3.2.2 SSP2 — STEP Tank (SPS2 Replacement)
This section details the Septic Treatment and Effluent Pumping (STEP) tank serving Bungalows 1–16, designated as SPS2 (replacing the former SSP2 distribution box and lift well).
Location: Opposite side of the causeway from SSP1, eastern end of Bungalow 16
Layout Diagram
Legacy System Decommissioned
The old SPS2 infrastructure — concrete distribution box, dual lift pumps, and 50 mm discharge pipe to SSP1 — has been decommissioned and replaced by this STEP tank.
Role in Collection Network
SPS2 serves Zone 2 of the collection network. Gravity sewer from Bungalows 1–16 discharges into this tank, which provides primary treatment and pumps primary clarified effluent to the WWTP.
Tank Specifications
| Item | Detail |
|---|---|
| Type | 22,000 L concrete tank with internal epoxy coating (H₂S attack prevention) |
| Manufacturer | Taylex Tanks (installed by Fastcall Plumbing NT) |
| Anti-flotation | Concrete ring-beam poured around base to prevent movement from seasonal groundwater |
| Lids | 2 × fibreglass lids with extended risers (Orenco) |
| Venting | Venting lid with activated carbon odour suppression kit |
| Access | Tank shield anti-access grate |
Pump System
| Item | Detail |
|---|---|
| Pump Package | Orenco Biovault Pump Package (PVU72-2425-L) with Effluent Filter |
| Discharge Pumps | 2 × Orenco PF(50Hz)500712 — 3/4 hp, 50 gpm, 380–415 V, 50 Hz, 1-phase |
| Effluent Filter | Biotube 24" cartridge — prevents pump clogging from rags, wipes, and debris |
| Controller | Orenco MVP Duplex Panel, 230 V (MVP-DAX2DM AU/NZ Style) |
Only primary clarified effluent is discharged from this tank. Solids remain in the underground tank for passive anaerobic treatment. Desludging is required approximately every 6–8 years.
Flow System
- Inflow: Gravity sewer from Bungalows 1–16 (DN150 common main via access chambers)
- Discharge: Primary clarified effluent pumped to WWTP Primary Tank 1 (PT-1)
Maintenance
SPS2-Specific Tasks (from O&M Manual Table 1)
| Task | Action | Frequency | Responsible |
|---|---|---|---|
| Check Biotube® Effluent Filters; clean as required | Inspect and clean 24" cartridge filter | Quarterly | ENVR |
| Check Biotube® Pump Vault Filters; clean as required | Inspect Biovault filter assembly | Quarterly | ENVR |
| Sludge accumulation assessment | Measure sludge and scum levels; organise de-sludge pump-out if required | Quarterly | ENVR |
See 3.2.15 OWMS Operations, Maintenance and Contingency for the full maintenance program.
Version Control
| Version | Date | Description |
|---|---|---|
| 1.0 | 2025-10-06 | Initial Release (legacy distribution box and lift well) |
| 2.0 | 2026-06-22 | Rewritten for STEP tank replacement per O&M Manual V1.1 |
| 2.0.1 | 2026-06-22 | Added STEP tank layout diagram |
Next Review Date: 2026-12-22