SANDAG staff members conceded Friday that to finish all the transportation projects promised in a 2004 sales tax extension, the agency will need to find as much as $17.5 billion from federal and state sources. No elected officials at the meeting said a word about the potential multibillion-dollar shortfall and any resulting impact on the communities they represent.

Protea Properties is optimistic it’s reached a deal with SANDAG to build roughly 40 condos, retail space and commuter parking for a new trolley station on three and a half acres at Clairemont Drive, on the new $2.1 billion Mid-Coast Trolley line set to open in 2021. The agency had held the threat of eminent domain over the developer’s head for months.

The chair of the Independent Taxpayer Oversight Committee, which monitors the TransNet tax, said he was unaware of the growing disparity between the tax’s projected revenue and the actual revenue it’s brought in, but the shortfall doesn’t fall within the group’s purview. Outside experts said that view leaves the program without meaningful oversight and transparency.

Aside from big questions surrounding whether SANDAG’s proposed sales tax increase will generate the amount the agency says it will, opponents point to other promises they think could go unfulfilled — like whether SANDAG will complete the highest-priority projects within 15 years, whether it will use local labor and whether the measure will do anything to improve water quality.

SANDAG is on track to collect billions of dollars less from Transnet, a sales tax hike voters approved 12 years ago, than the agency said it would — throwing into question whether it will have the money to pay for many of the projects that measure promised. The causes of the shortfall could also jeopardize many of the promises in Measure A, the sales tax hike on the November ballot. SANDAG leaders obscured the size of the Transnet shortfall in the one place they disclosed it.