Hydraulic_Bridge_TS&L_Report.pdf

Memorandum

Western Federal Lands Highway Division 610 E. Fifth Street

Vancouver, WA 98661-3801

TOM MINER CREEK AND ROCK CREEK BRIDGES

HYDRAULIC TS&L REPORT

To: Matthew Miller, WFLHD Project Manager From: James Neighorn, P.E., WFLHD Hydraulics Engineer Date: December 29, 2016 Project: MT PARK 63(1) – Tom Miner Creek Road Improvements

Background

Park County, Montana is replacing the bridges at Tom Miner Creek and Rock Creek. Park County will maintain the road and bridges. Western Federal Lands Highway Division (WFLHD) is designing the bridges. Both bridge designs will incorporate Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) design. Recommendations for the waterway width, skew angle, minimum bridge low chord elevations, abutment configuration, and scour are presented.

Tom Miner Creek Bridge Conclusions and Recommendations

Bridge Low Chord The expected potential for woody debris for the stream is low. A minimum bridge low chord elevation of

5048.0 feet (NAD83/2011) is recommended for passing the woody debris and providing clearance for bridge maintenance activities. The low chord elevation provides 2 feet of clearance above the 50-year water surface. The resulting low chord is above the estimated 100-year water surface which will help reduce scour at the GRS abutments. The clearances are consistent with FHWA design guidance. A bridge with this low chord elevation requires raising the road profile 1 to 2 feet. The predicted hydraulic capacity of the proposed bridge assumes a single span and excavating the stream bottom beneath the bridge as described in the following section. Bridge water surface elevations, clearances, and flow velocities for various flood recurrence intervals are listed in Appendix A, Table 2.

Channel Alignment and Geometry The existing stream channel beneath the bridge must be widened to match the natural channel. Remove the existing bridge abutments. Construct a 21 foot wide channel bottom with an elevation of 5041.3 feet at the centerline of the road and new channel centerline (Northing 349293.3 and Easting 1605558.3).

Grade channel side slopes at 1.5(h):1(v). Provide a minimum 40 foot bridge clear span to accommodate the resulting 40 foot wide waterway width produced by the new channel geometry during the design flow (50-year). Slope the channel 1.8 percent. The excavated channel length is approximately 100 feet, 50 feet upstream and 50 feet downstream of the bridge centerline. Skew the channel approximately 10 degrees relative to the bridge centerline. See the attached bridge plan and profile drawings.

Scour The cobble and boulder streambed appears vertically stable and degradation is expected to be minor.

Based on projecting an average stream gradient from the lowest scour pool elevation downstream up through the new bridge crossing, channel profile degradation to elevation 5039.3 (2 foot reduction) is

Hydraulic TS&L Report predicted for the life of the new bridge (50 years).

Based on geotechnical borings, the material in the stream channel is cobbles with boulders.

Approximately 5 to 10 feet below the channel bottom the material becomes sandy with various silts and clays. By providing a bridge that spans the full channel width, no scour due to contraction of flow is predicted. Abutment scour around the GRS is the primary scour mode. The combined long term degradation and abutment scour results in 100-year scour design flood and 500-year scour check flood elevations of 5037.9 and 5034.0.

When utilizing GRS abutment systems without scour countermeasures the top of the abutment footings need to be constructed to a depth equal to the scour check flood elevation 5034.0 feet or below. Footings at this depth in cobble and boulder material would be difficult to dewater and construct. Therefore, scour countermeasures will need to be installed at each abutment. By utilizing scour countermeasures the top of the GRS footings can be constructed to the combined long term degradation and contraction scour check flood elevation of 5039.3 feet.

Install scour countermeasures consisting of riprap revetments at each abutment to protect the GRS and road approaches from being undermined by abutment scour. Set revetment crests, 1 foot above the 50-year water surface, at elevation 5047.0 feet. Set the riprap revetment toe so that it is not undermined by channel degradation or contraction scour at elevation 5039.3 feet. Grade the revetment slopes at 1.5(h):1(v) using Class 4 riprap placed in a minimum of 3.5 feet thick layer. Place the riprap on a geotextile underlayment. Place streambed material and boulders conserved from the excavation on the riprap as needed for establishing the new channel grade. See the attached riprap plans and elevations.

Stream Impacts Placing the riprap below the expected channel degradation limits allows the stream to naturally incise and allows for increased hydraulic capacity below the bridge during large flood events. The maximum predicted degradation is 2 feet at the bridge. Constructing the abutments outside the active channel and flood way will allow natural sediment and wood debris transport.

During construction moderate amount of turbidity and sediment is expected to be released when the flow barriers are removed and stream flow is introduced into the newly constructed channels. The amount of turbidity and sediment will be reduced by removing the flow barriers gradually introducing the stream flow over an extended two to three hour time period.

Flooding Impacts A number of private structures (residence and barns) are located about 200 feet south of the bridge.

These structures are well above the flood elevations and outside areas of potential flood impacts. A private residence is located approximately 600 feet downstream (east) of the bridge. The residence and adjacent pasture is constructed on an upland area north of the creek. Survey cross sections were taken of the waterway and flood plain across the pasture and on the upstream side of the residence. Hydraulic modeling of existing conditions indicates that flooding occurs over the pasture, immediately adjacent to the creek. The private residence was outside areas impacted by flooding (500-year) with all flow being contained within the main creek channel. Modeling of the proposed bridge and channel shows no change in flood elevations within the pasture or adjacent to the residence.

Table 3A identifies the estimated flood elevations and average channel velocities under current and proposed conditions upstream and downstream of the site. No increase in base flood elevations is anticipated. Flood elevations will remain unchanged near the downstream residence. Immediately upstream of the bridge there will be a reduction in flood elevations where the existing bridge had previously constricted flows.

Construction Consider leaving the existing concrete bridge abutments in place to help maintain separation between the active stream and the new abutment excavation area during construction. The existing abutments may help in keeping the excavation dewatered. The existing abutments will need to be removed to construct the proposed channel and revetment below the new bridge. This will require diverting the stream flow and installing flow barriers. Flow diversion structures used August 1 through April 30 are to have a minimum flow capacity of 148 ft3/sec. Flow diversion structures used May 1 through July 30 are to have a minimum flow capacity of 295 ft3/sec. Culverts used for flow diversion are to have a minimum slope of 2 percent. Discharge culverts onto naturally armored stream bed or install energy dissipation as needed for controlling erosion. Height of upstream barrier must be adequate for effectively forcing diverted stream water through the diversion structure. Prevent overtopping of upstream barrier for all stream flows less than or equal to the diversion design flow. Contractor should submit diversion plan and HY-8-based calculations showing proposed diversion system has the required capacity.

Montana Fish, Wildlife and Park (FWP) and U.S. Environmental Protection Agency (US EPA) will restrict the release of turbidity from the work area into the stream. The agencies require turbidity control and monitoring, and should be contacted for specific requirements and allowable discharge limits. The agencies will likely require pumping the turbid water from the work areas before flow barriers are removed. Pumping will need to continue until the turbidity discharge limitations can be met. The work area water should be discharged at an upland settlement area. Flow barriers and erosion controls may be needed at the settlement area.

Rock Creek Bridge Conclusions and Recommendations

Bridge Low Chord The expected potential for woody debris for the stream is low. A minimum bridge low chord elevation of

4999.9 feet (NAD83/2011) is recommended for passing the woody debris and providing clearance for bridge maintenance activities. The low chord elevation provides 2 feet of clearance above the 50-year water surface. The resulting low chord is above the estimated 100-year water surface which will help reduce scour at the GRS abutments. The clearances are consistent with FHWA design guidance. A bridge with this low chord elevation would allow the road profile to remain the same or be dropped by 1 to 2 feet. The predicted hydraulic capacity of the proposed bridge assumes a single span and excavating the stream bottom beneath the bridge as described in the following section. Bridge water surface elevations, clearances, and flow velocities for various flood recurrence intervals are listed in Appendix A, Table 2.

Channel Alignment and Geometry The existing stream channel beneath the bridge must be widened to match the natural channel. Remove the existing bridge abutments. Shift the bridge approximately 5 feet downstream of the existing road centerline to avoid impacting fiber optic communication lines during construction. Construct a 16.75 foot wide channel bottom with an elevation of 4992.8 feet at the centerline of the road and new channel centerline (Northing 353613.2 and Easting 1606826.2). Grade channel side slopes at 1.5(h):1(v). Provide a bridge clear span to accommodate the resulting 32 foot wide waterway width produced by the new channel geometry during the design flow (50-year). Consider using a longer 40 foot span bridge design that matches the Tom Miner Creek design. Using consistent dimensions for both sites may provide efficiencies and savings during manufacturing and construction. Slope the channel 3.4 percent. The excavated channel length is approximately 80 feet, 50 feet upstream and 30 feet downstream of the bridge centerline. Construct the channel perpendicular to the bridge centerline. See the attached bridge plan and profile drawings.

Scour The stream has a cobble and boulder bed. Immediately downstream of the bridge, large rock weirs were installed as stream grade control. These weirs were installed to prevent degradation and undercutting of the existing road bridge after a downstream historic railroad culvert was removed. The boulders used in the weirs are oversized and designed as permanent in-stream features which appear stable. The proposed bridge design needs to account for some channel degradation due to shifting of boulders within the weirs.

Assuming partial shifting/failure of one or two weirs the projected channel profile could degrade to elevation 4990.3.

Based on geotechnical borings, the material in the stream channel is cobbles with boulders.

Approximately 5 to 10 feet below the channel bottom the material becomes sandy with various silts and clays. By providing a bridge that spans the full channel width, no scour due to contraction of flow is predicted. Abutment scour around the GRS is the primary scour mode. The combined long term degradation and abutment scour results in 100-year scour design flood and 500-year scour check flood elevations of 4984.9 and 4984.1.

When utilizing GRS abutment systems without scour countermeasures the top of the abutment footings need to be constructed to a depth equal to the scour check flood elevation 4984.1 feet or below. Footings at this depth in cobble and boulder material would be difficult to dewater and construct. Therefore, scour countermeasures will need to be installed at each abutment. By utilizing scour countermeasures the top of the GRS footings can be constructed to the combined long term degradation and contraction scour check flood elevation of 4990.3 feet.

Install scour countermeasures consisting of riprap revetments at each abutment to protect the GRS and road approaches from being undermined by abutment scour. Set revetment crests, 1 foot above the 50-year water surface, at elevation 4998.9 feet. Set the riprap revetment toe so that it is not undermined by channel degradation or contraction scour at elevation 4990.3 feet. Grade the revetment slopes at 1.5(h):1(v) using Class 4 riprap placed in a minimum of 3.5 feet thick layer. Place the riprap on a geotextile underlayment. Place streambed material and boulders conserved from the excavation on the riprap as needed for establishing the new channel grade. See the attached riprap plans and elevations.

Stream Impacts Placing the riprap below the expected channel degradation limits allows the stream to naturally incise and allows for increased hydraulic capacity below the bridge during large flood events. The maximum predicted degradation is 2.5 feet at the bridge. Constructing the abutments outside the active channel and flood way will allow natural sediment and wood debris transport.

During construction moderate amount of turbidity and sediment is expected to be released when the flow barriers are removed and stream flow is introduced into the newly constructed channels. The amount of turbidity and sediment will be reduced by removing the flow barriers gradually introducing the stream flow over an extended two to three hour time period.

Flooding Impacts A number of private structures (residences and out-buildings) are located 600 feet upstream and downstream of the bridge. All structures are located in upland areas outside areas of potential flooding with the exception of a stone storage building. This storage building is located approximately 260 feet upstream (west) of the bridge. The structure is constructed at the top of the creek bank. A survey cross section was taken of the waterway and flood plain at the west side of this structure. Hydraulic modeling of existing conditions indicates that flows are contained within the defined creek banks during flooding (500-year). Modeling of the proposed bridge and channel shows no change in flood elevations at this upstream location or downstream of the bridge.

Table 3B identifies the estimated flood elevations and average channel velocities under current and proposed conditions upstream and downstream of the site. No increase in base flood elevations is anticipated. Flood elevations will remain unchanged near the downstream residence. Immediately upstream of the bridge there will be a reduction in flood elevations where the existing bridge had previously constricted flows.

Construction Consider leaving the existing concrete bridge abutments in place to help maintain separation between the active stream and the new abutment excavation area during construction. The existing abutments may help in keeping the excavation dewatered. The existing abutments will need to be removed to construct the proposed channel and revetment below the new bridge. This will require diverting the stream flow and installing flow barriers. Flow diversion structures used August 1 through April 30 are to have a minimum flow capacity of 74 ft3/sec. Flow diversion structures used May 1 through July 30 are to have a minimum flow capacity of 148 ft3/sec. Culverts used for flow diversion are to have a minimum slope of 2 percent.

Discharge culverts onto naturally armored stream bed or install energy dissipation as needed for controlling erosion. Height of upstream barrier must be adequate for effectively forcing diverted stream water through the diversion structure. Prevent overtopping of upstream barrier for all stream flows less than or equal to the diversion design flow. Contractor should submit diversion plan and HY-8-based calculations showing proposed diversion system has the required capacity.

Montana Fish, Wildlife and Park (FWP) and U.S. Environmental Protection Agency (US EPA) will restrict the release of turbidity from the work area into the stream. The agencies require turbidity control and monitoring, and should be contacted for specific requirements and allowable discharge limits. The agencies will likely require pumping the turbid water from the work areas before flow barriers are removed. Pumping will need to continue until the turbidity discharge limitations can be met. The work area water should be discharged at an upland settlement area. Flow barriers and erosion controls may be needed at the settlement area.

Site Conditions

Within the vicinity of the project areas the streams flow through the basin valley floor and are flanked by grassland and meadows. The streams are perennial with moderate sinuosity. Both stream channels consist of pool riffle and step-pool formations. Bedrock was not observed in the channel banks or bottoms for either stream. Streambed material for both streams is predominantly cobbles and boulders.

Both the Tom Miner Creek and Rock Creek bridges are undersized and constrict flows. This has resulted in scour and erosion which has significantly undermined the existing abutments and wingwalls. The concrete foundation along the south abutment at Tom Miner Creek Bridge has been eroded and segments have become undercut. The southwest wingwalls at the Rock Creek Bridge have failed and are being held together by steel cable anchors. The northwest wingwall has a significant vertical fracture. The bridges do not meet current standards for lane widths and barrier protection. Both bridges have been prioritized as one of the top five sites within Park County needing replacement. Photos for each bridge site are attached in Appendix B.

Tom Miner Creek Bridge is approximately 1900 feet west of the confluence with the Yellowstone River.

The bridge is a single span 19 foot long by 16 foot wide concrete structure. The natural bankfull widths measured within the vicinity of the bridge ranged from 24 to 32 feet with a depth of approximately 2.5 feet. Flood benches along the channel measure 20 to 60 feet wide. Approximately 520 feet upstream of the bridge, a side channel diverts flow to a 48-inch irrigation culvert which crosses under the road 150 feet north of the bridge. Flow to through this culvert was assumed zero for conservative analysis of the proposed bridge. Minor degradation and bank erosion, occurring immediately upstream of the bridge, has undercut banks 6 to 12 inches along the outside of channel bends. Minor deposition has occurred about 175 feet downstream. Channel gradients upstream of the bridge range from 1 to 2.5 percent. Channel gradients downstream range from 1 to 3 percent. Boulders in the channel range in size from 12 to 30 inches. The potential for large woody debris is low. Larger 24-inch plus diameter trees which have fallen within the flood prone area do not appear to be transported by flood flows. Short 15 to 20 foot lengths of smaller woody debris, 18 inch in diameter, have been transported and have collected in small piles along the channel.

Bankfull widths in the vicinity of Rock Creek Bridge ranged from 16 to 22 feet. The bridge is a single span 17.5 foot long by 16 foot wide concrete structure. The flood prone area is well defined and appears to be contained within the channel banks. Little evidence can be seen outside the ordinary high water limits to suggest flooding beyond the top of channel banks. Some aggradation has occurred approximately 75 feet upstream of the existing bridge. Downstream of the bridge, a railroad culvert was removed as part of a stream restoration project. Rock weirs were installed to control degradation of the stream grade, protect the existing bridge abutment foundations from being undercut, and allow for fish passage. The weirs appear to be stable and functioning. Channel gradients upstream of the bridge range from 3 to 4 percent. Channel gradients downstream range from 6 to 9.5 percent. Boulders in the channel range in size from 12 to 36 inches. The potential for large woody debris is low. Larger 24 inch plus diameter trees which have fallen within the flood prone area do not appear to be transported by flood flows. Short 10 to 15 foot lengths of smaller woody debris, 18 inch in diameter, have been transported and have collected in piles along the channel.

Hydrology

A Tom Miner and Rock Creek are mountain streams that originate along the east slopes of Sheep and Fortress Mountains and flow east to the Yellowstone River. Tom Miner Creek and Rock Creek are unregulated and un-gaged. Therefore, peak discharges, drainage areas, and percent basin area above 6,000 feet elevation were estimated using USGS StreamStats program. StreamStats utilizes regression equations from Methods for estimating peak-flow frequencies at ungaged sites in Montana (USGS Report 2015–5019–F). Tom Miner Creek Bridge has a tributary drainage area of 65.4 square miles with 94 percent of the area over 6,000 feet elevation. Rock Creek Bridge has a drainage area of 28.5 square miles with 96 percent of the area over 6,000 feet elevation. Detailed StreamStats results have been attached to this report. Peak discharges are listed in Appendix A, Table 1.

Water Surface Elevations and Flow Velocities

Water surface elevations and flow velocities were estimated using the Hydrologic Engineering Center River Analysis System (HEC-RAS 4.1.0), a computer program that performs one- dimensional steady flow calculations. Cross sections of each channel and floodplain parallel to expected flow direction were generated using ground topographic survey data. At Tom Miner Creek Bridge the cross sections extended 320 feet upstream and 630 downstream. At Rock Creek Bridge the cross sections extended 280 feet upstream and 160 feet downstream. Manning’s roughness coefficients for the channel and flood plain were estimated using guidelines from FHWA-TS-84-204. The resulting water surface elevations and flow velocities for estimated flood frequencies at the proposed bridge crossings are listed in Appendix A, Table 2.

The proposed bridge geometry was based on the attached bridge drawings. Flow was assumed subcritical. The modeled 2-year event flow depths were compared with the measured ordinary high water (OHW) depths to verify the models accuracy. Using the maximum 90-percent prediction 2-year event resulted in model values that closely matched OHW values measured in the field. Therefore, further calibration of the model was not necessary.

Flood Rise Limitations

Executive Order 11988, Floodplain Management, established federal policies for protecting floodplains and floodways. The intention of the associated regulations is to avoid, to the extent practical, adverse impacts to floodplains; minimize the impact of floods to human safety, health, and welfare; and avoid supporting land use development that is incompatible with the natural and beneficial floodplain values.

When avoidance is not possible, the policies require appropriate consideration of methods to minimize adverse impacts.

The bridge site is not located within an area of special flood hazard designated by a Federal Emergency Management Agency (FEMA) flood insurance rate map (FIRM) or detailed mapping study (FIS).

The bridge site is not within a regulated floodplain. FHWA policy allow up to one-foot rise in the 100-year water surface elevations. The proposed bridges should not cause a flood rise impacting nearby structures.

Scour Analysis

A HEC-18 based scour analysis was performed for both sites using HEC-RAS. A geotechnical study conducted for the sites determined that bedrock will not be encountered within the maximum expected scour depth. The surface streambed material is predominantly cobbles and boulders with gravels.

Particle size data was obtained by visual estimates of D50 and digital images taken near each proposed bridge crossing. Digital images where analyzed using Hydraulics Toolbox 4.1 software developed by FHWA to produce gradation information. The following particle sizes were used for scour analysis:

Tom Miner Creek

D50 = 3.5 inches (89 mm)

Rock Creek

D50 = 4.9 inches (125 mm)

Assumptions used in the scour analysis include:

Abutments are vertical GRS with concrete block facing.

Analysis of scour is based on full exposure of the GRS due to lateral migration of the stream.

Particle sizes used in the analysis assume gravel, cobbles, and boulders found within the channel will be transported from upstream to continue providing surface armoring and limit effects of scour.

Scour calculations and analysis results are included in Appendix E.

Attachments: Appendix A - Tables Appendix B - Figures Appendix C - Photos Appendix D - Drawings Appendix E – Calculations

Appendix A – Tables

Table 1.

Peak Discharge Estimates (ft3/sec)

Table 2.

Proposed Bridges

Recurrence Interval

2-year 10-year 25-year 50-year 100-year 500-year

Tom Miner Creek Bridge

Water Surface Elevation (ft) 5043.8 5044.9 5045.6 5046.0 5046.4 5048.1

Clearance (ft) 4.2 3.1 2.4 2.0 1.6 -0.1

Flow Velocity (ft/sec) 5.1 6.9 7.6 8.1 8.6 7.4

Rock Creek Bridge

Water Surface Elevation (ft) 4995.8 4996.9 4997.5 4997.9 4998.4 4999.9

Clearance (ft) 4.1 3.0 2.4 2.0 1.5 0.0

Flow Velocity (ft/sec) 3.9 5.0 5.1 5.4 5.9 6.4

Site Drainage

Area

(sq. mi.)

Recurrence Interval

2-year 10-year 25-year 50-year 100-year 500-year

Tom Miner Creek Bridge

65.4 295 663 903 1100 1300 1830

Rock Creek Bridge

28.5 148 352 490 603 723 1040

Table 3A.

Flow Conditions at Tom Miner Creek

2-Year 10-Year 50-Year 100-Year 500-Year Upstream of Bridge

210 feet

Existing - Water Surface Elevation (feet)

5047.5 5048.4 5049.5 5050.0 5051.1

Proposed - Water Surface Elevation (feet)

5047.5 5048.4 5049.5 5050.0 5051.1

Existing - Average Flow Velocity (ft/sec)

6.5 8.9 10.1 10.4 10.7

Proposed - Average Flow Velocity (ft/sec)

6.5 8.9 10.1 10.4 10.7

Downstream of Bridge 120 feet

5041.1 5042.6 5043.4 5043.6 5045.5

Proposed - Water Surface Elevation (feet)

5041.1 5042.6 5043.4 5043.6 5045.5

Existing - Average Flow Velocity (ft/sec)

8.1 9.2 11.7 13.3 9.8

Proposed - Average Flow Velocity (ft/sec)

8.1 9.2 11.7 13.3 9.8

Table 3B.

Flow Conditions at Rock Creek

2-Year 10-Year 50-Year 100-Year 500-Year Upstream of Bridge

110 feet

4999.4 5000.2 5001.2 5001.6 5002.3

Proposed - Water Surface Elevation (feet)

4999.4 5000.2 5001.2 5001.6 5002.3

Existing - Average Flow Velocity (ft/sec)

5.5 7.8 8.4 8.2 9.0

Proposed - Average Flow Velocity (ft/sec)

5.5 7.6 8.4 8.2 9.0

Downstream of Bridge 65 feet

4991.8 4992.7 4993.5 4993.9 4994.7

Proposed - Water Surface Elevation (feet)

4991.8 4992.7 4993.5 4993.9 4994.7

Existing - Average Flow Velocity (ft/sec)

6.0 7.8 9.2 9.7 10.7

Proposed - Average Flow Velocity (ft/sec)

6.0 7.8 9.2 9.7 10.7

Appendix B – Figures james.g.neighorn Typewritten Text james.g.neighorn Typewritten Text james.g.neighorn Typewritten Text james.g.neighorn Typewritten Text james.g.neighorn Typewritten Text james.g.neighorn

Tom Miner Creek Basin Map james.g.neighorn

Rock Creek Basin Map

Appendix C – Photos

Tom Miner Creek Bridge

Looking south at bridge and roadway

Looking upstream (west) from bridge

Looking downstream (east) from bridge

Looking downstream at erosion along north abutment

Looking upstream at eroded north abutment

Channel conditions upstream of the bridge

Channel conditions downstream of bridge

Irrigation culvert crossing and ditch north of the bridge

Looking north at bridge and roadway

Upstream of bridge looking downstream (east)

Downstream of bridge looking upstream (west)

Failing abutment at southeast corner

Vertical crack at southeast abutment corner

Looking upstream at rock weirs during low flow

Upstream channel conditions during high flow

Upstream channel conditions during low flow

Stone wall and storage structure upstream of the bridge

Culvert outlet transporting sediment to upland area

Appendix D – Drawings

Appendix E – Calculations

To: By: James Neighorn, P.E.

Project: MT PARK 63(1) - Tom Miner Creek Road Improvements WFLHD Hydraulics Engineer

Bridge: Date:

BRIDGE STRUCTURE SUMMARY

Low Chord Elevation 5048.0 feet (Project Datum)

Minimum Design Freeboard 2.0 feet above the 50-year flood

Stream Bottom Elevation 5041.3 feet

Clearance to Stream Bot. 6.7 feet

Waterway Width 40 feet

Skew 10.5 degrees relative to stream

Bridge/Stream CL Sta 103+91.58 Bridge Start 103+65.58 Bridge End 104+17.58

Abutment Type Vertical GRS with riprap protection, clear span, no piers.

HYDRAULIC & HYDROLOGIC SUMMARY

Flood Frequency Yr 2 10 25 50 100 500

Exceedance Probability % 50 10 4 2 1 0.2

Discharge cfs 295 663 903 1100 1300 1830

Modeled Water Surface Elevation * Elev 5043.8 5044.9 5045.6 5046.0 5046.4 5048.1

Elevation Datum Conversion Ft 0.0 0.0 0.0 0.0 0.0 0.0

Project Water Surface Elevation Elev 5043.8 5044.9 5045.6 5046.0 5046.4 5048.1

Clearance above WS Ft 4.2 3.1 2.4 2.0 1.6 -0.1

Existing Water Surface Elevation * Elev 5044.8 5046.7 5047.9 5048.8 5049.7 5051.2

Predicted Flood Rise Ft -0.9 -1.8 -2.3 -2.8 -3.3 -3.1

Design Flow Velocity Ft/sec 5.1 6.9 7.6 8.1 8.6 7.4

Scour Base Elevation (Channel Thalweg) Elev 5041.3 5041.3

Contraction Scour Depth Ft 0.0 0.0

Stream Degradation Depth Ft 2.0 2.0

Left Abutment Scour Depth Ft 1.4 5.3

Right Abutment Scour Depth Ft 1.4 5.3

Total Left Abutment Scour Elevation Elev 5037.9 5034.0

Total Right Abutment Scour Elevation Elev 5037.9 5034.0

Pier Scour Depth Ft NA NA

Total Pier Scour Elevation Elev* NA NA

Streambed material grain size (inches) D100 13.7 D50 3.5 D15 1.3

Scour Design Basis

Project Elevation Datum

RECOMMENDED SCOUR COUNTERMEASURES

Type

Top Elevation 5047.0 Slope (H:V) 1.5:1

Bottom Elevation 5039.3 Toe Width (Ft) 3.5

Thick (Ft) 3.5 min Toe Thickness (Ft) 3.5

Riprap Design Basis

BRIDGE HYDRAULICS & SCOUR ANALYSIS SUMMARY

Matthew Miller, WFLHD Project Manager

12/16/2016Tom Miner Creek

* Elevations from upstream bridge cross section

NAD83/2011

HEC 18

Riprap, Class 4 (FP-14)

HEC-23

Tom Miner Creek Bridge Hydraulics Summary.xls

FOUNDATION SUMMARY

GEOTECHNICAL SUMMARY

STREAM PLAN & PROFILE STABILITY

The proposed bridge is located 1,900 feet upstream of the confluence with the Yellowstone River. The active channel width is 32 feet. OHW is approximately 2.5 feet. Stream gradient is approximately 2.0 percent. Large woody debris recruitment and transports potential is low. Debris flow potential is low. Banks are heavily vegetated, coarsely armored and stable. The stable banks limit channel migration. The cobble and boulder bed appear to be stable with low potential for degradation.

Based on geotechnical borings the material in the stream channel is cobbles with boulders. Approximately 5 to 10 feet below the channel bottom the material becomes sandy materials with various silt and gravel.

Abutment foundations are vertical GRS. Scour at abutments assume lateral migration of the stream and full exposure of the vertical GRS with 90 degree (perpendicular) flow angle.

Tom Miner Creek Bridge Hydraulics Summary.xls

Basin Characteristics Ungaged Site Report

Date: Tues June 7, 2016 1:44:24 PM GMT-7 Study Area: Montana NAD 1983 Latitude: 45.2011 ( 45 12 04) NAD 1983 Longitude: -110.902 (-110 54 07)

Label Value Units Definition

CONTDA 65.4 square miles Area that contributes flow to a point on a stream (total drainage area minus non-contributing areas within basin)

ELEV 7610 feet Mean Basin Elevation ELEVMAX 10300 feet Maximum basin elevation MINBELEV 5000 feet Minimum basin elevation RELIEF 5270 feet Maximum - minimum elevation EL6000 94 percent Percent of area above 6000 ft BSLDEM30M 32.3 percent Mean basin slope computed from 30 m DEM SLOP30_30M 47 percent Percent area with slopes greater than 30 percent from 30-meter DEM.

NFSL30_30M 17 percent Percent area with north-facing slopes greater than 30 percent from 30-meter DEM.

SLOP50_30M 19 percent Percent area with slopes greater than 50 percent from 30-meter DEM.

PRECIP 30 inches Mean Annual Precipitation FOREST 57 percent Percentage of area covered by forest

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1 of 1 6/7/2016 1:44 PM james.g.neighorn

Estimate Flood Discharges at Ungaged Sites in Montana -- (continued)

Summary of Estimation Parameters Selected:

Name for this estimation: Tom Miner Creek

Region: Upper Yellowstone

Estimation method: Basin and Climatic Characteristics Only

Drainage area in square miles: 65.4

Percent basin above 6,000 feet: 94

Flood Discharge Estimation:

(In the Flood Discharge table, RI is the Recurrence Interval, in years; STD ERR is the Standard Error; and 90% PRED. INTERVAL is the 90% Prediction Interval, in cubic feet per second)

METHOD: Regression on basin characteristics Flood frequency estimates for Tom Miner Creek Upper Yellowstone-Central Mountain Region: A = 65.40 E6 = 94.

RI DISCHARGE STD ERR OF 90% PRED. INTERVAL

(cfs) PREDICTION(%) 2 295. 93.6 79.2 1100.

5 498. 71.5 171.3 1450.

10 663. 62.1 256.8 1710.

25 903. 55.8 380.6 2140.

50 1100. 54.4 471.0 2550.

100 1300. 55.2 552.7 3060.

200 1520. 57.8 622.5 3700.

500 1830. 63.3 697.8 4790.

Montana Flood-Frequency and Basin-Characteristic Data Retrieved on: 2016.06.07 17:27:58 Department of the Interior, U.S. Geological Survey Privacy Statement || Disclaimer || Accessibility || FOIA

0.216

Montana Flood-Frequency and Basin-Characteristic Data http://wy-mt.water.usgs.gov/freq?page_type=gen_stats_4&estimate_nm...

1 of 1 6/7/2016 2:28 PM james.g.neighorn

HEC-RAS Version 4.1.0 Jan 2010 U.S. Army Corps of Engineers Hydrologic Engineering Center 609 Second Street Davis, California

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PROJECT DATA

Project Title: Tom Miner Creek Project File : TomMinerCreek.prj Run Date and Time: 12/15/2016 1:30:59 PM

Project in English units

PLAN DATA

Plan Title: Proposed Plan File : C:\Project Files\MT Tom Minor Creek\HEC RAS\TomMinerCreek.p04

Geometry Title: TomMiner Proposed Geometry File : C:\Project Files\MT Tom Minor Creek\HEC RAS\TomMinerCreek.g02

Flow Title : Tom Miner Creek Flows Flow File : C:\Project Files\MT Tom Minor Creek\HEC RAS\TomMinerCreek.f02

Plan Summary Information:

Number of: Cross Sections = 10 Multiple Openings = 0 Culverts = 0 Inline Structures = 0 Bridges = 1 Lateral Structures = 0

Computational Information Water surface calculation tolerance = 0.01 Critical depth calculation tolerance = 0.01 Maximum number of iterations = 20 Maximum difference tolerance = 0.3 Flow tolerance factor = 0.001

Computation Options Critical depth computed only where necessary Conveyance Calculation Method: At breaks in n values only Friction Slope Method: Average Conveyance Computational Flow Regime: Subcritical Flow

FLOW DATA

Flow Title: Tom Miner Creek Flows Flow File : C:\Project Files\MT Tom Minor Creek\HEC RAS\TomMinerCreek.f02

Flow Data (cfs)

River Reach RS 2yr 10yr 25yr 50yr 100yr 500yr hy1 TOMMINER 875.493 295 663 903 1100 1300 1830

Boundary Conditions

River Reach Profile Upstream Downstream hy1 TOMMINER 2yr Normal S = 0.025 hy1 TOMMINER 10yr Normal S = 0.025 hy1 TOMMINER 25yr Normal S = 0.025 hy1 TOMMINER 50yr Normal S = 0.025 hy1 TOMMINER 100yr Normal S = 0.025 hy1 TOMMINER 500yr Normal S = 0.025

SUMMARY OF MANNING'S N VALUES

River:hy1

Reach River Sta. n1 n2 n3 n4 n5 n6

TOMMINER 875.493 .07 .04 .07 .03

TOMMINER 760.756 .06 .03 .07 .04 .07 .03

TOMMINER 702.443 .06 .03 .07 .04 .07 .03

TOMMINER 637.910 .06 .03 .07 .04 .07 .03

TOMMINER 575.243 .06 .03 .07 .04 .07 .03

TOMMINER 552 Bridge

TOMMINER 530.256 .06 .04 .07 .03

TOMMINER 433.449 .06 .03 .06 .04 .07

TOMMINER 395.890 .06 .03 .06 .04 .07 .03

TOMMINER 303.873 .03 .06 .04 .07 .03

TOMMINER 0.000 .03 .06 .04 .07 .03

SUMMARY OF REACH LENGTHS

River: hy1

Reach River Sta. Left Channel Right

TOMMINER 875.493 114.7 114.7 114.7

TOMMINER 760.756 58.3 58.3 58.3

TOMMINER 702.443 64.7 64.7 64.7

TOMMINER 637.910 62.5 62.5 62.5

TOMMINER 575.243 45 45 45

TOMMINER 552 Bridge

TOMMINER 530.256 96.8 96.8 96.8

TOMMINER 433.449 37.6 37.6 37.6

TOMMINER 395.890 128 128 128

TOMMINER 303.873 343.25 343.25 343.25

TOMMINER 0.000 0 0 0

SUMMARY OF CONTRACTION AND EXPANSION COEFFICIENTS

Reach River Sta. Contr. Expan.

TOMMINER 875.493 .1 .3

TOMMINER 760.756 .1 .3

TOMMINER 702.443 .1 .3

TOMMINER 637.910 .1 .3

TOMMINER 575.243 .1 .3

TOMMINER 552 Bridge

TOMMINER 530.256 .1 .3

TOMMINER 433.449 .1 .3

TOMMINER 395.890 .1 .3

TOMMINER 303.873 .1 .3

TOMMINER 0.000 .1 .3

HEC-RAS Plan: Existing River: hy1 Reach: TOMMINER

Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

TOMMINER 875.493 2yr 295.00 5047.20 5049.53 5049.53 5050.23 0.020617 6.76 43.66 30.14 0.99

TOMMINER 875.493 10yr 663.00 5047.20 5050.72 5050.60 5051.69 0.015949 7.90 83.93 37.49 0.93

TOMMINER 875.493 25yr 903.00 5047.20 5051.18 5051.12 5052.40 0.016679 8.85 102.06 40.38 0.97

TOMMINER 875.493 50yr 1100.00 5047.20 5051.53 5051.53 5052.93 0.016270 9.50 116.56 43.69 0.98

TOMMINER 875.493 100yr 1300.00 5047.20 5051.87 5051.87 5053.43 0.015556 10.01 132.30 47.12 0.98

TOMMINER 875.493 500yr 1830.00 5047.20 5052.85 5052.76 5052.93 0.000254 1.52 833.75 213.13 0.13

TOMMINER 760.756 2yr 295.00 5044.87 5047.45 5047.31 5048.10 0.016022 6.47 45.58 27.12 0.88

TOMMINER 760.756 10yr 663.00 5044.87 5048.43 5048.43 5049.66 0.019246 8.88 74.77 32.22 1.01

TOMMINER 760.756 25yr 903.00 5044.87 5049.06 5049.06 5050.47 0.016713 9.52 95.88 34.86 0.98

TOMMINER 760.756 50yr 1100.00 5044.87 5049.48 5049.48 5051.07 0.015794 10.12 111.03 36.64 0.97

TOMMINER 760.756 100yr 1300.00 5044.87 5049.98 5049.98 5051.63 0.013744 10.35 132.98 61.39 0.93

TOMMINER 760.756 500yr 1830.00 5044.87 5051.05 5051.05 5052.69 0.010584 10.67 211.82 85.45 0.85

TOMMINER 702.443 2yr 295.00 5044.39 5046.40 5046.40 5047.04 0.020896 6.42 45.96 34.78 0.98

TOMMINER 702.443 10yr 663.00 5044.39 5047.41 5047.41 5048.34 0.017476 7.77 87.05 49.22 0.96

TOMMINER 702.443 25yr 903.00 5044.39 5047.90 5047.90 5048.98 0.015825 8.37 113.43 57.53 0.94

TOMMINER 702.443 50yr 1100.00 5044.39 5048.46 5048.18 5049.45 0.011626 8.13 150.40 79.40 0.83

TOMMINER 702.443 100yr 1300.00 5044.39 5049.50 5048.68 5050.10 0.005018 6.54 245.69 101.87 0.58

TOMMINER 702.443 500yr 1830.00 5044.39 5050.95 5049.37 5051.44 0.002958 6.17 419.33 163.96 0.47

TOMMINER 637.910 2yr 295.00 5043.23 5044.98 5044.98 5045.58 0.022873 6.23 47.33 40.06 1.01

TOMMINER 637.910 10yr 663.00 5043.23 5046.89 5047.22 0.004321 4.72 164.77 103.45 0.50

TOMMINER 637.910 25yr 903.00 5043.23 5048.03 5048.23 0.001906 3.94 311.10 156.60 0.35

TOMMINER 637.910 50yr 1100.00 5043.23 5048.88 5049.03 0.001141 3.48 458.13 183.84 0.28

TOMMINER 637.910 100yr 1300.00 5043.23 5049.74 5049.85 0.000747 3.15 634.79 241.88 0.24

TOMMINER 637.910 500yr 1830.00 5043.23 5051.17 5051.25 0.000447 2.84 1022.20 275.17 0.19

TOMMINER 575.243 2yr 295.00 5041.78 5044.75 5043.55 5044.95 0.003003 3.60 82.00 32.90 0.40

TOMMINER 575.243 10yr 663.00 5041.78 5046.74 5044.57 5047.02 0.002125 4.31 172.66 83.42 0.37

TOMMINER 575.243 25yr 903.00 5041.78 5047.89 5045.13 5048.12 0.001436 4.15 330.97 190.22 0.31

TOMMINER 575.243 50yr 1100.00 5041.78 5048.81 5045.57 5048.96 0.000905 3.65 518.25 217.39 0.25

TOMMINER 575.243 100yr 1300.00 5041.78 5049.70 5045.99 5049.81 0.000604 3.26 744.02 293.60 0.21

TOMMINER 575.243 500yr 1830.00 5041.78 5051.16 5047.41 5051.23 0.000361 2.84 1176.39 301.92 0.17

TOMMINER 552 Bridge

TOMMINER 530.256 2yr 295.00 5040.40 5043.17 5042.82 5043.60 0.011150 5.28 55.92 35.33 0.74

HEC-RAS Plan: Existing River: hy1 Reach: TOMMINER (Continued)

Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

TOMMINER 530.256 10yr 663.00 5040.40 5044.28 5043.84 5044.83 0.007777 6.25 138.52 102.51 0.67

TOMMINER 530.256 25yr 903.00 5040.40 5045.02 5044.46 5045.46 0.005019 5.90 227.57 135.17 0.56

TOMMINER 530.256 50yr 1100.00 5040.40 5045.65 5044.75 5046.00 0.003478 5.50 319.87 156.18 0.48

TOMMINER 530.256 100yr 1300.00 5040.40 5046.35 5045.00 5046.61 0.002316 4.98 433.32 178.34 0.40

TOMMINER 530.256 500yr 1830.00 5040.40 5046.56 5045.63 5047.01 0.003759 6.53 475.14 208.22 0.52

TOMMINER 433.449 2yr 295.00 5037.53 5041.05 5041.05 5042.08 0.021555 8.13 36.33 18.95 1.00

TOMMINER 433.449 10yr 663.00 5037.53 5042.62 5042.62 5043.80 0.013098 9.22 88.37 38.99 0.85

TOMMINER 433.449 25yr 903.00 5037.53 5043.18 5043.18 5044.61 0.013537 10.32 110.69 40.70 0.89

TOMMINER 433.449 50yr 1100.00 5037.53 5043.43 5043.43 5045.23 0.016064 11.68 120.87 42.43 0.98

TOMMINER 433.449 100yr 1300.00 5037.53 5043.59 5043.59 5045.91 0.019698 13.26 128.22 45.71 1.09

TOMMINER 433.449 500yr 1830.00 5037.53 5045.51 5045.51 5046.48 0.006757 9.80 358.19 182.70 0.68

TOMMINER 395.890 2yr 295.00 5037.61 5040.62 5040.85 0.005383 3.86 76.98 48.81 0.52

TOMMINER 395.890 10yr 663.00 5037.61 5041.56 5042.01 0.006157 5.48 130.30 66.54 0.59

TOMMINER 395.890 25yr 903.00 5037.61 5042.01 5042.59 0.006446 6.24 164.38 82.68 0.62

TOMMINER 395.890 50yr 1100.00 5037.61 5041.96 5041.62 5042.86 0.010279 7.77 159.53 81.29 0.79

TOMMINER 395.890 100yr 1300.00 5037.61 5042.06 5042.02 5043.21 0.012631 8.82 168.23 83.49 0.88

TOMMINER 395.890 500yr 1830.00 5037.61 5042.67 5042.67 5044.08 0.012739 9.96 222.76 98.28 0.91

TOMMINER 303.873 2yr 295.00 5036.64 5039.01 5039.01 5039.57 0.022586 6.04 48.99 45.27 1.00

TOMMINER 303.873 10yr 663.00 5036.64 5039.85 5039.85 5040.73 0.017190 7.62 93.07 59.71 0.96

TOMMINER 303.873 25yr 903.00 5036.64 5040.30 5040.30 5041.33 0.015519 8.30 122.23 72.79 0.94

TOMMINER 303.873 50yr 1100.00 5036.64 5041.09 5041.09 5041.70 0.006942 6.71 225.70 212.52 0.66

TOMMINER 303.873 100yr 1300.00 5036.64 5041.29 5041.29 5041.89 0.006778 6.90 268.36 217.94 0.66

TOMMINER 303.873 500yr 1830.00 5036.64 5041.63 5041.63 5042.31 0.007486 7.72 343.12 227.12 0.70

TOMMINER 0.000 2yr 295.00 5027.64 5030.38 5030.38 5031.16 0.020771 7.12 41.41 26.30 1.00

TOMMINER 0.000 10yr 663.00 5027.64 5031.61 5031.61 5032.67 0.017364 8.31 81.93 43.82 0.97

TOMMINER 0.000 25yr 903.00 5027.64 5032.15 5032.15 5033.37 0.015491 8.96 107.99 53.12 0.95

TOMMINER 0.000 50yr 1100.00 5027.64 5032.56 5032.56 5033.86 0.013990 9.33 131.35 60.76 0.92

TOMMINER 0.000 100yr 1300.00 5027.64 5033.06 5033.06 5034.31 0.011365 9.27 168.99 99.77 0.85

TOMMINER 0.000 500yr 1830.00 5027.64 5033.91 5033.91 5035.13 0.009136 9.55 265.45 125.77 0.79

HEC-RAS Plan: Proposed River: hy1 Reach: TOMMINER

Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

TOMMINER 875.493 2yr 295.00 5047.20 5049.53 5049.53 5050.23 0.020617 6.76 43.66 30.14 0.99

TOMMINER 875.493 10yr 663.00 5047.20 5050.72 5050.60 5051.69 0.015949 7.90 83.93 37.49 0.93

TOMMINER 875.493 25yr 903.00 5047.20 5051.18 5051.12 5052.40 0.016679 8.85 102.06 40.38 0.97

TOMMINER 875.493 50yr 1100.00 5047.20 5051.53 5051.53 5052.93 0.016270 9.50 116.56 43.69 0.98

TOMMINER 875.493 100yr 1300.00 5047.20 5051.87 5051.87 5053.43 0.015556 10.01 132.30 47.12 0.98

TOMMINER 875.493 500yr 1830.00 5047.20 5052.85 5052.76 5052.93 0.000254 1.52 833.75 213.13 0.13

TOMMINER 760.756 2yr 295.00 5044.87 5047.45 5047.31 5048.10 0.016022 6.47 45.58 27.12 0.88

TOMMINER 760.756 10yr 663.00 5044.87 5048.43 5048.43 5049.66 0.019246 8.88 74.77 32.22 1.01

TOMMINER 760.756 25yr 903.00 5044.87 5049.06 5049.06 5050.47 0.016713 9.52 95.88 34.86 0.98

TOMMINER 760.756 50yr 1100.00 5044.87 5049.48 5049.48 5051.07 0.015794 10.12 111.03 36.64 0.97

TOMMINER 760.756 100yr 1300.00 5044.87 5049.98 5049.98 5051.63 0.013744 10.35 132.98 61.39 0.93

TOMMINER 760.756 500yr 1830.00 5044.87 5051.05 5051.05 5052.69 0.010584 10.67 211.82 85.45 0.85

TOMMINER 702.443 2yr 295.00 5044.39 5046.40 5046.40 5047.04 0.020896 6.42 45.96 34.78 0.98

TOMMINER 702.443 10yr 663.00 5044.39 5047.41 5047.41 5048.34 0.017476 7.77 87.05 49.22 0.96

TOMMINER 702.443 25yr 903.00 5044.39 5047.90 5047.90 5048.98 0.015825 8.37 113.43 57.53 0.94

TOMMINER 702.443 50yr 1100.00 5044.39 5048.18 5048.18 5049.43 0.016470 9.07 130.03 62.22 0.98

TOMMINER 702.443 100yr 1300.00 5044.39 5048.68 5048.68 5049.83 0.012428 8.81 168.35 85.58 0.87

TOMMINER 702.443 500yr 1830.00 5044.39 5049.37 5049.37 5050.68 0.011391 9.63 232.29 99.24 0.86

TOMMINER 637.910 2yr 295.00 5043.23 5044.98 5044.98 5045.58 0.022873 6.23 47.33 40.06 1.01

TOMMINER 637.910 10yr 663.00 5043.23 5045.88 5045.88 5046.81 0.018880 7.73 86.53 53.82 0.99

TOMMINER 637.910 25yr 903.00 5043.23 5046.43 5046.43 5047.41 0.015139 8.00 121.12 75.65 0.92

TOMMINER 637.910 50yr 1100.00 5043.23 5046.85 5046.85 5047.79 0.012458 7.96 161.30 103.07 0.85

TOMMINER 637.910 100yr 1300.00 5043.23 5047.32 5047.11 5048.13 0.009231 7.58 213.80 121.43 0.75

TOMMINER 637.910 500yr 1830.00 5043.23 5048.65 5049.14 0.003990 6.29 416.02 178.52 0.52

TOMMINER 575.243 2yr 295.00 5041.80 5043.78 5043.34 5044.19 0.009205 5.14 57.40 31.96 0.68

TOMMINER 575.243 10yr 663.00 5041.80 5044.94 5044.38 5045.67 0.009666 6.88 96.43 35.44 0.73

TOMMINER 575.243 25yr 903.00 5041.80 5045.55 5044.93 5046.44 0.009693 7.61 119.72 40.38 0.75

TOMMINER 575.243 50yr 1100.00 5041.80 5046.01 5045.36 5047.01 0.009119 8.06 139.49 46.69 0.75

TOMMINER 575.243 100yr 1300.00 5041.80 5046.47 5045.74 5047.55 0.008460 8.41 162.08 52.13 0.73

TOMMINER 575.243 500yr 1830.00 5041.80 5048.17 5046.61 5048.87 0.003923 7.22 387.20 198.61 0.53

TOMMINER 552 Bridge

TOMMINER 530.256 2yr 295.00 5040.40 5042.68 5041.75 5042.89 0.003777 3.63 81.21 39.13 0.44

HEC-RAS Plan: Proposed River: hy1 Reach: TOMMINER (Continued)

Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)

TOMMINER 530.256 10yr 663.00 5040.40 5044.14 5042.69 5044.44 0.003178 4.49 171.18 98.78 0.44

TOMMINER 530.256 25yr 903.00 5040.40 5044.91 5043.17 5045.19 0.002461 4.54 259.99 131.46 0.40

TOMMINER 530.256 50yr 1100.00 5040.40 5045.55 5043.56 5045.80 0.001906 4.41 350.60 154.19 0.36

TOMMINER 530.256 100yr 1300.00 5040.40 5046.25 5044.15 5046.46 0.001381 4.12 464.37 168.20 0.31

TOMMINER 530.256 500yr 1830.00 5040.40 5046.55 5044.92 5046.88 0.002131 5.30 521.01 207.83 0.39

TOMMINER 433.449 2yr 295.00 5037.53 5041.05 5041.05 5042.08 0.021555 8.13 36.33 18.95 1.00

TOMMINER 433.449 10yr 663.00 5037.53 5042.62 5042.62 5043.80 0.013098 9.22 88.37 38.99 0.85

TOMMINER 433.449 25yr 903.00 5037.53 5043.18 5043.18 5044.61 0.013537 10.32 110.69 40.70 0.89

TOMMINER 433.449 50yr 1100.00 5037.53 5043.43 5043.43 5045.23 0.016064 11.68 120.87 42.43 0.98

TOMMINER 433.449 100yr 1300.00 5037.53 5043.59 5043.59 5045.91 0.019698 13.26 128.22 45.71 1.09

TOMMINER 433.449 500yr 1830.00 5037.53 5045.51 5045.51 5046.48 0.006757 9.80 358.19 182.70 0.68

TOMMINER 395.890 2yr 295.00 5037.61 5040.62 5040.85 0.005383 3.86 76.98 48.81 0.52

TOMMINER 395.890 10yr 663.00 5037.61 5041.56 5042.01 0.006157 5.48 130.30 66.54 0.59

TOMMINER 395.890 25yr 903.00 5037.61 5042.01 5042.59 0.006446 6.24 164.38 82.68 0.62

TOMMINER 395.890 50yr 1100.00 5037.61 5041.96 5041.62 5042.86 0.010279 7.77 159.53 81.29 0.79

TOMMINER 395.890 100yr 1300.00 5037.61 5042.06 5042.02 5043.21 0.012631 8.82 168.23 83.49 0.88

TOMMINER 395.890 500yr 1830.00 5037.61 5042.67 5042.67 5044.08 0.012739 9.96 222.76 98.28 0.91

TOMMINER 303.873 2yr 295.00 5036.64 5039.01 5039.01 5039.57 0.022586 6.04 48.99 45.27 1.00

TOMMINER 303.873 10yr 663.00 5036.64 5039.85 5039.85 5040.73 0.017190 7.62 93.07 59.71 0.96

TOMMINER 303.873 25yr 903.00 5036.64 5040.30 5040.30 5041.33 0.015519 8.30 122.23 72.79 0.94

TOMMINER 303.873 50yr 1100.00 5036.64 5041.09 5041.09 5041.70 0.006942 6.71 225.70 212.52 0.66

TOMMINER 303.873 100yr 1300.00 5036.64 5041.29 5041.29 5041.89 0.006778 6.90 268.36 217.94 0.66

TOMMINER 303.873 500yr 1830.00 5036.64 5041.63 5041.63 5042.31 0.007486 7.72 343.12 227.12 0.70

TOMMINER 0.000 2yr 295.00 5027.64 5030.38 5030.38 5031.16 0.020771 7.12 41.41 26.30 1.00

TOMMINER 0.000 10yr 663.00 5027.64 5031.61 5031.61 5032.67 0.017364 8.31 81.93 43.82 0.97

TOMMINER 0.000 25yr 903.00 5027.64 5032.15 5032.15 5033.37 0.015491 8.96 107.99 53.12 0.95

TOMMINER 0.000 50yr 1100.00 5027.64 5032.56 5032.56 5033.86 0.013990 9.33 131.35 60.76 0.92

TOMMINER 0.000 100yr 1300.00 5027.64 5033.06 5033.06 5034.31 0.011365 9.27 168.99 99.77 0.85

TOMMINER 0.000 500yr 1830.00 5027.64 5033.91 5033.91 5035.13 0.009136 9.55 265.45 125.77 0.79

Contraction Scour Left Channel Right

Input Data Average Depth (ft): 0.41 3.15 1.01 Approach Velocity (ft/s): 1.37 7.58 2.36 Br Average Depth (ft): 0.07 3.34 0.07 BR Opening Flow (cfs): 0.01 1299.98 0.01 BR Top WD (ft): 0.21 37.32 0.21 Grain Size D50 (mm): 89.00 89.00 89.00 Approach Flow (cfs): 13.23 1169.13 117.64 Approach Top WD (ft): 23.31 48.96 49.17 K1 Coefficient: 0.590 0.590 0.590

Results Scour Depth Ys (ft): 0.00 0.14 0.00 Critical Velocity (ft/s): 6.39 8.98 7.43 Equation: Clear Clear Clear

Abutment Scour Left Right

Input Data Station at Toe (ft): 193.32 242.82 Toe Sta at appr (ft): 163.68 224.82 Abutment Length (ft): 23.31 49.17 Depth at Toe (ft): -0.51 -0.57 K1 Shape Coef: 1.00 - Vertical abutment Degree of Skew (degrees): 90.00 90.00 K2 Skew Coef: 1.00 1.00 Projected Length L' (ft): 23.31 49.17 Avg Depth Obstructed Ya (ft): 0.41 1.01 Flow Obstructed Qe (cfs): 13.23 117.64 Area Obstructed Ae (sq ft): 9.66 49.83

Results Scour Depth Ys (ft): 3.33 8.13 Qe/Ae = Ve: 1.37 2.36 Froude #: 0.38 0.41 Equation: Froehlich Froehlich

Combined Scour Depths

Left abutment scour + contraction scour (ft):…