Honolulu Board of Water Supply officials told members of a City Council committee Wednesday that they worry a draft plan to make improvements at the Red Hill Bulk Fuel Storage Facility does too little over too long a period of time.

In January 2014, one of the facility’s 20 tanks leaked about 27,000 gallons of jet fuel oil, raising concerns that groundwater below it might be contaminated. While tests on drinking water samples taken since the incident have been largely within acceptable federal and state levels, state and city officials have expressed concerns about the continued use of the storage tanks.

A tentative agreement reached among the U.S. Environmental Protection Agency, the Navy and the state Department of Health on a plan to improve the facility is the subject of a public hearing set from 6:30 to 8:30 p.m. Thursday at Moanalua Middle School cafeteria. The plan calls for further study, more frequent testing and yet-to-be-determined upgrades to all 20 tanks over 20 years.

Earlier this week, the Board of Water Supply sent a letter to its 170,000 Oahu customers explaining “why you should be concerned” about the Red Hill meeting and urging them to attend. The letter noted that the fuel tanks are located above the groundwater aquifer that BWS uses to provide about 25 percent of the supply used for customers from Moanalua to Hawaii Kai.

On Wednesday, city Water Manager Ernest Lau and BWS water quality manager Erwin Kawata went even further, saying that the draft plan doesn’t go nearly far enough in making improvements to the World War II facility to make them comfortable about the future safety of the groundwater 100 feet below it.

The draft report of what is formally called the Administrative Order on Consent offers the perspective of federal and state agencies on how to protect the drinking water and surrounding environment, Lau said. “We believe that in its current form, this document is inadequate,” he said.

Regarding the draft report, area Councilman Brandon Elefante said, “It seems like it’s just study after study, and really no action per se.”

Kawata said: “We share your concern.”

The draft is lacking “in terms of what needs to be done and who needs to do it, when they need to do it, who’s going to be sure that the timelines are met — that level of specificity is not in the document,” Kawata said.

Among the recommendations being sought by the city is double-lining of each of the 12.5-million-gallon tanks. The draft plan does not include that recommendation.

Kawata said he’s also troubled that the draft ignores studies already done in 1998 and 2008 on how to improve the tanks. The same consultant, both times, “recommended taking out a couple of these tanks (and) putting the improvements so that they can better assess what is the cost, feasibility and timeline for doing that work,” he said.

The study “essentially says take that information and look at it again,” Kawata said. “So the question that we have is how much looking do you need to do and at what point is that going to translate to an actual action item for implementing improvements.”

One of the monitoring wells near the tanks consistently showed levels of total petroleum hydrocarbons as diesel at levels higher than acceptable state Department of Health contaminant levels since 2005, and then a spike shortly after the 2014 leak, Kawata said.

“The levels are continuously anywhere from 10 to 30 times above the Department of Health’s action limits, at least since 2005 up to the present day,” he said. As for the spike after the leak, “there seems to be some kind of correlation between the leak itself and the increase in levels that can be detected in the monitoring well.”

BWS officials also told committee members that about seven key support documents tied to the draft report have not been made public.

Lau said the water agency will seek additional time for the public to comment on the draft since not all the information they need to make an informed conclusion have been made available.