TOLEDO BEND PROJECT FERC NO FINAL LICENSE APPLICATION EXHIBIT B - PROJECT OPERATIONS AND RESOURCE UTILIZATION

Transcription

1 TOLEDO BEND PROJECT FERC NO. 235 FINAL LICENSE APPLICATION EXHIBIT B - PROJECT OPERATIONS AND RESOURCE UTILIZATION September 211 Copyright 211. Sabine River Authority of Texas and Sabine River Authority, State of Louisiana. All Rights Reserved.

2 Table of Contents EXHIBIT B - PROJECT OPERATIONS AND RESOURCE UTILIZATION BACKGROUND AND PROJECT PURPOSE DESCRIPTION OF THE TOLEDO BEND PROJECT Dam and Powerhouse Spillway Reservoir Electrical Facilities CURRENT AND PROPOSED OPERATION OF THE TOLEDO BEND PROJECT Agreements and Regulatory Requirements Affecting Current Project Operations Agreements Affecting Future Project Operations Day-to-Day Plant Operations and Control Operations during Normal, Dry, and Wet Years Spillway Operations Project Flows and Generation Project Flows Mean and Median Flows Critical Period Flows Flows Downstream of Toledo Bend Dam Project Generation Average Energy Production and Utilization Annual Plant Factor Estimate of Dependable Capacity Plant Capability versus Head Reservoir Operations RESOURCE UTILIZATION AND FUTURE DEVELOPMENT Proposed Spillway Flows Future Development LITERATURE CITED Page i

3 List of Tables Table Toledo Bend Project Operating Guide Rule Curve....9 Table Summary of annual Toledo Bend operations (22-29)...9 Table Ranked average annual reservoir inflow (cfs) Table Spillway operating guide Table Monthly outflows (cfs), USGS Gage Sabine River at Toledo Bend Reservoir tailrace near Burkeville, Texas Table Toledo Bend Project monthly energy production (MWh)...26 Table Minimum, median, and maximum head Table Toledo Bend Reservoir storage volume...29 Table Toledo Bend reservoir surface area Table Tailwater rating data Table Drought management measures for the proposed continuous flow...32 Table Proposed minimum flow generation unit equipment details Page ii

4 List of Figures Figure 1.-1 Toledo Bend Project location...3 Figure Toledo Bend mean daily discharge and reservoir elevation during February Figure Toledo Bend mean daily discharge and reservoir elevation during August Figure Toledo Bend mean daily discharge and reservoir elevation during December Figure USGS gage 15-minute data during typical Toledo Bend Project operations for the period August 16, 29 through September 6, Figure Toledo Bend discharge and reservoir elevations during 22 (normal year) Figure Toledo Bend discharge and reservoir elevations during 21 (wet year) Figure Toledo Bend discharge and reservoir elevations during 26 (dry year)...15 Figure Toledo Bend dam and downstream area...17 Figure USGS gage location at the Toledo Bend Reservoir tailrace Figure Downstream attenuation of flow from two-unit operation for six hours...2 Figure USGS gage locations downstream of Toledo Bend Dam...21 Figure Downstream attenuation of maximum change in stage on the Sabine River downstream of the Toledo Bend Project...22 Figure Backwater characteristics from two-unit operation at Toledo Bend Project as measured by USGS gage and temporarily placed water level loggers...23 Figure Temporary water level data logger locations August 29 - November Figure Toledo Bend powerplant capability versus net head Figure Toledo Bend reservoir storage volume curve....3 Figure Toledo Bend reservoir surface area....3 Figure Tailwater rating curve Page iii

5 List of Attachments ATTACHMENT B-1 - MONTHLY FLOW DURATION CURVES PREPARED FROM FLOWS RECORDED AT THE TOLEDO BEND DAM (USGS GAGE 82536) FOR THE PERIOD Page iv

6 EXHIBIT B - PROJECT OPERATIONS AND RESOURCE UTILIZATION The following excerpt from the Code of Federal Regulations (CFR) at 18 CFR 4.51 (c) describes the required content of this Exhibit. Exhibit B is a statement of project operation and resource utilization. If the project includes more than one dam with associated facilities, the information must be provided separately for each such discrete development. The exhibit must contain: (1) A statement whether operation of the powerplant will be manual or automatic, an estimate of the annual plant factor, and a statement of how the project will be operated during adverse, mean, and high water years; (2) An estimate of the dependable capacity and average annual energy production in kilowatthours (or a mechanical equivalent), supported by the following data: (i) The minimum, mean, and maximum recorded flows in cubic feet per second of the stream or other body of water at the powerplant intake or point of diversion, with a specification of any adjustments made for evaporation, leakage, minimum flow releases (including duration of releases), or other reductions in available flow; monthly flow duration curves indicating the period of record and the gauging stations used in deriving the curves; and a specification of the period of critical streamflow used to determine the dependable capacity; (ii) An area-capacity curve showing the gross storage capacity and usable storage capacity of the impoundment, with a rule curve showing the proposed operation of the impoundment and how the usable storage capacity is to be utilized; (iii) The estimated hydraulic capacity of the powerplant (minimum and maximum flow through the powerplant) in cubic feet per second; (iv) (v) A tailwater rating curve; and A curve showing powerplant capability versus head and specifying maximum, normal, and minimum heads; (3) A statement, with load curves and tabular data, if necessary, of the manner in which the power generated at the project is to be utilized, including the amount of power to be used on-site, if any, the amount of power to be sold, and the identity of any proposed purchasers; and (4) A statement of the applicant's plans, if any, for future development of the project or of any other existing or proposed water power project on the stream or other body of water, indicating the approximate location and estimated installed capacity of the proposed developments. Page 1

7 1. BACKGROUND AND PROJECT PURPOSE On October 14, 1963, the Federal Power Commission (FPC), predecessor to the Federal Energy Regulatory Commission (FERC), under the authority of the Federal Power Act (FPA) granted the Sabine River Authority of Texas (SRA-TX) and Sabine River Authority, State of Louisiana (SRA-LA), collectively known as the Authorities, a 5-year license to construct and operate the Toledo Bend Project (Project). This License was issued for the construction, operation, and maintenance of Project No. 235 to be located on the Sabine River in Texas and Louisiana, and affecting navigable waters of the United States and lands of the U.S. within the Sabine National Forest (SNF), subject to the terms and conditions of the Act, which is incorporated herein by reference as a part of this license, and subject to such rules and regulations as the Commission has prescribed under the provisions of the Act. (FPC 1963). The Toledo Bend Project was conceived, licensed, developed, and primarily functions as a water supply facility, with secondary uses of hydroelectric power generation and recreation. The Project was not designed as a flood control facility and lacks flood control capacity typically found at flood control reservoirs. The Toledo Bend Dam is located at river mile (RM) 147 (Sabine River Authority [SRA] 28a). The Toledo Bend Reservoir extends into Panola, Sabine, Shelby, and Newton counties, Texas, and Sabine, Vernon, and DeSoto parishes, Louisiana (Figure 1.-1). Construction of the dam, spillway and powerhouse began in April 1964 and operations commenced in 1969 (Toledo Bend 211). The current hydropower configuration of the Toledo Bend Project contains two turbine-generator units and a reservoir with a normal maximum elevation of 172 feet mean sea level (msl) (hereafter, all elevations are referenced to msl unless otherwise noted). The two turbine-generator units each have a minimum hydraulic capacity of approximately 3,4 cubic feet per second (cfs) 1 and a normal maximum hydraulic capacity of 7,5 cfs based on turbine performance testing performed in 1988 (HDR DTA 21). The Sabine River provides water for both consumptive and non-consumptive uses. Water uses include municipal, industrial, irrigation, mining, recreation, and hydroelectric power. At the Toledo Bend Reservoir, industrial withdrawals constitute the largest consumptive use. SRA-TX has water rights approved by the State of Texas to make non-consumptive use for the purpose of hydroelectric generation at the Toledo Bend Project not to exceed 21, cfs (Texas Commission on Environmental Quality [TCEQ] 1986a), well above the plant s normal maximum capacity of 15, cfs. Power production at the Toledo Bend Project is governed by a Power Sales Agreement between the Authorities and Entergy Gulf States, Inc., CLECO Power LLC, and Entergy Louisiana, LLC (the Power Companies). This agreement is scheduled to expire in 218, and FERC approved the agreement pursuant to Section 22 of the FPA by order dated April 7, Minimum hydraulic capacity is estimated at 4 percent of full gate flow. Page 2

8 Figure 1.-1 Toledo Bend Project location. Page 3

9 2. DESCRIPTION OF THE TOLEDO BEND PROJECT The Toledo Bend Dam is located at river mile (RM) 147 in Sabine Parish, Louisiana and in Newton County, Texas, and creates a reservoir of 185, surface acres at normal pool elevation of 172 feet. The Project reservoir is oriented in a southeast to northwest direction and extends approximately 7 miles (navigation miles) from Toledo Bend Dam upstream to above Logansport, Louisiana (i.e., Murvaul Bayou) at RM 279. The Toledo Bend powerhouse is located in Newton County, Texas, on the south abutment of the dam; the gated spillway is located on the north abutment in Sabine Parish, Louisiana. The Project is bounded on the eastern (Louisiana) side by State Highway 191, on the western (Texas) side by State Highways 7 and 87, and to the south in Texas by Highways 255 and 692 and Louisiana Highway 191. U.S. Highway 84, in Logansport, is just south of the northern limit of the Project Boundary. The major Project facilities include a dam, three saddle dikes, powerhouse, excavated tailrace channel, gated spillway, and excavated spillway channel, switchyard, and one primary transmission line. The Authorities began land acquisition in May 1963 and initiated construction of the dam, spillway, and powerhouse in April The closure section of the earthen embankment was completed in October The powerhouse began operation in early DAM AND POWERHOUSE The Toledo Bend Dam consists of a zoned rolled earth-fill embankment approximately 11,25 feet long (including saddle dikes) with a top width of 25 feet. The maximum height of the dam is approximately 112 feet, with a top of dam elevation of 185. feet. The upstream slope of the embankment is protected from erosion by a soil cement armoring. Louisiana State Highway 191 and Texas FM Road 692 both run along the toe of the dam and Louisiana State Highway 191 crosses over the spillway structure. The indoor powerhouse is located along the south dam abutment in Texas. The structure is approximately 18 feet wide x 8 feet long and 55 feet in height. The powerhouse contains two vertical Kaplan turbines rated at 58,5 horsepower each attached to water-cooled, umbrella type generators rated at 4,5 kilovolt amps (kva) at a 95 percent power factor. Normal maximum flow through the powerhouse is approximately 15, cfs depending on the lake level and the tailwater level. The powerhouse also includes a 2-ton gantry crane and a trashrack. Each unit has a normal maximum hydraulic capacity of 7,5 cfs releasing a combined capacity of 3, ac-ft of water per day based on index testing performed in 1988 and turbine performance (HDR DTA 21). Average annual power production since 1972 is approximately 239,635 megawatt hours (MWh). Operation of the powerhouse is performed on a contract basis by Entergy Texas (Entergy-TX), and both generators can be operated remotely from the Entergy- TX Sabine Plant located in Bridge City, Texas. 2.2 SPILLWAY The gated spillway is located along the north dam abutment in Louisiana. The overall length of the reinforced-concrete spillway structure is 838. feet and spillway discharge is controlled by Page 4

10 eleven 4-foot-wide-by-28-foot-high Tainter gates. The gated spillway also includes a concrete chute and baffle-block stilling basin exiting to an excavated channel. The elevation of the fixed crest of the spillway is 145, feet and the top of the gates is 173 feet. Also contained in the spillway structure is an 8.33-by-12-foot low-flow sluiceway with an invert elevation of 1 feet. The excavated spillway channel continues approximately 1.7 miles downstream, intersects Bayou Toro, and continues to the confluence of the original Sabine River at RM 145. The Sabine River then flows approximately 4 miles before being joined by the excavated tailrace channel which delivers flow from the Project powerhouse to the Sabine River at RM RESERVOIR The Toledo Bend Reservoir covers an area of approximately 185, surface acres and has a gross storage capacity of 4,477, ac-ft at a reservoir level of 172 feet (SRA-TX 211). The drainage area contributing to the Sabine River upstream of the Toledo Bend Dam is approximately 7,19 square miles. The Project Boundary extends to Murvaul Bayou at RM 279, encompassing an area of 24,9 acres. Since 27, power is typically only generated when the reservoir elevation is above 168 feet. The power pool is generally maintained between 168 and 172 feet as discussed in more detail in this Exhibit. 2.4 ELECTRICAL FACILITIES The station transformer, located immediately south of and adjacent to the powerhouse on an elevated concrete platform, steps up the voltage from 13 kv to 138 kv for transmission purposes. The switchyard includes four oil unit breakers in a circular bus system feeding three transmission lines, two to Central Louisiana Electric Company (CLECO) and one to Entergy- TX. The only primary transmission line associated with the Project is a 394-foot, 138 kv line leading from the Project s powerhouse to the Project switchyard, which is located immediately adjacent to the tailrace and within the Project Boundary. The Entergy-TX line connects directly to the switchyard. Power generated at the Project interconnects with the transmission grid at the switchyard. Page 5

11 3. CURRENT AND PROPOSED OPERATION OF THE TOLEDO BEND PROJECT 3.1 AGREEMENTS AND REGULATORY REQUIREMENTS AFFECTING CURRENT PROJECT OPERATIONS The storage and use of water for Project operations is managed in accordance with state water rights, the Sabine River Compact, the Power Sales Agreement, and the FERC license. State Water Rights (Texas) In most instances, Texas state law requires a water right for the use of surface water. Water right documents include certificates of adjudication and permits issued and administered on behalf of the state by the Texas Commission on Environmental Quality (TCEQ). On September 23, 1961, Permit No was issued to the SRA-TX granting the right to create Toledo Bend Reservoir with a gross storage capacity of 4,477, ac-ft (TCEQ 1961). The 1961 permit also states that SRA-TX can divert a total of 75, ac-ft of water per year for the following purposes: 1, ac-ft for municipal uses; 6, ac-ft for industrial uses; and 5, ac-ft for irrigation uses. Under the 1961 permit, SRA-TX is also permitted to make non-consumptive use of water for the purpose of hydroelectric power generation not to exceed 16, cfs and to use the bed and banks of the Sabine River to convey water. As part of the permit, the SRA-TX was required to construct a 1-square-foot sluiceway in the dam to insure water for delivery of downstream senior water rights. On October 3, 1974, the SRA-TX was authorized under Permit No. 1994A to transfer 8, ac-ft of water per year to the Neches River basin (TCEQ 1974). On April 29, 1986, Permit No. 1994B was issued stating that SRA-TX was authorized to construct an additional hydroelectric generating unit which was never implemented (TCEQ 1986a). This permit also authorized SRA-TX to change the release rate from 16, to 21, cfs for combined generating units. On December 16, 1986, Certificate of Adjudication No was issued to SRA-TX, which consolidated the previously issued water rights permits and set forth the following conditions (TCEQ 1986b): SRA-TX can impound 4,477, ac-ft of water; SRA-TX can divert water for the following uses: 1, ac-ft for municipal uses; 6, ac-ft for industrial uses; and 5, ac-ft for irrigation uses. A total of 8, ac-ft of the water uses described above can be diverted to the Neches Basin for municipal/industrial use; Page 6

12 SRA-TX can divert water for hydroelectric generation not to exceed 21, cfs; SRA-TX can use impounded waters for recreation purposes; SRA-TX can use bed and banks for downstream delivery of water; and, The impoundment of water in the reservoir for hydroelectric purposes is subordinate to the impoundment of water for municipal, industrial, and irrigation purposes. The estimated total Toledo Bend Reservoir minimum firm yield of 2,86,6 ac-ft/yr is shared between SRA-TX and SRA-LA. SRA-TX s current permitted portion of Toledo Bend Reservoir s minimum firm yield is 75, ac-ft/yr. State Water Rights (Louisiana) Louisiana s system of water law is set forth in the Louisiana civil code and is similar to a riparian system. Free flowing waters (i.e., surface waters) are considered state owned except where riparian claims have been made. With regard to the Sabine River basin, the Louisiana State Legislature, in creating the Sabine River Authority, State of Louisiana (SRA-LA), authorized SRA-LA, among other things, to conserve, store, control, preserve, utilize, and distribute the waters of the rivers and streams of the Sabine watershed. Sabine River Compact The Sabine River Compact is an interstate compact between Texas and Louisiana, approved by Congress, regarding the allocation of the waters of the Sabine River Basin between the two states. The Sabine River Compact apportions the waters of the Sabine River between Louisiana and Texas. Representatives from Texas, Louisiana, and the U.S. entered into the Sabine River Compact in January The purposes of the Sabine River Compact are as follows: The major purposes of this Compact are to provide for an equitable apportionment between the States of Louisiana and Texas of the waters of the Sabine River and its tributaries thereby removing the causes of present and future controversy between the States over the conservation and utilization of said waters; to encourage the development, conservation and utilization of the water resources of the Sabine River and its tributaries; and to establish a basis for cooperative planning and action by the States for the construction, operation and maintenance of projects for water conservation and utilization purposes on that reach of the Sabine River touching both States, and for apportionment of the benefits, therefrom. (Sabine River Compact 1953) Pursuant to the Sabine River Compact, the yield of the Toledo Bend Reservoir (2,86,6 acft/yr) is equally divided between Texas and Louisiana (Freese and Nichols 1999). Power Sales Agreement Power production at the Toledo Bend Project is governed by a Power Sales Agreement between the Authorities and Entergy Gulf States, Inc., CLECO Power LLC, and Entergy Louisiana, LLC (the Power Companies). The sale of power currently constitutes the principal source of revenue Page 7

13 for operation of the Project. The Power Sales Agreement requires the Authorities to make available 1.58 million ac-ft of water for power generation during the period May through September (referred to as Prime Power). This water provides approximately 65.7 million kilowatt hours (kwh) of on-peak power for the Power Companies use during the hot summer months (Sabine River Authority [SRA] 27). The Power Sales Agreement between the Authorities and the Power Companies was originally signed in April 1968 and is scheduled to expire on April 3, 218. FERC approved the Power Sales Agreement pursuant to Section 22 of the FPA by order dated April 7, The agreement, as recently amended (effective date May 31, 27) contains certain articles that are relevant to operation of the Project (SRA 27). These articles are summarized below: Operation and maintenance of the facilities. This article provides details on the maintenance of the Project except the generating facilities. The electric companies operate and maintain the generating facility on behalf of the Authorities. Other details include scheduled maintenance, right of access, right of removal, generating facility operation, and payment of services. Control of water. This article describes the Authorities right to operate the reservoir in such a manner as the Authorities deem necessary to manage the flow of the Sabine River for the purposes of performing the Authorities statutory purposes. The article also provides information on the indemnification of the electric companies, and the Authorities responsibilities towards the public, Sabine River Compact, and governmental regulations. Contractual obligations, operation of the reservoir, scheduling of production, coordination of flood releases, water requirements for purpose other than generation, and permits and reporting are also described. Miscellaneous covenants. Miscellaneous covenants include sale of power to the Authorities, any new generating facilities, rights-of-way, and catastrophic events. In keeping with the Project s primary purpose as a water supply facility, a provision of the Power Sales Agreement recognizes that water will be used for power generation unless it is needed for the purposes of municipal, domestic and industrial water supply. The operation of the Project provides a minimum firm yield of 2,86,6 ac-ft/yr, equally shared by SRA-TX and SRA-LA. Most of this water is currently discharged through the powerhouse and is available downstream of the Project for municipal, industrial, and agricultural purposes. 3.2 AGREEMENTS AFFECTING FUTURE PROJECT OPERATIONS The existing agreements described in Section 3.1, above, are expected to continue into the next FERC license term. There are no proposed additional settlements or agreements at this time. 3.3 DAY-TO-DAY PLANT OPERATIONS AND CONTROL Operation of the powerhouse is automated and controlled locally. Remote-control facilities are available at the Entergy-Texas (Entergy-TX) Sabine Plant located in Bridge City, Texas. The Project is operated in accordance with the Operating Guide Rule Curve (Table 3.3-1) that provides for the production of both primary and secondary power as defined by the Power Page 8

14 Sales Agreement. Primary power is produced from May through September and can be generated at any time the water surface elevation is above 168 feet. Secondary power is produced when the reservoir is above the seasonal elevations indicated in the Operating Guide Rule Curve. Table Toledo Bend Project Operating Guide Rule Curve. Month Reservoir Elevation (feet msl) Plant Operation October thru December Below 168 Above 168 No power generated. Operate plant up to full capacity based on available water January Below Above No power generated. Operate plant up to full capacity based on available water February Below 169 Above 169 No power generated. Operate plant up to full capacity based on available water March Below Above No power generated. Operate plant up to full capacity based on available water April 1-15 Below 17 Above 17 No power generated. Operate plant up to full capacity based on available water April 16-3 Below 171 Above 171 No power generated. Operate plant up to full capacity based on available water May Any stage Above 168 Above 172 Use Volume necessary to meet Prime Power Schedule (see Note 2.) Operate plant up to full capacity June Any stage Above 168 Above 172 Use Volume necessary to meet Prime Power Schedule (see Note 2) Operate plant up to full capacity July Any stage Above 168 Above 172 Use Volume necessary to meet Prime Power Schedule (see Note 2) Operate plant up to full capacity August Any stage Above 168 Above 172 Use Volume necessary to meet Prime Power Schedule (see Note 2) Operate plant up to full capacity September Any stage Above 168 Use Volume necessary to meet Prime Power Schedule (see Note 2) Notes: 1. Maximum turbine discharge capacity 3, ac-ft/day. 2. In accordance with Section 5.5 of the Power Sales Agreement, no more than 3,, kwh of prime power shall be scheduled during any one month of the Primary Power Period (May through September), except with prior written consent of the SRAs. 3. Releases for downstream flows shall be in accordance with Section 5.1 of the Power Sales Agreement. 4. When pool stage is at or above feet and inflow is greater than power plant capacity, operate spillway in accordance with Guide on Spillway Gate Operation. 5. During prime power season when stage of reservoir is near upper limit, inflow is monitored and releases for secondary power generation are made to avoid spillway releases if possible. The Authorities historically operated the reservoir with a normal maximum reservoir elevation of 172 feet and until 27, a normal minimum reservoir elevation of feet. Since the 27 amendment to the Power Sales Agreement, power is typically only generated when the reservoir elevation is above 168 feet. A summary of the Toledo Bend operations for the period 22 through 29 is provided in Table Table Summary of annual Toledo Bend operations (22-29). Year Total Power Output (MWh) Power Release (TAF*) Spillway Release (TAF) Total Release (TAF) Maximum Reservoir Elevation (feet) Date of Maximum Reservoir Elevation Minimum Reservoir Elevation (feet) Date of Minimum Reservoir Elevation ,566 3, , , Apr Oct ,22 2, , &3-Mar Nov Page 9

15 24 27,2 3, ,13.5 4, Feb Jan ,665 2, , Apr Dec 26 62, , May Oct ,729 3, , Jul Nov ,642 2, , &2-Apr Nov ,637 3, , Nov &11-Sep Notes: * TAF = thousand ac-ft 1. Total Power output (megawatt hours [MWh]) refers to gross generation values reported by the Authorities and does not include reductions for metering losses or station service. 2. Power and spillway releases are based on automated measurements at the Project. 3. Reservoir elevations represent the daily high and daily low for the given year based on measurements at the Project. During the May through September period when water is available for prime power production between reservoir elevations 168 and 172 feet, the typical daily operation consists of releasing either 7, or 14, cfs to the lower Sabine River (i.e., one- or two-unit operation, respectively) for six to eight hours to meet the afternoon and evening peak electrical demand. A primary advantage of the hydroelectric generation is the ability for the units to move from offline to full-load in less than 1 minutes per unit. In addition to the releases for generation, there is also a minimum continuous release of 144 cfs from the spillway to the spillway channel that joins with flow from Bayou Toro. Powerhouse leakage occurring when the units are offline has been estimated to range from to 3 cfs per unit (SRA 28b). Examples of typical operations during the three operational seasons of January through April, May through September, and October through December are provided in Figures 3.3-1, 3.3-2, and These figures show the Toledo Bend mean daily discharge (cfs) and headwater elevation (feet) across a typical three-week period of time, for the three operational seasons of the year 22, a year that is representative of a normal year. A representative example of normal peaking operations during the Prime Power season is provided in Figure which shows 15-minute USGS gage readings in the lower Sabine River over the period August 16 through September 6, 29. Reservoir Operation Under the current operating protocols, reservoir levels for power generation purposes typically vary during the year from a normal maximum pool level of 172 feet to a lower pool level of 168 feet. Typically, the reservoir is at its highest during the late winter and early spring months and, beginning in May, the Authorities gradually draw down the reservoir to reach its lowest level in the fall, completing the prime power season on September 3 each year. Page 1

16 Figure Toledo Bend mean daily discharge and reservoir elevation during February 22. Figure Toledo Bend mean daily discharge and reservoir elevation during August 22. Page 11

17 Figure Toledo Bend mean daily discharge and reservoir elevation during December 22. Figure USGS gage 15-minute data during typical Toledo Bend Project operations for the period August 16, 29 through September 6, 29. Page 12

18 Under the Authorities historical operating practices, the Project s reservoir level rarely dropped below 165 feet, although the Project license allows the Authorities to draw the reservoir down as low as feet for power production purposes under the five conditions outlined below. The Authorities seek to balance these conditions in the operation of the Project reservoir, and in doing so have routinely forgone power production benefits to provide other Project purposes and needs, such as public recreation, water supply, and shoreline protection. The current Power Sales Agreement establishes two levels of power production. Primary power generation occurs from 172 to 168 feet. Once the reservoir level falls below 168 feet, power generation below that level may only occur under the following conditions: The FERC orders or requires a reduction in the water level of the reservoir for purposes of inspecting or repairing the dam; An insufficient supply of electric power to the Power Companies firm or non-interruptible power users will result; Non-use of the waters of the reservoir for the generation of hydroelectric power will result in the failure to satisfy minimum downstream flow requirements necessary to meet water sales from the diversion canals of the Authorities; Non-use of the waters of the reservoir for the generation of hydroelectric power will result in the failure to deter saltwater encroachment; or The Authorities fail to make all credits owed to the Power Companies or fail to make full reimbursements as required in Sections 3.2A and 3.7 of the Consolidated Power Sales Agreement within the time identified in the current agreement. Toledo Bend continues to be operated such that reservoir elevations are typically rising from January through April. A winter drawdown to 168 feet allows filling by spring rains and gently rising water levels from January through April to full pool level of 172 feet on or around May 1 (Table 3.3-1). Daily on-peak power generation typically occurs five to six days per week during the May through September season depending on water supply and electrical demand. For the remainder of the year, generation flows are driven by reservoir levels to meet the Project Operation Guide Rule Curve, and can occur on a constant or pulsed basis depending on inflows and reservoir elevation. A summary of annual operations for the years 22 through 29 is shown in Table Operations during Normal, Dry, and Wet Years Table presents ranked average annual inflow (cfs) into the Toledo Bend Reservoir during the period from 1972 through 29. The table is based on mean daily synthesized hydrologic data developed to characterize reservoir inflows (HDR DTA 21). Hydrology was synthesized using changes in storage, calculated evaporation, and the U.S. Geologic Survey USGS gage Toledo Bend Reservoir near Burkeville, Texas, and USGS gage Sabine River at the Toledo Bend Reservoir tailrace. Page 13

19 Table Ranked average annual reservoir inflow (cfs) Flow Flow Calendar Year Calendar Year (cfs) (cfs) , , , , , , ,2 22 6, , , , , , , , , , , , , , , , , , ,956 Note: Annual average flows do not include a reduction for water supply withdrawals. Calendar Year Flow (cfs) 4,578 4,558 4,347 4,281 4,27 4,133 4,11 3,564 3,299 3,11 3,45 1,75 The calendar years 21, 22, and 26 are representative of wet, normal, and dry hydrologic years, respectively. Historical operations of the Toledo Bend Project during normal (22), wet (21), and dry (26) years are depicted in Figures , , and Mean daily discharge flows provided in these figures are based on mean daily outflow measurements reported by USGS for gage at the Toledo Bend Reservoir tailrace, which includes flows from the powerhouse, leakage during non-operating conditions, and the continuous flow release of 144 cfs to the spillway channel. Headwater elevations are based on automated reservoir measurements at the Project. Figure Toledo Bend discharge and reservoir elevations during 22 (normal year). Page 14

20 Figure Toledo Bend discharge and reservoir elevations during 21 (wet year). Figure Toledo Bend discharge and reservoir elevations during 26 (dry year) Page 15

21 3.3.2 Spillway Operations The spillway is located along the north dam abutment in Louisiana. The overall length of the spillway structure is 838 feet and the flow of water over the concrete gravity-type gated weir is controlled by eleven 4-feet-wide-by-28-feet-high Tainter gates. Spillway gates are operated independently of one another with electric motor hoists. An onsite operator controls the gates as there are no remote operations of the spillway gates. The elevation of the top of the gates is 173 feet when closed. The gated spillway also includes a concrete chute and stilling basin. Also contained in the spillway structure is an 8.33 feet wide-by-12-feet high low-flow sluiceway, lowflow sluiceway. The invert of the low-flow sluiceway is at an elevation of 1 feet. The spillway gates are normally operated when reservoir levels exceed feet. To meet flow requirements under the current license, a continuous release of 144 cfs (i.e., 286 ac-ft/day) is maintained in the spillway channel by releases through two 2-inch-diameter conduits located in the low-flow sluiceway. The spillway operating guide is provided in Table Table Spillway operating guide. Reservoir Elevation (feet) Flow Releases from Spillway (cfs) 4,916 9,624 2,119 31,73 42,681 67,775 1, , ,744 24, , ,381 Notes: 1. Information based on report by Brown & Root (Brown & Root 1994). An excavated spillway channel extends approximately 1.7 miles downstream to where it intersects Bayou Toro (drainage area 221 square miles) at RM 145.5, and then continues.4 miles to the confluence of the Sabine River (RM 145). The Sabine River then flows approximately 4 miles before being joined by the excavated tailrace channel, which conveys flows from the Project powerhouse to the Sabine River (Figure ). This spillway channel and the Sabine River that convey the Project s current continuous flow requirement of 144 cfs to the Sabine River is known as the 6-mile loop. The ability to operate the Project for flood control is limited. Flood control is not a Project purpose. The Project was not designed as a flood control facility and lacks flood control capacity typically found at flood control reservoirs. Therefore, the Project is not operated for flood control and does not have flood management pool. Page 16

22 Figure Toledo Bend dam and downstream area. Page 17

23 3.4 PROJECT FLOWS AND GENERATION Project Flows The USGS documents discharge in the Project s tailrace at gage (Figure ). This data captures total discharge from the Project through a combination of flow measurements from the spillway, gage measurements in the tailrace and pressure data from the penstocks of the two turbines. Turbine discharge is calculated with operation logs and scroll case differential relations by the USGS (211). Turbine leakage and continuous flow releases are determined using operation logs and USGS discharge measurements. A HEC-RAS model was developed to depict existing operations and to examine downstream hydraulic effects of Project operations (HDR DTA 211) Mean and Median Flows The mean annual outflow, computed from mean daily streamflow discharge records at USGS gage for the period of record 1972 through 29, is 5,794 cfs (USGS 211). The minimum annual outflow 49 cfs occurred in 1996, and the maximum of 1,948 cfs occurred in The mean monthly outflow at the Toledo Bend Dam for the period 1972 through 29 ranged from 1,363 cfs to 1,571 cfs with the highest mean monthly outflows occurring in March and the lowest in October (Table ). Table Monthly outflows (cfs), USGS Gage Sabine River at Toledo Bend Reservoir tailrace near Burkeville, Texas. Monthly Flow (cfs) Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean 8,465 9,442 1,571 7,816 6,875 5,2 4,83 3,888 3,21 1,363 2,743 5,36 Median 7,355 9,46 1,5 6,565 3,235 3,6 4,545 4,48 2, ,475 Notes: 1. Monthly mean and median flows derived from mean daily discharge measurements and operation logs. 2. Period of record is 1972 through Data provided by USGS gage Sabine River at Toledo Bend Reservoir near Burkeville, Texas (USGS 211). Monthly flow duration curves prepared from flows recorded at the Toledo Bend Reservoir tailrace (USGS gage 82536) for the period are provided in Attachment B-1. Page 18

24 Figure USGS gage location at the Toledo Bend Reservoir tailrace. Page 19

25 Critical Period Flows The critical streamflow for the period of record 1972 through 29 occurred in the calendar year This year represents the lowest annual Project outflow recorded at the USGS gage, and the lowest annual Project inflows based on mean daily synthesized hydrologic data developed to characterize reservoir inflows (HDR DTA 21) Flows Downstream of Toledo Bend Dam There is a continuous flow release of 144 cfs from the spillway to the spillway channel that joins with flow from Bayou Toro. When generating power, the Project typically releases on the order of 7, or 14, cfs through the units (i.e., one- or two-unit operation, respectively) to the lower Sabine River downstream of the Toledo Bend Dam. Typically, the units sequence from both off-line to one unit coming online and then the second unit going through the same sequence to their scheduled load in less than 1 minutes each. The flows from operations attenuate with distance downstream, resulting in a decrease in velocity, flow rate, and change in stage with distance from the dam. The progression of attenuation along the downstream river reaches depends on a number of factors including channel storage, geometry (i.e., width, depth, shape, and slope), vegetation, roughness, and sinuosity. Flow attenuation also depends on contributions from tributaries and other accretion flow characteristics downstream of the Toledo Bend Dam. Figure presents downstream flow attenuation from two-unit operation for six hours based on 15-minute flow data at four USGS gages. Figure shows the location of these gages. Figure Downstream attenuation of flow from two-unit operation for six hours. Page 2

26 Figure USGS gage locations downstream of Toledo Bend Dam. Page 21

27 Figure presents a comparison of maximum stage changes at the USGS gages for four flow scenarios. These scenarios provide examples of downstream attenuation resulting from the following four different flow events: Figure Downstream attenuation of maximum change in stage on the Sabine River downstream of the Toledo Bend Project. One-unit operation (five hours of generation at a flow rate of 6,95 cfs on September 25, 29); Two-unit operation (six hours of generation at a combined flow rate of 14,675 cfs on September 9, 29); Two-unit maintenance drawdown (11 days of continuous operation at an average combined flow rate of 15,6 cfs from September 1 to 21, 21); and, A rainfall event during one-unit operation resulted in a combined peak measured flow rate of 75, cfs on November 2, 29. This flow rate included flows discharged from the spillway and the powerhouse. The stage data in Figure are based on water level data from USGS gages (USGS 211) supplemented with water level measurements compiled from temporary, instream data logging equipment. The one and two unit scenarios show a general trend of stage change reduction with distance downstream. The effect of local river channel geometry is noticeable in the elevation trends where the stage changes rise at the USGS gage locations where the channel width is narrower. The stage attenuation pattern is repeated and exaggerated in the 11-day, two-unit continuous flow scenario (with the exception of the Ruliff gage), illustrating the influence of local stream geometry at higher river flows. The lower stage change at Ruliff is likely a result of overbank Page 22

28 distributary flow where stage change diminishes as flows spread into distributary channels into the bottomland floodplain. Figure shows the change in water elevation during two-unit operation for six hours at several locations in close proximity to the Toledo Bend Dam including the tailrace, the spillway channel and Bayou Toro. Stage information is based on USGS gage data (USGS 211) supplemented with water level measurements compiled from temporary, instream data logging equipment. Locations of data loggers used in water level measurements are provided in Figure Figure Backwater characteristics from two-unit operation at Toledo Bend Project as measured by USGS gage and temporarily placed water level loggers. Backwater characteristics from two unit operation for six hours range from a change in stage of 9 feet in the tailrace at USGS gage to a change in stage of about 4 feet in Bayou Toro at data logger 145-BT1 located about.2 miles upstream from the confluence with the spillway channel (Figure ). The rise of 4 feet at data logger 145-BT1 in Bayou Toro is similar to the rise of 4 feet measured at data logger 146a located at RM 146, about one mile downstream of the spillway. Page 23

29 Figure Temporary water level data logger locations August 29 - November 21. Page 24

30 3.4.2 Project Generation Water for the Toledo Bend turbines is passed through six foot wide by 29 foot high openings within the powerhouse intake structure controlled by vertically operated caterpillartype gates. The two vertical Kaplan turbines are each rated at 4.5 MW. The water-cooled, umbrella-type generators are each rated at 4,5 kva at a 95 percent power factor. The authorized installed capacity of the Project is 81 megawatts (MW). The maximum capability of the generating units under optimum conditions is 92 MW. Each unit has a minimum hydraulic capacity of 3,4 cfs2, and a maximum hydraulic capacity of 7,5, cfs releasing a combined capacity of about 3, ac-ft of water per day based on index testing performed in 1988 and turbine performance (HDR DTA 21). Operation of the powerhouse is performed on a contract basis by Entergy-TX and both units can be remotely operated from the Entergy-TX Sabine Plant located in Bridge City, Texas Average Energy Production and Utilization The average annual energy production of the Toledo Bend Project for the period 1972 through 29 is 239,635 MWh. The mean monthly energy production is 19,97 MWh for the 38-year period and is presented in Table Annual Plant Factor Based on the Project s authorized installed capacity of 81 MW and the historical average annual plant generation of 239,635 MWh, the Toledo Bend Project has an annual plant factor of 34 percent Estimate of Dependable Capacity The dependable capacity of the Toledo Bend Project is approximately 8 MW. This capacity is estimated using the storage capacity available within the power pool operating range of 168 to 172 feet for a four-hour period. Sufficient storage is always available to generate the units at their maximum output for a four-hour period within the Operating Guide Rule Curve Plant Capability versus Head The Toledo Bend Project currently operates over a 4-foot reservoir operating zone (primary power pool) from a lower pool elevation of 168 feet to a normal maximum elevation of 172 feet. Power can be generated between 168 feet and the minimum elevation of feet under the five conditions listed in Section 3.3. Combining the allowable variation of the reservoir, the expected turbine-generator performance values, and the estimated maximum turbine hydraulic capacity at various heads yields an estimate of the plant capability as shown in Figure The minimum, median, and maximum gross head are shown in Table Minimum hydraulic capacity is estimated at 4 percent of full gate flows. Page 25

31 Table Year Toledo Bend Project monthly energy production (MWh). Jan 5,252 45,56 59,664 61, ,177 4,64 18,816 1,864 52,327 19,399 22,481 45,23 5,318 56,29 28,948 17,418 51,44 54,65 47,73 4,349 59, ,295 59,655 59,878 2,1 6,21 28,213 33,6 1,278 28,86 1,314 35, ,539 Feb 19,985 31,12 53,76 54,888 9,62 21,896 16,186 55,97 41, ,938 23,94 21,124 34,99 23,222 25,419 44,258 55,21 55,28 55,737 53,1 17,91 56,561 2,576 42,369 53,445 54,166 1,848 54,88 27,837 12, , ,678 5, Mar ,62 25,26 61,2 22,21 39,145 17,84 58,869 27, ,448 56,777 46,239 3,758 59,54 39,714 32,472 6,113 6,58 59,77 4,412 61,147 62,345 1,875 59,794 6,6 39,155 2,488 6,545 23,819 31,93 6,232 2, ,543 17,674 Apr 3,569 57,36 21,34 36,717 15,997 38, ,511 44,112 2,898 6,495 17,879 2,222 14,896 8,35 28,691 18,113 46,678 57,41 39,514 34,813 57,1 12,87 56,1 1,65 29,479 22,113 3,998 2,431 44,67 3,23 13, ,98 1, ,777 24,144 May 14,548 45,42 29,64 52,95 24,28 15,813 9,161 52,774 36,946 7,55 26,538 11, ,424 9,493 7,92 7,341 31,485 6,49 57,914 6,866 33,416 16,944 55,34 1,762 43,36 6,47 12,472 14,345 13,363 6,425 5,7 29,1 9,791 9,946 9,981 23,721 35,173 Jun 8,946 35,48 17,993 35,248 32,5 12,54 8,428 4,182 1,566 7,73 7,11 26,436 13,479 12,674 49,995 7,273 7,82 58,348 35,53 24,17 14,23 19,795 18,52 18,871 1,687 14,226 9,27 14,147 8,426 9,756 8,269 9,934 24,955 13, 14,7 12,52 12,757 13,227 Page 26 Jul 7,411 32,76 19,82 22,145 28,555 1,839 7,92 13,419 1,637 18,99 12,28 22,992 12,98 14,443 31,51 18,417 3,278 32,571 18,254 8,889 22,892 36,86 12,565 15,355 1,667 15,97 17,721 15,231 19,34 15,978 16,76 17,631 27,748 15,159 12,842 46,968 16,211 14,143 Aug 18,98 15,32 18,931 19,474 28,619 17,255 6,196 15,146 6,269 2,953 13,217 6,99 2,267 6,148 12,156 11,858 4,395 17,39 18,838 19,61 19,53 17,77 2,141 19,992 1,56 2,732 12,688 16,363 16,478 17,515 23,533 16,34 19,779 18,298 17,116 25,143 14,783 9,964 Sept 16,976 19,414 15,94 17,589 16,996 16,359 9,94 16,593 8,687 2,39 2, ,872 4,975 3,98 2,227 4,877 16,384 4,569 28,727 11,5 22,944 22,657 15,977 1,524 9,181 11,943 7,64 11,467 35,827 12,121 16,68 9,426 8,42 2,761 3,137 5,827 4,22 Oct 1,5 5, ,765 2,49 5,623 1,876 15,134 2,554 2,399 5,391 4,159 27,414 4,13 2,811 16,494 1,881 1,184 11, ,438 1,217 17,56 1,29 1,54 1,655 1, ,531 22,457 Nov ,96 19, 1,898 4, ,723 1,991 3,378 1,549 11, ,843 2,27 2,384 1,66 3,172 21,913 1,71 13,298 49, ,478 11,293 16,264 2,44 5,25 1,217 8,476 1,52 34,934 1, ,15 47,132 Dec 12,935 55,64 6,376 5,965 7,14 23,35 1,11 33,869 26,563 23,4 29,73 39,149 35,983 2,662 4,793 9,54 29,784 22,3 11,944 43,578 1,598 1,115 23,716 48,449 2,265 2,79 14,496 27,115 1,515 59,821 1, ,692 54,682 Total 154,62 411, ,178 36, ,26 188,573 83, ,34 29,575 63,13 18, , ,83 194,26 273,39 249,49 174, ,73 343, , , , , ,626 18, , , ,761 15, , , ,22 27,2 182,665 62, , , ,637

32 Year Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Minimum ,687 1,667 1,56 64 Average 29,543 3,4 35,66 25,79 22,443 18,145 18,127 15,425 11,433 4,435 8,797 19,7 Maximum 61,772 56,561 62,345 63,511 6,49 58,348 46,968 28,619 35,827 27,414 49,376 6,376 Notes: 1. Energy production values represent historical power generation based on metered power as reported by the Authorities. 2. Energy production values are based on historical operation and reflect the change in the normal operating minimum reservoir pool elevation from feet prior 27 to 168 feet after March 27. Page 27 Total 18, , ,227 to March