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FIGURE 1

Figure 1

Kummer Landfill and the proposed location of
the highschool

APPENDIX 1

Estimating VOC Emissions

University of Minnesota (U of MN) staff estimated emissions rates from the passive vents at the Kummer landfill for 18 VOCs (Maier and Tam 1994). In order to estimate VOC emissions from the passive vents it is necessary to estimate flow rates through the vents as well as the concentrations of VOCs in the landfill gas itself. U of MN staff estimated the flow rates based on conservative and non-site specific assumptions. VOC concentrations used to estimate emissions were based on a one time sampling event of Kummer landfill gas conducted in August 1992.

In order to provide a better estimate of emissions from the landfill, MDH applied flow rates measured from the passive vents on the Kummer landfill. MDH assumed a flow rate of 791 liter per minute (L/min) which was the average flow rate taken from the 23 passive vents on May 26, 1993. These flow rates were then combined with NMOC landfill gas estimates used by the U of MN for estimating total VOC emissions. The emission rates for the four VOCs of highest concern are found on Table 1.

Table 1.

Estimated Emissions for Four VOCs Using the U of MN Method with Site Specific Flow Rates from the Passive Vents (Maier and Tam 1994 and MPCA 1993b)
Contaminant Average Emission Rate (megagrams /yr) Average Emission Rate (grams/second)
Benzene 2.0 E -2 6.3 E-4
Vinyl Chloride 1.9 E-3 6.0 E-5
Ethylene dibromide 1.2 E-2 3.8 E-4
Chloroform 1.0 E-2 3.3 E-4

USEPA Screening Model

The emission estimates in Table 1 were then applied to a USEPA air screening model to estimate air concentrations of these VOCs in the area where the school is proposed (USEPA 1995a). The following inputs were used in the volume source EPA screening model:

  • The landfill area is assumed to be 125 X 105 meters (Actually the landfill area is larger than this, however, MPCA staff believe most of the landfill gas is being emitted by a few vents that make up a 125 X 105 meter area. Therefore all the landfill gas vents are assumed to be in this smaller area. This assumption results in a more conservative estimate.

  • The source release height the pollutants is assumed to be 8 meters. This is the mid-point elevation for all the vents above the base elevation for the surrounding area.

  • The area is assumed to rural

  • The proposed school is assumed to be between 200 and 300 meters from the passive venting system.

  • The initial lateral dimension is assumed to be 29 meters (125 meters divided by 4.3)

  • The initial vertical dimension is assumed to be 1.6 meters (7 meters divided by 4.3).

The model results are reported below
Pollutant Average Annual Air Pollutant Concentrations estimated by EPA Screening Model between 200 and 300 meters (µ/m3)
Vinyl Chloride 0.03
Ethylene Dibromide 0.02
Chloroform 0.01
Benzene 0.03

 

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