The listed project consists of a solar facility, approximately 6.0 MW in size on a 16 acre track of land, in rural North Carolina. This case study involves remediation of the pre- cast concrete inverter and transformer pads which settled, compromising the equipment and wiring for the solar facility. There were 4 pad groups for this project, three of which had 3 separate pads, with two individual pads at the fourth location. Thus, there were a total of 7 inverter pads measuring 8’ x 14’ x 6” and 4 transformer pads measuring 8’ x 8’ x 6”. The Contractor noticed the pads had experienced settlement within the first year that ranged from 1” to 3.5”, except for one inverter pad which showed no signs of settlement.
Conventional construction methods were applied for the inverter and transformers placed on pre-cast concrete pads. That is, the wiring is run in conduit to the specific pad locations. Gravel backfill was used for pad support in addition to raising the elevations for the pads. Each pad in the group was placed to within 12” of each other to create a cluster for consolidating the equipment. The pads are set in place with the assistance of a lift, or crane, depending upon the actual loads. The wiring is extended through pre-cut openings for connection to the equipment. Photo 1 below illustrates the pad condition at one of the locations – typical of others.