Last month, as crews scrambled to patch an early-morning water main break near the University of Hawaii-Manoa, rushing waters closed all lanes along a stretch of Dole Street. The resulting lack of spigot flow shut down four area schools for a day and left nearby neighborhoods with no water service, followed by limited essential-needs use for two days.

The messy incident triggered by the ruptured 20-inch cast-iron main, installed beneath the street 90 years ago, illustrates an upshot of our dependence on an aging municipal water system.

According to the Board of Water Supply, Oahu is now seeing about 300 water main breaks a year. And unless ongoing pipeline replacement efforts are ramped up, the annual count of splits, tears and bursts is poised for an unabated climb in coming decades.

Currently, about 6 miles of pipeline get replaced a year. To fend off the more-breaks forecast, BWS wants to accelerate to 21 miles each year over the next decade.

“Pipelines are the biggest component of all our assets,” said Ernest Lau, BWS manager and chief engineer. “We need to be more aggressive” in installing upgrades to the 2,100-mile system, which includes some pipe sections that were buried under Honolulu more than century ago.

Over the next 30 years, BWS wants to invest in more than 800 infrastructure projects islandwide — with a total price tag of more than $5.3 billion.

Financially self-sufficient, the semi-autonomous city agency taps ratepayers as its primary source of funding. Altogether, its facilities and infrastructure deliver drinking water to nearly 1 million people — with 170,000 services, including residential, commercial and industrial customers.

BWS is now seeking to raise $60 million through rate increases over four years to help finance a stepped-up schedule for improving the island’s largest water system. Also, it would borrow money so that it could spend $271 million more during that period.

Two public hearings on the matter will be held this week: Monday at Kapolei Hale and Tuesday at Kaneohe’s Benjamin Parker Elementary School. Another, May 24 at Miliani Recreation Center No. 5. All three are set for 6:30-8:30 p.m.

Among proposed billing changes are tweaks aimed at fairness and conservation: a reduced rate for residential customers drawing less than 2,000 gallons monthly, and an increase for those using more than 30,000 gallons. The average single-family household now consumes 9,000 gallons.

The base cost of water for the average single-family household customer is proposed to rise by 19.3 percent over four years, starting in mid-2019. BWS describes its plan as a gradual approach — less likely to touch off customer “rate shock” when compared with the last round of hikes.

In 2011 BWS increased rates by 70 percent over five years. That was on the heels of a near-50 percent increase over five years, which started in 2006. Before that, the last rate increase had been in 1995. The agency maintained that the two spikes were needed to pay for a backlog of pipeline work. A few years into the catch-up effort, though, eyebrow-raising rate shock gave way to a rattling in customer confidence as the agency’s billing system fell into disrepair.

“Back in 2013, we did a lot of things too quickly at the same time,” Lau said.

For starters, while plans for a new billing system had been in the works since 2008, the switch was not launched until January 2013. Before converting, BWS had attempted to Band-Aid failing hardware with parts bought on Ebay — because the system’s outdated technology was no longer readily available.

Then, with the move to modernize underway, the BWS also converted its billing cycle from every two months to monthly. However, due to glitches in meter-reading, information was uploaded incorrectly — large numbers on actual readings were replaced with estimated numbers.

“The two conversions together,” Lau said, stirred up problems akin to “perfect storm” chaos. BWS spent much of 2013 correcting bills for more than half of its customers. They had received estimates showing charges higher or lower than actual usage — in some cases wildly off the mark, by thousands of dollars.

A subsequent city audit concluded that BWS, while able to quickly get to the root of its problems, had made several mistakes. Among them, the new billing system, which had been slated to cost $5 million and take 18 months to put in place, ended up costing $16.4 million and taking much longer to roll out.

The report also tasked the agency with improving its dialogue with the public, especially when it comes to justifying rate increases.

“We took that to heart,” Lau said — for example, to boost visibility, BWS board of directors monthly meetings are now taped and televised. Also, public input was folded into the shaping of the 2016 Water Master Plan, which serves as a map to the future — it’s a systemwide assessment, four years in the making.

The Master Plan tags slightly more than 200 miles of “critical mains,” or top candidates for replacement due to risks such ground settling from movement; internal pipe pressure; and corrosion caused by salty soil and water. Because that damage is exacerbated by erosion and sea level rise, BWS is looking to include more resilient plastic in pipeline design.

“Future generations are going to see the effect with fewer main breaks,” Lau said.

In addition to infrastructure concerns, the Master Plan document focuses on conservation incentives; maintaining sufficient funding for recovery from natural disaster, such as a hard-hitting hurricane; and establishing more equitable rates and charges in BWS customer brackets. The proposed rate hikes are based on Master Plan projections.

If the four-year bid is approved by the BWS board, Lau said, “This time around … we’re giving ourselves almost a year to get ready.” Still, he added, “There’s always an element of risk.”

Some uncertainty — including that of the deja vu sort — could be tied to a plan to install fresh battery units in BWS metering apparatus. Over the next two or three years, the agency wants to replace components that have run out their life cycle — installed in the early 2000s — at some 150,000 meter sites.

“We’re reading 80 percent of the driveby” meter readings, Lau said. Manual reads are used for most of the rest, and about 2 percent of bills are based on estimates due to stuck or blocked meters. BWS contends that the investment is needed to improve billing efficiency as it gears up to tackle emerging water-related challenges.

Right now, groundwater is Oahu’s only source of the potable water at our faucets. “Everything originates from rainfall,” Lau said, percolating into steep watersheds. From there it’s retrieved through groundwater wells and source pumps, and funneled through tunnels and shafts.

Barry Usagawa, program administrator for BWS’s Water Resources Division, said the sustainable yield for Oahu is 407 million gallons per day. The agency typically pumps less than half of that to meet the current average daily demand of 145 million gallons. However, population projections show major growth slated for Ewa, Central Oahu and the lower part of Honolulu’s urban edge and coastal areas.

“We’re going to have to develop more source capacity, new wells, to meet the 2040 demands,” Usagawa said.

What’s more, BWS maintains that it needs to further diversify water supply to contend with various threats to flow and quality, such as climate change. Heeding long-term projections that rainfall will decrease in West Oahu, but storm intensity will increase there and elsewhere, the agency is pursuing desalination to help “ride out those periods of drought and fluctuation,” Usagawa said.

A proposal for a desal plant, which surfaced a decade ago but stalled, is now resurfacing. The BWS Master Plan calls for construction of a facility, within the next few years, on land that was part of the Barbers Point Naval Air Station. Initially, it would provide an additional 1 million gallons of potable water to Ewa and Waianae, and would be capable of further expansion.

BWS has also acquired the state’s demonstration brackish water desalination plant facilities in Kapolei Business Park, which could be reconstructed to supplement potable water supply for Kapolei.

Usagawa said desalination had been put on hold, in part, due to strides in water conservation. Since the 1990s, Oahu has cut its daily water use by about 30 gallons per person, resulting in savings of more than 12 million gallons a day. BWS credits consumer-focused strategies — rain-barrel water for non-potable uses, xeriscaped gardens and energy-efficient home appliances, among other tactics — as well as conservation through pipeline maintenance and repair.

Even more fundamentally critical than conservation, which can reach saturation points, is the safeguarding of watershed terrain as a counterbalance to growing population.

Oahu has two main watersheds: one in the Koolau Mountains and another in the Waianae Mountains. The Koolaus, which run perpendicular to northeast trade winds, see the heaviest rainfall — about 250 inches of rain each year. The Waianae peaks sit in the Koolau rain shadow.

In a healthy watershed, there’s a multi-layered canopy forest that captures and retains rainfall, allowing it to seep into the underground aquifers.

BWS is working in tandem with other agencies and groups to protect watershed areas by limiting access to development and combating invasive species, such as groundwater-slurping albizia trees. Such species can weaken otherwise effective watershed vegetation, accelerating erosion runoff and landslides that can clog waterways and reduce groundwater supply.

Weighing those ecosystem challenges with others linked to climate change issues, Usagawa said, “If the future of Oahu is going to be decreased rainfall, the forests have to be healthier.” He added, “We have to look mauka. We cannot just look from the pump to the meter. We have to look at the resource, and how sustainable that is — we’re on an island in the Pacific and each watershed has to be sustainable.”