Call it a California gold rush, with a twist.

Rather than excavate wealth from the Golden State, third-party groups are dousing California with dollars ahead of its June 5 primaries. Some $2.4 million in independent expenditures has been spent on Golden State House primaries so far this cycle, according to Federal Election Commission records.

The overall outside spending total is actually higher than that, as issue advocacy advertising media buys are not reported to the FEC.

Nonpartisan redistricting, retirements and a modified primary format introduced newfound competition across the state’s Congressional landscape, from Eureka to San Diego. It’s turned a state relegated in recent years to a fundraising hotbed for candidates from everywhere else into a target for spending all its own.

“For a state that is orphaned from the presidential, and frankly from the U.S. Senate [races] this year, the fact that 20-25 percent of the state is in a very competitive Congressional district is really what’s going to drive the political conversation and spending out here,” Republican consultant Rob Stutzman said.

There were a few close races last cycle, when $5.6 million in independent expenditures was spent ahead of the general elections. But in the past decade, just one of California’s 53 districts has switched party control.

That will change this year, with a dozen or so competitive districts in play. So far, most of the independent expenditures have come in a handful of districts with unique primary situations, including a high-profile Member-vs.-Member race in a safe Democratic seat and two more Los Angeles-area districts affected by the state’s new “jungle primary.”

In the redrawn 30th district in the San Fernando Valley, Rep. Howard Berman is benefiting from a super PAC, the Committee to Elect an Effective Valley Congressman, that has already spent more than $400,000 in television advertising on his behalf.

Berman is facing fellow Democratic Rep. Brad Sherman in a race forced by an independent redistricting commission that drew the longtime colleagues into the same district. The outside spending piles on to what’s expected to be one of the most expensive House races ever. The Members have already spent about $1.5 million combined on TV ads ahead of the primary.

By running in the new 31st district, Rep. Gary Miller avoided an intra-delegation race of his own against fellow Republican Rep. Ed Royce. But thanks in part to the jungle primary, in which two candidates advance to the general regardless of party, Miller is still in danger of not being one of the top two vote-getters in a district wholly new to him.

Either Miller or state Sen. Bob Dutton (R) will likely advance along with Redlands Mayor Pete Aguilar, the heavy favorite among the Democrats running in the Democratic-leaning district. That possibility pushed the National Association of Realtors’ political arm to cough up a little more than $700,000 for TV ads and direct mail on Miller’s behalf.

“Congressman Miller’s been a longtime champion on the Financial Services Committee for us supporting mortgage interest deduction, responsible restructuring of the GSEs, homebuyer tax credits,” RPAC Political Director Scott Reiter said. “He comes from a realtor-developer background, so he understands our industry from the ground up. The ads basically touch all those points.”

Inland Empire Taxpayers for Jobs has spent about $50,000 on direct mail for Dutton, and Sacramento-based Restoring Our Community has spent more than $150,000 so far building and implementing a ground operation on behalf of Aguilar.

Perhaps the most intriguing primary of all is in the Ventura County-based 26th district, in which it’s possible Democrats won’t have a candidate on the general election ballot in an otherwise top pick-up opportunity.

As the only Republican running, state Sen. Tony Strickland is practically assured of advancing to the general. But with multiple Democrats on the primary ballot, Ventura County Supervisor Linda Parks, a one-time Republican who opted to run as an independent, poses a significant threat to Democrats.

Nearly all of the $755,000 outside groups have spent on the race so far was on behalf of Assemblywoman Julia Brownley, whom national Democrats view as their best bet to pick up the seat. House Majority PAC spent a total of $493,000 on TV ads that highlight Brownley to Ventura Democratic voters and on direct mail opposing Parks. The League of Conservation Voters and its California arm combined to spend $192,000 on direct mail supporting Brownley, and EMILY’s List spent $48,000 on mail for her.

“In November, Ventura County voters deserve more than a choice between a right-wing state Senator and a politically expedient county supervisor who spent 16 years as a Republican before changing her registration just as she announced her candidacy,” House Majority PAC spokesman Andy Stone said about the group’s involvement.

A La Jolla-based group called icPurple spent $24,000 each on online video production for Parks and Chad Condit, the son of former Rep. Gary Condit (D-Calif.), who is running as an independent in the Central Valley-based 10th district.

Elsewhere, Oxnard-based Citizens for Prosperity and Good Government reported spending $104,000 on radio advertising supporting state Sen. Doug LaMalfa (R) in the open 1st district, which will likely feature two Republicans in the general election. And House Majority PAC spent $76,000 last year on TV ads opposing Rep. Dan Lungren (R), who is being challenged again by physician Ami Bera (D), his 2010 opponent.