SALT RIVER PROJECT 

NAVAJO GENERATING STATION – UNITS 1, 2, 3 

SCR AND BAGHOUSE 

CAPITAL COST ESTIMATE DESIGN BASIS 

Prepared By: 

Project No. 12656-001 

April 16, 2010 

Revision B 

SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc TOC-1 

CONTENTS 

1. GENERAL .........................................................................................................................1

1.1 Design Basis Scope ......................................................................................................1

1.2 Site Climatic Data..........................................................................................................1

1.3 Design Emissions..........................................................................................................2

1.4 Coal, Ash, and Trace Element Analysis........................................................................3

1.5 Water Analysis ..............................................................................................................3

1.6 Boiler Operating Data....................................................................................................4

1.7 Design Life ....................................................................................................................6

1.8 Underground Utilities.....................................................................................................6

1.9 Fire Protection...............................................................................................................6

2. MECHANICAL...................................................................................................................6

2.1 SCR Option ...................................................................................................................6

2.2 SCR and Baghouse Option.........................................................................................10

3. ELECTRICAL/I&C ...........................................................................................................13

3.1 SCR OPTION..............................................................................................................13

3.2 SCR AND BAGHOUSE OPTION ................................................................................14

4. CIVIL/STRUCTURAL/ARCHITECTURAL/GEOTECHNICAL..........................................16

4.1 Geotechnical Design Basis .........................................................................................16

4.2 Civil Design Basis........................................................................................................16

4.3 Structural Design Basis...............................................................................................19

4.4 Architectural Design Basis ..........................................................................................21

ATTACHMENTS 

A. Design Basis Input Document List 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 1 

1. GENERAL 

1.1 DESIGN BASIS SCOPE 

a. The design basis documents the technical and functional requirements on 

which the capital cost estimate for SCR and Baghouses for the Navajo 

Generating Station Units 1, 2 & 3 will be based. The design basis covers 

performance requirements of the equipment, as well as reliability requirements, 

design life, operating requirements and process technology requirements. 

1.2 SITE CLIMATIC DATA 

Reference Elevation 4,355 ft MSL 

Barometric Pressure 12.49 psia 

Relative Humidity 28% - 100%; 

annual average =45% 

Maximum Ambient Temperature 

(Design): 

109 deg F dry bulb 

79 deg F wet bulb 

Annual Average Ambient 

Temperature: 

57.6 deg F dry bulb 

Minimum Ambient Temperature -11 deg F dry bulb 

Freeze Protection (new 

underground piping installations) 

Minimum 4 feet cover from 

the top of pipe per Annex A 

of NFPA 24 

Freeze Protection (existing 

underground piping) 

Match existing depth 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 2 

Storm Return Rainfall Duration 

Period 30 Minutes 1 Hour 24 Hours 

10-Year 0.62 inches 0.77 inches 1.51 inches 

25-Year 0.84 inches 1.04 inches 1.85 inches 

50-Year 1.04 inches 1.29 inches 2.12 inches 

100-Year 1.28 inches 1.59 inches 2.42 inches 

1.3 DESIGN EMISSIONS 

a. The following emissions rates will govern the design of new emissions control 

equipment: 

a1. NOX Inlet Emissions: 0.24 lb/MMBtu with Low NOx Burners and SOFA 

modifications only. 

a2. NOX outlet emission (permit limit) : 0.09 lb/MMBtu on a 30-day rolling average 

(to be negotiated with ADEQ). 

a3. NOX Outlet Design Emissions: 0.05 lb/MMBtu. The design will be based on the 

unit specific NOX. 

a4. Particulate Emissions from existing HESP: 0.03 lb/MMBtu 

a5. Design Particulate Emissions from Pulse Jet Fabric Filter (PJFF): 

0.01 lb/MMBtu 

a6. Ammonia Slip: 2 ppmvd @ 3% O2

a7. SO3 Outlet Design Emissions: No net increase in emissions after installation of 

SCR with use of sorbent injection. SCR will be designed to operate with ultra-low 

SO2 to SO3 conversion catalyst (<0.125% per layer). 

a8. SO2 Outlet Emissions : 0.04-0.07 lb/MMBtu (depending on coal sulfur content 

and levels of scrubbing in service). No net increase in emissions after installation 

of SCR. 

a9. Mercury - ppmd (wt.) in coal: 0.05 ug/g (dry). No net increase in emission after 

installation of SCR. 

a10. Chlorine - ppmd (wt.) in coal: 14 ug/g (dry). No net increase in emission after 

installation of SCR. 

a11. Other Pollutants: N/A 

b. Future discussions with the EPA may impact the above criteria and will be 

subject to revisions. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 3 

1.4 COAL, ASH, AND TRACE ELEMENT ANALYSIS 

a. The conceptual design of the new emissions control equipment that would be 

installed on Units 1, 2, and 3, at Navajo Generating Station will be based on 

the coal, ash, and trace element analysis provided: 

 AS RECEIVED DRY

% Moisture, Total ASTM D 3302 13.33 

% Ash 

ASTM D 

3174/5142 10.36 11.96

% Volatile Matter ASTM D 5142 35.61 41.08

% Fixed Carbon ASTM D 3172 40.7 46.96

Gross Calorific Value 

(Btu/lb) ASTM D 5865 10418 12020

% Sulfur ASTM D 4239 0.63 0.73

% Carbon ASTM D 5373 59.16 68.26

% Hydrogen ASTM D 5373 4.38 5.05

% Nitrogen ASTM D 5373 1.03 1.18

% Oxygen, (Calc) ASTM D 3176 11.1 12.82

% Sulfur, Pyritic - FOS ASTM D 2492 0.13 0.15

% Sulfur, Sulfate - FOS ASTM D 2492 <0.01 <0.01

% Sulfur, Organic - FOS ASTM D 2492 0.5 0.58

% Potassium Oxide - WSA 

ASTM D 1428-

56T 0.005 0.005

% Sodium Oxide - WSA 

ASTM D 1428-

56T 0.118 0.136

Date Sample From 3/1/2009 

Date Sample To 3/31/2009 

Sample ID N-8 “DMS Shipped” 

1.5 WATER ANALYSIS 

a. The conceptual cost estimate is based on the assumption that the water quality 

of the existing service water system is acceptable for equipment cooling water. 

In order to confirm this assumption the following water analysis should be 

provided by SRP: 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 4 

 Service Water 

Cations (ppm) 

Calcium 

Magnesium 

Sodium 

Potassium 

Anions (ppm) 

Alkalinity 

Chloride 

Sulfate 

Sulfide 

Nitrate 

Phosphate 

Fluoride 

General 

TSS (ppm) 

TDS (ppm) 

Spec. Cond. (μS/cm) 

pH 

Temp (oC) 

Ammonia 

Silica 

BOD 

CBOD 

TOC 

Kjeldahl N 

1.6 BOILER OPERATING DATA 

a. The boiler data identified in the following table will serve as the basis for new 

emissions control equipment. Since all three units are similar with respect to 

size, capacity, and operating conditions, one single set of values will be used 

as the design basis to allow the same equipment to be used to the fullest 

extent possible. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 5 

Boiler Inputs Value 

BMCR MW gross 812 

Heat Input mmBtu/hr 7,350 

Excess Air* 18% 

Air Heater In Leakage** 22% 

* Excess Air is taken from Steam Generator Equipment Data Manual 

** Air Heater In leakage is assumed to be 22% to match the stack O2 levels in the Acid Mist Sampling 

Summary (7.1% O2, dry) 

 Load 

Output Source Units 100% 75% 50% 

GMW Note 1 MW 812 604 403 

Coal to 

Burners 

Note 1 Mlb/hr 652 513 355 

Minimum SCR 

Inlet 

Temperature 

Deg F 580 580 580 

AH Flue Gas 

Outlet Flow 

Note 1 Klb/hr 7,275 5,763 4,411 

AH Flue Gas 

Outlet 

Pressure 

Note 1 INWG -14.9 -9.65 -5.85 

AH Flue Gas 

Outlet 

Temperature 

(w/ leakage) 

Note 1 Deg F 250 235 201 

NOX NGS PI Data LB/MMBTU 0.24 - - 

Stack O2 Acid Mist 

Report 

% Dry 7.1 - - 

WindboxFurnace 

Pressure 

Note 1 inH2O 3.5 3.1 3.0 

Furnace 

Pressure 

Note 1 inH2O 0 0 0 

Note 1: Data obtained from existing NGS Steam Generator Equipment Data Manual. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 6 

1.7 DESIGN LIFE 

a. All new equipment and components for the new emissions controls systems 

will be designed for a 30-year life. 

1.8 UNDERGROUND UTILITIES 

a. Existing underground utilities will be relocated to support installation of new 

structures. Relocated utilities will be designed for above ground installation 

onto existing or new pipe racks as required, it is assumed existing systems 

have sufficient capacity to support utility relocation. 

1.9 FIRE PROTECTION 

a. Fire protection for new emissions control equipment will be provided by the 

existing NGS fire protection system; this includes fire pumps, yard piping, 

hydrants, etc. It is assumed the existing fire protection system has sufficient 

capacity to meet these new demands. 

a1. SCR fire protection requirements: Fire protection for the SCR and auxiliary 

equipment will require fire hydrants located within 50 feet of the SCR structure. 

a2. Baghouse fire protection requirements: Fire protection for the baghouse and 

auxiliary equipment will require fire hydrants located within 50 feet of the 

baghouse structure. The baghouse will be designed with polyphenylene Sulfide 

(PPS) fabric bags to minimize fire potential. PPS fabric bags are neither 

flammable nor combustible. A fire water standpipe will provide water to the 

penthouse area with a hose connection for use during outages when flammable 

materials may be present. 

2. MECHANICAL 

2.1 SCR OPTION 

a. SCR 

Preliminary calculations indicate the following equipment will be required for an 

SCR system: 

a1. SCR Reactor: 2 x 50% for each unit. 

a2. The SCR reactors will be of a 4-catalyst layer design with 2 layers initially filled. 

a3. Catalyst Type: Plate / honeycomb 

a4. The SCR reactors will be designed with provisions for catalyst removal, i.e. 

monorail, trolley, jib cranes, etc. 

a5. The SCR system will be designed without flue gas bypass provisions around the 

reactor. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 7 

a6. The SCR reactors will be low-dust reactors with sonic horns utilized for mitigation 

of dust buildup on the catalyst layers. 

a7. An economizer side flue gas bypass will be required to maintain the flue gas 

temperature above 580F for load conditions between minimum load and 

approximately 700MW. 

a8. Reagent for the SCR system will be anhydrous ammonia. The anhydrous 

ammonia is vaporized to gaseous ammonia. Approximately 550 lbs/hr of 

gaseous ammonia will be required per unit. 

b. Reagent Unloading and Storage 

b1. Anhydrous ammonia will be delivered to the site via truck to a common ammonia 

unloading area. Anhydrous ammonia is unloaded (via onboard truck pumps) into 

a storage tank. The unloading area is sized to accommodate simultaneous 

deliveries to the ammonia tanks. 

b2. The ammonia storage facility will utilize three (3) horizontal tanks sized for 14 

days of continuous operation at full load for the site. 

b3. Four (4 x 33%) transfer pumps are provided to transfer the ammonia solution for 

use in the vaporizers. 

b4. Four (4) steam vaporizers (2 x 100% per reactor) will be provided for each unit. 

1,500 lbs/hr of low pressure steam is required per vaporizer. 

b5. Ammonia dilution air heater and blower: 1 x 100% skid per reactor; each skid 

consists of 2 x 100% blowers and heaters. The ammonia dilution air heaters will 

be sized to provide enough air to dilute the ammonia to 5% of the total injected 

air flow. The air will be heated to 300 oF to match the ammonia temperature out 

of the vaporizer. 

c. Sorbent Injection System (Trona or Hydrated Lime). 

c1. The sorbent injection system will be designed per the following basis: 

c1.1 The sorbent injection system will be sized for a feed rate of 200 lbm/hr. 

c1.2 The sorbent injection system consists of the following equipment and 

components: 

EQUIPMENT QTY/REDUNDANCY 

STORAGE SILO 1 X 100% (PER UNIT) 

SORBENT INJECTION BLOWERS 2 X 100% (PER UNIT) 

SORBENT INJECTION LANCES BY VENDOR 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 8 

c2. The storage silo will be sized for approximately seven days (7) of storage 

capacity with the silo diameter limited to a maximum of fourteen (14) feet. Larger 

storage capacities, per sorbent injection system vendors, would require 

additional silos due to shop fabrication and equipment shipping limitations. 

d. ID Fans 

d1. NGS utilizes four (4) ID fans per unit arranged in parallel. 

d2. Capacity: 4 x 25% per Unit – Original MCR rating of 675,000 acfm at 33.8 inwg. 

In 1996 Howden was contracted to complete a performance test to establish an 

As Tested Condition for the ID fans. Table 3 of the report, “Scrubber Converted 

Condition @ 300 F”, shows the operating point of the ID fans to be at 895,103 

acfm and 31.41 inwg. 

d3. Type: Centrifugal, Inlet vane control – Westinghouse-Sturtevant, size 4132 D, 

DWDI Airfold, arrangement 3. 

d4. Motor: Constant Speed – Originally 5,500 HP and upgraded to 8,000 HP for 

scrubber conversion. According to Howden performance test (Table 3) the 

current operating point is 6143 horsepower. 

d5. Evaluation of the existing ID fans to support the new SCR installation is based on 

the following inputs and assumptions: 

Input Value Source 

Coal Analysis %C-59.16 

%Moist-13.33 

SGS Coal Analysis 

Higher Heating Valve 10,418 btu/lb SGS Coal Analysis 

Gross Output 812 MW Questionnaire 

Heat Input to Boiler 7,350 * 10^6 btu/hr Questionnaire 

Excess Air 18% Draft System Data Sheet 

ESP Leakage 3% Standard Value 

SCR Leakage 0% No SCR bypass damper 

assumed 

Air Heater Leakage 22% Back calculated from 

stack O2

Site Elevation 4365 ft ID fan data sheet 

Static Pressure at Furnace 0 inwc Gas Profile 

Pressure Loss through 

SCR 

dp 10 inwc Estimate, w/ ductwork 

Pressure Loss through AH dp 7.2 inwc Gas Profile 

Wet FGD Pressure Loss dp 10 inwc Estimate w/ ductwork 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 9 

Pressure Loss from FGD 

through Stack 

3.9 inwc, at Test Block Assumed 

Air Heater Outlet Temp 251 deg F Gas Profile 

d6. Based on preliminary calculations the existing ID Fans will require modifications 

to support installation of new SCRs. 

d6.1 Existing rotating element will be replaced with a new rotor assembly (impeller, 

shaft and bearings) with maximum tipped blades in order to support the new 

SCR System. 

d6.2 Tipping a centrifugal ID fan of the existing size and arrangement will typically 

result in an increase of up to 7.5% flow, 15% pressure, and 27.5% brake 

horsepower. 

d6.3 Pressure Rise: Tipping the ID fans will increase the maximum pressure rise by 

15% from 41.5 inches water column to 47.7 inches water column at the 

calculated MCR flow of 890,000 acfm. The required pressure rise for the ID fans 

with a SCR addition is 42.3 inches water column. ID fans that were tipped would 

have a 12.8% pressure margin of the maximum capability of the fan above the 

required fan pressure rise. This pressure margin is less than the 15% margin 

that S&L typically uses in design work. With additional plant data from actual 

flow and pressure testing, the acceptable margin may be reduced to 12.8% 

because system duct losses will be better defined thereby allow less margin to 

be accepted. 

d6.4 Flow Increase: The addition of an SCR to the flue gas path at Navajo will 

increase the volumetric flow by approximately 4.5% due to the injection of dilution 

air with the ammonia. This increased flow will not affect fan performance. 

 Motor HP: From the 1996 performance test report issued by Howden, the ID 

fan motor is providing 6,143 brake horsepower at the current full load operating 

point. With the ID fans tipped, the brake horsepower requirement of the fan 

would be approximately 27.5% larger in value, resulting in an estimated 7,832 

brake horsepower. This larger horsepower requirement is acceptable for the 

existing fan motor because the ID fan motors are rated at 8,000 horsepower 

output. 

e. Compressed Air 

e1. The compressed air demand of the SCR systems will be provided by the existing 

service / instrument air systems. 

2.2 SCR AND BAGHOUSE OPTION 

a. SCR: Refer to Section 2.1.a. 

b. Reagent Unloading and Storage: Refer to Section 2.1.b. 

c. Sorbent Injection System (Trona): Refer to Section 2.1.c. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 10 

d. ID Fans 

d1. Refer to Section 2.1.d for configuration and performance data for existing ID 

Fans. 

d2. Evaluation of the existing ID Fans to support a new SCR and Baghouse is based 

on the inputs and assumptions defined in Section 2.1.d including the following: 

 

Input Value Source 

System Balance Point at existing ID fan 

discharge (-1 inwc at 

baghouse inlet) 

Industry standard for 

Baghouse to be under 

negative pressure 

Baghouse Pressure Loss dp 10 inwc Estimate w/ ductwork 

Booster Fan Pressure Margin 15% S&L standard 

Booster Fan Flow Margin 5% S&L standard 

d3. Based on preliminary calculations, new ID Booster Fans will be required to 

support installation of a new SCR and Baghouse. The cost estimate shall be 

based on the following ID Booster Fan configuration: 

d3.1 The 4 x 25% existing ID fans (per Unit) will be utilized. Two new 100% axial ID 

Booster fans (per Unit) will be added in-between the Baghouse outlet and Wet 

Scrubber inlet to account for the remaining system pressure loss. The following 

table identifies the calculated fan sizing parameters: 

PRELIMINARY DATA FOR EXISTING ID FAN 

FOR REVISED CONFIGURATION Test Block MCR 

Volumetric Inlet Flow, each existing ID fan acfm 945,000 890,000 

Fan Total Press in. wg 32.3 28.1 

Density at Fan Inlet lb/cuft 0.0431 0.0437 

Number of ID Fans 4 4 

Temperature at Fan Inlet deg F 251 251 

Fan Inlet Static Pressure in. wg -33.1 -28.8 

Fan Inlet Area sq ft 240 240 

Fan Outlet Static Pressure in. wg -1.2 -1.0 

Fan Outlet Area sq ft 182 182 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 11 

Motor Horsepower BHP 5,384 4,821 

 

PRELIMINARY DATA FOR NEW BOOSTER 

FANS Test Block 

MCR (Full Load, 

no margins) 

Volumetric Inlet Flow, each ID fan acfm 1,890,000 1,785,000 

Fan Total Press Rise in. wg 31.3 26.5 

Density at Fan Inlet lb/cuft 0.0443 0.0446 

Number of ID Fans 2 2 

Temperature at Fan Inlet deg F 274 272 

Fan Inlet Static Pressure in. wg -13.8 -12.0 

Fan Inlet Area sq ft 240 240 

Fan Outlet Static Pressure in. wg 16.0 13.1 

Fan Outlet Area sq ft 182 182 

Motor Horsepower BHP 9,968 8,714 

e. Baghouse (Pulse-Jet Fabric Filter) 

e1. A Pulse-Jet Fabric Filter (PJFF), if required, will be designed per the following 

basis: 

e2. A new Pulse-Jet Fabric Filter will collect the solid byproduct generated by the 

reaction between airborne SO3 and injected sorbent. The fabric filter will be 

designed with a gross air to cloth ratio of 6:1. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 12 

e3. The fabric filter consists of the following equipment and components per Unit: 

Equipment Qty/Redundancy 

Casing(s) 2 

Flue Gas Flow Configuration Flue Gas Inlet & Outlet on the 

Same Side 

Compartments 8 Compartments; 4 per side per 

baghouse casing (pending 

vendor design) 

Bag Type PPS fabric bags 

Pulse Air Compressor 2 x 100% 

Pulse Air Dryer 2 x 100% 

Pulse Air Receiver 2 x 100%; 1 wet receiver, 1 dry 

receiver 

 Pre-Filters 2 x 100% 

 After-Filters 2 x 100% 

Hopper Vibrators 2 x 100% per hopper 

e3.1 Compressor Type: Oil Free Centrifugal Compressor, 

e3.2 The compressor is sized for the Pulse Jet cleaning cycle of the baghouse 

delivering 125 psi instrument quality air. The compressed air system will also 

provide compressed air to new intermittent users (valves, instruments, tools, 

etc.). 

e3.3 Dryer Type: Heated blower purge type regenerative desiccant dryer (-40 deg F 

dew point). 

e4. Fabric Filter Waste Collection and Disposal 

e4.1 Waste collection and disposal will be designed per the following basis: 

e4.2 Reacted & unused sorbent collected in the baghouse hoppers will be transferred 

via a pneumatic system to waste storage silo. The waste storage silo will be 

sized for a 7-day storage capacity. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 13 

e4.3 The waste collection and disposal system consists of the following equipment 

and components: 

Equipment Qty/Redundancy 

Fabric Filter Waste Collection Silo 1 x 100% (per Unit) 

Fabric Filter Waste Collection Blowers 3 x 50% (per Unit, Units 2 & 3) 

2 x 100% (per PJFF, Unit 1) 

e5. Waste will be disposed to existing plant land fill via truck. 

f. Compressed Air System 

f1. Compressed instrument and service air for new users will be provided by the 

PJFF pulse air compressors. 

3. ELECTRICAL/I&C 

3.1 SCR OPTION 

a. SCR Electrical System 

a1. The existing 8000 HP ID fan motors are rated at 13,200 volts, 1.15 SF and 330 

FLA. During the initial field walkdown, it was noted that with the units operating at 

close to full capacity, the ID fan motors were operating at an average of 230 

amps. This confirms that although, fan modifications are required to overcome 

additional pressure drop due to the SCRs, the existing motors will have enough 

capacity to drive the modified fans. 

a2. Based on review of existing plant drawings, it was determined that new 480 V 

electrical distribution equipment will be required to handle the additional SCR and 

Sorbent Injection System loads. Two (2) new 4.16 KV – 480 V unit substation 

transformers (USTs) will be added to each unit. The power supply for those 

transformers will originate from the existing FGD 4.16 KV switchgear located in 

each FGD Pump House. The transformers will in turn supply power to a new 480 

V switchgear, which will distribute that power to new 480 V MCCs. 

a3. For each unit, the new USTs will be located to the east of the Pump House, and 

the 480 V switchgear will be located within the FGD Pump House. For Units 1 

and 3, the new SCR MCCs will be located in new PDCs near the SCRs. Due to 

space constraints by Unit 2, the MCCs will be located in the Unit 2 FGD Pump 

House 

a4. The Ammonia Delivery System associated with the installation of the SCRs for 

each of the three units will be located at the south end of the power plant. The 

Ammonia Delivery System will require new 480 V MCCs. The MCCs will be 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 14 

powered from the existing switchgears LSPA and LSPB located in the Limestone 

Prep Enclosure. 

a5. Miscellaneous equipment, such as UPS, UPS batteries, lighting transformers, 

distribution panels, etc, will also be include in the overall SCR electrical system 

design. 

b. SCR Distributed Controls System 

b1. The SCR system will be controlled by new DCS equipment that will be tied into 

the existing plant Foxboro DCS system. New DCS equipment for Unit 1 and Unit 

3 will be located in their respective EE buildings near the SCR. New DCS 

equipment for Unit 2 will be located in the existing Unit 2 FGD Pump House. The 

common DCS equipment for the anhydrous ammonia equipment will be located 

in the Anhydrous Ammonia Unloading and Storage Area. All new DCS 

equipment will tie into the existing network in the Environmental and Chemical 

Lab Control Room. The new Unit 1 and Unit 2 DCS equipment will tie into the 

existing cabinet 0-DCS-CABQ. The new Unit 3 and common DCS equipment will 

tie into the existing cabinet 0-DCS-CABR. Each Unit DCS will require 500 I/O 

points and the common DCS will require 100 I/O points. 

c. SCR Continuous Emissions Monitoring System 

c1. Each Unit’s SCR has two reactors. Each reactor will require an In-Situ NOx and 

O2 measurement on both the inlet and outlet side for a total of 4 measurements 

per Unit. In additions to these measurements, a common meteorological station 

will also be added. 

d. SCR Instrumentation 

d1. Each Unit will require approximately 100 balance of plant instruments. These 

instruments include various transmitters, switches, thermocouples, etc. for the 

various SCR reactor measurements interface. The common DCS will require 

approximately 10 balance of plant instruments. These instruments include 

various transmitters, switches, thermocouples, etc. for the anhydrous ammonia 

unloading tanks and transfer pumps. 

3.2 SCR AND BAGHOUSE OPTION 

a. SCR Electrical System: Refer to Section 3.1 above. 

b. Baghouse Electrical System 

b1. After reviewing existing plant drawings and the available auxiliary power study, it 

was determined that the new ID booster fans (estimated at 2 X 10,000 HP per 

unit) cannot be supported from the existing UATs. It is therefore necessary to 

add one (1) new UAT and two (2) 13.8KV switchgears for each unit to supply 

power to the booster fans. The additional 480V system loads will be handled by 

spare capacity from the new USTs and 480 V switchgear added for the SCR 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 15 

System. The 480 V switchgear will distribute power to new 480 V Baghouse 

MCCs. The new MCCs will be located in the existing FGD Pump Enclosure. 

b2. 13.8 kV distributions will be required to distribute startup and shutdown power for 

the new booster fans. The new common 13.8KV switchgears will be powered 

from the existing Station Service 13.8KV buses SSA and SSB. It is assumed 

that the RSS and MSS can handle the additional startup loads. 

b3. Each unit will be provided with a new 3-winding UAT. The UAT will be located in 

the vacant space adjacent to the existing UAT. The new UAT will tap into the 

existing isolated phase bus duct on the high side of the existing UAT and step 

down the voltage from 26 KV to 13.8 KV. 

b4. Two (2) new 13.8 KV switchgears will be provided for each unit. The 13.8 KV 

switchgears will be located in new PDC enclosures. The new 13.8 KV 

switchgears will have cable bus connections to the new UAT. 

b5. Common switchgears will be added for unit startup and shutdown. The two (2) 

additional common 13.8KV switchgears will be located in a common PDC 

enclosure. 

b6. To the extent possible each unit will have 480V MCCs located in their respective 

FGD Pump House, utilizing the available space that exists there. 

b7. Miscellaneous equipment, such as UPS, UPS batteries, lighting transformers, 

distribution panels, etc, will also be include in the overall baghouse electrical 

system design. 

c. SCR & Baghouse Distributed Controls System 

c1. The SCR and baghouse system will be controlled by new DCS equipment that 

will be tied into the existing plant Foxboro DCS system. New DCS equipment for 

Unit 1 and Unit 3 will be located in their respective EE buildings near the SCR, 

their respective PDC buildings, and their respective FGD Pump Houses. New 

DCS equipment for Unit 2 will be located in the existing Unit 2 FGD Pump House 

and the new Unit 2 PDC building. The common DCS equipment for the 

anhydrous ammonia equipment will be located in the Anhydrous Ammonia 

Unloading and Storage Area and the common PDC building. All new DCS 

equipment will tie into the existing network in the Environmental and Chemical 

Lab Control Room. The new Unit 1 and Unit 2 DCS equipment will tie into the 

existing cabinet 0-DCS-CABQ. The new Unit 3 and common DCS equipment will 

tie into the existing cabinet 0-DCS-CABR. Each Unit DCS will require 1000 I/O 

points and the common DCS will require 200 I/O points. 

d. SCR & Baghouse Continuous Emissions Monitoring System 

d1. Refer to Section 3.1.c above 

e. SCR & Baghouse Instrumentation 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 16 

e1. Each Unit will require approximately 150 balance of plant instruments. These 

instruments include various transmitters, switches, thermocouples, etc. for the 

various SCR reactor measurements, the new ID booster fans, and the new 

Baghouse equipment. The common DCS will require approximately 10 balance 

of plant instruments. These instruments include various transmitters, switches, 

thermocouples, etc. for the anhydrous ammonia unloading tanks and transfer 

pumps. 

4. CIVIL/STRUCTURAL/ARCHITECTURAL/GEOTECHNICAL 

4.1 GEOTECHNICAL DESIGN BASIS 

a. Existing Soil Conditions 

a1. Previous geotechnical reports compiled in support of the original construction at 

the site circa 1970 and of the FGD addition in the mid-1990s provide soil borings 

and other pertinent soil information. Refer to Bechtel Corporation’s “Report –

Foundation Investigation, Proposed Navajo Steam Plant, Near Page, Arizona, for 

Salt River Project” dated October 15,1969 and Stone & Webster’s “Geotechnical 

Report – Navajo Scrubber Project” dated April 1993. These reports form the 

technical basis for the design of the foundations. 

b. Foundation Types 

b1. Heavily loaded structures will be supported by caissons founded on rock. Lightly 

loaded structures will be founded on shallow foundation mats or footings. 

4.2 CIVIL DESIGN BASIS 

a. Civil and Sitework Design Requirements 

a1. The site development work is closely linked with buried utility and foundation 

work and will require the following activities in support of the installation of the 

proposed air quality equipment. 

a1.1 Providing temporary erosion control during all construction phases. 

a1.2 Demolition of existing roads, concrete paving, and structures, and disposal of 

waste. 

a1.3 Grading and earthwork to shape the existing grade for new work. 

a1.4 Construction of temporary construction roads and access ways, if necessary. 

a1.5 Construction of temporary and permanent drainage facilities, and providing 

permanent erosion and sediment control devices as required. 

a1.6 Installation of temporary and permanent fencing and gates for plant security. 

a1.7 Restoration of construction areas following project completion. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 17 

a1.8 Final grading, surfacing and permanent plant road construction. 

a1.9 Verification of the locations of existing underground utilities by subsurface 

investigation using ground-penetrating radar or similar means. 

a1.10 Surveying of the site areas impacted by the new work. 

b. Site Area, Location And Elevation 

b1. The overall property, including the existing station and other facilities covers 

approximately 50 acres. The cost estimate considers that the new work 

associated with the added SCRs and baghouses falls within the developed areas 

of the site. 

b2. New work will generally match existing grades and top of concrete elevations. 

c. Plant Site And Grid Datum 

c1. Coordinates for all points will be based on the existing Navajo Generation Station 

plant grid system. 

c2. Similarly, the vertical control shall be based on existing plant monuments. These 

permanent monuments have been established by SRP at various locations 

throughout the site, and each monument is tied to the plant grid system and 

referenced vertical datum. 

d. Drainage 

d1. General 

d1.1 The estimate considers that new equipment and building areas will be provided 

with appropriate drainage systems as listed below. The new drainage provisions 

added locally for new structures will be connected into the existing sewer 

systems to the greatest possible. The following items have been included in the 

cost estimate. 

d1.1.1 Storm water sewer system. 

d1.1.2 Oily water sewer system. 

d1.1.3 Process wastewater sewer system. 

d1.1.4 Sanitary sewer system. 

d2. Storm Water Sewer System 

d2.1 Generally all clean storm water runoff from developed site areas is collected by 

the existing storm sewer system. No new plant areas will be disturbed by the 

new work. New or relocated storm water runoff facilities will connect to the 

existing system and maintain similar erosion control methods and drainage 

patterns. 

d2.2 The existing storm water runoff system consists primarily of drainage trenches 

and storm sewers within the main power block and equipment areas. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 18 

d3. Oily Water Sewer System 

d3.1 An existing oily water sewer system collects discharges from equipment areas 

that have a potential for oil contamination, and drains to an existing oil water 

separator for treatment prior to being recovered for use. 

d3.2 New or relocated oily water runoff facilities will connect to the existing systems 

where practical, or discharge to a new oil water separator where required. The 

cost estimate considers that two new oil water separators will be necessary to 

work around the added items and handle any additional flow. 

d4. Process Wastewater Sewer System 

d4.1 For existing mechanical process drain systems and planned process drain 

system, see the Mechanical Design Basis. 

d5. Sanitary Sewer System 

d5.1 Existing sanitary sewage systems conflicting with new construction activities will 

be relocated. New sewer systems for new facilities or relocated systems will 

drain by gravity where practical and will connect to the existing sewer systems 

that will remain in-place. Where it is unfeasible or impossible to route sewage via 

gravity, a packaged lift station will be used. 

d6. High Water/ Flood Elevations 

d6.1 The existing Navajo Generating Station site is protected from storm water 

flooding by concrete lined swales and ditches, storm water runoff ponds, and 

recoverable water reservoirs. Since an adequate storm water management 

facility is in place, no additional flood protection measures are planned for new 

work within the developed areas of the site and no costs are included in the 

estimate for them. 

e. Roads and Surfacing 

e1. Construction laydown and material storage areas will be surfaced with a layer of 

crushed stone or gravel. 

e2. New surfacing work will be consistent with existing surfacing methods. Relocated 

plant roads will be surfaced in a similar manner to the original roads. 

f. Parking and Laydown Areas 

f1. Contractor parking and laydown will utilize previously developed laydown and 

parking areas to the greatest extent possible. 

g. Erosion and Sediment Control 

g1. Temporary facilities will be provided for control of erosion and turbid runoff during 

earthwork operations and from graded areas until they are provided with 

permanent erosion control measures. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 19 

g2. Permanent erosion control facilities for ditches and slopes will follow the Arizona 

Department of Environmental Quality (ADEQ) procedures and guidelines. 

4.3 STRUCTURAL DESIGN BASIS 

a. Structural Cost Estimate Basis 

a1. Structural work accounted for in the cost estimate includes all new reinforced 

concrete foundations and containment structures, structural steel utility racks, 

duct support structures and flue gas ductwork required by the new air quality 

equipment. 

a2. The structural portion of the cost estimate also includes an estimate of 

modifications to the existing flue gas ductwork and structural steel that are 

necessary to permit installation of new items required by the proposed air quality 

modifications. 

a3. Additionally, the structural portion of the cost estimate includes an estimate of the 

reinforcement needed for the existing flue gas ductwork downstream of the SCRs 

due to revised internal pressures in the ductwork that result from adding the new 

air quality equipment into the system. Quantities for required reinforcement of 

this ductwork’s support steel are also included. 

a4. The estimate does not include any costs associated with a condition assessment 

of any of the existing flue gas ductwork or structural steel. All estimated costs 

relating to modification and reinforcement of these in-place items assume that 

their condition has not degraded from the original installed condition in a way that 

affects their structural capacities. 

a5. The estimate does not include any costs associated with revised internal 

pressures in the existing flue gas ductwork upstream of added SCRs back to the 

boiler. The existing and new fans in the system require sufficient controls to 

ensure that there are no changes to internal pressures in this length of ductwork 

and the boiler. 

a6. The arrangements of the new flue gas ductwork, pipe racks and other structures 

and equipment will incorporate a minimum clearance above all roads of 25 feet 

for vehicle access wherever possible. Exceptions to this minimum value may be 

taken where the costs of maintaining a clearance of that height are significantly 

more than not doing so or where a clearance of that height would significantly 

impact the performance of the system because of added configuration restraints 

to an already congested arrangement. In no case will the clearance above a 

road be less than required by normal highway traffic. 

b. Design Codes and Standards 

b1. Structural design will be performed in accordance with the IBC 2006 and Sargent 

and Lundy standards. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 20 

c. Loading: Loads will be in accordance with the International Building Code (IBC) 

2006 and American Society of Civil Engineers (ASCE) 7-05. Loading 

combinations will be in accordance with IBC 2006 and ASCE 7-05 for steel 

structures and IBC 2006, ASCE 7-05, and American Concrete Institute (ACI) 

318-05 for foundations. 

c1. Live Loads 

c1.1 Grade floors, 350 psf 

c1.2 Elevated concrete floors, 100 psf 

c1.3 Galleries and grating areas 75 psf 

c1.4 Electrical Equipment Rooms 200 psf 

c1.5 Stairs 100 psf 

c2. Wind Loads 

A basic wind speed (3-second gust) of 90 mph, Importance Factor of 1.15, and 

Exposure Category C, will be used to calculate wind loads. Design wind 

pressure calculations will be based on IBC-2006 and ASCE 7-05. 

c3. Seismic Loads 

c3.1 Seismic loads will be based on IBC 2006 and ASCE 7-05 with Seismic Use 

Group II, Site Soil Class = C (Table 1615.1.1), and Seismic Importance Factor of 

1.25. 

c3.2 Seismic design parameters are as follows: 

c3.2.1 Ss=32% Figure 1615(1) 

c3.2.2 S1=10% Figure 1615(2) 

c3.2.3 Fa = 1.2 Table 1615.1.2(1) 

c3.2.4 Fv = 1.7 Table 1615.1.2(2) 

c3.2.5 Seismic Design Category “B” 

c4. Snow Loads 

c4.1 Snow loads are based on the following parameters; 

c4.1.1 Ground snow load = 5 psf 

c4.1.2 Exposure factor = 0.9 

c4.1.3 Snow importance factor = 1.1 

c4.1.4 A minimum roof live load of 20 psf will be considered per the tributary area 

requirements of IBC. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 21 

c5. Stability Loads 

c5.1 Designing for wind, seismic and other lateral loads will ensure adequate rigidity 

of the structures. P-Delta effects will be evaluated based on the analysis results 

for wind and seismic load cases. 

c6. Grade Slab Live Loads 

c6.1 All grade slabs are designed for a minimum live load of 350 psf. In addition, any 

grade slab subject to truck or forklift traffic will be designed for the appropriate 

wheel loads. 

4.4 ARCHITECTURAL DESIGN BASIS 

a. Architectural Features 

a1.1 All Power Distribution Centers (PDCs) are prefabricated buildings with metal 

siding, assembled whole or in parts, complete with all electrical equipment fully 

installed and wired. 

a1.2 A new Fabrication Shop will replace the existing one south of Unit 3 that will be 

demolished to make room for the Unit 3 SCRs. The new building will consist of 

masonry walls over a steel frame, matching the existing shop building. The new 

building will house the relocated bridge and jib cranes from the existing shop. 

a1.3 A new Tool Room will replace the existing one between Units 2 & 3 that will be 

demolished to make room for the Unit 2 baghouses. The new building will 

consist of metal siding over a metal frame. 

a1.4 New personnel elevators will be added adjacent to the baghouses for 

maintenance access. 

b. Codes And Standards 

b1. Recommendations in NFPA 850, “Recommended Practice for Fire Protection for 

Electric Generating Plants and High Voltage Direct Current Converter Stations” 

will be followed for power plant facilities. 

b2. Design for life safety will conform to NFPA 101, “Life Safety Code” and to 

workplace safety in U.S. 29CFR Part 1910 (OSHA). 

c. Building Occupancy And Construction Classifications 

c1. Building occupancy shall be classified as F1, Moderate Hazard in accordance 

with IBC 2006. The general construction classification is Type II, non-combustible 

unprotected steel construction. 

c2. Buildings and structures are considered not occupied for the purpose of 

determining egress and fire protection requirements and so forth, with the 

exception of fabrication shops and other such areas of the site where plant 

personnel are typically present. 
SALT RIVER PROJECT

Navajo Generating Station Units 1-3 Project No. 12656-001

SCR and Baghouse Capital Cost Estimate April 16, 2010

Design Basis Rev. B

Design Basis_Navajo_Rev B.doc 

ATTACHMENT A 

DESIGN BASIS INPUT DOCUMENT LIST