The Port of Grays Harbor in Washington state proposed using water from Ranney Collector Well No. 1 on the Chehalis River to supply potable water to the Satsop Business Park. Ranney Collector Well No. 1 was originally installed for the Washington Public Power Supply System’s Nuclear Project No. 3. Ranney wells are specifically designed to induce infiltration from a surface water source through permeable sediments, taking advantage of the vertical head drive and filtration this provides. Given this dual-source dynamic, the Washington State Department of Health (DOH) required a “hybrid approach” to protect both groundwater and surface water pathways from potential sources of contamination. DOH specifically recommended Terraphase for this work based on our prior successful hydrogeologic mapping work for the nearby City of Elma.
Scope of Services
Terraphase was selected to carry out the groundwater component of the Wellhead Protection Plan, including the wellhead protection area (WHPA) delineation and hazard inventory. After obtaining historical construction documentation for the Ranney well, our team reviewed well logs from 164 regional wells, selecting 91 to define the local potentiometric surface. Water levels were converted to elevations using Light Detection and Ranging (LiDAR) data, which also provided accurate surface elevations for the Chehalis and Satsop Rivers. An analytical model was developed to simulate drawdown from the Ranney well and create a pumped-surface map. Virtual particles released in the model were tracked to identify upgradient groundwater flowpaths for a 6-month time-of-travel; these flowpaths were extended upgradient, and hydrogeologic mapping was used to identify the1-, 5-, and 10-year time-of-travel zones. These zones were used to delineate the WHPAs.
To assess contamination risks, Terraphase mapped potential hazard sites within the WHPAs based on third-party environmental database research. Following field verification, these sites were ranked using a custom methodology developed through previous work with DOH. This ranking also considered land use patterns, transportation corridors, and waste disposal practices to ensure a comprehensive evaluation of contamination risks.
Notable Accomplishments
- Used LiDAR data to enhance groundwater elevation accuracy for potentiometric mapping
- Completed groundwater source protection for Ranney Collector Well No. 1
- Identified and ranked contamination risks within WHPAs
- Delivered a complete Wellhead Protection Plan
- Provided templates for agency and stakeholder notifications
