Attachment_J4_DrawingAddendum.pdf

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Nez Perce-Clearwater NFs - Crooked River Valley Restoration Phase 4
Solicitation number
12363N21R4001
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About this file

This addendum provides supplemental drawings and specifications for a federal construction contract to complete Phase 4 of the Crooked River Valley Rehabilitation Project on the Nez Perce-Clearwater National Forests. The work includes relocating the Crooked River from a temporary bypass channel back into the channel constructed in previous phases, constructing approximately 4 additional acres of floodplain, removing a temporary bridge and hauling it to Grangeville, grading 12 acres of levee and haul roads to complete floodplain construction and fill the bypass channel, and installing instream habitat features and riparian plantings. Material may be hauled from stockpiles in the lower floodplain area and south staging area. Drawings show adjustments to the channel alignment and diversion structure elevations, delineate areas for floodplain grading and fill, designate locations for depressions and high terraces along the floodplain edge, and identify an optional bid item to raise portions of the floodplain.

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A d d en d u m ju st ed C h an n el

A lig n m en t at D iv er si o n S tr u ct u re

This sheet shall be used in conjunction with Sheet

5.0 in the Phase 4 Plan Sheets. The channel will receive a small alignment adjustment as shown.

The Contractor shall stake the new alignment prior to construction to be approved by the CO. The Government can provide a GIS/GPS file of the channel location, however, field fitting will be required. The slope shall remain the same as the slope shown on Sheet 5.0 of the Plan Set.

Sheet 1.0

The elevation of the diversion structure was lowered in 2020 to allow more water to access the new channel at high flows.

The elevations of the diversion structure are shown below, as constructed in August 2020. This is to be used in conjunction with the Profile View shown on Sheet 5.0 of the Phase 4 designs. The elevations may have adjusted slightly after spring flows in 2021. A riffle has been constructed from approximately 32+25 to 33+25.

A d d en d

C ro o ke d R iv er

P h as e

D iv er si o n S tr u ct u re

3902.00

3903.00

3904.00

3905.00

3906.00

3907.00

3908.00

3909.00

31+43 31+48 31+68 32+25 32+50 32+75 33+00 33+25

Elevations at Diversion Structure

Diversion Structure

Sheet 2.0

Legend

Approx. outer bank alignment d en d u m Lo w er

A cr es o f

C ro o ke d R iv er

P h as e

Preservation Area

Potential access area from Road 233 to the lower floodplain. Any access at this site shall be decommissioned upon completion of the project to prevent future access.

The tailing pile outlined in red were not graded during the Phase 2 floodplain work. This pile shall be graded to match floodplain elevations between Phase 2 floodplain work and Phase 4 floodplain elevations. This material can be used to fill the bypass channel.

There is approximately 12,000 cy of material. These quantities have been addressed in the bid sheets, but are not shown in Phase 4 Grading Schedule or Quantities.

3.0

• Approximate area of additional floodplain fill for Optional Item A14.

• Approximately 400 cy of material shall be used to raise the elevation of the floodplain, outlined in blue by approximately 6 inches. The fill shall slope up towards the road surface. The road surface shall be decommissioned by roughening. Material will be hauled from the adjacent stockpile.

• The remaining floodplain area shall be graded to be sloped from the elevation of the road surface to approximately 1 foot higher along the east side of the floodplain for the length of the stockpile area.

A d d en d

O p ti o n al

It em

A

O p ti o n

F lo o d p la in

4.0

Legend

Grade floodplain fill

Import and grade fill d en d u m H ig h

T er ra ce

L o ca ti o n s

Several High Terrace areas were identified as areas to increase the floodplain height to prevent the river channel from recapturing the floodplain on the east side of the valley during high flow events. These areas are at natural high points along the edge of the valley. The elevations of these areas shall match the existing floodplain elevation on the floodplain, and slope up an additional 0.5 - 1 foot in elevation on the east side of the valley above the grade shown on Sheet 6.0 in the Plan Sheets.

The approximate area of the high terraces is provided in the Table.

There are several depressions that shall be left approximately 2 – 2.5 feet deep in the general areas shown above. The quantities saved in the depression will be used to grade the high terraces or used as general floodplain fill for the bypass channel.

High Terrace

Area (sq yd)

Depressi on

Area (sq yd)

T1 6,330 D1 1356

T2 4,441 D2 1608

T3 4,516 D3 1986

T4 7,737 D4 1077

D5 3098

D6 2646

Total Area

23,024 11,773

*ordered from downstream up

5.0

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