Pipestem Dam is an embankment dam

Embankment dam

An embankment dam is a massive artificial water barrier. It is typically created by the emplacement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a dense, waterproof...

 on Rapid Creek

Rapid Creek (South Dakota)

Rapid Creek is a tributary of the Cheyenne River, approximately 86 mi long, in South Dakota in the United States.It rises in southwestern South Dakota, in the Black Hills National Forest in the Black Hills in Pennington County. It flows east, is joined by Castle Creek, past Silver City and...

 in Pennington County, South Dakota

Pennington County, South Dakota

As of the census of 2000, there were 88,565 people, 34,641 households, and 23,278 families residing in the county. The population density was 32 people per square mile . There were 37,249 housing units at an average density of 13 per square mile...

. The purpose of the dam is flood control, water supply and recreation. The dam was approved by the Flood Control Act of 1944 and construction began on November 25, 1952 and the dam was complete on August 15, 1956.
The dam and reservoir are part of the Rapid Valley Unit. The dam is 230 ft (70 m) tall and 1225 ft (373 m) long while the dam and its auxiliary dams are 2236 ft (682 m) long. The dam has an uncontrolled overflow spillway

Spillway

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...

 with a maximum discharge capacity of 245000 ft3/s. Total reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

water storage is 99000 acre.ft while 43000 acre.ft of that is for flood control.