City commissioners at their meeting on Tuesday agreed to move ahead with a plan to add an extra level onto the proposed parking garage adjacent to the expansion of the Lawrence Public Library.

On a 4-1 vote, commissioners agreed to move forward with the extra level of parking and to pay for the project through a previously established benefit district that will add a special assessment to the tax bills of downtown property owners.

The project will add about 70 additional spaces to the garage, which already was designed to include 250 spaces. The extra level of parking is set to cost $840,000 to build. The city at-large will pay for about half the costs, while special assessments on downtown property tax bills will pay for the rest.

Owners of 23 of the 194 privately owned properties in the downtown district signed a petition objecting to the assessments, which figure to be about 30 cents per square foot on property they own. Property owners will have up to 10 years to pay for the assessment.

City Commissioner Mike Amyx was the lone commissioner to vote against the extra level of parking.