Attachment 10 - Pavement Memo.pdf

Page 1 of 5 Pages

Form FHWA-201 (Rev. 11-67)

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

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SUBJECT: Project MD NP CHOH 235(2), 241(1), ETC –Pavement Recommendations Addendum

TO MESSAGE/COMMENT FROM/DATE

Y. Kirtley Project Manager

C. Lyons Highway Design Manager

This is an addendum to the Pavement Memorandum for project MD NP CHOH 235(2), 241(1), ETC. located in Washington and Montgomery Counties, Maryland.

This addendum addresses revisions to the pavement rehabilitation recommendations based on additional scope added during the 70% plan in hand field review meeting.

The original pavement memorandum is included in Appendix A.

BACKGROUND

A plan in hand field review was held on March 24, 2024, with Eastern Federal Lands Highway Division (EFLHD) and National Park Service (NPS) representatives. From the meeting, two changes were made concerning the pavement treatment

Ankeney Lane (CHOH-0242) is to have the pavement rehabilitation extend 300 feet measured from the south portal of the Four Locks. The pavement included is experiencing high severity fatigue cracking across the entire roadway width. Additionally, approximately 43 feet of the paved approach from the north portal will undergo reconstruction.

Carderock Picnic Area Road (CHOH-0235) will be lower in grade south of the Carderock Tunnel to facilitate drainage.

Mccoy’s Ferry Tunnel (CHOH-0945) will undergo reconstruction on the southern approach to correct the current drop off.

PAVEMENT RECOMMENDATIONS

Based on the pavement conditions observed during the field view and the pavement cores, we recommend the following pavement rehabilitation strategies. The recommendations included here reference the FP-14, “Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects”.

Ankeney Lane South of Four Locks Tunnel (Station 23+45.29 to 26+45.00), Aknekeny Lane North of Four Locks Tunnel (Station 21+80 to 22+22.44).

The existing pavement south of Four Locks Tunnel exhibits high severity fatigue cracking, which is indicative of base and/or subgrade failure. The existing pavement condition will require pavement reconstruction. Additionally, approximately 43 feet of the north approach will require pavement reconstruction to tie into the slab replacement in Four Locks Tunnel.

We recommend placement of 4.0 inches of Asphalt Concrete (AC) split into two lifts and a 6.0-inch aggregate base, followed by a separation/stabilization geotextile. Table 1 presents the minimum pavement requirements for the Ankeney Lane reconstruction.

K. Nguyen Pavement Engineer

Through:

A. Maloche Acting Pavements Team Leader

10/30/2024

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Table 1. Reconstruction – Ankeney Lane, Stations 21+80 to 22+22.44 and 23+45.29 to 26+45.00

Layer

Minimum Thickness

(in) Comments

AC Surface Course 1.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 AC Tack Coat --- AC Tack Coat as per Section 412

AC Base Course 2.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 Graded Aggregate

Base 6.0

Roadway Aggregate, Method 2 as per Section 302

Geotextile --- Geotextile, Class 2, Type E as per

Section 207

Four Locks Tunnel Remaining Northern Approach The pavement recommendations for the north approach to McCoy’s Ferry Tunnel (1.5 -inch mill and overlay) remain unchanged. Please refer to Appendix A for the minimum pavement requirements.

Carderock Area Picnic Road

While Carderock Picnic Area Road is in good condition, the road west of the existing tunnel will require reconstruction to lower the grade and facilitate drainage out of the existing tunnel. We recommend reconstruction for this segment of the road (Station 100+00 to 102+95.00).

For the remaining length of Carderock Picnic Area road (Station 102+95.00 to 105+00), we recommend a 1.5-inch mill and overlay. Table 2 and 3 presents the minimum pavement requirements for the reconstruction and mill and overlay section, respectively.

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Table 2. Reconstruction – Carderock Picnic Area Road (Station 100+00 to 102+95.00)

(in) Comments

AC Surface Course 1.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 AC Tack Coat --- AC Tack Coat as per Section 412

AC Base Course 2.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 Graded Aggregate

Base 6.0

Roadway Aggregate, Method 2 as per Section 302

Geotextile ---

Table 3. Mill and Overlay – Carderock Picnic Area Road (Station 102+95 to 105+00)

(in) Comments

AC Surface (Existing)

1.5 AC Milling as per Section 413

AC Surface Course 1.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 Tack Coat --- AC Tack Coat as per Section 412

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Mccoy’s Ferry South Approach

The existing paved approach to Mccoy’s Ferry Tunnel is currently in good condition, but a 4-inch drop-off exists when transitioning from the concrete slab in the tunnel to the asphalt approach. We recommend reconstruction of the approach to alleviate the drop-off. Table 4 presents the minimum requirements.

Table 4. Reconstruction – South Approach to Mccoy’s Ferry Tunnel

(in) Comments

AC Surface Course 1.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 AC Tack Coat --- AC Tack Coat as per Section 412

AC Base Course 2.5 Asphalt Concrete Pavement, Type 1, ½” NMSA as per Section 403 Graded Aggregate

Base 6.0

Roadway Aggregate, Method 2 as per Section 302

Geotextile ---

McCoy’s Ferry Tunnel North Approach, The pavement recommendations for the north approach to McCoy’s Ferry Tunnel (6 -inch aggregate surface) remain unchanged. Please refer to Appendix A for the minimum pavement requirements.

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APPENDICES

Appendix A: Pavement Memorandum dated March 16, 2023 Appendix B : Pavement Design Analysis

Appendix A – Pavement Memo Dated March

23, 2023

Appendix B – Pavement Design Analysis

1993 AASHTO Pavement Design

DARWin Pavement Design and Analysis System

A Proprietary AASHTOWare Computer Software Product

Flexible Structural Design Module

Reconstruction at Mccoy's Ferry, Four Locks, and Carderock

Flexible Structural Design

18-kip ESALs Over Initial Performance Period 50,000 Initial Serviceability 4.2 Terminal Serviceability 2 Reliability Level 75 % Overall Standard Deviation 0.49 Roadbed Soil Resilient Modulus 4,500 psi Stage Construction 1

Calculated Design Structural Number 2.30 in

Specified Layer Design

Material Description

Struct Coef.

(Ai)

Drain Coef.

(Mi)

(Di)(in)

Width

(ft)

Calculated

SN (in) 1 AC Surface Course 0.44 1 1.5 12 0.66 2 AC Base Course 0.44 1 2.5 12 1.10 3 Aggregate Base 0.12 1 6 12 0.72

Total - - - 10.00 - 2.48