What was the Miami Circle: Facts Proving that it was not a Septic Drainfield


Facts Proving the Miami Circle Was Not a Septic Drainfield	"What was the Miami Circle?" September 28, 1999
by John Ricisak

The following evidence supports the conclusion that the Miami Circle was not constructed in recent historic times, nor was it part of a septic drainfield system linked to the modern concrete septic tank located at the south end of the circle.

I. Archival Documentation

Plumbing plans dating to the 1950 construction of the Brickell Point Apartments identifies the septic tank as a 900 gallon container that is the northernmost of two septic tanks serving Building Number 4. These plans indicate that the septic tank effluent pipe discharged to the south (away from the circle feature) and was linked, along with the southernmost tank, to a pipe at the south boundary of the parcel. This pipe ran to the eastern end of the property where it ultimately discharged into the bay. The plans indicate that no septic tank drainfields were used for the Brickell Point Apartment complex and that no additional drainage system existed either north of the tank (within the circle) or south of the tank.

II. Physical Evidence

The septic tank has a terra cotta outflow pipe located on its southern end. The pipe is cut into the limestone bedrock. If it had been a drainfield, the effluent would have been discharged at an elevation below the surface of the bedrock.

III. Archaeological Evidence

The archaeological excavations conducted above the circle feature encountered two distinct horizons: homogenous black midden directly above the bedrock, and crushed limestone fill on top of the midden. Most of the circle was uncovered using 5' by 5' squares excavated by hand These unit excavations failed to encounter any evidence of a drainfield; specifically pearock, drain tiles, or fill sediment often associated with a drainfield. Furthermore, no pipes or evidence of pipelines radiating or extending from the septic tank were observed in either the fill or midden horizons.

Excavations of soil from each of the cut basins revealed no intrusions of historic or modern fill, nor were any historic or modern artifacts encountered. Excavations revealed no evidence to indicate that the construction of the basins commenced from the modern fill zone, as no fill material penetrated into the underlying midden.

A view of the Circle's western profile depicting the three feet of modern fill lying above the black-dirt midden. This fill was located over about 85 percent of the Circle; how, then, could the Circle be modern? (John Ricisak/Miami-Dade Historic Preservation Division) [LARGER IMAGE]

The appearance of the basin walls is typically characterized by reformed carbonated lamination and concretions adhering pieces of rock, bone, and artifacts to the walls. The rock face has a grey patina and no indications of recently cut white rock is apparent. In contrast, the bedrock cut by the apartment footers, septic tank placement, and sewage pipe lines have a "fresh" white appearance even though these alterations are about 50 years old.

Pieces of bedrock exhibiting sections of the basin/posthole features were used as backfill in the septic tank trench. In addition, the septic tank trench itself impacted at least two of the main basins along the circle feature as well as several of the smaller circular features within the circle's interior. This clearly demonstrates that these features predate the installation of the septic system.

It should also be noted that both the septic tank and its terra cotta effluent pipe were installed in squared-off trenches that are typical in appearance to what would result from the use of a backhoe. In contrast, none of the other features located along, within, or outside the circle appear to have been created using machinery. To the contrary, each is somewhat irregular in form and many exhibit vertical striations along their interior surface which probably represent the marks left by a hand-held tool. This latter fact, along with the definite and relatively precise circular form of the main circle feature, also firmly discounts the possibility that the features are of natural origin (i.e. natural solution formations created by rainwater, groundwater, greywater, etc.). Field experiments using a conch-shell columella hafted to a cypress wood pole showed that such a tool was a capable and efficient means of cutting holes into the limestone bedrock. This tool also created the same vertical striations seen on the interior of many of the rock cut features. Shell columellas, many of which had worn or blunted ends, were a common artifact type at the Brickell Point site and were occasionally found within the features themselves.

John Ricisak is an archaeologist with Miami-Dade County Historic Preservation Division.

Back