Larimer Humane Society has submitted 18,000 signatures on a petition asking voters for a sales tax increase on the November ballot to pay for a new animal shelter.According to the Fort Collins Coloradoan, if at least 11,300 of those signatures are proven valid by the Larimer County Clerk & Recorder, voters will choose whether or not to add a penny-on-$10 sales tax in Larimer County to generate the $13 million needed to build the proposed 38,802-square-foot animal shelter. The increase would go into effect in January 2014.