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Project to Replace the Failing Wastewater Treatment Facility
Wind Cave National Park » Project to Replace the Failing Wastewater Treatment Facility » Document List
The Wind Cave National Park wastewater treatment lagoons are currently undersized and poorly located to accommodate the wastewater generated by park facilities. The existing evaporation ponds have 3.2 acres of surface area and are located at the base of a west-facing slope. This site is partially protected from wind and sun making for poor evaporation. Total inflow to the ponds consists of 2.5 million gallons of wastewater per year and 1.6 million gallons of rainfall.
At the current location, evaporation rates are not sufficient to remove this total annual input. Between 1989 and 2000, the ponds filled to capacity three times. Effluent from the ponds was then discharged onto designated "spray fields" within the park. This process requires a discharge permit from the South Dakota Department of Environment and Natural Resources. The state has notified the Park Service that additional one-time discharge permits will likely not be issued, and that a permanent means for resolving the park's wastewater problem must be sought.
In addition, water quality testing of cave waters has revealed in the past the presence of contaminants found in untreated wastewater. Although no cave passages have been found directly below the current lagoons, there is a good chance that they exist at this location and a breach of the liner could contaminate these resources.
In 2003, the NPS issued an environmental assessment and finding of no significant impact, proposing to construct a wastewater transmission line to convey the park's sewage to Hot Springs, SD for treatment. The NPS entered into consultation with Hot Springs and received approval from the City Council to pursue construction of the wastewater transmission line and connect to the municipal wastewater treatment system. In April 2004, the City of Hot Springs held a referendum on a measure to move forward with the wastewater agreement with the park. The measure was defeated by voters and further planning for the transmission line came to a halt.
This resulted in the park choosing a different alternative analyzed in the environmental assessment to address their long-term wastewater management needs. In order to utilize non-discharging lagoon treatment methods for managing wastewater at Wind Cave National Park, three larger lagoons will be constructed at an appropriate site. The new ponds will be constructed at a location just north and east of the existing lagoons, approximately 80 feet higher in elevation. This site is on a ridge bench where there is more space for larger lagoons, winds are stronger, and there is increased exposure to sunlight. The new ponds will allow, on average, evaporation to keep up with inflows. However, during the wetter years, the increased capacity of the lagoons would allow full retention without out any discharges.
At the current location, evaporation rates are not sufficient to remove this total annual input. Between 1989 and 2000, the ponds filled to capacity three times. Effluent from the ponds was then discharged onto designated "spray fields" within the park. This process requires a discharge permit from the South Dakota Department of Environment and Natural Resources. The state has notified the Park Service that additional one-time discharge permits will likely not be issued, and that a permanent means for resolving the park's wastewater problem must be sought.
In addition, water quality testing of cave waters has revealed in the past the presence of contaminants found in untreated wastewater. Although no cave passages have been found directly below the current lagoons, there is a good chance that they exist at this location and a breach of the liner could contaminate these resources.
In 2003, the NPS issued an environmental assessment and finding of no significant impact, proposing to construct a wastewater transmission line to convey the park's sewage to Hot Springs, SD for treatment. The NPS entered into consultation with Hot Springs and received approval from the City Council to pursue construction of the wastewater transmission line and connect to the municipal wastewater treatment system. In April 2004, the City of Hot Springs held a referendum on a measure to move forward with the wastewater agreement with the park. The measure was defeated by voters and further planning for the transmission line came to a halt.
This resulted in the park choosing a different alternative analyzed in the environmental assessment to address their long-term wastewater management needs. In order to utilize non-discharging lagoon treatment methods for managing wastewater at Wind Cave National Park, three larger lagoons will be constructed at an appropriate site. The new ponds will be constructed at a location just north and east of the existing lagoons, approximately 80 feet higher in elevation. This site is on a ridge bench where there is more space for larger lagoons, winds are stronger, and there is increased exposure to sunlight. The new ponds will allow, on average, evaporation to keep up with inflows. However, during the wetter years, the increased capacity of the lagoons would allow full retention without out any discharges.