Att 0002 - Reference FIO Drawings.pdf
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- Solicitation number
- W9128F26QA043
About this file
This document is Attachment 1 to a fiscal year 2026 federal contract opportunity for spillway drainage inspection services at Garrison Dam in North Dakota. It consists of reference drawings and technical documentation for information purposes only, providing historical context and design details for the drainage systems that require inspection.
The attachment includes comprehensive technical drawings and photographs documenting the spillway subdrain, relief wells, and box drain systems. Key components detailed include: spillway subdrain inspection and repair history from 2011-2016 with sediment collection data and defect summaries per segment; crest relief wells and lateral drain pipe configurations with original construction drawings; box drain section profiles and typical inspection imagery; drainage measurement data showing flow readings at various manhole locations; and a 2025 camera inspection overview documenting current conditions including fine sediment accumulation, gravel deposits, and frost blanket material in subdrain segments. The document also provides powerhouse drainage system maps showing the auxiliary switchyard toe drain network with replacement history (lines replaced in 2003, 2010, 2013) and flow observation data spanning multiple decades. Original construction drawings from the 1950s are included for spillway structures, slab manholes, lateral drains, and box drains. Supporting documentation includes drainage measurement graphs tracking flows at multiple monitoring points and historical flow observations at powerhouse relief wells, V-notch weirs, and bucket and stopwatch measurement locations. This reference material establishes baseline conditions and system specifications necessary for contractors to understand the scope of required inspection and potential repair work.
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FY26 Spillway Drainage Inspection Garrison Dam, ND
Attachment 1 – Reference Drawings
For Information Only
1. Spillway Subdrain, Relief Wells, and Box Drain Figures
Figure 1 through Figure 5 provide typical figures and photographs of the spillway subdrain, crest relief wells, and box drains.
Figure 6 provides an overview map of the spillway drainage features.
Figure 7 presents a summary of the spillway subdrain inspections and repairs completed after the 2011 flood through 2016. The figure includes tables summarizing the sediment collection per segment, drain defects observed per segment, and notes regarding the relief well and crest leader pipes along Row 1. Cured-in-place pipe repairs were subsequently completed in 2012 and 2014 at the highest priority pipe fractures, and these locations are presented on the map.
Figure 8 presents the drainage measurements in the spillway chute subdrain and box drains. The measurements at MH-W1 include inflows from the crest subdrain leaders and relief wells.
Figure 9 through Figure 12 provide additional details regarding the Row 1 drainage features. Photographs are provided of the sandbag ring and pumping needed to access Row 1 manholes for a camera inspection in 2025. The inspection was conducted by USACE without any flushing or cleaning of the pipes prior to operating the camera.
Additional photos show the locations where there is currently gravel and sediment identified along the Row 1 alignment.
Figure 13 through Figure 22 provide original construction drawings for the spillway drainage features.
2. Powerhouse Drainage Figures
Figure 23 through Figure 26 provide additional maps of the powerhouse drainage system and flow readings.
Example manhole, MH-W9 facing upstream segment.
Example lateral pipe, MH-W9 facing east inflowing segment.
Example lateral pipe, MH-C9 facing east segment.
Figure 1. Example subdrain inspection photos.
Figure 2: Crest Relief Well Detail
Figure 3. Chute subdrain lateral drain typical detail.
Figure 4: Box drain section and typical profile
Figure 5: Box drain typical inspection images
Figure 6. Drainage overview map.
Figure 7. Summary of Spillway drainage inspections and repairs, 2011-2016.
Figure 8. Drainage Measurements - Spillway
Figure 9. Spillway crest profile drainage detail.
Lateral drain pipe typical detail Row 1 manhole sandbag ring for access Row 1 manhole sandbag ring for access
Figure 10. Lateral drain diagram and Row 1 access photos
2025 Camera Inspection Overview
Figure 11. Crest Leaders Condition Summary, 2025.
Summarized 2025 camera inspection summary (no flushing performed) Drainage gravel present in a Row 1 manhole.
Pumping dry a Row 1 manhole for inspection Fine sediment and silt in a dry pipe segment Drainage sand and gravel in a partially inundated subdrain location.
Figure 12. Additional 2025 Row 1 Inspection Map and Photos
Figure 13. Crest relief wells original drawing (GS1, upper chute).
Figure 14. Spillway crest drainage original drawing (GS1, upper chute).
Figure 15. Row 1 manholes and typical lateral drains original drawing (GS1, upper chute)
Figure 16. Spillway slab manhole details original drawing (GS1, upper chute)
Figure 17. Spillway slab lateral drains original drawing (GS4, lower chute).
Figure 18. Spillway slab manholes original drawing (GS4, lower chute).
Figure 19. Spillway slab manholes original drawing (GS4, lower chute).
Figure 20. Box drain profile detail (GS1, upper chute)
Figure 21. Box drain profile original drawing (GS4, lower chute).
Figure 22. Box drain manholes original drawing (GS4, lower chute).
Figure 23. Powerhouse drainage network replacement history.
Figure 24. Powerplant Under Seepage Drain Network, original drawing.
Figure 25. Powerhouse drainage map (2013)
Figure 26. Drainage Measurements - Powerhouse
| 1. Spillway Subdrain, Relief Wells, and Box Drain Figures |
| 2. Powerhouse Drainage Figures |
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