Soos Creek Area Response

Keeping The Rural Area Rural

Black Diamond Traffic Problems

January 3, 2022

The following notes contain a good description of the traffic problems and lack of planning surrounding the huge housing build-outs in Black Diamond (ie Ten Trails & other Oak Point housing developments).

Peter is the prime worker leading efforts to identify and present to the county and south-end cities the traffic problems, current and future, associated with those developments.

Don Huling, SCAR Board Member


Hi. I hope all is well. I thought I’d give you an update on the traffic-related issues related to the Black Diamond MPDs.

First, one comment on the Monday, August 16, 2021, “At Ten Trails, it’s 500 down, 4300 to go: Oakpointe’s two large housing developments and big-box retail destination are humming along” article (https://www.courierherald.com/news/at-ten-trails-its-500-down-4300-to-go/). There is a paragraph that states:

“And Oakpointe plans to spend around $75 million on regional transportation infrastructure improvements to make sure southeast King County can keep up with it all. Those projects are scheduled through at least 2031.”

Yes, there is money being spent by OakPointe, but the agreement with the City calls for much Grant money (read that as “taxpayers”) to be sought for many improvements. In other words, no money currently exists for some of the needed improvements. So, OakPointe is not “mak(ing) sure southeast King County can keep up with it all.”

To make matters worse, we are now ~10 years into the 25-year 2011 Development Agreements between OakPointe (then called YarrowBay) and the City, and the traffic coming to and from the south of the city has grown quite a bit—adding to the overall traffic congestion that already exists. This is all before another ~5,500 homes (and commercial) are built! 

Plus, as we discussed briefly during our summer hike with Tim, et.al., there has never been a complete Traffic-Demand Model (TDM) and analysis exercise done for the entire MPDs. We cannot emphasize this point enough. During the 2009 Public Hearings on the MPD Permits and EISs before the city’s Hearing Examiner (HEX) it was clear that the TDM was grossly inadequate. So much so, that the HEX rejected all the traffic modeling and analyses and called for it to be redone (this is all documented in the HEX’s Recommendations in excruciating detail).

Unfortunately (for everyone but OakPointe) the HEX only makes recommendations (not decisions) on such Permit applications to the City Council. And, again unfortunately (for everyone but OakPointe) the City Council deferred such work until 850 building permits have been issued. This is all documented in detail in the MPD Permit Conditions of Approval (COAs)–especially COA 17a.

Now, ~10 years later, the MPDs slowly are approaching that 850 threshold—members of the Public eagerly have been waiting for this moment  Consequently, back win the Summer the City added a task to its Task-Order Contract with its Traffic Consultant, Parametrix, to build the TDM. Parametrix currently is conducting that task and the City has told us deliverables are expected at the end of January. However, since the Parametrix work already has been delayed, we expect that date could slide further. The key to Parametrix’s work will be the assumptions the City has provided

That last point is crucial, since the City already had provided its Traffic Consultant for its 2015 Major 8-Year Comprehensive Plan Update, DKS Associates, with incorrect assumptions—the worst being 4 lanes on SR-169 all the way to Four-Corners (e.g., SR-516) in Maple Valley. The City’s 2015 Major 8-Year Comprehensive Plan Update (kicked off in April 2014) was Conditionally Certified in February 2020, partially because PSRC rejected that assumption because the difference between 2 and 4 lanes on SR-169 is enormous to commuters and directly influences all other routes in and out of the city—primarily King County unincorporated roads. BTW,  full Certification of the City’s 2015 Major 8-Year Comprehensive Plan Update is still pending. [there are no typos in any of these dates.]

BOTTOM LINE: The planned transportation infrastructure in southeast King County (yes, the MPDs adversely will affect most of this region) will be grossly inadequate to support the full buildout (probably even half build-out) of the MPDs (actually, most of this transportation infrastructure already is inadequate even during normal commutes). 

Peter Rimbos
Leader and Transportation Focal
Citizens’ Technical Action Team (TAT)

Filed Under: News

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"Soos Creek Area Response (SCAR) will promote environmental education and awareness as well as protection and preservation of the environment surrounding Pacific Raceways and the co-existing area known generally as the Soos Creek Watershed. This area encompasses many small streams and surrounding wetland and environmentally-sensitive areas that are populated by a variety of animal life, including Chinook and Coho salmon. Particular emphasis will be placed on, although not limited to, the above-described general area within ten miles in all directions of the Green River as it crosses under Highway 18 and the nearby Soos Creek Salmon Hatchery. SCAR will hold periodic status and education/awareness meetings with the surrounding community. The organization will monitor, and, as necessary use advocacy and education at the federal, state and local government level to promote a balance between environmental and business concerns. SCAR will also promote maintaining the Soos Creek Watershed in a manner conducive to coexisting with the existing residential base. SCAR will solicit funds from the surrounding community as needed for situations that arise which may require funding to effectively fulfill its' mission. SCAR, like many advocacy organizations, has applied for and received grants offered by King County Local Services to support and promote local organizations like SCAR to help in providing information and supporting educational and advocacy efforts."

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