In many parts of this world, tap water comes down to this: Turn the faucet and take your chances. Even for many U.S. cities and municipalities, the life-sustaining liquid delivered to consumers, even when safe, can taste like the shallow end of a swimming pool.

That’s not so in Honolulu, where a remarkable system of deep wells beneath the city’s pavement (and elsewhere around the island) have been providing some of the purest water on the planet for more than a century.

“Up to several years ago, we only chlorinated 65 percent of our sources,” says Dean Nakano, deputy chief engineer with the Honolulu Board of Water Supply. “The purity of our sources is still excellent–it was EPA rules that finally made us change. Now we treat all of the water. But we only put in a little bit of chlorine. We try our best to maintain the esthetics of the water’s taste.”

Purity and taste aside, it is the vastness, the sheer volume of fresh water (estimated to be in the billions of gallons) lying in the aquifer–the fresh water in the lens sits atop a literal ocean of salt water–beneath Oahu that has, perhaps more than any of the island’s other, considerable natural attributes, allowed Honolulu to grow into today’s metropolis.

Early on, a vision

Yet it wasn’t a sure thing by any means. Exploiting the artesian gold was one thing–maintaining it, while extracting the resource via powerful pumps, year in, year out, through periods of cyclical drought, was quite another.

“By the turn of the [20th] century, cattle and feral animals basically ate away all the forests,” says Barry Usagawa, an engineer for the Board of Water Suppy. “When it rained, all that water ran off, the streams became polluted, and the water didn’t reach the aquifer. A lot of the old artesian wells in Honolulu got saltier and the yield went down.”

Early engineers and hydrologists realized that the upland forests of Palolo, Manoa, Nuuanu, and Kalihi valleys had to be restored. “So, the newly designated conservation districts were fenced off,” Usagawa continues. “Eventually the forests came back. And it is critical that they be preserved, just as they are today, and never developed. Because every time it rains, [the forest] slows down the runoff, allowing it to percolate down into the ground water and resupply the aquifer.”

Pump it up

In a time when sustainability has become fashionable, the Board of Water Supply would seem to be one of the few entities of city or state government that has been actually walking the walk–for a hundred years or more. Take a stroll in Kalihi, pause at the corner of Waiakamilo and King streets and encounter a building that has occupied this spot, in one form or another, since William McKinley was president.

On a recent morning, Arthur Aiu, a Board of Water Supply spokesman who leads tours of the historic pumping station, stands before the “old man of Kalihi,” a massive, original steam pump installed in 1899, straddling well shafts drilled approximately 400 feet deep. The pump, which is the centerpiece of the Board’s Fred Ohrt Museum, ran nearly continuously from the day the first shovel-full of coal was fed into its boilers until it was replaced by electric pumps in 1971.

“Lots of people can remember the tall white smokestacks that rose above this station and on Beretania,” Aiu says. (A pumping station of the same vintage sits next to the Board’s business offices near the Capitol). Aiu leads the tour into the modern addition of the building, where several large electric pumps are hard at work. “Although they go down for maintenance or repair, we always have some running–we never stop pumping.”

“We do use a lot of electricity,” says Nakano. “All of our water is raised from deep underground, up into the reservoirs you see around the island, and from there gravity feeds it down to our customers.”

In a power outage, the island would have no more than a 24-hour supply of water. “We do have the capability to move emergency generators to serve pumps, to temporarily maintain levels in the reservoirs,” Nakano explains. “But heaven forbid we should have an extended, island-wide blackout.”

In the last two decades the board has concentrated its efforts on conservation. The State has set the sustainable yield for Oahu’s underground water at more than 400 million gallons-per-day–but it pumps less than half of that.

“We’ve been pumping at the 150 million gallons per day level for the past 19 years,” says Usagawa. “Low-flow fixtures, primarily the toilets–that’s been the biggie. The really old toilets used seven gallons per flush. The next generation, 3-5 gallons. Now, the standard is 1.6 gallons–and the 1.2 gallon model will be next.”

Water on tap

Pumping fresh water that sits on top of salt water is fraught with consequences–especially for a city as physically remote as Honolulu. “Between the fresh water and salt is the transition, or brackish zone,” Nakano explains. “We monitor the salt in the water we pump. What you want to avoid is the up-coning of the transition zone water–you’ll see an uptick in the chloride level. It’s like sucking really hard on a straw. Up-coning is dangerous–you can damage the resource forever.”

Of course pumping water is just one side of the equation for the Board of Water Supply. Its employees like to stress that they are in the business of water delivery–which means they are into pipes. “The oldest functioning water main in the city is a cast iron pipe, downtown, over a hundred years old,” Nakano says. “We have a main break, on average, once a day–roughly 400 a year. Fortunately we have great crews that get in and out in a timely manner, no matter the conditions. It highlights the need, the constant battle we have, to shore up our aging infrastructure.”

The Board of Water Supply pays for its own upkeep–alone among the City agencies it has a degree of historic autonomy. “The city generates its funds from property tax–we do it from water sales,” Nakano explains. Board employees know well that there wouldn’t be a city here, spread along the southern coast of Oahu, without their continual stewardship of this hidden resource, discovered and exploited by their predecessors. They were conservationists long before it was cool. “We pump pretty hard,” says Barry Usagawa. “But it’s at a sustainable level–the past hundred years is proof of that. And we feel we can pump at this level in perpetuity.”