King County has sent letters to seven property owners on Vashon informing them that they’re now accruing $25-a-day fines — civil penalties for their alleged failure to respond to the county’s order to have their septic systems inspected or repaired.

The letters came with a bill of $750 for the first month worth of penalties, according to Dr. Ngozi Oleru, environmental health division director for Public Health — Seattle & King County. The fines will continue to accrue until the property owners respond to the county, she said.

“This is the final step in the enforcement process,” she said.

Only one of the seven property owners lives on Vashon. The rest own waterfront homes or cottages on Vashon but live in Seattle, Tacoma, Eastern Washington and California, according to a list of those who are out of compliance.

The fines are the latest chapter in the county’s multi-year effort to address failing septic systems, considered sources of pollution that are fouling beaches and closing geoduck beds to tribal and commercial shellfish harvesters. The county began its effort in 2007, identifying 263 homeowners in six different waterfront neighborhoods who needed to either prove to the county that their systems were in order or begin the process of figuring out if their system works.

The county, meanwhile, has secured nearly $400,000 that will be used to create a loan fund for those property owners who have stepped forward to address their failing on-site septic systems but can’t afford to do so, Oleru said. The fund likely won’t be enough to address all the financial needs among the waterfront property owners with failing systems, she said, but it’s a start.

“There’s still a lot of work to be done,” she said.

The Puget Sound Partnership, meanwhile, applauds the county’s action. The partnership, a small state agency established by Gov. Chris Gregoire and the state Legislature to clean up and restore Puget Sound, has identified the need to find and fix failing on-site septic systems as part of its 2012 action agenda, said Alecia Lawyer, a spokesperson for the agency.

“King County is taking this seriously,” she said. “These penalties are a last resort, and we support these efforts.”