Thanks everyone for the further input! Glenstache, I didn't know about cPAHs or pentachlorophenol, so I will look into it further.
If you know the soil concentrations in your impacted soil, you should see if the local landfill will also accept that impacted soil. Expect a tipping fee of about $30 to $40 per ton (~1.5 tons per cy). If you sell the house and you know there is contaminated soil, it should be a disclosure requirement. If you put contaminated soil in a right of way along the road at the base of the cliff, you are potentially contaminating someone else's property. Just do it right and be done with it with no reservations. It is unlikely that the chromium will be mobile enough in the chemical environment of your soil to be effectively phytoremediated, and doing actual on-site remediation may have state laws to ensure that remediation is done properly (not familiar with NY laws)
The cost of disposing of the soil will be $90/ton at the nearest facility (as recommended by our local town dump). The main issue I have with disposing of the soil is how to get it to the facility. I can easily cover the interior of my minivan with a tarp and move the timbers, but it seems to me that some sort of dump truck would be needed to move the soil.
There doesn't seem to be a single standard that defines acceptable levels of contaminants in garden soils, nor could I figure out what the law is regarding contaminants in residential soil, but I looked at NYS Department of Environmental Conservation Soil Cleanup Objectives, meant for brownfields/Superfund cleanup. The level of chromium, although higher than recommended for single residential/food gardening, is well under the recommended level for multi-unit housing (for which we are zoned.) So I think that will be okay.
My concern is about level of arsenic is about 17.5mg/kg, over the NYS SCO of 16 mg/kg. I was hoping that I could plant ferns the first year, dispose of them, and then test again.
I am not talking about dumping onto somebody else's property, only moving it from one place to another on my own property. I don't think that right of way is a concern, due to the shape and size of the lot. There is an approximately 75 x 35 foot long rocky strip of land, covered with about 0-2 inches of soil, at the foot of the little cliff. The city owns about 10 feet in from the curb, and we own another 20-25 feet. Even if we emptied my vegetable garden, the soil would be enough for only a 4 foot wide strip, 48 feet long. This means that there would still be 15-20 feet of our own property separating the new garden bed from the edge of city property, and 30 feet to the road. It will also be planted and mulched, which should reduce dust.
Furthermore, nobody walks there, as there is a sidewalk on the other side of the street, but none on our side because of the rock face that runs all along this side of the neighborhood. The cliff juts out on one side, blocking the area off from our neighbor. However, for whatever reason people often park by the side of our property and throw trash out, or it gets blown there. We also seem to get more than our fair share of police pulling people over there. I clean it up periodically and have planted groundcover in an attempt to beautify the area. However, I wanted to put more soil there so that it would be deep enough for low shrubbery and flowers, that might prevent blown trash and would make it look cultivated enough to discourage litterers.
At any rate, I guess I could revise my action plan to try:
1. dispose of timbers
2. find source for ferns, plant them this year, dispose of them
3. retest next spring ($75/test). If Arsenic level improved to standard, dump soil over cliff and garden at base of cliff.
4. If not improved to standard, either plant lawn and give up on vegetable garden, or look into paying to have soil replaced.
But what would really help would be ideas on getting rid of the soil and getting clean soil, without paying thousands. Or where to get ferns for phytoremediation.