Senior / Principal Environmental Engineer (Wastewater) Location: UK (Hybrid / Flexible Working Available) Full-time, Permanent We are looking for an experienced and driven Senior / Principal Hydraulic Modelling Engineer to take a leading role in the delivery of Catchment System Assessment (CSA) projects across the UK. This position is ideal for a highly capable professional who combines strong technical expertise with leadership ability and is ready to take ownership of complex modelling programmes and multidisciplinary teams. This is not just a delivery role, you will be leading teams, shaping project strategy, and acting as a key technical authority within the business. The Role As a Senior / Principal Engineer, you will be responsible for both hands-on technical delivery and leading, managing, and developing teams of modellers and engineers. You will oversee the full lifecycle of hydraulic modelling projects, ensuring outputs are technically robust, commercially viable, and delivered to programme. You will act as a technical lead and mentor, setting standards, reviewing work, and guiding less experienced engineers while maintaining your own portfolio of projects. Key responsibilities include: Leading and managing teams delivering wastewater hydraulic modelling projects, ensuring quality, consistency, and efficiency Planning, coordinating, and supervising flow and level surveys, CCTV surveys, and other data collection activities Building, refining, and maintaining 1D and 2D hydraulic models using industry-standard software Undertaking model verification and validation, ensuring models are fit for purpose and aligned with regulatory and client requirements Leading data analysis and interpretation, using tools such as Excel and other analytical platforms Producing and reviewing GIS-based outputs and plans using MapInfo Delivering solution development and scenario modelling, including optioneering to address capacity, flooding, and performance issues Acting as a technical reviewer and auditor of modelling work produced both internally and by external partners Driving best practice and innovation in modelling approaches and workflows Leadership & Team Responsibilities: A core part of this role is leading and developing people. You will: Provide day-to-day leadership to teams of engineers and modellers across multiple projects Allocate work, manage workloads, and ensure deadlines are achieved Mentor and coach junior and mid-level staff, supporting their technical and professional development Carry out technical reviews and quality assurance checks on team outputs Foster a collaborative and high-performing team culture Contribute to recruitment, onboarding, and capability development within the modelling team Project & Client Responsibilities: Act as a project manager or technical lead on key CSA programmes Manage project scope, programme, budget, and risk Lead client engagement, including meetings, presentations, and ongoing communication Translate complex technical outputs into clear, client-friendly insights and recommendations Prepare, review, and approve high-quality technical reports and deliverables Support commercial activities, including costing, bid support, and proposal development Looks interesting, apply direct.