Washington Valley Stormwater Upgrade – Stage 1

Building resilience beneath the streets.

Project Overview

Client Nelson City Council

Location Washington Valley, Nelson

Service Three Waters Infrastructure

Project Value $5.94M

Duration January 2022 – June 2023

Completed 2023

• At a Glance

  • $5.9M major infrastructure upgrade

  • 1800mm stormwater pipeline installation

  • Deep excavation and groundwater management

  • Heritage tree protection and contaminated ground management

  • Significant stakeholder and traffic management

  • Collaborative delivery with extensive additional scope

• The Challenge

  Washington Valley Stage 1 was one of Nelson's most significant recent infrastructure renewal projects, replacing ageing underground services with a modern stormwater network designed to improve flood resilience and support the city's future growth.

  Delivering infrastructure of this scale through an established residential and commercial area required far more than technical expertise. Deep excavations, large-diameter stormwater pipelines, wastewater renewals, watermain installations, utility relocations and contaminated ground all had to be managed while maintaining access for residents, businesses and essential services. As construction progressed, the project scope expanded considerably, introducing further complexity while maintaining pressure on programme, budget and stakeholder expectations.

• What Mattered

  The project wasn't simply about replacing underground infrastructure—it was about maintaining confidence throughout one of Nelson's busiest construction environments.

  Residents needed ongoing access to their homes, businesses required customers to keep arriving, and critical heritage oak trees lining Hastings Street demanded careful protection throughout construction. At the same time, groundwater, tidal influences, existing underground services and significant coal tar contamination all required proactive environmental and technical management. Success relied on balancing engineering complexity with genuine care for the surrounding community.

• Our Approach

  Tasman Civil approached the project with a collaborative, solutions-focused mindset from the outset. Detailed programming, regular communication and transparent financial reporting gave Nelson City Council confidence to make informed decisions as additional scope emerged throughout delivery. Rather than treating variations as obstacles, the team worked proactively with the client and engineers to develop practical methodologies that maintained momentum while delivering the best overall outcome for the project.

  Technically, the project demanded some of the most complex civil construction undertaken in the region. Deep excavations of up to 3.5 metres, installation of 1800mm diameter reinforced concrete stormwater pipelines, bespoke trench support systems, groundwater management, utility relocations and contaminated material handling all required careful planning and disciplined execution. Every stage of construction was supported by rigorous quality assurance and environmental controls.

  Equally important was the way the project was delivered. Tasman Civil maintained strong relationships with residents, businesses and stakeholders throughout the works, creating temporary parking areas, maintaining access wherever possible and communicating regularly as construction progressed. It was a practical demonstration that successful infrastructure delivery depends as much on people as it does on engineering.

• The Outcome

  Washington Valley Stage 1 has significantly strengthened Nelson's stormwater network, improving flood resilience while renewing critical underground infrastructure for future generations.

  Despite substantial increases in project scope, the works maintained planned construction productivity and delivered a high-quality outcome through collaborative project management, disciplined commercial control and proactive problem solving. Just as importantly, the project reinforced Tasman Civil's ability to successfully lead large, technically demanding infrastructure projects where engineering excellence, stakeholder relationships and long-term community outcomes all carry equal importance.

• Capabilities Demonstrated

  • Three Waters Infrastructure

  • Major Stormwater Networks

  • Large Diameter Pipeline Installation

  • Deep Excavations & Temporary Works

  • Groundwater & Dewatering

  • Contaminated Ground Management

  • Utility Relocation

  • Traffic & Stakeholder Management

  • Heritage Asset Protection

  • Collaborative Contract Delivery

  • Commercial Programme Management

  • Quality Assurance & Environmental Management