Atch_1c_Allied_Support_T-1_Sunshades_Design_Report.pdf

Design Report

Allied Support T-1A Sunshades Laughlin AFB, Texas

MXDP 17-1007

FA3099-13-D-0001/FA3099-17-F-0033

100% Submittal – 09/07/2018

47th Contracting Flight/LGCB 171 Alabama Ave., Building 7 Laughlin AFB, Texas 78843

URS Group, Inc.

9400 Amberglen Blvd.

Austin, Texas 78729

7 August 2018

Design Report

Allied Support T-1A Sunshades Laughlin AFB, Texas

MXDP 17-1007

FA3099-13-D-0001/FA3099-17-F-0033

100% Submittal – 09/07/2018

The professional responsibility of the undersigned Professional Engineer is limited to the content contained in this bound volume. The undersigned Professional Engineer disclaims responsibility for all other documents, including but not limited to geotechnical reports, which do not directly bear this professional seal and signature.

Civil

William G. Griffin, PE 09/07/2018

Texas Professional Engineer #36216 Expires 12/31/2018

Electrical

Ashok Aggarwal, PE 09/07/2018

Texas Professional Engineer #129637 Expires 12/31/2018

URS Group, Inc.

9400 Amberglen Blvd.

Austin, Texas 78729

512-454-4797 Texas Registered Engineering Firm F-15570

Expires 11/30/2018

Design Report Allied Support T-1A Sunshades MXDP 17-1007 FA3099-13-D-0001/FA3099-17-F-0033 Laughlin AFB, Texas

Prepared by URS Group, Inc. ii 100% Submittal – 09/07/2018

Table of Contents

Section 1 – Introduction

1.1 Foreword

1.2 Contract Details

1.3 About Laughlin Air Force Base

1.4 Project Schedule

1.5 Site Visits

1.6 Topographic Survey

1.7 Geotechnical Investigation

1.8 Work Completed to Date

1.9 Drawings Provided in the 100% Submittal

Section 2 – Reference Documents

2.1 Information Provided in the RFP

2.2 Publications Referenced in the RFP

2.3 Additional Publications

2.4 Appendices to the RFP

2.5 Technical Specifications

2.6 Administrative Specifications

Section 3 – Design Narrative

3.1 Project Justification

3.2 Proposed Improvements

3.3 Underground Utilities

3.4 Construction Phasing

3.5 Operational Safety during Construction

3.6 FAA Form 7460-1

3.7 Contractor Staging Area, Site Access and Haul Routes

3.8 Temporary Utilities for Construction

3.9 Radioactive Material

3.10 Demolition

3.11 Design Aircraft

3.12 Concrete Pavement Design for 16-inch Concrete Trench Patches

3.13 Concrete Pavement Slab Sizes

3.14 Concrete Slab Reinforcement

3.15 Joint Details

3.16 GPU Equipment Pads

3.17 Concrete Pavement Material Specification

3.18 Frost Penetration Depth

3.19 TCEQ TPDES General Permit TXR150000

3.20 Technical Approach to GPU Relocation

3.21 Wingtip Clearance Considerations

3.22 Tie-downs and Ground Receptacles

3.23 Conceptual Electrical Design

3.24 Provisions for Future Task and Obstruction Lighting

3.25 Waivers to UFC Design Criteria

3.26 Potential Issues for Discussion

Section 4 – Pavement Thickness Design for Apron Extension

4.1 Introduction

4.2 Aircraft Weight and Pass Levels

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4.3 Subgrade Westergaard K-Values

4.4 Pavement Thickness Design for 13-inch Concrete Apron Extension

4.5 Concrete Joint Pattern

4.6 Slab Reinforcement

4.7 Dowel Bars

4.8 Joint Details

4.9 Pavement Thickness Design for 6-inch Asphalt First Street Patch

4.10 Material Specification for Portland Cement Concrete (PCC) Pavement

4.11 Material Specification for Hot Mix Asphalt

4.12 Material Specification for Aggregate

4.13 Material Specification for Tack and Prime Coat

4.14 Material Specification for Joint Sealant

4.15 Frost

Section 5 – Construction Cost Estimate

5.1 Estimate of Probable Construction Cost

Appendix A – Statement of Work (Second Revision)

Appendix B – Conceptual Site Plan from RFP

Appendix C – Site Photos

Appendix D – Kickoff Meeting Minutes and Attendees

Appendix E – Requests for Information (RFI)

Appendix F – Cost Estimate Prepared by the Government

Appendix G – Suggested Technical Specifications for Sunshade Structure Procurement Project

Appendix H – Government Comments on Original (6+1 Layout) 35% Submittal

Appendix I – Government Comments on Revised (5+2 Layout) 35% Submittal

Appendix J – Government Comments on 95% Submittal

Appendix K – PCASE Pavement Design Software Output

Appendix L – Replacement GPU Cable Pricing Information

Appendix Z – Preliminary Construction Cost Estimate Prepared by URS

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Section 1 – Introduction

1.1 Foreword

On September 22, 2017, the Government issued Notice-to-Proceed (NTP) to URS Group, Inc. (aka “AECOM”) on a design project which involves the preparation of construction bid documents for the relocation of twenty existing duplex Ground Power Unit (GPU) installations on the T-1A parking apron at Laughlin Air Force Base in Del Rio, Texas. This preparatory project relates to a planned future project to install five new open-sided prefabricated sunshade structures to accommodate T-1A aircraft. The current layout contains eight uncovered aircraft parking positions per “row”. The original concept from the Government was a “6+1” layout, meaning six covered aircraft parking positions and one uncovered aircraft position per parking row. Because the structures were encroaching on First Street, the Government directed URS to submit a second 35% submittal with a “5+2” layout for analysis, meaning five covered positions and two uncovered positions per row. However, the “5+2” layout was ultimately abandoned, and a decision was made to revert to the “6+1” layout with a modest realignment of First Street to maintain wingtip clearance in the sunshades and avoid existing underground utilities. The initial construction cost estimate prepared by the Government indicated the value of the GPU relocation work is approximately $894,000.

1.2 Contract Details

The contracting mechanism for the design project to relocate the GPU installations is existing ID/IQ contract FA3099-3-D-0001 and the delivery order is FA3099-17-F-0033. The Laughlin AFB project number is MXDP 17-1007.

1.3 About Laughlin Air Force Base

Laughlin Air Force Base is a pilot training facility located Val Verde County, Texas near the city of Del Rio and the international border with Mexico. The installation is home of the 47th Flying Training Wing of the Air Education and Training Command (AETC). The airfield, which includes three large runways, is said to facilitate more takeoff and landing operations than any other airport in the country on weekdays. Aircraft based at the installation include the twinjet T-1A Jayhawk as well as the single-engine T-6A Texan II turboprop and twinjet T-38C Talon.

1.4 Project Schedule

The original design milestones established by the Government, which have changed over time, were as follows:

Milestone Completion Date 35% Design (rescheduled) Monday, December 4, 2017

Second 35% Design – “5+2” Layout Monday, April 9, 2018 95% Design (rescheduled) Friday, July 27, 2018

100% Design (rescheduled) Friday, September 7, 2018 Figure 1-1. Summary of Design Project Milestones.

1.5 Site Visits

URS Group, Inc. has visited the project site on two separate occasions to-date. The design firm initially visited the site on the morning of Tuesday, June 6, 2017 prior to submitting its detailed proposal to the Government to undertake the design work. During this visit, two civil engineers from URS spoke to staff from Laughlin AFB and toured the electrical equipment shelter (Building 219) which powers the existing GPU installations. URS also attempted a second site visit with personnel from the Base prior to the project kickoff meeting on Tuesday, October 17, 2017. Although two electrical engineers from URS were present, the design team was not able to access the electrical equipment shelter. Photographs from the two site visits are included in the Appendix C of this report. A copy of the sign-in sheet from the kickoff meeting is also included in the Appendix D of this report.

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1.6 Topographic Survey

The primary study of existing conditions and basis of design for this project is the detailed topographic field survey.

Initial field work for the survey was completed by a subcontractor, McGray & McGray Land Surveyors, Inc. from Austin, Texas, on Wednesday, October 18, 2017. The horizontal datum for the survey was NAD 83 Texas State Plane – South Central Zone (4204) and the vertical datum used was NAVD 88. Drawing C-01 EXISTING CONDITIONS PLAN, which is included in the drawing package, is based on the topographic survey conducted for this project. It should be noted when the survey was ordered and completed the project was not expected to involve the relocation of First Street or any extension of the aircraft parking apron.

1.7 Geotechnical Investigation

Because this project involves only conceptual design of the sunshade column foundations for the purpose of preliminary site design and layout, no detailed subsurface investigation was to be conducted. A subsurface geotechnical investigation will most likely be required by the prefabricated sunshade structure designer or vendor during the procurement process for the sunshade structures themselves. Existing pavement patches which must be removed to facilitate relocation of the GPU installations will simply be replaced with pavement sections of similar composition and equivalent strength. It should be noted the concrete apron expansion was not foreseen when the decision was made during scoping process for this design project to omit the subsurface investigation.

1.8 Work Completed to Date

The work products for this project include civil and electrical construction plans, technical specifications, design report, and construction cost estimate. Drawings were drafted in strict compliance with Release 5.0 of the A/E/C CAD Standard (the Department of Defense implementation of the US National CAD Standard) with Autodesk Civil 3D 2014 which can be readily converted to other versions. Specifications were prepared with SpecsIntact version

4.6.2 using current Unified Facilities Guide Specification (UFGS). The original 35% submittal was submitted to the Government on Monday, December 4, 2017 and the revised 35% submittal was submitted on April 9, 2018. The 95% submittal was tendered on July 27, 2018 and comments from the Government were received on August 9, 2018. Design comments received from the Government with URS responses are included in Appendix H, I and J of this report.

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1.9 Drawings Provided in the 100% Submittal

The following construction drawings were prepared by URS Group for review and comment by the Government:

• G-00 COVER SHEET & DRAWING LIST

• G-01 GENERAL NOTES & ABBREVIATIONS

• G-02 CONTRACT LAYOUT PLAN

• G-03 TEMPORARY TRAFFIC CONTROL PLAN – PHASE 1

• G-04 TEMPORARY TRAFFIC CONTROL PLAN – PHASE 2

• V-01 SURVEY CONTROL PLAN

• C-01 EXISTING CONDITIONS PLAN

• C-02 DEMOLITION PLAN – FIRST STREET

• C-03 DEMOLITION PLAN – ROWS “T” & “S”

• C-04 DEMOLITION PLAN – ROWS “R” & “Q”

• C-05 DEMOLITION PLAN – ROW “P” & TAXIWAY “G”

• C-06 GEOMETRY, PAVING AND JOINTING PLAN – FIRST STREET

• C-07 GEOMETRY, PAVING AND JOINTING PLAN – ROWS “T” & “S”

• C-08 GEOMETRY, PAVING AND JOINTING PLAN – ROWS “R” & “Q”

• C-09 GEOMETRY, PAVING AND JOINTING PLAN – ROW “P”

• C-10 PAVEMENT MARKING PLAN

• C-11 GPU PAD DETAILS

• C-12 MISCELLANEOUS DETAILS 1/2

• C-13 MISCELLANEOUS DETAILS 2/2

• C-14 JOINT DETAILS 1/2

• C-15 JOINT DETAILS 2/2

• C-16 CONCEPTUAL SUNSHADE PLAN AND ELEVATION

• E-01 GENERAL NOTES, ABBREVIATIONS & SCOPE OF WORK

• E-02 EXISTING CONDITIONS PLAN

• E-03 ELECTRICAL DEMOLITION PLAN – FIRST STREET

• E-04 ELECTRICAL DEMOLITION PLAN – ROWS “T” & “S”

• E-05 ELECTRICAL DEMOLITION PLAN – ROWS “R” & “Q”

• E-06 ELECTRICAL DEMOLITION PLAN – ROW “P”

• E-07 ELECTRICAL PLAN – FIRST STREET

• E-08 ELECTRICAL PLAN – ROWS “T” & “S”

• E-09 ELECTRICAL PLAN – ROWS “R” & “Q”

• E-10 ELECTRICAL PLAN – ROW “P”

• E-11 DUCT BANK DETAILS

• E-12 JUNCTION CAN DETAILS

• E-13 GPU DISTRIBUTION ONE LINE DIAGRAM

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Section 2 – Reference Documents

2.1 Information Provided in the RFP

The diagram provided by the Government in the RFP, which is included in Appendix B of this report, indicates five sunshade structures, each capable of accommodating six T-1A aircraft, are to be constructed as part of a future project. The diagram suggests the five rows of aircraft (Rows “P” to “T”) are to remain in the same location as existing. The diagram also suggests that footprint of the six-position sunshade structure may occupy more space than six of the existing aircraft parking positions and one parking position will be lost. It is clear from the text in the RFP the structures must be located at least 200 feet from the centerline of existing Taxiway G, which is as required by UFC 3-260-01, Table 5-1, Item No. 10.

On March 9, 2018, the Government directed URS to change the proposed layout from six covered positions and one uncovered position per row (“6+1” layout) to five covered positions and two uncovered positions per row (“5+2” layout). This directive was reversed through RFI #3 and the “6+1” layout with road relocation was adopted.

2.2 Publications Referenced in the RFP

The following additional publications were specifically referenced by the Government in the RFP:

Air Force Engineering Technical Letters (ETL)

• ETL 04-2 Standard Airfield Pavement Marking Schemes, with Change 1

Department of Defense/NIBS/WBDG

• Unified Facilities Guide Specifications (UFGS) 34 73 13 Mooring and Grounding Points for Aircraft

Department of Defense/NIBS/WBDG – Unified Facilities Criteria (UFC)

• UFC 4-022-01 Entry Control Facilities Access Control Points

International Code Council (ICC)

• International Building Code (replaced Uniform Building Code)

2.3 Additional Publications

The following additional publications are potentially applicable to the design portion of the project:

Department of Defense/NIBS/WBDG – Unified Facilities Criteria (UFC)

• UFC 1-300-02 Unified Facilities Guide Specifications (UFGS) Format Standard

• UFC 1-300-09N Design Procedures, with Change 9

• UFC 3-201-01 Civil Engineering

• UFC 3-220-10N Soil Mechanics

• UFC 3-250-04FA Standard Practice Manual for Concrete Pavements

• UFC 3-250-08FA Standard Practice for Sealing Joints and Cracks in Rigid and Flexible Pavements

• UFC 3-250-06 Repair of Rigid Pavements using Epoxy Resin Grouts, Mortars and Concrete

• UFC 3-260-01 Airfield and Heliport Planning and Design

• UFC 3-260-02 Pavement Design for Airfields

• UFC 3-535-01 Visual Air Navigational Facilities

Department of Defense/NIBS/WBDG

• Unified Facilities Guide Specifications (UFGS), August 2017 Masters

Air Force Instructions (AFI)

• AFI 13-213 Airfield Driving, March 19, 2012

• AFI 32-1042 Standards for Marking Airfields, October 27, 2005

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Air Force Engineering Technical Letters (ETL)

• ETL 97-18 Guide Specification for Airfield and Roadway Marking

• ETL 02-8 Silicone Joint Sealant Specification for Airfield Pavements

• ETL 02-9 Construction Signs

• ETL 06-2 Alkali-Aggregate Reaction in Portland-Cement Concrete (PCC) Airfield Pavements

Air Force Design Pamphlet (AFP)

• AFP 88-71 Design Guide for Army and Air Force Airfields, Pavements, Railroads, Storm Drainage…

CAD/BIM Technology Center

• A/E/C CAD Standard, Release 5.0, ERDC/ITL TR-12-X, September 2012

Texas Commission on Environmental Quality

• Texas Pollutant Discharge Elimination System – General Permit TXR150000, March 5, 2008

Texas Department of Transportation

• Standard Specification for Construction and Maintenance of Highways, Streets and Bridges

U.S. Army Corps of Engineers (USACE)

• EM 1110-3-394 Aircraft Characteristics for Airfield-Heliport Design and Evaluation

2.4 Appendices to the RFP

The following additional publications were included as appendices to the RFP prepared by the Government:

• Installation Excellence Guide

• LAFB Specific Environmental Requirements

• Green Procurement Plan

• ETL 04-2 Standard Airfield Pavement Marking Schemes

• UFGS 34 73 13 Mooring and Grounding Points for Aircraft

• Division 01 Specifications (Deliverables, Schedules, Safety, Quality Control, Environmental, Closeout)

• Site Plan

2.5 Technical Specifications

The following Unified Facilities Guide Specifications (UFGS) from August 2017 will be edited for this project:

• 02 41 00 05/10 DEMOLITION

• 03 30 53 05/14 MISCELLANEOUS CAST-IN-PLACE CONCRETE

• 03 42 13.00 10 05/16 PLANT-PRECAST CONCRETE PRODUCTS FOR BELOW GRADE CONSTRUCTION

• 03 99 99 N/A FLOWABLE FILL

• 26 00 00.00 20 07/06 BASIC ELECTRICAL MATERIALS AND METHODS

• 31 00 00 08/08 EARTHWORK

• 32 01 19 08/08 FIELD MOLDED SEALANTS FOR JOINTS IN RIGID PAVEMENTS

• 32 11 23 08/17 GRADED-CRUSHED AGGREGATE BASE COURSE

• 32 12 13 05/17 BITUMINOUS TACK AND PRIME COATS

• 32 12 17 08/09 HOT MIX BITUMINOUS PAVEMENT

• 32 13 14.13 11/17 CONCRETE PAVEMENT FOR AIRFIELDS

• 32 17 23 08/16 PAVEMENT MARKINGS

• 32 92 19 08/17 SEEDING

• 33 05 23.13 11/13 UTILITY HORIZONTAL DIRECTIONAL DRILLING

• 33 71 02 02/15 UNDERGROUND ELECTRICAL DISTRIBUTION SYSTEM

• 34 73 13 04/08 MOORING AND GROUNDING POINTS FOR AIRCRAFT

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2.6 Administrative Specifications

The Government has provided the following Division 01 “General Requirements” specifications for inclusion:

• Section 01-1 SUMMARY OF WORK AND GENERAL REQUIREMENTS

• Section 01-2 DELIVERABLES

• Section 01-3 PROJECT SCHEDULES

• Section 01-4 WORK IN CONTROLLED AREAS

• Section 01-5 PROJECT SAFETY REQUIREMENTS

• Section 01-6 CONTRACTOR QUALITY CONTROL

• Section 01-7 TEMPORARY CONSTRUCTION FACILITIES AND CONTROLS

• Section 01-8 ENVIRONMENTAL PROTECTION

• Section 01-9 CLOSEOUT PROCEDURES

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Section 3 – Design Narrative

3.1 Project Justification

The Statement of Work (SOW) included with the Request for Proposal (RFP) included in Appendix A indicates that performing aircraft maintenance in the elements with portable lights results in inefficiency and the installation of sunshades structures would protect valuable Air Force assets. A recent hail storm damaged numerous aircraft at Laughlin AFB and some of this damage could have been prevented if the aircraft were covered. This preparatory project does not include procurement or installation of the sunshade structures themselves, rather, it involves the repositioning of existing duplex GPU installations to coincide with future sunshade structure column locations.

3.2 Proposed Improvements

URS Group, Inc. has been actively engaged with Base staff to develop a schematic site plan to layout the future aircraft sunshade structures, and an amicable hybrid layout is depicted on the 100% design submittal. The GPU installations are to be relocated southwest between 33 and 80 feet along the existing 3.5-foot wide utility trench to coincide with future building columns. A duct bank of empty conduits between the proposed sunshades and Building 219 will be constructed to permit the installation of sunshade obstruction and task lighting in the future.

3.3 Underground Utilities

Plans obtained by URS from the recent “First Street Area and Airfield Drainage” project depict a large storm sewer running beneath First Street. A portion of the sewer adjacent to the work area is an eight-foot by four-foot concrete box culvert and another portion is a 36-inch diameter reinforced concrete pipe. The same documents indicate there is a water line directly adjacent to the storm sewer. In addition to the wet utilities, there are also significant electric and compressed air utilities beneath First Street. These underground facilities are depicted diagrammatically on the plans such as Drawing C-02 DEMOLITION PLAN – FIRST STREET for general information.

All underground facilities must be precisely located with standard modern Subsurface Utility Engineering practices and techniques prior to any construction activity. This should be a condition of obtaining a dig permit.

3.4 Construction Phasing

To avoid impacting the mission, the Airfield Manager developed the construction phasing approach for this project personally in August of 2018. The construction phasing is shown diagrammatically on Drawings G-03 and G-04.

Typically, if aircraft will be taxiing under power directly adjacent to the work area, 20 feet of wingtip clearance must be provided per UFC 3-260-01 Paragraph B14-6.1.2 and B14-6.7.3 and the Airfield Manager has approved the concept and clearances depicted on the drawings. The phasing is predicated on a 135 foot setback from Taxiway G that was closely coordinated with the Airfield Manager.

3.5 Operational Safety during Construction

Construction safety on airfields is addressed in Appendix B, Section 14 of UFC 3-260-01 which references Table 6-1.

To ensure worker safety and prevent property damage during construction, wingtip clearance must be maintained and good FOD control must be practiced, as required by Drawing G-01, GENERAL NOTES & ABBREVIATIONS and the Division 01 specifications provided by the Government.

3.6 FAA Form 7460-1

The Contractor must submit a Form 7460-1 NOTICE OF CONSTRUCTION OR ALTERATION to the FAA at least 30 days prior to the start of construction. The Contractor should note if vehicles taller than standard construction equipment (like cranes) are to be used, which may require a Temporary Construction Waiver from the Air Force.

This may not be a consideration for the GPU relocation project, but it will be a consideration for the sunshade installation project, which will involve heavy equipment for drilling foundation piers and structural steel erection.

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3.7 Contractor Staging Area, Site Access and Haul Routes

A proposed Contractor Staging Area (CSA) as well as contractor access into the Installation and recommended construction traffic haul routes are depicted on Drawing G-02 CONTRACT LAYOUT PLAN. These items were reviewed by the Government. It is understood work hours are 7:30 AM to 4:30 PM. Please refer to Division 01.

3.8 Temporary Utilities for Construction

It is in the interest of the Government to provide the Contractor with water and temporary electric service. The Government has recommended a connection point for temporary construction water and it was added to the drawings, along with several notes. A note was also added to contact the local utility for temporary electric power.

3.9 Radioactive Material

It is common on construction projects such this to use nuclear gauges that contain a small amount of radioactive material to check the compaction of soil. A note was added to Drawing G-01 GENERAL NOTES & ABBREVIATIONS requiring the Contractor to request permission to bring this equipment onto the Base at least 30 days in advance.

3.10 Demolition

All aspects of demolition and deconstruction will be addressed by UFGS Section 02 41 00 DEMOLITION. There is a note on the drawings that requires the Contractor to obtain a “dig permit” (AF Form 103) before commencing demolition activities. The primary demolition item is the selective removal of the 12-inch thick, 3.5-foot wide existing concrete pavement trench patch, which will generate approximately 250 cubic yards of concrete waste.

Concrete slab removals will be initiated with a double, full-depth vertical saw cut. This operation will most likely be completed with a hydraulic breaker attached to a large excavator. If a tracked excavator is used, it should be outfitted with rubber pads on the tracks to avoid damage to the pavement which is to remain in-place. This project will also generate soil, flowable fill and structural concrete waste. A note on Drawing C-03 DEMOLITION PLAN – ROWS “T” & “S” requires the Contractor to submit a waste disposal plan to the Government for approval.

3.11 Design Aircraft

The design aircraft for pavement design and airfield geometry (both wingtip clearance and tail height) purposes is the Raytheon T-1A Jayhawk twin-engine jet trainer, which is similar in size to the civilian Hawker 400. This aircraft has a maximum weight of 15,700 pounds and a wingspan of 43.5 feet. The tail height is approximately 14 feet.

3.12 Concrete Pavement Design for 16-inch Concrete Trench Patches

No subsurface geotechnical investigation was conducted for the GPU relocation project, although one will likely be required for the future sunshade structure procurement project for the purposes of detailed foundation design. It is the intent of the Designer to simply replace existing pavement trench patches in-kind, but slightly thicker (thickened edge instead of dowels) with careful attention to the joints. However, the Designer has attempted to determine the depth of the existing pavement and investigate the subgrade conditions. The existing concrete apron appears to be 11.25 inches thick and records indicate the patches installed as part of the CASS repair project in 2015 were intended to be 12 inches thick. Geotechnical reports from neighboring projects suggest that a subgrade CBR value of 4, or a Westergaard “k-value” or modulus of subgrade reaction of 100 is conservative. An initial cursory analysis conducted with PCASE version 2.09.05 suggests that approximately seven inches of concrete “on grade” (no base) would be adequate for unlimited operations of the T-1A aircraft, as noted in the screen capture. The Designer recommends installing a patch that is several inches thicker than the pavement around it to support the existing pavement edges that will be undermined during demolition. The “head” on the concrete patch should drive plastic concrete into the voids better than attempting to make the top of the flowable fill coincide with the bottom of the existing slabs. Increasing the thickness should improve patch performance.

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Figure 3-1. PCASE Screen Capture to Confirm Adequacy of 16-inch Concrete Trench Patches

3.13 Concrete Pavement Slab Sizes

The permissible range of the concrete slab sizes is dictated by Table 12-7 in UFC 3-260-02. For concrete pavements between nine and twelve inches in thickness, the spacing of transverse construction joints is to be between 15 and 20 feet. The existing slabs are typically 16-feet by 20-feet, so an attempt to respect those slab sizes will be made.

It is permissible to use 20-foot slab sizes if the thickness is greater than 12 inches, as in the apron expansion area.

3.14 Concrete Slab Reinforcement

Odd-shaped slabs and any rectangular slabs with dimensions exceeding a ratio of 1.25 are to be reinforced with 0.05% steel similar to Figure 13-3 in UFC 3-260-02. It should be noted partial demolition and patching of slabs in contrary to modern design practice, and there is no relevant design guidance or precedent, but the use of steel in the patches to hold any cracks that develop tight is strongly recommended by the Designer and depicted on the drawings. The Designer is unsure if the existing concrete patches were reinforced, if they were doweled into one or both of the neighboring slabs, or if bonding agent was used. The available drawings are not clear in this respect.

3.15 Joint Details

Concrete pavement joints should be constructed with industry-standard techniques consistent with the details in Chapter 12 of UFC 3-260-02. Details for construction, contraction and expansion joints are provided in the drawing set. The concrete trench patches placed in 2015 as part of the CASS project ran along either construction (cold) or contraction (dummy) joints that may have relied on dowel bars (if placed on different days) or aggregate interlock (if placed on the same day) for load transfer across the joint. It would not be advisable to bond both sides of the trench patch, would effectively create a single 16-foot by 40-foot slab with unusually high curl-and-warp stress around the patch. This phenomenon is evidenced by the reflective cracking in the GPU pads placed in 2015.

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3.16 GPU Equipment Pads

It is contrary to modern design practice to place concrete on top of concrete. The interfacing irregular surfaces are likely to lock together. One can imagine how difficult it would be to slide sandpaper over sandpaper. Because the GPU is very thin, and because it exposed to the magnified curl-and-warp stress on the edge of the slab below, and because the top heats quicker and cools faster each day, it will expand-and-contract more drastically than the pavement it is adhered to below. The end result is the concrete GPU pads placed over pavement joints just two years ago are failing at an alarming rate, and it is common to find reflective cracks (and frequently a pair of reflective cracks) over each joint. The Designer recommends using fiber-reinforced concrete with a thin sheet of HDPE acting as a bond-breaker between the two concrete masses. The Government has requested sawed joints in the equipment pad over all joints in the concrete pavement below. URS will comply, although this may be a redundant “belt and suspenders” approach with the HDPE sheet isolating the two separate concrete masses.

Figure 3-2. Premature Cracking in Existing Concrete GPU Pads Constructed in 2015.

3.17 Concrete Pavement Material Specification

The concrete for the equipment pads will be fiber-reinforced and specified per UFGS 03 30 53 MISCELLANEOUS CAST-IN-PLACE CONCRETE with a compressive strength of 4000 psi. Concrete used for the 13-inch apron extension pavement will be specified in accordance with UFGS Section 32 13 14.13 CONCRETE PAVEMENT FOR AIRFIELDS with a design flexural strength of 650 psi. Certain edits will be required to reflect the small size of the project. It would be acceptable for the contractor to use either type of concrete for the 16-inch concrete trench patches.

3.18 Frost Penetration Depth

Frost is an important aspect of pavement design and is addressed in Chapter 20 of UFC 3-260-02. Per NOAA, the depth of “extreme” frost penetration in Del Rio, Texas is less than six inches. Because both the concrete patches will be thicker than six inches, frost is not a design consideration, and the life of the pavement should be increased.

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3.19 TCEQ TPDES General Permit TXR150000

This project is subject to regulation by the Texas Commission on Environmental Quality (TCEQ). The Contractor must obtain a “Texas Pollutant Discharge Elimination System (TPDES) Construction General Permit TXR150000” prior to commencing operations if the disturbed area is large enough to trigger the regulatory requirements.

This permit is specifically applicable to storm water discharges from construction activities within the State of Texas. A Notice of Intent (NOI), as well as a Storm Water Pollution Prevention Plan (SWP3), must be prepared as part of the TXR150000 permit application process. The likelihood of contamination from construction operations reaching receiving bodies of water in significant quantities is very remote and should be readily mitigated by standard Best Management Practices (BMP) like inlet protection and strategically placed silt fence or straw wattle.

3.20 Technical Approach to GPU Relocation

The most economic method to achieve the project objective of relocating the existing GPU installations to nest within the support columns of future open-sided sunshade structures appears to be relocate the existing GPU installations toward First Street along the existing 3.5-foot wide pavement trench patch placed in 2015 as part of the “Repair CASS Air Distribution System” project and re-using most of the associated underground duct bank. All four of the existing duplex GPU installations on the five “branches” for each aircraft parking row must be relocated between 33 and 80 feet toward the “trunk” of the existing distribution system located under the First Street.

To reposition a duplex GPU installation along the existing 3.5-foot wide trench patch, the equipment from each pad (two GPU, one wireway and one equipment rack) must be removed from the pad and then the pad must be demolished. The drawings depict the demolition of a portion of the existing concrete trench patch under the former pad so the horizontal electrical conduits can be patched for re-use after the vertical risers are removed.

In the locations where the GPU installations are to be repositioned, the existing concrete pavement patch will be demolished at the joint lines. Unfortunately, the existing electrical conduits for the GPU are co-located with concrete-encased pneumatic lines, so a portion of this strong and bulky utility must be demolished for access which will render the system inoperable. The steel air lines are cathodically protected, and breaking the lines may compromise the cathodic protection system used to prevent corrosion of the system. Making changes to the air lines (other than incidental demolition) or modifying the cathodic protection system would require a significant design effort and is not included in the current scope of this design project.

Figure 3-3. Existing and Replacement Concrete Trenches.

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3.21 Wingtip Clearance Considerations

The intent of the RFP and the site layout depicted on the 100% submittal is to keep the aircraft rows in the existing locations and maintain 20 feet of wingtip clearance in the access taxilanes (with the structure columns, not the service vehicle drive aisle) and 10 feet of wingtip clearance within the sunshade structures. It is not a problem to maintain 20 feet of wingtip clearance against other aircraft noses, aircraft tails or building columns as required by UFC 3-260-01 Table 6-1, Item No. 5. Typically about 26 feet is provided in the schematic design provided for review and comment. However, it should be noted that vehicles cannot be parked in the existing/proposed 10-foot service vehicle drive aisle which runs along the front of each parking row. Also, it should be noted only about 17 feet of clearance will be provided between the wingtip and the sunshade “drip line” overhang located up in the air far above the wingtip of the aircraft. This type of arrangement is not necessarily foreseen by the design criteria.

URS Group designed for 12.5 feet of wingtip clearance for the parked aircraft because in certain aircraft maneuvers into and out of the sunshade structures an analysis conducted with aircraft turning movement software indicated the T-1A aircraft wingtip tends to “cut the corner”. If the target wingtip clearance in the middle of the sunshade when parked is just ten feet, the wingtip will pass within seven feet of the outside sunshade column during the turning maneuver turning into and out of the sunshade which is not desirable. The Government has agreed to this.

It should be noted, in the opinion of the Designer, the existing GPU installations appear to meet the definition of a “fixed obstacle” as defined in UFC 3-260-01, Table 3-2, Item No. 12 and do not qualify as a permissible deviation potentially eligible to be granted a waiver for stationary and non-frangible Ground Support Equipment noted in UFC 3-260-01, Appendix B, Section 13, Paragraph B13-2.20.2.7. Therefore it is not proper to place any portion of the two-foot wide GPU within the 10-foot buffer between the wingtip and the column of the sunshade structure.

A 10-foot buffer on each side of the two-foot wide GPU is proposed in the 100% drawing set.

The 100% submittal includes a pavement marking for a rolling fire extinguisher requested by the Government.

3.22 Tie-downs and Ground Receptacles

New tie-downs and ground pits are required for this project. All of the existing tie-downs are ground pits in the project area are to be removed. Details for combined tie-down and ground pit demolition, layout and installation are provided in the 100% submittal. The SOW seems to suggest six tie-downs and additional ground are required, which was confirmed. Typically only three are provided, especially when only one type of aircraft is present. It should be noted that removing and reinstalling tie-downs and ground pits causes significant trauma to the pavement which will impact its durability. The Government should re-verify the tie-down and ground pit typical layout shown on the plans prior to construction.

3.23 Conceptual Electrical Design

Electrical demolition is depicted graphically on drawings like E-04 DEMOLITION PLAN – ROWS “T” & “S” and the circuiting is depicted graphically on, Drawing E-08, ELECTRICAL PLAN – ROWS “T” & “S”, for example. The intent of the design is to re-use portions of the existing underground conduits. Existing GPU circuit conductors will be removed from the existing GPU installations to the large octagonal electrical manholes located alongside First Street. New wiring between the octagonal manholes and relocated GPU installations will be installed in existing and new sections of conduits by way of in-pavement junction cans. Existing feeders from a distribution panel in Building 219 to the octagonal manholes shall be reconnected to the new wiring.

3.24 Provisions for Future Task and Obstruction Lighting

The Statement of Work included in Appendix A says “The design shall also include an access point for secondary electrical distribution for future sunshade lighting.” Per RFI #4, an entirely new two-way, four-inch duct bank of empty conduits will be constructed for future task and obstruction lighting in the sunshade structures at significant

Prepared by URS Group, Inc. Page 13 of 69 100% Submittal – 09/07/2018 expense. New three-foot by three-foot by three-foot (internal dimensions) handholes near the future location of each sunshade structure lighting panel will be installed along the duct bank. From the handholes, a two-way, two-inch with one-way, three-quarter-inch duct bank will run over and stub up into the location for each lighting panel.

3.25 Waivers to UFC Design Criteria

The proposed design does not require any new waivers or the renewal of any existing waivers.

3.26 Potential Issues for Discussion

There are several potential issues that URS Group would like to bring to the attention of the Government:

1. The Designer is concerned about installing thin concrete pads to elevate the GPU equipment over existing concrete joints, as required by the SOW, will could result in reflective cracking or premature cracking. The Designer recommends using a sheet of HDPE to isolate the two concrete masses. However, the three-inch equipment pad is too thin for conventional reinforcement and the durability may be poor.

2. Trenching and patching concrete pavement is contrary to modern practice and could result in cracking.

Typically in airfield construction, the entire slab is removed and replaced if necessary.

3. This project will render the branches of the compressed air system permanently inoperable.

4. This project may compromise the cathodic protection system serving the trunk of the compressed air system. Modifications to the cathodic protection system serving the air lines is beyond the project scope.

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Section 4 – Pavement Thickness Design for Apron Extension

4.1 Introduction

Pavement design criteria applicable to this project is detailed in UFC 3-260-02, “Pavement Design for Airfields”.

The software package PCASE, version 2.09.05, from USACE was used throughout the pavement design process to perform iterative calculations.

4.2 Aircraft Weight and Pass Levels

The airfield type used for the purposes of this pavement design for the apron extension (not the trench patches) was “Light” as defined in Chapter 3 of UFC 3-260-02 and the apron was considered to be a Type A Traffic Area, which means the full takeoff weight of the aircraft is to be used. It is not necessary to consider the B-52 aircraft given the runway widths at Laughlin AFB as noted in the second footnote in the table. The aircraft gross weights and pass levels for all types and areas are shown in Table 3-1 in UFC 3-260-02:

Figure 4-1: Table 3-1 from UFC 3-260-02

4.3 Subgrade Westergaard K-Values

Pavement design is predicated on two major parameters, information about the weight and amount of traffic that will traverse the pavement as outlined above and information about the existing subgrade which will support the pavement section. Rigid pavement design is predicated on an engineering parameter known as the Westergaard “k-value” or modulus of subgrade reaction. It is possible to measure this parameter directly with full-scale plate load tests conducted in large test pits, but the standard industry practice is to conduct repeated Dynamic Cone Penetrometer Tests (DCPT) through relatively small boreholes at varying depths to determine the California Bearing Ratio (CBR) in the field, or the 96-hour soaked lab CBR, and equate those values to the k-value necessary for rigid pavement design. Flexible pavements, like the asphalt road patches, are designed directly with the CBR.

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No geotechnical investigation was conducted specifically for this project. The pavement design was completed with subgrade assumptions that are considered to be conservative for this area based on previous experience.

4.4 Pavement Thickness Design for 13-inch Concrete Apron Extension

The proposed concrete pavement design screen from PCASE is included below. The section was modeled as a concrete slab supported by a six inches of base resting on a subgrade with a Westergaard k-value of 125. For an Air Force “Light” aircraft mix and pass levels dictated for a Type “A” Traffic Area, the thickness of concrete required is rounded up to 13 inches. The proposed pavement section is depicted diagrammatically on drawings.

Figure 4-2: PCASE Screen Capture for 13-inch Concrete Apron Extension

4.5 Concrete Joint Pattern

The permissible range of the concrete slab sizes is dictated by Table 12-7 in UFC 3-260-02. For concrete pavements thicker than 12 inches, the maximum allowable nominal joint spacing is 20 feet. Slab sizes in the apron extension area were designed to be complementing the existing joint layout. The maximum size is approximately 20 feet.

4.6 Slab Reinforcement

Any odd-shaped slabs, rectangular slabs with dimensions exceeding a ratio of 1.25, or slabs with penetrations will be reinforced with 0.05% steel similar to Figure 13-3 in UFC 3-260-02 and per the detail provided on the drawings.

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4.7 Dowel Bars

Dowels will be provided in construction joints and contraction joints, either by drilling or with prefabricated baskets in compliance with UFC 3-260-02 as noted on the plan and details. The length, diameter and spacing of these dowels are dictated by Table 12-8 in UFC 3-260-02. For this project the dowels will be 20 inches in length,

1.25 inches in diameter and will be located on 15-inch centers at mid-depth. No dowels will be provided in the transverse thickened edge expansion joints. In these locations, load transfer provided by the increased thickness.

4.8 Joint Details

Concrete pavement joints will be constructed with industry-standard techniques consistent with the details in Chapter 12 of UFC 3-260-02 and as shown on the details provided in the drawing set. Details for construction, contraction, expansion and shoulder interface joints are provided in the 100% drawing set for construction.

4.9 Pavement Thickness Design for 6-inch Asphalt First Street Patch

Inputting a conservative estimated subgrade CBR value into PCASE indicates six inches of hot-mix asphalt over eight inches of “aggregate base course” is required for the asphalt patches in First Street necessary to accommodate the concrete apron extension construction. The screen capture presented below indicates this section is acceptable for subgrade CBR values as low as 10. Design traffic details are noted in Appendix K.

Figure 4-3: PCASE Screen Capture for 6-inch Asphalt First Street Patch

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4.10 Material Specification for Portland Cement Concrete (PCC) Pavement

Concrete for pavement will be specified in strict accordance with UFGS Section 32 13 14.13 CONCRETE PAVEMENT FOR AIRFIELDS, which is a new specification. The default design flexural strength of the concrete is limited to 650 psi. It should be noted for the purposes of scheduling that a formal test section is generally required. Profilograph testing was removed from the specification after considering the size of the project and the lack of aircraft traffic.

4.11 Material Specification for Hot Mix Asphalt

The asphalt used to reconstruct the roadway will be a 75-blow mix under light traffic, with a minimum stability of 1350. An edited version of UFGS Section 32 12 17 HOT MIX BITUMINOUS PAVEMENT will be included in the technical specifications. The asphalt binder used in the Job Mix Formula (JMF) will be Performance Grade (PG) 76-22 consistent with the guidance in UFC 3-260-02, Chapter 9, Paragraph 4.a.(b). A software package distributed by the Federal Highway Administration entitled LTPPBind 3.1 was used to verify the asphalt binder is proper for the climate in Del Rio. The aggregate gradation selected for use in the hot mix asphalt was “Gradation No. 2”.

Because fewer than 500 tons of material are anticipated, some of the standard Quality Control requirements in the specification may not apply.

4.12 Material Specification for Aggregate

The virgin aggregate base used for the replacement asphalt roadway will be the Graded-Crushed Aggregate Base Course type with a design CBR of 100 as specified in UFGS Section 32 11 23 GRADED-CRUSHED AGGREGATE BASE COURSE. This material has slightly more demanding material properties and installation requirements than the plain Aggregate Base Course specified in that same UFGS section. The gradation selected for the Graded-Crushed Aggregate is “Gradation No. 2”.

4.13 Material Specification for Tack and Prime Coat

Bituminous prime coat will be applied to the compacted aggregate surface before the asphalt is placed on the roadway. The material recommended for this purpose is ASTM D2397 Type CSS-1h asphalt emulsion. Asphalt cutbacks are not permitted in some jurisdictions for environmental reasons. Tack will be provided between asphalt lifts. The material to be used will be CSS-1h asphalt emulsion as specified in Section 32 12 13.

4.14 Material Specification for Joint Sealant

On similar projects at Laughlin AFB, the Government has accepted cold-poured ASTM D5893 silicone to seal most of the joints on the pavement. The sealant used at the interface of the new concrete pavement and new asphalt roadway, as well as the expansion joints, will be ASTM D6690 Type III hot-poured sealant. Requirements for poured sealants are addressed in Section 32 01 19 FIELD MOLDED SEALANTS FOR JOINTS IN RIGID PAVEMENTS.

Details for joint sealing consistent with the guidance in Figure 12-31 of UFC 3-260-02 are provided on the drawings.

4.15 Frost

Frost is an important aspect of pavement design and is addressed in Chapter 20 of UFC 3-260-02. Per NOAA, the depth of extreme frost penetration in Del Rio, Texas is less than six inches. Because both the concrete pavement and asphalt roadway sections will be thicker than six inches, frost is not a consideration.

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Section 5 – Construction Cost Estimate

5.1 Estimate of Probable Construction Cost

The Government prepared a construction cost estimate to reposition the existing GPU installations in order to complete DD Form 1391. The value of the work was determined to be $894,000 at that time. That document is included for reference in Appendix F.

A construction cost estimate prepared by URS with updated cost data is included in Appendix Z for planning purposes. This model indicates the cost of the proposed improvements is nearly $1.3 million. It should be noted the project is significantly more expensive than estimated at the 35% level because the Government directed URS shift the sunshade structures into the road (RFI #3) which required an extension of the concrete aircraft apron. In addition, the Government also requested an all-new purpose-built empty duct bank for future sunshade task and obstruction lighting (RFI #4). Neither of these items was in the original cost estimate prepared by the Government.

There are also unanticipated incidental costs such the replacement of the flexible 400 Hz GPU connector cables with longer units at the Government’s request. The installed cost of these replacement cables is expected to be nearly $3400 each, which results in an unanticipated cost associated with this simple request of nearly $135,000.

Please refer to the pricing information provided by the GPU manufacturer, Hobart, in Appendix L of this report.

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Appendices

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Appendix A – Statement of Work (Second Revision)

Mod 02 Attachment 1

FA309917F0033

Allied Support T-1 Sunshades

STATEMENT OF WORK

Allied Support T-1 Sunshades Project Location: Laughlin AFB, TX Base Project Number: MXDP 17-1007

REVISED: 11 Jul 2018

1.0 INTRODUCTION

Maintenance personnel currently do not have any weather protection for the T-1 aircraft and must use portable equipment to provide light to perform aircraft maintenance. The constant exposure to the elements along with the retrieval, setup and breakdown of lighting equipment has led to decreased efficiency. The installation of electrical utility lines and sunshades shall not only increase efficiency allowing more training missions to be executed, but shall also protect vital Air Force assets. This work shall consist of the design for Real Property items (sunshade infrastructure items).

As a result of the resubmittal of RFI 03, the sunshade structures will be shifted toward First Area to avoid interference of the future structure footings with recently installed box culverts running parallel to First Street and the necessary changes will be…