Alum Creek Lake

Infobox lake
lake_name = Alum Creek Lake
image_lake = USACE Alum Creek Dam and Lake.jpg
caption_lake = Alum Creek Dam and Lake. View is to the northwest.
image_bathymetry =
caption_bathymetry =
location = Ohio
coords = coord|40.185718|N|82.966636|W|region:US-OH_type:waterbody|display=inline,title
type =
inflow = Alum Creek
outflow = Alum Creek
catchment =
basin_countries = United States
length =
width =
area = convert|5|sqmi|km2|abbr=on
depth =
max-depth =
volume =
residence_time =
shore =
elevation =
islands =
cities = The Alum Creek Lake reservoir was built in 1974, covers 5 sq mi (13 km²) and has a maximum capacity of 134,800 acre feet (166,000,000 m³).

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 convert|10000|ft|m|abbr=on in length with a maximum height of convert|93|ft|m|abbr=on 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 convert|25|ft|m|abbr=on tainter gates supported by convert|8|ft|m|abbr=on wide concrete piers resting on concrete ogee sections. The ogee sections have a crest elevation of 878 and are founded at elevation 839.

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 convert|1|ft|m|abbr=on 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.

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.

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 convert|26|ft|m 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.

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 convert|17|ft|m 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.

References

* [http://www.wes.army.mil/REMR/pdf/cs/mr-8-4.pdf 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.

External links

* [http://newweb.erh.noaa.gov/ahps2/hydrograph.php?wfo=iln&gage=acro1 Alum Creek Lake current level graph]
* [http://www.dnr.state.oh.us/parks/parks/alum.htm Alum Creek State Park website]
* [http://www.photohio.org/view_images/trans.php?bib_num=599864 Alum Creek Dam Under Construction Photo #1]
* [http://www.photohio.org/view_images/trans.php?bib_num=599830 Alum Creek Dam Under Construction Photo #2]