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Project aims to provide additional water source and reliability to West Maui Water System 

By Staff | Apr 18, 2019

WEST MAUI – The County of Maui Department of Water Supply (DWS) is proposing the development of two existing exploratory wells, the Mahinahina Well and the Kahana Well, into permanent production wells on approximately 11.5 acres of land three miles east of Honokowai Beach Park below the foothills of the West Maui Mountains.

Referred to as the West Maui Source Development Project, the plan incorporates related improvements to integrate the wells into the West Maui Water System (WMWS), including the construction of a 500,000-gallon control tank, transmission waterlines and access roads.

The price tag is an estimated $18.4 million.

The site, situated 1.25 miles east of the existing DWS Mahinahina Surface Water Treatment Plant, has multiple owners, including the State of Hawaii Department of Hawaiian Home Lands, state Department of Land and Natural Resources and Maui Land and Pineapple Company.

It is located in the traditional District of Kaanapali.

The lands are classified as Agricultural by the State Land Use District, designated Agricultural and Open Space in the West Maui Community Plan and zoned Agricultural by the County of Maui.

With the action involving the use of state and county funds and the use of state lands, the preparation of an Environmental Assessment was triggered.

The EA was compiled to assess the “technical characteristics, environmental impacts and alternatives, as well as to advance findings relative to the proposed project.”

The over 150-page Draft Environmental Assessment (DEA) and Anticipated Findings of No Significant Impact (AFONSI) was published in the state Office of Environmental Quality Control’s April 8 edition of The Environmental Notice.

According to the DEA, the goal is to “provide additional water source and system reliability to the DWS West Maui Water System.”

Further, “The wells will support the planned growth that is projected to occur in the West Maui region.”

Maui Planning Department stats indicate the population of West Maui at the turn of the century was approximately 18,000. In 2010, the resident population grew by 23 percent to 22,200. By 2030, the Planning Department predicts the increase in population to reach about 29,000.

The West Maui Water System encompasses two regions – land north of Lahaina Civic Center and land south of the community hub – with customers on either side served by surface and groundwater sources.

The Mahinahina Surface Water Treatment Plant treats surface water from the Honokohau Stream, and the Lahaina Treatment Plant treats surface water from the Kanaha Stream. Multiple groundwater wells are found in both regions.

Both the Mahinahina and Kahana wells are intended to serve both the north and south regions.

Based on an operational schedule of 16 hours per day, the Mahinahina Well will draw 0.672 million gallons per day from the Honokowai Aquifer. From the Honolua Aquifer, the Kanaha Well projection is .96 million gallons per day.

The DEA notes that the closest residential and commercial communities are located makai of Honoapiilani Highway, an estimated two miles away from the lower reaches of the proposed 500,000-gallon control tank site, about 590 feet above sea level.

However, according to the DEA Cultural Impact Assessment (CIA), a lineal descendant, Kamaile Makekau, resides in close proximity to the Mahinahina Well, cultivating two acres of dryland taro.

According to the CIA, “Water rights, access to water, and the distribution of water were identified as a concern to families living in the vicinity of the project area.

“Specifically, there was concern that there is the potential for water to be taken away from the local Hawaiian population in an effort to provide water for tourists and for properties under private ownership.”

Previously, two separate Final Environmental Assessments were prepared, and Findings of No Signification Impact were published in 2011 and 2014 for the Mahinahina and Kahana exploratory wells, respectively.

The DWS drilled and tested both resources. The results indicated that these wells have reliable capacity capable of supporting new users or “backup redundancy for existing users.”

It’s not a free ride into the next phase for the West Maui Source Development Project.

A number of permits/approvals must be obtained, including federal, state and county: National Historic Preservation Act approval; Department of Health, NPDES Permit; Engineering Report for New Drinking Water Source; Department of Land and Natural Resources, Commission on Water Resource Management Pump Installation permit; and construction grading and grubbing permits.

The proposing and determining agency is the County of Maui Department of Water Supply. Contact Curtis Eaton at 270-7835 or DWS.Engineering@mauicounty.gov.

The project consultant is Yukino Uchiyama, Muneyiko Hiraga.

Comments on the DEA are being accepted by the Eaton and Uchiyama. The deadline is May 8.