Presented by: Colin Goodwin, P.Eng.

How to Clean Sewers that Are Large, Long, Deep and Submerged

Presentation Outline

1 Background

2Objectives

3 Planning

4 Tender Document

5 Inspection

6 Findings

7Conclusion

Background

Failure of critical infrastructure can have disastrous consequences. Knowing its condition is key to maintaining infrastructure.

1

Background – Existing Sewer• Orleans Cumberland Collector (OCC) is a 1676

mm dia. concrete sewer installed by tunnel methods in 1970’s

• 22% of City’s peak dry weather flow

• 5.1km long & 18m depth

• Limited access, up to 1590m between two of the access structures

• Pipe honeycombing and debris on sewer at WWTP

Plan – Orleans-Cumberland Collector

1590m 1530m 610m 725m 660m

New OCC Pump Station

Liquid Hauled Waste

Pipe Exterior Honeycombing

Honeycombing

Sections Observed With Sedimentation

Objectives

Due to recent findings, it was imperative to determine:• Severity of pipe defects• Debris quantity and profile

2

Planning

A proper understanding of what exists is key to developing an effective plan to meet the project objectives.

3

Planning• Data collection and field investigations to determine

volume of sediment and condition of OCC

• Preparation of drawings of OCC and shafts

• Determine access requirements

• Meetings with City of Ottawa (City) departmentsto determine operating requirements during inspection

• Permitting requirements with outside agencies

• Assess various inspection technologies

• Select technology to obtain required information

OCC Profile

Existing OCC Pipe Cross Section N.T.S

Tender Documents

Needed to be fair, account for project constraints, use theright tools and define data collection requirements.

4

Tender Documents• Selected multi-sensor platform (CCTV, Sonar and Laser)

• Ability to minimize drawdown time of pumping station to inspect OCC (<8hrs)

• Must coordinate with City Operations

• Must work with existing flow conditions

• Provided extensive drawing set for plan & profile including shaft details

• Must collect at least 80% of data within each reach

• Number of submittals required

Inspection

Development of a plan that considered project constraints and data capture needs.

5

Inspection• Contractor proposed a floating platform

for inspection (CCTV, Laser and Sonar)

• No umbilical cord(s) due to the lengths of inspection

• Battery operated (~3hr life)

• Deployment speed recommendedby the Contractor was 9 to 11 meters/minute, controlled by plasma tether and winch at upstream access

Inspection (cont.)• 3 days of field work to complete entire

length of OCC

• First run between less critical section Shaft 2-1 in order to ensure smooth operation (1,560m);

• Second run between Shaft 1 to the new Diversion Chamber required drawdown of OCC (1,590m)

• Third run from Shaft 5 to Shaft 2. (1,995m). Battery change at Shaft 3

Findings

Data collected definedrehabilitation needs.

6

Findings• 420 m3 of debris found mostly from Shaft 1to Diversion

Chamber

0

200

400

600

800

1000

1200

1400

1600

0 200 400 600 800 1000 1200 1400 1600

Dept

h (m

m)

Distance from Shaft No. 1 to WWTP (m)

OCC Debris Profile (Shaft No. 1 to WWTP)

Sonar data lost through active drop shaft.Debris reached maximum 45% of pipe

Findings (cont.)• Most debris accumulated around liquid

hauled waste connection

• Some grease in downstream section

• Some exposed aggregate at 12 o'clock position, mostly in the last 700m

• No major defects noted

Conclusions

Project findings established plan to move forward.

7

Conclusions• Keys to Success:

o Planning and understanding system limitationso Detailed specificationso Coordinationo Selecting correct technologieso Selecting qualified contractors:

• Inspection and reporting• Confined space work• Detailed paperwork for approvals

Conclusions (cont.)• No urgent repaired required

• Inspection result used for development of cleaning tender (fair to both contractor and client as conditions are known)

• Initial estimates of debris was 2,000m3, multi-sensor inspection found only 420m3

• Majority (95%) of the debris located within the lower section of the OCC

• Level of confidence with multi-sensor remote platform for inspection of other difficult trunk sewers

Acknowledgments• City of Ottawa

• PipeFlo Contracting Corp.

• RedZone Robotics

• Doran Contractors Ltd.

• Stantec Consulting Ltd.

8

Questions?

For more information:

Colin Goodwin, P.Eng., Environmental Engineer, Stantec Consulting. Ltd

Colin.Goodwin@stantec.com