July 13: This post has been corrected.

Much to Carol Nichols' surprise, there were no signs of any pre-construction activity on the Fort Duquesne bridge in Pittsburgh on July 4. Way back in May when Carol signed up to monitor the stimulus project for ProPublica, the state's Department of Transportation Web site listed July 6, 2009, as the project's start date. Knowing we relied on her to fact-check the start date provided by the DOT, Carol intentionally walked the bridge that night. "I was downtown for the Pittsburgh 4th of July celebration," Carol wrote me. "That bridge has a pedestrian walkway that I went over ... I guess I expected to see some signs up or cones on the side of the road ready to be moved out on Monday, but I don't know if that kind of stuff usually happens before the date or not."

On Sunday, Carol went back to the state DOT's Web site. She discovered that not only had the project's start date been changed from July 6 to August 3, but that the state's estimate for how much traffic passed over the bridge had, too. And by a lot -- from 16,052 to 85,140 cars per day.

Carol filed a report with ProPublica detailing all of this, and I followed up with the state DOT, which directed me to the PennDOT Engineering District 11. Its spokesman, James Struzzi, said that the start date and traffic estimate had not been changed. So, I went back to Carol with the DOT's account. Carol, who is a software engineer, used Yahoo!'s search cache to pull up previous versions of the DOT's Web pages. Sure enough, both the start date and traffic estimate had been changed. Carol had gotten it right.

A second call to PennDOT Engineering District 11 cleared up the matter. When the governor's office in Harrisburg, Pa., required the county DOTs to file project information so it could set up a Web site, Allegheny county sent along information assembled by its engineers. Since six of the seven stimulus-funded transportation projects in Allegheny were designed last year, some of the information -- like the bridge's start date -- was old, Struzzi said.

When Allegheny County puts contracts out to bid, it updates information about the projects on the Web site. When it put the Fort Duquesne bridge out to bid, Struzzi told me, some DOT employees must have updated the project's start date. On Monday, the county awarded a contract worth nearly $24 million to Trumbull Corp. of West Mifflin to repair the Fort Duquesne bridge.

Carol's sleuthing has paid off, and in more ways than one. Struzzi told me that PennDOT Engineering District 11 "is going back to its Web site and fixing some other project pages. Some ARRA projects listed for Allegheny County, for example, are actually in Beaver County." As for that traffic estimate of 16,000? That remains a mystery. "I have no idea where they got 16K for the bridge," he said.

Just think: Your first assignment after selecting a project to monitor is checking its start date. It's a simple task but, as Carol's experience shows, it can also have an impact.

Correction: This post imprecisely referred to the office within Pennsylvania's Department of Transportation as the Allegheny County DOT. It should be referred to as PennDOT Engineering District 11.