AK Ohmer AOP Report Final.pdf

Memorandum

Western Federal Lands Highway Division 610 E. Fifth Street

Vancouver, WA 98661-3801

SKILAK LAKE ROAD / UPPER SKILAK LAKE ROAD

LOWER OHMER CREEK AOP HYDRAULICS REPORT

To: Stacy Bluhm, WFLHD Project Manager

From: James Neighorn, P.E. and Vernon Bevan, WFLHD Hydraulics Engineer

Date: June 20, 2023

Project: Skilak Lake Road – AK FWS Kenai 1192(1)

Background

The Kenai National Wildlife Refuge (NWR) is proposing Aquatic Organism Passage improvements to culverts within the Kenai National Wildlife Refuge (KNWR) located on Skilak Lake Road and Upper

Skilak Lake Road. The purpose of the culvert improvements is to restore aquatic organism passage, protect visitor safety, preserve the KNWR roadway infrastructure, and ensure roadway drainage structures are of the latest design standards. As part of the project the NWR is replacing a culvert that carries Lower Ohmer

Creek under Upper Skilak Lake Road as it flows from Upper Ohmer Lake to Lower Ohmer Lake. The

Kenai NWR will maintain the new structure. Western Federal Lands Highway Division (WFLHD) is designing the replacement structure. Recommendations for the proposed aquatic organism passage (AOP) structure design are presented.

AOP Design Criteria

The proposed AOP structure has been designed following the requirements Culvert Design Guidelines for

Ecological Function (U.S. Fish and Wildlife 2021) and per Stream Simulation: An Ecological Approach to

Providing Passage for Aquatic Organisms at Road-Stream Crossings (USDA-Forest Service 2008). These documents provide simplified design methodologies intended to mimic natural stream processes within the culvert. Sediment transport, debris conveyance and streambed morphology within the culvert should replicate these processes as they occur in the natural channel upstream and downstream of the culvert.

Determination of the high and low fish passage design flows, water velocity, and water depth is not required for this method since the stream hydraulic characteristics within the culvert are intended to replicate the stream conditions upstream and downstream of the crossing. AOP culvert design utilizes streambed materials and sizes which occur in the natural channel, providing similar channel complexity, flow depth, flow velocities, and resting areas.

USFW Alaska Fish Passage Program (USFW/AFPP) Guidelines

The AOP design for the Lower Ohmer Creek outfall crossing is consistent with the 2021 U.S. Fish and

Wildlife (USFW) Service design guidelines. The 2021 document generally follows the U.S. Forest Service stream simulation approach with certain modifications. The basis for AOP design is the geomorphic analog method. The underlying philosophy of the geomorphic analog method is similar to the stream simulation approach. However, many of the design criteria are based on the 100-year flood event as opposed to a specifically selected design flood. The following USFW/AFPP requirements have been incorporated into the AOP design:

Flood and Debris Conveyance: Culvert capacity is designed to accommodate the 100-year recurrence flood without interfering with the functioning of the floodplain while providing adequate clearance above the flood stage for expected debris.

Memo to: Stacy Bluhm, WFLHD Project Manager

June 2023

Crossing Location: Crossing structure is placed within the pre-development natural channel alignment wherever possible.

Culvert Width: Must accommodate the design channel bankfull width plus additional width for construction of stable bank rocks along both sides of the channel inside the culvert. All culverts will meet design requirements for a 6-foot minimum diameter.

Channel Vertical Clearance: Clearance from bed to ceiling must be at least 4-feet to allow for ease of construction, maintenance, and debris removal. Where possible, clearance will be 5-feet or greater.

Channel Slope: Reconstructed streambed within the culvert approximates the average slope of the stream reference reach. The slope should not deviate by more than 25% from the natural stream slope of the reference reach.

Embedment: Bottoms of round culverts should be buried below the streambed thalweg a minimum of

40% of the pipe diameter. Box or pipe arch culverts should be buried a minimum of 20% of the culvert’s rise.

Maximum Length of Road Crossing: Length should be less than 150-feet.

Fill Materials: Fill materials are generally comprised of sediment similar in size composition to natural bed materials that form the natural stream channel above and below the road crossing. Larger material is added to assist grade retention and provide resting areas for migrating fish. A dense, well-graded mixture is specified, with washing in of fines between constructed lifts, to encourage the stream to flow on the surface.

Fill/substrate material for culverts without an adequate sediment supply, such as those situated below a lake or wetland, should be designed to resist the predicted critical shear forces of the 100-year flood.

Water Depth and Velocity: Bankfull water depths and velocities in the culvert must closely resemble those existing reference reach as specified in the 2021 USFW Service guidance document.

Lower Ohmer Creek AOP Culvert

The United States Fish and Wildlife Service (USFWS) has determined that the Lower Ohmer Creek crossing of Upper Skilak Lake Road requires an AOP structure (60.455489°, -150.310281°). Federal Lands

Highway Division conducted field reconnaissance of the crossing in 2020 and 2021. This reconnaissance data and fish passage assessment data from a FWS 2018 field survey were used to assess crossing and stream conditions.

The creek is a single thread channel which flows east to west, connecting Upper Ohmer Lake with Lower

Ohmer Lake. The crossing is located roughly 2,000 feet downstream of Upper Ohmer Lake and approximately 70-feet above Lower Ohmer Lake (Figure 1). The existing culvert layout and proximity to

Lower Ohmer Lake create a backwater effect on the stream. The creek crosses the road through a 36-inch diameter CMP with another 24-inch diameter CMP providing for flood relief overflow. Above the crossing, the stream has a riffle-pool morphology and bankfull channel are between 5 and 7 feet (Photo 3). Bankfull depths range from 0.9 to 2.0 feet. Small woody debris was observed within the channel and was likely supplied from the adjacent banks. The channel slope between Upper Ohmer Lake and Upper Skilak Lake

Road is approximately 2.3%.

After passing through the culvert, the stream travels roughly 70 feet before reaching the lake, which is bordered by a fringe wetland complex (Photo 5). Immediately downstream of the culvert, the bankfull channel width is approximately 7 feet (Photo 4). However, as the stream approaches the lake, the slope flattens and the bankfull width increases dramatically. Bankfull depths range from 0.7 to 1.5 feet.

A pebble count was conducted on the upstream reach. The pebble count data was processed using FHWA

Hydraulic Toolbox, version 4.2, to compute the resulting gradation: D100 6.4-inches, D85 3.86-inches, D50 1.82-inches, D15 0.6-inches, and D5 0.07-inches (Figure 3, Photos 6 and 7).

The 36-inch culvert is situated within the main channel and is active during low and high flows (Photo 1).

The 24-inch flood relief culvert is elevated and activated during higher flows (Photo 2). Excessive scour at the culvert outfall was not observed and both culverts appeared free of woody debris (Photos 8 and 9). The existing culvert is situated almost perpendicular to the roadway. However, it is not well-aligned with the stream which makes a roughly 90° turn to the left just prior to entering the culvert as well as immediately after exiting the culvert.

Recommendations:

The existing 36-inch culvert and 24-inch flood relief culvert do not meet USFWS standards for fish-bearing stream crossings and inhibit aquatic organism passage. Additionally, the current stream alignment through the primary culvert is poor. A larger pipe will be required to replace the two existing culverts as well as provide space for bankfull width, a natural channel bottom, and stable banks.

• Install a 98-foot long corrugated, metal, round culvert with a 9-foot diameter.

• Skew the new culvert to better align with the existing stream orientation and eliminate the sharp channel bends at the culvert inlet and outlet.

• Excavate a channel (approx. 36 feet) matching the existing stream geometry on the east side of the road to direct the stream into the new culvert inlet.

• Place the culvert at a 2.39% slope to simulate upstream channel slopes at the crossing by setting the inverts at elevation 401.91-feet upstream and at elevation 399.57-feet downstream (project datum).

• Embed the culvert 4.5 feet and backfill the culvert interior with streambed material conserved during excavation of the culvert. If the conserved streambed material quantity is insufficient for backfilling the culvert, use material similar to the natural streambed material. Streambed material will be augmented with Class D gradation cobbles specified in the attached Special

Contract Requirements (SCR) and Gradation Stability Calculations to provide a dynamically stable substrate.

• Allow clearance for debris passage and maintenance access by providing 4.5 feet of clearance from the crown of the culvert and the installed bed material.

• Construct a channel with a bankfull width of 7 feet and a bankfull depth of 1 foot including a low flow channel and streambanks inside the culvert to provide resting opportunities for fish.

• Install 4 rock weirs spaced at 28-foot intervals to help maintain banks and channel shape.

• Install 4 round boulders, approximately 24-inches in diameter, for inducing channel migration and providing low velocity fish resting areas.

• Install concrete collars to mitigate the influence of frost heaving at pipe ends.

• Install Class 3 riprap (FHWA FP-14), minimum 3 feet thick, at the inlet and outlet for controlling erosion near the culvert.

Construction

The Alaska Department of Fish and Wildlife instream work period is May 15 to July 15. Temporary flow deflectors 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 6-feet per second parallel flow. Use plastic-lined channels or pipes for temporally conveying stream flow through the construction area. Protect the outfalls from erosion. Ensure fish can pass smoothly through the diversion. Temporary stream diversions in place must provide an equivalent capacity to a 2.5-foot diameter pipe or demonstrate a minimum flow capacity equal to the 2-year discharge (35-cfs). Before installing the flow deflectors, remove fish from the work area to the level and methods meeting the 2009 ADF&G and FHWA Fish Habitat MOU requirements.

Full construction area dewatering is expected up to the groundwater level for excavation and installing the culvert, streambed material, backfill, and riprap. Water pumped from work area must be discharged at an upland treatment area near the site.

Temporary access route adjacent to the road embankment is needed for installing flow barriers, removing the channel debris, and completing culvert inlet, interior, and outlet work.

Stream Impacts

The proposed fish passage culvert is expected to dramatically improve stream flow conveyance, sediment transport, and woody debris transport to a level comparable to reaches upstream and downstream of the culvert. 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 time.

Operation and Maintenance

Scour or aggradation of the streambed is expected to occur to some extent, as would be expected for the natural stream. Monitoring at regular intervals, and ideally during flood events, will be especially important during the first few years to ensure that excessive debris accumulation, scour, or aggradation does not impair passage through the culvert. Increase the frequency of culvert inspections and debris removal for the first three years. Fish boulders placed within the culvert and stream channel should be inspected annually and after each extreme flood event to ensure effective backwater and bed retention. Replace or reposition dislodged rock or boulders. Additional rock may need to be installed to correct erosion or channel degradation. Riprap placed at the culvert inlet and outlet should be inspected annually and after each extreme flood event. Replace or reposition dislodged stone.

Floodplain and Flood-rise Impacts

Flood limits and elevations have not been mapped by the National Flood Insurance Program for the site.

The proposed culverts will improve hydraulic conveyance and is not expected to negatively impact flooding at the site.

Hydrology

The USGS StreamStats (version 4) web-based application was used for delineating the watershed and calculating drainage area (2 sq. miles) and mean annual precipitation (19-inches). Since delineations made by StreamStats can include inaccuracies for smaller watersheds and flat areas, the delineated watershed was verified by comparing it to both USGS TOPO maps and Digital Terrain Maps produced by the Alaska

Division of Geological and Geophysical Surveys. No significant deviations that would impact flow estimates were found.

Peak discharges were estimated with StreamStats using USGS regression equations from Magnitude and

Frequency at Gaged and Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada (USGS

WRIR 2016-5024). The watershed is mostly comprised of forested lands as well as several lakes and ponds including Upper Ohmer Lake (Figure 2). These lakes may influence the amount of runoff generated by the basin in two distinct manners. They have the potential to increase runoff due their large impervious surface area. However, lakes may also attenuate surface water flow withing the basin. This is especially true of

Upper Ohmer Lake as Ohmer Creek flows out of the lake and travels approximately 2,000 feet before passing through the culvert and immediately into Lower Ohmer Lake. Hydraulic modeling of the channel and the existing culverts indicate that the flows derived from the USGS regression equations are likely reasonable estimates of the basin’s hydrology. A summary of peak discharges and their corresponding water depths at the culvert

Dominant flooding is from snow melt. Larger floods typically occur in April and May. Rain-on-snow flood events can occur in October through December. Lower flows typically occur from January to February and

July through September.

Culvert Hydraulics

Water surface profiles and culvert capacities were estimated using the FHWA Culvert Hydraulics Analysis

Program, HY-8, version 7.7 (results attached). Floods larger than the 2-year were analyzed assuming culvert slope of 2.39 percent and Manning’s Roughness coefficient of 0.032 for the channel bottom and 0.024 for the culvert sides and top.

The computed outlet tailwater depth of 0.9 for the 2-year discharge was compared with the bankfull channel design depth of 1.0 feet and found to be within the measured range of 0.7 to 2.0 feet in the natural channel.

Hydraulic results are included in the attachments with headwater depths and ratios shown in Table 2.

Attachments: Table 1 – Peak Discharges

Table 2 – Headwater Depths and Ratios

Figures 1, 2, and 3

Photographs

HY-8 Calculations

USGS StreamStats Report

Drawings

Special Contract Requirements and Gradation Stability Calculations

Tables

Table 1. Peak Discharges Estimates Peak Annual Floods Discharge (ft3/2)

2-Year 34.3 5-Year 63.6

10-Year 87.6 25-Year 122 50-Year 149

100-Year 180 200-Year 211 500-Year 256

Table 2. Peak Discharges and Water Depths Peak Annual

Floods Discharge (ft3/2) Headwater Depth (ft) HW/D

(D=4.5 ft) 2-Year 35 1.21 0.27

50-Year 149 3.37 0.78 100-Year 180 3.85 0.86

D = Distance between culvert crown and streambed

Image date: 4/17/2011

Project AOP Culvert Site Location

Project Area Location

USGS Topographic Maps on Google Earth

N

FIGURE 1

OHMER CREEK

AOP CULVERT

SITE LOCATION

Ohmer Creek AOP

2500 feet0

Ohmer Creek

Skilak Lake RD

Lower Ohmer Lake Upper Ohmer Lake

Map printed from Google Earth, Image date 7/14/2017.

N

DA = 1.97 sq. mi.

FIGURE 2

OHMER CREEK

AOP CULVERT

DRAINAGE AREA

0 2500 feet

FIGURE 3

OHMER CREEK

AOP CULVERT

STREAMBED GRADATION

Photos

PHOTO 1

7/2021

PHOTO 2

7/2021

PHOTO 3

7/2021

Lower Ohmer Creek AOP

Looking upstream towards Upper Ohmer Lake. Woody debris observed within channel. Riffle-pool moprhology with a bankfull width of approximately 7-feet.

24" overlfow culvert. Approximately 2.2 feet of cover.

Channel upstream of culvert.

Active channel culvert outlet.

Looking upstream. 36" culvert outlet.

Outlet is perched. Approximately 3 feet of cover.

Overflow Culvert Inlet.

PHOTO 4

7/2021

PHOTO 5

7/2021

PHOTO 6

7/2021

Entry of Ohmer Creek into Lower Ohmer Lake.

Upstream streambed material

Lower Ohmer Creek AOP

Picture of streambed sediment showing cobble, pebbles and gravel.

Channel downstream of culvert.

Stream channel between culvert and Lower Ohmer Lake. Woody debris observed within channel. Bankfull width immediately downstream of culvert is approximately 7-feet.

Channel downstream of culvert at outlet to Lower Ohmer Lake.

PHOTO 7

7/2021

PHOTO 8

7/2021

PHOTO 9

9/2020

Downstream streambed material

Inside of existing 24" culvert.

Picture of streambed sediment showing pebbles and gravel.

Culver bottom is rusted. Culvert is free of debris.

Inside of existing 36" culvert.

Culver bottom is rusted. Culvert is free of debris.

Lower Ohmer Creek AOP

HY-8 Culvert Analysis Report – Proposed AOP Crossing Discharge Data Discharge Selection Method: Specify Minimum, Design, and Maximum Flow

Minimum Flow: 35.00 cfs

Design Flow: 149.00 cfs

Maximum Flow: 180.00 cfs

Table 1 - Summary of Culvert Flows at Crossing: Ohmer Creek Headwater Elevation (ft)

Total Discharge (cfs)

Ohmer Creek AOP Discharge (cfs)

Roadway Discharge (cfs)

Iterations

407.62 35.00 35.00 0.00 1

407.97 49.50 49.50 0.00 1

408.29 64.00 64.00 0.00 1

408.58 78.50 78.50 0.00 1

408.86 93.00 93.00 0.00 1

409.11 107.50 107.50 0.00 1

409.35 122.00 122.00 0.00 1

409.59 136.50 136.50 0.00 1

409.78 149.00 149.00 0.00 1

410.04 165.50 165.50 0.00 1

410.26 180.00 180.00 0.00 1

413.67 359.60 359.60 0.00 Overtopping

Rating Curve Plot for Crossing: Ohmer Creek

Culvert Data: Ohmer Creek AOP

Table 1 - Culvert Summary Table: Ohmer Creek AOP Total Discharge (cfs)

Culvert Discharge (cfs)

Headwater Elevation (ft)

Inlet Control Depth (ft)

Outlet Control Depth (ft)

Flow Type

Normal Depth (ft)

Critical Depth (ft)

Outlet Depth (ft)

Tailwater Depth (ft)

Outlet Velocity (ft/s)

Tailwater Velocity (ft/s)

35.00 cfs 35.00 cfs 407.62 1.21 0.0* 1- S2n

0.72 0.78 0.72 0.90 5.41 6.04

49.50 cfs 49.50 cfs 407.97 1.56 0.0* 1- S2n

0.90 0.98 0.90 1.10 6.15 6.77

64.00 cfs 64.00 cfs 408.29 1.88 0.0* 1- S2n

1.06 1.16 1.06 1.27 6.76 7.10

78.50 cfs 78.50 cfs 408.58 2.17 0.0* 1- S2n

1.22 1.33 1.22 1.41 7.28 7.25

93.00 cfs 93.00 cfs 408.86 2.45 0.0* 1- S2n

1.36 1.49 1.36 1.53 7.73 7.34

107.50 cfs 107.50 cfs 409.11 2.70 0.0* 1- S2n

1.50 1.64 1.50 1.64 8.13 7.40

122.00 cfs 122.00 cfs 409.35 2.94 0.146 1- S2n

1.64 1.79 1.64 1.73 8.50 7.46

136.50 cfs 136.50 cfs 409.59 3.18 0.456 1- S2n

1.77 1.92 1.77 1.82 8.83 7.51

149.00 cfs 149.00 cfs 409.78 3.37 0.734 1- S2n

1.88 2.04 1.88 1.89 9.09 7.55

165.50 cfs 165.50 cfs 410.04 3.63 1.119 1- S2n

2.03 2.19 2.03 1.98 9.41 7.61

180.00 cfs 180.00 cfs 410.26 3.85 1.469 1- S2n

2.16 2.31 2.16 2.05 9.67 7.66

* Full Flow Headwater elevation is below inlet invert.

Culvert Barrel Data Culvert Barrel Type Straight Culvert

Inlet Elevation (invert): 406.41 ft, Outlet Elevation (invert): 404.07 ft

Culvert Length: 98.03 ft, Culvert Slope: 0.0239

Culvert Performance Curve Plot: Ohmer Creek AOP

Water Surface Profile Plot for Culvert: Ohmer Creek AOP

Site Data - Ohmer Creek AOP Site Data Option: Culvert Invert Data

Inlet Station: 0.00 ft

Inlet Elevation: 401.91 ft

Outlet Station: 98.00 ft

Outlet Elevation: 399.57 ft

Number of Barrels: 1

Culvert Data Summary - Ohmer Creek AOP Barrel Shape: Circular

Barrel Diameter: 9.00 ft

Barrel Material: Corrugated Steel

Embedment: 54.00 in

Barrel Manning's n: 0.0240 (top and sides)

Manning's n: 0.0320 (bottom)

Culvert Type: Straight

Inlet Configuration: Beveled Edge (1:1)

Inlet Depression: None

Tailwater Data for Crossing: Ohmer Creek

Table 2 - Downstream Channel Rating Curve (Crossing: Ohmer Creek) Flow (cfs) Water

Surface Elev (ft)

Velocity (ft/s)

Depth (ft) Shear (psf) Froude Number

35.00 404.97 0.90 6.04 1.34 1.16

49.50 405.17 1.10 6.77 1.65 1.31

64.00 405.34 1.27 7.10 1.90 1.43

78.50 405.48 1.41 7.25 2.11 1.46

93.00 405.60 1.53 7.34 2.29 1.47

107.50 405.71 1.64 7.40 2.45 1.46

122.00 405.80 1.73 7.46 2.59 1.45

136.50 405.89 1.82 7.51 2.73 1.44

149.00 405.96 1.89 7.55 2.83 1.43

165.50 406.05 1.98 7.61 2.96 1.42

180.00 406.12 2.05 7.66 3.06 1.41

Tailwater Channel Data - Ohmer Creek Tailwater Channel Option: Irregular Channel

Channel Slope: Irregular Channel

User Defined Channel Cross-Section Coord No. Station (ft) Elevation (ft) Manning's n 1 0.00 410.00 0.0500 2 20.00 408.07 0.0400 3 46.50 405.07 0.0400 4 47.00 404.07 0.0320 5 53.00 404.07 0.0320 6 53.50 405.07 0.0400 7 80.00 408.07 0.0500 8 100.00 410.00 0.0000

Roadway Data for Crossing: Ohmer Creek Roadway Profile Shape: Constant Roadway Elevation

Crest Length: 100.00 ft

Crest Elevation: 413.67 ft

Roadway Surface: Gravel

Roadway Top Width: 24.00 ft

HY-8 Culvert Analysis Report - Existing Conditions

Crossing Discharge Data

Discharge Selection Method: Specify Minimum, Design, and Maximum Flow

Minimum Flow: 35.00 cfs

Design Flow: 149.00 cfs

Maximum Flow: 180.00 cfs

Table 1 - Summary of Culvert Flows at Crossing: Ohmer Creek Existing Conditions

Headwater Elevation (ft)

Total Discharge (cfs)

Ohmer Creek culvert Discharge (cfs)

Floodplain Overflow Discharge (cfs)

Roadway Discharge (cfs)

Iterations

407.92 35.00 24.16 10.84 0.00 5

408.44 49.50 33.86 15.65 0.00 4

409.07 64.00 44.79 19.22 0.00 4

409.84 78.50 55.65 22.86 0.00 4

410.77 93.00 66.31 26.69 0.00 3

411.11 107.50 69.88 28.01 9.46 12

411.20 122.00 70.75 28.34 22.79 6

411.27 136.50 71.45 28.60 36.32 5

411.32 149.00 71.97 28.81 48.03 4

411.39 165.50 72.61 29.05 63.72 4

411.44 180.00 73.11 29.25 77.60 4

411.00 96.35 68.75 27.60 0.00 Overtopping

Rating Curve Plot for Crossing: Ohmer Creek Existing Conditions

Culvert Data: Ohmer Creek culvert

Table 1 - Culvert Summary Table: Ohmer Creek culvert

Total Discharge (cfs)

Culvert Discharge (cfs)

Headwater Elevation (ft)

Inlet Control Depth (ft)

Outlet Control Depth (ft)

Flow Type

Normal Depth (ft)

Critical Depth (ft)

Outlet Depth (ft)

Tailwater Depth (ft)

Outlet Velocity (ft/s)

Tailwater Velocity (ft/s)

35.00 cfs 24.16 cfs 407.92 2.27 1.136 1-S2n 1.45 1.58 1.45 0.76 7.15 4.72

49.50 cfs 33.86 cfs 408.44 2.78 1.834 1-S2n 1.78 1.89 1.78 0.90 7.75 5.06

64.00 cfs 44.79 cfs 409.07 3.41 2.724 5-S2n 2.17 2.18 2.17 1.02 8.18 5.32

78.50 cfs 55.65 cfs 409.84 4.18 3.986 7-M2c 3.00 2.42 2.42 1.12 9.11 5.54

93.00 cfs 66.31 cfs 410.77 5.11 5.003 7-M2c 3.00 2.61 2.61 1.21 10.17 5.73

107.50 cfs 69.88 cfs 411.11 5.45 5.389 7-M2c 3.00 2.66 2.66 1.29 10.56 5.89

122.00 cfs 70.75 cfs 411.20 5.54 5.474 7-M2c 3.00 2.67 2.67 1.37 10.65 6.04

136.50 cfs 71.45 cfs 411.27 5.61 5.550 7-M2c 3.00 2.68 2.68 1.44 10.73 6.18

149.00 cfs 71.97 cfs 411.32 5.66 5.607 7-M2c 3.00 2.68 2.68 1.50 10.79 6.29

165.50 cfs 72.61 cfs 411.39 5.73 5.676 7-M2c 3.00 2.69 2.69 1.57 10.86 6.42

180.00 cfs 73.11 cfs 411.44 5.78 5.738 7-M2c 3.00 2.70 2.70 1.62 10.92 6.53

Inlet Elevation (invert): 405.66 ft, Outlet Elevation (invert): 404.81 ft

Culvert Length: 42.58 ft, Culvert Slope: 0.0201

Culvert Performance Curve Plot: Ohmer Creek culvert

Water Surface Profile Plot for Culvert: Ohmer Creek culvert

Site Data - Ohmer Creek culvert

Inlet Station: 0.00 ft

Inlet Elevation: 405.66 ft

Outlet Station: 42.57 ft

Outlet Elevation: 404.81 ft

Number of Barrels: 1

Culvert Data Summary - Ohmer Creek culvert

Barrel Shape: Circular

Barrel Diameter: 3.00 ft

Barrel Material: Corrugated Steel

Embedment: 0.00 in

Barrel Manning's n: 0.0240

Culvert Type: Straight

Inlet Configuration: Beveled Edge (1:1) (Ke=0.2)

Culvert Data: Floodplain Overflow

Table 2 - Culvert Summary Table: Floodplain Overflow

Total Discharge (cfs)

Culvert Discharge (cfs)

Headwater Elevation (ft)

Inlet Control Depth (ft)

Outlet Control Depth (ft)

Flow Type

Normal Depth (ft)

Critical Depth (ft)

Outlet Depth (ft)

Tailwater Depth (ft)

Outlet Velocity (ft/s)

Tailwater Velocity (ft/s)

35.00 cfs 10.84 cfs 407.92 1.72 1.770 2-M2c 1.31 1.18 1.18 0.76 5.62 4.72

49.50 cfs 15.65 cfs 408.44 2.21 2.284 7-M2c 2.00 1.43 1.43 0.90 6.53 5.06

64.00 cfs 19.22 cfs 409.07 2.66 2.917 7-M2c 2.00 1.58 1.58 1.02 7.23 5.32

78.50 cfs 22.86 cfs 409.84 3.21 3.688 7-M2c 2.00 1.70 1.70 1.12 8.02 5.54

93.00 cfs 26.69 cfs 410.77 3.89 4.614 7-M2c 2.00 1.80 1.80 1.21 8.96 5.73

107.50 cfs 28.01 cfs 411.11 4.15 4.956 7-M2c 2.00 1.83 1.83 1.29 9.30 5.89

122.00 cfs 28.34 cfs 411.20 4.21 5.044 7-M2c 2.00 1.83 1.83 1.37 9.39 6.04

136.50 cfs 28.60 cfs 411.27 4.26 5.113 7-M2c 2.00 1.84 1.84 1.44 9.46 6.18

149.00 cfs 28.81 cfs 411.32 4.30 5.168 7-M2c 2.00 1.84 1.84 1.50 9.52 6.29

165.50 cfs 29.05 cfs 411.39 4.35 5.231 7-M2c 2.00 1.85 1.85 1.57 9.58 6.42

180.00 cfs 29.25 cfs 411.44 4.39 5.284 7-M2c 2.00 1.85 1.85 1.62 9.64 6.53

Inlet Elevation (invert): 406.15 ft, Outlet Elevation (invert): 405.62 ft

Culvert Length: 40.06 ft, Culvert Slope: 0.0135

Culvert Performance Curve Plot: Floodplain Overflow

Water Surface Profile Plot for Culvert: Floodplain Overflow

Site Data - Floodplain Overflow

Inlet Station: 0.00 ft

Inlet Elevation: 406.15 ft

Outlet Station: 40.06 ft

Outlet Elevation: 405.62 ft

Number of Barrels: 1

Culvert Data Summary - Floodplain Overflow

Barrel Shape: Circular

Barrel Diameter: 2.00 ft

Barrel Material: Corrugated Steel

Embedment: 0.00 in

Barrel Manning's n: 0.0240

Culvert Type: Straight

Inlet Configuration: Beveled Edge (1:1) (Ke=0.2)

Tailwater Data for Crossing: Ohmer Creek Existing Conditions

Table 2 - Downstream Channel Rating Curve (Crossing: Ohmer Creek Existing Conditions)

Flow (cfs) Water Surface Elev (ft)

Velocity (ft/s) Depth (ft) Shear (psf) Froude Number

35.00 405.57 0.76 4.72 1.14 1.22

49.50 405.71 0.90 5.06 1.35 1.22

64.00 405.82 1.02 5.32 1.53 1.22

78.50 405.93 1.12 5.54 1.68 1.22

93.00 406.02 1.21 5.73 1.81 1.22

107.50 406.10 1.29 5.89 1.94 1.22

122.00 406.17 1.37 6.04 2.05 1.22

136.50 406.24 1.44 6.18 2.15 1.22

149.00 406.30 1.50 6.29 2.24 1.22

165.50 406.37 1.57 6.42 2.35 1.22

180.00 406.43 1.62 6.53 2.43 1.22

Tailwater Channel Data - Ohmer Creek Existing Conditions

Tailwater Channel Option: Irregular Channel

Channel Slope: Irregular Channel

User Defined Channel Cross-Section

Coord No. Station (ft) Elevation (ft) Manning's n

1 0.00 410.00 0.0500

2 20.00 408.07 0.0400

3 46.50 405.07 0.0400

4 47.00 404.81 0.0320

5 53.00 404.81 0.0320

6 53.50 405.07 0.0400

7 80.00 408.07 0.0500

8 100.00 410.00 0.0000

Roadway Data for Crossing: Ohmer Creek Existing Conditions

Roadway Profile Shape: Constant Roadway Elevation

Crest Length: 100.00 ft

Crest Elevation: 411.00 ft

Roadway Surface: Gravel

Roadway Top Width: 24.00 ft

SCALE IN FEET

10 0 10 20 30 40

OUTLETINLETPIPEHYDRAULIC INFORMATION

0 20 40 60 8020406080

LENGTH: 98 ft

PIPE SLOPE: 0.0239 ft/ft

HEADWALL: Riprap

FLOWLINE SLOPE: 0.0239 ft/ft

100 120100120140

Q : 35 CFS

Q : 149 CFS

BANKFULL CHANNEL WIDTH: 7.0 ft

TYPE: Metal Round Pipe SPAN: 9.0 ft RISE: 9.0 ft

LOWER BEVEL HEIGHT: 2.5 LOWER BEVEL HEIGHT: 2.5

BEVEL: 1.5h : 1v

HEADWALL: Riprap

BEVEL: 1.5h : 1v

Q : 180 CFS

INV N/E/EL: 2358542.26/1584498.22/401.91' /1584403.38/399.57'INV N/E/EL: 2358566.97

WALL THICKNESS: NA

:1

Existing ground

Fl ow

Remove Exisiting 36" CMP's

HW : 410.3 ft

Lo wer

Ohmer Cre ek

N

LC

OHW : 407.6 ft

Slope 2.39%

Line to be constructed

.5

BURIAL DEPTH: 4.5 ft BURIAL DEPTH: 4.5 ft

1:1

New culvert centerline metal round pipe culvert

9 foot diameter

255+04.93

254+76, 35.49 LT

255+37.92, 40.46 RT

PLAN AND PROFILE

CULVERT

LOWER OHMER CREEK

method B, class 3 [1]

Placed riprap method B, class 3 [1]

Placed riprap method B, class 3 [1]

Placed riprap method B, class 3 [1]

Placed riprap detail Sheet G.13

Backfill with streambed material per

FOOTNOTE:

See Sheet G.11 for riprap details.[1]

G.3

STATE PROJECT

NUMBER

SHEET

AK FWS KNA 1192(1)

V

B e v a n

J N e ig h o r n

/2

/2

C h e c k e d b y

D e s ig n e d b y

In t_ ft

D c p w w o r k \d

\a k r k e n a i1 h .d g n

Road centerline

Channel elev. 404.07

Channel elev. 406.41

Channel flowline

Road grade

:4

A

M

J u ly

F lo w

Cut and fill limits (typ.)

Cut and fill limits (typ.)

Concrete collar

Concrete collar E 1584555.11

N 2358573.16

End channel grading

E 1584348.42

N 2358566.09

Begin channel grading

Begin channel grading

Concrete collar

End channel grading

Concrete collar per detail sheet G.15

Install rock weirs at 28' spacing

8'

R

R

40'

R

E 1584530.60

N 2358552.90

E 1584371.66

N 2358569.91

7' Bankfull width

1:1

12" 9"

TYPICAL SECTION

CHANNEL GRADING

and seed

Place topsoil, 4" depth

NOTE:

FOOTNOTE:

beneath and at all sides of placed riprap.

Place earthwork geotextile between riprap and existing ground, Earthwork geotextile, type II-C is subsidiary to 251.

Contractor to field verify all invert elevations, prior to installation.

3.

2.

1.

shown on site specific details, whichever is greater.

Construct riprap end treatment to a thickness of 36-inches or as[3]

Riprap end treatment slope to match roadway embankment slope.[2]

Bevel to match roadway embankment.[1]

DETAILS

RIPRAP HEADWALL

Sl op e

PIPE BEVEL DETAIL

Sl op e

SKEW ANGLE DIAGRAM

c e n te r li n e

R o a d w a y

Cu lv er t ce nt er lin e

BOP

EOP

(DIAMETER OR SPAN GREATER OR EQUAL TO 48-INCHES)

(DIAMETER OR SPAN LESS THAN 48-INCHES)

.2

D o r R

.2

D o r R o r R is e

R

D ia m e te r

D o r R is e

R

D ia m e te r

D

W

RIPRAP END TREATMENT

Sl op e

FRONT VIEW SIDE VIEW

[2

24" shown in the plans

Streambed material where shown in the plans

Streambed material where

V a ri a b le R is e

W2

Variable W2 o r R is e

R

D ia m e te r

V a r ia b le

Placed riprap, class 3

Placed riprap, class 3

[3

" m in

[1]

[1] geotextile, class 1, type C

Separation and stabilization

Manufacturer's standards

0.25 D or R or per the

Optional

Skew

B e v n

N e ig h o r

/2

/2

C h e c k e d b y

D e s ig n e d b y

G.11

STATE PROJECT

NUMBER

SHEET

In t_ ft m y f il e s \p w p r o d u c ti o n

\d

\m t-a e z .d g n

AK FWS KNA 1192(1)

:5

A u g u s t

B e v

N e ig h o

/2

/2

C h e c k e d b y

D e s ig n e d b y

G.12

STATE PROJECT

NUMBER

SHEET

In t_ ft p w w o r k \d

\a k r k e n a i1 h .d g n

AK FWS KNA 1192(1)

:2 a y

SECTION VIEW

ANCHOR BOLT DETAIL

1.5

3'-0"

TYPICAL SECTION

THRU COLLAR

CONCRETE COLLAR

ISOMETRIC VIEW

3'-0"

3'

Sp an

3'

LC

Culvert crown

2' min. lap splice

#4 Reinf (6 total)

Culvert invert galvanized " Dia.4 bolt design - 4" hook

Acceptable anchorStructural plate pipe

18" o.c. See detail " Anchor bolt @4

#4

#4 stirrups m in

2' min. lap splice

#4 Reinf (6 total)

6" min.

To bedrock or 3' max.

To bedrock or 3' max.

COLLAR DETAILS

REINFORCED CONCRETE

LARGE CULVERT

SECTION A-A

PLAN

NOTE:

FOOTNOTE:

3.

2.

1.

Pipe arch culvert

W

Streambed sediment

Streambed cobble

Pipe arch culvert wall

Box culvert wall

Stagger in-channel fish passage boulders within the culvert span.

streambed cobble, and bank stone gradations.

See special contract requirements for streambed sediment, Mix streambed cobbles evenly throughout streambed sediment.

Channel flowline

Streambed sedimentRound pipe culvert wall Streambed top

Round culvert

B D

Culvert wall

LC

Flow

BB

A

W

X (typ.)

where specified on plan per detail Sheet G.14

Sediment retention sill on plan where specified detail Sheet G.15

Rock weir per culvert boulder within

Fish passage where specified on plan per detail Sheet G.14

Sediment retention sill specified on plan boulder where

Fish passage

NO SCALE

Streambed Material.

Infill informational quantities are incidental to ITEM 64704-1000 [4] dimension.

smallest 4 3 Embed fish passage boulders within active channel [3] sediment where listed in the infill quantities table.

Construct well defined banks with bank stone and streambed[2] parabolic shape.

Slope streambed aggregate towards flowline to ensure[1]

[1]Channel flowline

[2]Bank stone

[2]Bank stone

TREATMENT

STREAM CULVERT

SIMULATED

A Flow

SECTION B-B

(typ.)

36" min.

Streambed cobble

Culvert outlet where specified on plan per detail Sheet G.14

Sediment retention sill

[3]within culvert

Fish passage boulder

Streambed sediment X (typ.)

plan sheet or Length on

4' match rock weir spacing

Stagger fish boulders each side and

LC

specified on plan

Sheet G.15 where

Rock weir per detail outlet

Culvert

LOCATION

(FT)

X

(CUYD)

COBBLE

STREAMBED

(CUYD)

SEDIMENT

STREAMBED

(CUYD)

STONE

BANK

GRADATION

COBBLE

STREAMBED

(FT)

W

MITIGATION

FISH PASSAGE BOULDER

(IN)

DIA. NO.

[4]STREAMBED MATERIAL

TOTAL

B e v

N e ig h o

/2

/2

C h e c k e d b y

D e s ig n e d b y

G.13

STATE PROJECT

NUMBER

SHEET

In t_ ft m y f il e s \p w p r o d u c ti o n

\d

\m t-a e w

.d g n

AK FWS KNA 1192(1)

:4

A u g u s t

JEAN CREEK NA 10

LOWER OHMER CREEK NA 7

UNNAMED CREEK 3.8 6.7

D

D

D

(IN)

BD

d e p th

B u r ia l

B u r ia l d e p th

BD/3

3% (typ.)

Slope

Flow

F lo wA

A

(in)

DIAMETER

FOOTER ROCK

TOP ROCK AND

(no.)

QUANTITY

ROCK WEIR

MITIGATION

ROCK WEIR

(ft)

B

(ft)

[5] Z

(ft)

W

LOCATION

ELEVATION

PLAN

SECTION A-A

DETAIL

ROCK WEIR

NO SCALE

FOOTNOTE:

Align footer rocks flush against bed retention sills inside culvert. [5] and stable foundation for the top rocks.

Place footer rocks close together to create a tightly packed[4] streambed material.

Fill voids in top rock and footer rock with specified[3]

Space top rocks in center 1/3 only.[2]

Orient top rocks to deflect water towards center of stream.[1]

[4] [3]Footer rock

Z

D o w n s tr e a m f r o m c o n tr o l)

Top rock

Bottom of channel

Bottom of channel

[4] [3]Footer rock high water level

Ordinary normal low flow

Edge of water

Control point

[2] [1] [2] [1]

[2]

[3] [2]Top rock

[2]

[2] [2] [2]

[2] streambed material elevation or top of

Original streambed

[4] [3]Footer rock

[3]Top rock water level

Ordinary high

BWB

B W3

W 3

W3

B

W3

B e v

N e ig h o

/2

/2

C h e c k e d b y

D e s ig n e d b y

G.15

STATE PROJECT

NUMBER

SHEET

In t_ ft m y f il e s \p w p r o d u c ti o n \d

\m t-a e y .d g n

AK FWS KNA 1192(1)

:5

A u g u s t

JEAN CREEK 10.0 1.5 5.5 3

LOWER OHMER CREEK 7.0 1.0 4.5 4

UNNAMED CREEK 6.6 1.2 3.3 19

VAP

Existing ground

Roadway centerline

2000 50 100 15050100150 250

Lower Ohmer Lake

Ohmer Creek

Section 703. — AGGREGATE

703.18 Furnished Streambed Material. (Added Subsection).

Streambed material consists of streambed sediment and streambed cobbles (class A, B, C, D, or E as specified on the plans) with volumes of each specified on the plans. Provide a uniform mixture.

Furnish material consisting of hard, durable, free from seams, cracks, and other defects conforming to the following:

(a) Durability index, AASHTO T 210

(1) Course aggregate 35 min.

(2) Fine aggregate 35 min.

(b) Apparent specific gravity, AASHTO T 85 2.55 min.

(c) Los Angles abrasion, AASHTO T 96 50% max.

(d) Gradation, Streambed Sediment. Furnish material meeting the gradation requirements of Table 703-13. Conserve round or sub-round material from the culvert and roadway excavation meeting the requirements of Table 703-13 to use as streambed sediment.

Table 703-13 Streambed Sediment Gradation

Sieve Size

Percent by Weight Passing Designated Sieve

(AASHTO T 27 and T 11)

3 ½ inch 100

3 inch 80 – 90

1 ½ inch 55 – 65

¾ inch 40 – 50

No. 4(1) 15 – 25

No. 10 15 min.

(1) No more than 0.2 percent woody debris retained.

(e) Gradation, Streambed Cobbles. Furnish material meeting the requirements of Table 703-14. Conserve round or sub-round material from the roadway excavation meeting the requirements of Table 703-14 to use as streambed cobbles.

Table 703-14 Streambed Cobbles Gradation(1)

Nominal Size

Percent less than the nominal size Class

A B C D 18” 100 12" 60-70 10" 100 8" 100 75-80 30-40 6" 100 50-60 10-20 5" 65-75 4" 65-75 30-40 3" 35-45 25-35 0-10 2" 35-45

1 ½" ¾" 10-15 10-15

(1) Grading of the cobbles will be by visual inspection of material before it is placed, and if directed by the CO, by placing material on a flat surface and sorting and measuring a sampling of the cobbles..

Note: Approximate size can be determined by taking the average dimension of the three axes of the rock; length, width, and thickness by use of the following calculation:

𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿ℎ + 𝑊𝑊𝑊𝑊𝑊𝑊𝐿𝐿ℎ + 𝑇𝑇ℎ𝑊𝑊𝑖𝑖𝑖𝑖𝐿𝐿𝐿𝐿𝑖𝑖𝑖𝑖

= 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝑊𝑊𝐴𝐴𝐴𝐴𝐿𝐿𝐿𝐿 𝑆𝑆𝑊𝑊𝑆𝑆𝐿𝐿

Project:

Location/Stream:

New Stream Channel Design (Culvert, Rock Ramp)

FINE 50%

Using Corps of Engineers Equations - FHWA Circular on Development in the River System - Page 6.25. COARSE 50% FHWA NHI 01-004; River Engineering for Highway Encroachments, 2001 http://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=8&id=20

YELLOW ARE INPUTS

Safety Factor 1.2 Stability Coefficient for Incipient Failure 0.36 (0.36 round rock, 0.3 angular rock) Vertical Velocity Distribution Coeff 1.00 (1.0 for straight channels) Blanket Thickness Coeff 1 (1xD100 or 1.5 or D50 max, whichever is greater) Local depth of flow 1.88 ft for 50 year event Unit Weight of water 62.4 lb/ft^3 assumed Unit weight of rock 165 lb/ft^3 assumed Local depth-average velocity 9.09 ft/s from 100-year event avg. velocity in pipe Side Slope correction factor 1 Gravitational Acceleration 32.2 ft/s^2 D85/D15 1.7 (1.7-5.2) D50/D30 1 Note: This method is based on the minimum D30 size Riprap Design Method - Selecting Proper Gradation, Page 131.

Design Hydrology and Sedimentology for Small Catchments, Haan, Barfield and Hayes, 1981.

D15 0.3 ft 4.0 inches D30 0.6 ft 8.0 inches D50 0.8 ft 10.0 inches D85 1.3 ft 16.0 inches

D100 1.5 ft 19.0 inches

Using D50 size, used FHWA circular for Rip Rap design to spec out D100, D85 and D15.

D100 = 2.0D50

Fuller-Thompson Estimating for Maximum Density: D100 (inches) 19.0 Method Adapted from US Forest Service Stream Simulation Guidelines D30 8.0 Stability (D30):

D30 Req'd 8.0

YELLOW ARE INPUTS COARSE FINES

Custom Fine Aggreg. Combined %F-T EQN Check Coarse Material Design -D30 Required per FHWA Method RELATIVE % = 0.50 0.50 1.0000 Riprap D30 Riprap Req 8.0

Size (inches) Sieve Size % Passing % Passing % Passing % Passing % Passing D30 Size = 8.0 54 54 in 1.00 1.00 100% 169% 100% No OK 48 48 in 1.00 1.00 100% 159% 100% No 44 44 in 1.00 1.00 100% 152% 100% No 42 42 in 1.00 1.00 100% 149% 100% No 36 36 in 1.00 1.00 100% 138% 100% No 30 30 in 1.00 1.00 100% 126% 100% No 24 24 in 1.00 1.00 100% 112% 100% No 18 18 in 1.00 1.00 100% 97% 100% No 12 12 in 0.65 1.00 83% 79% 65% No 8 8 in 0.30 1.00 65% 65% 30% 8.00 6 6 in 0.10 1.00 55% 56% 10% 6.00 3 3 in 0.00 0.85 43% 40% 0% 3.00

1.5 1.5 in 0.00 0.60 30% 28% 0% 1.50

0.75 0.75 in 0.00 0.45 23% 20% 0% 0.75

0.187 #4 0.00 0.20 10% 10% 0% 0.19

0.0787 #10 Sand 0.00 0.15 8% 6% 0% 0.08

Gradation values should be within +/-5% of this gradation (Rice) AND we need to have at least 5% sand size (#10) or smaller (Forest Service) in the combined gradation

DATA for Graph & Fuller-Thomson Eqn Size (in) Combined % pa F-T equation n (F-T)=

54.000 100% 169% D100 (in) =

48.000 100% 159%

44.000 100% 152%

42.000 100% 149%

36.000 100% 138%

30.000 100% 126%

24.000 100% 112%

18.000 100% 97%

12.000 83% 79%

8.000 65% 65%

6.000 55% 56%

3.000 43% 40%

1.500 30% 28%

0.750 23% 20%

0.187 10% 10%

0.079 8% 6%

OK

MATERIAL PROPORTIONS

AK FWS Kenai 1102(1) - Skilak Lake Road

Ohmer Creek Culvert

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.010 0.100 1.000 10.000 100.000

P as si ng

Particle Size

Design

Fuller-Thomson http://www.fhwa.dot.gov/engineering/hydraulics/library_arc.cfm?pub_number=8&id=20

YELLOW ARE INPUTS

Desired tolerance (+/-): 5%

SIEVE % PASSING

18 in 1.00 12 in 1.00 8 in 1.00 6 in 1.00 3 in 0.8 to 0.9

1.5 in 0.55 to 0.65

0.75 in 0.4 to 0.5

#4 0.15 to 0.25 #10 Sand 0.15 min

Desired tolerance (+/-): 5%

SIZE % PASSING

54 in 1.00 48 in 1.00 44 in 1.00 42 in 1.00 36 in 1.00 30 in 1.00 24 in 1.00 18 in 1.00 12 in 0.6 to 0.7 8 in 0.3 to 0.4 6 in 0.1 to 0.2

3 in 0 to 0.1

COARSE MATERIAL

TABLE 1

FINE MATERIAL

TABLE 2

4-AOP Report Photos OhmerCreek

Roadway Data for Crossing: Ohmer Creek

Streambed Material Sizing Analyzer_Ohmer Creek