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Concrete Encasement Estimates
Concrete encasement is sometimes required for sewer pipes to provide additional strength, protection, and stability. This can be due to:
✅ Structural reinforcement needs (e.g., under roads, near structures).
✅ Protection from external loads (e.g., under high-traffic areas).
✅ Preventing soil movement or settlement issues.
In Sydney Water projects, concrete encasement follows specific Deemed-to-Comply (DTC) requirements, with two main types:
1️⃣ 12U (Unreinforced Concrete Encasement)
- Pipe is fully surrounded by plain concrete.
- No steel reinforcement is used.
- Simpler and more cost-effective.
2️⃣ 12R (Reinforced Concrete Encasement)
- Pipe is surrounded by a steel reinforcement cage, and then concrete is poured around it.
- Much stronger, required for high-load areas or deeper installations.
- Extra cost for steel reinforcement.
1. Estimating Costs for Concrete Encasement
🔹 For New/Proposed Sewer Pipes
- Excavation and trench preparation for the encased section.
- Concrete pouring cost based on volume.
- For 12R: Additional cost for reinforcement steel cages.
- Expansion joints if the encased section is long.
- AG Pipes (Subsoil Drainage Pipes) – These are laid alongside encased sections to prevent water from getting trapped and causing settlement issues.
🔹 For Existing Sewer Pipes (More Complex & Expensive)
Existing Service Considerations
May need to work around other underground utilities.
Site Access Challenges
- What size machine can operate in the area?
- How much space is available for digging and working?
Excavation Risks & Methodology
- Carefully exposing the existing sewer pipe without damaging it.
- Hand digging or vacuum excavation may be required in sensitive areas.
Traffic Control & Permit Costs
If in a roadway, all necessary council fees, road opening fees, road occupancy fees, and traffic control costs must be included.
2. Expansion Joints & Subsoil Drainage (AG Pipes)
If concrete encasement sections are long, expansion joints must be provided to prevent cracking.
💡 Why AG Pipes?
- Concrete can block the natural flow of groundwater.
- If water is trapped, it can pond at the edges, eventually leading to settlement and structural issues.
- AG pipes (subsoil drains) run alongside the concrete-encased section to drain excess groundwater away properly.
3. Factors That Can Impact Cost Significantly
✔ Depth of Sewer Pipe
- Deeper pipes = more excavation, more shoring costs, and longer work duration.
- Depths over 3 meters require Level 1 Geotech supervision.
✔ Type of Soil & Ground Conditions
- Rocky ground? Extra costs for rock-breaking.
- Soft ground? Possible need for additional stabilization.
✔ Size & Volume of Concrete
Larger pipes = More concrete needed = Higher costs.
✔ Reinforcement Complexity (For 12R)
Larger pipes need stronger reinforcement cages, increasing steel costs.
✔ Site Accessibility & Traffic Management
If in a high-traffic area, arranging road closures and permits adds cost.
✔ Disposal of Excavated Material
- If the site has contaminated soil, disposal costs can be very high.
- Road crossings require select fill material instead of reusing excavated soil.
4. Key Takeaways for Accurate Estimating
📌 Site Visit is Essential – To check depth, access, surrounding services, and traffic conditions.
📌 Separate Costs for 12U vs. 12R –
- 12U: Concrete only.
- 12R: Concrete + Reinforcement Steel (Higher cost).
📌 For Existing Sewer Pipes, Consider:
- Excavation method (machine vs. hand digging).
- Extra traffic control costs if near roads.
- Careful handling of existing services nearby.
📌 Account for AG Pipes & Expansion Joints – To prevent long-term settlement issues.
📌 Concrete Testing Fees – Sydney Water may require concrete strength testing.
📌 Shoring Costs – If depth is significant, hiring shoring boxes must be included.
Concrete Encasement Requires Precision in Costing
Underestimating steel, excavation, permits, or backfill requirements can lead to major cost overruns.
📧 Contact WSE Sydney for expert estimating:
📧 tenders@watersewerestimatingsydney.com.au
📞 +61 451 404 645