When state Land Use Commission hearings resume next month to consider urbanizing 1,554 acres of prime farmland in Ewa for 11,750 homes, there will be two additional opponents contesting the case.

The Sierra Club and state Sen. Clayton Hee received approval Friday to intervene in the case, giving them the power to call and question expert witnesses key to determining whether the $4.6 billion project called Ho‘opili will be developed.

The move creates powerful allies for community group Friends of Makakilo, which had been the lone intervenor directly challenging Ho‘opili’s developer, the local Schuler Division of Texas-based D.R. Horton.

Friends of Makakilo leader Kioni Dudley welcomed the support. “We’re up against an awful lot,” the retired teacher said. “We’re outmanned and outgunned.”

Schuler attorney Benjamin Kudo raised some concerns but didn’t object to the Sierra Club and Hee intervening.

However, nearly a dozen construction industry representatives and other project supporters told commission members that the two parties should not be allowed to enter the case, which began in 2007 but was halted in 2009 because Schuler did not adequately divide the project into phases.

The City and County of Honolulu also argued that allowing Hee to intervene would violate the separation of legislative and executive government powers.

Only one person testified in support of the Sierra Club and Hee. “We really need more intervenors,” said Pearl Johnson, a League of Women Voters past president. “The forces against Dudley … are formidable, and Dudley stands alone. Hee and the Sierra Club have resources necessary to represent the point of view of people opposed to Ho‘opili.”

Much of the objection to the intervention by the Sierra Club and Hee was that their arguments would be similar to what has already been presented by Friends of Makakilo — primarily about the loss of top-grade farmland, weakened food security, increased traffic and school crowding.

“It’s just another ploy to delay this project,” said Maeda Timson, a Makakilo resident and Ho‘opili supporter.

Some people questioned whether it was right for Hee (D, Kahuku-Kaneohe) to intervene in the case given that he was involved in confirming some land commissioners and that he is not the senator representing people who live in the project area.

“He should not be weighing in on a development that is not in his district,” said Lance Yoshimura, assistant business representative of the Hawaii Carpenters Union.

Sen. Will Espero (D, EwaHonouliuli-Ewa Beach), who supports Ho‘opili, questioned the propriety of legislators involving themselves in quasi-judicial state hearings, and said a more appropriate role would be to testify like other members of the public.

Sherrie Seki, an attorney representing Hee, said Hee’s interest is largely as a farmer and advocate of agriculture. She added that there is no conflict because Hee is only presenting an argument to the commission and isn’t dictating the commission’s decision. Hee attended the hearing Friday but let Seki speak on his behalf.

Commissioners voted 6-1 to approve Hee as an intervenor. The vote was 7-0 for the Sierra Club. The vote against Hee was from commissioner Thomas Contrades.

Hearings are slated to begin Oct. 20 and could continue in segments over several months.

It’s not exactly clear whether, or to what degree, previously discussed issues in the case may be reviewed.

The commission in August 2009 ruled that Schuler’s petition to urbanize the site was deficient. No decision was made on the merits of urbanizing the land, but expert testimony had pretty much been completed.

In May, the developer amended its petition, introducing new elements including a 5-megawatt solar power plant and 251 acres within the community for commercial farming, community gardens and home gardens.

In general, Schuler contends that the project, which would create a community with roughly as many homes as Mililani or Hawaii Kai, is appropriate because it is within the city’s urban growth boundary designated to accommodate population growth while preserving farmland elsewhere on Oahu.

The developer also said Ho‘opili’s position along the city’s planned rail route will create 7,000 jobs to expand opportunities for people living in Leeward Oahu to work close to where they live and not commute downtown.

In July, the Sierra Club was able to temporarily halt another major Oahu development, Koa Ridge, a planned community with 5,000 homes between Waipio and Mililani. The group won a ruling from Circuit Judge Karl Sakamoto saying the commission’s approval of the project’s approval in October was invalid.