WY FLAP NAT 505 BL 6409 Final Hydraulics Report.pdf

Casper Mountain Circle Drive and Muddy Mountain Road

WY FLAP NAT 505(1) & WY BL 6409(1)

FINAL Hydraulics Report

Federal Highway Administration, Central Federal Lands Highway Division

May, 2023

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page i

Certification I hereby certify that this FINAL Hydraulics Report for Casper Mountain Circle Drive and Muddy Mountain Road, WY

FLAP NAT 505(1) and WY BL 6409(1), was prepared by me (or under my direct supervision) in accordance with the provisions of the Federal Highway Administration, Office of Federal Lands Highway, Project Development and

Design Manual.

Keira Trujillo, P.E.

Registered Professional Engineer

State of Wyoming No. 19371

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page ii

Contents

Chapter Page

Certification i

1. Introduction

2. Project Background

2.1. Project Location

2.2. Field Reviews

3. Design Discussion

3.1. Design Criteria

3.2. Future Land Use

3.3. Wetlands and Waters of the U.S

3.4. Cultural Resources

3.5. Existing Structures

3.5.1. Casper Mountain Road

3.5.2. Muddy Mountain Road

4. Hydrology

4.1. Drainage Basins

4.2. Soils

4.3. Flood History

4.4. Hydrology Methodology

5. Recommended Design

5.1. Culverts

5.2. Ditches

5.3. Roadway Drainage Layer

5.4. Inlet and Pipe System

5.5. Paved Waterway

6. Summary

7. References

Appendices Appendix A. Resources

Appendix B. Hydrology

Appendix C. Hydraulics

Appendix D. Correspondence

Appendix E. Reference Sheets

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page iii

Tables Table 1: NOAA Atlas 2, Volume 2, Rainfall Depth Data

Table 2: Basin Peak Flows

Table 3: Casper Mountain Road Culvert Design Recommendations

Table 4: Muddy Mountain Road Culvert Design Recommendations

Table 5: Proposed Approach Culvert Design Recommendations

Table 6: Proposed Ditch Design Recommendations

Table 7: Casper Mountain Road Inlet Summary

Table 8: Casper Mountain Road Pipe Summary

Figures Figure 1: Project Limits

Figure 2: Existing Culvert 15 Entrance

Figure 3: Existing Culvert 15 Outlet

Figure 4: Existing Culvert 7 Entrance

Figure 5: Existing Culvert 7 Outlet

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page iv

Acronyms

BLM Bureau of Land Management

CE Categorical Exclusion

CFLHD Central Federal Lands Highway Division

DEM Digital Elevation Model

FEMA Federal Emergency Management Agency

FHWA Federal Highway Administration

FIRM Flood Insurance Rate Map

FLH Federal Lands Highway

HDS Hydraulic Design Series

HEC Hydraulic Engineering Circular

HSG Hydrologic Soil Group

HW/D Headwater to Diameter Ratio

NEPA National Environmental Policy Act

NOAA National Oceanic and Atmospheric Administration

NRCS Natural Resources Conservation Service

NWI National Wetland Inventory

PDDM Project Development and Design Manual

PDP Project Delivery Plan

PS&E Plans, Specifications, and Estimates

ROW Right-of-Way

SOW Scope of Work

STA Station

USFWS U.S. Fish and Wildlife Service

USGS U.S. Geological Survey

WOTUS Waters of the United States

WyDOT Wyoming Department of Transportation

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 1

1. Introduction The Scope of Work (SOW) for the WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY BL 6409(1) Muddy

Mountain Road Project is to perform final design, including roadway and hydraulics and hydrology design, and to provide project management services to deliver a final set of plans, specifications, and estimates (PS&E) to the

Federal Highway Administration (FHWA), Central Federal Lands Highway Division (CFLHD) for proposed improvements to approximately twelve miles of Casper Mountain Circle Drive and Muddy Mountain Road in

Natrona County, Wyoming.

The purpose of the project is to improve access, minimize safety concerns, and minimize drainage hazards. The work consists of resurfacing, restoration, and rehabilitation, with improvements to the roadway and parking surfaces, drainage, access, and safety.

Reconstruction will include minor alignment and grade changes, signing and striping enhancements, parking lot improvements, minor widening and changes to the geometric design, minor drainage improvements, and other safety-related features necessary to meet current design standards.

The purpose of this FINAL Hydraulics Report is to provide hydraulic recommendations for existing and proposed culverts (location and diameter), along with geometry for proposed roadway ditches for Casper Mountain Circle

Drive and Muddy Mountain Road.

2. Project Background

2.1. Project Location

Casper Mountain Circle Drive provides primary access to Muddy Mountain Road from south of Casper. The Casper

Mountain Circle improvements will address deteriorated pavement and aggregate base, along with widening for 5 miles. Approximately 2.33 miles of deteriorated pavement will undergo full depth reclamation, with an additional

2.65 miles of new pavement.

Muddy Mountain Road is located within Bureau of Land Management (BLM), State of Wyoming, and private lands.

This segment provides access to private property and campgrounds. Improvements will rehabilitate and resurface

6.14 miles of aggregate roads and add 1.35 miles of new pavement. There will be four new or improved parking areas within the campground, as well as improvements to safety and drainage.

2.2. Field Reviews

A scoping trip was conducted in June 2021 to assist in the development of the Project Delivery Plan (PDP) for this rehabilitation work as well as a 30% field review in June of 2022. A 70% field review was conducted in September

2022.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 2

Figure 1: Project Limits

Source: Google Earth Imagery (2021)

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 3

3. Design Discussion

3.1. Design Criteria

In January 2022, Atkins submitted the WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1)

Muddy Mountain Road Hydrologic and Hydraulic Criteria and Computational Methods Memorandum. This memorandum outlined the proposed design criteria and methodologies to be used for the project. Drainage criteria were developed using methods, guidelines, and standards set forth in the Federal Lands Highway (FLH) Project

Development and Design Manual (PDDM), FHWA Hydraulic Engineering Circulars (HEC) and Hydraulic Design

Series (HDS) publications, and the Wyoming Department of Transportation (WyDOT) Road Design Manual. For reference, the memorandum is attached in Appendix A.

3.2. Future Land Use

The project scope assumes that no land use analysis or documentation will be required as the proposed project will stay within the existing right-of-way (ROW) and will not increase roadway capacity. The land use designation is not anticipated to change.

The land use coefficients are based on the FHWA table, which can be found on the summary page of the rational calculations in Appendix B. Conservative coefficients were used using aerial imagery corresponding with short grass prairie or light wooded forest land uses.

3.3. Wetlands and Waters of the U.S.

Waters of the United States (WOTUS) are located adjacent to or within the project area. Included is Elkhorn Creek which crosses Casper Mountain Road. The National Wetland Inventory (NWI) of the U.S. Fish and Wildlife Service

(USFWS) identifies riverine open water, shrub wetlands, and emergent wetlands within the project area. It is anticipated that the project will result in the loss of less than 1/10 acre of wetlands, meaning a Section 404 permit is not required. Atkins environmental subcontractor, ERO, will provide a Categorical Exclusion (CE) to satisfy National

Environmental Policy Act (NEPA) documentation in the future. Additionally, because there will be no increase in impervious area within the project site, a No-Adverse Impact drainage analysis is not needed.

3.4. Cultural Resources

Cultural resources are included in the environmental assessment. This information will be found in the CE.

3.5. Existing Structures

3.5.1. Casper Mountain Road

Minor hydraulics work is anticipated. There are 17 existing culverts, all are minor culverts (less than 48-inches), within the project area that were evaluated for replacement. Several culverts are crushed, have sediment accumulation, or are rusted. The sedimented and vegetated Culvert 15 entrance and damaged outlet are shown in

Figure 2 and Figure 3, which provide examples of conditions requiring improvements based on field investigations.

See Appendix A for a surveyed culvert inventory with locations and pictures, along with pictures from the June

2021 PDP field review.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 4

Figure 2: Existing Culvert 15 Entrance

Figure 3: Existing Culvert 15 Outlet

There are no known storm drains within the project area. It is anticipated that local drainage conveyance will be through roadside swales.

3.5.2. Muddy Mountain Road

There are 66 existing culverts, all minor culverts (less than 48-inches), within the project area that were evaluated for replacement. Several minor culverts are crushed, have sediment accumulation, or are rusted. The damaged

Culvert 7 entrance and outlet are shown in Figure 4 and Figure 5, which provide examples of conditions requiring improvements based on field investigations. See Appendix A for a surveyed culvert inventory with locations and pictures, along with pictures from the June 2021 PDP field review.

Figure 4: Existing Culvert 7 Entrance

Figure 5: Existing Culvert 7 Outlet

There are no known storm drains within the project area. It is anticipated that local drainage conveyance will be through roadside swales.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 5

4. Hydrology

4.1. Drainage Basins

Using 20-foot contours from the U.S. Geological Survey (USGS) quad maps, USGS Digital Elevation Model (DEM), Google Earth software, and field survey conducted in October 2021, seven watershed basin delineations were prepared. Basin elevations varied from approximately 7,675 feet to 8,100 feet. Basin sizes ranged from 1.25 acres to 33.97 acres. Basin flow lengths, discharge points, and slopes were estimated from the USGS topographic mapping. Estimates of pervious and impervious areas were determined from aerial photos in Google Earth and the

June 2021 field review. Areas not delineated typically drain to existing ditches, culverts, or storm drains and are not expected to need improvements. A basin map is provided in Appendix B.

4.2. Soils

Soil types for the project area have been determined using the Natural Resources Conservation Service (NRCS)

Soil Survey. Based on NRCS, the project area contains soils of hydrologic soil group (HSG) Type A, B, C and D.

This indicates soil type varying by location in the project area which will be considered basin by basin. Soils will range from low infiltration rate and high runoff potential to high infiltration rate and low runoff potential (NRCS, 2021.

Type A soils have low runoff potential and high infiltration rates when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.

Type B soils, mainly silt loam or loam, have a moderate infiltration rate when wetted. These consist of moderately well to well drained soils with moderately fine to moderately course textures. Type C sandy clay loam soils have low infiltration rates when thoroughly wetted and impede downward movement of water. Type D soil type includes clay loam, silty clay loam, sandy clay, silty clay, or clay. This type of soil has very low infiltration rates and high runoff potential (NRCS).

4.3. Flood History

Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) Panel 56025C2350D has not been printed and has a Zone D designation. Zone D is an area with potential flood hazards, although none have been determined at this point since no flood hazard analysis has been conducted in this area. The FEMA documentation is in Appendix A, in the WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1)

Muddy Mountain Road Hydrologic and Hydraulic Criteria and Computational Methods Memorandum.

4.4. Hydrology Methodology

The Rational Method was used to determine all local runoff and onsite peak flows. The Rational Method was performed in accordance with the methods presented in Hydraulic Design Series Publication No. 2 (HDS 2), Highway Hydrology, using FHWA’s Hydraulic Toolbox in cooperation with Aquaveo. Additional information on this method is located in Appendix A, in WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1)

Muddy Mountain Road Hydrologic and Hydraulic Criteria and Computational Methods Memorandum.

Rainfall data from the National Oceanic and Atmospheric Administration (NOAA) Atlas 2, Volume 2, displayed in

Table 1, was used to produce peak flows. Appendix B contains the Hydraulic Toolbox output report containing all input values and results.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 6

Table 1: NOAA Atlas 2, Volume 2, Rainfall Depth Data

Storm Event Rainfall Depth (in)

2-year, 6-hour 1.1

100-year, 6-hour 2.5

2-year, 24-hour 1.6

100-year, 24-hour 3.4

Basin characteristic input values required for intensity and peak flow calculation methodology presented in HDS 2 include Manning’s Roughness Coefficient (n), Intercept Coefficient (k), and Runoff Coefficient (C). Values were determined using Table 2.1 and Table 2.2 from HDS 2, as shown in Appendix B. The project area soil data indicate sandy/heavy soils of flat to steep slope resulting in a C value range of 0.13-0.30. The project area contains short grass pasture and forest with light ground litter, indicating a k value of 0.213 and an n value range of 0.15-

0.40. Drainage areas delineated correlate to potential culvert replacements. Drainage basin maps are presented in

Appendix B, along with peak flow calculations. Peak flows are displayed in Table 2.

Table 2: Basin Peak Flows

Basin ID Basin Area (ac) 10-Year (cfs) 25-Year (cfs) 100-Year (cfs)

WY FLAP NAT 505(1) Casper Mountain Road

DA-12A 1.69 0.60 0.80 1.00

DA-12B 2.54 1.00 1.20 1.50

DA-10A 1.25 0.40 0.50 0.70

DA-9B 4.03 2.70 3.20 4.20

DA-9A 33.97 17.10 20.40 26.70

DA-D-205 9.67 3.30 4.00 5.20

WY BL 6409(1) Muddy Mountain Road

DA-66 0.71 0.50 0.60 0.80

DA-62A 1.67 0.90 1.10 1.40

DA-D-450 1.90 0.90 1.00 1.40

5. Recommended Design Within the limits of Casper Mountain Road, recommendations consist of three proposed cross culverts, seven proposed driveway culverts, three replacement driveway culverts, one inlet and pipe system, 190-LF of a roadway drainage layer, ditch reconditioning, and paved waterway. These recommendations are based on field observation, photographs, and survey.

Within the limits of Muddy Mountain Road, recommendations consist of one proposed driveway culvert, one culvert extension, one replacement culvert, and ditch reconditioning.

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5.1. Culverts

Aquaveo’s HY-8 culvert hydraulic analysis software was used to analyze culverts. Where survey was unavailable, culvert inverts and lengths were determined based on minimum pipe cover (18” for mainline culverts) and an assumed foreslope of 1:10. Calculations represent a 1.0% slope.

Headwater to Diameter Ratio (HW/D) of <1.5 is used as a design consideration to ensure the water depth does not exceed the height of the culvert by more than is allowed by Hydrologic and Hydraulic Criteria in Appendix A.2.

Culvert recommendations are presented in Table 3 and Table 4. HY-8 results can be found in Appendix C.

The existing culvert at 152+34 was evaluated for pipe lining due to visible rust on the flowline; however, it was determined that the cost to reline was comparable to a pipe replacement. As the culvert appears to be structurally stable and there are no signs of leaking, the county decided to replace the culvert as part of a separate future project.

Culvert 62A is an assumed replacement of an existing culvert located at Station (STA) 383+68. The existing culvert inlet could not be located during field visits and the outlet is at the bottom of a steep slope. If the culvert is found during construction and appears to be in good shape, the culvert may be retained at discretion of the onsite Project

Engineer. If the existing culvert is retained, then a flared end section and standard riprap apron shall be added to the inlet. If the existing culvert cannot be located or is in poor condition, the existing culvert shall be abandoned with a concrete plug as detailed in the FP-14. The proposed replacement will outfall at a higher elevation onto the foreslope with riprap outfall protection to reduce energy and disperse flow. The existing and proposed basin delineation is the same for this culvert, therefore existing calculations are not presented.

Culvert 66 located at STA 367+33 will be extended 5-ft on the upstream end to provide further separation between the inlet and the travel way.

Table 3: Casper Mountain Road Culvert Design Recommendations

Culvert

ID

Station

Q25 Design Flow (cfs)

Required Min.

Upstream

Ditch Depth (ft)

Size (Inch) Length

(ft) HW/D Recommendation

12B 133+00 1.20 3.2 28x20 32 0.26 Proposed Culvert

9B 153+78 3.20 3.2 28x20 41 0.45 Proposed Culvert

9A 156+52 20.40 3.1 Double 28x20 51 0.76 Proposed Culvert

Table 4: Muddy Mountain Road Culvert Design Recommendations

Culvert

ID

Station

Q25 Design Flow (cfs)

Size (Inch) Length

(ft) HW/D Recommendation

62A 383+68 1.10 24 38 0.27 Culvert

Replacement

66 367+33 0.60 18 5 0.25 Culvert Extension

There are several approach culverts proposed throughout the Casper Mountain and Muddy Mountain project areas. All approach culverts shall be 18” CMP or equivalent with flared end sections and riprap placed as recommended in the plans. Approach culverts were not analyzed as these areas were either replace in kind, upsized from existing, or proposed to provide an overall improvement to existing conditions. All approach culverts must be placed with a positive slope of at least 0.50% and cover of 1-ft. A summary of approach culverts recommended is in Table 5.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 8

Table 5: Proposed Approach Culvert Design Recommendations

Station Offset Size (Inch) Length

(ft) Recommendation

WY FLAP NAT 505(1) Casper Mountain Road

108+32 RT 18 30 Proposed Culvert

128+68 RT 18 58 Proposed Culvert

164+52 RT 21x15 33 Proposed Culvert

205+91 LT 18 42 Proposed Culvert

212+51 LT 18 40 Proposed Culvert

214+27 LT 18 100 Proposed Culvert

218+75 LT 18 34 Culvert Replacement

224+46 RT 18 34 Proposed Culvert

228+05 RT 18 30 Culvert Replacement

229+93 RT 18 42 Culvert Replacement

WY BL 6409(1) Muddy Mountain Road

630+96 LT 18 30 Proposed Culvert

Proposed culverts include flared end sections and outlet protection in the form of typical riprap designed to FLH

Detail C-251-50, at a minimum as designated on the plans. Additionally, to extend existing culvert life, design recommends cleaning most existing culverts of sediment and adding flared end sections and riprap to culvert entrances and exits except when otherwise noted. Existing culverts were assumed to be functioning and sized appropriately as there is no history of overtopping or drainage related issues in areas not discussed; therefore, existing culverts were not analyzed. Overall drainage recommendations will maintain existing drainage patterns.

5.2. Ditches

There are four proposed ditches. Existing ditches were not analyzed as there is no known history of flooding or overtopping.

Hydraulic Toolbox was used to analyze proposed ditch geometries. All proposed ditch reconditioning was designed as 2-ft deep triangular ditches with 1:3 (V:H) foreslope and backslope, and longitudinal slope matching the roadway profile. Proposed ditches will adjust grade near proposed culvert inlets to match invert elevations. Paved waterways were designed to special detail 608-04A. Additional information on proposed paved waterways is in

Section 5.5.

A proposed ditch summary is recorded in Table 6. Hydraulic Toolbox was used to confirm channel lining design. All proposed ditches with high velocities and erosion potential will be lined as stated in Table 6. Calculations are in

Appendix C.

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Table 6: Proposed Ditch Design Recommendations

Basin

ID

Approx.

Station

Beg.

Approx.

Station

End Side1 Length

(ft)

Long.

Slope

Avg.

Velocity

(fps)

Max Shear Stress (lb/ft2)

Depth (ft)

Design Flow (cfs)

Notes

DA-

9B

2.700.230.817.675.68210LT156+00153+90

Paved

Waterway (3-ft bottom)

DA-

9A

17.100.631.2310.933.141,025LT167+15156+90

Paved

Waterway (4-ft bottom)

DA-

D-205

3.300.520.984.053.00LT210+20

Ditch

Reconditioning in natural rock

DA-

D-450

0.900.261.374.298.30430LT453+00448+70

Riprap Lined

Ditch Reconditioning

1 Side of road, looking up-station

Existing ditch relief outlets will be reconditioned as stated in the plans between STA 265+00 and STA 362+80 to mimic existing conditions. There is severe erosion downstream of the ditch relief outlet near STA 308+00; however, this is located outside of project limits. Measures to remediate erosion may be included as future maintenance or in a separate project.

Additional grading necessary for positive drainage and tying into existing ground is called out in the plan sheets.

5.3. Roadway Drainage Layer

During the scoping field review, it was noted that the pullout area near STA 130+00 experiences frequent ponding that results in difficult muddy terrain and potential of damage to the roadway and shoulder. It is believed this is due to flows contributing from the hillside that do not infiltrate.

Additionally, there is evidence of subsurface flows beneath the pavement from approximately STA 131+10 to STA

133+00. This particular stretch has been noted by the county for historical drainage and pavement issues. At the

70% Field Review, the county requested use of a roadway drainage layer that consists of a 1-ft rock layer beneath the pavement for the 190-LF stretch. This fabric wrapped rock (Granular Backfill) will allow water beneath the surface to safely cross the roadway to the north without damaging the pavement. This design will reduce surface runoff as hillside flows are more easily infiltrated into the roadway drainage layer. At the downhill edge of the drainage layer, a perforated pipe will be installed to capture and relieve flow that may concentrate along that edge.

Discussions on the drainage layer design considered a 2-ft layer of Class II Riprap with no perforated pipe as an alternative; however, the chosen design of 1-ft of granular backfill is significantly more cost efficient and has historical success on projects in Colorado.

Further details of the roadway drainage layer system can be found on Special Detail 605-A. Correspondence related to the drainage layer is found in Appendix D.

A proposed culvert will be placed just upstream of the roadway drainage layer at STA 133+00 to capture all surface runoff prior to the drain system. This design will not eliminate all runoff contributing to the pullout near STA 130+00;

however, conditions will improve and the risk to pavement will be reduced.

213+75 294

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5.4. Inlet and Pipe System

Erosion due to concentrated flow was identified through the trailhead parking lot located at STA 152+40 LT. A

WyDOT M1 Type 3 Grate inlet conforming to Special Detail 604-A and single 24” pipe system is recommended to capture hillside flows before entering the parking area. The inlet shall be installed in a slight depression to create an artificial sag placed at least 1-in below the pavement base elevation to meet freeboard criteria. Due to the nature of the surrounding area, maintenance will be required to ensure the inlet is clear of forest litter and other debris as needed. A summary of the pipe system is summarized in Table 7 and Table 8. Calculations are located in Appendix C.

Table 7: Casper Mountain Road Inlet Summary

Inlet Type

Approx.

Station

Side1 Length (ft)

Width (ft)

Spread (ft)

Depth (in)

Design Flow (cfs)

Notes

M1 Type 3

151+78 LT 4.8 3 3.00 0.8 0.70

Grade inlet in Sag

Table 8: Casper Mountain Road Pipe Summary

Pipe ID Station Q25

Design Flow (cfs)

Size (Inch) Length

(ft)

Flow Depth

(ft) Recommendation

10A 151+93 0.70 24" 45 0.38 Proposed Pipe

5.5. Paved Waterway

Historically there is heavy erosion in the existing ditch between 153+90 and 167+15. This area receives flow from a parking lot and gravel road within the drainage area that is used for storage of soil. This is believed to be a result of steep slopes, high velocities, and high sediment transport. In downstream sections that have less steep slopes, the existing ditch has required sediment removal in the past.

A paved waterway conforming to special detail 608-A will be constructed from STA 153+90 LT to 167+15 LT to protect the channel from scour. The paved waterway will include the use of a 4-inch geo-grid that will increase flexibility of the pavement to allow expansion and contraction during temperature swings. The paved waterway will be traversable by snowplows and easily accessible for sediment removal if necessary.

Calculations related to the paved waterway are found in Appendix C.

The county has indicated a sediment trap will be constructed as part of a separate project to tie into the paved waterway at the upstream end to reduce sediment transport.

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6. Summary Within the limits of Casper Mountain Road, recommendations consist of three proposed cross culverts, seven proposed driveway culverts, three replacement driveway culverts, one inlet and pipe system, 190-LF of a roadway drainage layer, ditch reconditioning, and a paved waterway. These recommendations are based on field observation photographs and survey.

Within the limits of Muddy Mountain Road, recommendations consist of one proposed driveway culvert, one culvert extension, one replacement culvert, and ditch reconditioning.

Additional drainage recommendations include adding flared end sections and riprap aprons to designated existing minor culverts (equal to or less than 48 inches) as shown in the plans.

This Hydraulics Recommendations Report was prepared in accordance with the methods, guidelines, and criteria set forth in the Federal Lands Highway PDDM, FHWA HEC and HDS publications, and the WyDOT Road Design

Manual.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) FINAL Hydraulics Report Page 12

7. References Atkins North America, Inc. (Atkins). (2022). WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL

6409(1) Muddy Mountain Road Hydrologic and Hydraulic Criteria and Computational Methods

Memorandum. Denver, CO: Atkins.

Atkins North America, Inc. (Atkins). (2021). WY FLAP NAT 505(1) Casper Mountain Circle Drive Final Project

Deevelopment Plan. Denver, CO: Atkins.

Atkins North America, Inc. (Atkins). (2021). WY FTBL 6409(1) Muddy Mountain Drive Final Project Development

Plan. Denver, CO: Atkins.

Federal Highway Administration (FHWA). (2002). HDS 2: Highway Hydrology. Washington, DC: FHWA.

FHWA. (2015). Aquaveo Hydraulic Toolbox 4.4. Washington, DC: FHWA.

FHWA. (2019). Aquaveo HY-8 Version 7.60. Washington, DC: FHWA.

FHWA. (2014). Standard Detail C251-50. Washington, DC: FHWA.

FHWA. (2014). Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects (FP- 14). Washington, DC: FHWA.

Federal Highway Administration, Office of Federal Lands Highway. (2012). Project Development and Design

Manual. Washington, DC: FHWA.

Federal Emergency Management Agency (FEMA). (2019). Flood Insurance Rate Map, Natrona County, Wyoming.

Washington, DC: FEMA

FlowMaster 10.02.001 (Accessed 2020) Bentley.

Miller, Kirk. (2016). Peak-Flow Characteristics of Wyoming Streams. Water-Resources Investigations Report 03-

4107. Prepared by USGS in cooperation with Wyoming Department of Transportation.

National Oceanic and Atmospheric Administration. (1973). NOAA Atlas 2, Volume II, Wyoming, Precipitation-

Frequency Atlas of the Western United States. Washington, DC: NOAA.

Natural Resources Conservation Service. (2021). Web Soil Survey. Washington, DC: NRCS.

United States Geological Survey (2022) https://ngmdb.usgs.gov/topoview/viewer/#4/40.01/-100.06: USGS

Wyoming Department of Transportation. (2019). Road Design Manual. Cheyenne, WY: WyDOT.

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) Draft FINAL Hydraulics Report Page 11

Appendices

Atkins | WY FLAP NAT 505(1) and WY BL 6409(1) Draft FINAL Hydraulics Report

Appendix A. Resources

A.1. Culvert Inventory

Casper Mountain Existing Crossing Summary

FLAP Scoping Field Review Photo Summary

Assumptions:

• All crossings require cleaning unless otherwise specified

• Condition assessment and hydraulic recommendation are based on the Scoping Field Review, 30% field review, and 70% field review.

• Wingwalls were not considered at any of the crossings.

• Conceptual riprap sizing and extents used CFLHD C251-50, Placed Riprap at Culvert Outlets

• Riprap apron is recommended at culvert entrances as specified to mitigate sediment and debris transport through the culvert and reduce scour.

Culvert Inventory Table

ID Size Condition Hydraulic Recommendation

1 242+96 18" CMP Filled with sediment upstream and downstream.

Clear sediment.

2 234+54 18” CMP Driveway Culvert Clear sediment 3 229+93 12” CMP Driveway Culvert Replace with 18” CMP 4 228+05 12” CMP Driveway Culvert Replace with 18” CMP 5 226+89 4" PVC/12"CMP Driveway culvert - Upstream 4" PVC.

Downstream 12" CMP.

Protect in place

6 224+46 18” CMP Driveway Culvert Replace with 18” CMP 7 221+44 12” CMP Approach culvert filled with sediment. Clear sediment, grade to drain.

7A 218+82 18” CMP Driveway Culvert Clear sediment and debris.

8 175+15 18" CMP Debris upstream and downstream. Historic Headwall downstream.

Protect in place

9 156+72 18" CMP Upstream is damaged. Downstream has scour. FES upstream and downstream. Riprap downstream. (Outside Right of Way, no work proposed)

10 152+34 48" RCP/CMP Upstream is CMP with light sediment.

Downstream is RCP with light sediment.

Protect in place

11 143+89 18" RCP Filled with sediment upstream and downstream.

Clear sediment and debris. (No work, protect existing headwall)

12 129+89 36" RCP Upstream blocked by vegetation. Downstream partially filled with sediment.

Clear vegetation and sediment.

13 118+68 18" CMP Good - Driveway Culvert Protect in place 14 116+18 18" RCP Upstream contains much sediment. Protect in place. No work, do not disturb.

15 113+15 18" CMP Vegetation blocking the upstream.

Downstream end is crushed.

Clear sediment and debris. FES upstream and downstream.

16 109+85 18" RCP Downstream blocked by debris No work, do not disturb

17 101+01 18” CMP Buried Clear sediment and debris. Riprap upstream, FES downstream

Crossing #1

Existing 18” CMP Culvert Filled with sediment upstream and downstream.

Recommend:

Clear Sediment.

Upstream

Downstream

Casper Mountain Existing Crossing Summary 4

Crossing #2

Driveway Culvert

Recommend:

Protect in place

Casper Mountain Existing Crossing Summary 5

Crossing #3 Existing 12” CMP Culvert

Replace with 18” CMP.

Casper Mountain Existing Crossing Summary 6

Crossing #4

Casper Mountain Existing Crossing Summary 7

Crossing #5

Existing 4” PVC upstream, 12” CMP downstream Culvert Driveway Culvert.

Protect in place.

Casper Mountain Existing Crossing Summary 8

Crossing #6

No photos

No photos

Casper Mountain Existing Crossing Summary 9

Crossing #7

Approach Culvert filled with sediment.

Clear Sediment, grade to drain.

Casper Mountain Existing Crossing Summary 10

Crossing #8

Debris upstream and downstream. Historic headwall downstream.

Protect in place.

Casper Mountain Existing Crossing Summary 11

Crossing #9

Upstream damaged. Downstream is scoured.

Add FES upstream and downstream.

Riprap downstream. (Outside Right of Way, no work proposed)

Casper Mountain Existing Crossing Summary 12

Crossing #10

Existing 48” CMP/RCP Culvert Upstream is CMP, downstream is RCP. Light Sediment in both upstream and downstream ends.

Casper Mountain Existing Crossing Summary 13

Crossing #11 Existing 18” RCP Culvert Filled with sediment upstream and downstream.

Clear sediment and debris.

Casper Mountain Existing Crossing Summary 14

Crossing #12:

Existing 36” RCP Culvert Upstream blocked by vegetation. Downstream end partially filled with sediment.

Clear vegetation and sediment.

Casper Mountain Existing Crossing Summary 15

Crossing #13:

Existing 24” CMP Culvert

Casper Mountain Existing Crossing Summary 16

Crossing #14:

Upstream contains much sediment.

No work, do not disturb.

Casper Mountain Existing Crossing Summary 17

Crossing #15:

Vegetation blocking upstream.

Downstream end is crushed.

FES upstream and downstream.

Casper Mountain Existing Crossing Summary 18

Crossing #16:

Downstream blocked by debris.

No work, do not disturb

Casper Mountain Existing Crossing Summary 19

Crossing #17

Buried.

Riprap upstream.

FES downstream.

Muddy Mountain Existing Crossing Summary

BL Scoping Field Review Photo Summary

Assumptions:

• All crossings require cleaning unless otherwise specified.

• Condition assessment and hydraulic recommendation are based on the Scoping Field Review, 30% field review, and 70% field review.

• Wingwalls were not considered at any of the crossings.

• Conceptual riprap sizing and extents used CFLHD C251-50, Placed Riprap at Culvert Outlets

• Riprap apron is recommended at culvert entrances as specified to mitigate sediment and debris transport through the culvert and reduce scour.

Culvert Inventory Table

ID Station Size Condition Hydraulic Recommendation

1 720+19 18" CMP Driveway Culvert, Upstream is damaged, downstream is buried

Clear sediment. FES and riprap upstream and downstream

2 717+57 18" CMP Partially filled with sediment Clear sediment.

3 713+10 18" CMP Filled with sediment, not located. Abandon, no work.

4 712+77 18" CMP Driveway Culvert, filled with sediment. Downstream is damaged

Clear sediment. FES and riprap upstream. FES downstream

5 709+46 18" CMP Good Protect in place.

6 706+47 18" CMP Driveway Culvert, upstream is crushed, downstream is filled with sediment.

Clear sediment. FES upstream and downstream

7 705+88 18" CMP Full of sediment Abandon, no work

7A 705+03 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

8 702+51 18" CMP Downstream buried Clear sediment. FES and riprap upstream. FES downstream

9 699+99 18" CMP Good Protect in place.

10 696+02 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

11 691+80 18" CMP Upstream has minor damage.

Downstream partially filled with sediment.

Clear sediment. FES upstream and downstream

12 688+73 18" CMP Minor Damage upstream, slightly crushed downstream

Clear sediment. FES upstream and downstream

13 687+25 24" CMP Good Clear sediment.

14 673+42 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

14A 666+57 24" CMP Sediment and vegetation.

Boulders downstream.

Clear sediment. FES downstream.

Muddy Mountain Existing Crossing Summary 3

15 658+75 18" CMP Filled with sediment Clear sediment.

16 655+46 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

17 652+25 18" CMP Partially filled with sediment, Tree blocking upstream

Clear sediment. FES downstream

18 648+59 18" CMP Partially filled with sediment Clear sediment

19 640+29 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

20 625+83 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

21 624+63 18" CMP Trail Culvert, Upstream buried – not located in 70% review.

Abandon, no work

22 622+57 18" CMP Trail Culvert, sediment filled Clear sediment.

23 604+85 18" CMP Driveway Culvert, partially filled with sediment

Clear sediment.

24 603+46 18" CMP Upstream buried. Downstream filled with sediment

Abandon, no work

25 589+67 18" CMP Upstream buried. Clear sediment. FES upstream

26 582+67 18" CMP Minor sediment Clear sediment.

26A 577+59 18" CMP Partially filled with sediment Clear sediment. FES upstream 27 571+14 18" CMP Upstream buried. Downstream filled with sediment Clear sediment. FES upstream and downstream

28 568+23 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

29 565+39 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

30 562+63 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

31 558+76 18" CMP Upstream buried. Downstream filled with sediment

Clear sediment. FES upstream and downstream

32 555+05 18" CMP Partially filled with sediment Clear sediment and vegetation. FES upstream and downstream

32A 547+70 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

33 539+51 18" CMP Partially filled with sediment Clear sediment. FES upstream. Riprap downstream.

Grade to drain upstream.

33A 539+26 18" CMP Partially filled with sediment Clear sediment. Riprap upstream and downstream, FES downstream

34 536+89 18" CMP Partially filled with sediment Clear sediment. Riprap upstream, FES downstream

Muddy Mountain Existing Crossing Summary 4

35 532+37 18" CMP Upstream buried. Downstream filled with sediment

Clear sediment. FES upstream and downstream

36 527+11 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream.

Riprap upstream.

37 519+19 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

37A 515+03 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream

38 507+07 18" CMP Partially filled with sediment and debris

Clear sediment and debris.

39 500+29 18" CMP Minor Sediment Downstream Clear sediment

39A 497+45 18" CMP Partially filled with sediment Clear sediment

40 490+25 18" CMP Partially filled with sediment Clear sediment. Riprap upstream, FES downstream.

41 486+81 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream.

42 481+46 18" CMP Partially filled with sediment Clear sediment. Riprap upstream. FES downstream.

42A 479+52 18" CMP Driveway culvert filled with sediment.

Clear sediment

43 473+75 18" CMP Partially filled with sediment Clear sediment. Riprap upstream. FES downstream.

43B 467+56 Unknown size

CMP

Partially filled with sediment Clear sediment. Riprap upstream

43A 466+01 18" CMP Partially filled with sediment Clear sediment. Riprap upstream

44 464+21 18" CMP Partially filled with sediment Clear sediment. FES and riprap upstream and downstream.

45 455+21 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream.

46 448+53 18" CMP Partially filled with sediment Clear sediment. Riprap upstream and downstream.

47 447+20 18" CMP Scour downstream No work. Abandon.

48 446+14 18" CMP Partially filled with sediment Clear sediment. FES downstream. Riprap upstream

49 444+70 18" CMP Partially filled with sediment Clear sediment. FES and riprap upstream. FES downstream.

50 441+96 18" CMP Partially filled with sediment Clear sediment. Riprap upstream and downstream.

FES upstream

50B 431+69 18" CMP Partially filled with sediment Clear Sediment. FES upstream and downstream.

50A 424+76 18" CMP Partially filled with sediment Clear sediment.

51 421+75 18" CMP Partially filled with sediment Clear sediment.

52 418+17 18" CMP Partially filled with sediment Clear sediment.

53 414+26 18" CMP Partially filled with sediment Clear sediment. FES upstream and downstream.

Riprap downstream.

Muddy Mountain Existing Crossing Summary 5

54 405+65 18" CMP Sediment upstream Clear sediment. Riprap upstream.

55 402+77 18" CMP Sediment upstream Clear sediment. Riprap upstream.

56 401+58 18" CMP Downstream filled with sediment Clear sediment. Riprap upstream.

57 397+67 18" CMP Downstream filled with sediment Clear sediment. Riprap upstream.

58 396+62 18" CMP Downstream filled with sediment Clear sediment. Riprap upstream.

59 391+35 18" CMP Downstream filled with sediment Clear sediment. Riprap upstream.

60 388+68 18" CMP Downstream filled with sediment Clear sediment. Riprap upstream.

61 385+73 18" CMP Downstream filled with sediment Clear sediment. Riprap upstream.

62 383+68 18" CMP Filled in with sediment upstream, very deep

Abandon and replace with 24" culvert at higher invert elevation

63 380+09 18" CMP Upstream blocked by sediment and debris

Clear sediment. Riprap upstream.

64 378+50 18" CMP Upstream blocked by sediment and vegetation

Clear sediment. Riprap upstream.

65 373+14 18" CMP Partially filled with sediment Clear Sediment. FES downstream. Riprap upstream and downstream.

66 367+33 18" CMP Full of sediment Clear Sediment. Extend 5-ft upstream. FES and riprap upstream

Culvert ID #1

Driveway Culvert. Upstream is damaged. Downstream is buried.

Clear sediment FES and riprap upstream and downstream

Muddy Mountain Existing Crossing Summary 7

Culvert ID #2

Partially filled with sediment.

Muddy Mountain Existing Crossing Summary 8

Culvert ID #3

Filled with sediment. Not located at 70%. Flows redirected To culvert #4.

Abandon, no work.

Muddy Mountain Existing Crossing Summary 9

Culvert ID #4

Driveway Culvert, filled with sediment. Downstream is damaged

FES and riprap upstream. FES downstream.

Muddy Mountain Existing Crossing Summary 10

Culvert ID #5

Good.

Muddy Mountain Existing Crossing Summary 11

Culvert ID #6

Driveway Culvert. Upstream is crushed. Downstream is filled with sediment. Natural rock prevents scour.

FES upstream and downstream

Muddy Mountain Existing Crossing Summary 12

Culvert ID #7

Full of Sediment.

Muddy Mountain Existing Crossing Summary 13

Culvert ID #7A

No Photo

Muddy Mountain Existing Crossing Summary 14

Culvert ID #8 Existing 18” CMP Culvert.

Downstream buried.

FES and riprap upstream. FES downstream.

Muddy Mountain Existing Crossing Summary 15

Culvert ID #9

Good

Muddy Mountain Existing Crossing Summary 16

Culvert ID #10

Muddy Mountain Existing Crossing Summary 17

Crossing #11

Upstream has minor damage. Downstream is partially filled with sediment.

Muddy Mountain Existing Crossing Summary 18

Crossing #12

Minor damage upstream. Slightly crushed downstream.

Clear Sediment

Muddy Mountain Existing Crossing Summary 19

Crossing #13

Existing 24” CMP Culvert Good.

Muddy Mountain Existing Crossing Summary 20

Crossing #14

Muddy Mountain Existing Crossing Summary 21

Crossing #15

Filled with sediment. Trees stabilize area, cannot fit FES or riprap

Muddy Mountain Existing Crossing Summary 22

Crossing ID #16:

Muddy Mountain Existing Crossing Summary 23

Crossing ID #17:

Partially filled with sediment. Tree blocking upstream.

Muddy Mountain Existing Crossing Summary 24

Crossing ID #18

Partially filled with sediment

Muddy Mountain Existing Crossing Summary 25

Crossing ID #19

Muddy Mountain Existing Crossing Summary 26

Crossing ID #20

No Photos

No Photos

Muddy Mountain Existing Crossing Summary 27

Crossing ID #21

Trail Culvert. Upstream buried. Abandon, could not locate in 70% field review

No work, abandon.

Muddy Mountain Existing Crossing Summary 28

Crossing ID #22

Trail Culvert. Filled with sediment.

Muddy Mountain Existing Crossing Summary 29

Crossing ID #23

Driveway Culvert. Partially filled with sediment.

Muddy Mountain Existing Crossing Summary 30

Crossing ID #24

Upstream buried. Downstream filled with sediment.

No work, abandon

Muddy Mountain Existing Crossing Summary 31

Crossing ID #25

Upstream buried. Large rock downstream prevents FES placement

FES upstream

Muddy Mountain Existing Crossing Summary 32

Crossing ID #26

Minor sediment.

Muddy Mountain Existing Crossing Summary 33

Crossing ID #26A

FES upstream

Muddy Mountain Existing Crossing Summary 34

Crossing ID #27

Muddy Mountain Existing Crossing Summary 35

Crossing ID #28

Muddy Mountain Existing Crossing Summary 36

Crossing ID #29

Muddy Mountain Existing Crossing Summary 37

Crossing ID #30

Muddy Mountain Existing Crossing Summary 38

Crossing ID #31

Muddy Mountain Existing Crossing Summary 39

Crossing ID #32

Clear sediment and vegetation

Muddy Mountain Existing Crossing Summary 40

Crossing ID #32A

Muddy Mountain Existing Crossing Summary 41

Crossing ID #33

FES upstream, Riprap downstream Grade to drain upstream

Muddy Mountain Existing Crossing Summary 42

Crossing ID #33A

Clear sediment. Riprap upstream and downstream, FES downstream

Muddy Mountain Existing Crossing Summary 43

Crossing ID #34

Clear sediment. Riprap upstream

Muddy Mountain Existing Crossing Summary 44

Crossing ID #35

Muddy Mountain Existing Crossing Summary 45

Crossing ID #36

FES and riprap upstream. FES downstream

Muddy Mountain Existing Crossing Summary 46

Crossing ID #37

Muddy Mountain Existing Crossing Summary 47

Crossing ID #37A

Muddy Mountain Existing Crossing Summary 48

Crossing ID #38

Partially filled with sediment and debris.

Site limitations prevent FES or riprap placement.

Clear sediment and debris

Muddy Mountain Existing Crossing Summary 49

Crossing ID #39

Minor Sediment Downstream.

Muddy Mountain Existing Crossing Summary 50

Crossing ID #39A

Muddy Mountain Existing Crossing Summary 51

Crossing ID #40

Riprap upstream

Muddy Mountain Existing Crossing Summary 52

Crossing ID #41

Muddy Mountain Existing Crossing Summary 53

Crossing ID #42

Riprap upstream

Muddy Mountain Existing Crossing Summary 54

Crossing ID #43

Riprap upstream

Muddy Mountain Existing Crossing Summary 55

Crossing ID #43B

Existing unknown size CMP Culvert

Riprap upstream

Muddy Mountain Existing Crossing Summary 56

Crossing ID #43A

Muddy Mountain Existing Crossing Summary 57

Crossing ID #44

FES and riprap upstream and downstream

Muddy Mountain Existing Crossing Summary 58

Crossing ID #45

Muddy Mountain Existing Crossing Summary 59

Crossing ID #46

Riprap upstream and downstream

Muddy Mountain Existing Crossing Summary 60

Crossing ID #47

Scour downstream.

No work. Abandon

Muddy Mountain Existing Crossing Summary 61

Crossing ID #48

FES downstream

Muddy Mountain Existing Crossing Summary 62

Crossing ID #49

FES and riprap upstream, FES downstream

Muddy Mountain Existing Crossing Summary 63

Crossing ID #50

Riprap upstream and downstream. FES upstream

Muddy Mountain Existing Crossing Summary 64

Crossing ID #50A

Muddy Mountain Existing Crossing Summary 65

Crossing ID #51

Muddy Mountain Existing Crossing Summary 66

Crossing ID #52

Muddy Mountain Existing Crossing Summary 67

Crossing ID #53

FES upstream and downstream, riprap downstream.

Muddy Mountain Existing Crossing Summary 68

Crossing ID #54

Sediment upstream.

Muddy Mountain Existing Crossing Summary 69

Crossing ID #55

Sediment upstream.

Muddy Mountain Existing Crossing Summary 70

Crossing ID #56

Downstream filled with sediment.

Muddy Mountain Existing Crossing Summary 71

Crossing ID #57

Muddy Mountain Existing Crossing Summary 72

Crossing ID #58

Muddy Mountain Existing Crossing Summary 73

Crossing ID #59

Muddy Mountain Existing Crossing Summary 74

Crossing ID #60

Muddy Mountain Existing Crossing Summary 75

Crossing ID #61

Downstream filled with sediment

Muddy Mountain Existing Crossing Summary 76

Crossing ID #62

Filled in with sediment upstream, very deep.

Abandon and replace with 24" culvert at higher invert elevation

Muddy Mountain Existing Crossing Summary 77

Crossing ID #63

Upstream blocked by sediment and debris.

Muddy Mountain Existing Crossing Summary 78

Crossing ID #64

Upstream blocked by sediment and vegetation.

Muddy Mountain Existing Crossing Summary 79

Crossing ID #65

FES downstream Riprap upstream and downstream

Muddy Mountain Existing Crossing Summary 80

Crossing ID #66

Full of sediment.

FES and riprap upstream. Extend upstream 5ft

A.2. Hydrologic and Hydraulic Criteria and Computational Methods Memorandum

Atkins | Hydrologic and Hydraulic Criteria and Computational Methods | WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1) Muddy Mountain Road 1

Memo

To: Aaron Estep

From: Keira Trujillo Email: Keira.Trujillo@atkinsglobal.com

Date: March, 2022 Phone: (303) 209-2331

Ref: WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1) Muddy Mountain Road cc: Thomas Sohn Julian Maskeroni

Subject: Hydrologic and Hydraulic Criteria and Computational Methods Memorandum

1. Introduction The purpose of this memorandum is to specify the design criteria on which the WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1) Muddy Mountain Road proposed project improvements will be based.

2. Background and Description The Casper Mountain Circle Drive (WY 251, CR 505) and Muddy Mountain Road Project consists of two different funding sources that have been combined into one project due to proximity of the project locations and types of proposed improvements. Figure 1 shows the existing alignment of both roads with County Road 505 (South Circle Drive) dividing the Project between the two funding sources with Federal Lands Access Program (FLAP) to the north (Casper Mountain Circle Drive) and Federal Lands Transportation Program Bureau of Land Management (FTBL) to the south (Muddy Mountain Road). The total project length is approximately 12.34 miles and is in Natrona County, Wyoming.

Casper Mountain Circle Drive provides primary access to Muddy Mountain Road from Casper. The Casper Mountain Circle improvements will address deteriorated pavement and aggregate base, along with minor widening for 5 miles. Approximately 2.94 miles of deteriorated pavement will undergo full depth reclamation, with an additional 2.02 miles of new pavement. Improvements to safety and drainage are included.

Muddy Mountain Road is located within BLM, State of Wyoming, and private lands. This segment provides access to private property and campgrounds. Improvements will rehabilitate and resurface approximately 4.55 miles of 2 lane road and 2.83 miles of single lane aggregate roads. There will be four new parking areas within the campground, as well as improvements to safety and drainage.

2.1. Hydraulic Improvements

Within the WY FLAP segment, minor hydraulics work is anticipated. There are 17 existing minor culverts within the project area. Many existing culverts are filled with sediment and debris. The County did not note any history of flooding or request culvert replacement; therefore, it is recommended that existing

Atkins | Hydrologic and Hydraulic Criteria and Computational Methods | WY FLAP NAT 505(1) Casper Mountain Circle Drive & WY FTBL 6409(1) Muddy Mountain Road 2 culverts be cleared of debris, flared end sections be added upstream and downstream, and riprap added upstream and downstream.