With fewer than 250 signatures left to review, anti-tunnel Initiative 101 doesn't have enough valid signatures to qualify for the ballot.

The initiative, which seeks to prohibit the the state's use of city rights-of-way for construction of a Highway 99 tunnel, needs 20,629 verified signatures to be sent to voters. As of Tuesday, 19,128 had been verified, while 8,641 had been challenged, said Kim van Ekstrom, spokeswoman for King County Elections office, which certifies the signatures.

Of those signatures that have been challenged, some people did not live in Seattle, some were not registered voters, and some signed twice, van Ekstrom said.

Elections staff are now reviewing the challenged ballots. A final report to the Seattle city clerk likely won't be delivered until next week.

Sponsors of the initiative will have 20 days after the final report is delivered to try to get enough valid signatures to qualify for the ballot.

A referendum campaign, Protect Seattle Now, that wants to send the tunnel to a vote of the people, is trying to get enough signatures by March 29 to qualify for the ballot. That measure needs about 16,000 signatures.