Decommissioning at Monongahela River Locks and Dam No. 3

The contract consists of work associated with Monongahela River Locks and Dam No. 3 demolition, establishment of the new navigable channel and stabilization of the monoliths to remain after construction. All demolition elevations in the plans and specifications created for this project are shown in the NAVD 88 datum. The existing reference drawings are shown in the NGVD 29 datum or earlier. Specific features of work under the contract mentioned below do not represent a construction sequence. The contract features of work include, but are not limited to the following: (a) Breach the existing dam for pool equalization. This step in the construction sequence includes all activities required to prepare the dam for breaching. Breaching of the dam may occur through either blasting or mechanical removal means. A demolition plan detailing the preferred method will be submitted by the Contractor for approval. (b) Equalization of pools 2 and 3. Pool equalization is required to be a minimum of 3 days for environmental considerations. This time frame will allow enough time for mussels along the banks of Pool 3 to migrate to the new water elevation. Navigation will be notified at least 30 days in advance of the breach regarding closure limitations and durations. (c) Demolish the dam. The entirety of the dam will be demolished to EL710.1. Placement of the stability berms adjacent to the left dam abutment may begin once the dam is removed within the installation area of the berm. (d) Opening of the new navigable channel. Surveying 300 FT upstream and 600 FT downstream of the removed dam will occur to locate material above the required demolition elevation within the new navigable channel. Dredging will be required to remove any high spots identified. Navigation will be notified when the new navigable pass is open. At this time, the land and river chambers will be permanently closed for passage of traffic. Placement of the stability berms on the river face of the upper guide wall and filling of the flume way with preplaced aggregate concrete may begin. (e) Removal of mechanical and electrical equipment in the land and river chambers. (f) Demolition of the middle wall. The middle wall will be demolished to EL 713.1. Install the stability berms within the land chamber once the middle wall is fully demolished. (g) Demolition of the river wall. The river wall will be demolished to EL 713.1. This includes the upper guard wall cells and river chamber extension cells. (h) Complete installation of permanent stabilization measures for the flume wall, land wall, upper guide walls, and dam abutment. (i) Processing and disposal of remaining demolition material. Any remaining demolition material after reuse of the processed concrete rubble for construction of the stability berms and preplaced aggregate will need to be processed and disposed of at an approved disposal facility. This includes material not meeting the requirements for reuse.