SAN DIEGO  Over the last two years, some of this city’s darkest secrets have been dragged into the light  city officials with conflicts of interest and hidden pay raises, affordable housing that was not affordable, misleading crime statistics.

Investigations ensued. The chiefs of two redevelopment agencies were forced out. One of them faces criminal charges. Yet the main revelations came not from any of San Diego’s television and radio stations or its dominant newspaper, The San Diego Union-Tribune, but from a handful of young journalists at a nonprofit Web site run out of a converted military base far from downtown’s glass towers  a site that did not exist four years ago.

As America’s newspapers shrink and shed staff, and broadcast news outlets sink in the ratings, a new kind of Web-based news operation has arisen in several cities, forcing the papers to follow the stories they uncover.

Here it is VoiceofSanDiego.org, offering a brand of serious, original reporting by professional journalists  the province of the traditional media, but at a much lower cost of doing business. Since it began in 2005, similar operations have cropped up in New Haven, the Twin Cities, Seattle, St. Louis and Chicago. More are on the way.