Olympia Grapples with Flood Management, Sea Level Rise

Above: Under a surly afternoon sky, City of Olympia and Washington State Department of Enterprise Services staff were on flood watch and ready with sandbags at Capitol Lake in the late afternoon of December 10, 2015. “It’s a bit of a dance,” said Andy Haub, City of Olympia director of water resources, of the flood management process and roles played by the city and state.

City Staff Clarify Statement That Dam is Needed to Control Downtown Flooding

By Janine Gates

www.janineslittlehollywood.blogspot.com

The stunningly frank sea level rise report delivered by city public works staff to Olympia councilmembers earlier this week was loud and clear: develop a vision and a plan to begin adapting to sea level rise. Like, now.

But even without the extra burden of sea level rise, the protocol for managing current flood events in downtown Olympia requires a highly managed rapid response involving state and local agency coordination.

Above: When the lake gets too high, the city stormwater system backs up. A valve, located under Water Street, is shut off, preventing lake water from flowing “up” the stormwater outlet to the lake and discharging to the catch basin in the streets at Columbia and Water Street. A pump takes the stormwater and puts it into the lake.

The Department of Enterprise Services (DES), the state agency responsible for managing the 260 acre lake, regularly releases as much water through the 5th Avenue dam as each low tide allows.

DES closely monitors weather forecasts, streamflow on the Deschutes River, tide tables and more to determine when to lower the lake below the normal winter level in advance of major storms.

On December 10, 2015, a combination of record-setting rainfall, flooding on the Deschutes River and high tides in Puget Sound caused flooding around Capitol Lake and Heritage Park. So, when DES staff determined that the lake was going to flood, the department notified the City of Olympia and closed a section of Water Street and 7th Avenue.

The city implemented its flood response plan which includes pumping excess stormwater directly into Capitol Lake and placing sandbags in the area to protect nearby businesses.

By their own admission, city staff underestimated the rate at which the lake was rising and were later than usual in closing a valve, resulting in lake water flooding the streets and coming to within inches of the doors of Olympia Supply and other local businesses.

On December 11, 2015, the day after the somewhat minor flooding incident, Little Hollywood interviewed Andy Haub, City of Olympia director of water resources, who was onsite with staff during the emergency.

LH: Tell me about this valve...the water got to within four inches of Olympia Supply's doors. 

 

Haub: We close the valve in order to prevent lake water from flowing “up” the stormwater outlet to the lake and discharging to the catch basin in the streets at Columbia and Water. The pools of water in the streets are lake/Budd Inlet water.   Usually we close the valve before the lake starts backing up. Then, the only water we pump is precipitation from the Columbia and Water Street area. In other words, once we shut the valve in the stormwater pipe, we have to pump the upstream stormwater.

Yesterday (December 10, 2015), we underestimated the rate at which the lake was rising and so were later than usual in closing the valve. Once we started the pump, the water in the streets declined very quickly - 15 minutes….

LH: I was told that the Capitol Lake area is the lowest catch basin in downtown.

Haub: The two block area around Columbia and Water Street is the only real area that is at risk from flooding due to the lake backing up. At some point, the lake can't hold it all, so that's why DES folks were standing around (in the afternoon) waiting to see if the tide would rise too high, plus the water in the lake would make it all overflow like a bathtub. When the Deschutes is flowing very high, the State lowers the lake by opening the 5th Avenue dam during the low tide preceding the high tide. Then they close the dam when the tides turn to a high tide, thereby keeping the high tide out of the lake and providing room for the river flows. It’s a bit of a dance….

LH: Is that portable pump station always going to be down there with chain link fencing around it if it seems like this is a permanent problem area? 

Haub: We keep one of the pumps there during the peak of the winter.

Haub explained that other factors such as barometric measure, wind direction and speed, temperature, low pressure systems and the effect they have on high tides also dictate Olympia’s flooding risk.

“It’s very interesting to think about and understand. Our high tide was 1.95 feet higher than predicted, simply due to low barometric pressure. You and your audience would find this dynamic interesting….” said Haub.

LH: If this whole area reverted back to an estuary, would we even we worrying about all this?

Haub: Same dynamic.

At that point, Little Hollywood had taken up enough of Haub’s time.

Above: The valve near Capitol Lake that saves a portion of downtown from flooding. 

Fast Forward: Capitol Lake, The Dam and Flood Clarification

Along with Haub, Eric Christiansen, City of Olympia water resources planning and engineer manager, provided the staff report at last Tuesday night’s council study session on sea level rise issues.

Councilmember Jessica Bateman asked how its reverting back to an estuary would impact downtown and Christiansen responded that without the dam, downtown would flood more frequently.

This short response confused and alarmed community members active with lake management conversations.

On Thursday, Little Hollywood asked Christiansen to clarify his response to Bateman, which was in conflict with the Capitol Lake Adaptive Management Plan’s (CLAMP) final Deschutes Estuary Feasibility Study report of 2007.

The report says, in part:

“...The City of Olympia may require a FEMA-approved floodplain study as part of the permitting requirements for the proposed restoration project. However, it can be concluded that flooding in the restored estuary will be similar to current (managed lake) conditions at worst. A decided advantage of the restored estuary is that flood management will no longer depend on the correct functioning of a mechanical system – flooding under current conditions can be considerably exacerbated if the tide gate controls should fail.”

Christiansen responded:

“I maybe partially misspoke. There are a few blocks of downtown between Water and Columbia and 5th and 7th streets that are at a very low elevation, approximately two feet below the flood elevation. There are about 19 storm drain pipes that connect that area and the park with Capitol Lake. Only two of those pipes that I am aware of have valves to prevent water from flowing backward into the streets. The State manipulates the dam to keep lake levels low when tides are high, thus for the most part keeping water out of the streets. The last six to twelve inches of lake elevation make a big difference. We had about a dozen tides this winter that could have caused flooding.

“Without the dam, the drainage systems will need to be modified by adding additional valves and probably consolidating pipes. It will also help if the ground in key parts of Heritage Park is elevated. The railroad tracks pose an additional challenge,” said Christensen.

Above: The 5th Avenue dam on December 18, 2015.

In conflict with information city staff and local environmental advocates have been providing the city for years, multiple downtown development projects are underway in precisely the area destined to be first impacted by sea level rise. 

These vulnerable areas, built on fill, are well within the historic shoreline of Budd Inlet.

Next: Community Response to Sea Level Rise Report

For more information about community efforts and issues in Olympia regarding Capitol Lake, the Community and Economic Revitalization Committee, sea level rise, high tide events, CLAMP, Percival Landing, Moxlie Creek, LOTT Clean Water Alliance and more, go to Little Hollywood, www.janineslittlehollywood.blogspot.com, and type key words into the search button.