The Exploratorium’s new waterfront home will likely be smaller than originally envisioned, and its planned opening has been delayed until 2012.

The hands-on science museum has created more exhibits over 40 years than can fit inside its Palace of Fine Arts home in the Marina neighborhood. It plans to relocate to a rehabilitated building on Pier 15 at the end of Green Street, and then eventually expand to the adjacent Pier 17.

The plans call for the refurbishment, seismic retrofit and moderate expansion of the pier-top warehouse-style buildings that are destined to become the museum’s new home.

Prominent, historically significant elements of the buildings will be restored under the proposal.

But long concrete walls will be replaced with glass to help connect museum-goers with the surrounding estuarine environment, which will be explained to visitors through Bay-focused science exhibits.

The parking lot that separates the two piers is planned to be demolished, and the piers are proposed to be linked by a transparent walkway.

The proposed walkway was found in a recent environmental review to be a possible violation of historic-preservation laws, and it has been reduced in size and height, which will reduce its floor space by 25 percent, Planning Department documents show.

In another recent change to the project, the grand opening of the relocated museum has been delayed from 2011 until 2012, according to Exploratorium spokeswoman Leslie Patterson.

Museum officials remain enthusiastic about the planned relocation — a project that they say will increase its accessibility by public transit to visitors from southern San Francisco and from other cities.

“Ever since June of 2004, we have been convinced that this is the ideal new home for the Exploratorium,” Executive Director Dennis Bartels said recently. “In spite of the beauty of our current location, the piers’ location is truly accessible to everybody in the Bay Area, and it’s on The City’s front porch.”

The Port Commission is scheduled to consider approving the Exploratorium lease agreement and project plans during an Aug. 11 commission meeting.