GMVUAC: Issaquah-Hobart-Black Diamond Road


On Monday, November 5, the Area Council held a Special Event at its monthly meeting with ~40 people in attendance. Guest speakers from the Washington State Department of Transportation (WSDOT) and Traffic Consultant BergerABAM discussed their I-90 / Front St Interchange Justification Report / Study. Guest speakers from the King County Department of Transportation (KCDOT) and the City of Issaquah discussed their Issaquah-Hobart Rd / Front St Corridor Study. Please see: for all meeting materials.

Joint Transportation Initiative
Susan Harvey, Area Council Transportation Committee Chair opened the meeting by describing how the Area Council jointly works with other Unincorporated Area Councils and Associations to address regional transportation issues under the auspices of a Joint Transportation Initiative (JTI).

The JTI has identified the Issaquah-Hobart-Black Diamond Rd as a critical part of our regional transportation network. Ms. Harvey stated the JTI is looking at the road from a corridor perspective and tonight’s presentations and discussions would focus on the corridor’s north and central portions.

Ms. Harvey stated six speakers and participants from WSDOT, KCDOT, and City of Issaquah, and Traffic Consultant BergerABAM were sitting on a Guest Panel set up on the side of the room and would be available to answer questions during the evening.

I-90 / Front St Interchange Justification Report / Study
Kwengo Ndile, WSDOT Project Engineer; Tim Nau, WSDOT Assistant Project Engineer; and Jilma Jimenez, BergerABAM Project Manager, were introduced. Ms. Jimenez gave a presentation and discussed the interchange study. In 2012 the I-90 Bellevue to North Bend Corridor Planning Study was completed. It identified several intersections of concern to be addressed including the Front St Interchange, where, during peak times vehicles using the eastbound off-ramp sometimes backup onto I-90. Nearby streets also can experience severe congestion with cars trying to get through the intersections near the interchange or waiting to get onto or off I-90. The Washington State Legislature allocated funding in 2015 for WSDOT to study potential improvements to the I-90 / Front St interchange area in Issaquah, including both local and regional improvements.

The objectives of the study are to answer three key questions: (1) Are congestion problems due to local network issues or are they related to the interstate/interchange?; (2) If problems are interstate/interchange related, then what is the preferred alternative to improve congestion and address safety?; and (3) What are the costs of recommended improvements? Analyses of traffic data found major problems at the intersection at all four entry/exit ramps, especially dealing with limited turn-lane capacity resulting in queuing and systemic congestion.

This led to the following purposes: (1) Increase capacity through the intersection; (2) Improve local and regional circulation through the intersection; (3) Improve safety on approaches to and on the ramps; and (4) Provide solutions to improve mobility at the intersection to accommodate current and future growth.

The nearly year-long study included two phases: (1) Problem Definition and Preliminary Concepts and (2) Preferred Alternative Selection and Interchange Justification Documentation.

Thirty-six alternatives were identified including new I-90 crossings, widening of existing roads (e.g., potion of Issaquah-Hobart Rd and SR-18), new roads (e.g., revisiting a Sunset By-Pass), and interchange revisions. Each were screened with nine studied further through traffic modeling.

Four concepts were studied in further detail including environmental, highway, and traffic impacts: improvements two other interchanges, a “fly-over” ramp connection, and a “Diverging Diamond” intersection. The latter received the higher screening scores and will be subject to detailed analyses to develop a Cost Estimate by the end of the year.

Issaquah-Hobart Rd / Front St Corridor Study
Rose LeSmith, King County Traffic Engineering Manager; Aileen McManus, King County Traffic Engineer; and Kurt Seemann, City of Issaquah Transportation Manager, were introduced. Ms. LeSmith gave a presentation and discussed the study.

The study was initiated in 2017 and completed in February of this year, to address the area between I-90 and SR-18, not the entire Issaquah-Hobart-Black Diamond Rd corridor. It was intended to help better understand what is happening and to identify why there are problems in certain areas.

The goal was to evaluate and propose improvements that can help enhance safety and travel time reliability.

Ten projects were recommended for further study, but none scored very high in any of the three categories assessed: Safety, Mobility, and Implementation. The reason being that each project provides benefits to only specific locations or segments along the route, but by themselves, do not provide significant corridor-wide benefits.

For projects that were not recommended, they typically had an issue that was difficult to overcome or did not provide a significant benefit given the likely impacts and costs of the project. For example, for the road-widening options, costs and impacts were deemed too high with too little benefit to safety and operations.

Of the ten recommended projects, five are located in the City of Issaquah, three are located in Unincorporated King County, and two span across both jurisdictions. The estimated subtotal for the city is ~ $5.9 M. The estimated subtotal for the County is ~ $7.6 M. King County plans to perform a more detailed analysis for both the May Valley Rd ($2.4 M) and Cedar Grove Rd ($3.3 M) intersections prior to further design of any chosen improvements.

Following each presentation members of the Area Council and the Public asked many questions with several dealing with long-term solutions. Generally, it was felt a true regional perspective—possibly under the auspices of the Puget Sound Regional Council (PSRC)—was needed to pull various jurisdictions together to develop solutions that can be implemented and work.

Upcoming Monthly Meetings (All monthly meetings are from 7 – 9:30 PM and held at the Fire Station located at the SE corner of SE 231st St & SR-169 intersection across from the Maple Valley Police Precinct. All members of the Public are welcome. Each meeting begins with an open Public Comment period.)

Monday, December 3, 2018 — Tahoma School District (TSD) & Fire District (FD) 43 — Tony Giurado (New TSD Superintendent) and Aaron Tyerman (Chief, FD 43).

2019 Meetings — These currently are being planned. If you have a topic you would like to see discussed. Please e-mail your ideas to:

Upcoming Special Event
Friday, November 16 — Reserve Silica Site Cleanup — A “Special Event” with the State Department of Ecology (DOE) who will discuss the Agreed Order it is entering with Potentially Liable Parties, Reserve Silica and Holcim, responsible for cleaning up past practices at the Reserve Silica site in Ravensdale. This “Special Event” will be at our normal time and place: 7 – 9:30 PM; Maple Valley Fire Station located at the SE corner of SE 231st St & SR-169 intersection across from the Police Precinct. The Public Comment period is November 5 through December 7 (see:

Your Area Council serves as an all-volunteer, locally elected advisory body to King County on behalf of all rural unincorporated area residents living in the Tahoma School District. For more information, please visit: