Laserfiche WebLink
<br />Of)' 7"7 <br />,,~ 0 <br /> <br />For many years, the particulate matter standard included <br />all size ranges of particulates (thus total suspended <br />particulates). Measured values were dominated by fugitive <br />(wind blown) dust particles, which are larger than those <br />produced in combustion processes. These particles settled <br />relatively quickly, and presented a minimal health threat. <br />The Environmental Protection Agency (EP A) has recognized <br />thp.<:p. 1imitatin"~ hv cpttintr n,.,v danl'hl1"AC! fn1" norti"nlo.tll'"f:! <br />------ --..---............ ....J ......-.....eo ....w.. ...........--- ...... y-o...___........ <br />less than 10 microns in diameter, commonly called inhalable <br />particulates and abbreviated PM... The TSP standards may <br />be phased out over time. <br /> <br />Areas that consistently violate minimum Federal standards <br />because of man-caused activities are classified as "nonat- <br />tainment" areas, and a plan must be implemented to reduce <br />ambient levels below the maximum pollution standards. <br />Under the EPA "Fugitive Dust Policy," areas that violate <br />the TSP ambient air quality standards, but lack any <br />significant industrial particulate sources and have a <br />population less than 25,000, are designated as "unclassified" <br />(i.e., neither "attainment" nor "nonattainment"). "Unclas- <br />sified" areas are generally exempt from having to meet the <br />offset provisions, retrofit controls, and new source control <br />requirements established for "nonattainment" areas by the <br />Clean Air Act <br /> <br />To protect areas not classified as "nonattainment," Congress <br />established a system for the prevention of significaot <br />deterioration (PSD) through the Clean Air ActAmendments <br />of 1977, Areas were classified by the additional amounts <br />of allowable TSP and SO, degradation. PSD Class I areas, <br />predominantly natioual parks and certain wilderness areas, <br />have the greatest limitations; virtually any degradation would <br />be significant. Areas where moderate, controlled growth can <br />take place are designated as PSD C1ass II. PSD Class III <br />areas are those areas that allow the greatest degree of impacts. <br />Colorado established a similar program limiting additional <br />amounts ofSCh, and lands are classified Category I, Category <br />II and Category III (corresponding to greater permisSIble <br />levels of S(2). <br /> <br />Existing Air Quality <br /> <br />The entire resource area has been designated as either <br />"attainment" or "unclassified" for all pollutants; most of <br />the area has been designated PSD Class II. Within the <br />resource area, only the Great Sand Dunes, Weminuche, <br />and La Garita Wilderness Areas are PSD Class I/Colorado <br />Category I Areas (Map 2-2). For the most part, the air <br />quality in the San Luis Valley is excellent. <br /> <br />Although there is no gaseous pollutant monitoring in the <br />resource area, levels are estimated to be low and within <br />standards. Ozone levels in the Rocky Mountain West are <br /> <br />AFFECTED ENVIRONMENT <br /> <br />relatively high, but of unknown origin, The true reason for <br />elevated owne values is uncertain, but elevated concentra- <br />tions may be a result of long-raoge transport from urban <br />areas, subsidence of stratospheric ozone, or photochemical <br />reactions with natural hydrocarbons. Occasional peak <br />concentrations of CO and NO, may occur in the immediate <br />vicinity of combustion equipment. <br /> <br />Particulate matter concentrations are expected to be higher <br />near towns because of local combustion sources (PM..) and <br />unpaved roads (TSP); significant regional TSP levels are <br />probably due to fugitive dust (primarily wind blown). <br />Average and extreme particulate concentration data collected <br />at Alamosa are shown in Table 2-4. <br /> <br />Table 2-4 <br />SELECTED PARTICULATE <br />CONCENTRATION DATA (TSP) <br />(micrograms per cubic meter) <br /> <br />~ <br /> <br /> Annual 2nd <br />Station No. Geo. 24- <br /> hr <br />Name/Type Year Obs. Mean Max. <br />AlamosalUrban 1987 57 48 101 <br /> 1986 58 50 106 <br /> 1985 67 49 128 <br /> 1984 81 52 146 <br /> 1983 88 51 235' <br /> 1982 88 52 145 <br /> <br />~ <br /> <br />, Violation of Ambient Air Quality Standards. <br />Source: Colorado Department of Health, n.d. <br /> <br />PSD C1ass I regulations also address the potential for impacts <br />to air qnality related values (AQRVs). These AQRVs include <br />visibility, odors, and impacts to flora, fauna, soils, water, <br />geolugic, and cultoral features. A possible source of impact <br />to AQRVs is acid precipitation. Mechanisms of acid <br />precipitation formation are currently under study; <br />preliminary results bave correlated ambieot sulfuric and nitric <br />acids and combustion by-products (sulfates and nitrates). <br />Average and extreme acid precipitation data (wet deposition <br />pH) measured at Alamosa are shown in Table 2-5. <br /> <br />2-5 <br />