Mill woods Double Barrel-SESS SA1B/C Project

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ROUTING Utility Committee | DELEGATION - A. Laughlin, T. WymanFebruary 26, 2016 Integrated Infrastructure Services CR_3326Page 1 of 7

Mill woods Double Barrel-SESS SA1B/C ProjectProject History and Status (M. Nickel)

Recommendation:That the February 26, 2016, Integrated Infrastructure Services report CR_3326, berecieved for information.

Report Summary

This report provides information and history on the Mill Woods Double BarrelReplacement/SESS SA1B project, summarizes the challenges encountered andthe actions that were taken, and provides an estimate of the total project costs, arecommended budget increase and the final completion schedule.

Previous Council/Committee Action

At the October 20, 2015, City Council meeting, Councillor M. Nickel made the followinginquiry:

The Mill Woods Double Barrel-SESS SA1B Project involves the construction of amajor storm trunk to form the backbone infrastructure to mitigate flooding in theMillwoods area, thereby involving the construction of a major sanitary trunk along 91street (10 avenue to 28 avenue). A portion of this project also includes work along 23avenue and 85 street.

Originally planned for completion by 2014 with a budget of $56.9 million, the cost ofthe Mill Woods Double Barrel has escalated to a currently approved budget of $90.1

million and is projected to be completed in 2016.

Given these drastic cost and scheduling escalations, I would like Administration toprovide a report on the following:

1. A brief history of the overall projects from its inception, this is to includethe engineering rationale for this line and the underlying rationale of this projectsoriginal budget.

2. What has been done to understand the current nature and severity of the problemsassociated with this project of which shall include:

a. Worse than anticipated ground conditionsb. Resulting reduction in tunneling productivityc. Changes in construction methodsd. Additional geotechnical testing, project scope changes, and repair issues causedby poor supporting soil conditions


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Mill woods Double Barrel-SESS SA1B/C Project - Project History and Status(M. Nickel)

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3. As there have been at least three budget adjustment requests, what is theanticipated total overall costs of this project and what will be its firmcompletion/opening date?

Report

The Mill Woods Double Barrel Replacement/South Edmonton Sanitary Sewer StageSA1B project was approved by Council under Capital profile 08-31-9202. The projectscope includes two components: the Mill Woods Double Barrel Replacement and theSouth Edmonton Sanitary Sewer Stage SA1B. With a collective budget of $90.1 million,this is one of the largest and complex capital drainage projects undertaken by the Cityof Edmonton in over 35 years. The South Edmonton Sanitary Sewer Stage SA1Bproject was completed on schedule and within the allocated budget.

Mill Woods Double Barrel Replacement ($74.6 million) - Project HistoryAs a result of the significant rainfall events in July 2004, over 400 homes within the Mill

Woods area were flooded, prompting engineering studies to be commissioned toassess the causes of flooding and to develop a flood mitigation program in Mill Woodsand other areas of the City. Studies determined that in order to reduce the risk offlooding, the capacity of the existing double barrel trunk sewer in Mill Woods needed tobe increased as the primary conveyance system to support neighbourhood drainageimprovements. The existing Mill Woods Double Barrel carries sanitary and storm sewerflows in isolated chambers within the same pipe. Attachment 1 shows the location ofthe new trunk sewer, the neighbourhoods with ongoing and planned flood mitigationprojects, and the ultimate area where flooding will be mitigated when all of the projectsare complete.

The solution for increasing the existing stormwater capacity was to construct a newstorm trunk to accommodate the stormwater flows and to convert the double barrel pipeto convey only sanitary flows. This approach formed the basis of the Mill Woods DoubleBarrel Replacement project. Attachment 2 shows the alignment and diameter of thenew storm trunk, which runs from Gateway Boulevard/30 Avenue to 85Street/Knottwood Road. This is also the same alignment for the existing double barrelpipe. Key stages of the project include:

Conceptual design (as part of an overall Mill Woods flood relief program) (2006) Design Build of tunnel and storm sewer connections for:

o 30 Avenue (2009)o

91 Street (2011)o 23 Avenue (2012)o 85 Street (2013)o Converting existing double barrel into a full sanitary sewer (2013)

Once the Mill Woods Double Barrel Replacement and neighbourhood flood mitigationinfrastructure projects are completed, flooding risks will be reduced and the associatedneighbourhoods will be provided a storm system designed for a 1 in 100 year event.


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The conceptual design completed in 2006 did not include details related to connectionsbetween the Mill Woods Double Barrel and neighbourhood feeder pipes or detailedgeotechnical analysis. The detailed design process was initiated in 2007 and includedgeotechnical and formal risk assessments by external consultants. Boreholes weretaken along the proposed alignment of the new storm trunk sewer with an averagespacing of about 130 metres. Typically borehole spacing varies between 90 and 200metres.

This initial geotechnical investigation identified soil conditions as predominantly clay tilland bedrock material, and previous experience tunneling in these conditions have beenpositive. There are risks with glacial till as it is known to contain random water bearingsand layers and various sized rocks that could impede tunnel progress.

The initial budget of $41.4 million was approved based on estimates developed in the2006 conceptual design, historical tunnel cost information, and historical productivityrates. As the design and construction progressed along the 30 Avenue and 91 Street

tunnels, it was determined that the conceptual estimate was insufficient and the budgetwas adjusted to $56.9 million. As the initial budget was developed based on aconceptual design, the complexity and the costs of connections were not fullyunderstood and were underestimated. Given the lack of geotechnical informationavailable at the time, the productivity rates were also underestimated for soil conditionsthat were actually encountered.

ChallengesThe challenges with the Mill Woods Double Barrel portion of the project are primarilyattributed to lack of details during conceptual budget development and unanticipatedground conditions.

Scope DefinitionIn-house tunnel construction such as the Mill Woods Double Barrel Replacementtypically follows a design-build approach in which the conceptual design is developed,followed by the detailed design and construction occurring concurrently. This approachoffers efficiencies and schedule compression by allowing components of construction tostart when enough details have been developed. As construction progresses, theremaining design is completed. Under a design-bid-build model, the design iscompleted in full prior to construction being initiated. Additionally as this tunneling workis completed with internal resources, all risks are assumed by the City compared tousing an external contractor where a significant portion of the risk is transferred.

The overall sequence of events for in-house design and construction are: conceptualdesign progressing into design-build.

Conceptual design - During conceptual design, service levels are defined and differentalignment options are evaluated. Once a preferred alignment is selected, conceptualestimates are developed predominantly based on historical data and the experience of


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design and construction staff. Capital profiles are typically developed based on theconceptual estimates including the Mill Woods Double Barrel Replacement.

Design-build - During initial design, geotechnical investigations are performed,alignments/shaft locations/structure configurations are refined, project constructability isvalidated, and more detailed risks are assessed. Once these elements are completed,detailed design is initiated and some portions of construction begin. Detailed design andconstruction activities overlap through the progression of the project.

A cost estimate was developed in concept design and a capital budget was submittedprior to any detailed assessment of the neighbourhood connections from the new stormtrunk to the existing system. As the detailed design was developed, it was determinedthat the complexity and scope of the connections were underestimated, resulting inincreases to both the costs and the time to complete these connections from the originalbudget submission. Through the 2013 Supplementary Capital Budget Adjustmentprocess an additional $15.5 million was requested for a total of $56.9 million for the Mill

Woods Double Barrel Replacement project.

The development of the new Integrated Infrastructure Services department will helpaddress this issue by integrating the concept development and build functions to betterinform scope definition at the concept phase. In addition, based on the scale andcomplexity of projects, designs will be developed in more detail prior to capital budgetsubmissions to help address the variability between approved budgets and actual costs.

Soil conditions

The Mill Woods Double Barrel Replacement project encountered significantgeotechnical challenges near the intersection of 91 Street and 23 Avenue. As the

construction of the project proceeded along 91 Street approaching 23 Avenue, thetunnel excavation experienced poor soil conditions consisting of wet running sand. Soilmovement at 23 Avenue also caused significant damage to the recently completedSouth Edmonton Sanitary Sewer Stage SA1C. Repairs to the South Edmonton SanitarySewer Stage SA1C were included in the Mill Woods Double Barrel Replacement projectcosts. Mitigation measures were developed and implemented as each issue wasencountered. Attachment 3 provides a more detailed chronology of the issues andmitigation measures.

Utilizing the iterative approach in the design build methodology the first mitigation effortsincluded reducing water levels within the wet sand and performing additional

geotechnical investigations to delineate the limits of the wet sand. Following theseefforts, tunnel excavation continued and the tunnel alignment was ultimately modified tocurve from 91 Street to 23 Avenue to avoid the poor soil conditions at 23 Avenue.Tunnel excavation once again was halted to address a void created by wet sand in frontof the tunnel boring machine. The void was filled and excavation was able to continueuntil the tunnel boring machine was damaged by a boulder and was flooded with wetsand. Efforts were taken to stabilize the ground in front of the machine, however, the


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damage did not allow tunneling to continue. Additional geotechnical investigations along23 Avenue and ground stabilization designs were initiated once the tunnel machine wasdamaged. In an effort to minimize schedule impacts, an alternate method of using in-house sequential hand tunneling construction combined with ground stabilization of thesoil was initiated. Construction work proceeded along 23 Avenue in conjunction with theground stabilization design. The hand tunneling method was successful for a portion ofthe 23 Avenue tunnel, however unsafe conditions prevented the hand tunneling fromcontinuing. As a result of the challenging soil conditions between 91 Street and 23avenue, the unsuccessful attempts with City construction technology and additionalgeotechnical details a contractor was retained to implement a tunneling technologyspecific to variable wet sand conditions. Concurrently, in-house tunnel resourcescontinue construction on the remaining portions of the project.

As part of the 2015-18 Capital Budget process, an additional $17.7 million wasincorporated into the project to address the additional costs required to address the soil-related issues encountered. This revised the total Mill Woods Double Barrel

Replacement project budget from $56.9 million to $74.6 million. A detailed review of theprojects remaining scope has identified additional risks and construction costs of $6.4million associated for the remaining work. The final actual costs may be lower as aninsurance claim may recover costs associated with the damaged tunnel boring machine.

Administration will include this budget request in the Spring 2016 Capital Budgetadjustment for Councils consideration. The additional budget increase of $6.4 millionwould be debt financed over 25 years and will have minimal impact to Drainage Utilityrates.

Project Costs and ScheduleAs a result of the conceptual scope definition and the challenging soil conditions the

initial budget and schedule were not reflective of the actual needs associated with thecomplexity of the Mill Woods Double Barrel project. The iterative approach utilized todeliver the project has necessitated the need for budget and schedule adjustmentsthroughout the project. Costs associated with this project to-date are as follows:

Original Budget - Mill Woods Double Barrel Project$41.4million

Supplemental Capital Budget adjustment (2013) - Mill Woods Double BarrelReplacement, related to budget development

$15.5million

2015-18 Capital Budget process - Mill Woods Double Barrel Replacement,

related to soil conditions and connection complexities

$17.7

millionAdditional budget to be requested through Spring 2016 Supplemental CapitalBudget Adjustment

$6.4million

Total Required Budget - Mill Woods Double Barrel Project$81.0million

Total Budget - South Edmonton Sanitary Sewer Stage SA1B $15.5


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million

Total Overall Budget (Mill Woods Double Barrel Project + South EdmontonSanitary Sewer Stage SA1B)

$96.5million

The original schedule for the completion of the Mill Woods Double Barrel Replacementproject was December 2013. The estimated milestone dates for the remainder of theproject are:

30 Avenue Complete and in service

85 Street (excluding surface restoration) August 2016

23 Avenue (excluding surface restoration) December 2016

91 Street January 2017

Convert existing double barrel into a full sanitary sewer March 2017Site and surface restoration August 2017

As the project continues, Administration will continue to look for ways to complete theproject ahead of the revised schedule.

Lessons LearnedBased on the experience for this project, a number of actions will be implemented tohelp mitigate similar issues in the future, including:

Developing budgets to an appropriate level based on complexity and scale of the

project Regular communication to Council and citizens on the status of the project and

more frequent updates when experiencing issues Assessing the amount of geotechnical investigation required for tunnel projects Risk-based decision making process to select the appropriate construction

methodology

Budget/Financial Implications

The original approved budget was $56.9 million (Mill Woods Double BarrelReplacement $41.4 million, South Edmonton Sanitary Sewer SA1B $15.5 million). MillWoods Double Barrel Replacement budget adjustments of $15.5 million and$17.7 million were approved as part of the 2013 Supplemental Capital Budget

Adjustment and the 2015-18 Capital Budget, respectively. These adjustments bring thetotal approved budget to $90.1 million (Mill Woods Double Barrel Replacement$74.6 million, South Edmonton Sanitary Sewer SA1B $15.5 million).

Administration is recommending through the Spring 2016 Capital budget Adjustmentthat the budget for the Mill Woods Double Barrel Replacement project be increased to


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$81 million in order to complete the project. This would increase the entire capitalprofile, including the South Edmonton Sanitary Sewer SA1B projects, to $96.5 million.

Attachments

1. Mill Woods Flood Mitigation Program

2. Mill Woods Double Barrel New Storm Trunk Alignment3. Issues and Mitigation Chronology

Others Reviewing this Report

T. Burge, Chief Financial Officer and Treasurer and Acting General Manager,Corporate Services.

D. Wandzura, General Manager, Transportation Services

Documents

Mill woods Double Barrel-SESS SA1B/C Project