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Federal Register / Vol. 86, No. 97 / Friday, May 21, 2021 / Rules and Regulations
CNMOC. For landfills located in geographical areas with a 30-year annual average precipitation of less than 25 inches, as measured at the nearest
representative official meteorological site, the k value to be used is 0.02 per year.

iA Equation 1 must be used if the actual year-to-year solid waste acceptance rate is known.

n
MNMoc =

L2 k LoMie-kt; CNMoc3.6x10-9

Eq. 1

i=l
= 2LOR e-kc -

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Where:
MNMOC = Mass emission rate of NMOC, megagrams per year.
Lo = Methane generation potential, cubic meters per megagram solid waste.
R = Average annual acceptance rate, megagrams per year.
k = Methane generation rate constant, year 1.
t = Age of landfill, years.
CNMOC = Concentration of NMOC, parts per million by volume as hexane.
c = Time since closure, years; for an active landfill c = 0 and ekc = 1.
3.6 109 = Conversion factor.

B The mass of nondegradable solid waste may be subtracted from the total mass of solid waste in a particular section of the landfill when calculating the value of R, if documentation of the nature and amount of such wastes is maintained.
2 Tier 1. The owner or operator must compare the calculated NMOC mass emission rate to the standard of 34
megagrams per year.
i If the NMOC emission rate calculated in paragraph a1 of this section is less than 34 megagrams per year, then the owner or operator must submit an NMOC emission rate report according to 62.16724c and must recalculate the NMOC mass emission rate annually as required under 62.16714e.
ii If the NMOC emission rate calculated in paragraph a1 of this section is equal to or greater than 34
megagrams per year, then the landfill owner or operator must either:
A Submit a gas collection and control system design plan within 1
year as specified in 62.16724d and install and operate a gas collection and
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B The mass of nondegradable solid waste may be subtracted from the total mass of solid waste in a particular
Jkt 253001

e-kt CNMOC

3 .6 X 10-9

control system within 30 months according to 62.16714b and c;
B Determine a site-specific NMOC
concentration and recalculate the NMOC emission rate using the Tier 2
procedures provided in paragraph a3
of this section; or C Determine a site-specific methane generation rate constant and recalculate the NMOC emission rate using the Tier 3 procedures provided in paragraph a4 of this section.
3 Tier 2. The landfill owner or operator must determine the sitespecific NMOC concentration using the following sampling procedure. The landfill owner or operator must install at least two sample probes per hectare, evenly distributed over the landfill surface that has retained waste for at least 2 years. If the landfill is larger than 25 hectares in area, only 50 samples are required. The probes should be evenly distributed across the sample area. The sample probes should be located to avoid known areas of nondegradable solid waste. The owner or operator must collect and analyze one sample of landfill gas from each probe to determine the NMOC concentration using EPA Method 25 or 25C of appendix A7 of 40 CFR part 60. Taking composite samples from different probes into a single cylinder is allowed;
however, equal sample volumes must be taken from each probe. For each composite, the sampling rate, collection times, beginning and ending cylinder vacuums, or alternative volume measurements must be recorded to verify that composite volumes are equal.
Composite sample volumes should not be less than one liter unless evidence can be provided to substantiate the
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section of the landfill when calculating the value for Mi if documentation of the nature and amount of such wastes is maintained.
iiA Equation 2 must be used if the actual year-to-year solid waste acceptance rate is unknown.

Eq. 2

accuracy of smaller volumes. Terminate compositing before the cylinder approaches ambient pressure where measurement accuracy diminishes. If more than the required number of samples is taken, all samples must be used in the analysis. The landfill owner or operator must divide the NMOC
concentration from EPA Method 25 or 25C of appendix A7 of 40 CFR part 60
by 6 to convert from CNMOC as carbon to CNMOC as hexane. If the landfill has an active or passive gas removal system in place, EPA Method 25 or 25C
samples may be collected from these systems instead of surface probes provided the removal system can be shown to provide sampling as representative as the two sampling probes per hectare requirement. For active collection systems, samples may be collected from the common header pipe. The sample location on the common header pipe must be before any gas moving, condensate removal, or treatment system equipment. For active collection systems, a minimum of three samples must be collected from the header pipe.
i Within 60 days after the date of determining the NMOC concentration and corresponding NMOC emission rate, the owner or operator must submit the results according to 62.16724j2.
ii The landfill owner or operator must recalculate the NMOC mass emission rate using Equation 1 or Equation 2 provided in paragraph a1i or ii of this section using the average site-specific NMOC
concentration from the collected samples instead of the default value provided in paragraph a1 of this section.

E:FRFM21MYR2.SGM

21MYR2

ER21MY21.005

MNMOC

ti = Age of the ith section, years.
CNMOC = Concentration of NMOC, parts per million by volume as hexane.
3.6 109 = Conversion factor.

ER21MY21.004

Where:
MNMOC = Total NMOC emission rate from the landfill, megagrams per year.
k = Methane generation rate constant, year1.
Lo = Methane generation potential, cubic meters per megagram solid waste.
Mi = Mass of solid waste in the ith section, megagrams.