Groundwater recharge is an essential part of the LOTT Alliance (LOTT) Wastewater Resource Management Plan (Plan) for providing wastewater management services for the North Thurston County Growth Management Area. One of the primary objectives of the program is to recycle 100 percent of new wastewater demand by incrementally adding groundwater recharge capacity with service area growth. In lieu of a surface water discharge, groundwater recharge provides the failsafe discharge capacity necessary for LOTT to sustain service. The Plan focuses on a product-based approach to identify: • Where the water can be most beneficially used, • What water quality is required, and • What is the best delivery mechanism. Based on level of service goals and adopted public values, LOTT treats wastewater to Washington State Class A standards (equivalent to CA Title 22) prior to groundwater recharge using surface infiltration basins. To maximize the return on existing assets and minimize costs, the service area is managed to balance the supply (wastewater generation) and demand (groundwater recharge capacity / reuse) with key diversion points in the wastewater collection system. The program begins with developing facilities and operating practices around proven ability to beneficially recycle the water (groundwater recharge). This requires an understanding of how much water can be applied, describing where recharged water goes and how quickly, and determining potential impacts to water supplies in terms of water quality, quantity (flooding), and environmental / public health. Identifying candidate sites is an involved process and includes pilot testing, computer simulation and site development to understand the disposition of the recharged water. To minimize financial and program risk, we have developed a structured process to assure the groundwater recharge program is most successful. LOTT currently has procured two locations, one fully operating facility, and has several others in varying stages of this procurement process. To meet their buildout condition, LOTT anticipates groundwater recharge capacity of approximately 24 million gallons per day (MGD) (90.8ML/d) will be required; currently capacity is 8 MGD (30.3 ML/d). This paper describes the process and activities undertaken by LOTT to identify, select, procure, and implement groundwater recharge facilities integrated with their environmental documentation, while minimizing risk and controlling long-term costs in accordance with their Wastewater Resource Management Program. The objective is to gather information in a measured fashion to ascertain the risk and benefits for each site as additional investments are made. The Plan includes a combination of conservation, Plant process improvements, and the acquisition of groundwater recharge sites. A Business Case Evaluation (BCE) is being used to determine the most effective options as the plan is implemented.
Integrated Site Selection Process to Sustain LOTT's Groundwater Recharge Program
Authors: Chris Cleveland, Kim Murillo; Charles Ellingson (Pacific Groundwater Group, Seattle); Joel Massmann (Keta Waters, Mercer Island)
2007 WateReuse Conference