Tuesday night is the deadline for Colorado Springs voters to return their ballot for or against the Karman Line annexation in the special election.

The special election asks voters if they want to support the Colorado Springs City Council’s ordinance than annexed 1,876 acres of land east of the city limits. The Karman Line property used a ‘flagpole’ annexation of Bradley Road to connect the planned single-family home development to the city limits.

City residents who opposed the annexation used a signature campaign to qualify the decision for a special election. This is the first one-off special election Colorado Springs has held since August 2012, when voters approved a proposal to lease Memorial Hospital to the University of Colorado Health system.

Voters can return their ballot at one of 27 official drop boxes across Colorado Springs or the City Clerk’s Office. Ballots have to be returned by 7 p.m. Tuesday in order to be counted and it is too late for them to be mailed.

City spokesman Max D’Onofrio said the city had not received more complaints than normal from registered Colorado Springs voters who had not received a ballot. Replacement ballots can be picked up from the Clerk’s Office until 7 p.m. Tuesday.

At the other end of the process, City Clerk Sarah Johnson said some voters had received ballots where the official return envelope was sealed shut. Johnson said the ballots could be returned in a standard envelope or a return envelope that is taped shut, as long as the envelopes are signed and dated to ensure the city has a way to verify the voter’s signature.

Colorado Springs offers a ballot search feature on the city website to let voters check if their returned ballot has been received and processed.

Johnson said the special election was on track to have more voters turn out than April’s City Council elections. According to city election data, just over 60,000 voters returned their ballots for the special election as of Friday night. Around 18% of the registered voters in Colorado Springs have already cast a ballot for the Karman Line question.

The initial results for the special election will be released by Colorado Springs shortly after the 7 p.m. deadline.