Mammoth Spring Dam and Lake - Mammoth Spring, Arkansas - U.S. National Register of Historic Places on Waymarking.com

Constructed in 1884-88 by the Mammoth Spring Improvement and Water Power Company, the Mammoth Spring Dam powered the Mammoth Spring Roller Mill and Elevator, which ground soft wheat into flour, and the Mammoth Spring Cotton Mill and Cotton Gin. Turbines, which provided power to the mills, were located in turbine wells on each end of the dam; the roller mil1 was located adjacent to the south turbine well, while the cotton mill was near the north turbine well. The dam, located about one-eighth of a mile south of the Mammoth Spring head, creates a 9.5 acre water reservoir called Spring Lake. Mammoth Spring, Arkansas's largest natural spring, produces an average of 9.78 million gallons of water per hour at a constant temperature of 58 degrees Fahenheit. Because the water flow from the spring is constant, water continuously flows over the dam weir. Mammoth Spring is the source ofthe Spring River, whch flows south through the extreme eastern portion of Fulton County, eventually emptying into the Black River. The Spring River's dependable flow year-round made it ideal for powering manufacturing industries in the late nineteenth and early twentieth centuries, and it is now a popular destination for fishamen and canoeist & kayakers for the same reason.

The Mammoth Spring Dam is made of cut limestone set in a concrete footing on solid rock. The dam is approximately 198' in length, including the two turbine wells, with a 10' base and a 7' spillway. Steel dowel pins were drilled into the limestone for additional support. A cut limestone turbine well measuring 30' x 30' is situated on each end of the dam. Each turbine well contained three sluice gates, which directed water to one mine. In addition, two sluice gates were evenly spaced along the bottom of the dam spillway.

A reinforced concrete walkway with redwood sails extends along the top of the dam and is supported by 3" square steel tubing anchored to the limestone. The walkway is about 3.5' above the top of the concrete weir, which runs the length of the dam spillway, allowing water to flow continuously over the spillway between the walkway and the weir.

Mammoth Spring, Arkansas's largest natural spring and the seventh-largest spring in the world, constantly flows out of the ground about eighty feet below the surface of Spring Lake and forms the northern spring pool or spring hmd. The spring head flows over two small weirs and around an island to form Spring Lake. Mammoth Spring produces an average of 9.78 million gallons of crystal clear water each hour at a constant temperature of 58 degrees Fahrenheit, Spring Lake was originally around 16 acres in size, but it has been reduced to about 9.5 acres. A weigh station was to be constructed near the springhead in 1972 just to the east of U.S. Hwy. 63, so the western portion of Spring Lake was filIed with dirt to create enough space for it. The weigh station was never built, but the volume of Spring Lake was reduced. In addition, an island was built in the middle of the lake in the mid-1970s and a concrete cap was removed from the top of the dam, which further reduced tbe size of the lake.