CO FTBR CRYSTAL DAM(1) Pavement Report Signed.pdf

EAST PORTAL ROAD

MONTROSE COUNTY, COLORADO

CO FTBR CRYSTAL DAM(1)

PAVEMENT AND MATERIALS REPORT

JUNE 2019

Report prepared by:

U.S. Department of Transportation

Federal Highway Administration

Central Federal Lands Highway Division

Lakewood, Colorado http://www.google.com/imgres?sa=X&biw=1280&bih=819&tbm=isch&tbnid=gtpyJEKxSQX6SM:&imgrefurl=http://portal.hud.gov/hudportal/HUD?src=/press/press_releases_media_advisories/2010/HUDNo.10-242&docid=0hzyuk4oobnONM&imgurl=http://portal.hud.gov/hudportal/images/hudimg?id=dot_logo_41193.jpg&w=520&h=528&ei=uGw7Uoy6Ksjk4AOC_IDQBw&zoom=1&iact=hc&vpx=567&vpy=131&dur=635&hovh=226&hovw=223&tx=151&ty=150&page=1&tbnh=154&tbnw=162&start=0&ndsp=30&ved=1t:429,r:26,s:0,i:171

CO FTBR CRYSTAL DAM(1) East Portal Road ii

Written by: ________________________________________________________

Robert Norick, Staff Pavements & Materials Engineer

Reviewed by: ________________________________________________________

Mike Voth, Pavements & Materials Team Lead

Approved for distribution by:

Mike Voth, Pavements & Materials Team Lead

Electronic Distribution:

Construction Project Development Project Management Technical Services iii

TABLE OF CONTENTS

I. INTRODUCTION

II. CLIMATE

III. EXPLORATION

IV. EXISTING PAVEMENT & SOILS

V. PAVEMENT DESIGN INPUTS

VI. PAVEMENT RECOMMENDATIONS & DISCUSSION

VII. MATERIALS RECOMMENDATIONS

APPENDICES

A – Vicinity Map, Site Maps, & As-Builts

B – Boring Log and Lab Report

C – Site Investigation Photos

D – Pavement Design Calculations

E – Asphalt Binder Selection & Climate Data

F – Pipe Selection Criteria

I. INTRODUCTION

This report provides pavement and material recommendations for the CO FTBR

CRYSTAL DAM(1) East Portal Road project in Montrose County, Colorado. The

Bureau of Reclamation (BOR) maintains the 7.1 mile long, dead end road for access to its

Crystal dam and power plant from the South Rim Road within Black Canyon of the

Gunnison National Park (Milepost 0.0). The road intersects the South Rim Road just north of the park’s south entrance station. See Appendix A for vicinity and site maps.

The East Portal Road is located within both the national park (west 5 miles) and the

Curecanti National Recreation Area (east 2.1 miles). Besides dam and power plant access, the road also provides access for park housing (near Milepost 5.2), as well as, public recreational activities in the bottom of the canyon. The BOR gate is located at

Milepost 6.85 which delineates the end of public access along the road. East of the BOR gate, the road splits into an upper and a lower road for access to the top and toe of the dam. The upper road includes a 500’ long, 17’ wide tunnel. The project proposes to rehabilitate the publicly accessible section of the road (20 foot average pavement width).

The pavement design presented in Section VI is valid for rehabilitation alternatives that propose a widening of 2 feet or less (e.g. final pavement widths of 20 to 22 feet).

II. CLIMATE

Climate data was obtained from the Western Regional Climate Center for the Cimarron, Colorado weather station. The data is summarized in Table 1 below and provided in

Appendix E. The average precipitation for this area is approximately 13.45 inches. The project is located at an elevation that receives both snow and rain, dependent upon the time of year. The project ranges in elevation from ≈6,550 feet to ≈8,550 feet.

Table 1. Weather Data

Month Average

HIGH

Record

HIGH

Average

LOW

Record

LOW

Average

PRECIP.

January 33.9 60 0.5 -43 1.13

February 38.3 65 6.0 -40 0.89

March 47.9 81 16.7 -25 1.00

April 58.7 85 24.2 -9 1.01

May 69.2 91 30.8 4 1.04

June 80.2 96 36.7 19 0.83

July 85.3 98 43.8 29 1.24

August 82.9 94 43.0 27 1.48

September 75.3 94 34.2 13 1.53

October 64.1 86 24.4 0 1.33

November 47.6 72 15.2 -22 0.99

December 35.1 59 3.8 -33 0.98

Temperatures are in °F and precipitations are in inches.

III. EXPLORATION

On November 20, 2018, a pavement and subgrade investigation was conducted for the project, including 23 shallow borings (up to 5 foot depth). Boring depths less than 5 feet reflect borings that encountered refusal (boulders or bedrock). The road was drilled at approximately 1/3 mile increments, with boring locations alternating between lanes.

See Appendix A for boring site map and Appendix C for photos from the pavement investigation. CFL personnel logged the findings including depth of boring, visual soil classification, pavement and aggregate base thicknesses, areas of distress, and road width.

During the site visit, nine samples were collected. These samples were submitted to the

CFLHD laboratory for testing to determine the subgrade engineering properties. The boring logs and laboratory reports are provided in Appendix B.

IV. EXISTING PAVEMENT & SOILS

The East Portal Road was constructed in the early 1970s. The existing asphalt pavement has aged and is beyond its design life. The asphalt is highly oxidized with transverse cracks. The road received a chip seal pavement preservation in 2015, but the chip seal has experienced severe bleeding, shoving, and wash boarding, especially for the 3 mile section between Mileposts 2.1 and 5.1 (16% grades with hairpin curves). The pavement life cannot be extended with pavement preservation methods (e.g. chip seals and overlays). The existing pavement section consists of 4 to 6 inches of asphalt over a minimum of 5 to 7 inches of road base material. In some areas, the depth of the road base is significantly greater than these minimum values. The minimum combined depth of the existing asphalt and aggregate base is 10 inches. The underlying subgrade soils through the project limits vary considerably from lean clays and clayey sands on the high plateau between Mileposts 0 and 2.10 to silty sands with gravel within the canyon between

Mileposts 2.10 to 7.10.

V. PAVEMENT DESIGN INPUTS

The pavement design for the East Portal Road utilized design criteria established in the

Federal Lands Highway Project Development Design Manual (PDDM) and the 1993

AASHTO Guide for Design of Pavement Structures (AGDPS). The criteria shown in

Table 2 below were selected based on the project’s scope and traffic levels.

Table 2. Design Criteria

Design Performance Period (3R) 20 years

Initial Serviceability 4.2

Terminal Serviceability 2.0

Design Reliability Level 75%

Overall Standard Deviation 0.49

Annual Traffic Volume Growth Rate 2.0%

Directional Distribution (dead end road) 50%

Traffic

Traffic estimates for the East Portal Road are based upon the following sources:

1. Traffic counts from National Park Service (NPS) website.

2. Meeting with BOR’s Randy Kramer on June 14, 2016.

3. Site visits on June 14, 2016 and November 20, 2018.

The road provides BOR access for the Crystal dam and power plant, NPS access for employee housing, and public access for recreational activities. The public traffic is seasonal with higher ADTs during May through October and much less traffic during the winter months when it is closed to public traffic. Based upon the aforementioned sources, the road’s average annual two-way ADT is estimated to be 100 vehicles per day with approximately 5% FHWA Class 5-6 single unit trucks and motor homes. With the narrow road width, steep grades, and small radius curves, the road is not conducive for tractor trailer traffic. In fact, the NPS map for the park prohibits vehicles longer than 22 feet on the road. Accurate traffic load estimates expressed as 18-kip equivalent single axle loads

(ESALs) are critical for the pavement design. Load estimates are based on vehicle counts and classifications with a 20-year, 2% growth factor of 24.3. Standard load equivalency truck factors are used to convert the various vehicle axle loads to 18-kip ESALs. The following truck factors were assumed for the aforementioned vehicle classifications in accordance with PDDM Exhibit 11.2-A: 0.004 for Class 2-3 cars, pickups, and SUVs and 0.7 for Class 5-6 trucks and RVs. Based upon the design criteria and assumptions shown above and the 1993 AASHTO pavement design procedure, the project’s 20-year-

18-kip equivalent single axle loads are calculated to be 17,205 (see Appendix D).

According to PDDM Section 11.2.1.2, a minimum of 50,000 ESALs shall be used for the design of paved roads.

Subgrade Soil Resilient Modulus

Seven soil samples were submitted to the CFLHD laboratory to determine the

R-Values (resistance values on a scale of 0 to 100 per AASHTO T 190). The underlying subgrade soils through the project limits vary considerably from sandy lean clays and clayey sands on the high plateau between Mileposts 0 and 2.10 to silty sands with gravel within the canyon between Mileposts 2.10 to 7.10. The high plateau’s sandy lean clay (R-

Value of 8) and clayey sands (R-Value less than 5) have an average R-Value of 6.5. The canyon’s silty sands with gravel have much higher R-Values (32 to 73). The R-Value of

6.5 was conservatively used for the project’s pavement design. The subgrade Resilient

Modulus (MR) is calculated from the R-Value using the following correlation equation for fine grained soils from the AGDPS, Page I-14, Equation 1.5.3, MR (psi) = 1,000 +

555 x (R-Value). Based upon an R-Value of 6.5, a Resilient Modulus of 4,600 psi was used for the pavement design.

Structural Layer Coefficients

Standard CFLHD structural layer coefficients were selected for asphalt concrete pavement (0.44) and full depth reclamation (0.12) in accordance with Exhibit 11.2-C of the PDDM. A drainage coefficient of 1.0 was utilized for all proposed layers.

Structural Number Calculations

The 1993 AASHTO pavement design procedure is used to determine the required pavement structural number (SN) for the project. Based upon the ESALs, the subgrade

Resilient Modulus, and the aforementioned design criteria, the following required 20-year pavement design structural number is calculated (See Appendix D).

Required SN for East Portal Road = 2.28 inches

VI. PAVEMENT RECOMMENDATIONS & DISCUSSION

Project Recommendations

In accordance with the 1993 AASHTO design procedure, a 20 year pavement design requires a Structural Number (SN) of 2.28. After evaluating alternatives, the following pavement structural section is recommended for the project:

3 inches of Asphalt Concrete Pavement (SN = 3” x 0.44 = 1.32”)

8 inches of FDR - Pulverize (SN = 8” x 0.12 = 0.96”)

TOTAL SN = 2.28 inches

In the future, the portion of the road east of the BOR gate will also need to be rehabilitated, in addition to the BOR lots at the top and toe of the dam, as well as, the tunnel on the upper BOR road. Based upon the pavement borings, the upper and lower

BOR roads can be rehabilitated with the recommended 3 inches of asphalt over 8 inches of FDR. The future pavement design for the tunnel and BOR lots will require a core drilling investigation of the existing pavement thickness to assess whether an asphalt overlay or pavement removal and replacement are better solutions for these particular areas. The tunnel geometry probably precludes FDR for its 500 foot length.

VII. MATERIALS RECOMMENDATIONS, SCRs, AND

CONSTRUCTION CONSIDERATIONS

Selection of Asphalt Binder

The LTPPBind program, the PDDM standards, and the CDOT binder selection criteria were utilized for the selection of the asphalt binder for the project (See Appendix E).

Based on these considerations, a PG 58-34 binder should be used for the project. This binder grade is readily available and commonly used by the Colorado DOT.

Prime and Tack Coats, Fog Seal and Blotter

For this project, a Prime Coat and Blotter applied to the base prior to asphalt placement, a

Tack Coat applied between asphalt lifts, and a Fog Seal applied to the final pavement surface are recommended.

Materials for Culvert Pipe / Cement

The subgrade soil’s pH, resistivity, sulfates, and chlorides do not show a need to specify special culvert materials in accordance with the pipe selection criteria in Appendix F.

Based upon this information, the project soils are considered non-corrosive.

Bid Items

Suggested FP-14 pay items for the proposed structural section are shown in Table 3.

Table 3: Recommended Pay Items

Item

Number Item Description Unit Remarks

30401-5500 Full Depth Reclamation, Method 2, 8-Inch Depth MILE

40101-5600*

Asphalt Concrete Pavement, Gyratory Mix, 1/2-

Inch or 3/4-Inch Nominal Maximum Size

Aggregate, 0.3 To <3 Million ESAL

TON

40105-3000* Antistrip Additive, Type 3 TON

40301-0100* Asphalt Concrete Pavement, Type 1 TON

40601-0000 Fog Seal TON

41102-1000 Prime Coat, Method 1 SQYD

41105-0000 Blotter TON

41201-0000 Tack Coat TON

* Based upon funding, the proposed FDR and paving of the East Portal Road may be executed using more than one project. For projects with less than 6,000 tons of asphalt, Table 3’s 40301-0100 pay item is recommended for the asphalt concrete pavement. For projects with more than 6,000 tons of asphalt, Table 3’s 40101-5600 and 40105-3000 pay items are recommended for the asphalt concrete pavement.

SCRs and Construction Concerns

Between mileposts 2.1 and 5.1, 16% grades and hairpin curves are present. Contractors should select construction equipment and adjust operations accordingly to meet the specifications in the contract. CFLHD standard SCRs related to pavements and materials are expected to be used with the exception of Section 403 Asphalt Concrete. For CDOT asphalt mixes, the following shall be added to SCR Subsection 403.02:

(a) Type I. Delete the subsection and Table 403-1 and substitute the following:

Submit a state department of transportation volumetric JMF used locally and approved within the past 12 months for approval at least 30 days before production. For each proposed JMF, submit a production certification conforming to state department of transportation specifications.

Pavement Roughness

If Table 3’s 40301-0100 pay item is used for the asphalt pavement, it is recommended that pavement roughness be evaluated using Type IV straightedge in accordance with

FP-14 Section 403.11. If Table 3’s 40101-5600 and 40105-3000 pay items are used for the asphalt, it is recommended that roughness be evaluated as Type III-B and IV in accordance with FP-14 Sections 401.16(d) and 401.16(e) and Table 401-5.

APPENDICES

A – Vicinity Map, Site Maps, & As-Builts

B – Boring Log and Lab Report

C – Site Investigation Photos

D – Pavement Design Calculations

E – Asphalt Binder Selection & Climate Data

F – Pipe Selection Criteria

APPENDIX A – Vicinity Map, Site Maps, & As-Builts marquez Text Box MP 0.00 intersec. w/Black Cyn. Rd.

marquez Text Box MP 2.0, begin steep grades, severe pv't washboarding marquez Text Box NPS Maintiance Facility marquez Text Box marquez Text Box Campground access road, not work required marquez Text Box End of lower access rd.

marquez Text Box MP 5.15, end steep grades marquez Text Box marquez Text Box MP 7.1, End of upper access rd.

marquez Line marquez Line marquez Line marquez Line marquez Line marquez Line marquez Line marquez Text Box Tunnel marquez Line

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APPENDIX B – Boring Log and Lab Report

Sample

Number

Station or

Location

Offset

(from c/l) Date

Depth of

Bore Sample Type Requested Testing

0 to 6"

6" to 1.5' No sample

1.5' to 5'

0 to 5"

5" to 1' No sample

1' to 5'

0 to 6"

6" to 1.5' 5 gallon bucket Classification & R-Value

1.5' to 2.5'

2.5' to 4'

4' to 5'

0 to 5"

5" to 2.5' No sample 1, 2, 3, 4

2.5' to 5'

0 to 5"

5" to 1'

1' to 3' No sample

3' to 5'

0 to 4.5"

4.5" to 3' Classification, R-Value, 3' to 5' 5 gallon bucket pH, & Resistivity

0 to 5"

5" to 3'

3' to 5' 5 gallon bucket Classification & R-Value

0 to 6"

6" to 1' Classification, R-Value, 1' to 5' 5 gallon bucket pH, & Resistivity

0 to 5"

5" to 1'

1' to 3' 5 gallon bucket Classification & R-Value

3' to 5'

0 to 5"

5" to 10"

10" to 5' 5 gallon bucket Classification & R-Value

0 to 5"

5" to 1'

1' to 5' No sample

0 to 5"

5" to 1.5'

1.5' to 2' No sample

2'

0 to 4.5"

4.5" to 2'

2' to 3' No sample

3'

0 to 5"

5" to 2'

2' to 3' No sample

3'

0 to 5"

5" to 3' 5 gallon bucket Classification

3' to 5'

0 to 5"

5" to 2.5'

2.5'

0 to 5"

5" to 2' No sample

2'

0 to 4"

4" to 2' 5 gallon bucket Classification & R-Value

2'

0 to 4"

4" to 10"

10" to 4' No sample

4'

0 to 5"

5" to 10.5"

10.5" to 2.2' No sample

2.2'

0 to 4.5"

4.5" to 2' 5 gallon bucket Classification, 2' pH, & Resistivity

0 to 4"

4" to 1.5' No sample

1.5'

0 to 4.5"

4.5" to 1.5' No sample

1.5' brown aggregate base & subbase brown aggregate base & subbase golden silty sand w/ gravel brown aggregate base brown aggregate base brown aggregate base & subbase tan silty sand w/ gravel brown aggregate base & subbase tan silty sand w/ gravel brown aggregate base & subbase asphalt asphalt tan silty gravel w/ sand asphalt refusal

BH-18 MP 5.35 6'LT 11/20/2018 2'

BH-17 MP 5.00 5'LT 11/20/2018 2.5'

11/20/2018 3'

BH-15 MP 4.40 5'LT 11/20/2018 3'

BH-16 MP 4.65 4'RT 11/20/2018 5'

6'LTMP 0.70BH-3

BH-4

7'LT 11/20/2018 5'

BH-11

BH-7 MP 2.10 6'LT 11/20/2018 5'

5'

6'LTMP 0.00BH-1 5'

asphalt

BH-6 MP 1.80 6'RT 11/20/2018 5'

asphalt tan clay

BH-5 MP 1.40 11/20/2018

brown aggregate base & subbase asphalt

5'

MP 1.05 6'RT 11/20/2018 5'

6'LT

11/20/2018 asphalt brown aggregate base golden clayey sand brown aggregate base asphalt refusal asphalt golden brown silty sand w/ gravel asphalt tan silty sand w/ gravel asphalt redd-brown clayey sand w/ gravel asphalt golden brown silty sand w/ gravel asphalt refusal asphalt refusal red clay brown aggregate base & subbase brown aggregate base tan silty sand w/ gravel brown aggregate base & subbase brown aggregate base & subbase

BH-21 MP 6.55

BH-9 MP 2.60 4'RT 11/20/2018 5'

MP 3.00 5'LT 11/20/2018 5'

BH-12 MP 3.40

6'LT 11/20/2018 2.2'

BH-13 MP 3.70 4'RT 11/20/2018 2

BH-14 MP 4.00 4'LT

refusal

BH-20 MP 6.05

asphalt asphalt grey clay tan clay

Boring Observations (grey = sample depth ) tan clay tan clay asphalt brown aggregate base brown aggregate base tan clay brown aggregate base red clay brown aggregate base & subbase

3'RT 11/20/2018 4'

asphalt brown aggregate base brown silty gravel w/ sand

11/20/2018 asphalt brown aggregate base & subbase refusal

BH-2 MP 0.40 6'RT 11/20/2018 5'

asphalt tan clay refusal brown aggregate base

BH-19 MP 5.65 6'LT 11/20/2018 2'

asphalt refusal

BH-10 MP 2.80 4'RT 11/20/2018 5'

CO FTBR CRYSTAL DAM (1) EAST PORTAL ROAD BORING LOG (November 20, 2018) brown aggregate base & subbase

BH-23

Lower Access

MP 7.0

4'LT 11/20/2018 1.5'

asphalt brown aggregate base & subbase refusal

B-24 Upper Access

MP 7.0

5'RT 11/20/2018 1.5'

asphalt refusal brown silty gravel w/ sand refusal

BH-22 MP 6.85 8'RT 11/20/2018 2'

APPENDIX C – Site Investigation Photos

MP 0.0, BH-1, Looking Back at Intersection with NPS’ South Rim Road & Gate House

MP 0.4, BH-2, 5” Asphalt over 7” Brown Aggregate Base over Tan Clay Subgrade

MP 0.70, BH-3, Looking Ahead at Red Clay in Cut and Chip Seal Shoving & Bleeding

MP 1.2, Looking Ahead at Pavement Distresses (Pothole, Rutting, Shoving, & Bleeding)

MP 2.4, BH-8, Looking Ahead at Chip Seal Shoving & Bleeding on Steep Grade

MP 2.60, BH-9, Looking Ahead at Chip Seal Shoving & Bleeding on Steep Grade

MP 3.4, BH-12, Looking Back at Chip Seal Shoving & Bleeding on Steep Grade

MP 3.4, BH-12, Looking Ahead at Hairpin Curve in Cut and Chip Seal Distresses

MP 3.7, BH-13, Looking Ahead at Large Cut and Chip Seal Shoving & Bleeding

MP 4.0, BH-14, Looking Back at Large Rock Cut at Hairpin Curve

MP 4.65, BH-16, Canyon View, BH-17 is Downhill from Hairpin Curve in Distance

MP 5.0, BH-17, Looking Ahead at Chip Seal Shoving & Bleeding on Steep Grade

MP 6.05, BH-20, Looking Ahead at Road in Bottom of Canyon with River on the Left

MP 6.85, BH-22, BOR Gate & Wye to Upper & Lower Dam Access Roads

MP 7.0 on Upper Dam Access Road, Looking Ahead in Middle of Rock Tunnel

MP 7.1 on Upper Dam Access Road, Looking Back at East Tunnel Entrance

MP 7.1 on Upper Dam Access Road, Looking Ahead at Top of Dam & Appurtenances

MP 7.0 on Lower Dam Access Road, Looking Ahead at Dam and Power House

APPENDIX D – Pavement Design Calculations

ESAL Calculations

Project: CO FTBR CRYSTAL DAM(1) Date: 5/24/2019 Location: Montrose County, Colorado

Performance Period (years) 20 Two-Way Traffic (ADT) 100 Number of Lanes in Design Direction 1 Percent of Trucks in Design Lane 100% Percent of Trucks in Design Direction 50%

Accumulated Average Initial 18-kip ESALs for

Vehicle Percent Annual % Growth Truck Factor Performance Class of ADT Growth Factor (ESALs/Truck) Period

2-3 95% 2% 24.30 0.004 1,685 5-6 5% 2% 24.30 0.7 15,520

Total 17,205 Design ESALs 50,000

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APPENDIX E – Asphalt Binder Selection & Climate Data

Colorado Department of Transportation

2019 Pavement Design Manual

Table 6.9 Recommended SuperPaveTM Gyratory Design Revolution (NDES)

CDOT Pavement

Management System

Traffic Classification

(20 Year Design ESAL)

20 Year Total

18k ESAL in the Design

Lane

High Temperature Category

Very Cool Cool Moderate Hot

Low < 100,000 50 50 50 50

100,000 to < 300,000 50 75 75 75

Medium 300,000 to < 1,000,000 75 75 75 75

1,000,000 to < 3,000,000 75 75 75 100

High 3,000,000 to < 10,000,000 75 75 100 100

Very High 10,000,000 to < 30,000,000 --- --- 100 ---

Very Very High ≥ 30,000,000 --- --- 125 ---

Note: Based on Standard Practice for SuperPave™ Volumetric Design for Hot-Mix Asphalt (HMA), AASHTO

Designation R 35-04.

6.12.3 Binder Selection

Performance graded (PG) binders have two numbers in their designation, such as PG 58-34. Both numbers describe the pavement temperatures in degrees Celsius at which the pavement must perform. The first number (58 in the example) is the high temperature standard grade for the pavement, and the second number (minus 34 in the example) is the low temperature standard grade.

PG 64-28 (rubberized) or PG 76-28 (polymerized) or bituminous mixtures should only be placed directly on an existing pavement or milled surface that does not show signs of stripping or severe raveling. Cores should be taken to determine if stripping is present. Because of a limited number of tanks, Colorado local suppliers only have the capacity to supply a limited number of asphalt cement grades. Table 6.10 Available Asphalt Cement Grades in Colorado shows available grades that maybe used and/or available on CDOT projects.

Table 6.10 Available Asphalt Cement Grades in Colorado

Polymer Modified Unmodified

PG 76-28

PG 70-28

PG 64-28

PG 58-34

PG 64-22

PG 58-28

Note: The Region Materials Engineer may select a different gyratory design revolution for the lower HMA lifts.

C o lo ra d o

D ep ar tm en t o f

T ra n sp o rt at io n

P av em e n t

D e si g n M a n u al

F ig u re

.3 lo ra d o

P e rc en t

R el ia b il it y L

T P

P H ig h

P a v e m en t

T e m p e ra tu re

W ea th e r

S ta ti o n

M o d el s lo ra d o

D ep ar tm en t o f

T ra n sp o rt at io

P av em e n t

D e si g n M a n al ig u re lo ra d o

P e rc en t

R el ia b il it y L

T P

P L o w

P a v e m en t

T e m p e ra tu re

W ea th e r

S ta ti o n

M o d el

LTPPBind V3.1 Data

Climate Data

APPENDIX F – Pipe Selection Criteria

Hydrology and Hydraulics December 2012

7-48 Roadway Hydraulics

7.3.5.5 Recommended Methods

Design and evaluate the performance of energy dissipators according to the methods presented in HEC 14. HEC 14 also contains procedures for estimating scour hole dimensions at pipe outlets.

7.3.5.6 Reporting

The design of outlet protection for culvert, ditch, or storm drain outlets should be supported by documentation containing, at a minimum, the following information:

● Project identification

● Location of proposed installation

● Hydraulic design calculations

7.3.5.7 Plans

For the location and design of riprap outlet protection, prepare plans showing all details necessary to construct the improvements according to the hydraulic design, including the following:

● Location

● Dimensions and extent of riprap

● Gradation

● Bedding and Filter Material or Geotextile

● Grading or slope details

7.3.6 ALTERNATIVE PIPE MATERIALS

It is Federal Lands Highway policy to specify alternative drainage pipe materials on all projects where feasible and to comply with the provisions of 23 CFR 635.411. All suitable pipe materials, including reinforced concrete, steel, aluminum, and plastic will be considered as alternatives for all new cross culverts and storm drain pipes on Federal Lands Highway projects.

Not all pipe materials are appropriate or applicable for all storm drain applications. The design of alternative drainage pipe materials should consider functionally equivalent performance in three areas: structural capacity, durability and service life, and hydraulic capacity. The service life and hydraulic capacity issues are addressed in this section.

7.3.6.1 References

The following references provide source information for the development of the standards, criteria, and guidance of this subsection (most recent editions apply):

1. 23 CFR 635.411 Title 23 CFR 635.411 in 23 CFR 635D, General Material Requirements

Roadway Hydraulics 7-49

2. FHWA-FLP-91-006 FHWA, Durability of Special Coatings for Corrugated Steel Pipe, FHWA FLP-91-006

3. FHWA-RD-97-140 FHWA, Durability Analysis of Aluminized Type 2 Corrugated Metal Pipe, FHWA RD-97-140, 2000.

4. AASHTO HDG

Vol. IV

AASHTO Highway Drainage Guidelines, Volume IV – Hydraulic Design of Culverts

5. AASHTO HDG

Vol. XIV

AASHTO Highway Drainage Guidelines, Volume XIV – Culvert Inspection and Rehabilitation

6. Caltrans Chapter

California Department of Transportation Highway Design Manual, Chapter 850 – Physical Standards

7.3.6.2 Design Standards

7.3.6.2.1 Service Life

Design cross culvert and storm drain pipes with a minimum maintenance-free service life of 50-years, regardless of pipe material selection. A shorter service life may be used for temporary installations, and a longer service life may be considered in unusual situations.

7.3.6.2.2 Minimum Pipe Classification

Use Class II as the minimum for all reinforced concrete pipes. Determine appropriate pipe class from FLH fill height FLH Standard Drawings.

Use a minimum wall thickness of 0.0625” [1.63 mm] for all steel and aluminum pipes. The appropriate minimum structural metal thickness will be determined from approved FLH fill height tables.

7.3.6.3 Design Guidance

7.3.6.3.1 Service Life

The durability and service life of a storm drain pipe is directly related to the environmental conditions encountered at the site and the type of materials and coatings from which the pipe was fabricated. The two primary causes of early failure in drainage pipe materials are corrosion and abrasion.

Corrosion gradually wears away at the pipe walls by chemical action, and can occur from both the soil and water sides of the pipe. Abrasion wears away at the interior pipe wall by friction from suspended or bed-load sediment.

http://www.fhwa.dot.gov/publications/research/infrastructure/hydraulics/97140/97140.pdf http://www.fhwa.dot.gov/publications/research/infrastructure/hydraulics/97140/97140.pdf http://www.dot.ca.gov/hq/oppd/hdm/pdf/chp0850.pdf

7-50 Roadway Hydraulics

7.3.6.3.2 Data Collection

Corrosion

Representative pH and resistivity determinations are required in order to specify pipe materials capable of providing a maintenance-free service life. Samples are taken in accordance with the procedures described in AASHTO T 288 and T 289. Samples should be taken from both the soil and water side environments to ensure that the most severe environmental conditions are selected for determining the service life of the drainage pipe. Soil samples should be representative of backfill material anticipated at the drainage site. Avoid taking water samples during flood flows or for two days following flood flows to ensure more typical readings. In locations where streams are dry much of the year, water samples may not be possible or necessary. In areas of known uniform pH and resistivity readings, a random sampling plan may be developed to obtain the needed information.

In corrosive soil conditions where water side corrosion is not a factor, consider specifying less corrosive backfill material to modify the soil side environment. The mitigating effect of the specified backfill should be taken into account in making alternative pipe materials selections in situations where the soil side conditions control the design.

Abrasion

An estimate of the potential for abrasion is required in order to determine the need for invert protection. Four levels of abrasion are referred to in this guidance and the following guidelines are established for each level:

● Level 1. Nonabrasive conditions exist in areas of no bed load and very low velocities.

This is the condition assumed for the soil side of drainage pipes.

● Level 2. Low abrasive conditions exist in areas of minor bed loads of sand and velocities of 5 ft/s [1.5 m/s] or less.

● Level 3. Moderate abrasive conditions exist in areas of moderate bed loads of sand and gravel and velocities between 5 ft/s and 15 ft/s [1.5 m/s and 4.5 m/s].

● Level 4. Severe abrasive conditions exist in areas of heavy bed loads of sand, gravel, and rock and velocities exceeding 15 ft/s [4.5 m/s].

Abrasion levels are intended as guidance to help the engineer consider the impacts of bed-load wear on the invert of pipe materials. Sampling of the streambed materials is not required, but visual examination and documentation of the size of the materials in the stream bed and the average slope of the channel will give the designer guidance on the expected level of abrasion.

Where existing culverts are in place in the same drainage, the conditions of inverts should also be used as guidance. The expected stream velocity should be based upon a typical flow (i.e., 2-year flow and less) and not a 10-or 50-year design flood.

Roadway Hydraulics 7-51

7.3.6.3.3 Reinforced Concrete Pipe

Reinforced concrete pipe (AASHTO M 170M) is typically specified as an alternative whenever environmental conditions permit. The appropriate pipe class is determined from approved FLH fill height FLH Standard Drawings. If the following guidance on corrosion and abrasion limitations is used, reinforced concrete pipe can be assumed to have a minimum service life of

50 years.

Corrosion

Reinforced concrete pipe should not be specified for extremely corrosive conditions where the pH is less than 3.0 and the resistivity is less than 300 Ω-cm. Where the pH is less than 4.0, or the pipe is exposed to wetting and drying in a salt or brackish water environment, protective coatings (e.g., epoxy resin mortars, poly vinyl chloride sheets) should be used. When the sulfate concentration is greater than 0.2% in the soil or 2,000 parts per million in the water, Type

V cement should be specified. When the sulfate concentration is greater than 1.5% in the soil or 15,000 parts per million in the water, Type V cement should be used with a sulfate resistant pozzolan. A higher cement ratio may also be used (e.g., AASHTO Class V pipe design).

Abrasion

On installations in severe abrasive environments, consider using seven or eight sack concrete or increasing the cover over the reinforcing steel.

7.3.6.3.4 Steel Pipe with Metallic Coatings

Steel pipe will typically be specified as an alternative when the environmental conditions permit.

The appropriate minimum structural metal thickness is determined from approved FLH fill height tables. Federal Lands Highway design policy assumes that steel pipe will provide a useful, maintenance-free service life for a period of time beyond the point of first perforation. This assumes an acceptable risk for most Federal Lands Highway projects, but at locations with erodible soils, large traffic volumes, or high fills where replacement or repair would be unusually difficult or expensive, consider increasing the steel plate by one standard thickness. In unusual situations where very high fills and severe abrasion are combined, or where other environmental concerns would make replacement of a pipe culvert very costly or impractical, consider using a pipe one size larger in diameter to permit re-lining in the future by insertion of another pipe.

The following types of steel pipe with metallic coatings are considered as alternatives on

Federal Lands Highway projects:

● Galvanized steel (AASHTO M 218)

● Aluminum coated steel (Type 2) (AASHTO M 274)

Corrosion

Under non-abrasive and low-abrasive conditions, the service life of steel pipe with metallic coatings may be determined based upon corrosion (i.e., pH and resistivity) factors determined from Exhibit 7.3-B, which shows the relationship between service life and corrosion for plain

7-52 Roadway Hydraulics galvanized steel pipe. It has been adapted from the California Department of Transportation

“Method for Estimating the Service Life of Steel Culverts,” California Test 643. The curves have been modified to show the expected average service life of pipe with a steel thickness of

0.0625” [1.63 mm] assuming a useful, maintenance-free service life 25 percent longer than the number of years to first perforation. Under moderate and severe abrasive conditions, abrasion protection must also be considered.

Under nonabrasive and low abrasive conditions, the metal thickness of galvanized and aluminum coated steel (Type 2) alternatives should be determined from Exhibit 7.3-B based on the resistivity and pH of the site. The minimum metal thickness of steel pipe, as determined from FLH standard fill height tables, may have to be increased, or the additional life of a protective coating may have to be added, in order to provide a 50-year service life. The results included in FHWA-FLP-91-006 indicate that within the environmental range of 5.0 through

9.0 pH and resistivity equal to or greater than 1500 Ω-cm, aluminum coated steel (Type 2) can be expected to give a service life of twice that of plain galvanized pipe.

Exhibit 7.3-B can be used to determine various combinations of increased thicknesses, aluminum coated steel (Type 2), and protective coatings to achieve a 50-year service life, but in no case may the metal thickness specified by the structural requirements be reduced.

Abrasion

Under nonabrasive and low abrasive conditions, the metal thickness of the galvanized, galvalume, and aluminum coated steel alternatives, as determined from Exhibit 7.3-B, should be used.

On installations in moderate abrasive environments where protective coatings are not required for corrosion protection, the thickness of the metal should be increased by one standard metal pipe thickness determined from the diagram for average service life of plain galvanized culverts

(see Exhibit 7.3-B) or invert protection should be provided. Invert protection may consist of bituminous coating with invert paving with bituminous concrete, Portland cement concrete lining, installation of metal plates or rails, or velocity reduction structures.

On installations in severe abrasive environments where protective coatings are not required for corrosion protection, the thickness of the metal should be increased by one standard metal pipe thickness determined from the diagram for average service life of plain galvanized culverts (see

Exhibit 7.3-B) and invert protection should be provided. Invert protection may consist of installation of metal plates or rails, or velocity reduction structures.

Protective coatings are not suitable for corrosion protection in moderate-abrasive and severe abrasive locations. Metal pipes should not be specified in moderate and severe abrasive environments where coatings are required to protect against water-side corrosion.

Roadway Hydraulics 7-53

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7-54 Roadway Hydraulics

7.3.6.3.5 Non-Metallic Protective Coatings for Steel Pipe

Protective coatings may be used to provide additional protection from corrosion or abrasion resulting in an extended service life. Coatings to protect against corrosion may only be used in non-abrasive and low abrasive environments.

The additional service life noted below in bold for each type of protective coating, for corrosion protection, are from Part V of FHWA-FLP-91-006. The added service is applicable only to non-abrasive and moderate abrasive conditions. All of the following types of steel pipe with non-metallic coatings are considered as alternatives on Federal Lands Highway projects:

Bituminous coating

Bituminous coatings (AASHTO M 190) can be expected to add 10 years of service to the water side and 25 years life to the soil side service life of pipe as determined from Exhibit 7.3-B.

Bituminous-coated pipe should not be used in low abrasive environments.

Bituminous paving and coating

Bituminous paved invert with bituminous coatings (AASHTO M 190) can be expected to add

25 years life to water side locations. Under moderate abrasive conditions, bituminous paved pipe may be used for invert protection where corrosion protection is not required.

Concrete lining

Concrete lining (ASTM A 849) can be expected to add 25 years of service life. Due to the natural cracking of concrete, the concrete lining should be applied over an asphalt coating if corrosion protection is needed. Under moderate abrasive conditions, concrete lined pipe may be used for invert protection where corrosion protection is not required.

Polymer coating

Ethylene Acrylic Acid Film coatings (AASHTO M245 and M246) should provide an additional

30 years service life with a 0.009” [0.25 mm] thickness.

Aramid fiber bonded coating

Only limited data is available for the service life of aramid fiber bonded coated (ASTM A 885) and epoxy coated pipes. No additional service life is currently credited with this policy.

7.3.6.3.6 Aluminum Alloy Pipe

Aluminum alloy pipe (AASHTO M 196M) will typically be specified as an alternative when environmental conditions permit. The appropriate minimum structural metal thickness is determined from approved FLH fill height tables. Within the following limits of corrosion and abrasion, aluminum alloy pipe can be assumed to have a service life of 50 years. Additional service life may be achieved where required by abrasion with the addition of protective coatings or additional metal thickness as discussed below:

Roadway Hydraulics 7-55

Corrosion

An aluminum alloy should be allowed if the pH is between four and nine and the resistivity is greater than 500 Ω-cm. An aluminum alloy alternative can also be considered for use in salt and brackish environments when embedded in granular, free draining material.

Abrasion

On installations in non-abrasive and low-abrasive environments, abrasion protection is not required.

On installations in moderately abrasive environments, the thickness should be increased by one standard metal thickness or invert protection should be used. Invert protection may consist of bituminous coating and invert paving with bituminous concrete or Portland cement concrete, installation of metal plates or rails, or velocity reduction structures.

On installations in severe abrasive environments, the thickness of the metal should be increased by one standard metal pipe thickness from that determined for low-abrasive conditions and invert protection should be provided. Invert protection may consist of installation of metal plates or rails or velocity reduction structures.

7.3.6.3.7 Plastic Pipe

Polyethylene and polyvinyl chloride plastic pipe may be specified as alternatives for pipe diameters and minimum resin cell classifications shown in the AASHTO’s Standard Specifications for Highway Bridges, Division I Design, Section 18, Soil Thermoplastic Pipe

Interaction Systems. The thickness of the plastic alternatives must meet the structural requirements of AASHTO’s Standard Specifications. The assumed service life of plastic pipe designed in accordance with AASHTO Section 18 is 50 years. The maximum allowable fill heights for pipe materials listed below is determined from approved FLH standard fill-height tables which include the following plastic pipe materials:

● Smooth wall polyethylene (ASTM F 714)

● Corrugated polyethylene (AASHTO M 294)

● Ribbed polyethylene (ASTM F 894)

● Smooth wall polyvinyl chloride (AASHTO M 278 and ASTM F 679)

● Ribbed polyvinyl chloride (AASHTO M304 and ASTM F 794)

Corrosion

Plastic alternatives may be specified without regard to the resistivity and pH of the site.

Abrasion

Under nonabrasive and low-abrasive conditions, polyethylene and polyvinyl chloride alternatives should be allowed. Plastic alternatives should not be used under moderate and severe abrasive conditions without invert protection.

7-56 Roadway Hydraulics

Maximum Size

Limit the size of plastic pipe to 48” [1200 mm] under mainline roads.

The locations selected for use of plastic pipes should address partner agency concerns of possible damage due to fire, ultraviolet sunlight, and rodents.

7.3.6.4 Recommended Methods

Design and evaluate the design service life for galvanized steel culvert and storm drain pipes by the Modified California method presented in Exhibit 7.3B. Refer to FHWA-RD-97-140, Durability Analysis of Aluminized Type 2 Corrugated Metal Pipe, for design guidance on aluminized material.

7.3.6.5 Reporting

Documentation of the design service life of culvert and storm drain pipes should be included in the design reporting.

7.3.6.6 Plans

For culvert and storm drain pipes, include information on pipe material, size, class, gauge, and any special coatings in the Plan Drainage Summary.

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