Report_Hydraulics.pdf

Memo mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

To: Michael Tessitore From: Rob Monk

FHWA – Eastern Federal Lands Division Stantec – St. Paul, MN

File: 193804093 Date: April 16, 2018

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation

This memo provides the Hydraulics Documentation for twelve (12) culverts and one bridge across multiple roadways, as detailed in the table below.

Roadway Site Structure

Culvert Replacement FS 205 S10 Culvert

Culvert Replacement FS 205 S11 Culvert

Small Culvert Replacement/Cleaning FS 198 Various Culvert (10)

Bridge Abutment Rehabilitation FS 199 B2 Bridge

Culvert sizing was completed using the design criteria of the Federal Lands Highway (FLH) Project Development and

Design Manual (PDDM) and input from both the Federal Highway Administration (FHWA) and United States Forest

Service (USFS). This memo includes the project design criteria followed by hydrology, hydraulics, and sizing for each culvert and riprap sizing for the bridge.

Design Criteria

The guiding hydrologic and hydraulic design criteria for culvert replacement are contained within Chapter 7 of the FLH PDDM. Relevant design standards and criteria include:

• For cross culverts on Low-Standard roads, culverts will be designed to convey runoff from the 25-year flood.

This 25-year design standard was confirmed via correspondence with FHWA staff.

• A variety of hydrologic methods are available to compute the 25-year flood flow and other flood discharges, as described in the PDDM.

• Headwater elevations should be no higher than the elevations described in section 7.3.1.4.1 of the PDMM.

These include keeping the headwater elevation below the bottom of the aggregate base layer and the shoulder hinge point at the road low point, and keeping the HW/D ratio below 1.5 for new culverts.

Aquatic Organism Passage (AOP) is also a consideration. During project scoping, consideration was given to implementing the detailed design procedures of Hydraulic Engineering Circular 26 (HEC-26), Culvert Design for Aquatic Organism Passage. However, full HEC-26 procedures will not be used for culverts S10 and S11 for the following reasons:

• Collecting the field data necessary for HEC-26 design during winter months will be difficult or impossible, and would likely delay the overall project.

• Based on their knowledge and observations of site and stream conditions and similar culvert crossings, USFS staff believe that a simplified approach for these crossings will provide adequate AOP.

It was agreed upon by FHWA and USFS that a simplified approach to providing AOP will be implemented for the replacement of culverts S10 and S11. The designed culvert barrel width should match the adjacent bankfull stream width and the tailwater elevation should be provided through the culvert. USFS also requested that both culvert S10 and S11 be embedded between 0.5’-1.5’ (to create a natural channel bottom) and placed at a flat slope to meet expected permitting requirements. FS198 culverts will not be sized to provide AOP, but will simply be sized to meet Section 7.3.1 requirements of the FLH PDDM.

April 16, 2018

Michael Tessitore

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

Culvert Replacement, FS205, Site S10

Hydrology

Based on drainage basin characteristics, the USGS regional regression equation (WI, Area 2) was used to determine a peak 25-year flood flow of 143 cfs to culvert S10. Basin characteristics used in the regression equation are shown in

Table 1 below. The contributing watershed area to culvert S10 was determined using a combination of available WI

LiDAR data and USGS StreamStats, a web-based program used to determine watershed area and various watershed characteristics. Soil permeability of 48.355 in/hr (StreamStats) was lowered to 2.88 in/hr, the maximum allowable within the regression equation. Main-channel slope was manually calculated based on WI LiDAR data (StreamStats appears to give an erroneous result, much too high). A spreadsheet with basin characteristics and the regression equation computation is attached for review.

Table 1. Culvert S10 Basin Characteristics

Basin Characteristic Units Value

Area (A) Square Miles (mi2) 2.02

Soil Permeability (SP) Inches/Hour (in/hr) 2.88

Main-Channel Slope Feet/Mile (ft/mi) 42.2

25-Year Flood Flow Cubic Feet per Second (cfs) 143

Hydraulics

Hydraulic analysis of existing and proposed conditions for culvert S10 was completed using the FHWA computer-based

HY-8 Culvert Hydraulic Analysis Program. Program parameters include discharge (flow), tailwater (downstream cross section), roadway (overtopping), culvert (material and size), and site (invert and length) data. Discharge data includes the design flow calculated above. All other parameters were calculated or estimated based upon in-field survey data. The

HY-8 design file is attached for review.

For sizing, the proposed culvert was modeled as flat (no slope) with inverts placed 1-foot below the existing downstream invert. This results in the culvert being embedded 1.33’ upstream and 1.0’ downstream, allowing for a natural channel bottom to form. Culvert length was determined based on 2:1 step bevels and the proposed roadway profile, which also provided the road overtopping elevation. Based on USFS preference, the culvert was preliminarily sized to match bankfull width (8-11 feet), as determined by USFS staff in the field. A summary of the HY-8 analysis for the proposed condition during the 25-year flood is shown in Table 2 below.

Table 2. Culvert S10 Hydraulics

Proposed – 54’ long, 103-inch span x 71-inch rise CMP (arch)

Overtopping Elevation (ft) 1398.90

Headwater Elevation (ft) 1394.58

HW/D Ratio 0.97

Tailwater Depth (ft) 2.67

The analysis shows that the embedded 103-inch span by 71-inch rise CMP arch pipe, which matches the channel bankfull width, will have enough capacity to convey the 25-year flood per the design criteria of the FLH PDDM.

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

Culvert Replacement, FS 205, Site S11

Hydrology

Based on the watershed area not meeting minimum size requirements (0.37 mi2 actual vs. 0.56 mi2 required), the USGS regional regression equation (Area 2) could not be used for culvert S11. Thus, the NRCS curve number / unit hydrograph method, as implemented by HydroCAD software, was utilized to determine a peak 25-year flood flow of 73 cfs to culvert

S11. HydroCAD inputs are shown in Table 3 below. Curve numbers (CN) of 43 and 82 (woods/grass combination, fair condition) were used for Hydrologic Soil Group (HSG) A and D, respectively. The composite CN for the watershed is shown in the table below. Time of concentration was determined using the Lag/CN method, which is based on CN, hydraulic length, and average land slope. NOAA Atlas 14 precipitation data for the 25-year flood (5.26 inches) was used with a Type-II, 24-hour rainfall distribution for all calculations. A HydroCAD report for the S11 basin is attached for review.

Table 3. Culvert S11 Basin Characteristics

Basin Characteristic Units Value

Area Square Miles (mi2) 0.37

Area Acres (ac) 239.4

Composite CN Unitless 62

Time of Concentration (tc) Minutes 200

25-Year Flood Flow Cubic Feet per Second (cfs) 73

Hydraulics

Hydraulic analysis of existing and proposed conditions for culvert S11 was completed using the FHWA computer-based

HY-8 Culvert Hydraulic Analysis Program. Program parameters include discharge (flow), tailwater (downstream cross section), roadway (overtopping), culvert (material and size), and site (invert and length) data. Discharge data includes the design flow calculated above. All other parameters were calculated or estimated based upon in-field survey data. The

HY-8 design file is attached for review.

For sizing, the proposed culvert was modeled as flat (no slope) with inverts placed 0.5-feet below the existing upstream invert. This results in the culvert being embedded 0.5’ upstream and 0.83’ downstream, allowing for a natural channel bottom to form. Culvert length was determined based on 2:1 step bevels and the proposed roadway profile, which also provided the road overtopping elevation. Based on USFS preference, the culvert was preliminarily sized to match bankfull width (4 feet), as determined by USFS staff in the field. However, to meet the required HW/D Ratio (1.5), a wider arch pipe was necessary. Analysis showed that pipe size and not the downstream cross section were the determining factor for tailwater elevation. A summary of the HY-8 analysis for the proposed condition during the 25-year flood is shown in Table

4 below.

Table 4. Culvert S11 Hydraulics

Proposed – 56’ long, 64-inch span x 43-inch rise CMP (arch)

Overtopping Elevation (ft) 1400.60

Headwater Elevation (ft) 1397.74

HW/D Ratio 1.27

Tailwater Depth (ft) 1.38

The analysis shows that an embedded 64-inch span by 43-inch rise CMP arch pipe, which is slightly wider than the channel bankfull width, will have enough capacity to convey the 25-year flood per the design criteria of the FLH PDDM.

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

Small Culvert Replacement/Cleaning, FS 198, Various Sites – 10 Culverts

Hydrology

Based on the watershed areas not meeting minimum size requirements (≤0.10 mi2 actual vs. 0.56 mi2 required), the

USGS regional regression equation (Area 2) could not be used for FS198 culverts. Thus, based on conversations with

FHWA and USFS, the Rational Method (Q=ciA) was used to determine 25-year flood flows. Rational method inputs for each culvert are shown in Table 5 below. Runoff coefficients (c) were determined using the WisDOT Facilities Design

Manual for open space. NOAA Atlas 14 precipitation frequency data (inches/hour) was used to determine rainfall intensity

(i) for the 25-year flood.

Watershed areas were delineated based on culvert locations from both the FHWA FLH Damage Survey Report (DSR) for

FS198 MP 0.0 to 8.1, a USFS-provided “FR 198 Linear Features’ spreadsheet, and a Stantec field visit with staff (4/3/18).

Table 5. FS198 Culverts – Basin Characteristics

Basin Characteristic Units

MP

0.20

MP

0.25

MP

0.85

MP

1.10

MP

5.10

MP

5.60

MP

5.90

MP

6.40

MP

7.75

MP

8.10

Area mi2 0.003 0.032 0.004 0.093 0.016 0.006 0.044 0.084 0.088 0.100

Area (A) ac 2.0 20.2 2.4 59.6 10.5 3.7 28.4 53.9 56.3 64.1

Runoff Coefficient (c) unitless 0.37 0.21 0.27 0.20 0.23 0.32 0.32 0.30 0.34 0.35

Time of Concentration

(tc) minutes 6 54 16 119 34 12 25 46 36 47

Rainfall Intensity (i) (in/hr) 7.75 2.47 4.84 1.41 3.26 5.61 3.84 2.72 3.15 2.68

25-Year Flood Flow cfs 5.45 10.48 3.14 16.81 7.87 6.64 34.90 43.98 60.30 60.13

Hydraulics

Hydraulic analysis of proposed conditions for FS198 culverts was completed using the FHWA computer-based HY-8

Culvert Hydraulic Analysis Program. Program parameters include discharge (flow), tailwater (downstream cross section), roadway (overtopping), culvert (material and size), and site (invert and length) data. Discharge data includes the design flow calculated above. All parameters were estimated based upon the assumptions listed below as no survey information was available at the time of this report. When possible, USFS will gather culvert invert elevations and pipe cover to verify assumptions below. The HY-8 design file is attached for review.

• Culvert inverts were set at a relative location (100 ft) as no survey has been completed,

• Culvert slope was set at or just above 0.35%,

• Tailwater elevation was set at 1 foot above the downstream invert,

• Culvert sized to allow for a HW/D ratio of less than or equal to 1.5, and

• Road overtopping elevation adequate to accommodate 25-year storm event (provided HW/D ration < 1.5)

Based on discussions with FHWA and USFS, FS198 culverts will not be sized to provide AOP, but will simply be sized to meet Section 7.3.1 requirements of the FLH PDDM. As such, they will not be embedded and will not be sized based upon field-observed bankfull widths. Eight (8) culverts along FS198 are currently scheduled for replacement and hydraulic sizing was conducted for all these culverts. Two (2) additional culverts (MP 0.20 and MP 5.90) are scheduled for

‘cleaning’ at this time, and not replacement. However, hydraulic sizing was also done for these two culverts, should replacement be determined necessary during future field-assessments. A summary of the HY-8 analysis for the proposed condition during the 25-year flood is shown in Table 6 below.

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

Table 6. FS198 Culverts – Hydraulics

Culvert (MP) Length (ft) Existing Proposed HW/D

0.20 35 NA* 21" x 15" 1.22

0.25 35 28" x 20" 28" x 20" 1.07

0.85 35 13" x 17" 17" x 13" 1.19

1.10 35 24" 35" x 24" 1.27

5.10 55 28" x 24" 35” x 24" 0.65

5.60 35 13" x 17" 24" x 18" 0.99

5.90 35 NA* 42" x 29" 1.44

6.40 30 14" x 22" 49" x 33" 1.46

7.75 35 18” 57” x 38” 1.11

8.10 60 21" x 28" 57" x 38"** 1.29

*NA – existing sizes not available at the time of this report

**Culvert will be buried 6” based on surveyed cover concerns

Based on stated assumptions, each proposed culvert will adequately convey the 25-year flood flows per the design criteria of the FLH PDDM. FS198 culvert sizing completed using TR-55 (HydroCAD) methodology and submitted with the previous Hydraulics Documentation (70% plans – dated 2/19/2018) is attached for comparison. Basin area and hydraulics for the MP 5.10 culvert were updated based on information gathered during the field visit (4/3/18).

Bridge Abutment Rehabilitation, FS 199, Site B2

Hydrology

Based on the watershed area not meeting minimum size requirements (0.58 mi2 actual vs. 0.66 mi2 required), the USGS regional regression equation (Area 4) could not be used for bridge B2. Thus, the NRCS curve number / unit hydrograph method, as implemented by HydroCAD software, was utilized to determine a peak 100-year flood flow of 456 cfs to bridge

B2. HydroCAD inputs are shown in Table 7 below. CNs of 43, 65, 76, and 82 (woods/grass combination, fair condition) were used for HSG A, B, C, and D, respectively. The composite CN for the watershed is shown in the table below. Time of concentration was determined using the Lag/CN method, which is based on CN, hydraulic length, and average land slope. NOAA Atlas 14 precipitation data for the 100-year flood (7.10 inches) was used with a Type-II, 24-hour rainfall distribution for all calculations. A HydroCAD report for the B2 basin is attached for review.

The 100-year flood flow (not the 25-year flood flow) will be used to determine riprap sizing at the B2 bridge abutments.

Table 7. Bridge B2 Basin Characteristics

Basin Characteristic Units Value

Area Square Miles (mi2) 0.58

Area Acres (ac) 369.4

Composite CN Unitless 77

Time of Concentration (tc) Minutes 143

100-Year Flood Flow Cubic Feet per Second (cfs) 456

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

Hydraulics

Hydraulic analysis of the existing condition for bridge B2 was completed using the USACE Hydrologic Engineering Center computer-based River Analysis System software (HEC-RAS). Modeled cross sections were cut from a combination of in-field survey data and available WI LiDAR data. Estimated channel cross sections were used when survey data was unavailable. The modeled bridge opening was based on the original bridge plans (dated 03/01/2006) and in-field survey data. Based on the steep channel slope, a mixed flow regime (subcritical and supercritical) was used to calculate water surface elevations. Normal depth (channel slope) was used as the reach boundary condition for both upstream and downstream with values of 0.0168 and 0.0157, respectively. The HEC-RAS model is attached for review.

Riprap size was determined using FHWA HEC-23, Volume 2, Design Guideline 14 for the 100-year flood flows under existing conditions. The HEC-RAS analyses for both the upstream and downstream bridge face were examined and the more conservative sizing (upstream) is detailed below. Bridge B2 has a Froude Number of 0.77 (equation (V/(gy)1/2)), thus the Isbash relationship, shown below, was used to determine the median stone diameter (D50). The set-back ratio (SBR) for each abutment was determined to be less than 5. Values used in the Isbash relationship and riprap size are shown in

Table 8 below. A spreadsheet with both riprap sizing computations (upstream and downstream bridge face) is attached for review.

Table 8. Bridge B2 Riprap Sizing

Parameter Units Value

V ft/s 8.74

Ss unitless 2.65 g ft/s2 32.2 y ft 3.96

K unitless 1.02

D50 ft 1.47

D50 in 17.60

To account for the 100-year flood flows, the D50 for bridge B2 needs to be at least 1.47 feet (17.6 inches). This D50 most closely corresponds to Class 5 riprap or ‘Heavy Riprap’ per WISDOT specifications (606.2.1).

Reference: WI ERFO FS 2016-1(2), Various Locations – Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\pdh_memo_99%\hydraulicdocumentation_041618.docx

If you have any questions about the results of the Hydraulic Documentation please let me know using the contact information below.

Stantec Consulting Services Inc.

Rob Monk

Phone: (651) 604-4713 Fax: (651) 636-1311 rob.monk@stantec.com

Attachment: Regression Spreadsheet (S10) HydroCAD Output (S11, B2) Riprap Sizing Spreadsheet (B2) TR-55 Sizing Documentation (FS198) HY-8 Model Files (S10, S11, FS198) HEC-RAS Model Files (B2)

c. Michelle Garrigan, Stantec Aaron Volkening, Stantec Theresa Maahs-Henderson, Stantec

WI ERFO FS 2016-1(2), FS205, Site S10 Regional Regression Equation (WI, Area 2) Proj. No. 193804093 2/19/2018

A 2.02 Area (square miles) SP 2.88 Lowered to maximum allowable from 48.355 in/hr (USGS StreamStats) SP 42.2 Manually calculated from WI LiDAR (ft/mi)

Q2 52 13 0.884 -0.630 0.382 Q5 87 15.4 0.900 -0.682 0.486

Q10 110 16.3 0.910 -0.710 0.541 Q25 143 17.3 0.922 -0.740 0.600 Q50 167 17.9 0.929 -0.758 0.636

Q100 190 18.3 0.936 -0.775 0.669

Type II 24-hr 2yr Rainfall=2.82"Hydrology_S11-B2 Printed 2/19/2018Prepared by Stantec Consulting Ltd.

Page 1HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment S11:

Runoff = 11.35 cfs @ 15.11 hrs, Volume= 6.565 af, Depth= 0.33"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 2yr Rainfall=2.82"

Area (ac) CN Description

14.360 98 Water Surface, 0% imp, HSG D

93.370 82 Woods/grass comb., Fair, HSG D

131.670 43 Woods/grass comb., Fair, HSG A

239.400 62 Weighted Average

239.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs)

200.1 5,680 0.0110 0.47 Lag/CN Method, Type II 24-hr 5yr Rainfall=3.55"Hydrology_S11-B2

Page 2HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment S11:

Runoff = 25.27 cfs @ 14.89 hrs, Volume= 12.749 af, Depth= 0.64"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 5yr Rainfall=3.55"

Area (ac) CN Description

14.360 98 Water Surface, 0% imp, HSG D

93.370 82 Woods/grass comb., Fair, HSG D

131.670 43 Woods/grass comb., Fair, HSG A

239.400 62 Weighted Average

239.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 10yr Rainfall=4.22"Hydrology_S11-B2

Page 3HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment S11:

Runoff = 41.78 cfs @ 14.68 hrs, Volume= 19.604 af, Depth= 0.98"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=4.22"

Area (ac) CN Description

14.360 98 Water Surface, 0% imp, HSG D

93.370 82 Woods/grass comb., Fair, HSG D

131.670 43 Woods/grass comb., Fair, HSG A

239.400 62 Weighted Average

239.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 25yr Rainfall=5.26"Hydrology_S11-B2

Page 4HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment S11:

Runoff = 73.00 cfs @ 14.46 hrs, Volume= 31.947 af, Depth= 1.60"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 25yr Rainfall=5.26"

Area (ac) CN Description

14.360 98 Water Surface, 0% imp, HSG D

93.370 82 Woods/grass comb., Fair, HSG D

131.670 43 Woods/grass comb., Fair, HSG A

239.400 62 Weighted Average

239.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 50yr Rainfall=6.14"Hydrology_S11-B2

Page 5HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment S11:

Runoff = 103.65 cfs @ 14.46 hrs, Volume= 43.627 af, Depth= 2.19"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 50yr Rainfall=6.14"

Area (ac) CN Description

14.360 98 Water Surface, 0% imp, HSG D

93.370 82 Woods/grass comb., Fair, HSG D

131.670 43 Woods/grass comb., Fair, HSG A

239.400 62 Weighted Average

239.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 100yr Rainfall=7.10"Hydrology_S11-B2

Page 6HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment S11:

Runoff = 140.02 cfs @ 14.45 hrs, Volume= 57.351 af, Depth= 2.87"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=7.10"

Area (ac) CN Description

14.360 98 Water Surface, 0% imp, HSG D

93.370 82 Woods/grass comb., Fair, HSG D

131.670 43 Woods/grass comb., Fair, HSG A

239.400 62 Weighted Average

239.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 2yr Rainfall=2.82"Hydrology_S11-B2

Page 1HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment B2:

Runoff = 89.93 cfs @ 13.84 hrs, Volume= 29.190 af, Depth= 0.95"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 2yr Rainfall=2.82"

Area (ac) CN Description

22.160 43 Woods/grass comb., Fair, HSG A

59.110 65 Woods/grass comb., Fair, HSG B

22.160 76 Woods/grass comb., Fair, HSG C

265.970 82 Woods/grass comb., Fair, HSG D

369.400 77 Weighted Average

369.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

143.2 6,900 0.0130 0.80 Lag/CN Method, Type II 24-hr 5yr Rainfall=3.55"Hydrology_S11-B2

Page 2HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment B2:

Runoff = 144.82 cfs @ 13.84 hrs, Volume= 45.182 af, Depth= 1.47"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 5yr Rainfall=3.55"

Area (ac) CN Description

22.160 43 Woods/grass comb., Fair, HSG A

59.110 65 Woods/grass comb., Fair, HSG B

22.160 76 Woods/grass comb., Fair, HSG C

265.970 82 Woods/grass comb., Fair, HSG D

369.400 77 Weighted Average

369.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 10yr Rainfall=4.22"Hydrology_S11-B2

Page 3HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment B2:

Runoff = 199.41 cfs @ 13.84 hrs, Volume= 61.120 af, Depth= 1.99"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 10yr Rainfall=4.22"

Area (ac) CN Description

22.160 43 Woods/grass comb., Fair, HSG A

59.110 65 Woods/grass comb., Fair, HSG B

22.160 76 Woods/grass comb., Fair, HSG C

265.970 82 Woods/grass comb., Fair, HSG D

369.400 77 Weighted Average

369.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 25yr Rainfall=5.26"Hydrology_S11-B2

Page 4HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment B2:

Runoff = 289.05 cfs @ 13.84 hrs, Volume= 87.485 af, Depth= 2.84"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 25yr Rainfall=5.26"

Area (ac) CN Description

22.160 43 Woods/grass comb., Fair, HSG A

59.110 65 Woods/grass comb., Fair, HSG B

22.160 76 Woods/grass comb., Fair, HSG C

265.970 82 Woods/grass comb., Fair, HSG D

369.400 77 Weighted Average

369.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 50yr Rainfall=6.14"Hydrology_S11-B2

Page 5HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment B2:

Runoff = 367.77 cfs @ 13.83 hrs, Volume= 110.870 af, Depth= 3.60"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 50yr Rainfall=6.14"

Area (ac) CN Description

22.160 43 Woods/grass comb., Fair, HSG A

59.110 65 Woods/grass comb., Fair, HSG B

22.160 76 Woods/grass comb., Fair, HSG C

265.970 82 Woods/grass comb., Fair, HSG D

369.400 77 Weighted Average

369.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

Type II 24-hr 100yr Rainfall=7.10"Hydrology_S11-B2

Page 6HydroCAD® 10.00-15 s/n 00429 © 2015 HydroCAD Software Solutions LLC

Summary for Subcatchment B2:

Runoff = 456.28 cfs @ 13.69 hrs, Volume= 137.164 af, Depth= 4.46"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.01 hrs Type II 24-hr 100yr Rainfall=7.10"

Area (ac) CN Description

22.160 43 Woods/grass comb., Fair, HSG A

59.110 65 Woods/grass comb., Fair, HSG B

22.160 76 Woods/grass comb., Fair, HSG C

265.970 82 Woods/grass comb., Fair, HSG D

369.400 77 Weighted Average

369.400 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description

WI ERFO FS 2016-1(2), FS199, Site B2 Rock Riprap at Bridge Abutments FHWA HEC-23, Vol. 2, DG 14 Proj. No. 193804093 3/16/2018

US Froude # 0.77 (V/(gy)^0.5) ft in D50 1.47 17.60

V 8.74 (HEC-RAS)

Ss 2.65 (NRCS - limestone, dolomite) g 32.2 y 3.96 (HEC-RAS) K 1.02 (vertical wall abutment)

DS Froude # 1.14 (V/(gy)^0.5) ft in D50 1.46 17.56

V 11.92 (HEC-RAS)

Ss 2.65 (NRCS - limestone, dolomite) g 32.2 y 3.37 (HEC-RAS) K 0.69 (vertical wall abutment)

February 19, 2018

Reference: WI ERFO FS 2016-1(2), Various Locations – Preliminary Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\phd_memo_021418\prelimhyddoc_021918.docx

Small Culvert Replacement/Cleaning, FS 198, Various Sites – 9 Culverts

Hydrology

Based on the watershed areas not meeting minimum size requirements (≤0.10 mi2 actual vs. 0.56 mi2 required), the

USGS regional regression equation (Area 2) could not be used for FS198 culverts. Thus, the NRCS curve number / unit hydrograph method, as implemented by HydroCAD software, was utilized to determine peak 25-year flood flows at each culvert. Variable HydroCAD inputs are shown in Table 5 below. CNs of 30, 55, 70 and 77 (woods/grass combination, good condition) were used for HSG A, B, C, and D, respectively. A composite CN for each watershed is shown in the table below. Time of concentration was determined using the Lag/CN method, which is based on CN, hydraulic length, and average land slope. NOAA Atlas 14 precipitation data for the 25-year flood (5.26 inches) was used with a Type-II, 24-hour rainfall distribution for all calculations. A HydroCAD report for the each FS198 basin is attached for review.

Watershed areas were delineated based on culvert locations from both the FHWA FLH Damage Survey Report (DSR) for

FS198 MP 0.0 to 8.1 and a USFS-provided “FR 198 Linear Features’ spreadsheet.

Table 5. FS198 Culverts – Basin Characteristics

Basin Characteristic Units

MP

0.20

MP

0.25

MP

0.85

MP

1.10

MP

5.10

MP

5.60

MP

5.90

MP

6.40

MP

8.10

Area mi2 0.003 0.032 0.004 0.093 0.094 0.006 0.044 0.084 0.100

Area ac 2.0 20.2 2.4 59.6 60.0 3.7 28.4 53.9 64.1

Composite CN unitless 75 74 77 67 68 70 69 65 73

Time of Concentration (tc) minutes 6.1 54 16 119 42 12 25 46 47

25-Year Flood Flow cfs 9.5 29.7 8.6 35.5 82.7 11.8 58.3 59.7 99.7

Hydraulics

Hydraulic analysis of proposed conditions for FS198 culverts was completed using the FHWA computer-based HY-8

Culvert Hydraulic Analysis Program. Program parameters include discharge (flow), tailwater (downstream cross section), roadway (overtopping), culvert (material and size), and site (invert and length) data. Discharge data includes the design flow calculated above. All parameters were estimated based upon the assumptions listed below as no survey information was available at the time of this report. When possible, USFS will gather culvert invert elevations and pipe covert to verify assumptions below. The HY-8 design file is attached for review.

• Culvert inverts were set at a relative location (100 ft) as no survey has been completed,

• Culvert slope was set at or just above 0.35%,

• Tailwater elevation was set at 1 foot above the downstream invert,

• Culvert sized to allow for a HW/D ratio of less than or equal to 1.5, and

• Road overtopping elevation adequate to accommodate 25-year storm event (provided HW/D ration < 1.5)

Based on discussions with FHWA and USFS, FS198 culverts will not be sized to provide AOP, but will simply be sized to meet Section 7.3.1 requirements of the FLH PDDM. As such, they will not be embedded and will not be sized based upon field-observed bankfull widths. Eight (8) culverts along FS198 are currently scheduled for replacement. Hydraulic sizing was conducted for all these culverts except MP 7.75, which has just been identified for replacement. Two (2) additional culverts (MP 0.20 and MP 5.90) are scheduled for ‘cleaning’ at this time, and not replacement. However, hydraulic sizing was also done for these two culverts, should replacement be determined necessary during future field-assessments. A summary of the HY-8 analysis for the preliminary proposed condition during the 25-year flood is shown in Table 6 below.

February 19, 2018

Reference: WI ERFO FS 2016-1(2), Various Locations – Preliminary Hydraulics Documentation mr u:\193804093\design\hydrology_hydraulics\phd_memo_021418\prelimhyddoc_021918.docx

Table 6. FS198 Culverts – Preliminary Hydraulics

Culvert (MP) Length (ft) Existing Proposed HW/D

0.20 35 NA* 24" x 18" 1.31

0.25 35 28" x 20" 42" x 29" 1.10

0.85 35 13" x 17" 24" x 18" 1.19

1.10 35 24" 42" x 29" 1.27

5.10 55 28" x 24" 57" x 38" 1.47

5.60 35 13" x 17" 28" x 20" 1.18

5.90 35 NA* 49" x 33" 1.44

6.40 30 14" x 22" 49" x 33" 1.46

7.75 35 18” TBD TBD

8.10 60 21" x 28" 64" x 43" 1.29

*NA – existing sizes not available at the time of this report

The analysis shows that each existing culvert will not have enough capacity to convey the 25-year flood flows per the design criteria of the FLH PDDM. Based on stated assumptions, each proposed culvert will adequately convey the 25-year flood flows per the design criteria of the FLH PDDM.

Bridge Abutment Rehabilitation, FS 199, Site B2

Hydrology

Based on the watershed area not meeting minimum size requirements (0.58 mi2 actual vs. 0.66 mi2 required), the USGS regional regression equation (Area 4) could not be used for bridge B2. Thus, the NRCS curve number / unit hydrograph method, as implemented by HydroCAD software, was utilized to determine a peak 100-year flood flow of 456 cfs to bridge

S11. HydroCAD inputs are shown in Table 7 below. CNs of 43, 65, 76, and 82 (woods/grass combination, fair condition) were used for HSG A, B, C, and D, respectively. The composite CN for the watershed is shown in the table below. Time of concentration was determined using the Lag/CN method, which is based on CN, hydraulic length, and average land slope. NOAA Atlas 14 precipitation data for the 100-year flood (7.10 inches) was used with a Type-II, 24-hour rainfall distribution for all calculations. A HydroCAD report for the B2 basin is attached for review.

The 100-year flood flow (not the 25-year flood flow) will be used to determine riprap sizing at the B2 bridge abutments.

Table 7. Bridge B2 Basin Characteristics

Basin Characteristic Units Value

Area Square Miles (mi2) 0.58

Area Acres (ac) 369.4

Composite CN Unitless 77

Time of Concentration (tc) Minutes 143

100-Year Flood Flow Cubic Feet per Second (cfs) 456

Hydraulics

Hydraulic analysis of existing and proposed conditions for bridge B2 was completed using the FHWA computer-based

HY-8 Culvert Hydraulic Analysis Program. Program parameters include discharge (flow), tailwater (downstream cross