Sea Level Rise Collaborative Team updates the projects and studies conducted in 2023 

The Seal Level Rise Collaborative Team updated the public on the status of various studies and projects underway to help the region prepare for rising sea levels.  

At the SLR Collaborative-Executive Committee meeting on Friday, December 1, the staff provided the 2023 Workplan updates, such as tide gauge installation, groundwater study, subsidence survey, and finance and governance evaluation.  

New tide gauge 

Susan Clark, Olympia's Engineering and Planning supervisor, gave a brief update on installing a new tide gauge at the Port of Olympia's shipping berth in Budd Inlet. She noted that Stormwater Utility staff have begun monitoring water level data from the gauge and have set alarms to alert when tide heights reach 17 feet to provide advanced warning of potential downtown flooding, given that much of the area is between 18 to 20 feet in elevation.  

In her presentation, Clark showed a dashboard reflecting current tide levels and water pressure readings as well as the following steps to work on making the data accessible to other groups to support local monitoring of tidal conditions and flood risks. 

Tye Menser, representing the Thurston Board of County Commission, wanted to understand how the gauge data would help determine how sea level rise progresses when specific rise amounts are discussed. 

Clark responded that the tide gauge would allow them to measure tide levels over time and see how the average changes as sea level rises. While she is not an expert in how tide gauges work, the data is collected continuously and stored in the Cloud so they can monitor trends.  

Eric Christensen, ex-officio committee member, added that forecasts currently show a gradual but consistent increase in sea level rise for the Seattle area based on existing gauges. However, the new gauge in Olympia will provide real-time, localized data that can be compared to predictions to understand better the impacts of events like strong storms that cause higher tides and flooding. 

Groundwater study 

For the groundwater study, Wendy Steffensen, project manager for the groundwater study, presented the key points about the three phases of the study: 

• Phase 1 was to evaluate existing groundwater information and identify any data gaps. A Geographic Information System database was developed containing the locations of shallow groundwater wells, which the consultant surveyed to measure elevation, depth to groundwater, and salinity. They also gauged wells along the shore during low and high tides to determine tidal influence on groundwater levels and generated groundwater contour and salinity maps. Steffensen said this phase is now complete.  
• Phase 2 was intended to fill in any identified data gaps. However, after evaluation, they found no data gaps to fill. Therefore, Phase 2 was skipped since it was unnecessary. 
• Phase 3 will start in spring 2024. This phase will involve additional groundwater monitoring and developing a groundwater model to evaluate the impacts of sea level rise on groundwater levels. Steffensen mentioned that the estimated cost for this phase is $50,000.  

According to Steffensen, the purpose of the study is to assess the potential impact of SLR on: 

• Groundwater elevations 
• Proposed adaptation measures  
• Buried storm and sewer lines 
• Surface water ponding due to daylighting groundwater 

An update was also provided on efforts to conduct a land subsidence study for the Port peninsula and vulnerable portions of Olympia to understand how much land levels in the area may be lowering due to natural processes like sediment compaction.  

Shawn Gilbertson, Port of Olympia Environmental director, discussed the challenges of finding the right partner to provide the level of detail needed. Initially, they engaged 3V Geomatics to determine the relative elevation of the land. However, the consultant group did not have the necessary resolution or breadth to provide what they needed.  

Gilbertson informed the committee that he is setting up a meeting with the University of Washington Climate Impacts Group to explore their expertise and connections that could help advance the study since their statewide survey did not have the local specificity required.  

"We will be exploring other opportunities and perhaps other consultants and partners to help us achieve the subsidence study we need," Gilbertson added.  

Olympia Assistant City Manager Rich Hoey said the firm CohnReznick was selected to help with funding and governance in response to rising sea levels.  

He reminded the committee that the $ 50,000 worth of study would evaluate potential funding and financing options for implementing the sea level rise response plan and examine governance structures and potential legislative changes needed. An initial kickoff meeting with city and port staff is scheduled for the following week, with most of the work in early 2024 and a final report to be presented to the collaborative by mid-May.