UNAVOIDABLE ADVERSE IMPACTS 

CHAPTER 6 
6.0 Unavoidable Adverse Impacts 

The vertical line in the margin identifies text that has been modified in this Final EIS and 

differs from the corresponding text in the Draft EIS 

Unavoidable adverse impacts are the effects on natural and human resources that would remain after 

mitigation measures have been applied. Table 6-1 contains a summary of those impacts. 

Table 6-1 Summary of Unavoidable Adverse Impacts 

Soils. A small fraction of the construction ROW and ancillary facility topsoil that would be graded, 

stockpiled, and replaced would be mixed, buried, or lost from the ROW or site because of wind and water 

erosion, especially across sensitive soils. 

Native Vegetation/Wildlife Habitats. Clearing and grading native and non-native grassland, shrubland, 

and forest communities would result in long-term changes in species composition and community 

structure (height and density) within the pipeline construction ROW and ancillary sites. Based on 

reconnaissance of existing pipeline ROWs, recovery of pre-existing vegetation cover and diversity for 

grassland communities after disturbance generally is 5 years. Shrubland forest communities would begin 

to regenerate within 10 years. 

Land Use – Utility use conversion. Private land would be converted to utility uses within new 

permanent utility ROWs during the 30-year project life. Land uses that would not interfere with pipeline 

operations (e.g., farming, livestock grazing, etc.) would continue. 

Land Use – Conversion to industrial land uses. Rangeland and agricultural land would be converted 

to pipeline products terminals, pump stations, and pressure control stations for the project life. The 

Proposed Action could result in conversion of 9 acres to industrial land uses. 

Water Quality. Unavoidable temporary impacts to water quality could occur during construction at river 

crossings. Turbidity and sedimentation could be increased, although mitigation measures would minimize 

extent and duration of impacts. Similarly, unplanned releases of drilling mud could occur during 

installation of HDD stream crossings, but if this occurs, it would be quickly mitigated. 

Wildlife Resources. Aquatic habitat could be unavoidably disturbed, either in the short term or the long 

term at river crossings. Trenching activities could result in localized mortalities to fish, macroinvertebrates, 

and amphibians. Egg and juvenile life stages would be the most vulnerable to equipment. Depending on 

the time of construction, crossing of the Green River, Chief Creek, and North Fork of the Republican 

River could cause mortalities to fall-spawning fish, such as kokanee salmon and brown trout. If open-cut 

crossings of the Hams Fork River and one of the Blacks Fork River (RP 18.9) were improperly restored, 

long-term effects on special status fish species habitat could occur. Potential scouring also could affect 

fish movements during low flow periods. Terrestrial biota could be disturbed, removed, or, in rare 

instances, killed during construction activities. Measures would be taken to reduce potential effects on 

special status species. 

Public Safety. Installation of a pipeline has some degree of unavoidable potential impact with regard to 

public safety. Risk analysis indicates the occurrence of a pipeline accident affecting the public is unlikely. 

The pipeline is new and incorporates safety features and design aspects that increase safety. 

Aesthetics. The presence of the pipeline and associated facilities has an unavoidable aesthetic effect. 

Early in the project the pipeline would be visible, as vegetation re-establishes. 

Cultural Resources. Construction could result in the loss of unique or significant archaeological 

information. Required surveys reduce this potential. 

6-1