No your not being too paranoid, I would be concerned as well! Plant roots tap fairly deep in the soil, no I cannot see raised beds being any help for that, your raised bed will be flooded as well! That being said, I don't see why your're overthinking this if the flood was merely a rare occurrence. Even if you are experiencing a kittle runoff from rain, if it is flowing to your neighbors backyard than down the hill to your garden, I wouldn't worry about it. My thought is the ground it travels before it hits your is going to "soak up" all the harmful substances. Even if your vegetables did get runoff from minute harmful substances, plants can chelate and detoxify the ground and the water.. That being said, I wouldn't eat root vegetables as they can "store" the toxins,etc... Use your own intuition. If your city cleans/salts the street, or your neighbor is spraying pesticide and other poisons I would move the garden to the spot you think is best to resolve that matter.. Either way, as long as your aware of what's going on, you will unknowingly naturally try your best to resolve it... I give you respect. You are doing far more for your health growing your own food.. Even if it did get contaminated, what do you think you are buying at the store?

Good luck,

Joe

No your not being too paranoid, I would be concerned as well! Plant roots tap fairly deep in the soil, no I cannot see raised beds being any help for that, your raised bed will be flooded as well! That being said, I don't see why your're overthinking this if the flood was merely a rare occurrence. Even if you are experiencing a kittle runoff from rain, if it is flowing to your neighbors backyard than down the hill to your garden, I wouldn't worry about it. My thought is the ground it travels before it hits your is going to "soak up" all the harmful substances. Even if your vegetables did get runoff from minute harmful substances, plants can chelate and detoxify the ground and the water.. That being said, I wouldn't eat root vegetables as they can "store" the toxins,etc... Use your own intuition. If your city cleans/salts the street, or your neighbor is spraying pesticide and other poisons I would move the garden to the spot you think is best to resolve that matter.. Either way, as long as your aware of what's going on, you will unknowingly naturally try your best to resolve it... I give you respect. You are doing far more for your health growing your own food.. Even if it did get contaminated, what do you think you are buying at the store?

Good luck,

Joe

1. No you are not. There are some valid concerns about the contaminants found in street water - auto oils and fluids, gas, emission residues, coatings used, chemical leaks, etc. How much of a concern there is will vary depending on the amount and type of traffic on the road and the amount of run-off.

If that water never reaches your yard except during this rare flood event then subsequent rains, soil filtration, etc. will compensate for much of it. It it drains regularly into your soil then the potential for threat is much greater.

The solution would be to have your soil tested professionally with special attention paid to testing for contaminants.

2. Building a raised bed filled with off-site soil will certainly help, the deeper the better. Personally I'd recommend a minimum of 18" so that even deep root vegetables would be minimally exposed to the native soil.

Most plants have a built-in filtration system of sorts that prevents uptake of many contaminants but they can only cope with so much and then they die. So a soil test will tell you what degree of risk you may have to deal with.

Container gardening is another option for you and given the extensive shade you have to deal with there in your picture, it may even be the best option if you have a sun-exposed spot you can use.

Good luck.

Dave

I would do raised gardens, and also dig a simple ditchline/swale to catch the runoff and direct it away from your garden area.

I am no expert, but I agree that raised beds could help. I have nearly 22" deep raised beds, and my veggies don't use up the whole 22" (except maybe my tomatoes.) I would imagine that fresh/clean soil/compost would be safer than your native soil to avoid all that runoff...... assuming that the soil/compost hasn't been subjected to anything negative either.

yes raised beds for sure, but also are you able to redirect that runoff elsewhere?

also that area looks particularly shady, vege's mostly need a good 6 hours sun, we give ours full sun.

Here is a link that might be useful: lens bale garden

There is reason to be concerned...

"Toxins" is a very amorphous term and I think it's worth breaking down those concerns specifically. I think of a few major concerns:

1) pathogenic bacteria, most likely from sewer or septic tank overflow, poorly composted animal wastes, etc. This could be compounded if water sat for a while, and if it was hot out. Use common sense. Nature can easily take care of a dog turd or two, but a sewer overflow would be a serious concern. Adding beneficial soil biota (aerobic compost tea, fungi, EM bokashi, etc.) can resolve this issue in a matter of days unless the problem is severe.

2) Synthetic chemical toxins, including pesticides, herbicides, plastics, etc. These would be my least concern. Synthetic chemicals are broken down by microbes of all sorts, and they are unlikely to be taken up by plants in really significant quantities, with the exception of root crops. Adding good aerobic compost tea, EM Bokashi, & mycorrhyzal fungi will all help break down chemical residues faster. It has even been demonstrated that lactobacillus will break down BPA (biosphenol A) inside the human gut.

3) Elemental toxins - specifically heavy metals such as lead & arsenic or radionuclides. To me, these items are the most serious long-term concern, because they don't break down and some of them, such as lead and cesium are metabolized and concentrated in fruits & vegetables.

The most common concern would be lead. If you live in an area that was built in the 1950's or earlier, there is the likelihood of lead paint around houses and other structures. Lead gasoline was finally completely banished in 1996, but many states banned it much earlier. So, depending on how old and how busy the road is, that could be an issue. Spinach is a well-known lead accumulator.

FYI, even store bought organic produce can have high levels of lead. Farmers are not required to test their soil. Lead-arsenate was used very widely as an agricultural pesticide until DDT came along, so a great deal of commercial farmland is contaminated, especially older apple orchards. Many farmers do not test, because if the result comes back bad, they are then required to report it. So, it's don't ask, don't tell. Dirty little secret.

Here is a link that might be useful: lead-arsenate

This post was edited by yukkuri_kame on Fri, Mar 15, 13 at 1:07

Thanks so much for your help everyone! The picture makes things look a lot shadier in my back yard than it is. I have done some measuring back there and the yard does get 6 hours of sunlight. I think the suggestion to try container gardening is great; I can make sure the sunlight is enough (and if it's not I can move them around) and I can control the soil quality until I'm sure the native soil is safe. They're re-paving my road this summer so that will hopefully direct the water to the storm drain where it belongs.