981. The LAVQAR Specific Plan describes a “Chain of Lakes” reclamation concept, where mining

operators would convert excavated gravel quarries into a series of open lakes that use them for storage and

groundwater recharge. After mining is completed and quarry sites are reclaimed, the Chain of Lakes are to

be dedicated to Zone 7 of the Alameda County Flood Control and Water Conservation District (Zone 7) for

use in managing the groundwater basin. According to the SMP-23 Reclamation Plan (1987), and consistent

with the LAVQAR Specific Plan, mining at the Site will result in the formation of two lakes:

• Lake A will be located north of Vineyard Avenue, between Isabel Avenue (State Route 84) and Vallecitos

Road.

• Lake B will be located north of Vineyard Avenue, between Isabel Avenue (State Route 84) and the

Shadow Cliffs Regional Recreation Area.

The SMP-23 Reclamation Plan (1987) indicates that excavation at Lakes A and B will extend as far south as

Vineyard Avenue, and that Arroyo del Valle will flow into and through the pits during active mining operations.

Two large concrete spillways would be constructed to control flows into each pit, one at Vallecitos Road and

one at Isabel Avenue. Outflow from Lake B would occur over a rock-lined overflow weir at Lake B’s west end,

returning to Arroyo del Valle. The SMP-23 Reclamation Plan (1987) does not include provision for the

restoration or reconstruction of the channel for Arroyo del Valle, indicating that the arroyo would be routed

through Lakes A and B and the spillways would remain in place after mining was completed.

The proposed SMP-23 Reclamation Plan Amendment (June 2013) reconfigures the footprints of both Lakes

A and B to maintain the channel for Arroyo del Valle separate from Lakes A and B. CEMEX would no longer

excavate Lake A as far south as Vineyard Avenue such that the existing Arroyo del Valle channel could

remain intact. Lake B still would extend south through the currently disturbed Arroyo del Valle channel

alignment, but CEMEX would construct a new channel alignment closer to Vineyard Avenue, to restore the

initial hydraulic and biological function of the arroyo. Given that the channel would no longer flow through

Lakes A and B, the reclamation plan would no longer need to include large concrete spillways at Vallecitos

Road and Isabel Avenue, or the large rock-lined overflow weir at the west end of Lake B.

After reviewing the Amendment submitted to the County in June 2013, ACCDA sent a letter to CEMEX dated

July 8, 2013, with several comments that focused on the following two issues related to the water diversion

and conveyance facilities:

• Hydraulic impacts: Conduct technical analyses (e.g., hydraulic modeling) to demonstrate that the

restored channel will remain stable, and that neither the channel modifications nor the diversion

structure will increase flood hazards.

• Design feasibility: Present a complete design concept (e.g., schematic plans) and demonstrate that the

elements of the reclamation plan designed to address diversion and conveyance into the Chain of Lakes

can be feasibly constructed in compliance with known regulatory requirements. For example, the

proposed diversion structure would require a bypass flow feature (e.g., fish ladder) and a screen

cleaning system (or equivalent fish protection provisions) to be in compliance with current fish habitat

requirements.

The remainder of this document addresses the “design feasibility” comment. A separate technical memo-

randum, TM 1, addresses the “hydraulic impacts” comment.


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Section 3: Design Requirements As described in the previous section, the Amendment calls for Arroyo del Valle to be separated from Lakes A

and B under reclaimed conditions. Therefore, the Amendment includes a diversion structure and conduits

between Lakes A, B, and C to facilitate water transfer from Arroyo del Valle into the Chain of Lakes. BC

reviewed existing documents for information provided by Zone 7 to identify key design requirements for the

diversion and conveyance structures, including diversion criteria (Section 3.1), fish passage and exclusion

requirements (Section 3.2), diversion locations (Section 3.3), and additional design considerations (Section

3.4).

3.1 Diversion Criteria

After the Site is reclaimed, Lake A, Lake B, and all appurtenant diversion and conveyance structures will be

dedicated to Zone 7 for use in water management. According to a memorandum provided by Zone 7 (August

16, 2013), Zone 7 plans to use these facilities to divert water from Arroyo del Valle into the Chain of Lakes to

“replace loss of water through evaporation, mitigate the concentrations of salts in the water due to evapora-

tion, recharge the groundwater basin, and enhance regional flood protection,” consistent with the objectives

of the Specific Plan.

The Specific Plan (1981) states that “the diversion structure from Arroyo del Valle within Lake A into Lake C

will be capable of diverting at least the first 500 cubic feet per second of flow from the Arroyo.” The Specific

Plan does not explicitly discuss water diversion from Arroyo del Valle to Lake A. This lack of clarity was not an

issue for the 1987 Reclamation Plan because Arroyo del Valle was to continue to flow directly into Lake A

after the site was reclaimed. However, the Amendment (June 2013) calls for the Arroyo del Valle channel to

remain intact adjacent to Lake A and to be restored adjacent to Lake B. Therefore, direct transfer of surface

flow from Arroyo del Valle to the Chain of Lakes would require a diversion structure (see Figure 2).

Figure 2. Surface flows related to Arroyo del Valle and the Chain of Lakes


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The existing agreement between Zone 7 and RMC Lonestar (a predecessor to CEMEX) dated March 29,

1988 (Agreement) was developed based on the 1987 Reclamation Plan, which assumed that Arroyo del

Valle would flow through Lake A and called for a diversion structure from Lake A to Lake C that would be

capable of diverting at least the first 500 cubic feet per second (cfs). Given the changes described in the

previous paragraph, CEMEX has been discussing new design criteria with Zone 7 assuming that the diver-

sion will now be located on the Arroyo del Valle channel. In an e-mail from Zone 7 to BC dated August 16,

2013, Zone 7 provided a document containing draft design criteria for the new diversion structure. The

document included the following specific criteria relating to diversion and bypass flow rates:

• Divert the first 500 cfs of water from Arroyo del Valle into the Chain of Lakes in an environmentally

sensitive manner. More specifically:

− Provide the ability to control diverted flow rates in increments of 20 to 25 cfs up to the first 250 cfs

− Provide the ability to control diverted flow rates in increments of 50 to 100 cfs between 250 and

500 cfs

− Divert up to 500 cfs during flood releases greater than 1,000 cfs from Del Valle Reservoir, without

any dams or other obstructions in place

• Provide for controlled bypass flows as follows:

− 1 cfs to 40 cfs in winter/spring

− 6 cfs to 15 cfs in summer/fall

While CEMEX’s actual requirements and obligations are defined by the Agreement, BC investigated the

feasibility of various diversion design options in light of the above-described performance criteria. Section 4

below provides a summary of BC’s findings.

3.2 Fish Passage and Exclusion

The California Department of Fish and Wildlife (CDFW) requires fish passage and fish screening for diver-

sions located within salmon- or steelhead-bearing waters of the state. The National Oceanic and Atmospher-

ic Administration (NOAA) also consults on projects impacting fish habitat where federally listed species such

as steelhead are present.

Arroyo del Valle is a tributary stream to Alameda Creek, which has historically been a spawning area for fish

species including central California coastal rainbow trout/steelhead (Oncorhynchus mykiss) and coho

salmon (Oncorhynchus kisutch) (SFEI, 2013). Fish barriers currently exist on Arroyo del Valle downstream of

the Site; however, in recent years numerous fish passage projects have been constructed on Alameda Creek

and its tributaries to remove barriers to and encourage anadromous fish migration into the upper creek

system. For example, San Francisco Public Utilities Commission (SFPUC) has worked on fish passage and

screening improvements for its diversion dam on upper Alameda Creek, a channel reach identified as having

suitable habitat for steelhead.

Hanson et al. (2004) investigated the current and historical occurrence of steelhead in the Valley for Zone 7.

The report provided the following findings:

• Historically, steelhead passage in Arroyo del Valle occurred infrequently, in response to high flow events

that provided suitable surface water connectivity between Arroyo del Valle and lower Alameda Creek.

• It is unlikely that the Arroyo del Valle watershed historically provided consistent suitable habitat condi-

tions for steelhead passage, spawning, and/or juvenile rearing to support self-sustaining populations.

• Suitable habitat exists for steelhead spawning and rearing in the reach immediately downstream of Del

Valle Reservoir; however, management actions would be required to achieve these benefits.


7


BC contacted CDFW regarding permitting requirements for a water diversion structure on Arroyo del Valle.

Based on a conversation with Michelle Lester of CDFW (January 23, 2014), it is too early at this point to

conclude that fish screens or passage will be required given the uncertainties regarding the quantity and

size of the diversion, as well as uncertainty regarding the suitability of the habitat.

Fish habitat studies are ongoing, and new information will become available in the coming years. According

to CDFW, Zone 7 recently commissioned a study titled “Arroyo del Valle and Arroyo de la Laguna Steelhead

Habitat Assessment”; however, this study has not yet been finalized. In a related effort, the Alameda Creek

Alliance is working with Zone 7 and several other agencies to assess instream flows for migratory fish in

Arroyo del Valle. According to the Alameda Creek Alliance Web site:

The Alameda Creek Alliance is working with 16 agencies conducting studies and modeling to determine the range, timing, duration, frequency, and location of the water flows needed to restore the steelhead fishery in Alameda Creek. The Alameda County Water District is nego-tiating with regulatory agencies to determine appropriate bypass flows for future fish ladders in the lower watershed. In the northern watershed, the Alameda Creek Alliance has prompt-ed Zone 7 Water Agency to begin assessing instream flows for migratory fish in Arroyo Mo-cho, Arroyo del Valle and Arroyo de la Laguna through Livermore and Pleasanton.3

Notwithstanding the uncertainties discussed above, for this feasibility study, BC will assume that a diversion

structure on Arroyo del Valle will need to meet requirements for anadromous fish passage and screening.

Specific criteria are described as follows:

• Fish passage: Cross-channel structures should include a passable flow bypass structure, and off-channel

flow diversions should include return flow channels to avoid trapping.

• Bypass flows: In the draft design criteria document cited previously, Zone 7 requested that the Arroyo del

Valle diversion allow for controlled diversion bypass flows of up to 40 cfs in winter/spring and 15 cfs in

summer/fall (e-mail correspondence on August 16, 2013).

• Fish screening: CDFW criteria require fish screens to be sized such that the approach velocity entering

the screen does not exceed 0.33 feet per second (ft/s) for all self-cleaning screens located in on-stream

installations. For screens without automatic cleaning, the approach velocity is limited to one-fourth of the

self-cleaning screens. Fish screens are typically sized by dividing the desired diversion flow (e.g., 500 cfs)

and the limiting approach velocity (e.g., 0.33 ft/s), which results in the minimum area of fish screen re-

quired. For example, a 500 cfs diversion limited to 0.33 ft/s approach velocity would require at least

1,515 square feet (ft2) of fish screen. The U.S. Bureau of Reclamation (USBR) (2006) recommends the

use of a 10 percent safety factor, which would increase the required area in this example to 1,667 ft2.

These criteria should be revisited during detailed design as part of consultation with CDFW. It may be

feasible to request a variance from CDFW for the approach velocity restrictions during certain times of year

when fish fry are not present. For example, with such a variance, a diversion structure designed to screen

210 cfs at 0.33 ft/s approach velocity during periods when fry may be present could also be used to screen

500 cfs at 0.8 ft/s (maximum velocity allowed by CDFW) during periods of the year when anadromous fish

fry are not present (likely during summer and fall).

3.3 Diversion Location

Locating the diversion structure at the east end of Lake A (i.e., the most upstream location along Arroyo del

Valle) would provide the most design flexibility in terms of elevations and hydraulic head. However, in

3 Discussion of “Key Accomplishments, Stream Flows for Native Fish” on the Alameda Creek Alliance Web site at:

http://www.alamedacreek.org/about-us/key-accomplishments.php.


8


conversations with Zone 7, and in the August 2013 draft design criteria document, Zone 7 has requested

that the diversion be located “as close to Isabel Avenue/[Highway] 84 as possible” and that any impound-

ments at the diversion would “avoid [creating] large pools that stretch under Vallecitos Bridge and into

Sycamore Grove Park.” BC addressed the latter concern with preliminary hydraulic modeling of the Arroyo

del Valle channel, which found that “an in-channel diversion with an obstruction as high as 10 feet at the

upstream end of Lake A [approximately 1,100 feet downstream of Vallecitos Road] would increase water

surface elevations in the vicinity immediately upstream of the diversion; however, those increases diminish

rapidly and are negligible beyond Vallecitos Avenue.” (BC, February 2014). Therefore, flooding impacts

upstream of Vallecitos Road are not considered to be a constraint as long as the proposed diversion struc-

ture does not include an in-channel obstruction greater than 10 feet in height.

For the purposes of this feasibility study, BC initially assumed that the diversion would be located at the east

end of Lake A because it provides the most design flexibility. However, after the preferred alternative was

selected (see Section 5), BC compared elevations along Arroyo del Valle to Lake A water levels to determine

if there is potential for moving the structure downstream (see Section 6).

3.4 Additional Design Considerations

BC identified additional design considerations based on discussions with Zone 7 and Alameda County. The

following conditions should be considered when screening options and comparing alternatives:

• The proposed diversion project should avoid increased flooding risks to nearby residences and infra-

structure, such as Vallecitos Road, and including Sycamore Grove Park.

• The proposed diversion project should minimize channel disturbance and visual impacts, and preserve

the riparian nature of the area for future park and trail access.

• The proposed diversion project should minimize both capital and long-term maintenance costs.


9


Section 4: Options Investigation The Arroyo del Valle diversion system will consist of several interrelated components. The schematic repre-

sentation shown in Figure 3 identifies six major components as follows:

1. Intake and fish exclusion: Water is diverted

away from the Arroyo del Valle channel

through an intake structure that incorpo-

rates a device (e.g., screen) to prevent fish

from being captured or trapped by the di-

version. Section 4.1 describes several op-

tions, discusses preliminary sizing, and

identifies up to three options for further

evaluation as alternatives (Section 5).

2. Hydraulic grade control: Upstream water

levels are raised to create controlled hy-

draulic head for diversions and bypass

flows. Section 4.2 describes several op-

tions and then identifies a preferred option

based on an initial screening assessment.

3. Fish passage and/or bypass: This compo-

nent allows fish to pass any physical barri-

ers created by the hydraulic grade control

structure. Section 4.3 describes several

options and then identifies a preferred op-

tion based on an initial screening assessment.

4. Diverted flow control structure: This structure is used to control flow through the intake, and should

include a device to adjust release rates (e.g., gate or valve) and a device to measure the discharge (e.g.,

a weir or flume). BC develops recommendations for these devices as part of the description of the pre-

ferred alternative (Section 6). Specific equipment should be evaluated as part of the detailed design.

5. Conduit into Lake A: This component consists of a pipeline and/or open channel to convey diverted

water into Lake A. BC develops recommendations for this conveyance structure as part of the description

of the preferred alternative (Section 6).

6. Conduit from Lake A to Lake C: This component consists of a pipeline to convey water from Lake A to

Lake C. Evaluations and recommendations for this component are not included as part of the conceptual

design presented in this document, but will be addressed in a subsequent document.

Sections 4.1 through 4.3 below discuss options for components 1 through 3 described above.

4.1 Intake and Fish Exclusion Devices

A variety of methods and devices have been used to exclude fish from diversions on anadromous fisheries.

The USBR Water Resources Technical Manual, Fish Protection at Water Diversions (USBR, 2006) presents a

summary of typical options. Selection of an appropriate method depends on many factors such as diversion

discharge, stream channel characteristics, fish species present, anticipated operational scenarios, and

hydraulic grade and control capabilities.

BC identified two basic approaches to diverting flow while excluding fish:

• Fish screening: This commonly used approach uses barriers to prevent fish from entering into diversion

channels or intakes.

Figure 3. Schematic representation of diversion system

Although not part of the Arroyo del Valle diversion system, a conveyance

connection is shown between Lake B and Lake C; this represents the planned

installation of a 30-inch-diameter pipe, consistent with the Specific Plan and

the 1988 Agreement between Zone 7 and RMC Lonestar.

23

1 54

6

LAKE B LAKE C

LAKE A

AR

RO

YO D

EL V

ALL

E


10


• Infiltration and seepage: This approach precludes the need for fish screens by transmitting water

through gravel or other permeable media.

These approaches are described in more detail in the following sections.

4.1.1 Fish Screening

Figure 4 illustrates the process BC used to select fish screening options based on our understanding of

CDFW’s preferences and the flow conditions in Arroyo del Valle.

Figure 4. Decision flow chart for selecting fish screen options

Text shaded in gray indicates options that were eliminated from further consideration.

Two general types of fish protection are typically employed at water diversions: positive barrier screens (e.g.,

fish screens) and behavioral barriers (e.g., lights, bubble curtains, sound, etc.). Because behavioral barriers

are less proven, less effective, and less favored by regulatory agencies, we eliminated them from further

consideration. Alternatives for fish protection presented herein include only positive barrier screens.

Positive barrier screens can be further divided based on their location relative to the main channel:

• On-stream barriers are located within the main channel of the watercourse and are typically along the

channel bank (see Figure 5).

• Off-stream or in-canal barriers are located within a side channel or canal; fish that enter the diversion

channel/canal are screened and then directed back into the main channel through a return channel or

bypass pipe (see Figure 6).

The CDFW fish screen criteria specifically state that CDFW prefers on-stream fish screen placement where

feasible. On-stream systems typically create fewer disturbances to the fish species of concern because they

do not remove fish (even temporarily) from the existing stream. Although off-stream placement may be

feasible for the Arroyo del Valle diversion, BC selected on-stream placement as the preferred configuration

for this evaluation due to CDFW’s preference.

Positive Barriers (physical screen barriers)Provides proven protection.

Behavioral Barriers (Lights, bubble curtains, sounds)

Less proven, generally not favored by CDFW.

On-streamKeeps fish in the stream.

Preferred by CDFW.

Off-stream/In-canalRequires fish bypass into downstream

area to avoid trapping. CDFW calls for on-

stream barriers to be used where feasible.

Linear Inclined ScreenRequires more bank length, but less

footprint in channel. Diversion amount

depends on screen submergence.

Submerged ScreenRequires greater footprint in channel, but can be

somewhat modular. Once submerged, diversion rate

does not vary. More expensive than linear screen.

Fish Screen Selection


11


Figure 5. Example of an on-stream fish screen (USBR, 2006)

Wilkens Slough fish screen system on the Sacramento River has a screen length of 225 feet and was designed to divert 700 cfs (capable of diverting

up to a maximum of 830 cfs) given substantial flow depths in the range of 11 to 25 feet (USBR, 2006).

Figure 6. Examples of an in-canal fish screen (USBR, 2006)

Schematic (left) shows typical in-canal fish screen, including bypass pipe

to direct fish back to river. Highline Canal on right uses two V-shaped fish screens.


12


4.1.1.1 Options for On-Stream Screening

Fish screens can be constructed as flat-plate linear screens or modular submerged screens. Figure 7 shows

an example of a linear screen designed for Savage Rapids Diversion Dam near Grants Pass, Oregon. Figure

8 shows cylindrical submerged screens that have been installed by Alameda County Water District in lower

Alameda Creek. Figure 9 shows conical submerged screens installed by Santa Clara Valley Water District.

Both linear and submerged screens are typically equipped with automated screen cleaning systems that

require electrical power at the site.

Figure 7. Example of inclined linear fish screens (USBR, 2009)

Savage Rapids Diversion Dam near Grants Pass, Oregon.

Figure 8. Example of cylindrical fish screens

Lower Alameda Creek diversion for Alameda County Water District; four 42-inch-diameter by 200-inch-long cylindrical screens used to divert up to

150 cfs when fully submerged.


13


Figure 9. Example of conical screens

Kirk Diversion Dam for Santa Clara Valley Water District; two 10-foot conical screens used to divert up to 85 cfs when fully submerged at a depth

of approximately 3 feet above the base of the cone. Images and detail drawing courtesy of Intake Screens, Inc.

4.1.1.2 Preliminary Sizing

Fish screening requirements are often the limiting factor in diversion capacity design due to the screen area

needed to pass the diverted flow without exceeding maximum approach velocities. Screen area depends on

water depth. BC used a HEC-RAS hydraulic model to calculate water surface profiles over a full range of

flows observed in Arroyo del Valle since the construction of Del Valle Reservoir4. Figure 10 shows discharge-

depth and frequency-depth relationships based on the modeling results.

4 The reader should refer to Technical Memorandum 1 (BC, February 2014) for details on hydraulic model development and flow

frequency analyses.


14


(a) Discharge-depth rating curve (b) Frequency-depth

Figure 10. Hydraulic depth relationships in Arroyo del Valle near east end of Lake A

Hydraulic depth data based on HEC-RAS modeling results at Station 246+03.

Refer to Technical Memorandum 1 (BC, February 2014) for details on hydraulic model development.

The data shown in Figure 10(b) suggest that, historically, flow depths in Arroyo del Valle are less than 1 foot

about 90 percent of the time and rarely get above 2 feet. If larger flows such as 500 or 1,000 cfs are

released from Del Valle Reservoir for the purposes of diversion, then flow depths increase to approximately

2.5 or 3.3 feet, respectively (see Figure 11).

Figure 11. Existing Arroyo del Valle channel geometry near east end of Lake A

Water surface elevations for 500 and 1,000 cfs based on HEC-RAS modeling results at Station 246+03.

Refer to Technical Memorandum 1 (BC, February 2014) for details on hydraulic model development.

0

1

2

3

4

5

6

0 1,000 2,000 3,000 4,000

Flo

w D

ep

th (

ft)

Discharge (cfs)

0

1

2

3

4

5

6

0% 20% 40% 60% 80% 100%

Flo

w D

ep

th (

ft)

Percent Time Exceeded

400 450 500

432

434

436

438

440

442

Station (ft)

Ele

vation

(ft)

500 cfs

1000 cfs


15


Zone 7 requested that the proposed diversion structure “divert up to 500 cfs during flood releases greater

than 1,000 cfs from Del Valle Reservoir, without any dams or other obstructions in place.” BC used the

depth associated with a 1,000 cfs flow condition (3.3 feet) to do a preliminary fish screen sizing calculation

(see Table 2). However, it should be noted that this calculation assumes a constant depth of 3.3 feet over

the fish screen(s). In reality, the flow depth would decrease as water is drawn from the channel unless a

hydraulic grade control structure is in place. Nevertheless, the calculation in Table 2 provides insight regard-

ing sizing feasibility. Additional discussion regarding the need for hydraulic grade control is provided in

Section 4.2.

Table 2. Preliminary Sizing for On-Stream Fish Screen Options

Screen option

Maximum

approach

velocity

Unit diversion

capacity at a depth of

3.3 feet

Size needed to

divert 500 cfs

Approximate

length of stream

bank needed for

installation

Notes

Linear/flat-panel 0.33 ft/s 1.1 cfs per linear foot 459 linear feet 460 feet Assume vertical screen panel, an inclined

screen could provide additional capacity

Cylindrical 0.33 ft/s 28 cfs per 36-inch unit 18 cylinder

screens 264 feet

36-inch unit is 13 feet 8 inches long; assume

minimum of 1 foot of space between units

Conical 0.33 ft/s 56 cfs per 14-foot unit 9 conical screens 144 feet Assume minimum of 2 feet of space between

units

Notes: 1. Velocity criterion based on CDFW requirements for a fish screen with automated cleaning; no safety factor applied.

2. A constant flow depth of 3.3 feet was assumed; a hydraulic grade control structure may be necessary to maintain this condition.

The results shown in Table 2 indicate that fish screens designed to divert up to 500 cfs will require a sub-

stantially large structure stretching from at least 144 feet to as much as 460 feet along the stream bank.

For reference, the diversion shown in Figure 8 has a 150 cfs capacity, and the diversion in Figure 9 has an

85 cfs capacity. Diversions as large as 500 cfs are typically located on considerably larger watercourses. For

example, the 500 cfs Red Bluff diversion is located on the Sacramento River (see Figure 12).

Figure 12. Example of a 500 cfs diversion using conical screens

Red Bluff Pumping Plant on the Sacramento River; images courtesy of Intake Screens, Inc.


16


4.1.2 Infiltration and Seepage

A second approach to diverting water away from Arroyo del Valle would be to collect water through infiltra-

tion, percolation, and/or seepage. Two basic methods were investigated as described below.

4.1.2.1 Infiltration Gallery

An infiltration gallery uses perforated conduits that are buried in gravel to facilitate rapid infiltration and sub-

surface drainage through a permeable gravel layer along the stream bottom and/or bank (see Figure 13).

Although infiltration rates would need to be relatively high, they would still be well below the approach

velocity criterion for fish screening, thereby replacing the need for a fish screen.

Figure 13. Conceptual sketch of a lateral infiltration gallery

Sizing and Feasibility Considerations. Infiltration galleries are commonly used for low flow applications, but

could be expanded beyond typical applications by adding more laterals. Preliminary sizing calculations were

performed using an equation from USBR (1995):

� = �� 2� 2��

where:

L is the computed length of screen to yield desired discharge (ft) Q is the desired discharge (cfs)

r is the radius of the drainage pipe

K is the permeability coefficient for the gravel fill (ft/s)

H is the depth of water over the gravel fill (ft)

d is the distance from the ground surface to the center of the drain pipe (ft)

Assuming a desired flow rate of 500 cfs, permeability coefficient of 0.04 ft/s, 1-foot diameter pipe, 3-foot

depth of pipe, and 1-foot depth of water, the required screen length comes out to be approximately 3,565

feet. This could be accomplished using many parallel drainage pipes; for example, thirty-six 100-foot pipes. If

the pipes are placed approximately 5 feet apart, the length of the infiltration bed along the stream bank

would be 200 feet. Thus, the infiltration bed would have a surface area of 20,000 ft2. A diversion rate of 500

cfs over an area of 20,000 ft2 would result in an inflow velocity of approximately 0.025 ft/s across the

surface of the infiltration bed and a pore velocity of 0.08 ft/s, assuming a porosity of 0.3 for the gravel in the

bed. Thus, the inflow velocity would be much less than what would occur for the fish screens evaluated in

Section 4.1.1.2, above.

Infiltration galleries are commonly used in conjunction with pumps to convey water to higher elevations.

However, at the selected diversion site, elevation drop from the Arroyo del Valle channel to Lake A is ade-

quate for drainage and conveyance pipes to be sloped to allow for gravity flow, substantially reducing

operation and maintenance (O&M) requirements.

INFILTRATION

OUTFLOW

GRAVEL

PERFORATED PIPE

STREAM CHANNEL


17


4.1.2.2 Permeable Berm

A berm (i.e., levee or dike) could be constructed along the stream bank using high-permeability gravel or rock

to facilitate seepage from Arroyo del Valle into Lake A (see Figure 14). The flow on the down-gradient side

would need to be collected and conveyed to the lake using a collector channel or drainage piping. As with

the infiltration gallery, flow into and through the berm would likely be well below the approach velocity

criterion for fish screening.

Figure 14. Conceptual sketch of a permeable berm

Sizing and Feasibility Considerations. Preliminary sizing calculations were performed by estimating seepage

through a gravel berm using the Schaffernak-Van Iterson method as described in the U.S. Army Corps of

Engineers Seepage Analysis and Control for Dams manual (USACE, 1986). The following equations were

used:

� = �cos� − � ��cos� � − ℎ�sin� �

� = �� sin� tan�

where:

q is the seepage discharge per unit width (cfs)

k is the permeability of the berm (ft/s)

all other parameters are defined by the sketch shown in Figure 15

Figure 15. Definition sketch for calculating berm seepage (USACE, 1986)

OUTFLOW SEEPAGE

STREAM CHANNEL

GRAVEL/ROCK BERM


18


A variety of berm configurations, water depths, and permeability coefficients were evaluated, and all resulted

in unit discharge rates in the range of 0.05 to 0.20 cfs per foot of berm. These values result in berm lengths

of 2,500 to 10,000 feet to attain diversion rates of as high as 500 cfs. Based on these results, the permea-

ble berm option is considered to be infeasible.

4.1.3 Selection of Options for Further Evaluation

BC selected three options for further evaluation based on the preliminary sizing and feasibility findings

described in the previous sections. Selected options and justification are as follows:

• Linear screen: This option was selected because of its simplicity and flexibility in design. For example,

the screen area can be increased indefinitely with hydraulic depth, while cylindrical screens or conical

screens are limited once submerged.

• Conical screens: This option was selected because it is a widely used, proven technology and is available

in modular manufactured units. Conical screens were selected over cylindrical screens because they

provide more screen area at shallow depths and require less bank area for installation.

• Infiltration gallery: This option was selected because it precludes the need for fish screens and has the

potential to divert 500 cfs with relatively low hydraulic head.

Design alternatives based on each of these options are evaluated in Section 5.

4.2 Hydraulic Grade Control Structure

Hydraulic grade control structures are typically used to impound water and provide controlled hydraulic head

at open-channel diversions. This is particularly important in streams like Arroyo del Valle with low base flows

and shallow ordinary water depths. As discussed in Section 4.1.1.2, even if 1,000 cfs is flowing in Arroyo del

Valle, a hydraulic grade control structure would be necessary to maintain a constant depth across the

intake/fish screening structure. Furthermore, both the Specific Plan and the 1988 Agreement between Zone

7 and RMC Lonestar, a predecessor to CEMEX, state that the diversion structure should have the capability

to divert the first 500 cfs from Arroyo del Valle. Subsequent correspondence from Zone 7 also includes the

need to provide controlled bypass flows in the range of 6 to 40 cfs (see Section 3.1.1). To achieve both the

diversion and bypass flow criteria, a hydraulic grade control structure would be needed to provide sufficient

hydraulic head to divert 500 cfs while discharging only a small bypass flow downstream.

The following subsections describe several potential options for providing hydraulic grade control, followed

by a discussion of sizing and feasibility.

4.2.1 Design Options

The following paragraphs describe several options for hydraulic grade control structures, ranging from simple

to complex. The reader should note that the options presented below were selected based on hydraulic

needs and spatial constraints; however, focused geotechnical investigations regarding site suitability have

not been conducted at this time. Geotechnical investigations are necessary for the design of any structure

that impounds water and will need to be conducted prior to detailed design.

Rock Weir

Although not commonly used for this purpose, large rock structures placed within the channel can create

backwater conditions that form pools upstream. Rocks can be placed in various configurations such as U-

shaped weirs or cross-vanes, which funnel water toward the middle or one side of the channel. At low flows

water would be concentrated into one or more narrow flow paths through the rock structure to maintain fish

passage. The reader should note that the increases in upstream water surface elevations are relatively small


19


and have relatively little effect during large flows. Figure 16 shows two examples of in-channel rock struc-

tures that pool water upstream.

Figure 16. Examples of in-channel rock structures that could pool water upstream

Left: Big Springs 3 Diversion Enhancement Project (image and information obtained from http://www.usbr.gov/river/pahsimeroi.html).

Right: image from USBR and obtained from an online presentation by NOAA titled “Fish Passage Design for Boulder Weirs”

(http://www.cbfwa.org/Committees/FSOC/meetings/2010_0913/PresentationFSOC_2010_BoulderWeirs.pdf).

Flashboard Weir

Flashboard weirs have long been used to impound and divert water, providing a simple and adjustable way

to control flows. Upstream water levels are manually adjusted in board-size increments by adding or remov-

ing boards from slotted sections. Although simple and cost-effective, the need for manual adjustments can

be a problem when changes need to be made quickly; for example, if boards need to be removed on short

notice prior to a flood event or large flow release. In addition, flashboard weirs often create fish barriers and

necessitate the addition of a side channel or fish ladder. Figure 17 shows an example of a flashboard weir.

Figure 17. Example of a flashboard weir used to impound water on a stream

(Images obtained from: http://www.oart.org.uk/projects/morph-buxted.htm)


20


Inflatable Rubber Dam

Inflatable rubber dams are used at numerous locations by Alameda County Water District in lower Alameda

Creek and other sites throughout the Bay Area. They are able to deflate and collapse to a low profile when

not in use. Operators can inflate or deflate the bladder to control water levels; however, these dams do not

provide precise controls and water releases cannot be controlled laterally across the dam. A level concrete

foundation is typically required within the channel and on the channel bank. A side channel or fish ladder is

likely necessary to allow for fish passage during periods when the dam is inflated. Figure 17 shows an

example of an inflatable dam from an installation on Alameda Creek.

Figure 18. Example of an inflatable rubber dam

Lower Alameda Creek diversion for Alameda County Water District; the dam spans the entire channel, which is roughly 400 feet wide.

(Images obtained from: http://mrbill.homeip.net/albums/mt_hamilton.2011.04.16/pages/page_64.html)

Pneumatic Gates

Pneumatically actuated gates, such as the ones manufactured by Obermeyer Hydro, can be raised to control

upstream water levels when needed, and collapsed to a low profile when not in use. The gates can be

installed in modular sections to allow operators to laterally adjust gate heights and release flow at various

locations along the structure. Substantial channel disturbance, including concrete foundations and the

pneumatic gates (which cannot easily be removed during low flow periods), are necessary. A side channel or

fish ladder is likely necessary to allow for fish passage during periods when the gates are raised.

Figure 19. Examples of pneumatically actuated (Obermeyer) gates

(Images from Obermeyer Hydro, information can be obtained at http://www.obermeyerhydro.com/)


21


Low-Head Concrete Diversion Dam

Low-head concrete dams have been used for river and stream diversions for many years. According to USBR

(1987), a low concrete gravity dam can be founded on alluvial foundations if adequate cutoffs are provided.

Therefore, this option is considered viable for conceptual design purposes; however, additional geotechnical

investigations will need to be conducted as part of the detailed design to confirm site suitability. Figure 20

shows two examples of low-head concrete diversion dams.

Figure 20. Examples of low-head concrete diversion dams

Left: Youngs Creek hydropower facility constructed for Snohomish County Public Utility District in 2011 (photo used with permission).

Right: Kyburz Diversion Dam and fish bypass (left in photo) owned by the El Dorado Irrigation District (photo used with permission).

Historically, low-head concrete diversion dams have created barriers to fish; however, under current regula-

tions, a side channel or fish ladder would typically be required. Concrete dams can be used in conjunction

with weirs, gates, and flumes to provide precise controls of water surface elevations and diversion flow rates,

as well as bypass flows and overflow rates. Natural earth materials, such as boulders or riprap, can also be

incorporated into the dam surface to visually blend into the streambed and riparian environment.

4.2.2 Options Screening

The options described in the previous section cover a wide range of structures with the potential for numer-

ous design variations. Selection of the best option will depend on site suitability, operational flexibility,

potential impacts to fish and riparian habitat, and cost. Table 3 provides a general summary of some of

these key design considerations for each type of hydraulic grade control structure.

Table 3. Comparison of Hydraulic Grade Control Options

Type

Design considerations

Sizing and spatial constraints Operational flexibility Fish habitat/riparian impacts Cost

Rock weir • Typically used for small to medium streams

• Rock placed in channel to create pool, but height is limited and upstream water surface increases are relatively small

• Highly scalable; size and number of rocks can be adjusted to channel dimensions

• Passive structure that does not provide precise control of water levels

• Minimal head difference provides limited diversion capacity

• Natural materials reduce visual impacts

• Does not require large founda-tions or cutoff walls

• Rock structures are typically low head and placed such that water is funneled into a narrow channel that is fish-passable at low flows

Low to moderate


22


Table 3. Comparison of Hydraulic Grade Control Options

Type


Sizing and spatial constraints Operational flexibility Fish habitat/riparian impacts Cost

Flashboard weirs

• Typically used for small to medium streams with relatively low head differentials

• Flashboard weirs are installed in slotted segments allowing the structure to span wide channels if necessary

• Upstream water levels are manually adjusted in board-size increments

• Manual removal can be difficult under significant head pressure and could require equipment

• Boards can be difficult to seal and often result in leakage

• Requires foundation and frames to hold flashboards

• A fish passage structure is likely necessary if flashboards cross entire channel

Moderate

Inflatable rubber dam

• Manufactured in various sizes, but most often used in medium to large streams

• Upstream water depths can range from a few feet to greater than 10 feet

• Operators have some/limited adjustment of water levels by inflating/deflating the bladder

• Overflow discharge location cannot be adjusted laterally across channel

• Bladder can be deflated or removed to minimize obstruction when not in use

• Requires concrete foundation

• Must be deflated and/or removed when not in use

• Fish passage structure is required for periods when dam is inflated

• Fish passage structure may also be needed to bypass foundation given the potential for very low seasonal flows

High

Pneumatic gates

• Gate systems are modular, which allows for installations of various widths

• Typically used for medium to large streams that are several hundred feet wide

• Upstream water depths can range from a few feet to greater than 10 feet

• Operator can control heights of specific gate sections to vary ponded water levels

• Gates can also be adjusted laterally to direct overflow dis-charges to one side of channel or the other

• Bladders can be deflated and gates can be lowered to low profile to minimize obstruction when not in use

• Requires concrete foundation and substantial channel disturbance for installation

• A fish passage structure is likely necessary for periods when gates are up

• Fish passage structure may also be needed to bypass foundation given the potential for very low seasonal flows

Very high

Low-head concrete diversion dam

• Diversion dams can be construct-ed with concrete, providing a high degree of flexibility in terms of size, shape, and configuration

• Can be engineered to provide precise controls of water surface elevations and diversion flow rate

• Often used in conjunction with weirs, gates, and/or flumes

• Likely to be constructed with concrete foundation, sill, and cutoff walls; however, natural features such as rocks could be incorporated into the design

• Cross-channel structure likely to be a fish barrier, thus requiring a fish passage structure

Moderate to very high

Based on the above design considerations, a low-head concrete diversion dam was selected as the pre-

ferred option, given the flexibility of the design, low operation and maintenance, potential for incorporating

natural rock features, and moderate cost. The other options were eliminated based on the following consid-

erations:

• Rock weir: Although a rock weir would be a good option from a cost and fish habitat standpoint, it

provides only a minimal head increase for the upstream diversion intake. More importantly, it would not

allow for precise control and measurement of low flows for controlled bypass.

• Flashboard weirs: Although flashboard weirs are highly adjustable, special equipment is often required

to remove boards due to hydraulic pressure head and safety concerns. Such equipment could require

additional infrastructure for access.


23


• Inflatable dam: Although an inflatable dam can be deflated or removed when it is not needed, the

construction cost and long-term maintenance costs would be substantial. Installation of the concrete

foundation would result in substantial bed and bank disturbance, and unlike a concrete diversion dam,

rocks cannot be incorporated into the design to provide a more natural riparian appearance.

• Pneumatic gates: Although pneumatic gates provide operational flexibility, the construction cost and

long-term maintenance costs would be substantial. Installation of the concrete foundation would result

in substantial bed and bank disturbance, and unlike a concrete diversion dam, rocks cannot be incorpo-

rated into the design to provide a more natural riparian appearance.

4.3 Fish Passage or Bypass Structures

As discussed in the previous section, a cross-channel hydraulic grade control structure such as a low-head

concrete diversion dam would require provisions for fish passage. The following subsections describe some

potential options for fish passage followed by a discussion of sizing and feasibility.

4.3.1 Design Options

Numerous options are available for fish passage structures. A useful summary of options is presented in

Anadromous Salmonids Passage Facility Design, National Marine Fisheries Service, Northwest Region, 2011

(NMFS, 2011) and by Thorncraft and Harris (2000). Three different types are described below, ranging from

simple to complex.

Bypass Channel

Bypass channels are low-gradient earthen or rocky channels that mimic the structure of natural streams to

allow for fish passage. Bypass channels typically include bends and/or meanders to decrease the gradient

and maintain sufficient flow depth for fish passage. Figure 21 shows two examples of rock-lined fish bypass

channels.

Figure 21. Examples of fish bypass channels

(Images obtained from http://www.co.pierce.wa.us/index.aspx?NID=1850 and

http://www.biotactic.com/Northern_Pike_Telemetry_and_Passage.htm)

Rock Fishway

Rock fishways are similar to rock-lined bypass channels, but are typically shorter with a more “ramped” (i.e.,

steeper) gradient. According to Thorncraft and Harris (2000), rock-ramp fishways were developed as a low-


24


cost alternative to more formally engineered fishway designs, and are particularly well-suited for low barriers.

Figure 22 shows a conceptual sketch of a rock ramp fishway from Thorncraft and Harris (2000).

Figure 22. Conceptual layout of a partial-width rock ramp fishway

(Image obtained from Thorncraft and Harris, 2000)

Vertical-Slot Fish Ladder

Vertical-slot fish ladders are widely used to provide fish passage for salmon and steelhead (NMFS, 2008).

These structures consist of a rectangular concrete channel with a series of narrow vertical slots and pools

(see Figure 23). Structures can be designed to achieve specific velocities depending on the fish species of

interest and can operate under variable headwater and tailwater levels. Figure 24 shows a conceptual

sketch of a vertical-slot fish ladder from Thorncraft and Harris (2000).

(a) 3-dimensional view (b) plan view

Figure 23. Sketch of a vertical-slot fish ladder (NMFS, 2011)


25


Figure 24. Example of vertical-slot fish ladder

(Image obtained from Thorncraft and Harris, 2000)

4.3.2 Options Screening

Selection of the best option for fish passage or bypass depends on spatial constraints, operational flexibility,

fish passage/habitat benefits, and cost. Table 4 provides a general summary of some of these key design

considerations for each type of fish passage or bypass structure.

Table 4. Comparison of Fish Passage and Bypass Options

Type


Sizing and spatial constraints Operational flexibility Fish passage benefits Cost

Bypass channel • Requires space outside the main channel to create a low-gradient bypass channel alignment

• Bypass flows of 40 cfs could require a channel that is roughly 1 to 2 feet deep and10 to 20 feet wide

• Bypass flow rates would need to be controlled using a secondary control structure

• Hydraulic conditions are highly variable with bypass rates

• May require maintenance for erosion and/or sedimentation

• Intended to mimic the structure and function of natural streams

Moderate

Rock fishway • Requires space downstream of dam to accommodate ramp-down at 20:1 slope

• Bypass flows of 40 cfs could require a channel that is roughly 1 to 2 feet deep and 8 to 12 feet wide


• Hydraulic conditions are highly variable with bypass rates

• Large fish may require relatively high bypass flows to be passable

• Not widely used

Moderate


26


Table 4. Comparison of Fish Passage and Bypass Options

Type


Sizing and spatial constraints Operational flexibility Fish passage benefits Cost

Vertical-slot fish ladder

• Requires space along one of the dam abutments and in the chan-nel just downstream of the dam

• Can accommodate a wide range of dam heights


• Can be designed to accommodate a wide range of bypass flows

• Can be designed to accommodate a wide range of headwater and tailwater elevations

• Design has been used widely and has proved to be effective

• Structure can be designed to meet specific flow conditions (i.e., velocities) for the fish species of interest

High

Based on the above design considerations, a bypass channel, rock fishway, or similar structure was selected

as the preferred option. Although a vertical-slot fish ladder provides some advantages in terms of operation-

al flexibility and performance reliability, the cost is typically very high due to the need for intricate concrete

form work (NMFS, 2008). Furthermore, a rock-lined bypass channel or fishway would help to preserve the

natural riparian conditions of the stream.

4.3.3 Provision for Controlled Bypass Flows

Zone 7 requested that the Arroyo del Valle diver-

sion system provide for controlled bypass flows of

1 to 40 cfs in winter/spring seasons, and 6 to 15

cfs in summer/fall seasons (see Section 3.1). This

can be accomplished by installing a flow meas-

urement device at the entrance to the fish bypass

channel, which would allow operators to estimate

bypass flow rates and adjust diversion rates

accordingly.

One option would be to install a cutthroat flume

(see Figure 25). A flume is preferable to a weir or

orifice because it requires less vertical drop and

has a free surface, thus making it more amenable

to fish passage. A cutthroat flume may be more

suitable than other flumes because it has a flat

floor and functions well under both free flow and

submerged flow conditions. Furthermore, cutthroat

flumes are simple to construct using concrete

forms, or can be obtained in various prefabricated

sizes.

One disadvantage is that cutthroat flumes are typically not as accurate as other flow measurement flumes

unless entrance conditions are carefully controlled. Nevertheless, cutthroat flumes do offer design flexibility

in that they can be scaled to the desired flow range. In addition, multiple flumes could be installed in either

nested or parallel configurations to increase the depth-to-flow ratios for improved accuracy.

Figure 25. Dimensions of a cutthroat flume

A rectangular cutthroat flume has a flat floor and no throat length; the

inlet converges at a 3:1 ratio and the outlet diverges at a 6:1 ratio.


27


Section 5: Evaluation of Conceptual Design Alternatives BC developed conceptual design alternatives for the diversion and conveyance of water from Arroyo del Valle

to Lake A based on the design requirements described in Section 3 and the results of the options investiga-

tion in Section 4. Section 5.1 describes each of the conceptual design alternatives. Section 5.2 evaluates

and compares the alternatives based on weighted design criteria.

5.1 Formulation of Alternatives

As discussed at the beginning of Section 4, complete design alternatives consist of an intake with fish

exclusion, hydraulic grade control structure, fish bypass structure, diverted flow control structure, and

conduit into Lake A. Each intake’s fish exclusion mechanism is the key differentiating feature among the

alternatives because that component is the primary driver for the size, flow capacity, and construction and

maintenance costs of the diversion system. Selected options for the remaining components will be common

to all alternatives, and are described below:

• Hydraulic grade control (i.e., diversion dam): As discussed in Section 4.2.2, BC selected a low-head

concrete diversion dam as the preferred method for hydraulic grade control given the flexibility of the

design, low maintenance, potential for incorporating natural rock features, and moderate cost. Concep-

tual design parameters were determined as follows:

− The length of the dam crest is 140 feet (the approximate width of the channel minus estimated

width of the bypass fishway).

− The height of the dam crest varies depending on the alternative; it is calculated based on the head

required to pass the peak diversion capacity plus the head required to discharge minimum flows

through the fish bypass.

• Fish bypass: As discussed in Section 4.3.2, BC selected a bypass channel/rock fishway at the preferred

method for providing fish passage because it preserves the natural riparian conditions of the stream.

Conceptual design parameters were determined as follows:

− The channel/fishway is roughly 2 feet deep and 10 feet wide, assuming a 2 percent slope on the

channel.

− Two cutthroat flumes installed near the entrance to the channel/fishway would measure bypass

flows. A small flume with a throat width of 2 feet is used to pass up to approximately 8 cfs with 1

foot of head. A larger, parallel flume with a throat width of 6 feet is used in combination with the first

flume to pass a total flow of approximately 40 cfs with 1.2 feet of head.

• Diverted flow control structure and conduit into Lake A: These components will be discussed as part of

the preferred design alternative (see Section 6).

Building on these common elements, four different conceptual design alternatives were developed around

the following intake configurations:

1. 100-by-200-foot infiltration bed

2. 400-foot linear screen

3. Two 14-foot-base conical screens

4. Nine 14-foot-base conical screens

While Alternatives 3 and 4 use the same screen option, both were included to provide a comparison of

diversion rates at two different sizes with different impacts to the creek bank. The following sections de-

scribe each of these alternatives in more detail.


28


5.1.1 Alternative 1: Infiltration Bed

For Alternative 1, a 100-foot deep (i.e., extending in the horizontal direction perpendicular to the stream

bank) by 200-foot-long gravel infiltration bed is constructed on the north bank of Arroyo del Valle. The

infiltration bed consists of approximately 4 feet of gravel with forty 100-foot perforated horizontal drain pipes

(laterals) buried at an average depth of 3 feet. Figure 26 shows a schematic sketch of Alternative 1.

Figure 26. Schematic sketch of Alternative 1 (plan view)

Water impounded behind the diversion dam will create a pool that inundates the infiltration bed. When the

flow control gate is open, impounded water will be allowed to infiltrate through the gravel and into the

drainage laterals, which are sloped away from the arroyo toward a manifold. The manifold then connects to a

main conduit that drains by gravity to Lake A.

Key design parameters for Alternative 1 include the following:

• The lowest elevation of the surface of the infiltration bed is set at an elevation of 434.0 feet, approxi-

mately 1 foot above the channel bottom to allow for sedimentation.

• The approach velocity at the surface of the gravel bed is estimated to be 0.023 ft/s at 500 cfs, which is

well below the CDFW fish screening criterion of 0.33 ft/s.

• Assuming the gravel is capable of infiltrating water at a rate of 30,000 gallons per day per square foot

(gpd/ft2), or 0.046 ft/s (i.e., the hydraulic conductivity of the gravel), the infiltration bed could pass 500

cfs at an estimated depth of 0.64 foot (see equation presented in Section 4.1.2.1). Based on this result,

the head required to reach the 500 cfs peak diversion capacity is conservatively assumed to be 1 foot.

• The invert elevations of the bypass cutthroat flumes are set at an elevation of 435.0 feet; this allows

operators to reach maximum diversion capacity without bypassing any flows and thus providing the

greatest operational flexibility.

• The dual cutthroat flumes described previously require 1.2 feet of head to discharge 40 cfs into the fish

bypass; therefore, the minimum elevation of the dam crest is calculated to be 436.2 feet.

• A flow control gate is installed on the outlet conduit to Lake A to control diversion rates.

• Periodic maintenance of the gravel bed will be required to prevent accumulation of fine sediments and

clogging the drainage laterals, which could reduce system capacity over time.

BYPASS FLOW

ROCK FISHWAY

DIVERTED FLOW

GRAVEL INFILTRATION BED

100 FT x 200 FT

ARROYO DEL

VALLE FLOWOVERFLOW

PERFORATED PIPE LATERALS x 40

GRAVEL BED AT 434.0 FT ELEVATION

DAM CREST ELEVATION AT 436.2 FT

2 CUTTHROAT FLUMES

AT 435.0 FT ELEVATION

2-FT, 6-FT THROAT WIDTHS

CHANNEL BOTTOM AT APPROX.

433.0 FT ELEVATION

Not to scale

FLOW ONTO BED

(INFILTRATED)

FLOW CONTROL GATE


29


• Final design must include provisions for maintenance access and safety equipment in accordance with

applicable standards.

5.1.2 Alternative 2: Linear Screen

For Alternative 2, a linear fish screen and housing structure is installed on the north bank of Arroyo del Valle

with a total of 400 linear feet of screen panels inclined at an angle of 45 degrees. Figure 26 shows a

schematic sketch of the Alternative 2.


The diversion dam will impound water to provide up to 3 feet of depth on the screens. When the flow control

gate is open, water will flow through the screen panels into a manifold chamber, then transition to a main

conduit that flows by gravity to Lake A.


• The screens’ bottoms are set at an elevation of 434.0 feet, approximately 1 foot above the channel

bottom to allow for sedimentation.

• Screens were sized based on the CDFW approach velocity criterion of 0.33 ft/s and a safety factor of 1.1

as follows:

�0.33#$/&1.1 ( )√2+,3#$-,400#$- = 509#$1/&

• The invert elevations of the bypass cutthroat flumes are set at an elevation of 437.0 feet; this configura-

tion allows operators to reach maximum diversion capacity without bypassing any flows and thus provid-

ing the greatest operational flexibility.



• A flow control gate installed on the outlet conduit to Lake A controls diversion rates.

• An automated screen cleaning mechanism must be included as part of the detailed design to allow the

use of the 0.33 ft/s approach velocity criterion. Operation of the automated cleaning system will require

power at the site.

BYPASS FLOW

ROCK FISHWAY

DIVERTED FLOW

ARROYO DEL

VALLE FLOW

OVERFLOW

BOTTOM OF SCREEN

AT 434.0 FT

ELEVATION

DAM ELEVATION AT 438.2 FT


433.0 FT ELEVATION

Not to scale

SCREENED FLOW

SCREEN PANELS (400 LINEAR FEET)

INCLINED AT 45o ANGLE

FLOW CONTROL GATE2 CUTTHROAT FLUMES




30


• A trash rack or series of bollards and a debris boom are installed to protect the screens from trash and

floating debris.



5.1.3 Alternative 3: Two Cone Screens

For Alternative 3, two conical fish screens and housing are installed on the north bank of Arroyo del Valle.

The screens have a 14-foot base width and a maximum discharge of 60 cfs per screen (assuming a 0.33

ft/s approach velocity). Figure 28 shows a schematic sketch of Alternative 3.


The diversion dam will impound water to create up to 4 feet of depth over the screens. When the flow control

gate is open, water will flow through both screens into a lateral pipe that flows to a header pipe or manifold

chamber, and then will transition to a main conduit that flows by gravity to Lake A.


• The bottoms of the screens are set at an elevation of 434.0 feet, approximately 1 foot above the chan-

nel bottom to allow for sedimentation.

• Screens were sized based on the Intake Screens, Inc. specification, which assumes an approach velocity

criterion of 0.33 ft/s, consistent with CDFW requirements.







• Brushed cone screens, such as the ones manufactured by Intake Screens, Inc., include automated

screen cleaning systems, allowing for the use of the 0.33 ft/s approach velocity criterion. Operation of

the automated cleaning system will require power at the site.

BYPASS

FLOW

ROCK FISHWAY

DIVERTED

FLOW2 x 14-FT CONE SCREENS

ARROYO DEL

VALLE FLOW

OVERFLOW

BOTTOM OF SCREENS AT

434.0 FT ELEVATION



433.0 FT ELEVATION

Not to scale

SCREENED

FLOW





31



floating debris.



5.1.4 Alternative 4: Nine Cone Screens

For Alternative 4, nine conical fish screens and housing are installed on the north bank of Arroyo del Valle.

The screens have a 14-foot base width and a maximum discharge of 60 cfs per screen (assuming a 0.33

ft/s approach velocity). Figure 29 shows a schematic sketch of Alternative 4.


The diversion dam will impound water to create up to 4 feet of depth over the screens. When the flow control

gate is open, water will flow through all nine screens into a lateral pipe that flows to a header pipe or mani-

fold chamber, then transitions to a main conduit that flows by gravity to Lake A.


• The bottoms of the screens are set at an elevation of 434.0 feet, approximately 1 foot above the chan-

nel bottom to allow for sedimentation.

• Screens were sized based on the Intake Screens, Inc. specification, which assumes an approach velocity

criterion of 0.33 ft/s, consistent with CDFW requirements.







• Brushed cone screens, such as the ones manufactured by Intake Screens, Inc., include automated

screen cleaning systems, allowing for the use of the 0.33 ft/s approach velocity criterion. Operation of

the automated cleaning system will require power at the site.

BYPASS

FLOW

ROCK FISHWAY

9 x 14-FT CONE SCREENS

ARROYO DEL

VALLE FLOW

OVERFLOW

BOTTOM OF SCREENS AT

434.0 FT ELEVATION



433.0 FT ELEVATION

Not to scale

SCREENED FLOW

DIVERTED

FLOW





32



floating debris.



5.2 Evaluation of Alternatives

BC compared each of the conceptual design alternatives using a design criteria matrix and a simple

weighted rating system as described in the USACE Institute for Water Resources’ Planning Manual (Yoe and

Orth, 1996). This method allocates point values to selected evaluation criteria, and then scores each

alternative relative to those criteria. This method provides a transparent way to assess qualitative as well as

quantitative criteria, while reflecting value judgments. BC defined the evaluation criteria for the Arroyo del

Valle diversion project as follows:

• Achieve diversion capacity: The proposed diversion system should divert the first 500 cfs of water from

Arroyo del Valle into the Chain of Lakes. In other words, the proposed diversion system should have

enough capacity to divert 500 cfs without letting any flow downstream. Note that the requirement to “di-

vert up to 500 cfs during flood releases greater than 1,000 cfs from Del Valle reservoir, without any

dams or other obstructions in place” was determined to be infeasible because sufficient head depth

could not be maintained across a large diversion structure without hydraulic grade control in place (see

Section 4.1.1.2). Therefore, it was not considered necessary to meet this “diversion capacity” require-

ment.

• Provide operational flexibility: Given the uncertainty surrounding future operating scenarios, operational

flexibility will be important for efficient water management. Therefore, the proposed diversion system

should include an adjustable diversion control structure that will allow operators to divert as much water

as possible while discharging only the minimum required bypass flows downstream. More specifically,

the proposed diversion system should:

− Provide the ability to control diverted flow rates in increments of 20 to 25 cfs up to the first 250 cfs

− Provide the ability to control diverted flow rates in increments of 50 to 100 cfs between 250 and

500 cfs

− Provide the ability to control bypass up to 40 cfs

• Meet fish screening and fish passage requirements: The proposed diversion system should avoid

impacts to fish. CDFW requirements include:

− The intake structure for the proposed diversion system should meet CDFW fish screening criteria by

not exceeding approach velocities of 0.33 ft/s.

− A fish bypass structure should be included to provide passage past the proposed diversion dam.

• Minimize potential for increased flood risk: In TM 1 (February 2014), BC found that “an in-channel

diversion with an obstruction as high as 10 feet at the upstream end of Lake A [approximately 1,100

feet downstream of Vallecitos Road] would increase water surface elevations in the vicinity immediately

upstream of the diversion; however, those increases diminish rapidly and are negligible beyond Valleci-

tos Avenue.” Because all of the proposed dam heights are less than 10 feet, none of the proposed alter-

natives are expected to cause substantial increases in flood risk. Nevertheless, low dam heights are

considered preferable from a relative risk standpoint. Therefore, the alternatives were evaluated based

on their required dam heights.


33


• Minimize disturbance and visual impacts: The proposed diversion system should minimize potential

disturbance areas along the channel bed and banks to avoid impacts to riparian areas. Alternatives that

preserve the riparian nature of the area are preferred over ones with larger, more conspicuous features.

• Minimize capital and long-term maintenance costs: The preferred alternative should be cost-effective in

terms of construction cost and long-term O&M costs.

BC evaluated each conceptual design alternative with respect to the above design criteria, and then as-

signed ratings based on the weighted scoring system explained in Table 5. The results of the evaluations are

presented in Table 6, and the composite score for each alternative is graphed in Figure 30.

Table 5. Ratings for Evaluation of Design Criteria

Category Criterion Points available

(out of 100)

Scoring

Rating choices Percentage of points

awarded

Diversion criteria Achieve diversion capacity 20 Yes 100

No 0

Provide operational flexibility 20 Yes 100

No 0

Meet fish screening and fish passage requirements

15 Yes 100

No 0

Additional

considerations

Minimize potential for increased flood risk—based on dam height

15 Less than 4 feet 100

Less than 5 feet 75

Less than 6 feet 50

Less than 7 feet 25

Minimize disturbance and visual impacts 15 Excellent 100

Good 67

Moderate 33

Poor 0

Minimize capital and long-term maintenance costs

15 Excellent 100

Good 67

Moderate 33

Poor 0


34


Table 6. Evaluation of Design Alternatives based on Design Criteria

Alternative Evaluation criteria

Diversion criteria Additional considerations

No. Description

Achieve

diversion

capacity

(20 points)

Provide

operational

flexibility

(20 points)

Meet fish

screening and

fish passage

requirements

(15 points)

Minimize

potential for

increased

flood risk

(15 points)

Minimize disturbance

and visual impacts

(15 points)

Minimize capital and

long-term maintenance costs

(15 points)

1 Infiltration bed

Yes Yes Yes Dam height = 3.2 feet

Rating: Good

• Approximately 200 linear feet of bank would be disturbed for construction of the infiltration bed

• Graded to match surrounding topography; gravel bed consists of natural earth materials

• Visual impacts less than more intrustive screening structures

• Does not require trash rack, bollards, or debris boom

Rating: Good

• Low construction cost relative to other alternatives

• Would require annual cleaning to remove debris and plant growth

• Would require periodic maintenance due to potential for fine sediment to accumulate and cause clogging

2 Linear screen


Rating: Poor

• Approximately 400 linear feet of bank would be disturbed for construction of the screen system

• Significant bank disturbance and visual impact

• Might require extensive fencing to avoid safety issues and/or vandalism

• Requires trash rack, bollards, and debris boom in streambed

Rating: Poor

• High construction cost relative to other alternatives

• Screens and cleaning system would require significant operation and maintenance

• Would require periodic inspection of and maintenance for mechanical, electrical, and control equipment

• Screen, trash rack, and debris boom would require periodic cleaning


35


Table 6. Evaluation of Design Alternatives based on Design Criteria

Alternative Evaluation criteria

Diversion criteria Additional considerations

No. Description

Achieve

diversion

capacity

(20 points)

Provide

operational

flexibility

(20 points)

Meet fish

screening and

fish passage

requirements

(15 points)

Minimize

potential for

increased

flood risk

(15 points)

Minimize disturbance

and visual impacts

(15 points)

Minimize capital and

long-term maintenance costs

(15 points)

3 Two conical screens

No Yes Yes Dam height = 6.2 feet

Rating: Good


• Somewhat reduced bed/bank and visual impact



Rating: Moderate

• Moderate to high construction cost relative to other alternatives




4 Nine conical screens


Rating: Moderate


• Significant bank disturbance and visual impact



Rating: Poor

• High construction cost relative to other alternatives





36


Figure 30. Overall ratings based on weighted evaluation criteria

The results shown in Figure 30 indicate that Alternative 1 is the preferred alternative based on the weighted

scoring system described in Table 5 and the evaluation results summarized in Table 6. Alternative 1 also has

another distinct advantage over the other options, in that the diversion capacity is linearly proportional to the

water depth (or head) above the bed surface (see equation in Section 4.1.2.1). Therefore, as flow rates and

water surface elevations increase in Arroyo del Valle, additional discharge capacity beyond 500 cfs is

available because the approach velocity is well below the CDFW criteria. In contrast, the linear and cone

screen options are limited to a maximum diversion rate of 500 cfs independent of any increase in head

during higher flow events because they are already sized at the approach velocity limit.

Section 6: Recommendations for Preferred Alternative For diverting water from Arroyo del Valle into the Chain of Lakes, BC selected Alternative 1, the infiltration

bed alternative, as the preferred alternative, based on Section 5.2 comparison. Some of the key advantages

of this method include:

• High diversion rates at low hydraulic head

• Lower hydraulic grade control/dam height

• Relatively minor visual impacts

• Relatively low construction cost

• No mechanical or electrical components present in the streambed

• Substantially lower O&M costs

• Significantly reduced potential for safety and vandalism issues

Some of the key disadvantages include:

• Potential for fine sediments to permeate the gravel layer and result in clogging

60

50

63

90

0.0 20.0 40.0 60.0 80.0 100.0

Alternative 4(9 Cone Screens)

Alternative 3(2 Cone Screens)

Alternative 2(Linear Screen)

Alternative 1(Infiltration Bed)


37


• Sediment, debris, and vegetative growth on top of the gravel bed could reduce permeability requiring

annual maintenance

• Bed covers a large area

These disadvantages are considered to be less significant than those for the other alternatives. Annual

maintenance to remove sediment, debris, and vegetative growth is fairly simple and straightforward. In

addition, even though the bed covers a large area, it will consist of natural earth materials similar in color

and texture to those that exist in the streambed and the bed can be screened with native vegetation around

the perimeter.

Building on the concept presented in Section 5.1.1, BC developed a site layout and additional conveyance

features (Section 6.1), performed preliminary sizing of project elements and prepared a concept-level cost

estimate (Section 6.2), and investigated the potential for moving the diversion structure downstream

(Section 6.3). These sections are followed by recommendations for further study (Section 6.4).

6.1 Conceptual Layout and Conveyance into Lake A

A conceptual site layout of the proposed diversion system with locations of major features is provided in

Figure A-1 (Attachment A). As described previously, the infiltration bed contains forty 100-foot lateral pipes

draining into a header pipe/manifold that then joins into a main conduit. Additional features are specified for

conveyance into Lake A as follows:

• The main conduit begins as an 84-inch-diameter

pipeline, then discharges through an 8-by-8-foot

headgate into an open channel. The headgate

functions as a diversion control structure and can

be raised or lowered to different levels to control

diversion discharge rates.

• From the headgate water discharges into a 10-

foot-wide by 12-foot-deep concrete rectangular

channel, consisting of four sections:

− Stilling basin: dissipates energy and controls

turbulent discharges from the headgate

− Tranquil flow section: develops suitable ap-

proach conditions for the Parshall flume

− Parshall flume section: for flow measurement

(see Figure 31)

− Downstream transition: leads to riprap chute

• The riprap chute downstream of the concrete

channel is a trapezoidal riprap-lined channel that

slopes down steeply into Lake A. A riprap pad con-

tinues below the typical water surface elevation of

412 feet.

6.2 Concept-Level Plans and Cost Estimate

BC developed the conceptual design and performed preliminary sizing calculations to estimate dimensions

and quantities for use in developing a concept-level cost estimate. Figure A-2 (Attachment A) shows a

Figure 31. Dimensional sketch of Parshall flume

(FOA, 1993)


38


conceptual design plan and Figure A-3 (Attachment A) shows three sections. Conceptual design features and

assumptions (in addition to those discussed in previous sections) are described below:

• The gravel infiltration bed top surface will slope down toward the Arroyo del Valle channel at 0.5 percent

to direct fish toward the channel during times when water levels drop.

• A clay cutoff wall is installed along the edge of the infiltration bed closest to the stream to prevent

horizontal subsurface flow from the channel from draining into the laterals at elevations less than 434.0

feet.

• A geotextile filter fabric should be used to limit the transport of fine sediments and reduce clogging.

• The infiltration bed transitions back to existing grade at a 2:1 slope; use erosion control practices on

exposed slopes and revegetate to stabilize soils.

• Electrical power is required for the sluice gate, which will need to be motorized due to the size.

• A flow meter is installed at the Parshall flume to record diversion rates and potentially provide feedback

to modulate the control gate to achieve the required discharge rate.

• For costing purposes, assume that the low-head dam is formed with a concrete core (e.g., crest, base,

and cutoff walls) and 4:1 sloped rock fill at the upstream and downstream faces.

• Assume 6-foot chain-link fencing installed around the open channel for safety.

• Lateral, manifold, and main pipes were sized using Manning’s equation (see summary of pipe sizes,

Table 7).

Table 7. Summary of Pipe Sizing

Component Material Slope

(percent)

Sizing

Number Diameter

(inches)

Total length

(ft)

Laterals PVC 1 40 12 1,200

PVC 1 40 18 2,800

Manifold PVC 1 2 36 60

RCP 1 2 48 80

RCP 1 2 60 60

Main RCP 2 1 84 30

PVC: polyvinyl chloride; RCP: reinforced concrete pipe. Note that high density polyethylene pipe might be a

suitable substitute for PVC.

Table B-1 (Attachment B) summarizes the concept-level cost estimates for Alternative 1. The total estimated

construction cost is $3.3 million.

6.3 Potential Downstream Location

A substantial ephemeral tributary stream enters Arroyo del Valle about 2,450 feet upstream of Isabel

Avenue. This tributary drains the watershed located south of Lake A and west of Del Valle Reservoir. Zone 7

staff have previously expressed interest in the potential to capture storm flows from this tributary after they

enter Arroyo del Valle and have requested that the diversion be located “as close to Isabel Avenue/[Highway]

84 as possible” (see Section 3.3).

BC investigated the potential for moving the Arroyo del Valle diversion downstream toward Isabel Avenue by

taking the streambed profile and subtracting the head differential needed to convey water and measure


39


discharge through the diversion system. This differential was conservatively estimated to be approximately 9

feet. The elevation profile was then plotted with the future anticipated average water level in Lake A of 412

feet mean sea level (personal communication between Andrew Kopania, EMKO Environmental, Inc., and

Colleen Winey, Zone 7) to identify where the two lines crossed (see Figure 32). Using this comparison, BC

estimated that diversion locations closer than about 2,970 feet upstream of Isabel Avenue may not provide

enough elevation difference to meet the head requirements.

The results of this assessment indicate that the diversion structure could not be located far enough down-

stream to capture the tributary inflow without substantial modifications to the diversion system to reduce the

hydraulic profile or increase the head behind the grade control structure.

Figure 32. Comparison of required diversion head differential with Lake A water surface

390

400

410

420

430

440

450

460

19000 20000 21000 22000 23000 24000 25000 26000

ELE

VAT

ION

(F

T)

CENTERLINE STATION (FT)

Existing Channel Bottom

Channel minus 9 feet

Lake A Water Surface

Vallecitos Rd Bridge

Isabel Ave Bridge

2,970 FT

ISA

BE

L A

VE

VA

LLE

CIT

OS

RD

TR

IBU

TA

RY

IN

FLO

W

CU

RR

EN

TLO

CA

TIO

N


40


6.4 Recommendations for Further Study

Detailed analyses of project components were beyond the scope of this study; however, the following studies

should be considered for supporting final design:

• Detailed hydraulic analyses of conduits and open channels, including analyses of pressurized flow and

minor losses, peak flow velocities, rapidly varied flow transitions in the rectangular channel, and en-

trance/submergence conditions related to flow measurement devices

• Geotechnical investigations and dam foundation design

• Stable riprap sizing for rock-lined chute and at the dam face

• Gravel filter design and considerations for reverse flow/flushing system


41


References Alameda County Community Development Agency (ACCDA), June 2013. Letter from James Gifford to Ron Wilson titled

“Completeness Review of Application to Amend Surface Mining Permit and Reclamation Plan No. 23.”

California Department of Fish and Wildlife, Fish Screening Criteria: http://www.dfg.ca.gov/fish/Resources/Projects/Engin/Engin_ScreenCriteria.asp

California Department of Fish and Wildlife (CDFW), January 2014. Verbal communication between Aren Hanson (Brown and Caldwell) and Michelle Lester of CDFW on January 23, 2014.

California Department of Water Resources, 2001. South Bay Aqueduct (Bethany Reservoir and Lake Del Valle) 4/01. http://www.water.ca.gov/pubs/swp/south_bay_aqueduct__lake_del_valle_and_bethany_reservoir_/south-bay-aque.pdf

EMKO Environmental, 2013. Hydrology and Water Quality Analysis Report, Lake A And Lake B Expansion, CEMEX Eliot Quarry – SMP-23, Pleasanton, California. Prepared by: EMKO Environmental, Inc. 551 Lakecrest Drive, El Dorado Hills, California 95762, June 7, 2013.

Food and Agriculture Organization of the United Nations (FAO), 1993. Field measurement of soil erosion and runoff by N. W. Hudson Silsoe Associates, Ampthill, Bedford United Kingdom Rome. http://www.fao.org/docrep/T0848E/T0848E00.htm

Hanson, Dr. Charles H., August 2004. Evaluation of the Potential Historical and Current Occurrence of Steelhead within the Livermore-Amador Valley. Prepared for Zone 7 Water Agency 5997 Parkside Dr. Pleasanton, CA 94588. Prepared by Hanson Environmental, Inc. 132 Cottage Lane Walnut Creek, CA 94595. http://www.alamedacreek.org/reports-educational/pdf/Zone%207%202004.pdf

Kamman Hydrology & Environmental Engineering, Inc. (Kamman), 2009. Phase 2 Technical Report, Sycamore Grove Recovery Program, Sycamore Grove Park, Livermore, California. Prepared for Livermore Area Recreation and Park District 4444 East Avenue, Livermore, California 94550 and the Zone 7 Water Agency 100 North Canyons Parkway, Livermore, California 94551. Edited by Kamman Hydrology & Engineering, Inc., 7 Mt. Lassen Drive, Suite B250, San Rafael, California 94903.

LSA Associates, 2013. “Results of Biological Surveys, CEMEX Eliot Quarry, Alameda County, California.” Letter to Ron Wilson, CEMEX, 5180 Golden Foothills Parkway, El Dorado Hills, California 95762 from Malcolm J. Sproul, LSA Associates, Inc., 157 Park Place Point, Richmond, California, 94801.

National Marine Fisheries Service (NMFS), February 2011. Anadromous Salmonids Passage Facility Design. National Marine Fisheries Service Northwest Region.

San Francisco Estuary Institute (SFEI), February 2013. Alameda Creek Watershed Historical Ecology Study.

Santa Clara Valley Water District, 2011. Kirk Diversion Dam Replacement and Fish Screen Project, Engineer’s Report.

Spinardi Associates (Spinardi), June 2013. Reclamation Plan Amendment, CEMEX SMP-23, 1544 Stanley Boulevard, Pleasanton, California 94566, Unincorporated Alameda County, Submitted to: Alameda County Community Development Agency Neighborhood Preservation and Sustainability Department, 224 W. Winton Ave, Suite 205, Hayward, California 94544, Prepared by: Spinardi Associates, 265 Sea View Avenue, Piedmont, California 94610

Thorncraft and John H. Harris, May 2000. Fish Passage and Fishways in New South Wales: A Status Report Garry Office of Conservation NSW Fisheries. Sydney Cooperative Research Centre for Freshwater Ecology Technical Report 1/2000

U.S. Army Corps of Engineers (USACE), September 1986. Seepage Analysis and Control For Dams Engineer Manual 1110-2-1901. Department of the Army, U.S. Army Corps of Engineer, Washington, DC 20314-1000.

U.S. Bureau of Reclamation (USBR), 1987. Design of Small Dams, 3rd Edition. 860 pp.

U.S. Bureau of Reclamation (USBR), 1995. Ground Water Manual. Water Resources Technical Publication. U.S. Department of the Interior, Bureau of Reclamation.

U.S. Bureau of Reclamation (USBR), April 2006. Water Resources Technical Publication "Fish Protection at Water Diversions" A Guide for Planning and Designing Fish Exclusion Facilities. U.S. Department of the Interior, Bureau of Reclamation. http://www.usbr.gov/pmts/hydraulics_lab/pubs/manuals/fishprotection/

U.S. Bureau of Reclamation (USBR), April 2009. Water Resources Technical Publication “Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities.” U.S. Department of the Interior, Bureau of Reclamation.


42


Yoe, Charles E., and Kenneth D Orth, November 1996. Planning Manual. U.S. Army Corps of Engineers (USACE), Water Resources Support Center Institute for Water Resources, IWR Report 96-R-21.

Zone 7, August 2013. E-mail correspondence from Colleen Winey to Nathan Foged. August 16, 2013. “RE: CEMEX Eliot Facility Rec Plan -- Data needs for Arroyo del Valle hydraulic study.” Attachment: “Z7 Diversion Criteria.docx” [Draft Design Criteria for the Arroyo Del Valle Diversion Structure.]


A-1


Attachment A: Conceptual Design Figures

Figure A-1. Arroyo del Valle Diversion Infiltration Bed Conceptual Design

Figure A-2. Arroyo del Valle Diversion Infiltration Bed Conceptual Design Plan

Figure A-3. Arroyo del Valle Diversion Infiltration Bed Conceptual Design Sections


A-2



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B-1


Attachment B: Construction Cost Estimate

Concept-level Cost Estimate for Infiltration Bed Alternative


B-2



Eliot Facility Reclamation Plan Amendment Preliminary Construction

Cost Estimate

Arroyo del Valle Diversion and Conveyance Feasibility

Per unit Total

Excavation CY 14,500 5 72,500 5.5' max gravel depth x 200' x 100' plus 10%

Additional 10,000 CY for bank excavation and 2:1 slopes

Pea Gravel Backfill CY 4,500 45 202,500 5.5' max gravel depth x 200' x 100' plus 10%

Subsurface clay cut-off wall CY 300 30 9,000 8' depth x 5' width x 200' length

Geofabric SF 30,000 2 60,000 220' x 120' plus 10%

Slope erosion protection SF 3,200 5 16,000 For 2:1 side slopes surrounding bed; use 4 ft average rise

12" Dia. Perforated Pipe LF 1,200 60 72,000 Wrapped in geofabric

18" Dia. Perforated Pipe LF 2,800 90 252,000 Wrapped in geofabric

36" Diameter LF 60 180 10,800 C905 PVC

48" Diameter LF 80 240 19,200 C905 PVC

60" Diameter LF 60 255 15,300 RCP

84" Diameter LF 30 610 18,300 RCP

Connections EA 40 840 33,600 Tee connections for laterals into manifold

Junction box EA 1 10,000 10,000 Manifold into 84" main conduit

Concrete Channel CY 250 1,200 300,000 10' wide by 12' deep 1 ft thick walls, formed-in-place

Stilling basin blocks EA 8 100 800 Stilling basin block forms for energy dissipation

Parshall flume EA 1 5,000 5,000 Parshall flume (8-ft throat width) for flow measurement

Gravel bedding for channel CY 100 45 4,500 12' x 2' x 100 plus 10%

8' x 8' Motorized Sluice Gate ea 1 74,000 74,000 Vendor quote for 7'x7' scaled on area, plus $10,000 for installation

Flow Meter (ultrasonic) ea 1 10,000 10,000

Riprap, dumped with bedding CY 267 150 40,050 Chute dimensions of 40' wide x 60' long x 3' thick

Excavation CY 400 5 2,000 140' width x 6' depth x 12' length

Formed Concrete CY 145 1,100 159,500 140' width x (2 x 6' cutoff walls + 4' crest height + 12' cantilever

base)

Rock fill for up/downstream faces CY 450 150 67,500 assume 4:1 slopes

Earthwork cut and fill CY 300 5 1,500 4' x 2% slope = 200' length times 10' width times 4' depth

Wood, planting, riparian features LF 200 50 10,000 4' x 2% slope = 200' length

Rock and cobble, placed CY 75 175 13,125 4' x 2% slope = 200' length times 10' width times 4' depth

Chain link fencing LF 420 30 12,600 6' chain link fencing along drainage channel, to preventfall hazard

Electrical Services ea 1 15,000 15,000

Construction Subtotal 1,506,775

Contractor's Mobilization/Overhead percent 10 --- 150,678

Subtotal 1,657,453

Contractor's Mark Ups percent 10 --- 165,745

Subtotal 1,823,198

Contingency percent 40 --- 729,279

Subtotal 2,552,477

Bonding and Insurance percent 5 --- 127,624

Subtotal 2,680,101

Engineering and Administration percent 20 536,020

Design Engineering, Engineering Asssitance During Construction

and Legal and administrative costs such as Project-Specific CEQA

compliance, permitting, special studies,etc.costs, and

Total 3,216,121

3,300,000 round up to nearest $100,000

Notes:

1. Costs reflect those for a publically bid project in the San Francisco Bay Area Winter 2014.

2. Estimated prepared at AACEI Class 5, Order of Magnitude accuracy level.

Table B-1. Concept-level Cost Estimate for Infiltration Bed AlternativeTable B-1. Concept-level Cost Estimate for Infiltration Bed AlternativeTable B-1. Concept-level Cost Estimate for Infiltration Bed AlternativeTable B-1. Concept-level Cost Estimate for Infiltration Bed Alternative

Design Element

Total Construction Cost

Cost (dollars)Units Quantity Comments

P:\CEMEX\144718 Arroyo del Valle Hydraulic Study\500 Deliverables\TM02 Attachments\superseded\CEMEX_AdVHS_TM02_AttC_20140221.xlsx TM02 | Attachment B

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