Economic analysis of artificial recharge and recovery of water in Butler Valley, Arizona
Item Type Thesis-Reproduction (electronic); text
Authors Abe, Joseph M.
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Link to Item http://hdl.handle.net/10150/191885 ECONOMIC ANALYSIS OF ARTIFICIAL RECHARGE AND RECOVERY OF WATER IN BUTLER VALLEY, ARIZONA
by
Joseph Michael Abe
A Thesis Submitted to the Faculty of the DEPARTMENT OF HYDROLOGY AND WATER RESOURCES In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE WITH A MAJOR IN WATER RESOURCES ADMINISTRATION In the Graduate College THE UNIVERSITY OF ARIZONA
1986 STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.
SIGNED:
APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below:
77/k6/4-dA Michael D. Bradley /96 Professor of Hydrology and Water Resources ACKNOWLEDGMENTS
I wish to express sincere thanks to Dr. Michael D.
Bradley, Dr. Bonnie C. Saliba, Dr. Daniel D. Evans, and Floyd L. Marsh for their comments and guidance during the preparation of this thesis. Significant technical contributions were received from Dr. L. G. Wilson and Michael D. Osborn of the Water Resources Research Center, the University of Arizona and Dr. D. N. Contractor of the Department of Civil Engineering, the University of Arizona. I also wish to thank Jessie Fryer for her outstanding job of typing the document and Ann Cotgageorge and Marie Engle for their excellent graphics work. My greatest thanks are extended to my family and close friends whose love and support made this achievement possible. The work upon which this thesis is based was supported in part by funds provided by the U.S. Geological Survey, U.S. Department of the Interior, Washington, D.C., under the Federal Water Resources Research Institute Program. Contents of this publication do not necessarily reflect the views and policies of the U.S. Department of the Interior, nor does mention of trade names or commercial products constitute their endorsement by the U.S. Government. iii TABLE OF CONTENTS
Page LIST OF ILLUSTRATIONS vi LIST OF TABLES viii NOMENCLATURE ix ABSTRACT
1. INTRODUCTION 1 Purpose and Scope 1 Physical Setting 4 Institutional Setting 7
2. LITERATURE REVIEW 9 Artificial Recharge Methods 9 Surface Spreading 10 Recharge Wells 17 Comparing Methods 21 Economic Assessment of Artificial Recharge 24 Defining the Economic Problem 25 Benefits of Artificial Recharge. • • • 35 Costs of Artificial Recharge 38 Comparing Alternatives 39 Summary 41 3. PROJECT ALTERNATIVES 43 Selection 43 Technical Constraints 44 Description of Project Alternatives 47 Design 56 Conveyance System 58 Recharge Facilities 67 Estimating Engineering Costs 69 Capital Costs 70 Annual costs, Maintenance and Energy Costs 75 Computing Unit Costs 79 iv TABLE OF CONTENTS--Continued
Page
4. COST-BENEFIT ANALYSIS 82 Comparing Project Alternatives 82 Recharge Schemes 83 Recharge vs. No Recharge 85 Sensitivity Analysis 91 Benefits 97 Seasonal and Long-Term Storage . . . 97 Existing Ground-Water Resources. . . 99 Option Value 101 Opportunity Costs 103 Water, Energy and Land 103 Other Resources 105 Social Impact Analysis 105 Distributional Effects 106 Environmental Effects 108 5. SUMMARY AND CONCLUSIONS 110 APPENDIX A: DESIGN PARAMETERS FOR CONVEYANCE SYSTEM 116 APPENDIX B: DESIGN OF RECHARGE AND RECOVERY FACILITIES 126 APPENDIX C: COST ESTIMATES AND COMPUTATIONAL PROCEDURES 132 SELECTED BIBLIOGRAPHY 164 LIST OF ILLUSTRATIONS
Figure Page
1.1 Map showing physical boundaries of Butler Valley; inset map showing location in Arizona. . 5 2.1. Map view of interconnected spreading basins and supply ditch (modified from Ansano, 1985) 11 2.2 Series of recharge ponds along section of stream channel (modified from Ansano, 1985). . 15 2.3 Diagram of recharge well showing cone of impression and recharge conduits 18 2.4 Conceptual plan of dual-purpose well field and treatment facilities 20 3.1 Hydrologic continuity between stream sediments and aquifer (after Herndon, 1985). . 45 3.2 Basin hydrogeology of similar alluvial basins in the region; recharge areas shown along basin margins (after Pool, 1984) 46 3.3 Plan A--spreading basins/recovery wells . . • • 49 3.4 Plan B--recharge/recovery wells 51 3.5 Plan C--spreading basins and in-channel recharge/recovery wells (route Y) 53 3.6 Plan D--spreading basins and in-channel recharge/recovery wells (route z) 55 3.7 Map showing selected transmission routes into Valley 60 3.8 Transmission route profile showing total delivery head and components 63
vi vii
LIST OF ILLUSTRATIONS--Continued
Figure Page
4.1 Comparison of Project unit costs with agricultural, municipal and industrial average unit costs in Arizona 89
4.2 Unit cost versus discount rate for Plans A-D 93 4.3 Unit Cost versus design period for Plans A-D 94 4.4 Unit cost versus power rate for Plans A-D 96 LIST OF TABLES
Table Page
4.1 Advantages and disadvantages of Plans A-D. . . . 86
viii NOMENCLATURE
Abbreviation Meaning AF acre-foot (acre-feet) AF/yr acre-feet per year BHP brake horsepower cost (dollars) $/AF cost per acre-foot $/cy cost per cubic yard $/hp cost per unit horsepower $/kwh cost per kilowatt-hour $/lf cost per linear foot cfs cubic feet per second cy cubic yard ft foot (feet) ft/sec feet per second fqyr feet per year ft feet squared gpd gallons per day gpm gallons per minute H total delivery head in inch kw kilowatt(s) kwh kilowatt-hour(s) mg million gallons mgd million gallons per day mi mile O&M operation and maintenance OM&E operation, maintenance and energy ppm parts per million volumetric flow rate sec second WHP water horsepower
ix ABSTRACT
Costs per acre-foot of water artificially recharged and recovered are estimated for selected plans in assessing the economic viability of conjunctive management of Butler Valley, Arizona and imported surface water delivered by the Central Arizona Project (CAP) aqueduct. Proposed artificial recharge methods which are consistent with previous technical studies in the Valley include spreading basins, channel modification and recharge wells. Calculated recharge/recovery costs for selected plans range from $94 to $488, depending on discount rate, design period and power rate. Identified benefits of the Butler Valley Project include seasonal and long-term storage, development of existing ground-water resources and value of assuring access to future water supplies under uncertain physical and socioeconomic conditions. With the implementation of proper water-management strategies, preliminary results indicate that conjunctive management of Butler Valley and CAP water might offer potential benefits to municipalities, industry and agriculture in Arizona. CHAPTER 1
INTRODUCTION
Overdraft of existing ground-water resources in Southern Arizona has directed attention toward measures that might secure future water supplies. Conjunctive management of imported surface water and ground-water basins is one of the alternatives being investigated. Several alluvial basins located along the construction route of the Central Arizona Project (CAP) aqueduct are being examined to determine their conjunctive-use potential (Marsh, 1984;
Herndon, 1985). By storing excess surface water in the alluvial basins during wet periods, reduced water deliveries during seasonal and long-term shortages could be supplemented by ground-water withdrawals. Artificial recharge in the context of this investigation is the process by which surface water is placed into the alluvial basins. Assessment of the desirability of a particular recharge project requires examination of technical, institutional and economic factors.
Purpose and Scope Butler Valley, an alluvial basin adjacent to the CAP aqueduct in west-central Arizona, is a potential site for
1 2 conjunctive-management operations. The purpose of this study is to assess the economic viability of artificial recharge and recovery of water using the Valley aquifer. To accomplish this goal, the following tasks are undertaken: 1. literature review of artificial recharge methods with particular emphasis on economic analysis, 2. selection, design and cost estimation of feasible Project alternatives, 3. cost-benefit analysis of Project alternatives, 4. summarize results, draw conclusions and recommend future investigations. Review of literature on artificial recharge aids in problem formulation and provides insight into methods of project appraisal. Technical studies describe artificial recharge methods used for specific sites. Reported physical characteristics affecting project design include basin hydrogeology, quantity and quality of recharge water, distance and lift requirements to convey recharge water and availability of land, energy and other resources used to conduct recharge operations (Asano, 1985). Selected economic studies identify costs and benefits of artificial recharge and describe procedures used to compare project alternatives. Selection and design of Project alternatives are based on technical studies in the Valley, literature review and discussions with personnel from the University of 3
Arizona, state agencies and private firms. Estimates of engineering costs are derived from consultants' reports, government studies and personal communication. Cost-benefit analysis of the Butler Valley Project consists of two components: 1. quantitative analysis of direct costs, 2. qualitative discussion of benefits and indirect costs. The cost-benefit analysis compares four recharge schemes with each other and against the baseline scheme of no recharge project. Direct project costs are converted to cost/acre-foot of water recovered for each recharge scheme. Subsequent analysis of these costs involves the following questions: 1. Which of the four recharge schemes yields the lowest unit cost? 2. How do these unit costs compare with average unit costs of water in agricultural, industrial and municipal uses? 3. How do discount rate, design period, energy rate, and other variables affect the desirability of Project alternatives? Benefits attributed to conjunctive-management operations in Butler Valley include seasonal and long-term storage, potential use of existing ground-water resources and value of assuring access to future water supplies. 4
Resources used for project development, such as water, land and energy, are identified as opportunity costs. Social impact analysis examines potential distributional and environmental effects of the Project. This study follows the technical prefeasibility report on Butler Valley (Herndon, 1985). The final chapter of this report summarizes results, draws conclusions and recommends future investigations.
Physical Setting Butler Valley is a flat alluvial basin located in west-central Arizona approximately 40 miles southeast of Parker, Arizona (Figure 1.1). The basin, encompassing about 160 square miles, lies between the Bill Williams River and the CAP Granite Reef Aqueduct. The upper end of the Valley is about four miles south of the Alamo Reservoir on the Bill Williams River, while the lower end is less than one mile up gradient from the Cunningham Wash siphon of the CAP aqueduct. Butler Valley is almost completely surrounded by mountains (Figure 1.1). Rectangular in shape, the Valley is bounded by the Buckskin Mountains to the northwest, the Little Buckskin Mountains to the northeast and the Harcuvar Mountains to the southeast. Except for a 1.5-mile wide narrows through which Cunningham Wash drains, the Granite Wash Mountains and Bouse Hills enclose the southwest end of the Valley.
5
1 : j....3.4.3.....1..6., 00° / 10 y ;.. I, , AO/ 4 .€ 1 ‘'1'14 ° >1 .••••"' .----/ ouc'# > e / • I- y >" .4 x 1 )...„. y ...... /....*. ""•n••. 4 ef )•••5° ••%,.. #( e•..,• .< .,------..,e tic.) '‘.._.l r -x—... - - ....-- -. Y 7\ /*;: X 7i ..\ f -.--..- ,‹ ...x x X r-6- A -i ,.00,.. A .ln;'- BOUSE 1 ont HILLS 7 .(04 4 THE NARROWS 4 4 4 'X 4 x A Miles ". Scale: 6 5 ..' ) Y X ...... ! ••' A A dk,
..i. ). e. , _ #141, r .S.1/ Parker CAP GRANITE REEF AQUEDUCT
EXPLANATION -r BOUNDARY BETWEEN PERMEABLE AND IMPERMEABLE ROCKS
Figure 1.1. Map showing physical boundaries of Butler Valley; inset map showing locatiCn in Arizona. 6
Surface drainage of the basin occurs primarily through Cunningham Wash and its tributaries. With the Valley receiving only 8 to 16 inches of precipitation annually, flow in these streams is intermittent (Manera, 1970; Karnielli, 1985). Elevations of the Valley floor range from 1345 feet above sea level near The Narrows to 2000 feet near the Little Buckskin Mountains. Ground slope to the southwest averages about 30 feet per mile. The technical prefeasibility study of Butler Valley evaluated the general hydrogeologic characteristics of the ground-water basin (Herndon, 1985). Gravity and seismic surveys by University of Arizona personnel were used to delineate the basin's perimeter and bottom. The boundary between permeable and impermeable rocks shown in Figure 1.1 also marks the boundary of the alluvial ground-water system. The average saturated thickness of the aquifer above the bedrock is estimated to be 700 to 800 feet. Outflow of ground water through the notch in the southwestern edge of the basin appears to be negligible indicating that the aquifer is a closed hydrologic system. Herndon (1985) evaluated the storage and transmissive properties of the Valley aquifer by evaluating geologic and geophysical logs, analyzing aquifer tests and synthesizing water level and other pertinent data from previous reports. At the current static water level of about 1275 feet above mean sea level (the water level is 7 relatively flat), the quantity of ground water in storage is estimated to be about 12 million acre-feet. Artificial recharge of water into the basin was simulated with a ground-water model (Herndon, 1985). The model indicates between 200,000 to 600,000 acre-feet of storage exists between the current static water level (1275 feet) and the model's upper bound of 1350 feet. Model simulations also indicate that outflow through The Narrows remains negligible even at higher water-level elevations. Recharge plan designs and projection of Project operation in this investigation are consistent with the Herndon (1985) study. Unit costs computed for the four recharge plans represent the cost per acre-foot of water recharged and recovered between the current water-level elevation of 1275 and the upper bound of 1350 feet. Actual regulatory management of the basin could involve pumping water from beneath the current static level (1275 feet), but the cost per acre-foot of this natural water should be evaluated separately from artificially recharged waters. Economic evaluation of existing native ground water is left to future investigations in the Valley.
Institutional Setting The institutional side of the Butler Valley Project is both dynamic and complex. Unresolved institutional problems at the time of this writing include: 8
1. granting authority to the Central Arizona Water Conservation District (CAWCD) to recharge municipal allotments of CAP water into Butler Valley, 2. alteration of existing surface water laws to declare artificial recharge to be a "reasonable and beneficial use," 3. interaction of water and electric power: debate over apportionment of electric power between the CAWCD and two electric power utilities--Arizona Public Service (APS) and Salt River Project (SRP), 4. conflict between municipalities and agricultural groups over availability of recharge water, 5. equity of providing subsidized power rates to a private recharge operator, 6. role of Federal government in artificial recharge projects. In order for the economic analysis to proceed, a recharge project in Butler Valley is assumed to be institutionally feasible. Factors such as available power rates and delivery constraints are discussed in following sections of this report. Subsequent institutional studies could better define the potential for conjunctive-management operations in Butler Valley. CHAPTER 2
LITERATURE REVIEW
Review of literature focuses on technical and economic aspects of artificial recharge. Technical documents provide an overview of available artificial recharge methods and expose important criteria used in selection and design of project alternatives. The economic literature describes problem formulation, identifies costs and benefits of artificial recharge and explains economic procedures used to compare project alternatives. Review of this material exposes some gaps between technical and economic studies on artificial recharge. Technical studies frequently ignore or superficially treat economic factors affecting project desirability. Economic studies, which are few in number, often do not apply to "real world" situations encountered by the water resources planner. An important accomplishment of this study is the integration of technical and economic information in a manner that can be applied to actual project feasibility studies.
Artificial Recharge Methods Artificial recharge describes the set of methods used to replenish aquifers. Reasons for artificial recharge
9 1 0 include seasonal and long-term storage, creation of salt-water barriers, flood mitigation, control of subsidence, and disposal of liquid wastes (Asano, 1985). Butler Valley, a potential underground reservoir for imported surface water, could be used for seasonal and long-term storage. Wilson (1979) divides artificial recharge into two categories: (1) surface spreading (basins, pits and channel modification), and (2) wells and shafts. Selected recharge schemes in Butler Valley include spreading basins, in-channel recharge and recharge wells.
Surface Spreading Surface recharge occurs when water introduced at land surface passes through permeable geologic material and enters into the underlying aquifer (Figure 2.1A). In arid regions, a substantial unsaturated zone usually exists between the land surface and the aquifer. As water infiltrates beneath the channel or basin, a wetting front develops as moisture content of the soil exceeds field capacity (Asano, 1985). Recharge occurs when the wetting front reaches the water table. A ground-water mound develops beneath the basin or channel as infiltrated water reaches the aquifer (Figure 2.1A). Movement and shape of the ground-water mound depends on basin/channel geometry, duration and rate of recharge and 11
SURFACE-SPREADING FACILITY
UNSATURATED l-WETTING FRONT ZONE n
GROUND-WATER MOUND ....------, WATER TABLE -1 - - n -' ) 1/4-- AQUIFER
Figure 2.1A. Development of wetting front and ground-water mound under surface-spreading facility.
Figure 2.1 Map view of interconnected spreading basins and supply ditch (modified from Asano, 1985). 12 hydrogeologic characteristics of underlying material (Freeze & Cherry, 1979).
Initially, a large volume of water is required to wet the zone between land surface and aquifer. However, as spreading occurs year after year, this initial volume becomes less and less significant. Long-term losses from surface spreading are predominantly due to evapotranspiration (Asano, 1985).
Technical factors affecting the feasibility of surface spreading include infiltration rates, depth to water and degree of hydrologic continuity between recharge surface and the aquifer (Wilson, 1979). Basin or channel infiltration rates are controlled by sediment and biological clogging, shallow perching, air entrainment, and temperature and salinity of recharge water (Wilson, 1979; Scalmanini & Scott, 1979). Periodic maintenance such as wet-dry cycling, scraping and discing help maintain maximum infiltration rates (Asano, 1985).
Surface recharge should be avoided in areas underlain by deep water levels (Wilson, 1979). With the presence of a thick unsaturated zone, the travel time between application and recharge may be excessive. In addition, uncertain stratigraphy with depth may cause exploratory drilling to be prohibitively expensive.
The degree of hydrologic continuity between the recharge surface and the aquifer influences the feasibility 13 of surface recharge. The presence of one or several continuous low-permeability layers prohibits surface spreading (Wilson, 1979). Discrete low-permeability layers, although allowing passage of the wetting front, lower the efficiency of recharge/recovery operations. Lateral movement created by these layers may divert recharge water away from intended storage/recovery areas. Even if applied water eventually reaches the aquifer, the time interval between recharge and recovery may be excessive due to the circuitous flow path. Spreading Basins. Spreading basins are shallow surface water impoundments in areas underlain by permeable geologic material (Figure 2.1A). Basins are constructed by excavations and/or building dikes, depending on the local terrain. Conveyance systems such as ditches, canals or pipelines transport recharge water to the basins (Figure 2.1B). Multiple basins constructed in series parallel to supply ditches offer several advantages (American Society of Civil Engineers, 1961). Interconnected basins constructed at successively lower elevations allow delivered water to pass through the system. Basins situated in the upslope areas are often used for sedimentation and recharge (Figure 2.1 3 ). With suspended material largely removed, maximum infiltration rates are maintained in downslope basins. 14 Supply ditches running parallel to the series of basins permit isolation of basins for drying and renovation. Basin shape and orientation affect recharge efficiency. Long, narrow basins allow greater lateral development of the wetting front and reduce the effects of shallow perching (American Society of Civil Engineers, 1961). Placing the length of the basin perpendicular to the prevailing wind direction minimizes evapotranspiration and wave-created dike erosion. Basin facilities are equipped with flow-control devices and monitoring networks (U.S. Army Corps of Engineers, 1979). Devices such as pipes and valves, gates and small dams control flow into and out of basins. A monitoring network measures spreading operations, underground flow and changes in water quality. Monitoring instruments include observation wells, piezometers, tensiometers, weirs, and flow meters. In-Channel Recharge. Artificial recharge using modified stream channels resembles the operation of off-channel spreading basins. Water from artificial or natural sources is conveyed down a series of shallow surface-water impoundments placed along a stream channel (Figure 2.2). Dikes used to confine the water are constructed from channel or nearby sediments. As in the case of off-channel basins, recharge occurs when the wetting front reaches the underlying aquifer. 15 16 Inflatible dams anchored by concrete slabs are often used to regulate flow through the system of recharge ponds. When the dams are inflated, excess water spills over the dam and is distributed to downstream ponds. Dam deflation allows individual ponds to be isolated for drying and renovation. Monitoring networks for in-channel recharge facilities are similar to those described for off-channel basins. Stream characteristics affect the design, operation and maintenance of in-channel recharge ponds (Scalmanini & Scott, 1979). Abandoned stream channels adjacent to a meandering stream may be used with the present channel to increase the spreading area. In order to expose older channel systems to ponded recharge water, fine-grained flood deposits are often removed with earthmoving equipment. The excavated material may in turn be used for dike construction. The magnitude and recurrence interval of natural streamflows influence the operation and maintenance of modified channels. Pond dikes destroyed by large floods are usually replaced at least once a year. Scouring action associated with these high flows also removes fine sediments and algae mats that inhibit infiltration rates. Whenever possible, lower flows captured by the series of ponds are conjunctively managed with artificial water supplies to maximize recharge. 17
Recharge Wells Artificial recharge by wells is most appropriate under three conditions (Wilson, 1979): (1) fresh-water barriers are required to block salt-water intrusion, (2) high land value or restrictions on surface spreading, and (3) presence of one or several low-permeability layers prohibits surface spreading. Recharge wells with some modifications are constructed similarly to ordinary water wells. During recharge, a mound or cone of impression develops around the recharge well (Figure 2.3). The driving force of well recharge is the difference between the head inside the well and the head in the surrounding aquifer (Freeze & Cherry, 1979). Recharge rate is directly proportional to this head difference. Other factors controlling well intake rates include silt and microbial clogging, air entrainment and chemical reactions between recharge water and aquifer (Wilson, 1979). In order to maintain high intake rates, operation and maintenance of a recharge well system includes water treatment prior to recharge and periodic well development (Asano, 1985). Water treatment which includes flocculation, sedimentation, filtration, and chlorination removes fine sediments, bacteria and algae that tend to clog the well openings and surrounding aquifer material. Periodic well development maintains the gravel pack surrounding the well 18
DUAL-PURPOSE WELL
7
PUMP COLUMN (USED AS RECHARGE CONDUIT)
CONE OF IMPRESSION
\ WATER TABLE
RECHARGE CONDUIT 2 WELL OPENINGS
)
••n110
4fn •n•••••n••
Figure 2.3. Diagram of recharge well showing cone of impression and recharge conduits. 19 that enables free passage of recharge water into the aquifer. Sternau (1967) and Wilson (1979) recommend dual-purpose well systems. By using the same wells for both recharge and recovery, well construction and conveyance-system capital costs can be greatly reduced. Two operational advantages of dual-purpose wells are: (1) installed pumps may be used for well development and recovery of stored water, and (2) recently recharged water may be recovered quickly. Recharge water may be conducted down the pump column and/or down small-diameter pipes placed in the annular space between the well casing and pump column (Sternau, 1967; Figure 2.3). To maximize recharge and pumping efficiency, the bottom openings of recharge conduits should remain submerged (Sternau, 1967; Contractor, 1985). By maintaining a closed-flow system, pumping costs are reduced by minimizing the required delivery head. Air entrainment which reduces intake rates is also avoided. Conveyance systems such as buried concrete pipelines transport water to and from the recharge/recovery well field (Figure 2.4). Valves installed at the wellheads and along the pipe network control the movement of water. A monitoring network measures pipe flow, ground-water movement and water-quality changes (U.S. Army Corps of Engineers, 1979). 20
WELL FIELD r
OBSERVATION WELL
RECHARGE/RECOVERY WELL a DISTRIBUTION MAIN
TREATMENT PLANT TO WATER DELIVERY 1 1 SYSTEM
SETTLING BASINS
STREAM
...... •n•••••••n......
Figure 2.4. Conceptual plan of dual-purpose well field and treatment facilities. 21
Monitoring instruments include flow meters, observation wells and water-level recorders.
Comparing Methods Comparing surface spreading with recharge wells provides insight into the selection of Project alternatives. Advantages of Surface Spreading: 1. Construction costs are generally much lower for spreading facilities than recharge wells. This is particularly true in areas where land and earthwork are inexpensive. 2. Operation and maintenance costs are generally lower. In many cases, little or no water treatment is required prior to surface recharge. Conveyance costs are minimal in areas where natural channels and unlined ditches may be used. 3. Large volumes of water may be recharged rapidly. Surface recharge is particularly suitable for flood mitigation and conjunctive use with surface reservoirs (U.S. Army Corps of Engineers, 1979). Combinations of channel modification and off-channel spreading are often used for this purpose. 4. Temporary storage prior to recharge is offered by surface facilities. In addition, head buildup enhances infiltration rates at a low cost (Wilson, 1979). 22 5. Channel modification takes advantage of natural hydrologic connections with the underlying aquifer. Channel sediments are often highly permeable. Recharge in streams also provides aesthetic and environmental benefits. Disadvantages of Surface Spreading: 1. Percentage of applied water actually recharging the aquifer is lower than that of recharge wells. Evapotranspiration accounts for most of these losses. 2. Time interval between recharge and recovery may be substantial. Factors affecting the recharge/recovery interval include basin hydrogeology and the distance from recharge site to recovery wells (Asano, 1985). 3. Land proposed for recharge might be high-valued or unsuitable for surface spreading. Economic, institutional and environmental factors may restrict land use (U.S. Army Corps of Engineers, 1979). 4. Natural factors may affect the operation and maintenance of surface facilities. Floods and rodents may cause severe damage to dikes and other structures. Algae growth can inhibit infiltration rates (Wilson, 1979). 5. Surface recharge may be hazardous or annoying in
urban areas if proper measures are not taken . . Problems associated with improper design, operation 23
and maintenance of surface impoundments include flash flooding, potential for drownings and insect breeding (Scalmanini & Scott, 1979). Advantages of Recharge Wells: 1. Recharge wells introduce water directly into the aquifer without loosing significant quantities to evapotranspiration and the unsaturated zone. If water treatment costs are minimal, recharge wells can be competitive with surface spreading (Cella Barr Associates, 1985). 2. Recharge by wells may be the only viable means of artificial recharge. Conditions prohibiting surface spreading include land resrictions and the presence of continuous low-permeability layers (Wilson, 1979). 3. Water recharged by wells may be recovered quickly and efficiently. The time between well recharge and recovery is short when compared with the lag period between surface spreading and recovery. In addition, slow movement of stored water often allows recovery of water via the same well used for recharge. These considerations may be significant for seasonal or short-term conjunctive management plans. 24
4. Recharge wells may reduce conveyance costs. By maintaining a closed-flow system, pumping costs may be lowered due to a decrease in delivery head (Contractor, 1985). Disadvantages of Recharge Wells: 1. Construction costs of recharge-well systems are generally much higher than surface-spreading facilities. Well and treatment plant construction are the major capital costs. 2. Operation and maintenance costs of recharge-well facilities are higher due primarily to water treatment prior to recharge (Asano, 1985). In some cases, maintaining the head gradient between the well and aquifer is expensive (Scalmanini & Scott, 1979). 3. Recharge capacity of wells is much smaller than surface-spreading facilities. Contributing factors include limited recharge surface and minimal storage prior to recharge (American Society of Civil Engineers, 1961).
Economic Assessment of Artificial Recharge Economic assessment of an artificial recharge project involves problem formulation, identification of costs and benefits and determining the best method for comparing project alternatives (National Water Commission, 1973). Although technical material on artificial recharge is 25 abundant, those articles and reports dealing specifically with economic assessment of recharge projects are few in number. Much of the identified economic literature deals with mathematical models that are developed for the conjunctive management of surface water and ground water Chun, Mitchell, & Mido, 1964; Dracup, 1966; Mawer & O'Kane, 1970). While aiding in the operation of existing recharge facilities, these models fail to provide guidance at the feasibility level of project development. Some economic literature pertaining to the evaluation of natural resources point out useful criteria used in project appraisal (Hartman & Seastone, 1970; Kelso, Martin, & Mack, 1973; Jeske et al., 1980). Economic handbooks such as Sassone and Schaffer (1978) describe general methods used in cost-benefit analysis. While helping to set up the basic economic problem, all of the above material provide little assistance in addressing site-specific problems. Butler Valley provides a unique opportunity to blend technical and economic methods into an integrated procedure for assessing the economic desirability of artificial recharge. The procedure developed by this study might prove useful in feasibility studies of other recharge projects.
Defining the Economic Problem In early stages of cost-benefit analysis, considerable time and effort should be spent on defining the 26 economic problem (Sassone & Schaffer, 1978). By explicitly stating the direction of analysis, problems such as unnecessary data collection and inconsistent planning may be avoided. Sassone and Schaffer (1978) list the following components of problem formulation: 1. selection and design of project alternatives, 2. determine scope of study, 3. identification of data sources, 4. determine project constraints, 5. selection of variables for sensitivity analysis, 6. direction and scope of social impact analysis.
Project Alternatives. Selection and design of Project alternatives evolve as technical and institutional information become available. Initially, three sources of recharge water were considered: 1. diversion from the CAP aqueduct near the southwest end of the Valley (The Narrows area), 2. diversion of Bill Williams River water from Alamo Lake (northeast end of Valley), 3. capture of natural runoff within the Valley. To facilitate the analysis, the economic study considers only diversion of CAP water. Excessive lift (about 950 feet) and institutional constraints eliminate the Bill Williams River alternative. Runoff volume (about 15,000 acre-feet/year) as reported by Manera (1970) and Karnielli (1985) is considered insignificant when compared to 27 potential CAP diversions (up to 250,000 acre-feet/year) (Dozier, 1985). The final set of Project alternatives consist of four artificial recharge schemes using CAP water and the baseline scheme of no recharge project (see Chapter 3). Important criteria affecting the selection of recharge schemes are basin hydrogeology and topography.
Scope of Study. The scope of study is determined by addressing two questions: 1. What benefits and costs should be attributed to the Project? 2. Who would be affected by the Project? Benefits and costs should reflect changes in society's well-being, or social welfare, brought about by project alternatives (Mishan, 1976; Saliba, 1985). Four Project alternatives expose potential changes in social welfare due to an artificial recharge project in the Valley. The fifth or baseline alternative examines social welfare if no recharge plan is implemented. In reality, changes in social welfare cannot be measured. Estimates of social welfare changes are expressed in monetary terms whenever possible (Sassone & Schaffer, 1978). Project costs such as construction, operation and maintenance can easily be evaluated in dollar terms. Other items such as benefits due to securing water supplies are difficult to measure. Cost-benefit analysis provided in 28
Chapter 4 assesses both quantitative and qualitative effects attributed to Project alternatives. Direct project costs should include only those costs arising from proposed diversion, recharge and recovery operations within the Project area (Saliba, 1985). Post-recovery delivery expenses are justifiably excluded from the quantitative analysis of direct costs. Project costs attributed directly to Butler Valley are capital costs and annual operation, maintenance and energy costs. Unit costs (Vacre-foot) calculated for the four recharge schemes are derived exclusively from these estimates. Important operational expenses normally attributed to recharge projects are costs associated with diversion rights (Hartman & Seastone, 1970). These costs may include purchase of water and canal space to the point of diversion. However, in the case of Butler Valley, the purchase price of water and institutional arrangements needed for diversion are uncertain elements at the time of this writing. For these reasons, costs associated with diversion rights are omitted from the quantitative analysis of direct costs. Opportunity costs of diverting recharge water are discussed qualitatively in Chapter 4. General benefits and indirect costs are identified by reviewing economic studies on artificial recharge (Mawer & O'Kane, 1970; Nebraska Water Resources Institute, 1975; Saliba, 1985; et al.). Factors used to isolate specific 29 items associated with the Butler Valley Project include project objectives, geographic location and resources used in recharge schemes. Society describes those people and regions affected by a particular project (Sassone & Schaffer, 1978). Society for the Butler Valley Project as chosen by the author includes only individuals served by the CAP aqueduct. Reasons for this decision are: 1. The primary Project objective is conjunctive management of imported water and the Butler Valley aquifer. The CAP aqueduct is the principal vehicle used to import water into Arizona. 2. Regulatory storage in the Valley may dampen fluctuations in CAP deliveries. Offering flexibility to the CAP system, the benefits and costs would strongly affect individuals served by the system. 3. Practical constraints such as time and budget limit the analysis to Arizona. Furthermore, the CAP will serve most of the State's population. Municipalities, agriculture and industry are the three major water-using groups in Arizona. The effects of the Butler Valley Project on each of these groups are discussed in Chapters 4 and 5. Data Sources. Important data sources identified by the author include government documents, engineering consultants' reports, conference papers and selected 30 bibliographies. In addition, personal communication with personnel from the University of Arizona, state agencies and private firms aided in all aspects of this study. Project Constraints. Technical and institutional factors are chosen as the principal constraints affecting this study. The previous technical study by Herndon (1985) describes basin hydrogeology, identifies potential recharge areas and simulates recharge in the Valley with a computer model. Coupling this technical information with perceived institutional constraints enables the selection, design and analysis of Project alternatives. Institutional constraints include operational criteria, available power and interest rates, and distributional and environmental effects of the Project. In addition, time and budgetary constraints dictate the depth of economic analysis. Sensitivity Analysis. Sensitivity analysis examines the impact of selected variables on the desirability of project alternatives (Sassone & Schaffer, 1978). The principal variables selected in this study are discount rate, power rate and design period. Social Impact Analysis. Social impact analysis in this study is divided into two parts: (1) distributional effects and (2) environmental effects. The first section addresses the following questions: 1. Which groups or individuals will benefit from the Project? 31
2. Which groups or individuals will bear the Project costs? 3. Are the benefits and costs equitably distributed? The second section examines potential environmental changes attributed to the Project: 1. aquifer degradation, 2. impact on Valley wildlife and vegetation,
3. impact on current land use in the Valley. While enumeration of the study's components provides a basis from which to address the problem, the complexity of the economic issues merits further discussion. Fundamental questions to be addressed by Arizona water planners are: 1. Is there a need to increase the water supply? 2. If supply augmentation is necessary, what size and
type of project(s) should be built and when?
3. What are the most suitable locations for the
project(s)? Relatively low prices for water in many parts of the West have lead to wasteful use even in an arid environment.
Kelso, Martin and Mack (1973) refer to the water valuation problem in Arizona in the following passage: "the Arizona water problem is more a problem of the lack of man-made institutions (policies) for developing and transferring water than a problem of physically short supplies." 3 2 These authors suggest that water should be dealt with as an economically scarce resource. By increasing the price of water, the lowest-valued (often high volume) uses are reduced. Modification of water demand through pricing strategies is gaining popularity as an alternative to supply augmentation (Kindler & Russel, 1984). Reasons for the increased popularity include expense of water projects, scarcity of available sites, increasing energy costs, water-transfer disputes and decreasing Federal involvement. An important goal of the water resources planner is to equate water supply with growing water demand (Goodman, 1984). A frequent error in water planning is to project water demand as being singularly dependent on population growth (Kindler & Russel, 1984). Planners assume a constant water use per capita and build a supply system to meet extrapolated demand. An expensive water project is built which ultimately leads to higher water rates. Consumers respond to higher rates by using less water. Because the planners fail to consider the effect on changing water rates on water demand, the net result is water-supply development before it is needed. The location of the water project affects the magnitude and distribution of associated benefits and costs (Hartman & Seastone, 1970). Although water carries a low monetary price in the arid Southwest, the importance of the resource is exemplified by the growing number of water 33 disputes (Arizona v. California, 1963; El Paso v. Reynolds,
1984). The legal ramifications of a water project should be carefully examined prior to the commencement of construction. While reducing water demand can postpone water-supply development, it is only one of several policies needed to satisfy Arizona's future water needs. Arguments favoring pricing strategies as suggested by Kelso et al.
(1973) and Kindler and Russel (1984) assume water to be a market good. In Arizona, the current political atmosphere favors a perception of water as a public good. Passage of the 1980 Groundwater Management Act and the recall of Tucson water officials after a water rate increase (Martin, Ingram,
Laney, & Griffin, 1984) demonstrate an unwillingness to allow market forces to fully control water use. Persuasive advertisement and public awareness programs are the preferred methods for lowering water demand. Given the reluctance to adopt rigid pricing strategies, supply augmentation will continue to play a significant role in Arizona's future. The optimal size and timing of a project such as Butler Valley are determined by subsequent technical, economic and institutional studies. A pilot project refines technical and economic information by conducting small-scale recharge/recovery operations at the project site. Research goals of a pilot study include: 34
1. identifying the best area(s) for recharge, 2. identifying the best recharge method(s), 3. establishing the time interval between recharge and recovery, 4. monitoring environmental effects of the project, 5. estimating available storage within the aquifer 6. establishing the recharge/recovery efficiency (engineering), and 7. recording the cost of recharge/recovery operations. An important goal of subsequent economic studies is to examine the relationship between water supply and demand as it affects the Project's feasibility. Ideally, the appropriate size and timing of a recharge project are determined by equating marginal costs of project development and operation with marginal benefits of the project (Mishan, 1976). Available economic models on artificial recharge might prove useful in determining the optimal development of recharge projects (Chun, Mitchell & Mido, 1964; Dracup, 1966; Mawer & O'Kane, 1970). Both economic and institutional studies provide assistance in determining the best location for a recharge project. Economic studies comparing Butler Valley with other proposed recharge sites in Arizona could provide information to decision-makers on the relative merits of each project. Institutional studies could identify the best management schemes, assess the political impact of selected 35 recharge projects, and propose useful solutions for overcoming institutional conflicts.
The principal goals of this study are (1) estimate direct costs, (2) discuss benefits and indirect costs, and
(3) describe potential socioeconomic effects of the Project. By accomplishing these goals, this study provides the framework for subsequent investigations in Butler Valley and other recharge studies in Arizona.
Benefits of Artificial Recharge General benefits attributed to artificial recharge are identified by reviewing Harpaz (1970), Mawer and O'Kane
(1970), Nebraska Water Resources Institute (1975), and Asano
(1985). Benefits exposed by this review include: 1. seasonal and long-term storage, 2. establish gradients to prevent intrusion of low-quality waters, 3. reduce overdraft and water-level decline, 4. control of subsidence, 5. dispose of and/or purify wastewater, 6. reduce dangers inherent with surface impoundment of water, 7. minimize evapotranspiration losses, 8. mitigation of floods,
9. recharged aquifer acts as delivery system. Specific benefits identified for the Butler Valley
Project are items 1, 6 and 7. Seasonal and long-term storage 36 of imported surface water are considered the most important benefits of the Project. By storing water during the off-peak months (September through May), sufficient supplies would be available during peak demand (June, July and August). Long-term storage in anticipation of dry years might free Arizona water consumers from inevitable fluctuations in the Colorado River. Benefits 6 and 7 are considered intrinsic advantages of underground storage over surface reservoirs. Water, once stored deep beneath the ground, is removed from evapotranspiration losses common to surface impoundments. Associated benefits realized by eliminating surface-storage facilities include: 1. continued access to land and associated resources--minerals, timber, farmland, wildlife, and amenities, 2. elimination of risk due to potential dam failure, 3. reduced expenditures for land purchase, insurance and environmental impact studies. The remaining benefits not attributed to Butler Valley are generally afforded in urban and coastal areas. Significant advantages of artificial recharge in urban areas include reduction of ground-water overdraft, control of subsidence and replenishment of ground-water resources with treated wastewater and surface runoff (Harpaz, 1970). In urban areas that are largely dependent on ground water (e.g. 37
Tucson, Arizona and Long Island, New York), the underlying aquifer also acts as a distribution system to users (Asano,
1985). Orcutt (1967) mentions the benefits of continued high-valued land use and aesthetic quality of recharge ponds on parks and golf courses. Benefits realized in populated areas in the form of cost-savings include (Asano, 1985): 1. reduced lift costs, 2. reduced well-replacement costs, 3. mitigation of damage caused by subsidence, and 4. natural filtration of percolating wastewater reduces treatment expenses. Prevention of salt-water intrusion is a considerable benefit of artificial recharge in coastal areas. Two areas in the United States, Orange County, California and Long Island, New York, have used recharge wells for this purpose for many years (Asano, 1985; Johnson, 1975). Both examples indicate that artificial recharge by wells is an expensive operation. Butler Valley, removed from urban areas and salt-water bodies, lacks the previous benefits attributed to urban and coastal areas. However, the remoteness of the Valley may facilitate institutional arrangements needed to conduct a recharge/recovery program. Recharge in populated areas often involves substantial litigation costs over the protection of 38 recharged waters. This is not the case in Butler Valley. While the 1980 Groundwater Management Act removed absolute state ownership of water beneath the Valley, state control over 95% of the land discourages illicit withdrawals from the Valley (Rusinek, 1984). This fact coupled with the Valley's proximity to the CAP aqueduct and the Colorado River provide significant incentives for strategic storage in the Valley. Establishing recharge and recovery rights in Butler Valley could be significantly less expensive than providing the same rights in urban recharge areas.
Costs of Artificial Recharge Costs associated with artificial recharge projects are identified by reviewing Mawer and O'Kane (1970), Nebraska Water Resources Institute (1975), Scalmanini and Scott (1979), U.S. Army Corps of Engineers (1979), and Asano (1985). Important factors contributing to the cost of an artificial recharge project include: 1. quantity and quality of recharge water, 2. recharge method, 3. distance from diversion point to recharge site, 4. availability and value of land, 5. energy requirements and available power rates, 6. hydrogeologic characteristics of aquifer, 7. institutional constraints, 8. opportunity costs of storing water. 39
All of the above items influence the costs of • proposed recharge schemes in Butler Valley. The significance of each item with respect to the desirability of Project alternatives is discussed in Chapters 3, 4 and 5.
Comparing Alternatives Determining the best method for comparing project alternatives is accomplished by reviewing selected handbooks on cost-benefit analysis (Mishan, 1976; Sassone & Schaffer, 1978). The most acceptable procedure advocated by these authors is the net present value method (NPV). This method requires summing the time stream of benefits minus costs for each project alternative. The general form of the equation is: + B -C + B +C + B-C B0-0 0 1 1 t t n n NPV = 1 t (1+1) ° (1+1) (1+1) (1+1)n (eq. 2.1) where C t = costs estimated in dollars at time t, in dollars at time t, B t = benefits estimated B t -C t = net benefits, i = discount rate, and n = design period of the project, in years. A single project yielding a net present value of zero or greater is considered economically desirable. Among a set of project alternatives, the project yielding the highest net present value is the preferred alternative. The most significant problem with this method is the choice of 40 discount rate (i). For this reason, a range of values is normally used in cost-benefit analysis. Equation 2.1, however, is not appropriate for this study since monetary estimates are only assigned to direct costs. Estimating the dollar value of benefits is left to future investigations. The following equation, a modified version of equation 2.1, includes only cost terms in the numerator: Co •+ C C C 1 + t + n ) 1 n PV (Costs) = (1+1° (1+1 (1+1)t (11)+ where (eq. 2.2) PV (costs) = the sum of present values of costs incurred at the end of each time period, t and Ct , i and n are as previously defined. Equation 2.2 is used to convert projected capital costs and annual operation maintenance and energy costs into their present values. By discounting future costs, plans with different time streams of costs may be compared in an equivalent manner. To allow comparison of recharge alternatives on an annual basis, an additional equation equivalent to equations 2.1 and 2.2 is also used in the analysis. Referred to as the annual cost method, this equation converts the sum of discounted capital costs and annual operation, maintenance and energy costs into constant annual costs over the chosen design period of the project (Goodman, 1984): 41
X [i (1+1) n I AC = PV (costs) (eq. 2.3) where AC = equivalent annual cost. The term within the brackets is commonly known as the "capital recovery factor." Subsequent division of annual cost by the annual average recharge/recovery rate during Project operating years yields the cost per acre—foot ($/AF) for each recharge scheme: Cost($/AF) = Annual cost($) Annual Average Recharge/Recovery Rate (AF/yr) (eq. 2.4) Obtaining the unit cost of each recharge scheme enables: 1. comparison between alternative recharge schemes, 2. comparison with average costs of agricultural industrial and municipal water uses.
Summary Literature review of technical and economic aspects of artificial recharge provides the preliminary framework needed to address the Butler Valley economic problem. Important data gathered by the review include: 1. general design and operation of recharge facilities, 2. technical and economic considerations affecting selection and design of project alternatives, 42 3. steps used in problem formulation, 4. effects of complex economic issues on project development, 5. general benefits and costs of artificial recharge, 6. economic procedures used to analyze project alternatives. Cost-benefit analysis attempts to expose differences in social welfare with or without a proposed project. In predicting the social consequences, the analyst assesses both quantitative and qualitative effects attributed to the project. As applied to Butler Valley, cost-benefit analysis compares four recharge schemes with each other and against the baseline scheme of no recharge project. Calculating the unit cost ($/AF) is identified as the best method for comparing Project alternatives. While the general approach to the problem is identified, this review also exposes a need to fuse technical and economic studies on artificial recharge. All too frequently investigators from different disciplines proceed along separate paths while evaluating the same project. Synthesizing information from a variety of fields is an essential function of the water resources planner. This study helps fill some of the gaps that exist between technical and economic investigations on artificial recharge. CHAPTER 3
PROJECT ALTERNATIVES
Synthesis of technical, institutional and economic information enables the selection, design and cost estimation of Project alternatives. The set of five Project alternatives consists of four recharge schemes and the baseline scheme of no recharge project. Design of each recharge scheme includes: (1) conveyance system, (2) recharge facilities, and (3) recovery system. Estimates of capital costs and annual operation, maintenance and energy (0M&E) costs are derived from government documents, engineering consultants' reports and personal communication with personnel from the University of Arizona, state agencies and private firms.
Selection Selection of recharge schemes is based primarily on technical constraints. Important technical factors include basin hydrogeology and topography. Brief descriptions of selected Project alternatives are provided at the end of this section.
43 44
Technical Constraints Basin Hydrogeology. Herndon (1985) identifies two potential areas as suitable for surface recharge: 1. Cunningham Wash and its major tributaries, and 2. basin margins along the mountain fronts. These findings by Herndon (1985) are based on field hydrogeologic investigations, review of previous technical studies and recharge simulations with a computer model. Recharge along Cunningham Wash and its tributaries is strongly dependent on hydrologic continuity between the channel bed and the underlying aquifer (Figures 3.1A and B). Figure 3.1A shows a low-permeability layer restricting the passage of recharge water. For in-channel recharge to occur in the Valley, basin hydrogeology must be as shown in Figure 3.1B. Under these conditions, recharge water passes freely through sediments beneath the channel and into the underlying aquifer. Mountain-front recharge implies hydrogeologic conditions in Butler Valley are similar to other alluvial basins in the region (Figure 3.2) (Pool, 1984). The absence of low-permeability layers along basin edges allows recharge water to pass freely into the underlying aquifer. Herndon (1985) identifies the northwest and southeast edges of the Valley as potential recharge areas. The approximate land 45
CUNN/NGHAM WASH PERCHED WATER
EXPLANATION
..6 PERMEABLE STREAM SANDS AND GRAVEL LOW-PERMEABILITY SEDIMENTS PERMEABLE ALLUVIUM
Figure 3.1A. Non-hydrologic continuity between stream sediments and aauifer ('fter Herndon, 1985).
CUNN/NGHAA1 WASH
EXPLANATION 40 0 ,0, • 0 0 1 PERMEABLE STREAM SANDS AND GRAVEL LOW-PERMEABILITY SEDIMENTS PERMEABLE ALLUVIUM
Figure 3.1. Hydrologic continuity between stream sediments and aauifer (after Herndon, 1985). 46 47 elevations of these areas are 1600 and 1700 feet, respectively.
Herndon (1985) and Wilson (1985) identify the central, lower portion of the Valley as the most suitable location for both dual-purpose and recovery wells. Unrestricted by the presence of low-permeability layers, wells placed in the central portion of the Valley penetrate the greatest thickness of the aquifer thus allowing maximum recharge and recovery. Due to the low elevation and proximity to the CAP aqueduct, placement of wells in this area also reduces pumping and pipeline expenses. Topography. Using topographic maps of the Valley, potential transmission routes are identified by observing breaks in relief near the southwest end of the Valley. Selected recharge schemes incorporate different transmission routes to help distinguish the most economical route into the Valley.
Description of Project Alternatives Given available technical information, conceptual plans are developed to reflect possible Project alternatives. Assumptions made in design of recharge schemes are discussed in the next section. The set of five Project alternatives selected for cost-benefit analysis consist of: 1. Plan A: spreading basins/recovery wells,
2. Plan B: recharge/recovery wells, 48
3. Plan C: spreading basins and in-channel recharge/recovery wells (route Y), 4. Plan D: spreading basins and in-channel recharge/recovery wells (route Z), 5. Plan E: baseline scheme--no recharge project. Plan A. Plan A proposes delivery of CAP water to recharge basins near the northwest and southeast edges of the basin (Figure 3.3). The diversion point is near the inlet of the Cunningham Wash siphon of the CAP aqueduct. As shown in Figure 3.3, recharge water is distributed to basins via transmission mains and unlined ditches (not all ditches are shown). A small siphon under Cunningham Wash and its major tributary allows continuation of the unlined ditch to the southeast spreading area. Design capacity of the recharge facilities is 100,000 acre-feet/year (AF/yr). One-hundred-twenty-six spreading basins each 11-acres in area lie within the two stipled areas shown in Figure 3.3. Distribution ditches adjacent to the basins deliver recharge water and allow isolation of individual basins. During monthly spreading operations, only 63 basins receive recharge water during the first two-week period. Awaiting recharge 14 days later, the remaining 63 basins dry and undergo renovation. A monitoring network measures spreading operations, underground flow and water-quality changes. 49
EXPLANATION
-i--!- r BOUNDARY BETWEEN PERMEABLE AND IMPERMEABLE ROCKS TRANSMISSION MAIN
UNLINED DITCH
• RECOVERY WELL SIPHON SPREADING AREA ( BASINS)
Figure 3.3. Plan A--spreading basins/recovery wells. 50
The well field is designed to recover 100,000 AF/yr. Thirty-nine recovery wells each with a capacity of 2,000 gallons per minute (gpm) are installed in the low central area near the Valley outlet. A transmission main and lateral
networks convey pumped water back to - the CAP aqueduct. Plan B. Plan B proposes a rectangular network of 78 dual-purpose wells arranged parallel to the strike of the basin (Figure 3.4). Branching laterals and dual-transmission mains (two pipes laid side by side) convey water to and from the well field. A system of valves along the pipes and at the wellheads control flow through the system. Monitoring wells measure ground-water flow and water-quality changes. When compared with the other three recharge plans, Plan B requires a larger pipe cross-sectional area for both recharge and recovery operations. Reasons for the greater cross-sectional area include: 1. lower pipe velocities are more compatible with well recharge operations, 2. permits full utilization of 78-well recovery system within suggested pipe velocity limits (Henningson, Durham & Richardson, 1984), 3. pumping costs during recharge are reduced by maintaining low pipe velocities. Cross-sectional area may be increased by using a larger pipe or two pipes. Plan B is designed with dual mains rather 51
EXPLANATION -r -r BOUNDARY BETWEEN PERMEABLE AND IMPERMEABLE ROCKS TRANSMISSION MAIN TREATMENT FACILITY
o RECHARGE/RECOVERY WELL
Figure 3.4. Plan B--recharge/recovery wells. 52 than a single larger-diameter pipe because of certain advantages: (1) cross-overs between dual mains allow for pipeline maintenance without shutting down, and (2) pipe diameters remain in the range of standard-size pipes. Material costs of non-standard pipe are considerably higher than those of standard pipe. To prevent clogging of well openings and aquifer material, an on-site treatment facility removes fine sediments, algae and bacteria from the CAP water prior to recharge. Treatment processes include flocculation, filtration and chlorination. During the recharge phase, both the pump column and annular space between column and well casing are used to conduct treated water down to the well openings. The average recharge rate per well is 1000 gpm. The design capacity of the recharge phase is 100,000 AF/yr. Recovery capacity of each well is 2000 gpm. The network of 78 wells is capable of capturing 200,000 AF/yr. Plan C. Plan C proposes delivery of CAP water to the southeast spreading basins and into the Cunningham Wash and its major tributary about 11 miles northeast of the basin outlet (Figure 3.5). Diverted near the outlet of the Cunningham Wash siphon of the CAP aqueduct, CAP water is delivered to recharge facilities at lower cost by reducing delivery head and pipeline length. Unlined ditches are used 53
orPt 40- ‘14
0'6'4
,.. // Ibi >. / Scale: Mils e '''ISIt"...x ,,,. / i• 6 X A, ‘7-- -r -r -r.
Bill Williams Rise,
SUTLER VAL'-:Y Phoenix CAP GRANITE REEF AQUEDUCT
EXPLANATION
-r -r BOUNDARY BETWEEN PERMEABLE AND IMPERMEABLE ROCKS TRANSMISSION MAIN
n n al on= •••• UNLINED DITCH • RECOVERY WELL IN—CHANNEL RECHARGE SPREADING AREA (BASINS)
Figure 3.5. Plan C--spreading basins and in-channel recharge/recovery wells (route Y). 54 whenever possible to distribute water to recharge facilities. About 43,000 acre-feet (AF) of water are spread on fifty-four 11-acre basins in the southeast area. The remaining 57,000 AF are conveyed to a series of sixty-five 6-acre ponds along Cunningham Wash and its major tributary. Monthly spreading operations and monitoring networks for both facilities are similar to those described in Plan A. Total annual recharge capacity is 100,000 AF/yr. The recovery well field, identical to the one described in Plan A, has a recovery capacity of 100,000 AF/yr. Plan D. Plan D proposes delivery of CAP water to the same areas described in Plan C (Figure 3.6). Diverted near the Cunningham Wash siphon outlet (same as Plan C), CAP water is delivered to an unlined ditch via the same transmission main used to recover water. Unlined ditches sloping away from the delivery point convey recharge water to the channels and the southeast spreading basins. Spreading operations are identical to those described in Plan C (43,000 AF to spreading basins; 57,000 AF to in-channel ponds). Total annual recharge capacity is 100,000 AF/yr. 55
p
EXPLANATION
BOUNDARY BETWEEN PERMEABLE AND IMPERMEABLE ROCKS -r -r -r TRANSMISSION MAIN — — UNLINED DITCH • RECOVERY WELL ' —IN—CHANNEL RECHARGE SPREADING AREA (BASINS)
Figure 3.6. Plan D--spreading basins and in-channel recharge/recovery wells (route Z). 56
As described in Plans A and C, thirty-nine wells each with a capacity of 2,000 gpm are in place to recover 100,000 AF/yr.
Design Designs of recharge schemes are consistent with available technical information on the Valley and standard engineering-design principles. Diversion-point elevations along the CAP aqueduct range from 1308 to 1312 feet. Elevations of recharge areas within the Valley are: 1. 1440 to 1680 feet along the central axis of the dual-purpose well field (Plan B), 2. 1520 to 1600 feet along the northwest edge of the basin (Plan A), 3. 1570 to 1595 feet at the recharge intake of Cunningham Wash and its major tributary (Plans C and D, respectively), 4. 1660 to 1700 feet along the southeast edge of the basin (Plans A, C and D). As suggested by the elevation differences between diversion points and recharge areas, recharge water must be lifted up into the Valley. Lifting water is accomplished with pumping plants and buried concrete pipelines. Plans A, C and D reduce conveyance costs by using unlined ditches to distribute pumped water to recharge facilities within the Valley. Delivery of recharge water to the southeast 57 spreading area requires an additional lift. Elevations of spreading areas are the same for similar schemes. With the exception of the recovery phase of Plan B, annual single-purpose (recharge or recovery) design capacity is 100,000 AF/yr for all four plans. Reasons for using this particular design capacity include: 1. Given the potential storage and diversion volumes, 100,000 AF/yr seems to be a reasonable number (Wilson & Bradley, 1985). 2. The Herndon (1985) model uses 100,000 AF/yr in simulation runs. 3. This number facilitates project design and computation of costs. To remain consistent with the unit cost calculations of the other three plans, Plan B is limited to only one-half of its recovery capacity (or 100,000 AF/yr). The optimum design capacity is normally determined in later stages of project development. Given the level of information at the time of this writing, the assumed value of 100,000 AF/yr is adequate for the purposes of this study. All four recharge plans are designed to operate at maximum capacity during 80% of the year (292 operating days). The main reason for this decision is the likely inability to recharge during peak water-demand periods. Other factors include potential downtime due to machinery 58 failure, uncertainty in water demand, inaccessibility to low power rates, and institutional conflicts. To accommodate 100,000 AF within 292 operating days, all phases of operation are oversized by 25%. Selected recharge schemes are designed with the following components: (1) conveyance system, (2) recharge facilities, and (3) recovery system (U.S. Army Corps of Engineers, 1979).
Conveyance System The conveyance system refers to all engineering works required to transport recharge water from the CAP aqueduct to recharge facilities within the Valley. To simplify the discussion, the conveyance system is divided into the following categories: 1. transmission routes, 2. pumping plants, 3. pipelines, 4. discharge works, 5. unlined ditches. Transmission Routes. Transmission routes represent the closed sections of the conveyance system through which water is pumped to higher elevations. Potential transmission routes for the proposed recharge plans are identified by examining topographic maps of the southwest 59
end of the Valley. Transmission routes identified by this study include (Figure 3.7): 1. route V: Bouse Hills pumping plant to northwest spreading area, 2. route W: Cunningham Wash siphon inlet to northwest spreading area, 3. route X: unlined ditch to southeast spreading area, 4. route Y: Cunningham Wash siphon outlet to unlined ditch along southeast edge of basin, 5. route Z: Cunningham Wash siphon outlet to unlined ditch in central portion of basin. Route V was originally considered to take advantage of existing pumps, service equipment and electrical power at the Bouse Hills pumping plant of the CAP aqueduct. However, institutional constraints and rugged topography eliminate this alternative (Gatlin, 1985). Route W is proposed in Plan A. This route takes advantage of the natural notch (The Narrows) at the southwest end of the Valley. Initially, this route was chosen to minimize the elevation head difference between the diversion point (near the siphon inlet) and recharge areas in the Valley. However, when pipeline friction is taken into account, the savings in lift due to reduced elevation head (about 4 feet) are insignificant.
6 0
t45
01 l •
.A., /CS n ...... ' X oç,....„, S t.1N- A t4 ›1›... x ...... --- — \..\4.5 OG14)4 >1 .1 k oc 1, YXx X Y • / '4.- )0' ...... /I-0* ''...... - X .>•›.. ' ••,... .. r X e' " 110.112". . . 7 • \_24 .. -4— ' - %....-_,,. 7\ X Y : I : '-' x *./ \ v \• -n d I .1 1 , -..< 00...\--/ A b MIL— N SOUSE C" o X HILL5 / ..l 4 .< 4 ot41°5 .../ 4 Çi ROUTE X A. -6---THE ,/ oe 4 x NARROWS *.›. A ,mil as 1. Scale: 5
EXPLANATION
BOUNDARY BETWEEN PERMEABLE AND IMPERMEABLE ROCKS TRANSMISSION MAIN ---UNLINED DITCH
Figure 3.7. Map showing selected transmission routes into Valley.
5t? 61
Route X with some variations in length is proposed in Plans A, C and D to lift recharge water to the southeast spreading area (Figure 3.7). Originally, Plans A and D placed route X along the northeast edge of the spreading area. After careful examination of the cost tradeoffs between pipeline length, pumping and ditch construction, the southwest edge was identified as the best location of route X for all three plans. Route Y, proposed in Plan C to convey water into the Valley, takes advantage of a small notch in the Granite Wash Mountains. Requiring the shortest length of pipeline, route Y may prove to be the most economical route for delivering CAP water into the Valley. Route Z, coinciding with the route used to recover water, is proposed for Plans B and D. This alternative examines the cost effectiveness of using the same transmission main for recharge and recovery. A system of pump/hydropower turbines might prove to be economically desirable with such a plan. Commonly used with pump-storage facilities, these dual-purpose devices would pump water during recharge and generate electricity during recovery. The generated power could help offset some of the lift costs associated with the network of wells (Matlock, 1985). Pumping Plants. Pumping plants in series convey water through buried reinforced concrete pipelines to higher 62 elevations within the Valley. Preliminary design of pumping stations along a transmission route involves calculating: (1) total delivery head, (2) water horsepower, (3) brake horsepower, and (4) electric power. Total delivery head is the sum of suction head, elevation head and friction head (American Society of Civil Engineers, 1975). To facilitate the calculation of delivery head, suction head is combined with elevation head. Total delivery head in feet (ft) along a transmission main is simply the sum of the elevation difference between the pipe intake and discharge and friction loss along the pipeline (Figure 3.8): TOTAL DELIVERY HEAD (FT) = ELEVATION + FRICTION DIFFERENCE (FT) LOSS (FT) (eq. 3.1) Water horsepower (WHP) is the energy required to move water at a given volumetric flow rate (Q) against the total delivery head (H) of the water delivery system. If Q is expressed in gpm, WHP is calculated with the following equation (American Society of Civil Engineers, 1975): QXH WHP = 3960 (eq. 3.2) where Q = volumetric flow rate (gpm), and H = total delivery head (ft). Mechanical energy required to pump water through a delivery system always exceeds the WHP due to losses in 63
a.%
••n••
o u.t cc u- U) U. fa El 0 1 -I Z 0 0 P ' 2 4 I.- > (..) w I CI. - I IAA 1 64 energy conversion. Brake horsepower (BHP), the actual power needed to move water through the system, is calculated by dividing wHp by the efficiency (%) of energy conversion. Using an efficiency of 75% (Henningson, Durham, & Richardson, 1984), the equation for calculating brake horsepower is: WHP BHP = 0.75 (eq. 3.3) Conversion from brake horsepower to electic power in kilowatts (kw) involves (Metcalf & Eddy, Inc., 1979): ELECTRIC (KW) = BHP X 0.745700 (eq. 3.4) POWER Appendix A provides sample calculations of equations 3.1-3.4 and tabulates values of discharge, total delivery head, water horsepower, brake horsepower and electric power for Plans A-D. Pipelines. The choice of reinforced concrete as the pipe material is consistent with similar-scale recharge projects (Nebraska Water Resources Institute, 1975). Selection of pipe diameter involves a tradeoff between installed pipe costs and pumping costs (Walker, 1978). Unit costs of installed pipe in dollars per linear foot ($/lf) rise dramatically with increasing pipe diameter. In contrast, pumping costs which are directly related to pipe velocites decrease with larger pipe diameters. Reasonable engineering design dictates pipe velocities to be in the general range of 4 to 6 feet per second (ft/sec) to reach a 65 near-optimal tradeoff between pipeline costs and pumping costs (Henningson, Durham, & Richardson, 1984). Velocities in this range also preclude settling of fine sediments in the pipeline. Pipe-diameter selection in Plans A, C and D is consistent with the suggested velocity range of 4-6 ft/sec (American Society of Civil Engineers, 1975). Plan B adopts a slightly broader range (2.5-6 ft/sec) to accommodate the slower velocities associated with well recharge and utilize the full recovery capacity of the well field. Pipe lengths and diameters used in Plans A-D are provided in Appendix C. Discharge Works. Water carried in the transmission mains flows at several times the velocity of channel flow in the unlined ditches. To regulate flow from pipelines to the ditches, Plans A, C and D use (1) lateral pipes and valves and (2) transition canals. Lateral pipes from the transmission mains allow diversion of recharge water at various elevations in the northwest and southeast spreading areas (Appendix A). Due to high pressures in the mains, isolation valves are used to regulate flow from the pipes (Walker, 1978). To prevent erosion in the unlined ditches, transition canals are situated along the first 100 feet in the vicinity of pipe discharge. Narrow and deep at the discharge point, the canals gradually widen and maintain a 66 flat grade throughout the entire canal length. The sides and bottom are lined with 3-inch thick concrete (Gatlin, 1985). Unlined Ditches. Recharge water pumped into the Valley is distributed by unlined ditches to recharge facilities (Plans A, C and D). The design velocity of the ditches is 1.5 ft/sec. This velocity allows for adequate transport and maximizes recharge potential from the ditches (Wilson, 1985). The minimum cross-sectional area (A) of each ditch is calculated with the following equation:
A = — V where, (eq. 3.5) Q = volumetric flow rate in cubic feet per second (cfs) v = average velocity in ditch (ft/sec) Ditches are designed with trapezoidal cross sections and two-to-one side slopes (Henderson, 1966). Nominal cross-sectional areas are slightly larger than the cross-sectional area (A) calculated in equation 3.5 to accomodate the influx of sediments. The slope required to maintain a uniform velocity of 1.5 ft/sec in each ditch is calculated by using a modified form of the Manning equation (Henderson, 1966): vn s 1 . 486R2/3 =[ (eq. 3.6) where, n = Manning's roughness coefficient (dimensionless) A R = hydraulic radius = f (ft) 67
A = cross-sectional area
P = wetted perimeter
and v is as previously defined. Appendix A provides sample calculations of equations
3.5 and 3.6 and tabulates elevations, hydraulic variables
and dimensions of ditches used in Plans A, C and D. Design parameters for the siphon in Plan A are also included.
Recharge Facilities Surface Spreading. The area (A) required for surface spreading is a function of the long-term infiltration rate
(I) and the application rate (Q) (Wilson, 1979): A = 2 where
A = land-surface area (acres),
Q = annual application rate (AF/yr)
I = long-term infiltration rate, feet per year (ft/yr)
A sample calculation using equation 3.7 and acreage
requirements for Plans A, C and D are provided in Appendix
B.
Two values of I are used in the study: (1) 182.5 ft/yr in the northwest and southeast spreading areas and (2)
365 ft/yr in the Cunningham Wash and its major tributary. Channel sediments appear to be significantly more permeable than soils along the basin margins (Abe & Osborn, 1985;
Herndon, 1985). Both estimates of I are somewhat 68 conservative when compared with similar projects in California (California Department of Water Resources, 1983; Wilson & Marsh, 1985). Future soil surveys could better establish infiltration rates in the Valley. Designs of spreading facilities conform closely with criteria described in Chapter 2. Conceptual plans for spreading basins and in-channel ponds are presented in Appendix B. Recharge Wells. The number and spacing of wells parallel the assumptions used in the Herndon (1985) model of the Valley. Recharge rate per well is assumed to be one-half the discharge rate. Frictional losses accompanying the reverse flow (i.e. through recharge conduits, well openings and aquifer material) account for the reduced efficiency during recharge (Sternau, 1967; Appendix A). Seventy-eight wells each with a capacity of 1000 gpm are capable of recharging 100,000 AF within 292 operating days. Conceptual design of proposed dual-purpose wells is provided in Appendix B. Treatment plant design mimics the design of proposed facilities for treating CAP water prior to delivery to Tucson, Arizona residents (Tucson Water, 1983). Removal of sediments, algae and bacteria which prevents clogging of well openings and aquifer material is recommended for 69
long-term operation of recharge wells (Wilson, 1979; Asano, 1985). Recovery System. Design and discharge capacity of recovery wells are similar to irrigation wells in the Valley area. With each well capable of recovering 2,000 gpm, 39 wells are needed to recover 100,000 AF in 292 days. Centrifugal pumps driven by electric motors lift water to the land surface. Appendix B contains the conceptual design of recovery wells. Laterals and mains convey pumped water back to the CAP aqueduct. Pipe diameters are selected to conform with suggested flow velocity limits (4 to 6 ft/sec; Henningson, Durham & Richardson, 1984).
Estimating Engineering Costs Engineering costs for each recharge plan consist of capital costs and annual OM&E costs. Appendix C contains itemized costs for Plans A-D. Cost estimates are derived from engineering consultants' reports, government documents and personal communication with personnel from the University of Arizona, state agencies and private firms. Given the level of this study, sources dated within one year of this study are considered sufficiently accurate. Unit costs are used whenever possible to facilitate future cost refinement. Two reviews were conducted to verify cost estimates and procedures: 70 1. internal review among University of Arizona personnel, and 2. external review by personnel from State agencies and private firms. Suggested revisions identified by these reviews were used to refine final estimates of project costs.
Capital Costs Land and Easements. Implementing a recharge project in Butler Valley requires State control over land in the Valley (Bradley, 1985). At the time of this writing, a land swap between the United States Bureau of Land Management and the Arizona State Land Department is in progress (Bibles, 1984). Federal lands in Butler Valley are to be exchanged for various State parcels. The State land acquired by the Federal government will be used in a larger transaction to compensate the Zuni and Navajo Tribes. Uncertain costs of the land swap include (Bibles, 1984): 1. administration and litigation costs, 2. decontamination of military lands in the Valley (parts of the Valley were used to train General Patton's tank corp), 3. surveying 16,525 acres in the Valley prior to title exchange, and 4. land appraisals. 71 Given the difficult task of evaluating the above costs, a lump sum of $500,000 is included in each of the recharge plans to cover these expenses. A better estimate could be established at later stages of project development. Conveyance System. Conveyance system costs include the following items: 1. pipelines and control valves, 2. pumping stations, 3. discharge works, and 4. unlined ditches. Estimates of pipeline expenses are calculated by multiplying the lengths of selected-diameter pipelines by their associated unit costs ($/lf). Unit costs which include material and installation are derived from Henningson, Durham and Richardson (1984). Unit costs of control valves are also obtained from this report. Estimates of pumping station costs are calculated by multiplying total brake horsepower of each plan by cost/unit horsepower ($/hp) (Appendix A). The unit cost of $850/hp is established by examining cost curves prepared by James M. Montgomery (1985), reviewing Henningson, Durham and Richardson (1984) and communicating with Johnson-Brittain & Associates (1985). Discharge works include lateral pipes, control valves and transition canals. Unit costs of laterals and 72 valves are derived from Henningson, Durham and Richardson (1984). Construction costs of transition canals are estimated by multiplying unit cost of in-place concrete ($200/cubic yard (cy)) by volume of concrete used in construction (Johnson-Brittain & Associates, 1985). Unlined ditch construction costs include the excavation cost and construction cost for weirs along the ditches. The unit cost ($2.50/cy) for excavation is established from personal communication with Gatlin (1985) and Johnson-Brittain & Associates (1985). Multiplying total excavated volume by unit cost determines the ditch construction cost for each plan. Given the unit cost of in-place concrete ($200/cy), a sum of $500/mile is considered sufficient to cover weir construction expenses. Recharge and Recovery Facilities. Both spreading and in-channel ponds are constructed largely with earth material. Making use of on-site soils, the construction cost is calculated by multiplying the volume of earth used in construction by the unit cost of earthwork ($/cy). Communications with Gatlin (1985) and Johnson-Brittain & Associates (1985) produce a unit cost of $2.50/cy as a rough estimate for earthwork. Field inspection by contractors is necessary to obtain more accurate estimates. Review of U.S. Army Corps of Engineers (1979) and recent engineering documents aided in establishing initial 73
cost estimates of control devices and monitoring networks for the basins, ponds and wells. Comments received from the previously mentioned reviews and communication with Wilson (1985) provide the following refined estimates: 1. $10,000/basin--control valves, gates and pipes, 2. $5,000/basin--monitoring network, 3. $38,000/pond--inflatable dam with anchoring concrete structures, 4. $2,500/pond--monitoring network, 5. $5,000/well--flow meter and instrumentation. Cost estimates of recovery wells and dual-purpose wells are obtained from reviewing Arizona Field Crop Budgets, La Paz County (1985) and communicating with private well drillers in Arizona. Conceptual designs of both well types are presented in Appendix B. Cost per well are as follows: 1. $120,000/recovery well, 2. $150,000/dual-purpose well. The higher cost for dual-purpose wells takes into account design modifications that are needed for well recharge. Costs of the treatment facility used in Plan B are crudely estimated by reviewing Tucson Water (1983). The actual costs which might vary significantly are usually refined at later stages of project development. 74
Other Costs. Additional capital costs include the following items: 1. structures, equipment and site improvements, 2. services and contingencies, 3. interest during construction. Structures, equipment and site improvements refer to those secondary items essential to the operation of a recharge/recovery facility. These items include buildings, site work, maintenance roads, equipment and miscellaneous tools and accessories (Nebraska Water Research Institute, 1975; Asano, 1985). Cost estimates are obtained by reviewing reports on similar-scale projects and communication with technical personnel from the University of Arizona, state agencies and private firms. Services include the professional expertise of engineers, planners, hydrogeologists, soils scientists, surveyors, and other qualified personnel used in the development of a recharge project. Contingencies are the unexpected design alterations and cost overruns that are experienced during construction. Both items are approximated as ten percent of the total capital cost of each plan (Goodman, 1984). Interest during construction is an estimate of the cost of providing capital during the construction period. All four plans assume a construction period of three years. 75
Interest during construction is calculated with the following equation (Goodman, 1984): INTEREST DURING = TOTAL COST INCLUDING CONSTRUCTION SERVICES AND CONTENGENCIES X ONE-HALF THE CONSTRUCTION X PERIOD (1 1/2 years)
X INTEREST RATE (i).
(eq. 3 .8 )
Annual Operation, Maintenance and Energy Costs Operation and Maintenance. Initial estimates of operation and maintenance (O&M) costs were obtained by reviewing reports on similar-scale projects (Nebraska Water Resources Institute, 1975; California Department of Water Resources, 1983). Comments received from the two reviews and refinement by the author produce the following list of costs: 1. project staff and overhead, 2. renewals and replacements, 3. road maintenance, 4. conveyance system O&M, 5. recharge facility O&M, 6. recovery system O&M. 76
Professional staff for each plan include a civil engineer as project manager, a hydrogeologist and two hydrologic technicians. Supporting staff and overhead include secretaries, lab assistants, laborers, and miscellaneous administrative expenses. Estimates of these costs parallel current salaries and expenses for similar projects in Arizona. Renewals and replacments refer to the costs of maintaining structures and equipment in good operating condition over the project design period (Goodman, 1984). These costs are estimated roughly as ten percent of the annualized capital cost for each plan. Access to project facilities in the Valley is required for routine operation and maintenance. Given the layout of each plan, estimates of maintenance road mileage and construction cost are provided in Appendix C. One and one-half percent of the road construction cost is used as an estimate for annual road maintenance cost for each plan. Estimates of conveyance system O&M costs are obtained from the reviews of Henningson, Durham and Richardson, Inc. (1984) and California Department of Water Resources (1983). Each plan provides 1.5% of the capital cost/conveyance system to cover these expenses. Recharge facility O&M costs for spreading basins and in-channel ponds consist of basin/channel renovation, dike 77 replacement and pest control. A fee of $20/acre is estimated as the unit renovation cost by examining costs of scraping and discing as reporting in Arizona Field Crop Budgets, La Paz County (1985). The cost of basin/channel renovation for each plan is calculated by: ANNUAL RENOVATION COST = UNIT RENOVATION COST ($20/acre) X MONTHLY SPREADING AREA (acres/month) X SPREADING PERIOD (months/year). (eq. 3.9) Annual dike replacement costs are assigned a percentage of the initial capital cost: 1. basin dikes--10% of capital cost, 2. pond dikes--100% of capital cost. Recharge ponds operating within a channel are subject to substantial flood damage. For this reason, plans using in-channel recharge ponds assume total dike replacement averages at least once a year. Pests such as rodents and mosquitoes often need to be controlled while operating surface spreading facilities. A sum of $10,000/year is assigned to Plans A, C and D for this purpose (Rhone, 1985). 78 Recharge O&M for Plan B is expected to be proportionately more expensive than other forms of O&M due to treatment facility operation (Johnson-Brittain & Associates, 1985). Plan B uses three percent of the recharge facility capital cost as an estimate of this cost. Recovery system O&M costs for all four plans are based on an annual unit cost of $5,000 per well. This estimate is derived from a fee of $100/hour established by private well drillers for well maintenance and development. Energy Consumption. Electrical energy consumption for all four plans consists primarily of two components: (1) conveyance to recharge facilities and (2) pumping of recovery wells. Appendix A lists the quantities of electrical power (kw) that are required for delivering CAP water to recharge facilities in Plans A-D. Annual electrical energy consumption (kilowatt-hours, kwh) during recharge operations is calculated with the following equation:
ANNUAL ELECTRICAL = ELECTRICAL X 24 hours/day ENERGY CONSUMPTION (kwh/year) POWER (kw) X 292 operating days/year (eq. 3.10)
The conveyance cost varies with the cost per kilowatt-hour ($/kwh): 79
ANNUAL CONVEYANCE = ANNUAL ELECTRICAL COST ($) ENERGY CONSUMPTION X ENERGY (Kwh) RATE ($/kwh) (eq. 3.11) The energy cost associated with pumping recovery wells varies with depth to water (ft) and volume of water recovered (AF). To simplify calculations, an average lift of 284 feet is assumed to represent the recovery well fields for Plans A-D (see Appendix C). Calculating the lift costs per acre-foot ($/AF) involves the following equation (Arizona Field Crop Budgets, La Paz County, 1985):
1.024 (LIFT (ft)) LIFT COST/AF - 0.54 X POWER RATE ($/kwh) (ea. 3.12) Calculating the recovery cost ($) for each plan involves multiplying recovery volume (AF) by the unit lift cost
($/AF). An additional sum of $30,000 is included in all; four plans to cover other forms of energy consumption. These include heating and cooling of buildings and fuel used by equipment and vehicles.
Computing Unit Costs Computing unit cost ($/AF) includes the following procedures: 80
1. calculating the present value of capital costs over the 3-year construction period, 2. calculating the present value of projected OM&E costs, 3. summing the above present values and calculating their equivalent annual costs over selected design periods, 4. dividing total annual costs by average annual recharge/recovery rate during the Project operating years. To simulate a feasible project development schedule, grand total capital costs are divided equally over three years of construction (Appendix C). The equivalent present value of the three construction increments is calculated by using equation 2.2. Annualized capital costs for recharge scheme are calculated with equation 2.3. Approximation of annual OM&E costs is accomplished by using three selected operational scenarios (Appendix C). These scenarios are developed arbitrarily to provide a range of average recharge/recovery rates over the operating years of the Project--26,000, 50,000 and 57,000 AF/year. Given the level of this study, this method for projecting operation, maintenance and energy is considered adequate. Subsequent studies might incorporate a coupled physical-economic model to simulate Project operations (Maddock, 1974). 81
Four annual functional modes are considered in this study: 1. recharge (292 days) 2. recovery (292 days) 3. recharge (292 days)/recovery (73 days) 4. recharge (3 months)/recovery (3 months) The cost of each of these modes in 1985 dollars is determined by segregating appropriate OM&E expenses (Appendix C). Present values of projected costs (using scenarios 1, 2 and 3) are calculated and summed with equation 2.2. Equation 2.3 calculates equivalent annual costs of OnE over the selected design periods. Total annual cost for each scheme is obtained by adding annualized capital costs and annualized OM&E costs Dividing total annual cost by annual average recharge/recovery rate produces an estimate of cost/AF for each plan. A computer program developed by the author facilitates the above calculations and allows substitution of different values for discount rate (i), design period (n) and power rate (PR). Copies of the program, input and output files are provided in Appendix C. CHAPTER 4
COST-BENEFIT ANALYSIS
Cost-benefit analysis assesses the potential impact of the five Project alternatives on people served by the CAP system. The three major water-using groups served by the system are municipalities, industry and agriculture. Estimating changes in social welfare involves quantitative analysis of direct costs and qualitative discussion of benefits and indirect costs. Components of the cost-benefit analysis are: 1. comparing Project alternatives, 2. discussion of benefits, 3. discussion of opportunity costs, and 4. social impact analysis.
Comparing Project Alternatives Project alternatives are compared by examining the following relationships: 1. recharge schemes with each other, 2. recharge schemes against the baseline alternative of no recharge project (Plan E), and
82 83 3. sensitivity analysis--assessing the impact of discount rate, design period, power rate, and other variables on the desirability of Project alternatives.
Recharge Schemes Unit costs for Plans A-D range from $94 to $488 per acre-foot recovered, depending on various input variables (Appendix C). These variables include 1985 capital and OPME costs, discount rate, power rate, and design period. The three chosen scenarios which reflect potential Project operation sequences also affect unit costs. Among the set of values examined by this study, specific values of discount rate, design period and power rate are considered most appropriate: 1. discount rate (i) = 8%, 2. design period (n) = 27 years, 3. power rate (PR) = $0.036/kwh. A discount rate of 8% approximates the rate of 8 3/8% established by the United States Department of Interior for evaluating all Federal water resources development projects in fiscal year 1985 (Federal Register, 1984). A design period of 27 years which includes 3 years of construction and 24 operating years is considered a sufficient projection, given the level of this study. Longer projections require more accurate estimation of renewal and 84 replacement costs since many Project elements could wear out by this time (Goodman, 1984). Shorter design periods, on the other hand, might neglect future Project benefits prior to their fruition. Finally, a power rate of $0.036/kwh which represents generation from the Navajo Power Plant seems to be the most likely power rate allocation to the Project at the time of this writing (Rusinek, 1985). Assuming the above values for discount rate, design period and power rate, the following unit costs ($/AF) are computed for scenario 1:
Plan A Plan B Plan C Plan D $153 $248 $130 $137 Scenario 1 represents the simplest version and lies between the other two extremes (scenarios 2 and 3; Appendix C). Note that Plan C yields the lowest unit cost of the set. Review of Appendix C indicates that Plan C produces the lowest unit cost under all tested conditions. Savings attributed to transmission route Y appear to be most significant factors contributing to the low unit cost of Plan C. Plan B, the most expensive alternative under all tested conditions, is strongly affected by: (1) capital costs of the 78 dual-purpose wells and (2) capital and O&M costs of the treatment facility. These results are consistent with cost estimates of similar well recharge operations in other parts of the nation (Asano, 1985). 8 5
Each of the four plans has intrinsic advantages and disadvantages. Table 4.1 lists some of the identified items.
Recharge vs. No Recharge Comparing the four recharge schemes against the baseline scheme of no recharge project is accomplished by examining the average unit costs of water ($/ AF) facing agricultural, municipal and industrial users under the present condition of no recharge project in the Valley. Prior to this analysis, a short discussion of costs of supplying water to these users is required. The cost of supplying each acre-foot of water to the three major water-using groups may include the following components: 1. capture and conveyance cost from water source to site of use, 2. cost of storing water, and 3. treatment costs. Depending on the type of water use, geographic location and time of use relative to demand, the total unit cost of supplying water for a particular use may include some or all of the above items. Recharge/recovery costs arising from the Butler Valley Project would be only part of the supply costs facing potential users. In addition, the actual distribution of costs to different groups and areas within •
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• • r-i (N) V") 'Tr 88 the State is dependent on institutional arrangements regulating the use and transfer of water. Figure 4.1 depicts graphically the differences between Project unit costs and total average unit costs of agriculture, municipalities and industry (Bush, 1984; Johnson, 1985; Stinett, 1985). Average unit costs are used to simplify the analysis. Actual total costs facing the three major water-using groups may range significantly from these estimated values. Comparison of Project unit costs with total average unit costs is somewhat misleading in that some cost items are deliberately deleted. Actual total costs facing direct beneficiaries of the Project would likely include purchase price of water, delivery costs and treatment costs. However, the uncertain value of these items and the study's scope limit the depth of analysis. The purpose of Figure 4.1 is to expose differences between existing total unit costs and potential recharge/recovery costs of the Project. Figure 4.1 shows the unit costs of all four plans exceed the average unit costs of agricultural uses in areas served by the CAP. Total private costs of farmers using ground water in these areas is about $60/acre-foot (Bush, 1984). Given the low rate of inflation during the 1985 year, estimates by Bush (1984) for farmers using future deliveries of CAP water are adequate for this study. Average cost per 89
500 500
400 400
lii Or 300
tee 248 220 200
153 137 130 100 85 60
0 A BCD AGG AGS PIM TI TM
EXPLANATION BUTLER VALLEY PROJECT (Recharge! Recovery Costs) PLAN A: Spreading Basins/Recovery Wells PLAN B : Recharge/Recovery Wells PLAN C : Basins and In-Channel Recharge/Recovery Wells (Route Y) PLAN D : Basins and In-Channel Recharge/Recovery Wells (Route Z) MAJOR WATER-USING GROUPS (Total Costs) AGG: Agriculture Using Ground Water in CAP-Served Areas AGS Agriculture Served by CAP PIM: Phoenix Industrial and Municipal Use T I : Tucson Industrial Use TM Tucson Municipal Use
Figure 4.1. Comparison of Project unit costs with agricultural, municipal and industrial average unit costs in Arizona. 90 acre-foot of CAP water delivered to these farmers is estimated to be about $85. Although Project costs appear too high for agriculturalists, the Project may still yield benefits to many farmers in CAP-served areas. Several factors may offset the apparent differences between Project unit costs and average unit costs of agriculture: 1. Both Project unit costs and agricultural unit costs are only estimates. Future studies might depict a more favorable economic picture for agriculture. 2. Private costs of pumping ground water do not reflect the true social cost of ground-wa t er overdraft. Social costs include the adverse effects (i.e., reduced water levels, subsidence) caused by the individual pumper on other ground-water users. The overall social cost to both present and future users might exceed Project unit costs. 3. Indirect project benefits may be substantial. Increased water supplies might allow water exchanges between agriculture and other water users. Unit costs for Plans A, C and D are substantially lower than municipal and industrial average unit costs in both Tucson and Phoenix (Figure 4.1). Plan B, on the other hand, appears to be too expensive for the Phoenix area under the present pricing structure. These results suggest that a 91 recharge program in Butler Valley at least deserves further scrutiny. Finally, all four plans are considerably below the current average costs of industrial and municipal use in Tucson. Butler Valley may prove to be a useful storage facility for Tucson, especially in light of the CAP construction schedule. Diversion of Tucson's allotment of Colorado River water into the Valley prior to completion of the Tucson reach of the CAP aqueduct would allow capture of waters that otherwise would be used by other downstream users--principally California and the Republic of Mexico. The potential use of the Valley as a strategic underground reservoir for imported surface waters is gaining political support in the State (Bradley, 1985). All of these findings are preliminary and require additional inspection. To be economically desirable, benefits from the Project should outweigh the costs of implementing the Project. In other words, Arizonans served by the CAP should be better off with the Project than without the Project. Subsequent evaluation of Project benefits could better determine potential changes in social welfare.
Sensitivity Analysis Several factors influence the unit costs of Project alternatives. The principal variables examined in this study 92 are discount rate, design period and power rate. Other factors include the timing and scale of project development and the physical efficiency of recharge/recovery operations. Discount Rate. Three values of discount rate (i), 4%, 8%, and 10%, provide a sufficient range of unit cost estimates. Figure 4.2 shows the changes in unit costs with respect to i for Plans A-D. Unit costs of A, C and D appear to change at about the same rate (i.e., same slope) throughout the selected range. Plan B, however, shows a much steeper slope and hence a greater sensitivity to discount rate. The high capital cost of Plan B relative to the other three plans explains this behavior. Design Period. The results of varying design period (n) are as anticipated: 1. increase design period, 2. further discounting of future costs, 3. lowers unit costs of Project. Using n=27 and 51 years, Figure 4.3 demonstrates declining unit costs with greater design periods. A strategy of extending the design period can be misused to make expensive projects appear more desirable. Note the greater unit cost reduction (i.e., negative slope) of Plan B when compared to the other plans. Power Rate. Three feasible power rates are examined in this study (Rusinek, 1985): 93
300 -
g,
-
100 -
0 I I I 4 8 10
DISCOUNT RATE (i),%
Figure 4.2. Unit cost versus discount rate for Plans A-D. 94
cIIIIQ Z z Z Z zI szt < < __JI J —J --i a_I oJaiIO -
1 i I i 1 0 0 0 0 0 O 0 tO 10 0 -tO N N
(J.4 - 3:13 /Ciit) 1S00 liNn 95
1. $0.008/kwh--Hoover Dam A, 2. $0.011/kwh--Hoover Dam B, 3. $0.036/kwh--Navajo Power Plant. Figure 4.4 shows lower unit costs for all four plans with lower power rates. Close examination of the slopes of these lines reveals Plan B to be less sensitive to reductions in power rates than Plans A, C and D. The small conveyance cost relative to the high overall cost explains this difference.
Other Factors. Unit costs of Plans A-D are also affected by the time and scale of Project development and the physical efficiency of recharge/recovery operations. Project unit costs are inversely related to annual average recharge/recovery rates over the Project's operating years (equation 2.4). This average rate in turn is strongly dependent on the timing and capacity expansion of the Project with respect to water supply and demand. In other words, optimal use of the Project involves building a facility which equates " marginal costs of expansion with marginal benefits of additional capacity " (Saliba, 1985). Subsequent economic studies could determine: 1. whether or not additional storage is needed, and 2. if needed, the size and time of construction. The physical efficiency of recharge/recovery operations is dependent on hydrogeologic and engineering considerations discussed in Chapter 2. Surface spreading may 96
03 4 CI C.)
Z Z Z <<4 —J —J —1 —.I a. 0-
O 0 0 0 0 O to 0 (iA-3aowS) isoo
9'1 97 be particularly sensitive to this factor. A pilot study could address the following: 1. How much of the applied water is actually recharged? 2. What is the lag period between recharge and recovery? Based on the pilot study's results and the fact that unit costs are inversely related to recharge/recovery efficiency, unit costs could be modified accordingly.
Benefits The three major benefits of the Butler Valley Project are: 1. seasonal and long-term storage, 2. provides access to existing ground water resources in the Valley, 3. option value--the benefits of securing future water supplies.
Seasonal and Long-Term Storage Seasonal. Excess waters during spring flows of the Colorado River could be stored in the Valley. Extractions of these waters during the summer months could help offset peak water demand in Phoenix and Tucson. Depending on the scale of the Project, capture and recharge of natural runoff in the Valley might prove to be beneficial as well. 9 8
Conjunctive management of Butler Valley with surface reservoirs and perhaps other ground water basins is a possibility. However, as noted in Chapter 2, benefits of this nature are best realized when excess waters may be recharged rapidly (i.e., by gravity flow). The value of seasonal storage depends on seasonal differences between water supply and demand. If additional storage is needed, the next step is to compare Butler Valley with other potential storage sites. Long-Term. Since the signing of the Colorado River Compact in 1922, considerable debate has arisen over the long-term water supply potential of the Colorado River. Some individuals argue that the River has already been greatly overallocated. Still others indicate that long-term projections of water supply are more than adequate to meet the needs of Arizona and the other Compact states (Dozier, 1985). Given this uncertainty, the long-term benefits of the Project depend on the existence of future deficits between available water supply and demand. If deficits are predicted and actually occur, Butler Valley and similar projects could prove to be quite valuable. On the other hand, if supplies are adequate and reliable for the foreseeable future, storage projects should be delayed until additional supplies are needed. Construction before this 99
time is not economically justified. However, as Phoenix and Tucson continue to grow, increased demand for water seems inevitable. The important question then is not whether additional supplies are needed, but rather, when they are needed.
Existing Ground-Water Resources Herndon (1985) estimates about 12 million AF of natural ground water exists in the Valley aquifer at the current water elevation of 1275 feet. Additional storage above this level in areas proposed for recharge is about 300,000 AF.
A recharge/recovery program in the Valley would likely remove some of the naturally stored water. Natural ground-water withdrawal accomplishes two things: (1) increases available supply to the CAP system and (2) creates additional aquifer storage capacity for recharged water. Given the cost of potential recharge alternatives and the large volume of good quality water in the Valley, three potential strategies are available: 1. mine the aquifer with no intention of replacing the water, 2. do nothing, 3. use the aquifer for regulatory storage and conjunctive management of surface water and ground water. 100
Mining the aquifer has been contemplated by some political groups and individuals in the State (Bradley, 1985). While this idea appears lucrative, long-range planning suggests that this action is economically undesirable for the following reasons: 1. In addition to the value of existing ground water, the storage potential of the aquifer holds considerable benefits--especially with respect to its proximity to the CAP aqueduct and Colorado River. Severe dewatering of the Butler Valley aquifer could cause irreversible loss of storage due to compaction of sediments. 2. Ground-water exploitation, in the near future might neglect more distant future benefits if water becomes extremely scarce relative to demand. 3. Practical limits do exist for recharge/recovery operations. Severe water-level declines might make future recharge programs impractical. The second or "do nothing" alternative may or may not apply in the foreseable future. Careful examination of water supply-demand relationships and economic comparisons with other recharge sites in the State could help determine the timing and site-desirability of the Butler Valley Project. 101
Regulatory storage in Butler Valley allows timely withdrawals of natural ground-water while retaining the full storage potential of the aquifer. Available economic models on conjunctive management of ground water and surface water might help determine the most efficient scheduling of natural ground-water withdrawals (Maddock, 1974). The value of this natural water depends on water supply-demand differences and the costs of recovering the water. Subsequent economic studies on the benefits of the Project could estimate the monetary value of existing ground-water supplies.
Option Value Economic assessment of the Butler Valley Project would be incomplete without a discussion of an economic concept known as "option value." Option value may be defined as the value of assuring access to a resource when future use is uncertain (Bishop, 1982). Two conditions make option value relevant to a particular natural resources situation:
(1) incomplete information, and (2) the potential for irreversible changes. At least in the short run, both conditions seem to prevail in Butler Valley. Uncertainty in future supply (long-term average flow of the Colorado River) and demand (future value of water) suggest a severe lack of information. Examples of potential irreversible changes in Butler Valley include: 102
1. mining of ground water could greatly reduce the aquifer's storage potential, 2. Project is not implemented and future supply-demand deficits arise, 3. timing of Project development is premature--excessive capital is invested unnecessarily. The value of assuring the option of access to future water supplies seems quite high in Arizona, particularly in light of the recent Scottsdale-Planet Ranch transaction to acquire surface water rights (The Arizona Republic, June 30, 1985). Without a definite means of conveying water to potential users, the City of Scottsdale has gone to great expense in securing future water supplies from the Bill Williams River. City officials have done so by purchasing a tract of land adjacent to the Bill Williams River known as "Planet Ranch." The surface water rights associated with this land are hoped to augment the City's projected CAP deliveries. Butler Valley, not far from the Bill Williams River, may be considered as the delivery conduit to the CAP as well as an intermediate storage facility. Bishop (1982) discusses several non-market valuation methods used in assessing the option value of natural resources. As suggested by the previous discussion, option value may be a significant benefit for the Butler Valley 103
Project. The methods described by Bishop (1982) may be useful in evaluating the benefits of securing water supplies in the Valley aquifer.
Opportunity Costs Opportunity cost of a natural resource refers to the value of the next best alternative to a proposed resource use. Opportunity costs should be included in economic studies to adequately assess the potential impact of a project. Major resources used in Project development are water, energy and land. Other items such as pipelines, equipment, human resources, and finances are also absorbed by the Project.
Water, Energy and Land Water. To obtain maximum. benefits from a recharge/recovery project, recharge water should have zero or low opportunity costs (Saliba, 1985). In other words, the water would not, in the absence of recharge, be allocated to an available use. Excess supplies such as seasonal floods fit into this category. Recharging water of this nature is of little or no consequence to existing water users. While some water is clearly in excess of current demand, other quantities may provide ongoing benefits to users of low-priced water. Recharge of water under this 104
second category may require compensation of adversely affected groups or individuals who would certainly not agree to give up water without something in return for that water. Payment may be in the form of subsidies, extensions of water rights or political agreements and concessions. Whatever the form, compensation costs should be included as inseparable costs of the recharge project.
Energy. As shown in the comparison of recharge scheme unit costs, the quantity and cost of energy affect the Project's economic desirability. As mentioned in Chapter 1, competing uses of electrical energy in Arizona already are being challenged by opposing groups. Apportionment of low power rates may decide the fate of several water projects in the State.
The principal opportunity cost of energy consumed by the Project is the energy needed to pump water through the CAP system. When fully operational, the CAP will be the single largest consumer of electrical power in the State (Woodard, 1985). Recharge potential in Butler Valley will strongly depend on the availability of cheap power. Land. Lying in a remote part of Arizona, the opportunity costs of land in Butler Valley are minimal, especially when compared to potential recharge sites in urban areas. Except for the disruption of some of the wildlife and vegetation, access to land use will remain 105
open. Minor agricultural practices already in the Valley could continue unhindered by the Project.
Other Resources Many other resources would be used during Project development. The financing of the Project is perhaps the single largest item. Capital expended on a recharge project in Butler Valley might produce greater social net benefits if spent on other projects yielding greater social utility. Additional resources include human resources, equipment and materials used in the Project. Human resources refer to the planning, engineering and operational skills of all individuals connected with the Project. Equipment and materials include pipelines, pumping plants, wells, tractors, bulldozers, and all other items essential to the construction and operation of proposed facilities. All of these resources have potential use elsewhere or at other times. Planners should bear this in mind while contemplating the selection and development of recharge sites.
Social Impact Analysis Social impact analysis assesses the distributional and environmental effects of the Project. Distributional effects are concerned with equity issues: 1. Which group(s) receive(s) benefits from the project? 106
2. Which group(s) bear(s) Project costs? 3. Are the benefits and costs fairly distributed? Potential environmental effects include aquifer degradation, impact on Valley wildlife and vegetation and impact on current land use in the Valley.
Distributional Effects Capturing benefits from the Project depends on: (1) the ability or willingness of each water-using group to pay for the recharge/recovery services and (2) institutional arrangements governing the use and transfer of water. Review of Figure 4.1 shows considerable disparity between the average unit costs of agriculture, municipalities and industry. Based on these unit-cost differences, potential Project benefits appear to be unevenly distributed: 1. Tucson municipal and industrial uses--high potential benefits, 2. Phoenix municipal and industrial uses--medium potential benefits, 3. Arizona agricultural uses--some gains, depending on institutional arrangements. The distribution of Project costs depends on: (1) the nature of the operating entity--public vs. private and (2) opportunity cost of recharge water. Under the current political climate, a private operator is the favored alternative. Using the market- 107 pricing mechanism, most of the Project costs could be passed directly to Project beneficiaries. In addition, the interested private organizations have offered up-front financing of the Project, rather than the usual public funding (i.e., bond raising). However, exclusion of individuals and groups on the basis of ability to pay contradicts the State's attitude toward water resources allocation. To alleviate this distributional imbalance, price controls, subsidies and political agreements may be required to satisfy all competing water users in the State. Equitable distribution of Project benefits and costs is affected largely by the magnitude of society's positive net benefits. Evaluation of project benefits remains for future economic investigations in the Valley. Once the total net benefits of the Project are assessed, water planners in the State should ask: 1. Are positive net benefits great enough to compensate all adversely affected groups and individuals? 2. How will these groups and individuals be compensated? 3. How does Butler Valley compare with other recharge sites in the State? Subsequent institutional studies could examine potential institutional schemes that would satisfy the needs of competing water users in the State. Groups not directly 108 benefiting from the Project could be given indirect benefits (i.e., exchange of water rights).
Environmental Effects Aquifer Degradation. Existing ground water appears to be quite good, with total dissolved solids ranging from 351 to 507 parts per million (ppm) (Herndon, 1985). Some high fluoride concentrations (7.5 ppm) have been detected, but average fluoride concentration in the Valley is about 3.2 ppm. Potential recharge water from the CAP aqueduct is of lower quality than native ground water in the Valley. Total dissolved solids of CAP water averages about 683 ppm (Ince, 1976). Mixing of CAP water with native ground water would likely produce water of intermediate quality, still quite suitable for drinking purposes. Herndon (1985) discusses potential ground-water degradation caused by percolating recharge waters beneath surface-spreading facilities. Soluble constituents in the soils might include chlorides, sulfates, nitrates, and heavy metals. Nitrates, in particular, may be a problem in areas recently retired from agricultural operations (Bouwer, 1980). In addition, sodium cations introduced by the CAP water may alter clay units present in the Valley. Future hydrochemical investigations could better define the effects 109 of recharge operations on the aquifer material and native ground water. Valley Wildlife and Vegetation. Depending on the plan implemented, recharge operations could alter wildlife habitats and native vegetation. Prior to Project acceptance, an Environmental Impact Statement (EIS) would have to be filed with the U.S. Environmental Protection Agency. Surface spreading operations would entail clearing and grubbing of recharge sites and subduing vegetative growth (i.e., removal of phreatophytes). Environmental effects due to wells installation would be less severe than construction of basins and ponds. All adverse effects, however, must be considered as costs to the Project. Current Land Use. Agricultural operations are minimal, involving mostly cotton production. These operations could probably continue uninterrupted by recharge/recovery operations. CHAPTER 5
SUMMARY AND CONCLUSIONS
The results of this study indicate that artificial recharge and recovery of water using the Butler Valley aquifer might be economically attractive. More conclusive results could be determined by estimating the monetary value of Project benefits. This task is left to future economic investigations in the Valley. An additional goal of subsequent economic studies is to assess projected water supply-demand relationships in Arizona as they affect the conjunctive-management potential of the Valley. In particular,these studies should determine the optimal timing, size and location of future storage facilities that would be necessary to meet Arizona's future water demand. An important aspect of this study is the integration of technical and economic methods into a proccedure that can be used to evaluate the economic viability of recharge projects. Selection, design and cost estimation of Project alternatives are consistent with the Herndon (1985) study, accepted engineering-economic analytical methods and on-going recharge operations identified by the literature review. Synthesizing information from a variety of
110 111 disciplines is a necessary skill of the water resources planner. The procedure used to evaluate the Butler Valley economic problem might be applicable to other feasibility studies in Arizona and elsewhere. Unit costs for the four recharge plans range from
$94 to $488 per acre-foot recovered, depending on various control variables. Sensitivity analysis examines the impact of discount rate, design period and power rate on the unit cost of individual plans. Plan B, the most expensive alternative, is most sensitive to discount rate and design period and least sensitive to power rate. The sensitivity of
Plans A, C and D to the three control variables appears to be about the same over the tested range of values. The computer program used to calculate unit costs is adequate for the level of this study. However, without certain improvements its use is somewhat restricted. First of all, the projection of future Project operations is greatly oversimplified. An economic model capable of forecasting water supply-demand relationships along the CAP system would prove quite useful in estimating recharge and recovery quantities during Project operating years. Furthermore, interfacing one of the available ground-water management models with the Herndon (1985) model would allow better simulation of physical-economic interactions in the basin (Maddock, 1974). Preliminary cost estimates in this 112 study could provide useful information for future economic investigations, such as, the development of a cost function for recharge/recovery operations in the Valley. Among the four selected recharge plans, Plan C yields the lowest unit cost ($/AF) under all tested conditions. Plans D and A, respectively, yield the second and third lowest costs per acre-foot recovered. All three of these plans use surface spreading as the means of introducing water into the aquifer. Plan B, by far the most expensive alternative uses well recharge. Depending on future technical investigations, each of the four plans or hybrid plans may be most appropriate. Future technical studies should include an exploratory drilling program and a pilot study. Test drilling would expose hydrogeologic conditions beneath the basin margins and sections of Cunningham Wash and its tributaries. A pilot study or small-scale demonstration project could refine both technical and economic information by actually conducting recharge/recovery operations in the Valley. Coordinating the pilot study with the drilling program could enhance the efficiency of data collection. Wells completed in test holes could be used: (1) as a source of recharge water, (2) to conduct recharge and aquifer tests, and (3) to monitor hydrochemical changes in the aquifer. 113 Comparison of Project unit costs with the average unit costs of agriculture, municipalities and industry in Arizona indicates some differences in the ability or willingness of each water-using group to pay for Project services. Based on these unit-cost differences, Project benefits would be unevenly distributed among the three groups: 1. Tucson municipal and industrial use--highest benefits received, 2. Phoenix municipal and industrial--intermediate benefits received, 3. Arizona agricultural--some gains, depending on water management alternatives. Although private operation of the basin is the preferred alternative at this time, the inequitable distribution of benefits suggests the need for institutional control. Compensatory payments in the form of subsidized prices or extended water rights might be required prior to the Project's acceptance. Future institutional studies could evaluate the privatization concept and propose management policies to correct the imbalance in the distribution of Project benefits. In addition, these studies could examine available means of removing political and legal obstacles to the Project. Depending on the difficulties encountered, the 114 necessary actions should be assessed as additional Project costs. The principal Project benefits as identified by this study are seasonal and long-term storage, value of existing ground-water resources and option value. Seasonal and long-term storage are conventional advantages of water-storage facilities along supply systems. Ground-water development, an intrinsic benefit of the Project, offers two bonuses: (1) augments the supply of the CAP system, and (2) creates storage for subsequent recharge operations. Option value, the value of assuring access to a resource when use is uncertain, is a relatively new concept as applied to the field of water resources. Considering the political and economic importance of water in the arid Southwest, option value may bear significant weight in the minds of policy-makers. Studies by Bishop (1982) might prove useful in evaluating option value for Butler Valley and other supply augmentation plans in the State. Assessing the overall social consequences of the Butler Valley Project should include estimating benefits and indirect costs of the Project. Future economic studies in the Valley should focus on estimating the monetary value of seasonal and long-term storage, existing ground-water resources and option value to people served by the CAP system. Indirect costs such as aquifer degradation and 115 impact on the Valley's ecosystem should also be assessed in later stages of Project evaluation. APPENDIX A
DESIGN PARAMETERS FOR CONVEYANCE SYSTEM
116 117 PART I. Estimating Lift Requirements for Plans A-D Sample Calculations (eq. 3.1-3.4) Example: Cunningham Wash Siphon inlet of CAP aqueduct to Ditch NW-1 in northwest spreading area Elevation of Cunningham Wash siphon inlet: 1312 ft Elevation of discharge point into Ditch DW-1: 1520 ft Elevation difference: 208 ft Length of pipeline: 8.3 mi Friction loss along 8.3 miles of 72-inch pipeline (from Amer. Soc. Civil Eng., 1975) (8.3 mi) (5280 ft/mi) (1.5 ft/1000 ft) 66 ft eq. 3.1: TOTAL DELIVERY HEAD (ft) = ELEVATION DIFFERENCE (ft) + FRICTION LOSS (ft) TOTAL DELIVERY HEAD, H = 208 ft + 66 ft 274 ft
eq. 3.2: wHp Q3LI-01
Q = 78,000 gpm
(78,000 gpm) (274 ft) WHP = 3960
WHP = 5397
eq. 3.3: BHP = /6071-1175)
BHP = 50 3. N = 7196
eq. 3.4: ELECTRIC POWER (kw) = BHP X 0.745700 = 7196 X 0.745700 = 5366 118
SUMMARY OF CALCULATIONS AND PROCEDURES Plan A
Lift 1 Q (gpm) H (ft) WHP BHP Electric Power (kw) NW-1 Ditch 78,000 274 5397 7196 5366 (1520') NW-2 Ditch 68,000 42 721 961 717 (1560') NW-3 Ditch 53,500 41 554 739 551 (1600') 8896 6634
Lift 2
SE-1 Ditch 33,660 94 799 1065 794 (1660')
SE-2 Ditch 22,440 22 125 167 125 (1680')
SE-3 Ditch 11,220 23 65 87 65 (1700') 1319 1984
Total: 10,215 7,618 119
Plan B
Maximum Lift Requirements Segments Along Single Transmission Main. Initial Priming of Recharge-Well System. Elevation Q (gpm) H (ft) WHP BHP Electric Power (ft) (kw) 1453 78,000 181 3565 4753 3544 1475 70,000 28 495 660 492 1495 62,000 24 376 501 374 1515 54,000 23 314 419 312 1528 46,000- 20 232 309 231 1560 38,000 37 355 473 353
1585 30,000 34 256 341 254
1. 610 22,000 34 189 252 188
1640 14,000 46 163 217 162
1675 6,000 48 73 97 72 Total: 8022 5982
Laterals Upslope from Main. Diameter Q (gpm) H (ft) WHP BHP Electric Power (in) (kw) 24 4,000 12 12 16 12
20 2,000 22 11 15 11 31 23
10 laterals X 31 bhp = 310 bhp 10 laterals X 23 kw = 230 kw 120 Grand Total of Maximum Lift Requirements
Brake horsepower 8022 + 310 8332 hp
Electric power 5982 + 230 6212 kw Long-Term Lift Requirements During Well Recharge Assumes single-well average represents entire well field and both mains are used to convey water.
1275 + 1350 1313 ft Average water level in aquifer: 2 = Estimating cone of impression in an individual well assuming law of superposition holds; Neuman, 1985): 2 s = BQ + CQ (eq. A.1; Jacob, 1947) where s = mound in well (ft), BQ = formation or aquifer loss, 2 CQ = well loss, Q = well recharge (cfs), 3 B = the aquifer loss constant (sec/ft ), 2 5 C = well loss constant (sec /ft ) Calculating B:
1 itI B = ln - 0.5772 eq. a.2: Jacob, 1947) 4TrT [ r2 S
where T = aquifer transmissivity (ft 2 /sec), S = aquifer storativitv (dimensionless), r = effective radius of well (ft) Let r = 1.0 ft, from Herndon (1985): 2 -2 2 T = 6700 ft /day = 7.755 X 10 ft /sec S = 5 X 10 -4 121
Substituting values of 4, T and S into eq. A.2, B = 23.52 2 5 From Walton (1962), C = 10 sec /ft for c1ischargin,7 well just starting to clog. This value is assumed to be approximately equivalent to resistance encountered during recharge. Recalling Q = 1000 gm = 2.33 cfs
Substituting values of B and C into eq. A.1: 3 3 s = (23.52 (sec/ft ) (2.23 ft /sec) + 2 5 3 (10 sec /ft ) (2.23 ft /sec) s = 102 ft
Average operating elevation = 1313 ft + 102 ft = 1415 ft
Siphon outlet elevation: = 1308 ft Elevation difference = 107 ft Calculating friction loss in pipes (American Society of Civil Engineers, 1975): Diameter Q (gpm) H(f) Pipe Length Friction (in) (ft/1000 ft) (mi) Loss (ft) 72 39,000 0.37 4.6 9.0 72 31,000 0.23 3.0 3.6 60 21,000 0.27 2.0 2.9 24 4,000 0.15 0.25 1.5 20 2,000 0.72 0.50 1.9 12 1,000 2.70 0.25 3.6
Recharge (approximated) 2.0 Conduits Total: 24.5 122
Calculating Total Delivery Head, .H (ft) H (ft) = Elevation Difference (ft) + Friction Loss (ft) = 107 ft + 25 ft = 132 ft Calculating WHP:
1000 gpm x 132 ft WHP = QxH3960 3960 WHP = 33.3 Approximating for entire well field: 75 wells x 33.3 WHP/well = 2597 WHP Summary of Results for Long-Term Operation
Q (gpm) Ave. H (ft) WHP BHP Electric Power (kw) 78,000 132 2597 3463 2582 123
Plan C
Lift 1 Q (gpm) H (ft) WHP BHP Electric Power (kw) Main Ditch 78,000 317 6244 8325 6208 (D-C; 1600') Lift 2 SE-1 Ditch 33,000 68 578 771 575 (1660') SE-2 Ditch 22,440 22 125 167 125 (1680') SE-3 Ditch 11,220 23 65 87 65 (1700') Total: 9350 6973
Plan D
Lift 1 D-D Ditch 78,000 380 7485 9980 7442
Lift 2 SE-1 Ditch 33,660 74 629 839 626 (1660') SE-2 Ditch 22,440 22 125 167 125 (1689') SE-3 Ditch 11,200 23 65 87 65 (1700') Total 11,073 8258 124
Part II. Design Parameters of Unlined Ditches for Plans A, C and D Sample Calculations (eq. 3.5 & 3.6) Example: Ditch NW-1
(eq. 3.5: A- 2V Q = 22 cfs, = 1.5 ft/sec 22cfs A 1.5 ft/sec = 14.67 ft2 Nominal cross-sectional area selected for trapezoidal- 2 shaped channel: 15.2 ft eq. 3.6: vn 1.486 R2/3 v = 1.5 ft/sec n = 0.025 (Henderson, 1966) P = 12.29 ft A 15.2 ft 2 R = P- - 12.29 ft - 1.24 ft 2 s= (1.5 ft/sec) (0.025) (1.486) (1.24) 2/3 s = 0.00048
125
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.c .c 41 4/ 113.4 0.4 ri No 044 0 o 0 In in in C ..1 • 4-.. 0 E 0E ii P. ..a - 4; 40. Of ii...... 4 •-• 4 C n me 0 .4.4 er a. 4.) .00 on 2 .-I 0 •-• 1-0 Cow . 17. 0 44 0' .4 0 ii I4 44 14 40 . 1440 0 .... .1 - O .0 U .0 CO C m o 0. vs 0 0 0 0 0 0 0 0 0 ioi o 44 CO as .444 N 0 0 0 CD 0 .4 0 ma En on US ID 40 410 in an sia 10 in r 4, .-I .. RI ...... 4 as c >44 >0. .4 m o. e .4 1 WI Cio 10
In ri w ii .c.0 .0 U 1 U 0 0 u - . - 0 3 ; ii I 7 7 "I 4. 0 Z 0 0 0 --o 3 i 3 iii al 41 w O Z Z ro to ie 0 APPENDIX B
DESIGN OF RECHARGE AND RECOVERY FACILITIES
.
126 127 Assuming long-term infiltration rates of: Daily rate, i Annual Rate, I (ft/day) (ft/yr)
Basin margins 0.5 182.5
Channels 1.0 365
Sample Calculation equation 3.7: _ A Y where, = 100,000 AF/yr I = 182.5 ft/yr
100,000 AF/yr A = 182.5 ft/yr
A = 548 acres (wetted)
Taking into account 50%-50% wet-dry cycling, actual area is:
548 X 2 = 1096 acres
Including the design constraint of 292 operating days: 1096 acres X 125% = 1370 acres
Spreading Area Requirements for Plans A, C and D
Basin Spreading Channel Spreading (acres) (acres)
Plan A 1370
Plan C 589 390
Plan D 589 390 128
O 0 (NI rn a_ a.
,09£ 129
N
— ... co — C rfl - a) rt.) 0 - — ('J ..: ZI N *.- cri o U) — 0 o a) >-. E o H-T-1-1„ / ,t co O o re) / Q) o -0 a)
N 1- to N 0 a) 02 12c N- c o 0 21 "c- .c a -o E .- co a) 0 0 5 ).. do ol 0 .. g . ,.., 2. 0.8. 13 Q)• to c o. o o 0 - o ....- TA 0 6 u a .c o a) o o c a) In 0 0 21 o .c -o ,...... o au E a) 0 0 o 8 a) ° 67 E E coc" .,7 -a 0 ‘_ a)" 0 c a) > o 0 > ci 2 Cl. > <2
3 130
DEPTH =1000 feet WELL DIAM.=16 inches BORE DIAM.= 24 inches
771
PUMP COLUMN (USED FOR RECHARGE AND RECOVERY)
RECHARGE CONDUIT
WELL OPENINGS
Figure B.3. Conceptual design of recharge/recovery wells. 131
DEPTH =1000 feet WELL DIAM.= 16 inches BORE DIAM.=24inches V777
PUMP COLUMN
WELL OPENINGS
)
Figure B.4. Conceptual design of recovery wells. APPENDIX C
COST ESTIMATES AND COMPUTATIONAL PROCEDURES
132 133 PLAN A
CAPITAL COSTS
Land and Easements Quantity Unit Total Cost Cost Administration of land swap, surveying, decontamination of lump military lands. 160 sa. mi sum 500,000 Subtotal: 500,000 Conveyance System
Pumping plants 10,215 hp $850/hp 8,683,000 Transmission mains 72-inch reinforced concrete pipe 8.8 mi $190/ft 8,828,000 54-inch reinforced concrete pipe 1.1 mi $126/ft 732,000 48-inch reinforced concrete pipe 0.3 mi $120/ft 190,000 30-inch reinforced concrete pipe 0.2 mi $ 52/ft 55,000 Discharge works laterals calculated individually 6,000 control valves 183,000 transition canals 81 cy $200/cy 16,000 Ditch construction
excavation 285,208 $2.50/cy 713,000 weir construction 39.2 mi $500/mi 20,000 Siphon 54-inch reinforced concrete pipe 1.5 mi $126/1f 998,000 Subtotal: 20,424,000 134
Quantity Unit Cost Total Cost Recharge Facilities Basin Construction dike construction 1,260,000 cy $2.50/cy 3,150,000 control valves, gates and pipes 126 basins $10,000/ 1,260,000 basin monitoring network 126 basins $5,000/ 630,000 basin Subtotal: 5,040,000 Recovery Well Field Well construction 39 wells $120,000/ 4,680,000 well Monitoring network observation wells 10 30,000/ 300,000 well Flow meters and instrumentation 34 5,000/ 195,000 well Transmission mains and laterals 72-inch reinforced concrete pipes 5.8 mi $190/1f 5,819,000 60-inch reinforced concrete pipes 1.0 mi 136/1f 718,000 48-inch reinforced concrete pipes 1.0 mi 120/1f 634,000 30-inch reinforced concrete pipes 1.0 mi 52/1f 275,000 24-inch reinforced concrete pipes 2.5 mi 38/1f 502,000 20-inch reinforced concrete pipes 4.5 mi 31/1f 737,000 12-inch reinforced concrete pipes 10.25 mi 16/1f 866,000 Control Valves 12-inch isolation valves 39 $1,500/valve 59,000 14-inch isolation valves 10 17,000/valve 170,000 Electrical installation 27.7 82,000/mi 2,271,000 Subtotal: 17,226,000 135
Quantity Unit Cost Total Cost Structures, Equipment and Site Improvements Buildings and lump sum 500,000 site work Maintenance roads 76 mi $53,000/mi 4,028,000 Equipment, tools and accessories tractor w/acc 2 75,000/tractor 150,000 4X4 pickup truck 2 15,000/truck 30,000 Misc. tools and equipment lump sum 200,000
Subtotal: 4,908,000
Total Excluding Services and Contingencies: $48,098,000 Engineering, Surveying and Other Technical Services (10%): - 4,810,000
Contingencies (10%): 4,810,000 Total Including Services and Contingencies: 57,718,000 Interest During Construction (8%, 1.5 years): 6,926,000 Grand Total 1985 Capital Costs: $64,644,000 Construction Over 3 years (8%): Year Cost PV (Cost) 1 21,548,000 19,952,000 2 21,548,000 18,474,000 3 21,548,000 17,105,000 55,531,000 Equivalent Uniform Annual Cost (8%, 27 years): 5,078,000 136
ANNUAL OPERATION, MAINTENANCE AND ENERGY COSTS Operation and Maintenance Civil engineer (manager) 45,000 Hydrogeologist 35,000 Hydrologic technicians (2) 40,000 Supporting staff & overhead 100,000 Renewals & replacements (10% of annual cost) 508,000 Road maintenance (1.5% of capital cost) 60,000
Conveyance system 0 & . M (1.5% of capital cost) [a] 306,000 Recharge facilities 0 & M [b] ($20/acre X 1370 acres/month X 9.6 month/year) 263,000 dike replacement (10% of capital cost) 315,000 pest control 10,000 Recovery well field 0 & M 292 days (39 wells X $5,000/well [c] 195,000 92 days (3 months; 31.5% of $195,000)[d] 61,000 73 days (25% of $195,000) [e] 49,000 Annual Energy Consumption Electrical conveyance to recharge facilities53,400,000 khw X $0.036/kwh [14] 1,922,000 pumping of recovery wells 292 days 100 000 AF X $19.39 AF [x] 1,939,000 92 days 32,000 AF X $19.39/AF [y] 620,000 73 days 25,000 AF x $19.39/AF [z] 485,000 Other 30,000 Total Annual Operation, Maintenance and Energy Costs (1985$) Recharge (292 days) [excluding c,d,e,x,y, & z] 3,393,000 Recovery (292 days) [excluding a,b,d,e,w,y, & z] 2,952,000 Partial OM & E Costs (1985$) Recovery of 25,000 AF during recharge year [e & z only] 534,000 137 Recharge [3 months; 31.5% of annual recharge cost] 1,069,000 Recovery [same year; d & y only] 681,000
PLAN B
CAPITAL COSTS
Land and Easements Quantity Unit Cost Total Cost Administration of land swap, surveying, decontamination 160of military lands sq. mi. lump sum 500,000 Subtotal: 500,000 Conveyance System Pumping plant (recharge only) 8332 hp $850/hp 7,082,000 Transmission main laterals 72-inch reinforced concrete pipe 15.2 mi $190/1f 15,249,000 60-inch reinforced concrete pipe 4.0 mi 136/1f 2,872,000 48-inch reinforced concrete pipe 2.0 mi 120/1f 1,267,000 42-inch reinforced concrete pipe 2.0 mi 94/1f 993,000 30-inch reinforced concrete pipe 2.0 mi 52/1f 549,000 24-inch reinforced concrete pipe 6.5 mi 38/1f 1,304,000 20-inch reinforced concrete pipe 9.5 mi 31/1f 1,555,000 12-inch reinforced concrete pipe 20.5 mi 16/1f 1,732,000 Control Valves 12-inch isolation valves 78 $1500/valve 117,000 24-inch isolation valves 30 17,000/valve 510,000 Subtotal: $33,320,000 138 Quantity Unit Cost Total Cost Recharge/Recovery Facilities Well construction 78 wells $150,000/ 11,700,000 well Monitoring network observation wells 15 30,000/ 450,000 well Flowmeters and instrumentation 78 5,000/well 390,000 Electrical installation 48.1 mi 82,000/mi 3,944,000 Treatment facility (recharge only)
plant 120 mgd 27,000,000 27,000,000 equalization reservoir (1) 12 mg 2,000 2000 clearwell covered reservoirs (2) 30 mg 4,000,000 8,000,000
Subtotal:. 53,484,000
Structures, Equipment and site Improvements Buildings and site work lump sum 500,000
• Maintenance roads 48.1 mi $53,000/mi 2,549,000 Equipment, tools, accessories lump sum 230,000
Subtotal: $3,279,000 Total Excluding Services and Contingencies: 90,583,000 Engineering, Surveying and Other Technical Services (10%): 9,058,000
Contingencies (10%): 9,058,000 Total Including Services and Contingencies: 108,699,000 139
Interest During Construction (8%, 1.5 years): 13,044,000
Grand Total 1985 Capital Costs: 121,743,000 Construction Over 3 Years (8%):
Year Cost PV (Cost)
1 40,581,000 37,575,000 2 40,581,000 34,792,000 3 40,581,000 32,214,000
Equivalent Uniform Annual Cost (8%, 27 years): 9,564,000
ANNUAL OPERATION, MAINTENANCE AND ENERGY COSTS Operation and Maintenance Civil engineer (manager) 45,000 Hydrogeologist 35,000 Hydrologic technicians (2) 40,000 Supporting staff & overhead 100,000 Renewals and replacements (10% of annual cost) 1,113,000 Road maintenance (1.3% of
capital cost) • 38,000 Conveyance system 0 & M (1.5% of capital cost) [a] 500,000 Recharge facilities 0 & M (3% of capital cost) [b] 1,605,000 Recovery well field 0 & M 292 days (39 wells X $5,000/well [el 195,000 92 days (3 mon; 31.5% of $390,000) [d] 61,000 73 days (25% of $390,000) [e] 49,000 Annual Energy Consumption Electrical
conveyance to recharge wells [w ] 18,095,000 kwh $0.036/kwh 651,000 pumping of recovery wells 292 days [x] 100,000 acre- ft $19.39/acre-ft 1,939,000 92 days [y] 32,000 acre-ft $19.39/acre-ft 620,000 72 days [z] 25,000 acre-ft $19.39/acre-ft 485,000 Other 30,000 140
Interest During Construction (8%, 1.5 years): 13,044,000
Grand Total 1985 Capital Costs: 121, 743,000
Construction Over 3 Years (8%): Year Cost PV (Cost) 1 40,581,000 37,575,000 2 40,581,000 34,792,000 3 40,581,000 32,214,000 Equivalent Uniform Annual Cost (8%, 27 years): 9,564,000
ANNUAL OPERATION, MAINTENANCE AND ENERGY COSTS Operation and Maintenance Civil engineer (manager) 45,000 Hydrogeologist 35,000 Hydrologic technicians (2) 40,000 Supporting staff & overhead 100,000 Renewals and replacements (10% of annual cost) 1,113,000 Road maintenance (1.5% of capital cost) 38,000 Conveyance system O&M (1.5 % of capital cost [a] 500,000 Recharge facilities O&M (3% of capital cost) [b] 1,605,000 Recovery well field O&M 292 days (39 wells X $5,000/well [c] 195,000 92 days (3 months; 31.5% of $195,000) [d] 61,000 73 days (25% of $195,000) [e] 49,000 Annual Energy Consumption Electrical conveyance to recharge wells 18,095,000 kwh X $0.036/kwh [w] 651,000 pumping of recovery wells 292 days 100,000 AF X $19.39/AF [x] 1,939,000 92 days 32,000 AF X $19.39/AF [y] 620,000 72 days 25,000 AF X $19.39/AF [z] 485,000 Other 30,000 141 Total Annual Operation, Maintenance and Energy Costs (1985$):
Recharge (292 days) [excluding c,d,e,x,y,&z] 4,157,000 Recovery (292 days) (excluding a,b,d,e,w,y,&z] 3,535,000 Partial OM&E Costs (1985$) Recovery of 25,000 AF during discharge year (e & z only) 534,000
Recharge [ -3 month 31.5% of annual recharge cosf] 1,309,000 Recovery [same year; d & y only] 681,000
PLAN C
CAPITAL COSTS Land and Easements
Quantity Unit Cost Total Cost
Administration of land 160 sa. mi.. lump sum 500,000 swap, surveying, decon- tamination of military lands Subtotal: 500,000 Conveyance System
Pumping plants 9350 hp $850/hp 7,948,000 Transmission mains 72-inch reinforced concrete pipe 3.1 mi $190/1f 3,110,000 54-inch reinforced concrete pipe 0.8 mi $126/1f 532,000 48-inch reinforced concrete pipe 0.3 mi $120/1f 190,000 30-inch reinforced concrete pipe 0.2 mi $ 52/1f 55,000 Discharge works laterals calculated individually 3,000 control valves & gates 168,000 transition canals 61 cy $200/cy 12,000 Ditch construction excavation 233,042 cy $2.50/cy 583,000 weir construction 27 mi $500/mi 14,000 Subtotal: 12,615,000 142 Quantity Unit Cost Total Cost
Recharge Facilities Basin construction (54 11-acre basins) dike construction 540,000 cy $2.50/cy 1,350,000 control valves, gates & pipes 54 basins $10,000/ 540,000 basin monitoring network 54 basins 5,000/ 270,000 basin Channel modification (65 6-acre ponds) dike construction 46,930 cy $2.50/cy 117,000
inflatible dams 65 $38,000/dam 470,000 monitoring network 65 $2500/pond 163,000 Subtotal: 2,910,000 Recovery Well Field
Well construction 39 wells $120,000/ 4,680,000 well Monitoring network observation wells 10 30,000/ 300,000 well flow meters and construction 39 5,000/ 195,000 well Transmission main and laterals 72-inch reinforced concrete pipe 5.8 mi $190/1f 5,819,000 60-inch reinforced concrete pipe 1.0 mi $136 1 1f 718,000 48-inch reinforced concrete pipe 1.0 mi $120/1f 634,000 30-inch reinforced concrete pipe 1.0 mi $ 52/1f 275,000 24-inch reinforced concrete pipe 2.5 mi $ 38/1f 502,000 20-inch reinforced concrete pipe 4.5 mi $ 31/1f 737,000 12-inch reinforced concrete pipe 10.25 mi $ 16/1f 866,000 Control valves 12-inch isolation valves 39 $1500/valve 59,000 24-inch isolation valves 10 17,000/valve 170,000 Electrical installation 27.7 mi 82,000/mi 2,271,000 Subtotal: 17,226,000 143
Quantity Unit Cost Total Cost Structures, Equipment and Site Improvement
Buildings and site work lump sum 500,000 Maintenance roads 66 mi $53,000/mi 3,498,000 Equipment, tools and accessories tractors w/acc. 2 75,000/ 150,000 tractor 4X4 pickup truck 2 15,000/ 30,000 truck misc. tools and equipment lump sum 200,000 Subtotal: 4,378,000 Total Excluding Services and Contingencies: 39,629,000 Engineering, Surveying and Other Technical Services (10%): 3,963,000 Contingencies (10%): 3,963,000 Total Including Services and Contingencies: 47,555,000 Interest During Construction (8%, 1.5 years): 5,707,000
Grand Total 1985 Capital Costs: 53,262,006 Construction Over 3 Years (8%): Year Cost PV (Cost)
1 17,754,000 16,439,000 2 17,754,000 15.221,000 3 17,754,000 14,094,000
Equivalent Uniform Annual Cost (8%, 27 years): 4,184,000 144 ANNUAL OPERATION, MAINTENANCE AND ENERGY COSTS
Operation and Maintenance
Civil engineer (manager) 45,000 Hydrogeologist 35,000 Hydrologic technicians (2) 40,000 Supporting staff and overhead 100,000 Renewals and replacements (10% of annual cost) 418,000 Road Maintenance (1.5% of capital cost) 52,000 Conveyance system O&M (1.5% of capital cost) [a] 189,000 Recharge of facilities O&M [b] basin renovation ($20/acre X 589 acres/month X 9.6 month/yr) 113,000 Basin dike replacement (10% of capital cost) 110,000 Channel renovation ($20/acre X 390 acres/month X 9.6 month/yr) 75,000 Pond dike replacement (100% of capital cost) 117,000 Pest control 10,000 Recovery well field O&M 292 days (30 wells X $5000/well) [c] 195,000 92 days (3 months; 31.5% of $258,000) [d] 61,000 73 days (25% of $258,000) [e] 49,000 Annual Energy Consumption Electrical conveyance to recharge facilities 48,900,000 kwh X $0.036/kwh [w] 1,760,000 pumping of recovery wells 292 days 100,000 AF X $19.39/AF [x] 1,939,000 92 days 32,000 AF X $19.39/AF [y] 620,000 73 days 25,000 AF X $19,39.AF [z] 485,000 Other 30,000 145
Total Annual Operation, Maintenance and Energy Costs (1985$):
Recharge (292 days) [ -excluding c,d,e,x,y, & z] 3,119,000 Recovery (292 days) [excluding a,b,d,e,w,y, & z ] 2,854,000 Partial OM & E Costs (1985$): Recovery of 25,000 AF during recharge year e and z only 534,000 Recharge (3 months, 31.5% of annual recharge cost) 982,000 Recovery [same year; d & y only] 681,000
PLAN D
CAPITAL COSTS
Quantity Unit Cost Total Cost
Land and Easements
Administration of land 160 sq. mi. lump sum 500,000 swap, surveying, decontamination of military lands
Subtotal: 500,000 Conveyance System
Pumping plants 11,073 $850/hp 9,412,000 Transmission mains 72-inch reinforced concrete pipe 11.1 mi $190/1f 11,136,000 54-inch reinforced concrete pipe 0.9 mi $126/1f 599,000 48-inch reinforced concrete pipe 0.3 mi $120/1f 190,000 30-inch reinforced concrete pipe 0.2 mi $ 52/1f 55,000 Discharge works laterals calculated individ- 3,000 ually control valves 6 gates 163,000 transition canals 61 cy $200/cy 12,000 146
Quantity Unit Cost Total Cost Ditch construction excavation 138,189 cy $2.50/cy 345,000 weir construction 22.2 mi $500/mi 11,000 Subtotal: 21,926,000 Recharge Facilities Basin construction (54 11-acre basins) dike construction - 540,000 cy $2.50/cy 1,350,000 control valves, gages and pipe 54 basins $10,000/ 540,000 basin monitoring network 54 basins $5,000/ 270,000 basin Channel modification (65 6-acre ponds) dike construction 46,930 cy $2.50/cy 117,000 inflatable dams 65 38,000/dam 2,470,000 monitoring network 65 2,500/pond 163,000
Subtotal: 4,910,000
Recovery Well Field
Well construction 39 wells $120,000/ 4,690,000 well Monitoring network observation 30,000/wells 1 0 300,000 well flow meters and 5,000/instrumentation 39 195,000 Transmission main well (same pipe used in conveyance system)
147
Quantity Unit Cost Total Cost Laterals 24-inch reinforced concrete pipe 2.5 mi 502,000 20-inch reinforced concrete pipe 4.5 mi 737,000 12-inch reinforced concrete pipe 10.25 mi 886,000 Electrical installation 27.7 mi $82,000/mi 2,271,000
Subtotal: 9,780,000 Structures, Equipment and Site Improvements Buildings and site work lump sum 500,000 Maintenance roads 62 mi $53,000/mi 3,286,000 Equipment, tools & accessories tractors w/acc. 2 75,000/ tractor 150,000 4X4 pickup trucks 2 15,000/ truck 30,000 misc. tools & equip. lump sum 200,000
Subtotal: 4,166,000 Total Excluding Services and Contingencies 41,282,000 Engineering, Surveying and Other Technical Services (10%) 4,128,000 Contingencies: 4,128,000 Total Including Services and Contingenices 49,538,000 Interest During Construction (8%, 1.5 years): 5,945,000 Grand Total 1985 Capital Costs: 55,483,000 Construction over 3 years (8%) Year Cost PV (cost) 1 18,494,000 17,124,000 2 18,494,000 15,856,000 3 18,494,000 14,681,000 47,661,000 Equivalent Uniform Annual Cost (8%, 27 years): 4,359,000 148
ANNUAL OPERATION, MAINTENANCE AND ENERGY COSTS Operation and Maintenance Civil engineer (manager) 45,000 Hydrogeologist 35,000 Hydrologic technicians (2) 40,000 Supporting staff & overhead 100,000 Renewals & replacements (10% of annual cost) 436,000 Road maintenance (1.5% of capital cost) 49,000 Conveyance system O&M (1.5% of capital cost) [a] 329,000 Recharge facilities O&M [b] basin renovation ($20/acre X 589 acres/month X 9.6 months/year)113,000 basin dike replacement (10% of capital cost 135,000 channel renovation ($20/acre X 390 acre/month X 9.6 months/year) 75,000 pond dike replacement (100% of capital cost) 117,000 pest control 10,000 Recovery well field O&M 292 days (39 wells X $5,000/well) [c] 195,000 92 days (3 months; 31.5% of $195,000) [d] 61,000 73 days (25% of $195,000) [e] 49,000
Annual Energy Consumption
Electrical conveyance to recharge facilities 57,900,000 kwh X $0.036/kwh [w] 2,084,000 pumping of recovery wells 292 days 100,000 AF X $19.39/AF [x] 1,939,000 92 days 32,000 AF X $19.30/AF [y] 620,000 73 days 25,000 AF X $19.39/AF [z] 485,000 Other 30,000 149
Total Annual Operation, Maintenance and Energy Costs (1985$): Recharge (292 days) [excluding c,d,e,x,y, & z] 3,598,000 Recovery (292 days) [excluding a,b,d,e,w,y, & z] 2,869,000 Partial OM&E Costs (1985$) Recovery of 25,000 AF during recharge year [e&f only] 534,000 Recharge [3 months; 31.5% of annual recharge cost] 1,133,000 Recovery [same year; d&y only] 681,000 150
Basic Information Regarding the Computer Program and Unit Cost Calculation.
1. Unit costs represent recharge and recovery of water between water-level elevations 1275 and 1350 feet. 2. Recovery cost is approximated by calculating average lift cost/AF of water. a. Average water level in aquifer: 1275 ft + 1350 ft = 1313 ft 2
b. Drawdown in a single recovery well is approximated with the Theis equation (Freeze and Cherry, 1979) and by using hydrogeologic parameters reported by Herndon (1985):
= W(u) 4ffT (eq. C.1)
where r 2 S u - rTt (eq. C.2)
Let r = 0.67 ft t = 30 days From Herndon (1985) S = 5 X 10 -4 T = 50,000 gpd/ft Substituting values into eq 3.2: -11 u = 4.0 X 10 Referring to Freeze and Cherry (1979), p. 318, Table 8.1: W(u) = 23.36
Noting that
Q = 2000 gpm (1440 min/day) = 2.88 X 10 6 gpd 151
and returning to eq. C.1,
_ 2.88 X 10 6 gpd - 47r(50000 gpd/ft) X 23.36
s = 107 ft
Average pumping elevation 1313 ft - 107 ft = 1206 ft
Land - surface elevation in center of well field: 1490 ft Average depth to water 284 ft Using eq. 3.12: . 1.024 (LIFT(ft) X POWER RATE LIFT COST/AF 0.54 ($/kwh) Since Lift = 284 ft LIFT COST/AF = 538.5 X POWER RATE ($/kwh) and... RECOVERY COST = VOLUME RECOVERED (AF/ft) X LIFT COST /AF
3. Construction costs for all four recharge plans are divided equally over first three years of the Project's life. The present value of each construction increment is calculated. Then, all three present values are summed together. 4. Input costs into the computer program are in thousands of dollars. 5. Recharge and recovery expenses are segregated by
• using small letter indices with brackets "[ l" -- see itemized expense sheets. 152
6. Program assumes 100% of applied water is recharged and recovered. 7. Potential recharge/recovery operations are represented by three arbitrarily chosen scenarios: Scenario 1 t (year) Recharge Recovery Net Storage (1000AF) (1000 AF) (1000 .A.F) 1 2 3 4 100 100 5 100 200 6 100 300 7 100 8 100 100 9 100 0 10 100 100 11 100 200 12 100 300 13 100 200 14 100 100 15 100 0 16 100 100 17 100 200 18 100 300 19 100 200 20 100 100 21 100 0 22 100 100 23 100 200 24 100 200 25 100 200 26 100 100 27 100 0 Annual average recharge/recovery rate = 50,000 AF/yr 153 Scenario 2 t (year) Recharge Recovery Net Storage (1000 AF) (1000 AF) (1000 AF)
1 2 3 4 100 100 5 100 200 6 200 7 200 8 200 9 100 100 10 32 32 100 11 32 32 100 12 100 13 100 200 14 100 300 15 16 100 200 17 200 18 32 32 200 19 32 32 200 20 32 32 200 21 22 32 32 200 23 32 32 200 24 25 26 100 27 100
Annual average recharge/recovery rate = 26,000 AF/yr 154
Scenario 3 t (year) Recharge Recovery Net Storage (1000 AF) (1000 AF) (1000 AF)
1 2 3 4 100 25 75 5 100 25 150 6 100 25 225 7 100 25 300 8 100 200 9 100 100 10 100 0 11 100 25 75 12 100 25 150 13 100 25 225 14 100 25 300 15 100 200 16 100 100 17 100 0 18 100 75 75 19 100 25 150 20 100 25 225 21 100 25 300 22 100 200 23 100. 100 24 100 0 25 100 25 75 26 100 25 150 27 100 25 225 28 100 25 300 29 100 200 30 100 100 31 100 0 Annual average recharge/recovery rate = 57,000 AF/yr 155
C JOSEPH MICHAEL A3E d C DEFINITION OF VARIABLES
• INPUT VARIABLES • TOCAP = TOTAL CAPITAL COSTS LESS INTEREST DURING CONSTRUCTION • FOME = FIXED OPERATION. MAINTENANCE AND ENERGY COSTS • RGOM = RECHARGE OPERATION AND MAINTENANCE COSTS • RYOM = RECOVERY OPERATION AND MAINTENANCE COSTS • CSP = CONVEYANCE SYSTEM POWER COMSUMPTION (KWH) • CSOM = CONVEYANCE SYSTEM OPERATION AND MAINTENANCE COSTS • DR = DISCOUNT RATE. i (Z) • DP = DESIGN PERIOD. n (years) • PR = POWER RATE. PR (S/kwh)
• IMPORTANT VARIABLES CALCULATED IN PROGRAM
• GTCC = GRAND TOTAL CAPITAL COSTS • CRF = CAPITAL RECOVERY FACTOR • ACC = ANNUAL/ZED CAPITAL COSTS • AOME = ANNUALIZED OPERATION, MAINTENANCE AND ENERGY COSTS • AEPC = ANNUAL ELECTRIC POWER COSTS • LCAF = LIFT COST / ACRE-PT
• ANNUAL COST VARIABLES FOR FUNCTIONAL MODES
• RG292 = RECHARGE (292 DAYS) • RY292 = RECOVERY (292 DAYS) RR73 = RECHARGE (292 DAYS) / RECOVERY (73 DAYS) • RR92 = RECHARGE (3 MONS) / RECOVERY (3 MONS) • MAJOR OUTPUT VARIABLE
• UNIT = COST / ACRE-FT OF WATER RECHARGED AND RECOVERED
PROGRAM ITERA REAL TOCAP,FOME.RGOM.RYOM.CSP.CSOM.DR.PR.GTCC.CRF.ACC.AEPC. +LCAF.RG292.RY292.RR73.RR92,SUM.DOME.AOME.UNIT.GTCCO 3 .PVCC.CC 5 UM INTEGER I.J.II.N.JJ.M.NN.DP.KK OPEN (5.FILE = 'ITERA.DAT') OPEN (6.FILE = 'OUT.RES'.STATUSNEW)
DO 100 1=1.4 WRITE (6.8) I 8 FORMAT ('1'.38X.'PLAN '.I1/) 156
C INPUT VARIABLES READ FROM DATA FILE.
READ (5,*) TOCAP.FOME.RGOM.RYOM.CSP.CSOM DO 75 J=1.11
READ (5.*) DR.DP.PR
C CALCULATE INTEREST DURING CONSTRUCTION (3 YEARS) AND GRAND TOTAL C CAPITAL COSTS.
GTCC = 1.5 * DR * TOCAP + TOCAP
C DIVIDE CAPITAL COSTS EQUALLY OVER 3 YEARS OF CONSTRUCTION. CALCULATE C PRESENT VALUES AND SUM. GTCCO3 = GTCC/3 CCSUM = 0.0 DO 9 KE=1.3 PVCC = (1/(1+DR)**KK) * GTCCO3 CCSUM = CCSUM + PVCC 9 CONTINUE
C CALCULATE CAPITAL RECOVERY FACTOR AND ANNUALIZED CAPITAL COSTS.
CRP = (DR*(1+DR)**DP)/((1+DR)**DP - 1) ACC = CCSUM * CRF
C CALCULATE ELECTRIC POWER COSTS FOR CONVEYANCE SYSTEM AND LIFT COST/ACRE-FT C FOR WELLS.
AEPC = CSP * PR LCAF = 0.53855 * PR C CALCULATE ANNUAL OM & E COSTS FOR RECHARGE (292 DAYS). RECOVERY (292 C DAYS). RECHARGE (292 DAYS) / RECOVERY (73 DAYS) AND RECHARGE (3 MONS) / C RECOVERY (3 MONS).
RG292 = TOME + (0.10*ACC) + CSOM + RGOM + AEPC RY292 = FOME + (0.10*ACC) + RYOM + (LCAF*100000) RR73 = FOME + (0.10*ACC) + CSOM + RGOM + AEPC + (0.25*RYOM) + +(LCAF*25000) RR92 = (0.315*RG292) + (0.315*RYOM) + (LCAF*32000)
IF (DP .EQ. 31) THEN GO TO 60 ELSE
C CALCULATE UNIT COST ($/ACRE-FT) FOR SCENARIO 1.
SUM = 0.0 DO 20 I1=4.DP.6 N = 11+2 DO 10 JJ=II.N DOME = RG292 * (1/(1+DR)**JJ) SUM = SUM + DOME 10 CONTINUE 157
M = II + 3 NN = II + 5 DO 15 K=M.NN DOME = RY292 * (1/(1+DR)**K) SUM = SUM + DOME 15 CONTINUE 20 CONTINUE AOME = SUM * CRP' UNIT = (AOME + ACC) / 50 WRITE (6.24) 24 FORMAT (36X,'SCENARIO 1') WRITE (6,25) DR,DP,PR.UNIT 25 FORMAT (14X,'FOR DR = 1 .F4.2.2X.'DP = 12.2X, 'PR = ',F5.3,4X.'COS +T/AF = ',F4.0/)
IF (DP .EQ. 51) THEN GO TO 75 ELSE
C CALCULATE UNIT COST (8/ACRE-FT) FOR SCENARIO 2. SUM = 0.0 DO 30 N=4,5 DOME = RG292 * (1/(1+DR)**N) SUM = SUM + DOME 30 CONTINUE DOME = RY292 *(1/(1+DR)**9) SUM = SUM +DOME DO 35 N=10,11 DOME = RR92 *(1/(1+DR)**N) SUM = SUM + DOME 35 CONTINUE DO 40 N=13.14 DOME = RG292 * (1/(1+DR)**N) SUM = SUM + DOME 40 CONTINUE DOME = R7292 * (1/(1+DR)**16) SUM = SUM + DOME DO 45 N=18.20 DOME = RR92 * (1/(1+DR)**N) SUM = SUM + DOME 45 CONTINUE DO 50 N=22,23 DOME = RR92 * (1/(1+DR)**N) SUM = SUM + DOME 50 CONTINUE DO 55 N=26,27 DOME = RY292 * (1/(1+DR)**N) SUM = SUM + DOME 55 CONTINUE AOME = SUM * CRF UNIT = (AOME + ACC)/26 WRITE (6.56) 56 FORMAT (36X.'SCENARIO 2') WRITE (6.57) DR.DP,PR.UNIT 57 FORMAT (142E,'FOR DR = 1 .F4.2,21(.'DP = = '.F5.3,4X,'COS +T/AF = '.F4.0/) END IF END IF GO TO 75 158
C CALCULATE UNIT COST (S/ACRE-FT) FOR SCENARIO 3.
60 SUM = 0.0 DO 70 II=4.DP.7 N = II + 3 DO 65 JJ=II.N DOME = RR73 * (1/(1+DR)**JJ) SUM = SUM + DOME 65 CONTINUE M = II + 4 NN = II + 6 DO 67 IC=M.NN DOME = RY292 * (1/(1+DR)**10 SUM = SUM + DOME 67 CONTINUE 70 CONTINUE AOME = SUM * CRF UNIT = (AOME + ACC)/57 WRITE (6.72) 72 FORMAT (361. 'SCENARIO 3') WRITE(6.74) DR.DP.PR.UNIT 74 FORMAT (14X.'FOR DR = 1 .F4.2.27E.'DP = '.I2.21.'PR = +T/AF = '.F4.0/) 75 CONTINUE 100 CONTINUE END 159
57718 310 588 195 53400 306 0.04 27 0.036 0.08 27 0.036 0.10 27 0.036 0.08 27 0.008 0.08 27 0.011 0.04 31 0.036 0.08 31 0.036 0.10 31 0.036 0.08 31 0.008 0.08 31 0.011 0.08 51 0.036 108699 288 1605 195 18095 500 0.04 27 0.036 0.08 27 0.036 0.10 27 0.036 0.08 27 0.008 0.08 27 0.011 0.04 31 0.036 0.08 31 0.036 0.10 31 0.036 0.08 31 0.008 0.08 31 0.011 0.08 51 0.036 47555 302 450 195 48900 189 0.04 27 0.036 0.08 27 0.036 0.10 27 0.036 0.08 27 0.008 0.08 27 0.011 0.04 31 0.036 0.08 31 0.036 0.10 31 0.036 0.08 31 0.008 0.08 31 0.011 0.08 51 0.036 49538 299 450 195 57900 329 0.04 27 0.036 0.08 27 0.036 0.10 27 0.036 0.08 27 0.008 0.08 27 0.011 0.04 31 0.036 0.08 31 0.036 0.10 31 0.036 0.08 31 0.008 0.08 31 0.011 0.08 51 0.036 160
PLAN A
SCENARIO 1 FOR DR = .04 DP = 27 PR = .036 COST/AF = 122.
SCENARIO 2 FOR DR = .04 DP = 27 PR = .036 COST/AF = 184.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .036 COST/AF = 153.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .036 COST/AF = 246.
SCENARIO 1 FOR DR = .10 DP = 27 PR = .036 COST/AF = 169.
SCENARIO 2 FOR DR = .10 DP = 27 PR = .036 COST/AF = 279.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .008 COST/AF = 130. SCENARIO 2 FOR DR = .08 DP = 27 PR = .008 COST/AF = 223.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .011 COST/AF = 132. SCENARIO 2 FOR DR = .08 DP = 27 PR = .011 COST/AF = 225. SCENARIO 3 FOR DR = .04 DP = 31 PR = .036 COST/AF = 108. SCENARIO 3 FOR DR = .08 DP = 31 PR = .036 COST/AF = 136.
SCENARIO 3 FOR DR = .10 DP = 31 PR = .036 COST/AF = 151. SCENARIO 3 FOR DR = .08 DP = 31 PR = .008 COST/AF = 113. SCENARIO 3 FOR DR = .08 DP = 31 PR = .011 COST/AF = 115. SCENARIO 1 FOR DR = .08 DP = 51 PR = .036 COST/AF = 142. 161
PLAN B
SCENARIO 1 FOR DR = .04 DP = 27 PR = .036 COST/AF = 187.
SCENARIO 2 FOR DR = .04 DP = 27 PR = .036 COST/AF = 306.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .036 COST/AF = 248.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .036 COST/AF = 423. SCENARIO 1 FOR DR = .10 DP = 27 PR = .036 COST/AF = 281. SCENARIO 2 FOR DR = .10 DP = 27 PR = .036 COST/AF = 488. SCENARIO 1 FOR DR = .08 DP = 27 PR = .008 COST/AF = 234.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .008 COST/AF = 410.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .011 COST/AF = 235. SCENARIO 2 FOR DR = .08 DP = 27 PR = .011 COST/AF = 411.
SCENARIO 3 FOR DR = .04 DP = 31 PR = .036 COST/AF = 161. SCENARIO 3 FOR DR = .08 DP = 31 PR = .036 COST/AF = 217.
SCENARIO 3 FOR DR = .10 DP = 31 PR = .036 COST/AF = 247. SCENARIO 3 FOR DR = .08 DP = 31 PR = .008 COST/AF = 202. SCENARIO 3 FOR DR = .08 DP = 31 PR = .011 COST/AF = 204. SCENARIO 1 FOR DR = .08 DP = 51 PR = .036 COST/AF = 228. 162
PLAN C
SCENARIO 1 FOR DR = .04 DP = 27 PR = .036 COST/AF = 105.
SCENARIO 2 FOR DR = .04 DP = 27 PR = .036 COST/AF = 156.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .036 COST/AF = 130.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .036 COST/AF = 206. SCENARIO 1 FOR DR = .10 DP = 27 PR = .036 COST/AF = 143. SCENARIO 2 FOR DR = .10 DP = 27 PR = .036 COST/AF = 233. SCENARIO 1 FOR DR = .08 DP = 27 PR = .008 COST/AF = 108.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .008 COST/AF = 184.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .011 COST/AF = 110.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .011 COST/AF = 186. SCENARIO 3 FOR DR = .04 DP = 31 PR = .036 COST/AF = 94.
SCENARIO 3 FOR DR = .08 DP = 31 PR = .036 COST/AF = 116. SCENARIO 3 FOR DR = .10 DP = 31 PR = .036 COST/AF = 128.
SCENARIO 3 FOR DR = .08 DP = 31 PR = .008 COST/AF = 94. SCENARIO 3 FOR DR = .08 DP = 31 PR = .011 COST/AF = 96. SCENARIO 1 FOR DR = .08 DP = 51 PR = .036 COST/AF = 121. 163
PLAN D
SCENARIO 1 FOR DR = .04 DP = 27 PR = .036 COST/AF = 111. SCENARIO 2 FOR DR = .04 DP = 27 PR = .036 COST/AF = 165.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .036 COST/AF = 137.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .036 COST/AF = 218. SCENARIO 1 FOR DR = .10 DP = 27 PR = .036 COST/AF = 151. SCENARIO 2 FOR DR = .10 DP = 27 PR = .036 COST/AF = 246.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .008 COST/AF = 113.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .008 COST/AF = 193.
SCENARIO 1 FOR DR = .08 DP = 27 PR = .011 COST/AF = 116.
SCENARIO 2 FOR DR = .08 DP = 27 PR = .011 COST/AF = 196. SCENARIO 3 FOR DR = .04 DP = 31 PR = .036 COST/AF = 100. SCENARIO 3 FOR DR = .08 DP = 31 PR = .036 COST/AF = 123.
SCENARIO 3 FOR DR = .10 DP = 31 PR = .036 COST/AF = 136. SCENARIO 3 FOR DR = .08 DP = 31 PR = .008 COST/AF = 99.
SCENARIO 3 FOR DR = .08 DP = 31 PR = .011 COST/AF = 101.
SCENARIO 1 FOR DR = .08 DP = 51 PR = .036 COST/AF = 129. SELECTED BIBLIOGRAPHY
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