The Water Mine Family Swimmin' Hole, a popular regional water park with an Old West theme, began its seventh season last weekend at Lake Fairfax Park in Reston. Since the Water Mine replaced a 25-year-old lap pool, much of the rest of Lake Fairfax has seemed outdated.

Now Fairfax County park officials are proposing a three-stage, $13.5 million redevelopment of the rest of Lake Fairfax's main area, making it compatible with the Water Mine by updating facilities that have long needed renovation or replacement. One of the park's signature attractions -- a 16-gauge miniature train -- would be brought back after the original one was shut down a few years ago. Plans also call for a miniature golf course and six new slides at the water park.

"Essentially, right now, the lakefront infrastructure is a 30-year-old concept," said Jim Duncan, the county Park Authority's Lake Fairfax project manager. "We're going to make it more friendly to the users."

Lake Fairfax, acquired by the Park Authority in 1966, is the largest park in the Reston-Herndon area and a site for such regional events as concerts and Fourth of July fireworks. On its 479 acres are the fishing and boating lake, campgrounds, picnic areas, ballfields, trails, a carousel and playgrounds. The Water Mine, one of the park system's biggest moneymakers, helps the park pull in more than $1 million a year in user fee revenue.

But the park offices and restrooms are too small, in buildings that need repairs. The main park roads are not wide enough to handle traffic, and many are in poor condition. Lake Fairfax lacks trails for visitors to walk safely within the park. The Water Mine has exceeded expectations, and its 800-person capacity is too small to meet the demand. During busy periods, the water park asks customers to wait, sometimes an hour or longer, to get in; many give up and leave.

Under the three-stage plan, the park's core area would get a makeover. The area includes the park offices, water park, waterfront activities, food services, restrooms, carousel, playground and parking areas.

The first phase is scheduled to begin this year, park officials said, with completion scheduled for fall 2005. Improvements in the $1.6 million stage include a new boat dock, marina, boathouse, boat storage racks and stairways, walkways, ramps and boardwalks accessible to the disabled. New playground equipment will be installed near the carousel.

A 1998 park bond program approved by the Park Authority Board will cover the initial phase of the redevelopment. But money for the next two stages has not been identified, Duncan said, so there is no timetable for those plans.

In April, county officials rejected a request by the Park Authority to increase the $50 million in park bonds being put to voters in a referendum Nov. 2, even though park officials said they will need as much as $376 million in the next decade to expand and improve the county's playgrounds, trails, athletic fields and open spaces, including those at Lake Fairfax. County officials countered that Fairfax has too many competing needs.

If the money can be found to complete Lake Fairfax's makeover, the park will get new picnic pavilions, restrooms, shelters for summer day camp programs, an 18-hole miniature golf course, the train, parking lot improvements and new administration buildings.

At the Water Mine, a slide pool with six slides would be added along with another bathhouse, concessions building and covered picnic area and group pavilions. Park roads also would be expanded or rebuilt.

Studio 3 architects of McLean have worked on a design that meets the requirements of a project team of Park Authority staff members who favored an overall plan complementing the existing water park, said Park Authority spokesman Judy Pedersen.

Duncan said the planned improvements probably will require closing the waterfront and marina for about four months during the operating season, affecting people who usually boat and fish at the lake.

The Water Mine Family Swimmin' Hole, now in its seventh season, is so successful that customers sometimes can't get in. Officials hope eventually to add a slide pool with six slides, a bathhouse and a concessions building.