City Council plans to spend the summer coming up with a new set of boundaries for its 10 districts.

Former Councilman Rick Mariano says it may be a long, hot summer - regardless of the weather.

He remembers visiting a recreation center in Rhawnhurst about 10 years ago when he got an urgent call from one of his aides. Several of Mariano's colleagues, the aide reported, were meeting in the Council president's office, privately reviewing a map of proposed revisions in districts to deal with 2000 census figures.

Mariano had not been invited. "You better get down here," the aide told his boss, he recalled.

Dealing with a divorce, Mariano owned two houses in his district, one in Northwood, the other in Juniata Park. The map he saw when he got to City Hall had both addresses in other districts, he said.

"This ain't going to happen," Mariano told his colleagues, adding a string of expletives, according to his account and those of others who were in the room.

Then-Councilman Angel Ortiz, long an advocate for increasing the number of Hispanic voters in Mariano's district, said something about the difficulty of drawing new lines.

"You're threatening my job. You ain't going to do that," Mariano replied. "I'll knock out your teeth and throw you out the window."

No blows were struck, and the two councilmen later proclaimed their friendship. "I didn't handle it well," Mariano said in an interview last week.

But his reaction reflected the strong feelings that redistricting can provoke in Council members trying to protect the turf that made them public officials.

"It's not that hard of a job, and the pay is good," Mariano said. "As soon as you get elected, you start worrying about the next time."

Council passed three redistricting plans in 2001 and 2002 before then-Mayor John F. Street was willing to sign the final boundaries.

Council members went without paychecks for five months for missing the redistricting deadline spelled out in the City Charter. Mariano helped cover his bills by allowing a metal-processing business to pay $5,400 for his gym membership and $23,445 toward his credit-card bills - a decision that eventually sent him to federal prison, upending his political career.

Ten years later, Council expects to spend another summer on redistricting, drawing new boundaries with approximately equal populations to reflect last year's census.

Members must come up with a plan by September or give up their paychecks until they succeed.

No one expects the standoffs and fireworks that dominated the proceedings in 2001 - reflecting political tension between Council and Street, and a feud between labor leader John "Johnny Doc" Dougherty and then-State Sen. Vincent J. Fumo, each with his Council allies.

But a broad population shift east toward the Delaware River, pulling residents away from four adjacent Council districts, poses a major problem.

The "main challenge we face is that the four districts that have lost significant population . . . are all located on the west side of the city and adjacent to each other," Council President Anna C. Verna said in a memorandum distributed last week. "This means that redistricting cannot be accomplished simply by 'tweaking' existing Council borders. There will be no avoiding significant redrawing of the map."

Verna named a five-member committee to oversee redistricting: herself, Democratic leaders Marian Tasco and Darrell L. Clarke, Republican leader Brian O'Neill, and first-term Councilwoman Maria Quiñones-Sánchez, whose district has been the focus of organizing efforts by the city's Hispanic community for the last 30 years.

How the committee will proceed, with public hearings, backroom negotiations, or both, has not been spelled out. But if Council follows past practice, using current boundaries as the starting point, it will already be off to a difficult start.

Two of the 10 districts - Clarke's Fifth and Quiñones-Sánchez's Seventh - are already among the most badly designed in the country, cutting willy-nilly across disparate neighborhoods, according to Azavea Inc., a Philadelphia software and consulting firm that has compared municipal redistricting in 50 cities.

Each of the two districts stretches more than eight miles, with some sections less than a block wide.

In 2006, Azavea came up with an index to measure the distortion of political boundaries and described the Seventh District as the country's most "gerrymandered" - a term derived from early-19th-century Massachusetts Gov. Elbridge Gerry, blamed for a congressional district that reminded observers of a salamander.

When voters approved a new City Charter in 1951, the Council boundaries were relatively simple - 10 clumps of wards broadly aligned with the major neighborhoods: South Philadelphia, Southwest Philadelphia, Center City, West Philadelphia, Northeast Philadelphia, Northwest Philadelphia, etc.

The charter specified that the ward configurations be changed every 10 years so that each Council district contained "as nearly as possible" one-tenth of the city population.

During the last 60 years, two factors have undermined the boundaries' simplicity:

First, in redrawing their own districts, Council incumbents are inclined to go after constituencies that can help them politically - friendly ward leaders, favorable party-registration figures, similar racial demographics, compatible political views, or wealthy neighborhoods where developers and other potential contributors will need the Council member's approval for zoning changes or other favors.

Second, a 1971 legal opinion from City Solicitor Levy Anderson advised Council that splitting wards between Council districts was permissible if necessary to keep the districts of equal size. In effect, Anderson's opinion gave Council the authority to manipulate its districts with smaller, more versatile building blocks - 1,695 voting divisions instead of the 69 wards.

Anderson cited several U.S. Supreme Court decisions from the 1960s, setting a "one-man, one-vote principle" for congressional districts.

In fact, according to J. Gerald Hebert, a veteran of the Justice Department's civil rights division who is executive director of the Campaign Legal Center in Washington, the Supreme Court has been much more flexible about municipal redistricting than it has been with congressional districts, permitting local districts to vary in population by as much as 10 percent.

"At the congressional level, you can't have much variation at all," Hebert said. "But there's reason for more flexibility at the local level, neighborhood boundaries and geographic boundaries that often need to be taken into account."