Spokane County Regional Water Reclamation Facility DBO – Owner’s Representative
In early 2000, Spokane County began a planning process with HDR as their principal consultant and advisor to develop long-term wastewater management strategies that would provide reliable service, protect the environment and be economical to local ratepayers. HDR developed a programmatic approach to providing wastewater service, including TMDL negotiations with the Washington State Department of Ecology. HDR prepared a facility plan for the County, that recommended a new treatment plant be constructed with a discharge to the Spokane River. The County selected a membrane bioreactor (MBR) facility with an initial capacity of 8 MGD, expandable to 12 MGD.
In addition to preparing the facility plan, HDR developed a preliminary design which included a detailed process analysis and model to evaluate water quality impacts to the Spokane River and the underlying aquifer. This design was required to meet the lowest effluent phosphorus limits in the nation, 0.05mg/l, and provide effluent reuse, aquifer recharge and wetlands restoration.
HDR also developed an innovative Water Quality Offset (trade) under the existing Washington Administrative Code for a nonpoint source load reduction of phosphorus from sewering 15,000 on-site septic systems over the Spokane Valley/Rathdrum Prairie Aquifer to compensate for the new wastewater effluent point source discharge to the Spokane River.
- This is one of the largest MBR plants in the world with an expandable capacity of 12 MGD.
- As Spokane County's owner's representative, HDR developed and is managing the DBO procurement for the water reclamation facilities, and the project is currently on schedule and budget.
- Minimizing the owner's process risk for biological and chemical phosphorus removal was a key project challenge. HDR created a DBO procurement that required proposers to develop technically sound and cost competitive process solutions to phosphorus removal.
- HDR assisted the County with siting a new treatment facility and long-term planning needs to meet stringent discharge limits. Effluent phosphorus must be less than 50 micrograms per liter, one of the lowest limits in the U.S.
- Use of alternative delivery, in this case Design/Build/Operate. HDR is the owner's representative assisting the County with procurement and selection of a DBO contractor.