Solutions to Expand Treatment and Disposal Capacity of a Lagoon Facility in Environmentally Sensitive Area

The Callville Bay lagoon treatment and disposal facility, located in Lake Mead National Recreation Area, is currently operating at more than 85 percent of its capacity and has no capacity for future development demand. There is no volume redundancy for hydraulic dampening or for adequate maintenance. The infiltration pond is currently not functioning.A design analysis was conducted by HDR to evaluate the treatment and disposal capacity of the facility under current and future flow conditions, present potential alternatives to increase the facility treatment and disposal capacity to meet future wastewater demands, and identify the most cost-effective and environmentally-friendly alternative using NPS required method of analysis.The analysis results indicated that the existing lagoon facility should have enough treatment capacity to meet current and expected future flow demands. The existing facility does not have enough disposal capacity for the expected future flow. A total of 5.1 million gallons per year of disposal capacity is needed. An off-site space will need to be selected within the beach resort area to provide extra disposal capacity. Because the location is in an environmentally sensitive area, selecting a suitable location that does not create negative aesthetic impacts or public health issues for the resort was a challenge. In addition, NPS requires that the new pond be low maintenance and have low energy consumption. One alternative to expand the treatment capacity and three alternatives to expand the disposal capacity of the facility were presented. All the alternatives were further evaluated using the NPS/DSC Mini VA - CBA process to select the most cost effective and environmentally friendly method to expand the existing facility. Results indicate that keeping the existing facility unchanged and converting the abandoned lagoons to infiltration ponds with raised levees would be an acceptable alternative.