Normally, water released from the reservoir passes through the dam and into the river below by way of the powerplant. However, there are times when it is necessary to pass substantial quantities of water downstream quickly for flood control purposes. The spillway, located on top of the dam, contains 12 large gates, each 40 ft. by 35.5 ft., for the quick release of water from the lake. Water can be released at the rate of 5.8 million gallons* per minute with all floodgates open one foot (gates can be opened to five feet or more).
The concrete bucket at the toe of the spillway deflects the flow upward to dissipate its destructive energy and prevent erosion of the foundation. The training walls of the concrete structure at each end of the spillway direct the flow into the river channel below the dam. Water released through the floodgates cannot be used to generate electricity.
The floodgates at Hartwell Dam have been opened four times for flood control purposes – in 1964, 1994, 2013 and 2016. The three Corps-managed dams and lakes on the Savannah River have prevented over $40 million in flood damages since 1954.
*Figure based on lake elevation of 660 ft. msl.
Clemson Diversion Dams:
In addition to the main dam, two diversion dams were constructed from 1960 - 1961 to divert the flow of the Seneca River around Clemson University, preventing inundation of a large portion of Clemson property that was developed before the lake was created.
The construction of the diversion dams created an interior drainage area of 1,659 acres, with 125 acres being the Clemson bottoms or levied area. This required the construction of a pumping station to remove the water from this area and to control the elevation between 610’ and 614’. Water flowing into the basin comes from several sources:
- Hunnicut Creek - a free flowing natural stream.
- Old Seneca River Channel - several springs supply water to this channel.
- Upper and Lower Diversion Dams - these have a continuous flow of seepage from the reservoir into the pumping station basin.
- Storm water - from local rains.
The pumping station is equipped with two 40 HP vertical turbine electric pumps, with a pumping capacity of 2,000 gallons per minute (each). Under normal weather conditions with little or no rainfall, these two electric pumps will maintain the specified water level elevations of 610’ to 614’. The two emergency pumps are 30 ft. in diameter vertical turbine type pumps, with a capacity of 23,500 gallons per minute each. They are powered by D-398 caterpillar engines rated at 660 HP each.