Froehling & Robertson, Inc. was retained by the Boy Scouts of America to perform dam break flood inundation mapping for Lake Merriweather located in Goshen, Virginia. The Lake Merriweather drainage area was 82.4 square miles while the entire project study area encompassed more than 3,000 square miles of drainage area. F&R studied the inundation area for approximately 49.4 miles downstream from Lake Merriweather Dam. The resulting inundation zone impacted eight bridges, nearly 900 homes, and multiple roadways. F&R also conducted an Incremental Damage Assessment to reduce the required capacity to 0.43 PMF.
F&R then prepared a Preliminary Engineering Report showing several options and associated costs for bringing this dam into compliance. Ultimately, the Boy Scouts requested F&R to develop the design for an open cut Auxiliary spillway on the east end of the dam and a parapet wall on top of the dam to further increase the capacity.
Pre-design work included extensive survey and a significant geotechnical investigation including 20 borings down to and into the bedrock and a Geophysical survey performed to determine the durability of the rock. The design uses a 550 foot wide spillway control section to pass 89,000 cfs of storm water and makes use of the bedrock layer for cutback protection.