ML17300A796

Annual Environ Operating Rept for 1986.

ML17300A796
Person / Time
Site:	Palo Verde
Issue date:	12/31/1986
From:	Carpenter M ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:
Shared Package
ML17300A795	List: ML17300A794 ML17300A796
References
NUDOCS 8705060380
Download: ML17300A796 (21)

Text

ARIZONA NUCLEAR POWER PROJECT PALO VERDE NUCLEAR GENERATING STATION ANNUAL ENVIRONMENTAL OPERATING REPORT FOR 1986 PREPARED BY MANNIE L. CARPENTER ANPP ENVIRONMENTAL LICENSING SUPERVISOR 8705060380 870430 PDR ADOCK 05000528 R PDR

TABLE OF CONTENTS Introduction Page 1 Environmental Monitoring Summaries and Analysis Page 2 Plant Design and Operation Changes Page 3 EPP Noncompliances . Page 3 Nonroutine Reports Page 3 References Page 4

I. INTRODUCTION The Palo Verde Nuclear Generating Station (PVNGS) is located in Haricopa County, Arizona, approximately 50 miles west of the Phoenix metropolitan area. The PVNGS site comprises approximately 4050 acres. Site eIevations range from 890 feet above mean sea level at the southern boundary to 1030 feet above mean sea level at the northern boundary. When completed, the station will consist of three pressurized water reactor electrical generating Units with a nominal generating capacity of 1270 Mie per unit.

PVNGS was issued low power operating licenses NPF-34 and NPF-46 for Units 1 and 2 by the United States Nuclear Regulatory Commission (NRC) on December 31, 1984 and December 9, 1985, respectively. The Unit 1 full 'power operating license NPF-41 was issued June 1, 1985. The Unit 2 full power operating license NPF-51 was issued April 24, 1986. Appendix B to these operating licenses is entitled the "Environmental Protection Plan (Non-Radio-logical)". The Environmental Protection Plans (EPP) of each of the current operating licenses are identical.

On January 27, 1986, the PVNGS Unit 1 reactor was placed into commercial operation.

On April 18, 1986, the PViVGS Unit 2 reactor achieved initial criticality.

Following power ascension testing, the Unit 2 reactor was placed into commer-cial operation on September 18, 1986.

PVNGS Unit 3 was still under construction at the end of 1986.

The EPP has as its stated purpose the "protection of environmental values during construction and operation of the nuclear facility." In conjunction with this general purpose, the EPP also has the principal objectives:

(1) Verify that the station is operated in an, environmentally acceptable manner, as established by the FES (Final Environmental Statement) and other NRC environmental impact assessments.

(2) Coordinate NRC requirements and maintain consistency with other Federal, State and local requirements for environmental protection.

(3) Keep NRC informed of the environmental effects of facility construction and operation and of actions taken to control those effects.

This report is intended to satisfy the requirements of section 5.4.1 of the EPP regarding the submittal of an Annual Environmental Operating Report to the Commission. This report describes the activites during the year 1986 related to the .PVNGS EPP. For purposes of this report, references to the EPP shall be considered to be the EPP of either NPF-41 or NPF-51 unless other-wise specified.

~ j II. ENVIROQKV1'AL MONITOR'ING SUMMARIES AND ANALYSIS A. Cultural Resources Section 4.2.1 of the EPP requires that an archaelogical= survey be per-formed when final alignment of the PVNGS-to-Saguaro transmission line is completed. As of the date of this report, plans for this transmis-sion line have been placed on indefinite hold. Therefore, there has been no further activity in this area of the EPP.

B.

Section 4:2.2 of the EPP requires that the provisions of the Salt Depo-sition and Impact Monitoring Plan (Revision 4, May, 1985) be implemented by the onset of commercial operation of the first unit. The EPP further stipulates ,that the monitoring plan continue for a minimum of three full years:after the onset of operation of all three units or until shown;to not be necessary.

There'ere no changes made to the Salt Deposition and Impact Monitoring Pla'n (Revision 4) or to the implementing procedures during 1986.

The Annual Re ort for the PViVGS Salt De osition Monitorin Program January" December 1985 (NUS-4831) which was included with the 1985 Annual,'Environmental Operating Report did not contain a complete compari-son between 1985 monitoring results and preoperational studies due to unavailability of 1984 monitoring results. A supplemental report titled Com arison Re ort of 1984 to 1985 Analytical Results for the PVNGS Salt Monitorin Pro ram (NUS-4897) was completed in March, 1987, and is in-eluded as an enclosure to this 1986 Annual Environmental Operating

. Report. This comparison study indicated that due to limited operation of the PVNGS Units during 1985, the results could be considered to be consistent with other preoperational years. Therefore, with the excep-tion of the data from five onsite monitoring stations, the 1985 monitor'-

ing data has been incorporated into the preoperational data base, provid-ing a statistically stronger database for future comparisons.

The enclosed report, Annual Report for the PVNGS Salt De osition Mon-itorin Pro ram January December 1986 (NUS-4999) describes the re-sults of the salt drift monitoring activities during 1986. The report concludes that at onsite monitoring locations where detectable amounts of salt drift are observed, the amount of salt deposition measured com-pares very favorably with estimates obtained by inputing plant operating data into the FOG computer model. Furthermore, the measured offsite salt deposition is well under the levels anticipated to produce any significant adverse environmental impact. It should be noted, however, that during 1986, plant operation was less than 50K of anticipated capa-city when all three units are in commercial operation.

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III. PLANT DESIGN AND OPERATION CHANGES Section 3..1 of the EPP allows changes in station design or operation or the performance of tests or experiments affecting; the environment. provided that such changes, tests or experiments do not constitute an 'unreviewed environ-mental question and do not require a change to the EPP. Changes, tests or experiments in which all measureable nonradiological effects are confined to the on-site areas previously disturbed during site preparation and plant construction or in which the environment is not affected, are exempt from the evaluation and reporting requirements of Section 3.1. Section 3.2 of the EPP also exempts changes, tests, or experiments which are required to comply with other Federal, State or local environmental regulations.

The following is a list of items reviewed during 1986:

Installation of a system to return relatively good quality water in the PVNGS evaporation pond to the inlet of the Mater Reclamation Facil-ity (WRF), where it would be blended with incoming effluent prior to treatment and reuse in the plant circulating water system. This tempor-ary pumpback system was installed to allow reuse of water which had been used for system flushing and other construction and start-up related activities. It is expected to be used for approximately one year, de-pending upon acceptable water quality.

2. A revision to procedure 74AC-9ZZ04, Systems Chemistry Specifications Which would allow addition of up to 0.5 ppm zinc to the spray pond spec-ification for enhanced corrosion inhibition.

3. Addition of an approximately 225 acre evaporation pond lined with 80 mil thick high density polyethylene (HDPE).

No unreviewed environmental issues were identified during 1986.

IV. EPP NONCOM'LIANCES There were no instances of noncompliance with the EPP identified during 1986.

V. NONROUI'INE REPORTS There were no nonroutine reports required by. Section 5.4.2 of the EPP submit-ted during 1986.

REFER EiVCES NUS-4831, NUS Corporation, Annual Re ort for the PVNGS Salt De osition Monitorin Pro ram Januar December 1985 April, 1986.

NUS-4897, NUS Corporation, Com arison Re ort of 1984 to 1985 Anal tical Results for the PVNGS Salt Monitorin Pro ram March, 1987.

NUS-4999, NUS Corporation, Annual Report for the PVNGS Salt De osition Monitorin Pro ram January December 1986, April, 1987.

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1 INTRODUCTION NUS Corporation (NUS) is conduct1ng a salt deposit1on and 1mpact monitoring.

program in the vic1nity of the Palo Verde Nuclear Generating Stat1on (PVNGS) for the Arizona Nuclear Power. Project (ANPP). The objective of this monitoring program is to determ1ne the env1ronmental impact, if any, of salt drift emissions from the operation of the PVNGS mechan1cal draft cooling towers.

This annual report presents the results of laboratory analyses of samples collected from January through December 1986 and an assessment of their signif1cance. The media sampled include agr1cultural crops, 1ndigenous vegetation, soil, dustfall, particulates collected by low-volume air filters, and cooling tower basin water. Additionally, this report also compares the data collected during plant operation with those collected during the preoperat1onal period as required by the PVNGS Units I and 2 Environmental Protection Plans, Sect1ons 4.2.2 and 5.4.1, Terrestrial Ecology Monitoring (Appendix B to Facility Operating License NPF-41 and NPF-51). Data collected from 1983 through 1985 (excluding Sites 16, 20, 80, 81, and 83 for 1985) represent the preoperat1onal period, determ1ned from the results of a previous study (NUS, 1987a).

The assessments in subsequent sections of this report include: (I) levels and variations of airborne soluble and insoluble depos1ts, (2) chemical analyses of surficial soils, (3) salt t1ssue load1ng of the 1ndigenous plant coomuni-ties, and (4) salt t1ssue load1ng of crops and yield of cotton crops. Inter-relationships observed between measured parameters are also presented.

Additionally, this report provides a descr1pt1on, in the form of a climato-,

logical summary, of the area meteorology as measured at the PVNGS meteoro-logical tower dur1ng the report period, and a modeling assessment of the salt deposition during the period using actual cooling tower operating data and site meteorological data. Append1ces present tabulations of the plant oper-at1ng data upon wh1ch the assessments are based. Meteorological data sumnaries are presented 1n another report for 1986 (NUS, 1987b).

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List of Tables (Continued)

Table ~Pa e 9-18 A Comparison of Background and 1986 Mean Ionic,Content

(~g/g dry weight) + S.E. of Cotton Leaf Tissue ............... 9-42 9-19 A Comparison of Mean Cotton Yield (Lbs/Acre) + S.E. at Agricultural Monitoring Sites, 1983-1986 ...................... 9-43 9-20 A Comparison of Background and 1986 Mean Ionic (ug/g dry weight) + B.E. of Creosote-Bush (Larrea divaricate) Leaf TTssue .......................'............... 9-44 9-21 A Comparison of Background and 1986 Mean .Ionic Content (vg/g dry weight) + S.E. of Salt-Bush (Arrl lex ~ol car a) Leaf Tissue s

9-45 9-22 Means of Parameters Measured in All Agricultural Soils, Background to 1986 Comparison .........;...................... 9-46 9-23 Comparison Between Background and 1986 Meaps of Soil Parameters for Individual Agricultural Sites ................. 9-47 9-24 Yearly Means of Parameters Measured in All Native Soils, Background to 1986 Comparison ..............'............. "". 9-49 9-25 Comparison Between Background and 1986 Means of Soil Parameters for Individual Native Sites ....................... 9-50 9-26 Dustfall, Soil, and Crop Comparison, Background Period to 1986 ......;............................. 9-52

List of Tables (Continued)

Table Pa<ac 9-3 PVNGS Thermal Energy and Drift Production, 1986 ............... 9-25 9-4 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. at Agricultural Monitoring Sites, Background to 1986 Comparison .. 9-26 9-5 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. at Each Agricultural Site for Sodium, Calcium, and ChToride, Background to 1986 Comparison 9-27 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. at Native Monitoring Sites, Background to 1986 Comparison ............... 9-28 9-7 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. at the Supplemental Monitoring Sites, Background to 1986 Comparison .. 9-29 9-8 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. At Native Monitoring Sites within 1 mile (Excluding the Supplemental Sites), Background to 1986 Comparison ......................... 9-30 9-9 Mean Annual Deposition (Lbs/Acre-Year) + S.E. at Native Monitoring Sites from 1 to 2 Miles from the PVNGS, Background to 1986 Comparison ................................. 9-31 9-10 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. at Native Monitoring Sites Beyond 2 Miles from the PVNGS, Background to 1986 Comparison ................................. 9-32 9-11 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. for Each Native Site for Sodium, Calcium, and Chloride, Background to 1986 Comparison ................................. 9-33 9-12 Mean Monthly Deposition Rates (Lbs/Acre-Month) + S.E. for Selected Native Sites for Sodium and Chloride, (September-December only), Background to 1986 Comparison ...... 9-35 9-13 Mean Annual Deposition Rates (Lbs/Acre-Year) + S.E. for Agricultural and Native Control Sites, Background to 1986 C omparison .................................................... 9-36 9-14 Net Deposition (Lbs/Acre-Year) (Excluding Background) at the Onsite Monitoring Sites During 1986 .................... 9-38 9-15 Measured Versus Predicted Deposition (Lbs/Acre-Year) at the Onstte Monitoring Sites During 1986 ....................... 9-39 9-16 Sequence of Crops Planted at the Agricultural Monitoring Sites in the Vicinity of the PVNGS, 1983-1986 ................. 9-40 9-17 A Comparison of Background and 1986 Mean Ion Content (wg/g dry weight) + S.E. of Alfalfa Leaf Tissue .............. 9-41

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List of Tables (Continued)

Table Pacae 5-8 Ratios of Ionic Constituents in Dustfall Samples and Cooling Tower Basin Water, 1986-............................... 5-18 5-9 Monthly Mean Concentrations of Suspended Particulates (wg/m3) Collected by Low-Volume Air Sampler at Selected Monitoring Locations, January 1-December 31, 1986 ............. 5-19 5-10 Correlation Values, R, Between Deposition and Airborne Concentration of Predominant Ions at Selected Locations, January 1-December 31, 1986 ................................... 5-20 6-1 Mean Ion Content (wg/g dry weight) + S.E. of Alfalfa Leaf Tissue, 1986 ............................................. 6-8 6-2 Mean Ion Content (vg/g dry weight) + S.E. of Cotton Leaf T i ssue e 1986 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 6-9 6-3 Mean Ion Content (eg/g dry weight) + S.E. of Creosote-Bush (Larrea divaricata) Leaf Tissue, 1986 .................... 6-10 6-4 Mean Ion Content (p g/g dry weight) + S.E. of Salt-Bush

(~Atr1 lex ~ol car a) Leaf T1ssue, 198&, ........................ 6-11 6-5 Species Composition, Cover (5), and Diversity of the Flora in Five Creosote-Bush (Larrea divaricata) Comunities in the Vicinity of PVNGS, 1986 ....................................... 6-12 Species Composition, Cover (5), and Diversity of the Flora in Three Salt-Bush (Atri lex spp.) Comunities in the Vicinity of PVNGS, 198 6-14 7-1 Sumary of the 1986 Color Infrared (CIR) Photomission at the PVNGS and Vicinity .................""."."""""" 7-3 8-1 Means and Standard Errors of Parameter Measured in Agricultural and Native Soils, 1986 ........................... 8-4 8-2 Means and Standard Errors of Parameters Measured in Upper and Lower Samples of Agricul.tural and 'Native Soils, 1986 ...... 8-5 8-3 Means and Standard Errors for Parameters Measured in Agricultural Soils During April, August, and December, 1986 ... 8-7 8-4 Means and Standard Errors for Parameters Measured in Agricultural Soils, 1986 ...................................... 8-8 9-1 Monthly Average Meteorological Data for PVNGS, 1986 ........... 9-23 9-2 Monthly Average Meteorological Data for NWS Phoenix, 1986 ..... 9-24

List of Tables Table Pacae 3-1 Monthly Averages of Meteorological Data for.PVNGS and NWS Phoenix for 1986 .......................................... 3-4 3-2 Number of Days with Precipitation Events >0.01 Inch Recorded at PVNGS and NWS Phoenix for 1986 .................... 3-5 3-3 Number of Occurrences of Wind Gusts in Excess of 50 Mph as Recorded at PVNgS for 1986 ....................................

3-4 Monthly Percent Frequency Distributions of Stability Classes Based on Delta T (200 ft-35 ft) for PVNGS for 1986 ............ 3-7 3-5 Meteorological Data Recovery (Percent) at PVNGS for 1986 ...... 3-8 4-1 PVNGS Cooling Tower Source Term Monthly Average Parameters, Unit 1, January-December, 1986 ................................ 4-5 4-2 PVNGS Cooling Tower Source Term Monthly Average Parameters, Unit 2, January-December, )986 ................................ 4-6 4-3 Predicted 1986 Drift Deposition at the Onsite Dustfall Monitoring Locations 4-7 4-4 1986 Cooling Tower Basin Water Analyses Mean Concentrations (mg/1) and Ion Ratios ......................................... 4-8 4-5 Conductivity: TDS Correlation Analyses ....................... 4-9 5-1 Dustfall Program Detection Limits ............................. 5-11 5-2 Deposition Rates (Lbs/Acre-Year) for All Agricultural and All Native Sites for the Period January 1-December 31, 1986 ... 5-12 5-3 Ratios of Deposition Rates (Lbs/Acre-Year) at Agricultural and Native Sites for the Period January 1-December 31, 1986 ... 5-13 Analysis of Annual Means and Standard Errors (Lbs/Acre-Year) of Deposition Rates for Chloride, Sodium, and Calcium for Agricultural Sites, 1986 .................................. 5-14 5-5 Analysis of Annual Means and Standard Errors (Lbs/Acre-Year) of Deposition Rates for Chloride, Sodium, and Calcium for Native Sites, 1986 ........................................ 5-15 5-6 Annual Deposition Rates (Lbs/Acre-Year) at Native Sites by Location, 1986 ............................................. 5-16 Dustfall Deposition Rates (Lbs/Acre-Year) at Agricultural and Native Control Sites for January 1-December 31, 1986 ...... 5-17

Table of Contents (Continued),

~Pa e 9.3 Dustfall Deposition ....................;.................... 9-2 9.3.1 Dustfal1 Deposition Comparisons and Methodology;. 9-4 9.3.2 Dustfal1 Deposition Comparisons at Agricultural S i tes ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 9-5 9.3.3 Dustfall Deposition Comparison at Native (Non-9.3.4 Agricultural) Sites ..............................

Dustfall Deposition Comparison at Agricultural and 9-6 9.3.5 Native Control Sites .............................

Deposition Measurement and Prediction Compari'sons 9-8 9-9 9.3.6 Dustfall Summary and Conclusions ................. 9-10 9.4 Agricultural Crops and Native Vegetation .................... 9-11 9.4.1 Agricultural Crops ................................... 9-11 9.4.1.1 Alfalfa ......................... 9-12 9o4 1o2 Cotton

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o' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ 9-12 9.4.1.3 Cotton Yield .................... 9-13 9.4.2 Native Vegetation .................................... 9-14 9.4.2.1 Creosote-Bush ................... 9-14 9.4.2.2 Salt-Bush .......................

9 .5 Soils Analyses ...........;..................................

9.5.1 Introduction .............................

9-15 9-16

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9.5.2 Methodology .............................. 9-16 esults ..................................

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9.5.3 R ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 9-18 9.5.3.1 Agricul tural Soils .............. 9-18 9.5.3.2 Native Soils .................... 9-19 9.6 Su+nary and Conclusions ..................................... 9-20 10 References ...................................................... 10-1 APPENDICES Appendix A Plant Operating Data Appendix B Cooling Tower Basin Water Appendix C Dustfall Data Appendix D Suspended Particulate Matter Data Appendix E Indigenous Vegetation Data Appendix F Agricultural Vegetation Data Appendix G Soils Data Appendix H Remote Sensing 0

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Table of Contents (Continued)

~Pa e 5.3 E

Suspended Particulate Hatter ..............*.................. 5-8 5.3.1 Sample Collection .................................... 5-8 5 .3.2 Data Analysis ........................................ 5-9 5.3.3 Comparison of Airborne Concentrations and

'ustfall Data ........................................ 5-9 6 Analyses of Agricultural Crops and Native Vegetation ............. 6-1 6.1 Concentration of Selected Ions in Leaf Tissue ............... 6-1 6.1.1 Agricultural Crops ................................... 6-2 6.1.1.1 Alfalfa ..................................... 6-2 r 6~1 ~ 1 ~ 2 Cotton ~ ~ 0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 6-2 g'\

6.1.2 Native Vegetation ....................................

6.1.2.1 Creosote-Bush ...............................

I 6-3 'IV 6.1.2.2 Salt-Bush ...................................

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6 .2 Cotton Yield ................................................ 6-5 6.3 Structure of Native Plant Communities ....................... 6-5 6.3.1 Creosote-Bush ........................................ 6-'6 6 .3.2 Salt-Bush ............................................ 6-.7 7 Remote Sensing/Aerial Photography ................................ 7-1 8 Soil Analyses .................................................... 8-1 8.1 Physical Analyses ....................................... 8-1 8.2 Chemical Analyses ....................................... 8-1 8.2.1 Comparisons of Agricultural and Native Sites ..... 8;1 8.2.2 Ion Comparisons of Agricultural Soils ............ 8-2 8.2.3 Ion Comparisons of Native Soils .................. 8-3 9 Discussion of Comparisons of Parameters ...................... ",

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.1 Meteorology ............................................ " ..' 9-1 9.1.1 General Meteorology and Climatological Comparisons ~ ~ ~ ( 9 1 9.1.2 Effects of Meteorological Parameters on Dustfall, Soils, and Vegetation ............................ 9-1 II 9..2 Plant Operations 9-2

TABLE OF CONTENTS Pa<ac 1 Introduction o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

2 Monitoring Program Su+nary ....................................... 2-1 2.1 Onsite Meteorological Measurements Program .............. 2-1 2.2 Cooling Tower Emissions and Modeling .................... 2-2 2.2.1 Cooling Tower Basin Water ........................ 2-2 2.2.2 Emissions Modeling ............................... 2-2 2.3 Salt Deposition (Dustfall) Measurements ................. 2-3 2.4 Soils Measurements ...................................... 2-4 2.5 Vegetation Measurements ................................. 2-5 2.5.1 Indigenous Vegetation ............................ 2-5 2.5.2 Agricultural Crops ....................,.......... 2-5 2.5.3 Aerial Photography/Remote Sensing ................ 2-6 2.6 Airborne Salt Measurements .................................. 2-6 3 Climatological Summary ........................................... 3-1 3.1 General Climatology ..................................... 3-1 3.2 Meteorological Summary .................................. 3-1 3.3 Meteorological Data Recovery ............................

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~ ~ ~ ~ 3-3 4 Plant Operation .................................................. 4-1 4.1 Cooling Tower Operation ................................. 4-1 4.2 Drift Deposition Modeling ............................... 4-2 4.3 Cooling Tower Basin Water Quality ....................... 4-3 5 Salt Deposition .................................................. 5-1 5 .1 Introduction ............................................ 5-1 5.2 Dustfall Data Collection Summary ........................ 5-1 5.2.1 Special Considerations in Data Evaluation ........ 5-3 5.2.2 Dustfall Deposition Results ...................... 5-3 5.2.2.1 Dustfall Deposition at Agricultural Sites 5-4 5.2.2.2 Dust fa 1 Depos i ti on at Nati ve (Non-1 Agricultural) Sites ..................... 5-5 5.2.2.3 Agricultural Versus Native Paired Control S ites ................................... ~ ~ ~ ~ 5-6 5.2.2.4 I on Rat i Os ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ t ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 5-7 5 .2.3 Conclusions .......................................... 5-7