Case Studies

Design of Wetland Rectification Works

Discipline

Environmental Management

Client

Melbourne Water

Start Date:

February 2016

Completion Date:

March 2017

Project Overview & Outcome

Overview

Melbourne Water engaged Engeny to assess the hydraulic regime and recommend rectification works of five wetlands across Melbourne. Melbourne Water identified that these wetlands are not functioning as per their design intent.

Outcome

The outcomes for this project included:

Sharing of design and operational issues for wetlands between consultants, Melbourne Water engineering staff and Melbourne Water operational staff
Review of Melbourne Water wetland assets built using earlier standards
Development of design solutions to improve wetland performance and vegetation
Innovations were applied to inlet and outlet details to achieve significant incremental improvements for the performance of five Melbourne Water wetlands.

Project Details

The Problem

These wetlands have minimal aquatic vegetation present, which is assumed to be the result of extended periods of inundation or raised normal top water levels (NTWL). The wetlands should have a draw down period to NTWL of up to 72 hours, and times of no inundation to ensure the survival of the vegetation within the wetland. The key factor that distinguishes a wetland from other water bodies is the presence of vegetation. Constructed wetland systems rely on vegetation, both emergent and submerged, to provide nutrient uptake from the stormwater. Without the extensive vegetation coverage, the wetland is not functioning in accordance with the intent of the asset.

The Response

Engeny visited all five wetlands with Melbourne Water wetland planning and operations staff, documented all of the issues with the wetland and designed rectification works to resolve various issues.

The Details

Wetland design details have changed over the decades, so the design details, including outlets were compared with current Best Practice and optimal hydrologic regimes.

The Result

Engeny made recommendations for cost effective works to adjust the wetlands, particularly outlet structures to improve their performance.

Project Relevance

Review of performance of existing wetlands relative to design criteria
Engeny applied our knowledge of wetland design, Best Practice and first principles of hydrology and hydraulics to improve Melbourne Water wetland asset performance.

This project demonstrates how Engeny can work closely with Melbourne Water on complex wetland projects.

Project Innovation

Engeny applied the latest Best Practice to the operation of 5 Melbourne Water wetlands

Engeny reviewed specific details for each wetland, and allowed for non-standard existing conditions to adjust Best Practice design objectives to each site
Engeny developed individual rectification works to suit each of the five wetlands to improve their operation and conditions to encourage better vegetation coverage and stormwater treatment.
Engeny worked closely with Melbourne Water to share the learnings from the input of all team members.

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