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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