Mamala Bay Study Commission Issues Draft Report on Coastal Pollution

posted in: December 1995 | 0

How clean is the water in Mamala Bay?

That was the sixty-four — make that the nine million — dollar question posed to three respected scientists as a result of the City and County of Honolulu settling a lawsuit brought against it in 1990 by the Sierra Club and Hawai`i’s Thousand Friends. The two groups claimed that the city had violated the federal Clean Water Act thousands of times at its Sand Island sewage treatment plant, which each day discharges up to 82 million gallons of primary-treated sewage into the bay.

Under terms of a consent decree filed in November 1991 with the federal district court, the city agreed to provide $8 million to underwrite a comprehensive study of water quality in Mamala Bay, the bight extending from Diamond Head to Barber’s Point along the southern coast of O`ahu. When the city lost a second similar lawsuit — this time for violations at the city’s Honouliuli sewage treatment plant — the court required payment of $1 million more into the Mamala Bay Study Commission fund.

Almost exactly four years after the initial settlement, the commission has issued its draft report, consisting of three bound volumes containing more than two dozen separate studies, with two additional volumes of appendices and supplemental reports. Were that not enough, several additional studies were not available for inclusion at the time the draft report was put together; these studies are to be released before the year’s end.

(Public comment on the report is being solicited, and in January, another public hearing is scheduled. Copies of the report were to have been placed in public libraries on O`ahu. Address comments and inquiries to the Mamala Bay Study Commission, c/o The Hawai`i Community Foundation, 900 Fort Street Mall, Suite 1300, Honolulu, Hawai`i 96813.)

Integrated Investigations

Soon after the court settlement, three scientists were selected to serve as commissioners who would decide what studies would be done and by whom. The three were Rita R. Colwell, of the Maryland Biotechnology Institute at the University of Maryland; Gerald T. Orlob, professor emeritus of civil and environmental engineering at the University of California at Davis; and Jerry R. Schubel, president of the New England Aquarium in Boston and professor emeritus of the Marine Sciences Research Center, State University of New York at Stony Brook.

In an overview of their work, commissioners provide a summary of what they regarded as their primary tasks:

“Principal concerns of the Study included assessment of the health and viability of aquatic ecosystems within Mamala Bay and evaluation of public health impacts due to use of Mamala Bay waters. Environmental resources at risk within the Study area were considered to include all those potentially affected by changes in water quality in Mamala Bay due to either point or non-point sources of pollution. Public health impacts were considered to include any that resulted from accidental ingestion of, or contact with, contaminated ocean water or use of environmental resources in the bay.”

The study commission was also instructed to make recommendations on ways to improve the environmental quality of Mamala Bay. The commissioners’ list of recommended actions appears in Volume III of the draft report (as “Water Quality Management in Mamala Bay,” Project MB-11). The first two among the nine suggested actions involve steps needed to upgrade the level of wastewater treatment at Sand Island and Honouliuli “to the level of chemically enhanced primary treatment.” The third recommendation is to disinfect the ocean outfall discharges at both plants, possibly by means of ultraviolet disinfection rather than chlorination (fifth recommendation).

Recommendation 4 calls for the City and County of Honolulu to study the feasibility of various measures to reduce contamination in the Ala Wai Canal.

Recommendations 6 through 8 concern ongoing study of the bay, maintenance of the data base developed by the study, and regular monitoring of water quality stations established during the study.

Finally, the ninth recommendation calls for establishing an “Integrated Coastal Management Forum,” which would bring together scientists, managers, “and representatives of stakeholder groups with the objective of providing a sustained environment within which the results of the Mamala Bay Study are applied for the benefit of all interests.”

Internal Differences

To a great extent, the various teams undertaking studies for the Study Commission attempted to coordinate their work. Still, nearly every individual study contains its own set of recommendations, often contradicting those made by the commissioners and by other researchers.

One of the most frequent points of disagreement arises over the issue of upgrading the Honouliuli and Sand Island sewage treatment plants. Both plants were designed to provide primary treatment of raw sewage before sending effluent into ocean outfalls; since 1994, according to the report, the Honouliuli plant has not managed to function regularly even at this level. Neither plant disinfects its effluent, and nearly every study that considered the question concluded that the outfalls account for much of the bacterial contamination of the bay.

But when authors of the various reports made their individual recommendations, a broad range of views emerged about the need to upgrade the sewage treatment plants. A study (MB-9B) by Richard W. Grigg, of the University of Hawai`i, on the effect of pollution on coral reefs in Mamala Bay concluded: “The findings of this study … do not alone warrant any changes in existing wastewater treatment practices for effluents discharged into Mamala Bay.”

On the other hand, a report (MB-10A) by Joseph M. O’Connor and Katherine Courtney, of Santa Cruz and Honolulu, respectively, found: “Upgrading Sand Island and Honouliuli [wastewater treatment plants] from primary treatment to enhanced primary treatment … is required.”

Contamination?

Nor were the authors unanimous in their ideas about the extent to which the city’s sewage treatment plant outfalls affected water quality at the beaches fronting Mamala Bay — beaches that include Waikiki and Ala Moana, some of the most heavily used and economically important strands in the state.

One study (MB-5, by Alan F. Blumberg and John P. Connolly, of HydroQual, Inc., a New Jersey firm) calculated the frequency with which state water quality standards at Diamond Head, Queen’s Surf, Waikiki, Ala Moana, Sand Island, Ewa, and Oneula beaches were exceeded over a given year. During their one-year simulation of weather and current conditions, they found 17 instances where fecal coliform standards were exceeded, with 16 of those instances “due solely to the outfall sources.” A total of 402 violations of enterococci standards occurred at the same beaches over the same period. “Approximately 50 percent of these were due to outfall sources,” they wrote.

Directly contradicting this was the finding of Roger S. Fujioka, of the University of Hawai`i Water Resources Research Center. Fujioka has done much work under contract with the City and County of Honolulu that tends to support the county’s position that outfalls play a relatively minor part in water quality degradation. In a study (MB-7A) of the microbiological quality of water in Mamala Bay, Fujioka concluded that “the primary treated and non-disinfected sewage from these two ocean outfalls are rapidly diluted by ocean water and currents predominately transport the sewage away from the land. Thus, the fecal indicator concentrations at the shoreline sites were not measurably increased as a result of these two ocean outfalls.”

Yet another study (MB-10E) considered the likelihood that four selected disease-causing pathogens in the bay (Giardia, Cryptosporidium, Salmonella, and enteroviruses) might pose a risk to the people using the beaches. That report, by Robert C. Cooper and Adam W. Olivieri, of Oakland, California, used a novel, if not controversial, approach to risk assessment to determine that a person swimming in any of the recreational waters of Mamala Bay did not increase his or her chance of contracting a disease associated with any of these pathogens. The swimmer’s chance of contracting a disease as a result of water-borne exposure, they found, was statistically no greater or no less than that what they described as the “background” risk to which all people in a given society are exposed.

‘Onshore Excursions’

A study (MB-4) of how plumes of effluent behave in ocean and tidal currents was conducted by Philip J.W. Roberts, of the Georgia Institute of Technology. Roberts concluded that plumes of sewage from the Sand Island outfall might surface more than 60 percent of the time in winter months. However, his model suggested that the outer edges, or contours, of the plumes “do not intersect the Waikiki beaches, implying that the probability of impaction there is vanishingly small.”

Roberts’ model did not take wind into account, but he assumed that trade winds would “blow the visitation frequency contours offshore” — that is, they would make it even less likely that the sewage plumes would reach the beach. “Occasional onshore excursions may occur,” he wrote, “but dilutions will be very high.”

And, even if the plumes reach the shore, Roberts wrote, dilution will be great and most of the “bugs” in the plume would likely be killed off by exposure.

Washing Ashore

A completely different scenario is offered in the very next study (MB-5), which, in addition to discussing water quality impacts (mentioned earlier), also describes the fate of organisms in the sewage plumes. According to the modeling done by authors Blumberg and Connolly, conditions that occurred in May 1994 allowed a relatively concentrated plume of sewage from Sand Island to arrive at Waikiki Beach. They write:

“The event to be analyzed here, which occurred on May 22, 1994, is of special interest because it happened under hydrodynamic conditions that have previously been considered highly unfavorable for the transport of outfall effluent to the beaches.” Among the “unfavorable” conditions was the fact that trade winds had prevailed the previous week. In addition, “the water column in Mamala Bay was stratified during this period.” Stratification refers to the temperature difference between surface and bottom layers; almost any difference will result in the plume remaining submerged, despite the natural tendency of the freshwater plume to be buoyant in salt water. This meant that “the Sand Island outfall plume was trapped in the lower half of the water column for at least one week before the May 22 event.”

Two and a half days earlier, subsurface ocean currents shifted from a westerly to an easterly direction, while the wind-influenced surface currents continued to flow westward. The effluent plume began to be transported eastward at a depth of 70 meters on May 20. Even stronger eastward currents on May 21 brought the plume to a point offshore of Waikiki Beach, though most of it remained at depth. From midnight May 21 to noon May 22, the plume extended to the surface, where currents transported parts of it to nearshore regions from Ala Moana to Waikiki beaches.

In winter months, when the water column is relatively unstratified and Kona winds occur, conditions are even more likely to result in transport of the outfall plume to the beaches, Blumberg and Connolly concluded.

Do the Bugs Die?

But if, as author Roberts suggests, the active ingredients in the sewage plume die quickly in the marine environment, then the impact on human health of the plume reaching the beaches is minimal. To be sure, the knowledge that one is frolicking in a tincture of effluent might dampen the joy of an outing to Waikiki. Still, if it’s not infectious, what’s the harm?

Fujioka’s study, mentioned earlier (MB-7A), found that fecal coliform and other microbial indicators of sewage tended to be “inactivated” — although not killed outright — when exposed to sunlight. In this inactive state, cells are described as being viable but not culturable — that is, they do not reproduce when placed on a growing medium, but are still living.

Fujioka’s study, based on laboratory experiments, does not consider the fate of pathogens that are transported across the bay at depth in a relatively intact plume, out of reach of most of the harmful sunlight, before surfacing at Waikiki. It is precisely this scenario, described earlier by Blumberg and Connolly (MB-5), that is the “worst-case” event for transport of microbes ashore — and one on which Fujioka’s conclusions would seem to have little bearing.

Environmental Effects

Several studies were undertaken to determine the impact, if any, of the outfalls on the health of aquatic animals and plants. The conclusions of one (MB-9C, Part A, by E.A. Kay, J.H. Bailey-Brock, and R.E. Brock, all of the University of Hawai`i) were that “there is no quantitative evidence supporting the view that the discharge of sewage is impacting the shallow reef resources shoreward of the two sewage outfalls.” In fact, the authors found, the armor rock placed over the outfall pipe provides excellent habitat for fish and coral communities.

Another study (MB-9F) considered the effects of sewage discharge on the microscopic but biologically vital phytoplankton communities in Mamala Bay. Principal investigators Edward A. Laws, of the University of Hawai`i, and David Ziemann, of The Oceanic Institute of Honolulu, concluded: “Although the sewage discharges are undoubtedly having some impact on water quality and the biological community in Mamala Bay, there is virtually no evidence to indicate that water quality or the phytoplankton community at recreational beaches is being impacted by sewage.”

The effects of chemical stressors from point- and non-point source pollution were studied by Joseph O’Connor (MB-10B). The outfalls were determined to be likely sources of cadmium, chromium, copper, and zinc, at levels that were within the same order of magnitude for maximum concentrations established by state water quality standards. Non-point source pollutants of concern include organotins from anti-foulant paints. Organotins, O’Connor writes, should be included as chemical stressors of concern “because there are so few data available, and because the organotins have the potential to have a devastating effect on the reef flat and reef communities of Mamala Bay.”

Other chemical stressors from non-point source pollution include zinc and copper (both of which can be extremely harmful to coral growth, even at low concentrations), diazanon, and high molecular weight polycyclic aromatic hydrocarbons.

Ecosystem Custodians

Despite the wide range of approaches and recommendations contained in the various studies, a statement by O’Connor and Courtney (MB-10A) sums the report up nicely:

“Public use of the beach resources on the shoreline of Mamala Bay does not appear to be threatened by point source and nonpoint source discharges. Nonetheless, the masses and types of pollutants discharged to the bay, and their long-term impacts, if any, are not clearly defined by the knowledge that we have at the present time….

“We recommend a long-term monitoring program to be carried out to gather data on living resources, habitats, and pollutant levels… The objective of the monitoring program would be to measure trends in various indicators of ecosystem health (water quality, habitat integrity, population structures, ecosystem function, maintenance of marine resources) and to allow the custodians of the ecosystem to determine whether additional management and treatment alternatives for the control of pollution must be implemented.”

— Patricia Tummons

Volume 6, Number 6 December 1995

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