They used oil to heat the ash hot enough to melt the ash into a glass-like substance, which should make it less likely to contaminate groundwater supplies, etc.
(a glass-like substance; should make; it less likely to contaminate groundwater supplies, etc.) (it; to contaminate; groundwater supplies, etc.) (They; used; oil; to heat the ash hot enough to melt the ash into a glass-like substance) Context(They used,List([0, 9))):(They; used oil to heat; the ash hot enough to melt the ash into a glass-like substance)
They used,List([0, 9))
a glass-like substance it They They
should make to contaminate used used oil to heat
it less likely to contaminate groundwater supplies, etc.
groundwater supplies, etc.
oil to heat the ash hot enough to melt the ash into a glass-like substance
the ash hot enough to melt the ash into a glass-like substance