Frequent Questions

In the LDR regulations at 40 CFR 268.45, Table 1, footnote 3, EPA defines "clean debris surface?, part of which is "limited to no more than 5% of each square inch of surface area?. How is the 5% surface area defined?

A ''clean debris surface'' is a surface that, when viewed without magnification, is free of all visible contaminated soil and hazardous waste, except that residual staining caused by soil and waste consisting of light shadows, slight streaks, or minor discolorations. EPA allows minor residual staining caused by soil and waste as, well as soil and waste itself, to remain in cracks, crevices and pits up to 5% of each square inch in surface area. The 5% surface area criterion is applied to each square inch of the debris surface that has been contaminated with hazardous waste. The area covered by large stains cannot be averaged against large unstained areas. Only 5% of the area within any square inch can contain a residual stain (57 FR 37194, 37230, footnote 31; August 18, 1992).

EPA considers this a reasonable and practical method to ensure that the toxic contaminants are not allowed to remain at levels that could pose a hazard to human health and the environment absent Subtitle C regulation, and should remove contaminants so that threats posed by disposal of the debris are minimized. EPA notes that staining such as rust stains on concrete adjacent to steel reinforcing bars is not indicative of the potential presence of hazardous waste and need not be removed nor considered in determining compliance with the maximum 5% surface area limit on residual staining.

You can obtain a copy of the August 18, 1992, Federal Register at the following URL: 

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