RO_100per_Final_Hydraulics_Report.pdf

I

Contents Section Page

1 Introduction ............................................................................................................................. 1-1

1.1 General ................................................................................................................................... 1-1

1.2 Project Location and Identification ........................................................................................ 1-1

2 Existing Site Conditions ............................................................................................................. 2-1

2.1 General ................................................................................................................................... 2-1

2.2 Bridge ..................................................................................................................................... 2-1

2.3 Kipapa Stream ........................................................................................................................ 2-1

2.4 Culverts .................................................................................................................................. 2-1

2.5 Roadside Ditches .................................................................................................................... 2-2

2.6 Floodplain .............................................................................................................................. 2-2

2.7 Wetlands/Waters of the United States ................................................................................. 2-2

2.8 Water Quality ......................................................................................................................... 2-2

2.9 Utility Lines ............................................................................................................................ 2-2

3 Design Criteria and Methodology .............................................................................................. 3-1

3.1 Applicable Drainage Criteria .................................................................................................. 3-1

3.2 General Design Criteria .......................................................................................................... 3-1

3.3 Hydrologic Design .................................................................................................................. 3-1

3.4 Hydraulic Analysis .................................................................................................................. 3-2

3.5 Criteria for Temporary Drainage Facilities ............................................................................. 3-3

3.6 Other Criteria and Methodology ........................................................................................... 3-3

3.7 Fish Passage ........................................................................................................................... 3-3

4 Hydrologic and Hydraulic Analyses ............................................................................................ 4-1

4.1 Hydrologic Analysis ................................................................................................................ 4-1

4.1.1 General...................................................................................................................... 4-1

4.1.2 USGS StreamStats ..................................................................................................... 4-1

4.1.3 Precipitation Data ..................................................................................................... 4-1

4.1.4 Hydrology for Bridge Deck Drainage......................................................................... 4-2

4.1.4.1 Proposed Conditions ................................................................................. 4-6

4.2 Hydraulic Analysis .................................................................................................................. 4-6

4.2.1 Existing Bridge ........................................................................................................... 4-6

4.2.2 Proposed Bridge Rehabilitation ................................................................................ 4-6

4.2.3 Roadside Ditches ....................................................................................................... 4-6

4.2.4 Bridge Deck Drainage Collection System .................................................................. 4-8

4.2.5 Bridge Scour .............................................................................................................. 4-8

5 Summary .................................................................................................................................. 5-1

6 References ............................................................................................................................... 6-1

CONTENTS

II

Appendices

A Hydrology B Hydraulics C Scour Analysis D Photographs E HDS Addendum

Figures

1-1 Vicinity Map (Google earth) ................................................................................................................. 1-1 2-1 Delineated Non-Wetland Waters ........................................................................................................ 2-3 4-1 Drainage Map Existing Conditions ....................................................................................................... 4-3 4-2 Drainage Map Proposed Conditions .................................................................................................... 4-5 4-3 Roosevelt Bridge 50-year Water Surface Profiles ................................................................................ 4-7 4-4 Roosevelt Bridge Pier Locations ........................................................................................................... 4-9 4-5 Upstream Scour Diagram for Roosevelt Bridge – 100-year Flood Event ............................................ 4-17 4-6 Downstream Scour Diagram for Roosevelt Bridge – 100-year Flood Event ....................................... 4-18 4-7 Upstream Scour Diagram for Roosevelt Bridge – 200-year Flood Event ............................................ 4-19 4-8 Downstream Scour Diagram for Roosevelt Bridge – 200-year Flood Event ....................................... 4-20

Tables

3-1 Recurrence Intervals for Hydrologic Design ........................................................................................ 3-1 4-1 Summary of Peak Flows for Kipapa Stream at Roosevelt Bridge from StreamStats ........................... 4-1 4-2 Summary of 25 Year Peak Flows, Existing Conditions ......................................................................... 4-2 4-3 Summary of 25 Year Peak Flows, Proposed Conditions ...................................................................... 4-4 4-4 Sediment Regime Parameters – 100-Year Event ................................................................................. 4-9 4-5 Sediment Regime Parameters – 200-Year Event ................................................................................. 4-9 4-6 Summary of Contraction Scour Parameters and Results – 100-Year Event ...................................... 4-10 4-7 Summary of Contraction Scour Parameters and Results – 200-Year Event ...................................... 4-10 4-8 Summary of Pier Scour Parameters and Results – 100-Year Event ................................................... 4-13 4-9 Summary of Pier Scour Parameters and Results – 200-Year Event ................................................... 4-14 4-10 Summary of Roosevelt Bridge Scour Depth and Elevation Results – 100-Year Event ....................... 4-15 4-11 Summary of Roosevelt Bridge Scour Depth and Elevation Results – 200-Year Event ....................... 4-16

1-1

SECTION 1

Introduction

1.1 General

Central Federal Lands Highway Division (CFLHD) is working with the Hawaii Department of Transportation (HDOT) to provide bridge replacements for multiple bridges throughout the Hawaiian Islands. This report presents the results of a site reconnaissance and final drainage analyses performed for the Roosevelt Bridge site located in the central region of the island of Oahu in the state of Hawai’i. This report includes a final hydraulic analyses and design for the rehabilitation of the existing bridge.

1.2 Project Location and Identification

The Roosevelt Bridge spans Kipapa Stream at MP 14.4. Roosevelt Bridge is located along Kamehameha Highway, Route 99 on the island of Oahu in the state of Hawai’i. Kamehameha Highway is functionally classified as an urban principal arterial roadway on the National Highway System. Based on the North American Datum of 1983 (NAD 83), Roosevelt Bridge is located at 21°25’38”N latitude and 158°0’43”W longitude. See Figure 1-1 - Vicinity Map (Reference 1).

Figure 1-1 Vicinity Map (Google earth)

2-1

SECTION 2

Existing Site Conditions

2.1 General

A site investigation of Roosevelt Bridge was conducted on January 7th, 2014 by CFLHD, HDOT, CH2M HILL, ParEn (Hydraulics), Hirata (Geotechnical), and KSF (Structural). The bridge is located on a two-lane asphalt paved road with 11-foot lanes and 4-foot shoulders. The roadway is maintained by the HDOT and is located in the HDOT right-of-way (ROW). The roadway is generally crowned and runoff from the bridge deck currently drains to 4-inch scuppers along the curbs and discharge into the gulch below.

2.2 Bridge

The existing Roosevelt Bridge was constructed in 1933. The existing bridge is a 2 lane bridge with 16 spans for a total length of about 484 feet. The width is about 30 feet face of rail to face of rail with an 11-foot wide traffic lane and 4-foot shoulder in each direction. The total width of the bridge measured from outside face of rail is approximately 34 feet. The superstructure consists of a waffle grid of reinforced concrete tee beams and girders with a concrete deck.

The bridge is founded on shallow square pier footings resting on erodible material consisting of clayey silt or sandy silt. On the north abutment end, two piers and footings are buried under the fill slope. Whereas, on the south abutment end, three piers and footings are buried under the fill slope. Two low flow guide walls transversely connect a pair of piers on each side of the stream.

The bridge is located within Zone D, areas where there are possible but undetermined flood hazards. The existing bridge opening is more than adequate to pass the 100-year and 500-year peak discharge rates with 2 feet minimum freeboard. There have been no reports of overtopping at this bridge site. See Appendix D for existing bridge photographs.

2.3 Kipapa Stream

Kipapa Stream at Roosevelt Bridge is a small, intermittent stream that drains approximately 7,360 acres (11.5 square miles) of the western slopes of the Koolau mountain range and a portion of central Oahu. The stream drains agricultural lands, military lands and a portion of the Mililani residential development within the lower watershed area. The upper watershed area primarily consists of undeveloped forested lands. Silt, sand, gravel, cobbles and large boulders were observed along the stream bed during the field investigations.

Kipapa Stream has a narrow floodplain, is probably incised and has semi-alluvial channel boundaries. No natural levees were observed during the site investigation. Based on the aerial photograph in Google earth, the stream may be considered sinuous in the vicinity upstream and downstream of Roosevelt Bridge. The stream does not appear to be braided and anabranched.

Field observations indicate that filling of the floodplain may have occurred along the right overbank area (looking downstream) upstream of the bridge. The relatively steep embankment along Kipapa Stream and generally constant slope along the right overbank area suggest that the landowner filled the floodplain.

Erosion was observed along a portion of the embankment immediately upstream of the bridge, including the area in the vicinity of the concrete guide walls and piers adjacent to the stream. See photographs in Appendix D.

2.4 Culverts

There are no culverts within the project limits.

2 EXISTING SITE CONDITIONS

2-2

2.5 Roadside Ditches

There are existing ditches located within the project area. Roadside ditches drain runoff at the south approach to the bridge. A drainage ditch is located at the north approach to the bridge on the north side of a private driveway. No adjustments will be required for the drainage ditch located at the north approach to the bridge. Adjustments will be required for the drainage ditch/gutter at the south approach to the bridge.

2.6 Floodplain

Roosevelt Bridge is not located within a FEMA-regulated floodplain according to the FEMA Flood Insurance Rate Map, Community Panel No. 15003C0236G dated January 19, 2011. The project is located within Zone D of the Special Flood Hazard Area.

2.7 Wetlands/Waters of the United States

No wetlands were identified in the survey area. A single non-tidal, non-wetland feature (Kipapa Stream) was delineated in the survey area (Reference 2). See Figure 2-1 Delineated Non-Wetland Waters in the vicinity of Roosevelt Bridge.

2.8 Water Quality

The project will not add more than 1.0 acre of new impervious surfaces. Therefore, no permanent storm water quality facilities are required for this project. Appropriate temporary erosion and sediment control BMPs will be required during construction.

2.9 Utility Lines

There are four existing conduits attached to the Roosevelt Bridge and existing overhead lines that cross the bridge. There is also an existing Board of Water Supply 12” waterline attached on the west side of the bridge. These utility lines will be relocated as required for the proposed rehabilitation work.

2-3

Figure 2-1 Delineated Non-Wetland Waters

3-1

SECTION 3

Design Criteria and Methodology

3.1 Applicable Drainage Criteria

Criteria and methods will be consistent with the HDOT Highways Division “Design Criteria for Highway Drainage”, dated October 2010 (Reference 3). For criteria and guidance not included in the HDOT manual, the guidance in the Federal Lands’ Project Development and Design Manual (PDDM) Chapter 7 (Reference 4) will be followed. The following sections are excerpts from the HDOT Manual, using only information that is applicable to the Roosevelt Bridge rehabilitation project. The last section, Other Criteria and Methodology, outlines applicable guidelines and criteria not found in the HDOT manual.

3.2 General Design Criteria

The following are general guidelines and policies for highway design projects.

Capacity of proposed facilities shall not be less than the capacity of the existing facilities

The condition of the existing drainage facilities within the project limits shall be coordinated with the appropriate maintenance personnel. If warranted, the existing facilities shall be repaired or replaced.

The proposed design shall take into consideration the accessibility of maintenance personnel to inspect and clean the facilities.

Utilities and conduits shall not be installed inside of the proposed drainage facilities, including bridges and culverts.

3.3 Hydrologic Design

Roosevelt Bridge is located on Kamehameha Highway, Route 99 at Mile Post 14.4. Kamehameha Highway is functionally classified as an urban principal arterial roadway and is a part of the National Highway System.

As such, the design recurrence interval selected in the analysis of existing and proposed drainage facilities shall be in accordance with the following:

Table 3-1 Recurrence Intervals for Hydrologic Design

RECURRENCE INTERVALS (yrs)

Functional Classification

Bridge/Culvert Crossing

Roadway (at grade)

Roadway (sump)

Principal Arterial 50 or Match Existing Capacity, whichever is greater (See Other Criteria)

25 25

The project site is not located within a mapped FEMA floodplain. Therefore, the design of the rehabilitated bridge is not required to comply with the National Flood Insurance Program’s regulations and requirements.

The bridge shall be analyzed for the 50 year storm event.

Ditches and channels designed to intercept and divert runoff from off-site shall be based on a recurrence interval used for roadway crossings.

For recurrence intervals used to determine scour potential at bridges, refer to applicable FHWA Hydraulic Engineering Circulars.

Point rainfall values shall be interpolated from the National Oceanic and Atmospheric Administration’s (NOAA) Precipitation Frequency Data Server website:

http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_hi.html.

http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_hi.html

3 DESIGN CRITERIA AND METHODOLOGY

3-2

The following hydrologic methods were selected to determine peak discharge for this project. Refer to the Roosevelt Bridge Hydraulic Recommendations Report (Reference 5) for a description of other hydrologic methods analyzed.

Rational Method (as needed for roadway runoff analysis) – The rational method shall be used to estimate peak flow rates for drainage areas up to 200 acres. This method is applicable at small culvert crossings, and can be exclusively used for on‐site roadway drainage. The minimum time of concentration shall be 10 minutes.

U.S. Geological Service (USGS) Regression Equations – This method is used to estimate peak discharge for medium and large watersheds. Statewide Regression Equations are applicable for culvert crossings and bridges and can be accessed from the following website: http://pubs.usgs.gov/sir/2010/5035/ (Reference 6). The USGS in cooperation with the HDOT has developed a web‐based interactive Geographic Information Systems (GIS) application that uses the Statewide Regression Equations for estimating peak discharge rates.

This web‐based application, StreamStats, (Reference 7) will be used to facilitate the estimation of peak discharge rates.

The 5 year peak discharge estimate has been included in this hydraulic report for consideration by the Contractor during their design of temporary drainage facilities.

3.4 Hydraulic Analysis

Bridge Crossings

• Bridges shall be designed with a minimum freeboard of two feet. Freeboard shall be defined as the vertical distance between the approach design water surface elevation and the low chord of the bridge.

• Bridge abutment face shall be set back from the main stream channel section to minimize potential abutment scour. Design smooth transition from the abutment to the upstream channel embankment.

• Bridges shall be designed for scour for the 100‐year recurrence interval.

• The minimum cross‐slope of the bridge deck shall be 1.5%.

• The minimum longitudinal slope along the bridge deck shall be 0.5%. Longitudinal slopes less than the minimum may be accepted in areas restricted by physical parameters.

• Runoff discharge directly into the stream channel shall be minimized.

• Water surface elevations and peak flow rates for the 50‐ and 100‐year storm events shall be shown in the Contract Plans.

Inlet Locations

• Inlets located on continuous slope shall be designed for a minimum of 70% catch and 30% by‐pass. The width of flow on the pavement surface shall not exceed 1/3 the width of the travel lane measured from the edge of pavement adjacent to the gutter or shoulder. For this project, the spread shall not exceed

10.66 feet.

• Inlets located at the low or sag points shall be designed for no encroachment on the travel way. Flanker inlets shall be designed on each side of the low point inlet structure.

• Spacing of inlet structures shall be based on hydraulic requirements, economics, and engineering judgement.

Roadside Gutters and Ditches

• Maximum cross‐slope within the highway clear zone shall be 6:1. Preferred cross‐slope within the clear zone is 12:1.

• The backslope of V‐shaped gutters in cut sections shall be no greater than the slope of the cut‐section.

3-3

3.5 Criteria for Temporary Drainage Facilities

The Contractor shall provide the drainage design for construction-related drainage facilities, including roadway detours. Design, layout and construction of the detour road, including erosion and sediment control BMPs, shall be performed by the Contractor. HDOT criteria states “The recurrence interval for detour road crossings shall be equivalent to a five year storm event.” See Appendix B of HDOT’s Design Criteria for Highway Drainage manual for further guidelines for the design of temporary drainage facilities.

Temporary channel diversions not associated with the roadway diversion shall be designed to convey, at a minimum, the five year storm event.

3.6 Other Criteria and Methodology

Bridge deck drainage design shall follow the guidance of HEC-21 Design of Bridge Deck Drainage.

Section 7.3.3.5 Bridge Deck Design Guidance of the PDDM shall be considered in the bridge design.

Section 7.4.2.4.4 Bridge Scour of the PDDM shall be considered when designing for debris at piers.

Section 7.4.3.4.1 Capacity Design of the PDDM shall be considered for freeboard when the potential for woody debris is significant.

In addition to the above criteria, applicable sections of the attached HDS Addendum to Design Flood Criteria dated April 16, 2015 shall apply to this project. See attachment in Appendix E.

3.7 Fish Passage

There are no requirements for fish passage design for this project. Any encroachment into Kipapa Stream for the construction of the bridge replacement will be on a temporary basis and the channel geometry below the normal flow of the stream will be restored to its original configuration.

4 HYDROLOGIC AND HYDRAULIC ANALYSES

4-1

SECTION 4

Hydrologic and Hydraulic Analyses

4.1 Hydrologic Analysis

4.1.1 General

Multiple methods were employed to analyze the hydrology for the Roosevelt Bridge drainage basin including Natural Resources Conservations Services (TR‐55) (Reference 8), USGS StreamStats (Reference 6 and 7), and the City and County of Honolulu, Rules Relating to Storm Drainage Standards, Plate 6, dated January 2000 (Reference 9). Because the drainage area did not exceed 25 square miles, the NRCS TR‐55 method was used for comparison. Details of each method are described in the Hydraulics Recommendation Report for the Roosevelt Bridge Rehabilitation (Reference 5). A description of the selected hydrologic method is included below.

4.1.2 USGS StreamStats

The USGS StreamStats for Hawaii web‐based GIS application provided peak flow results for various recurrence intervals for the analysis and design of the Roosevelt Bridge rehabilitation. The application uses the USGS regression equations that were developed for the various islands in the state of Hawaii. The results of the peak flow estimates appeared the most reasonable for the following reasons:

• The results show good correlation with the results from the TR‐55 method.

• USGS StreamStats is an acceptable methodology to HDOT and CFLHD.

• This methodology provides for consistent peak flow estimates for all bridge projects on Oahu.

Below is a table summarizing the design peak flows for the proposed Roosevelt Bridge replacement project.

Table 4-1 Summary of Peak Flows for Kipapa Stream at Roosevelt Bridge from USGS StreamStats

Summary of Peak Flows (cfs) at Roosevelt Bridge from USGS StreamStats

Storm Frequencies (based upon drainage area of approximately 11.5 mi2) Q(2) Q(5) Q(10) Q(50) Q(100) Q(200) Q(500)

2,630

4,680

6,400

10,900

13,100

15,300*

18,900

*The Q(200) value was estimated through graphical interpolation. See Reference 5.

A copy of the USGS StreamStats analysis is included in Appendix A.

4.1.3 Precipitation Data

The precipitation value for the analysis of roadway runoff was obtained from the NOAA Atlas 14 website for Hawaii (Reference 10). The 25‐year precipitation rate was determined to be 7.71 inches/hour based on a minimum time of concentration of 10 minutes. See Appendix A for rainfall data.

4-2

4.1.4 Hydrology for Bridge Deck Drainage

Hydrologic analyses were conducted for the existing and proposed bridge deck drainage collection systems, which include 3-inch and 4-inch diameter scuppers on Roosevelt Bridge. Results of the hydrologic analysis were used for the design of new deck drains.

The hydrologic analysis estimated the 25-year peak flows using the Rational Method for both the existing and proposed conditions. According to the HDOT Drainage Design Criteria (Reference 3), principal arterial roads should be designed for the 25-year recurrence interval. The peak flow estimates will be used to evaluate the impact the project may have on the proposed bridge deck drainage features. The following sections summarize the results of the hydrologic analysis.

4.1.4.1 Existing Conditions

The results of the hydrologic analysis for the existing conditions are shown below in Table 4-2. The hydrologic calculations for existing conditions are shown in Appendix A. See Figure 4-1 for the Drainage Map.

Table 4-2 Summary of 25-Year Peak Flows, Existing Bridge Deck Surface Drainage Conditions

Drain Area No.

Deck Drain

Location C i25, in./hr.

Area, acre

Q25, cfs

1 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.136 1.00

2 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.024 0.17

3 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.025 0.18

4 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.021 0.16

5 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.025 0.19

6 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.022 0.16

7 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.023 0.17

8 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.019 0.14

9 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.021 0.15

10 (1) 3”ø Roosevelt Bridge (south side) 0.95 7.71 0.003 0.02

11 (1) 3”ø Roosevelt Bridge (south side) 0.95 7.71 0.009 0.06

12 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.012 0.09

13 (1) 3”ø Roosevelt Bridge (south side) 0.95 7.71 0.015 0.11

14 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.013 0.10

15 (1) 3”ø Roosevelt Bridge (south side) 0.95 7.71 0.013 0.10

16 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.013 0.09

17 (1) 3”ø Roosevelt Bridge (south side) 0.95 7.71 0.011 0.08

18 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.011 0.08

19 (1) 3”ø , (2) 4”ø Roosevelt Bridge (south side) 0.95 7.71 0.021 0.16

20 (1) 3”ø , (2) 4”ø Roosevelt Bridge (north side) 0.95 7.71 0.021 0.15

21 (1) 3”ø , (2) 4”ø Roosevelt Bridge (south side) 0.95 7.71 0.016 0.11

22 (1) 3”ø , (2) 4”ø Roosevelt Bridge (north side) 0.95 7.71 0.015 0.11

23 (1) 4”ø Roosevelt Bridge (south side) 0.95 7.71 0.002 0.02

24 (1) 4”ø Roosevelt Bridge (north side) 0.95 7.71 0.002 0.02

25 (1) 3”ø Roosevelt Bridge (south side) 0.95 7.71 0.009 0.06

26 (1) 3”ø Roosevelt Bridge (north side) 0.95 7.71 0.008 0.06

TOTAL 0.509 3.73

HI HI STP SR 99 (1)

ROOSEVELT BRIDGE

KAMEHAMEHA HIGHWAY, ROUTE 99

DISTRICT OF WAIPIO, ISLAND OF OAHU, HAWAII

4-1

FIGURE 4-1

DRAINAGE MAP

LINEAR SCALE (FEET)

40 20 0 20 40 80

EXISTING CONDITIONS

DA-11

DA-19

DA-4

4-4

Drainage Areas Nos. 1 through 18, 25, and 26 contribute stormwater runoff to existing 3-inch diameter bridge scuppers. Drainage Area Nos. 23 and 24 contribute stormwater runoff to existing 4-inch diameter bridge scuppers. Drainage Area Nos. 19 through 21 each contribute stormwater runoff to one (1) existing 3-inch diameter bridge scupper and two (2) existing 4-inch diameter scuppers in sump conditions.

4.1.4.2 Proposed Conditions

The results of the hydrologic analysis for the proposed conditions are shown below in Table 4-3. The hydrologic calculations for proposed conditions are shown in Appendix A. See Figure 4-2 for the Drainage Map.

Table 4-3 Summary of 25-Year Peak Flows, Proposed Bridge Deck Surface Drainage Conditions

Drain Area No.

Deck Drain

Location C i25, in./hr.

Area, acre

Q25, cfs

1 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.025 0.18

2 A-9P GDI Roosevelt Bridge (south side) 0.95 7.71 0.025 0.19

3 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.027 0.20

4 A-9P GDI Roosevelt Bridge (south side) 0.95 7.71 0.028 0.20

5 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.028 0.21

6 A-9P GDI Roosevelt Bridge (south side) 0.95 7.71 0.026 0.19

7 A-9P GDI Roosevelt Bridge (south side) 0.95 7.71 0.029 0.21

8 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.034 0.25

9 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.094 0.69

10 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.081 0.59

11 A-9P GDI Roosevelt Bridge (north side) 0.95 7.71 0.163 1.20

TOTAL 0.559 4.09

The proposed bridge and roadway improvements will alter the drainage patterns. The existing bridge scuppers will be replaced with eleven (11) HDOT standard A-9P grated drain inlets (GDI). The widening of the proposed bridge will also increase the total drainage area and stormwater runoff.

A hydraulics analysis was performed for the proposed bridge deck surface drainage system. See Section

4.2.4 for the results of the hydraulic analysis.

HI HI STP SR 99 (1)

ROOSEVELT BRIDGE

KAMEHAMEHA HIGHWAY, ROUTE 99

DISTRICT OF WAIPIO, ISLAND OF OAHU, HAWAII

4-2

FIGURE 4-2

DRAINAGE MAP

LINEAR SCALE (FEET)

40 20 0 20 40 80

PROPOSED CONDITIONS

4-6

4.2 Hydraulic Analysis

4.2.1 Existing Bridge

The existing bridge has an approximate length of 484 feet and width of 34 feet measured from the outside face of the concrete railings. The superstructure consists of a waffle grid of reinforced concrete tee beams and girders with a concrete deck. It has 16 spans that range between 24 to 42 feet with the median span being 30 feet in length. Each pier has a square nose and a width of 2.5 feet and length of 4.5 feet. There are also two low flow guide walls that transversely connect a pair of piers adjacent to the main channel. The upstream and downstream slopes of Kipapa Stream were estimated to be 0.022 and 0.005, respectively.

Survey data was obtained for Kipapa Stream and Roosevelt Bridge and was used to create cross sections for the hydraulic modeling in HEC‐RAS (Reference 11). Based on the HEC‐RAS model of the existing Roosevelt Bridge, the bridge opening is more than adequate to pass both the 100‐year and 200‐year floods. The existing bridge provides approximately 49 feet of freeboard during the 50‐year flood event and approximately 45 feet of freeboard during the 200‐year flood event. See Appendix B for the HEC‐RAS model output for the existing bridge conditions.

The proposed rehabilitated bridge will have a width of 36 feet measured from the inside face of the concrete railings. The proposed bridge will have two 11‐foot wide traffic lanes and 7‐foot shoulders in each direction. The total width of the bridge measured from outside face of rail is 38’‐4”. The superstructure, span, piers, and total length will have the same properties as the existing bridge. The existing bridge piers will not be removed.

4.2.2 Proposed Bridge Rehabilitation

The project proposes to rehabilitate the existing bridge. Since the existing bridge has adequate capacity to pass the 50‐year design flood with approximately 49 feet of freeboard, improvements to the bridge and stream channel are not required to meet the hydraulic criteria. Hydraulic calculations were performed to support the scour analysis and determine the need for scour countermeasures. See Figure 4‐3 for the 50‐ year water surface profile of the existing bridge.

4.2.3 Roadside Ditches

The existing roadside ditch located at the north approach to the bridge will not be affected by the project.

Adjustments will be required for the roadside ditch located at the south approach to the bridge to accommodate the widening of the bridge deck and new finished road grades.

4-7

Figure 4-3 Roosevelt Bridge 50-year Water Surface Profiles

0 200 400 600 800 1000 1200 1400 1600

El e va ti o n ft

M

SL

Channel Station [ft.]

Roosevelt Bridge-Existing Water Surface Profile

Exist. Ground Surface

Exist. 50-yr Water Surface

Exist. Roosevelt Bridge

4-8

4.2.4 Bridge Deck Drainage Collection System

Hydraulic calculations were performed for the existing and proposed deck drains on Roosevelt Bridge.

Calculations for gutter flow and inlet capacity were completed to determine the effectiveness of the proposed drainage improvements.

Results from the hydraulic calculations indicate that the proposed deck drains on Roosevelt Bridge have adequate capacity for the runoff generated from the tributary areas. All flow on Roosevelt Bridge will be collected by the eleven (11) HDOT standard A‐9P grated drain inlets along the north and south sides of the bridge. Bypass stormwater runoff will not exit Roosevelt Bridge. The spread at each deck drain will not enter the adjacent travel lane, which meets the HDOT criteria (Reference 3) of gutter flow not exceeding 1/3 the width of the travel lane.

4.2.5 Bridge Scour

4.2.5.1 Site Geology

Borings were performed by Hirata & Associates, Inc. (Reference 12) within the overbanks of Kipapa Stream below Roosevelt Bridge. The borings indicate that subsurface materials primarily consist of clayey silt, sandy silt, and some weathered rock to depths ranging from 30 to 31 feet in two (2) of the borings. This material consists of older alluvium deposits that have stiff characteristics. Kipapa Stream is generally underlain by basalt rock formation of the Koolau Volcanic Series. Residual and saprolitic soils may be found in the upper portion of the basalt rock.

Groundwater was encountered at elevations of 231.9 feet and 234.7 feet above mean sea level on the overbanks of Kipapa Stream. Soil samples were taken from the Kipapa Stream bed below the existing Roosevelt Bridge. The material consists of grayish brown sandy gravel. Results of a Wolman pebble count indicate that the D50 and D90 particle sizes are approximately 11.4 millimeters and 13.0 millimeters, respectively.

4.2.5.2 Scour Design Flows

The 100‐year and 200‐year flood event flow rates that were used in the scour analysis are shown below:

• Q100 = 13,100 cfs

• Q200 = 15,300 cfs

4.2.5.3 Scour Parameters

As recommended by HEC‐18 (Reference 13), long‐term stream degradation, contraction scour, and local scour were considered for the existing bridge. The following sections discuss the development of the parameters used in the equations to calculate each type of scour.

Long-term Stream Degradation

Review of the as‐built plans for Roosevelt Bridge and the topographic survey of Kipapa Stream indicate that degradation has not occurred over a period of about 80 years. The 1932 Roosevelt Bridge plans show Kipapa Stream to have an invert elevation of about 238 feet above mean sea level at the bridge. The 2014 topographic survey map indicates that the stream invert elevation at the bridge is also about 238 feet above mean sea level. See Appendix C for a copy of the Roosevelt Bridge as‐built plans.

For the purpose of bridge scour design, the analysis will assume that no long‐term stream degradation will occur.

4-9

Contraction Scour The parameters used in the contraction scour equations were determined from the HEC-RAS model for proposed conditions based on the 100-year flood event. River Station 650, which is located approximately 86 feet upstream of Roosevelt Bridge, was selected as the approach cross section. Parameters from River Station 650 were compared to the parameters at the contracted bridge section (River Station 564) to determine the magnitude of the contraction scour.

Based on the average approach velocity (V) and critical velocity (Vc) of the median particle size, the live-bed contraction scour equation was used for the main channel. All flows will be contained within Kipapa Stream banks for the 100-year flood. Contraction scour does not occur at the right and left overbanks because there is no flow in the overbanks of the upstream approach section. Table 4-4 and Table 4-5 show the parameters used to calculate the sediment regime in the main channel and overbanks for the 100-year and 200-year events.

Table 4-4 Sediment Regime Parameters – 100-Year Event

Parameter Left Overbank Main Channel Right Overbank Unit

Ku N/A 11.17 N/A y N/A 8.56 N/A ft.

D50 N/A 0.0374 N/A ft.

V N/A 16.66 N/A ft./s

Vc N/A 5.34 N/A ft./s

Sediment Regime N/A Live-bed N/A

Table 4-5 Sediment Regime Parameters – 200-Year Event

Parameter Left Overbank Main Channel Right Overbank Unit

Ku N/A 11.17 N/A y N/A 9.26 N/A ft.

D50 N/A 0.0374 N/A ft.

V N/A 17.32 N/A ft./s

Vc N/A 5.41 N/A ft./s

Sediment Regime N/A Live-bed N/A

The width at the contracted bridge section, W2, is the bottom width of the channel at Roosevelt Bridge less the total width of the proposed piers. Within this analysis, no piers in the main channel were included in the contraction scour calculations. However, there are a total of 4 piers adjacent to the stream channel. The contraction scour depth will be applied to all bridge piers adjacent to the stream channel that are subject to scour. The bottom width of the contracted section was determined to be approximately 25.97 feet.

The width at the approach section, W1, is defined as the bottom width of the channel that is transporting bed material. Based on the project topographic survey map, the width of the main channel of Kipapa Stream at the approach section was determined to be approximately 26.33 feet.

Flow depths (y1 and yo) and flow rates (Q1 and Q2) for the approach and contraction sections were obtained from the HEC-RAS model for River Stations 650 and 564, respectively.

4-10

Negative values were obtained in the contraction scour calculations. Therefore, no contraction scour is anticipated. The negative values for contraction scour may have resulted because even though the channel width contracts, there is less flow in the main channel and a higher flow depth at the contracted bridge section.

Table 4-6 and Table 4-7 summarize the parameters that were used to calculate contraction scour for the 100-year and 200-year events, respectively. The results are present at the bottom of the tables. The contraction scour calculations are included in Appendix C.

Table 4-6 Summary of Contraction Scour Parameters and Results – 100-Year Event

Parameter Left Overbank

Main Channel Right Overbank

Unit y1 N/A 8.56 N/A ft.

Yo N/A 10.94 N/A ft.

Q2 N/A 12,339.50 N/A ft.3/s

Q1 N/A 13,100.00 N/A ft.3/s

W1 N/A 26.33 N/A ft.

W2 N/A 25.97 N/A ft.

K1 N/A 0.64 N/A y2 N/A 8.20 N/A ft.

ys (contraction scour depth)

N/A 0.00 N/A ft.

Table 4-7 Summary of Contraction Scour Parameters and Results – 200-Year Event

Parameter Left Overbank

Main Channel Right Overbank

Unit y1 N/A 9.26 N/A ft.

Yo N/A 12.00 N/A ft.

Q2 N/A 14,136.56 N/A ft.3/s

Q1 N/A 15,300.00 N/A ft.3/s

W1 N/A 26.33 N/A ft.

W2 N/A 25.97 N/A ft.

K1 N/A 0.64 N/A y2 N/A 8.73 N/A ft.

ys (contraction scour depth)

N/A 0.00 N/A ft.

4-11

Pier Scour The parameters used in the pier scour equation were also determined from the HEC-RAS model for existing conditions based on the 100-year and 200-year flood events. The existing bridge consist of fifteen (15) upstream piers and fifteen (15) downstream piers. A pair of upstream piers connect to a pair of downstream piers by low flow guide walls. The upstream piers were analyzed separately from the downstream piers. A total of seven (7) upstream piers and eight (8) downstream piers will be subject to scour during the 100-year storm event. A total of seven (7) upstream piers and nine (9) downstream piers will be subject to scour during the 200-year storm event. Figure 4-4 shows the locations of the piers subject to scour.

The HEC-18 pier scour equation was used for the analysis. Scour from debris on piers was also included in the analysis. The width of the debris for each pier was assumed to be 5-feet on each side of the pier and the height of the debris varied depending on the water depth at each pier. The maximum height of debris was limited to 6-feet high, with the exception of the upstream pier at station 38+51.23. The height of the debris at the upstream pier at station 38+51.23 was set to 8-feet because it is more likely to be subjected to more debris due to the bend in Kipapa Stream. The shape of debris accumulations was generally idealized as triangular. The flows from the 100-yr and 200-yr recurrence intervals (13,100 cfs and 15,300 cfs, respectively) were used for the scour analyses.

The Roosevelt Bridge piers are skewed to the flow in Kipapa Stream. An angle of attack ranging from 35 to 45 degrees was used to account for these skewed flows. Due to the skewed flows, a revised pier width of

4.5 feet was used for the hydraulic analysis in the HEC-RAS model. The actual pier size of 2.5 feet width and

4.5 feet length were used when calculating pier scour with debris because a correction factor for angle of attack, K2, is included in the analysis.

Table 4-8 and Table 4-9 summarize the estimated pier scour depths with debris for the 100-yr. and 200-yr.

storms for the existing bridge piers. The downstream (DS) and upstream (US) piers are displayed in black text and red text, respectively.

Roosevelt Bridge - Piers Subject to Scour (Indicated in Red)

Figure 4-4

4-13

Table 4-8 Summary of Pier Scour Parameters and Results – 100-Year Event

Column Angle of

Attack [deg]

K1 K2 K3 a [ft]

L [ft]

K1’ H [ft]

W [ft] a*d [ft]

Ground Surface

El.

[ft]

W.S. El. Y1 [ft]

V1 [ft/s]

Fr1 Ys [ft]

37+49.23 US 45 1.0 1.56 1.1 2.5 4.5 0.21 3.87 12.5 4.66 249.60 253.37 3.77 5.96 0.54 11.39

37+49.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 0.13 12.5 4.77 253.06 253.18 0.12 5.63 2.86 7.09

37+79.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 3.74 243.24 253.37 10.13 9.71 0.54 13.67

37+79.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 4.51 12.5 4.70 248.87 253.18 4.31 5.63 0.48 10.89

38+09.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 3.45 240.05 253.37 13.32 9.71 0.47 13.44

38+09.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 4.23 245.91 253.18 7.27 9.80 0.64 13.87

38+33.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 3.51 240.66 253.18 12.52 9.80 0.49 13.20

38+51.23 US 45 1.0 1.56 1.1 2.5 4.5 0.21 8.00 12.5 3.58 237.81 253.37 15.56 9.71 0.43 14.34

38+75.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 3.62 242.08 253.37 11.29 9.71 0.51 13.56

38+75.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 3.33 237.97 253.18 15.21 9.80 0.44 13.10

39+05.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 5.26 12.5 4.64 248.21 253.37 5.16 4.32 0.34 10.13

39+05.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 3.78 243.33 253.18 9.85 9.80 0.55 13.42

39+35.23 US 45 1.0 1.56 1.1 2.5 4.5 0.21 1.56 12.5 4.74 251.91 253.37 1.46 4.32 0.63 8.83

39+35.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 5.88 12.5 4.67 247.50 253.18 5.68 5.67 0.42 11.81

39+65.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 2.45 12.5 4.79 250.93 253.18 2.25 5.67 0.67 10.58

39+95.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 0.00 12.5 --- 253.38 --- 0.00 0.00 --- ---

Where:

K1: Correction factor for pier nose shape (1.1 for square nose) K2: Correction factor for angle of attack of flow K3: Correction factor for bed condition a: Width of pier L: Length of pier K1’: Correction factor for shape of debris (0.21 for triangular debris)

H: Height of debris W: Width of debis a*d: Effective pier width when debris is present Y1: Flow depth directly upstream of pier V1: Mean velocity of flow direction upstream of pier Fr1: Froude number directly upstream of pier Ys: Scour depth

4-14

Table 4-9 Summary of Pier SCOUR Parameters AND RESULTS – 200-YEAR EVENT

Column Angle of

Attack [deg]

K1 K2 K3 a [ft]

L [ft]

K1’ H [ft]

W [ft] a*d [ft]

Ground Surface

El.

[ft]

W.S. El. Y1 [ft]

V1 [ft/s]

Fr1 Ys [ft]

37+49.23 US 45 1.0 1.56 1.1 2.5 4.5 0.21 4.95 12.5 4.65 249.60 254.43 4.83 6.55 0.53 12.26

37+49.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 1.17 12.5 4.64 253.06 254.21 1.15 6.12 1.01 9.79

37+79.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 3.63 243.24 254.43 11.19 10.14 0.53 13.82

37+79.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 5.55 12.5 4.68 248.87 254.21 5.34 6.12 0.47 11.60

38+09.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 3.38 240.05 254.43 14.38 10.14 0.47 13.65

38+09.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 4.02 245.91 254.21 8.30 10.08 0.62 13.81

38+33.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 3.43 240.66 254.21 13.55 10.08 0.48 13.32

38+51.23 US 45 1.0 1.56 1.1 2.5 4.5 0.21 8.00 12.5 3.51 237.81 254.43 16.62 10.14 0.44 14.55

38+75.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 3.52 242.08 254.43 12.35 10.14 0.51 13.74

38+75.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 3.28 237.97 254.21 16.24 10.08 0.44 13.24

39+05.23 US 40 1.0 1.53 1.1 2.5 4.5 0.21 6.00 12.5 4.53 248.21 254.43 6.22 5.07 0.36 10.95

39+05.23 DS 35 1.0 1.49 1.1 2.5 4.5 0.21 6.00 12.5 3.66 243.33 254.21 10.88 10.08 0.54 13.48

39+35.23 US 45 1.0 1.56 1.1 2.5 4.5 0.21 2.64 12.5 4.70 251.91 254.43 2.52 5.07 0.56 10.12

39+35.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 6.00 12.5 4.38 247.50 254.21 6.71 6.08 0.41 11.93

39+65.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 3.49 12.5 4.73 250.93 254.21 3.28 6.08 0.59 11.39

39+95.23 DS 45 1.0 1.56 1.1 2.5 4.5 0.21 0.74 12.5 4.60 253.68 254.21 0.74 6.08 1.25 9.15

Where:

K1: Correction factor for pier nose shape (1.1 for square nose) K2: Correction factor for angle of attack of flow K3: Correction factor for bed condition a: Width of pier L: Length of pier K1’: Correction factor for shape of debris (0.21 for triangular debris)

H: Height of debris W: Width of debis a*d: Effective pier width when debris is present Y1: Flow depth directly upstream of pier V1: Mean velocity of flow direction upstream of pier Fr1: Froude number directly upstream of pier Ys: Scour depth

4-15

4.2.5.4 Scour Results

The results of the scour analysis are summarized in Table 4-10 and Table 4-11 for the 100-year and 200-year events, respectively. These tables show the lowest existing ground elevation at each pier and the lowest scour depth elevation. The downstream (DS) and upstream (US) piers are displayed in black text and red text, respectively. The highlighted cells indicate the scour critical piers, where the estimated scour depths are below the bottom of footing.

Table 4-10 SUMMARY OF ROOSEVELT BRIDGE SCOUR Depth AND Elevation RESULTS – 100-YEAR EVENT

Pier

Scour Component

Long-Term Degradation

[ft]

Contraction Scour Depth

[ft]

Local Scour Depth

[ft]

Total Scour Depth

[ft]

Ground Elevation [ft. msl]

Scour Depth

[ft. msl]

37+49.23US 0.00

0.00

11.39 11.39 249.60 238.21

37+49.23DS 0.00

7.09 7.09 253.06 245.97

37+79.23US 0.00

13.67 13.67 243.24 229.57

37+79.23DS 0.00

10.89 10.89 248.87 237.98

38+09.23US 0.00

13.44 13.44 240.05 226.61

38+09.23DS 0.00

13.87 13.87 245.91 232.04

38+33.23DS 0.00

13.20 13.20 240.66 227.46

38+51.23US 0.00

14.34 14.34 237.81 223.47

38+75.23US 0.00

13.56 13.56 242.08 228.52

38+75.23DS 0.00

13.10 13.10 237.97 224.87

39+05.23US 0.00

10.13 10.13 248.21 238.08

39+05.23DS 0.00

13.42 13.42 243.33 229.91

39+35.23US 0.00

8.83 8.83 251.91 243.08

39+35.23DS 0.00

11.81 11.81 247.50

..50

235.69

39+65.23DS 0.00

10.58 10.58 250.93 240.35

4-16

Table 4-11 Summary of Roosevelt Bridge Scour Depth and Elevation Results – 200-Year Event

Pier

Scour Component

Long-Term Degradation

[ft]

Contraction Scour Depth

[ft]

Local Scour Depth

[ft]

Total Scour Depth

[ft]

Ground Elevation [ft. msl]

Scour Depth

[ft. msl]

37+49.23US 0.00

12.26 12.26 249.60 237.34

37+49.23DS 0.00

9.79 9.79 253.06 243.27

37+79.23US 0.00

13.82 13.82 243.24 229.42

37+79.23DS 0.00

11.60 11.60 248.87 237.27

38+09.23US 0.00

13.65 13.65 240.05 226.40

38+09.23DS 0.00

13.81 13.81 245.91 232.10

38+33.23DS 0.00

13.32 13.32 240.66 227.34

38+51.23US 0.00

14.55 14.55 237.81 223.26

38+75.23US 0.00

13.74 13.74 242.08 228.34

38+75.23DS 0.00

13.24 13.24 237.97 224.73

39+05.23US 0.00

10.95 10.95 248.21 237.26

39+05.23DS 0.00

13.48 13.48 243.33 229.85

39+35.23US 0.00

10.12 10.12 251.91 241.79

39+35.23DS 0.00

11.93 11.93 247.50

..50

235.57

39+65.23DS 0.00

11.39 11.39 250.93 239.54

39+95.23DS 0.00 0.00 9.15 9.15 253.68 244.53

Total scour depth was calculated by adding long-term degradation, contraction scour, and pier scour.

Abutment scour and pressure flow scour were not analyzed because Roosevelt Bridge is not subject to these scour conditions. The Roosevelt Bridge abutments and deck do not make contact with the water surface during the 100-year and 200-year storm events.

Figure 4-5 through Figure 4-8 show the upstream and downstream scour diagrams for the existing Roosevelt Bridge based on the 100-year and 200-year events.

The results of the scour analysis based on the 100-year flood event indicate that several existing bridge piers will be exposed to scour and many of those are scour critical piers, where the estimated scour depth extend below the bottom of the existing spread footing located adjacent to the Kipapa Stream. The geotechnical engineer has indicated that the spread footings appear to be resting on erodible material consisting of clayey silt or sandy silt. Therefore, Roosevelt Bridge should be listed as a scour critical bridge. Pier scour countermeasures should be installed to protect these piers from scour.

Due to project schedule constraints and the anticipated delay in obtaining a Section 401 Water Quality Certification from the State Department of Health for work within the ordinary high water mark, the construction of scour countermeasures should be deferred to a future project. The HDOT should prepare and implement a scour critical bridge plan of action to monitor and address potential scour prior to installation of scour countermeasures.

4-17

The potential risk to defer the installation of scour countermeasures to a future project may be low considering:

1. HDOT does not have any reports of serious scour issues during the 80 years that Roosevelt Bridge has been in service.

2. Erosion was observed behind the existing concrete guide walls adjacent to the stream, but there is no evidence of pier scour to the magnitude estimated in the scour analysis.

3. There are no signs of lateral migration and stream degradation based on field observations and a comparison of the as-built plans to the current topographic survey information.

4. The large bed material consisting of cobbles and boulders may provide armoring of the scour hole for the piers located adjacent to the stream.

5-1

SECTION 5

Summary There have been no reports of overtopping at Roosevelt Bridge. Peak discharges from USGS regression equations (StreamStats) were selected for the analyses and design of the bridge rehabilitation project. The 50-year design peak discharge of 10,900 cfs was used for the hydraulic analysis.

The results of the hydraulic analysis for the existing bridge indicate that the bridge may convey the 50-year peak discharge with approximately 49 feet of freeboard.