This document describes the proposed EPA action regarding wastewater treatment facilities for the City of Boulder, Colorado. Alternative facilities involving advanced waste treatment techniques were considered to meet NPDES permit requirements for Boulder Creek. Principal alternatives considered include land treatment by infiltration/percolation, modified activated sludge/trickling filters, chemical treatment, aeration/polishing ponds, and agricultural reuse. A form of activated sludge followed by trickling filters was chosen. Environmental reports were assessed for this plan including effects on water quality, groundwater levels, groundwater quality, odor generation, fog or aerosol formation, increased energy demand, land use patterns, public health problems, soil productivity and visual effects.