WF Mill Creek AOP Report.pdf

WF Mill Creek AOP December 7, 2020

WF Mill Creek Aquatic Organism Passage Design Report

INTRODUCTION AND BACKGROUND

This report presents the geomorphic, hydrologic, hydraulic, and ecological considerations for a proposed Aquatic Organism Passage (AOP) structure at the WF Mill Creek crossing on Yale-Kilgore Road. WF Mill Creek is a perennial stream and bears fish.

The existing culvert is adequately sized with a HW/D ratio of 0.76 for the 50-year flood. However, the proposed highway design includes a new recreation trail that crosses WF Mill Creek about 15’ downstream of the road crossing. As a USFS requirement for fish bearing streams on this project, the new recreational trail crossing is to meet AOP standards. With the road and trail crossings being close in proximity, it makes the most sense to replace the road crossing with an AOP compliant structure to open up more habitat (if only the trail crossing was brought to AOP standards, only about 15’ of habitat would gained). The first iteration of this design included two separate structures for the road and trail crossing. The two structure layout would include a 54’ long structure for the road, 28’ long structure for the trail and an 12’ stretch of exposed stream between the two crossings. It’s to be noted that the trail cannot be moved further away from the road due to right-of-way constraints. To avoid an awkward transition between the road and trail, the design was revised to consolidate the two crossings by realigning the trail to run alongside the road. This design would utilize a single 78’ long structure, which would reduce the overall structure length and disturbance. The road and trail are currently laid out with 10’ of separation between edge of road and edge of trail. This design meets Idaho Transportation Department separation requirements, but this gap can be narrowed and the length of the structure can be shortened if a guardrail is to be placed between the road and trail.

GEOMORPHIC CHANNEL DESCRIPTION

The Rosgen stream classification method used to evaluate the general geomorphic characteristics for this reach. In the vicinity of the Yale-Kilgore Road crossing, WF Mill Creek most closely resembles a Rosgen E3 Stream. The average grade of the stream is 1.12% and the longitudinal profile is very uniform with no major grade breaks. The channel substrate is predominately comprised of small gravel with sands accounting for the finer particles (See attached pebble count for gradation). The channel banks are nearly vertical and comprised of organic sandy material held in place by grassy vegetation. In the vicinity of the new crossing, the stream is shrouded in a thick grove of willows. The bedforms observed consist primarily of riffle-pool sequences with the pool tail crests comprised of loose gravel materials.

The channel has almost no entrenchment with no apparent confining floodplain banks. In the designated Reference Reach, the channel is rectangular with a 5’ bankfull width and a 1’ bankfull height.

Photo 1: Reference Reach - Located upstream of crossing (See

Appendix A - Longitudinal Profile)

CHANNEL DATA

Rosgen Classification: E3 Bankfull Width = 5 ft Bankfull Depth = 1.0 ft Average Slope = 1.12% Substrate Gradation:

D16 = 3 mm D50 = 10 mm D84 = 41 mm

Average Key Piece Size = 240 mm Bedforms = Riffle-Pool comprised of gravel and sand Sinuosity = 1.7 Entrenchment Ratio = Unable to calculate Bankfull Width to Depth Ratio = 5

See appended Supporting Files folder for Pebble Count Data

CHANNEL STABILITY

The stability of the channel was evaluated using both qualitative and quantitative analysis. The following data were collected prior to the evaluation: aerial photos, topographic maps, stream channel survey, hydrologic estimates, and anecdotal crossing history.

According to Rosgen’s research, type “E” streams can be characterized as having moderate sinuosity, gentle channel gradients, and very low entrenchment ratios. The streambanks are composed of materials finer than that of the dominat channel bed materials, and are typically stabilized with dense riparian or wetland vegetation. Rosgen asserts about E3 channels: “The narrow and relatively deep channels maintain a high resistance to plan from adjustment, which results in channel stability without significant downcutting. The E3 stream channels are very stable unless the streams are disturbed, and significant changes in sediment supply and/or streamflow occur.” To summarize: E3 channels are considered by Rosgen to be very stable and there for should be at little risk of compromising the footings of the proposed structure.

Channel stability, vertical adjustment potential (maximum degradation), and proposed culvert profile design was determined through longitudinal stream profile analysis procedures established by the U.S. Forest Service. The USFS Longitudinal Profile Procedure can be found in the appended Supporting Files folder. See Appendix A - Longitudinal Profile for WF Mill Creek.

The analysis uses the following processes to determine vertical adjustment potential and proposed culvert profile:

1. Draw segmented lines on the profile that span from the top of grade controls. The segments represent the average stream slope between grade breaks.

2. Measure the maximum pool depth for each section (distance from segmented lines to the bottom of pool)

3. Offset the segment by the maximum pool depth value multiplied by a safety factor of

2.0 corresponding to a riffle stream with gravel-cobble substrate (for factor of safety values, see page 20 of USFS Longitudinal Profile Procedure in the Appended report folder). The resulting offset segment line represents the potential for vertical adjustment.

The channel profile is very uniform with no major grade breaks observed. The lack of knickpoints suggests that the channel is relatively stable in the vicinity of the crossing.

STRUCTURE SELECTION

The proposed structure for the crossing is an open-bottom structural plate arch (10’-0” span x 4’-5” rise) placed on concrete footings. The span of the arch is sized to accommodate the bankfull width of the reference reach (5’) plus 18” banks on both sides.

In structure selection considerations, a pipe arch (117” span x 79” rise) was considered but rejected due to construction and maintenance difficulties. A pipe arch of this size and length (78’) would require more labor to infill with streambed simulation material, as most of this work would have to be placed and compacted by hand. In comparison, an open bottom structure would allow placement of the footings, followed by streambed channel construction. Streambed material can be by an excavator and compacted with no headroom issues. After the streambed is constructed, the plate arch can be placed on the footings.

HYDROLOGIC & HYDRAULIC CONSIDERATIONS

USGS StreamStats was used to estimate the flood magnitude for the 2- and 100-year events at the crossing (see Appendix C – StreamStats Report). The results for the 0.66 square-mile tributary area were:

Q2 = 12.1 CFS

Q100 = 52.4 CFS

Using FHWA hydraulic modeling program, HY-8, a capacity analysis was performed for the Q100 event. The resulting headwater depth ratio was 0.67.

Photo 4: Upstream reach Photo 5: Downstream reach

Photo 2: Culvert Inlet Photo 3: Culvert Outlet

Appendix A: Longitudinal Profile

0+00 0+50 1+00 1+50 2+00 2+50 3+00 3+50 4+00

6,340 6,340

6,342 6,342

6,344 6,344

6,346 6,346

6,348 6,348

6,350 6,350

6,352 6,352

6,354 6,354

6,356 6,356

6,358 6,358

6,360 6,360

6,362 6,362

6,364 6,364

6,366 6,366

6,368 6,368

6,370 6,370

6,372 6,372

6,374 6,374

6,376 6,376

Proposed Design Grade

Existing Culvert

1.11%

EL. 6354.24

Bottom of Proposed Footing

EL. 6355.11

Bottom of Proposed Footing

1.10%

1.17% along thalweg of the stream

Approximate Existing Ground

Adjustment Potential

Maximum Vertical

LONGITUDINAL PROFILE

WF MILL CREEK AOP

Precast Concrete Footing

STATE PROJECT

NUMBER

SHEET

ID CLARK 6805(1) 1

FREMONT 6805(1)

:3

A

M

M a r c h

L o n g P r o f il e

S h e e t]

F

.0

W

F L

H D

Y a le

-K il g o re R o a d

D e s ig n \D

G N

\i d

-a

Y a le

-K il g o re \i d -a

W F

M

IL

L C

R E

E K

.d g n

Appendix B: Surveyed Stream Cross Sections

DOWNSTREAM CROSS SECTION - STA 3+07.75

-0+10 0+00 0+20

UPSTREAM CROSS SECTION - STA 0+91.56

-0+10 0+00 0+20

WF MILL CREEK

STREAM CROSS SECTIONS

MARCH, 2020&

ENGINEERS

PLANNERS

SURVEYORS

Appendix C: StreamStats Report

StreamStats Report

Basin Characteristics

Parameter Code Parameter Description Value Unit

DRNAREA Area that drains to a point on a stream 0.66 square miles

PRECPRIS10 Basin average mean annual precipitation for 1981 to 2010 from PRISM

30.5 inches

Peak-Flow Statistics Parameters[Peak Flow Region 6 and 8 2016 5083]

Region ID: ID Workspace ID: ID20200303034838129000 Clicked Point (Latitude, Longitude): 44.46690, -111.43379 Time: 2020-03-02 20:48:55 -0700

Parameter Code Parameter Name Value Units

Min Limit

Max Limit

Parameter Code Parameter Name Value Units

Min Limit

Max Limit

DRNAREA Drainage Area 0.66 square miles

2.77 3740

PRECPRIS10 Mean Annual Precip PRISM 1981

30.5 inches 18.9 54.6

Peak-Flow Statistics Disclaimers[Peak Flow Region 6 and 8 2016 5083]

One or more of the parameters is outside the suggested range. Estimates were extrapolated with unknown errors

Peak-Flow Statistics Flow Report[Peak Flow Region 6 and 8 2016 5083]

Statistic Value Unit

1.25 Year Peak Flood 6.89 ft^3/s

1.5 Year Peak Flood 9.09 ft^3/s

2 Year Peak Flood 12.1 ft^3/s

2 33 Year Peak Flood 13.7 ft^3/s

5 Year Peak Flood 20.4 ft^3/s

10 Year Peak Flood 27.2 ft^3/s

25 Year Peak Flood 36.2 ft^3/s

50 Year Peak Flood 43.3 ft^3/s

100 Year Peak Flood 52.4 ft^3/s

200 Year Peak Flood 60.4 ft^3/s

500 Year Peak Flood 74.3 ft^3/s

Peak-Flow Statistics Citations

Wood, M.S., Fosness, R.L., Skinner, K.D., and Veilleux, A.G.,2016, Estimating peak-flow frequency statistics for selected gaged and ungaged sites in naturally flowing streams and rivers in Idaho: U.S. Geological Survey Scientific Investigations Report 2016–5083, 56 p.

(http://dx.doi.org/10.3133/sir20165083)

USGS Data Disclaimer: Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty http://dx.doi.org/10.3133/sir20165083 expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.

USGS Software Disclaimer: This software has been approved for release by the U.S. Geological Survey (USGS). Although the software has been subjected to rigorous review, the USGS reserves the right to update the software as needed pursuant to further analysis and review. No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. Furthermore, the software is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use.

USGS Product Names Disclaimer: Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Application Version: 4.3.11

Appendix D: HY-8 Results – Capacity Analysis

HY-8 Culvert Analysis Report

Crossing Discharge Data

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

Minimum Flow: 52.4 cfs

Design Flow: 52.4 cfs

Maximum Flow: 52.4 cfs

Table 1 - Summary of Culvert Flows at Crossing: WF Mill Creek Headwater Elevation

(ft) Total Discharge (cfs) Culvert 1 Discharge

(cfs) Roadway Discharge

(cfs) Iterations

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6361.52 52.40 52.40 0.00 1

6365.80 141.24 141.24 0.00 Overtopping

Rating Curve Plot for Crossing: WF Mill Creek

Table 2 - Culvert Summary Table: Culvert 1 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)

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

52.40 52.40 6361.52 2.028 3.411 3-M1t 2.971 1.546 3.513 3.513 2.077 2.290

Straight Culvert

Inlet Elevation (invert): 6358.11 ft, Outlet Elevation (invert): 6357.24 ft

Culvert Length: 78.00 ft, Culvert Slope: 0.0112

Culvert Performance Curve Plot: Culvert 1

Water Surface Profile Plot for Culvert: Culvert 1

Site Data - Culvert 1

Site Data Option: Culvert Invert Data

Inlet Station: 0.00 ft

Inlet Elevation: 6358.11 ft

Outlet Station: 78.00 ft

Outlet Elevation: 6357.24 ft

Number of Barrels: 1

Culvert Data Summary - Culvert 1

Barrel Shape: User Defined

Barrel Span: 9.85 ft

Barrel Rise: 4.83 ft

Barrel Material: Corrugated Metal Riveted or Welded

Embedment: 0.00 in

Barrel Manning's n: 0.0350 (top and sides)

Manning's n: 0.1000 (bottom)

Culvert Type: Straight

Inlet Configuration: Thin Edge Projecting

Inlet Depression: None