I've completed remedial investigations for landfills that contained 100% fly ash from coal fired power plants. The leachate and resulting groundwater plume contained several heavy metals including arsenic. The chemistry is controlled by the type of coal and pH buffering capacity of the water, redox, etc. The following is an excerpt from an old report I was able to dig up:
"Statistical data indicates that groundwater at the monofill is impacted by aluminum, antimony, arsenic, boron, calcium, COD, chloride, magnesium, nitrate, nitrite, pH, sodium, specific conductance, sulfate, TDS,TOC, and vanadium. Additional sampling and analyses will be necessary to verify statistically significant exceedances of chromium, copper, nickel, selenium, and zinc."
The question is whether the metal species are soluble/insoluble. They should have chemical data on the material including total metals analyses and leach test results.
The presence of metals does not mean that they will go into solution in your pond water. They may stay bound to the liner material and will most likely be locked in once organic sedimentation occurs. Some may leach out the bottom into groundwater.
If the material does contain elevated metals, there may be implications just bringing it onto your property depending on your state laws. It's possible that the power plant has pre-certified the material with the regulators for placement on clean properties. I'd be cautious any time someone is offering "free" material.
