Maui County is moving ahead with plans to build a $4.5 million rock seawall to protect its Wailuku-Kahului sewage treatment plant from erosion eating away at the beach fronting the facility.
The public has until Oct. 8 to submit comments on a draft environmental impact statement that calls for reinforcing the Wailuku-Kahului Wastewater Reclamation Facility, which is next to Kanaha Beach Park.
The county's Department of Environmental Management is proposing to extend an existing 450-foot seawall that was
built in the 1970s by adding about 1,100 feet of new rock mound.
Plans for the project have been modified since an environmental assessment was prepared last year to "minimize impacts to biological resources and recreational beach area," the updated study says. The wall will instead be built farther inland.
The draft environmental impact statement notes that between 2007 and 2011, annual erosion for the site averaged 3.7 feet, with a maximum annual erosion rate of 6.7 feet. Long-term studies put the average erosion rate at 2.4 feet per year.
"Erosion threatens several structures at the facility, including structures that cannot
be moved," according to the draft EIS prepared by Munekiyo & Hiraga. "Without the shoreline protection measures, the beach will continue to erode and threaten the upland area, creating a greater potential flood and tsunami hazard
at the site, as well as loss of land."
Existing injection wells could be threatened within three years, and the existing sludge holding tank within four years, if no protection measures are implemented, the study said.
"A no-build alternative puts the facility at a high risk of damage due to erosion, which would threaten the facility's ability to meet the wastewater treatment needs of Central Maui and presents a significant potential environmental hazard," the study said.
The project will require about 29,000 tons of armor and underlayer rock.
Some of the potential environmental impacts addressed in the study include effects on marine life in the area (mostly algae, zoanthids and other invertebrates); critical habitats in the nearby Kanaha Pond Wildlife Sanctuary; and beach water quality during construction.
The County Council at one time considered building a new facility farther inland at a cost of hundreds of millions of dollars, but reinforcing the existing plant was identified as the preferred route.
The sewage treatment plant, built in 1973, has an existing treatment capacity of 7.9 million gallons a day. It's projected to reach capacity in 2029, when it will require upgrades and expansion. Reinforcing the shoreline now is expected to help accommodate that added future growth.
The county anticipates receiving necessary permits and approvals for the seawall project in early 2013 and expects construction will take about a year.
The draft EIS can be viewed online at oeqc.doh.hawaii.gov.
* Nanea Kalani can be reached at nkalani@mauinews.com.
