And like their counterparts across the nation, some local property owners are discovering that their homes are now shown to be within redrawn floodplains. And that they have to buy flood insurance.
Those payments can mean hundreds or even thousands of dollars annually - a prospect about as inviting as shoveling more snow.
"It's an emotional issue," said Bollinger, a hazard-mitigation specialist in FEMA's Philadelphia region who has tried to explain it all at countless community briefings over the last two years in his five-state territory. "People are upset with us at times."
Ask Amy Marren.
"It never occurred to me to buy flood insurance," said Marren, who lives in the Wayne section of Radnor Township near a humble, nameless tributary that on most days would not be mistaken for the Mississippi.
In fact, when she first received notice from her lender that she needed flood insurance, Marren chucked it, assuming it was junk mail. She is now the not-so-proud owner of a $2,400 annual policy. The insurance agent told her the house was zoned as though it were "a beach house."
The maps affect not only insurance rates. They are important to local governments because they become official documents consulted in building-permit decisions.
Regardless of how people feel about the results, there seems to be little disagreement that the map project was overdue.
Some of the maps date to the 1960s, according to David Conrad, water-resources specialist at the National Wildlife Federation. Much has changed in that time to affect which properties flood on a regular basis and which don't.
But given the magnitude of the project and the limits of its budget - about $1.5 billion - county and local officials who are dealing with property-owner complaints say the new maps compiled by FEMA contractors are not always precise.
