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“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
CONTACT:
Kartik Venkatraman
Director
Acacia Waste Management Solutions Pty Ltd
www.acaciawaste.com.au
kartik@acaciawaste.com.au
Mo: 0437 919 262
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