How to manage contaminated soil in the garden?

[dang-ouch-tim]

Hi there, we bought a property with a nice large garden space some time ago. Keen to get a garden started, we sent away some soil samples to GardenSafe and discovered the whole yard had extremely high lead levels. 

We've been thinking about ways to manage this and keep the yard safe for a small child. The cost of removing and replacing soil is completely unfeasible, so we have landed on covering the existing soil with a layer of geofabric, before covering with another 10-15cm of soil (and in some places toppings) and planting a mix of decorative plants, shrubs, perhaps grass on top of that.

Our thinking is that this will reduce our concern when small child drops their snacks in the dirt and then takes a bite, and dramatically reduce dust from the contaminated soil reaching the house. Water will still flow through the geofabric as it is permeable. There are places where we will cut holes/gaps in the geofabric around existing plants and shrubs that have deeper roots. Still, any edible plants we grow will be in raised vege beds with imported soil.

Before laying the geotextile, we are loosening the contaminated soil and adding compost, in the hope that it improves the fairly heavy clay soil and based on some limited reading about compost affecting the bioavailability of lead in soil. Also good for the existing plants. 

My question is basically whether this all seems sound, whether there are any other factors we should consider. And what kind of geotextile might be most appropriate for the job... Woven/non-woven, etc.

Appreciated!

[MitchellMc]

Welcome to the Bunnings Workshop community @dang-ouch-tim. It's wonderful to have you join us, and many thanks for your question about managing contaminated soil.

Given your extremely high lead levels, it would be remiss of me to advise anything other than directing you to a lead abatement service for professional advice. Your plan aligns somewhat with the advice given in this document from Macquarie University on dealing with soil that might be lead-contaminated:

• Cover bare soil in gardens and areas beside the house with wood chips or mulch. 

• Grow grass where the soil is bare, or place wood chips or mulch on bare soil. 

• Prevent children from playing in bare soil; if possible, provide them with sandboxes filled with clean and tested sand – available from hardware stores. If using a sandbox, parents should also cover the box when not in use.

It would be best to have a professional service advise on whether your plan would provide an adequate level of protection for your family. Although at this time it is unfeasible for you to have the contaminated soil removed, I would highly suggest you consider this as an option, despite the cost. I'm not sure if your testing showed how deep the high levels of lead have penetrated the soil, but if only 100mm of soil needs to be scraped off the yard, the cost might not be as high as you'd think.
 

Please let me know if you have any questions.

Mitchell
 

[Jason]

Any thoughts you could add to this discussion @robchin?

Many thanks,

Jason 

[dang-ouch-tim]

Thank you @MitchellMc, they are helpful suggestions and we will follow up by seeking professional advice!

[CristinaZ]

Hey there,

Wondering if you could send through an update on what you’ve ended up doing and services you contacted. I’ve found myself in a very similar position with a baby on the way, we’re keen to minimize the risk of exposure in our garden!

We are thinking of removing the soil for peace of mind but unsure of where to look in terms of services.

Cheers,

Cristina

[JacobZ]

Hi @CristinaZ,

Welcome to the Bunnings Workshop community it's great to have you with us.

Allow me to tag @dang-ouch-tim so they're notified of your question.

Jacob

[dang-ouch-tim]

Hey @CristinaZ and thanks @JacobZ . We haven't got around to acting yet, but from some further investigation it seems the contamination runs deep and we really don't have the means to move the soil. We're going to follow through with the geotextile temporary solution, and then cover with clean soil. It's not perfect, but it will decrease the likelihood of contaminated dust, dirt reaching the child or entering the house. 

Depending on where you are , Earthsure might be a place to contact about removal if in Victoria. They are a site that can receive soil in an EPA approved manner ... But digging the soil out is another job. 

https://www.veolia.com/anz/our-facilities/landfills/earthsure-veolia-ventia-joint-venture

Hope that helps, I'm sorry you have to deal with it at this moment. 

All the best

[robchin]

Hi @dang-ouch-tim 

Sorry it has taken me some time to respond to this. It's bad luck that you have this problem. I think you have received some good advice here.  Good to put the textile down. You can also use Mulch as a preventive. This website is Australian and has some good advice for you - so worth a look:  A Guide To Dealing With Soil That Might Be Lead-Contaminated

I work for Bunnings and we sell a number of geotextile fabrics that will help with this: GRUNT 1 x 10m Non Woven Geotextile Membrane Drain Mat Fabric - Bunnings Australia

One of the things that hasn't been addressed as far as I can tell is what is the source of the lead? Have you been able to ascertain this? I would always be concerned to know this. If the problem is just in the soil - you are managing this with the above. If it is an on-going problem - you need to establish the source and manage it appropriately. Eg Lead paint (older houses), heavy metal pollution (house near very busy road with lot's of stopping and starting or nearby mining which may have high metals in the dust from the mining processes. 

Not sure there's more to be added that hasn't been already noted from others in this thread. 

Good luck.