CA ERFO SIERRA NF 05S07(1) Final Pavement Memo.pdf

Memorandum

Subject: CA ERFO SIERRA NF 05S07(1)

Norris Creek Bridge Final Pavement Recommendations

Date: January 31, 2022

From: Robert Norick

Through:

Pavement & Materials Engineer

Mike Voth Pavement & Materials Team Lead

To: Mike Daigler, PM Joshua Kaplan, Lead Designer

Project Description:

This memorandum provides the pavement structural section recommendations for the CA ERFO SIERRA NF 05S07(1) Norris Creek Bridge in Madera County, California.

The Norris Creek Bridge is located approximately 37 miles northeast of the Town of Oakhurst along Forest Route 05S07 (Beasore Road) within the Sierra National Forest, crossing Norris Creek. Page 3 includes a location map for the bridge. The previous timber bridge was destroyed by fire in 2020 and will be replaced with a prefabricated bridge with rolled steel girders, structural steel decking, and asphalt fill.

Geotechnical Investigation:

On November 2, 2021, CFL’s Geotechnical Group conducted a geotechnical investigation for the project consisting of one 28-foot deep geotechnical boring (at east bridge abutment) using a truck mounted hollow stem auger. Standard penetration tests (SPT) and sampling were performed at 5-foot intervals, in addition to, a bulk subgrade sample for the top 5 feet. CFL personnel logged the findings including depth of boring and subgrade soils, SPT data, visual soil classification, and asphalt thickness. SPT and bulk subgrade samples were collected and submitted to the CFLHD lab for testing to determine the soil classifications. The investigation found a 2½ inch depth of asphalt directly on a silty sand subgrade, a “good” quality subgrade. Based upon Exhibits 11.4.2.B and 11.4.2.C of CFLHD’s supplement to the PDDM, the resilient modulus (MR) of “good” subgrade soils can be estimated to be 8,000 psi.

Pavement Recommendations:

The two-way average daily traffic (ADT) along the forest route is estimated to be less than 100 with a minimal number of trucks; i.e. a “low” traffic level. According to PDDM Section 11.2.1.2, a minimum of 50,000 ESALs shall be used for the design of paved roads. Based upon 50,000 ESALs, the subgrade resilient moduli (MR), and the PDDM pavement design criteria, the 1993 AASHTO procedure requires 20-year pavement Structural Numbers (SN) of 1.85. After evaluating alternatives, the following pavement structural sections are recommended for the project.

Norris Creek Bridge Deck

Corrugated steel decking with asphalt fill in 2 lifts as follows.

First asphalt lift to fill steel decking corrugations.

Second asphalt lift to extend 1.5 inch minimum above steel decking.

Norris Creek Bridge Approaches (SN = 1.92)

3 inches of Asphalt Concrete Pavement (SN = 3” x 0.44 = 1.32”) 6 inches of Crushed Aggregate Base (SN = 6” x 0.10 = 0.60”)

Additional recommendations include a tack coat applied to the steel decking and between asphalt lifts (subsidiary to asphalt).

Recommended Pay Items for this Project:

Item Number Item Description Unit

30202-2000 Roadway Aggregate, Method 2 Ton 40301-0100 Asphalt Concrete Pavement, Type 1 Ton

The pay items above are to be constructed using the FP-14. CFLHD’s standard Special Contract Requirements (SCRs) related to pavements and materials are expected to be used apart from a 403 SCR to incorporate Caltrans 85 gyration asphalt mixes (see attached). Any additional SCRs may be developed as needed.

Norris Creek Bridge Vicinity Map

Section 403. — ASPHALT CONCRETE

Description

403.01 Add the following:

Use an Asphalt binder that would be specified for the project location and is designated according to AASHTO M 320.

Construction Requirements

403.02 Composition of Mix (Job-Mix Formula). Add the following:

The CO may perform mix design-verification testing to confirm the mix meets the contract requirements. If verification testing is required, submit a loose mix sample to the CO 14 days prior to placement.

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

Submit a state department of transportation 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 and conforming to design parameters (a), (b), or (c) for the type of mix submitted and conforming to design parameter (d) in Table 403-1.

Table 403-1

Asphalt Concrete Mix Requirements Design Parameters Specification

(a) Volumetric hot asphalt concrete pavement (AASHTO M 323, AASHTO R 35, and AASHTO T 312)

Gyratory compaction level Volumetric properties at 0.3 to 3 million ESAL’s (AASHTO M 323)

8, 85, 130 see Table 401-1

(b) Hveem (AASHTO T 246 and AASHTO T 247) Stabilometer, minimum Percent Air Voids (1)

3.0 – 5.0

(c) Marshall (AASHTO T 245)

Stability, pounds (kilonewtons), minimum Flow, 0.01 inches (0.25 millimeters) Percent Air Voids (1) Compaction, number of blows each end of test specimen

2000 (8.9)

8 - 16

3.0 – 5.0

(d) Moisture Susceptibility (AASHTO T 283)

Tensile strength ratio, minimum

0.80

(1) The percent of air voids are based on AASHTO T 166, AASHTO T 209 and AASHTO T 269.

403.09 Compacting. Add the following:

For HMA, do not roll the mix after the surface cools below 175 ºF (80°C).

Along forms, curbs, headers, walls, and other places not accessible to the rollers, compact the mix with alternate equipment to obtain the required compaction.

403.12 Acceptance. Add the following:

During production placement of the mix, sample loose mix and compacted cores according to Table 403-2 and submit to the CO for acceptance. Materials that do not meet the approved job-mix formula are considered unacceptable.

Delete Table 403-2 and substitute the following:

Table 403-2

Sampling, Testing, and Acceptance Requirements

Material or

Product (Subsection)

Type of Acceptance (Subsection)

C ha ra ct er is tic

T es t M et ho ds

Sp ec ifi ca tio ns

Sampling Frequency

Point of Sampling Sp lit

Sa m pl e

Reporting Time

R em ar ks

Mix Design Asphalt concrete mixture Type I

(403.02(a))

Measured and tested for conformance

(106.04)

Job-mix formula

Subsection 403.02(a)

When requested by the CO.

Flowing mix stream (bin or belt discharge) or behind the paver before compaction.

Yes Before approval of job-mix formula

Tested by the

CO

Production Asphalt concrete, Type I

(403.02(a))

Measured and tested for conformance

(106.04)

Job-mix formula

Density (1)

Maximum specific gravity

Subsection 403.02

AASHTO

T 166

AASHTO T

209 (2)

1 per 700 tons

(650 metric tons)

Behind the paver before compaction.

In-place after Compacting

Behind the paver before compaction

Yes

Deliver cores to

CO

for testing

Surface Tolerance

Straightedge measurement Subsection

403.11

Continuously, after compaction

Finished pavement surface

No −

Placement temperature

− First load and as determined by

CO

thereafter

Hauling vehicle before dumping, or windrow before pickup

No Upon completion of measurement

Table 403-2 (continued)

Sampling, Testing, and Acceptance Requirements

Material or Product

(Subsection)

Type of Acceptance (Subsection)

C ha ra ct er is tic

T es t M et ho ds

Sp ec ifi ca tio ns

Sampling Frequency

Point of Sampling Sp lit

Sa m pl e

Reporting Time

R em ar ks

Production Process control (153.03)

Gradation at the plant

AASHTO

T 27 & T 11

Contractor determined

Cold feed or hot bins as applicable

No 24 hours

Moisture content of aggregates

AASHTO

T 255

" Stockpile No " −

Density ASTM D2950

1 per 500 feet

(150 meters)

In-place after compacting

No " −

Asphalt concrete, Type II

(403.02(b))

Measured and tested for conformance

(106.04)

" " 3 per 700 tons

(650 metric tons)

In-place after compacting

No " −

(1) Dry cores to constant mass at 125±5°F (52±3 °C) or vacuum dry, ASTM D7227 before testing. For asphalt concrete Type I, cut two 6-inch (150-millimeter) diameter side by side cores. Remove them with a core retriever and fill and compact the core holes with asphalt concrete mixture. Label the cores and protect them from damage due to handling and temperature. Submit one core for verification testing. Dry the other core to constant mass at 125±5 °F (52±3 °C) or vacuum dry it according to ASTM D7227 before performing the core density and measuring the thickness. Use

62.245 pounds per cubic foot (997.1 kilograms per cubic meter) to convert specific gravity to density. Use AASHTO T 166 regardless of the volume of water absorbed. Use the average maximum specific gravity value (AASHTO T 209) of the first three samples to determine the percent compaction of each Lot.

(2) Do not use the dry back method (Section 11 of AASHTO T 209).