Poking Around The Iao Stream Flood Control Project
September 28, 2011 | 11:28 AMEarly last week, as a caravan of rental cars poured past a locked gate above Mokuhau Park at the corner of Kahawai and Nenea streets in Happy Valley, early last week, one 'Iao stream-side resident remarked, "Very unusual." Periodic inspections occur annually, so save the occasional adventuring keiki, it is unusual to see anyone–especially official-looking, engineer types–traipsing the 'Iao Stream Flood Control Project.
This 10-square miles of concrete basin-and embankment was constructed by the U.S. Army Corps of Engineers in the early 1980's, and for 30 years has been protecting Wailuku Town from "destructive floods by channelizing high velocity floodwaters into the Pacific Ocean."
But since its construction, erosion has and continues to pose egregious threats and correction of the project's "design deficiency" is necessary. Proposed renovations, which include a debris basin, diversion levees and channel improvements are forthcoming, following "a draft Environmental Impact Statement (EIS) expected to be released in 2012 [which] will be available for public review and comment," says Joseph Bonfiglio, the corps' Chief of Public Affairs.
Running through the most famous valley on the Valley Isle, 'Iao Stream feeds from four West Maui streams–Nakalaloa, Poohahaoahoa, Kinihapai and Ae–which converge near the 'Iao Valley State Monument, according to corps map. Over slick stones and under air heady with guava rot when the fruits in season, the stream meanders down from the State Park through the County's Kepaniwai Heritage Gardens, and further through the residential length of 'Iao Valley Road. There it crests at a final (mostly) natural waterfall at a place colloquially called Kamani Trees, before petering out into a weedy marshland cut off by a thick debris wall which marks the beginning of a concrete basin that extends until the stream's mouth sadly kisses the sea.
This 2.5 mile-long foot of 'Iao stream is a bit like a bikini-clad beauty queen making her pageant promenade in a plaster orthopedic cast, after having broken her leg while attempting to save a baby from drowning. Tragic beauty at its finest, the area's best viewed from the bridge on North Market Street near Takamiya Market, the bridge on Waiehu Beach Road near Sack 'N Save or from the stunning lookout at Helekii-Pihana Hei'au State Monument located off Hea Place.
As shocking as it may be to see the stark, sheer concrete walls of the industrial end of 'Iao–dappled with rubbish, Happy Valley Boys' graffiti and water rarely running above an algae-thickened trickle–it's not always evident that this is all a well-meaning attempt to mitigate risks to an area historically wrought with flooding problems.
"Flooding in agricultural and residential areas has resulted in loss of life and extensive damages to properties," reports Environet, a Native Hawaiian and veteran-owned environmental engineering and consulting firm which "specializ[es] in risk avoidance, waste remediation, and regulatory compliance," and which manages a website (iaostreameis.com) that provides a project overview.
The project was "designed to provide the town of Wailuku with protection against a 222-year flood (0.5 percent chance of flooding in any given year)," according to the Department of Defense. Environet adds that "the existing project has been successful in preventing more than $50 million in damages to the community (and expected annual benefits at approximately $3 million per year)."
Discussion of flood control in the area began in the 1950's and resulted in the U.S. Army Corps of Engineers' completion of the existing project in October 1981, authorized under by the Flood Control Act of 1968. But, as Environet reports, "During initial construction in January 1980, a flood occurred that caused extensive erosion of the sacrificial berm and undermined portions of the completed levees. Repairs were made, but shortly after the project completion, high stream flows again caused extensive erosion of the stream bottom and additional corrective work was required. Since that time, numerous storm events of high velocity flows have continued to result in recurring damages to the steeply sloped stream."
To this day, "erosion and scouring of the levee and stream bottom continues," says Environet, "and corrective action is needed to prevent further damages that could result in the levees collapsing or overtopping."
According to a 2008 corps report, "investigations were initiated because of the extensive erosion to the levee toe and the potential for project failure... [and] to correct the existing levee system to enable the Project to function in the manner as it was originally intended." At the time of the report, construction was slated to begin in the Fall of 2011 (i.e. now), but as it stands, neither cost nor timeline has been determined.
Last week, a team which included "a geotechnical engineer, a structural engineer and a hydrology/hydraulic engineer" conducted a periodic inspection, says Bonfiglio.
"The purpose [was] to verify proper operation and maintenance, evaluate operational adequacy and structural stability, " he says. "[And] review design critiera to identify changes in current design standards, identify project features to monitor over time, and communicate the overall condition of the project to the County of Maui.'
While these inspections do not provide a forum for public participation, Bonfiglio notes that the forthcoming draft EIS will.Consideration has already been given to comments made by community members in 2003 and 2009 (a summary of which can be found online at iaostreameis.com), as well as recent comments sourced in April and May of this year.
Some of the community's concerns include the desire for "percolation basins [which] allow water to [recharge the] aquifer," a push toward returning the stream to its "natural state" and adding more "shady vegetation," in hopes that "recreational components [will] be considered" and concern for native fauna (like 'o'opu) which migrate upstream but are stymied by low stream flow.
For those wanting to participate in the continued discussion, project manager Nani Shimabuku says that the corps is currently revising their calendar and will soon announce another opportunity for public comment; which can then be emailed to email@example.com or mailed to the U.S. Army Corps of Engineers [Honolulu District Civil and Public Works Branch (CEPOH-PP-C) Building 230].
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