Pavements_Report.pdf

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August 21, 2019 Proposal No. 217-306

Muller Engineering Company, Inc.

777 S. Wadsworth Boulevard 4-100 Lakewood, Colorado 80226

Attn: Ms. Karen Fuhr, P.E.

Subject: Review of Recommended Pavement Structural Section, Donner Pass Road Improvements, Nevada and Placer Counties, California, CA FLAP NEV 40(1)

Dear Ms. Fuhr:

Yeh and Associates, Inc. is providing geotechnical services for the design of the Donner Pass Road Improvements in Nevada and Placer Counties California and submitted a Pavement Design and Geotechnical Report for the project dated February 22, 2019. The pavement structural sections recommended in the report were based on traffic information provided by Nevada County and presented in the Scoping Report for the project prepared by Muller and submitted June 19, 2015. The average daily traffic for Donner Pass Road was estimated as 1,596 vehicles per day, with 2 percent trucks and projected over 20 years at 1 percent growth. The purpose of this letter is to summarize additional pavement calculations performed by Yeh to help evaluate whether the recommended structural section can account for snow removal equipment the County has stated may not be accounted for in their previous traffic counts, specifically 950 Front End Loaders.

The recommended structural sections are generally composed of 3 inches of hot mix asphalt (HMA) pavement over a variable thickness of pulverized asphalt concrete compacted using full-depth reclamation, cracked and seated Portland cement concrete pavement, or a County minimum of 8 inches of base course material. The thickness of base course below the HMA generally exceeds the minimum structural number needed to support the projected traffic loads using AASHTO pavement design methods described in the report. Yeh performed a sensitivity analysis to consider whether additional traffic loads that may be applied by snow removal equipment would be exceed the capacity of the recommended structural sections.

The calculation sheet for the recommended structural sections is attached. The calculation includes the estimated structural number needed to support 2 percent trucks, and an additional calculation with the percent trucks increased to 5 percent. The required structural number based on the traffic loads and subgrade conditions encountered is 1.92 for Nevada County and 2.88 for the Placer County section (where poorer subgrade conditions were encountered.) The calculations for the http://www.yeh-eng.com/

Pavement Structural Section Project No. 217-306 Donner Pass Road Improvements August 21, 2019 recommended structural sections have a structural number of 2.28 (3 inches HMA/8 inches base course) to 4.08 (3 inches HMA/cracked and seated concrete). The required structural number based on an assumed 5 percent trucks (about 3 times the number of equivalent 18-kip single axle loads) is

2.23 for the Nevada County sections and 3.34 for the Placer County sections. The estimated structural number for the recommended pavements structural section exceeded the minimum structural number needed to allow for 5 percent trucks in all cases.

We appreciate the opportunity to be of service. Please contact Jon Blanchard at 805-481-9590 or jblanchard@yeh-eng.com if you have any questions or require additional information.

Sincerely, YEH AND ASSOCIATES, INC.

Jonathan D. Blanchard, GE2312 Robert G. La Force, P.E.

Geotechnical Engineer Senior Materials Engineer

Enclosures: Pavement Design Calculations (2 sheets)

Flexible Pavement Thickness Design - Spreadsheet

Client Name: Muller Engineering Project Number: 217-306 Project Name: Donner Pass Road 3R, I-180 East to Truckee Town Limit, PM 0-6.54 Date: by: J. Blanchard checked: R. LaForce Case: Snow removal sensitivity

Ref.

Mr Correlation: 1 Min W18: 50000 for HMA 10000 for aggregate surface

(a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l) (m) (n) (o) (p) (q)

R-value Wt18, EDAL's

Design ESAL's

Design Life

Reliablility

(3) Req'd SN(1) W18

(4) log(W18) ZR

Std.

Dev.

So

(2) po pt ∆psi S1

MR

(psi) log(W18) difference

1 Road (1% growth) 60.0 44 391793 20 75 1.92 391793 5.593 -0.674 0.49 4.2 2.5 1.7 7.87 18259 5.592 0.001 2 Clayey tuff subgrade 28.0 44 391793 20 75 2.88 391793 5.593 -0.674 0.49 4.2 2.5 1.7 5.04 6416 5.592 0.001 3 Road (5% trucks) 60.0 110 974414 20 75 2.23 974414 5.989 -0.674 0.49 4.2 2.5 1.7 7.87 18259 5.989 0.000 4 Clayey tuff subgrade 28.0 110 974414 20 75 3.34 974414 5.989 -0.674 0.49 4.2 2.5 1.7 5.04 6416 5.989 0.000 5 0 0

1) find req'd SN by using goal-seek to set "difference" column to zero by changing the value in the "SN" column in the same row

2) per FHWA (2008) PDDM, Ch. 11 use 0.49 for flexibile pavement design, use 0.39 for rigid pavement design

3) per FHWA (2008) PDDM, Ch. 11 use 75% for < 2,500 ADT; 85% for 2500-5000 ADT, 90% for >5000 ADT (CFL uses 75%)

4) per FHWA (2008) PDDM, Ch. 11 use min. 50,000 ESAL/W18 or 10,000 for aggregate surface roads.

I. AASHTO R-value Conversion and data summary: II. AASHTO CBR conversion and data summary:

Sample: 17P-02 17P-04 17P-08 17P-13 17P-15 Average Grindings Sample:

~Post Mile:

Soil: gSP SM SC SMg SMg AC Avg Soil:

R-value 73 66 28 63 72 60 67 60.4 CBR CBR = 18.6 14.8 4.3 13.4 18.0 12.3 15.3 13.6 MR = 1500xCBR (psi):

Subgrade MR (psi) 27925 22214 6416 20140 27027 18499 22953 20370 Equivalent R-value:

Equations/Definitions: 8644.07 Col. (f), Req'd SN = Structural number of pavement needed for subgrade and traffic condition

Col. (e), W18 = predicted number of 18-kip single axle loads to end of service life

ESALn = EDAL0 n(1 + i )n-1 x 365

Col. (h), log (W18) = log of W18 from column (g) where:

ESAL = equilvalent 18-kip single axle loads over life of project

Col. (p), log (W18) = EDAL0 = equivalent daily 18-kip single axle loads at start of project (t=0) i = annual rate of increase in traffic where: n = number of years to ESALn , typically design life of project W18 = predicted number of 18-kip single axle loads to end of service life for a value of SN

ZR = standard normal deviate from Lookup value in Table III specified reliability in Col. (e) SO = prescribed combined standard error of the traffic prediction and performance prediction

∆PSI = difference between initial design (po) and terminal (pt) servicibility indices; col (k) - (l) MR = resilient modulus (psi), commonly correlated to R-value, CBR or soil type (see Tables I and II )

IV. Calculation of design equivalent number of single axle loads (ESALs) Reliability ZR

50 0 Traffic Data 60 -0.253 Case: 1 2 3 4 5 Notes:

70 -0.524 Current ADT 1596 1596 1537 in scoping report, 1409 per 07/2016 data 75 -0.674 Annual Growth, i 1% 1% limited potential for growth on route 80 -0.841 Lanes (each direction) 1 1 85 -1.307 Design Life, n 20 20 for 3R 90 -1.282 91 -1.34 Traffic Mix (#/100) 92 -1.405 Passenger Cars (2) 0.980 0.950 93 -1.476 Pickup Trucks/SUV (3) 0.000 0.000 94 -1.555 Buses (4) 0.000 0.000 95 -1.645 RV /5-axle trucks (9) 0.020 0.050 assumed 96 -1.751 Check sum: 1.000 1.000 0.000 0.000 0.000 97 -1.881 Load Equiv./Truck Factor 98 -2.054 99 -2.327 Passenger Cars (2) 0.0004 0.0004

99.9 -3.09 Pickup Trucks/SUV (3) 0.004 0.004 max value

99.99 -3.75 Buses (4) 1.25 1.25 avg value

RV /5-axle trucks (9) 2.3 2.3 max value

Direction distribution/lane factor: 0.6 0.6 0.6 0.6 0.6 default per CFL

Traffic Load EDAL0 74 184 0 0 0 daily axle loads ESALn 652988 1624024 0 0 0 lifetime axle loads n(1 + i )n-1 x 365 24.2 Factored

EDAL 44 110 0 0 0 distributed Design ESALn 391793 974414 0 0 0 > 50000 HMA, >10,000 ASR

August 21, 2019

Case

III. Lookup Values

AASHTO Guide for Design of Pavements Structures, American Association of State Highway officials, Washington D.C., copyright 1993.

ENTER "1" for NCHRP 128 (CDOT) or "2" for AASHTO 1993

FHWA, Federal Lands Highway Project Development and Design Manual , Chapter 11 – Pavements, U.S. Department of Transportation, issued March 2008.

𝑐𝑐𝑐𝑐𝑐𝑐 𝑐𝑐 • 𝑐𝑐𝑐𝑐𝑐𝑐 (𝑑𝑑) • 365 days/year

𝑍𝑍𝑅𝑅𝑆𝑆𝑂𝑂 + 9.36 log(𝑆𝑆𝑆𝑆 + 1) − 0.20 + log ∆𝑃𝑃𝑃𝑃𝑃𝑃

4.2 −1.5

0.4+ 1094

𝑃𝑃𝑆𝑆+1 5.19

+ 2.32 log𝑀𝑀𝑅𝑅 − 8.07

JBlanchard

JB

Structural Section Thickness Calculations

Client Name: Muller Engineering Project Number: 217-306 Project Name: Donner Pass Road 3R, I-180 East to Truckee Town Limit, PM 0-6.54 Date: 8/21/2019

Road (1% growth) Clayey tuff subgrade

Notes ESALs 974414 974414 5% trucks, ~3x ESALs Initial Serv. 4.2 4.2 Term Serv. 2.5 2.5 Reliability 75% 75% Over. Std Dev 1.7 1.7 Stage Const 1 1 Min. SN req'd: 2.23 3.34 Snmin = 1.92, 2.88 for 2% truck Rsg= 60 28

Material

Layer Coef.

ai

Drain Coef. mi

Thickness, Di

(inches) SNi Comments

Surface Course New HMA 0.44 1 3 1.32 Minimum section with FDR Cold Recycle CIPR 0.30 1 0 N-2 WB (SN>2.23 @ 5%) Aggregate base ABC 0.14 1 0 Widen Section Rubblized PCC PCC-r 0.20 1 0 County min. = 8" base Crack-n-seat PCC PCC-cr 0.40 1 0 N-5a Base Course FDR - pulverized 0.12 1 8 0.96 Select Borrow 0.08 1 0 Subgrade

Total SN: 2.28

Material Layer Coef.

ai Drain Coef. mi

Thickness, Di

(inches) SNi Comments

Surface Course New HMA 0.44 1 3 1.32 N-1 Section (SN>2.23) Cold Recycle CIPR 0.30 1 0 Aggregate base ABC 0.14 1 0 Rubblized PCC PCC-r 0.20 1 0 Crack-n-seat PCC PCC-cr 0.40 1 0 Base Course FDR - pulverized 0.12 1 10 1.2 Select Borrow 0.08 1 0 Subgrade

Total SN: 2.52

Material Layer Coef.

ai Drain Coef. mi

Thickness, Di

(inches) SNi Comments

Surface Course New HMA 0.44 1 3 1.32 N-2 Section (SN>2.23) Cold Recycle CIPR 0.30 1 0 P-3 Section (R=28, SN>3.34) Aggregate base ABC 0.14 1 0 ~1" leveling course neglected Rubblized PCC PCC-r 0.20 1 0 0 Crack-n-seat PCC PCC-cr 0.40 1 6 2.4 Base Course FDR - pulverized 0.12 1 0 Select Borrow existing AB 0.00 1 10 0 Subgrade

Total SN: 3.72

Material Layer Coef.

ai Drain Coef. mi

Thickness, Di

(inches) SNi Comments

Surface Course New HMA 0.44 1 3 1.32 N-4 (SN>2.23) Cold Recycle CIPR 0.30 1 0 Aggregate base ABC 0.14 1 0 Rubblized PCC PCC-r 0.20 1 0 Crack-n-seat PCC PCC-cr 0.40 1 6 2.4 Base Course FDR - pulverized 0.12 1 3 0.36 above crack n seat Select Borrow 0.08 1 0 Subgrade

Total SN: 4.08

Material Layer Coef.

ai Drain Coef. mi

Thickness, Di

(inches) SNi Comments

Surface Course New HMA 0.44 1 3 1.32 N-5b (SN>2.23) Cold Recycle CIPR 0.30 1 0 Aggregate base ABC 0.14 1 0 Rubblized PCC PCC-r 0.20 1 0 Crack-n-seat PCC PCC-cr 0.40 1 0 Base Course FDR - pulverized 0.12 1 11 1.32 Select Borrow 0.08 1 0 Subgrade

Total SN: 2.64 Equations/Definitions:

Req'd SN = Structural number of pavement needed for subgrade and traffic condition (from page 1 ) SN = Calculated structural number summed for all layers SNi = Calculated structural number for the layer thickness, drainage condition, and material type noted where:

ai = prescribed layer coefficient for material type noted

Di = layer thickness in inches mi = drainage coefficient

𝑆𝑆𝑆𝑆 = 𝑎𝑎1𝐷𝐷1 + 𝑎𝑎2𝐷𝐷2𝑚𝑚2 + 𝑎𝑎3𝐷𝐷3𝑚𝑚3 + . . .