22.100 PVMT Report Addendum 1.pdf

Project No. - 110938-001_Add1.docx

5900 W. 38th Avenue Wheat Ridge, Colorado 80215 303 825-3800 www.shannonwilson.com

March 26, 2025

Jordan Leiminger, PE HDR Engineering, Inc.

1670 Broadway, Suite 3400 Denver, Colorado 80202

RE: ADDENDUM NO. 1, PAVEMENT DESIGN REPORT, TX FLAP UV CR203(1), FISH

HATCHERY ROAD, UVALDE, TEXAS

Shannon & Wilson completed an October 4, 2024, pavement design report1 for the reconstruction of the Fish Hatchery Road (County Road 203) in Uvalde, Texas. Based on discussions with the design team, we understand that the grades of the proposed access road can be raised to accommodate the installation of drainage swales. Exhibit 1 shows the proposed 24-foot-wide roadway cross section with drainage swales.

Exhibit 1: Proposed Cross Section of the Fish Hatchery Road

Preventing surface water from entering the pavement section is critical for the long-term performance of pavements, especially when underlain by expansive subgrade soils (refer to

1 Shannon & Wilson, 2014, Pavement Design Report, TX FLAP UV CR203(1), Fish Hatchery Road, Uvalde, Texas; prepared to HDR Engineering, Inc.; dated October 4, 2024.

http://www.shannonwilson.com/

Jordan Leiminger, PE HDR Engineering, Inc.

March 26, 2025

110938-001_Add1.docx 110938-001

Section 5.1 of our October 2024 report). Water infiltrating through cracks or joints in the pavement surface can become trapped in crushed aggregate base (CAB) and saturate the subgrade soils (formation of a ‘bathtub’ as a result of no exit point for groundwater), reducing the strength and leading to subgrade swelling. In our opinion, the above drainage swales will allow for free drainage of a proposed CAB layer within the pavement section.

With the proposed installation of the drainage swale, Exhibit 2 provides our recommended pavement section.

Exhibit 2: Revised Pavement Recommendations

Paving Alternatives

Alt. 1* 5‐½ in. of full depth ACP

Alt. 2* 3 in. of ACP overlying 6 in. of FDR with cement treatment

Alt. 3* 3 in. of ACP overlying 8 in. of CTS.

Alt. 4 3 in. of ACP overlying 7 in. of Composite CAB, FDR, or ACP Millings(3)

NOTE:

Paving alternatives noted with an asterisk were previously recommended in our October 2024 pavement design report.

Paving materials discussed in Section 6.3 of our October 2024 pavement design report apply.

Alternative 4 requires installation of drainage swales, allowing for free drainage of the CAB.

ACP = Asphalt Concrete Pavement; Crushed Aggregate Base = CAB; CTS = Cement Treated Subgrade; FDR = Full Depth Reclamation

We understand that Alternative 4 will be selected for construction based on Central Federal Lands (CFL) preference for reusing existing paving materials. Typical FDR projects pulverize to 6 inches or deeper. While the observed pavement thickness in borings SW-04 through SW-06 consisted of 2-1/2 inches HMA over 3-1/2 inches CAB to achieve this typical pulverization, we understand that the plan is to do a reduced pulverization of only 2 inches (see Exhibit 1) to provide sufficient swale depth for drainage. The pulverized FDR material in Alternative 4 will have the same function as CAB within the pavement section. Due to the relatively thin section of FDR required, an alternative construction method could consist of using asphalt milling equipment in lieu of specialty FDR equipment.

CLOSURE

This letter was prepared for the exclusive use of the CFL and HDR in the proposed Fish Hatchery access road reconstruction. The opinions, conclusions and recommendations made in our October 2024 report still apply, including the limitations presented in Section 7 of that report, unless specifically superseded herein.

SHANNON & WILSON, INC.

Location: TX FLAP UV CR203(1), Uvalde Fish Hatchery Road Comment: Analysis based on the 1993 AASHTO Guide for the Design of Pavement Structures

Alt. 4: Asphalt Concrete Pavement (ACP) over Crushed Agg. Base (CAB daylighting to Drainage Swales)

1. Pavement Design Life: (PDDM) for Reconstruction Projects 25.0 years

2. Traffic Loading (W18): (Refer to 18-kip ESAL worksheet) 18k ESALs: per lane

3. Serviceability:

p0: 4.2 (PDDM) ∆PSI: 2.2 pt: 2.0 (PDDM) for ADT < 500 vehicles per day

4. Subgrade Resilient Modulus (MR):

TxDOT R-value to MR correlation MR=2,550(CBR)^0.64 (Section 4.4)

CBR 3.6

MR: 5,789 psi

5. Reliability:

R: 75 % (PDDM) for ADT < 2500 vehicles per day ZR: -0.674

6. Design Standard Deviation (So):

So: 0.49 (PDDM)

7. Required Structural Numbers (SNi):

SN1: 1.049 0.0

SN2: 2.098 0.0

SN3: -NA- #VALUE!

Layer Analysis

8. Pavement Materials Characterization:

Layer

1 a1: 0.40 2 a2: 0.13 m2: 1.00 3 a3: m3:

9. Solutions for thicknesses: [ Figure 3.2, Part II of 1993 AASHTO] SN*1 = a1D*1 >= SN1

SN*2 = a1D*1 + a2D*2m2 >= SN2

SN*3 = a1D*1 + a2D*2m2 + a3D*3m3 >= SN3

Layer SN*i SNi

1 3.0 inches 1.200 1.049 2 7.0 inches 2.110 2.098 3 inches

Note: Required SN <= Pavement SN, Design is Acceptable

Flexible Pavement Design Worksheet

50,000

Analysis MR

30,000

5,789

-NA-

Material Structural Layer Coefficients

Drainage Coefficients

Layer Modulus (psi)

Recommended Thicknesses Material Thickness (D*i)

ACP - -

CAB 30,000

ACP

CAB

07.8)(log32.2

)1( 109440.0

5.12.4 log

20.0)1(log36.9)(log 10

19.5

101810 −+

+−++= RoR M

SN

PSI

SNSZW

TX Uvalde - Flexible Pavement Worksheet_Rev2.xlsm Page 1 of 1 110938-001

Closure