Pavement Memo Addendum.pdf

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Form FHWA-201 (Rev. 11-67)

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Use this form in lieu of transmittal slips within Dept. of Trans. When message comment is to be retained as file material. Do not prepare carbons. Not to be used in lieu of Form FHWA- 121 for informal correspondence. MINUTE-MEMO

\\fhfl15fileserve.flhd.fhwa.dot.gov\Data\PROJECTS\nama\20(2)_502(6)_503(4)\Techserv\Pavement\Correspondence\memo\NAMA 20(2) 502(6) 503(4) Pavement Memo Addendum.doc

SUBJECT: Pavement Recommendations for NAMA 20(2), 502(6), 503(4)

TO MESSAGE/COMMENT FROM/DATE

S. Hailegiorgis Project Manager

And:

J. Johnson Highway Design Manager

This is an addendum to the Pavement Memorandum for NAMA 16(2), 20(2), etc., dated March 2, 2015. This addendum addresses revisions to the pavement rehabilitation recommendations based on further analysis. The redefined project NAMA 20(2), 502(6), 503(4) is located near the Tidal Basin and National Mall in Washington, DC. The project consists of rehabilitating and resurfacing of 17th Street (Route 20), eastbound (EB) Independence Avenue (Route 502), westbound (WB) Independence Avenue (Route 503), EB to WB Tidal Basin Turnaround (Route 515), and WB to EB Tidal Basin Turnaround (Route 516).

The initial rehabilitation methodology was to mill the existing asphalt concrete pavement to expose and repair existing Portland Cement Concrete (PCC) base slabs and slab joints. However, the existing asphalt pavement thickness varies significantly from 4 to 5.5 inches along 17th Street and 2.5 to 11 inches along Independence Avenue. This addendum will provide guidance to reduce milling depth variability. In addition, after further review of as-built plans for previous projects, we consider the condition of the existing Portland Cement Concrete (PCC) base slabs to be adequate without the need for extensive repairs along most of the project alignments. Therefore, recommended milling depths have been reduced as follows:

17th Street SW (Route 20) Recommendations for rehabilitating pavement along 17th Street may potentially include PCC slab and joint repair. Therefore, the pavements group recommends that the existing AC pavement be removed to the PCC base and overlaid with AC pavement according to the requirements in Table 1. A wedge and level course will be required prior to the overlay to establish grade and curb reveal for positive drainage.

Table 1. 17th Street Pavement Recommendation

Layer Minimum Thickness

(in)

Comments

AC Surface Course

1 ½ GACP, 3 to 30 x 106 ESAL’s, 3/8”

NMSA, Type II roughness

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

AC Base Course 2 ½ GACP, 3 to 30 x 106 ESAL’s, ¾”

NMSA

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

K. Ngozi- Bullock Pavement Engineer

Through:

M. Elias Pavement Team Leader

01/10/2019

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TO MESSAGE/COMMENT FROM/DATE

Wedge and Level

Varies GACP, ≥ 3 x 106 ESAL’s, ½” (or 3/8”)

NMSA

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

After milling has been performed, the condition of lower pavement layers can be determined. Based on the field observations, it may be necessary to perform PCC base slab and joint repairs at the discretion of the CO.

17th Street SW PCC Slab and Joint Repair Potentially up to 50% of the PCC slabs and joints will need to be repaired. After removing the existing asphalt pavement, check the condition of the existing PCC slabs and joints. Clean and seal cracks wider than 1/8 inch in accordance with Section 502 of the FP-14 Specifications. Where directed by the CO, repair deteriorated PCC pavement joints and patch deteriorated slabs according to Section 502.

Damaged PCC slabs that need to be patched or replaced should be removed along with the aggregate base and subbase in accordance with Section 502.06 of the FP-14 Specifications. It is anticipated that less than 10% of the existing PCC slabs may need to be replaced. Excavation depths depend on depth of unsuitable subgrade soils. Subexcavate areas of unsuitable subgrade soils as directed by the CO and backfill in accordance with the recommendations outlined in the table below.

Table 2. 17th Street PCC Slab Repair

Layer Minimum Thickness

Aggregate Base

Maximum 6-inch lifts

Base Aggregate, Grading C or D, as per Section 703 of the FP-14 Specifications

Geotextile --- Separation Geotextile Class 2 – Type E, as per Section 714 of the FP-14 Specifications

Any sub excavation beyond what is outlined in the above table should be backfilled with Aggregate Base Course, Grading C or D, over Geotextile, Class 2 – Type E.

It should be noted that PCC slab and joint repair may take up to two weeks.

Independence Avenue Eastbound and Westbound (Routes 502 & 503) The pavements group recommends that the existing AC pavement be milled 2-inches and overlaid with AC pavement according to the requirements in Table 3.

Additional milling or an asphalt wedge and level course may be required within curb lanes to achieve adequate curb reveal.

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Table 3. Independence Avenue Pavement Recommendation

Layer Minimum Thickness

GACP, 3 to 30 x 106 ESAL’s, 3/8”

NMSA, Type II roughness

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

Wedge and Level

Varies GACP, ≥ 3 x 106 ESAL’s, ½” (or 3/8”)

NMSA

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

There may be localized sections where the PCC base will be exposed post-milling, however, PCC base slab and/or joint repairs are not planned along these routes.

Tidal Basin Turnarounds – East and West (Routes 515 & 516) We recommend that the existing AC pavement be milled 3 inches and overlaid with AC pavement according to the requirements in Table 4. A wedge and level course will be required prior to the overlay to establish grade on curb reveal for positive drainage. PCC base will not be exposed post-milling.

Table 4. Tidal Basin Turnarounds Pavement Recommendation

Layer Minimum Thickness

1 ½ GACP, 3 to 30 x 106 ESAL’s, 3/8”

NMSA, Type II roughness

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

AC Base Course 1 ½ GACP, 3 to 30 x 106 ESAL’s, 3/8”

NMSA

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

Wedge and Level

Varies GACP, ≥ 3 x 106 ESAL’s, ½” (or 3/8”)

NMSA

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications