Elllo! Sorry for the wait, but I got a small prompt for ya!
The waters of Magnolia Town's river have been tainted by some strange substance that turned it dark-green and causes people who sniff it for too long to grow nauseous and dizzy. Fearing a bacterial outbreak, yours truly has been working on a drug stored in an arm-long tube that will deal with the bacteria spreading out, but you must find the source of the sick, green stash - from that point, the drug can be distributed to the rest of the river system in town.
The river leads into underground tunnels, where someone had mistaken it for a sewer and thrown reactive trash out. Get rid of it and the bacteria emitting from the pile of garbage, but watch out for the hordes of rats who are heavily attracted to the harmful substances.
Good luck, your minimum WC must be 1,000! >:D