More than 40 years ago, Jerry and Lu Parks spent millions of dollars transforming a patch of marsh on the Salmon River estuary into an amusement park they hoped would rival Disneyland.

As it turned out, Pixieland, with its log flume ride, opera house and "Little Toot" train encircling the perimeter, was a short-lived affair - closing within four years of its June 1969 dedication by Gov. Tom McCall.

Although blackberries and Scotch broom quickly engulfed the abandoned structures, the effects of the park's extensive system of dikes and ponds on the estuary were not so easily removed.

Now, the U.S. Forest Service is leading an effort to restore the Pixieland site to its natural state, reworking 25,000 cubic yards of earth to remove the dikes and fill the ponds with the aim of allowing the area to return to marshland.

George Buckingham, Hebo district ranger with the forest service, said properly functioning estuaries are crucially important for the health of many plant and animal species, particularly salmon.

"It provides a really important interface between fresh water and the sea," he said.

Corrina Chase, co-ordinator for the Salmon Drift Creek Watershed Council, said estuaries provide an area where salmon can transition from fresh water streams into the ocean.

She said a poorly functioning estuary can leave salmon with only a brief period in which to make the journey, putting the population at risk if they emerge into bad ocean conditions.

Watershed council President Paul Katen said estuary side channels also give salmon a place to hide during heavy rain events, so they are not swept into the ocean prematurely.

The task of restoring the estuary to its natural state began in 1974, when the U.S. Congress designated it as part of the 9,670-acre Cascade Head Scenic Research Area.

The forest service, charged with making the restoration happen, condemned the 35-acre Pixieland site in 1981, going on to buy the adjacent 11-acre RV park seven years later.

One of the first steps in the restoration process was to remove almost all the Pixieland buildings. Later, the forest service supervised the removal of the roads and parking lots, with more than 4,000 cubic yards of asphalt being trucked away from the site.

Now, attention has turned to restoring the marshlands, a task Chase said is both massive and precise.

"It's really easy to put the fill in but taking it out and restoring it to what it should be is really difficult," she said, adding: "The soil structure and the structure of all the tidal channels is going to take a very long time to recover."

Chase said the success of the newly restored marshlands depends on contractors getting the elevations of the reworked earth just right to foster the growth of the tufted hair grass that is the signature species of a healthy marsh.

As well as playing a major role in setting out restoration goals for the project, the watershed council has responsibility for handling contracts and administering funds.

Chase said the forest service has been very cooperative in letting the watershed council split the earthmoving work into three separate contracts to allow the work to go to three local contractors rather than a firm from out of the area.

Kami Ellingson, Siuslaw National Forest watersheds program manager, said a previous restoration project at Tamara Quays, just west of the Pixieland site, has been successful, with the tides bringing tufted hair grass seed to the site naturally to help with the revegetation.

However, Ellingson said full tidal flow will not come back to the Pixieland area until the forest service recreates the natural path of Fraser Creek, which was diverted into a ditch along the east side of Highway 101 when the park was built.

She said restoring the creek's original path will require building a bridge to carry the highway over the top, something the Oregon Department of Transportation has said is not a possibility until 2014 at the earliest.

Ellingson said the lack of a fully restored creek makes it difficult to estimate the eventual salinity of water making its way through the marshes, meaning the site will have to be manually replanted with tufted hair grass to prevent it being overrun with invasive species.

Finding hands to help with the planting is another job for the watershed council, which has responsibility for handling public outreach and giving people a chance to volunteer at a site which, when finished, will be open to all as a place to birdwatch, fish or walk the dog.

To register as a volunteer, e-mail Corrina Chase at coordinator@salmondrift.org.

The forest service is planning an open day at the restoration site on Oct. 23, with details expected to follow soon.