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l~ CHAPTERTHREE Affected Environment Thirteenmile Creek Tongue of the Green River Fonnation. This is the same formation on which the threatened and endangered plants of the Piceance Basin are found. Inventories have also shown the ponderosa to be reproducing, thus having a diverse age structure. This indicates that ponderosa pine are acting as a narrow endemic within the Piceance Basin. Considering that these pines aze an isolated population, they may have developed unique genetics as a result of their unique environmental growing conditions. Given the relatively small number of trees and the limited habitat, all effort should be placed on avoidance of the trees and the Thirteetunile Creek Tongue formation, on suitable slopes and aspects. Figure 3.7-1 identifies these suitable habitats. One stand; however, located in the 25-30 yeaz mining panel has been designated as a remnant vegetation association (RVA). The location of this RVA is shown on Figure 3.7-1. The RVA is about 30 acres in size, which includes a small buffer zone sufficient for protection of potential reproduction (BLM no date). 3.7.2 Pipeline Corridor The project pipeline route may be described according to three geographicalljurisdictional segments. The first segment extends from the initial processing plant at the Piceance Site and generally southeast to the Greasewood Compressor Station, which is located on an existing north-south natural gas pipeline corridor. This first segment is approximately 9 miles long, including 2 miles that are within the Piceance Site, and primarily occupies BLM land. The last 2 miles of this segment parallel an existing east-west natural gas pipeline corridor. The beginning of the pipeline route, which lies within the Piceance Site, traverses all five of the upland plant communities described for the Piceance Site above. Immediately upon exiting the Piceance Site, the pipeline route crosses the cultivated hayfields that occupy the Piceance Creek valley bottom. On the east side of Piceance Creek and Piceance Creek Road, the pipeline route ' ascends Hatch Gulch. The bottom of Hatch Gulch is occupied by sagebrush vegetation with some pinyon juniper on the sideslopes. As the pipeline route comes up out of Hatch Gulch and begins to follow the existing east-west Questar natural gas pipeline corridor, the upland areas to 1 the Greasewood Compressor Station primarily support open pinyon-juniper woodlands. The second pipeline corridor segment includes approximately 12 miles paralleling the existing north-south pipeline corridor and extending from the Greasewood Compressor Station south to about two miles north of the Rio Blanco-Gazfield County Line. Virtually all ridge and upland sites in this segment support pinyon juniper woodlands for a total of about 3 miles traversed ' (Steigers 19986). This segment also crosses about 7 miles of sagebrush vegetation, mostly along the bottom of Stewart Gulch and about one-fourth mile of irrigated hay meadows at Piceance Creek at about MP 14. Approximately 2 miles of the Mountain Shrub Association would be crossed between MPs 9 and 10 and between MPs 19 and 20. The Mountain Shrub Association has been described by the BLM (1994} and Tiedeman and Terwilliger (1978) as follows. Mountain Shrub Association The Mountain Shrub Association occupies higher elevations on east. west, and north slopes, extending to lower elevations on cool exposures. The primary environmental factor affecting the association is available moisture, as influenced by elevation, soils, topography, and wildfire. It is Vegetation 3-29