Historic Estate Upgrades 8 Properties with Modern Sewage Treatment Systems

WCI completed a comprehensive septic tank upgrade project at the prestigious Cothelstone Estate in Somerset, located within a designated National Landscape (formerly Area of Outstanding Natural Beauty). This ambitious phosphate mitigation scheme transformed wastewater treatment across eight historic properties, reducing nutrient pollution while preserving the estate’s heritage character.

The Challenge: Outdated Septic Systems in a Protected Landscape

The Cothelstone Estate, home to the same family since 1791, features a beautiful stone manor house and period cottages with original septic tank and drainage systems. Before planned estate redevelopment could proceed, these aging private drainage systems needed modernisation to meet current environmental standards.

Key project challenges included:

• Multiple properties with varying sewage treatment requirements (5 to 110 person equivalent)
• Heritage site sensitivity in National Landscape designation
• Need to separate surface water from foul drainage networks
• Coordination across eight simultaneous installations
• Minimising disruption to occupied properties

Somerset Phosphate Mitigation Scheme: Free Septic Tank Upgrades

In 2023, the Cothelstone Estate became one of the first to register for free septic tank upgrades under WCI’s nutrient neutrality scheme in Somerset. This initiative addresses phosphate pollution in sensitive catchment areas by replacing old septic tanks with advanced sewage treatment plants.

By managing all eight property upgrades as a single coordinated project, WCI maximised efficiency and minimised disruption from machinery and material deliveries to this rural location.

Pre-Installation Phase: Comprehensive Drainage Surveys

Before any groundwork began, our project engineers conducted detailed property surveys across the estate, including:

• Assessment of existing septic tank and drainage infrastructure
• Site analysis for sewage treatment plant positioning
• Scope definition for each individual property
• Identification of surface water separation requirements
• Tenant briefings to ensure smooth project execution

This thorough preparation phase took several months but ensured optimal system design and minimal complications during installation.

Installation: GRAF One2Clean Sewage Treatment Plants

Over an eight-week installation period, WCI replaced the existing septic systems with GRAF one2clean sewage treatment plants across the estate. These advanced systems were specifically selected for:

Superior Phosphate Reduction Performance

• Exceptional effluent quality for nutrient-sensitive areas
• Proven phosphate removal capabilities
• Compliance with Environmental Permitting Regulations
• Long-term reliability and low maintenance requirements

Flexible Capacity Range

• Systems from 5 person to 110 population equivalent (pe)
• Tailored solutions for each property’s specific needs
• Scalable technology for varying occupancy levels

Drainage Remediation: Surface Water Separation

At several properties, WCI conducted essential remedial works to separate surface water from foul drainage networks. This separation is critical for:

• Preventing hydraulic overload of sewage treatment systems
• Improving treatment efficiency
• Reducing phosphate discharge to watercourses
• Meeting current drainage regulations

Professional Commissioning and Site Restoration

Each new sewage treatment system was commissioned by a WCI British Water Accredited and GRAF Trained Service Engineers, ensuring:

✓  Optimal system performance from day one
✓  Compliance with manufacturer specifications
✓  Full regulatory compliance
✓  Long-term treatment efficiency

All installation sites were restored to a high standard, preserving the estate’s aesthetic appeal within this protected landscape.

Project Outcomes: Environmental and Regulatory Compliance

The Cothelstone Estate now benefits from:

Environmental Impact

• Significant reduction in phosphate pollution to Somerset waterways
• Protection of sensitive National Landscape watercourses
• Contribution to nutrient neutrality targets
• Enhanced environmental stewardship

Modern Infrastructure

• Compliant with Environmental Permitting Regulations
• Reliable, low-maintenance sewage treatment
• Future-proofed wastewater management
• Support for estate development plans

WCI’s Somerset Phosphate Mitigation Scheme

This project demonstrates the success of WCI’s nutrient neutrality initiative in Somerset. Property owners in phosphate-sensitive catchments may be eligible for free septic tank upgrades to help reduce nutrient pollution while ensuring regulatory compliance.

Does your property need a septic tank upgrade? If you’re in Somerset or other nutrient-sensitive areas, contact WCI to discuss phosphate mitigation solutions and potential upgrade schemes.