Hearings to consider approval of the proposed Ho’opili community with 11,750 homes in Ewa are scheduled to begin Oct. 20, and when they get underway three opponents intend to directly contest the project by D.R. Horton’s Schuler Division.

The Sierra Club and state Sen. Clayton Hee have filed petitions to argue against Ho’opili before the state Land Use Commission.

Hee and the environmental group, if their requests are granted, would join Friends of Makakilo as “intervenors” in the case. Friends of Makakilo, a community group led by Kioni Dudley, challenged Ho’opili during a round of hearings in 2009 that forced Horton to resubmit its development plan earlier this year before a vote on the merits of the case.

Additional intervenors in the case could make it more difficult for Horton, which believes that modifications it has made to its plan, including the dedication of some land for commercial farming and home gardens, have improved the project’s viability.

Last month, the Sierra Club and Hee said they intended to intervene in the case, and since then have formally applied to participate in the hearings with the ability to introduce expert testimony and question Horton witnesses with the assistance of attorneys.

The Sierra Club announced today that it had formally applied to contest the estimated $4.6 billion project, which would be built on about 1,500 acres that includes some of the best and most actively farmed agriculture land on Oahu.