June 23, 1987. After years of planning and negotiating the maze of permits needed for major coastal undertakings, the Natural Energy Laboratory of Hawai`i was ready. On this day, work was to start on its biggest project to date, the installation of a 40-inch pipe to deliver deep seawater to the research and aquaculture facilities at Keahole Point on the Big Island.
The cold-water pipe – vital for the state’s efforts to develop ocean thermal energy conversion technology – and another, smaller one for warmer surface water were to be buried in a trench running across the coastal shelf. Blasting of the trench — planned to be about 15 feet wide, 20 feet deep, and some 350 feet long — began at 10 o’clock, when 2,000 pounds of explosives were detonated along the area to be trenched to about 50 yards offshore.
Four hours later, a second shot, this time of 2,500 pounds of explosives, blasted out a channel to the end of the shelf. At 4:15 p.m., a third detonation of 600 pounds broke up rock on fast land, extending the trench toward the site of the future pump house.
One more shot was placed July 14, to take down a high point in the trench floor, but apart from that, the trench was essentially dug in a day. Engineers had thought about 30 days of blasting would be needed to do the job, but what they had thought was a solid floor of basalt turned out to be a veneer. Two or three feet below the surface were deposits of loose volcanic cinder — a fact that did not turn up in the pre-blast test bores that were to have been conducted.
From an engineering perspective, the blasting operations were a remarkable success. In 1989, the Consulting Engineers Council of Hawai`i gave supervising engineering firm, R.M. Towill Corp, its Grand Concept or Engineering Excellence Award for the firm’s role in the project.
Mounds of Cinder
From an environmental perspective, the consequences have been devastating.
The alignment of the trench had been intended to minimize coral loss. However, because the final size of the trench turned out to be much larger than planned, with a width of 30 feet and a depth of nearly 40 feet, much more coral was lost as a direct result of the blasting than had been anticipated.
The dredged spoils, consisting mainly of the clinkery volcanic cinder, were allowed to be piled alongside the trench since plans called for using it to bury the pipes. But very little of the dredged spoils were used as backfill in the trench. Indeed, there was not much room left for fill by the time the operators of the NELH and the state’s neighboring Hawaii Ocean Science and Technology (HOST) Park had put their pipes into the trench. Besides two main pipes (the 40-inch coldwater intake pipe, and a 24-inch warm water intake pipe), as many more pipes as would fit were placed into the trench. These are thought to number three or four: one 24-inch diameter pipe, and two or three 18-inch pipes.
Removing the dredged spoils would have been a costly, tedious operation. The Corps of Engineers permit did not require it, in any case, so the material was simply left behind (along with a substantial amount of construction debris) on the seafloor after the trench was capped with a thick layer of tremie concrete.
A year after the blasting, E.C. Fullerton, regional director of the National Marine Fisheries Service, complained of the devastation to the permitting federal agency, the Army Corps of Engineers, in a letter July 29, 1988. Occasioning Fullerton’s letter was a report on a survey of the site about two weeks earlier.
“On either side of the trench there remain mounds of lava cinder and rubble which have spread out over a large area of the bottom covering former rich reef habitat in depths of approximately 20 to 45 feet of water along the length of the trench. This unconsolidated material not only smothered the coral when it was originally stockpiled, but it now prevents the settling of coral planulae and the eventual recovery of the area.” NMFS also noted the abandoned construction equipment that had not yet been removed more than a year after work had ceased.
‘Sincere Regrets’
A biological survey of the area, made in September 1988 pursuant to the Corps of Engineers permit, bore out Fullerton’s report. In November 1988, Col. F.W. Wanner of the Corps indicated his displeasure with NELH’s conduct in a letter to its director at the time, Jack Huizingh. Wanner wrote: “I am very concerned about this matter and have considered several options available to me including a directive to restore the area and referral of the case to the U.S. Attorney for civil action and monetary penalties. However, I understand that removal of the spoils material at this stage … would likely cause further damage to the ocean floor.” Wanner then insisted that NELH remove the abandoned construction equipment and undertake an additional biological survey in the spring of 1989.
At the time, the NELH had pending before the Corps an application for a general permit to cover installation of up to 15 more permanent intake pipes and pump stations. Following the trenching and the unexpected consequences of that, the Corps held up work on the general permit for more than two years. In his letter to Huizingh of November 1988, Wanner informed Huizingh that because of what had happened with the first trenching, the Corps would require, as a condition of the general permit, that “all dredged materials be stockpiled out of the water.”
Huizingh responded by letter dated December 20, 1988. “We sincerely regret any damage that has occurred… In regards to the construction equipment, … it has been removed.” Huizingh was evidently alarmed by the threat to condition the general permit on the removal of all dredged materials from the water. “We request that this condition be discussed further,” he wrote, since it “would add significantly to the cost of construction.” The requested biological survey, he wrote, “will be submitted to your office by July 1989.”
Continuing Impact
It was fall of 1989 before NELH arranged for the survey, which was done by Richard E. Brock and Alan Kam, scientists at the University of Hawai`i who had conducted the three previous surveys. The 1989 report, based on a survey in September, said that the ash was “continuing to impact the benthic community.” Fish numbers were recovering and were projected to return to pre-blast conditions by the end of 1991. “In the benthic community,” they wrote, “the mean number of coral species per station has decreased by 44 percent, coral cover declined by 65 percent and the mean number of individual macroinvertebrates has decreased by 38 percent. On the positive side, the mean number of macroinvertebrate species encountered at a station increased by 50 percent. The presence of volcanic ash and rubble lingers; the September 1989 survey found that 47 percent of the substratum is still occupied by this material. This material is expected to be swept into deeper water with high energy (storm) conditions. However, since pipeline construction there have been no major storm events impact the Keahole Point region.”
Coral had been expected gradually to cover the trench cap itself. However, Brock and Kam found coral on just 0.03 percent of the area of the tremie cap. They wrote: “If growth of coral coverage on the tremie were linear and the 0.03 percent was representative of two years’ growth, more than 900 years would be required to attain preconstruction coverage (i.e., 14 percent).”
Their conclusion: “thus far, recruitment rates for fishes suggest that within two years from the September 1989 survey the fish community should be similar to that measured prior to construction. Because of the slow growth characteristics, it is surmised that the coral community in the area of impact will require 20 years or more to attain a preconstruction status.”
Soft and Spongy
Other problems were noted by Brock and Kam, and by agents from the National Marine Fisheries Service who accompanied them on their September 1989 survey. Brock and Kam’s report includes a photograph of what they term a “blowhole” in the tremie concrete cap. As they explain, surging ocean water works its way under the concrete at the terminus of the trench (where the coastal shelf drops off). Water pressure under the cap builds to the point that it breaks through the concrete, creating holes, some more than a foot long.
Also, they wrote, “[i]n many areas the tremie concrete cap is either breaking up by surface flaking or is soft and spongy, much like clay, thus eroding as fine particulate material. A surface with these characteristics is inappropriate for the successful settlement of most benthic species.”
The NMFS registered its concern formally in a letter October 11, 1989, to the Corps of Engineers from Fullerton, the regional administrator. “Equipment debris from trench construction, which was reported to your office after an earlier post-construction site survey in July 1988, is still in place and rubber grout pipes, rope, chain, coils of cable, and miscellaneous smaller items” were scattered about – this despite Huizingh’s assurance in December 1988 that the construction equipment had been removed. (A spokesman for the Natural Energy Laboratory of Hawai`i Authority, the successor agency following an act of the Legislature merging HOST Park with NELH, told Environment Hawai`i that the construction debris was finally cleaned up in summer 1990 — that the delay was owing to several outstanding disputes between the contractor and the Department of Accounting and General Services, which managed the contract for the state.)
The Corps of Engineers, in response to Fullerton’s letter of October 1989, wrote NELH, expressing concern over the deterioration of the tremie cap and reminding NELH that it was required to keep structures in good condition. William Coops, then managing director of NELH, forwarded to the Corps of Engineers a copy of a memo from the Department of Accounting and General Services, stating that “the reported deterioration of the tremie cap is being investigated.”
Tom Daniel, laboratory director at NELHA, told Environment Hawai`i that a recent inspection of the trench showed that the holes in the concrete had not increased in size since the 1989 survey. No further flaking or deterioration of the concrete surface was noted, Daniel said.
Daniel was asked whether the devastating storm that hit the Kona Coast last January had swept away the volcanic cinder from the seafloor, as Brock and Kam (and others) had been predicting. It had not, he said, attributing this failure to the northerly direction of the waves. The seafloor “looks not much different than it did a year ago.”
No More Trenching
In June 1989, NELH and HOST Park obtained from the Corps of Engineers the general permit they had applied for in 1986 and a decision on which had been held in abeyance pending resolution of issues related to the deep trench. The final general permit banned the installation of future pipelines in trenches, insisting that they be surface mounted, “anchored with concrete collars or bolted down through the surf zone.” The permit continued: “Blasting would be permissible only to the extent necessary to facilitate the dredging of the high spots and isolated coral outcrops along the pipeline’s alignments. All dredged spoils would be removed from the water for disposal at an upland site.”
In a section relating to management practices, the permittee was urged to consider “slant-drill access tunnels from shore to the desired depth offshore” as an alternative to surface-mounted pipes. “This method,” the permit states, “would incur the least environmental damage and greatly reduce potential injury or mortality of sea turtles.”
Work on the first slant-drilled hole at Keahole Point is to begin in June. That hole, a 5-inch bore, if successful, will be used as a conduit for a cable to supply power and receive fiber optic information from the Department of Energy’s DUMAND (for Deep Underwater Muon and Neutrino Detection) experiment. (DUMAND involves a giant array of optical sensors at a depth of 16,000 feet about 20 miles west of Keahole Point.)
The state has appropriated $2.5 million for the slant-hole drilling project, which is being undertaken by the Hawai`i Institute of Geophysics (at the University of Hawai`i). Up to seven shafts will be drilled, in lengths of from 500 to 1,000 feet and diameters ranging from 5 inches to 46 inches. According to the HIG’s proposal, “we will examine the use of this technology to drill large pipelines in order to convert carefully selected mid-Pacific lagoons into giant facilities for ocean thermal energy conversion and seawater aquaculture.”
Volume 1, Number 11 May 1991
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