By Tracy Record
West Seattle Blog editor
After two community meetings in the past five days, residents of Sunrise Heights and Westwood know exactly which planting strips the county is eyeing for potential “bioswales” to keep rainwater from causing combined sewer overflows (CSO) at Barton Pump Station, miles downhill – specific spots along the 31 blocks identified in early March.
They also know how the county hopes to keep them from “ponding” during all but the heaviest rains – through a complex underground “underdrain” system.
The ghost of that problem-plagueed city project has long loomed over this county plan, despite reassurances, promises, and explanations of how the two situations differ. There were more of those Wednesday night at the first gathering inside Westside School (the second meeting was Saturday at High Point Community Center), even as project manager Mary Wohleb tried to keep Ballard from being the proverbial elephant in the room.
Early on, Wohleb said: “I want to talk straight on about Ballard – it was fast-tracked, less than 4 months from study to construction. We’ve been studying this for almost a year, (and have a) clear understanding of soils, technology, how to take the water into underdrains and move it on down, way deep, far away from people’s homes so we can control the bioswale overflow … Having said all that, I understand this is a change, and that’s scary, and you’ve heard some nasty things …”
Chief among those “nasty” things – at least in context, for residents – would be residents having heard that the soil right beneath their homes is drainage-challenged “hardpan” – just like Ballard. Right beneath it, though, engineers say, is a different type of soil, “Vashon Advance Outwash,” and that’s what the county plans to drain this soil into. “We’ve been taking time to understand this neighborhood,” said consultant Steve Burke from SVR Design Company.
“We are going to be moving it down and away,” is how Wohleb put it.
In the absolute heaviest of rainstorms, there could still be “ponding” from one to 12 inches of water, which the county says would clear out within 24 hours. Residents remain worried about the possibility children could fall in and drown, since it is often warned that a small child needs only an inch or two of water to drown, and many of these streets are on the way to, or near, facilities such as E.C. Hughes Playground or Westside School.
“High Point has never had a person fall into its bioretention swales,” Wohleb noted. A High Point photo was shown as part of the presentation:
And about the concerns that someday money might run out and King County would suddenly abandon maintenance of the “bioswales”? “This is a facility,” she declared. “We are responsible for maintaining our facilities. We’re starting to put together a maintenance plan.”
She was joined at the meetings by consultants, primarily from SVR Design, which worked on the High Point project.
This all comes more than two years after the county’s Wastewater Treatment Division initiated the state-mandated process of figuring out how to cut down on the CSOs from pump stations including Barton; in December 2010, it announced that the “green stormwater infrastructure” plan was its choice for the “basin” feeding Barton, while for the basin feeding Murray Pump Station at Lowman Beach, it would instead put in a huge new underground storage tank (for which it has purchased and will demolish a block full of residential properties across from the city-owned beach park). This is the first time the county has tried this kind of project, and that too has caused trepidation among residents.
This round of meetings came at the end of the “preliminary design” phase; the county expects to start construction next year. The meetings were formatted with a presentation up front – here’s the complete PowerPoint that was shown (large PDF) – and then small-group breakouts, neighborhood by neighborhood, so that the targeted locations could be discussed with people who live on those blocks.
During the presentation, one Wednesday attendee requested the chance to ask a question in front of the whole group, but was told “this isn’t really the forum for that.” Attendees were directed to the small groups. The county says the questions it collected will be posted online, though.
Questions we heard on Wednesday night included “how will the pipes (underdrain) not clog?” (Answer: Crews will have access to cleanouts.) “How were streets chosen (or excluded)?” Arterials were left out because of “permitting and restrictions on traffic flow,” for example, while a few streets got a pass because they “have a separate storm system.” A wide planting strip was considered ideal – that’s what we saw, for example, last Monday night, when meeting with concerned neighbors in the 7900 block of 30th SW:
One concern in that conversation: What about the trees? The briefers promised that “preservation of large existing trees is a priority,” as well as that they would “protect large trees on private property adjacent to the right-of-way.” But “small or unhealthy trees in the right-of-way may be removed or replaced.” The 30th SW neighbors had noted a recent visit by workers measuring to see if tree trunks were at least six inches wide; it was explained in the small-group discussion, that’s a city standard. One more tree note: Some of the underdrain boring would go UNDER the trees and their root zones – at least five feet down, says the project team.
The curb cuts for private driveways – the section that goes over the sidewalk – would be dug up while the underdrain is being installed, though project-team members say that wouldn’t take more than a day or two at each site. And then there are the potential curb bulbs (also marked on the very dense schematic at the end of this large PDF), which would jut out five feet into the existing street.
More uneasiness seemed to center on the “steppable zone” between bioswale “cells.” It was described as about six feet wide, with landscaping you could “step” on, “pretty easy to cross,” according to Jennifer Lathrop from SVR.
“(The rendering) shows a car blocking the ‘steppable zone’,” one resident pointed out.
Jennifer acknowledged that could happen.
The “cells” would have a failsafe, in case of that mega-storm – which could send the water back out into the street and into a drain that would connect to the combined-sewer system, if there was just no place left for the water to go.
The small group we observed on Wednesday night included the block along 30th where we met neighbors two nights earlier. In twos and threes, they stepped forward to the rendering on the wall depicting their specific block, to find out where the bioswales might be placed, and why those specific planting strips were chosen. “It’s custom,” explained SVR’s Peg Staeheli. “The detail changes on every block.”
WHAT’S NEXT: The project team is moving into “final design.” In early summer, they plan to come out to the neighborhoods, block by block, to meet with residents about specific locations, while continuing to evaluate the locations revealed at the meetings. Later in the summer, a workshop to look at the plants proposed for bioswales – then “continuing to work on final design with you.” In the meantime, they promised to continue adding information to the project website (which starts here). And here’s the timeline shown as a graphic in the public-meeting presentation:
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