Eco-Friendly Sewage Treatment Upgrade for RSPB Freiston Shore Nature Reserve

Compromised Septic Tank, Non Compliant Septic Tank
Marsh Sewage Treatment Plant
Boston, Lincolnshire.
Dry

Client: RSPB
Location: Freiston Shore Nature Reserve, Lincolnshire
Project: Installation of a new sewage treatment system for visitor facilities and workshop
System Installed: 60PE Marsh Ultra Polylok with Pumped Outlet & 2000 Gallon Marsh Cesspool

Project Background

Mantair was commissioned by the RSPB to provide a compliant and sustainable foul drainage solution for the newly constructed visitor toilet block at Freiston Shore, Lincolnshire. The site previously lacked a dedicated foul drainage system, meaning the new facilities required a purpose-built sewage treatment solution.

The proposed system needed to accommodate visitor numbers, manage high ammonium loads due to urine, and cope with the wetland site’s high water table. Mantair conducted a detailed site survey and system sizing, in collaboration with Marsh Industries, to identify the most suitable solution.

Site Survey Findings

Key findings included:

Visitor Toilet Block: No existing drainage system. Previous sizing underestimated ammonium levels, necessitating a 60PE system to ensure correct treatment and compliance.
Site Conditions: Wetland environment with a high water table, making a traditional drainage field unsuitable.
Discharge: A nearby ditch was identified as a suitable discharge point, located over 500 metres from the SSSI.
Workshop & Outbuildings: Currently served by a septic tank with illegal discharge; recommended replacement with a 2000-gallon cesspool due to minimal usage.

The survey confirmed that a Marsh Ultra Polylok system with a pumped outlet would provide effective treatment and safe discharge for the visitor facilities, while the cesspool would manage low-use ancillary buildings.

Solution

Mantair installed a 60PE Marsh Ultra Polylok Sewage Treatment System for the toilet block and a 2000-gallon cesspool for the workshop. Key considerations included:

Pumped Outlet: Required due to the high water table, preventing backflow and ensuring reliable operation.
Shallow Excavation: Smaller diameter tanks allowed reduced excavation depth, important in wetland conditions.
Aeration-Based Treatment: Marsh Ultra Polylok systems use aeration to generate aerobic bacteria and biomass, treating foul waste to Environment Agency standards with minimal odour and noise.

The cesspool was installed on a concrete base with dry lean mix surround, intercepting the existing illegal septic discharge and providing an environmentally safe solution. Future conversion to a pump station was considered if usage increases.

Installation Process

Mantair implemented a comprehensive, safety-focused installation:

Site Preparation: Installation of Heras fencing, signage, and ground protection to ensure public safety and minimise disruption.
Excavation & Shoring: Machinery and shoring equipment used to maintain excavation stability in high water table conditions.
Tank Installation: Marsh system installed on level concrete base, backfilled with lean mix concrete, and filled with water for commissioning.
Pumping & Electrical: Pumping mains and outlet chamber installed to the boundary watercourse. Electrical connections for air blowers and kiosk control panels completed by NICEIC-accredited electricians.
Reinstatement: Trenches backfilled, surfaces reinstated with soil, stone, or concrete. Existing septic tanks decommissioned and infilled.

Commissioning & Handover

Following installation, Mantair conducted full commissioning, including:

Testing and adjusting valves and discharge rates.
Demonstrating system operation to RSPB staff.
Providing detailed handover documentation.

Outcome

The project delivered a fully compliant, sustainable foul drainage system for Freiston Shore:

Ensures visitor toilet block wastewater is treated to Environment Agency standards.
Provides safe, odour-free, and low-maintenance operation.
Manages high ammonium loads and accommodates future site requirements.
Replaces illegal septic discharge from workshop/outbuildings with a safe cesspool solution.

Mantair successfully navigated the complexities of a wetland site with public access, providing a safe, efficient, and environmentally responsible installation.

Key Benefits