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1H',')~~1 ~ 1 "J ~ --.... -- The most northerly box (Box 1) is at the top of the valley, uI;Mind of the resort during drainage winds. 80x 2 defines the area of the planned resort develor;ment in the north meadow. Box 3 is defined by the valley's south meadow area, ending at the county line. Box 4 is the area in the valley downwind of the Wolf Creek Valley resort during drainage winds. During upslope winds, which generally occur during mid-day, Box 4 becomes the u[.\'iil'c I:;ox (i.e., uI;Mind of the development) and Eox I becorres the downwind box. During early model runs, it was determined that Box 4 was not the box of maximum pollutant impact. Thus, the length of 80x 4 was extended in certain cases to pagosa Springs to consider carryover of pollutants carried c.cwn-valley during the evening drainage previous to the day of interest. Pollutant carryover is a term used to describe the back and forth movement of pollutants which are readily dispersed in the atmos{tlere due to low wind speeds and/or temperature inversions. 1. Particulates Under worst case meteorological episodes, the estimated 24 hour total suspended particulate (TSP) concentrations are summarized in Table IV-IO. As can be seen, the maximum 24 hour TSP impacts of 82 ug/m per cubic foot was estimated to occur with meteorological Scenario 2 (strong evening inversion with low aver<Jge wind speed) on January 12, 1984 in Box 3 located in the south meadow area. Addition of the existing background TSP level of 18 ug/m per cubic foot to the maximum impact concentration results in a maximum 24 hour ambient TSP concentration of 100 ug/m per cubic foot. This TSP concentration is considerably below the Colorado and National 24 hour TSP secondary standard of 150 ug/m per cubic foot and primary standard of 260 ug/m per cubic foot, although it would be subst<Jntially higher than the measured highest TSP of 27 ug/m per cubic foot (Table IV-IO). The affected counties (Mineral and Archulet<J) could reduce the levels of potential TSP increase by passing ordinances constraining the number of wood burning appliances or setting more stringent TSP standards. I An additional evalu<Jtiof1 of the effect of pollutant carryover, by lengthening 80x 4, was performed for the highest impact day, January 12, 1984. TI1e effect of pollutant carryover is not considered to be a significant factor in determining the maximun, impact. This appears reasOfIable because of the usual inversion breakup and dispersal of pollutants during mid-day hours. I , I I 185