PHYTOCAPPING

LETS CAP IT!

“Phytocapping is a capping technique that utilises

vegetation as a natural pumping system to reduce

water being stored in the soil and then gravity fed

into the covered waste. This in turn reduces the

amount of water reacting with the buried waste and

being released as leachate”

Phytocapping

Concept

Drainage =

(Rainfall + Irrigation) – Canopy Interception – Run-off -Soil Storage – Soil Evaporation - Transpiration

D = (RF + I) – CI – RO – SS –SE -T

Soil Cover

Waste

Soil

Water table

Canopy interception

Bio-pump

Storage

Phytocapping Concept

Assess the pros & cons of Phytocapping

Determine if this system will work in your region:

Step 1

Rule of Thumb: Potential Evapotranspiration (ET) > Annual Rainfall

Step 2

Determine the source of soil & soil type

Step 3

Prequalification tests/modelling

Step 4

Develop a business case to EPA for approval

Step 5

Discuss the concept with relevant departments for ongoing maintenance

Understanding the Concept

✓ Pre-design Stage: Checklist

Step 1

Discuss the concept and proposed masterplan with relevant departments

Step 2

Ascertain the depth of interim cap (for consistency)

Step 3

Determine the source of soil

Step 4

Make a list of Auditors who have worked on similar projects

Step 5

Make a list of Geotechnical Investigation & Testing Authority (GITA)

On Approval

✓ Design Stage: Checklist

Step 1

Explain the masterplan to the designer

Step 2

Thoroughly check the lysimeter design

Step 3

Thoroughly check the Construction Quality Assurance (CQA) plan (Major costs are

associated with CQA plan)

Step 4

Selection of plants & rehabilitation plan

Step 5

Raise all queries and make changes prior the documents are sent to Auditor for review

On Approval

State Guidelines emphasise on soil and does not factor in the vegetation.

There will be some flexibility around making practical suggestions/changes to

the proposed design.

For e.g. testing frequency, slope, compaction, drainage, level 1 supervision

etc.

Guidelines

Step 1

Ascertain the quantity of soil required

Step 2

Ascertain the quantity of mulch required

Step 3

Ensure all data/information on waste and interim cap is accurate to avoid

unforeseen situations and costs.

Step 4

Thorough analysis of soil & plant species selection

Step 5

Contractor to supply seedlings and replace seedlings after 1 year (check survival)

Tender for Construction

Step 1

Meet and discuss the CQA plan and construction plan with the Auditor and GITA

Step 2

Time of planting the seedlings is vital and should be discussed early

Step 3

Level 1 supervision by GITA costs around $1,200/day (this may cost a lot)

Level 1 supervision is not required on a daily basis. Discuss with auditor.

Step 4

Sites with minimum or no records can pose issues/challenges

Step 5

Soil test requirements are strict.

However the frequency or the numbers of tests may be negotiated with the Auditor

During Construction

Conventional cap on an average $100/m2 (depending on suitable

clay material available onsite).

Phytocaps on a average cost around $35 - $60/m2 depending on

soil availability and cost.

Ongoing monitoring of lysimeter of 5 years

Ongoing weeding and maintenance

Irrigation for the first 12 months

Cost

Lysimeter to be monitored and reported for 5 years

However, most trees close their canopies only in the 2nd or 3rd year.

This factor needs to be discussed or raised with the EPA

Test Requirement

Understand the Concept

Get it right

Involve the right people

Communicate and liaise with EPA

Undertake a complete cost analysis prior making a decision to

Phytocap

“Phytocap is not always the cheaper option”

Get the pre-qualification tests right

Tree species selection is as important as the soil

Summary

Recreational & aesthetic value

Socially acceptable, cost-effective & sustainable

Low maintenance

Natural Habitat for native wildlife

Great Community Project

Mallacoota Landfill

Case Studies – East Gippsland Shire

Council

Orbost Landfill

Bosworth Road Landfill - Bairnsdale

Special Thanks to

East Gippsland Shire Council

Acknowledgement

CONTACT:

Kartik Venkatraman

Director

Acacia Waste Management Solutions Pty Ltd

www.acaciawaste.com.au

kartik@acaciawaste.com.au

Mo: 0437 919 262