Downtown Olympia faces significant flooding risks and infrastructure strain as rising sea levels push groundwater levels higher, a groundwater study revealed at the Olympia Sea Level Rise Collaborative meeting on Friday, Dec. 6.
Hydrogeologist Nathan Starr of PIONEER Technologies Corporation emphasized the urgency of addressing these vulnerabilities.
“This evaluation was to look at the potential impact of sea level rise on groundwater elevations, the proposed adaptation measures, buried storm and sewer lines, and surface water ponding due to daylighting on groundwater,” Starr said.
The study focused on Olympia’s shallow groundwater, largely influenced by its proximity to Budd Inlet and Capitol Lake, and modeled scenarios with sea level rises of 24, 36, 48, 60 and 68 inches.
According to Starr, the study identified several pressing challenges for Olympia’s downtown area:
Stormwater systems in downtown Olympia, which were not built to manage groundwater, are already draining excess water in some downtown areas.
Starr shared a specific example from Chestnut Street.
“I went out to where the Chestnut Street line drains into East Bay and looked at the flow. You can see it’s flowing (at) a couple hundred gallons a minute, and it hadn’t rained for at least a month," Starr said.
The flow highlights the limits of existing infrastructure. Starr noted, “A storm drain can’t drain lower than sea level.”
Upgrading stormwater systems, including adding lift stations, is necessary to maintain their effectiveness.
“Lift stations would enable stormwater lines to continue to drain groundwater,” Starr proposed.
Meanwhile, the Capitol Lake Estuary Restoration Project is expected to provide temporary relief by lowering the lake’s water level to match Budd Inlet’s mean sea level of 4.3 feet.
“Capitol Lake estuary restoration project is going to lower the lake water level to Budd Inlet’s water level. So right now, the water level in Capitol Lake is 9 feet, so it’s going to be decreasing to 4.3 feet msl,” Starr explained. With this reduction, it is expected to temporarily reduce groundwater levels near the lake.
He added, “You’re going to see drawdown around Capitol Lake that extends into downtown in the groundwater,” cautioning that this mitigation effect would diminish as sea levels rise further.
“Sea level rise will eventually overwhelm this mitigation effect once it reaches 57 inches,” he warned.
While shoreline barriers are vital to Olympia’s flood management, Starr’s study pointed to potential complications.
“We assume that the shoreline barriers are not going to include installing sheet pile walls,” Starr explained.
Sheet piling walls, he said, “act as groundwater dams and would prevent groundwater from discharging into Budd Inlet and Capitol Lake.”
Improperly planned barriers could trap groundwater behind them, worsening flooding risks.
Starr noted that many existing shoreline barriers are weight-based and do not penetrate deeply into the ground, limiting their effectiveness.
The study also faced calibration challenges in certain areas, as mentioned by Starr.
“Our model groundwater levels are 1 to 3 feet too high in the vicinity of State and Washington streets,” Starr said.
The lack of detailed elevation data for stormwater and sewer lines also hindered accurate modeling.
“Without knowing the discharge points or elevations for the stormwater lines, it’s hard to know whether they’ll be ponding,” Starr explained.
Additionally, there were no monitoring wells in residential areas.
“There aren’t groundwater wells in that area,” said Starr, further limiting the study’s scope.
Starr recommended additional measures to mitigate flooding risks, including upgrades to stormwater systems and coordinated planning for shoreline barriers.
In terms of concerns about coordination, they were also raised during the meeting, with committee member Eric Christensen addressing infrastructure.
“There’s a (Seventh Avenue) from roughly Cherry to Columbia,” he said. “You see groundwater seeping into it and dripping down at times.”
Port Commissioner Jasmine Vasavada highlighted the need for alignment.
“The port is investing, like, a million dollars in a planning effort. We need to sync this with the sea level rise work,” she said.
Climate Program Director Pamela Braff emphasized collaboration.
“The collaborative partners would work together to develop those longer-term adaptation strategies focusing primarily on those publicly owned parcels,” Braff said.
The collaborative team is pursuing grant funding to address some of the gaps identified in the study, including modeling and feasibility studies for separating stormwater and sewer systems.
“If awarded, the grant funds would support some monitoring, modeling and feasibility planning to help inform some of those next steps,” Braff said.
The study’s final report, expected in early 2025, will provide additional recommendations to guide Olympia’s long-term response to rising sea levels.
10 comments on this item Please log in to comment by clicking here
HarryBranch
Olympia is an artesian discharge zone. The groundwater level is above the surface.
Tuesday, December 10, 2024 Report this
hptrillium
The whole downtown will eventually be underwater so it should be moved to higher ground. No sense spending a lot of money to keep the water away. It will just keep rising.
Wednesday, December 11, 2024 Report this
BevBassett
Harry Branch's simple two sentence comment states the most glaring fact of them all; however, Harry did not go into some of the history and detail that this topic so richly deserves. And the facts are so numerous that one hardly knows where to begin...
That "Chestnut Street drain" into East Bay is Moxley Creek which technically ceased existing when it was put into a culvert. However, it does drain multiple streams and it is a year round "drain".
Most of Olympia north of about 4th or 5th Ave is on dredge spoils/fill--much of it incredibly toxic with dioxin and it continues to contaminate sediments in ways that the Port and DOE studiously avoid investigating...
In the past, concerned aware citizens have reasonably advocated for strategic retreat from the Port Peninsula. These citizens have paid for attorneys out of their own pockets to fight corrupt and stupid development at sea level in Olympia and they have lost in court every time--fought by City and Port attorneys paid for out of property tax dollars to fund development which should never have been allowed. And it continues to this day.
Sea level rise will, in time, put a lot of downtown Olympia under water. The costs of failing sea walls and futile drainage systems will all be paid for by the property taxpayers. And the developers will continue to be enabled by our corrupt politicians who refuse do act ethically.
Wednesday, December 11, 2024 Report this
jwiley
This has been discussed for decades now. It was the argument for estuary restoration back then as well. Olympia was warned over and over again about the failing infrastructure for storm water and sea level rise. "Back in the day" it was just Andy Hobbs who was tasked with the enormous job of investigating climate change on the downtown below the streets infrastructure in his "extra time" of maintaining the aging system. After that it was Steve Thompson who walked into the mess of a massive flooding Plum Street due to the Moxlie creek drain being plugged up. I am not sure who is in charge of this department now. Yet all along, major infrastructure kept being built on Port Property and around downtown, all on FEMA Flood zoned lands. Expensive housing subsidized by tax payers. It is all built on that huge toxic waste disposal zone, called the Port Peninsula and part of downtown Oly, to quote some leaders who did not want to come out publicly. The folks that had the idea to wall in Capitol Lake thought the wall and their little berm would protect downtown, sorry but this is all temporary too, and ground water will just go where it goes.... I have been assured that the artesian well that was inadvertently discovered in that Federal Super Fund Site near KGY and Anthony's hearthfire, that has a device placed on it to filter out the dioxins from the everflowing artesian spring within the most toxic buried compounds on the planet, will be able to function even if the whole thing is underwater. But, come on, what does that mean if the whole place is underwater in the future? And those toxins still exist bound to fine sediments all around the port beyond the arbitrary line that was drawn to dredge them out. I hope that something can be done sooner rather than later.
Wednesday, December 11, 2024 Report this
jwiley
Is there a video of this meeting on December 6th?
Wednesday, December 11, 2024 Report this
BillString
Yeah, I foresee a hugely expensive boondoggle that will fleece the taxpayer and end in failure. Not to mention the thousands of hours and millions of dollars wasted in consultants and committees. Keep OLY inefficient.
Wednesday, December 11, 2024 Report this
CrabbyWill
And yet, they keep building down there. Probably because the tax payers that don't get any money from any downtown business will foot most of the bill.
Wednesday, December 11, 2024 Report this
Porter
Ahahhahahhaha. Hahhahahhahaha. Sorry. How 'bout we lift the buildings up and install pilings underneath them? Or pump the water onto ships and take them to the desert. Of course we'll have to build a canal. Oh, I don't know, just take my money and tell me it's fine.
Wednesday, December 11, 2024 Report this
BobJacobs
The city of Olympia has steadfastly refused to consider the option of retreating ahead of rising water levels. Won't even analyze it.
I suggested 25 years ago, as a city councilmember, that the least we could do would be to require enforceable hold harmless promises from those developing new buildings in the flood zone. This could protect us from lawsuits blaming the city for allowing the new construction. My colleagues did not support this.
Bob Jacobs
Thursday, December 12, 2024 Report this
OlyKid88
I've seen quite a few of these types of reports and heard many of the discussions around this topic. The future increases that are being modeled are significant.
Is there a resource, or analysis, that has measured the actual historical sea level rise experienced in Budd Inlet? I would like to see how these actual measurements compare to the future estimates. How far off have previous estimates been versus actual increases over time.
This is important because there is a disconnect between these reports and analysis and those making large public and private investments downtown with a 50+ year useful life. For City, Port, LOTT and private developers downtown, they seem willing to invest and risk $30mm - $50mm that their investments won't be financially impacted by sea level rise in Budd Inlet.
Is this a rational decision based on the history of sea level rise in Budd Inlet downtown?
Thursday, December 12, 2024 Report this