heavy metal contamination in urban fill

A week or so ago, I posted a thread here asking for advice about possible lead contamination. Other things have turned up recently, (literally, a steel I-beam, angle iron, some large concrete chunks) so I am posting this hoping to get more advice on other heavy metals.

I am the organizer of a small Urban farming group in Lakewood, Colorado. We have a 3 quarter acre urban farm site. It was never developed, but apparently one of the previous owners made money by letting people dump fill on the land. We have turned up chunks of concrete, rock, brick, and terra-cotta drain pipe. Also one small (one foot long) section of steel I-beam, with the flanges filled with concrete. Again, nothing suggesting toxic waste, just urban excavation. I am wondering if excavation material from former factory sites might have ended up in a small site such as this. (It was dumped after the property was its current size.) I can deal with lead from houses, commercial buildings, etc; we are currently testing for it, and have plans for dealing with it in place, if it is found. What I can't deal with is figuring out if rarer toxins are present; each dump truck load could have had a different source and makeup, and the amount of tests necessary would cost a fortune. I know that there are plenty of contaminated factory and federal sites in Lakewood; were any of them excavated before people realized that they had to be careful with that stuff? Where would I find answers to this question?

How much should I worry about this?

If my lead test comes back with reasonable levels, could I just forget about the other stuff, add a lot of organic matter (we are adding about a foot of it anyway) mulch the soil and keep it mulched, and not grow root crops in the soil? Would this work if there were moderate amounts of other heavy metals?

And am I correct in thinking that any heavy metals in the soil would have been rather diluted, since most contamination would have been right on the surface?

Gilbert, In the fungi forum there are topics on remediation with mushrooms, have you seen that?
Also, are you tied to the site so much that you cannot just go somewhere else?

Hello Miles,

Thanks for the comments.

I have seen the mycoremediation threads. (And I have read about plants and fungi being used to suck up heavy metals in other places.) The problems are, as I see them, that adding phosphorus and organic matter, and having a high soil pH, will prevent them from working. Also that it would take a long time, and be rather expensive to get rid of the materials properly. I certainly would not want to go through the bother without being sure that they were there; which is what is hard to find out.

If you could help me understand this better, that would be great.

Land prices are very high here. We can use this piece for free, there is free water in irrigation ditches and a cistern, and there are people on site to watch it. It would be hard to find this set of conditions again. Also, contamination is rather widespread. (Water is horribly expensive here.)

Could vetiver grass be used to surround areas deep into the soil?

Erich

MOST heavy metals only become an issue with low pH, they just aren't soluble, so plants won't uptake them in to their roots. I'll be damned if I can find anything on this, however(outside of the normal chart showing plant nutrients at pH). Compost is an amazing substance and can make some highly toxic substances inert and it also raises the pH. Again, finding a source of information is troublesome. But at least this is a starting point for your research. If I were doing this project, I'd just turn the entire lot in to one big compost pile and let nature take her course for about a year. See what grows, how well it does and let observation be your guide.

It's all theory til you get the results, but you've got a bit of a dilemma alright!
I've got some heavily contaminated soil, but it's basically around the house 'dripline'.
Here's a kind of off-topic lead thread
From what I've researched, and to repeat others, organic matter and extremely heavy mulches allow you to garden reasonably safely in contaminated soils.
I'm the only person that gardens at my place, so I can totally control what happens, and make informed decisions about my toxin comfort-levels.
I wonder how you'd deal with things like random babies eating soil and avoiding future garden activities that could be unsafe, etc?

Hello All, I had to register for the forums just to respond to this one.

After doing several environmental investigations of former coke, forge and steel plants back east, I began to notice something: nothing (no grass, weeds, etc) grows in the contaminated areas. We would sample everything, and spend thousands of dollars, but it would just match what our eyes were telling us.

My recommended course of action: Go buy some cheap cover crop, evenly distribute the seed on all the fill areas. Observe. If nothing grows, don't amend/treat/etc, just remove it. Amend with some topsoil, if you need to.

However, I you want to find out what is causing the problems, it should only run around $500 for a VOC, SVOC, TPH-d, and CAM 17 Metals test. (ask for 8260, 8270, 8015M, and total 17 metals) Leachability (TCLP/SLP) is better, but you are paying a high premium for something that total metals can tell you. Sample collection is easy. Just fill a jar (1 Quart mason jar, or lab supplied container) with the suspect soil, and drop it off at the lab. (I recommend Test America in Denver)

Good luck.
Matt

Hello Matt,

Thanks so much for taking the trouble.

What exactly is it that killed the plants in those sites? I am curious.

We have a healthy growth of weeds on the suspect areas; bindweed, a mallow species which is a tenacious spreading weed in this area, dandelions, poison hemlock! and a few alfalfa plants. There is also a bit of rough grass, and a few other things, but those listed above are the dominant species.

So, in you opinion, would this mean that we are safe?

Anyway, I will be doing a cheap soil test in one area, to see what I find. (It will cost me 25 dollars. The main reason I worried about the expense is the non-uniformity of the fill field— we would need a lot of tests.) So I guess we will see!

What do you get for the $500 soil test? Is it just metals, or complete contaminants? Maybe I am overly optimistic, but I am hoping that fungi will break down anything else.

Most often at the coke plants it was benzene (and other volatile organics) and heavy metals (lead, arsenic, mercury). The former forges and steel plants were metals with some toxic solvents (they liked to have the metal look shiny).

Yes, if you have healthy growth, then most likely you don't have a problem at the surface. (note: at the surface) I would recommend heavy mulching/amending/adding and building soil, and don't disturb the subsurface unless you have to. Nature will tell you whats going on. Pay attention to plants that have deep tap roots, if they don't survive in a certain area, note that, you may have a problem 2-3-5+ feet down.

Any I would agree, fungi, bacteria and yeasts will breakdown everything, it is just time. (its called Natural Attenuation in the environmental cleanup world)


As for the lab stuff,
http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/8260b.pdf (volatilizes in air (smelly), bunch of stuff from acetone to MEK, to Nitrobenzene, to Vinyl Chloride.) ($85)

http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/8270d.pdf (non volatile (cant smell it), like PCBs, most of the rest of the bad chemicals that are not in 8260 and not metals) ($125)

EPA 8015M will mainly be used to tell you how much heavy Petroluem is in the soil (light petroleum is in 8260) ($45)

Cam 17 is 17 metals that the state of California uses to determine what is hazardous. Antimony, arsenic, barium, beryllium, cadmium, chrom (total), cobalt, copper, lead, mercury, molybdenum, nickel, selenium, silver, thallium, vanadium, zinc. ($8-10 a metal) or $170 for all

Matt McClellan wrote:
Yes, if you have healthy growth, then most likely you don't have a problem at the surface. (note: at the surface) I would recommend heavy mulching/amending/adding and building soil, and don't disturb the subsurface unless you have to. Nature will tell you whats going on. Pay attention to plants that have deep tap roots, if they don't survive in a certain area, note that, you may have a problem 2-3-5+ feet down.

Welcome to Permies, Matt, and thanks for signing up to comment. I hesitated to give a remote diagnosis from 2000 miles away, but I agree with your observation that if weeds are growing, the surface layer is most likely OK. Also, unless it is a former industrial site that used noxious chemical processes (like a dry cleaners, smelting operation, solvent cleaning, oil refining, shooting range, electrochemical processing, etc.) it's unlikely that the trash is a problem. Concrete and steel don't generally contain heavy metals and problem organics. They will add iron and calcium to the soil, both elements that are necessary for plant metabolism.

Now if he was in Leadville instead of Lakewood, maybe there would be some concern about the ambient level of heavy metals in the environment. However, all this discussion is academic until the lab results come in and the real concentrations are known.

This study about vetiver grass for metal remediation might be helpful. The vetiver has many other uses.

The only choice you have aside from excavation is phytoremediation. The tests will tell you there are metals in the soil and ground water, as you already suspect.

Ground cover, yes, as always. But, you need something to work deep into the soil.

http://www.vetiver.org/ICV3-Proceedings/CHN_heavy_metal.pdf

I'm no expert on any of this, but I would note that bindweed and mallow can be spreading plants, so it could look like the ground is covered with growth when it is mostly bare, covered only with large plants. One bindweed plant can cover a lot of area!

Hello Everyone,

Thanks for the answers.

I looked at the vetiver grass, but I don't think it would work for me. For one thing, I doubt it would tolerate a zone five desert, but correct me on this if I am wrong.

Secondly, and more importantly, it leaves all metals on site, waiting to contaminate anything else which gets planted. True, it would slowly build organic matter in the subsoil, but so would a lot of other plants. (Alfalfa, say.) And there does not seem to be anything in my soil that will kill plants; weeds seem to grow very well, and there are plenty of worms in the soil.

Do worms indicate anything about heavy metal contamination?

Gilbert Fritz wrote:

Do worms indicate anything about heavy metal contamination?

There are many invertebrates that are studied as indicator species, and in general healthy soil without heavy metals in it is more conducive to high numbers of invertebrates. Here is a reference that looks at many different species and the relation between their populations and their distance from a zinc smelter.

Gilbert Fritz wrote:Hello Everyone,

Thanks for the answers.

I looked at the vetiver grass, but I don't think it would work for me. For one thing, I doubt it would tolerate a zone five desert, but correct me on this if I am wrong.

Secondly, and more importantly, it leaves all metals on site, waiting to contaminate anything else which gets planted. True, it would slowly build organic matter in the subsoil, but so would a lot of other plants. (Alfalfa, say.) And there does not seem to be anything in my soil that will kill plants; weeds seem to grow very well, and there are plenty of worms in the soil.

Do worms indicate anything about heavy metal contamination?

I've browsed studies of vetiver in Kuwait. Revegation is the only way to deal with metals in the soil other than excavation. I'm not sure what you mean by, "leaves metals on site". The plant takes what it needs and in that process makes surplus available to other plants, microbes, and so on...The process of alleviating high concentrations of metal or whatever is simply getting plants to digest it, poop or secrete it. Your worms are doing just that right now in the soil. The stuff is spread around, etc..

Vetiver roots can easily go 6 or 7 meters deep in a couple of years. They also have strange microbe and fungi collections on their roots that no one really understands.

This kind of revegetation, soil balance, etc.. is the basic role of grass everywhere on the planet.

I feel like I am not really making sense for what you need, so I will respectfully leave the discussion.

Cheers.

Hello Erich,

Sorry that I misunderstood you.

I realize that adding organic matter can tie up metals, but I thought, (mistakenly, ) that vetiver grass was simply metal tolerant, and would be used to block direct access to contaminated soil, leaving them as bad as before. Definitely not something I want to do.

And it seems, on a little more research, that it might be able to grow here.

If I find that there are heavy metals, I will try and procure some starts. Anyone else have success with Vetiver grass in Zone Five Colorado? It looks like the top growth would die back, but the roots would remain viable under mulch.

Thanks Erich

Hello Everyone,

Here is what I have decided to do. I am certainly still open to advice and opinions! It will be interesting to see what you think of this.

So, the master plan.

After reading all your suggestions, and lots of other contradictory advice on the web, I am taking about twenty samples in a two thousand square foot area, at a depth to contact the top of the fill, about eight inches down. ( The deepest we have dug on this site is a foot and a half. All the rubbish is right under the surface. ) I am getting the composite sample tested cheaply for the common heavy metals.

Once the results come back, I will know what the top eight inches are like.

If they are safe, I will lay down a foot of mulch (or in some areas, four feet of hugelkulture) and plant whatever the group wants. But, to analyze the deeper layers of this rather complicated site, I will plant some tap-rooted metal accumulators, and get their leaves tested this fall. If they show that deeper layers are contaminated, I will continue to grow and remove them, and grow a lot of deep rooted soil builders (vetiver, alfalfa, comfrey, etc) to pump organic matter down there.

If the metal results come back moderate, I will follow the same strategy as above, with out any root crops, and with the addition of lots of accumulator plants to be removed from the site.

If the results come back really high, I will rent an excavator and bulldozer, and dig five foot wide trenches, two feet deep, on contour five feet apart. The stuff coming out will get mounded up over logs and brush in the spaces between trenches. I will then line the trenches with landscape fabric, and fill them with giant hugel-sheet mulches to grow things in. On the contaminated soils, I will plant soil builders and metal accumulators, as well as woody fruit bearing crops. Then, over time, the whole site should become safe, and we will get a yield in the mean time.

This last strategy would take a lot of organic matter, but in Denver there we can get lots of stuff delivered free.

Some rather strange test results

I just got back my basic soil test results. Lead was 2.9 ppm. Since lead is this low, should I just not worry about the other heavy metals?

Soil pH was 7.8. Expected.

The soil is over the top in many nutrients, and sufficient in all except nitrogen, and even this was not bad. Here are the results. P 71 ppm, K 1011 ppm, Ca 6641, Mg 448 ppm, Sulfur 63 ppm, Maganese 10 ppm, Zinc 7.6, and Copper 1 ppm.

What do excesses of this sort mean as far as soil toxicity and plant growth, and what do they mean as far as my heavy metal situation?

I am also starting a new tread with this post.

Everything you are looking at seems resonable. As with any process it all comes down to cost. If any one sollution costs to much it can not be done, if any sollution takes to long the cost is to high and should not be done. Are you really really attached to your plot? If so and you are still concerned, bury the contaminated zones. Mark the contaminated zones off and work around them. Raised beds, huguelkulture,etc. If you have large acreage you are paying to fix someone elses problem so keep it simple.