### MIRANT DELTA, LLC - DRAFT

Mirant Proposed BDCP Covered Activities

Goal : To generate electric power at the Delta Plants to meet the demands of the California and Western electric grid.

Brief Covered Activity Description : Mirant's Covered Activities are those activities associated with the generation of power at its Pittsburg and Contra Costa Po wer Plants (together the Delta Plants). These activities can be divided into three categories: (1) current power generation ac tivities and water intake and discharge flows associated with those activities; (2) recurrent maintenance activities required to ensure continued operation of those existing faci lities; and (3) potential future unit replacement projects at both plants, which would be anticipa ted to have much lower associated intake and discharge flows than the existing power generation facilities. The Pittsburg Power Plant is located on the southern shore of Suisun Bay n ear Pittsburg, California (Figure X-1), and the Contra Costa Power Plant is located 12 miles upstream on the southern bank of San Joaquin River near Antioch, California (Figure X-2) [Figures to be inserted].

Initially the Mirant activities to be covere d by the BDCP are conti nued operation of the Delta Plants, which are dependent on the withdr awal of cooling water for non-consumptive oncethrough cooling purposes. Thus the primary goal fo r Mirant's initial Cove red Activities will be to maintain existing levels of operation and associ ated water flows, but Mirant expects that its Covered Activities will evolve over the next few years as the BDCP process continues. Additionally, Mirant's operations are constrained by its Clea n Water Act National Pollution Discharge Elimination System (NPDES) permits and specifically by Clean Water Act section 316(b) of the federal Clean Water Act. Mirant's operations are also constrained by regulatory requirements imposed by federal and state ener gy agencies. These independent regulatory constraints may alter Mirant's Covered Activities for the purposes of the BDCP in both the shortterm and long-term.

Longer-term Covered Activities may incl ude the replacement of existing power generation units, and Mirant an ticipates that any new units would not utilize once-through cooling technology. Accordingly, the impacts to covered species associat ed with longer-term water intake and discharge activitie s are expected to be much less than those associated with the initial Covered Activities.

Expanded Covered Activity Description :

• Existing Plants Operation

Mirant's Delta Plants have a total genera ting capacity of 2,090 gross megawatts (1,985 net megawatts). Mirant's generating units burn natural gas and are designed to be cooled by water from the San Joaquin-Sacramento River De lta. Cooling water is drawn into the plants through 9.5 mm (3/8 inch) screens, pumped to conde nsers, used to cool spent steam and then discharged immediately back into the San Joa quin-Sacramento Delta. Source waters for the Delta Plants' cooling water systems are characteristic of this part of the Bay-Delta that separates the upstream, freshwater Delta from the downstream, saltwater bays.

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### MIRANT DELTA, LLC - DRAFT

o Pittsburg Power Plant

The Pittsburg Power Plant (PPP) consists of seven natural gas-fired generating units, four of which have been retired. PPP Units 5&6 were built in 1960 and 1961, respectively, and generate a total of 660 gMW of power. PPP Un it 7 was built in 1972 and generates 740 gMW. Cooling water for the PPP is withdrawn from Suisun Bay through two adjacent shoreline intake structures. Units 5&6, both once-through cooled units, are each serviced by two variable frequency circulating water pumps (CWP) that withdraw water from the Units 5&6 intake structure. Each pump has a maximum design flow of 115.6 million gallons per day (MGD)(354.7 acre-feet(AF)/day) or 231.1 MGD (709.1 AF/day) per unit (Table X-1). The approach water velocity in front of the bar racks can range from 0.5 to around 0.2 feet per second depending on how much electric generation is needed and the number of the variable frequency pumps in operation. Unit 7, which is equipped with two me chanical-draft cooling towers and a large cooling water canal, withdraws make-up water th rough the Units 1-7 intake structure. Unit 7’s closed-cycle system uses up to 44 MGD (135 AF/day) of make-up water.

In addition to the Units 5-7 cooling water intake requirements, the PPP withdraws water from the Units 1-4 intake structure for station water supplies, for intermittent intake screen washing, and for fire suppression purposes. At maximum operation, these additional uses account for approximately 43.6 MGD (133.8 AF/day). The total current design flow for all PPP operations is approximately 565.2 MGD (1,734 AF/day)(Table X-1).

Table X-1. Total PPP design maximum flows by subsystem Flow (GPM) Flow (MGD) Flow (AF/Day ) Circulating Water Pumps Unit 5 Unit 6 Subtotal 160,500 160,500 321,000 231.1 231.1 462.2 709.1 709.1 1,018.2 Continuous Pumps Unit 7 Make-up Water Pump Station Service Pumps (1) Jockey Pump (Fire Suppression) Subtotal 30,300 27,000 20 57,320 43.6 38.9 0.03 82.5 133.8 119.4 0.1 253.3 Intermittent Pumps Units 1-4 Screenwash Pumps (2) Units 5&6 Screenwash Pumps (3) Fire Suppression-Main Pump (4) Fire Suppression-Auxiliary Pump (4) Subtotal 6,750 5,400 2,000 0 14,150 9.7 7.8 2.9 0 20.4 29.8 23.9 8.9 0 62.6
TOTAL 392,470 GPM 565.2 (MGD) 1,734 (AF/Day)

1. Since the retirement of Units 1-4 in 2004, one of the six station service pumps operates 24 hours per day (6.5 MGD). 2. Since the retirement of Units 1-4 in 2004, two of the three screenwash pumps are still operated about 1 hour/week for maintenance (0.04 MGD). 3. Design flows for pumps are reporte d. Two of the three pumps typically operate for a total of 90 minutes per day (3.9 MGD). 4. The fire suppression pumps are always available for emergency s ituations. The normal operating flows are based on testing each pump up to one hour per w eek to assure pump reliability and occasionally to flush the header system. Flows are calculated assu ming the main pump is used for 25% of the year.



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o Contra Costa Power Plant

The Contra Costa Power Plant (CCPP) consists of seven natural gas-fired generating units, five of which have been retired. Units 6&7 were built in 1964 and generate a total of 690 gross megawatts (gMW) of power. Units 6&7 are equipped with on ce through cooling which utilizes water withdraw n from the San Joaquin River. Units 6&7 are each serviced by two variable frequency circulating water pumps (C WP) that each have a ma ximum design flow of 152,800 gpm, or 220 MGD (675 AF/day) (Table 2-1). The total design flow for both Unit 6 and Unit 7 is approximately 305,600 gpm, or 440 M GD (1,350 AF/day). The approach water velocity in front of the bar racks can range from 0.6 to around 0.2 feet per second depending on much electric generation is needed and the number of the variable frequency pumps in operation.

In addition to the Unit 6 and Unit 7 cooling water intake requirements, the CCPP utilizes water for station water supplies, for intermittent intake screen washing, and for fire suppression purposes. At maximum operation, these additio nal uses account for approximately 22 MGD (67.5 AF/day). The total current design flow for all CCPP operations is approximately 462 MGD (1,418 AF/day) (Table X-2).

Table X-2. Total CCPP design maximum flows by subsystem

Flow (GPM) Flow (MGD) Flow (AF/Day) Circulating Water Pumps
Unit 6 152,800 220 675
Unit 7 152,800 220 675

Subtotal 305,600 440 1,350
Continuous Pumps Station Service Pumps 12,000 17.3 53 Jockey Pump (Fire Suppression) 20 0.03 0.1

Subtotal 12,020 17.309 53.1
Intermittent Pumps Units 6&7 Screenwash Pumps (1) 5,400 3.9 11.9 Fire Suppression (Main Pump) (2) 2,000 0.7 2.1

Subtotal 7,400 4.6 14.1

TOTAL 325,020 GPM 462 MGD 1,418 AF/Day

(1) Assumes that all three screenwash pumps operate for two hours every four hours per day.
(2) The fire suppression pumps are always available for emergency situati ons. The normal operating flows are based on testing each pump up to one hour per week to assure pump reliability and to occasionally flush the header system. Flows are calculated assuming the main pump is used for 25% of the year.



### o Variable Frequency Drive (VFD) Circ ulating Water Pump Operations

The circulating water pumps at CCPP Units 6&7 and PPP Units 5-6 are mixed flow vertical centrifugal pumps equippe d with A-C induction motor drives. The drives have been modified to utilize VFD controls, as well as to operate at full rated sp eed. The VFD controls provide a means to vary drive speed by varyi ng frequency. For a centrifugal pump, flow is proportional to pump speed. Therefore as freq uency and drive/pump speed are reduced, pump flow is also reduced proportionally (i .e., 50% pump speed => 50% pump flow).

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When operating in VFD mode, the circulating water pump speed/flow is typically at its minimum level when the unit is at minimum lo ad. The minimum circulating water pump speed/flow is limited by both the pump and motor de sign and the system head requirements. For PPP Units 5&6 and CCPP Units 6&7 minimum flow is 50% of design and minimum load is ~25–45 MW. As unit load increases, pump speed a nd flow are increased in accordance with unit conditions. Maximum circulating water speed/flow, 95–100% of design, is typically reached at ~90–145 MW for PPP Units 5&6 and CCPP Units 6&7. River water te mperature, tide, condenser vacuum, steam flow, etc., all have an e ffect on circulating water flow requirements.

o Current Actual Operational Cooling Water Flows

Actual flow rates at the Delta Plant have steadily decreased in recent years to be consistently substantially below all maximum pe rmitted flow limits. Capacity utilization rates (the ratio between the annual net generation of power and the total net capability of the facility to generate power) at the Plants ha ve steadily declined over the last five years, and intake flows have correspondingly decreased. For example, the combined 2006 total flow for CCPP Units 6 & 7 and PPP Units 5 & 6 of 40,753 MG (0.13 milli on AF) was 83% lower than the comparable figure in 2002. See Table X-3. While the Calif ornia Independent System Operator (CAISO) requires that the Delta Plants be available at any time during the year , the Delta Plants are primarily used during California’s peak energy demand periods, particularly in the crucial summer months. The Plants’ water intake sp iked in 2001 when California’s unprecedented energy crisis required almost continual operation to meet electrical demand. Despite this unique circumstance, the overall use of cooling water du ring the last 20 years shows that water intake has been steadily decreasing, but has been sharply reduced in the last few years. See Figure X-3.

Table X-3. Electrical capacity utilization and coo ling water flows for CCPP and PPP from 2002 to 2006.

Plant/Year Capacity Utilization (MWh/(MW Capacity * hours of generation) Combined Annual Cooling Water Flows (MG/yr) Combined Annual Cooling Water Flows (million AF/yr) CCPP Unit 6 Unit 7 Units 6&7 Units 6&7 2002 28.7 37.4 117,099 0.36 2003 1.9 16.4 46,740 0.14 2004 4.1 21.7 60,926 0.19 2005 1.2 10.1 29,875 0.09 2006 0.8 3.9 15,641 0.05 PPP Unit 5 Unit 6 Unit 7 Units 5&6 Units 5&6 2002 19.9 24.5 43.2 120,340 0.37 2003 27.1 7.1 17.2 80,876 0.25 2004 24.0 20.8 9.5 74,991 0.23 2005 12.5 7.3 1.8 34,710 0.10 2006 7.7 5.3 1.4 25,112 0.08



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5 0 500 1,000 1,500 2,000 2,500

1986 1 987 1 988 1 9 8 9 1 9 9 0 199 1 199 2 1993 1994 1 995 1 9 9 6 1 997 199 8 1 9 9 9 2000 200 1 2002 2003 2 004 2005 2 006Million Gallons per Day

Actual Daily Average Intake Permitted Intake

Figure X-3. Average daily flows (MGD) of the CCPP and PPP from 1986 through 2006.



### o Discharge Flows (including Stormwater)

In addition to once-through cooling flows, Mirant discharges pr ocess wastewater and stormwater (quantity and quality of discharges are subject to permits issued by the State Water Resources Control Board and San Francisco and Central Valley Regional Water Quality Control Boards).

• Recurrent Plant Maintenance and Modification Activities and Monitoring Activities

o Maintenance Dredging, Equipment Main tenance and Modifications, and Levee and Flood Control Maintenance

Maintenance and modification activ ities includes those routine activities that maintain the capacity and operational features of the existing power generation facilities at the Delta Plants described above. These activitie s include periodic maintenance dredging in front of and in the plant cooling water intake structures to rem ove naturally occurring accumulated sediments to ensure that the approach velocity of cooling wa ter entering the intake structure remains relatively uniform across the intake screen and as close to design levels as possi ble and to prevent undue damage to the facility from sediment in the c ooling water and the relate d abrasion and wear of power plant equipment, such as condenser tubes and circulating water pumps. Dredging is also sometimes required around the docks and in the di scharge outfalls to remove the sediment build so that these structures can f unction and operate as designed. These activities also include

### MIRANT DELTA, LLC - DRAFT

recurrent equipment maintenance and modifications (such as shoreline and pier maintenance, maintenance and repair of all improvements, in frastructure, roads, electrical facilities, underground linear facilities, vege tation management, etc.), as we ll as modifications to existing facilities and infrastructure as needed to ensu re continued power genera tion; levee maintenance (such as placement of riprap for shoreline prot ection and erosion control) as needed to protect the power generation facilities; and flood control maintenance (such as maintenance of Willow Creek at the PPP) as needed.

o Aquatic Studies & Covered Species Monitoring

Mirant is conducting, and will recurrently c onduct, aquatic and covered species studies and monitoring, specifically involving data collection in the vicinity of the plants, in front of the intake and outfall structures, and within the cooling water system.

• Planned & Prospective Unit Replacement Projects

Future power generation projects at the Delta Plants would involve the construction of new units and associated infrastr ucture. New units would likely re quire some use of river water (e.g. for station water supplies or cooling tower ma ke-up water), but Mirant anticipates that any new units would not utilize once- through cooling technology and w ould therefore require only a small fraction of the water required by existing PPP Units 5-6 and CCPP Units 6-7.

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