In a process that will determine the political representation of residents throughout Charleston, City Council reviewed more proposals for redrawing council district boundaries Tuesday.

Each plan would reduce the number of black majority council districts in the city.

And each would force at least one current council member out, by putting at least two incumbents in a single district.

The process is driven by the release of 2010 Census data, which is used for redrawing political boundaries to reflect the current population.

Each of the 12 council districts, for example, should have about the same number of voters when the process is done, but the city is also required to maximize the number of minority-majority districts.

After the 2000 Census, there were five black majority districts, but today only one of those districts has a majority-black population, due to changes in the city's population.

One issue Tuesday was the question of what should count as a minority-majority council district. City planners and state demographers have focused on voting-age black residents, but Councilman William Dudley Gregorie suggested that all minorities should be counted, which would change the benchmarks the city is using.

Frances Cantwell, an attorney for the city, said there are reasons to focus on the black voting-age population.

"The whole reason we are subject to Justice Department review is the Civil Rights Act of 1964 and 1965, which was aimed at preventing overt and covert discrimination against African-Americans," she said.

Due to historic racial discrimination, voting district changes in South Carolina are subject to federal review, and are scrutinized to see that black voters are not disenfranchised.

Maximizing the number of black-majority districts is a challenge, because the city's black population has dropped from 35 percent of residents in 2000 to 27 percent today.

Map-drawers also have the challenge of accounting for suburban population growth and a sharp decline in the number of black residents living on the Charleston peninsula, which is home to four of the five black City Council members.

With the November 2011 election getting closer each day, council would need to adopt a plan in May in order to have it approved by the Justice Department in time for candidates to register in August.

The four plans considered so far by the city include one prepared by the state, and three prepared by the city. City officials have favored city-drawn plans, which combine fewer existing districts and result in more black-majority districts.

In all three of the city's plans, West Ashley District 7 would remain a majority black district, and council Districts 3 and 5 would be combined into a new majority-black District 3. Incumbent councilmen James Lewis (District 3) and Jimmy Gallant (District 5) would have to compete for the new District 3 council seat, assuming both seek re-election this year.

Each of the city's plans would also create a third majority-black district. Two of the plans call for District 6 to be that third majority-minority district, and one plan would make District 4 the third such district.