Black also said that progress was being made on revisions to a 2010 annual citywide audit, which the city paid accounting firm Ernst & Young nearly $1 million to fix in part due to errors in water billing. It should be completed in November. Black said he believed overcharges and undercharges from water bills will largely balance out in the annual audit.
"There are a certain amount of underbillings and a certain amount of overbillings," he said. "I believe the difference is going to be a positive number but immaterial in terms of total city activity."
Curtis Bay activist Linda Stewart, who has studied the city's water bills in depth, said she believed schools have been overcharged for years.
She referred to an incident in 2011 when the bill at old Highlandtown Middle —boarded up while a developer completes plans to turn it into apartments — jumped from $24,700 to $438,700, only to fall to $1,100 months later.
In 2007, Stewart said she brought a batch of school bills that she believed were too high to school administrators. They all later received credits, she said.
"It's very seldom that they get a credit," Stewart said.
This week, Rawlings-Blake outlined a series of improvements her staff implemented in the water-billing system. The city increased its staff of meter readers by almost 30 percent and hired temporary employees to assist with the adjustment of 70,000 accounts, she said. The city also opened a "one-stop" customer care center, the mayor said, and increased customer service representatives from seven to 11.
"One by one by one, we're making progress," Rawlings-Blake said. "We want to get it right. We want people to not just have good-quality, safe water, but to know that what they're being charged is for the water they're using. Money's too tight. Under my administration, it's not going to go on. We're going to fix it."
School water bills on the rise
Quarterly water bills at the following schools shot up, according to a Baltimore Sun analysis of city records:
In August, Eutaw-Marshburn Elementary's bill skyrocketed from $976 to $198,000.
In July, Vivien T. Thomas Medical Arts Academy's bill spiked from $1,700 to $49,800.
In April, Walter P. Carter Elementary and Middle's bill leapt from $6,300 to $20,600 and, then, in July, to more than $42,300.
In April, Paul Laurence Dunbar Middle's bill jumped from $6,200 to $23,000.
In September, Commodore John Rodgers Elementary and Middle's bill nearly tripled from $6,300 to $18,600.
In August, Southeast Middle's bill rose from $1,700 to $9,600.