The Puzzle Of The Tunnels How Did Ancient Israelites Build A Waterworks Under Jerusalem? A New Study Indicates They Adapted What Was Already There.

January 25, 1992|By DAVID L. CHANDLER, Boston Globe

Thanks to King Hezekiah`s rapid action and clever engineering in 701 B.C., Jerusalem`s water supply was protected and the invading Assyrians, frustrated in their siege, eventually gave up and went home.

Centuries later, Hezekiah`s solution presented a puzzle for archaeologists: How, with primitive tools and little time, could the Israelites have built such a complex waterworks -- a long winding tunnel that carried water from a spring outside the city walls to a reservoir inside? And why was it built as it was, meandering beneath the city?

And there was another, related puzzle: The age and design of a much earlier tunnel inside the walls through which people could walk to a well-like shaft leading to a pool fed by the same spring waters. That complex has been dated by some to a period earlier than people were thought capable of such engineering feats, and it plunges at an angle too steep to be practical.

The puzzle of the tunnels appears to have been solved by a geological study which underscores the ingenuity of their creators: What had been seen as inexplicable design features may have been clever adaptations of what nature had already put there.

The findings may also explain a biblical passage describing King David`s conquest of Jerusalem. David`s army was apparently able to take the city by sneaking in through the older of the two tunnels. Until now, archaeologists had thought they were built after that conquest.

Today, 2,700 years later, the tunnel Hezekiah built to save the city still works, and the waters of the spring of Gihon, outside the ancient city walls, still flow through Hezekiah`s tunnel to the pond of Siloam. Although the water is polluted, these ancient waterworks still work.

How it was built so rapidly by people who had no instruments to guide them underground, and no way to provide ventilation in the 1,750-foot-long passage, has long been a mystery. But a solution has been proposed by Dan Gill of the Geological Survey of Israel. He argues in a recent paper published in the journal Science that the tunnels are a system of natural caves in the city`s limestone bedrock.

Rather than digging the passageways from scratch, Gill believes, Hezekiah`s workers -- and the Canaanites centuries before them -- enlarged and adapted the existing caverns.

``This interpretation ... provides a unified explanation for the apparent errors in design, and explains how the builders overcame the problems of underground orientation and ventilation,`` Gill writes.

Most archaeologists familiar with the site have not yet seen Gill`s report, but in interviews, several supported his conclusion.

``It seems to me quite plausible,`` says William Dever of the University of Arizona, who has spent 30 years conducting excavations in Israel. He has examined Hezekiah`s Tunnel and the earlier Canaanite tunnel called Warren`s Shaft.

``I don`t know that a geologist had ever really examined`` these tunnels before, Dever says.

The fact that the tunnels are modifications of natural caves ``would have been obvious to any geologist who would visit the place,`` Gill says. His paper mentions the irregular dimensions of the tunnels, the way they follow weaker layers in the rock, and coatings that form on the rock surfaces.

The Canaanite water system may be the earliest such waterway in the region, according to some archaeologists. It was probably built long before 1000 B.C., when the Israelites conquered the city. The shaft consists of a very steep upper passageway inside the city that ends at a vertical shaft 52 feet deep. At the bottom of the shaft, a horizontal passage connects to the spring itself.

In time of siege, the city`s people would descend steps carved in the passage and lower a bucket attached to a rope down the shaft into the water. The steepness of the shaft would have prevented invaders from clambering up into the city.

The steep shaft almost thwarted the archaeologists who discovered it. Access tunnels were blocked by fallen rock and dirt, and the shaft had been forgotten from biblical times until 1867, when Capt. Charles Warren, of London`s Palestine Exploration Fund, penetrated its lower passageway.

Except for one treasure-hunting expedition in 1909, no one else attempted the perilous climb until the 1970s, when the late archaeologist Yigal Shiloh began excavations in the City of David.

Shiloh and his team excavated the lower passage and located the blocked upper entrance. After several failed attempts to ascend the sheer shaft, Shiloh enlisted the help of mountaineers, and with them climbed to the top in 1979. The climb was discouraging, though, because it revealed that a daunting mass of rock and earth had blocked the old tunnel from the surface. Shiloh eventually found help from a team of miners.

``Hezekiah`s laborers were surely no more enthusiastic than our volunteers, who were obviously aware of the historical parallel,`` Shiloh wrote in an account of his work in Biblical Archaeology Review.

Warren`s shaft, difficult as it is to climb, has been interpreted by some scholars as the tsinnor (pipe) in a biblical account of King David`s conquest of Jerusalem. The passageway, they thought, could have provided a way for Joab and the Israelites to infiltrate the city.

The clincher for the geologist`s argument comes from bits of a crust formed on the walls of Warren`s Shaft -- a crust that forms only after the rock is exposed -- which Gill has had radiocarbon-dated. That process, he says, shows the shaft to be more than 42,000 years old.

Thus, Joab may indeed have used the shaft to sneak behind the enemy`s walls. ``The present findings provide support to Joab`s exploit,`` Gill writes, ``based on geologic fact rather than linguistic assumptions.``

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