King County Metro has whittled down candidate sites for a new all-electric battery bus base. With significantly constrained bases, Metro is in need of more space under existing operations and that need will only grow as the number of buses required to meet demand and the county’s bold initiative, Metro Connects, rolls out through 2040. By that point, the fleet is projected to jump 70% with an additional 625 buses. Metro’s new base could open by 2030 and top $480 million in cost.

“With new base capacity, Metro will be positioned to meet the transit needs of our growing region,” King County Executive Dow Constantine said. “We are committed to greening our Metro fleet, and operating a zero-emission bus base in South King County will provide cleaner air to a part of the region where residents have historically experienced a greater share of pollution from cars and trucks.”



An illustration of the conundrum Metro faces if nothing is done to expand base capacity. (King County)

The three candidate sites are located in the Green River valley: one in Kent and two in Auburn. Whichever site is chosen, it would be the first base located in South King County. This is a strategic choice since the South Base in Tukwila is the most southern Metro base serving the countywide bus network, which has a substantial number of bus routes operating in Southwest and Southeast King County. Adding more capacity in the area will reduce the length of deadhead trips to bases, when buses are out of service but need to make the trip back to base. This is beneficial because Metro can leverage operational savings to provide more service hours and better respond to local network issues in the southend.

Illustrative of the problem Metro faces with bases at capacity is the transit agency’s inability to increase service, particularly at peak hours. In 2017, the City of Seattle sought to purchase an additional 100,000 annual service hours. Metro, however, was unable to meet that request, initially only promising 15,000 annual service hours but ultimately increasing them by 26,000 annual service hours.

Peak hour capacity, however, is only one facet of the challenge. Equipment operating, in the right places, and sufficient staffing are other interrelated issues. And of course, operational efficiencies, such as optimized routes, off-board fare payment, stop balancing, and transit priority equipment and facilities all play a role in system capacity, especially when bus base operations and storage are at their limits.

The capacity constraints that are increasingly hamstringing and affecting service deliver across the county bus network. (King County)

Current base locations, candidate sites, and going all-electric

Metro currently operates seven bus bases spread across Seattle (three locations), Bellevue (two locations), and Tukwila and Shoreline (each one location). The new south bus base could end up at one of the following locations: SE 196th St and 68th Ave S (Kent), S 277th St and D St NE (Auburn), or 37th St NW and B St NW (Auburn).

While Metro plans for the new base to be a fully all-electric battery bus facility, the transit agency has an ambitious goal of converting to a 100% zero-emission fleet by 2040–much needed in light of climate goals. All bus equipment will be converted to either battery electric or electric trolleybus. This means that base facilities and other targeted locations will need to be equipped with electric charging capabilities or catenary wire and support facilities.

Metro’s timetable to go all-electric by 2040. (King County)

By 2030, over half of the bus fleet will be powered by electric only. Diesel hybrid buses will begin being phased out next year and see their exodus accelerate beginning in 2023. The bulk of diesel hybrids will be retired by 2032 and then slow to a trickle until they are fully retired in 2040. Notable in the plan, however, is the curious and decreasing share of electric trolleybuses which are already a proven, economical electric approach.

Candidate site details

The site selection process originally started with 20 possible locations before Metro trimmed the list down to three, based upon various operational and environmental factors. The list will be further narrowed down in the next phase, ideally to select a 30-acre site capable of accommodating 250 electric battery buses.

The candidate Kent site is situated just north of the Boeing plant on one of the last vacant industrial properties in the area. The total site acreage could range from 25 to 38 acres, depending upon how many parcels Metro is able to negotiate for. The nearest highway access point is about two miles away. The site generally appears to be free of critical area constraints and has flexible development standards that would apply to it due to the M1-C zoning.

Kent candidate site at SE 196th St and 68th Ave S. (King County)



The largest of the two candidate sites in Auburn is also the furthest south site being studied and happens to be the biggest site, with as many as 38 acres available for development. The nearest highway access point is about one-and-a-half miles away. With industrial (M2) zoning, the site has a lot of development flexibility. However, there are notable constraints to it with evident critical areas in the northeast corner that are presumably entirely unbuildable.

First candidate site in Auburn at 37th St NW and B St NW. (King County)

The smaller of the two Auburn candidate sites ranges from 18 to 26 acres on property that once featured the Valley Drive-In movie theater and is only a mile from the nearest highway access point. A portion of the candidate site contains property is largely undeveloped. While the commercial (C4) zoning allows bus bases and fairly flexible development standards, the eastern portion of site appears to be at risk of critical areas constraints with notable wetlands and known flood hazards. It is curious then why the eastern portion of the site or even the site as a whole is under consideration at all.

Second candidate site in Auburn at S 277th St and D St NE. (King County)

Interim expansion efforts will still move ahead

How bus base expansions and new facilities will alleviate strain on the system. (King County)

Metro plans to move ahead with interim expansion efforts before 2030. In March, the transit agency published a capacity expansion plan, which will put an emphasis on making more efficient use of existing bus bases and physical expansions of them. The expansion plan is expected to top $775 million at existing bases and increase bus storage capacity by 400 spaces. The plan is proposed to roll out as follow:

2019 : Metro will convert a former Kaiser Permanente garage at South Base for Metro use at a cost of $3 million.

: Metro will convert a former Kaiser Permanente garage at South Base for Metro use at a cost of $3 million. 2020 : Metro will construct an interim base expansion at the South Base, which will provide facilities for electric battery buses, and add temporary capacity for 125 buses. The estimated cost is $33 million.

: Metro will construct an interim base expansion at the South Base, which will provide facilities for electric battery buses, and add temporary capacity for 125 buses. The estimated cost is $33 million. 2022 : Metro will convert four body shop bays at Central Base to maintenance bays, which will add 60 bus spaces at a cost of $20 million.

: Metro will convert four body shop bays at Central Base to maintenance bays, which will add 60 bus spaces at a cost of $20 million. 2023-2025 : Metro will begin an ongoing permanent expansion of Central Base by acquiring additional property to construct more bus facilities and parking. The expansion is expected to provide capacity for an extra 90 buses at a cost of $159 million.

: Metro will begin an ongoing permanent expansion of Central Base by acquiring additional property to construct more bus facilities and parking. The expansion is expected to provide capacity for an extra 90 buses at a cost of $159 million. 2024 : Metro will expand the Central Base on adjacent property (between 6th Ave S and light rail line) owned by the transit agency to provide space for new support facilities at a cost of $60 million.

: Metro will expand the Central Base on adjacent property (between 6th Ave S and light rail line) owned by the transit agency to provide space for new support facilities at a cost of $60 million. 2025: Metro will construct a new annex at South Base by relocating nonessential operational functions, removing and relocating structures, and building new facilities on the site. This will help realize additional capacity for 250 buses (replacing 125 spaces from the interim base expansion) at a cost of $337 million.

The expansion plan details the expected planning, acquisition, permitting, and construction timeframe for each of these base redevelopment and expansion projects. If all goes according to plan, Metro’s constrained operations will begin to see relief under both the baseline fleet expansion plan and Metro Connects plan.

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Stephen Fesler Stephen is an urban planner with a passion for promoting sustainable, livable, and diverse cities. He advocates for smart policies, regulations, and implementation programs that enhance urban environments by committing to quality design, accommodating growth, providing a diversity of housing choices, and adequately providing public services. Stephen primarily writes about land use and transportation issues.