The board overseeing Oahu’s municipal water system adopted a plan Monday for responding to water shortages in the event of an emergency, such as a severe drought, damage to infrastructure or water contamination as in the case of 2021’s Red Hill disaster.

The plan outlines triggers that would prompt voluntary and mandatory water restrictions, the imposition of fines for water users who exceed allocations and moratoriums on water meters for development projects.

The Honolulu Board of Water Supply is already empowered to take such actions, and earlier this year put out an alert to Oahu residents asking for a 10% voluntary reduction in water use after 2021’s fuel spill at Red Hill contaminated the groundwater and prompted the BWS to take three wells offline to protect drinking water. The alert is expected to remain in place during the summer months for several years as BWS develops new water sources.

BWS formulated the plan, in part, to help the state Commission on Water Resource Management better coordinate water restriction efforts during emergencies. The commission ensures that water throughout the island’s aquifer is pumped at sustainable levels.

“In a long-term drought, we can control what we pump, but we have no control over private and military and agricultural wells. But the Water Commission has that authority. So it’s important to coordinate our efforts so we can get all well users to comply,” Barry Usagawa, a BWS program administrator, told the board during its Monday meeting.

Water restrictions are triggered when water demand exceeds the capacity of wells, or levels of chloride in the water become too high.

Under a water alert, BWS will request a 10% or more reduction in water use, according to the plan. If the water shortage becomes critical, BWS can implement progressively restrictive mandates, including targeted water use reductions, water allotments, restrictions on water flow, rate surcharges and a moratorium if system improvements extend for more than two years.

Under a critical water shortage, customers who exceed their allotted share of water can face stiff financial penalties. If their water use is 25% above their allotment, BWS can double their water rate. If they use twice their allotment, they can be charged 20 times their rate.

Water customers can be granted exemptions if the water restrictions would cause financial hardship, affect health and safety, or if more than four people are living in a household.

The BWS also has the ability to restrict new development. It can limit the size of new water meters or not approve them. The BWS also can require customers to use alternative water sources, such as gray water — recycled water from nonsewage sources such as showers, washing machines and sinks.

In the event of building restrictions, the BWS’ plan prioritizes certain development, including affordable and homeless housing and Department of Hawaiian Home Lands projects.

A building moratorium would require approval from the Water Board.

Meanwhile, the Navy and BWS are looking at drilling more monitoring wells to gauge whether an underground fuel plume from Red Hill may be moving to other areas of the aquifer. The Navy has said it’s looking at drilling about two dozen more wells. BWS might drill seven wells, according to Ernie Lau, manager and chief engineer of BWS.

Lau told the Honolulu Star-Advertiser’s “Spotlight Hawaii” livestream program Monday that each monitoring well could cost $1 million. BWS is also looking at developing new drinking water sources given the indefinite shutdown of three of its wells in the fallout from the Red Hill contamination. Lau estimated that it could cost $200 million to replace the lost capacity from its Aiea and Halawa wells and Halawa shaft.

Lau has sought federal funding for those projects to protect local ratepayers from having to absorb the costs, but said as of yet there is no federal commitment.