The remains from the original Lock 4 built on the Monongahela River in the 1800s still stand today near Charleroi, Pennsylvania, Aug. 6, 2024. The U.S. Army Corps of Engineers replaced the facility when it constructed a newer Monongahela River Locks and Dam 4 in 1931, now known as the John P. Murtha Locks and Dam. The U.S. Army Corps of Engineers Pittsburgh District conducted a shoreline survey to protect potential cultural resources. Cultural resources can include archaeological artifacts or historical sites. Recently, the Pittsburgh District lowered the river level by approximately two feet on a portion of the Monongahela River after breaching a fixed-crest dam in Elizabeth. As part of the Lower Monongahela River Project, the removal requires the district to mitigate and avoid damage to sites with cultural value. Lowering the river exposed shorelines along approximately 18 miles of the Monongahela, rendering sites with potential cultural or historical value exposed and more vulnerable to the elements. The team surveyed soil samples and sediment layers and recorded any archaeological artifacts found along the way to designate sites of potential cultural significance. (U.S. Army Corps of Engineers Pittsburgh District photo by Michel Sauret)