Mayor Annise Parker is lowering the drainage fee that city property owners start paying next month after complaints from Houstonians receiving larger bills than the $5-a-month average advertised in last year's campaign to gain voter approval of the fee.

The mayor has ordered the Department of Public Works and Engineering to exempt 1,000 square feet of impervious surface at each property paying the fee. The mayor said reducing the amount of square footage in the assessment will lower the median bill from $8.25 a month to between $5 and $6.

Parker said she made the change "so that the drainage fees that voters expected to receive when they faced this item on the ballot last November are actually the fees that they will be paying moving into the future. It's about fairness. It's about trust."

Parker estimated last year that a typical home would pay about $5 a month. That estimate was appropriated by the Proposition 1 campaign, run in part by the political operatives who also run Parker's campaigns, and used in advertisements and promotions for the measure.

Last week, however, the mayor acknowledged that her staff was researching a public records request from the Houston Chronicle when they realized that the $5-a-month estimate was too low. The typical Houston home had close to 1,000 square feet more impervious surface than her administration previously had estimated.

The arrival of sample bills at homes last month touched off widespread anger among voters who claimed that they had been misled by last fall's campaign. Voters narrowly approved the measure that creates a 20-year, $8 billion program to shore up the city's drainage system.

On Thursday, Parker repeated her caveat that individual bills will vary. She also repeated her recommendation that people calculate their own bills and file a protest if they think they have been overcharged. She extended the deadline for filing a protest to the end of the year.

"We want to make it right for the voters," Parker said. "This is about being fair to the voters who went out and voted for this program."

'Constant state of fixes'

Critics pounced on Thursday's announcement as the latest in a series of changes and mistakes in rolling out the controversial fee.

"She's just in a constant state of fixes," former county tax assessor Paul Bettencourt said of Parker. "This is not being done by public vote. This is not being done by council vote. It's being done by a mayor standing up at a press conference and saying, 'We're changing things.' "

City Councilman Mike Sullivan said the program continues to be beset by problems that include placing the onus on property owners to prove the city's mistakes on bills. He said lowering the bills has not assuaged his dissatisfaction.

"It is one concession on many still persistent problems that haven't been addressed," Sullivan declared.

Parker: City understands

He added a new problem to the list Thursday — the mayor's statement that the city may not raise the needed $125 million a year through the drainage fee, though that was the message of the pro-Proposition 1 campaign.

Parker said lowering the bills will leave the city about $15 million short in fiscal year 2012. She proposes closing the gap by having the city's airport system and water utility system prepay next year's fees at a discount. After year one, she explained, the voter-approved charter amendment does not require that the city raise $125 million through the fee.

Bettencourt called that "borrowing," and said it was a violation of the program's pay-as-you-go mandate.

Parker said the prepayments would not constitute borrowing because the city would not pay the airport and water systems back.

As for the continuing criticism of the program, Parker said, voter approval of the fee in the midst of troubled economic times proves that Houstonians understand the importance of flood protection.

"We can't continue to grow as a city if we can't keep water out of people's homes and businesses. There is no free lunch," Parker said.

chris.moran@chron.com