Expedia is pulling back the curtain on its long-term vision for the 40-acre site the company bought for its new Seattle headquarters in April.

The company is considering options that show it could grow the campus to as much as 1.9 million square feet of office space by 2030 — enough room for about 12,000 workers by standard real estate industry estimates. Today, the company employs about 3,000 people in the region with plans to grow up to 4,500 by the time it moves into the new headquarters in 2018.

GeekWire first reported on Expedia’s anticipated headquarters expansion on Wednesday, after transportation planning documents outlined redevelopment plans considerably larger than those disclosed by the company when it first announced plans to move to Seattle from Bellevue.

Now, Expedia has shared its Major Phased Development plan with GeekWire, revealing more specific details about what those additional facilities may look like. A company spokeswoman says these plans were drafted because of routine requirements from the city to “evaluate its on-site growth needs through 2030.”

A large swath of the site, which formerly housed biotech giant Amgen, is vacant today. But one of Expedia’s mockups shows how it could build up to six additional buildings on the property. Another alternative shows five new buildings, and a third option represents no changes at all. With each option, the company plans to maintain its 65-foot heigh limit and current geographic footprint of the property. Plans also include examining “opportunities to improve public amenities along the waterfront.”

Here’s a look at the two main alternatives, along with Expedia’s description of the changes.

Alternative 1 (Figure 1)

This alternative includes retention of the site’s current six buildings (P1, U, A, B, C and D) including expansion of three structures (A, B and C). It also includes creation of six new buildings (L, P3, K, E, G and F) and a parking garage expansion (P2). With all existing, expanded and new buildings, this alternative totals approximately 1.9 million gross square feet of development and 3,300 parking spaces.

A break out of the total proposed square-footage includes:

Existing buildings: 670,834 chargeable s.f.

New buildings: 1,230,000 gross s.f.

Existing parking structure: 1,230 parking stalls

New parking structure: 2,070 parking stalls

Alternative 2 (shown in Figure 2)

This alternative is a less-dense approach and includes retention of five buildings (P1, U, A, B, C and D) including expansion of three structures (A, B and C). It also includes creation of five new buildings (L, P3, K, E, and F) and a parking garage expansion (P2). With all existing, expanded and new buildings, this alternative totals approximately 1.6 million gross square feet of development and 3,300 parking spaces.

A break out of the total proposed square-footage includes:

Existing buildings: 670,834 chargeable s.f.

New buildings: 930,000 gross s.f.

Existing parking structure: 1,230 parking stalls

New parking structure: 2,070 parking stalls

The company also outlined this scenario, showing no major changes to the site.

The first two options bring to light a much more ambitious vision for the new headquarters than previously expected. Much of the development would take place on the vacant plot of land adjacent to the former Amgen buildings, commonly known as Pier 89.

It was a bit of a surprise when the company first announced the Interbay neighborhood location, since that area generally lacks the kind of amenities tech giants tend to migrate toward. But with a campus like this, Expedia may be able to offer all the amenities its workers would need.

“Expedia’s goal is to re-imagine the biotech-focused campus and configuration into a series of modern office buildings that reflect the company’s culture and mission and meets its growth needs through 2030,” a spokeswoman wrote in an email to GeekWire.