The first statewide stream macroinvertebrate bioassessment in Washington State with a relative risk and attributable risk analysis for multiple stressors

•Statewide bioassessment and stressor analysis of macroinvertebrate communities.•Nearly one-third of stream kilometers assessed in poor biological condition.•Biological impairment nearly four times more likely with elevated sand/fines.•Reducing elevated sand/fines may improve biological impairment by up to 60%.•Biological impairment of macroinvertebrates associated with loss of sensitive taxa.