With its business growing, Costco wants to add 1.5 million square feet to its corporate headquarters in Issaquah. To do so, it will need to enter into a development agreement with the city said Keith Niven, the city’s economic development director.

Niven said the expansion would most likely be in the form of new buildings rather than adding onto the current headquarters building.

Costco headquarters and one of its stores are in Pickering Place, which is, for the most part, built out. Niven said he doesn’t know whether the project would remain in Pickering Place or be built elsewhere in the city.

Adding 1.5 million square feet also adds a substantial amount of new employees, so the need for quality transportation is added to the equation. Costco is already prepared to pay it share of a local improvement district in north Issaquah to improve access to the area. The LID is pending, waiting on appraisals, which will determine the affect on area property owners.

“The LID improves capacity for Costco as it does some of the other businesses in Pickering,” Niven said.

Niven said Costco would like to stay in the same area, but wherever it expands, it would be within walking distance of the current corporate headquarters.