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<br />Daub & Associates, Inc. Page 3-16 2015 NS Mine Plan Modification <br />1/5/2016 Section 3 General Site Conditions <br />Nitrogen Dioxide <br />Ambient levels of NO2 in remote areas of the Piceance Creek Basin has ranged from <br />2.0 to 30.0 μg/m3, while levels in the more developed regions run slightly higher, to <br />50.0 μg/m3 on an annual average. The Basin is still well below the developed region <br />average; however, it does reflect the effects of increased human activities. <br />Total Suspended Particulates (TSP) <br />TSP is generally split into two sub-components, Particulate Matter that is less than <br />10 microns (PM10) and Particulate Matter that is less than 2.5 microns (PM2.5). The <br />annual average levels for PM10, from reporting stations on the Western Slope range <br />from 16.9 to 24.4μg/m3 (Colorado 2012 Air Quality Data Report, Air Pollution Control <br />Division). Twenty-four hour PM10 maximums from these stations ranged from 50 to <br />176 μg/m3. One station, in Grand Junction, reported PM2.5 values for a 3-Year <br />Weighted Average of 7.8 μg/m3 and a 3-Year Average of 98th percentile value of <br />27.9 μg/m3. <br />Ozone <br />Ozone levels in the Basin have been found to be relatively high, with hourly <br />averages ranging from 118 to160 μg/m3. The specific causes for these elevated <br />levels are as yet undefined, but may be the result of stratospheric injection, long- <br />range transport from urban sources in the northwest or photochemical reaction of <br />natural hydrocarbons. <br />Carbon Monoxide <br />The one-hour standard for CO is 35 PPM. The Colorado Department of Public <br />Health and Environment (CDPHE) reported a decreasing trend of ambient CO <br />values for the Western Slope from 12 PPM in 1991 down to 2 PPM in 2011. <br />Air quality measurements made in remote and urban areas of the region from 1976 <br />through 1981 are presented in Table 3-3. During this time, the nearest stations to <br />the project site collecting air quality data were located at Federal Lease Tract C-a.