[Code of Federal Regulations]
[Title 40, Volume 26]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR503.21]

[Page 839-840]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 503--STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE--Table of Contents
 
                       Subpart C--Surface Disposal
 
Sec. 503.21  Special definitions.

    (a) Active sewage sludge unit is a sewage sludge unit that has not 
closed.
    (b) Aquifer is a geologic formation, group of geologic formations, 
or a portion of a geologic formation capable of yielding ground water to 
wells or springs.
    (c) Contaminate an aquifer means to introduce a substance that 
causes the maximum contaminant level for nitrate in 40 CFR 141.62(b) to 
be exceeded in the ground water or that causes the existing 
concentration of nitrate in ground water to increase when the existing 
concentration of nitrate in the ground water exceeds the maximum 
contaminant level for nitrate in 40 CFR 141.62(b).
    (d) Cover is soil or other material used to cover sewage sludge 
placed on an active sewage sludge unit.
    (e) Displacement is the relative movement of any two sides of a 
fault measured in any direction.
    (f) Fault is a fracture or zone of fractures in any materials along 
which strata on one side are displaced with respect to strata on the 
other side.
    (g) Final cover is the last layer of soil or other material placed 
on a sewage sludge unit at closure.
    (h) Holocene time is the most recent epoch of the Quaternary period, 
extending from the end of the Pleistocene epoch to the present.
    (i) Leachate collection system is a system or device installed 
immediately above a liner that is designed, constructed, maintained, and 
operated to collect and remove leachate from a sewage sludge unit.
    (j) Liner is soil or synthetic material that has a hydraulic 
conductivity of 1x10-7 centimeters per second or less.
    (k) Lower explosive limit for methane gas is the lowest percentage 
of methane gas in air, by volume, that propagates a flame at 25 degrees 
Celsius and atmospheric pressure.
    (l) Qualified ground-water scientist is an individual with a 
baccalaureate or post-graduate degree in the natural sciences or 
engineering who has sufficient training and experience in ground-water 
hydrology and related fields, as may be demonstrated by State 
registration, professional certification, or completion of accredited 
university programs, to make sound professional judgments regarding 
ground-water monitoring, pollutant fate and transport, and corrective 
action.
    (m) Seismic impact zone is an area that has a 10 percent or greater 
probability that the horizontal ground level acceleration of the rock in 
the area exceeds 0.10 gravity once in 250 years.
    (n) Sewage sludge unit is land on which only sewage sludge is placed 
for final disposal. This does not include land on which sewage sludge is 
either stored or treated. Land does not include waters of the United 
States, as defined in 40 CFR 122.2.
    (o) Sewage sludge unit boundary is the outermost perimeter of an 
active sewage sludge unit.
    (p) Surface disposal site is an area of land that contains one or 
more active sewage sludge units.
    (q) Unstable area is land subject to natural or human-induced forces 
that

[[Page 840]]

may damage the structural components of an active sewage sludge unit. 
This includes, but is not limited to, land on which the soils are 
subject to mass movement.

[58 FR 9387, Feb. 19, 1993, as amended at 64 FR 42570, Aug. 4, 1999]