MARTINEZ (CBS SF/BCN) — With the 2020 Census in the books, counties like Contra Costa are seeing their political landscapes evolve.

The Contra Costa Board of Supervisors on Tuesday unanimously approved a redistricting plan moving Diablo, Blackhawk and the Camino Tassajara area from Supervisor Diane Burgis’ District 3 to that of District 2 Supervisor Candace Andersen.

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The new map expands Andersen’s reach to the east, putting the three Tri-Valley communities into the same district as Danville and San Ramon — cities with which they’re already associated based on geography and demographics.

The new plan puts all of Pinole in Supervisor John Gioia’s District 1. Pittsburg’s Tuscany Meadows moves to Supervisor Federal Glover’s District 5, with Antioch split at Somersville Road and Auto Center Drive, up Railroad Avenue between Glover and Burgis.

Morgan Territory Road area inside the Mt. Diablo Unified School District moves to District 4. Concord would be split at the former railroad right-of-way and highways 4 and 242. District 2 would now extend through Tilden Regional Park, almost to Kensington. Walnut Creek would split between districts 4 and 2 at state Highway 24 and Interstate Highway 680. The Saranap and Castle Hill areas would be in Andersen’s District 2.

Throughout the process, there’s been push from some areas to keep cities intact, which is difficult to do, given the requirements.

“It may feel like you’re being divided in a way, but there’s actually benefits,” said Burgis. “Not only are you having two supervisors service a city; Supervisor Glover and I share Antioch, and I don’t say ‘Well, where is that?’ I say ‘Oh, it’s Antioch. I’m going to help them. And I’m sure that that happens with Supervisor Glover as well. We don’t look at the lines.”

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Tuesday was the last of five required public hearings before a final plan has to be in place by Dec. 15. Re-drawings of district lines happens every 10 years and is based on U.S. Census numbers.

The 2020 Census showed Contra Costa County growing by 11.35% since 2010, from 1,049,025 in 2010 to 1,168,064 residents in 2020.

The biggest population gain came in Burgis’ District 3, with an additional 36,560 residents in the area covering much of Antioch, Oakley, Brentwood, and unincorporated East County.

The least amount of growth happened in Supervisor Karen Mitchoff’s District 4 (10,442 residents), an area covering Concord, much of Walnut Creek, Pleasant Hill and Clayton.

The goal is to create districts as equal in population as possible, while meeting all federal and state legal guidelines, such as respecting geographic integrity of an area, or a census-designated place, or local community of interest.

Burgis said district maps should be updated on the county website by early December at the county website.

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