-Title
Groundwater Study Update
Recommended Action
Information only. No action requested.
Report
Issue:
Update and discussion on the groundwater study conducted to evaluate the potential impact of sea level rise on groundwater levels in downtown Olympia.
Staff Contact:---
Pamela Braff, PhD, Director of Climate Programs, 360.753.8249
Presenter(s):
Wendy Steffensen, LOTT Clean Water Alliance
Nathan Starr, Pioneer Technologies Corporation
Background and Analysis:
In March 2019, the City of Olympia, LOTT Clean Water Alliance, and the Port of Olympia completed the Olympia Sea Level Rise (SLR) Response Plan. The Plan outlines strategies to protect key areas-including downtown Olympia, the Port Peninsula, and the LOTT Budd Inlet Treatment Plant-from flooding caused by projected sea level rise. It provides a comprehensive framework for adapting to rising sea levels in both the short and long term.
In addition to physical and operational strategies to address flood risks, the Plan also identifies a range of informational strategies to address data and knowledge gaps in our understanding of local flood risks and vulnerabilities. Improving our understanding of local conditions will help the Collaborative better plan for and respond to sea level rise.
One key knowledge gap identified in the Plan is the potential impact of sea level rise on future groundwater levels. As tide elevations rise above the land, hydraulic pressure could cause groundwater levels to exceed the land surface, potentially undermining the effectiveness of flood barriers.
To address this knowledge gap, in 2023-2024, the Collaborative initiated a groundwater study. The study aimed to assess the potential impact of projected sea level rise on:
• Groundwater elevations in downtown Olympia
• Proposed adaptation measures
• Buried storm and sewer lines
• Surface water ponding due to daylighting groundwater
In 2023, LOTT Clean Water Alliance contracted with PIONEER Technologies Corporation (Pioneer), on behalf of the Olympia Sea Level Response Collaborative, to evaluate the impacts of sea level rise on groundwater in downtown Olympia. This assessment consisted of three primary phases:
• Review existing groundwater data to understand current conditions.
• Fill data gaps through additional monitoring and measurement.
• Model the impact of sea level rise on groundwater levels and assess potential future risks.
During phase 3, Pioneer conducted a groundwater gauging event at the end of the wet season, generated a groundwater model for sea level rise, and applied the model to evaluate groundwater rise due to projected sea level rise.
In September 2024, Pioneer presented preliminary findings to the Collaborative Technical Workgroup. Staff requested minor modifications to the analysis, including three additional modeling runs to further refine the analysis of impacts at different sea level and groundwater elevation scenarios.
The groundwater modeling analysis is now nearly complete. During this presentation, staff and the project consultants (Pioneer) will provide an update on the analysis and discuss the key findings of the assessment.
Climate Analysis:
The groundwater modeling analysis will help inform climate resilience strategies by enabling the Collaborative to more effectively plan for future flooding and groundwater impacts that will be exacerbated by sea level rise.
Equity Analysis:
The groundwater modeling study is focused on assessing physical impacts. If necessary, the equity implications of groundwater rise and related mitigation strategies will be considered at a later stage.
Neighborhood/Community Interests (if known):
There is considerable community interest in sea level rise planning and implementation of flood protection measures in downtown Olympia.
Options:
Not Applicable. No action is requested.
Financial Impact:
There are no immediate financial impacts associated with this study. However, the long-term costs of implementing sea level rise preparedness strategies are anticipated to
be significant. Understanding how future groundwater conditions will interact with sea level rise response measures will help the Collaborative plan more effectively and ensure the sustainability of flood protection efforts over time.
Attachments:
None