City's Traffic Model, Concurrency to be Discussed at Special City Council Meeting Tonight

Release Date: August 20, 2019

The City's traffic model, including the manner in which the adopted six-year Transportation Improvement Plan is incorporated into the traffic model for purposes of determining traffic concurrency will be discussed in a public forum with a Special City Council meeting that will be held today, August 20, at 4 p.m. in City Hall – the meeting will include time for Public Comment.  

The Public Comment time will be at approximately 6 p.m., to allow those who cannot attend at 4 p.m. to still get to the meeting in time to make their comments.

For those who cannot attend because of the timing of the meeting, family responsibilities, travel, etc., the meeting will be live streamed; it will also be recorded for later viewing on the City's YouTube channel.

The agenda for the meeting is at:

The City received emails from about 14 residents who are greatly concerned about the Concurrency Certificate that was recently issued to STCA for two proposed projects in the Town Center. This does not include phone calls received by the City or Council, or emails that have gone directly to council members.    

Following is a summary of their most common questions and the City’s responses. Please click on this link for more information which the City published on August 15, 2019.

Why was the concurrency test done while the Council was on recess and the City Manager on vacation?

The City is required to conduct a concurrency test in the order received per the Sammamish Municipal Code (SMC14A.10.040) when the applicant submits a completed concurrency application. Traffic concurrency is a legal, non-discretionary permit eligibility requirement based on prescriptive technical standards and the City’s adopted codes and Comprehensive Plan. Timing of the issuance or denial is a function of when a completed concurrency application is received and the time necessary for review. Review of concurrency applications is an administrative process conducted by City staff. It is not contingent on the absence or presence of the City Council or the City Manager (who was at a conference out of town when the test results were received). Without a Traffic Concurrency Certificate, a project is not eligible to apply for a land use permit. 

What are the steps to conducting a concurrency test?

  1. Applicant submits a concurrency application and required fee following attendance at a required preapplication meeting with staff. The concurrency application must include an estimated number of trips which will be generated by the development based on the land use adopted in the current Comprehensive Plan. The methodology for calculating the number of trips must be supported by the most recent Institute of Transportation Trip Generation Manual, the City’s Public Works Standards, and the Sammamish Municipal Code.
  2. Once the City deems the concurrency application complete, it is sent to the City’s traffic modeling consultant who:
    1. Assigns the development to one or more of the applicable ~300 existing city Transportation Analysis Zones (TAZs).
    2. Imports updated land uses into the travel demand model if they’re not already reflected in the model.
    3. Updates any new roadway geometrics in the travel demand model if they’re not already reflected in the model.
    4. Assigns trips between TAZs. The traffic model uses a complex equation to model traffic between any two TAZs. This equation is run over 450,000 times during a concurrency test, depending on the size and complexity of the proposed project.
    5. Updates any new roadway geometrics in the traffic operations model if they’re not already reflected in the model.
    6. Imports vehicle demands to Synchro (intersection traffic model).
    7. Summarizes intersection operations.
    8. Updates summaries, charts, and figures.
    9. Compiles and submits the final report.
  3. Staff reviews the report for accuracy and completeness and issues or denies a Concurrency Certificate, depending on the test results.

What were the results of the STCA concurrency test?

STCA and City staff followed the City’s concurrency test procedures as described in Question II for the two proposed Town Center projects, both of which passed concurrency.  The Concurrency Test Reports can be made available by submitting an online Public Record Request.

STCA’s two proposed projects consist of the following:

  • Town Center B and C zones, which include 62 single family homes, and
  • Town Center A-1 zone, which includes:
    • 300 apartment units,
    • 57 townhomes -12 of these are live/work units, and
    • 82,000 square feet of commercial space, of which
    • 56,000 square feet will be retail space,
    • 22,100 square feet will be sit-down restaurant space, and
    • 3,900 square feet will be high-turnover restaurant space

What role does the Council, City Manager, and staff have in authorizing and performing the concurrency test?

The Council authorizes the concurrency policies, procedures and standards which are documented in the City’s Comprehensive Plan, Sammamish Municipal Code 14A.10, and the Sammamish Public Works Standards.

The City Manager ensures that these are adhered to through the staff who oversee the process.

Once staff determines that a concurrency application is complete, the determination of whether a project passes or fails concurrency is a result of following a prescriptive, non-discretionary procedure consistent with SMC 14A.10.040 and the Comprehensive Plan Transportation Element.

The Council is not involved in the review, approval or denial of individual concurrency applications.

Once the test results and report are reviewed and finalized, the City is obligated to inform the applicant of the status shortly thereafter. This prompt communication is consistent with the type of good customer service expected of staff and of our stated commitment to run concurrency tests and inform the applicant of the results within two to three weeks of receiving a complete concurrency application.