The state released safety inspection reports for all 54 of Kaua‘i’s dams and reservoirs Friday, and even though the reports found faults with every dam, officials were quick to say there is no imminent danger of another failure.
“There were no dams or reservoirs on Kaua‘i that faced an immediate concern,” said state Department of Land and Natural Resources chairperson Peter Young.
“However, there are areas of concern with various dams and reservoirs,” he said.
In a summary of the reports, U.S. Army Corps of Engineers Lt. Col. David Anderson says, “The inspection teams found at least one of the following detrimental conditions exists on every dam inspected on Kaua‘i, which if not corrected could lead to failure.”
The 11 conditions (see sidebar) pertained to erosion, seepage, inadequate or nonexistent outlet works and spillways and detrimental vegetative growth.
“Many of the dams have lacked basic monitoring and maintenance programs for what appears to be an extended period,” Anderson says.
The inspections were conducted in late March by officials from DLNR and the Army Corps of Engineers, as well as dam owners or their designated representatives.
Anderson notes that the inspections were visual, and not a formal Phase I or Phase II dam safety inspection. Areas downstream of the spillway or upstream of the reservoirs were not inspected.
“Additionally, the inspections did not include reviews of designs, construction, operations or maintenance documentation,” he says.
The inspection teams also did not include specialists, such as geologists or civil, geotechnical, structural or hydraulics engineers.
“Those inspections were emergency inspections,” DLNR chair Young said. “The Corps has recommended that (further) inspections take place.”
Young said the DLNR requested and received $5 million from the state Legislature this month to cover additional, more thorough inspections.
“We’re working on a schedule and plan now in order to deal with that subsequent inspection process,” he said.
Of the 24 dams classified by the DLNR and Kauai Civil Defense as “high hazard,” Twin Reservoir in Kawaihau needs the most attention.
“That one caught my eye,” said Hawai‘i’s adjutant general, Maj. Gen. Robert Lee. “Out of the 54 (dams on Kaua‘i), for that one to catch my eye, it certainly needs some work.”
The 19-page report on Twin Reservoir includes pictures and lists numerous problems with the spillways and monitoring controls.
Of the three reported spillways, one was collapsed, another was only partially lined and the third was never located.
In the spillways that were observed, there was blockage and severe erosion. The report also questions if the spillways were large enough to handle a maximum flood.
“The spillway appeared to be in unsatisfactory condition and (is) not expected to fulfill its intended function,” the report states. “Urgent corrective action is required.”
Furthermore, the report mentions recommendations from past inspections that were ignored.
“Previous inspection reports in 1979 and 1997 found similar deficiencies which have not been addressed,” the report states.
The 1979 inspection was done by the Army Corps of Engineers for the DLNR, and the 1997 inspection was conducted by the DLNR.
“The dam did not appear to be maintained on a regular basis,” the new report states.
Additionally, inspectors call for a structural engineer to evaluate the integrity of the catwalk leading to the outlet tunnel, which is the only means of controlling the level of the reservoir since the spillways are inoperable.
“Since the spillways are unusable, dam safety depends on reservoir control,” the report states. “It is imperative that the reservoir level be controlled.”
Inspectors also suggest further evaluation on the stability of the slopes of the dams and the outlet control.
“The previous inspection reports recommended extending the outlet conduit beyond the downstream slope,” the report states. “This has not been done and the erosion damage has increased.”
The report lists George Hoffberg, Leonard Kaui and East Kauai Irrigation as the landowners for Twin Reservoir. A list of dam owners available on the DLNR Web site lists Bette Midler as the owner.
“It is imperative that the owners retain professional hydrologic personnel to provide operating guidance and spillway analysts and repair guidance,” the report concludes.
Other hot-button reservoirs
Two other reservoirs that have been the focus of recent public outcry were also found to have significant faults.
Grove Farm’s Waita Reservoir, by far the island’s largest and located upstream from Koloa Town, was the subject of a town hall meeting in April attended by various state and local officials, including Gov. Linda Lingle.
Inspectors in March found the downstream channel to be in unsatisfactory condition and unable to fulfill its intended function.
“Urgent corrective action is required,” the report states.
Dense vegetation was also observed on the left side of the dam, and there are trees on the upstream slope.
“Trees have been identified as the (probable) cause of piping failures, and can possibly cause severe damage to the embankment if they are uprooted during high winds,” the report states. “Corrective action is required to remove the tree hazards from the dam.”
Alexander Reservoir in Kalaheo was also found to have significant issues with trees on the dam slopes.
“The existing trees have been allowed to grow so large in some cases that there is concern that seepage and piping (internal erosion) along root systems may develop,” the report states. “There is additional concern that cutting and killing the trees will lead to rotten roots and greater potential for such seepage and piping.”
The inspectors note further evaluation is needed to decide on a proper course of action.
Furthermore, inspectors observed a gully in the south abutment approximately 140 feet from the reservoir.
“This gully is approximately 130 feet (long) and appears to have been quarried,” the report states. “There were at least two recent debris falls in the gully. A recent notch in the upper right corner of the gully also shows debris fall activity.”
Inspectors observed water flowing from the notch and down the face of the gully at an estimated rate of 20 gallons per minute to 50 gallons per minute.
Inspectors also observed a recent “relatively large rock slide” adjacent to the gully that was apparently caused by the heavy rains but posed no threat to the safety of the dam.
The report states that the spillway might not be large enough to handle a maximum flood and is blocked in the channel and approach areas.
Inspectors also observed water seepage on the downstream slope carrying away dirt and soil particles and recommended the installation of a weir or plume to monitor the rate and volume of seepage.
Inspectors also recommend grading and filling to compensate for ruts and erosion on the crest road atop the Alexander Dam.
Owners cooperating now
Due in no small part to the March 14 Ka Loko disaster, landowners are heeding recommendations this time around, officials said.
“The owners have been very responsive,” Peter Young said. “There’s been a lot of attention on dams and reservoirs over the last few months.”
The DLNR sent copies of the reports to dam owners two weeks ago and have been working with them since. Young said some owners have already sent in newly-required Emergency Action Plans. Previously, only owners of “high hazard” dams were required to have EAPs on file with the government.
Young said there is no definite timetable on receiving the EAPs, and that the DLNR will continue to work with owners to ensure the future safety of their dams and reservoirs.
While the DLNR’s $5-million budget boost will go to further inspections and any maintenance and repair to state-owned reservoirs, private owners are still responsible for any upkeep of their dams and reservoirs.
While no reservoirs or dams on Kaua‘i raised immediate concern, one abandoned reservoir on O‘ahu, the Kailua Reservoir, required immediate action, Young said.
“A sinkhole was forming in the dam,” he said. “It was a very serious concern.”
Young said the sinkhole was repaired and there are plans to dismantle the dam.
Lee said officials are cutting an emergency breach on the dam at state-owned Kealia Field 2 Reservoir on Kaua‘i, but there are no plans to dismantle the dam. Kealia Field 2 is also abandoned.
• Ford Gunter, associate editor, may be reached at firstname.lastname@example.org, or 245-3681 (ext. 224).