Design Summary Report Ih 635 Managed Lanes Project Re-Evaluated Design Schematic

DRAFT

DESIGN SUMMARY REPORT

FOR THE

IH 635 MANAGED LANES PROJECT

RE-EVALUATED DESIGN SCHEMATIC

PREPARED FOR:

TEXAS DEPARTMENT OF TRANSPORTATION December 2006

This draft document is released on December 20, 2006 for information and reference purposes only under the authority of:

Randall J. Poucket, P.E. #90495 George R. Teetes, P.E. #81151 Constance D. Bills, P.E. # 83877 Syed N. Aftab, P.E. #80137 Charles Edward Hood, P.E. #61366 Abenet Bekele, P.E. #86055 Michael J. Bauer, P.E. #94128 Robert K. Lindsey, P.E. #86979 Walter T. Ragsdale, P.E. #56735

It is not to be used for final design considerations.

TABLE OF CONTENTS

CHAPTER 1 - INTRODUCTION...... 1 1.1 Purpose ...... 1 1.2 Project Description and Limits...... 1 1.2.1 IH 635 West Section...... 2 1.2.2 IH 635/IH 35E Interchange...... 2 1.2.3 IH 35E Section ...... 3 1.3 Value Engineering (VE) Process...... 4 1.4 Constraints and Criteria ...... 5 1.5 Design Exceptions ...... 8 CHAPTER 2 - CIVIL DESIGN ...... 8 2.1 Roadway...... 8 2.1.1 Geometric Design Criteria ...... 8 2.1.2 Roadway Geometric Design...... 11 2.2 Drainage...... 16 2.2.1 Drainage Design Criteria ...... 16 2.2.2 Preliminary Drainage Design...... 20 2.3 Construction Schedule and Traffic Control...... 21 2.3.1 Construction Sequencing, Phasing and Schedule ...... 21 2.3.2 Traffic Control...... 26 CHAPTER 3 - GEOTECHNICAL...... 28 3.1 Available Geotechnical Data ...... 28 3.2 Geologic Setting (IH 635 West Section)...... 29 3.2.1 Overburden ...... 29 3.2.2 Eagle Ford Shale...... 30 3.2.3 Austin Chalk...... 31 3.3 Geotechnical Considerations for the Re-Evaluated Design Schematic...... 32 3.3.1 General ...... 32 CHAPTER 4 - STRUCTURAL DESIGN ...... 34 4.1 Surface Structures – Bridges ...... 34 4.1.1 Structural Criteria ...... 34 4.1.2 Structural Elements...... 34 4.2 U-Wall Structures...... 35 4.2.1 General ...... 35 4.2.2 Alignment and Profile Parameters ...... 36 4.2.3 Dimensional Parameters ...... 36 4.2.4 Fire and Life Safety Considerations...... 37 4.2.5 Structural System Determination and Description...... 37 4.2.6 Ancillary Facilities...... 38 4.3 Cut-and-Cover Tunnel Structures ...... 38 4.3.1 General ...... 38 4.3.2 Alignment and Profile Parameters ...... 38 4.3.3 Dimensional Parameters ...... 39 4.3.4 Fire and Life Safety Considerations...... 39 4.3.5 Loading Criteria:...... 39 4.3.6 Structural System Determination and Description...... 40 4.3.7 Ancillary Facilities...... 40

ii 4.4 Mined Tunnels ...... 41 4.4.1 General ...... 41 4.4.2 Tunnel Length and Portal Locations ...... 41 4.4.3 Dimensional Parameters ...... 42 4.4.4 Tunnel Rock Properties for Design...... 42 4.4.5 Tunnel Excavation...... 42 4.4.6 Ground Response to Excavation ...... 42 4.4.7 Initial Ground Support ...... 43 4.4.8 Waterproofing for Mined Tunnels and Underground Structures...... 43 4.4.9 Tunnel Final Lining...... 44 4.4.10 Ancillary Facilities...... 44 4.4.11 Fire and Life Safety Considerations...... 44 4.5 Ancillary Facilities ...... 44 4.5.1 General ...... 44 4.5.2 Emergency Exit Stairways...... 45 4.5.3 Utility Rooms...... 45 4.5.4 Structures Combining Ventilation Shafts, Maintenance/Emergency Exits, and Utility Rooms...... 45 4.5.5 Cross Passageways...... 46 4.5.6 Low-Point Pump Stations ...... 46 4.6 Tunnel Finishes ...... 46 CHAPTER 5 - MECHANICAL, ELECTRICAL, AND POWER DESIGN...... 48 5.1 Tunnel Ventilation System Design ...... 48 5.1.1 General Background Information...... 48 5.1.2 Assumptions...... 49 5.1.3 Design Standards & Design Objectives ...... 49 5.1.4 Other Design Considerations ...... 49 5.1.5 Tunnel Ventilation System Modeling – General...... 50 5.1.6 Tunnel Ventilation Analysis During a Fire Emergency ...... 52 5.1.7 Vehicular Emissions Under Non-emergency Conditions...... 52 5.1.8 Ambient Temperature within the Tunnel...... 55 5.2 Fire Protection System Design...... 58 5.2.1 Fire Protection – General ...... 58 5.2.2 Assumptions...... 58 5.2.3 Tunnel and Depressed Managed Lanes Fire Protection Design Criteria ...... 59 5.2.4 Fire Protection System Basic Configuration...... 59 5.3 Tunnel Drainage System Design...... 61 5.3.1 Tunnel Drainage – General ...... 61 5.3.2 Drainage Design Criteria ...... 62 5.3.3 Preliminary Drainage Design...... 62 5.4 Depressed Managed Lane Lighting ...... 62 5.4.1 Partially Covered Depressed Managed Lanes Lighting Baseline Fixture Choice...... 62 5.4.2 Tunnel Lighting Fixture Choice...... 63 5.4.3 Design Considerations ...... 63 5.5 SCADA System ...... 64 5.5.1 Design Considerations ...... 64 5.6 Intrusion Detection System ...... 64 5.6.1 Design Considerations ...... 64 5.7 Fire Alarm and Detection System...... 65

iii 5.7.1 Design Considerations ...... 65 5.8 Communications System ...... 65 5.8.1 Design Considerations ...... 65 5.9 Electrical Systems...... 65 5.9.1 Design Considerations ...... 65 5.9.2 Tunnel System Electric Utility Service ...... 66 5.9.3 Source Reliability and Redundancy...... 66 5.9.4 Primary Distribution System Configuration ...... 66 5.9.5 Secondary Distribution System Configuration...... 67 5.9.6 Electrical Load Classification...... 67 CHAPTER 6 - AESTHETICS AND LANDSCAPING...... 69 CHAPTER 7 - TRAFFIC ANALYSIS...... 70 7.1 Travel Demand Model...... 70 7.1.1 Overview ...... 70 7.1.2 Introduction ...... 70 7.1.3 Model Boundaries ...... 71 7.1.4 Analysis...... 71 7.1.5 Conclusions...... 72 7.2 VISSIM Analysis to Evaluate IH 635/IH 35E for the Interim and Ultimate Conditions...... 73 7.2.1 Overview ...... 73 7.2.2 Interim Condition (2020)...... 73 7.2.3 Ultimate Condition (2030)...... 74

iv EXHIBITS

Exhibit Number Discipline & Title

Key Map 1.1.1 IH 635 (LBJ Freeway) - Managed Lanes Project - West End

Civil 1 Roadway Plan – IH 35E from Spur 482 to North of Lombardy Lane 2 Roadway Plan – IH 35E from Lombardy Lane to Manana 3 Roadway Plan – IH 35E from Manana to Crown Road 4 Roadway Plan – IH 35E & IH 635 Interchange 5 Roadway Plan – IH 35E North of IH 635 6 Profiles – IH 635 From Luna Road to East of Denton Drive 7 Plan & Profiles – IH 635 from East of Denton Drive to East of Webb Chapel Road 8 Plan & Profiles – IH 635 from East of Webb Chapel Road to East of Midway Road 9 Plan & Profiles – IH 635 from East of Midway Road to East of Preston Road 10 Plan & Profiles – IH 635 from East of Preston Road to West of Coit Road 11 Profile – IH 635 General Purpose Lanes 12 Profile – IH 635 General Purpose Lanes 13 Profile – IH 635 General Purpose Lanes 14 Profile – IH 635 Managed Lanes 15 Profile – IH 635 Managed Lanes 16 Profile – IH 635 Managed Lanes 17 Profiles – IH 635 Ramps 18 Profiles – IH 635 Ramps 19 Profiles – IH 635 Cross Streets and IH 35E Ramps 20 Profiles – IH 635 EB Frontage Road 21 Profiles – IH 635 EB Frontage Road 22 Profiles – IH 635 WB Frontage Road 23 Profiles – IH 635 WB Frontage Road 24 Profiles – Elevated Collectors and Direct Connectors

v Civil (continued) Re-Evaluated Design Schematic Managed HOV Lanes Alternate 2

8 Plan & Profiles – IH 635 from East of Webb Chapel Road to East of Midway Road 9 Plan & Profiles – IH 635 from East of Midway Road to East of Preston Road 15 Profile – IH 635 Managed Lanes 16 Profile – IH 635 Managed Lanes 17 Profiles – IH 635 Ramps 18 Profiles – IH 635 Ramps 20 Profiles – IH 635 EB Frontage Road 21 Profiles – IH 635 EB Frontage Road 22 Profiles – IH 635 WB Frontage Road 23 Profiles – IH 635 WB Frontage Road

Construction Staging 2.3.1 Typical Roadway Construction Sequence For MSE Wall Installation 2.3.2 Typical Roadway Construction Sequence For Non-MSE Wall Installation 2.3.3 Typical Roadway Construction Sequence At Underpass Locations 2.3.4 Typical Roadway Construction Sequence At Overpass Locations 2.3.5 Typical Roadway Construction Sequence At Cut-and-Cover Tunnel Locations

Geotechnical 3.1.1 Geotechnical Profile – Sta. 35+00 to Sta. 205+00 3.1.2 Geotechnical Profile – Sta. 205+00 to Sta. 385+00

Bridge 4.1.1 Typical Overpass Configuration 4.1.2 Typical Underpass Configuration

Depressed Managed Lanes 4.2.1 IH 635 Schematic Plan – General Purpose and Managed Lanes 4.2.2 Typical Depressed Managed Lanes - MSE Walls Section 4.2.3 Typical Depressed Managed Lanes - Variable General Purpose Lane Overhang Section

vi Depressed Managed Lanes (continued) 4.2.4 Typical Depressed Managed Lanes – General Purpose Lanes Overhang Section 4.2.5 Typical Depressed Managed Lanes - Soil Nail & Rock Bolts Section

Cut-and-Cover Tunnel Typical Sections 4.3.1 Cut-and-Cover Tunnel – Minimum Clear Dimensions 4.3.2 Cut-and-Cover Tunnel - Section 4.3.3 Cut-and-Cover Tunnel - Appurtenances and General Arrangement

Mined Tunnel Typical Sections 4.4.1 Mined Tunnel – Minimum Clear Dimensions 4.4.2 Typical Tunnel Section 4.4.3 Typical Tunnel Support - Type 1 4.4.4 Typical Tunnel Support - Type 2 4.4.5 Typical Tunnel Support - Type 3 4.4.6 Tunnel Niches – Plan and Sections 4.4.7 Typical Portal Elevation

Mechanical and Fire Protection Drawings 5.1.1 Tunnel Profile with Typical Ancillary Items – Sheet 1 or 2 5.1.2 Tunnel Profile with Typical Ancillary Items – Sheet 2 of 2 5.1.3 Tunnel Ventilation - Typical Equipment Schedule 5.1.4 Typical Ventilation Building Plan – Lower Level 5.1.5 Typical Ventilation Building Plan – Mid Level 5.1.6 Typical Ventilation Building Plan – Upper Level 5.1.7 Typical Ventilation Building – Transverse Section 5.1.8 Typical Ventilation Building – Longitudinal Section 5.1.9 Fire Protection Diagram for Depressed Highway 5.1.10 Fire Protection Diagram for Tunnels 5.1.11 Fire Protection Details 5.1.12 Tunnel Drainage Sump Plan 5.1.12 Tunnel Drainage Sump Section

vii Electrical Drawings 5.2.1 Tunnel Service and Primary Distribution Diagram 5.2.2 Power Center Single Line Diagram 5.2.3 Power Center Building Plan 5.2.4 Electrical Equipment Space Allocation – C&C Tunnel 5.2.5 Electrical Equipment Space Allocation – Mined Tunnel 5.2.6 Tunnel Systems SCADA Functional Diagram

viii CHAPTER 1 - INTRODUCTION

1.1 Purpose In November 2005, the LBJMP Team was directed by TxDOT to conduct a Value Engineering (VE) exercise for the IH 635 Managed Lanes Project. The purpose of the VE effort was to identify opportunities to reduce capital, operations and maintenance costs by evaluating potentially less expensive schematic alternatives. Through the VE effort, the LBJMP Team systematically evaluated various alternatives before arriving at a proposed schematic design. The proposed schematic design is referred to herein as the Re-Evaluated Design Schematic.

This Design Summary Report documents the preliminary engineering conclusions and design criteria used in development of the Re-Evaluated Design Schematic, and summarizes the corresponding preliminary design effort. This report is not intended for use in directing the final design of the IH 635 Managed Lanes Project, and is made available to future designers for reference information only.

1.2 Project Description and Limits The IH 635 Managed Lanes Project (Project) includes reconstruction of the IH 635 general purpose lanes (between IH 35E and US 75), construction of surface and subsurface managed lanes, reconstruction and new construction of IH 635 frontage roads, construction of elevated direct connectors along IH 35E, and construction of portions of the IH 635/IH 35E interchange.

The project limits along IH 635 extend from Luna Road to Merit Drive. Along IH 35E, the limits extend from south of Valwood Parkway and continue south through the IH 35E/Loop 12 split to Northwest Highway along Loop 12, and to Storey Lane along IH 35E.

Municipalities located adjacent to the corridor include the cities of Dallas and Farmers Branch.

Following are the components of the IH 635 and IH 35E facility for the Re-Evaluated Design Schematic.

1.2.1 IH 635 West Section The IH 635 West section of the Re-Evaluated Design Schematic extends from east of Denton Road to west of Merit Drive. This section includes the construction of at-grade and Depressed managed lanes and reconstruction of general purpose lanes from the west end of the Denton Drive bridge to approximately 400’ west of Merit Drive. The section includes construction of access ramps between managed lanes, general purpose lanes and frontage roads. The continuous frontage road system consists of new or reconstructed frontage roads on both sides of IH 635 starting from Harry Hines Boulevard to approximately 400’ west of Merit Drive. In addition, this section includes the reconstruction of cross streets, including; Denton Drive, Forest Lane, Ford Road, Anaheim Drive, Josey Lane, Webb Chapel Road, Marsh Lane, Rosser Road, Valley View Lane, Midway Road, Welch Road, Montfort Drive, Preston Road, Hillcrest Road and Park Central Boulevard, and portions of the interchange at Dallas North Tollway (DNT). Reconstruction of the Joe Ratcliff pedestrian bridge is also part of the IH 635 West section.

1.2.2 IH 635/IH 35E Interchange The IH 635/IH 35E interchange improvements include construction of the interchange direct connectors from Crown Road on IH 35E to the back of gore of the proposed general purpose lanes on IH 635. These connectors will provide for traffic movements from northbound (NB) IH 35E to eastbound (EB) IH 635 and from westbound (WB) IH 635 to southbound (SB) IH 35E. These ramps will connect to the northern ends of the elevated direct connectors to be constructed along IH 35E. In addition, the SB IH 35E to EB IH 635, and WB IH 635 to NB IH 35E direct connectors are included.

Also included is the construction of the managed lanes beginning east of Luna Road through the IH 635/IH 35E interchange to Denton Drive.

The impacts to traffic movements due to the addition of the WB IH 635 to NB IH 35E connector required adjustments in the existing NB ramps north of IH 635. The existing NB Harry Hines Boulevard entrance ramp to the connector was moved north to tie into the general purpose lanes just north of Valley View Lane. To provide sufficient weaving distance on the NB Frontage Road, the exiting NB Valley View Lane exit ramp from IH

2 35E to the frontage road was realigned. The proposed general purpose and frontage road gore locations are approximately 220’ and 400’, respectively, of their existing locations. Because the proposed Harry Hines Boulevard entrance ramp alignment is located within the limits of the existing Valley View Lane entrance, the existing ramp was moved north. Geometric design criteria and traffic movements dictated that the Valley View Lane entrance ramp and Valwood Parkway exit ramps be reversed to provide sufficient weaving distances.

The Re-Evaluated Design Schematic provides for an interim Project configuration through the IH 635/IH 35E interchange, but the requirements for the ultimate interchange configuration were accounted for in the presented design.

1.2.3 IH 35E Section The IH 35E section improvements consist of providing elevated direct connectors adjacent to the existing at-grade main lanes. These direct connectors extend from the Loop 12 split to connect to the IH 635/IH 35E interchange direct connectors.

At the IH 35E/Loop 12 split, improvements include construction of direct connectors that extend from approximately 1600’ north of Storey Lane along IH 35E, and the north end of the Northwest Highway bridge along Loop 12. In addition, relocation of the exit ramp from NB IH 35E to Northwest Highway north of Storey Lane, relocation of the entrance ramp from Northwest Highway to SB IH 35E north of Storey Lane, and relocation of the exit ramp from SB IH 35E to Northwest Highway at Loop 12 are also provided.

Further improvements are provided by construction of ramps north of Walnut Hill Lane between the frontage roads and the elevated direct connectors, construction of the SB frontage road from Joe Field Lane to Walnut Hill Lane, and the NB frontage road from Walnut Hill Lane to the NB elevated direct connector entrance ramp.

Construction improvements (to the extent required to provide the direct connectors) to cross streets including Northwest Highway, Lombardy Lane, Manana Drive, Walnut Hill Lane and Merrell Road are also provided for in the Re-Evaluated Design Schematic.

3 The Re-Evaluated Design Schematic provides for an interim Project configuration through the IH 35E/Loop 12 interchange, but the requirements for the ultimate interchange configuration were accounted for in the presented design.

1.3 Value Engineering (VE) Process The VE effort undertaken by the LBJMP Team was conducted using a multi-disciplinary team to identifying potential Project cost savings. Throughout the process, TxDOT was regularly briefed on the status of the effort and provided input and direction on desired configuration and proposed preliminary design solutions. At all times, careful consideration was given to the following:

a) Evaluation of life safety issues and application of NFPA 502 & NFPA 1710 b) Compliance with the previous Environmental Assessment (2004) c) Evaluation and application of Project constraints d) Evaluation of overall Project scope and application of design criteria e) Promoting public safety and mobility

A detailed description of the VE approach is not provided in this report; however, the following list broadly summarizes the steps taken during the effort to arrive at the Re- Evaluated Design Schematic:

a) Identification of various surface and subsurface configurations b) Ranking of alternatives and further evaluation of top ranked alternatives c) Selection of two alternatives to further evaluate to a 5%-10% preliminary engineering level of design d) Selection of the preferred alternative e) Evaluation of construction staging scenarios f) Preparation of a construction cost estimate g) Preliminary validation of the proposed alternative for access, connectivity, functionality, and constructability h) Documentation of the above effort in the form of computations, estimates, and production of the Re-Evaluated Design Schematic

4 This effort resulted in a proposed schematic that provided for the reconstruction of the general purpose lanes in the IH 635 West section, and construction of subsurface managed lanes comprised of approximately 7,265-ft of tunnels roughly centered longitudinally under the Dallas North Tollway (DNT), and approximately 16,550-ft of depressed managed lanes west of the tunnel and 6,445-ft of depressed managed lanes east of the tunnel. Due to Project constraints, the depressed managed lanes sections consist of partially covered and uncovered configurations, with the overhang dimensions varying based on geometric constraints.

In June 2006, an alternative proposed solution to replace the tunnels with a continuous depressed managed lanes highway section was proposed and subsequently incorporated into the Re-Evaluated Design Schematic in an effort to further reduce the overall Project cost. In particular, elimination of tunnels significantly reduces long-term operations and maintenance costs. While there are cost savings benefits to a continuous depressed managed lanes section, there are disadvantages in the form of reduced Parkway width and impacts to other transportation facilities. The depressed managed lanes solution will require reconstruction of portions of the DNT/IH 635 interchange, and added impact to traffic mobility on IH 635 and impacted cross streets.

Therefore, the VE effort has resulted in two alternate solutions for the Project. For the purpose of this report, these proposed solutions are identified as the tunnel alternative, and the no tunnel alternative. The Re-Evaluated Design Schematic produced for environmental approval depicts both alternatives. It is anticipated that this approach will provide the necessary documentation for approval of each alternative, and provide a broader framework for the proposing Developer Teams to seek sound design solutions for the IH 635 Managed Lanes Project. This Design Summary Report is structured to address both alternatives by documenting the preliminary engineering conclusions and design criteria used in development of the Re-Evaluated Design Schematic, and summarizes the corresponding preliminary design effort.

1.4 Constraints and Criteria Project constraints were developed to establish the basic parameters for the IH 635 Managed Lanes Project. Several of the original constraints, published with the Request for Qualification (RFQ), were re-evaluated to allow for greater innovation and possible

5 further cost reductions. As VE alternatives were developed, all constraints were evaluated for violation, applicability, and general impact to potential solutions. The following is a list of constraints from the RFQ and for the current Re-Evaluated Design Schematic, with comments.

6 Table 1.4 – Project Constraints

Issue Constraint as of RFQ Constraint for Re- Comments issuance (May 23, 2006) Evaluated Design Schematic (December 2006) Managed Lanes Minimum of 3 Managed Minimum of 3 Managed No change to Lanes in each direction. Lanes in each direction. Constraint

Right of Way Avoid Linear ROW Avoid Linear ROW No change to Acquisition. Acquisition. Constraint Maintenance of Maintain 4 General Purpose Maintain 4 General No change to Traffic Lanes in both directions Purpose Lanes in both Constraint during peak hour traffic directions during peak hour periods; traffic periods; Can use Lane Rental; Can use Lane Rental; Shoulders on General Shoulders on General Purpose not required. Purpose not required. Constructability Assure both interim and Assure both interim and No change to ultimate facility ultimate facility Constraint constructability. constructability. Access Locations Maintain Access Locations in Maintain access locations accordance with the approved in accordance with Re- schematic, T&R assumptions Evaluated Design and IAJ report. Schematic. Managed Lane Incorporate toll/gantry and Toll/gantry and declaration Declaration Functionality declaration lanes at every lanes at entry point to the Zones access point to the Managed Managed Lane facilities. evaluated for Lane facility. Provide Provide an ETC system feasibility Electronic Toll Collection compatible with TTA’s (ETC) compatible with TTA’s statewide and NTTA’s local statewide and NTTA’s local ETC system. ETC system. Future DART Future DART tunnel Future DART tunnel No change to Tunnel awareness. Provide envelope. awareness. Provide Constraint envelope. Design Criteria Design Criteria. Avoid design Minor changes to Design Design exceptions. Criteria for the interim exceptions are Project. Avoid design listed below. exceptions for the ultimate configuration. Aesthetic Aesthetic Objective. Aesthetic Objective. No change to Objectives Constraint Relative Elevation Relative Elevation of Relative Elevation of No change to of Improvements approved schematic. approved schematic. Constraint to Existing Grade Ultimate IH 635 Reduced median width to Meet TxDOT design criteria Median reduced Facility Median meet TxDOT design criteria. for the ultimate in the interim Width configuration. configuration west of Webb Chapel Road. Table 1.4 Notes: 1) Initial Project constraints are documented in the RFQ.

The Project criteria for the Re-Evaluated Design Schematic was very similar to the criteria used to develop the Environmental Schematic (2004). The current criteria was established from AASHTO, TxDOT Manuals, Standards, and Guidelines, and direction from TxDOT. Some of the criteria for the Re-Evaluated Design Schematic were modified in order to incorporate potential cost savings associated with the VE configurations. Exceptions to AASHTO criteria are provided below in Section 1.5.

1.5 Design Exceptions Design exceptions identified during development of the Re-Evaluated Design Schematic generally correspond with potential for cost savings and/or constructability improvements. The identified design exceptions are intended for operations during the interim condition prior to reconstructing the IH 635/IH 35E interchange. The design of the interim condition shall ensure that the design exceptions do not apply to the ultimate configuration. Identified design exceptions are listed in Table 1.5.

Table 1.5 Design Exceptions for the Re-Evaluated Design Schematic Description AASHTO Provided Notes Recommended Main Lane Shoulder 10 feet 4 feet For three or more lanes in each Width (Inside) direction from Denton Drive to east of Webb Chapel Rd. for the interim configuration prior to completion of the IH 635/IH 35E interchange. Managed Lane Not defined 2 foot Approved schematic = 4 feet/8 feet Shoulder Width min./10 feet (Inside/Outside) normal

8 CHAPTER 2 - CIVIL DESIGN

2.1 Roadway

2.1.1 Geometric Design Criteria The Re-Evaluated Design Schematic geometric design criteria were based on the TxDOT Roadway Design Manual and are summarized in Table 2.1.1.

Table 2.1.1 Roadway Geometric Design Criteria [1] Ultimate General Subsurface Managed Surface Managed Description Purpose Lanes Lanes Lanes Roadway Classification Urban Freeway Urban Freeway Urban Freeway Design Speed 60 mph 60 mph 60 mph Horizontal Alignment Control Location Centerline/Inside Centerline/Outside Inside edge of lane edge of lane edge of lane Stopping Sight 570 ft 570 ft 570 ft Distance (SSD) Minimum Radius [2] 1340 ft 1340 ft 1340 ft Superelevation e(max) = 6% e(max) = 6% e(max) = 6% Equivalent Maximum 1:222 (0.45%) 1:222 (0.45%) 1:222 (0.45%) Relative Slope Vertical Alignment Control Location Inside edge of lane Inside edge of lane Inside edge of lane Maximum Grade 3.00% 3.00% 3.00% Minimum Grade 0.50% 0.50% 0.50% Crest Curve K-Value 151 151 151 Sag Curve K-Value 136 136 136 Vertical Clearance Under Bridge 16.5 ft 16.5 ft 16.5 ft Structure/In Tunnels Under Sign Structure 16.5 ft 16.5 ft 16.5 ft Cross Sectional Elements Lanes-per direction Schematic Lane Widths Through Lanes 12 ft 12 ft 12 ft Usable Shoulder Widths Inside 10 ft 2 ft [3] 4 ft 2-lane: 8 ft Outside 10 ft 10 ft [3] 3-lane: 10 ft Cross Slope Lanes 2.00% [4] 2.00% 2.00% Shoulder 2.00% [4] 2.00% 2.00% Median Type Width [5] 24 ft N/A 10 ft Side Slopes Within Clear Zone 6:1 N/A 6:1 Outside Clear Zone 4:1 N/A 4:1 Clear Zone Width 30 ft N/A 30 ft

8 Table 2.1.1 (Continued) Roadway Geometric Design Criteria Description Frontage Roads Cross Streets Design Speed 45 mph 45 mph Horizontal Alignment Control Location Outside edge of lane Centerline Stopping Sight Distance 360 ft 360 ft Minimum Radius [2] 665 ft 665 ft Superelevation e(max) = 4% e(max) = 4% Equivalent Max Relative Slope (Superelevation 1:185 (0.54%) 1:185 (0.54%) Runoff) Vertical Alignment Maximum Grade 6.00% 6.00% Uncurbed: 0.50% Uncurbed: 0.50% Minimum Grade Curbed: 0.30% Curbed: 0.30% Crest Curve K-Value 61 61 Sag Curve K-Value 79 79 Vertical Clearance Under Bridge Structure 16.5 ft 16.5 ft Under Sign Structure 16.5 ft 16.5 ft Cross Sectional Elements Lanes (per direction) Schematic Lane Widths Through Lanes 11 ft 11 ft Turning Lanes 11 ft 11 ft U-turns 20 ft 20 ft Usable Shoulder Widths (uncurbed) On grade: 6 ft Inside N/A On structure: 8 ft Cross Slope Lanes and Shoulder 2.00% 2.00% Median Type N/A Curbed Width N/A 4 and 8 ft Curb Offset Inside 1 ft 1 ft Outside 1 ft 1 ft Side Slopes Within Clear Zone 24:1 24:1 Outside Clear Zone 4:1 4:1 Clear Zone Width 1.5 ft 1.5 ft

9 Table 2.1.1 (Continued) Roadway Geometric Design Criteria Ramps and FR/Cross Elevated Collectors/Direct Description Street By-Passes Connectors Design Speed 45 mph 50 mph Horizontal Alignment Control Location Outside edge of lane/ Outside edge of lane Inside edge of lane Stopping Sight Distance 360 ft 425 ft Minimum Radius [2] 660 ft 835 ft Superelevation e(max) = 6% e(max) = 6% Equivalent Max Relative Slope (Superelevation 1:185 (0.54%) 1:200 (0.50%) Runoff) Vertical Alignment Maximum Grade 5.00% 5.00% Minimum Grade 0.50% 0.50% Crest Curve K-Value 61 84 Sag Curve K-Value 79 96 Vertical Clearance Under Bridge Structure/In 16.5 ft 16.5 ft Tunnels Under Sign Structure 16.5 ft 16.5 ft Cross Sectional Elements Lanes-per direction Schematic Lane Widths Single Lane: 14 ft Through Lanes 14 ft Multiple Lanes: 12 ft Usable Shoulder Widths At-grade: 2 ft 1 & 2-lane: 4 ft Inside Retained fill/Structure: 4 ft 3-lane: 8 ft At-grade: 6 ft 1 & 2-lane: 8 ft Outside Retained fill/Structure: 8 ft 3-lane: 10 ft Cross Slope Lanes 2.00% 2.00% Shoulder 2.00% 2.00% Side Slopes Within Clear Zone 6:1 Elevated: N/A 6:1 Outside Clear Zone 4:1 Elevated: N/A 4:1 Clear Zone Width 16 ft Elevated: N/A 20 ft Notes: 1. Functional highway classifications are provided in Technical Provision 8. 2. The minimum radii criteria are based on roadways designed with superelevation. 3. Sight distance criteria may require greater shoulder widths. 4. For three or more General Purpose Lanes, cross slope shall be increased to 2.50% for the third lane and any additional pavement beyond the third lane The minimum radii criteria are based on roadways designed with superelevation. 5. The median widths are based keeping in mind the alternate tunnel configuration. 6. Vertical clearance for pedestrian underpasses shall be 17.5 feet.

10 2.1.2 Roadway Geometric Design The following presents the geometric design approach used in development of the Re- Evaluated Design Schematic. The re-design of the existing roadway is presented in segments to facilitate the description.

a) West Gateway The Re-Evaluated Design Schematic west gateway extends from east of IH 35E to west of Marsh Lane and includes general purpose lanes, managed lanes, frontage roads, declaration lanes, bypass lanes, direct connectors/elevated collectors and ramps. Entrance into and exit out of the EB and WB managed lanes are also -located in this section.

From west of the existing Harry Hines Boulevard bridge to east of Webb Chapel Road, The WB general purpose lanes were modified to include a 6-lane section at the Webb Chapel Road overpass to provide better traffic operation during the interim configuration before the completion of the IH 635/IH 35E interchange. To provide this new 6-lane section, an additional lane was introduced prior to the Webb Chapel Road entrance ramp. The revised configuration resulted in 5 general purpose lanes at the entrance ramp approach. The WB and EB horizontal alignments were correspondingly modified to accommodate this change. The EB lanes were shifted to the south in order to maintain a consistent offset dimension between the EB and WB lanes. Additional design changes to the EB lanes included modifications in the area between Denton Drive and the Josey Lane exit ramp. These lanes were revised to accommodate the existing EB traffic movements, which include the existing EB IH 635 lanes, the existing SB to EB direct connector, and the existing 2-lane NB IH 35E to EB IH 635 connection. As a result, the EB lanes are now located further south into the clearance. Revisions to the general purpose lanes as discussed above required that horizontal alignment changes also to be made to the WB ramps and bypass lanes at Webb Chapel Road. The EB Josey Lane and Webb Chapel Road exit ramp horizontal alignments were also modified. The vertical and horizontal geometry for the WB managed lanes to general purpose ramp at Josey Lane was modified to incorporate the revised managed lanes profile as well as the horizontal alignment changes to the general purpose lane s.

The Re-Evaluated Design Schematic provides two lanes on each of the wishbone ramps located west of Josey lane to provide direct access between the managed lanes and the IH 635/IH 35E direct connectors to enhance traffic operations.

b) DNT – No Tunnel Alternative From east of Webb Chapel Road to Preston Road, the no tunnel alternative of the Re-Evaluated Design Schematic reflects the ultimate configuration for the IH 635 corridor. The managed lanes are depressed lanes in the center of the IH 635 corridor. The depressed managed lanes consist of a six lane section–three lanes in each direction separated by a 2 ft Concrete Traffic Barrier (CTB). The depressed managed lanes include a 4 ft inside shoulder and a 10 ft outside shoulder in each direction. The general purpose lanes are cantilevered over the managed lanes to minimize Right-Of-Way needs.

Access ramps to and from the depressed managed lanes section were provided west of Marsh Lane for Webb Chapel Road traffic. In addition, west of Midway Road, single lane access ramps are provided to and from the managed lanes to general purpose lanes. c) DNT – Tunnel Alternative For the tunnel alternative of the Re-Evaluated Design Schematic, the roadway tunnels include sections of cut and cover tunnel and mined tunnel under the DNT extending from Welch Road to Monfort Road. The horizontal and vertical alignments of the tunnels were coordinated with the envelope required for a potential future light rail transit tunnel located under the WB general purpose lanes and frontage roads of IH 635. The tunnel alternative also reduces the impact to structures and the surface drainage in and around the DNT. d) East Gateway The Re-Evaluated Design Schematic east gateway configuration extends from east of Preston Road to west of Coit Road and includes general purpose lanes, managed lanes, frontage roads, declaration lanes, and ramps. Exits out of and

12 entrances into the WB and EB managed lanes are located between Preston Road and Hillcrest Road.

The subsurface managed lanes transitioned to at-grade managed lanes west of Hillcrest Road. Horizontal and vertical alignments for IH 635 general purpose lanes are realigned and transitioned back to existing, east of Preston Road. The at-grade managed lanes east of Hillcrest Road consist of two lanes in each direction with a single reversible lane in the middle. The reversible lane will be connected to Dallas High Five Managed/HOV lane system near Coit Road.

Between Hillcrest Road and Merit Drive the frontage roads and Park Central ramps were designed by others. The design and associated Park Central frontage road plans have been incorporated in the Re-Evaluated Design Schematic and are labeled “design by others”. e) Frontage Roads The Re-Evaluated Design Schematic configuration provides for continuous frontage roads in both the EB and WB directions from Harry Hines Boulevard to Merit Drive. f) IH 635 / IH-35 Interchange The Re-Evaluated Design Schematic configuration for the IH 635/IH 35E interchange includes the NB-EB, WB-SB, SB-EB and WB-NB direct connector ramps. These proposed direct connectors are added to the elements of the existing interchange with minimal impacts to the existing IH 35E main lanes. The existing interchange remains functional. The NB to EB connector alignment was modified to reduce reconstruction of existing roadways, reduce span length, and reduce encroachments from the proposed structure foundations onto existing facilities.

As a result of the addition of the four proposed connectors, all of the proposed and ultimate connector profiles at the interchange must be raised due to vertical clearance conflicts with the existing interchange elements. Since the profile revisions ranged from 22’ to 25’, an option of reversing the top two connector

13 levels was studied. Reversing the connector levels required that both the proposed SB to EB and the ultimate NB to WB connectors be raised approximately 70’ from their original locations as shown in the approved Environmental Schematic (2004). Additionally, raising the profiles by this amount requires that the gores for the NB to WB connector be shifted in order to meet minimum “K” values and not exceed maximum grades. Shifting the gores reduces the weaving distance for the ultimate WB general purpose lanes at Farmers Branch Creek. The WB to NB connector, not included in the Reference Schematic, would remain the same. g) IH 35E Ramping (North of the IH 635/IH-35 Interchange) The addition of the WB to NB connector to the Re-Evaluated Design Schematic configuration required that modifications be made to existing ramps along NB IH 35E. This connector’s interim tie-in location conflicts with the existing NB entrance ramp at Rawhide Creek. Keeping the existing entrance gore in close proximity to its current location, the ramp was shifted to the east to maintain access in the interim condition.

Furthermore, in order to help traffic movement and to reduce the weaving distance, the entrance ramp gore to NB IH 35E was shifted north. This ramp now crosses over Valley View and hence requires the existing Valley View Bridge to be widened. Based on the new traffic movement, it also required that the existing ramps located between Valley View Lane and Valwood Parkway be reversed. For the interim condition the entrance ramp from the frontage road to IH 35E (south of Valwood Parkway) matches the ultimate gore configuration. The exit ramp from NB IH 35E to the frontage road has been moved further north of Branch View Lane to facilitate traffic flow. h) IH 35E/Loop 12 Interchange The Re-Evaluated Design Schematic configuration for the IH 35E/Loop 12 interchange includes the NB and SB direct connectors for IH 35E and Loop 12. These proposed direct connectors are added to the elements of the existing interchange with minimal impacts to the existing IH 35E and Loop 12 General Purpose lanes. The direct connector alignments were modified to reduce

14 reconstruction of existing roadways, reduce span length, and reduce encroachments from the proposed structure foundations onto existing facilities. Temporary transitions on retained fill sections are required at the south ends of the IH 35E and Loop 12 direct connectors. The Re-Evaluated Design Schematic configuration is developed so that the ultimate interchange configuration could be constructed with minimal loss of interim infrastructure.

The existing local access is maintained in the Re-Evaluated Design Schematic configuration by modifying or shifting various ramps. The existing exit ramp from NB IH 35E to Northwest Highway was realigned because the proposed NB IH 35E direct connector cuts across the existing exit ramp. This interim ramp’s alignment avoids the widening of the existing general purpose lane bridge over Joe’s Creek. Because the SB IH 35E direct connector impacts the SB IH 35E entrance ramp from Northwest Highway, a realigned entrance ramp is also provided that consists of part of the ultimate frontage road/ramp bridge over Joes’ Creek. To enhance interim traffic operations, the SB Loop 12 exit ramp to Northwest Highway is replaced with a ramp north of the existing SB IH 35E/Loop 12 divergence, but its design does not address ultimate configuration operational issues. The Re-Evaluated Design Schematic configuration also requires that the NB IH 35E exit ramp to Mañana Road be moved south and realigned to clear the direct connector structures, but the final design was not performed and the ramp design is not included in the Re-Evaluated Design Schematic drawings. Widening of existing general purpose lane pavement will be required at these ramp locations.

The Re-Evaluated Design Schematic includes frontage roads in specific locations to maintain existing local access. A part of the SB Loop 12 frontage road is added to maintain access between the relocated ramp and the Northwest Highway. i) IH 35E Elevated Direct Connectors The Re-Evaluated Design Schematic includes the NB and SB elevated direct connector roadway that runs parallel to the existing IH 35E general purpose lanes between the IH 35E/Loop 12 and the IH 635/IH 35E interchanges. The

15 proposed elevated structure foundations are spaced to reduce encroachments onto existing facilities. In the Re-Evaluated Design Schematic configuration, adding frontage roads and modifying or adding various ramps preserves the existing local access. The existing interchanges at Walnut Hill Lane and Royal Lane are retained with minor adjustments to the ramps to avoid the elevated structures.

Local access is also maintained by the addition of a NB IH 35E frontage road from Walnut Hill Lane to a proposed NB ramp that ties to the NB IH 35E elevated direct connector south of Joe Field Road. An additional SB IH 35E frontage road extends from Walnut Hill Lane to Joe Field Road to replace the section of Joe Field Road impacted by the SB IH 35E elevated direct connector. An exit ramp that provides access to Walnut Hill Lane from the SB IH 35E elevated structure is included in the Re-Evaluated Design Schematic configuration.

2.2 Drainage

2.2.1 Drainage Design Criteria A summary of the drainage design criteria is presented in Table 2.2.1

Table 2.2.1 Drainage Design Criteria [1] General Purpose Description Managed Lanes Direct Connectors Lanes Method for Determining Peak Runnoff Less than 200 [2] Rational Method Rational Method Rational Method acres Natural Resources Natural Resources Natural Resources Greater than 200 Conservation Service Conservation Service Conservation Service acres [3] Runoff Curve Number Runoff Curve Number Runoff Curve Number Method Method Method Culvert Crossings Design Storm [4] Minor: 50-year Minor: 50-year Minor: 50-year Major: 100-year Major: 100-year Major: 100-year Check Storm [4] 100-year 100-year 100-year Headwater Control [5] < Or = Existing < Or = Existing < Or = Existing Headwater Elevation Headwater Elevation Headwater Elevation Lined: 12 fps Lined: 12 fps Lined: 12 fps Maximum Outlet [6] Vegetated clay: 8 fps Vegetated clay: 8 fps Vegetated clay: 8 fps Velocity Vegetated sand: 6 fps Vegetated sand: 6 fps Vegetated sand: 6 fps Minimum Outlet Lined: 2.5 fps Lined: 2.5 fps Lined: 2.5 fps Velocity [7] Vegetated: 2 fps Vegetated: 2 fps Vegetated: 2 fps Storm Sewers and Inlets Design Storm [8] 50-year 50-year 50-year Check Storm [8] 100-year 100-year 100-year Design Storm No encroachment into 2 feet of encroachment 2 feet of encroachment Allowable Ponding [9] the travel lanes into the travel lanes into the travel lanes Width Check Storm One lane free of One lane free of One lane free of Allowable Ponding [9] encroachment encroachment encroachment Width Pipe Material [10] Concrete Concrete Concrete Minimum Pipe Size [11] Laterals: 18 inch Laterals: 18 inch Laterals: 18 inch Trunklines: 24 inch Trunklines: 24 inch Trunklines: 24 inch Minimum Pipe [12] 3 fps 3 fps 3 fps Velocity Maximum Pipe [12] 12 fps 12 fps 12 fps Velocity

Table 2.2.1 (Continued) Drainage Design Criteria [1] Description Ramps By-Passes Elevated Collectors Method for Determining Peak Runoff Less than 200 Rational Method Rational Method Rational Method acres [2] Natural Resources Natural Resources Natural Resources Greater than 200 Conservation Service Conservation Service Conservation Service acres [3] Runoff Curve Runoff Curve Runoff Curve Number Method Number Method Number Method Culvert Crossings Design Storm [4] Minor: 50-year Minor: 50-year Minor: 50-year Major:100-year Major:100-year Major:100-year Check Storm [4] 100-year 100-year 100-year Headwater < Or = Existing < Or = Existing < Or = Existing Control [5] Headwater Elevation Headwater Elevation Headwater Elevation Lined: 12 fps Lined: 12 fps Lined: 12 fps Maximum Outlet Vegetated clay: 8 fps Vegetated clay: 8 fps Vegetated clay: 8 fps Velocity [6] Vegetated sand: 6 Vegetated sand: 6 Vegetated sand: 6 fps fps fps Minimum Outlet Lined: 2.5 fps Lined: 2.5 fps Lined: 2.5 fps Velocity [7] Vegetated: 2 fps Vegetated: 2 fps Vegetated: 2 fps Storm Sewers and Inlets Design Storm [8] 50-year 50-year 50-year Check Storm [8] 100-year 100-year 100-year Design Storm 2 feet of 2 feet of 2 feet of Allowable Ponding encroachment into encroachment into encroachment into Width [9] the travel lanes the travel lanes the travel lanes Check Storm One lane free of One lane free of One lane free of Allowable Ponding encroachment encroachment encroachment Width [9] Pipe Material [10] Concrete Concrete Concrete Minimum Pipe Laterals: 18 inch Laterals: 18 inch Laterals: 18 inch Size [11] Trunklines: 24 inch Trunklines: 24 inch Trunklines: 24 inch Minimum Pipe 3 fps 3 fps 3 fps Velocity [12] Maximum Pipe 12 fps 12 fps 12 fps Velocity [12]

18 Table 2.2.1 (Continued) Drainage Design Criteria [1]

Description Frontage Roads Cross Streets Method for Determining Peak Runoff Less than 200 ac [2] Rational Method Rational Method Natural Resources Conservation Natural Resources Conservation Greater than 200 ac [3] Service Runoff Curve Number Service Runoff Curve Number Method Method Culvert Crossings Design Storm [4] Minor: 50-year Minor: 50-year Major: 100-year Major: 100-year Check Storm [4] 100-year 100-year Headwater Control [5] < Or = Existing Headwater Elevation < Or = Existing Headwater Elevation Lined: 12 fps Lined: 12 fps Maximum Outlet Vegetated clay: 8 fps Vegetated clay: 8 fps Velocity [6] Vegetated sand: 6 fps Vegetated sand: 6 fps Minimum Outlet Velocity [7] Lined: 2.5 fps Lined: 2.5 fps Vegetated: 2 fps Vegetated: 2 fps Storm Sewers and Inlets Design Storm [8],[13] 25-year 25-year Depressed: 50-year Depressed: 50-year Check Storm [8],[14] 50-year 50-year Depressed: 100-year Depressed: 100-year One-lane for a 2-lane Frontage Design Storm Allowable Road One lane open to traffic in each Ponding Width [9] One-and-a-half lanes for a 3-lane direction Frontage Road Check Storm Allowable 50-year – no overtopping of curb 50-year – no overtopping of curb Ponding Width [9] Pipe Material [10] Concrete Concrete Minimum Pipe Size [11] Laterals: 18 inch Laterals: 18 inch Trunklines: 24 inch Trunklines: 24 inch Minimum Pipe Velocity [12] 3 fps 3 fps Maximum Pipe Velocity [12] 12 fps 12 fps Notes: 1. Design criteria taken from the Drainage Criteria Manual for the Proposed IH 635 (LBJ Freeway) Improvements Luna Road to U.S. 80 (IH 635 DCM), which was prepared for TxDOT Dallas District based on the TxDOT Hydraulic Design Manual, November 2002 . Refer to the IH 635 DCM for more detailed drainage design criteria. 2. Refer to the IH 635 DCM, Chapter 4.5. 3. Refer to the IH 635 DCM, Chapter 4.6. 4. Design for the 100-year even will be required for drainage areas greater than 200 acres. Refer to the IH 635 DCM, Table 4.2.1. 5. This applies to cross structures. Refer to the IH 635 DCM, Chapter 7. The same headwater controls that apply to storm sewer apply to internal culverts. For internal drainage hydraulic grade line requirements, refer to the IH 635 DCM, Chapter 6. 6. Velocities of 6 and 8 fps apply to vegetated sandy and clay channels, respectively. Refer to the IH 635 DCM, Table 5.5.1. 7. Velocities of 2 and 2.5 fps apply to proposed unlined and lined channels, respectively. Any modifications to existing channels shall match the existing channel as close as possible. Refer to the IH 635 DCM, Table 5.5.1. 8. Refer to the IH 635 DCM, Table 4.2.1. 9. Refer to the IH 635 DCM, Table 6.4.1. 10. Refer to the IH 635 DCM, Chapter 6.7. 11. Pipe sizes 18 and 24 inch refer to laterals and trunks, respectively. Refer to the IH 635 DCM, Table 6.7.1. 12. Refer to the IH 635 DCM, Table 6.7.1. 13. For Frontage Roads and side streets along IH 35E south of Crown Road, the 10-year design frequency applies. In all cases for depressed sections, design will be for the 50-year event. For further discussion, refer to the IH 635 DCM, Chapter 6.2. 14. 100-year HGL allows for one travel lane to be free of encroachment. Refer to the IH 635 DCM, Table 6.7.1.

2.2.2 Preliminary Drainage Design The preliminary drainage design for the Re-Evaluated Design Schematic included updating portions of the design presented in the Drainage Design Report for the Proposed IH 635 (LBJ) Freeway) Improvements, West Section – Luna Road to Skillman Street in order to accommodate the revised roadway configuration. Overall drainage patterns will remain the same as the study but because the study. The road configuration changed fro the approved Environmental Schematic (2004). The tunnel and no tunnel alternatives required a reconfiguration of the three large trunk lines to adequately drain the Re-evaluated Design Schematic’s proposed roadway sections.

The tunnel alternative's longer depressed managed lanes ections required that the single drainage system on the general purpose lanes be separated into two systems. The trunk lines are generally located under the outside shoulder of the general purpose lanes. On the west end approximately 750 feet west of Josey Lane, the main westbound trunk line will be located between general purpose lanes and the frontage road so that it fits within the foundations of the SB IH 635-Loop 12 & IH 35E connector. East of Harry Hines Boulevard after the SB-NB direct connector split, the trunk line turns to the northwest and outfalls on the west side of Harry Hines Boulevard in to the proposed water quality areas within the IH 35E and IH 635 interchange.

On the west end, the EB general purpose lanes trunk line will shift to the south to fit between the foundations of the NB IH 35E-IH 635 connector near Anaheim Drive. This trunk line runs parallel to the connector until approximately 650’ west of Harry Hines Boulevard. Then it turns to the south to outfall downstream of Harry Hines Boulevard between the existing NB-EB connector and Forest Lane. This shifted from the location in the drainage study to clear the existing connector as it will remain in place for the Project configuration. To daylight the trunk line in to the proposed wetland areas, further design is required to regrade the downstream channel and an add a culvert across the existing connector.

Because the proposed EB general purpose lanes trunk is located in the drainage study’s EB frontage road trunk line location, the trunk line was moved to run beneath the frontage road until approximately 430’ east of Harry Hines Boulevard. It then shifts to

20 the north between the connector bents to run parallel to and outfall adjacent to the EB general purpose lanes trunk line.

The tunnel alternative also required the design of a trunk line for the depressed managed lanes section. The trunk line is located on the north side of the managed lanes section. East of Josey Lane it shifts to the north to cross beneath the WB general purpose lanes trunk line and runs parallel to it. Because this trunk line is too deep to outfall to the wetland areas, it will outfall at Farmers Branch Creek Tributary.

The WB frontage road trunk line design was expanded beyond the critical point at Denton Road. The profile was updated to match the revised frontage road profile and extended upstream to analyze additional critical points along the frontage road.

Most of the redesign was focused on the west end. East of the DNT, drainage patterns remain the same as detailed in the drainage study. Adjustments to the general purpose lanes trunk lines upon further study will be similar to the west end revisions.

The no tunnel alternative requires further study. Culverts W44 and W51 as shown in the drainage study are impacted by the depressed managed lanes section. The managed lane profile runs beneath these crossings. To maintain existing drainage patterns, a combination of pumps, siphons, and aqueducts may be required.

2.3 Construction Schedule and Traffic Control

2.3.1 Construction Sequencing, Phasing and Schedule This section describes a method of construction sequencing for both the tunnel and no tunnel alternatives of the Re-Evaluated Design Schematic. As a part of the preliminary engineering effort, the following items have been developed:

a) Typical construction cross-section sequence drawings. (Refer to Exhibits) b) A series of plan view phase drawings. (Not Included) c) A summary level construction schedule. (Not Included)

21 The sequencing analysis was limited to the IH 635/IH 35E interchange and the IH 635 West section of the IH 635 Managed Lanes Project. No construction drawings or schedule work was completed for the IH 635 East section or the elevated connectors along IH 635.

The purpose for the exercise was to confirm the following:

a) The roadway portion of the project can be constructed while maintaining the minimum number of required traffic lanes. b) Bridge construction can be completed while maintaining the minimum number of required traffic lanes. c) The project can be constructed in the amount of time prescribed by TxDOT and TTA.

To provide a necessary level of detail for the construction phase drawing and layout portion of the work, a series of typical construction cross-section sequence drawings were developed. The developed drawings are as follows:

a) Typical Roadway Construction Sequence for MSE Wall Installation Exhibit 2.3.1 reflects the managed lanes and general purpose lanes construction sequences (1, 2, 3, and 4) between approximate Sta. 75+00 and Sta. 166+00. For the Re-Evaluated Design Schematic, the depressed managed lanes sections between these stations will utilize Mechanically Stabilized Earth (MSE) walls, and Exhibit 2.3.1 reflects the approximate excavation limits for MSE construction. The frontage roads are outside the limits of the typical drawing cross-section that is shown.

b) Typical Roadway Construction Sequence for Non-MSE Wall Installation Exhibit 2.3.2 reflects the construction sequences (1, 2, 3 and 4) for the managed lanes and general purpose lanes from approximate Sta. 166+00 to Sta. 360+70. For the Re-Evaluated Design Schematic, the vertical wall section within these station limits utilizes soil nailing and rock reinforcement with fascia panels. Exhibit 2.3.2 shows a generalized vertically supported wall with no additional

22 excavation limits shown. The frontage roads are outside the limits of the typical drawing cross-section that is shown.

c) Typical Bridge and Roadway Construction Sequence at Underpass Locations Exhibit 2.3.3 reflects the typical managed lanes and general purpose lanes construction sequences (1, 2A, 2B and 3) beneath either new or existing cross street overpass bridges. The approximate inside limits of the frontage road alignment are shown on the typical cross-section drawing. Exhibit 2.3.3 typically applies to cross streets at Marsh Lane, Rosser Road, Welch Road, Montfort Road and Preston Road.

d) Typical Construction Sequence at Overpass Locations Exhibit 2.3.4 reflects the typical IH 635 general purpose lanes overpass bridge sequences (1, 2, 3 and 4) at the major cross street intersections. Based upon the Re-Evaluated Design Schematic (and as reflected in Exhibit 2.3.4), the managed lanes will be depressed at these intersections with a new, cross street bridge on top. The frontage roads are outside the limits of the typical cross- section that is shown. Figure 2.3.4 applies to cross streets at Webb Chapel Road, Valley View Lane and Midway Road.

e) Typical Roadway Construction Sequence for the Tunnel Alternative Exhibit 2.3.5 reflects the typical roadway construction sequence for the tunnel alternative and the cut and cover tunnel sections located on the east and west ends of the mined tunnels. The approximate limits of the work are from Sta. 229+50 to Sta. 241+26 and Sta. 281+00 to Sta. 302+15. The actual separation width and depth of the tunnels will depend upon the location of the typical cross- section. The frontage roads are outside the limits of the typical cross-section that is shown.

Using the typical cross-sections as described above, a total of nine construction Work Area limits were defined. These Work Area limits are described below, and were generally based upon the existing roadway cross-section; the anticipated variance in foundation conditions and associated construction requirements; and the different

23 managed lanes configurations developed during the Re-Evaluated Design Schematic work (i.e., depressed managed lanes sections, cut and cover tunnel or mined tunnel).

a) Work Area No. 1: Work Area No. 1 primarily encompasses the elevated bridge work for the WB IH 635 to NB IH 35E connector; the SB IH 35E to EB IH 635 connector; and the EB and WB managed lane bridges from the west side of the existing IH 635/IH 35E interchange at Luna Road to Sta. 40+00.

b) Work Area No. 2: Work Area No. 2 encompasses the at-grade and elevated transition section of the managed lanes system from Sta. 40+00 to Sta. 75+00; the depressed managed lanes section that incorporates MSE wall construction from Sta. 75+00 to Sta. 166+00; and all associated general purpose lanes and frontage road components between Sta. 40+00 and Sta. 166+00.

For the Re-Evaluated Design Schematic, Sta. 166+00 is the location at which the wall construction for the depressed managed lanes sections was assumed to change from MSE to soil nails and rock reinforcement with fascia panels.

Work Area No. 2 also includes portions of surface works between Midway Road and Webb Chapel Road.

c) Work Area No. 3: Work Area No. 3 begins at Sta. 166+00 and ends at Sta. 229+50, the potential portal of the west side cut and cover tunnels. Work Area No. 3 also includes all general purpose lanes and frontage road components.

Work Area No. 3 also includes portions of surface works between Midway Road and Webb Chapel Road.

d) Work Area No. 4: Work Area No. 4 encompasses subsurface managed lanes for both the no tunnel and tunnel alternatives and all associated general purpose lanes and frontage road components between Sta. 229+50 and Sta.

24 241+26. For the no tunnel alternative, the depressed managed lanes in this area would be constructed as shown in the “Typical Roadway Construction Sequence for Non-MSE Wall Installation” phasing drawings. e) Work Area No. 5: Work Area No. 5 includes the section approximately centered on the DNT. For the no tunnel alternative, this section would be constructed similar to the “Typical Construction Sequence at Overpass Locations”. For the tunnel alternative the work sequence would be similar to the sequence necessary to replace overpass structures, but does not require phasing to construct the managed lanes. f) Work Area No. 6: Work Area No. 6 encompasses subsurface managed lanes for both the no tunnel and tunnel alternative and all associated general purpose lanes and frontage road components between Sta. 288+00 and Sta. 302+15. For the no tunnel alternative, the depressed managed lanes in this area would be constructed as shown in the “Typical Roadway Construction Sequence for Non-MSE Wall Installation” phasing drawings. g) Work Area No. 7: Work Area No. 7 extends from Sta. 302+15 to Sta. 414+00 and for the tunnel alternative includes all of the managed lanes, general purpose lanes and frontage roads from the east end of the east managed lanes cut and cover tunnel to the east end of the Dallas High Five.

Work Area No. 7 also encompasses the early frontage roads between Hillcrest Road and Merit Drive. h) Work Area No. 8: For the tunnel alternative, Work Area No. 8 includes all of the Mechanical, Electrical and Piping (MEP) systems for the cut and cover and mined tunnels between Sta. 229+50 and Sta. 302+15. In addition, Work Area No. 8 includes all of the off-site and surface components of the tunnel MEP system. Typical MEP installations and industry production rates were used to develop the Work Area No. 8 construction phasing and associated schedule.

25 i) Work Area No. 9: Work Area No. 9 is the Operations Control and Customer Service Centers. No additional drawings for either of the centers have been developed to allow detailed phase schedule development. As such, typical commercial structures similar in size and complexity were used to define the Work Area No. 9 schedule.

Utilizing the cross-section sequence drawings and the established Work Area limits, plan view construction phasing drawings were developed for the following:

a) To confirm the ability to maintain the minimum requirements for traffic lanes during the construction of the roadways and bridge. b) To allow the use of Material Takeoff (MTO) information and industry production rates for completion of a time line estimate of the required major construction activity durations. c) To assist in the preliminary analysis of construction schedule.

For the development of the typical cross-section sequencing and construction phasing drawings, typical roadway cross-section and dimension parameters were used as follows:

a) A minimum of 4 general purpose lanes are required to be open in each direction at all times. b) A total width of 52 feet was assumed for the 4 general purpose lanes in each direction. The 52 foot width includes all shoulder widths between barriers or edge striping. c) Barrier dimension requirements were in addition to the 52 foot width. The barrier dimension requirements generally added an approximate 2 feet to either side of the typical roadway cross-section width.

2.3.2 Traffic Control The Project constraints define the typical traffic control requirements for the duration of construction. The typical minimum requirements for construction traffic control are as follows:

26 a) Peak Traffic hours (Mon – Thu, 6 - 9 am and 3:30 - 7 pm; Fri, 2 – 9 pm): • Three general purpose lanes are required to be open in each direction at all times. • An additional HOV lane is required to be open in each direction at all times.

b) Weekday Off-Peak hours (Mon – Thu, 9 am to 3:30 pm; Fri, 9 am to 2 pm): • Three general purpose lanes are required to be open in each direction at all times. • The HOV lane may be used as an additional general purpose lanes.

c) Weekend Off-Peak hours (Sat and Sun, 9 am to 9 pm): • Three general purpose lanes are required to be open in each direction at all times. • The HOV lane may be used as an additional general purpose lanes.

d) Low Traffic Nighttime and Weekend hours (Mon - Thu, 7 pm - 6 am; Fri, 9 pm - Sat, 6 am; Sat, 9 pm - Sun, 9 am; Sun, 9 pm - Mon 6 am): • Two general purpose lanes are required to be open in each direction at all times.

During the development of the construction phasing and associated schedule, traffic control requirements more stringent than the times defined above were used. As such, it is assumed that these traffic control requirements will not impact the results of the preliminary construction phasing and schedule exercise.

The construction sequencing description and attachments indicated that both the tunnel and no tunnel alternative for the Re-Evaluated Design Schematic are constructible. The future designer is responsible for determination of the final construction sequencing plan.

27 CHAPTER 3 - GEOTECHNICAL

3.1 Available Geotechnical Data Three separate geotechnical investigation programs have been conducted for the West section of the IH 635 Managed Lanes Project, the results of which were presented in the reports listed below. These include a 1998 investigation by Terra-Mar, Inc., and two subsequent investigations by Fugro Consultants LP, starting in 2003 and extending into 2005. The Terra- Mar, Inc. investigation was performed to evaluate the LBJ corridor for specific managed lane configurations at the feasibility level, while the Fugro investigations were performed in a phased approach to expand the coverage of available geotechnical information along the proposed alignment and to gather necessary geotechnical parameters to be used for later design efforts. The geotechnical reports produced from these investigations are as follows:

a) Geotechnical Data Report, LBJ Corridor Study Project, Dallas, Texas, Terra-Mar, Inc., December 29, 1998

b) Phase 1 Geotechnical Data Report, IH 635 (LBJ Freeway) Corridor, Section 4 – West Fugro South, Inc., April 6, 2004

c) Phase 1 Geotechnical Baseline Report, IH 635 (LBJ Freeway) Corridor, Section 4 – West, Fugro Consultants LP, May 12, 2004

d) Phase 2 Geotechnical Data Report, IH 635 (LBJ Freeway) Corridor, Section 4 – West, Fugro Consultants LP, May 18, 2005

e) Addendum No. 1, Geotechnical Documents, IH 635 (LBJ Freeway) Corridor, Section 4 - West, Fugro Consultants LP, February 8, 2006

f) Addendum No. 2, Geotechnical Documents, IH 635 (LBJ Freeway) Corridor, Section 4 - West, Fugro Consultants LP, February 9, 2006

g) Addendum No. 3, Geotechnical Documents, IH 635 (LBJ Freeway) Corridor, Section 4 – West, Fugro Consultants LP, April 26, 2006

28 An additional geotechnical investigation was performed for the IH 35E section of the Project, and the results are presented in the following report: • Geotechnical Investigation IH 635 (LBJ Freeway) West Procurement Engineering, Mas-Tek Engineering & Associates, Inc. March 3, 2006

3.2 Geologic Setting (IH 635 West Section) Along the IH 635 portions of the Project alignment, the surficial geologic strata of relevance are the Eagle Ford Group, the Austin Group, the overlying weathered rock and residual soils derived from them, sandy and clayey alluvial soils and fill.

3.2.1 Overburden Soil deposits along the alignment consist mainly of residual soils derived from the Austin and Eagle Ford Groups, and sandy and clayey alluvial soils. In addition, due to the developed nature of the existing IH 635 corridor, a thin veneer of fill exists at the ground surface over much of the investigated area and was sampled in most borings along the alignment.

3.2.1.1 Fill Fill materials may be encountered throughout the alignment. These are typically very stiff to hard clays of medium to high plasticity, reflecting to some degree the local native soils, which are presumed to have served as borrow sources. In many places the strength and plasticity of the fills are indistinguishable from the underlying native soils. The thickness of the fill is highly variable across the site, with the thickness recorded in the borings ranging from several inches to as much as 15 ft.

3.2.1.2 Alluvial Soils Two broad classes of alluvial soils exist along the IH 635 West section, described here as sandy and clayey alluvial soils. The sandy alluvial soils are attributable either to riverbed deposits or lower terraces of the ancestral Trinity River (Eubank 1965), while the clayey alluvial soils are attributable either to upper terrace deposits of the Trinity River (Eubank 1965), or are soils that are the product of erosion and nearby deposition of residual soils or intermittent streams. These erosional/depositional soil deposits will be referred to herein as colluvial soils.

Sandy alluvial deposits exist in the Trinity River floodplain and extend down to the top of bedrock, which may be as much as 60 feet below existing grade at the western end of the IH-

29 635 West section, and potentially deeper in the actual floodplain. These soils tend to be composed of sands and gravels. Where these granular deposits exist along the alignment, generally west of Webb Chapel Road, they tend to be found below a depth of 18 feet, and are typically of limited thickness (e.g., about 5 feet), suggesting their origin could be a buried channel or stream meander. A few borings indicated these granular deposits could be deeper, in some cases extending down to bedrock.

The clayey alluvial soils that are believed to be remnants of terraces from the ancestral Trinity River (Eubank 1965) are generally found from the ground surface down to a depth of approximately 15 feet, and are mainly high plasticity clays. Such clayey alluvial soils are encountered in borings at the west end of the IH 635 West section along the gentle slope rising out of the Trinity River bottom up to the ridge formed in the more resistant Austin Group, and on the east end of the Project on the bluff dropping down into the White Rock Creek drainage.

The other class of clayey alluvial soils, described above as colluvial soils, which are higher up on the hillsides along the alignment, originated primarily as residual clays and are likely to exist on the eastern and western slopes at each end of the IH 635 West section.

3.2.1.3 Residual Soils The residual soils to be encountered are generally high plasticity clayey soils developed by weathering of the parent Eagle Ford and Austin Groups. In the Project area, the residual soil of the Eagle Ford Group is described by the Soil Conservation Service (SCS) as the Houston Black-Urban Land Complex within the Houston Black-Heiden map unit (SCS 1980). The residual soil derived from the Austin Group is described in the same reference as the Austin- Urban Land complex within the Eddy-Stephen-Austin map unit.

3.2.2 Eagle Ford Shale Based on the Project configuration presented in the Re-Evaluated Design Schematic, the Eagle Ford Group will not be encountered in the tunnel alternative, but will be encountered in the depressed managed lanes sections on the west end of the IH 635 West section to approximately Station 166+00. The Eagle Ford Group underlies the Austin Group and is frequently referred to as the “Eagle Ford Shale.” It consists of two primary members, the Arcadia Park and the Britton member, of which the upper member, the Arcadia Park, will be encountered for a considerable distance along the alignment. The Arcadia Park member

30 consists primarily of a dark-gray to black, montmorillonitic, calcareous to non-calcareous, laminated clay-shale with high shrink-swell potential (Allen and Flanigan 1986). Surles (1987) described the Arcadia Park in the Dallas area as “consisting of gray to dark gray, fissile, calcareous mudstone or clay shale with thin laminae of siltstone, sandstone, and fragmental limestone”.

3.2.3 Austin Chalk Along the IH 635 West section, the contact between the Eagle Ford Shale and the overlying Austin Group occurs just east of Marsh Lane, where it may be covered by about 20 feet of residual soil. The Austin Group unconformably overlies the Eagle Ford Shale and will be encountered from approximately Station 166+00 to Station 360+00. The contact between these strata is an erosional unconformity, and sediments deposited on this surface at the base of the Austin Group are known as the “Fishbed Conglomerate”. The Fishbed Conglomerate typically varies from 1 to 12 feet in thickness in the Dallas area, and is described as arenaceous limestone with abundant marine fossil debris, phosphate nodules, pyrite and marcasite crystals, and reworked materials derived from the underlying Eagle Ford Shale and older sediments (Allen and Flanigan 1986).

The Austin Group is locally referred to as the Austin Chalk. The Austin Chalk is characteristically subdivided into upper, middle, and lower members. The upper and lower members are similar, consisting of limestone with interbedded marl and argillaceous limestones and shales. The middle member is primarily a marl or argillaceous limestone with interbedded limestone. There is a regionally persistent 9-12 inch thick bentonite layer, which is close to the separation of the lower and middle members, and is referred to locally as the Bentonite Marker Bed. Additional continuous to nearly continuous bentonite seams were identified in the borings and are discussed in more detail in the GIR (LBJMP 2006). It has also been interpreted that the lower member of the Austin Chalk thickens to the north, with the Bentonite Marker Bed having been observed in north central Texas at varying heights above the Eagle Ford Group. The geologic data gathered for this Project indicates that the Bentonite Marker Bed is on the order of 100 feet above the Eagle Ford Shale across the IH 635 West section alignment.

31 3.3 Geotechnical Considerations for the Re-Evaluated Design Schematic

3.3.1 General Exhibits 3.1.1 and 3.1.2 present a simplified geologic profile prepared during the development of the Re-Evaluated Design Schematic. The profile was generated from the geologic profile presented in the GIR (LBJMP 2006) and essentially takes the previously separate eastbound and westbound profiles and interpolates the geology along the centerline of IH 635 across the IH 635 West section.

The Re-Evaluated Design Schematic provides for both no tunnel and tunnel alternatives. Both of these alternatives represent a significant increase in the amount of depressed managed lane roadway when compared to the Environmental Schematic (2004). This increase in the length of depressed managed lane section subsequently results in the construction of high (i.e., on the order of 30 ft) walls through the plastic, low-strength clays and soft rock that exist over much of the western half of the IH 635 West section.

Based on the geology along the alignment and the depth of excavation required for the depressed managed lanes sections, the primary geotechnical considerations impacting the selection of potential wall designs through this area include the following:

a) The presence of low strength alluvial and residual clays, and weathered and fresh clay shale. (i.e., effective friction angle, Φ´, of 13 degrees). The at-rest earth pressure coefficient based on this low friction angle is high and will result in high lateral loads on rigid walls.

b) Groundwater levels at or near the ground surface. Depending on the Developer's drainage system, this may result in substantial long-term hydrostatic pressures against the walls of the depressed managed lanes section.

c) The high shrink/swell capacity of the alluvial and residual clay soils and weathered and fresh Eagle Ford Shale. The presence of expansive soil and rock can result in significant additional lateral pressure on the walls of the depressed managed lanes sections.

32 When combined, the depth of excavation and the lateral pressures from these factors eliminate the viability of some wall systems commonly used in the Dallas area. Therefore, an approach was adopted throughout preliminary design to avoid the impact of these conditions by utilizing MSE walls where possible. Additional information pertaining to the selection and design of wall systems along the IH 635 West section is presented in Chapter 4.

33 CHAPTER 4 - STRUCTURAL DESIGN

4.1 Surface Structures – Bridges

4.1.1 Structural Criteria The AASHTO Standard Specifications for Highway Bridges was used for preliminary design of the bridge elements in the Re-Evaluated Design Schematic. Additional shear design requirements incorporated ACI 318, Building Code Requirements for Structural Concrete. Load Factor Design (LFD) was used in all cases, except for the design of prestressed concrete elements and structural steel elements which utilized Allowable Stress Design. TxDOT Standards were also used as reference during the preliminary engineering effort.

Loading criteria was also based on AASHTO Standard Specifications for Highway Bridges, and included HS-25 truck/lane live loads for vehicular structures, and standard pedestrian loading for the Joe Ratcliff pedestrian walkway.

4.1.2 Structural Elements For ramps and direct connectors, the bent locations were proposed in coordination with the roadway geometry in an effort to minimize the number and length of straddle bents or asymmetric single column bents. For cross street bridges, bent locations were proposed in coordination with general purpose lanes, managed lanes and cross street geometry, and took into consideration construction phasing requirements. The cross street overpasses were also lengthened to accommodate the practical construction limits of the Mechanically Stabilized Earth (MSE) retaining walls used for the depressed managed lanes.

4.1.2.1 Superstructure The proposed superstructure type along the majority of the direct connectors and other elevated structures of the Re-Evaluated Design schematic consists of Type U-54 prestressed concrete beams. These beams were utilized based on both aesthetic and economic considerations. The Type U-54 beams were proposed in spans up to 150’ considering the use of advanced construction techniques. For longer spans, precast post-tensioned concrete box spans were proposed base on their similar shape, aesthetic consistency and costs. For the cross street structures, Type U-54 and U-40 beams were considered because of the relatively short spans required and to maintain consistency with the remainder of the Project.

Dimensionally, the superstructure depths of the Type U-40 and U-54 beams used were 4.17 ft and 5.33 ft, respectively, plus any additional depth required by the roadway cross slope (i.e., superelevation). For the segmental box beam superstructure, the preliminary sizes were established using FHWA Article 6.0 General guidelines for Preliminary Design for Segmental Concrete Box Girder Superstructure.

4.1.2.2 Substructures The proposed substructures are single column, multi-column, and straddle bents placed such that the number of straddle bents or asymmetric single column bents is minimized. Consideration was given during preliminary design to the placement of bents in an effort to produce a repetitive substructure and superstructure design, which provides for a more aesthetic and economical Project.

The bent caps utilized in the preliminary design are inverted “T” type with a constant ledge thickness for multicolumn bents and varying ledge thickness on the longer cantilevers of the single column bent caps. The use of this type of cap will maintain the desired aesthetic appearance while increasing the maximum length of the simple prestressed beam span.

4.1.2.3 Foundation The proposed bridge foundations for the Re-Evaluated Design Schematic are assumed to be composed of multiple drilled shafts with pile caps to support the various column sizes and configurations.

4.2 U-Wall Structures

4.2.1 General Several structural configurations were considered for the IH 635 West section of the Project. The Environmental Assessment (2004) limited these configurations to at-or-below grade profiles. The additional limitations on ROW width and minimum number of total lanes require a configuration with overlapping lanes. This can be accomplished by either/or a combination of tunnels, depressed sections and bridges. The general cost of both tunnels and depressed sections were evaluated during this effort and a decision was made to maximize the length of depressed section and minimize the length of tunnel. The depressed managed lanes with

35 overhanging general purpose lanes configuration fits the constraints, and the preliminary cost estimate indicates it has lower long-term operation and maintenance requirements.

4.2.2 Alignment and Profile Parameters Flexibility of the managed lanes horizontal alignment is dependant on whether the no tunnel or tunnel alternative of the Re-Evaluated Design Schematic is utilized. The alignment associated with the tunnel alternative does not have to be either centered or parallel with the general purpose lanes alignment. However, the depressed managed lanes would need to be both centered and parallel with the general purpose lanes alignment in order to standardize the overhang dimension as well as standardize staging and design details.

In terms of vertical alignment, the no tunnel alternative of the Re-Evaluated Design Schematic makes use of depressed managed lanes under the Dallas North Tollway (DNT). The maximum height of retaining wall used for preliminary design of the depressed managed lanes was 30’, but is actually less in many locations. A result of the height limitation is a depressed managed lanes profile approximately parallel with the general purpose lanes profile.

The vertical alignment considerations for the tunnel alternative are further defined in Section 4.3. In general however, the tunnel alternative under the DNT interchange reduces reconstruction of the interchange, minimizes coordination with North Texas Tollway Authority, and simplifies construction staging in that area. Traffic congestion and impact to the area is less with a tunnel under the DNT.

4.2.3 Dimensional Parameters The depressed managed lanes structure width was calculated using the roadway design criteria presented in Table 2.1.1. This results in a 52’-0” horizontal dimension from the centerline of the depressed managed lanes to each finished wall surface. No additional shoulder width was deemed necessary to meet the required line of sight criteria; however, final determination of line of sight criteria compliance is dependent on the final horizontal alignment.

The typical horizontal overhang dimension of the general purpose lanes over the depressed managed lanes varies along the IH 635 West section, but is typically 30’. The maximum overhang dimension increases to 34’-0” due to the general purpose lanes configuration at the surface and other constraints.

The total vertical clearance used in preliminary design of the depressed managed lanes was 19’-6” measured from the high point of roadway to low point of the inverted T straddle bent. The 19’-6” clearance dimension includes a 6” allowance for a future wearing surface, 16’-0” travel clearance and 3’-0” allowance for a one-line Variable Message Sign (VMS).

4.2.4 Fire and Life Safety Considerations Fire and life safety requirements for the depressed managed lanes were developed for the preliminary engineering effort in coordination with the Fire, Security, and Life Safety Committee (FSLSC). Several key requirements include: maintaining a tenable environment, providing emergency response times in accordance with NFPA 1710, and requirements for water supply.

In addition, a preliminary CFD ventilation analysis of a typical depressed managed lane section was done to get an indication of how smoke and heat will develop from a vehicle fire, identify if mechanical ventilation may be necessary, and determine if additional walls or taller barriers were necessary to control or direct smoke. The analysis indicated that no additional structure or ventilation equipment is required to control smoke.

4.2.5 Structural System Determination and Description Considerations for selection of the structural system for the depressed managed lanes walls and general purpose lanes above the depressed managed lanes include ground conditions, alignment and profile constraints, construction staging feasibility and estimated construction costs.

In general, the following process was used to select the appropriate structural system:

a) Develop geologic profiles along the alignment b) Identify a limited number of “typical” ground types with similar geologic conditions c) Develop U-wall structural configurations for each ground type d) Assess structure type to specific lengths of depressed managed lanes e) Evaluate general construction costs associated with each type of structural configuration

37 In final selection of structural systems for the depressed managed lanes, focus was given to: minimizing the negative effects of earth materials with high shrink/swell potential and low strength, reducing the impacts of a potentially high water table, and maximizing the use of the strength of the Austin Chalk.

In addition, detailing and design considerations to accommodate deflections (horizontal and vertical), thermal movement, and potential for differential movement between dissimilar structural elements was discussed at length. A longitudinal expansion joint may be necessary between the general purpose lanes over the depressed managed lanes and general purpose lanes on grade. The location of the longitudinal expansion joint or joints should be at a lane line or near the center of a lane. These are considered important final design issues and should be appropriately addressed at that time.

4.2.6 Ancillary Facilities Potential ancillary facilities in the depressed managed lanes sections include utility rooms and emergency egress stairs. These facilities, as required, will need to be incorporated into the design of the U-wall structural systems during final design. Additional information regarding ancillary facilities is described in Section 4.5.

4.3 Cut-and-Cover Tunnel Structures

4.3.1 General For the tunnel alternative of the Re-Evaluated Design Schematic, two lengths of cut-and-cover tunnels were located between the ends of the mined tunnels and ends of the depressed managed lanes sections. These cut-and-cover tunnels are necessary to make the transition between the mined tunnels and the depressed managed lanes. The depressed managed lanes to cut-and-cover tunnels transition was located to minimize the excavation wall heights. Whereas, locations of the cut and cover tunnels to mined tunnels transitions were defined to provide additional rock cover over the crown of the mined tunnel excavation. Additional requirements regarding the location of the mined tunnels are presented in Section 4.4.2.

4.3.2 Alignment and Profile Parameters The horizontal alignments of the cut and cover tunnels serve as a transition between the mined tunnels and the depressed managed lanes sections. The parallel mined tunnels are physically

38 separated at the cut and cover tunnels to mined tunnels transition, in order for the rock between the two tunnels to better withstand the stresses induced from the two tunnel excavations. The space between cut-and-cover tunnel structures may be unexcavated ground or could potentially be excavated in order to provide space for ancillary facilities. This space was utilized for ancillary space in the Re-Evaluated Design Schematic. At the depressed managed lanes to cut-and-cover tunnel transitions, the alignment of EB and WB depressed managed lanes are essentially together, resulting in a combined cut and cover tunnel structure in which both sides of the structure -share a common center wall.

4.3.3 Dimensional Parameters The cut-and-cover tunnel horizontal interior dimension was assumed to be 53’-6” between finished wall surfaces. Additional space for tunnel finishes is dependent on the type of finish used. No additional shoulder width was deemed necessary to meet the line of sight criteria.

For the cut-and-cover tunnel a minimal vertical clearance of 16’-6” was used, measured from the high point of roadway. The 16’-6” clearance dimension includes a 6” allowance for a future wearing surface. The clearance dimension applies to shoulders as well as travel lanes. An additional 6’-0” vertical height above the minimum vertical clearance was assumed for placement of jet fans, signs and associated supports. The total minimum dimension above the high point of the roadway surface to underside of the roof structure is assumed to be 22’-6”.

4.3.4 Fire and Life Safety Considerations Fire and life safety components of the preliminary design incorporated requirements of NFPA 502 and items from discussions with the Fire, Security and Life Safety Committee (FSLSC). The cut-and-cover tunnels incorporated several fire, security and life safety elements, including dry standpipes, ventilation structures and shafts, raised grade separated safety walks, emergency egress via cross passageways, and emergency exit stairs at the tunnel to depressed managed lanes transition. The cut-and-cover tunnel design must include, as a minimum, provisions for support of ventilation equipment, signage, lighting, detection equipment, conduit for safety systems, CCTV, and fire protection systems.

4.3.5 Loading Criteria: For the tunnel alternative of the Re-Evaluated Design Schematic, the cut-and-cover tunnels are assumed to be located in the Austin Chalk formation. Vertical cuts with minimal ground support

39 are assumed for temporary excavations. Backfill is considered to be select, low Plasticity Index (PI) material with little potential for volume change due to moisture change. A high water table was assumed for purposes of the preliminary analysis, and typical backfill soil unit weights and properties were utilized.

4.3.6 Structural System Determination and Description During the preliminary engineering effort several structural alternatives were considered including: • Placing the exterior structural walls against the temporary shoring (i.e., zero excavation line); • Placing lower weight backfill material over the top slab to decrease the overburden load on the structure; • Varying the depth of the top slab; • Arching the top slab; and • Utilizing various types of pre-cast concrete elements. In the end, a conventional cast-in-place reinforced concrete box was assumed. The top and bottom slab thicknesses were based on the depth required to accommodate the calculated shear. High strength concrete and no shear reinforcement were assumed. Use of shear reinforcement is an acceptable alternative in top and bottom slabs, but was not assumed in order to reduce rebar steel required and minimize labor associated with placement. The wall thicknesses are proportional to the top and bottom slab thicknesses.

4.3.7 Ancillary Facilities Types of ancillary facilities anticipated in the potential cut-and-cover tunnel portion of the subsurface managed lanes include ventilation structures, power centers, cross passageways, utility rooms, and emergency egress stairways. Underground structures adjacent to the cut- and-cover tunnels were considered during the Re-Evaluated Design Schematic development to combine several ancillary functions. Additional information regarding ancillary facilities is presented in Section 4.5.

40 4.4 Mined Tunnels

4.4.1 General The tunnel alternative for the Re-Evaluated Design Schematic included the mined roadway tunnels and associated ancillary facilities.

4.4.2 Tunnel Length and Portal Locations The tunnel alternative was designed to accomplish the following key objectives:

a) Avoid reconstruction of portions of the IH 635/Dallas North Tollway (DNT) interchange and associated surface and traffic impacts by constructing mined tunnels under the DNT from just east of Welch Road on the west, to just west of Montfort Road on the east. b) Minimize the length of mined tunnel in order to decrease operating and maintenance costs associated with the ventilation, lighting and other electrical and mechanical systems over the life of the concession.

In addition to these objectives, the following design considerations were utilized to assist in determining the horizontal and vertical alignment of the mined tunnels beneath the DNT:

a) Construct all mined tunnel and associated underground structures within the fresh Austin Chalk, considered an excellent host material for underground openings of large cross-section. b) Provide a minimum of 20 ft of fresh Austin chalk above the tunnel crown and at each mined tunnel portal location. c) Provide a minimum of 45 ft separation, excavation to excavation, between the adjacent tunnels at both the east and west portals where the fresh rock cover is minimal. This separation was maintained in order to reduce the potential impact of one tunnel excavation on the other. This distance was increased to 60 ft, over the first approximately 500 ft from each portal. d) Provide approximately 2 tunnel diameters between the excavated crown elevation of the mined tunnel and the DNT. e) Minimize the length of mined tunnel by utilizing 3% roadway grades on either side of a low point beneath the DNT.

41 f) Minimize the length of mined tunnel excavation that will potentially be impacted by the Bentonite Marker Bed by utilizing the 3% roadway grade.

4.4.3 Dimensional Parameters The assumed mined tunnel horizontal and vertical interior dimensions are presented in Exhibits 4.4.1 and 4.4.2. A minimum vertical clearance of 16'-6" was used, measured from the high point of the roadway. The 16'-6" clearance dimension includes a 6" allowance for a future wearing surface. This clearance dimension applies to shoulders as well as travel lanes.

In addition, the mined tunnel geometry determined during preliminary design accommodates the required additional vertical clearance for jet fans, signage and associated equipment.

4.4.4 Tunnel Rock Properties for Design Geomechanical properties for the earth materials to be encountered during tunnel excavation were developed based on data from the three previous geotechnical investigations for the IH 635 West sections of the Project, and on available data from previous analyses and numerical modeling efforts in the Austin Chalk. Typical values and ranges for these properties are also provided in the GIR (LBJMP 2006).

4.4.5 Tunnel Excavation It is anticipated that the mined tunnels and associated ancillary facilities will be excavated using mechanical means. The relatively low-strength Austin Chalk lends itself well to mechanical excavation, specifically by roadheaders equipped with either an axial or transverse type cutterhead and carbide bits, or by a tunnel boring machine (TBM) equipped with disc cutters. Mined tunnel excavation by drill and blast methods is not permitted on this Project.

4.4.6 Ground Response to Excavation The ground response and stability of underground excavations in the massive, relatively low- strength Austin Chalk will be controlled largely by one or a combination of the following factors:

a) in situ stresses and induced stresses that will develop in response to excavation; b) the location, thickness and strength of bentonite seams and argillaceous zones above, within and below the tunnel envelope; and the tendency of these seams to deteriorate or swell in response to exposure and/or water; and

42 c) the frequency and orientation of discontinuities in the rock mass and by the characteristics and shear strength of these discontinuities.

4.4.7 Initial Ground Support The initial ground support for the mined tunnels and associated ancillary facilities was assumed to be comprised primarily of rock dowels and fiber reinforced shotcrete. At the portals, lattice girders and spiling were assumed, and if highly fractured ground is encountered, additional lattice girders and/or spiling may be required. Based on the encountered ground conditions, lengths and spacing of rock reinforcement will vary, as will the required thicknesses of shotcrete. For the mined tunnels, an observational approach to initial support installation was assumed. Based on the preliminary engineering effort, this approach provided designs for three classes of ground support to be used in conjunction with excavation of multiple drift openings with variable spans and lengths, and which can be adjusted depending on encountered ground conditions.

In general, the ground classifications and initial support designs presented in the previous Design Summary Report (LBJMP 2005) have been utilized for this Re-Evaluated Design Schematic. The previous report also described the approach taken during the preliminary design, and the analytical, empirical and numerical means used to arrive at the initial ground support requirements. The three initial ground support types developed and assumed in the cost estimate for the Re-Evaluated Design Schematic are presented in Exhibits 4.4.3 to 4.4.5. Type 1 ground support is the lightest and was assumed for the best ground conditions. Type 2 is heavier support and was generally assumed when the Bentonite Marker Bed was within 15 ft of the crown of the tunnel. The Type 3 ground support, which includes both spiling and lattice girders was assumed at each of the mined tunnel portals where a thinner cover of fresh rock is located above the crown.

4.4.8 Waterproofing for Mined Tunnels and Underground Structures For the Re-Evaluated Design Schematic, a PVC membrane waterproofing system has been assumed. This system includes a layer of leveling shotcrete to ensure a suitable substrate for application of the waterproofing system. After the leveling shotcrete is applied, a layer of drainage fabric is placed and detailed to conduct intercepted groundwater flow to the tunnel drainage system. The PVC membrane is then placed prior to casting of the final reinforced concrete structural liner.

4.4.9 Tunnel Final Lining For the Re-Evaluated Design Schematic, an eighteen inch (18 in) cast-in-place concrete lining was assumed. During preliminary design, nominal design effort was given to the specification of the final tunnel lining; rather, the finite difference model, FLAC, was utilized to calculate the thrusts, moments and shear forces in the lining utilizing the loadings developed from several of the loading scenarios described in the previous Design Summary Report (LBJMP 2005). These forces were then compared to the structural capacity of the proposed final liner section and reinforcement.

4.4.10 Ancillary Facilities Within the Re-Evaluated Design Schematic, ancillary facilities are required in order to accommodate fire and life safety considerations and to house utility system components. These facilities include but are not limited to cross passageways between the parallel mined tunnels, utility rooms, ventilation shafts and associated equipment rooms and duct passages, niches, sumps, and low-point pump stations. The configurations and locations of these elements are shown in the attached Exhibits. Additional information regarding ancillary facilities is described below in Section 4.5.

4.4.11 Fire and Life Safety Considerations Fire and life safety components of the preliminary design incorporated requirements of NFPA 502 and items from discussions with the Fire, Security and Life Safety Committee (FSLSC). The mined tunnels incorporated several fire, security and life safety elements, including dry standpipes, raised grade separated safety walks, and emergency egress via cross passageways. The mined tunnel design must include, as a minimum, provisions for support of ventilation equipment, signage, lighting, detection equipment, conduit for safety systems, CCTV, and fire protection systems.

4.5 Ancillary Facilities

4.5.1 General Ancillary facilities are essential secondary structures required for both the tunnel and no tunnel alternatives of the Re-Evaluated Design Schematic, and are critical to supporting the operation

44 and maintenance of the managed lanes. Ancillary facilities for the Re-Evaluated Design Schematic include but are not limited to the following:

a) Emergency exit stairways b) Utility rooms c) Structures combining ventilation shafts, maintenance/emergency exits, and utility rooms d) Cross passageways e) Low-point pump stations

4.5.2 Emergency Exit Stairways Based on NFPA 502 requirements for emergency egress from underground excavations, emergency exit stairways have been located at the cut and cover tunnel portals where the roadway transitions to a depressed managed lanes section. These stairway structures are accessible from the walkways within the cut and cover tunnels, and exit to the surface in a pressurized environment in order to protect the exiting public from smoke. Stair widths are 6 ft wide based on preliminary calculations that indicate 275 people exiting during an emergency event. A head-house is included at surface level to facilitate exiting.

4.5.3 Utility Rooms For the Re-Evaluated Design Schematic, roadway level utility rooms are provided approximately every 500 feet along each of the managed lane tunnels. The rooms are located at roadway level and are anticipated to be a minimum inside dimension of 12’x12’. The purpose of the room is to house electrical distribution equipment.

4.5.4 Structures Combining Ventilation Shafts, Maintenance/Emergency Exits, and Utility Rooms For the tunnel alternative of the Re-Evaluated Design Schematic, the cut and cover tunnel sections at each end of the mined tunnel provide a key transitional section of roadway, taking the central six-lane depressed managed lanes section and separating it into two three-lane roadways, and at the same time taking the roadway from the relatively shallow depressed managed lanes section down to a depth which will provide more fresh rock cover above the crown of the mined tunnels. In addition, these transitional sections have been assumed to

45 accommodate space for housing ventilation shafts, a maintenance/emergency exit, and power and utility facilities.

For the tunnel alternative, one combined structure is located in the west cut and cover transitional section, and two combined structures are located in the east cut and cover transitional section (Exhibit 5.1.1). At each location, the maintenance/emergency exit will typically be configured as described above. For the ventilation shafts, four ventilation shafts are anticipated at each of the combined structures. For this schematic, a 10’ x 10’ inside dimension has been assumed. The ventilation shafts provide the path for air to pass between the roadway level ventilation equipment and the above grade air. The height of the ventilation structure above grade was not detailed during this preliminary design effort, but was assumed to be 12’.

4.5.5 Cross Passageways Per the requirements of NFPA 502, cross passageways are located in the cut and cover tunnel and mined tunnel portions of the Re-Evaluated Design Schematic (Exhibit 5.1.1). The cross passageways are spaced at the maximum spacing allowed by code, and at each location the excavations have been sized for two self-closing swing doors, with one opening in each direction. A removable panel above the 1-hour rated fire doors has also been provided to facilitate moving equipment to utility rooms. SCADA points for the doors, lighting, and pressurization of the interior space are anticipated.

4.5.6 Low-Point Pump Stations A low-point pump station, as the name implies, is located at a low-point along the roadway alignment. Its' function is to collect groundwater and water from other sources and discharge it to outside drains by means of pumps. A low-point pump station is an essential component of the pressure relief system. Groundwater collected from the waterproofing and drainage system will drain by gravity to the low-point pump station where it will be retained and then pumped-out by means of electrically controlled submersible pumps. For the tunnel alternative, the low-point pump station has been located at the low-point of the mined tunnels, adjacent to Cross Passageway No. 6 (Exhibit 5.1.1).

4.6 Tunnel Finishes The preliminary engineering design for the Re-Evaluated Design Schematic included the installation of an interior tunnel wall finish that is durable, washable and that meets

46 recommended reflectivity standards. The type of finish, though not indicated on the attached drawings, was presumed to be 8 in x 8 in porcelain tile or porcelain enamel steel panels. The finish material was assumed to be installed on the tunnel walls up to the height of the defined 16 ft - 6 in vertical clearance envelope.

47 CHAPTER 5 - MECHANICAL, ELECTRICAL, AND POWER DESIGN

5.1 Tunnel Ventilation System Design

5.1.1 General Background Information Proper ventilation is critical to life safety and providing a tenable environment during normal traffic operations and is necessary to remove and control smoke and heated gases in the event of a tunnel fire.

Two configurations for the subsurface managed lanes were evaluated for a potential fire. The goal was to determine basic requirements to maintain a tenable environment. The two configurations are as follows:

a) Short Tunnel Configuration: The short tunnel configuration is presented as an alternative in the Re-Evaluated Design Schematic. The tunnel alignment consists of approximately 4,575 ft of parallel mined tunnels and two cut and cover sections of 1,175 ft and 1,515 ft long on both the east and west ends of the mined tunnel. Within the subsurface managed lanes the tunnels are roughly centered longitudinally under the Dallas North Tollway (DNT). The balance of the subsurface managed lanes is comprised of partially covered and uncovered depressed managed lanes sections.

b) Partially Covered depressed managed lanes Configuration: The no tunnel alternative of the Re-Evaluated Design Schematic consists of partially covered depressed managed lanes through the entire length of the West section subsurface managed lanes. A preliminary CFD analysis was performed for a typical depressed managed lanes section and is described in a report entitled, “IH 635 Managed Lanes Project Depressed Managed Lanes; Preliminary Tunnel Fire Simulation; December 1, 2006”.

The preliminary ventilation system design has been developed with the goal of identifying a conceptual system that will meet the identified Project requirements and for preparation of a preliminary cost estimate. The design of the ventilation system utilized many fundamental assumptions that will require reevaluation during final design. The preliminary design was

48 generated using basic tunnel ventilation system design tools and it is expected that the Developer’s final design will be generated through the latest technology such that the system can be optimized. The ventilation system conceptual design prepared for and reflected in the Re-Evaluated Design Schematic was not optimized due to the conceptual nature of the design effort and in no way represents a final design configuration.

5.1.2 Assumptions The basic alignment and geometry are indicated in the Re-Evaluated Design Schematic and attachments to this document. The following represents some of the ventilation design considerations associated with the tunnel alternative.

5.1.3 Design Standards & Design Objectives The standard used for the design of tunnel ventilation system is the National Fire Protection Association (NFPA) 502 “Standard for Road Tunnels, Bridges, and Other Limited Access Highways”, 2004 Edition.

The design fire size (heat release rate) produced by a vehicle within the tunnel is a major element used to design the emergency ventilation system. The selection of the design fire size considered the types of vehicles that are expected to utilize the tunnel. Assuming that vehicles carrying hazardous materials will be prohibited from entering the tunnel the fire heat release rate for this project was originally identified as 20 MW. Many tests performed in Europe indicate that bus fires are 30 MW or higher and other recent research performed in Europe indicates that heavy goods truck fires can reach up to 200 MW (Large-scale fire tests in the Runehamar Tunnel in Norway in 2003). A fire size of 30 MW was utilized for the preliminary ventilation system conceptual design for the project.

5.1.4 Other Design Considerations Traffic and toll revenue estimates prepared by Wilbur Smith Associates for 2015 and 2025 traffic volumes, and the Vehicle Class Distribution Table provided by TxDOT were used in the determination of the traffic mix anticipated to utilize the subsurface managed lanes.

Table 5.1.1 below represents the traffic mix that was used in the emissions analysis portion of the ventilation system design. The emissions analysis was performed for the idle traffic

49 condition (or moving at 2.5 mph). The Developer is responsible for the determination of the anticipated traffic mix for the purpose of final design.

Table 5.1.1 Vehicle Mix for Emissions Analysis

Vehicle Type Cars Heavy Trucks Light Trucks/Buses Percentage 93.02% 3.58% 3.4% * *Assumes 1.4% school busses and 2% transit and urban buses

5.1.5 Tunnel Ventilation System Modeling – General The basic computational model utilized for the preliminary level ventilation system design is the US Department of Transportations’ Subway Environmental Simulation program. This program was developed for subway tunnel ventilation systems, however there are modeling techniques commonly used that adapt the program for modeling road tunnel ventilation systems.

5.1.5.1 Ventilation System Type The preliminary level ventilation system assumed for preliminary design is a combination of an ejection shaft type ventilation system with capabilities to exhaust air along the tunnel. It also is supported by a jet fan ventilation system. In this configuration, the ventilation system must generate sufficient longitudinal air velocity to prevent back layering of smoke (movement of smoke and hot gases against ventilation airflow in the tunnel roadway), and to provide a sufficient amount of fresh air to dilute tunnel vehicle emissions to acceptable concentration levels.

5.1.5.2 Ventilation System Details The ventilation system preliminary design layout consists of two ventilation structures that are combined with the emergency egress stair structures located at both ends of the mined tunnel, and one similar structure located at the middle of the east cut-and-cover tunnel section. Each ventilation structure houses four axial flow tunnel ventilation fans of approximately 220,000 CFM that may operate via a two-speed motor or a variable frequency drive to conserve energy during normal operation. The configuration of the fans and dampers within the vent structure allow the fans to perform either supply or the exhaust functions, while operating in one direction, however the arrangement does not allow for the vent structure to both supply air and exhaust air simultaneously.

50 The system is supported with reversible jet fans that will aid in:

a) Ejecting air from the entrance portal; b) Improving the supply ejection nozzle operation; c) Mitigating the adverse wind effect; d) Meeting and maintaining the critical air velocities during fire emergency; e) Reversing the tunnel airflow if and when necessary for fire fighting operations;

Based upon the results of initial simulations with the US Environmental Protection Agency’s (EPA) Mobile 6 Program and US Department of Transportation Subway Environmental Simulation (SES) analysis, the following preliminary tunnel ventilation system configuration was developed for the tunnel alignment as the Re-Evaluated Design Schematic and includes:

a) Emergency egress stairway/ventilation structure with mechanical/electrical rooms and housing four uni-directional multi-speed tunnel ventilation fans in each structure; b) Ventilation structures at each end of the mined tunnels section and one in the middle of the east cut-and-cover tunnel. c) 4-ft diameter jet fans in sets of three in a row along the tunnel as follows: • At a spacing of 300-ft, and; • Next to each of the stairway/ventilation structure

The following Exhibit descriptions present the tunnel ventilation plans that are included as attachments to this report:

a) Exhibit 4.3.1 provides a typical cut-and-cover tunnel cross-section showing the vertical clearance minimum to accommodate the jet fans, the jet fan installation details and vehicle clearance criteria. b) Exhibits 5.1.1 and 5.1.2 present locations of ventilation structures and jet fans. c) Exhibits 5.1.3 includes the tunnel cross passageway ventilation details. d) Exhibits 5.1.4 thru 5.1.8 provide emergency egress stair/ventilation structure configurations including tunnel ventilation fans, fan room arrangement and other mechanical equipment. Power Centers and other service rooms are also shown conceptually.

51 5.1.6 Tunnel Ventilation Analysis During a Fire Emergency Several iterations were necessary to analyze the tunnel ventilation system for fire emergencies. The basic method of analyzing the fire scenarios was to select fire locations that are known to be the worst cases, while analyzing other fire locations to confirm the suspected worst-case fire locations and confirm that in all cases the critical velocity criteria required per NFPA 502 were met.

5.1.7 Vehicular Emissions Under Non-emergency Conditions The tunnel ventilation system is a critical system for controlling smoke propagation during a fire emergency; however it also has a critical role during normal operation of the tunnel. The tunnel ventilation system is relied upon to dilute and/or remove vehicular emissions such that safe conditions are maintained within the tunnel.

5.1.7.1 Acceptable Levels of Vehicular Emissions The following table represents the EPA’s 1989 recommendations for the maximum CO levels in tunnels located at or below an altitude of 5,000 ft.

Table 5.1.2 - Maximum Acceptable CO Emission Levels in Tunnels below 5,000 ft

Maximum Exposure of Carbon Monoxide Duration of Exposure (minutes) (CO), (parts per million) 120 15 65 30 45 45 35 60

Tunnels that are staffed 24 hours per day fall under the jurisdiction of the US Occupational Safety and Health Association (OSHA) requirements. OSHA has established the Threshold Limit Value (TLV) as adopted by the American Conference of Governmental and Industrial Hygienists, as the environmental level for the working environment. These permissible levels can be applied to the tunnel environment. The table below illustrates the application of these time-weighted averages to the tunnel environment.

52 Table 5.1.3 - Permissible Excursion Limits +as applied to Tunnel Environment

Contaminant Threshold Limit Permissible Short Term Value (TLV) Excursion limit Excursion Limit (ppm) (ppm) (ppm) Carbon Monoxide 50 75 400 (CO) Nitric Oxide (NO) 25 37.5 35 Nitrogen Dioxide 5 5 5 (NO 2) Note: Table source is “Tunnel Engineering Handbook, 2 nd Edition”

5.1.7.2 Vehicular Emissions Predictions-General Vehicle emissions of CO, NOx, and hydrocarbons for any given calendar year can be predicted for cars and trucks operating in the US by using the MOBILE modeling software developed by the US Environmental Protection Agency. The current version is MOBILE 6.2 (EPA 2002). The MOBILE program is used to estimate hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) emission factors for gasoline and diesel fueled vehicles. The program estimates the current and future emissions from various types of highway vehicles. The estimates of emissions are based upon factors such as ambient temperature, vehicle speed, vehicle age, and based upon the calendar year 2015. The MOBILE program produces the resulting contaminant emission rates in grams per mile per vehicle. The following practice and assumptions are typical and were used in performing the contaminant emission rate analysis:

a) CO emissions are higher during acceleration and deceleration than at constant speed. This effect was accounted for by adding a 10% safety factor to the computations. b) The effect of negative or positive grades up to 2% is usually neglected and engineering judgment or available data should be used in applying a correction factor for positive grades greater than 2%. For this preliminary effort, a 3% grade was used. c) Traffic is assumed to move as a unit, with a constant space interval between vehicles, regardless of the grade. d) The average passenger vehicle dimensions are assumed where specific vehicle data is unavailable.

53 e) A general safety factor can be applied due to various levels of uncertainty for the project. A 10% factor was applied for the effort to account for the unknowns associated with this preliminary level analysis.

5.1.7.3 Vehicular Emissions Results The analysis was performed using idle traffic conditions (0-2.5 mph) during the summer time, and using the traffic mix identified in Section 5.1.4 for the year 2015. Vehicle emission analyses depend on the local traffic information that is usually obtained from the local authorities. Mobile 6.2 simulations were performed based on recommendations and information received from EPA Region 6 and from the North Central Texas Council of Governments. The results indicate an average CO emission for the summer season of 17.1 grams/mile/vehicle and average NOx emissions of 1.191 grams/mile/vehicle. The winter season emissions are anticipated to be less, based on previous sensitivity analyses conducted for other tunnels. The results have been adjusted via the previously mentioned correction factors for acceleration/deceleration and grade and are as follows:

Table 5.1.4 – Vehicular Emissions Analysis Results

Description Carbon Monoxide (CO) Oxides of Nitrogen (NOx) gram/veh/mile gram/veh/mile Mobile 6.2 Base Result 17.1 1.191 With Acceleration & 18.8 1.31 Deceleration Adjustment: +10% (ASHRAE) With Tunnel Grade 19.5 1.36 Adjustment: +3% (PIARC) With General Safety Factor 21.5 1.5 Adjustment: + 10%

5.1.7.4 Dilution of Contaminants The tunnel ventilation system must dilute the vehicle emissions sufficiently over the length of the tunnel such that acceptable levels are maintained within the tunnel. This review entailed a calculation of the total contaminant level in the tunnel as well as calculation of the air volume necessary to provide sufficient dilution. The ventilation system’s dilution effectiveness required various iterations of ventilation shaft locations, fan sizes, and fan operating modes to ultimately determine a conceptual ventilation scheme that meets the dilution requirements. In the case of

54 the specific alignment depicted in the Re-Evaluated Design Schematic, the ventilation system’s capacity to handle fire emergencies was less than that required to provide the necessary dilution air. Introducing outside air through the three ventilation shafts and ejecting inside air through the portals by utilizing jet fans installed along the tunnel achieved the necessary dilution effect in the selected ventilation scheme.

The preliminary level design did not include a stack emissions analysis to determine potential impacts or contaminant levels in the areas adjacent to the ventilation stacks. There were no environmental criteria identified at the conceptual level, therefore no consideration was given to this aspect of the system design.

5.1.8 Ambient Temperature within the Tunnel The hot climate in the Dallas area and the expectation of congested stopped traffic within the tunnel required consideration to be given to the expected ambient temperature in the tunnel. The outdoor air design data, based upon ASHRAE, identifies the summer outdoor air design dry bulb temperature as 100 deg F and the wet bulb temperature as 74 deg F. Preliminary calculations were performed for congested/stopped traffic conditions occurring in the summer season to determine the heat input to the tunnel from vehicle exhaust and air conditioners. The amount of heat input to the tunnel cannot be cooled with 100 deg F supply air delivered by the ventilation system at rates that accommodate the CO dilution and fire emergency requirements. A significant increase in the ventilation system capacity would be necessary to cool the tunnel with supply air at a temperature of 100 deg F, therefore a cooling system may be warranted.

NFPA 502 identifies the maximum tunnel ambient temperature during fire incidents to be 140 deg. F. The ASHRAE Handbook for underground facilities does not list a maximum acceptable ambient temperature for underground roadway tunnels; however there is some general information available regarding underground subway stations. Since there is no specific temperature requirement, the design temperature used was 105 deg F as defined by the “Apparent Temperature”, which defines various temperature and humidity combinations. Further information regarding these criteria is provided in Section 5.1.8.1.

Further evaluation and development of this concept was beyond the scope of the ventilation system preliminary design.

55 5.1.8.1 Ambient Temperature Criteria within the Tunnel The heat index combines the effects of heat and humidity. Overheating can cause serious, even life-threatening conditions such as heat stroke. The Apparent Temperature, which combines the temperature and relative humidity, is a guide to the danger of heat and humidity. Below is the heat stress index based on the Apparent Temperature.

Apparent temperature heat stress index

Category Apparent temperature Dangers

Caution 80-90°F Exercise more fatiguing than usual

Extreme caution 90-105°F Heat cramps, exhaustion possible

Danger 105-130°F Heat exhaustion likely

Extreme danger Greater than 130°F Heat stroke imminent

Based on the Apparent Temperature Heat Stress Index Table above and the Heat Index Table below, we applied an Apparent Temperature of 105 deg F as an ambient design temperature for inside the tunnel during worst case traffic scenarios; and also applied the fire scenario ambient temperature maximum of 130 deg F (normal temperature) per the NFPA 502 design criteria.

Below is a psychrometric chart that indicates an extreme danger zone, a danger zone and outside design conditions. It is desirable to stay within the extreme caution zone, avoiding the danger zone and never getting to the extreme danger zone under normal operating conditions, hence the use of the 105 deg F Apparent Temperature criteria for this analysis.

5.2 Fire Protection System Design

5.2.1 Fire Protection – General The fire protection system is a critical life safety system that is used in the event of a fire in the tunnel and depressed managed lanes. Proper design and installation is critical to response time and the ability of the fire department to effectively fight a fire.

The fire protection system design concept was developed with the goal of identifying a system concept that will meet the design requirements and provide a basis for preparation of a preliminary cost estimate. The design of the fire protection system utilized fundamental assumptions that will require reevaluation during final design. The fire protection system preliminary design was generated using basic tunnel and depressed managed lanes system design concepts and it is expected that the final design will be generated through the latest technology such that the system can be optimized.

5.2.2 Assumptions The tunnel alignment and depressed managed lanes sections shown on the mechanical plans were used for the conceptual level design effort which includes mined tunnels, two cut-and-

58 cover sections and two depressed managed lanes sections. The tunnel has cross passageways spaced at a maximum of 656 ft and emergency egress stairs located no further than 1000 feet from another emergency exit.

The fire department connection locations for the depressed managed lanes and the egress stair head houses are general at this time. The final fire department connection locations shall be predicated on firewater availability and the final design.

The preliminary design incorporates governing codes as well as the intent of the codes.

5.2.3 Tunnel and Depressed Managed Lanes Fire Protection Design Criteria The governing standards used for preliminary design of the tunnels and depressed managed lanes fire protection system are NFPA 502 and NFPA 14.

a) Fire Hydrant Water Supply For the purpose of this effort, it was assumed that the water supply is adequate and meets the requirements of NFPA 14 for standpipe systems.

It was assumed that pressure regulating valves will not be used in fire water supply mains and meters will not be installed in fire water supply mains.

b) Portable Fire Extinguishers Portable fire extinguishers were provided in accordance with NFPA 502 section 7.9 for the tunnel alternative. No such provision was made for the depressed managed lanes.

c) Fire Detection Systems Tunnel fire detection was provided as required by NFPA 502.

5.2.4 Fire Protection System Basic Configuration A dry standpipe system was selected to mitigate the detrimental effects of freezing in the winter time. The following describes the preliminary design of the fire protection system for the depressed managed lanes and the tunnel.

59 a) Depressed Managed Lanes The assumed fire protection system is shown on the attached depressed managed lanes fire protection riser diagram (Exhibit 5.1.9). The system consists of: • Fire department connection • Concrete vault • ABD (automatic ball drip) valves located at low points in concrete vaults and at low points in the depressed managed lanes fire protection system. • Check valve on the fire department connection line • Combination air release/vacuum breaker valve • SCADA operated semiautomatic deluge valve • Backflow preventor • Hose valves 275 feet apart • Butterfly valves • Pipes and fittings The standpipe system is a semiautomatic standpipe system, however, the semiautomatic feature is not in strict compliance with the requirements of NFPA 14. The semiautomatic filling feature is intended to be immediately activated remotely upon notification of an incident within the tunnel. The SCADA system monitors the position of the deluge valves and is capable of opening them. Further, the preliminary design intends that the Central Supervisory Station (CSS) operator will activate the semiautomatic standpipe system for standpipe zones that have an incident and that require the fire department response.

The semiautomatic standpipe system is arranged and designed such that each standpipe is connected to a water source that, upon activation, will fill the standpipe with water in accordance with the time limits specified in NFPA 502. Each standpipe is provided with three points of fill. The first point of fill is semiautomatic and is connected directly to a water line. The second and third points of fill are fire department connections located at opposite ends of each standpipe system. The system incorporates the appropriate valves at the fire department connections. The standpipe system is designed to provide protection in the event of all reasonable event scenarios.

Although fire hydrant locations were not determined for this effort, it is intended that they are provided within 400 feet of each fire department connection.

60 The system was design to be sloped so that when drained no water remains in the system. The main water supply is protected from contamination by means of a backflow preventor. At the tunnel portals the system is cross connected with manual operated butterfly valves to provide redundancy and options for filling the system.

b) Tunnel The assumed fire protection system is designed as shown on the attached tunnel fire protection riser diagram (Exhibit 5.1.9). The system consists of: • Fire department connections • Concrete vault • Automatic ball drip (ABD) valves located at low points in the concrete vault and tunnel. • Check valve on the fire department connection line • Combination air release/vacuum breaker valve • Semiautomatic deluge valve • Backflow preventor • Hose valves 275 feet apart • Portable fire extinguishers • Butterfly valves • Pipes and fittings The tunnel fire protection system is the same as the partially covered depressed managed lanes described above, with the addition cross passageways. At the portals, and at each cross passageway, the system is cross connected with manual operated butterfly valves. This cross connection was designed such that the fire department can section off and re-route water as need in case of damage to the system.

5.3 Tunnel Drainage System Design

5.3.1 Tunnel Drainage – General The purpose of the tunnel drainage system is to collect, store and discharge effluent from the tunnel. This report addresses the tunnel drainage system only.

61 5.3.2 Drainage Design Criteria The governing standard used for the tunnel roadway drainage system is NFPA 502, specifically Chapter 7, Section 11.

5.3.3 Preliminary Drainage Design

5.3.3.1 In-Tunnel Drainage System Basic Configuration The in-tunnel drainage system consists of the following basic components: roadway gutter drains, interconnecting piping and low point pump stations (LPPS). There is a low point pump station located in the mined tunnel and it serves both of the parallel roadway tunnels.

LPPS Components The preliminary LPPS design is based upon three pumps that are rated for 350 GPM each. The pump capacity is based upon the flows anticipated into the tunnel drainage system from the following sources: simultaneous flow rate of 250 GPM per hose from two fire hoses, tunnel washing operations, and other inflows such as groundwater infiltration, vehicle carryover/drippings and minor spills. A nominal head of 50 feet has been used for pump selection at this time, however, this is based upon previous experience and is expected to change based upon the Developer’s final design.

The interconnecting piping for the gutter drain size assumed is 12” diameter, based upon previous experience. The pipe material is ductile iron pipe which is standard for the application and complies with the NFPA 502 requirements.

The pump stations and the storage tanks were designed with monitoring capabilities for hydrocarbons, with alarms indicating locally and at a remote supervising facility.

5.4 Depressed Managed Lane Lighting

5.4.1 Partially Covered Depressed Managed Lanes Lighting Baseline Fixture Choice For purposes of estimating costs for lighting the partially covered depressed managed lanes, a typical “Cobra-Head” fixture was used with supplemental lights located under the general purpose lanes overhang. It was assumed that “Cobra-Head” fixtures will be mounted in a staggered configuration across the roadway and be spaced 200’-0” apart with a mounting height

62 of 40’-0” above the roadway. The preliminary design assumes that the partially covered depressed managed lanes have the same lighting conditions as the tunnel sections, and are assumed to be a tunnel for the purposes of lighting. It is recognized that this assumption may be considered conservative, but given the varying exposure to natural light and the outdoor elements, this approach was chosen to simplify the preliminary design effort.

5.4.2 Tunnel Lighting Fixture Choice Based on current industry standards, a tunnel lighting system that utilizes fluorescent and high intensity discharge (HID) fixtures was selected. The fluorescent fixtures offer a linear path of light that directs the driver through the tunnel, along with the addition of high intensity discharge fixtures in the threshold and transition zones to help maintain required light levels.

5.4.3 Design Considerations

a) Fluorescent Design Considerations The fluorescent fixture type used as the basis for preliminary design was chosen for its ability to withstand the harsh conditions found in a tunnel environment along with its ease of maintenance. The following mounting considerations are for one row of fluorescent fixtures utilizing threaded rod with a longitudinal strut and transverse slotted struts at a minimum of (3) per (8’-0”) of wireway. This particular fixture is designed to withstand high pressures resulting from tunnel washing machines. This fixture utilizes an integral wireway that assists with maintenance. The entire fixture can be unplugged from the wireway (without tools) and detached so maintenance can be performed away from the tunnel environment. Internal to the fixture is a removable ballast tray that can also be removed and repaired away from the tunnel environment.

b) High Intensity Discharge Design Considerations The high intensity discharge (HID) fixture type used as the basis for preliminary design was chosen for its ability to withstand the harsh conditions found in a tunnel environment along with its ease of maintenance. This particular fixture is designed to withstand high pressures resulting from tunnel washing machines. The fixture can easily be removed from the tunnel environment for maintenance and also contains a removable ballast tray.

c) Preliminary Design Preliminary design was based on the ANSI / IESNA RP-22 – Recommended Practices for Tunnel Lighting.

d) Calculations Preliminary calculations were completed using GE Aladan software.

5.5 SCADA System

5.5.1 Design Considerations The SCADA system monitors and controls various life safety equipment such as tunnel ventilation fans and electrical system configuration. The system must function under all operating conditions, and must be in operation regardless of the operational status of the managed lanes. The system must also allow modifications and repair without any loss of functionality. A dual ring configuration for the backbone was chosen because it has proven to be very reliable in several previous tunnel designs. All equipment except the actual monitoring devices is redundant. SCADA equipment in non-environmentally controlled areas is designed to operate without the need for active cooling or heating support. A dual ring topology will ensure that at least one data path between each field node and the server node is always available. Redundant servers were included in the design to prevent loss of control and data in the event of equipment failure.

Only equipment necessary for life safety is assumed to be monitored, and only equipment that must be operated in an emergency is assumed to be remotely operated. This arrangement minimizes the system cost while still providing emergency monitoring and control. The preliminary system design allows for a significant increase in monitoring and control points.

5.6 Intrusion Detection System

5.6.1 Design Considerations The intrusion detection system is designed to detect the unauthorized access to tunnel facilities. The system is stand-alone including reporting intrusions, and the means of detection is through door alarm switches.

5.7 Fire Alarm and Detection System

5.7.1 Design Considerations The fire alarm and detection system is designed to meet the requirements of NFPA 502. The primary means for detection of incidents in the tunnel is a CCTV camera system, which provides 100% coverage of the tunnel roadway. Pan-tilt-zoom cameras were selected and the system includes the ability to record the output of any camera. Primary camera control is allocated to the tunnel operator, with secondary control to TxDOT. Connections are available to the area fire departments and police for viewing the camera outputs. Manual pull stations are the second means of fire detection, with fire alarm control panels (FACP) providing alarm functions. The FACPs are connected to the SCADA system.

5.8 Communications System

5.8.1 Design Considerations The communications system is designed to meet the requirements of NFPA 502. The design includes radio repeaters for police, fire, and other emergency response agencies. In addition, hard line telephones are provided between all subsurface ancillary facilities and the CSS. This is intended for operating by the Developer and emergency personnel.

5.9 Electrical Systems

5.9.1 Design Considerations The electrical system design serves the tunnel, depressed managed lanes, ramps, and ancillary facilities. The design includes power centers, switchgear, raceway, conductors, and other equipment required to complete a system capable of delivering power to all subsurface systems. Facilities not supporting the tunnel or depressed managed lanes will be supplied by electrical systems as necessary. Given the complexities, only the subsurface systems are covered herein.

The electrical system is designed to meet the requirements of NFPA 502. The system will provide adequate power under all operating conditions. The primary and secondary power sources are the local electric utility. Standby generators and UPS systems are incorporated to

65 provide uninterrupted power to standby, essential, and emergency loads. Multiple circuits ensure that a failure of one circuit will not cause a complete loss of ventilation, lighting, or other services in any area. Maximum use of embedded raceways is made to reduce the possibility of failures due to accidents or fire.

5.9.2 Tunnel System Electric Utility Service Major improvements in the utility distribution system are anticipated in order to bring two (2) separate sources, each capable of carrying the entire tunnel demand load to the site. Improvements, extending as far as two (2) miles into the utility distribution network may be necessary to handle the demand load. The area is served by a combination of 15 kV and 27 kV class distribution networks. TXU reports that each 15 kV distribution feeder has a maximum power capacity of approximately 11 mVA, thus six (6) or more feeders could be required to serve the project with redundant sources of supply.

5.9.3 Source Reliability and Redundancy The tunnel electrical power system design meets the NFPA 502 requirement to maintain two separate sources of power to all life safety and/or emergency loads throughout the tunnel length. The primary source of electrical service is the local electric utility. Due to the large demand, the secondary source is a separate utility source. It is assumed that a single event within the utility system cannot affect both the primary and secondary source. Tie breakers are used to enable switching between sources at both the service and utilization voltage levels.

5.9.4 Primary Distribution System Configuration The primary distribution system is based on a primary selective system with both utility sources made available to all distribution substations serving the tunnel and tunnel ancillary facility essential systems. This primary selective system is non-automatic. This is typical for tunnels of this configuration and length.

The conceptual primary distribution system was designed to carry both services from the eastern project limit to the western project limit by means of an open-primary loop configuration. One full capacity source originates at the west limit and extends to the eastern project limit and separately, a second full capacity source originates at eastern limit and extends to the western project limit.

66 A service and distribution system is furnished at a voltage level commensurate with the demand and the availability of service from TXU Electric Delivery. USA standard voltages are used throughout the system.

5.9.5 Secondary Distribution System Configuration The secondary distribution system is based on a secondary selective system with both utilization voltage sources made available to all distribution substations serving the tunnel and tunnel ancillary facility essential systems. This secondary selective system is automatic.

Primary and alternate utilization voltage switchboards and associated circuit breakers are provided which is used to power all tunnel related systems and equipment. The primary and alternate switchboards individually have the capacity to supply the sum of the loads connected to both primary and secondary switchboards in any given power center, including future capacity. This is assumed for life safety loads where continuity of service is important and also where equipment must be taken out of service for maintenance or repair.

A tie circuit breaker connection between the primary and alternate switchboards in each power center is provided. In the event of an under voltage condition at either one of the switchboard main circuit breakers in the power center, the tie circuit breaker is designed to automatically close and supply power from the energized switchboard to the switchboard which has the under voltage condition. Closing of the tie circuit breaker automatically opens the affected main circuit breaker on the switchboard experiencing the under voltage condition.

Restoration of the main and tie circuit breakers to normal status after an under voltage condition is by manual operation.

5.9.6 Electrical Load Classification The electrical power system is designed to be arranged to serve four (4) distinct classifications of loads: normal, essential, standby and emergency. Standby loads are those loads classified as such by federal, state, local, or municipal codes or regulations. They are required to be supplied by two (2) separate and distinct source of power.

Essential loads are those loads that are deemed, by the engineer, to offer enhanced tunnel and tunnel ancillary facility operations and protection through their continued availability during a

67 total loss of commercial (utility) electrical supply. Essential loads are primarily served by the utility electrical supply and backed-up by an on-site alternate during a total loss of the respective primary supply. If a standby generator is used, it is not intended to serve as the second required source for the standby system or emergency system. The design assumes the use of on-site generators for backup supply.

Emergency loads are those loads legally required and classified as emergency to meet municipal, local, state, federal or government codes, or to meet authority having jurisdictional requirements. Emergency loads are supplied by an emergency system meeting the requirements of NFPA 70, NFPA 110, NFPA 11, NFPA 101 and NFPA 502. The design assumes the use of battery backed UPS systems.

68 CHAPTER 6 - AESTHETICS AND LANDSCAPING The preliminary engineering design effort for the Re-Evaluated Design Schematic incorporated the aesthetic concepts and guidelines that are presented in the Technical Provisions. These guidelines define strategies for Project-wide aesthetic enhancements that are required by the Developer, and that focus on achieving a recognizable design theme.

The IH 635 Managed Lanes Project design theme has been established based on the natural character of the corridor. The existing site provides a topographic change and a change on geological materials that has defined a ‘Strata’ theme. By using a Strata theme and an architectural approach, the corridor will become a progressive facility that utilizes shape, form and color to provide a fluid driving environment for the users. The design aesthetics are indicative of the contemporary character of the Project corridor, and the construction technology and techniques that are responsive to the era in which the Project is built.

69 CHAPTER 7 - TRAFFIC ANALYSIS

7.1 Travel Demand Model

7.1.1 Overview A Travel Demand Model (TDM) uses roadway and transit networks along with population and employment information to forecast the expected demand on the highway and roadway system. The North Central Texas Council of Governments (NCTCOG) maintains this regional model using a program called TransCAD. Within the model, mathematical equations are used to represent each individual’s decision-making process and represent this as a trip on the network. First the program is calibrated using existing information (1999). Next, future year (2007, 2010, 2025) data is inserted into the program for a forecast. The forecast is calculated through a four- step process.

a) The trips are generated based on demographic data (population, employment) b) The trips are distributed to the networks c) The mode of the trips are assigned d) The trips are assigned to the proper system (roadway, HOV, transit)

The aggregate impacts of roadway volumes and travel times can be used to determine a planning level roadway impacts. These impacts can also be compared to each other to determine general performance parameters. These results can then be used in “Next Generation Modeling” or Microscopic models to determine design level performance.

7.1.2 Introduction NCTCOG’s current TDM efforts for the Dallas/Fort Worth (DFW) metropolitan area already include TransCAD models for the years 1999, 2007, and the horizon year 2030. Each model includes the corresponding land-use plans and roadway networks, existing and committed. TDM's are useful tools to determine the regional traffic demands and basic corridor impacts for system capacity restraints, interchange impacts and major changes in land use, such as employment centers. However, these models only represent the traffic conditions at an aggregate level and do not account for the operational issues of the traffic flow. These effects are particularly critical for a congested network, especially during the peak hours.

70 The current reconstruction plans along the IH 635 corridor will effect the traffic operations on the area roadway system on two levels, local and regional. The local effects of the construction phasing sequences proposed along the IH 635 corridor can be evaluated through a microscopic traffic simulation model. However, the regional effect on the freeway and major arterial system is best modeled through the planning approach of the regional TDM. Therefore, in order to realistically evaluate the regional impact of various traffic phasing plans on the travel patterns, we utilized the NCTCOG’s regional TDM. The NCTCOG’s model description and traffic assignment steps are presented in the detailed summary report.

7.1.3 Model Boundaries One of the main decisions made prior to the start of the modeling effort was the definition of the model’s boundaries. These boundaries had to include the freeways and major arterials that are likely to be impacted by the construction phasing. We used the NCTCOG’s model for the purpose of this study. However, the area of interest for this Project is encompassed by IH 35E on the west, President George Bush Turnpike (PGBT) on the north and east (including the Super Connector), and IH-30 on the south. The area of interest is further sub-divided into east and west sections with US 75 being the border line. This analysis focused on the changes in the traffic volumes along the roadway facilities listed below:

a) PGBT, including the eastern extension and the Super Connector; b) SH 161, SH 78; c) IH 35E, IH 30, IH 635; d) US 75, US 80; e) Dallas North Toll-way (DNT); and f) Loop 12, Northwest Highway, Beltline Road.

7.1.4 Analysis The TDM results regarding the changes in the link volumes of the different closure scenarios do not show any irregularities. The capacity reduction in the IH 635 corridor has resulted in the diversion of traffic to the parallel routes. Forest Lane and Royal Lane are most affected in all the above scenarios. The IH 635 corridor will carry an average of 5% less traffic in the 4-0-0-4 scenario between US 75 and IH 35E, during the peak periods. This reduction in the IH 635 corridor traffic volume averages -21%, -48%, and -72% in the 3-0-0-3, 2-1-1-2, and 1-1-1-1 scenarios for all the time periods. The results also indicate that the closure of the HOV lanes

71 along the west section of the IH 635 corridor causes the least amount of traffic diversion to the parallel routes when compared to other closure scenarios. It is observed that the closure of one HOV lane in each direction will result in an average reduction of -3.85% in the peak period traffic along the IH 635 Corridor. However, the closure of each general purpose lanes introduces an average of about -16.8% reduction in the total daily IH 635 corridor traffic volume. This linear relation between number of closed HOV and general purpose lanes along the IH 635 corridor and the reduction in the corridor total daily traffic can be traced throughout the analysis scenarios. This results in a maximum increase of +42% in the AM and +28% increase in the PM peak period traffic volume along eastbound and westbound of Forest Lane, respectively, in the 1-1-1-1 scenario. The corresponding values for Royal Lane are +41% and +22%. The shift in the traffic volumes will also reflect in the reduction of the corridor average travel speeds. The IH 635 corridor experienced a maximum reduction of -58% in the average AM peak period travel speed in the westbound direction under the 1-1-1-1 scenario. The increase of traffic on the parallel routes introduces a speed reduction of -1% to -12% along the major and minor roadways in the study area. The change in the travel pattern described above is also reflected in the critical volume to capacity ratios (V/C) on the roadway network. Scenario 4-0-0-4 results in an increase of about +5% to +10% in the V/C ratio on the critical sections of the parallel routes. This value increases to around +10% to +30% under scenario 3-0-0-3. A short segment of Forest Lane close to IH 35E will experience an increase in the V/C ratio of up to +40%. However, in scenarios 2-1-1-2 and 1-1-1-1 the parallel routes will experience an increase of +20% to +40% in the V/C ratio on their critical sections. A maximum increase of about +60% is observed on the western segments of Forest Lane. The analysis results also indicate that scenarios 2-1-1-2 and 1-1-1-1 introduce high levels of increase in the V/C ratio at the two main entry points to the study area, the interchanges at US 75 and IH 35E. The above bottlenecks will prevent the vehicles approaching the IH 635 corridor from the eastern and western ends from accessing other viable routes.

7.1.5 Conclusions The implementation of any lane-closure scenario during the construction phase of the IH 635 Managed Lanes Project will introduce some levels of congestion to the network. However, the higher the congestion levels, the less the opportunities exist for mitigating them through the implementation of local improvements. The preliminary engineering level analysis results above show that the 4-0-0-4 and 3-0-0-3 closure scenarios introduce an average of about -10% decrease in the travel speeds of the IH 635 corridor and the parallel routes, a maximum

72 increase of about +20% in the average traffic volume on the parallel routes, and an average increase of less than +10% in the average travel times along the parallel routes. These levels of congestion could potentially be mitigated through the introduction of local improvements. The amount of these improvements will require a closer look at corridor traffic operations. This can be achieved through the development of a microscopic simulation model of the study area. However, this is most likely not the case with the 2-1-1-2 and 1-1-1-1 scenarios.

The above study and findings are presented in the LBJ (IH 635) Corridor Construction Scenario Analysis (2006).

7.2 VISSIM Analysis to Evaluate IH 635/IH 35E for the Interim and Ultimate Conditions

7.2.1 Overview A Traffic Operation Model was created to analyze the IH 635/IH 35E interchange for the Interim (2020) and Ultimate (2030) conditions. The microscopic simulation software, VISSIM was used to perform this analysis. The daily volume on each ramp was compared against the available capacity. If the volume on a General Purpose ramp was found to be higher than the available capacity, then the extra volume on the General Purpose ramp can be expected to shift to the managed lanes since they operate at a lower level of congestion. This philosophy was used wherever there was an option for traffic to shift to the direct connect managed lane ramps. The traffic volume using the managed lane itself was preserved from the Traffic Revenue Study (2006).

7.2.2 Interim Condition (2020) During the interim condition, the construction of the direct connect ramps connecting IH 635 and IH 35E on the east side are partially completed. Vehicles traveling northbound on IH 35E can either use the general purpose ramps or the managed lane ramps (to avoid congestion on the general purpose lanes at the merge) to access eastbound IH 635. Similarly, vehicles traveling southbound on IH 35E also have the option of using the managed lane ramps to access eastbound general purpose IH 635 lanes. Traffic was found to be slowing down at the beginning of the eastbound study section of IH 635, where drivers have to decide between continuing through on the general purpose lanes, exiting to IH 35E ramps and entering the managed lanes. The third location where a major bottleneck was observed was at the merge of eastbound/westbound IH 635 to northbound IH 35E. The length of the acceleration lane

73 (around 400 ft) was found to be inadequate to serve the demand at this location. The length of the eastbound and westbound ramp merge was also found to be too short.

7.2.3 Ultimate Condition (2030) Traffic volumes were generated for the year 2030 by applying a growth rate of 1.6% to the 2020 General Purpose volumes. The managed lane volumes were generated by applying growth rates from the Traffic Revenue Study to the 2025 volumes. The operation of the interchange in 2030 was found to be similar to the 2020 condition. The weaving section between the southbound/northbound to eastbound ramp and the entrance ramp to eastbound managed lane was found to operate fine, even in 2030.

A detailed study was prepared to document these findings.