WY_26(1)_Red Grade Road_Hydraulics Memo_ADDENDUM.pdf
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- Attached to
- WY FLAP SHE 26(1), Red Grade Road, Phase 1
- Solicitation number
- 6982AF25B000010
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Summary
This is a Final Hydraulics Memo Addendum dated January 2026 from the Federal Highway Administration (FHWA) Central Federal Lands Highway Division (CFLHD) addressing the WY FLAP SHE 26(1) Red Grade Road project in Wyoming. The addendum supersedes hydraulic recommendations from the October 2023 Final Hydraulics Memo due to roadway alignment changes implemented to reduce impacts to existing right-of-way (ROW) limits. While culvert recommendations remain unchanged, the addendum provides updated stationing for 23 ditch segments along the project corridor.
The ditch specifications remain consistent across all segments with triangular cross-sections, 2.0 horizontal-to-1.0 vertical (H:1V) foreslopes and backslopes, and a Manning's roughness n-value of 0.070. Flow depths vary from 0.3 to 1.0 feet across the segments, with all segments requiring Class 1 Riprap lining for erosion protection. Ditch segments are distributed across the project length, spanning from station 151+66 to 279+75, with most segments located on the right road side except D-OUT3, which is positioned on the left side between stations 2006+20 and 264+09.
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Subject: WY FLAP SHE 26(1) Red Grade Road – Final Hydraulics Memo Addendum Date: January 2026
To: Steven Davis, PE, Project Manager, CFLHD
From: Katie Kelehan, PE, Hydraulic Engineer, CFLHD Signature: ________________________
Through: Luis Calderón, PE, CFM, Hydraulics Team Lead, CFLHD Signature: ________________________
This Addendum is intended to supersede the recommendations shown in the Final Hydraulics Memo dated October 2023 for the subject project. As a result of changes made to the roadway alignment to reduce impacts to existing ROW limits, stationing for culverts and ditch segments along the project were shifted. Culvert recommendations as made in the Final Hydraulics Memo are unaffected. The following table provides updated ditch recommendations:
Segment Identifier
Station (Start)
Station (End)
Road Side Shape Foreslope
(_H:1V) Backslope
(_H:1V)
Manning’s Roughness (n-value)
Flow Depth
(ft)
Required Lining
D-C01 151+66 161+00 Right Triangular 2.0 2.0 0.070 0.3 Class 1 Riprap D-OUT1 161+50 166+62 Right Triangular 2.0 2.0 0.070 0.9 Class 1 Riprap D-C04 166+62 177+88 Right Triangular 2.0 2.0 0.070 1.0 Class 1 Riprap D-C05 177+88 181+53 Right Triangular 2.0 2.0 0.070 0.6 Class 1 Riprap D-C06 181+53 183+80 Right Triangular 2.0 2.0 0.070 1.0 Class 1 Riprap D-C20 183+80 189+13 Right Triangular 2.0 2.0 0.070 0.4 Class 1 Riprap D-C21 189+13 193+84 Right Triangular 2.0 2.0 0.070 1.0 Class 1 Riprap D-C19 193+84 199+78 Right Triangular 2.0 2.0 0.070 0.8 Class 1 Riprap D-C22 199+78 205+26 Right Triangular 2.0 2.0 0.070 0.9 Class 1 Riprap D-C07 205+26 1001+74 Right Triangular 2.0 2.0 0.070 0.5 Class 1 Riprap D-C08 1001+74 1005+50 Right Triangular 2.0 2.0 0.070 0.4 Class 1 Riprap D-C09 1005+95 220+73 Right Triangular 2.0 2.0 0.070 0.5 Class 1 Riprap D-C10 220+73 225+22 Right Triangular 2.0 2.0 0.070 0.5 Class 1 Riprap D-C11 225+22 228+65 Right Triangular 2.0 2.0 0.070 0.5 Class 1 Riprap D-C12 228+65 232+77 Right Triangular 2.0 2.0 0.070 0.6 Class 1 Riprap D-C13 232+77 234+16 Right Triangular 2.0 2.0 0.070 0.4 Class 1 Riprap D-C14 234+16 240+00 Right Triangular 2.0 2.0 0.070 0.5 Class 1 Riprap D-C23 242+50 245+00 Right Triangular 2.0 2.0 0.070 0.7 Class 1 Riprap D-C15 245+00 2001+00 Right Triangular 2.0 2.0 0.070 0.5 Class 1 Riprap
D-OUT3 2006+20 264+09 Left Triangular 2.0 2.0 0.070 0.7 Class 1 Riprap D-C16-U 2017+15 268+34 Right Triangular 2.0 2.0 0.070 0.8 Class 1 Riprap D-C16-D 268+34 277+66 Right Triangular 2.0 2.0 0.070 0.9 Class 1 Riprap
D-C17 278+16 279+75 Right Triangular 2.0 2.0 0.070 1.0 Class 1 Riprap
| 2026-01-05T12:55:44-0700 | |
| MARY KATHLEEN KELEHAN |
| 2026-01-05T12:59:35-0700 | |
| LUIS GERARDO CALDERON |
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