how to clean sewers that are large, long, deep and submerged · · 2014-06-06how to clean sewers...
TRANSCRIPT
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
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
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• 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• 420 m3 of debris found mostly from Shaft 1to Diversion
Chamber
0
200
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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• 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