Client: Regency Living
Location: Tall Trees, Christchurch, Dorset
Project: Replacement of non-compliant septic system with Marsh Ultra Polylok Sewage Treatment Plant
System Installed: 250PE Marsh Ultra Polylok, Twin Pumped Outlet
Project Background
Mantair was approached by Regency Living to review and upgrade the foul drainage system at Tall Trees, a residential park in Christchurch, Dorset. The site was previously served by a large outdated septic tank (tank 7) and six smaller septic tanks (tanks 1-6) that were showing structural issues, blocked outlets or incomplete pipework. These tanks were discharging into a soakaway / drainage field which had failed, which in turn was polluting a watercourse. Before Regency Living took ownership, the site had been expanded multiple times, without the thought for a long-term suitable drainage system.
The existing system was non-compliant and causing environmental pollution, including odour issues and untreated foul water discharge. Mantair undertook a comprehensive survey, including CCTV of all tanks and drain runs, to determine the optimal long-term solution.
Site Survey Findings
Key findings included:
- Large Tank (Tank 7): Non-functional, with discharge into failed soakaway / drainage field.
- Small Tank 6: Required bypassing or conversion to a raw pump station to feed the new system.
- Small Tanks 1-5: Various defects, including missing T-pipes, sludge pits, root ingress, and partially collapsed walls.
- Drain Runs: Multiple defects throughout, requiring review and repairs following system installation.
The survey highlighted that replacing the main septic tank with a bespoke treatment system, while addressing smaller tanks sequentially, would create a compliant, odour-free, and efficient drainage network for the site.
Solution
Mantair proposed a bespoke Marsh Ultra Polylok 250PE Sewage Treatment System, comprising of two tanks, with a twin pumped outlet. The system was selected based on:
- Site occupancy: Allowing for visitor fluctuations.
- Compliance: Discharge to watercourse treated to Environment Agency standards and Building Control signoff.
- Robust design: Heavy-duty reinforced tanks with Polylok Filter for enhanced biological treatment.
- Smaller legacy tanks were bypassed and decommissioned, as appropriate.
- Trenching, inspection chambers, pumping mains, and seasonal soakaways were installed to ensure efficient flow to the nearby ditch.
Installation Process
Mantair implemented a rigorous installation plan prioritising safety, compliance, and minimal disruption to residents:
- Site Preparation: Safety fencing, signage, and ground protection boards were installed. Machinery access was escorted by Mantair engineers acting as banksmen. Hazard mapping, scanning for underground services, and asbestos/archaeological risk management were conducted.
- Tank Installation: Excavations supported by shoring or hydraulic bracing were prepared for the two Marsh tanks. Tanks were installed on level concrete bases and backfilled with lean mix concrete, with water-filled commissioning during installation.
- Electrical & Mechanical: Air blowers, kiosks, and pump stations were installed with full electrical connections, including high-level alarms.
- Drainage Integration: Pumping mains were installed from the converted Tank 6 (raw pump station) to the Marsh system, and onward to the boundary watercourse. Legacy tanks 1-5 were repaired or bypassed to integrate with the new system.
- Reinstatement: Trenches were backfilled, surfaces reinstated with soil and seed, tarmac patches, or stone as required. Tank 7 was decommissioned and infilled, leaving the site clean and safe.
Commissioning & Handover
Upon completion, Mantair conducted full commissioning of the treatment plant and associated pump stations, ensuring:
- Correct discharge rates and valve settings.
- Compliance with Environment Agency requirements.
- Building Control sign-off
- Odour-free and efficient operation.
Comprehensive documentation was provided to Regency Living, including: Marsh Warranty & Guarantee, Mantair Commissioning Certificate, Environment Agency Permit to Discharge, Building Control Completion Certificate, Electrical Part P Certificate, Condition & Installation Photo Record, and a Bespoke Maintenance Agreement
Outcome
The installation at Tall Trees delivered a sustainable, compliant, and odour-free foul drainage solution. The bespoke Marsh Ultra Polylok system replaced the non-compliant septic tank, addressed the legacy issues of smaller tanks, and ensured treated effluent could be safely discharged to the nearby watercourse.
Mantair successfully managed all site complexities, including resident access, hazardous conditions, and integration with existing infrastructure, completing the project efficiently within three weeks.
Key Benefits
- Full compliance with Environment Agency regulations
- Reliable and efficient treatment of foul waste
- Reduced odour and environmental pollution
- Minimal disruption to residents
- Long-term maintenance and support package
