Village of Taos Ski Valley Wastewater Treatment Plant

With influent wastewater flow and loading during Spring Break and Christmas holiday periods exceeding the mountain community's existing wastewater treatment plant current capacity and faced with the need to expand the plant capacity by an approximate factor of 2.5 times - on a plant site limited by adjacent National Forest land - the public works department of the Village of Taos Ski Valley, New Mexico, required a focused and site-specific solution.

Wastewater treatment plant (WWTP) treated effluent limits are constrained by a total maximum daily load (TMDL) set of limitations which was developed and approved by NMED and USEPA Region 6 for this Rio Hondo stream segment. Plummer’s teaming partner, LRE Water, developed a set of effluent discharge concentrations that are consistent with the TMDL limits for the increased WWTP design flow.  Additionally, LRE Water supported the Village of Taos Ski Valley with portions of the Environmental Assessment during the WWTP planning stages and with renewal of the USEPA Region 6 WWTP discharge permit.

Working in conjunction with the Village, Plummer selected an innovative application of MBR process technology for the expansion and substantial retrofit of the mountain village’s wastewater treatment plant to provide the community with a high-performance, low-cost, technically and publicly defensible pathway to attaining stringent total nitrogen and phosphorus effluent limits, while fully utilizing existing treatment basin infrastructure and minimizing additional treatment basin construction.

The WWTP provides treatment to the Village along with the ski corporation base area, hotels, and associated commercial buildings and housing and has a maximum design flow of 0.44 MGD during peak ski season, yet only a fraction of the flows during the summer. Plummer was selected to provide planning, design, bid, and construction engineering services. Design included retrofitting the existing headworks to fit a new 2 mm mechanical screen and a nested Parshall flume, reusing the existing influent equalization tank, and converting the existing treatment tanks to MBR tanks and anoxic tanks.  New aeration and post-anoxic tanks were also added. The design included the return of high concentration MLSS from the MBR tanks to the pre-anoxic tanks at the head of the secondary treatment process through deoxygenation zones. The plant has a strict effluent total nitrogen concentration of less than 7 mg/L. Design was based on a mixed liquor temperature of 8 degrees Celsius.  

During construction, a contractor-owned temporary MBR was installed to bypass the existing plant and treat wastewater flows. Total project cost was approximately $8.6 million, and construction was completed in 12 months.

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