A06_Attachment_03_Squaw_Creek_Design_Report_20210312_30percent.pdf

Preliminary Design Report

Squaw Creek Fish Barrier P.O. #140F0219P0147

Natural Channel Design, Inc.

2900 N. West St, STE #5

Flagstaff, AZ 86004

March, 2021

Preliminary Design Report

P.O. #140F0219P0147

Submitted to:

US Fish and Wildlife Service

Arizona Fish and Wildlife Conservation Office

Point of Contact:

Zachary Jackson

Zachary_jackson@fws.gov

March, 2021

Prepared by:

2900 N West St, STE #5 Flagstaff, AZ 86004 mailto:Zachary_jackson@fws.gov

Squaw Creek Fish Barrier 30% Design Report

Flagstaff, Arizona i March 2021

TABLE OF CONTENTS

Table of Contents ........................................................................................................................................... i List of Figures ............................................................................................................................................ i List of Tables ............................................................................................................................................ii Attachments ............................................................................................................................................. ii

Executive Summary Project Description

Location Project Objectives

Existing Conditions Hydrology Current Site Layout Current Culvert Hydraulics Geophysical Investigation

Barrier Design Analysis Fish Jumping Ability Fish Barrier Design

Alternatives Considered Alternative 1 – Full height Barrier and Footer Alternative 2 – Sunken barrier and excavated channel Alternative 3 – Sunken Barrier near existing barrier site Construction Impacts to Site Old Barrier Removal and channel excavation Institutional and Jurisdictional Considerations

Results, Conclusions, Recommendations References Construction Drawings and Specifications Appendix 1

LIST OF FIGURES

Figure 1 Location map Figure 2. Jump trajectory at 13.5 feet per second Figure 3. Jump height vs. tailwater velocity Figure 4: Profile for a Straight Drop Spillway Structure Figure 5: Cross-Section for a Straight Drop Spillway Structure (FHA 2006) Figure 6: Alternative 1 Plan and Profile Figure 7: Alternative 2 Plan and Profile Figure 8: Alternative 3 Plan and Profile Figure 9: Limits of Construction Figure 10: Typical Channel Cross-Section (below barrier) ii March 2021

LIST OF TABLES

Table 1: Peak Design Flow from NSS Table 2: ATLAS-14 Precipitation Frequency Table 3: Rational Method Peak Flow Table 4: Jump Height at Drop Structure Table 5: EOPC ALTERNATIVE 1 – FULL HEIGHT BARRIER AND FOOTER Table 6: EOPC ALTERNATIVE 2 – SUNKEN BARRIER AND EXCAVATED CHANNEL Table 7: EOPC ALTERNATIVE 3 – SUNKEN BARRIER NEAR EXISTING BARRIER SITE

ATTACHMENTS

Attachment 1 .............. Squaw Creek Fish Barrier, Geotechnical Evaluation Report, Western Technologies Attachment 2 .......................................................... Squaw Creek Fish Barrier, 30% Plans Design Submittal

1 March 2021

EXECUTIVE SUMMARY

This report provides an analysis of the feasibility of replacing the existing fish barrier on Squaw Creek on White Mountain Apache Tribal lands. In April of 2010, NCD reviewed and recommended changes to several fish barriers for the White Mountain Apache Tribe. In that report, NCD concluded that the existing Squaw Creek fish barrier is not an effective fish barrier. The current barrier consists of gabion baskets capped with shotcrete.

Hydrology and hydraulic estimates of flow depth and velocity over the barrier are provided and compared to fish jumping ability. The barrier is designed as a two stage notch, the first notch will pass the bankfull flow events, ~43 CFS, and the second notch will pass the 100-year event. Outside of the 100-year event flow will overtop the barrier wing walls, scour has been considered in the design, but not completed. The best alternative is the jump barrier that meets these basic design criteria. The alternatives are about where you place it in relation to the current barrier which drives the extend of inundation, the amount of earthwork and the total height of the wall needed to provide the barrier height and still connect to bedrock.

Based on site exploration made on 10/28/2019, NCD believes the most advantageous location for the fish barrier is approximately 200-feet upstream of the current barrier location, North of the Y-55 road on Squaw Creek. The proposed fish barrier (Alternative 2) consists of a Cast-In-Place Concrete Retaining wall style barrier, keyed into a basalt bedrock approximately 6’ below existing grade. The barrier effectiveness would require the removal of the existing fish barrier, and re-grading the creek channel by removing the aggraded material that has filled in upstream of the current barrier. The excavated material would be placed behind the newly constructed barrier. The volume of impounded water would be negligible due to the ability to waste all the excavated channel material upstream of the new barrier.

Conceptual level costs are provided for three alternatives to the basic scheme of a jump height barrier in this location. The low cost scheme involves setting the new barrier foundation at 6’ below existing stream bed grade to ensure connectivity to bedrock, and lowering the streambed thalweg by 3’ to maintain a 9’-6” height in the barrier. This would require an excavation amount approximately equal to the pooling and sediment accumulation volume upstream of the barrier, and the excavated material would be used to fill that volume. The barrier could be raised, to avoid the reshaping of the creek channel, and leave the existing fish barrier, however this adds to the cost of the retaining structure, increases the impoundment and sediment loading timeline, as well as increase the disturbance to the creek. The third alternative is to demolish the existing fish barrier, and construct a new jump barrier near the same location, this raises the fish barrier just over 2.5 feet, but greatly increases the amount of concrete needed for the barrier and wing walls, as well as increases the water impoundment.

2 March 2021

PROJECT DESCRIPTION

Introduced nonnative fish species are rapidly being identified as a major factor in the decline of native fish species in the southwest. Fish barriers, which prevent non-natives from moving upstream into headwater habitats, are an important and powerful conservation tool for native trout. In order to remain reliable, barriers require inspection and occasional maintenance. Importantly, existing barriers, based on older designs may exert negative impacts on stream morphology, function and stability as well as barrier effectiveness.

The current gabion structure on Squaw Creek is not performing adequately to prevent upstream movement of nonnative fish. The purpose of this study is to develop a 30% design for replacement or enhancement of the barrier. The conceptual design should minimize impacts to the site, preserve the existing road and road prism requirements and minimize cost for construction and maintenance.

Analysis for the design is expected to include:

• Site selection- determine feasibility of nearby potential barrier locations

• Hydrology- development of estimates of peak discharge for the site to be utilized for design.

Reassess existing Q2, Q5, Q10, Q25, Q50, and Q100 for new sites (estimates are minimum requirements)

• Geomorphology- determination of suitability, stability of the site for an impoundment, determination of sediment transport considerations, and requirements for barrier shape and height;

• Hydraulics- Analysis of tailwater hydraulics related to fish swimming and jumping ability at design flows to determine design barrier height;

• Fish jumping ability-modeling fish jumping ability under specific hydraulic conditions to determine proposed barrier effectiveness.

A conceptual design (30%) level with conceptual level cost analysis and site impact analysis will be provided to aid in planning for funding and environmental impacts.

LOCATION

The barrier is located in Squaw Creek, 300-feet upstream of its intersection with the Y-55 road, in Apache County, Arizona, east of Whiteriver, Arizona. The location is on White Mountain Apache Tribal land.

The site is located at 7840 ft in elevation, with a watershed area of 5.22 square miles. The streambed and side slopes are relatively steep and forested. Rock outcroppings are found in the area, and geotechnical investigation (Western Technologies, 2020) found bedrock at 6’ below the surface at test pit #4, with potential outcropping nearer to the surface near the creek bed. See Appendix A- Geotechnical Report.

3 March 2021

Figure 1 Location map.

The project is located on Squaw Creek at the intersection of the Y-55 road about 30 miles east of Whiteriver, Arizona.

PROJECT OBJECTIVES

The objective of the project is to determine the concept for an effective fish barrier on Squaw Creek in the vicinity of the existing barrier. The concept must be detailed enough to provide a basis for a cost estimate and analysis of environmental effects for permitting purposes. Several specific tasks will be required to meet the objective.

Task 1- Site investigation, providing:

Determination of access points, construction parameters, site suitability and geotechnical (depth to bedrock and bedrock suitability;

Deploying a Geotechnical crew and design engineer;

Deliverable to include a geotechnical report describing depth of bedrock if pertinent, suitability of bedrock or soil for anchoring or bearing weight of the barrier and other key design considerations

Task 2- Barrier concept development (30% design), providing:

Hydrology- development of estimates of peak discharge for the site to be utilized for design.

Assess peak flows at Q2, Q5, Q10, Q25, Q50, and Q100

Geomorphology- determination of suitability, stability of the site for an impoundment, determination of sediment transport considerations, and requirements for barrier shape and height;

Project Site

4 March 2021

Hydraulics- Analysis of tailwater hydraulics related to fish swimming and jumping ability at design flows to determine design barrier height; Fish jumping ability-modeling fish jumping ability under specific hydraulic conditions to determine proposed barrier effectiveness

EXISTING CONDITIONS

Topographic surveys of the site were conducted on September 16 and 25, 2020, using survey grade GPS equipment. These measurements were utilized to build hydraulic models for analysis. Additionally, Western Technology conducted a geotechnical investigation of underlying materials which was utilized to determine need for footings or excavation of bedrock, etc. The results of the geotechnical surveys are provided as an Appendix to this report.

HYDROLOGY

Two methods were used to determine the site hydrology, the Rational Method using ATLAS-14 data, and National Streamflow Statistics program (Paretti et al 2014). NSS results for flood frequency are provided in Table 1. Atlas -14 Precipitation estimates and Rational Method Results are provided in Table 2 and Table 3, respectively. Comparison of results determined that the NSS method was conservative in large events and similar to the Rational Method for more frequent events. For this analysis we utilized the NSS output for the 2, 5, 10, 25, 50 and 100-year event peak flows.

Table 1: Peak Design Flow from NSS

Recurrence Interval (yr) 2 5 10 25 50 100 200 500 Flow (ft³/s) 51.4 118 180 279 367 466 579 751

Using the Rational Method, where Q=CIA, Q is flow in in·acre/ hour, “C” is a coefficient based on land surface characteristics, “I” is the intensity of the storm in inches per minute (based on ATLAS-14 data) and “A” is the area of the watershed in acres. Inch·acre/hour is very close to cubic feet per second (ft³/s), a multiplier of 1.008 is used to convert inch·acre/hour to CFS. The ATLAS-14 data is shown in Table 2, and the corresponding rational method peak flows is shown in Table 3. The estimated time of concentration is about 36 hours, and so we used the 24-hour design storm as the standard.

Table 2: ATLAS-14 Precipitation Frequency

PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)

Duration Average recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

5-min 0.324 0.416 0.539 0.63 0.746 0.832 0.919 1 1.11 1.2

10-min 0.494 0.634 0.821 0.958 1.14 1.27 1.4 1.53 1.69 1.83

15-min 0.612 0.785 1.02 1.19 1.41 1.57 1.73 1.89 2.1 2.27

30-min 0.824 1.06 1.37 1.6 1.9 2.12 2.33 2.55 2.83 3.05

60-min 1.02 1.31 1.7 1.98 2.35 2.62 2.89 3.16 3.5 3.78

2-hr 1.15 1.47 1.87 2.19 2.62 2.95 3.3 3.64 4.09 4.45

3-hr 1.23 1.55 1.95 2.28 2.73 3.09 3.46 3.84 4.36 4.77

6-hr 1.47 1.83 2.27 2.64 3.17 3.58 4.01 4.46 5.05 5.53

12-hr 1.81 2.26 2.79 3.23 3.84 4.33 4.84 5.36 6.07 6.63

24-hr 1.96 2.43 2.99 3.44 4.05 4.52 5.01 5.5 6.16 6.68

2-day 2.45 3.05 3.76 4.34 5.13 5.75 6.39 7.04 7.93 8.62

5 March 2021

Table 3: Rational Method Peak Flow

Duration Q2 Q5 Q10 Q25 Q50 Q100 Q200 Q500 hr CFS CFS CFS CFS CFS CFS CFS CFS 24 112.5 138.5 159.3 187.5 209.3 232.0 254.7 285.3

CURRENT SITE LAYOUT

The current fish barrier is located approximately 50 feet upstream of an existing 7’ by 11’ squash pipe culvert with the pipe invert approximately 20 feet below the roadway surface. The barrier is a concrete capped gabion structure with a low earthen wing wall on the right bank side. There has been considerable aggradation of fine sediments behind the barrier since construction. The sediment has filled to the top of the 5-foot tall barrier, decreasing stream slope to under 0.5% approximately 170-feet upstream of the existing barrier. An access ramp exists on the upstream side of the road to the existing fish barrier that can enable access to the construction area and provide a staging area. The effectiveness of the current barrier was previously determined as marginal (Natural Channel Design, 2010). Subsequently nonnative fish have been found upstream of the barrier.

There is a noticeable bed rock wall on the side of the canyon just upstream of the current barrier. Which provides a narrower valley setting and the potential to connect with bedrock. This alternative site was investigated along with other potential sites downstream, accessible by road. However, the current barrier site and the site just upstream in the narrower portion of the valley provide opportunities for construction of a successful barrier and these sites were further investigated for this study.

CURRENT CULVERT HYDRAULICS

The road prism is just over 20-feet tall. The existing roadway culvert is a seven-foot (high) by eleven-foot (wide), corrugated metal pipe, with a profile slope of 1.5% and is approximately 100 feet long. When modeled using HY-8, a culvert analysis program from FHWA (see Appendix 1), we found that during the Q-100 event the headwaters upstream of the culvert create a backwater that nearly overtops the existing fish barrier, the Q-50 backwater elevation (7884.83) was used to determine the Alternative 3 barrier notch elevation (7889.10) but would otherwise not impact the design elevations of the barrier at the preferred location.

GEOPHYSICAL INVESTIGATION

In the late fall of 2020, a geophysical crew from Western Technologies was utilized to investigate soils and depth to bedrock in the vicinity of the barrier site. Test pits were dug at the proposed site upstream of the existing barrier. The surface layers consisted of soil/cobble colluvium. However, the test pits found bedrock outcrops roughly six feet below the surface. The pit locations and bedrock elevations indicated that the bedrock sill likely slopes down hill at roughly the same slope as the surface of the floodplain.

6 March 2021

The extent of this slope is unknown without more extensive testing. Detailed results of the geophysical testing is provided in Appendix 1.

BARRIER DESIGN ANALYSIS

A jump height barrier was considered to be the most promising concept for the sites in consideration. We utilized an iterative method to determine minimum height requirements based on the streams estimated Q50 discharge, weir and tailwater dynamics combined with fish jumping ability. The method and assumptions are outlined below.

FISH JUMPING ABILITY

Fish jumping ability was estimated using a ballistic equation after Bell (1991). Jump height varies as a function of relative velocity at the time the fish leaves the water and angle of attack. Relative velocity is based on maximum burst swim velocity minus the water velocity. Adequate depth for jumping is also required but is often not limiting (>0.5 ft). For the purposes of this design, it is assumed that fish will always have a suitable depth to jump from. Bell (1991) suggests adding the length of the fish to the jump height to accommodate continued propulsion until the fish’s tail has left the water. While adding the length of fish to estimate jump height is recommended, it is problematic to estimate fish length over the many different populations. Instead, focus was on estimating maximum burst velocity for the largest fish in the population, and then calculating a factor of safety which can incorporate fish body length.

Maximum velocity for burst speed used in this report is 13.5 feet per second (fps) for full-sized adult Rainbow trout; Brown trout is slightly less (13 fps). Estimating reasonable burst speeds is critical to the calculation of barrier height, but problematic. Several authors have compiled information on trout swimming performance and many references are available in the literature dealing with fish passage. However, many of these estimates come from laboratory experiments, utilizing caged fish. Estimates of burst swimming or jump height for wild, motivated trout are not available. The approach utilized herein is a consensus of literature and experts to come up with a narrower range of values that was compared to known successful jumps over barriers. Swimming performance was back-calculated using trajectory formulas, size of fish, and barrier conditions at the time of the barrier attainment.

Angle of attack is an important aspect of jumping height with angles close to 90° providing maximum height but less forward motion. Some barrier geometries may force very low angles of attack and limit jump height;

however, a maximum angle of attack of 80° which maximizes height while ensuring forward motion to propel fish over the barrier was used.

Using the ballistics equation, 𝑦𝑦 = 𝑐𝑐y + 𝑉𝑉y × 𝑡𝑡 − 𝑔𝑔 × 𝑡𝑡 , where cy is the length of the fish, Vy is the burst speed

13.5fps times the sin of the angle of attack, g is gravitational acceleration and t is the time in seconds, we get a jump height of 2.8 ft (Figure 2) for an 80° angle of attack (when cy is 0). This does not take into account the length of the fish, however to account for the fish length we use a Factor of Safety multiplier of 1.5, we get a jump height of 4.2 feet. Accordingly, the relative height of the barrier at any flow would need to be greater than

4.2 feet. Minimum barrier height is defined as the height between the surface of the tailwater pool and the top of the barrier. This distance diminishes as flows increase. For a conservative estimate of jump height, it is assumed that fish can find enough zero velocity water at the base of the falls to jump from. Thus, tailwater velocity is not considered for barrier effectiveness in this design. However, the preferred design has a concrete apron with steep slopes expected to maintain higher velocities that will limit relative swim velocity. While tailwater velocity can provide a significant reduction in jump height (Figure 3), leaving tailwater velocity out of the jump height calculations provides another layer of safety to prevent passage.

7 March 2021

Figure 2. Jump trajectory at 13.5 feet per second

Jump trajectories were calculated from the ballistic equation utilized by Bell (1991) using a range of trajectory angles.

Trajectories are based on burst velocity of 13.5 fps. No correction for fish length was made.

Figure 3. Jump height vs. tailwater velocity

Figure shows the reduction in jump height due to increasing tailwater velocities.

FISH BARRIER DESIGN

The Fish Barrier was modeled as a two stage weir with downstream pool and tailwater to determine the height necessary to prevent fish passage. Using the parameters and equations from Figure 4 and Figure 5Figure 5, we determined that a Drop Height (h0) of 9.5 feet was necessary to maintain a jump height of

4.2 feet for Q50 of 367 ft³/s. The first stage weir (the notch) depth and width were determined using

8 March 2021 regional curve information to approximate bankfull flow (43 ft³/s) and average bankfull width (16 ft). The barrier wing walls tie into the two stage weir wall approximately two and a-half feet above the weir notch in order to contain the Q100 discharge with larger flows spilling over the entire width of the weir. The width of the Weir Notch (Ln) approximates the bankfull width of the existing channel. Table 4 provides the jump heights for flows over the weir.

Figure 4: Profile for a Straight Drop Spillway Structure

Figure 5: Cross-Section for a Straight Drop Spillway Structure (FHA 2006)

Weir hydraulic parameters are as follows:

• Q = Discharge (cfs)

• L = Weir Length

• H = Stage or Flow Depth (ft)

Geometric parameters are as follows:

• L = Weir Notch Length

• Hn = Weir Notch Height

• ho = Drop Height

Hydraulic parameters were determined as follows:

• yc = Depth of the Weir Crest (ft)

• Ln = Length of Weir Notch (ft)

• An = yc L Flow Area of Weir Notch for a Given Depth (ft2)

• qn = Q/L Unit Discharge through the Weir Notch (cfs/ft)

• Nd = qn2/gho3 Drop Number Gives a Quantitative Number for Drop

• y1 = 1.0hoNd0.22 Pool Depth under the Nappe (ft)

• HJ = ho-y1 Jump Height is the Difference between Drop Height and Pool Depth (ft)

• Vn= Q/An Average Velocity through the Weir for a Given Depth (ft/s)

• HD = (ho+yc)-y2 Head Differential between the Reservoir Surface Elevation and the Depth of Flow at the Beginning of the Hydraulic Jump (ft)

9 March 2021

• VF = (2gHD)1/2 Velocity of the Falling Water as it Enters the Plunge Pool (ft/s)

A safety factor (SF) was estimated to help determine effectiveness of the barrier design. The safety factor is a ratio of the calculated jump height divided by the theoretical jump height of 2.8 feet. Bell (1991) suggested that leaping fish may be able to utilize their entire body length rather than just tail propulsion during landing at the top of jumps. He therefore suggested that body length be added to jump height based on ballistics equation. Given a hypothetical fish length of one foot a jump height of 3.8 feet could be overcome and a minimum safety factor of 1.3 should be targeted as a minimum to prevent fish passage of moderately large fish in Squaw Creek. Larger safety factors can account for larger fish and other unknowns in the environment.

As an additional safety measure, it is planned that the base of the drop will be built as a sloped ramp away from the base of the barrier. The slope and height of the ramp will be such that pool formation will be away from the base of the barrier and prevent low velocity site at the base for a fish to jump from.

10 March 2021

Weir Inputs C

Top Height 9.5 Q = CLH3/2 3.1

Top Length 40 H_0n 8.583333

Notch Depth 0.916667 L_t 24

Notch Length 16

Flood Q2 Q5 Q10 Q25 Q50 Q100 Discharge (cfs) 51 118 180 279 367 466

Y_c

Q Nappe Depth

Jump Height

Velocity

Flow Depth

Tailwater Depth

Q

Area

Unit Q

Drop #

Nappe De

Flow Dept

Jump Heig

SF

ft. cfs ft. ft. ft./s ft. ft. cfs ft^2 cfs/ft. ft. ft. ft. ft. Red < 1.5 < Green

0.25 6.20 2.02 6.56 1.55 0.28 2.42 6.20 0.00 4.00 0.39 0.00 1.40E-03 2.34

0.50 17.54 2.54 6.04 2.19 0.44 3.20 17.54 0.00 8.00 1.10 0.00 3.97E-03 2.16

0.75 32.22 2.91 5.68 2.68 0.57 3.77 32.22 0.00 12.00 2.01 0.00 7.29E-03 2.03

~Q bankfull 0.92 43.53 3.11 5.48 2.97 0.65 4.09 43.53 0.00 14.67 2.72 0.00 9.84E-03 1.96

`Q2 1.00 51.39 3.20 5.39 2.85 0.69 4.24 49.60 1.79 18.00 3.10 0.07 1.12E-02 2.44E-04 1.52 0.15 1.67 7.98 1.92 2.85

1.25 83.64 3.44 5.14 2.99 0.79 4.64 69.32 14.32 28.00 4.33 0.60 1.57E-02 1.95E-03 2.41 0.36 2.93 7.09 1.84 2.53 ~Q5 1.50 124.27 3.65 4.93 3.27 0.89 5.00 91.12 33.15 38.00 5.70 1.38 2.06E-02 4.51E-03 2.90 0.52 3.67 6.60 1.76 2.36

1.75 171.42 3.84 4.74 3.57 0.98 5.32 114.83 56.60 48.00 7.18 2.36 2.60E-02 7.71E-03 3.26 0.65 4.24 6.24 1.69 2.23 `Q10 1.80 181.55 3.88 4.70 3.63 1.00 5.38 119.78 61.77 50.00 7.49 2.57 2.71E-02 8.41E-03 3.32 0.67 4.34 6.18 1.68 2.21

2.00 224.18 4.02 4.57 3.87 1.07 5.61 140.29 83.89 58.00 8.77 3.50 3.17E-02 1.14E-02 3.55 0.77 4.71 5.95 1.63 2.12 ~Q25 2.25 281.95 4.18 4.41 4.15 1.15 5.89 167.40 114.55 68.00 10.46 4.77 3.79E-02 1.56E-02 3.80 0.88 5.13 5.70 1.57 2.03

2.50 344.29 4.32 4.26 4.41 1.23 6.14 196.06 148.23 78.00 12.25 6.18 4.43E-02 2.02E-02 4.03 0.98 5.50 5.47 1.52 1.96 ~Q50 2.60 370.43 4.38 4.20 4.52 1.26 6.24 207.94 162.49 82.00 13.00 6.77 4.70E-02 2.21E-02 4.11 1.02 5.64 5.39 1.50 1.93

2.75 410.88 4.46 4.12 4.67 1.31 6.38 226.19 184.69 88.00 14.14 7.70 5.12E-02 2.52E-02 4.23 1.07 5.83 5.27 1.47 1.88 ~Q100 2.95 467.03 4.57 4.02 4.86 1.37 6.57 251.31 215.72 96.00 15.71 8.99 5.68E-02 2.94E-02 4.37 1.15 6.08 5.13 1.43 1.83

3.00 481.45 4.59 3.99 4.91 1.38 6.61 257.73 223.72 98.00 16.11 9.32 5.83E-02 3.05E-02 4.41 1.16 6.14 5.09 1.43 1.82

3.25 555.79 4.72 3.87 5.15 1.46 6.83 290.61 265.18 108.00 18.16 11.05 6.57E-02 3.61E-02 4.58 1.25 6.43 4.92 1.38 1.76

Table 4: Jump Height at Drop Structure

Chosen top height of weir was calculated via iterative attempts to achieve appropriate Safety Factor (SF) >1.5.

Report

30% Design

Natural Channel Design, Inc.

11 March 2021

ALTERNATIVES CONSIDERED

Retrofitting of the existing culvert at this site was not considered because of the extensive amount of road fill over the culvert and the limited ability to steepen the culvert slope. Additionally, retrofit of the existing barrier was not considered because of the poor structural condition of the gabion structure and the disparity between existing and desired barrier height. Consequently, alternatives were formed by placing the desired outlet height and width into several locations within the site to explore costs, site impacts and determine additional data needs. All alternatives considered an additional requirement that footers for the barrier be tied to underlying bedrock to prevent piping through the colluvial material caused by increased hydraulic head created by the barrier impoundment. We provide three basic alternatives for a concept design for consideration.

ALTERNATIVE 1 – FULL HEIGHT BARRIER AND FOOTER

Alternative 1 – Full height barrier and Footer, this alternative would be built at the upstream site within the relatively narrow canyon in close proximity to the existing bedrock walls. The concrete weir structure would be built approximately 9.5 feet above the existing streambed. The barrier wall would have to extend approximately 6 feet below the surface to tie to bedrock. Wing walls would have to extend entirely across the valley floor (~75 feet) with smaller footings tied to bedrock. In order to contain the Q50 flow within weir, the wing walls would extend 2.5 feet above the top of barrier, with channel walls constructed downstream of the barrier face, and extending 20-feet, with a concrete apron between the channel walls. See Figure 6 for a plan and profile view showing the barrier configuration. This alternative would minimize impacts to the downstream channel. However, it is recommended that the existing barrier be removed and the grade of the channel be stabilized in the area immediately upstream of the existing barrier.

Figure 6: Alternative 1 Plan and Profile

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Natural Channel Design, Inc.

12 March 2021

ALTERNATIVE 2 – SUNKEN BARRIER AND EXCAVATED CHANNEL

This alternative would be built in the same location as Alternative 1. However, footer and wingwall construction would be minimized by lowering the downstream channel and thus the depth to bedrock.

The channel would have to be excavated and stabilized downstream past the existing barrier and just upstream of the road culvert. The excavated channel would be sized appropriately with an appropriate floodplain and vegetation for the area. See Figure 9 for a plan and profile view showing the barrier location and configuration.

Figure 7: Alternative 2 Plan and Profile

ALTERNATIVE 3 – SUNKEN BARRIER NEAR EXISTING BARRIER SITE.

Development of this alternative was undertaken in an effort to minimize earth moving quantities while taking advantage of a diminished top height to bedrock distance. The barrier would be located just upstream of the existing barrier, far enough upstream from the culvert to prevent back watering to the base of the barrier. The channel would be dug lower into the colluvium to allow a shorter footer wall to contact with bedrock. Unfortunately, the exact depth to bedrock in this area can only be inferred from the dip angle estimated from the geotechnical pits. Additionally, the wing wall would be very long to reach the valley sides (~110 feet). The area of inundation would be 9,645 square feet, or 0.22 Acre, and would impound approximately 730 cubic yards, or 0.45 acre-feet. See Figure 8 for a plan and profile view showing the barrier location and configuration.

30% Design

Natural Channel Design, Inc.

13 March 2021

Figure 8: Alternative 3 Plan and Profile

CONSTRUCTION IMPACTS TO SITE

Construction should take place when the flow is seasonally the lowest. During the September 2020 survey, the measured flow was approximately 5 cfs. We anticipate that the construction of this fish barrier will begin with construction of the dewatering system. The dewatering system is expected to consist of a temporary diversion approximately 450-feet upstream of the roadway culvert. Using an 18” flexible pipe running along the east bank, outside of the construction area and discharging into the roadway culvert. We also anticipate a 6” trash pump will be installed upstream of the barrier location, with pipe running along the east bank, outside of the construction area and discharging into the roadway culvert. The length of stream that would be dewatered is approximately 550-feet. The limits of construction activities can be seen in Figure 9.

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Natural Channel Design, Inc.

14 March 2021

Figure 9: Limits of Construction

With dewatering in place, excavation for the barrier wall can commence. When excavation for the barrier and wing walls is complete, the foundations can be formed, steel and concrete placed. During initial foundation cure, the existing barrier can be removed and excavation of the re-aligned channel can begin. After foundation concrete has initially cured, the walls for the barrier and wingwalls can be formed, steel and concrete placed. During initial cure of the barrier and wingwalls, the foundation for the channel walls can be excavated, formed, steel and concrete placed. After initial cure of the Channel wall foundations, the walls for the channel walls can be formed, steel and concrete placed.

After initial cure of the channel walls the aggregate base for the slope apron can be placed and compacted, and then steel placed and concrete poured for the channel apron. During these operations the channel hardening can be installed including installation of a rip rap scour pad, and rock sills as needed. Finally planting and removal of the dewatering system can occur.

When removing the dewatering system, first the trash pump will be shut off and then the diversion will be slowed but not completely shut down to allow continuous flow throughout squaw creek. When flow over the fish barrier reaches the end of diversion, then the remaining portion of the dewatering system can be removed.

OLD BARRIER REMOVAL AND CHANNEL EXCAVATION

The existing fish barrier is to be removed as part of this project, in order to improve channel flow the flow downstream of the fish barrier. We do not know what work was performed in the creek during the construction of the fish barrier but suspect that the aggregated soils behind the fish barrier will be easily removed using the excavator needed for the barrier foundation excavation. It is expected that from the commencement of dewatering to the time that the barrier foundations are excavated, two to three weeks, that the soils would be dry enough for removal and stockpiling for fill behind the barrier and fill between the channel walls and wingwalls, as well as to provide ramp access behind the

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15 March 2021 barrier. We expect approximately 1,000 cubic yards of spoil material to be removed during the barrier removal and channel reconstruction work. The bulk of the work is confined to the area between the downstream edge of the fish barrier to the existing fish barrier, and is largely filled with sediment. We expect that the materials removed from the channel regrading will be used to fill the area upstream of the new culvert inlet structure.

A channel that is capable of containing the bankfull flow, of approximately 43 cubic feet per second was designed, for the channel regrading, consisting of a 12-foot bottom width and a depth of 9-inches with 2:1 side slopes that then spread out with a 5-foot floodplain that then catches into the existing embankment with 4:1 side slope on the right bank and a 2:1 side slope on the left bank. Reducing these slopes would create excessive excavation, cutting well into the existing bank slopes. Figure 10 shows the typical channel reconstruction. The proposed channel will contain well over the 100-year peak runoff, over 466 CFS.

Figure 10: Typical Channel Cross-Section (below barrier)

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16 March 2021

INSTITUTIONAL AND JURISDICTIONAL CONSIDERATIONS

Construction of this project will require permitting through tribal environmental clearances and a Clean Water Act Section 404 permit via the Army Corps of Engineers. Review by tribal roads management and recreation departments is highly recommended.

RESULTS, CONCLUSIONS, RECOMMENDATIONS

The proposed Alternative 2 – Sunken Barrier and Excavated Channel, located approximately 200 feet upstream of the existing fish barrier, is the most cost effective barrier reviewed. While there is additional site disturbance compared to the other two alternatives analyzed, the end result will be an effective fish barrier and restored creek alignment downstream of the barrier.

The least expensive of the alternatives will create some ponding and sedimentation upstream of the barrier, however a bulk of the sedimentation will be offset by using the existing aggraded soils upstream of the existing fish barrier. There will be no adverse impacts to the roadway or the existing roadway culvert, during or after construction.

Construction of Alternative 2 requires the removal of the existing downstream barrier and excavation of a new channel through the accumulated sediments to provide adequate channel flow downstream of the proposed fish barrier.

Additional engineering is required to produce construction plans and specifications for the project.

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20 March 2021

REFERENCES

The National Streamflow Statistics Program, Paretti, N.V., Kennedy, J.R., Turney, L.A., and Veilleux, A.G., Methods for estimating magnitude and frequency of floods in Arizona, developed with unregulated and rural peak-flow data through water year 2010: U.S. Geological Survey Scientific Investigations Report 2014-5211, 61 p., http://dx.doi.org/10.3133/sir2014521

HY-8, Culvert Hydraulic Analysis Program, United States Department of Transportation, Federal Highway

Administration

Gordian RSMeans Data, Site Work & Landscape Costs, 2017, Construction Publishers & Consultants, Rockland, MA

NRCS, Cross -Section Hydraulic Analyzer, Uniform flow hydraulic parameters, Version xsecAnalyzerVer18.xlsm, United States Department of Agriculture, Natural Resources Conservation Service http://dx.doi.org/10.3133/sir2014521

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21 March 2021

CONSTRUCTION DRAWINGS AND SPECIFICATIONS

Cover Sheet Staging Area & Construction Sequence Plan & Profile Alternate 1 Plan & Profile Alternate 2 Plan & Profile Alternate 3 Alternative Cross Sections

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22 March 2021

APPENDIX 1

Project Notes

HY-8 Culvert Analysis Report

Project Title: Squaw Creek Existing Culvert Crossing

Designer: J. Ebers

Project Date: Friday, March 12, 2021

Site Data - Culvert 1 Site Data Option: Culvert Invert Data Inlet Station: 0.00 ft Inlet Elevation: 78.60 ft Outlet Station: 100.00 ft Outlet Elevation: 77.10 ft Number of Barrels: 1

Culvert Data Summary - Culvert 1 Barrel Shape: Pipe Arch Barrel Span: 128.00 in Barrel Rise: 83.00 in Barrel Material: Steel or Aluminum Embedment: 0.00 in Barrel Manning's n: 0.0270 Culvert Type: Straight Inlet Configuration: Projecting Inlet Depression: None

Tailwater Channel Data - squaw creek Tailwater Channel Option: Trapezoidal Channel Bottom Width: 20.00 ft Side Slope (H:V): 1.50 (_:1) Channel Slope: 0.0150 Channel Manning's n: 0.0350 Channel Invert Elevation: 77.00 ft

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23 March 2021

Roadway Data for Crossing: squaw creek Roadway Profile Shape: Constant Roadway Elevation Crest Length: 100.00 ft Crest Elevation: 100.96 ft Roadway Surface: Gravel Roadway Top Width: 20.00 ft

Table 1 - Culvert Summary Table: Culvert 1

Total

Discharge (cfs)

Culvert

Discharge

Headwater Elevation

(ft)

Inlet

Control Depth (ft)

Outlet

Control

Flow Type

Normal

Critical

(ft/s)

(ft/s)

41.00 41.00 80.26 1.662 0.0* 1-S2n 1.034 1.092 1.034 0.571 5.483 3.446

83.50 83.50 81.07 2.474 0.176 1-S2n 1.469 1.588 1.469 0.872 7.008 4.493

126.00 126.00 81.74 3.142 0.686 1-S2n 1.824 1.987 1.824 1.114 8.051 5.218

168.50 168.50 82.36 3.759 1.190 1-S2n 2.141 2.334 2.141 1.324 8.855 5.790

211.00 211.00 82.94 4.338 1.707 1-S2n 2.438 2.649 2.438 1.512 9.513 6.266

253.50 253.50 83.47 4.874 2.247 1-S2n 2.723 2.941 2.723 1.685 10.063 6.679

296.00 296.00 83.99 5.385 2.814 1-S2n 3.003 3.216 3.003 1.846 10.532 7.044

338.50 338.50 84.49 5.891 3.412 1-S2n 3.280 3.475 3.280 1.997 10.939 7.372

367.00 367.00 84.83 6.233 3.832 1-S2n 3.466 3.643 3.466 2.093 11.182 7.576

423.50 423.50 85.54 6.940 4.708 5-S2n 3.839 3.959 3.844 2.276 11.583 7.947

466.00 466.00 86.11 7.509 5.408 5-S2n 4.128 4.185 4.128 2.406 11.864 8.203

* Full Flow Headwater elevation is below inlet invert.

Straight Culvert

Inlet Elevation (invert): 78.60 ft, Outlet Elevation (invert): 77.10 ft

Culvert Length: 100.01 ft, Culvert Slope: 0.0150

24 March 2021

Culvert Performance Curve Plot: Culvert 1

Water Surface Profile Plot for Culvert: Culvert 1

25 March 2021

Table 2 - Downstream Channel Rating Curve (Crossing: squaw creek)

Flow (cfs) Water Surface Elev (ft) Depth (ft) Velocity (ft/s) Shear (psf) Froude Number

41.00 77.57 0.57 3.45 0.53 0.82

83.50 77.87 0.87 4.49 0.82 0.87

126.00 78.11 1.11 5.22 1.04 0.90

168.50 78.32 1.32 5.79 1.24 0.93

211.00 78.51 1.51 6.27 1.42 0.94

253.50 78.68 1.68 6.68 1.58 0.96

296.00 78.85 1.85 7.04 1.73 0.97

338.50 79.00 2.00 7.37 1.87 0.98

367.00 79.09 2.09 7.58 1.96 0.98

423.50 79.28 2.28 7.95 2.13 0.99

466.00 79.41 2.41 8.20 2.25 1.00

Crossing Discharge Data

Discharge Selection Method: Specify Minimum, Design, and Maximum Flow Minimum Flow: 41 cfs Design Flow: 367 cfs Maximum Flow: 466 cfs

Table 3 - Summary of Culvert Flows at Crossing: squaw creek

Headwater Elevation (ft)

Total Discharge (cfs) Culvert 1 Discharge

Roadway Discharge

Iterations

80.26 41.00 41.00 0.00 1

81.07 83.50 83.50 0.00 1

81.74 126.00 126.00 0.00 1

82.36 168.50 168.50 0.00 1

82.94 211.00 211.00 0.00 1

83.47 253.50 253.50 0.00 1

83.99 296.00 296.00 0.00 1

84.49 338.50 338.50 0.00 1

84.83 367.00 367.00 0.00 1

85.54 423.50 423.50 0.00 1

86.11 466.00 466.00 0.00 1

100.96 1083.47 1083.47 0.00 Overtopping

26 March 2021

Rating Curve Plot for Crossing: squaw creek