Although the ultimate cost is not yet known, officials are moving forward to fix a slope that collapsed because of erosion along Medea Creek in Oak Park, resulting in a sinkhole that gobbled up a paved path used by walkers and bicycle riders.

The Rancho Simi Recreation and Park District allocated more than $120,000 for construction design work that has been completed and for acquisition of permits, which is under way.

Meanwhile, a temporary fence keeps people away from the sinkhole, which is about 100 feet west of Kanan Road and about 250 feet southeast of the Oak Park Library.

District officials don't know if the permits being sought will be approved; they also don't know the cost of construction.

"The scope of the project will determine the cost of the project," said Larry Peterson, general manager of the Park District.

"Our initial thoughts were that the project would be quite complicated as a result of the multiple agencies involved and the likely actions each would require" of the Rancho Simi district, Peterson said in an e-mail.

"However, as we have further evaluated and discussed proposed corrective actions, it has become more likely that the project will be less expensive than we originally anticipated," he added.

At a July 17 budget hearing at the Oak Park Community Center, officials described the project to stabilize the creek bank. The Medea Creek Bank Stabilization Project cost was listed at $122,136 for complete design and securing of permits.

At the same session, a district staff member said the project could begin in September and be completed in October.

However, Ed Hayduk, assistant general manager of the district, said the necessary permits, such as from the state Water Resources Control Board and Department of Fish and Game, are still being obtained by the district's environmental consultant, Rincon Consultants.

Peterson said the permit process might lead to modifications or even conceivably a rejection of the plan, and that construction bids would be based upon an approved plan.

In a written report earlier this year, Hayduk said the path was undercut by creek flows that formed a large sinkhole because of bank and creek bed erosion.

"The path will be repaired by filling the sinkhole with an estimated 240 cubic yards of large boulders and 660 cubic feet of gravel fill," Hayduk wrote.

He said the site is in a "willow riparian woodland" habitat, with a "riparian corridor bordered on the upper edges by a canopy of coast live oaks, transitioning to scrub habitat."

During construction, a water diversion plan will reduce effects on the perennial creek's downstream resources, said Rincon's report to Wayne Nakaoka, district development supervisor.

Permits figure into the repair because "riparian woodlands are typically crucial habitat for several species of wildlife," said the Rincon report. "

Many mammals and bird species rely on surface water for drinking, while other species may rely on the increased vegetation structure provided in this habitat for cover."