First of all, don't forget to send your story idea to your local paper as well, which often has more resources and time to devote to investigational stories.
It sounds like the issue you speak of is an important one. There are several ways to get the attention of the local media, here are some tips:
1. Write a letter outlining the problem and be prepared to be quoted and/or back up your claims with proof. Send your letter to the news editors of every local TV station, as well as your local paper. Trying to get an editorial/opinion letter printed wouldn't hurt either. Make sure to include your contact information.
2. Create a little notoriety yourself. Can you organize an official grassroots group or PAC to represent the interests of the residents? Can you circulate a petition calling for open government or government accountability? What about a protest outside city hall? All these things, when done by concerned citizens in an organized, non-violent manner, generate public and media interest and lend support to your cause.
3. Write your local government or get an attorney involved and send copies to your local media. Sometimes "officialness" carries more weight.
4. Be patient and persistent, but don't be a pest. Most journalists are very busy juggling many stories at once and sometimes can't respond as quickly as you believe they should. Be respectful and make your communications intelligent and you're more likely to be regarded as having a legitimate concern. Try communicating not only with local reporters, but with the editors in charge as well.
Good luck!
Newarview