EXPERT DRAINAGE SOLUTIONS
Expert Drainage Strategy Design for Flood Risk, SuDS & Nutrient Neutrality
We design technically sound, policy-compliant drainage strategies that protect both the environment and your bottom line. With over 35 years of combined civil and environmental engineering experience, our team delivers foul and surface-water drainage strategies for schemes ranging from single dwellings to strategic developments exceeding 1,000 homes.
OUR MISSION
Balancing Environmental Performance with Commercial Viability
Unchecked urban growth can increase flood risk and degrade water quality; our mission is to prevent that—balancing environmental performance with commercial viability. We deliver drainage strategies that satisfy regulators while protecting your development timeline and budget.
POLICY FRAMEWORK
National Policy & Technical Standards
Our drainage designs follow the latest UK policy and best-practice guidance, ensuring full compliance with national and local requirements. Every strategy we produce is grounded in robust technical standards that stand up to scrutiny.
National Planning Policy Framework (NPPF)
Section 14 sets out requirements to manage flood risk using Sequential and Exception Tests and to incorporate sustainable drainage.
Planning Practice Guidance (PPG)
Expands on NPPF policy, outlining FRA expectations, climate-change allowances, and drainage design principles.
Non-statutory SuDS Standards
The national baseline for water quantity and quality design criteria.
CIRIA C753 – The SuDS Manual
Core best practice for SuDS design, maintenance and performance.
CIRIA C808 – Nutrient Neutrality
Section 14 sets out requirements to manage flood risk using Sequential and Exception Tests and to incorporate sustainable drainage.
CIRIA C815 – Biodiversity Benefits
Section 14 sets out requirements to manage flood risk using Sequential and Exception Tests and to incorporate sustainable drainage.
TECHNICAL EXCELLENCE
Comprehensive Flood Risk & Design Approach
We evaluate all sources of flooding—fluvial, tidal, pluvial (surface water), groundwater, sewer, and reservoir—in line with NPPF and PPG. Our Sequential Test steers development to areas of lowest risk; where unavoidable, we apply the Exception Test, demonstrating the scheme's safety and sustainability.
Our Flood Risk Assessments (FRAs) and Drainage Strategy Reports address baseline flood levels and flow routes, finished-floor and exceedance design, safe access/egress during flood events, climate-change rainfall and river allowances, and integration of Sustainable Drainage Systems (SuDS) for runoff control and water quality improvement.
SUSTAINABLE SOLUTIONS
SuDS That Work Harder
Unlike traditional attenuation-only systems, our SuDS designs deliver the four SuDS pillars—water quantity, water quality, biodiversity, and amenity. Through our partnerships, including BN Ecology, and our extensive work on nutrient neutrality, we maximise pollutant removal and ecological value.
Our SuDS Toolkit
Permeable paving systems
Swales and bioretention features
Filter drains and soakaways
Detention basins and wetlands
Retention ponds and wet ponds
Blue-green roofs
Smart-control flow systems
Design Standards
CIRIA C753 compliance
CIRIA C808 nutrient control
CIRIA C815 biodiversity gains
Climate change allowances
Water quality treatment stages
Adoption standards compliance
Measurable ecosystem benefits
SPECIALIST EXPERTISE
Off-Mains Drainage & Non-Mains Systems
Enviren Ltd are not just experts in on-mains drainage; we are among the UK's most experienced firms in off-mains drainage design. Through our collaboration with the National Rivers Consortium, which delivers Septic Tank Upgrades (STUs) for multiple LPAs, we have completed over 300 off-mains assessments and reviewed 400+ system surveys.
This experience makes us uniquely qualified to design off-mains systems that comply fully with Environment Agency General Binding Rules, Environmental Permitting Regulations, and Building Regulations (Part H). Few UK consultancies combine this level of technical depth with an understanding of nutrient management, SuDS integration and regulatory compliance.
Drainage Fields & Mounds
Design of compliant drainage fields and mounds based on percolation testing and site-specific constraints.
Package Treatment Plants
Specification of PTPs with appropriate treatment capacity and discharge quality for sensitive receiving waters.
Zero-Discharge Solutions
Design of willow-bed facilities and other zero-discharge systems for the most sensitive locations.
Permitting & Compliance
Advice on permitting requirements, sampling protocols, and maintenance schedules for long-term compliance.
OUR PROCESS
Seamless, Evidence-led Delivery
Front-Loaded Viability
Before quoting, we assess the site's drainage viability—identifying constraints, connections and opportunities
Complete Coordination
We liaise with surveyors, contractors and statutory bodies to obtain all required data and testing
Design Development
From outline to detailed construction, we develop robust drainage and SuDS strategies
Approval Success
Integration of environmental compliance with buildability for swift planning approval
REGIONAL KNWOLEDGE
Local Standards & LLFA Approvals
We maintain detailed knowledge of region-specific LPA and Lead Local Flood Authority (LLFA) drainage standards. Every strategy we produce integrates local policy, discharge-rate criteria, and maintenance expectations to secure quick, trouble-free approvals.
Why Choose Enviren
35+ Years Experience
Combined civil and environmental drainage design expertise
National Recognition
Expertise in SuDS, nutrient neutrality, and off-mains systems
Full Compliance
Designs satisfy NPPF, PPG, and CIRIA guidance
End-to-End Service
Complete coordination delivering cost-effective solutions
750+ Projects
Proven track record across all development scales
94% Success Rate
Near-perfect approval rate at first submission
Frequently Asked
Questions
What is a drainage strategy for planning?
A drainage strategy outlines how foul and surface water will be managed within a development, demonstrating compliance with NPPF, PPG, and SuDS Standards to prevent flood risk and pollution.
What does a Flood Risk Assessment include?
An FRA evaluates all potential sources of flooding, assesses existing risk, and proposes mitigation—ensuring development remains safe, sustainable, and climate-resilient.
What is SuDS and why is it important?
Sustainable Drainage Systems (SuDS) mimic natural drainage to control runoff, improve water quality, boost biodiversity, and enhance amenity—meeting C753, C808, and C815 best practice.
How does drainage relate to nutrient neutrality?
SuDS and treatment systems help reduce phosphorus and nitrogen loads in runoff, supporting nutrient neutrality under CIRIA C808 guidance and Natural England requirements.
What if my site is not connected to a mains sewer?
Enviren specialises in off-mains drainage, designing systems that meet the Environment Agency General Binding Rules and Permitting Regulations, including Package Treatment Plants, drainage fields, and willow beds.