KAILUA-KONA — Every day cesspools throughout Hawaii send an excess of harmful nutrients pouring into nearshore ocean waters and threaten to infiltrate the freshwater drinking supply.
Hawaii Island is home to tens of thousands of them, representing nearly half of the known cesspools used throughout the state.
With a deadline of 2050 to shut down every one of them, the state Department of Health has scheduled informational community meetings in both Kailua-Kona and Hilo to discuss the elevated risk cesspools pose and gather community feedback on the issue.
The department will host the Kona meeting from 6-8 p.m. Friday at the West Hawaii Civic Center’s Council Chambers. The Hilo meeting is set for 5-7 p.m. July 25 at University of Hawaii in Hilo.
The Department of Health wants first to address threats to human health.
“Where there is a somewhat elevated risk is from bacteria in shallow wells,” said Edward Bohlen, deputy attorney general who represents the department’s Wastewater Branch.
Bill Kucharski, director of the Hawaii County Department of Environmental Management, said this is a particularly sensitive concern in Keaau. The region is home to 9,300 cesspools and is considered a Priority 2 area by DOH, meaning there are potential impacts to drinking water.
When cesspool seepage intermingles with ground water, it can find its way into aquifers drawn on by the county. This is generally less of a concern at deep well sites, which can range between 1,000 and 2,000 feet in depth and supply Hawaii Island with most of its drinking water.
However, Kucharski said people in parts of Keaau have shallower drinking wells, some only 100 feet deep or so. Bohlen said he was unaware of any documented cases of illness linked to cesspool contamination of drinking water in Hawaii but that the possibility would remain until the state adequately addresses the problem.
And drinking water isn’t the only concern.
“The other vector would be people swimming in water where wastewater has come out of cesspools,” Bohlen added.
The department has branded places like Hilo Bay, with 8,700 cesspools, and coastal Kailua-Kona, with 6,500 cesspools, Priority 3 areas. Those regions are characterized by cesspools that pose a potential impact to sensitive waters.
The issue in Hawaii Island’s major population hubs is more sewage runoff into nearshore waters, carrying with it an excess of nutrients like nitrogen and phosphorous.
According to the U.S. Environmental Protection Agency, nutrient surpluses can cause illness in humans, as well as create algal blooms that produce toxicity fatal to marine life and create dead zones in water bereft of oxygen, rendering them uninhabitable.
Perhaps as great a concern as the threats Bohlen mentioned is the fact that septic tanks, the typical alternative to cesspools when sewering isn’t an option, aren’t much better at managing nutrient outflow into nearshore ocean water — home to Hawaii Island’s coral reefs.
“The solids are maintaining. You pump those out and they go to a sewage treatment plant, so in that regard (septic tanks) are better,” Kucharski said. “But when you take a look at our concerns for nearshore waters … the septic tank does not deal with the nitrogen and phosphorous loads that are going in much better than cesspools.”
Sewering Hawaii County to a meaningful extent would cost hundreds of millions of dollars, and the island’s geology makes wide-scale sewering a dubious proposition. Compared to other islands in the state, Hawaii Island is young, and blue rock and fractured lava are more prevalent than soil.
The Legislature passed a bill this year to create a working group, contract a consultant and examine different financial and technological solutions to a statewide problem that is nevertheless Hawaii Island-centric.
“It can be very expensive to upgrade cesspools, so we want to make sure we do it in the most cost effective way and without harming homeowners,” said Bohlen, who didn’t mention any specific alternatives but noted identifying those options would be the purpose of the working group.
Projections for the average cost to homeowners switching from a cesspool to a septic tank or connecting to the sewer system range between $10,000 and $20,000 per property.
Hawaii County has turned to sewage treatment plants to manage wastewater in major population areas like Kona and Hilo. That’s also the plan in Naalehu, with one twist.
Instead of discharging treated wastewater that eventually finds its way to the ocean, like what happens at the Kealakehe Wastewater treatment plant, the site in Naalehu will function as a water uptake system.
Wastewater will undergo secondary treatment, then the facility will use aerobic ponds and vegetative uptake that removes nitrogen and reduces some of the phosphorous, Kucharski said.