Exhibit_1_-_SNWR_-_Canal_Master_Plan_Technical_Report_Redacted.pdf

Sacramento National

Wildlife Refuge

Canal 26.2 Restoration

Master Plan

Technical Report

Revision 1

June 2023

This page intentionally left blank.

Sacramento NWR Canal Restoration Master Plan Technical Report

Rev. No. 1 / June 2023 i

Table of Contents

Executive Summary

Hydraulic Analysis

Existing Conditions

Alternative Analysis

Feasibility Study

Construction Packages

Conclusions and Recommendations

1.0 Introduction and Purpose

1.1 Authorization

1.2 Purpose

2.0 Project Background

2.1 Canal and Road Background

2.2 Canal and Road Design Criteria

2.2.1 Existing Criteria

2.2.2 Proposed Criteria

3.0 Hydraulics

3.1 Existing Canal

3.1.1 Physical Conditions

3.1.2 Canal Hydraulics

3.2 Canal Alternatives

3.2.1 Alternative 1: Canal Vegetation Removal and WCS Cleaning

3.2.2 Alternative 2: Canal Vegetation Removal and Replacement of 3 Siphons

3.2.3 Alternative 3: Canal Vegetation Removal and Replacement of 5 Siphons

3.2.4 Canal Dredging

3.2.5 Additional Canal Crossings

3.3 North Flume

3.3.1 Physical Conditions

3.3.2 Hydraulics

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4.0 Alternatives Evaluation

4.1 Gravel Access Road Evaluation

4.2 Canal and WCS Alternatives Evaluation Procedure

4.2.1 Physical Conditions

4.2.2 Protected Habitat

4.2.3 Lifecycle

4.2.4 Risk Reduction

4.2.5

4.3 Alternative 1

4.4 Alternative 2

4.5 Alternative 3

4.6 Analysis

5.0

6.0 Recommended Construction Package

7.0 Conclusions and Recommendations

8.0 References

List of Figures

Figure 1-1. Vicinity Map

Figure 2-1. Access Road Spot Repairs

Figure 2-2. Access Road Resurfacing

Figure 2-3. Access Road Reconstruction

Figure 3-1. Canal Freeboard

Figure 3-2. Alternative 1 Freeboard

Figure 3-3. Alternative 2 Freeboard

Figure 3-4. Alternative 3 Freeboard

Figure 3-5. Proposed Canal Crossing Locations

Figure 3-6. North Flume Bypass

List of Tables

Table 3-1. Estimated Existing Canal Capacity

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Executive Summary

The Sacramento National Wildlife Refuge (NWR) manages over 10,775 acres of wetlands, riparian forests, native grasslands, and vernal pools that support over 250 species of birds.

From providing refuge and breeding habitat to migratory birds and other wildlife to managing habitat for endangered, threatened, or sensitive species, the NWR provides multiple opportunities for hunting and wildlife viewing year-round.

The USFWS operates Canal 26.2 that delivers the water supply to the NWR. The canal has been unable to operate at the desired flow rate of 90 cubic feet per second (cfs) with 1 foot of freeboard, and the USFWS would like to implement improvements that would allow them to meet the desired operational constraints.

This Master Plan establishes the rational for and feasibility of constructing selected alternatives by evaluating the existing conditions and focusing on the most critical canal infrastructure, that is, those generating the least acceptable freeboard conditions through the length of the canal. The selected priority locations were evaluated with respect to hydraulic performance and minimum operational requirements and grouped into different recommended improvements to provide the basis for evaluating alternatives.

Hydraulic Analysis

A hydraulic analysis of Canal 26.2 was prepared for the NWR using the latest release of the

Hydrologic Engineering Center River Analysis System (HEC-RAS) model. Existing 1D HEC-

RAS models for Canal 26.2, and WCSs were developed to establish baseline flow capacity for the length of the canal. Further model runs included the incorporation of suggested improvements and alternatives for both the canal and WCSs. The results were used as the baseline condition, and improvements were considered to target canal capacities.

Existing Conditions

The hydraulic analysis of the existing conditions shows that the existing freeboard is generally greater than 1 foot except for the canal section between “Logan Cr flume at T12.1” (WCS-38) to “Logan Cr flume at T11.3” (WCS-41) and the southernmost canal section. The reduced freeboard through these sections results from a lack of hydraulic capacity at WCS-38 along with lower levee elevations through the upgradient reach.

Alternative Analysis

Multiple alternatives were evaluated to maintain the minimum 1-foot freeboard throughout the canal while increasing the flow capacity to the preferred 90 cfs.

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Alternative 1 consists of general repair and maintenance of the existing canal and WCSs and includes the following:

• Remove trees and overgrown vegetation from canal footprint.

• Clean all five siphons of debris and sediment.

The hydraulic analysis indicated that the minimum freeboard is less than 0.6 feet upstream of

“Logan Cr flume at T11.3” (WCS-41) when using an inflow of 90 cfs and does not meet the minimum 1-foot freeboard requirement. The freeboard south of WCS-01(southernmost on-site

WCS) remained well below the 1-foot minimum.

Alternative 2 was developed to meet the minimum operational requirements of maintaining a minimum of a 1-foot freeboard while meeting the 90 cfs operational flows. This alternative includes the following:

• Remove trees and overgrown vegetation from canal.

• Clean siphons “T21 Ditch inlet from 26.2” (WCS-14) and “Logan Cr Flume at 26.2”

(WCS-46) of debris and sediment.

• Replace siphons “26.2 inline at T15.1” (WCS-31), “Logan Cr flume at T12.1” (WCS-

38), and “Logan Cr flume at T11.3" (WCS-41).

• Remove WCS-30 and WCS-37, associated with WCS-31 and WCS-38, respectively.

Alternative 2 model results showed that a minimum 1-foot freeboard can be maintained upstream of WCS-41 and throughout most of the canal with a maximum inflow of 90 cfs. The exception is south of WCS-01 that remained below the minimum freeboard requirement.

Alternative 3 is like Alternative 2 in that it maintains the minimum 1-foot freeboard; however, rather than cleaning WCS-14 and WCS-46, they were considered for removal and replacement along with the other three siphons. This alternative includes the following:

• Remove trees and overgrown vegetation from canal.

• Replace siphons WCS-14, WCS-31, WCS-38, WCS-41, and WCS-46.

• Remove WCS-30 and WCS-37, associated with WCS-31 and WCS-38, respectively.

Alternative 3 results in a minimum freeboard of 1 foot upstream of WCS-41 for a canal inflow of 90 cfs. Most of the canal would be capable of handling the increased flow rate of 90 cfs while maintaining the minimum 1-foot freeboard criteria, like Alternative 2. The freeboard south of WCS-1 would remain below the 1-foot minimum.

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Conclusions and Recommendations

Following hydraulic analysis and feasibility evaluation, the following improvements are recommended to meet the 90 cfs inflows while maintaining the 1-foot freeboard.

• Remove trees and overgrown vegetation from within the canal footprint.

• Replace siphons WCS-14, WCS-31, WCS-38, WCS-41, and WCS-46.

• Remove WCS-30 and WCS-37 and associated berms, and grade to drain.

Performance and technical specifications can be readily developed, and a D-B procurement strategy can be used to help save USFWS time and budget.

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1.0 Introduction and Purpose

This section presents the authorization and purpose of this Technical Report.

1.1 Authorization

McMillen, Inc. (McMillen) was retained by the U.S. Fish and Wildlife Service (USFWS) to provide Architectural-Engineering (A-E) Design Services for the Sacramento National Wildlife

Refuge (NWR) Canal 26.2 Master Plan per Order Number 140F0322F0034 dated July 18, 2022. Services include engineering assessment, alternative analysis, and infrastructure repair recommendations in cooperation with the USFWS.

1.2 Purpose

The purpose of the Canal 26.2 Master Plan is to provide an evaluation of the existing canal and levee road system and to prioritize improvements for both the canal and water control structures (WCSs). The evaluation of the existing access road is based on providing a series of solutions that can be implemented, from spot repairs to access road reconstruction. The evaluation of the existing canal is based on current conditions, performance, life cycle, and impacts to the surrounding habitat. The results of this Technical Report will assist the NWR with meeting operational objectives over the next 20 to 30 years through rehabilitation of select canals and WCSs while maintaining public hunting and recreational needs. Figure 1-1 shows a map of the area.

This Technical Report establishes the rational for and feasibility of the selected canal alternatives by evaluating the existing conditions and focusing on the most critical canal infrastructure, that is, those generating the least acceptable freeboard conditions through the length of the canal. The selected priority locations will be evaluated with respect to the minimum operational requirements and grouped into different recommended improvements to provide the basis for evaluating alternatives.

Consideration is given to the available USFWS budget, operation, and maintenance needs.

While there are several improvements available to improve the overall canal performance, focus is on prioritizing those improvements critical to maintaining the minimum freeboard, safety, and operational requirements.

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Figure 1-1. Vicinity Map

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2.0 Project Background

The Sacramento NWR was created in 1937 as a refuge and breeding habitat for wildlife and birds on their seasonal migrations. The NWR was initially developed to help with the management of sensitive, threatened, or endangered species while mitigating impacts to crops throughout the valley. Initially known as the Colusa Plains, with windswept grasses, shrubs, and forbs, it was later improved through a series of levees, canals, water control structures, and ditches to create and sustain wetlands throughout the NWR.

The Sacramento NWR currently functions as the headquarters for the entire Sacramento NWR

Complex, while supporting over 250 species of migratory and resident birds and wildlife. Most notable are the large wintering concentrations of waterfowl that support hunting and other recreational activities throughout the region.

2.1 Canal and Road Background

The Canal 26.2 is the primary water delivery source for the NWR and is responsible for delivering water to thousands of acres of wetlands. The unlined canal runs north to south and is supported by the east and west levees. The canal is the westerly boundary of the NWR and lies immediately adjacent to I-5, Old Highway 99, and the California Northern Railroad (CFNR) to the west. County Road 68 crosses the canal roughly half-way through the project area, with

USFWS Headquarters’ Road 8013 crossing north of that. Current conditions can be found in

Appendix A.

Glenn-Colusa Irrigation District (GCID) provides the water source for Canal 26.2, where the inflows are controlled according to the NWR’s operation needs and upon USFWS request.

Canal water is diverted to supporting canals and ponds through multiple water control structures (WCSs) as it flows from north to south. Inline stoplog structures are used as diversions to control the flow to the adjacent wetlands. Multiple large inline flumes and siphon structures are located along the canal, many of which are damaged and are leading to localized insufficient flow capacity. These structures continue to impact the adjacent levees, causing inundation and resulting in erosion. Several existing canal crossings are unusable, leading to the lack of access to the west levee for maintenance and repair.

Both levees show signs of damage, with the west levee exhibiting the worst wear. Large sections of the west levee are currently inaccessible, leading to little or no maintenance over the years. Damaged areas continue to grow due to lack of maintenance. Dense vegetation and large trees are present within the west levee slope that further degrades the functional operation of the canal and potentially degrades its stability. There is no access road located along the west levee.

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The east levee includes the primary access road used to service the various water control structures. Current gravel road surfacing continues to deteriorate which has led to the inability for water management to continue year-round due to lack of access during inclement weather.

There are areas of dense vegetation and some medium to small trees on the east levee that impact the function of the canal. The canal itself has been inundated with sediment, trees, and invasive primrose, leading to reduced operational capacity.

2.2 Canal and Road Design Criteria

2.2.1 Existing Criteria

2.2.1.1 Canal

Canal 26.2 is operated at a flowrate between 70 and 90 cubic feet per second (cfs), with the intent to operate the canal at a minimum freeboard of at least 1.0 foot. Currently the minimum freeboard is only attainable at 70 cfs.

The existing levee side slopes range between 2.5H:1V to 3H:1V, with localized areas of steeper and shallower slopes. There is heavy vegetation located on both the east and west levees, and over some localized areas of the canal bed. Large to small trees are present both in the canal and levee walls. This condition leads to reduced flow capacity and negatively impacts the canal’s hydraulic performance.

With a decrease in capacity, the water surface increases in elevation, encroaching within the available 1.0-foot freeboard. A reduced freeboard increases the risk of potential impact to both the levees and the adjacent railroad tracks.

Several of the WCSs are overgrown with vegetation, sedimentation, and debris that leaves them with a substantially reduced flow capacity. The most severe of these locations have been identified and are included in the recommended alternatives.

2.2.1.2 Road

The canal road is currently in relatively poor condition with evidence of deterioration, desiccation cracking, erosion, animal burrows, and potholes. The road is at grade, with no apparent road embankment. The road surfacing consists of granular materials, presumably aggregate base, comingled with the adjacent and underlying soils.

Certain sections of the road are inaccessible during periods of inclement weather. Canal management cannot be provided year-round due to lack of access to certain areas, primarily during wet winter months.

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2.2.2 Proposed Criteria

2.2.2.1 Canal

Following the evaluation of existing canal conditions discussed in Section 3.1, a series of improvements have been identified that will maintain the minimum 1 foot of operational freeboard over much of the canal. The canal reach below WCS-1 will remain at less than

1-foot freeboard but does not contain any more WCSs before leaving the site at WCS-0.

Minimum improvements include the following:

• Remove trees and vegetation from canal and levee walls.

• Replace siphons WCS-31, WCS-38, and WCS-41.

• Clean the remaining two siphons.

• Remove WCS-30 and WCS-37, both located immediately downstream of WCS-31 and WCS-38, respectively.

2.2.2.2 Road

Under current conditions, the existing canal access road is impassable at certain times of the year, primarily during wet winter periods. To increase the efficiency of water distribution during the winter months, the USFWS wishes to have year-round access to the canal. Rather than perform an overall feasibility evaluation, three overall solutions were considered with consideration of USFWS budget constraints. These include spot repairs, resurfacing, and reconstructing.

Spot Repairs

Several locations along the existing access road experience severe rutting during wet periods.

When these localized areas become saturated, they become impassable and may lead to trucks and personnel being stranded. To address this situation, rather than resurface or reconstruct the entire access road, a localized repair procedure can be performed consisting of a Class B1 woven polyester, subgrade enhancement geotextile underlying a 6-inch-thick, 3/4-inch Type II aggregate base (Caltrans Specifications 26-1.02B) layer. Class B1 geotextile has high tensile strength and puncture resistance, which can withstand the loads from vehicular traffic, and the Class 2 aggregate base can be easily compacted. The repair can be completed as shown in Figure 2-1.

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Figure 2-1. Access Road Spot Repairs

The benefits of using this method are that it can be quickly implemented, and it addresses the needed repairs to gain year-round access to the canal. A roll of Class B1 geotextile can be purchased and if properly stored, i.e., covered for UV protection and lifted off the ground, it can last until another role is needed. Additionally, a stockpile of Class 2 aggregate base can be established, allowing for quick repairs as necessary. This would be the least expensive solution for small repairs. The drawback is that it can be costly when there are large areas requiring repair.

Burrowing Animal Repair

If portions of the road become undermined due to burrowing animals, spot repairs could include introduction of a biotic barrier consisting of riprap overlain by Class B1 geotextile to keep backfill soils from comingling with the riprap.

Repair procedures would include removing enough material to expose the underlying burrow and allow placement of riprap. Once the area was exposed, backfill with riprap to approximately 6” above the burrow. The geotextile would then be placed over the riprap followed by fill soils to reach the subgrade elevation for the access road spot repairs.

Resurfacing

A longer-term solution for the road is to resurface the entire roadway or, at a minimum, address long sections of the road that are experiencing deleterious conditions. This requires surface preparation that consists of scarification and recompaction of the existing gravel access roadway and placement of an additional surface layer of the Class 2 aggregate base.

Resurfacing can be performed as shown in Figure 2-2.

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Figure 2-2. Access Road Resurfacing

The benefit to resurfacing is that spot repairs can be identified and addressed like as previously mentioned while scarifying and recompacting the existing gravel roadway prior to placement of the surface course. The drawback is the existing road material remains in place regardless of its ability to maintain the structural integrity of the roadway. This may lead to early repairs and further long-term maintenance costs.

Reconstruction

Constructing a robust gravel access road will help maintain seasonal access throughout the

NWR and reduce maintenance costs over a longer period. Depending on the structural section of the roadway (subgrade, base, and surfacing course), reconstruction consists of either preparing or removing the existing roadway, preparing the subgrade, placing a base course, and placing a surfacing course. The recommended canal road and thickness are shown in

Figure 2-3.

Figure 2-3. Access Road Reconstruction

The gravel thickness would be determined based on a low-use access road structural section such as a minimum 6-inch-thick base course overlain by a minimum 2-inch surfacing course.

USFWS may further refine the structural section should the funding become available to

Rev. No. 1 / June 2023 12 implement road reconstruction by using the design guidance American Association of State

Highway and Transportation Officials (AASHTO) Guidelines for Geometric Design of Low-

Volume Roads.

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3.0 Hydraulics

An engineering assessment of Canal 26.2 was prepared for the NWR using the latest release of the Hydrologic Engineering Center River Analysis System (HEC-RAS) model. HEC-RAS is a hydraulic software designed to perform one-dimensional (1D) or two-dimensional (2D) hydraulic computations for a network of natural or engineered drainage systems. Culverts, siphons, stoplog structures, and other WCSs are modeled in the system and can be modified to evaluate surface profiles following implementation of suggested improvements.

Existing 1D HEC-RAS models for Canal 26.2, and WCSs were developed to establish baseline flow capacity for the length of the canal. Further model runs included the incorporation of suggested improvements and alternatives for both the canal, and WCSs where the results were compared against baseline and target canal capacities. The hydraulic analysis can be found in Appendix B.

3.1 Existing Canal

3.1.1 Physical Conditions

Ducks Unlimited (DU) performed a topographical survey of the canal between October 2022 and January 2023. The survey information and a digital terrain model (DTM) created from the surveyed ridge lines, top of bank, toe, depressions, and thalweg elevations provided the foundation for the cross sections. The survey included invert elevations, wall elevations, and dimensions of the different WCSs that were used to help further refine the HEC-RAS model.

The model showed that the canal bottom elevation dropped 25 feet from north to south along the 5.2 miles length, which resulted in an approximate 0.09% slope over the length of the canal.

3.1.2 Canal Hydraulics

The HEC-RAS model uses Manning’s formula to determine the flow characteristics at a specific cross section. Manning’s roughness coefficients (n-values) are used along the perimeter of the cross section to emulate field conditions observed during the field assessment (McMillen

2022). Most cross sections were assigned an n-value of 0.04, which corresponds to straight channels with weeds. Cross sections where significant vegetation growth occurred were assigned n-values of 0.07 or 0.10 (Chow 1959).

The WCSs were modeled using inline and lateral structures such as stoplogs, culvert crossings, flumes, and siphons. Inline and lateral structures such as gates and culvert features are modeled to represent the WCS’s geometry and operational conditions. Lateral structures were used to represent stoplog diversions and their operational conditions. A total of 20

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Implementing Alternative 1 by removing vegetation, cleaning siphons, and modifying operations showed that while the modifications will increase the capacity of the canal, the minimum 1-foot freeboard criteria will not be met.

3.2.2 Alternative 2: Canal Vegetation Removal and Replacement of 3 Siphons

Alternative 2 was modeled by implementing tree and vegetation removal throughout the canal; removing and replacing siphons WCS-41, WCS-38, and “26.2 inline at T15.1” (WCS-

31) with flumes; and removing culvert crossings WCS-37 and WCS-30 located immediately downstream of WCS-38 and WCS-31, respectively. The flumes for WCS-41 and WCS-38 were modeled at 6 feet wide with WCS-31 at 5 feet wide. WCS-37 and WCS-30 would be removed, and the slopes restored to match the existing canal cross section. As with Alternative

1, n-values of 0.04 were used to reflect the canal vegetation removal and the remaining siphons “Logan Cr Flume at 26.2” (WCS-46) and “T21 Ditch inlet from 26.2” (WCS-14) were modeled without obstructions. Some operational changes were identified at select stoplog structures to help facilitate maintaining the 1-foot freeboard.

The results for Alternative 2 showed that a minimum 1-foot freeboard can be maintained upstream of WCS-41 and throughout most of the canal with a maximum inflow of 90 cfs. The exception is south of WCS-01 which remained below the minimum freeboard requirement.

Figure 3-3 shows the canal freeboard for Alternative 2.

Figure 3-3. Alternative 2 Freeboard

By removing vegetation from the canal; cleaning sediment from WCS-46 and WCS-14; and replacing siphons WCS-41, WCS-38, and WCS-31 with flumes, most of the canal would be capable of handling the increased flow rate of 90 cfs while maintaining the minimum 1-foot freeboard criteria. The exception is south of WCS-01 which is consistent across models.

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3.2.3 Alternative 3: Canal Vegetation Removal and Replacement of 5 Siphons

Alternative 3 consists of removing trees and overgrown vegetation from the canal; replacing existing siphons WCS-46, WCS-41, WCS-38, WCS-31, and WCS-14 with flumes; and removing culvert crossings WCS-37 and WCS-30 located immediately south of WCS-38 and

WCS-31, respectively. WCS-46, WCS-41, and WCS-38 were modeled with six-foot-wide flumes, and WCS-31 and WCS-14 were modeled with five-foot-wide flumes. WCS-37 and

WCS-30 would be removed, and the slopes restored to match the existing canal cross section.

Consistent with previous alternatives, an n-value of 0.04 was assigned to the canal sections to reflect canal vegetation removal. Some operational changes to stoplog structures were also considered.

Alternative 3 results in a minimum freeboard of 1 foot upstream of WCS-41 for a canal inflow of 90 cfs. Figure 3-4 shows the canal freeboard for Alternative 3.

Figure 3-4. Alternative 3 Freeboard

By removing vegetation from the canal and replacing siphons WCS-46, WCS-41, WCS-38, WCS-31, and WCS-14 with flumes, most of the canal would be capable of handling the increased flow rate of 90 cfs while maintaining the minimum 1-foot freeboard criteria, like

Alternative 2. The freeboard south of WCS-1 would remain below the 1-foot minimum.

3.2.4 Canal Dredging

Additional HEC-RAS model runs were performed to evaluate the potential flow capacity increase through dredging and removal of 1 to 2 feet of material as well as removing trees and vegetation from within the canal footprint. Dredging was represented by lowering the bottom of the existing canal DTM by 1 foot. The results indicated that an average of 0.2 feet of additional freeboard could be obtained by removing 1 foot of sediment when compared to the freeboard obtained from vegetation removal alone. Increasing sediment removal by 2 feet could result in an average of 0.25 feet of additional freeboard compared to vegetation removal alone.

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In general, the benefits of dredging 1 to 2 feet of soil material will result in less than 0.3 feet in increased freeboard, indicating that the WCSs are the primary limiting factors for efficient canal operations.

3.2.5 Additional Canal Crossings

At the request of USFWS, two additional canal crossings were considered at the locations shown on Figure 3-4.

Figure 3-5. Proposed Canal Crossing Locations

The crossings were simulated as 6-foot-wide by 4-foot-tall concrete box culverts with invert elevations maintained at existing canal inlet and outlet locations. Based on the results of the

HEC-RAS modeling, the proposed crossings would not significantly affect the hydraulic capacity of the canal for the 90 cfs flow simulation. See Appendix A for the potential layout of the crossings.

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4.0 Alternatives Evaluation

A feasibility level alternatives analysis was performed to assist with developing recommendations and costs for rehabilitation of the canal and replacement of identified WCSs, and access road repair alternatives.

4.1 Gravel Access Road Evaluation

The gravel access road analysis consisted of reviewing the overall condition of the access road and presenting the options in Section 2.2.2.2 for USFWS consideration. Funding to address the access road may be through maintenance to perform spot repairs or full reconstruction of the entire length. The recommendation is to use current funding to address the performance of the

WCSs and perform spot repairs as necessary to allow for all-season access.

4.2 Canal and WCS Alternatives Evaluation Procedure

A series of generalized criteria were developed to help evaluate the feasibility of implementing each canal and WCS alternative. Criteria used for this evaluation included current physical conditions, value of protected habitat, life cycle, risk reduction, and cost.

4.2.1 Physical Conditions

An on-site Field Observation Report (FOR; McMillen 2023) was prepared to document the assessment of the canal and conditions of the WCSs performed in August 2022. The intent of the FOR was to present the current conditions and to help inform the restoration strategy presented in this report.

The physical conditions of the canal and WCSs range from generally good condition to poor. A rating of 1 through 3 is used to weight the existing and expected condition of the canal and

WCSs, with a rating of 1 for good, 2 for moderate, and 3 for poor condition.

4.2.2 Protected Habitat

The Sacramento NWR is home to a wide diversity of wildlife with an ecosystem consisting of wetland, upland, and riparian habitats. The Sacramento NWR Planned Habitat Management

Plan 2021-22 and the Sensitive Habitat Plan 2021-22 were reviewed for impacts to recognized habitat for each of the canal and WCS alternatives.

Habitat impacts from canal and WCS replacement were ranked on a scale of 1 through 3 where 1 represents little impacts, 2 represents moderate impacts, and 3 represents major impacts to the adjacent habitat.

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4.2.3 Lifecycle

The lifecycle of each alternative is evaluated to determine the anticipated replacement period along with the expected remaining life of the canal and WCSs. Consideration was given to old yet adequate WCSs, degrading WCSs, and newly constructed structures.

For facilities that are in good operating condition, little to no cracking, and no observable damage, including newly constructed facilities, 1 is used for good condition, 2 for moderate condition, and 3 for poor condition.

4.2.4 Risk Reduction

The risk associated with each alternative is considered as a factor because each alternative has its own associated risk. Cleaning instead of replacing old WCSs also carries a risk due to an increase of the potential for failure over removal and replacement.

Alternatives with a low risk, such as removal and replacement, are assigned a 1, a medium risk a 2, and a high risk a 3.

4.3 Alternative 1

Alternative 1 consists of general repair and maintenance of the existing canal and WCSs. This alternative includes the following:

• Remove trees and overgrown vegetation from the canal footprint (identical for other alternatives).

• Clean all five siphons of debris and sediment.

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The hydraulic analysis indicated that the minimum freeboard is less than 0.6 feet upstream of

WCS-41 when using an inflow of 90 cfs and does not meet the minimum 1-foot freeboard requirement. The freeboard south of WCS-01 remained well below the 1-foot minimum.

The physical conditions for this alternative are considered the baseline because it will not affect any of the existing WCSs. This means that all existing structures remain regardless of condition. A baseline of 3, or poor condition, is appropriate.

The impacts to protected habitat are consistent throughout this and the other alternatives.

Because this is considered baseline, the impacts to habitat are considered good, or 1, because the other alternatives require further improvements.

Lifecycle impacts would be considered poor, or 3, for this baseline condition, as would the risk reduction. These are both baseline conditions used to compare against other alternatives.

4.4 Alternative 2

Based on the hydraulic analysis, the following improvements are the minimum required to maintain a minimum of 1-foot freeboard above WCS-1. Some of the recommended improvements are typical for other alternatives and are not considered when comparing the screening criteria. This alternative includes the following:

• Remove trees and overgrown vegetation from canal (identical for other alternatives).

• Clean siphons WCS-14 and WCS-46 of debris and sediment.

• Replace siphons WCS-31, WCS-38, and WCS-41. Work includes:

• Demolish existing headwalls, pipe, and siphon.

• Excavate and backfill around new WCSs.

• Construct concrete headwalls.

• Construct flume (assumed concrete, may be other material)

• Place bank protection.

• Remove WCS-30 and WCS-37, associated with WCS-31 and WCS-38, respectively.

• Remove culverts.

• Excavate, backfill, and grade culvert embankment.

See Appendix B for further details.

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The physical conditions for this alternative are considered better than baseline because three of the five siphons are being removed. This leaves fewer existing siphons but focuses on

WCSs with greater influence on canal operations. Because this alternative leaves some existing structures in place, the alternative results in moderate improvements to the physical condition of the canal. A baseline of 2, or a moderate condition, is appropriate.

There are several additional impacts to adjacent wetlands with the implementation of this alternative. Replacing WCS-31 and WCS-38 could affect the adjacent alkali meadow and sensitive habitat. Replacing WCS-41 would affect a seasonal wetland and is not adjacent to any sensitive habitat. Impacts to adjacent habitat for this alternative is considered moderate, or

2, because it could potentially affect the adjacent wetlands in two of three locations.

Lifecycle impacts and risk would be considered moderate, or 2, because leaving two aging siphons increase the risk of future sedimentation and possible failure.

4.5 Alternative 3

Alternative 3 is like Alternative 2 in that it maintains the minimum 1-foot freeboard while replacing siphons. However, rather than cleaning WCS-14 and WCS-46, they were considered for removal and replacement along with the other three siphons. This alternative includes the following:

• Remove trees and overgrown vegetation from canal (identical for other alternatives).

• Replace siphons WCS-14, WCS-31, WCS-38, WCS-41, and WCS-46. Work includes:

• Demolish existing headwalls, pipe, and siphon.

• Excavate and backfill around new WCSs.

• Construct concrete headwalls.

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• Construct flume (assumed concrete, may be other material)

• Place bank protection.

• Remove WCS-30 and WCS-37, associated with WCS-31 and WCS-38, respectively.

• Remove culverts.

• Excavate, backfill, and grade culvert embankment.

See Appendix B for further details.

There are several additional impacts to adjacent wetlands with the implementation of this alternative. Replacing WCS-31 and WCS-38 could affect the adjacent alkali meadow and sensitive habitat. Replacing WCS-41 would affect a seasonal wetland and is not adjacent to any sensitive habitat. Impacts to adjacent habitat for this alternative is considered moderate, or

2, because it could potentially affect the adjacent wetlands in two of three locations.

The physical conditions for this alternative are considered better than baseline because three of the five siphons are being removed. This leaves fewer existing siphons but focuses on

WCSs with greater influence on canal operations. Because this alternative leaves some existing structures in place, the alternative results in moderate improvements to the physical condition of the canal. A baseline of 2, or a moderate condition, is appropriate.

There are several additional impacts to adjacent wetlands with the implementation of this alternative. Replacing WCS-14, WCS-31, and WCS-38 could affect the adjacent alkali meadow and vernal pool complex as well as sensitive habitat. Replacing WCS-41 and

WCS-46 could affect seasonal wetlands, irrigated seasonal wetlands, and watergrass, but neither are adjacent to sensitive habitat. Impacts to adjacent habitat for this alternative is considered moderate, or 2, because it would generally affect the same type of wetlands.

Lifecycle impacts and risk would be considered good, or 1, by replacing the remaining siphons subject to future sedimentation and possible failure.

Rev. No. 1 / June 2023 28

5.0

Rev. No. 1 / June 2023 32

8.0 References

Chow, V. T. 1959. Open Channel Hydraulics. New York: McGraw-Hill.

McMillen 2022. Field Observation Report – Sacramento National Wildlife Refuge Canal

Restoration Master Plan.

Rev. No. 1 / June 2023

Appendix A. Canal 26.2 Drawings

Appendix B. Hydraulic Technical Memorandum

Sacramento National Wildlife Refuge Canal Canal Hydraulics

Rev. No 0 /May 2023. 2

Figure 2-1. Vicinity Map

Rev. No 0 /May 2023. 3

In August 2022, McMillen staff conducted an observational assessment of the Canal 26.2 and

57 WCS (McMillen, LLC 2022). The WCS were separated into the six categories as presented in Table 2-1.

Table 2-1. Types of Water Control Structures

Quantity Description

8 Flumes/siphons

9 Inline stoplogs

8 Inline culvert crossings

16 Lateral stoplogs/diversions

3 Lateral slide gates

13 Steel drain crossings

The purpose of the flumes and siphons is to bypass drainage from agricultural fields located west of Interstate I-5 directly to the Refuge’s wetlands without interference with Canal 26.2.

The flumes and siphons have multiple configurations including various combinations of channel flumes, culverts, gates, and siphons. These structures are not used by the USFWS to manage the canal operations. The steel drain crossings are associated with the bypass flumes and provide drainage from the agricultural fields and railroad directly to the wetlands on the east side of the 26.2 Canal.

The inline stoplog structures can be used to control the canal flow. The flow and the necessary hydraulic head for the lateral diversions are controlled by adding or removing boards in the stoplog structures. Lateral stoplog diversions are the most common water control structures in the canal. Their purpose is to divert water from Canal 26.2 to ditches or directly to the neighboring wetlands. The lateral slide gates serve the same purpose as lateral stoplogs.

The inline culvert crossings provide a connection between the west and east sides of the canal. However, they are generally considered unsafe for vehicle passage due to lack of cover over the conduits and dense vegetation. The canal itself has been subject to sediment accumulation and presents dense vegetation growth in some sections.

The Canal 26.2 WCSs were numbered/labeled from south to north in this report. Appendix A presents a table that relates the WCSs labels to the track location used by USFWS.

Rev. No 0 /May 2023. 4

2.2 Canal Flows and Operation

Flows to Canal 26.2 are provided by the Glenn-Colusa Irrigation District according to the

Refuge’s operation needs and upon USFWS request. The canal water is diverted to wetlands through multiple WCSs as it flows downstream. Flow measurements in the canal and at diversions are not performed as part of the canal operations. According to USFWS staff, presently, approximately 70 cfs can be safely conveyed in the most upstream section of the canal with a freeboard of about 1 foot. However, flows up to 90 cfs have been conveyed in the past. One of the primary goals of the canal rehabilitation is to increase the conveyance capacity to 90 cfs with a minimum freeboard of 1 foot. Figure 2-2 presents the post rehabilitation target canal flows at main diversions provided by USFWS.

Figure 2-2. Target Canal Flows

Rev. No 0 /May 2023. 14

Figure 4-3. Alternative 2 Water Surface Profile

Alternative 2 results in a minimum freeboard of 1 foot upstream of WCS-41 and within the majority of the canal for a canal inflow of 90 cfs. Figure 4-4 shows the canal freeboard for

Alternative 2.

Figure 4-4. Alternative 2 Freeboard

The freeboard in the southernmost section of the canal is less than 1 foot in the vicinity of

WCS-1, which is the shallowest section of the canal. Replacing siphons WCS-41, WCS-38, and WCS-31 with flumes increases the capacity of the canal and the 1-foot freeboard criteria is met in the majority of the canal.

Rev. No 0 /May 2023. 17

Figure 4-7. Proposed Canal Crossing Locations

The crossings were simulated as 6-foot-wide by 4-foot-tall concrete box culverts. The invert elevation of the box culverts were assumed to be the same as the invert elevation of the canal at the crossing locations. Based on the results of the HEC-RAS modeling, the proposed crossings would not significantly affect the hydraulic capacity of the canal for the 90 cfs flow simulation.

5.0 Hydraulic Analysis of Existing North Flume

The North Flume is located on the North Canal, which runs along the northern edge of the

Refuge. The North Canal can be used as an alternative route to deliver water to the wetlands if Canal 26.2 is not usable. The objective of the North Flume analyses was to evaluate if the flume is able to convey a flow of 10 cfs. USFWS has not been able to convey flow through the flume in recent years.

Rev. No 0 /May 2023. 21

The analyses indicate that the siphons are primarily responsible for limiting the capacity of

Canal 26.2. These structures are subject to sediment accumulation that reduce conveyance capacity when periodic maintenance is not performed. Replacing the existing siphons with flumes will reduce the need for maintenance and increase the hydraulic capacity of the canal.

Three alternatives were evaluated that generally include removal of dense vegetation from the canal and replacement of select WCSs. Additional evaluations were performed to model dredging and placement of crossings.

Based on the alternative evaluations, McMillen recommends the removal of dense vegetation in the canal, replacement of all five siphons with flumes, and the removal of culvert crossings

WCS-37 and WCS-30. At a minimum, siphons WCS-41, WCS-38, and WCS-31 are recommended to be replaced with flumes to increase the capacity of the 26.2 Canal.

Dredging alone will not significantly increase the capacity of the canal. However, when combined with the replacement of siphons, it could lead to an additional 0.5 feet of freeboard for the target flow of 90 cfs. McMillen recommends that dredging be performed in the southernmost sections of the canal, which is subject to significant sediment accumulation. The addition of culvert crossings in either or both of the proposed locations would not affect the capacity of the canal.

The North Flume does not significantly affect the capacity of the North Canal. A more complete study of this reach is recommended.

7.0 References

Chow, V. T. 1959. Open Channel Hydraulics. New York: McGraw-Hill.

McMillen, LLC. 2022. Field Observation Report: Sacramento National Wildlife Refuge Canal

Restoration Master Plan.

Rev. No 0 / May 2023

Appendix A. Water Control Structures Tracking Log

Summary of Water Control Structures

Name USFW Name Structure Type Major? U.S. River XS Stationing Node D.S. River XS Stationing Survey Structure Size McMillen Field Mment Weir Shape Gate Height Invert El. Entrance Loss Exit Loss Mannings N wcs #57 N Boundary Ditch inlet at 26.2 Lateral Stoplog Structure Y 27459 27443.27 27425 60" 68" Broad Crested 5.8 103.5 N/A N/A N/A wcs #56 26.2 inline at T1.1 Inline Stoplog Structure N/A 27425 27420 27411 60" 68" Broad Crested 6.2 103.2 N/A N/A N/A wcs #53 Logan Cr flume at T1.2 Flume-Syphon N/A 26029 26013 25998 36" Steel

60" N/A

N/A

Broad Crested

N/A

5.3

102.4

102.6

0.5

N/A

N/A

0.0156

N/A wcs #52 T4 Ditch inlet at 26.2 Lateral Stoplog Structure Y 24877 24865 24846 24" HDPE 24 N/A N/A 102.8 0.5 1 0.0144 wcs #51 26.2 inline at T4.1 Inline Stoplog Structure N/A 24846 24836 24824 60" 66.5" Broad Crested 6.4 101.4 N/A N/A N/A wcs #49 T8 Delivery inlet from 26.2 Lateral Stoplog Structure Y 23574 23573 23563.25 36" Steel Pipe 24 N/A N/A 102.1 0.5 1 0.0144 wcs #48 26.2 inline at T6/7 Inline Stoplog Structure N/A 23563.25 23552.95 23544 60" 66.5" Broad Crested 6.4 100.6 N/A N/A N/A wcs #46 Logan Cr Flume at 26.2 Flume-Syphon N/A 21388 21387 21366 36" Steel

4'W x 3'H N/A N/A N/A

101.4

96.6

0.5

N/A

N/A

0.0156

N/A wcs #45 26.2 inline (Entrance Road) Inline Culvert/Road Crossing N/A 19739 19724 19690 48" CMP 36 N/A N/A 95.1 0.7 1 0.0288 wcs #44 Inline Culvert/Crossing N/A 19050 19039.5 19014 60" CMP 60 N/A N/A 94.4 0.9 1 0.0288 wcs #41 Logan Cr flume at T11.3 Flume-Syphon N/A 18987 18985 18967 36" Steel

4'W x 3'H 36 N/A N/A

96.7

91.1

0.5

N/A

N/A

0.0156

N/A wcs #38 Logan Cr flume at T12.1 Flume-Syphon N/A 17799 17798 17779 36" Steel

4'W x 3'H 36 N/A N/A

94.8

89.4

0.5

N/A

N/A

0.0156

N/A wcs #37 Inline Culvert/Crossing N/A 17739 17737 17708 60" CMP 60 N/A N/A 93.5 0.9 1 0.0288 wcs #36 T12.1 inlet Lateral Stoplog Structure N 17151 17146 17128 24" HDPE 24 N/A N/A 95.4 1 1 0.0156 wcs #35 T12 Ditch inlet from 26.2 Lateral Stoplog Structure Y 16759 16758 16745 36" Conc 36 N/A N/A 94.1 0.5 1 0.0156 wcs #34 26.2 inline at T12.2 Inline Stoplog Structure N/A 16739 16738 16727 60" 65.5 Broad Crested 5.9 94.0 N/A N/A N/A wcs #31 26.2 inline at T15.1 Flume-Syphon N/A 16522 16521 16498 Siphon 8'Wx4'H 60 N/A N/A 88.1 N/A N/A N/A wcs #30 Inline Culvert/Crossing N/A 16479 16478.5 16430 52" CMP Squash 60 N/A N/A 92.4 0.9 1 0.0288 wcs #29 Inline Culvert/Crossing N/A 13898 13897 13851 52" CMP Squash 60 N/A N/A 91.8 0.9 1 0.0288 wcs #28 T15.2 inlet from 26.2 Lateral Stoplog Structure N 12811 12793 12767 24" HDPE 36 N/A N/A 93.0 1 1 0.0156 wcs #27 Logan Cr inlet from 26.2 at T10.1 Lateral Stoplog Structure N 12718 12702 12689 36" HDPE 36 N/A N/A 91.9 1 1 0.0156 wcs #24 26.2 flume at T19.1 Flume-Syphon N/A 12689 12681 12659 36" Steel

60" Flume

N/A

Broad Crested

N/A

6.3

92.0

91.7

0.5

N/A

N/A

0.0156

N/A wcs #23 T19.1 inlet Lateral Stoplog Structure N 12159 12151 12132 24" HDPE 24 N/A N/A 93.6 1 1 0.0156 wcs #22 26.2 siphon at Rd 68 Inline Culvert/Road Crossing N/A 11424 11420 11308 2 x 36" Conc 36 N/A N/A 90.3 0.5 1 0.0156 wcs #21 Rd 68-S Ditch inlet from 26.2 Lateral Stoplog Structure Y 11308 11302 11289 60" 60 Broad Crested 5.5 92.5 N/A N/A N/A wcs #20 26.2 inline at T21.1 Inline Stoplog Structure N/A 11282 11281 11272 60" 60 Broad Crested 6.7 91.3 N/A N/A N/A wcs #19 unknown at NW corner T21.1 Lateral Slide Gate N 11272 11271 11259 36" CMP 36 N/A N/A 90.9 1 1 0.0288 wcs #18 Inline Culvert/Crossing N/A 11242 11241 11191 60" CMP 60 N/A N/A 90.7 0.9 1 0.0288 wcs #17 26.2 inline at T24.1 Inline Culvert/Crossing N/A 9995 9994 9956 60" CMP 60 N/A N/A 90.4 0.9 1 0.0288 wcs #14 T21 Ditch inlet from 26.2 Flume-Syphon N/A 9946 9945 9927 36" Steel

4'W x 3'H 36 N/A N/A

91.4

87.7

0.5

N/A

N/A

0.0156

N/A wcs #13 T24.1 inlet Lateral Stoplog Structure N 9229 9228 9208 24" HDPE 24 N/A N/A 91.5 1 1 0.0156 wcs #12 (U) Inline Culvert/Crossing N/A 8576 8575 8540 48" CMP Squash N/A N/A N/A 90.1 0.9 1 0.0288 wcs #12 (D) 26.2 inline at T27.1 Flume-Syphon N/A 8540 8539 8514 60"

36" Steel

Broad Crested

N/A

5.6

N/A

90.1

90.0

N/A

0.5

N/A

N/A

0.056 wcs #11 Lateral Stoplog Structure N 8463 8462 84440 18"HDPE 24 N/A N/A 91.6 1 1 0.0156 wcs #10 T27.1 inlet Lateral Stoplog Structure N 7383 7382 7359 18" HDPE 24 N/A N/A 93.2 1 1 0.0156 wcs #9 (U) Lateral Stoplog Structure N 7183 7182 7138 18" HDPE N/A N/A N/A 94.3 1 1 0.0156 wcs #9 (D) T27/28 Ditch inlet from 26.2 Lateral Stoplog Structure Y 7101 7100 7067 36" CMP 36 N/A N/A 91.5 0.5 1 0.0288 wcs #8 26.2 inline at T30 Inline Stoplog Structure N/A 7067 7066 7051 60" 60 Broad Crested 6.4 91.3 N/A N/A N/A wcs #7 T34/35 Ditch inlet from 26.2 Lateral Stoplog Structure N 3893 3892 3851 30" HDPE 24 N/A N/A 90.4 1 1 0.0156 wcs #6 T34.1 inlet Lateral Stoplog Structure N 3513 3548 3549 24" HDPE 24 N/A N/A 90.6 1 1 0.0156 wcs #5 T38 Ditch inlet from 26.2 Lateral Stoplog Structure Y 3236 3235 3220 36" CMP 36 N/A N/A 90.3 0.5 1 0.0288 wcs #4 26.2 inline at T34.1 Inline Stoplog Structure N/A 3219.5 3219.5 3204 60" 60 Broad Crested 5.3 90.1 N/A N/A N/A wcs #3 26.2 inline at T37 Lateral Slide gate N 2166 2150 2137 36" CMP 36 N/A N/A 87.9 1 1 0.0288 wcs #2 T40.1 inlet Lateral Stoplog Structure N 777 774 762 24" HDPE 24 N/A N/A 88.5 1 1 0.0156 wcs #1 Inline Stoplog Structure N/A 762 761 726 18" Steel 24 N/A N/A 89.0 0.5 1 0.0156 wcs #0 Inline Culvert/Crossing N/A 69 68.5 51 18" CMP N/A N/A N/A 88.5 0.5 1 0.0288 wcs #50 Abandoned inlet to T6/7 Ditch Lateral Slide Gate N/A 18" CMP N/A N/A N/A 103.4 1 1 N/A

Appendix C. Engineer’s Opinion of Probable Cost

Total Capital Costs

Replace WCS 14, WCS-31, WCS-38, WCS-41, WCS-46

Add 2 Crossings

Remove 2 Crossings

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