Dam that Muddy Creek! Lake Arthur dam siting, design, and construction story
Gary Fleeger, P.G.
Glacial Geologist - Retired (Pennsylvania Geological Survey)
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Who should attend: Geologists, geotechnical engineers, park enthusiasts
Webinar Overview: The dam that forms Lake Arthur in Moraine State Park was built from 1965 to 1968, and the 3225-acre lake was initially filled in 11 months from May, 1969 to April, 1970. The lake lies in the site of a former glacier-dammed lake of 140,000 years ago.
The location of the dam was particularly difficult to select because of the geology of the area. Much of the valley is underlain by more than 100 feet of compressible lacustrine clay deposited in the glacial lake, which is unfavorable as a dam foundation. Cavernous Vanport Limestone crops out at the western end of the lake, adding additional complication for dam site selection. The Vanport threatened leakage around the initially-favored damsite, and also potentially affected the ability of the reservoir to hold water. As a result, 15 sites were evaluated before selecting a final site with the precise combination of thin lacustrine sediment over bedrock.
Design and construction of the dam were likewise complicated by the presence of the lacustrine clays and limestone. Details of the design were revised during the course of construction.
After being lost from DCNR files for many years, the documents specifying these details of damsite selection, design, and construction were found in the Ralph Peck Library at the Norwegian Geotechnical Institute in Oslo, Norway.
About our presenter: Gary Fleeger - Retired glacial geologist (BS- Bucknell Univ, MS- Univ of Illinois) with the Pennsylvania Geological Survey, where I wrote the geologic guide to Moraine and McConnells Mill State Parks. Grew up near Moraine State Park when it was under construction in the 1960s, where I developed my interest in geology as a career. While at the Survey, I sited the park's 2 million gallon per day water supply well, which went online in February, 2021, and have conducted shoreline erosion studies for 15 years. Since retirement in 2018, have been a volunteer working on an erosion and sedimentation map of Lake Arthur, done an inventory of bench marks within the park, scanned the park's historical collection of about 2000 plans (including dam design plans) and maps and 3000 photographs, compiled a history of the evolution of their water systems, including recovering 10 of the 12 original water wells drilled in the park in 1966, assisted in the development of their Park Management Plan, and work on the education committee of the Moraine Preservation Fund.