BACHMAN INTERCEPTOR

A SUCCESSFUL 48-INCH

MICROTUNNEL AROUND AN URBAN LAKE

PRESENTERS

� Erick Steitle – DWU Project Manager

� Troy R. Hotchkiss, P.E. – Project Engineer

� Ashok Varma, P.E. – Project Principal

UCTA

NORTH TEXAS CHAPTERMay 19, 2016

INTRODUCTION

GENESIS-HISTORY� Bachman Dam Rehabilitation

� Comprehensive Wastewater Collection System Assessment

� Overlapping Priorities & Infrastructure Renewal Needs

� Schedule

PRESENTATION OVERVIEW

� Project Challenges

� Public Relations Campaign

� Design Considerations, Bidding Constraints

� Third Party Construction Management Services

� Results and Takeaways

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PROJECT LOCATION

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PROJECT NEEDS

BACHMAN DAM

� Aged Interceptor under right

arm of main dam embankment

� Conventional pipe trench/fill

may contribute to leakage

EXISTING PIPELINE CONDITION

� Age – 50-years

� Materials - RCP

� Deflected, corroded

CAPACITY

� Exist. pipe capacity = 25-mgd

� Forecast 2040 flow = 33-mgd

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PROJECT CONSTRAINTS

LAND USE

� Bachman Lake and Park

� Bachman Hike/Bike Trails

� Bachman Rec. Center

� Unique “Urban Forest Setting”

EXISTING INFRASTRUCTURE

� FAA Air Traffic Controls

� Existing Overhead Power

� UG Power, Gas, Telecom

� Unknown Private Lines

� Conventional pipe trench/fill

may contribute to leakage

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CONSTRAINTS ANALYSES

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PROJECT ISSUES AND CONSTRAINTS

� Right-of-Way

� Stakeholder coordination

� Public impacts

� Hydraulic analysis

� Traffic volume

� Utility conflicts

� Environmental constraints

� Constructability

� Geotechnical

� Permitting

� Long range planning

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APPROACH TO

COMMUNITY COORDINATION

� Early detection, identification and

prioritization of risks

� Better control and project execution

� Micro tunneling and open cut work

� Proactive public relations strategy

� Coordination with Parks Department

� English and Spanish public notices

� Multiple public meetings

� Coordination with contractor

� Led to minimization of risks

� Opportunities for successful delivery

� Outcome = Success

� Minimal complaints from public

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GROUND CONDITIONS

STAGED GEOTECHNICAL

INVESTIGATION

� Desktop Study

� Wide-spaced borings

� Borings at shaft locations

� Piezometers and Slug Tests

MIXED FACES

� Soft Rock lower 1,000-LF +/-

� Running Sands/Gravels

majority of alignment

� Clayey Sands / Sandy Clay

pockets suspected

GROUNDWATER

� Next to Lake + Sandy Ground

= HIGH GROUNDWATER

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TUNNELING METHOD SELECTION

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TUNNELING METHOD SELECTION

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TUNNELING METHOD SELECTION

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DEVELOPMENT OFCONSTRUCTION CONTRACT

� By other than open cut

� Used for road /railroad Crossings

� Very little owner control

� Local = Hand mining

� Business as usual

� Local construction capabilities

� Agency expertise and experience

� Is project big enough for “tunneling”?

AT THE SPEED OF LIGHT UCTA

BIDDING OF MICROTUNNEL CONSTRUCTION

� Provided detailed specifications� Included microtunnel methods

� Provided for tree protection

� Assured protection of public

� Attracted competitive bids� Three bidders

� Bids were close to engineer’s OPCC

� Bids were within DWU’s budget

� Final construction cost was within

budget

Project considered a success UCTA

SPECIAL CONTRACT REQUIREMENTS

� ASCE Standard 36-01 microtunnel guide

� Earth pressure balance microtunneling

� High groundwater impact

� Public safety

� Impact on park and community

� Risks recognized:

“If, in the sole opinion of and at the full risk attributable

to the CONTRACTOR, the work may be safely

accomplished by alternative methods on the same or

better schedule, the CONTACTOR may submit a

request to use alternative tunneling methods.

Requests for alternative construction techniques

prepared in accordance with Section 01640 and

detailing the means and methods of performing the

work will be reviewed by the OWNER on a case-by-

case basis.”

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SPECIAL CONTRACT REQUIREMENTS

� Tunnel safety considered (S-35)

� ANSI/ASSE A10.16-2009 – Safety

Requirements for Tunnels, Shafts, and

Caissons

� Protection of public considered (S-36)

� ANSI/ASSE A10.34-2001 (R2005) –

PROTECTION of the Public on or Adjacent

to Construction Sites

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TREE PROTECTION IN PRACTICE

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CONSTRUCTION CONTRACT DEVELOPMENT

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THIRD PARTY

CONSTRUCTION MANAGEMENT

� Submittal review by all parties

� DWU , PARD and FAA, stakeholders

� Limited project issues and risks

� MS One Drive sharing technology

� Instantaneous information sharing

� Planned coordination & communication

� Better decisions

� Verified contractor’s execution of the work

� Contractor oversight

� Better quality assurance and control

� Minimization of risks to the owner

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PROJECT SUMMARY

• Schedule

– Completed in 586 continuous working days

– Within allotted time as extended

– Acceptance on 3/25/2016

• Budget

– Budget cost = $15,291,612

– Final cost = $15,273,856

• Coordination:– Major effort and continuing focus

• Management

– City involved in design & construction

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TAKEAWAYS FROM A SUCCESSFUL PROJECT

� Holistic planning

� Alignment study and early Stakeholder buy-in

� Detailed technology evaluation

� Microtunneling solution

� Had to be resolute

� Assumption of appropriate risks

� Use of 3rd party CM

� Focus on community impacts

� Public relations

� Stakeholder coordination

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