NV_FLAP_CR_196(2)_Silver_Peak_Road_Pavement_Report_Signed.pdf

SILVER PEAK ROAD

ESMERALDA COUNTY, NEVADA

NV FLAP CR 196(2)

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

NV FLAP CR 196(2) Silver Peak 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 SOILS & GEOLOGY

V. PAVEMENT DESIGN INPUTS

VI. PAVEMENT RECOMMENDATIONS & DISCUSSION

VII. MATERIALS RECOMMENDATIONS

APPENDICES

A – Location & Boring Maps

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 second phase of the

Silver Peak Road projects in west central Nevada. On the east, Silver Peak Road begins at the intersection with US Route 95, approximately 4.5 miles north of Goldfield and 23 miles south of Tonopah. On the west, Silver Peak Road terminates at State Highway 265

(Nivloc Road) in the Town of Silver Peak, Nevada (population of approximately 100).

The route is approximately 25 miles in total length. Silver Peak Road’s first phase consisted of the rehabilitation of the east 16.5 miles of the road in 2017. Silver Peak

Road’s second phase begins at the west terminus of the phase 1 asphalt pavement (just west of the sharp bend in the road) and extends 2.45 miles to the west as shown on the location maps in Appendix A. This section of road is currently gravel with an average width of 28 feet. The project proposes a 26 foot pavement width with 12 foot lanes and 1 foot shoulders in each direction. The project includes raising the road with fill material and ditch grading to direct storm flows to proposed pipe and concrete box culverts.

II. CLIMATE

Climate data was obtained from intellicast.com. This data is summarized in Table 1 below and is provided in Appendix E. The project is within a desert area which has an average precipitation of approximately 4.46 inches/year. The project ranges in elevation from about 4,300 feet to 4.400 feet. The project area receives moisture by both snow and rain depending upon the time of year. Often the rain comes in quick thunderstorms or monsoonal events that create flash flooding of dry ravines.

Table 1. Weather Data

Month Average

HIGH

Record

HIGH

Average

LOW

Record

LOW

Average

PRECIP.

January 47 72 19 -22 0.39

February 54 77 24 -21 0.31

March 62 87 32 4 0.53

April 69 91 39 11 0.47

May 80 102 49 26 0.37

June 90 107 57 35 0.37

July 98 111 62 37 0.45

August 95 111 59 36 0.39

September 86 104 50 28 0.25

October 73 104 38 12 0.40

November 57 79 26 -2 0.31

December 46 69 18 -14 0.22

Temperatures are in °F and precipitations are in inches.

III. EXPLORATION

On October 25, 2018, a pavement and subgrade investigation was conducted for the project consisting of six shallow hand augered borings (1 to 2.5 feet deep). The locations of the soil borings (BH-1 through BH-6) are shown on the Boring Map in Appendix A.

CFL personnel logged the findings including depth of boring and visual soil classification. During the site visit, five soil samples were collected. These samples were submitted to the CFLHD laboratory for soil classification and additional testing. The boring log and laboratory report are provided in Appendix B. Borings BH-1 through

BH-5 were along the project’s 2.45 miles of roadway. Boring BH-6 was located at the existing County stockpile approximately 3.5 miles east of the project along Silver Peak

Road. Only one sample was taken from the stockpile, and therefore, the test results may not necessarily be representative of the entire stockpile.

IV. EXISTING SOILS & GEOLOGY

The second phase of the Silver Peak Road project (2.45 miles long) lies entirely within an alluvial fan. The current roadway is a gravel road constructed of the native soils. This material requires frequent maintenance year round. Additionally, the roadway frequently washes out in flash flooding events, resulting in periodic closures for several days while the road and ditches are regraded and reconstructed. The subgrade investigation found

Silver Peak Road’s subgrade soils to generally consist of silty sand with gravel (ASTM

SM soils / AASHTO A-1 and A-2-4 soils). The boring log and laboratory report are provided in Appendix B. The project is located in an area of historic precious metal mining including gold and silver. Currently, the only lithium mine in the United States is located immediately northwest of the project. Boulder and cobble size rocks proliferate the surrounding landscape; many of the rocks having volcanic origins.

V. PAVEMENT DESIGN INPUTS

The pavement design for Silver Peak 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 60%

Traffic

There is currently very little traffic on Silver Peak Road. The road appears to have two primary generators of traffic: 1) commuter and supply traffic for the lithium mine and 2) traffic associated with the small town of Silver Peak. Based upon the FLAP application and scoping site visit, Silver Peak Road has an average two-way ADT of 200 vehicles per day with approximately 5% trucks (10 trucks per day). The County has indicated that less than 1% of the ADT are tractor trailers (FHWA Class 8-10 vehicles) with the remaining trucks being FHWA Class 5-6 single unit trucks (4% of the ADT).

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, 0.7 for Class 5-6, and 2.0 for Class 8-

10. 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

(ESALs) are calculated to be 55,000 (see Appendix D).

Subgrade Soil Resilient Modulus

Two subgrade soil samples were submitted to the CFLHD laboratory to determine their

R-Values (resistance values on a scale of 0 to 100 per AASHTO T 190). The two subgrade samples were found to be silty sands with gravel with R-Values of 77 and 79. In accordance with PDDM Subsection 11.2.1.4, crushed aggregate base has R-Values greater than 80 with a Resilient Modulus (MR) value around 25,000 psi. In conclusion, Silver Peak Road’s existing subgrade material has engineering properties similar to aggregate base. On the other hand, the project proposes to raise the road using borrow material that will likely be AASHTO A-1 and A-2-4 soils; “very good” roadbed material.

Based upon PDDM Exhibit 11.4.2.C, “very good” roadbed material will likely have a

Resilient Modulus (MR) greater than 10,000 psi. As such, a conservative Resilient

Modulus (MR) value of 10,000 psi was used for the project’s pavement design.

Structural Layer Coefficients

Standard CFLHD structural layer coefficients were selected for asphalt concrete pavement (0.44) and crushed aggregate base (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 numbers (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 numbers is calculated (See Appendix D).

Required SN for Silver Peak Road = 1.72 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 1.72. 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”)

4 inches of Crushed Aggregate Base (SN = 4” x 0.12 = 0.48”)

TOTAL SN = 1.80 inches

VII. MATERIALS RECOMMENDATIONS, SCRs, AND

CONSTRUCTION CONSIDERATIONS

Selection of Asphalt Binder

The LTPPBind program and the PDDM standards were utilized for the selection of the asphalt binder for the project (See Appendix E). A PG 64-28 NV binder is recommended for the project’s asphalt pavement. The Nevada DOT uses this grade exclusively for areas north of Las Vegas.

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 project’s soils were found to be very corrosive with resistivity as low as 50 ohm-cm, chloride contents as high as 8,400 ppm, and sulfate contents as high as 5,200 ppm. To address the corrosive soils, the following culvert materials are recommended for the project: plastic pipe and concrete pipe and box culverts manufactured with Type II/V cement. Additionally, Type II/V cement is recommended for all concrete headwalls.

SCRs and Construction Concerns

CFLHD standard SCRs related to pavements and materials are expected to be used with the exception of the following FP-14 sections: Section 601 Minor Concrete Structures;

Section 602 Culverts and Drains; and Section 702 Asphalt Material. The 601 SCR to require Type II/V cement for all minor concrete. The 602 SCR to specify the following materials for culverts: plastic pipe, concrete pipe manufactured with Type II/V cement, and precast concrete box culverts manufactured with Type II/V cement. The 702 SCR to be tailored for the NDOT PG 64-28 NV binder. Any additional SCRs may be developed as needed.

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.

30101-0000 Aggregate Base 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

APPENDICES

A – Location & Boring Maps

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 – Location & Boring Maps

NV FLAP 196(2) SILVER PEAK ROAD

LOCATION MAP

Project Location

Proposed Silver Peak Road Project

Previous Phase of Silver Peak Road

N V

FL

AP

C R

6(

2) S ilv er

P ea k Ro ad

B O

R

IN

G M

A P

APPENDIX B – Boring Log and Lab Report

Sa m p le u m b e r

M ile p o st ff se t fr o m c

/l D at e

S a m p le d

D ep th o f

B o re Sa m p le T yp e

R eq u e st e d T es ti n g

C la ss if ic at io n

, R -V al u e, p

H re si st iv it y, s u lf at e s, c h lo ri d es

C la ss if ic at io n

, R -V al u e, p

H re si st iv it y, s u lf at e s, c h lo ri d es

C la ss if ic at io n

, f ra ct u re d f ac e s, an d s o d iu m s u lf at e s o u n d n es s

B H

-6 a t st o ck p ile

.5 m ile s ea o f p ro je ct

/2

/2

B H

-5 M

P

.3

'L

/2

/2

.5

N V

F

LA

P C

R

(2

SI

LV

ER

P

EA

K

R O

A D

B O

R

IN

G L

O G

O ct o b er

, 2

B H

-2 M

P

.1

'R

/2

/2

M P

.3

'R B

H -1

B o ri n g O b se rv a ti o n s

(g re y sa m p le d ep th

/2

/2 t o b ro w n s ilt y sa n d w it h g ra ve l g al lo n b u ck et

B H

-4 M

P

.0 a t c/ l

/2

/2 t o b ro w n s ilt y sa n d w it h g ra ve l

B H

-3 M

P

.3

'L

/2

/2 t o t o b ro w n s ilt y sa n d w it h g ra ve l f ro ck p ile , 3

.5 m ile s ea st o f p ro je ct g al lo n b u ck et t o b ro w n s ilt y sa n d w it h g ra ve l b ro w n s ilt y sa n d w it h g ra ve l f ro m r ad w in d ro w m at e ri al

Zi p lo ck b ag

S o il C la ss if ic at io n

S o il C la ss if ic at io n g al lo n b u ck et t o

.5 b ro w n s ilt y sa n d w it h g ra ve l g al lo n b u ck et

APPENDIX C – Site Investigation Photos

BH-1, MP 0.3, Looking West, Regraded Road & Ditches Following Recent Flooding

BH-4, MP 2.0, Looking West, Regraded Road & Ditches Following Recent Flooding

BH-5, MP 2.3, Looking East, Location of Hand Augered Boring

BH-5, MP 2.3, Subgrade Material to 2.5’ Depth

County Stockpile at Silver Peak Road Pit, 3.5 Miles East of Project

BH-6, Sample Location at County Stockpile, 3.5 Miles East along Silver Peak Road

APPENDIX D – Pavement Design Calculations

ESAL Calculations

Project: NV FLAP CR 196(2) Silver Peak Road Date: 12/27/2018

Location: Esmeralda County, Nevada

Performance Period (years) 20

Two-Way Traffic (ADT) 200

Number of Lanes in Design Direction 1

Percent of Trucks in Design Lane 100%

Percent of Trucks in Design Direction 60%

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 4,044

5-6 4% 2% 24.30 0.7 29,798

8-10 1% 2% 24.30 2 21,284

Total 55,127

Design ESALs 55,000

S H

T O

F L

E X

IB

L

E P

A V

E M

E N

T D

E S

IG

N

S N

D e te rm in a ti o n

D e s ig n I n p u ts

W

,0

E S

A L s A p p lic a ti o n s O v e r D e s ig n P e ri o d

T y p

R a n g e k t o m ill io n

R

R e lia b ili ty

T y p

R a n g e t o

S o

.4

S ta n d a rd D e v ia ti o n A

A S

H T

O S ta n d a rd

M R

,0 p si

S u b g ra d e R e s ili e n t M o d u lu s T y p

R a n g e t o p s i

P i

.2

In it ia l S e rv ic e a b ili ty

T y p

R a n g e

.2 t o

.4

P t

T e rm in a l S e rv ic e a b ili ty

T y p

R a n g e

.0 t o

.0

D E

S

IG

N S

N

.7

APPENDIX E – Asphalt Binder Selection & Climate Data

LTPPBind V3.1 Data

LTPPBind V3.1 Data Continued

LTPPBind V3.1 Data Continued

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

Exhibit 7.3-B ESTIMATING STEEL PIPE SERVICES LIFE F

E D

E R

A L

L A

N D

S H

IG

H

W A

Y M

O D

IF

IE

D C

A L

IF

O

R N

IA

M

E T

H O

D C

H A

R T

F

R

E S

T

IM

A T

IN

G

S E

R V

IC

E

L

IF

E O

F P

L A

IN

G

A L

V A

N

IZ

E D

S T

E E

L C

U L

V E

R e rv ic e

L if e

E s ti m a ti o n C h a rt f o r

A v e ra g e S e rv ic e

L if e o f

P la in G a lv a n iz e d C u lv e rt s

T E

S

T h e c u rv e s i n t h is

C h a rt a re b a s e d o n t h e d a ta i n F

H W

A -F

L P

-9 -0 w h ic h u s e s t h e f a c to rs i n C a lif o rn ia T e s t

“M e th o d f o r

E s ti m a ti n g th

S e rv ic e L if e o f S te e l C u lv e rt e s e f a c to rs i n c re a s e d t ti m a te d s e rv ic e l if e b y a ft e r fi rs t p e rf o ra ti o n

T h e C h a rt h a s a ls o b e e n m o d if ie d t o r e fl e c t a m in im u m m e ta l th ic k n e s s o f .0 i n c h o r g a g e

.6 m m

U n d e r c o n d it io n s w it h p

H b e tw e e n a n d a n d a b o v e R th a v e ra g e s e rv ic e l if e d e te rm in e d f o r p la in g a lv a n iz e d c u lv e rt s s h o u ld b m u lt ip lie d b y

.0 f o r

A lu m in u m c o a te d s te e l, T y p e

H

IC

K

N E

S S

F A

C T

O

.1

.2

.6 te

M u lt ip ly t h e a v e ra g e S e rv ic e L if e b y t ic k n e s s F a c to r

.1

.5

.1

.0

.6

.3

.8

IC

K

N E

S S in c

G

G E

IC

K

N E

S S

F

C T

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.