Trencher; U.S. Navy photo

Science in the Trenches

In Memoriam Harold G. Jaffer (1904-1995)

Supporting his mother and sister from the age of 15, my father had no opportunity for college. He read voraciously throughout his life; amassing an extraordinary wealth and breadth of knowledge. I had not realized the extent of his scientific and engineering acumen until recently; which is why I write this article.

After a career as a garment buyer in New York, Harold moved to Miami Florida in 1950. He joined his friend Caryl Stern in the irrigation business; and continued after Stern retired. Initially, they served homeowners by installing wells, pumps, and lawn sprinkler systems. The effort required to collect payments from consumers motivated them to shift their focus to commercial and industrial clients.

To be successful in such an enterprise, one must employ methods suited to the geology peculiar to South Florida.

Miami Oolite

Calcium carbonate settling out of the water coated tiny bits of shell or sand in layer upon layer. The resulting spherical grains of limestone are called ooids. The ooids later cemented into rock known as Miami Oolite.
oolite section

The land in and around Miami has a thin layer of soil (or not) covering this oolitic limestone. Laying pipes for irrigation involves cutting this limestone with a pickaxe or a mechanized trench-digger.

Potable (drinking) water is precious in South Florida and is not used to water lawns. So each irrigation project must have its own well tapped into a fresh-water aquifer, but not the aquifer supplying drinking water.


The drilling technology used for oil exploration involves expensive rotating heads and continuous pumping of drilling mud, which can contaiminate aquifers. And that technology is far in excess of what is required to drill through soft limestone.

Instead, a rig akin to a pile-driver pounds steel pipe through limestone. Instead of the threaded pipes used by rotary drillers, each new pipe section is welded onto the top of the ones already driven. This welded pipe is the well casing. No head must be extracted; no new sleeve inserted. Water flushes out the chips and sand.

Well drillers were scarce far from the oil fields, but essential to the business. Buck was their driller, welder, and mechanic for over 30 years. True to oilmen's reputation for wildness, he built and raced cars for excitement.

Well rig

South Florida Geology

South Florida is very flat. The Atlantic Coastal Ridge is the tallest geologic feature in Miami, peaking at 7.m altitude (the height of a two story building).

This ridge slopes imperceptibly downwards towards the interior. Although Miami has a river, one sees little evidence of erosion. Receiving of rainwater per year, downpours delivering are not unusual. So where does the rainwater go?

Rainwater (being slightly acidic) disolves limestone. Because the land is so flat, the only path for the rainwater is downward. So the Miami oolite is porous. Not only can the water flow down, it can also flow laterally. This porous layer of limestone is the surfacial aquifer. USGS Map of Biscayne aquifer


Below the surfacial aquifer are layers of clay, sand, and limestone. The sand and limestone are porous, forming other aquifers. Some carry fresh water; some are sea water; some brackish (mixtures of fresh and salt). The Biscayne Aquifer forms the fresh water supply for Miami. In a deeper layer the Floridan aquifer flows from Georgia and northern Florida.
USGS Map of Floridan aquifer system

The depth and contours of underground aquifers are much more complicated than the flat land above them suggests. This is because the falling ooids and other sediments filled in the valleys formed by earlier geologic processes and reefs. USGS Hydrogeologic section showing composition of the Floridan aquifer system

These variations of aquifer depth made estimation of drilling costs risky. The company was barely breaking even with stiff competition in the 1970s. Choosing between losing money when drilling costs exceeded their estimates and losing jobs with higher bids weighed heavily on my father.

Buck had an incredible memory for the details of the wells he had drilled. My father tried interpolating from Buck's memory of depth and strata (which affects drilling speed) in order to estimate well depth and difficulty. Their next three jobs made money!

Harold was then a man with a mission. They systematically recorded every well depth Buck could remember. Not content with just wells, he developed estimators for every bid component. When I visited him at the office, instead of just one or two blueprints on his table, there were five or six with another half dozen finished and rolled in tubes.

They could now safely and quickly bid nearly every job in their area. They didn't win more jobs initially, but every job was profitable. When a competitor undercut them, that competitor would often lose money. In subsequent years competitors shrank, went out of business, or moved to other areas.


Miami averages of rain per year. The porous oolitic limestone was very efficient at draining even the heaviest downpours. But downtown Miami was growing in density. With nearly all the ground paved or built upon there was no place for the water to go. After heavy downpours streets and parking lots would be flooded for days.
Rain Storm

Suburban expansion and paving caused lesser flooding throughout South Florida. When land is so flat, drainage over large areas must be designed, and installed. The building codes and permitting process did not mandate such a large degree of coordination.


There are commercial uses of wells besides irrigation. Air conditioners need a sink for the heat they remove from buildings. Summer air in Miami is so humid that evaporative cooling towers must be impractically large. One alternative is to circulate ground water from one well through the cooling coils; then pump it back into the aquifer. After drilling a pair of wells for this application, they are tested by measuring the flow of water pumped from one well to the other.

On a day when a downpour had flooded the parking lot where they were working, the drilling crew was testing the flow between two wells in this manner. My father then had them measure the flow into one of the wells while sourcing the water from the parking lot. The flow was nearly as high as the up and down test.

From this flow measurement Harold could calculate how large a well was necessary in order to drain a parking lot at a given rate by gravity alone. Thus the disposal well was born!

Disposal Wells

Since then, hundreds of disposal wells have been drilled in South Florida. It seems a better method of flood control than culverts and canals, because it puts water into the aquifers which paving would otherwise prevent.

In 1987 my father sold the business, which continues as Jaffer Associates LTD. Their building sports a time and temperature sign visible from Interstate-95 in Miami.

I am a guest and not a member of the MIT Computer Science and Artificial Intelligence Laboratory.  My actions and comments do not reflect in any way on MIT.
Copyright © 2002 Aubrey Jaffer
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