page_title: Spring Creek Dam
section_title: Events prompting construction
hierarchical_section_title: Spring Creek Dam / History / Events prompting construction
caption_attribution_description: English: Acidic sludge in Keswick Reservoir, forebay of the Shasta Dam near Redding
context_page_description: Spring Creek Debris Dam is an earthfill dam on Spring Creek, a tributary of the Sacramento River, in Shasta County in the U.S. state of California. Completed in 1963, the dam, maintained by the U.S. Bureau of Reclamation, serves primarily to collect severe acid mine drainage stemming from the Iron Mountain Mine. The dam forms the Spring Creek Reservoir, less than 1 mile long. Spring Creek and South Fork Spring Creek flow into the reservoir from a 16-square-mile watershed. The dam is directly upstream from the city of Keswick, California and the Keswick Reservoir.
  The operation is part of the Trinity River Division of the Central Valley Project.
  The primary purpose of the Spring Creek Dam was to collect acid mine drainage from the old Iron Mountain Mine, which was heavily polluting Spring Creek and its tributaries. The dam was built in response to these pollutants that were contaminating the Sacramento River, the primary water supply for millions of Californians. Although the watershed is small in comparison to that of the Sacramento River, the stream is among the most polluted and acidic in the world.
context_section_description: The construction of Shasta Dam and its afterbay (regulating downstream dam), Keswick Dam, in 1943 and 1950, respectively, severely impaired the capability of the Sacramento River to flush away pollutants from the mine. Acid mine drainage flowed, unfettered, down Spring Creek directly into the Keswick Reservoir, depositing contaminated sediment and turning a portion of the water a rusty red shade. Previously, the water would have continued down the creek into the river, and flushed to the Pacific Ocean. The pooling of the water, however, made it extremely difficult for the pollutants to be removed. From 1955 to 1962, open pit mining began on the site. At its peak, the mine discharged 5 tons of iron, 650 pounds (290 kg) of copper, and 1,800 pounds (820 kg) of zinc into the stream per day. By then, the water flowing down the drainage was so contaminated that it necessitated the construction of a holding dam, the Spring Creek Dam.
  Spring Creek Dam was begun in 1961, when a company named Gibbons and Reed was awarded the contract. The clearing operations began in July of that same year, and the dam was officially dedicated by the Bureau of Reclamation on September 12, 1961. Construction of the dam began on October 20, 1961, with the placing of the dam embankment, which at least partially consists of acidic sediment dredged from Spring Creek.Riprap was laid on the upstream face of the dam beginning November 9 of that year. In 1962, a series of labor strikes impacted communities in the Central Valley, also affecting construction of the dam, which was temporarily halted on May 3 of that year. After work restarted on June 26, pervious core material for the dam was soon out of supply, so impervious material was used to complete the dam core.
  Eventually, the Iron Mountain Mine closed, but pollution continued and still continues, and in 1983, the Iron Mountain Mine was listed on the National Priorities List. The Iron Mountain Mine is known for having the most acidic naturally found water content on Earth, with samples having up to a −3.6 pH value when tested in the early 1990s, which is roughly 100 times the acidity of battery acid. However, this pH value is only found inside and near the mine, as the average pH of water entering the Spring Creek Reservoir is 4.12.
caption: Contaminated sludge draining from Spring Creek into the Keswick Reservoir created this change in hue of the surface.
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