Extensive root removal from the sewer was necessary before internal CCTV inspection could be carried out. Once CCTV had identified the location of the collapsed section, it was exposed using hydro-excavation and hand digging. Timber shoring was installed to ensure the excavation did not collapse. The collapsed section of sewer was replaced with UPVC sewer pipe and embedded in stabilised sand.

Cleaning was completed prior to CCTV inspection confirming the main was in a suitable condition for The entire sewer was then lined with Expanda, installed from existing maintenance holes. Site restoration included backfilling of the excavation with a pumped cement stabilised slurry with the timber shoring left in-situ. A feature survey was conducted on the houses to ensure there was no movement/sinking during the works.

The challenge

Large voids were appearing in the narrow access path between two houses. The voids were potentially undermining the foundations of both.

Internal CCTV inspection showed that a section of the sewer running between both houses had collapsed. The sewer was six metres deep. Roots were entering from other cracked and leaking joints along the line. Repairs needed to be completed without risk to the structure of these houses.

The solution

Interflow was able to restore the full operating capacity of this main by installing a high strength Interflow proposed excavating and replacing the damaged section, then installing a structural Expanda liner to renew the full length of the rest of the sewer. A methodology was developed that allowed for working without damaging house foundations.

Conclusion

The project was successfully completed without incident in these complex and sensitive conditions. The temperatures during this period were in the mid-thirties and the work was arduous.

Interflow’s crew was complimented for the commitment they showed in carrying out the works safely and efficiently, with exceptional consideration to the householders who were affected.

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