AOP_Brownie_Creek_Hydraulics.pdf

Memorandum

Western Federal Lands Highway Division 610 E. Fifth Street

Vancouver, WA 98661-3801

BROWNIE CREEK FISH PASSAGE IMPROVEMENTS

HYDRAULICS CONSTRUCTION HANDOFF

To: Helen Oppenheimer, WFLHD Project Manager From: Sven Leon, P.E., WFLHD Hydraulics Engineer Date: May 9, 2018 Project: Umpqua 2016 Repairs – OR FS ERFO 2016(1)-15(3)

Background

The US National Forest Service (FS) is replacing a failed culvert on the Brownie Creek Road, Umpqua National Forest, Douglas County, Oregon (Fig. 1). FS will maintain the new culvert structure. Western Federal Lands Highway Division (WFLHD) is designing the culvert. Critical design and construction elements are presented.

Design

Remove existing open-bottom CMP arch and concrete footings.

Install an 80-feet long, open-bottom CMP arch, with 24.0-foot span, 12.0-foot rise, and approximately 3 feet high cast-in-place concrete footings.

Embed footings in hard, competent bedrock 1 foot.

Adjust cast-in-place concrete footings height as needed for obtaining design elevations, culvert slope, and adjusting for an irregular bedrock surface and footing embedment depth.

Use existing naturally rough bedrock for providing fish passage flow roughness.

Reduce flow submergence risk by not placing conserved streambed material or fish passage stones inside culvert.

Install culvert at 2.8 percent slope.

Bevel culvert inlet and outlet.

Install concrete collar and Class 3 riprap (FHWA FP-14) headwall.

Seed and plant any disturbed areas with local native vegetation.

Provide at least 4 feet of cover over the proposed culvert crown.

Construction

Work within the ordinary-high-water limits can only be performed between July 1 and September 15.

Temporary flow defectors placed for isolating the work area and diverting the stream flow must have a minimum height of 3 feet above the stream bottom and be stable assuming 8 feet per second parallel flow and 2 feet maximum water depth. Use plastic-lined channels or pipes for temporally conveying stream flow through the construction area. Protect the outfalls from erosion. Fish passage downstream through the temporary flow diversions is required. Ensure fish can pass smoothly from the upstream diversion

Memo to: Helen Oppenheimer, WFLHD Project Manager May 9, 2018 point to the downstream diversion point. Locate diversion points in the main stream channel. Fish passage upstream is not required. Assuming in-stream construction occurs July 1 through September 15;

temporary flow diversions must have a minimum flow capacity equal to 50 cubic feet per second (cfs).

Temporary stream diversions in place beyond July 1 through September 15 must have minimum flow capacity equal to the 2-year discharge noted on the plans. Before installing the flow deflectors, remove fish from the work area to the level and methods specified in the environmental permits.

Access for culvert installation work will be accomplished within the existing road embankment footprint.

Temporary access routes down and adjacent to the road embankments are needed for installing flow barriers and completing culvert foundation, inlet, interior, and outlet work. Constructing the proposed culvert and in-stream work may require heavy track-mounted equipment operating on the stream bed, possibly in water up to 2 feet deep.

The State of Oregon and the U.S. Fish and Wildlife Service will restrict the release of turbidity from the work areas into the stream. The agencies require turbidity control and monitoring, and should be contacted for specific requirements and allowable discharge limits. A 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 culvert. 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 period.

Attachments: Figure 1 – Site Location

AOP Culvert Location

Project Site Location

Map printed from Google Earth Pro, image date 7/2015.

N

42.862 / -122.876

FIGURE 1

BROWNIE CREEK CULVERT

SITE LOCATION

0 800 feet