You can't see them, but there are underground monitoring wells on the grounds of Tripler Army Medical Center.
The sentinel wells are an early alert system to tell if any petroleum is threatening either the military or the city's drinking water wells.
But two months after a sample turned up positive for diesel, the military is now saying that not one, but two new test results show an all clear.
The Navy conducted one, and the Army did another and both turned up negative.
"It was important that both independently conducted tests showed the same results," said Capt. Mike Williamson, Commander Navy Region Hawaii.
A statement released to KITV indicated that the results have been provided to the Department of Health which has indicated that further sampling from this well is not required.
But state health officials who have yet to officially see the data say -- not so fast.
"That has yet to be determined. Basically the Navy really needs to put in more monitoring wells to check for offsite migration. It's unclear whether this well will be suitable for that purpose," said Stewart Yamada, chief of the State Health Department’s Environmental Management Division.
The concern is whether any fuel from the Navy’s Red Hill underground facility is threatening the aquifer that provides water for Honolulu residents.
"Really, it’s not just the January release that's an issue, it is all the historical releases," Yamada said.
The state is pushing for the military to install monitoring six wells, three on either side of the underground tank farm.
So far, the Navy has only agreed to two.
Both sides are also in talks about a regulatory agreement that would take into account past spills.
There are some references in military records to spills of up to a million gallons but reports are sketchy.
"The concern is whether or not the contamination is moving offsite and not just toward their own drinking water source, but to the others, the Board of Water Supply's Halawa shaft and the Moanalua wells," said Yamada.
So, was that first test from the Tripler monitoring well a false positive?
No one is sure why diesel turned up in high levels in the first place and if it came from Red Hill or from an underground fuel tank operated by the Army.
The State Health Department is holding a public meeting next Tuesday night to discuss the water issues with the military.
So far, 17 holes have been found in a tank that recently leaked some 27,000 gallons of fuel.
The Environmental Protection Agency is expected to be on hand for that meeting.
It will be held at Radford High School starting at 5:30 p.m.