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300 PETROLEUM CONTAMINATED SOILS ESTIMATES FOR HYDROCARBON VAPOR EMISSIONS 3i)1 <br /> Table 1 Compos don o1 a Regular Gasoline Table 1. Continued <br /> Mw Weight Mole Pl"(20`C) Mw Weight Mole PI"t20 C <br /> Compound Name (g) Fraction Fraction (atm) Compound Mame (g) Fraction Fraction (aim) <br /> propane 441 011005 00001 850 1,2,4,5-te iarnethylbenzene 1342 00511 00354 000046 <br /> Isobutane 581 00085 00137 293 1,2 3,4-tetramethytbenzene 1342 00053 0 OD37 0 00033 <br /> n-butane Sol 00259 00415 211 1,2,44nmelhyi-5-athylbenzene 1482 001191 00120 0 00029 <br /> trenS-2 buten* 561 00019 00032 197 n-dodocane 1703 0 0050 0 OD27 000040 <br /> cm-2-butene 661 00018 0 003D 179 naphihalene 1282 0 DD41 0 OB30 000014 <br /> a-metho 1-butene 701 00010 00013 096 methylnaphthalene 1422 0 0061 00040 000005 <br /> Isopentane 722 00916 01181 078 Total 0 996 0 999 <br /> 1-pentene 701 00032 00042 070 <br /> 2-methyl"Mone 701 0 0068 00090 067 For these values, Figure I indicates that Equation 3 is applicable below a residu <br /> 2-melhyl 1,3-butadiene 6B 1 00068 00092 065 <br /> n-pentane 722 00628 00810 057 al soil contamination level of about 54()mg-gasoblkg <br /> ne -sod.Above this resitlu,i <br /> bans 2-pentene 701 00138 00184 053 concentration level, however, Equation 3 predtcts increasing vapor concenlr.i <br /> 2-methyl 2-butene 701 00129 00171 051 lions with increasing msldual levels,while the complete model predicts that vapo <br /> 3-mothy6l 2-butadiene 681 00003 00004 046 concentrations become independent of the residual concentration level This limn <br /> Cyclopentane 701 00185 00245 035 ing behavior is predicted by Equation 4 One roust be very careful when ustnl <br /> 2,3-dimethylbutane 862 00114 0 04 20 026 <br /> 2 methylpentans 86.2 00515 00556 021 transpari models based on a "three-phase model," such as Equation 3, beCauS <br /> 3 methylpentane 852 0 0314 00340 020 they will overpredicl vapor concentrations and emission rates for many sdua <br /> n4iexane 862 0 041 t 00444 016 tions Usually there are no internal checking procedures in these models to cn <br /> melhytcyclopentane 842 00214 00237 016 sure that unrealistic tiapor concentrations are not being predicted <br /> 2,2 dlmathylpantane 1002 00077 00071 Oil <br /> benzene 78 1 00172 00205 010 7 liroughout this chapter, Equation 4 is used la predict egiiifibnum vapor cora <br /> cyclohexane 642 00059 00065 0 fo centrations because it is most applicable for the residual concentration levels c it <br /> 2,3-dime1hytpentane 1002 00063 00058 0 072 Countered at typical service station spill sites <br /> 3 methylhexane 1002 00099 00092 0 064 <br /> 3 ethylpentane 1002 0 0166 00155 0 060 112 Vapor Flux Models <br /> n heplane 10D 2 0 0355 00331 0 045 <br /> methylcyclohaxane 98 2 000-55 00052 0 048 <br /> 2,2-dimethy1hexane 1142 00046 00035 0 035 In the following analysis,models are presented for computing conservaw c c ti <br /> tolusne 92 1 00899 00908 0029 timates for emissions resulting from processes associated with typical ser+icc ,I.t I <br /> 2-melh}thepiana 114 2 00026 0OD23 0021 tion reniediations Specifically, we will consider emissions associated wnli tali; <br /> 3 mathylhoplane 114 2 0OD62 0 0051 0020 excavation, in-situ soil venling,and the pumping of groundwater and free liquid <br /> n-octane 1142 00647 00528 0 014 <br /> 2,4 4-trimelhythexane 1283 00015 00011 0 013 hydrocarbons <br /> 2,2-dirnelhytheptane 1283 0 OD03 00002 0 811 <br /> ethylbenzene 1062 00205 0 0180 0 0092 11 2a Emissroris Associated with Tank or Sort Excavatrcn <br /> p xylene 1062 00153 00134 0 0086 <br /> o xylene 1062 00221 00194 0 0066 During tike excavation of leaky Storage tanks, tank backfill material (u-,ualh <br /> n nonane 1283 00155 00112 00042 <br /> 3,3,5-trimethylheptane 1423 00033 00022 00037 pea gravel) is removed from die tank area and placed in a pile In somt Stdlt <br /> n propylbenzene 1202 00346 00268 00033 the pile of contaminated soil can remain uncovered as long as the excavation dca< <br /> 1,3 Sdnmethylbenzene 120 2 00201 0 0156 00024 not cease for more than an hour (a '`cine-liour working pile") Figure 2 illus <br /> 1,2,4 Inmethylbanzens 1202 00061 00047 00019 trates this operation Both the excavated soil pile and the empty tank pit are potea <br /> n-deeane 1423 00343 00224 00036 tial sources of hydrocarbon enussions In addition, during the excavation pro((-,,, <br /> methylpropylbenzene 1342 00210 0 0146 00010 fine particulate material may be released to the atmosphere In this stud) into, <br /> dimethylelhylbenzene 1342 00173 00120 000070 <br /> n-undecanD 1563 00078 00046 000W port of particulate materials is neglected <br />