I want to clean part of a church 12 inch storm drain.
No, there isn't enough volume to make them possible. Your best bet of cleaning is to tie a rope to a Brick (if heavily clogged) or Cinder Block (if lightly built-up). You throw the scraping item in as far as you can (from both ends) and drag it back out to discard the debris.
Repeat until mostly clean. Another option is to put the head of a Garden Hoe onto a swimming pool Cleaning Pole and use that to scrape the build-up out. You want a small amount of removal with each pass so your scraper doesn't get stuck and you can still pull the debris out.