Report 2_Pavement Memo.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

M:\PROJECTS\maca\15(3)\Techserv\Pavement\Correspondence\FLTP-MACA 15(3) Pavement Memo.doc

SUBJECT: Pavement Recommendation for FLTP-MACA 15(3)

TO MESSAGE/COMMENT FROM/DATE

M. Tessitore PS&E Project Manager

And:

M. Carruthers Highway Design Manager

Through:

F. Cintron- Ramos Highway Design Engineer

In response to the scoping meeting site visit on December 1, 2016, we’re submitting our preliminary findings and recommendations for FLTP-MACA 15(3). The project site is located in Mammoth Cave National Park in south central Kentucky. The project consists of the rehabilitation of approximately 5.1 miles of Brownsville Road from Route 2325 (Silent Grove Road) to Mammoth Cave Parkway. Upon completion of further analyses, recommendations herein are subject to change, and will be included as an addendum to this memo.

Brownsville Road (Route 15) Brownsville Road is a 22-foot wide, two-lane, two-directional, major park access road with no paved shoulder. Refer to photograph no. 1 attached showing typical road conditions. Due to the project schedule and budget, soil borings or pavement cores were not performed. Based on as builts provided by the park, the existing pavement was constructed in the early 1960s. The as builts indicate that the road was constructed of partial cut and fill zones, approximately 6 inches of crushed gravel or crushed stone, a prime coat, and layer of AT-50 Bituminous surface treatment (a.k.a. chip seal). During the scoping site visit, 3-4 distinct asphalt layers were observed, suggesting multiple overlays were performed after the initial construction, to include a 1-inch overlay in 2005.

Proposed work may include pavement rehabilitation, shoulder widening or shoulder hardening, minor drainage improvements, minor guardrail repair/replacement, and re-striping. EFLHD performed a scoping site visit on December 1st, 2016. During the site visit, the following observations were made:

1. Adjacent to Brownsville Road, approximately 1.2 miles east of Silent Grove Road, is a parking lot designated as Turnhole Bend Nature Trail parking, Route 0912, shown in photo nos. 2 and 3 attached. The parking lot is a 6,046 square-foot, asphalt covered surface. The asphalt is raveling and paint markings are faded or nonexistent. The existing curb, approximately 2 to 4 inches in height and 210 feet in length, is in poor to fair condition, and may be replaced as part of the rehabilitation of Brownsville Road.

2. Low to high severity edge cracking was observed, particularly on the down-gradient and up-gradient outside/inside curve edges of Brownsville Road. Edges cracks were generally observed near the pavement fog line and typically consisted of scalloped or alligator cracking as well as edge raveling, see photo no. 4. At high severity edge crack locations, the pavement was raveling, delaminating and fractured, creating a lane-to shoulder drop off (photo no. 5). It is posited that the pavement edge cracking may be a result of a thinner section of pavement at the road edge, constructed during an asphalt pavement overlay. The width of the roadway was measured at a total of 23 feet, slightly wider than previously reported.

K. Ngozi- Bullock Pavement Engineer

S. O’Brien Pavement Team Leader

L. Gress Acting Technical Services Engineer

3/27/2017

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3. Shoulder drop-offs of approximately 2 to 6 inches were observed in localized areas, particularly where edge cracking was severe enough for pavement raveling and fracturing. Areas of distress were observed adjacent to curves and existing barriers as shown in photo no. 6. Crushed stone was present adjacent to lane-to-shoulder drop off and saw cut areas.

Park maintenance reported replacing crushed stone every 6 to 8 months.

In some areas, grass pavers were installed adjacent to saw cut pavement areas. Lane-to shoulder drop-off with medium to high severity edge cracking was observed along approximately 2,280 linear feet of the roadway.

4. Low severity transverse cracking was encountered in localized areas, particularly near existing culverts and intersections. A photo of a typical transverse crack is shown as photo no. 7. Transverse cracking was typically less than ¼ inch in width and on the order of 3 to 22 feet in length.

5. Beyond approximate MP 3.2 and extending to about MP 4.5, the eastbound pavement edge was observed to end abruptly at or prior to the fog line along the eastbound lane, as shown in photo no. 8. The pavement edge was neat and straight, implying that the pavement had been saw cut.

The cut has generated a shoulder drop-off that should be addressed during pavement rehabilitation.

6. In addition to the shoulder drop-offs, several safety concerns were discussed with the park to include rehabilitating existing barriers, the addition of rumble strips in localized areas, and the placement of a high friction surface treatment on localized downgradient curves. The park is willing to incorporate all items as necessary. This memo will discuss pavement recommendations. Recommendations to address safety concerns will be discussed under separate cover.

The Southeast Region Pavement Preservation Program assessed National Park Service roadways within the Road Inventory Program in 2010-2013, and based on a forecasted pavement condition rating, Brownsville Road would be due for preventative maintenance by 2019. The recommended preventative maintenance generally consists of chip seal, slurry seal and/or microsurfacing. The most recent roadway condition survey (cycle 6), indicated that the roadway is in excellent condition.

Therefore, proposed rehabilitation of Brownsville Road is not considered critical at this time, however; the pavement edge cracks could be addressed to reduce further deterioration of the pavement structure. Mammoth Cave National Park is requesting pavement rehabilitation that will provide a design life of 20 years.

We recommend rehabilitating the pavement edges in localized areas and applying a surface treatment to the overall roadway. The shoulder drop off and

Page 3 of 5 Pages shoulder hardening can be remediated with the placement of aggregate.

Pavement Edge Rehabilitation Pavement edge rehabilitation should be performed in accordance with Section 418 of FP-14, full depth patching, type 1 (FDP-1). During patching, the saw cut area should extend from the pavement edge to approximately 18 inches laterally towards the pavement centerline. During removal of the existing pavement and aggregate base, the aggregate may be left in-place if considered suitable. New asphalt should be placed to match existing. For planning purposes, the existing pavement section at patch locations is estimated as 6 inches of aggregate overlaid by 4 inches of Asphalt Concrete (AC). However, pavement cores were not performed, therefore actual conditions may vary.

Table 1. Brownsville Road Pavement Edge Rehab – FDP-1

Layer Minimum Thickness

(in)

Comments

AC Surface Course

1½

Asphalt Concrete Pavement – Hveem or Marshall Method (HACP), < 0.3 x 106 ESAL’s, 3/8” Nominal Maximum Size Aggregate (NMSA), Type III-B smoothness Asphalt Tack

Coat

AC Tack Coat as per Section 412 of the FP-14 Specifications

AC Base Course 3 HACP, <0.3 x 106 ESAL’s, ¾” NMSA Crushed

Aggregate

Roadway Aggregate, Method 2, per Section 302 of the FP-14 Specifications

The area of proposed pavement edge rehabilitation should consist of locations with severe edge cracking and fracturing, estimated at approximately 10 percent (%) of the roadway or about 2,693 linear feet. The pavement edge rehabilitation should be performed in conjunction with shoulder hardening, and prior to Brownsville Roadway rehabilitation as outlined below.

Shoulder Drop-Off and Shoulder Hardening Rehabilitation In addition to full depth patching at severe edge crack locations, the shoulder at these same locations should be rehabilitated. The existing shoulder material at the pavement edge, and approximately 18 inches laterally away from the pavement, should be removed to a depth of 6 inches and replaced with crushed aggregate, in accordance with Section 302 of FP-14. Prior to the placement of aggregate, a geotextile should be placed in accordance with Section 207 of FP- 14 and wrapped (>6 inches) around the shoulder edge.

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Table 2. Brownsville Road Shoulder Rehab – Shoulder Hardening

Layer Minimum Thickness

Crushed Aggregate

Roadway Aggregate, Method 2, per Section 302 of the FP-14 Specifications

Geotextile --- Separation and Stabilization Geotextile Class 2 – Type E, per Section 207 of

FP-14

The new pavement patch and aggregate shoulder should be constructed together with a safety edge to mitigate shoulder drop-offs. If rumble strips are incorporated into the pavement edge, they should be placed after roadway rehabilitation is complete.

During construction, any vegetative material should be removed prior to placement of the geotextile and crushed aggregate.

Brownsville Road Pavement Rehabilitation We are recommending the existing AC pavement be overlain with 1½ inches of asphalt in accordance with the following table.

Table 2. Brownsville Road Alternative I –Asphalt Overlay

Layer Minimum Thickness

AC Surface Course

1½ HACP, < 0.3 x 106 ESAL’s, 3/8”

NMSA, Type I smoothness

Asphalt Tack Coat

AC Tack Coat as per Section 412 of the

FP-14 Specifications

This alternative has an expected design life of approximately 10 to 15 years.

This work can be performed in conjunction with the proposed pavement edge rehabilitation discussed above. If so, the pavement edge rehabilitation should be performed first. In the event that a high friction surface treatment is desired, we can provide additional asphalt specifications to meet desired roughness.

Alternatively, we recommend the entire roadway be treated with a double chip seal course (type 2B) in accordance with Table 3 below.

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Table 3. Brownsville Road Alternative II – Double Chip Seal

Layer Minimum Thickness

Double Chip Seal 2B

Double Course Chip Seal Type 2B, per

Section 407 of the FP-14 Specifications, Table 407-2

This preservation treatment may extend the pavement service life an additional 5 to 10 years. However, existing transverse cracks and edge cracks may reflect through the chip seal surface treatment within 1 to 3 years. This option can be performed in conjunction with the pavement edge rehabilitation discussed above.

If so, the pavement edge rehabilitation should be performed first. Due to the roughness factor of a chip seal surface course, a high friction surface treatment is not necessary.

Turnhole Bend Nature Trail Parking (Route 912) Rehabilitation The parking area adjacent to Brownsville Road at about MP 1.3 may be rehabilitated in conjunction with the rehabilitation of Brownsville Road discussed above. We recommend that the rehabilitation alternative chosen for Brownsville Road (either 1½-inch AC overlay or double chip seal) is also performed on the adjacent parking area. In addition, the existing 210 linear feet of curb, measuring 2 to 4 inches in height may be replaced. If the curb is not replaced, hand milling of the pavement may be required at the existing curb to expose the appropriate curb depth. Refer to section below for additional pavement rehabilitation recommendations.

cc: Pavement (S. O’Brien), Highway Design (M. Carruthers), Hydraulics (L. Gress), Environmental (L.

Landers) w/ attachments

FLTP‐MACA 15(3) Pavement Recommendations

Appendix A1

Photo No. 1 – Brownsville Road (Route 15) showing typical conditions.

Photo No. 2 – Brownsville Road approaching adjacent parking lot, Turnhole Bend Nature Trail Parking Lot, Route 0912, at about Mile Post (MP) 1.3.

Appendix A2

Photo No. 3 – Turnhole Bend Nature Trail Parking, Route 0912 showing pavement raveling and faded to nonexistent pavement markings.

Photo No. 4 – Brownsville Road showing typical edge cracking.

Appendix A3

Photo No. 5 – Brownsville Road showing typical edge cracking, delaminating and fracturing.

Photo No. 6 – Brownsville Road showing typical lane to shoulder pavement drop-off.

Appendix A4

Photo No. 7 – Brownsville Road showing typical isolated transverse crack.

Photo No. 8 – Brownsville Road showing saw cut pavement edge observed between approximate MP 3.2 to 4.8.