Trunk Main Case Study - Typepad
Transcript of Trunk Main Case Study - Typepad
Telephone: +64 9 963 2700Facsimile: +64 9 963 2701Email: [email protected]:www.projectmax.co.nz
Condition Assessment and RehabilitationPump Station 5 Gravity Mains
North Shore City
WWTP
PS5
Pump Station No.5
• Daily flows: 20,000 to 60,000 cum/day. • Storage: 6,500cum
Pumps Flowrate (l/s)1 350-420l/s2 650l/s3 1,100l/s
Rising Mains
PS5
View Rd
Gravity Main
Hydrogen Sulphide Attack
View Rd
Surface Damage
Surface Damage Location
Gravity Main
Areas of Hydrogen Sulphide Attack
• Near Manholes• Bends• Debris in sewer
Dig Up Samples
Areas of Hydrogen Attack
View Rd Trunk
Cured-in-place Pipe
Pump Station No.5
• Daily flows: 20,000 to 60,000 cum/day. • Storage: 6,500cum
Pumps Flowrate (l/s)1 350-420l/s2 650l/s3 1,100l/s
Backflowing through rising main
Bypass Pumping
Bypass Pumping
Pump Trials
• Pumps less efficient than expected• Leak in bypass main• Practiced contingency measures
CIPP Lining
CIPP Lining
Finished Liner
Stage 2 Rehabilitation
Issues
• Minimise Reduction of Cross Sectional Area
• Minimise Impact on Residents & Public • Minimise Risk of Sewer Overflows • Track Record and Experience• Cost
Options Considered - Discounted
Option IssuesCIPP Bypass pumpingOpen Cut Excavation Disruption. Higher CostSliplining Long lead in pitsSpayed Coating Non-structuralShort Patch Liner Turbulent flow at end of patchTroliner Unproven in New Zealand
Installer not experience with NSCC
Item Spiral Wound Liner Segmented Slip Lining
Reduction in Diameter 74mm liner can accommodate changes indiameter & minor deviations in pipe alignment.This relates to 88 % X sectional area of ex pipe.
• 80mm (20mm thickness & 20mmannulus). If the pipes are straight thenreduction in ID will be similar to SpiralWound Liner.
• If the ex host pipe deviates the IDreduction will be more. For example a 1ºdeflection will equate to 80 % of Xsectional area.
Impact on Residents • Access required to each manhole for Oneor Two days.
• Minimal excavation required ( possibleremoval of MH throat & cover ).
• Equipment can be removed at the end ofeach working day.
• 7m long launching pits required to beexcavated at 5 locations. 2 located onprivate property, 3 in road reserve butvery close to private property.
• Launch pits required for up to a week ateach location.
• Pits can be covered at the end of eachday but some equipment & materials willremain.
Risk of Overflows • Can be installed during pump shut downperiods.
• Equipment can be removed & flowsrecommenced with 30 min warning.
Similar to Spiral Wound Liner
Track Record & Relevant Experience • 1 project completed in NZ ( Hastings ).• Used extensively in Aust.• An experienced installation crew would
be mobilized from Aust.
• Similar work has not been usedundertaken in NZ.
• Segmented Slip Lining with GRP pipeshas been used extensively in India &Europe.
• Maskells ( the proposed pipemanufacturer) can call on experience inEurope through their relationship withTrueflow.
Item Spiral Wound Liner Segmented Slip Lining
Cost < $2,000 / m based on rates submitted for ViewRd lining Contract.
Estimated rate is $2,120 / m.
Risk Least Risk.• Contractor experienced with rehabilitation
method• Liner to accommodate changes in pipe
diameter & alignment.
Most Risk.• Contractor not experienced in installation
method• Construction delays possible which could
cause issues with residents & public• Cost overrun & variation claims possible.• Cross sectional area of liner may need to
be decreased to accommodate variationsin pipe alignment. Extent cannot beconfirmed until prover pulled throughpipe.
• Residents may object to largeexcavations on their properties.
• Resource Consent may be required forNoise.
Spiral Wound Liner Selected
• Proven method with experienced contractor• Reduction in Cross Sectional area known and not
affected by variations in host pipe alignment.• Far less disruption to residents & public• Less risk of cost or time over runs.• Expected to be the cheapest option.
Rotoloc – Liner Installation
Rotoloc - Grouting
Issues
• Man-Entry required• Flows Shutdown• Bends• Change in Diameter
Summary
• Condition assessment, risk approach• Select the most appropriate method for
each circumstance• Construction & maintenance practices
can influence H2S• Bypass Pumps do no perform as
expected• Trial everything
Summary
• The bigger the pipe, the more complex the rehabilitation
• Greater the consequence of a problem• Team effort• Planning, planning, planning