Built for the mountains: upgrading wastewater treatment in one of Colorado’s most remote towns
Tucked into a narrow valley at 8,671 feet in the San Juan Mountains, Lake City, Colorado is the kind of place where the nearest traffic light is an hour away. About 700 people call it home year-round, but every summer the population swells dramatically as anglers, hikers, and off-road enthusiasts pour in to take advantage of some of the most spectacular terrain in the American West. That seasonal surge, combined with punishing high-altitude winters, makes running a reliable wastewater treatment plant here a genuinely unique challenge.
Lake City’s existing lagoon system has served the community well, but with population projections pointing toward steady growth, the town recognized that its current infrastructure would need reinforcement. Rather than a wholesale replacement, they implemented a two-fold approach for increasing their treatment capacity: expanding the existing lagoon volume while also installing Entex’s WavTex Fixed Media System for process intensification. With the 2043 design scenario projecting influent flows up to 0.275 MGD, and BOD and TKN loads more than double current levels, building in that added treatment capacity now was a forward-looking move.
Lagoon-based treatment is common in rural Colorado communities, but conventional lagoons rely on suspended biomass that slows significantly in cold weather, making it difficult to consistently meet effluent limits through winter. Fixed-film media addresses this by giving beneficial microorganisms a permanent surface to colonize. The media maintains biological activity even as liquid temperatures approach freezing, ensuring compliance of future effluent NH₃ limits ranging from 6 mg/L in the summer to 9 mg/L in the winter.
The Lake City installation consists of nine WavTex modules, each loaded with 8,265 ft² of EnTextile media, a high-surface-area woven textile media that provides an ideal substrate for biofilm growth. Each module measures approximately 15 ft long × 6 ft wide × 10.5 ft tall.
Aeration is handled by an integrated dual coarse and fine bubble grid. The coarse bubble grid, positioned directly beneath the media, scours the biofilm to maintain healthy thickness, supplying up to 100 scfm per unit. Meanwhile, the fine bubble grid below provides energy-efficient process air of up to 121 scfm per unit. An expanded metal shroud on all four outer walls channels rising air upward through the full media height, driving mixing across a zone of influence of roughly 50 to 70 feet per unit.
Lake City faced an additional design challenge; in addition to intensifying treatment, they wanted to fit their lagoon with an insulated cover for year-round temperature control. Through close collaboration between the Entex team, the design engineer, and the selected cover supplier, the WavTex system was designed to minimize above-water appurtenances, maintaining compatibility with the cover system. The WavTex frames were adapted so that only the aeration drop pipe connection, sitting six inches above the water line, passes through the cover, with a dedicated support structure handling that connection. All other frame components remain submerged.
The lagoon floor has a 2% slope along its length. Each WavTex frame was sloped to match, keeping the aeration grids level in the water for even air distribution across all nine units, regardless of position on the grade. To minimize field assembly in this remote location, all air piping below the waterline was pre-assembled before delivery. The two aeration drop pipes serve as the primary field connection point per module.
The first phase system, consisting of five modules, had a successful start-up in September 2025, with another four modules planned for installation in the coming months. The successful startup is a meaningful milestone for a small mountain community navigating a short construction season, some genuinely demanding site conditions, and a solid foundation for the growth Lake City has ahead of it.