B.07.W912EE25BA009_TSLSC_Pre-Bid Meeting Slides_8.12.25.pptx
PPTX presentation 9 MB Posted
- Solicitation number
- W912EE25BA009
About this file
The file is a pre-bid meeting presentation for a U.S. Army Corps of Engineers contract (Solicitation Number W912EE25BA009) for Stoplog Slot Construction at Thatcher Lock and Dam in Calion, Arkansas. The project involves installing stoplog slots at 3 locations (6 total slots) to enable dewatering of miter gates or the entire lock chamber, with work to be completed within 210 days starting around December 2025. The scope includes removing existing concrete, installing new concrete and rebar, fabricating and installing bulkhead recess inserts, sill beams, support struts, and replacing handrails, with government-furnished stoplogs to be placed in the newly constructed slots.
Key contract details include recommended use of cell-type cofferdams, work sequencing starting from upstream slots and moving downstream, and subcontracting limitations requiring that subcontractors may not perform more than 85% of the contract amount. The project is subject to water level constraints, with the best work periods being mid/late summer through winter to avoid seasonal high water events. The contractor will have access to potable water and electrical systems but must provide their own drop service, temporary water lines, and sewage facilities. The pre-bid meeting was scheduled for August 12, 2025, via Microsoft Teams, with the solicitation issued by the Vicksburg District of the U.S. Army Corps of Engineers.
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Text version
8/10/2025
Vicksburg district
THATCHER STOPLOG SLOTS CONSTRUCTION
PRE-BID MEETING
AUGUST 12, 2025
U.S. ARMY CORPS OF ENGINEERS
General project information and project history The existing dewatering system for Thatcher Lock (Poiree Dam) has been retired due to safety concerns. Stackable stoplogs have become the standard equipment for lock dewaters nationwide.
Thatcher Lock and Dam is the last of the Ouachita River locks to have stoplog slots installed (Jonesville, Columbia, Felsenthal previously installed).
The work will be completed in 3 locations (6 slots total). Once completed, either of the miter gates or the entire lock chamber will be able to be dewatered.
480v utilities are shallowly embedded in the concrete downstream of the upper miter gate, preventing the 4th location to be cut.
Site layout
Shown is a site layout map from the plans. The stoplog barge is planned to be moored just upstream of the lock for the beginning of construction. The contractor will be responsible for moving this barge after delivery by the government. The contractor will be able to connect to our potable water and electrical systems, The contractor will be required to provide the drop service and temporary water lines. The contractor will be responsible for providing their own sewage.
Removal of existing concrete and handrails in locations where new stoplog slots will be constructed.
Installation of new concrete, rebar, and steel bulkhead recess inserts (6 locations total) - Work includes the fabrication of bulkhead recess inserts as shown on the drawings.
Fabrication/installation of the new sill beams and sill beam support struts.
Placement of Government furnished bulkheads into newly constructed slots and valve culverts.
Placement of concrete around new sill beams and sill beam support struts.
Replacement of handrails around work areas.
For the purpose of acceptance, the Stoplog Slots must be in place as shown in the drawings and must allow for dewatering of the miter gates and lock chamber.
Scope of work
Work is anticipated to start at the upstream slots and work downstream. Once the upstream slots are constructed, the sill beam can be lowered into place attached to the bottom stoplog. The lower pool will be drawn down to 59.0 EL and the water behind the miter gate sill will be pumped out creating a dry area to work. Sill beam struts and concrete will be placed as shown in the plans. The contractor can then move to the downstream slot locations and begin work.
The contractor may submit alternative construction methods and sequences for government approval.
SEQUENCE OF WORK
8/12/2025
Monolith 5 section view.
SILL BEAM SUPPORT STRUT
SILL BEAM
UPSTREAM
DOWNSTREAM
This is what we anticipate based on how this has been previously in the past.
GOVERNMENT FURNISHED STOPLOGS
Government furnished stoplogs stack to adjust height of dewatering.
Three different sizes/types of stoplogs: Types A, B, and C (C’s are largest and go on bottom).
Stacking orders will be provided prior to construction.
Lifting devices for the stoplogs shown in the As-Built drawings (Pick-up truss) are no longer used.
Steel cable slings (Government provided) are now used.
Stoplogs in newly constructed slots at Felsenthal Lock and Dam.
Placement of a bottom stoplog using steel cable slings.
Coordinate with Ops with showing contractor how we use these slings and lift the stoplogs.
Cofferdams Cofferdams previously used on the Ouachita River locks for stoplog construction have been cell type cofferdams.
The use of cofferdams that dewater an entire monolith of the lock are not prohibited but are not recommended due to strict water elevation requirements.
.Cell type cofferdams can be built to the top of the lock wall.
The stability analysis done at initial construction limits dewatering full monoliths of the lock unless the upper pool is at 77.0 EL and the lower pool is at 65.0 EL (maximums) concurrently.
These elevations are considered “normal pool” for Thatcher L&D.
Due to the flashy characteristics of this portion of the Ouachita River, this CAN be difficult to maintain during flood season
So again, The use of celled cofferdams is recommended to avoid being shut down every time the elevations exceed these levels.
UPPER POOL HYDROGRAPH (LAST 10 YEARS)
Seasonal high water typically occurs in the late winter and can carry into the late spring/early summer. The mid/late summer and into winter provide the best opportunities to complete this work.
We intend to keep the pool down upstream and downstream as much as possible during construction.
The pool levels are influenced by localized rain events. We are intending to manipulate the pools when seasonal conditions are favorable.
LOWER POOL HYDROGRAPH (LAST 10 YEARS)
8/11/2025
Felsenthal L&D is downstream and will help control lower pool to an extent.
Contract Administration – Duration and Time Extensions Duration is 210 Days (see Amendment 1).
Amendment 1 revised the NTP to be issued on or about 1 December 2025 to allow for unwatering and maintenance at Jonesville Lock and Dam. However, Jonesville Lock unwatering has been rescheduled. The NTP date will be amended to immediately after verification of bonds.
Jonesville Lock unwatering is anticipated for the summer of 2026. The Government will coordinate with the Contractor to minimize any impacts to the Thatcher stop log slot construction due to this closure including allowing passage of vessels through Jonesville Lock.
A noncompensible excusable delay will be granted for high water events preventing work including unwatering at the structure.
Bullet these
Contract Administration – Subcontracting Limitations
Per FAR 52.219-14 Limitations on Subcontracting , subcontractors may not perform more than 85% of the amount paid by the Government for contract performance excluding the cost of materials.
Within 7 days of bid opening, the apparent low bidder shall submit a Small and Disadvantaged Business Subcontracting Plan. This does not apply to small business concerns.
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QUESTIONS?
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