Dahlia Ponds Tunnel Project Case History

DAHLIA PONDS TUNNEL PROJECTCASE HISTORY

Presented By: Nathan Soule, PE, PG Brierley Associates&

Brenden Tippets, Project Executive, BTrenchless

Dahlia Ponds Tunnel Project

OutlineDahlia Ponds Tunnel Project

Owner’s Approach Design & Engineering Construction

Project LocationDahlia Ponds Tunnel Project

Project LocationDahlia Ponds Tunnel Project

Modified Design-BuildDahlia Ponds Tunnel Project

Denver Urban Drainage needed a new approach to tunnel construction Past problems with O’Brian Canal Tunnel

Hired tunneling expert – Brierley Associates (Lyman Henn division)

Retained Qualified Contractor BTrenchless early on

Independent estimator – Bids must be within 10%

EngineeringDahlia Ponds Tunnel Project

Evaluate feasible/allowable methods Subsurface exploration with Contractor

involvement

Test PitsDahlia Ponds Tunnel Project

Cobbles & Boulders Groundwater

Tunneling/Trenchless MethodsDahlia Ponds Tunnel Project

Method Details Advantages Complications

Microtunnel Closed Face• Slurry• EPB

Works for most conditions

High costCobbles < 1/3 TBM dia

Pipe Ramming – Common

Rapid & lost costPenetrates through cobbles

Limited distanceLine & grade deviations

Pipe Ramming – Guided

• Pilot tube• HDD

Accurate line & grade Pilot tube penetrationMultiple up-sizes

Conventional Shield • Sand shelves• Breasting

VersatileAdaptable

Above water tableMed – large dia. only

Open Face TBM Rotating headInexpensive* Limited application

Not well suitedAuger Bore Jacked pipe w/ auger

Ground Improvement • Grouting• Dewatering

Available as supplement

Trial Horizontal Directional DrillDahlia Ponds Tunnel Project

Multiple Attempts

Stopped by cobbles/boulders

Determined guided ram not feasible

Team decided on microtunneling for I-76

Team Effort

Owner •Urban Drainage/ Adams County

Engineer •ICON Engineering/Lyman Henn, a division of Brierley Associates, LLC

Contractor •Btrenchless, a division of BT Construction, Inc.

SUBS •Kelley Dewatering, Garza Concrete, Inlet Structures, Ralph Martinez trucking.

Suppliers •Akkerman, Derrick, Microtunneling, Inc., Wyo-ben, Inc.


Project Purpose

BTrenchless completed one 240 LF microtunnel and one 60 ft rescue tunnel.

Design/build of two tunnels for storm sewer, including test pits of existing ground conditions.

240 LF of 54” Tunnel to be completed without disruption of above I-76 highway.

60 LF of 84” rescue Tunnel to be completed online and grade to match existing failed tunnel 30 ft below grade.




Project Scope

Various construction methods used to account for the diverse ground conditions:

Microtunnel Hand Tunnel

Sizes of the installed tunnels ranged from 54” to 84” diameter.


Project

Test pit ground conditions

HDD Pilot hole

MTBM (Microtunnel

Boring Machine)Separation Plant

Entry Shafts and Seals

GeneratorsAutomatic Bentonite

Injection System

Dewatering system


Microtunnel Machine

AKKERMAN

Microtunnel Boring Machine SL 51 125 HP Head


Microtunnel MachineDahlia Ponds Tunnel Project

Microtunnel Machine

Akkerman MC-4 Jacking Frame


Separation Plant

DERRICKSeparation Plant

(3) FLC 2000 4-Panel High “G” Shaker Decks

(1) FLC 2000 Mud Cleaner Hydrocyclone System


Separation PlantDahlia Ponds Tunnel Project

Separation PlantDahlia Ponds Tunnel Project

Quantifying Material (Onboard Weighing System )

Product Totals Multiple Point Weighing Split Weighing Auto Target Function Auto Tare Function Error Alarms Data Fields Unit Conversion Multiple Batching Modes Tip-off Weighing Zeroing Auto Add Mode Data Analysis Remote Add Button


Entry Shafts

GME – Slide Rail System


Exit / Entry Seal

Microtunnel Inc. Entry Seals


Generators

400 KW Generator 550 KW Generator

(3) 75 KW Generators


Automatic Bentonite Injection System

MICROTUNNELING, INC.


Dewatering System

Ground water contamination

treatment:

(6) Weir tanks(1) Air Sparging 300 cfm (4) Mezzi air injection

units


Known Significant Challenges

Schedule Purchase of Equipment- Short time frame Shaft Construction Contaminated ground water up to 2000 GPM Shallow cover of tunnel under I-76


Proposed Solutions

CHALLENGE•Schedule

SOLUTION•Internal weekly meetings•Detailed scheduling•Other existing tunnel

contracts


Scheduling

Successful scheduling- project completed 30 days ahead of original schedule.

Provide the owner with feasible schedule in order to anticipate possible changes.


Proposed Solutions

CHALLENGE•Purchase of

Equipment

SOLUTION•In-house evaluation of all equipment

needed•Research other industry leaders and their

equipment•Interview other contractors about

performance of the equipment•Date of delivery


Dahlia Microtunnel Equipment

Base Microtunnel MTBM #1 MTBM #2 MTBM #3 Separation Equipment MTBM #1 MTBM #2 MTBM #3 Intermediate Jacking Equipment MTBM #1 MTBM #2 MTBM #3

Control Container Slurry Volume Hydraulic Hose

Microtunneling Head Shaker Jacking Force

Steering Head OD Hydrocyclones First Stage Trust Rings

Steering Head Length Excl Cutter Hydrocyclones Second Stage Hydraulic Cylinders

Steering Pressure Unit Size High Pressure Jetting

Number of Steering Cylinders Slurry Tank MTBM #1 MTBM #2 MTBM #3 Jetting Pump

Steering Cylinder Stroke First Chamber Length Jetting Starter Hose

Steering Cylinder Force Second Chamber Length Jetting Tunnel Line

Bypass Valve Overflow Height Bentonite System MTBM #1 MTBM #2 MTBM #3

Drive Motor Guidance System MTBM #1 MTBM #2 MTBM #3 Bentonite Pump

OD Ring Electric Control Box

Power Cable Connections and Extensions MTBM #1 MTBM #2 MTBM #3 Valve and Junction

Stand Alone Unit Tunneling Connections Tunnel Cords

Starter Set Trunk Line Volume

Steering Angle Trunk Line Storage Max Pressure

Computer Hardware Aux Equip Power Cable Pressure Can

Nominal Drive Torque Main Control Cable Supply Can

Trailer Section Length Booster Pump Cable Volume Mixer

Trailer Section OD Hydro Elec Launch Connections Volume Storage

Lead Can Weight Connection Cable Container Electrical Power

Trailer Section Weight Steering Cable Head Power Supply Cable

Cutter Head Weight Extension Hose Hydraulic Bentonite Pipe

Operating Pressure Distance Wheel Auto Bentonite Lube System MTBM #1 MTBM #2 MTBM #3

Slurry Circulation System MTBM #1 MTBM #2 MTBM #3 Emergency Shut Off

Slurry Feed Pump Connection Cable Power Supply Head Entr/Recep Seal for Pipes MTBM #1 MTBM #2 MTBM #3

Slurry Return Pump Drive Motor Cooling

Circulation System Starter Set Purchase Items Training and Service MTBM #1 MTBM #2 MTBM #3

Slurry Line Pipe Jacking Equipment MTBM #1 MTBM #2 MTBM #3 Travel Time

Slurry Line Launching Set Jacking Frame Weekdays

Set of Flow Meter Jacking Pit Overtime and Saturdays

Slurry Container Jacking Force Sundays and Holidays

Length Max Pipe OD

Width Pipe Length

Height Operating Pressure

Inlet Diameter Number of Strokes

Outlet Diameter Jacking Unit Drive

Hydraulic Oil Tank Capacity

Jacking Unit Extension

Proposed Solutions

CHALLENGE•Shoring of wet shafts In

cobble and running sands

SOLUTION•Provide a realistic approach

to anticipated GPM. •Determine best/cost

effective method of construction.


Shaft ConstructionDahlia Ponds Tunnel Project

Proposed Solutions

CHALLENGE•Handling of

contaminated ground water

SOLUTION•Discuss potential problems up front

with owner. •Involve state regulatory agency, so

they are aware and will be on-board with potential problems.

•Evaluate most cost effective treatment.


Contaminated ground water

Treatment of 2000 GPM system

Treatment of Dissolved Manganese Total Iron Dissolved Iron


Proposed Solutions

CHALLENGE•Shallow cover of tunnel

SOLUTION•Lengthen bore to enter

farther down slope•Monitor entry point for

possible settlement


Shallow cover

Slurry returning to the surface

Install foam injection to stabilize face


Completion of Work

Overall BTrenchless completed the two tunnels in 3 months, including all structures and appurtenances approximately 1 month ahead of schedule

Maintained good relationships with owner, engineers and the community, with little disruptions


Lessons Learned

Think outside of the box (never accept “this is how we’ve always done it”)

Practice teamwork and adhere to advice from other industry leaders

Success comes from lessons learned


Questions?


Phone: 303-286-0202Fax: 303-286-1262

www.BTrenchless.com

Phone: 303-469-0199Fax: 303-466-8309

www.BTConstruction.com

9885 Emporia Street Henderson, Colorado

80640

110 16th St. #700Denver, Colorado

80202

Phone: 303-534-1100Fax: 303-534-1777

www.lymanhenn.com

Documents

Dahlia Ponds Tunnel Project Case History