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Remove Existing Sewer Mains

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In sewer removal jobs, the existing sewer main is either completely removed or left in place and grout-filled. The purpose of removal could be:
✔ Upgrading the sewer main.
✔ Diverting flow to a new alignment.
✔ Disusing an old sewer that is no longer required.

A site visit is crucial for pricing these jobs correctly, as factors such as depth, structures, ground conditions, and disposal costs significantly impact costs.

1. Two Methods of Sewer Main Removal

A. Full Removal of Existing Sewer Main

✔ The entire sewer pipe and structures are removed from the ground.
✔ Requires excavation to full depth of the sewer line.
✔ Manholes and structures must be demolished and disposed of.
✔ After removal, the trench must be backfilled with imported fill and compaction tested.

💰 Cost Considerations for Full Removal:
🔹 Exact sewer depths must be determined to estimate excavation costs.
🔹 Manhole & structure removal requires demolition and disposal.
🔹 Tip fees for disposal (concrete, general waste, PVC contamination).
🔹 Import fill for backfilling must be included in pricing.
🔹 Compaction testing by geotech companies adds additional costs.

B. Disconnection & Grout Filling (Disused Sewer Main)

✔ The sewer pipe is left in the ground but must be grout-filled to prevent collapses or voids.
✔ Requires a survey to locate the start and end points of the disused section.
✔ Grouting must be closely monitored to avoid overspilling (laser bore grout is expensive).
✔ Any structures/manholes in the disused section must be assessed for grouting or demolition.

💰 Cost Considerations for Grout Filling:
🔹 Surveying costs to confirm pipework locations.
🔹 Pipe size and total length of disused run impact grout quantity.
🔹 Number and depth of manholes (if part of the disused system).
🔹 Crew size must allow for monitoring grout flow and stopping at the right time.
🔹 Avoiding waste of expensive laser bore grout.

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2. Site Visit – Crucial for Accurate Pricing

📌 Before quoting a sewer removal job, a site visit is essential to:
✔ Identify the exact sewer alignment and depth.
✔ Determine the type of manholes & structures in the run.
✔ Assess site access for excavation & disposal.
✔ Check if backfilling materials need to be imported.
✔ Contact disposal sites (tips/recyclers) for accurate fees.

3. Manhole & Structure Removal – Estimating the True Cost

A. PVC Maintenance Shafts

✔ Easy to remove – cut out and dispose.
✔ Disposal is straightforward, but PVC may be classified as contaminated waste.
✔ Check with disposal sites for PVC pipe tipping fees before quoting.

B. Concrete Manholes

✔ Much harder to remove – must be excavated, demolished, and disposed of.
✔ Requires breaking into smaller pieces for transport.
✔ Tip vs. Concrete Recycler:

  • Concrete recyclers accept clean concrete at a lower rate.
  • If the concrete is contaminated (e.g., with sewage residues), the tip will classify it as general waste, which costs more.
    ✔ Calling the tip beforehand is recommended to confirm disposal rates.

💰 Cost Factors for Concrete Manhole Removal:

🔹 Excavation depth affects time and cost.
🔹 Breaking and loading costs – large excavators and rock breakers may be required.
🔹 Transport and tip fees – confirm pricing with disposal facilities.

4. Disposal Cost Considerations

✔ PVC Sewer Pipes: Some tips classify PVC as contaminated waste, which costs more to dispose of.
✔ Concrete Manholes: Must be broken down before disposal.
✔ General Waste vs. Recyclable Concrete:

  • If disposed at concrete recyclers, the cost is lower.
  • If taken to a general waste tip, costs can be significantly higher.
    ✔ Contacting the disposal facility in advance ensures accurate costing.

5. Backfilling & Compaction Testing

Once the sewer main and structures are removed:
✔ The trench must be backfilled with approved material.
✔ Imported select fill may be required, adding to costs.
✔ Compaction testing by geotechnical engineers is mandatory to meet Sydney Water standards.

💰 Cost Considerations for Backfilling & Compaction:
🔹 Material type and quantity – select fill is more expensive than ordinary backfill.
🔹 Compaction layers – testing is required every 150mm for deep trenches.
🔹 Geotech supervision – Level 1 compaction testing required for depths over 3m.

6. Summary – Key Takeaways for Sewer Removal Estimates

✔ Determine if the sewer is to be completely removed or grout-filled.
✔ Conduct a site visit to confirm pipe depth, structures, and access.
✔ If grout-filling, calculate exact lengths & volumes to avoid wastage.
✔ Manhole removal is expensive – PVC is easier, concrete requires demolition & disposal.
✔ Disposal costs vary – call tips before quoting to confirm fees for PVC, concrete, and general waste.
✔ Backfilling & compaction testing must be accounted for.

💰 Accurate estimating is critical to avoid major cost blowouts.

At WSE Sydney, we ensure all site conditions, disposal fees, and structural requirements are properly costed—minimizing financial risk for contractors.

📧 tenders@watersewerestimatingsydney.com.au
📞 +61 451 404 645

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