Kevin R. Bodge, Ph.D., P.E.
Senior Engineer/Vice-President, Olsen Associates, Inc.
From: Kevin Bodge
Date: August 20, 2004
To: Rick Bernstein
Here is copy of letter I sent re: Natatorium back in ’98. Based upon changing conditions, years’ passing, observed experience, I’d triple the cost projections in that letter (and add more for demo etc.) . . . . but that still leaves the price tag well within/under current funding levels. Keep me posted. – Kevin
November 21, 1998
Dr. Charles Fletcher
Professor, SOEST; Department of Geology and Geophysics
University of Hawaii
Post 721, 1680 East-West Road
Honolulu, HI 96822
FAX (808) 956-5512
Dear Professor Fletcher:
I was surprised to learn that there is continued interest in permitting the Natatorium restoration project in its proposed, mostly enclosed configuration. Based upon my brief review of the project’s documents and limited site visits, I do not believe that the proposed design will function as intended or claimed.
Offhand, three potential problems with the proposed design concern me. First, the groins will principally impound sand — not water for circulation. The re-curved (shore-parallel) heads of the groins, in particular, are known to be highly effective in promoting sand deposition, even when ambient littoral transport rates are low. The accumulation of sand in the groins’ lee will ultimately block the circulation intakes (despite their elevation above the seabed); or, certainly, greatly reduce their flow capacity.
Second, the design depth of the sheltered pool is mostly greater than the ambient seabed, and thus represents an effective “sink” into which fine sediments will settle. The result will be a degraded bottom condition dominated by silts and clays that originate, mostly unseen, from the ambient coastal waters. The weak currents and absence of waves within the pool preclude flushing of these objectionable sediments. I have witnessed this phenomena repeatedly in the Caribbean; and am at present engaged in no less than six different projects in the Bahamas to “fix” the problem of fine-sediment deposition within artificial basins connected to the sea. The requisite solutions routinely require opening the basins to the sea, mechanical circulation (pumps), and/or high-frequency suction dredging.
Third, the location of the intakes on the Diamondhead side inherently conflict with the profile of the Sans Souci beach. At present, that beach’s active profile appears to fully extend to the seaward end of the Natatorium wall. If the intake could be maintained in an open state, it is altogether reasonable to expect some erosion or deflation of the Sans Souci beach by the introduction of a “vent” at its toe.
Overall, the designers’ prediction of water flow through the basin appears counter-intuitive. Even assuming that the intakes remain unobstructed by sand, it does not seem reasonable to expect that the claimed nearshore current magnitudes — and flushing — will be realized. On each of the three [arbitrary] days that I recently visited the site (once in February, twice in November), the nearshore waters were very calm and there was little or no indication of significant currents. The E.A. claims that this condition occurs only 2% of the year, or 7.3 days per annum. It seems odd that my three visits happened to coincide with half of the site’s annual occurrence of calms. The groins cannot create a current. Intuitively, even where a current is present, their very short lengths are more likely to divert the current offshore than toward the intakes; or, at least, to be minimally effective.
If an enclosed swimming area is, indeed, desired, then the only reasonable engineering solution is to completely isolate the basin and to exchange and circulate its waters by mechanical pumps and proper filtration. This is surely no more expensive than the groins, intake baffles, and long-term maintenance requirements of the proposed design.
A more prudent solution, though, would be to create a semi-protected swimming beach, open to the sea, with stabilizing groins on each side. These groins could potentially incorporate the existing sidewalls of the Natatorium, though armored with boulders. The existing seaward wall and the interior decks would be removed. The facade, of course, could remain as an architectural feature. As you know, I have designed over a dozen beach restoration projects of identical size, with stabilizing T-head groins, that have been constructed and have performed per predictions — with no requirement to-date for beach renourishment — over the past decade, throughout the Caribbean and the southeast U.S. The construction cost of these beach restoration projects, including sand fill and rock groins, ranged from $400 to $900 per front foot of beach [mainland price]. For this 400-ft long site, assuming the high-end limit, the construction cost would be $360,000. To this, add, say 40% contingency ($140K), 25% engineering allowance ($125K), and generous demolition allowance ($275K) — for a total cost of, say, $900,000. This excludes architectural restoration of the facade or upland (park) enhancements. Such a project would in no way “disrupt” or otherwise conflict with potential future beach improvements at Waikiki.
These observations are based upon my considerable personal experience with the preparation of engineering plans, construction supervision, monitoring, and the attendant calculations and analyses associated with beach restoration and bathing projects that are very much similar to the Natatorium project. Recently, in fact, much of my work has particularly focused upon “cleaning up” beach swimming-area projects in the Caribbean, designed by others, that have failed to perform per expectations, and which suffer from degraded water quality and objectionable siltation. In so many of those cases, the original project designs were based upon academic principles; that is, they did not adequately recognize the practical realities of coastal engineering field experience.
To the degree that you may find possible, I would urge you to bring the above-referenced concerns to the attention of those responsible for permitting and/or funding the proposed Natatorium project. In my opinion, I believe that there are far more economical and reliable schemes by which to restore the Natatorium area for the safe bathing enjoyment of the public, and so as to satisfy the directives of the City and County of Honolulu in regard to the Management Policy for Kapiolani Park.
Kevin R. Bodge, Ph.D., P.E.