The polluted Kahaluu Lagoon on Oahu’s Windward side should shock the conscience.

Instead, sewage spills and the fouling of Hawaii’s nearshore waters has become so commonplace that they no longer generate outrage or sustained action.

Kahaluu Lagoon is a case in point. The state determined that the lagoon and channel leading to Kaneohe Bay contain unacceptably high levels of sewage and put up warning signs. That was two years ago, after users of the waterway complained of rashes and skin infections. The University of Hawaii’s Water Resources Research Center launched an extended study, with the prime suspect being the area’s more than 700 aging cesspools.

If the results confirm the suspicion, cleaning up the water will be difficult to achieve and a long way off — a distressing thought. When it comes to individual wastewater systems, i.e., those not hooked up to a municipal sewer line, cesspools are by far the worst option.

A cesspool is simply a hole, perhaps lined with bricks or concrete blocks, containing untreated sewage; the liquid percolates directly into the ground. Too many communities in Hawaii still rely on cesspools for lack of a better alternative — Kahaluu, for instance, isn’t on the city’s priority list for additional sewer lines because the city must first complete more urgent projects elsewhere on Oahu per a federal consent decree.

The cost of replacing a cesspool with a more environmentally friendly individual system, such as a septic tank, is prohibitive, from $10,000 on up. And a modest state tax incentive to replace cesspools doesn’t appear to be gaining traction. The state may need to sweeten the tax credit deal to encourage more participation.

The bottom line: Hawaii has about 90,000 cesspools, the most in the U.S., according to the Environmental Protection Agency. Of those, about 87,000 pose a risk to the state’s water resources, according to state Department of Health’s Wastewater Branch. Most of the cesspools in the state, nearly 50,000, are on Hawaii island; Kauai has about 14,000, Maui 12,000, Oahu more than 11,000, and Molokai more than 1,400.

Those cesspools release about 55 million gallons of untreated sewage into the ground every day, the DOH’s website says.

DOH’s administrative rules, amended in March to prohibit new cesspools, acknowledge the problem: “Hawaii is long overdue in eliminating construction of wastewater disposal systems depositing untreated sewage into the environment, such as cesspools.”

Long overdue is right. The continuing use of cesspools should be intolerable in a state that depends on groundwater for drinking and clean coastal waters for fishing and recreation — not to mention a tropical paradise with a fragile native ecosystem.

Moreover, cesspools are only part of the problem. Wastewater spills happen with depressing regularity. In the past month alone, 8,000 gallons of wastewater spilled over a three-day period on Oahu, with much of the muck entering the stormwater system, which drains into the ocean. A spill in August sent about 13,000 gallons of wastewater into a storm drain that leads to the Ala Wai Canal.

The consequences may be dire for our oceans. A new study by UH scientists reported a significant correlation between coastal areas of Maui where treated wastewater was discharged into the ground, and an increase in harmful nutrients in adjacent nearshore ecosystems.

DOH has convened a working group to address the cesspool issue, and that’s a good start. The persistent pollution problem requires a long-term mitigation plan, with the state and counties in lockstep, and the commitment to back it up. Even in tight fiscal times, surely more can be done to protect Hawaii’s nearshore waters — one of our most precious assets — from raw sewage.