Alum Creek
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Alum Creek is a tributary of Big Walnut Creek, which drains into the Scioto River. A storage dam north of Columbus, Ohio provides one third of the city's drinking water and offers flood protection as well. The Alum Creek Lake reservoir was built in 1974, covers 5 sq mi and has a maximum capacity of 134,800 acre-ft.
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[edit] History
The Alum Creek valley was inhabited by the Adena over 2,000 years ago. This mound builder culture constructed seven mounds along Alum Creek. The Lenape (Delaware) Indian tribe later established many settlements near the creek.
One of the first European settlers was Colonel Moses Byxbe, who constructed his home on Alum Creek in 1805. Colonel Byxbe owned or co-owned 38,000 acres along the creek.
As a defensive measure during the War of 1812, local residents built four blockhouses in the area, including one on Alum Creek. The blockhouse, Fort Cheshire, was a 2-storey log fortress, constructed so as to provide a place from which to shoot, drop boiling water, and defend against the threat of fire. The blockhouse was subsequently used as a schoolhouse and remained intact until the Civil War. The fort is commemorated by a bronze plaque where the blockhouse once stood.
The history of Alum Creek is also notable for its connection to the Underground Railroad, by which many slaves found their freedom. The Underground Railroad's Sycamore Trail ran along Alum Creek. Africa Road, near Alum Creek, is so named because of the nearby settlement of thirty freed slaves from North Carolina. [1]
[edit] Columbus Drinking Water
Alum Creek is one of three main sources of drinking water for the City of Columbus. Water is stored in Alum Creek Lake, and then released into Alum Creek to flow down to the Morse Road Treatment Plant.
[edit] Dam Construction (1970 - 1974)
Alum Creek Dam which was constructed between 1970 and 1974 is located on Alum Creek, a tributary of Big Walnut Creek, which drains into the Scioto River. The dam is a rolled earth-fill embankment 10,000 ft in length with a maximum height of 93 ft. The spillway is located high on the right abutment with the raceway dropping off in front of it to the stilling basin below. Control is provided by three 34 by 25 ft. tainter gates supported by 8 ft wide concrete piers resting on concrete ogee sections. The ogee sections have a crest elevation of 878 and are founded at elevation 839.
[edit] Potential Dam Failure and Retrofit (1975-1978)
On April 24, 1975 during a periodic inspection of the completed dam, the Army Corps of Engineers expressed concern about the safety of the spillway monoliths. The rock underlying the dam is Ohio Black Shale which is a largely hard, massive silt shale. It is highly fractured below the base of weathering. Within this shale are several light gray, silty to clayey shale seams up to 1 ft. thick. It may be possible that the spillway monolith and its underlying bedrock could slide forward on one of these seams, opening a gap between the monolith and the rolled earth dam leading to rapid and catastrophic erosion of the dam.
[edit] Testing
Twelve, 6-in. diameter core holes were drilled in the raceway directly in front of the ogee weirs. At least six of these cores exhibited a clayey seam about elevation 830 (nine feet below the ogee foundations). Testing of this material and deep-seated sliding analysis indicated that the dam did indeed face a safety issue.
[edit] Retrofitting
To prevent the concrete monolith from sliding forward, it was decided to install seven cable anchors deep into the bedrock. Each anchor consisted of bundled, high strength steel cables that were concreted into the bottom of the holes. They were then hydraulically tensioned and the holes filled with grout. Achors were installed at a 45 degree angle to a depth of 813, or 26 feet below the foundation of the ogees. On March 2, 1977 the project was bid to VSL Corporation for $254,777. Drilling for the anchors began on June 7, 1977. The final loading on each anchor was 1300 kips. On September 28, 1977, one of the anchor's foundations failed and had to be re-concreted. By 1978, the project was completed.
[edit] The January, 2005 Flood
On January 16, 2005 Alum Creek Dam's reservoir reached its highest level since construction was completed in 1974, an elevation of 898.94, about 17 feet above normal level. At this level control was maintained through the discharge pipe and it was not necessary to open the three main spillway gates.
This extreme event was caused by an average of 5-8 inches of rain falling over Central Indiana and Ohio during January 4-14, 2005. This rain combined with snow melt and saturated ground to produce record breaking runoff. Other reservoirs also set pool level records, including Deer Creek, Delaware Lake, Paint Creek, Atwood Lake, Bolivar Dam, Charles Mill Lake, Dillon Lake, Dover Dam, Mohawk Dam and Wills Creek.
[edit] See also
- Friends of Alum Creek - group formed in 2002 dedicated to preserving and improving the watershed.
[edit] References
- Army Corps of Engineers Alum Creek Retrofit Case History, 1985
- Barnes, William D., Anchoring of Spillway Monoliths, Alum Creek Lake, Ohio, Concrete Structures Repair and Rehabilitation, Vol C-82-1, September, 1982, US Army Engineer Waterways Experiment Station, Vicksburg, MS.
