2017-05-23_GENERAL DOCUMENTS - M1977472

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maximums would be similar to the hottest summers that have occurred in past 100 years. Precipitation projections are less clear, with individual models showing a range of changes by 2050 of-5%to +6% for RCP 4.5%, and -3%to +8%under RCP8.5. Nearly all of the models predict an increase in winter precipitation by 2050, although most projections of snowpack (April 1 SWE) show declines by mid-century due to the projected warming. Late-summer flows are projected to decrease as the peak shifts earlier in the season, although the changes in the timing of runoff are more certain than changes in the amount of runoff. In general, the majority of published research indicates a tendency towards future decreases in annual streamflow for all of Colorado's river basins. Increased warming, drought, and insect outbreaks, all caused by or linked to climate change, will continue to increase wildfire risks and impacts to people and ecosystems. 5.2.3. Environmental Consequences — No Action Alternative As described in the general description of the No Action Alternative for this Environmental Assessment, under the No Action Alternative, none of the proposed project components described in the Proposed Action would take place. Air quality impacts for the No Action Alternative would be minimized and mainly limited to the activities for any pit reclamation related activities. 5.2.4. Mitigation Measures As previously described, the bulk of the activities for the proposed action will primarily have temporary negative air quality impacts for criteria pollutants (primarily PM) and HAPs related air quality during surface disturbing and material processing events when persistent dry weather conditions exist, and are not predicted to cause a significant impact to visibility at the nearest Class I area. To ensure additional protection from project-related dust emissions, the following good management practices/mitigation measures should be implemented for the project: - • Reduce vehicle speed on unpaved surfaces (minimizes dust emissions—PM emissions can be a direct linear relationship with vehicle speed; reduce speed by 10% to reduce PM emissions by 10%); • Minimize surface disturbing activities when windy episodes are forecasted and dry weather conditions exist (minimizes dust emissions—operating on days when the wind gusts [not sustained wind speed] do not exceed critical threshold velocity [—43 mph] almost eliminates wind erosion PM emissions for that day); • Apply water or other dust control measures to unpaved surfaces that will experience multiple daily traffic trips or surface disturbance associated with extraction/mining during dry weather conditions; especially at areas on unpaved roadways near residences, places of business or similar(minimizes dust emissions—routine application of water can reduce PM emissions by 50%; greater dust control efficiency can be achieved for other dust control measures); • Minimize surface disturbing activities during windy events and/or for long periods when steady winds are forecasted that would transport dust in the direction of human populated areas DOI-BLM-CO-N020-2017-0003 23