glac01045_RevisedFinalHydraulicMemo.pdf

Prepared for:

WESTERN FEDERAL LANDS HIGHWAY DIVISION

REVISED FINAL HYDRAULIC DESIGN

MEMORANDUM

Upper McDonald Creek Bridge Replacement

MT PRA GLAC 10(45)

IDIQ Contract No. DTFH7015D00007 Task Order No. 69056721F000007

July 2021

Prepared by:

ROBERT PECCIA &

ASSOCIATES

Helena, Montana

Upper McDonald Creek Bridge Replacement, MT PRA GLAC 10(45)

Revised Final Hydraulic Design Memorandum

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TABLE OF CONTENTS

Abbreviations/Acronyms ........................................................................ ii

1.0 Project Background

2.0 This Memorandum

3.0 Drainage Characteristics

4.0 Existing Culvert Inventory

5.0 Existing Bridge Assessment

6.0 Existing Stream Assessment

7.0 Hydrology

7.1 Drainage Basin Delineation

7.2 Hydrologic Methods and Analysis

7.2.1 Design Flood Frequency and Freeboard Requirements

7.2.2 USGS Regional Regression Equations and Flow Summary

8.0 Bridge Analysis and Recommendations

8.1 Existing Condition HEC-RAS Model and Calibration

8.2 Proposed Bridge HEC-RAS Model

8.3 Proposed Bridge Scour

8.4 Proposed Bridge Abutment Riprap

Tables

Table 1: Existing Culverts Table 2: Existing Streambed Gradation (Visually Estimated) Table 3: Upper McDonald Creek Peak Flows Table 4: Upper McDonald Creek Bridge Hydraulic Comparison – High Lake Table 5: Proposed Bridge Scour – Low Lake Conditions Table 6: Proposed Bridge Scour – High Lake Conditions

Figures

Figure 1: Project Vicinity Map Figure 2: Existing Bridge Elevation View Figure 3: Existing East Bridge Pier, (Bent 2) Figure 4: Existing Bridge Center Pier, (Bent 3) Figure 5: Existing West Abutment and Upstream Bank Figure 6: Existing Upstream Channel Figure 7: Existing Downstream Channel Figure 8: Upper McDonald Creek Overview Figure 9: Existing Bridge Pier OHW Marks Figure 10: Spring 2011 Highwater

Revised Final Hydraulic Design Memorandum

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Appendices

Appendix A: Existing Drainage Culvert and Bridge Photographs

Appendix B: Upper McDonald Creek Hydrology Analysis

Appendix C: Existing Bridge HEC-RAS Analysis

Appendix D: Proposed Bridge HEC-RAS Analysis

Appendix E: Proposed Bridge Scour Analysis

Appendix F: Proposed Bridge Abutment Riprap Analysis

ABBREVIATIONS/ACRONYMS

cfs cubic feet per second

FHWA Federal Highway Administration

FEMA Federal Emergency Management Agency

FETS Flared End Terminal Section

GPS Global Positioning System

GTSR Going-to-the-Sun Road fps feet per second

HEC-RAS Hydrologic Engineering Center River Analysis System

NEPA National Environmental Policy Act

NCHRP National Cooperative Highway Research Program

OHW Ordinary High Water

PDDM Project Development and Design Manual

Q# #-year design flow

RCP Reinforced Concrete Pipe

RPA Robert Peccia and Associates

RS River Station

USGS United States Geological Survey

WSE Water Surface Elevation

HEC Hydraulic Engineering Circular

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1.0 PROJECT BACKGROUND

The Federal Highway Administration (FHWA) is intending to complete the design and NEPA documentation for the Upper McDonald Creek Bridge Replacement project.

The proposed project is located Glacier National Park, running along Upper McDonald Creek Road (aka Kelly Camp) in Flathead County, Montana. The proposed project comprises an approximate 0.4-mile section roadway approach (split equally on each side of the bridge) and replacement of the existing Upper McDonald Creek Bridge with a new single span bridge structure. The existing bridge is a four span timber structure that is beyond its predicted service life, functionally obsolete, and has restricted load limits which impacts Park operations.

The project starts near the intersection of Upper McDonald Creek Road and Going-to-the-Sun Road (GTSR) and ends near the intersection of Upper McDonald Creek Road and McDonald Creek Trailhead.

The project also includes clearing, excavation, grading, drainage, aggregate base and asphalt surface course, guardrail, revegetation, piling, concrete, existing bridge demolition, new bridge construction, right of way documentation, and phone line and power line relocation.

The proposed project is located approximately 10 miles north of the town of West Glacier in Flathead County, Montana. Approximate Global Positioning System (GPS) coordinates for the center of the project are 48°38'7.37"N, 113°52'0.64"W. A project vicinity map is shown in Figure 1.

Figure 1: Project Vicinity Map

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2.0 THIS MEMORANDUM

The purpose of this memorandum is to document the hydraulic conditions associated with the existing drainage and bridge structures along the proposed project corridor, as well as the hydraulic analysis and design recommendations for proposed culverts and the new bridge structure over Upper McDonald Creek.

This memorandum will discuss drainage characteristics, hydrologic and hydraulic assessments, and a summary of proposed culvert and bridge hydraulic recommendations. Potential floodplain encroachments are also discussed in this memorandum. Sections 8.3 and 8.4 are revised from the Final Hydraulics Memorandum submitted April 2021. Proposed bridge scour calculations and abutment riprap recommendations are updated to reflect modifications to the proposed bridge foundation type at the western bridge end.

3.0 DRAINAGE CHARACTERISTICS

The project area lies within Glacier National Park approximately 10 miles north of the town of West Glacier in Flathead County, Montana. The topography of the area is characterized as mountainous with steep timber and glaciated slopes. The project area falls within the Northwest hydrologic region as described in the United States Geologic Survey (USGS) Scientific Investigations Report 2015-5019. Timbered slopes with peaks extending above tree line, and glaciated timbered valleys dominate the area. Upper McDonald Creek is the primary stream crossing along the project corridor. This creek includes approximately 109.4 square miles of drainage area contiguous within the park. Approximately 0.2 miles below the project bridge site, Upper McDonald Creek discharges to Lake McDonald.

4.0 EXISTING CULVERT INVENTORY

An existing culvert inventory was completed in December 2020 along the project corridor. During this field investigation, one existing drainage culvert was located. This culvert is generally located east of the bridge site and near the toe of fill associated with GTSR. This 18-inch CMP culvert functions as a relief pipe connecting low areas on both the north and south sides of Upper McDonald Creek Road and there is no evident drainage basin or flow channel associated with it.

The existing culvert location, type, size, and condition were documented for this memorandum. However, this culvert will likely not be impacted by the construction limits of this project and will not be replaced.

Therefore, the existing culvert capacity along with allowable headwater and tailwater controls are not evaluated for this pipe.

A summary of the existing culvert inventory is listed in Table 1 and photos of existing culvert are included in Appendix A.

Table 1: Existing Culverts

Proposed Station

Existing Culvert Field Notes Photo #

Diameter (in) Material Length (ft) Slope % Condition Service Life

3+07 18 CMP 52.3 1.4 Good 20+ Years FETS both ends 1,2

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5.0 EXISTING BRIDGE ASSESSMENT

The existing Upper McDonald Creek Bridge (Kelly Camp Bridge) was constructed in 1965 following a large flood event in 1964 that washed out the previous bridge structure. The existing bridge is noted as federal bridge structure 1430-001P and is a 4 span, 200-foot-long timber structure. An elevation view from the 1965 As-built plans is shown in the following figure.

Figure 2: Existing Bridge Elevation View

The deck roadway width is approximately 14 feet, and the structure is generally perpendicular to the stream channel. The low beam elevation of the existing bridge is governed by the two center spans and was surveyed at 3168.67 feet. This elevation is approximately 15.7 feet above the thalweg of the stream surveyed at an elevation of 3152.93 feet. The structure depth is approximately 4.4 feet.

The existing bridge substructure consists of 16-inch 24-ton treated timber piles. Bents 2 and 4 consist of 5 timber piles typical of the following photo.

Figure 3: Existing East Bridge Pier, (Bent 2)

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Bent 3 (center pier) is constructed with 8 timber piles wrapped with treated boards and fit with an angled steel nose on both ends. Bent 3 (center pier) is shown in the following photo.

Figure 4: Existing Bridge Center Pier, (Bent 3)

The existing bridge end abutments are protected by large riprap (Class 5 or larger) on approximate 1V:2H slopes from the channel edge to the face of the abutments. Some of the existing riprap stones measure 3- 4 feet on the long axis.

The existing eastern bridge abutment appears to encroach into the floodway and a backwater condition is likely upstream of this abutment. The western bridge abutment does not appear to encroach into the floodway however the western stream bank, upstream of the existing abutment, is very steep and unstable.

Slope sluffing and exposed tree roots near the top of the bank, shown in the following photo, are evidence of bank instability that will likely require mitigation as part of the proposed bridge replacement. Photos of the existing bridge are included in Appendix A.

There is no delineated floodplain associated with Upper McDonald Creek in this area.

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Figure 5: Existing West Abutment and Upstream Bank

6.0 EXISTING STREAM ASSESSMENT

Upstream of the bridge crossing, Upper McDonald Creek is a moderate to high velocity mountain stream with a large waterfall occurring approximately 0.32 miles upstream of the bridge. In this section the stream channel is generally straight and sloped at approximately 0.68%. The bank full width is approximately 160- 170 feet and the ordinary highwater depth is approximately 9.0 feet. The 50-year flood depth is approximately 13 feet.

Upstream of the bridge site, the stream channel is moderately stable and characterized by gravels, cobbles and large boulders across the channel bottom with an estimated Manning’s (n) value of 0.07. However, the west bank of the stream is steep (approximately 1V:1H) and comprised of moderately erodible soils.

These soils are generally unstable and sluffing into the stream channel exposing tree roots and potentially affecting the existing west bridge abutment. The east bank of the stream is generally stable and lined with large trees and heavy brush. The channel is not aggrading or degrading in this area. The upstream channel extending to the existing waterfall is shown in the following photo.

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Figure 6: Existing Upstream Channel

Through the bridge crossing, the stream channel geometry is generally consistent with the upstream channel. However, the channel slope is generally flat through the crossing area. The bank full width near the bridge site is approximately 160-170 feet and the ordinary highwater depth is approximately 9.0 feet.

The 50-year flood depth is approximately 12 feet. The number of large boulders in the stream channel diminishes through the crossing area with gravels and cobbles beginning to dominate the channel material.

Minor pier scour is noted at both the existing western and eastern bridge piers. No significant pier scour was noted at the center pier. Some woody debris is noted in this section and is evident on various existing bridge piers.

Near the crossing location a gradation of the existing streambed material was visually estimated and is summarized in the following table.

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Table 2: Existing Streambed Gradation (Visually Estimated)

Stream Name Gradation

D15 (ft) D50 (ft) D85 (ft) D95 (ft)

McDonald Creek

0.004 0.164 0.410 0.0. 0.476476

Downstream of the bridge site the stream channel begins to broaden on a gentle grade and transition to the alluvial fan at the lake interface approximately 0.2 miles downstream of the bridge. In this area the bank full width ranges from 200 to 400 feet and the 50-year flood depth is approximately 10 feet. Similarly, the channel bottom material transitions to finer material and is composed primarily of finer gravels and small cobbles. The downstream channel shows minor backwash and streambed deposition as flow slows and spreads out near the lake. The main channel banks downstream of the bridge site are stable and well vegetated with large trees and heavy brush extending to the highwater level of Lake McDonald. Large woody debris is evident in this section. The downstream channel is shown in the following photo.

Figure 7: Existing Downstream Channel

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An overview of Upper McDonald Creek and the bridge site is shown in the following figure. Additional photos of the existing stream channel are included in Appendix A.

Figure 8: Upper McDonald Creek Overview

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7.0 HYDROLOGY

7.1 DRAINAGE BASIN DELINEATION

The drainage basin associated with Upper McDonald Creek at the project crossing was delineated with the USGS StreamStats program and cross referenced with available as-built information and bridge inspection reports. At the project crossing, the McDonald Creek basin encompasses 109.4 square miles extending to the north. A drainage basin delineation map along with a listing of basin characteristics is included in Appendix B.

7.2 HYDROLOGIC METHODS AND ANALYSIS

There are no USGS gauges associated with McDonald Creek. Therefore, the USGS Regional Regression Equations were used to calculate peak design flows for the bridge crossing. A discussion of this analysis is included in the following sections of this memorandum.

7.2.1 Design Flood Frequency and Freeboard Requirements

Per chapter 7.4.3.3.1 of the Federal Highway Administration Project Development and Design Manual (PDDM), the design flood for a bridge structure is the 50-year event for both Low and High Standard roadways. The check flood event is the greater of the 100-year flood or the overtopping flood as the standard check flood for water surface increase caused by the crossing.

Freeboard requirements for the Upper McDonald Creek bridge are set in accordance with Section 7.4.3.4.1 of the PDDM. In this case the required freeboard for the proposed Upper McDonald Creek bridge will be 3.5-5.0 feet as the potential for woody debris is significant. Additional freeboard to account for ice flows during flood season will not be necessary per FHWA.

7.2.2 USGS Regional Regression Equations and Flow Summary

The USGS Rural Regression Equations use statistical methods to draw peak flow conclusions from gauge data at surrounding sites. They provide not only estimated peak flows, but also standard errors of prediction that define a probable range of accuracy. As stated, the Upper McDonald Creek basin is located entirely within Montana’s Northwest Hydrologic Region. The primary variable used in the USGS equations for this region is drainage basin area. Peak discharges for the Upper McDonald Creek basin were determined through the USGS StreamStats Program which utilizes the applicable USGS Regression Equations.

Results of the drainage basin peak flow calculations are summarized Table 3 and included in Appendix B.

Table 3: Upper McDonald Creek Peak Flows

Stream Q2

(cfs) Q10 (cfs)

Q25 (cfs)

Q50 (cfs)

Q100 (cfs)

Q200 (cfs)

Q500 (cfs)

Upper McDonald Creek 1,350 3,100 4,930 6,930 9,690 13,500 20,900

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8.0 BRIDGE ANALYSIS AND RECOMMENDATIONS

The existing Upper McDonald Creek Road is a critical access route for leased seasonal residences along the west side of Lake McDonald. This roadway is the sole egress and emergency access route for these residences and the roadway will remain open in a partial width condition during the proposed bridge replacement. To facilitate partial width and staged construction, the proposed bridge is located approximately 13.5 feet north of the existing bridge.

A discussion of the hydraulic analysis of the existing and proposed bridges is included in the following sections of this memorandum.

8.1 EXISTING CONDITION HEC-RAS MODEL AND CALIBRATION

The Hydrologic Engineering Center River Analysis System (HEC-RAS) Program, Version 5.0.5, was used to create a working model of Upper McDonald Creek and the existing bridge structure. Channel cross sections were located along the analyzed reach of the stream beginning immediately upstream of Lake McDonald and extending approximately 590 feet upstream of the existing bridge. Six channel cross sections were entered into the existing conditions HEC-RAS model left to right looking downstream. These included four cross sections downstream of the bridge site and two upstream. Nine additional cross sections were interpolated in various sections of the model reach for a total of ten cross sections downstream and five cross sections upstream of the bridge site. The modeled reach was terminated approximately 590 feet upstream and 970 feet downstream of the existing bridge.

The existing bridge information was gathered from as-built information and survey data at the bridge site.

This data was used to enter the existing bridge structure, sloping abutments and existing pier structures within the existing conditions model at River Station (RS) 986.639. Ineffective flow areas were then entered into the model per the recommendations in the HEC-RAS User’s Manual and following a 1:2 flow expansion downstream of the existing bridge and a 1:1 flow contraction upstream of the existing bridge.

Levees were also added along the banks of the main channel downstream of the bridge site as portions of the overbank areas are lower than the channel banks and these areas cannot convey flow unless the main channel bank is overtopped.

In this case, the water elevation in Lake McDonald affects the flow characteristics of Upper McDonald Creek through the bridge site. Therefore, the downstream most cross section along the model reach was located to accurately represent the channel section of Upper McDonald Creek at the lake interface. With a cross section at this location, an estimation of both the low lake water elevation and the high lake water elevation could be used as downstream boundary conditions.

The general assumption for the low lake condition is that peak flows along Upper McDonald Creek interact with the lake in early spring before the lake has filled to full pool. Similarly, the assumption for the high lake condition is that peak flows in Upper McDonald Creek interact with the lake later in the year when the lake elevation is at or near full pool. These scenarios are illustrated by two different ordinary high water (OHW) marks noted on the existing bridge center pier and shown in Figure 9, that vary in elevation by approximately 1 foot.

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Figure 9: Existing Bridge Pier OHW Marks

Under the low lake scenario, the lake water elevation was estimated to match the OHW mark on the west bank of the downstream most cross section. This elevation was surveyed at 3158.7 feet and generally matches the lake shore elevation below the debris line. Additional OHW marks were included at each cross section downstream of the existing bridge and entered into the model as observed water surface elevations.

These OHW elevations, along with the lower OHW mark on the existing bridge pier were used in calibrating the existing conditions model under a low lake condition.

Calibration of the existing HEC-RAS model began with the low lake condition. Manning’s (n) values at each cross section were adjusted iteratively until the Q2 water surface profile generally became a best fit line through the observed OHW marks along the channel banks and the lower OHW mark at the existing bridge pier. Manning’s (n) values were selected from Table 3-1 of the HEC-RAS Hydraulic Reference Manual and compared with site photos of the existing stream and bridge. Final Manning’s (n) values in the lower end of the model reach were set to 0.05 in the channel, corresponding to the upper range for a mountain stream with a channel bottom comprised of gravels, cobbles, and few boulders. Near the bridge site and upstream, the channel Manning’s (n) values were increased to 0.07 corresponding to a mountain stream with a channel bottom comprised of cobbles with large boulders. Along the channel overbanks, field notes and site photos showed large trees and heavy brush. The Manning’s (n) values across the over bank areas were set at 0.18 corresponding to upper range of a floodplain covered with trees and dense willows.

FHWA provided a photo taken at the existing bridge site in late May 2011. This photo was taken during a runoff event and was noted by the FHWA Project Engineer as the highest flow occurring during a bridge maintenance project that spring. From this photo, the water surface elevation is estimated at approximately 3160 feet and corresponds to the lower Ordinary Highwater (OHW) mark on the existing bridge pier shown in Figure 9 and correlates to a springtime low lake condition.

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With no gauge data available on McDonald Creek, the gauge data on the Middle Fork of the Flathead River, near West Glacier Montana was reviewed. On May 24, 2011, the Middle Fork gauge recorded a discharge of 17,800 cfs. This discharge is similar to the 2-year Peak Discharge for the Middle Fork of the Flathead calculated at 19,200 cfs. Understanding that the Middle Fork of the Flathead had a much larger drainage basin than McDonald Creek, it is reasonable to assume that the photo taken in late May 2011 corresponds to approximately the 2-year event at the bridge site and confirms that the OHW elevation used in calibration of the Existing Conditions HEC RAS model is reasonable.

Figure 10: Spring 2011 Highwater

Under the high lake condition, the lake water elevation was estimated at 3161.0 feet and generally matches the highwater mark at the top of the debris line along the lake shore on the extreme western end of the downstream cross section. This lake elevation was used as a downstream known water surface boundary condition and evaluated through the existing conditions HEC-RAS model.

As a final calibration check of the existing conditions model, the Q2 water surface profile under the high lake condition was found to nearly match the highest observed OHW mark on the existing bridge pier surveyed at 3162.2 feet. With this correlation, the existing conditions HEC-RAS model was considered calibrated. Output tables from the existing conditions HEC-RAS analysis are included in Appendix C.

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8.2 PROPOSED BRIDGE HEC-RAS MODEL

The proposed bridge structure for this crossing is a 27’-4” wide, 213-4” long, single-span structure measured centerline of bearing to centerline of bearing. This structure spans the width of the stream 13.5 feet upstream of the existing bridge. The proposed bridge has a 209’-4” clear span opening and 1:2 abutment slopes at both ends that tie to the natural stream banks above the ordinary highwater mark. This proposed bridge has an approximate structure depth of 9 feet at the abutments with a haunched girder.

The design low chord elevations are 3169.03 feet at the east abutment and 3171.13 feet at the western abutment.

The proposed bridge structure was entered into a proposed condition HEC-RAS model at the appropriate location and ineffective flow areas were adjusted per the recommendations in the HEC-RAS User’s Manual to account for the 1:2 flow expansion downstream of the proposed bridge and the 1:1 flow contraction upstream of the proposed bridge.

Ice and debris were not identified as a significant issue with this crossing location and were not included in the hydraulic model. Additionally, the proposed bridge structure spans the entire stream channel and will have negligible impacts to the fish passage characteristics of Upper McDonald Creek.

The proposed condition HEC-RAS model was evaluated for comparison with the existing conditions and results indicate that the new bridge is a hydraulic improvement in comparison with the existing bridge under both the low lake and high lake conditions. Under both conditions, the proposed bridge slightly drops the water surface elevations through the crossing area. The proposed bridge provides 4.98 feet of freeboard evaluated at the Q50 design flow under the low lake condition as well as 4.89 feet of freeboard under the high lake condition. The freeboard calculation is based on the controlling low chord elevation of the proposed bridge at the eastern abutment. The low chord elevation across the channel opening is significantly higher due to the longitudinal grade of the bridge structure and the haunched shape of the proposed girders. Therefore, the actual freeboard provided by the proposed bridge is higher across the main channel.

The hydraulics of the proposed bridge are compared with the hydraulics of the existing bridge, under the high lake condition, at the Q50 and Q100 flow rates in Table 4. Output tables from the proposed bridge HEC-RAS analysis and a detailed hydraulic comparison of the existing and proposed bridge structures are included in Appendix D.

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Table 4: Upper McDonald Creek Bridge Hydraulic Comparison – High Lake

Structure WSE at Upstream

Bridge Face (ft)

Freeboard at Upstream Bridge Face

(ft)

Backwater Change from Existing Bridge at

Upstream Bridge Face (ft)

Max Velocity Through Structure

(fps)

Q50 Q100 Q50 Q100 Q50 Q100 Q50 Q100

Existing 4-span, 200-foot Timber Bridge

3164.16 3165.43 4.51 3.24 6.09 7.22

Proposed single-span, 213’-4”Conc.

Bridge

3164.14 3165.40 4.89 3.63 -0.02 -0.03 5.90 6.99

8.3 PROPOSED BRIDGE SCOUR

Contraction, pier and abutment scour depths were calculated at the 50-year, 100-year and 200-year flows and under both low lake and high lake conditions for the proposed bridge. The stream channel material gradation, used in the scour analysis, was determined visually as summarized in Table 2.

Clear water contraction scour was calculated using the equations listed in the current edition of the Federal Highway Administration Hydraulic Engineering Circular No. 18 (HEC 18). Results of the contraction scour analysis are valid for flows up to the 200-year event as the proposed bridge does not function under a pressure flow scenario.

While the proposed bridge is a single span structure and does not include piers, course bed pier scour calculations were completed at each proposed bridge end. These calculations were completed at the direction of FHWA to account for as scenario in which each proposed bridge end acts as a pier if roadway embankment is lost during a flood event.

Abutment scour was calculated by the National Cooperative Highway Research Program (NCHRP) Abutment Scour Approach. In this case, the proposed western bridge abutment is close to the main channel. The projected length of western embankment divided by the width of the floodplain at the abutment is greater than 0.75 and the NCHRP Condition A equations are valid. The proposed eastern bridge abutment is farther from the main channel. The projected length of eastern embankment divided by the width of the floodplain at the abutment is less than 0.75 and the NCHRP Condition B equations are valid.

The NCHRP abutment scour calculations were based on spill through abutments and include the previously discussed clearwater contraction scour. Therefore, the results of the NCHRP abutment scour results are considered a combination of both abutment and contraction scour results. Total scour elevations are calculated by subtracting course bed pier scour and NCHRP abutment scour depths from the existing stream thalweg elevation of 3,152.96 feet. Results of the scour analysis for the proposed bridge opening are summarized in Table 5 and Table 6. The proposed scour depths resulting from low lake conditions are the controlling scour values. These values are shown bold in Table 5. All scour calculations are included in Appendix E.

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Table 5: Proposed Bridge Scour – Low Lake Conditions

Structure Flow Frequency

Contraction Scour Depth Clear Water

(ft)

Pier Scour Depth

Course Bed (ft)

Abutment (Total) Scour Depth NCHRP

(ft) Total Scour Elevation LT

(ft)

Total Scour Elevation RT

(ft) (East) LT (West) RT

Proposed single-span, 213’-4” Conc.

Bridge

50-year 0.0 1.0 2.0 1.2 3,149.96 3,150.76

100-year 0.0 1.5 3.5 1.3 3,147.96 3,150.16

200-year 0.0 2.0 6.3 1.4 3,144.66 3,149.56

Table 6: Proposed Bridge Scour – High Lake Conditions

Structure Flow Frequency

Contraction Scour Depth Clear Water

(ft)

Pier Scour Depth

Course Bed (ft)

Abutment (Total) Scour Depth NCHRP

(ft) Total Scour Elevation LT

(ft)

Total Scour Elevation RT

(ft) (East) LT (West) RT

Proposed single-span, 213’-4” Conc.

Bridge

50-year 0.0 1.0 1.9 1.2 3,150.06 3,150.76

100-year 0.0 1.5 3.5 1.3 3,147.96 3,150.16

200-year 0.0 2.0 6.2 1.3 3,144.76 3,149.66

8.4 PROPOSED BRIDGE ABUTMENT RIPRAP

The proposed single span bridge structure provides a significant reduction in flow impingement and debris collection compared to the existing four span structure. Proposed bridge abutments will not impact the existing stream channel below the ordinary highwater mark and existing bridge abutment riprap stones that are currently impinging on the stream channel will be relocated higher up the existing channel bank.

Riprap sizing calculations for the proposed bridge abutments followed the guidelines and equations presented in Design Guideline 14.3 of HEC 23, Vol II. Results of the analysis indicate that Class 4 Riprap will adequately protect the proposed bridge abutments up to the 100-year event flow. However, the existing bridge abutments are protected with Class 5 riprap. To maintain continuity along the stream banks, Class 5 riprap is recommended for the proposed bridge abutments. Results of the riprap sizing calculations are included in Appendix F.

Through coordination with FHWA Geotechnical, the previously designed micro piles supporting the western bridge end have been replaced with 30-inch diameter steel pipe piles. These piles match the proposed 30-inch pipe piles supporting the eastern bridge end. All proposed bridge end pipe piles are designed to withstand calculated 200-year scour depths. Therefore, the proposed abutment riprap is surface placed and not keyed into the stream channel. Additionally, as coordinated with FHWA and the National Parks Service, the proposed abutment riprap layouts do not impact the existing stream channel below the ordinary highwater elevation on either side of the stream channel. The ordinary highwater elevation is accepted as the 2-year flood water surface elevation calculated at the upstream face of the proposed bridge within the HEC RAS model. Under the high lake condition, the calculated 2-year ordinary highwater elevation is 3,161.27 feet.

The proposed abutment riprap is located between the ordinary highwater line of the existing stream channel and the proposed bridge abutment cap. From the abutment cap, the riprap extends on a maximum 1:2 slope that ties to the existing channel bank. A detail of the proposed abutment riprap is included in Appendix F.

APPENDIX A

Existing Drainage Culvert and Bridge Photographs

Photo 1: 3+07, Existing 18” CMP Inlet Photo 2: 3+07, Existing 18” CMP Outlet

Photo 3: Existing Bridge East Abutment, South Side Photo 4: Existing Bridge East Abutment, South Side

Photo 5: Existing Bridge East Abutment, North Side Photo 6: Existing Bridge East Abutment, South Side

Photo 7: Existing Bridge Center Pier, Upstream Photo 8: Existing Bridge Center Pier, Downstream

Photo 9: Existing Bridge Center Pier, Upstream Photo 10: Existing Bridge Center Pier, Downstream

Photo 11: Existing Bridge West Abutment, North Side Photo 12: Existing Bridge West Abutment, South Side

Photo 13: Existing Bridge West Abutment, South Side Photo 14: Existing Bridge West Abutment, North Side

Photo 15: Existing Bridge West Abutment, North Bank Photo 16: Existing Bridge Deck, Looking East

Photo 17: Existing Upstream Channel Photo 18: Existing Downstream Channel

Photo 19: Existing Channel Bottom Downstream

Photo 20: Existing Bridge, Looking Downstream

APPENDIX B

Upper McDonald Creek Hydrology Analysis

12/9/2020 StreamStats https://streamstats.usgs.gov/ss/ 1/3

StreamStats Report

Basin Characteristics

Parameter Code Parameter Description Value Unit

CONTDA Area that contributes flow to a point on a stream 109.4 square miles

PRECIP Mean Annual Precipitation 63.32 inches

General Disclaimers

Upstream regulation was checked for this watershed.

Region ID: MT Workspace ID: MT20201209214335006000 Clicked Point (Latitude, Longitude): 48.63512, -113.86651 Time: 2020-12-09 14:43:53 -0700

12/9/2020 StreamStats https://streamstats.usgs.gov/ss/ 2/3

Peak-Flow Statistics Parameters[NW Region BasinC 2015 5019F]

Parameter Code Parameter Name Value Units Min Limit Max Limit

CONTDA Contributing Drainage Area 109.4 square miles 2.43 1560

Peak-Flow Statistics Flow Report[NW Region BasinC 2015 5019F]

PIl: Prediction Interval-Lower, PIu: Prediction Interval-Upper, SEp: Standard Error of Prediction, SE:

Standard Error (other -- see report)

Statistic Value Unit PIl PIu SEp

1.5 Year Peak Flood 1090 ft^3/s 233 5100 115

2 Year Peak Flood 1350 ft^3/s 377 4840 88.9

2 33 Year Peak Flood 1460 ft^3/s 449 4750 80.4

5 Year Peak Flood 2190 ft^3/s 958 5000 52.8

10 Year Peak Flood 3100 ft^3/s 1780 5400 34.4

25 Year Peak Flood 4930 ft^3/s 4430 5490 9.1

50 Year Peak Flood 6930 ft^3/s 6060 7920 11.3

100 Year Peak Flood 9690 ft^3/s 8260 11400 13.6

200 Year Peak Flood 13500 ft^3/s 11200 16300 16

500 Year Peak Flood 20900 ft^3/s 16700 26200 19.3

Peak-Flow Statistics Citations

Sando, Roy, Sando, S.K., McCarthy, P.M., and Dutton, D.M.,2016, Methods for estimating peak-flow frequencies at ungaged sites in Montana based on data through water year 2011:

U.S. Geological Survey Scientific Investigations Report 2015–5019–F, 30 p.

(https://doi.org/10.3133/sir20155019)

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Upper McDonald Creek

Mt PRA GLAC 10(45)

USGS Hydrologic Peak Flow Calculation

Basin

Characteristic Needed?

Input Value from

StreamStats

A Needed 109.42

P Not needed

F Not needed

E5000 Not needed

SLP30 Not needed

ETSPR Not needed

E6000 Not needed

AEP Q Lower PI Upper PI exceed 3p/n?

Q66.7 1092.03 145.21 8212.50 False

Q50 1346.19 231.34 7833.47 False

Q42.9 1462.33 270.78 7897.07 False

Q20 2193.92 508.10 9473.15 False

Q10 3100.60 848.39 11331.72 False

Q4 4928.53 1488.16 16322.41 False

Q2 6933.04 1856.64 25889.23 False

Q1 9694.96 2208.64 42556.63 False

Q0.5 13527.74 2601.94 70332.01 False

Q0.2 20920.03 3081.89 142006.29 True

Select Region

FHWA Provided Photo of May 2011 Flood Event

Table 1-1 Table 1-2 Table 1-3 Table 1-4 Table 1-5 Table 1-6

1,125 73 STATION 14,900 user 45,000 historic 1916 103

66.7 50 42.9 20 10 4 2 1.0 0.5 0.2 18,000 19,200 19,800 25,200 32,000 44,800 58,200 76,000 99,800 144,000

366.7 50 342.9 20 10 4 2 1.0 0.5 0.2 19,200 20,400 21,400 27,100 35,100 51,200 69,100 94,000 129,000 196,000 16,800 17,900 18,900 23,700 29,700 40,300 50,900 64,600 82,100 113,000

5Flood-frequency results not reported because of too many values less than the low-outlier threshold used in the analysis.

Upper and lower 95-percent confidence intervals, in cubic feet per second, for indicated annual exceedance probability, in percent

1Definitions of types of outlier thresholds include:

default: outlier threshold calculated using Bulletin 17B default procedures (U.S. Interagency Advisory Council on Water Data, 1982);

historic: outlier threshold determined from a peak flow designated as a historic peak;

user: outlier threshold determined from a user-selected systematic peak flow.

2Confidence interval value manually calculated.

3Peak-flows with a value of zero are plotted as 0.1 in figure 1-1.

4In cases where the month, day, or both are not present in the date of a peak flow (as indicated by adjacent slash marks with no intervening values), the month, day, or both are unknown.

Peak flow, in cubic feet per second, for indicated annual exceedance probability (bold values), in percent

High-outlier threshold, in cubic feet per second

Type of high-outlier threshold1

Water year of peak flow for user or historic high-outlier threshold

Length of historic period, in years

Drainage area, in square miles

Number of years of peak-flow records in analysis period

Skew type used in analysis

Low-outlier threshold, in cubic feet per second

Type of low-outlier threshold1

12358500 Middle Fork Flathead River near West Glacier, Montana Map number 708

Analysis period of record, water years: 1916, 1940–2011 Analysis period of record considered unregulated

[Water year is the 12-month period from October 1 through September 30 and is designated by the year in which it ends.]

99.99

99.9

99.8

99.5

99 98 95 90 80 70 60 50 40 30 20 10 5 2 1 0.5

0.2

0.1

0.0

0.0

1,000

10,000

100,000

1,000,000

P ea k fl o w

, i n c u b ic f e et p er s e co n d

Exceedance probability, in percent

EXPLANATION

Peak flow

Peak flow greater than or equal to high-outlier threshold

Peak flow less than or equal to low-outlier threshold

Peak-flow frequency curve

Upper and lower 95-percent confidence intervals

Figure 1-1. Annual peak flows (plotting positions determined using the Cunnane formulation; Helsel and Hirsch, 2002) and peak-flow frequency curve.

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

P ea k fl o w

, i n c u b ic f ee t p er s ec o n d

Water year

EXPLANATION

Peak flow

5-value moving averageFigure 1-2. Peak flows and 5-value moving average.

1916 //19164 45,000 -- 1964 6/9/1964 140,000 36.46 1940 5/12/1940 12,800 6.66 1975 6/20/1975 63,600 19.42 1941 5/14/1941 7,620 5.22 1916 //19164 45,000 -- 1942 5/24/1942 15,700 7.50 1991 5/19/1991 35,000 12.41 1943 6/18/1943 20,600 9.00 1954 5/20/1954 34,500 13.01 1944 5/20/1944 11,300 6.30 1990 11/12/1989 33,700 12.07 1945 6/1/1945 16,400 7.80 1997 5/17/1997 33,000 11.96 1946 5/29/1946 18,500 8.34 1948 5/23/1948 32,600 12.40 1947 5/9/1947 23,600 9.80 1974 6/18/1974 31,900 11.60 1948 5/23/1948 32,600 12.40 2008 5/19/2008 30,700 11.23 1949 5/14/1949 19,500 8.56 1972 6/2/1972 29,600 10.99 1950 6/6/1950 23,600 9.69 1956 5/22/1956 28,300 11.28 1951 5/12/1951 20,100 8.71 1967 5/23/1967 27,900 10.80 1952 4/28/1952 18,100 8.29 1961 5/27/1961 27,100 10.58 1953 6/13/1953 24,800 10.14 1959 6/6/1959 25,800 10.24 1954 5/20/1954 34,500 13.01 2011 6/8/2011 25,200 9.79 1955 6/14/1955 17,500 8.19 1953 6/13/1953 24,800 10.14 1956 5/22/1956 28,300 11.28 1957 5/5/1957 24,200 10.10 1957 5/5/1957 24,200 10.10 1971 5/28/1971 23,900 9.49 1958 5/13/1958 19,400 8.50 1947 5/9/1947 23,600 9.80 1959 6/6/1959 25,800 10.24 1950 6/6/1950 23,600 9.69 1960 6/4/1960 21,500 9.10 1970 6/5/1970 23,400 9.34 1961 5/27/1961 27,100 10.58 1996 6/9/1996 23,300 9.42 1962 5/20/1962 13,900 6.99 1976 5/11/1976 22,600 9.15 1963 5/31/1963 12,700 6.64 2006 6/16/2006 22,500 9.08 1964 6/9/1964 140,000 36.46 2002 5/31/2002 22,400 9.10 1965 6/19/1965 20,900 8.93 1979 5/27/1979 21,600 8.96 1966 5/31/1966 18,400 8.24 1960 6/4/1960 21,500 9.10 1967 5/23/1967 27,900 10.80 1965 6/19/1965 20,900 8.93 1968 6/3/1968 18,000 8.15 1982 5/26/1982 20,800 8.74 1969 5/15/1969 14,200 7.08 1943 6/18/1943 20,600 9.00 1970 6/5/1970 23,400 9.34 1980 5/26/1980 20,500 8.64 1971 5/28/1971 23,900 9.49 1999 5/26/1999 20,400 8.64 1972 6/2/1972 29,600 10.99 1985 6/8/1985 20,200 8.58 1973 5/18/1973 17,900 7.91 1951 5/12/1951 20,100 8.71 1974 6/18/1974 31,900 11.60 1993 5/15/1993 19,900 8.40 1975 6/20/1975 63,600 19.42 2003 5/26/2003 19,800 8.32 1976 5/11/1976 22,600 9.15 1981 5/22/1981 19,600 8.41 1977 5/11/1977 10,400 5.83 1949 5/14/1949 19,500 8.56 1978 6/6/1978 17,600 7.84 1958 5/13/1958 19,400 8.50 1979 5/27/1979 21,600 8.96 1986 5/30/1986 19,400 8.27 1980 5/26/1980 20,500 8.64 2009 5/31/2009 19,100 8.16 1981 5/22/1981 19,600 8.41 1989 5/11/1989 19,000 8.14 1982 5/26/1982 20,800 8.74 1987 5/1/1987 18,700 8.06 1983 5/27/1983 17,400 7.78 2007 11/8/2006 18,700 8.05 1984 5/31/1984 18,200 7.98 1946 5/29/1946 18,500 8.34 1985 6/8/1985 20,200 8.58 1966 5/31/1966 18,400 8.24 1986 5/30/1986 19,400 8.27 1984 5/31/1984 18,200 7.98 1987 5/1/1987 18,700 8.06 1952 4/28/1952 18,100 8.29 1988 5/13/1988 13,100 6.48 1968 6/3/1968 18,000 8.15 1989 5/11/1989 19,000 8.14 1973 5/18/1973 17,900 7.91 1990 11/12/1989 33,700 12.07 1978 6/6/1978 17,600 7.84 1991 5/19/1991 35,000 12.41 1955 6/14/1955 17,500 8.19 1992 5/1/1992 13,000 6.43 1983 5/27/1983 17,400 7.78 1993 5/15/1993 19,900 8.40 1945 6/1/1945 16,400 7.80 1994 5/13/1994 15,200 7.12 1942 5/24/1942 15,700 7.50 1995 6/7/1995 14,900 7.04 2000 5/23/2000 15,300 7.14 1996 6/9/1996 23,300 9.42 1994 5/13/1994 15,200 7.12 1997 5/17/1997 33,000 11.96 1995 6/7/1995 14,900 7.04 1998 5/27/1998 12,800 6.48 2010 5/19/2010 14,300 6.85 1999 5/26/1999 20,400 8.64 1969 5/15/1969 14,200 7.08 2000 5/23/2000 15,300 7.14 1962 5/20/1962 13,900 6.99 2001 5/26/2001 13,000 6.45 1988 5/13/1988 13,100 6.48 2002 5/31/2002 22,400 9.10 1992 5/1/1992 13,000 6.43 2003 5/26/2003 19,800 8.32 2001 5/26/2001 13,000 6.45 2004 5/5/2004 11,100 6.02 1940 5/12/1940 12,800 6.66 2005 6/4/2005 12,800 6.50 1998 5/27/1998 12,800 6.48 2006 6/16/2006 22,500 9.08 2005 6/4/2005 12,800 6.50 2007 11/8/2006 18,700 8.05 1963 5/31/1963 12,700 6.64 2008 5/19/2008 30,700 11.23 1944 5/20/1944 11,300 6.30 2009 5/31/2009 19,100 8.16 2004 5/5/2004 11,100 6.02 2010 5/19/2010 14,300 6.85 1977 5/11/1977 10,400 5.83 2011 6/8/2011 25,200 9.79 1941 5/14/1941 7,620 5.22

Peak-flow data3 Ranked (largest to smallest) peak-flow data3

Water year

Date Peak flow, in cubic feet per second

Gage height, in feet

Water year

Date Peak flow, in cubic feet per second

Gage height, in feet

12358500 Middle Fork Flathead River near West Glacier, Montana Map number 708

Analysis period of record, water years: 1916, 1940–2011 Analysis period of record considered unregulated

[Water year is the 12-month period from October 1 through September 30 and is designated by the year in which it ends.

--, not applicable or not available]

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Current Conditions Geographic Area:

Montana GO

GODays (17)

-- or -- Begin date

2011-05-15

End date 2011-06-01

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Click to hide state-specific text Questions or concerns about USGS streamflow data in Montana and Wyoming can be directed to Kirk Miller (kmiller@usgs.gov; 307-775-9168).

Updated September 18, 2020 - USGS water-resources monitoring activities were restored effective August 17, 2020 at the following site:

• 06088500 Muddy Creek near Vaughn, Montana (POR: 82 years)

Updated June 11, 2020 - USGS water-resources monitoring activities will be restored at the following sites:

• 12323600 Silver Bow Creek at Opportunity, Montana (POR: 31 years)

• 12323750 Silver Bow Creek at Warm Springs, Montana (POR: 35 years)

* IMPORTANT: Next Generation Station Page

USGS 12358500 M F Flathead River near West Glacier MT

PROVISIONAL DATA SUBJECT TO REVISION

Available data for this site Time-series: Current/Historical Observations GO

Click to hidestation-specific text

(About shift-adjusted ratings).

Station operated by the USGS Wyoming-Montana Water Science Center in cooperation with Bonneville Power Administration and the U.S. Bureau of Reclamation .

Leaving USGS: U.S. Coast Guard boating safety tips.

This station managed by the Helena Field Unit.

Available Parameters Available Period

All 2 Available Parameters for this site 00060 Discharge 1995-10-01 2020-12-18

00065 Gage height 2020-06-25 2020-12-18

Output format Graph Graph w/ stats Graph w/o stats Graph w/ (up to 3) parms Table Tab-separated

Summary of all available data for this site Instantaneous-data availability statement

Discharge, cubic feet per second

00:00 MDT 15,100A 15,100A 16,400A 13,800A 11,800A 11,400A 11,900A 13,000A 14,800A 17,100A 17,300A 15,600A 17,500A 15,000A 12,800A

00:15 MDT 15,200A 15,100A 16,400A 13,900A 11,800A 11,400A 11,900A 13,000A 14,900A 17,100A 17,300A 15,600A 17,500A 15,000A 12,800A

00:30 MDT 15,200A 15,200A 16,400A 13,800A 11,800A 11,400A 11,900A 13,000A 15,000A 17,100A 17,300A 15,600A 17,500A 15,000A 12,800A

00:45 MDT 15,200A 15,200A 16,400A 13,800A 11,800A 11,400A 11,900A 13,100A 15,000A 17,100A 17,300A 15,600A 17,500A 14,900A 12,800A

01:00 MDT 15,300A 15,200A 16,400A 13,800A 11,800A 11,400A 12,000A 13,100A 15,100A 17,100A 17,300A 15,600A 17,500A 14,900A 12,700A

TIME

May

May

May

May

May

May

May

May

May

May

May

May

May

May

May

Page 1 of 4USGS Current Conditions for USGS 12358500 M F Flathead River near West Glacier MT

12/18/2020https://nwis.waterdata.usgs.gov/mt/nwis/uv?cb_00060=on&format=html&site_no=12358...

01:15 MDT 15,300A 15,300A 16,400A 13,700A 11,800A 11,500A 12,000A 13,200A 15,100A 17,100A 17,300A 15,600A 17,500A 14,800A 12,700A

01:30 MDT 15,300A 15,300A 16,400A 13,700A 11,800A 11,500A 12,000A 13,200A 15,100A 17,100A 17,300A 15,600A 17,500A 14,800A 12,700A

01:45 MDT 15,400A 15,300A 16,300A 13,700A 11,800A 11,500A 12,000A 13,200A 15,200A 17,100A 17,200A 15,700A 17,500A 14,800A 12,700A

02:00 MDT 15,400A 15,400A 16,300A 13,700A 11,800A 11,500A 12,000A 13,300A 15,200A 17,100A 17,200A 15,700A 17,500A 14,800A 12,700A

02:15 MDT 15,400A 15,400A 16,300A 13,700A 11,800A 11,500A 12,000A 13,300A 15,300A 17,100A 17,200A 15,700A 17,500A 14,700A 12,700A

02:30 MDT 15,500A 15,400A 16,300A 13,600A 11,800A 11,600A 12,000A 13,300A 15,400A 17,100A 17,200A 15,700A 17,400A 14,700A 12,700A

02:45 MDT 15,500A 15,500A 16,300A 13,600A 11,800A 11,600A 12,000A 13,400A 15,400A 17,200A 17,200A 15,800A 17,500A 14,700A 12,600A

03:00 MDT 15,500A 15,500A 16,300A 13,600A 11,800A 11,600A 12,000A 13,400A 15,500A 17,100A 17,200A 15,800A 17,400A 14,600A 12,600A

03:15 MDT 15,500A 15,500A 16,300A 13,600A 11,800A 11,600A 12,100A 13,500A 15,500A 17,200A 17,100A 15,800A 17,400A 14,600A 12,600A

03:30 MDT 15,600A 15,600A 16,300A 13,600A 11,800A 11,600A 12,100A 13,500A 15,600A 17,200A 17,100A 15,800A 17,400A 14,600A 12,600A

03:45 MDT 15,600A 15,600A 16,300A 13,500A 11,800A 11,600A 12,100A 13,500A 15,600A 17,200A 17,100A 15,900A 17,400A 14,500A 12,600A

04:00 MDT 15,700A 15,700A 16,200A 13,500A 11,800A 11,700A 12,100A 13,600A 15,700A 17,200A 17,100A 15,900A 17,400A 14,500A 12,500A

04:15 MDT 15,700A 15,700A 16,200A 13,500A 11,800A 11,700A 12,200A 13,600A 15,800A 17,300A 17,100A 15,900A 17,400A 14,500A 12,500A

04:30 MDT 15,700A 15,800A 16,200A 13,500A 11,800A 11,700A 12,200A 13,700A 15,800A 17,300A 17,100A 15,900A 17,400A 14,500A 12,500A

04:45 MDT 15,800A 15,800A 16,200A 13,500A 11,800A 11,700A 12,200A 13,700A 15,800A 17,300A 17,100A 15,900A 17,400A 14,400A 12,500A

05:00 MDT 15,800A 15,800A 16,200A 13,500A 11,800A 11,700A 12,200A 13,700A 15,900A 17,300A 17,000A 15,900A 17,400A 14,400A 12,500A

05:15 MDT 15,800A 15,900A 16,200A 13,400A 11,800A 11,700A 12,200A 13,800A 16,000A 17,300A 17,000A 16,000A 17,300A 14,400A 12,500A

05:30 MDT 15,800A 15,900A 16,200A 13,400A 11,800A 11,700A 12,200A 13,800A 16,000A 17,300A 17,000A 16,000A 17,300A 14,400A 12,400A

05:45 MDT 15,900A 15,900A 16,200A 13,400A 11,900A 11,800A 12,200A 13,800A 16,100A 17,300A 17,000A 16,000A 17,300A 14,400A 12,400A

06:00 MDT 15,900A 16,000A 16,200A 13,400A 11,900A 11,800A 12,300A 13,900A 16,100A 17,300A 17,000A 16,000A 17,300A 14,300A 12,400A

06:15 MDT 15,900A 16,000A 16,100A 13,300A 11,900A 11,800A 12,300A 13,900A 16,200A 17,400A 17,000A 16,100A 17,300A 14,300A 12,400A

06:30 MDT 15,900A 16,000A 16,100A 13,400A 11,900A 11,800A 12,300A 13,900A 16,200A 17,400A 17,000A 16,100A 17,300A 14,300A 12,400A

06:45 MDT 15,900A 16,100A 16,100A 13,300A 11,900A 11,800A 12,300A 14,000A 16,300A 17,400A 16,900A 16,100A 17,200A 14,300A 12,400A

07:00 MDT 15,900A 16,100A 16,000A 13,300A 11,900A 11,800A 12,300A 14,000A 16,300A 17,400A 16,900A 16,200A 17,200A 14,300A 12,300A

07:15 MDT 15,900A 16,200A 16,000A 13,300A 11,900A 11,800A 12,300A 14,100A 16,400A 17,400A 16,900A 16,200A 17,200A 14,200A 12,300A

07:30 MDT 16,000A 16,200A 16,000A 13,300A 11,900A 11,900A 12,300A 14,100A 16,400A 17,400A 16,900A 16,200A 17,100A 14,200A 12,300A

07:45 MDT 16,000A 16,200A 16,000A 13,300A 11,900A 11,800A 12,300A 14,100A 16,500A 17,500A 16,900A 16,300A 17,100A 14,200A 12,300A

08:00 MDT 16,000A 16,300A 16,000A 13,300A 11,900A 11,900A 12,400A 14,100A 16,600A 17,500A 16,800A 16,300A 17,100A 14,100A 12,300A

08:15 MDT 16,000A 16,300A 16,000A 13,200A 11,900A 11,900A 12,300A 14,200A 16,600A 17,500A 16,800A 16,300A 17,100A 14,200A 12,300A

08:30 MDT 16,000A 16,300A 15,900A 13,200A 11,900A 11,900A 12,400A 14,200A 16,600A 17,500A 16,800A 16,300A 17,100A 14,100A 12,300A

08:45 MDT 16,000A 16,400A 15,900A 13,200A 11,900A 11,900A 12,400A 14,200A 16,700A 17,600A 16,700A 16,400A 17,000A 14,100A 12,200A

09:00 MDT 16,000A 16,400A 15,900A 13,200A 11,900A 11,900A 12,400A 14,200A 16,700A 17,600A 16,700A 16,400A 17,000A 14,100A 12,200A

09:15 MDT 16,000A 16,400A 15,900A 13,200A 11,900A 11,900A…