Hydraulic Design Narrative for Construction.pdf
PDF 124 KB Posted
- Attached to
- AK PRA DENA 10(36), Replace Ghiglione Bridge Federal contract opportunity
- Solicitation number
- 69056725B000009
About this file
This memorandum from the Western Federal Lands Highway Division (WFLHD) provides hydraulic design guidance for the replacement of the Ghiglione Bridge, located in AK PA DENA 10(36). The document outlines specific construction requirements for water diversions and erosion and sediment control, referencing a Hydraulic Line and Grade Report from April 5, 2019. Key instructions include constructing diversion berms at least 2 feet above the channel bottom, designing diversions to accommodate a 20 cfs flow, and implementing best management practices (BMPs) to protect bridge abutment slopes from runoff and prevent sediment-laden water from entering adjacent waterways.
The memorandum emphasizes that the erosion and sediment control plans represent minimum requirements and must be updated by the contractor throughout the project to reflect construction activities, sequencing, techniques, and site conditions. The contractor may need to remove and reinstall BMPs, and might be required to provide additional erosion control measures beyond the initial plan. The document is addressed to Brandon Stokes, the WFLHD Project Manager, and copies Tyler Yeoman, the WFLHD Highway Design Engineer, indicating an internal communication about critical construction design considerations.
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Text version
Memorandum
Western Federal Lands Highway Division 610 E. Fifth Street
Vancouver, WA 98661-3801
TO: Brandon Stokes, WFLHD Project Manager
FROM: James Neighorn, WFLHD Hydraulic Engineer
DATE: June 2, 2020
SUBJECT: AK PA DENA 10(36) Replace Ghiglione Bridge, Hydraulic Design Narrative for Construction
A Hydraulic Line and Grade Report, dated April 5, 2019, was prepared for this project.
Construction staff should review the report for detailed information regarding the methodology, recommendations, and conclusions made for the bridge waterway design.
Additional guidance for construction of the drainage is provided below:
Water Diversions:
• Diversions may be required for pier and bridge deck construction. Construct diversion berms to a minimum height of 2 feet above the channel bottom.
• Diversions will serve to separate the active flows from the work area, but will not provide a work area free of water.
• Diversions should beginning at the upstream end of the site with a berm tying into a stable overbank area. The diversion should extend downstream with a berm tying into an overbank area downstream of the proposed work.
• Diversion shall be designed to accommodate a flow of 20 cfs.
Erosion and Sediment Control:
• The bridge abutment slopes will need to be protected from runoff from the bridge deck and approaching roadway ditches. It will be important to place and adjust riprap slope protection so that it catches the flows from the ditches and bridge deck to prevent flows from eroding the embankment. Since vegetation is sparse to non-existent in this location, even small amounts of flow can cause significant erosion over time on the steep embankment.
• The erosion and sediment control plans are intended to identify the minimum BMP elements necessary to address construction site runoff. Plans will need to be updated by the contractor throughout the course of the project to reflect contractor construction activities, sequencing, techniques, and site conditions.
• The contractor may need to remove and re-install BMPs to accommodate construction sequencing. Providing additional BMPs over and above the minimum requirements shown on the plans may be necessary to address conditions created by the contractor.
• The BMPs shown on the plans must be constructed prior to or in conjunction with all clearing and grading activities in such a manner as to ensure that sediment-laden water does not enter adjacent waterways.
cc: Tyler Yeoman, WFLHD Highway Design Engineer
File details come from the government source that posted it. Updated .