WV NP NERI 107(3)_HYD_Memo_adv.pdf

FHWA: S.Jurek:3549:JS:

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Form FHWA-201 U.S. DEPARTMENT OF TRANSPORTATION (Rev. 11-87) FEDERAL HIGHWAY ADMINISTRATION

MINUTE - MEMO

Use this form in lieu of transmittal slips within Dept. of Trans. when message comment is to be retained as file material. Do not prepare carbons. Not to be used in lieu of Form FHWA-121 for informal correspondence.

SUBJECT: WV NP NERI 107(3) Storm Drain System Memo

TO MESSAGE/COMMENT FROM/DATE

Yanina Kirtley Project Manager

Shoukat Nawaz Highway Design Manager

We have completed the preliminary storm drain system analysis for Cunard River Access Road (NPS Route 107), Stations 112+00-117+00, along the proposed soldier pile retaining wall. The project is located in Fayette West Virginia, within the New River Gorge National Park and Preserve.

The proposed storm drain system is designed to meet the Project Development and Design Manual (PDDM) criteria and guidance:

1. The design flow was analyzed for a 10-year design event.

2. Minimum pipe size and slope shall be such as will provide for a minimum velocity of 3 feet per second at the design flow rate to prevent deposition of sediment. Storm sewer slopes that produce velocities in excess of 10 feet per second when flowing full should be avoided. When full flow creates higher velocities the use of drop structures should be considered.

3. The limit of spread for a low standard road should be limited to half of one travel lane for gutter flow, both on grade and in roadway sags. The limit of spread for this road is 5 feet into the road. Including the width of the gutter, the total allowable spread is 6.5 feet.

4. The minimum size for storm drainpipe is 18”. However, short laterals less than 100ft in length a 12-in size may be used if required by limited cover space.

5. The minimum recommended capture efficiency for on-grade inlets is 70%.

6. Inlets located in a sag or sump point, should be designed for a 50% clogging factor.

7. Where a grate inlet is used at the low point of a sag vertical curve it is desirable to install a grate with twice the opening of the design requirement because of the vortices and the tendency to collect trash at these low points.

8. Minimum cover between the top of the pipe and the bottom of the pavement structure should be equal or greater than 3ft. Under no case should the cover of the pipe be less than 1 ft.

9. In storm drain sections where the hydraulic gradeline for the design flood must exceed the pipe soffit (i.e., the pipe flows under pressure), the hydraulic gradeline for the design flood will remain below the ground elevation at all inlets and access structures, and watertight gaskets should be specified for the pipe joints.

10. Water should not be carried across intersections and should not be allowed to overflow at driveway openings where the latter are on a descending grade from the gutter.

Samantha Jurek Hydraulic

THROUGH

Wendy Hiciano Hydraulics Team Leader

3/25/25

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Existing Conditions

Cunard Road has two failures sites within the project limits. There are four existing culverts near the site of the proposed soldier pile retaining wall: one 18”x44.4’ CMP at STA 112+20 that will remain undisturbed, two 18” CMP culverts that are within the proposed wall location at STA 113+90 and STA 115+30, respectively, and one 18”x42’ CMP after the proposed wall location at STA 116+85. The pipes are silted, and the outfalls are washed out. There is an existing V-shaped parallel ditch, 3ft wide.

Recommendations

A storm drain system consisting of two pipes and a gutter is proposed instead of a series of cross pipes due to the proposed soldier pile wall. The locations of the pipes through the wall would require much more complicated design and long term maintenance. Additionally, due to the sharply increasing slope of the existing terrain at the proposed pipe locations, storm drains with drop inlets will prevent an increased limit of disturbance for the project.

Hydrology (peak flow rates) was performed via Bentley Open Flow StormCAD software (ORD) using the Rational Method. The IDF curves were obtained from the NOAA Precipitation Frequency Data Server and imported into ORD. The drainage areas were delineated using georeferenced USGS quad maps within the software. Each drainage area contains a Catch Basin (CB) inlet. Table 1 shows the hydrology summary, and Table 5 shows the CB hydraulics summary.

Table 1: Drainage Area Hydrology Summary Hydrology Summary

Label Catch Basin

Station of CB (ft)

Area (ac)

Time of Concentration

(hours)

Runoff Coefficient

( C )

Catchment Intensity

Q10 (cfs)

DR-01 CB-01 113+03 0.766 0.26 0.207 3.874 0.62

DR-02 CB-02 116+55 9.623 0.28 0.213 3.770 7.78

Hydraulic design was performed via Bentley Open Flow StormCAD software (ORD) (2022 Release 3) using the HEC-22 (Urban Drainage Design Manual) headloss method, third edition.

Each pipe should have inlet 4D and a free end section (FES). The plan view for the system is shown in Attachment 2 and the profiles for the pipes are shown in Attachments 3 and 4. Table 2 shows the storm drain pipe summary, Table 3 shows the pipe summary, and Table 4 shows the summary of the inlet and outfalls.

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Table 2: Pipe and Gutter Hydraulics Summary Link Summary

Label Station (ft)

Q10 Flow (cfs)

Velocity (ft/s)

HGL In (ft)

HGL Out (ft)

Depth In (ft)

Depth Out (ft)

Pipe-01 113+03 0.43 4.09 1,110.42 1,109.65 0.22 0.15 Pipe-02 116+55 5.22 9.61 1,102.41 1,101.04 0.81 0.50

Gutter-01 113+03

116+55

0.19 (N/A) (N/A) (N/A) 0.21 0.17

Table 3: Storm Drain Pipe Summary

Pipe Summary

Label Station Diameter

(in) Length

(ft) Slope Invert

Start Invert Stop Material

(ft) (%) (ft) (ft)

Pipe-01 113+03 24 38 2% 1,110.20 1,109.50 HDPE

Pipe-02 116+55 24 44 2% 1,101.60 1,100.54 HDPE

Table 4: Inlet and Outlet Summary

Node Summary

Label Q10 Flow (Total In)

(cfs)

Q10 Flow (Total Out)

(cfs)

Elevation (Ground)

(ft)

Elevation

(RIM)

(ft)

Elevation (Invert)

(ft)

EGL In (ft)

EGL

Out (ft)

CB-01 0.43 0.43 1,113.79 1,113.79 1,110.54 1,110.54 1,110.52

FES-01 (N/A) 0.43 1,111.76 (N/A) 1109.5 1,109.65 1,109.65

CB-02 5.22 5.22 1,104.80 1,104.80 1,101.60 1,102.83 1,102.77

FES-02 (N/A) 2.64 1,102.80 (N/A) 1100.54 1,101.04 1,101.04

Table 5: Catch Basin Hydraulics Catch Basin Inlet Summary

Label Station (ft) Flow

(Captured) (cfs)

Flow (Total Bypassed)

(cfs)

Depth (Gutter)

(in)

Spread / Top Width

(ft)

CB-01 113+03 0.43 0.19 0.407 3.078

CB-02 116+55 5.22 2.74 2.014 3.882

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The recommended inlet type is Type 4D. A modified Type 4D inlet is also recommended for CB-02. All inlets will be Type 4D, as shown in Attachment 5. The inlet summary is shown in table 6.

Table 6: Inlet Summary

We also recommend riprap at each outfall. The scour countermeasures were checked using the Riprap Analysis Hydraulic Toolbox V5.2, which is based on HEC-14 (Hydraulic Design of Energy Dissipators for Culverts and Channels, Third Edition). The standard riprap detail (E251-

01) will provide sufficient outlet protection for both pipes. Table 7 shows a summary of the riprap aprons.

Table 7: Scour Countermeasures – Riprap Summary Riprap Summary

Label Culvert Size (in)

Riprap Class D50 (in) Apron

Length (ft)

Width at End of

Apron (ft)

Apron Depth (ft)

Pipe-01 24 2 9 8 6.5 1.5 Pipe-02 24 2 9 8 6.5 1.5

To assist Highway Design determining the appropriate lining for the parallel ditch, HYD conducted a stability analysis using the Channel Analysis Hydraulic Toolbox (V5.2), based on HEC-15 (Design of Roadside Channels with Flexible Linings, Third Edition). Based on our analysis results, considering a slope of 6.6% and a maximum Q10 of 13.8cfs, we recommend an asphalt paved ditch as seen in EFLHD Detail E608-A. The larger ditch geometry will accommodate the spread of the flow. Please see attachment 8 for calculation details.

Please let us know should you have any questions.

Inlet Summary

Label Type of inlet Depth, H (ft) On-grade vs Sag % Clogging

CB-01 4D 2.92 On-grade N/A

CB-02 Modified 4D 3.20 On-grade N/A

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Attachments:

• Attachment 1 – Storm Drain System Plan View

• Attachment 2 – Pipe-01 – Station 113+03 Profile View

• Attachment 3 – Pipe-02 – Station 116+55 Profile View

• Attachment 4 – Inlet 4D

• Attachment 5 – Paved Asphalt Waterway

• Attachment 6 – Calculation Detailed Summary

• Attachment 7 – Gutter Hydraulics

STA 116+55

Pipe-02

STA 113+03

Pipe-01

(Detail E251-01)

Riprap Apron at Outfall

Free End Section

Inlet 4D (Detail E604-02)

24" x 38' Circular HDPE

(Detail E251-01)

Riprap Apron at Outfall

Free End Section

(Detail E604-02A)

Modified Inlet 4D

24" x 44' Circular HDPE

Storm Drain System Plan View

Attachment 1

WV NP NERI 107(3) HYD Memo

-20 -10 0 10 20

1,100 1,100

1,110 1,110

1,120 1,120

1,130 1,130

Invert 1110.20' Invert 1109.50'

Slope 2%

38' Length

24" Round HDPE

Pipe-01

Inlet 4D

CB-01

Elev. 1113.79'

Inlet Ground

Free End Section

FES-01

1110.42'

HGL In

1109.65'

HGL Out

Attachment 2: Pipe-01

Profile View

STA 113+03

30 40

-30 -20 -10 0 10 20 30 40

1,090 1,090

1,100 1,100

1,110 1,110

1,120 1,120

1,130 1,130

Modified Inlet 4D

CB-02

Invert 1101.60' Invert 1100.54'

Free End Section

FES-02

Elev. 1104.80'

Inlet Ground

44' Length

24" Round HDPE

Pipe-02

Slope 2%

1101.04'

HGL Out

1102.41'

HGL In

Attachment 3: Pipe-02

Profile View

STA 116+55

1:6.1

3 -1.6% -1.6% -2.3%

Calculation Detailed Summary Element Details

110ID Notes Base AnalysisLabel

Hydraulic Summary

Backwater AnalysisFlow Profile Method Actual

Uniform Flow Velocity

Average Velocity Method

5Number of Flow Profile Steps ft0.00Minimum Structure Headloss ft0.00Hydraulic Grade Convergence Test hours0.083Minimum Time of

Concentration

Inlets

FalseNeglect Side Flow? Grate and Curb

Active Components for Combination Inlets In Sag

FalseNeglect Gutter Cross Slope For Side Flow?

Grate and Curb

Active Components for Combination Inlets on Grade

HEC-22 Energy Losses (Second Edition) ft0.50Elevations Considered Equal Within 1.000Depressed Unsubmerged

Factor

TrueConsider Non-Piped Plunging Flow?

0.950Half Bench Submerged Factor

1.000Flat Submerged Factor 0.150Half Bench Unsubmerged Factor

1.000Flat Unsubmerged Factor 0.750Full Bench Submerged Factor 1.000Depressed Submerged Factor 0.070Full Bench Unsubmerged

Factor

Headloss (AASHTO)

0.350Expansion, Ke 0.500Shaping Adjustment, Cs 0.250Contraction, Kc 1.300Non-Piped Flow Adjustment, Cn

Bend Angle vs. Bend Loss Curve

Bend Loss Coefficient, KbBend Angle (degrees)

0.0000.00 0.19015.00 0.35030.00 0.47045.00 0.56060.00 0.64075.00 0.70090.00

Gravity Hydraulics

Pipe with Maximum QV

Governing Upstream Pipe Selection Method

Page 1 of 376 Watertown Road, Suite 2D Thomaston, CT

06787 USA +1-203-755-1666

3/26/2025

Drainage and Utilities [10.12.02.04]

Bentley Systems, Inc. Haestad Methods Solution Center

03-WV_NP_NERI_107(3)_HYD_70%Updates -- Design IntlFt.stsw

Catchment Summary

Catchment CA (acres)

Runoff Coefficient (Rational)

Time of Concentration (hours)

Area (User Defined) (acres)

Label

0.1580.2070.2600.766DR-01

2.0470.2130.2839.623DR-02

Catchment Rational Flow (cfs)

Catchment Intensity (in/h)

0.623.874 7.783.770

Conduit Summary

Flow (cfs)

Subnetwork OutfallBranch IDSection TypeLabel

0.43FES-012CirclePipe-01 5.22FES-021CirclePipe-02

Depth (Out) (ft)

Depth (In) (ft)

Hydraulic Grade Line (Out) (ft)

Hydraulic Grade Line (In) (ft)

Velocity (ft/s)

0.150.221,109.651,110.424.09 0.500.811,101.041,102.419.61

Node Summary

Flow (Total Out) (cfs)

Flow (Total In) (cfs)

Subnetwork OutfallElement TypeLabel

0.430.43FES-01Catch BasinCB-01 5.225.22FES-02Catch BasinCB-02 5.21(N/A)(N/A)HeadwallFES-02 0.43(N/A)(N/A)HeadwallFES-01

Energy Grade Line (Out) (ft)

Energy Grade Line (In) (ft)

Elevation (Invert) (ft)

Elevation (Ground) (ft)

1,110.521,110.541,110.201,113.79 1,102.771,102.831,101.601,104.80 1,101.041,101.04(N/A)1,102.80 1,109.651,109.65(N/A)1,111.76

Inlet Summary

Flow (Captured) (cfs)

Catalog InletCatalog Inlet TypeInlet TypeLabel

0.43Inlet Generic DitchDitchDitchCB-01 5.22Inlet Generic DitchDitchDitchCB-02

Spread / Top Width (ft)

Depth (Gutter) (in)

Capture Efficiency (Calculated)

Bypass TargetFlow (Total Bypassed) (cfs)

3.0780.40769.5CB-020.19

3.8822.01465.6(N/A)2.74

Pond Summary

Page 2 of 376 Watertown Road, Suite 2D Thomaston, CT

06787 USA +1-203-755-1666

3/26/2025

Drainage and Utilities [10.12.02.04]

Bentley Systems, Inc. Haestad Methods Solution Center

Pond Summary

Flow (Total Out) (cfs)

Flow (Total In) (cfs)

Subnetwork OutfallElement TypeLabel

Volume (gal)

Hydraulic Grade (ft)

Page 3 of 376 Watertown Road, Suite 2D Thomaston, CT

06787 USA +1-203-755-1666

3/26/2025

Drainage and Utilities [10.12.02.04]

Bentley Systems, Inc. Haestad Methods Solution Center

Hydraulic Analysis Report

Project Data Project Title:

Designer:

Project Date: Wednesday, November 13, 2024

Project Units: U.S. Customary Units

Notes:

Channel Analysis: Channel Analysis Notes:

Input Parameters

Channel Type: Triangular

Side Slope 1 (Z1): 3.6000 ft/ft

Side Slope 2 (Z2): 3.6000 ft/ft

Longitudinal Slope: 6.6000 ft/ft

Manning's n: 0.0081

Flow 13.8000 cfs

Result Parameters

Depth 0.1976 ft

Area of Flow 0.1406 ft^2

Wetted Perimeter 1.4768 ft

Hydraulic Radius 0.0952 ft

Average Velocity 98.1491 ft/s

Top Width 1.4229 ft

Froude Number: 55.0239

Critical Depth 0.9819 ft

Critical Velocity 3.9760 ft/s

Critical Slope: 0.0013 ft/ft

Critical Top Width 7.07 ft

Calculated Max Shear Stress 81.3905 lb/ft^2

Calculated Avg Shear Stress 39.2106 lb/ft^2

Channel Lining Analysis: Channel Lining Design Analysis Notes:

Lining Input Parameters

Channel Lining Type: Riprap, Cobble, or Gravel

D50: 0.00 mm

Riprap Specific Weight: 165 lb/ft^3

Water Specific Weight: 62.4 lb/ft^3

Riprap Shape is Angular

Safety Factor: 1

Calculated Safety Factor: 1

Lining Results

Angle of Repose: 0 degrees

Relative Flow Depth: 9.7375e-312 ft

Manning's n method: Bathurst

Manning's n: 0

Channel Bottom Shear Results

V*: 0

Reynold's Number: 0

Shield's Parameter: 0

Shear stress on channel bottom: 0 lb/ft^2

Permissible shear stress for channel bottom: 0 lb/ft^2

Channel bottom is NOT stable

Stable D50: 0 mm

Channel Side Shear Results

K1: 0

K2: 0

Kb: 0

Shear stress on side of channel: 0 lb/ft^2

Permissible shear stress for side of channel: 0 lb/ft^2

Stable Side D50: 0 lb/ft^2

Side of channel is NOT stable

Channel Lining Stability Results 2

The channel is NOT stable

Channel Summary

Name of Selected Channel: Channel Analysis

Selected Profile: FHWA Profile (read‐only)

Culvert Assessment Profiles

Culvert Assessment Profile Name: Standard (read‐only)

Maximum Excavation Depth: 20.00 ft

Maximum Shallow Cover: 4.00 ft

Maximum Small Pipe Size: 36.00 ft

Minimum Manned Entry Size: 48.00 in

Riprap Classes

Riprap Class Name:CLASS I

Riprap Class Order:1

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 304.80 mm

D85: 228.60 mm

D50: 165.10 mm

D15: 114.30 mm

Riprap Class Name:CLASS II

Riprap Class Order:2

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 457.20 mm

D85: 330.20 mm

D50: 241.30 mm

D15: 177.80 mm

Riprap Class Name:CLASS III

Riprap Class Order:3

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 609.60 mm

D85: 431.80 mm

D50: 317.50 mm

D15: 228.60 mm

Riprap Class Name:CLASS IV

Riprap Class Order:4

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 762.00 mm

D85: 533.40 mm

D50: 393.70 mm

D15: 266.70 mm

Riprap Class Name:CLASS V

Riprap Class Order:5

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 914.40 mm

D85: 647.70 mm

D50: 469.90 mm

D15: 330.20 mm

Riprap Class Name:CLASS VI

Riprap Class Order:6

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 1066.80 mm

D85: 762.00 mm

D50: 546.10 mm

D15: 381.00 mm

Riprap Class Name:CLASS VII

Riprap Class Order:7

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 1257.30 mm

D85: 889.00 mm

D50: 647.70 mm

D15: 444.50 mm

Riprap Class Name:CLASS VIII

Riprap Class Order:8

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 1524.00 mm

D85: 1079.50 mm

D50: 800.10 mm

D15: 558.80 mm

Riprap Class Name:CLASS IX

Riprap Class Order:9

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 1828.80 mm

D85: 1295.40 mm

D50: 965.20 mm

D15: 660.40 mm

Riprap Class Name:CLASS X

Riprap Class Order:10

The following values are an 'average' of the size fraction range for the selected riprap class.

D100: 2133.60 mm

D85: 1511.30 mm

D50: 1130.30 mm

D15: 787.40 mm