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MesquitePower Permits

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The air permit is a Title V permit registered with the State of Arizona.  It regulates the air quality requirements of the gas turbines, cooling towers, dust control, VOC usage, and chemical solvents, wipe cleaners and paints associated with air emissions.  The governing agency is the Maricopa County Environmental Services Department (MCESD).

Table 1:  Emission Limits

Gas turbine limits






Normal - Mode 6

2.5 ppm

4.0 ppm


3-hr. rolling average corrected to 15% O2

22.2 lbs./hr.

21.6 lbs./hr.


Hourly limit


10 ppm

24-hr. rolling average





Extended Startup For power block




An Extended start is one in which the combined cycle system (Unit) has not reached Mode 6 operation in the 72 hours prior to initiating the startup sequence

Regular Startup For power block




A Regular start is one in which the combined cycle system (Unit) has reached Model 6 operation during the 72 hours prior to initiating the startup sequence.

Shutdown For power block




There is also a maximum pounds per hour emission limit for CO of 260 lbs/hr for Combined Cycle System #1 and #2 (power block 1) combined, and 260 lb/hr for Combined Cycle System #5 and #6 (power block 2) combined

Table 2: Particulate Limits

Cooling tower limits





3.86 lbs./hr.

Calculated using Total Recirculation Rate and Total Dissolved Solids (TDS)


Air Permit   Aquifer Permit   Evaporation Pond Permit   ADWR   Special Use Permit

Air Permit

1.  Startups-Shutdowns:  Limited to 1400 hours combined startup and shutdown per power block per year.

For any exceedance, we will always attempt to establish an “Affirmative Defense”.  The conditions for this include:
*We have complied with the reporting requirements in a timely manner and demonstrated the following:
A. Excess emissions resulted from:
  1. Sudden and unavoidable breakdown of process or air pollution control equipment.
  2. Unavoidable conditions during startup or shutdown. Unavoidable conditions during an upset of operations.
  3. Greater or more extended exceedance would result unless scheduled maintenance is performed.
B. The source's air pollution equipment, process equipment, or processes were being maintained and operated properly.
C. If repairs were required, they were performed in the most expeditious manner possible, including using off-shift labor and overtime.
D. The amount and duration of the excess emissions were minimized to the maximum extent possible.
E. The excess emissions were not part of a recurring pattern indicative of inadequate design, operation, or maintenance.
3.  For any exceedance, an investigation into the cause should start immediately.  The cause should be diagnosed as an Operations (startup/shutdown, DLN mode, ammonia, etc.) or a CEMS issue:
A. Operations exceedance:
  1. Goal is to minimize the duration of the exceedance
  2. Repair problem or get into mode 6 as soon as possible
  3. If exceedance has not been resolved after one hour, inform Compliance Engineer with following information:
    1. Source of exceedance:  unit, pollutant, amount of exceedance
    2. Duration of exceedance to that point
    3. Cause if known
    4. Corrective actions taken
    5. Plan of action including estimated time of repair
B. CEMS issue:
  If daily cal failed:
  1. Attempt to determine if reason for failure, i.e. cal occurred during startup, mode change or during a ramp, cal gas bottle pressure low, etc.
  2. If cal occurred during startup, mode change or ramp, re-cal when plant stabilized
  3. If no apparent reason for failure, call a CEMS Tech with following information:
    1. What part of cal failed and by how much
    2. Time of failure
    3. Operating conditions
  4. Inform Compliance Engineer

Other CEMS alarms:
If emission exceedance is due to CEMS equipment issue and has not been resolved within one hour, call a CEMS Tech and Compliance Engineer.

D. Cooling Tower exceedance:
The PM-10 (particulate magnitude) limit per the permit is calculated using the Total Recirculation Rate and the Total Dissolved Solids (TDS) of the Circulating Water.  Actions would include:
  1. Lower TDS through blowdown
  2. limit for TDS is 30,000 mg/l
  3. Sample Circulating Water for TDS to verify controller accuracy
  4. Inform Compliance Engineer
4.  Opacity (Visible Emissions):
A. Opacity readings not required on steam or cooling tower discharge.
B. No opacity readings should exceed 20% except:
  1. Startup and Shutdown
  2. Emergencies
  3. Diesel fire pump for short period of time (startup, shutdown, unavoidable combustion irregularities
  4. These should not exceed 3 minutes in length and not exceed 40% opacity

Visible emissions are required:

  1. Monthly facility walkthrough observing each stack and the diesel fire pump
  2. If gas turbine or diesel fire pump has been operating for 10 hours in a week, then a visible emissions observation must be performed that week
  3. If any visible emissions are noted and last for three days, then an official visible emissions reading by a certified VE reader must be performed
  4. Currently have (3) certified VE readers: Henry Krautter, George Williams, Steve Perrizo
5.  Duct Burner Operation:
A. A duct burner “operating day” is a 24-hr period from 12:01 AM and ending at 12:00 midnight during which gas was combusted for the entire 24 hours.
B. The CEMS must obtain valid data for at least 18 of every 24 hours in at least 22 of every 30 consecutive days of operation.

Record any period of time that NOx emissions data is not available.

6.  Diesel Fire Pump: 
A. Only to be used for emergency conditions or routine maintenance checks.
B. Actual hours of operation and reason for operation to be logged.
7.  The CEMS, SCR, and CO catalyst will be operated and maintained per their O&M plans.
8.  CEMS:
A. Will be operation any time fuel is being combusted except:
  1. Calibration
  2. Quality assurance
  3. Preventative maintenance
  4. Repairs
  5. Backups of data from DAHS
  6. Recertification
  7. Any malfunctions are reported
B. Certifications:
  1. Annual:  RATA, Bias check
  2. Quarterly:  CGA, Linearity
  3. Daily:  Calibrations
    1. A cal is required after any maintenance that could affect CEMS
    2. Ammonia injection rate monitored
  4. Inform Compliance Engineer
9.  An odor log must be kept to record any complaints from off-site.
10.  Other Requirements:
A. Daily:  Cooling tower conductivity recorded
B. Monthly: 
  1. GCV for natural gas obtained and inputted into DAHSGCV for natural gas obtained and inputted into DAHS
  2. Cooling tower drift eliminators inspected
  3. TDS content of cooling tower water measured
  4. Inform Compliance Engineer
C. Quarterly:   Natural gas sampled for total sulfur
D. Annual: Stack testing for VOC, PM-10
E. Every 5 yrs:  Stack testing for NOx, CO, NH3
11. VOC's:
An inventory of any material containing VOC's along with their VOC content will be kept and monthly amount used.
12. Other permit subjects:
  1. Dust generating
  2. Spray coating
  3. Abrasive blasting
  4. Cold degreasers
  5. Wipe cleaning
  6. Acid rain


* Currently being amended
1. The APP is the permit that regulates the usage of the (2) 60-acre evaporation ponds.  The governing agency is the Arizona Department of Environmental Quality (ADEQ).
2. Each evap pond consists of:
  1. A 60-mil thick upper layer made of high-density polyethylene (HDPE)
  2. A 40-mil thick lower layer (HDPE)
  3. A geonet layer that separates the layers
  4. A geo-synthetic clay layer under the lower liner
  5. 225-300 ft. of impermeable clay
3. Each 60-acre pond will hold 1320 acre-ft of water with 2 ft. of freeboard.  The maximum operating depth of the pond is 8 ft.
4. The ponds receive effluent from the oil-water separators (2) and the waste-water collection sump.  Effluent includes:
  1. Cooling tower blowdown
  2. Oil-water separators
  3. HRSG boiler blowdown
  4. HRSG boiler draining
  5. RO reject water
  6. RO cleaning water
  7. Surge tank overflow
  8. Storm water runoff
5. A butterfly valve at the north end of each pond allows for the ponds to be put into service or isolated.
6. Leakage Collection and Return System (LCRS):
  The LCRS consists of the geonet layer between the upper and lower HDPE layers.  This layer channels any leakage from the upper liner to a network of 6” perforated PVC pipes under the upper liner.  These pipes direct the water to the LCRS collection sump at the south end of each pond.
  When the water level of the sump reaches a preset height (30 in.) a submersible pump turns on and pumps the water through a flow totalizer back to the pond.  The pump shuts off automatically when the sump level is reduced to 12 in.  The totalizer reading is read at the DCS along with a time-stamp to indicate when the pump last ran.  These parameters determine the average gallons per day leak rate of the liner.  This value is also displayed on the DCS and recorded by the Compliance Engineer.
7. Monitoring Requirements:
  Monitoring began with the first cooling tower blowdown into the pond.  The east pond became operational with the first fire of CT-1 on Jan. 21, 2003.  The west pond did not become operational until the commissioning of the LCRS system in November, 2003.
  A discharge characterization (profile) of the effluent must be collected and analyzed within 60 days of full operation (block 2 commercial).  The profile must be of a “normal” discharge, which in our case means the cooling towers operating at 15 cycles.  The characterization is a one-time requirement.
  Other monitoring requirements include:
  1. Daily LCRS gal per day readings
  2. Weekly, monthly inspections of the liner, dam, and mechanical systems.
  3. Inspections after a significant rain (1/10 ”)
8. Contingency Requirements:
  The contingency actions required in the case of a discharge limitation or alert level violation can be found in Section 2.6 of the permit.  These and the important actions include:
A. Exceeding freeboard limit (< 2 ft.)
  1. Immediately stop discharging to the affected pond
  2. Pump water from affected pond to the other pond until freeboard requirement is met
B. Exceeding Alert Level #1 for the LCRS (15,750 gpd)
Within 5 days:
  1. Determine if water in sump matches pond by taking pH, conductivity
  2. Notify ADEQ
  3. Assess the condition of the liner
C. Exceeding Alert Level #2 for the LCRS (501,500 gpd)
Within 24 hours:
  1. Determine if water in sump matches pond by taking pH, conductivity
  2. Notify ADEQ
  3. Assess the condition of the liner
  4. Immediately cease discharging to the affected pond
  5. Within 5 days of discovery, collect sample from LCES sump and submit to lab for analysis
D. Liner failure, Containment structure failure, Unexpected loss of fluid:
  1. Immediately cease discharging to affected pond
  2. Within 24 hours of discovery notify ADEQ
  3. Within 5 days remove remaining water from pond and record amount removed.  Take sample of water and submit for lab analysis.
E. Overtopping an impoundment:
  1. Within 24 hours of discovery notify ADEQ
  2. Immediately cease discharging to affected pond
  3. Remove excess water and record amount.  Log amount.
  4. Within 5 days collect and analyze water sample.
F. Discharge of unauthorized material to pond:
Within 5 days:
  1. Notify ADEQ
  2. Identify source and eliminate discharge immediately. 
  3. Evaluate compatibility with liner


  This permit is governed by the Arizona Department of Water Resources (ADWR) and regulates the use of the evap pond containment structures.  Because of the height of the berms and the potential amount of water they could hold back, the containment berms are registered dams in the state of Arizona.  This permit is governed by the Arizona Department of Water Resources (ADWR) and regulates the use of the evap pond containment structures.
  The dam permit consists of an O&M plan that dictates the monitoring requirements.  These include:
  1. Weekly and monthly inspections on the berm and pond liner
  2. Semiannual surveying of the dam to determine if any settling is occurring


  This permit is also administered by the ADWR and regulates the operation of the cooling towers.  In addition to a lot of operating data to be submitted in an annual report, this permit is the one that requires that the cooling towers be operated at 15 cycles.  This is a requirement on all large power plants built after 1984 that use groundwater as their main makeup water source.


  The Special Use Permit is also referred to as the “Site Use Permit”, and includes a lot of conditions on the use of the site.  Included in these requirements are:
  1. The check for dead birds at the evap ponds
  2. Keeping the evap pond berms clear of vegetation
  3. The Groundwater Use Permit which puts limits on the annual amount of water each well pump can put out in addition to an overall annual water limit from the wells.

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