01 35 13.01 10_AM001.pdf

SECTION 01 35 13.01 10

SPECIAL PROJECT PROCEDURES - FLOOD CONTROL

PART 1 GENERAL

1.1 POOL ELEVATION MONITORING

Pool level maintenance and river flow adjustments via operation of the spillway Tainter gates will be the responsibility of the Government and the required work must be scheduled accordingly.

Wilbur Mills Dam and Lock 2 are operated together as a single purpose navigation project as a part of the McClellan-Kerr Arkansas River Navigation System. Under normal conditions (river flows less than 45,000 cfs)the project's release rates are set to match its inflows as produced by upstream projects while maintaining the upstream pool level near elevation 162.0 during the non-agricultural season (October through April)and near elevation 163.0 during the agricultural season (May through September).

The Arkansas Electric Cooperatives Corporation (AECC) operates a non-federal run-of-river hydropower facility adjacent to Mills Dam with 3 turbines capable of making releases from 4,000 cfs up to approximately 50,000 cfs. The AECC facility coordinates its releases with Government's lock and dam operator in accordance with the established water control plan to maintain the pool level and pass project inflows. During normal flow conditions, project releases will be made through the hydropower facility's available turbines. The hydropower facility turbines may become unavailable at any time due a planned or unplanned outage. Any inflow that exceeds the capacity of the available turbines is released through the spillway Tainer gates.

The Government cannot control the magnitude of Arkansas River flows.

During higher flows, the available spillway capacity and river flow conditions will require a flood demobilization. Restiction of no more than 3 gate will be allowed at anytime.

When Arkansas River flow exceeds 70,000 cfs a small craft advisory is issued. Adverse impacts to commercial navigation begins at 75,000 cfs, however, the impacts substantially increase when flow rises above 125,000 cfs.

When flow is expected to reach or exceed 70,000 cfs, floating plants and work crews conducting activities in the vicinity of the Tainter gates shall move to a secure location away from the spillway and stand down until river flows recede to a safe level.

The spillway crest for Wilbur D. Mills Dam is at elevation 134.0. The top of the Tainter gates in the closed position are at elevation 164.0. The stilling basin drops down to elevation 119.0. The dam is located approximately 26 miles upstream of the Arkansas and Mississippi Rivers confluence. The tailwater level of the dam can be impacted by water levels on the Mississippi River.

Because Wilbur D. Mills Dam is a navigation project and is not a flood control project, it does not have flood control storage and the government

SECTION 01 35 13.01 10 Page 1

PN480415

WILBUR D. MILLS, POOL NO. 2

TAINTER GATE PAINTING

ARKANSAS COUNTY, ARKANSAS SOLICITATION NO. WS9127S20R0011

AMENDMENT TO SOLICITATION NO.

W9127S20R0011 ON 08/28/2020

cannot deviate from the water management plan in order to allow the contractor to work during higher flows.

1.2 RIVER FLOW AND WATER LEVEL MONITORING

The Contractor shall monitor the Little Rock District (SWL) website for real-time and forecasted river flows and water levels.

Real-time Arkansas River water levels and releases for the lock and dams can be monitored using the weblink, http://www.swl-wc.usace.army.mil/pages/arkansas_river_projects.htm

The spillway crest for Wilbur D. Mills Dam is at elevation 134.0. The top of the Tainter gates in the closed position are at elevation 164.0. The stilling basin drops down to elevation 119.0. Wilbur D. Mills Dam, real-time pool elevation, tailwater elevation, power release, and spillway release shall be monitored using the weblink, http://www.swl-wc.usace.army.mil/pages/data/tabular/htm/d02.htm

Arkansas River 4-day flow forecasts are updated on weekdays and shall be monitored using the weblink, http://www.swl-wc.usace.army.mil/pages/reports/remote/ark4cast.htm

The National Weather Service (NWS) forecasts river levels below Toad Suck Lock and Dam near Conway, AR. An Arkansas River at Toad Suck Lock and Dam tailwater level of 259.0 corresponds to an approximate flow of 70,000 cfs.

The travel time of river flow from Toad Suck Lock and Dam to Wilbur D.

Mills Dam for flows of 70,000 cfs is approximately 1.5 to 2 days. NWS forecasts for the Arkansas River at Toad Suck Lock and Dam tailwater near Conway, AR shall be monitored at the weblink, https://water.weather.gov/ahps2/hydrograph.php?wfo=lzk&gage=toda4

The Contractor shall monitor at a minimum the daily river levels. The contractor is responsible for monitoring and keeping the work site secure against a high water event. The contractor is responsible for communicating with the government for any water management issues. The Contractor is responsible for knowing the navigational capabilities of his fleet. If river conditions are forecasted to exceed 70,000 cfs, or the fleet capabilities, the Contractor shall remove all floating plant equipment from the face of the dam and obtain proper and secure dockage in advance of those conditions so that the fleet does not become stranded in front of the dam and/or gates, and does not present a hazard to the gates or structure.

The Contractor shall monitor the upstream Arkansas River lock and dam river gauges, and forecasts, continuously and notify the Contracting Officer within 24 hours of when river flows are forecasted or expected to reach 70,000 cfs at Mills Dam. Once the Contractor notifies the Contracting Officer, the Contractor, Contracting Officer, and the MKARN System Engineer shall immediately coordinate to determine if a flood demobilization is necessary.

If the Contractor is demobilized for flood control purposes, the Contractor shall continue to monitor river levels and flows and notify the Contracting Officer when the river flow is expected to recedes below 70,000 cfs. Once the Contractor notifies the Contracting Officer of the appropriate river flow condition, the Contractor, Contracting Officer, and the MKARNS System Engineer shall coordinate to determine if remobilization

SECTION 01 35 13.01 10 Page 2

PN480415

WILBUR D. MILLS, POOL NO. 2

TAINTER GATE PAINTING

ARKANSAS COUNTY, ARKANSAS SOLICITATION NO. WS9127S20R0011

is possible. Once the Contractor is notified to remobilize, the Contractor shall remobilize to the site within 14 days of notification.

1.3 ACCESS PLAN

The Contractor shall submit an access plan indicating the process for executing all flood demobilization procedures within 24 hours of notification. No work will be allowed until the plan has been approved.

1.3.1 Flood Demobilization Procedure

Flood demobilization shall consist of complete removal of the contractor's work equipment, staging, scaffolding, and work barges from within the spillway, stoplogs removed and stored, and the Tainter gate(s) returned to operable condition. The Tainter gate shall be considered operable only when the gate can be fully opened, or closed, without the use of external equipment not normally used to open or close the gate, and when all seal components are in place to prevent any water leakage past the gate.

1.3.2 Gate Access

The contractor may have access to no more than 2 Tainter gates at anytime, unless otherwise approved by the Contracting Officer. The intent of the Government is for all work to be completed on each Tainter gate prior to beginning work on subsequent gates. Due to typically seasonal high flows, the Tainter gates may not be available between February 1 and May 31. Work may only be conducted during this period with prior approval of the contracting officer, and there will be no modification to the contract duration or payment(s) made for flood demobilization (CLIN 0009)

1.4 FLOOD DEMOBILIZATION CAUSED BY EMERGENCY CONDITIONS & FLOOD CONTROL

If the Contractor is directed to remove construction equipment because of high water, flood control, or other emergency operation not otherwise required for the normal execution of the work as shown and specified, a time extension shall be granted for lost work days in accordance with 01 14 00.00 46 WORK RESTRICTIONS (SWL) section 1.6 TIME EXTENTIONS, however, no adjustment in cost shall be made other than those costs associated with the CLIN Flood Demobilization. No adjustments will be made to the contract for demobilizations made by the contractor will work from a floating plant when flows are not forcasted to be above 70,000 cfs, unless explicitly requested by the COR. (AM001) The contractor shall be required to completely demobilize from the site and return the gates to operational condition at flows less than 70,000 cfs if one of the following conditions were present:

(AM001) (1) Tulsa District Storage is forecasted to exceeded the seasonal storage threshold requiring 150,000 cfs flows based upon rainfall that has occurred upstream of its flood control reservoirs. (2) There is high confidence in a NWS forecast of substantial upstream rainfall that could cause flood crests exceeding 150,000 cfs. (3) The contractor plans to remove its work crew from the site for 10 days or longer or for an indefinite period of time.

1.5 SUBMITTALS

Government approval is required for submittals with a "G" designation;

SECTION 01 35 13.01 10 Page 3

PN480415

WILBUR D. MILLS, POOL NO. 2

TAINTER GATE PAINTING

ARKANSAS COUNTY, ARKANSAS SOLICITATION NO. WS9127S20R0011

submittals not having a "G" designation are for information only. When used, a designation following the "G" designation identifies the office that will review the submittal for the Government. Submit the following in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:

SD-01 Preconstruction Submittals

Access Plan; G, AO

PART 2 PRODUCTS

Not Used

PART 3 EXECUTION

Not Used

-- End of Section --

SECTION 01 35 13.01 10 Page 4

PN480415

WILBUR D. MILLS, POOL NO. 2

TAINTER GATE PAINTING

ARKANSAS COUNTY, ARKANSAS SOLICITATION NO. WS9127S20R0011