Monks Mound - Preservation

Preservation

From the time the original urban society collapsed, the great mound became overgrown with trees, the roots of which helped stabilize its steep slopes. In the 20th century, researchers removed the trees in the course of work at the mound and park preparation. Reduction of groundwater levels in the Mississippi floodplain during the 1950s caused the mound to dry out, damaging the clay layers within. When heavy rainfall occurred, it caused new slumping, starting about 1956. The increasingly violent weather of recent decades has exacerbated the problem. In 1984-5 there were several slumps, and the state government brought in surplus soil to make repairs to the major scar on the eastern side. A decade later, there was further slumping on the western side, so irregular that repair was impractical. Drains were installed to reduce the effects of heavy rain. It was during this process that workers discovered a mass of stone deep within the mound.

The repairs of the 1980s and 1990s were only partly successful. In 2004-5 more serious slumping episodes occurred. These demonstrated that adding new earth to repair the major slump on the east side had been a mistake. Experts decided to take a new approach. In 2007, backhoes were used to dig out the entire mass of earth from this slump and another at the northwest corner, to a level beyond the internal slippage zone. Engineers created a series of anti-slip "steps" across the exposed face before the original earth (minus the imported repair material) was replaced at its original level. To avoid introducing water deep into the mound's interior, the work was carried out in high summer, and as quickly as possible. In parallel with the repair work, teams of archaeologists studied the evidence that was being revealed. The eastern sliding zone penetrated more deeply within the mound than originally estimated, and the excavation had to be very large- 50 feet (15 m) wide, to a height of 65 feet (20 m) above the mound base. This heightened concerns about a conflict between conservation and archaeology.