A company trying to build what would be the third wind farm on Oahu’s North Shore has obtained its last discretionary state approval after a contentious proceeding and almost five years of work.

The state Board of Land and Natural Resources voted 5-1 last week to accept a habitat conservation plan largely focused on limiting Hawaiian hoary bat deaths from eight wind turbines spinning on a 707-acre site in Kahuku.

An affiliate of California-based Champlin/GEI Wind Holdings LLC received the approval following a BLNR contested case that began about a year ago at the request of community group Keep the North Shore Country and Kahuku resident Elizabeth Rago.

Champlin’s affiliate, Na Pua Makani Power Partners, expects it can start construction later this year and produce what would be the cheapest electricity from a Hawaii wind farm late next year.

“We’re really pleased that we got to this point,” said Mike Cutbirth, Champlin’s president and CEO. “This is a huge milestone for the project.”

Champlin said the 25-megawatt farm will produce enough renewable energy to power about 9,000 homes at half the cost of burning oil.

Under a contract with Hawaiian Electric Co. approved in 2015 by the state Public Utilities Commission, Champlin will sell power to the utility at 15 cents per kilowatt-hour over 20 years, helping lower consumer energy costs.

The state Department of Land and Natural Resources said the wind farm will eliminate $4 million of annual foreign oil imports, reduce carbon dioxide emissions by 1 million tons over 20 years and help meet the state’s goal of deriving all electricity from renewable sources by 2045.

The Na Pua Makani project was first proposed by another developer in 2009 and was taken over by Champlin in 2013. Initially, Champlin proposed increasing the wind farm’s size to 45 megawatts from 25 megawatts with 14 turbines. The generation size and number of turbines were later reduced, though the height of the turbines and blade lengths were increased.

Kahuku residents were divided, with some opposing the project because of its proximity to schools and homes.

Kent Fonoimoana of Makani Pono o Kahuku contended that the nearest turbine in a 2013 version of the plan was around 1,200 feet from Kahuku Elementary School. Based on the size of the turbines at the time, city permitting rules allowed turbines as close as about 450 feet.

After plan revisions, Champlin said in 2016 that the nearest turbine would be about 2,000 feet away from homes and 2,205 feet from the school.

Yet negative impacts on endangered species became a more contentious issue, especially after DLNR’s Division of Forestry and Wildlife reported last year that Hawaii wind farms were killing far higher numbers of endangered hoary bats than expected.

The DOFAW report said Hawaii’s five major wind farms had killed 146 bats in 6.4 years while permitted bat deaths at those projects were limited to 187 over 20 years.

Champlin produced its habitat conservation plan in 2016 using some of the same data in DLNR’s report. The company developed the plan through consultation with DOFAW, the U.S. Fish and Wildlife Service and a scientific panel, the Endangered Species Review Committee, that advises DLNR’s board.

A big influence in the plan was an adjacent existing wind farm that has operated with 12 turbines since 2011. This project reduced bat deaths by turning its blades parallel to the wind whenever it was under 11 miles per hour and between sunset and sunrise from April to November because bats are more likely to be active during these hours and months and in light wind.

Champlin will follow the same practice. Keep the North Shore Country argued for idling turbines under 14.5 mph wind. Typically, wind farms produce electricity in wind as light as about 8 or 9 mph.

The company’s conservation plan expects that 34 bats will be killed over 20 years and calls for changes if more are killed, with a kill limit of 51.

To compensate for the expected loss, Champlin will spend $1.8 million to help improve and preserve bat habitat being destroyed by feral pigs and invasive weeds at Poamoho Ridge. The company must spend another $894,000 on such mitigation if more than 34 bats are killed, and will spend $100,000 on research to help keep bats from being killed by wind turbines.

Champlin also will spend around $400,000 to enhance habitat for several native bird species facing more minimal potential of death from the wind farm. In all, DLNR said the company could spend as much as $4.6 million on environmental benefits. Another $10,000 per wind turbine per year, or up to $2 million over 20 years, will go into a fund to benefit the Kahuku community.

BLNR initially considered the conservation plan in late 2016, but the community group and Rago sought a contested case that allows expert witness testimony and cross-examination.

Local attorney Yvonne Izu, who served as the hearings officer in the contested case and held evidentiary hearings in August, issued a recommendation in November for BLNR to deny the plan primarily over bat issues. Izu had supported the 14.5 mph minimum wind speed to run turbines.

BLNR heard arguments directly during a January hearing. In a written decision filed Wednesday, the board sided with Champlin and said it appeared that Izu did not give sufficient weight to the scientific advisory panel and DOFAW or accept the preservation of bat habitat away from windmills as mitigation for windmills killing bats.

Board members in the majority were Chairwoman Suzanne Case, James Gomes, Thomas Oi, Samuel Gon III and Chris Yuen. Keone Downing dissented. Stan Roehrig recused himself.