Loma del Rio: Prehistory in Papago Park

Loma del Rio (“Little Hill by the River”) was a small Hohokam residence that was occupied during the Classic Period, some time between A.D. 1200 and 1450. It was home to approximately 15 to 20 people belonging to an extended family. Several generations of parents, grandparents, siblings, aunts, uncles and cousins probably lived together. The site is located on the top of a hill in Papago Park, overlooking Tempe Town Lake (the Salt River bed) directly north of Hayden Butte.

Site Layout

The site contains the remains of a block of six rooms, an isolated room, a stone-paved area and agricultural terraces on the slope of the hill immediately to the southwest of the habitation. The single room on the east side appears to have been used for cooking and processing food. The remaining six rooms were built as residences. However, some time during the occupation of the site, the doors of three of the rooms on the north and west side of the room block were sealed off, probably so they could be used for storage. They would have been entered from an opening in the roof. The concentration of rocks on the southeast side of the site appear to form the surface of an open area that was used for a variety of domestic activities.

Adobe Wall Construction

The walls of the rooms at Loma del Rio were constructed by forming adobe around a core of stones. The stones were taken from the local bedrock formation. The adobe was made by mixing clay from the river banks with water. Wooden forms may have been placed on either side of the stone core in order to build up the adobe walls. The surfaces of the walls may have been plastered with caliche, a hard-packed soil that contains high concentrations of lime (calcium carbonate).

Terraced Gardening

The location of Loma del Rio is unique for this area because it is ideal for growing agave. The Hohokam residents built terraces into the hillside for this purpose. They ate the nutritious heart of the agave and used fibers from its leaves to make rope. It is possible that they traded some of the agave with other villages for items that they might have needed. Other crops such as corn, beans and squash could have been planted below in fields, irrigated by water from the Salt River.

A Site in Trouble

The adobe walls of Loma del Rio were covered in 1994 in order to minimize further erosion and deterioration. In 1928, archaeologists estimated that the partially buried walls were at least six feet high. Today, the walls are no more than three feet high and have collapsed in many places. If left exposed, the site would have faded completely into the landscape. There is no effective means of treating the adobe to stop deterioration. Covering the structure will preserve what remains for future generations. The walls can be uncovered for further study, or in the event that a technique is developed to preserve and stabilize adobe.

How Was the Site Stabilized?

Loma del Rio was excavated in 1984 and 1985 by archaeologists from Arizona State University. After the excavation was completed, plastic sheeting and soil were placed over the site. These materials have been left in place. When the stabilization began in 1994, a special synthetic textile was placed over the existing surface to provide a moisture-resistant layer while allowing air to circulate through the soil. Then the mound was built layer upon layer using soil similar in chemical composition to the natural terrain. Each layer was compacted to minimize erosion. The surface of the mound was graded to provide runoff. Historic photographs were used to make the mound look much as it did before it was excavated. In the last decade natural vegetation has grown over the mound, holding the soil in place and further minimizing erosion.