Final 

Petroleum Association of Wyoming 

Technical Review and Analysis of Kuipers' / 

NPRC Documents Related to the Management of 

CBNG Produced Water in the Powder River 

Basin 

December 21, 2004 
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Contents 

List of Figures 

List of Tables 

Section 1 Introduction 

1.1 Summary of Kuipers' Study Findings................................................1-1 

1.2 Industry’s Major Concerns with Kuipers’ Study..............................1-2 

1.3 Project Objectives ..................................................................................1-4 

1.4 About CDM............................................................................................1-4 

Section 2 Feasibility of Injection of CBNG Produced Water 

2.1 Hydrologic Storage Considerations for Injection .............................2-1 

2.2 Injection and Interaction with CBNG Production............................2-2 

2.3 Compatibility of Injected Water..........................................................2-2 

2.4 Injection and Land Subsidence ...........................................................2-3 

2.5 Injection Testing and Operations in the PRB ....................................2-4 

2.6 Surface Disturbance ..............................................................................2-6 

2.7 Injection and Aquifer Depletion .........................................................2-7 

Section 3 Feasibility of Treatment 

3.1 Evaluation of RO Technical Issues .....................................................3-1 

3.1.1 Water Quality and Flow Variations ....................................3-1 

3.1.2 Treatment Objectives.............................................................3-2 

3.1.3 System Recovery ....................................................................3-2 

3.1.4 Pretreatment ...........................................................................3-3 

3.1.5 Location...................................................................................3-5 

3.1.6 Brine Disposal.........................................................................3-5 

3.2 Evaluation of Kuipers' RO Treatment Costs.....................................3-6 

3.2.1 Assumptions...........................................................................3-6 

3.2.2 Recalculation of Costs Using Kuipers' Model....................3-7 

3.3 CDM's Cost Estimate for RO Treatment ...........................................3-9 

3.3.1 Design and Cost Assumptions...........................................3-10 

3.3.2 Cost Estimate Results ..........................................................3-12 

 3.4 Alternative Treatment Options.........................................................3-13 

 3.4.1 Conventional Ion Exchange (IX)........................................3-13 

 3.4.2 Counter-Current IX..............................................................3-13 

 3.4.3 Hydro Process ......................................................................3-14 
 3.4.4 HERO Process.......................................................................3-14 

 3.4.5 Zeolites ..................................................................................3-14 

 3.4.6 Mechanical Evaporation/Crystallizer ..............................3-14 

 3.4.7 Cost Comparison .................................................................3-15 

Section 4 Beneficial Use 

4.1 Water Quality Comparison..................................................................4-1 

4.2 Managed Irrigation for Beneficial Use ...............................................4-3 

Section 5 CBNG Economics 

Section 6 Conclusions 

6.1 Injection of CBNG Produced Water ...................................................6-1 

6.2 Treatment ...............................................................................................6-2 

6.3 Beneficial Use.........................................................................................6-3 

6.4 CBNG Economics..................................................................................6-3 

6.5 Flexible Water Management................................................................6-4 

Section 7 References 

Appendices 

Appendix A Feasibility, Design, Operation and Monitoring of CBNG 

Managed Irrigation Systems 

Appendix B Re-evaluation of Kuipers’ Reverse Osmosis Treatment Cost 

Estimates 

Appendix C CDM Cost Estimates for Reverse Osmosis Treatment 

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List of Figures 

Figure 2-1 Modeled Drawdown vs. Time for Selected Upper 

Fort Union Monitoring Locations ..............................................2-8 

Figure 3-1 Alternative 5a. RO Treatment with Commercial Brine 

 Disposal .........................................................................................3-9 

Figure 3-2 Alternative 5b. RO Treatment with Injection Brine 

 Disposal .........................................................................................3-9 

Figure 3-3 Comparison of CDM Cost Estimate to Original 

Estimate for Alternative 5a .......................................................3-13 

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List of Tables 

Table 2-1 Fort Union Formation Injection Well Data from Two 

Operators in the PRB....................................................................2-5 

Table 2-2 Lance and Fox Hills Injection Well Data from Two 

Operators in the PRB....................................................................2-6 

Table 3-1 Kuipers' Assumptions for RO Treatment of PRB 

 Produced Water............................................................................3-7 

Table 3-2 Revised Cost Estimates Using Correct Data.............................3-8 

Table 3-3 Design Assumptions for CDM's RO Treatment 

 Cost Estimate...............................................................................3-10 

Table 3-4 Comparison of CDM and Kruipers' Cost Estimates 

for RO Treatment........................................................................3-12 

Table 3-5 Comparison of Estimated Costs for Various 

 Treatment Options .....................................................................3-15 

Table 4-1 Selected Water Quality Characterization Data for 

CBNG Well Fields in North America ........................................4-2 

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Section 1 

Introduction 

CDM, Inc. was contracted by the Petroleum Association of Wyoming (PAW) to 

complete a technical evaluation and review of key information presented in the two 

documents prepared by Kuipers and Associates (Kuipers) for the Northern Plains 

Resource Council (NPRC). The PAW is based in Casper, Wyoming and members 

include companies from all segments of the petroleum industry including 

exploration, production, well service, drilling, transportation, land, environmental, 

and processing. The NPRC is based out of Billings, Montana and is a non-profit 

organization that is active in the debate over coal bed natural gas (CBNG) 

development underway in the Powder River Basin (PRB). The following two 

documents were prepared by Kuipers for NPRC and are the subjects of this review: 

Kuipers, J.R. Machardy, K., Merschat, W., and Myers, T. 2004. “Draft-Coal Bed 

Methane Produced Water: Management Options for Sustainable Development”. 

Prepared for the NPRC, Billings, Montana. August. 

Kuipers and Associate 2004. “Draft Technology Based Effluent Limitations for Coal 

Bed Methane-Produced Wastewater Discharges in the Powder River Basin of 

Montana and Wyoming”. Prepared for the NPRC, Billings, Montana. August. 

For the purposes of this review, the first report will be referred to as the “management 

options report” and the second as the “effluent limitations report.” The combined 

documents are referred to as “Kuipers’ study” or the Kuipers study.” The documents 

as well as the study brief prepared by the NPRC were obtained electronically from the 

NPRC website located on the internet at: http://www.northernplains.org/

CDM also reviewed the draft, unpublished United States Environmental Protection 

Agency (EPA) report Guidance for Developing Technology-Based Limits for Coal-Bed 

Methane Operations: Economic Analysis of the Powder River Basin, which was referenced 

as providing base information used in the Kuipers study. This document was given 

to CDM by PAW member companies. 

1.1 Summary of Kuipers’ Study Findings 

The management options report provides a very general overview of CBNG 

produced water management issues, including a discussion of produced water 

management options, potential environmental effects, treatment alternatives, and an 

evaluation of the benefits and costs associated with selected options under a 

“sustainable management” analysis. This document was presumed to be directed at 

CBNG management issues in the PRB. 

The effluent limitations report was prepared as a companion document and provides 

a cursory analysis of the technical feasibility and economics of each of the water 

management options and recommends to the permit writers in Montana and 

Wyoming that technology-based limits be established for CBNG produced water 
Section 1 

Introduction

discharges in the PRB. As stated in the document, much of the technical and 

economic information used to complete this analysis was taken from an unpublished 

EPA report Guidance for Developing Technology-Based Limits for Coal-Bed Methane 

Operations: Economic Analysis of the Powder River Basin. 

According to the Kuipers study briefing document, key assertions are: 

The most harmful disposal options for the CBNG produced water are direct discharges to 

rivers, streams, unlined impoundments and soils. These disposal options unnecessarily 

put agricultural water resources at risk and damage soils. 

It is practical and affordable to return CBNG produced water to aquifers – either by 

reinjecting it into the aquifer from which it came or injecting it into other suitable

formations. Reinjection and injection are proven technologies and affordable given current 

and foreseeable gas prices. 

In cases where reinjection/injection are not feasible, treating all water prior to discharge is 

feasible via a number of treatment technologies –particularly reverse osmosis – and 

affordable for industry. 

As a result of these findings, Kuipers’ major recommendations to the EPA and both 

the Wyoming and Montana Departments of Environmental Quality are to adopt the

following technology-based effluent limitations in accordance with the Clean Water 

Act’s “mandate” that industries use the “best available technology” to eliminate the 

discharge of pollutants into the Nation’s waters:

ZERO DISCHARGE. Kuipers proposes that no discharge of CBNG produced water 

should be allowed to surface water. Kuipers suggests that companies can achieve this 

“Tier 1” mandate by returning the CBNG produced water to the aquifer from which it 

came or injecting it into other appropriate formations.

TREATMENT. Kuipers concludes that if a company demonstrates that returning the 

CBNG produced water to the ground is technically feasible for a portion of the produced 

water, the company should be required to treat 100% of the water prior to discharge to 

achieve this “Tier 2”. 

1.2 Industry’s Major Concerns with Kuipers’ Study 

Prior to fully engaging CDM to complete a technical evaluation of Kuipers’ study, the 

PAW issued a statement to the media that presents an overview of the major issues 

and concerns about the findings and recommendations presented in Kuipers’ study. 

The following list is a summary of concerns and issues: 

 Produced water quality in the PRB is very good compared to other producing 

basins in the United States. Consequently, PRB produced water has a high 

potential for direct discharge or beneficial use and should be managed

accordingly. Experience has shown that many landowners want the water for 

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Section 1 

Introduction

irrigation and livestock and are opposed to injecting the water back into the 

ground. Injecting good quality water into a formation containing poorer water 

quality results in a loss of the water for beneficial use and does not make sense. 

The beneficial uses of produced water and its positive impacts are not adequately 

discussed or addressed in Kuipers’ study. 

 Kuipers’ study fails to take into account site specific issues related to water 

management, including injection and treatment. Selecting and practically 

implementing the best water management option, including treatment and 

injection, must consider a number of site specific factors, such as geologic 

formations; geographic location within the basin; technical feasibility; practicality, 

simplicity and reliability of water management options; dynamics of produced 

water production rates, and seasonal variation and conditions. 

 Kuipers’ fails to address the single most important site specific issue: The 

landowners’ desires to use the CBNG produced water and contractual 

agreements negotiated by landowners or their representatives on their behalf. 

With few exceptions, landowners want access to CBNG produced water for their 

stock, agricultural, and industrial uses. 

 Injecting produced water in the Powder River Basin is not technically feasible 

in many locations. As indicated in Kuipers’ study, the petroleum industry is not 

opposed to injection, which it regularly practices in many parts of the United 

States, including the Powder River Basin. However, few viable formations have 

been found to exist with sufficient porosity, permeability, and reservoir extent that 

can accept the volume of water produced. In several attempts to inject water into 

sands in the Fort Union, Lance, and Fox Hills Formations, operators have found 

that they would need to drill one injection well for every one to two producing 

wells. This issue was not addressed in Kuipers’ study. 

 Water treatment technologies, specifically for coal bed natural gas operations, 

are an emerging and evolving science. Water treatment makes sense when it 

takes place near where the treated water can be discharged, such as a year-round 

river system, or used in a managed irrigation system. However, when the CBNG 

operation is in a remote area water treatment may not be the best water 

management tool. Industry realizes treatment is necessary in some situations and 

is currently testing and using different water treatment technologies throughout 

the basin. 

 Kuipers’ study fails to recognize and/or grossly underestimates many of the 

costs to treat and manage the concentrated byproducts associated with 

treatment. The logistics and costs associated with managing and disposing of the 

concentrated waste brine are the greatest challenges when implementing 

treatment options. 

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Introduction

 Kuipers does not consider the lost production and revenues, including royalties 

and state tax revenues, resulting from significantly increased CBNG operating 

costs if the study recommendations are implemented. Increasing operating costs 

greatly decreases the economic life and recovery from a well. 

Industry regulators and operators require flexibility to manage CBNG produced 

water so that they accommodate site specific factors, satisfy landowners, protect the 

environment and ensure long-term economic viability of operations. Where it makes 

sense and is technically feasible, CBNG operators consider injection and water 

treatment opportunities as management options. However, while the Kuipers studies 

lead the public to believe that injection and water treatment are widely available 

management tools, it is industry’s experience in the PRB that these options are only 

technically feasible on a site-specific basis and within limited geographic areas. 

1.3 Project Objectives 

CDM’s key objectives are to provide an independent technical evaluation of Kuipers’

main findings, primarily related to: 

 Injection, including surface impacts, land subsidence and aquifer depletion. 

 Treatment using reverse osmosis, ion exchange and other methods. 

 Beneficial use with a focus on managed irrigation. 

 CBNG economics. 

This study concludes that continuing flexible water management practices in the PRB 

is necessary to allow beneficial use of produced water where applicable, manage sitespecific characteristics, minimize the environmental effects and maximize the 

economic benefits of coal bed natural gas production in both Wyoming and Montana. 

Project objectives were achieved using a variety of in-house and external resources. 

CDM relied on experts in the areas of water and wastewater treatment, injection, and 

managed irrigation; water quality and economic data provided by PRB operators; 

industry experience using a variety of water management tools, including water 

treatment, injection, and managed irrigation; industry-wide publications and 

references; and discussions with agency personnel. Wherever possible, technical 

evaluations, engineering calculations and cost estimates were completed using typical 

produced water quality and industry data. 

1.4 About CDM

CDM is one of the largest full service engineering consulting firms in the United 

States. Headquartered in Cambridge, Massachusetts and established in 1947, CDM 

has over 3,700 professionals in more than 100 offices worldwide, including Montana. 

We offer global consulting, engineering, construction, and contract operations 

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Section 1 

Introduction

services to both the public and private sectors. CDM is an employee-owned company 

with annual revenues exceeding $650 million last year. 

With respect to water treatment, CDM is consistently ranked by Engineering News 

Record as one of the top 10 water/wastewater treatment firms and top fifteen 

environmental firms in the country. As a company, we have considerable experience 

developing, designing, constructing and operating water/wastewater treatment 

systems for municipal and industrial sectors using conventional and advanced 

treatment technologies, such as reverse osmosis. In fact, a large percentage of CDM’s 

business revolves around water resource development, supply, and treatment issues. 

CDM has substantial experience and capabilities for developing and/or improving 

water and wastewater management and treatment strategies for purposes of meeting

stringent discharge limits, water conservation, water reuse and reducing operating 

costs. 

CDM personnel have experience developing, testing and evaluating advanced 

systems, including reverse osmosis and ion exchange processes, for management and 

treatment of CBNG produced water since the late 1990s. This, combined with CDM’s 

extensive experience providing design/build/operate services to the

water/wastewater industry, gives us an excellent understanding of the technical 

challenges, logistical issues and costs associated with water treatment and disposal of 

CBNG water. In addition, CDM has several geologists with registrations in Wyoming 

that have a wide range of injection-related experience in several states. 

CDM contracted the services of Kevin Harvey, an independent consultant specializing 

in soil science. Mr. Harvey is a well known expert in the PRB area for issues related to 

water management and permitting. During the past several years, he has assisted 

many operators with the development and implementation of managed irrigations 

systems to maximize the beneficial use of produced water where feasible. 

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Section 2 

Feasibility of Injection of CBNG Produced 

Water 

The Kuipers studies present two of the preferable or most sustainable development 

options for CBNG water as: 

1. Injection or percolation into depleted aquifers with water treatment as required, 

protecting and/or enhancing water quality. 

2. Reinjection into aquifers depleted or otherwise affected by CBNG production. 

Kuipers considers aquifer recharge by injection/reinjection as a very favorable 

beneficial use water management practice for CBNG produced water within the PRB. 

To assess the feasibility of injection, CDM reviewed results from two active injection 

projects in the PRB and evaluated several technical issues that must be considered for 

injection to be an option. In addition, a discussion of land subsidence and aquifer 

depletion issues, which the Kuipers study indicates would be alleviated by injection, 

is also included. 

2.1 Hydrologic Storage Considerations for Injection

The Kuipers study presents injection (or re-injection into the depleted coal bed) as the 

preferred option for the PRB and states that several factors are important for 

successful injection, including: 

To be suitable for injection, a formation must have sufficient porosity, permeability, 

and storage capacity to hold and transmit the water; and static water pressures low 

enough to allow water movement from the injection well to the formation. 

While subsurface injection is a viable water management option that is successfully 

applied in other CBNG producing basins (e.g., the Uinta Basin in Utah), injection has 

not been proven to have wide spread viability (technical or economical) in the PRB. 

The feasibility of injection must consider not only the total porosity and storage 

capacity of the target zone, but also the storage capacity available. Most of the 

potential target zones for injection in the PRB are fully saturated, with the exception 

of shallow sandstones in the Wasatch or Fort Union Formations near the basin 

margins, or near surface alluvial deposits. When this pore space is full, the available 

storage capacity is small. 

The aquifer property that relates the change in storage capacity as a function of 

pressure is the storage coefficient. This describes the amount of water released from 

an aquifer under a unit change in pressure. In an unconfined aquifer, such as the 

shallow unconfined alluvial deposits in stream valleys, this volume of water is 

associated with physical drainage or re-saturating of the pore space. As water levels 

rise in the unconfined alluvial aquifer, the pore space fills with water. In the case of 
Section 2 

Feasibility of Injection of CBNG Produced Water 

deeper confined aquifers that are already fully saturated with water, such as the Fort 

Union sandstones, adding water results in a change in the pressure within the 

confined aquifer, since water is nearly incompressible. 

The difference between the physical pore volume and storage capacity under 

confined conditions is very large. For example, the storage capacity of an unconfined 

alluvial sand and gravel aquifer may range up to 25 percent of its volume, so an 

increase of one foot of water level in this aquifer over one acre would provide storage 

for about 81,500 gallons of water. By comparison, a confined coal bed or sandstone 

aquifer in the Fort Union Formation, at depths of 1,000 to 2,000 feet, is under pressure 

from both the overlying water column and geological materials and has a very small 

fraction of volume available for water storage (often less than 1 percent). In this case, 

water storage can only be accomplished by increasing the pressure in the available 

pore spaces which are already saturated. Injecting CBNG water into these formations

is limited by the regulation of the injection pressure, which must remain under the 

pressure at which the formation will be artificially fractured as required by state and

federal Underground Injection Control (UIC) regulations. Water can only be injected 

into the receiving formations within this narrow pressure envelope, which severely 

limits the available storage capacity for CBNG water. 

2.2 Injection and Interaction with CBNG Production 

The Kuipers study states the following: 

CBM production involves dewatering of a coal seam which subsequently leads to a 

decrease in hydrostatic pressure, compaction, and subsidence. Reinjection into a 

dewatered coal seam (post-CBM production) or reinjection into a coal seam concurrent 

with CBM production could be used beneficially to reduce and/or minimize such 

effects. 

Any injection alternative must consider both lateral and vertical proximity of the 

depressurization zone for CBNG wells and the injection wells. Since the storage 

capacity of the sandstone and coal bed aquifers is very low, pressure changes due to 

pumping or injecting will rapidly spread over large distances. Injecting water into 

receiving formations near producing coal zones that are being depressurized for 

CBNG production may cause recirculation of some of this water, increasing pumping 

requirements. The potential loss of recoverable CBNG due to increased pumping and 

water management costs would also significantly impair the economic viability of the 

project. In addition, reinjecting into depleted coal bed zones must also consider their 

formation characteristics, which make the coal beds poor receiving formations due to 

their low porosity, storage capacity, and fracture pressure. 

2.3 Compatibility of Injected Water 

The geochemistry of the injected water and the native waters must also be considered. 

The formation can be fouled if the injected water is not compatible with formation 

water and precipitation of minerals occurs when the waters mix. Precipitating 

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Feasibility of Injection of CBNG Produced Water 

minerals will cause plugging within the formation in the vicinity of the injection well 

either rendering the well inoperable or greatly reducing its injection capacity. When 

this occurs, the well generally requires chemical reconditioning or replacement. 

2.4 Injection and Land Subsidence 

The Kuipers study states the following: 

There is also potential for ground subsidence related to CBM-produced water 

withdrawal (Case, 2004). Reinjection would decrease or eliminate the potential for 

subsidence by replacing the water in coal seam aquifers. 

Subsidence occurs when pressure is reduced in fine grain sediments that are not fully 

compacted. Hydrogeologic conditions in which measurable subsidence has occurred 

are in areas where a heavily pumped, confined sedimentary aquifer is situated above 

or below low permeability aquitards of saturated clay or silt. These saturated clays 

and silts are not fully compacted due to rapid deposition and burial, or they have 

been hydrologically cut off from release of abnormal pore pressure. 

Pumping lowers the water pressure in the aquifer, which in turn causes water to 

slowly drain from adjacent clay and silt beds. The reduction in water pressure causes 

a loss of support for the uncompacted clay and silt beds. Because these beds are still 

compressible, they compact (become thinner) due to the overlying lithostatic load no 

longer being supported by the previous pore water pressure. The effect is a slow 

lowering of the land surface over the area of pressure reduction and is known as land

subsidence. Land subsidence is a permanent compaction of the adjacent aquitards 

and cannot be compensated or recovered (U.S. Geological Survey, 1999). 

The Kuipers study incorrectly claims that reinjection into the depressurized aquifer or

other zones, either concurrently or post-production, will mitigate or reverse 

compaction. An evaluation of the potential for land subsidence from CBNG 

extraction in the PRB was performed by the Wyoming Geological Survey (WGS). 

That study showed that the maximum compression of the Wyodak coal bed from 

depressurization in the Gillette area would be 1⁄2 inch (1.3 cm) or less (Case and others

2000). The report also indicated that the entire compression may not be transmitted to

the surface. 

Additional field observations support this study. The WGS also reported that 

significant quantities of groundwater had already been pumped from a sandstone 

unit underlying the Wyodak Coal Zone in the eastern PRB. This unit supplied 

drinking water to Gillette prior to CBNG development. No surface subsidence has 

been observed in the Gillette area associated with this groundwater withdrawal or the 

subsequent withdrawals from the overlying Fort Union Formation Wyodak coal units 

beginning in the 1990s.

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Feasibility of Injection of CBNG Produced Water 

In describing the potential impacts from CBNG production, the Kuipers study also 

concludes that: 

Impacts associated with drawdown are loss of the aquifer storage capacity as a result of 

collapse or compaction of aquifer and land surface subsidence, which can occur if the 

aquifer material is unconsolidated. 

Surface subsidence may also be evident if the aquifer collapse is significant. This could 

cause excessive damage to buildings, roads, and other infrastructure (i.e., bridges, 

railroads) located over the collapsing aquifer; however, if the coal aquifer is located in 

stable consolidated rock, then aquifer collapse probably will be minimal and not be

noticed at the ground surface. 

Again, as explained above and supported by long term evaluations of subsidence by 

the U.S. Geological Survey and site specific evaluations by the WGS, compaction of 

the coal bed and adjacent units is insignificant and immeasurable at the surface in the 

PRB. In addition, the term “collapse” is not used in any studies evaluating regional 

subsidence related to groundwater pumping. Using the term collapse in the Kuipers 

study as a descriptor of the land subsidence process is misleading. 

Geologic conditions in the PRB are not the same as in those areas where significant 

land subsidence has occurred. The Fort Union Formation within the PRB is fully 

consolidated. Furthermore, the amount of groundwater withdrawn from the low 

permeable coal beds is insignificant in the context of supporting the overlying 

lithostatic load. 

2.5 Injection Testing and Operations in the PRB

CBNG operators are actively injecting produced CBNG water in areas of the PRB 

where evaluation of subsurface geological data identified zones with potential to 

receive water. These operations began more three years ago in Wyoming. Injection 

wells are currently operating in the eastern and northwest portions of the basin. 

Target receiving zones include the Fort Union Formation and the deeper Lance and

Fox Hills Formations. 

Tables 2-1 and 2-2 present testing and operational results of injection wells completed 

by two CBNG operators in both the shallow (541 to 2,320 feet) Fort Union Formation 

and the deeper (4,000 to 4,470 feet) Lance and Fox Hills Formations. Successful wells 

are defined as those that were able to continuously receive water at injection 

pressures below the formation fracture pressure. As shown, some wells were able to 

receive water for a period of time, but eventually exceeded the fracture pressure of the 

formation and injection was stopped (except as noted in Table 2-1 for well 36A). The 

overall success ratio for the Fort Union injection wells was 47.6 percent (10 out of 21) 

and the average injection rate was calculated to be 36.7 gpm. 

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Deeper injection testing was also conducted in the Upper Cretaceous Lance and Fox 

Hills formations, which have poorer water quality. Testing of the Lance and Fox Hills 

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Feasibility of Injection of CBNG Produced Water 

formations indicates an overall success of 25 percent as shown in Table 2-2. However, 

the actual success ratio may be much lower since the size of the data set is small and it 

appears that the risk of finding a successful receiving zone in the Lance and Fox Hills 

may be much higher. Insufficient data are available to determine a reasonable 

average injection rate in these formations. 

Table 2-1 

Fort Union Formation Injection Well Data from Two Operators in the PRB

Injection Well

Total

Depth 

(ft) 

Receiving 

Formation 

Cumm. 

Injection

Volume 

(gallons) 

Cumm. 

Duration 

(days) 

Average 

Injection

Rate 

(gpm) 

Successful

Ivy Creek SR-1 1,621 Ft. Union New 0 0 Yes 

Laney SR-1 1,648 Ft. Union 0 0 0 No 

LS Draw 12-28 I 541 Ft. Union 21,631,386 359 42 Yes 

LS Draw 5-28 I 568 Ft. Union 15,735,132 539 20 Yes 

LS Draw 6-28 I 630 Ft. Union 15,082,452 539 19 Yes 

S J Wolff SR-2 2,050 Ft. Union 0 0 0 No 

S J Wolff SR-3 2,320 Ft. Union Test Only 0 0 No 

S J Wolff SR-4 2,000 Ft. Union Test Only 0 0 No 

Steinhoffel SR-1 1,508 Ft. Union 125,040,426 1,169 74 Yes 

Steinhoffel SR-4 1,404 Ft. Union 23,063,082 811 20 Yes 

Steinhoffel SR-2 1,500 Ft. Union 188,600 34 4 No 

Steinhoffel SR-3 1,507 Ft. Union 366,400 23 11 No 

Sunburst SR-1 1,400 Ft. Union 2,052,900 28 51 Yes 

Sunburst SR-2 1,000 Ft. Union 7,121,700 102 48 Yes 

Tietjen 7-33 722 Ft. Union 43,583,862 729 42 Yes 

Wolff SR-1 1,864 Ft. Union 20,812,600 198 73 No 

7A-3 1,614 Ft. Union 4,601,982 4,380 9(1) No 

36A 1,632 Ft. Union 151,654,314 13,140 96(1) Yes 

36B 1,700 Ft. Union 50,769,474 5,475 77(1) No 

14-34 1,591 Ft. Union 59,879,610 4,380 112(1) No 

Unknown NA Ft. Union NA NA NA No

Average 1,441 36.7(2) SR = 0.48

Notes: 

gpm = gallons per minute; SR = success ratio; NA = Not Available 

(1) Wells were operated at injection pressures exceeding the receiving formation fracture pressure for an 

unspecified period of time: therefore data was not used in average injection rate calculation

(2) Calculated from all successful wells with injection rate history except well 36A 

Overall, based on this data, approximately two successful injection wells in the 

shallow Fort Union Formation are required to handle the volume from 10 producing 

wells having an average flow of 60-gpm. However, the data also indicates that due to

the low success ratio, approximately four injection wells will need to be drilled to find

two successful wells capable of handling the flow from a 10-well producing system. 

Injection into the deeper Lance and Fox Hills Formations carries a substantially higher 

risk and likely loss of beneficial use due to the poor water quality in the receiving 

formations. 

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Feasibility of Injection of CBNG Produced Water 

Table 2-2 

Lance and Fox Hills Formations Injection Well Data from Two Operators in the PRB

Injection Well

Total

Depth 

(ft) 

Receiving 

Formation 

Cumm. 

Injection

Volume 

(gallons) 

Cumm. 

Duration 

(days) 

Average 

Injection

Rate 

(gpm) 

Successful

Inkline 5-23 I 4,228 

Lance-Fox 

Hills 67,477,074 427 110 Yes

Caballo SR-1 4,066 Fox Hills 0 0 0 No 

Duncan SR-2 4,000 Fox Hills 0 0 0 No 

Green Mansion 4,470 

Lance-Fox 

Hills 2,040,360 42 34(1) No 

Average 4,191 SR = 0.25

Notes: 

gpm = gallons per minute; SR = success ratio 

(1) Wells were operated at injection pressures exceeding the receiving formation fracture pressure for an 

unspecified period of time, data not used in average injection rate calculation

In summary, the injection well data from these two CBNG operators reflects the 

uncertainty in subsurface geologic conditions where porous and permeable zones in 

the Fort Union Formation and deeper Lance and Fox Hills Formations have limited 

extent and therefore limited storage capacity. This limited success and high 

exploration risk associated with locating successful injection wells also adds 

appreciable economic uncertainty, which significantly reduces the viability of 

injection as a water management tool. The results indicate that injection of CBNG 

water may be a management option in only a small portion of the PRB. 

2.6 Surface Disturbance 

Implementing injection to manage CBNG throughout the basin would cause a 

significant increase in surface disturbance. This surface disturbance was not fully 

evaluated by the Kuipers study and was underestimated in the cost model 

evaluations (Alternative 4a in the technology limits report). The Kuipers model 

accounts for only one acre of surface disturbance and reclamation costs for a 10 well 

(800 acre) development. However, using the actual injection success data presented 

in this report, the following additional and expanded surface disturbance would 

occur: 

 An additional two acres would be disturbed for the extra drill pads and access 

roads needed for drilling and testing a minimum of four (Fort Union) injection 

wells to get two successful injection wells capable of handling the flow as

proposed in Kuipers’ cost model. 

 The storage and settling pond for the injection wells would require approximately 

a 1-acre pond for a 30-day storage capacity (2.6 million gallons) of produced 

water. 

 The well piping estimate of 10,000 feet in Kuipers’ cost model to connect the 

producing wells to a centralized injection well is too low for a well spacing of 80 

acres/well. More than 20,000 feet are needed to accommodate the two Fort Union 

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Feasibility of Injection of CBNG Produced Water 

injection wells necessary for handling the average injection rate of 60 gpm, 

resulting in a temporary disturbance of about 1.8 acres. 

Overall, based on actual operator data, the total surface disturbance associated with 

injection as a preferred water management method is approximately 4.8 acres per 10-

well producing system, or more than four times that considered in Kuipers’ model. 

2.7 Injection and Aquifer Depletion 

As previously discussed, where receiving formations are available, injection is a 

valuable management tool for permanent storage of CBNG water in the subsurface. 

However, injection alone will not provide a means to restore depleted pressure to the 

coal beds. This process will occur naturally through leakage from adjacent 

formations, which will equilibrate with the depressurized coal bed over time. The 

depressurization is measured by water levels in wells completed or screened in the 

producing coal beds. A common misconception that is used in the Kuipers study is 

that lowering water levels in wells, or “drawdown,” created during pumping 

operations immediately causes an equivalent water level decline across confining 

shale units and other formations adjacent to the coal bed. It also does not equate to 

lowering shallow unconfined “water table” elevations. 

As discussed in Section 2.1, the water storage capacity of the coal beds is very small 

compared to shallow unconfined sands or even to more porous Fort Union Formation 

sandstones. CBNG production operations only remove a fraction of water stored in 

the coal to recover the adsorbed gas. Once CBNG pumping production ceases at 

economic limits (approximately seven years in the PRB), the pressure in the coal bed 

will begin to equilibrate with surrounding formations, and leakage from the adjacent 

formations will ultimately restore pressure to preexisting conditions. Slight pressure 

drops will be observed in surrounding formations during this recovery period, 

depending on the hydraulic communication between the coal bed and surrounding 

formations. Based on an intensive development scenario, the BLM (2003) Wyoming 

EIS evaluated the pressure response (as drawdown) throughout the basin and 

demonstrated that 75 to 85 percent of the depleted pressure would be recovered 

within approximately 15 years after production ceases (Figure 2-1). The propagation 

of this pressure response into other units would result in a fraction of the decline 

measured in coal bed wells. 

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Figure 2-1 

Modeled Drawdown vs. Time for Selected Upper Fort Union Monitoring Locations 

Applied Hydrology Associates. 2002. “Technical Report-Groundwater Modeling, Powder River Basin Oil 

and Gas Environmental Impact Statement” prepared for the U.S. Bureau of Land Management, Buffalo 

Field Office. December. 

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Feasibility of Treatment 

Kuipers’ management options report presents an overview of a wide range of 

treatment technologies that are being used or being developed for treating CBNG 

produced water in the PRB. Some of the technologies listed include reverse osmosis 

(RO), ion exchange, freeze-thaw/evaporation, and mechanical evaporation. Kuipers’ 

technology limitations report focuses on RO as the preferred alternative and was used 

as the basis for the economic calculations that conclude that RO treatment is proven, 

available and can be broadly applied as a technically feasible and “affordable” 

treatment technology to industry. 

This section presents the results of an independent review by experienced CDM 

personnel of the technical feasibility and the economics of applying RO as a broadbased treatment alternative. In addition, a discussion of other treatment options and 

their applicability and costs is presented to provide a better understanding of the 

variety of methods available. 

CDM personnel have direct experience with the development and testing of several of 

the technologies (and combinations of technologies) mentioned in the management 

options report. Specifically, these technologies include the Hydro process and High 

Efficiency Reverse Osmosis (HERO) process. CDM has also installed numerous largescale RO treatment systems world-wide for the conversion of brackish groundwater 

resources into beneficial use as municipal drinking water supplies. 

3.1 Evaluation of RO Technical Issues 

Before selecting RO as a preferred treatment alternative, there are many important 

site-specific and technical factors that must be carefully considered. Unfortunately, 

most of these factors were not discussed or considered in the technical discussion or 

economics sections of the Kuipers study. This section presents a summary of the 

important technical factors that were not adequately addressed in Kuipers’ study to 

support RO as a broad-based treatment technology. 

3.1.1 Water Quality and Flow Variations 

The quality of water produced during CBNG development varies widely from basin 

to basin, within a basin, and over the lifetime of the CBNG well (ALL Consulting, 

2004). The same holds true for flow. The flow of water is generally the highest near 

the beginning of the well life and then tapers off. 

Variations in water quality present technical challenges when designing and 

operating an RO system and make it difficult to apply the same treatment system at 

different locations within the basin. Changes in water quality can cause pressure 

fluctuations in the RO membrane system, increased membrane fouling, increased 

maintenance costs, higher level of operator attention, and a much greater potential for 

system “down time.” To manage fluctuations in water quality, selecting the 

appropriate pretreatment is critical for long-term success. 
Section 3 

Feasibility of Treatment 

Fluctuations in feed flow at a single site make it difficult to cost-effectively size an RO 

system to handle initial peak flows and the long-term average flow. Assuming a 10-

well system having a peak well flow of 25-gpm and an average flow of 6-gpm, the 

treatment system would need to be capable of treating flows ranging from 60-gpm to 

250-gpm. RO systems operate at a fixed flow rate. Fluctuations in flow are handled 

either by providing feed storage capacity or designing the system to handle the peak 

flow. Regardless of the method employed, the capital requirements for designing an 

RO treatment system to handle wide fluctuations in flow are much higher than 

indicated in Kuipers’ study. 

The assumed method for managing fluctuations in flow and quality in the Kuipers 

study is by using a storage pond. Using a storage pond upstream of the RO system

will help stabilize fluctuations in both flow and water quality, but it also increases the 

potential for membrane fouling. CDM’s general experience is that collecting and 

storing groundwater in a pond ahead of an RO system significantly increases the 

potential for membrane fouling due to aeration, precipitation of minerals and 

biological growth on the membrane surface, which results because oxygen is added. 

3.1.2 Treatment Objectives 

The cost of treatment systems depends not only on the flow, the quality of water, total 

system recovery, but also the treatment objectives. The Kuipers study makes no 

mention of the target treatment objectives. Such objectives are important since they, 

among other things, directly or indirectly determine the type of treatment required, 

equipment, labor, chemicals, waste disposal, and operating costs. For example, if a 

comparison of the feed water quality and treatment objectives indicate that only 

cation removal is required, ion exchange may be a better treatment choice. Therefore, 

treatment objectives need to be a part of any discussion that relates treatment 

technology to cost. 

3.1.3 System Recovery 

Treatment using RO technology makes two streams: permeate (treated water) and 

reject (concentrated brine). The RO system recovery refers to the volume of permeate 

produced per volume of feed water. For example, a system designed for 90 percent 

recovery produces 90 percent permeate and 10 percent reject brine. 

RO systems can be designed for a wide range of recoveries and are generally limited 

by the precipitation of a feed water component or osmotic pressure. Since nearly all 

of the ions in solution are taken out of the water by the membrane, the higher the 

recovery the higher the concentration of dissolved salts in the reject solution. A 

system designed for 75 percent recovery, will concentrate feed water salts by four 

fold; at 90 percent recovery the concentration factor is 10-fold; and at 95 percent 

recovery, the salt concentration factor is 20-fold. Consequently, the higher the 

recovery, the greater the chance for membrane fouling to occur due to precipitation of 

sparingly soluble salts. 

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Conventional, “off-the-shelf” RO systems are designed for a recovery of between 75 

percent and 85 percent. With some minor changes, the recovery of these systems can 

often be increased to 90 percent. However, above 90 percent recovery, customized 

systems are required and are more expensive. Based on CDM’s experience, the total 

system recovery for a typical brackish-water RO system treating CBNG produced 

water is generally limited to about 90 percent. In some cases, a higher recovery can be 

achieved. Silica is often the limiting factor that prevents higher recoveries from being 

achieved even with sea water RO systems. 

3.1.4 Pretreatment 

Some form of RO pretreatment is required for any system treating produced water. 

In general, the higher the RO system recovery and/or the poorer the feed water 

quality, the greater the need (and complexity) for pretreatment. The Kuipers study 

presents three RO pretreatment options, but does not include these options in the 

costs. In addition, two of the three pretreatment options presented (sodium carbonate 

and aeration) would likely do little, if anything, to prevent membrane fouling and 

could potentially have the opposite. Aeration will form precipitate (requiring 

filtration) and enhance the potential for biological fouling. Adding sodium carbonate 

would likely not precipitate minerals, as intended, since the water already contains 

high concentrations of bicarbonate. Acid (hydrochloric or sulfuric) addition is an 

appropriate selection for controlling calcium carbonate scaling, but may exacerbate 

potential scaling from barium sulfate (if sulfuric acid is used). Adding antiscalants 

and cartridge filtration are the two most common forms of pretreatment used to 

control mineral and particulate fouling on RO membranes. However, these options 

were not mentioned in Kuipers’ study. Regardless, none of the costs associated with 

any of these pretreatment options mentioned in the Kuipers study was included in 

Kuipers’ RO cost estimate. 

Since RO treatment results in the concentration of dissolved solutes on the membrane

surface, one of the most important considerations for successful design and operation 

of a RO system is selection of the appropriate pretreatment system. In general, there

are four objectives of pretreatment: 

 Insure the compatibility of the feed water with the RO membrane. Thin film 

composite membranes usually cannot tolerate chlorine or other chemical oxidants 

or high concentrations of hydrocarbon solvents. The membranes also cannot 

tolerate any oil and grease. 

 Reduce or eliminate the potential for mineral scales to form on the membrane 

surface. Mineral scale can form from the precipitation of sparingly soluble salts 

including calcium carbonate, calcium sulfate, calcium fluoride, barium sulfate, 

strontium sulfate and silica, to name a few. 

 Reduce or eliminate the potential for organic, biological and colloidal particulate 

fouling. Biological and colloidal foulants are two of the greatest challenges for 

design and operation of an RO system. Biological foulants are among the most 

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Feasibility of Treatment 

difficult to control and remove. Iron precipitation and silt can cause colloidal 

fouling by settling onto the membrane surface. 

 Reduce the RO membrane cleaning frequency by minimizing or eliminating the 

fouling potential of the feed water. Increased membrane cleaning results in 

reduced membrane life and higher operating costs. 

The resultant performance effects of RO membrane fouling are: 

 Loss of or decline in specific membrane flux, resulting in a lower water 

productivity or increased feed water pressure to maintain a constant permeate 

flow. 

 Reduction in permeate quality. 

 Increase in differential pressure leading to higher energy consumption. 

 Frequent chemical cleanings, triggering an increase in operating and maintenance 

(O&M) costs. 

 Shortened membrane service life. 

There are a wide range of methods used to prevent and/or control membrane (and 

equipment) fouling. For produced water in the PRB, pretreatment may include: 

 Filtration. All membrane systems include cartridge filtration, but if the total 

suspended solids (TSS) concentration is more than about 5 mg/L, a multi-media 

sand filter should be considered. Filtration results in a waste stream and adds both 

capital and operating costs. 

 Chemical Addition. Adding acid and/or antiscalants is often necessary to control 

mineral scales. This results in the need to haul, store and manage chemicals on-site 

and adds costs. 

 Activated Carbon. Carbon polishers are sometimes used ahead of an RO system to 

remove trace organics or oil and grease. While effective, using carbon adds a waste 

stream to the process; increases the potential for biological fouling of the RO 

membranes; and adds costs. 

 Ion Exchange Softeners. To increase the recovery of RO systems and/or prevent 

mineral scales on the membrane surface, ion exchange softeners may be required. 

The purposes of the softeners are to remove polyvalent cations that form sparingly 

soluble salts in solution. Polyvalent cations removed in a softener include iron, 

barium, calcium, magnesium and strontium. While extremely effective as a 

pretreatment option, softeners necessitate the need to handle chemicals, produces a 

waste stream that requires management and disposal, and adds costs. 

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These are a few of the major pretreatment issues that may need to be considered. 

However, identification of the best pretreatment system is site specific and depends 

on a variety of factors, including feed water chemistry, system recovery, treatment

objectives and cost. Again, Kuipers’ study mentions pretreatment but it does not 

include either the capital or operating costs in the economic analysis. 

3.1.5 Location 

A benefit of RO systems is that they are skid-mounted and can be installed in mobile 

trailers for flexible, adaptable application even in remote locations. However, if 

treatment is required in a remote location, which is very likely in the PRB, other issues

need to be considered. Some of these include operator safety, road access, power, 

chemical hauls, waste disposal and discharge location. None of these issues were 

discussed in Kuipers’ study. 

Many operators in the basin have found that discharging “clean” water into 

ephemeral drainages located a fair distance from the receiving stream sometimes 

results in the dissolution of salts present on the ground. Consequently, the water 

reaching the receiving stream could be similar or worse in quality than the untreated 

produced water. An obvious solution would be to install a pipeline to the discharge 

location. However, this adds cost and environmental effects that were not addressed 

in Kuipers’ study. 

3.1.6 Brine Disposal 

The feed water quality and recovery of the RO system dictates the volume and quality 

of the of brine stream requiring disposal. At 90 percent recovery, 10 percent of the 

feed flow would require disposal. For example, a 10-well system operating at 90 

percent recovery and having an initial peak flow of 250-gpm would result in a 25-gpm 

brine stream requiring disposal. At the longer-term average feed flow of 60-gpm for a 

10-well system, the average brine rate would be 6-gpm at 90 percent recovery. 

The logistics and costs associated with the management and disposal of the 

concentrated waste brine are the greatest challenges with implementing RO and other 

treatment options in the PRB. The Kuipers study almost completely ignores the 

discussion of brine disposal options and greatly underestimates the disposal cost. 

In CDM’s experience, there are three main options for disposing of concentrated 

brine. They include injection, natural evaporation and commercial disposal. 

According to operators, injection sites for RO brine rarely exist and are not considered 

a viable option. In any case, the selection of the best option, if any, can only be 

determined after considering a number of site-specific factors, including landowner 

requirements, distance to the nearest commercial disposal site, availability of a 

deepwell injection site, permitting requirements, atmospheric evaporation rates and 

cost. 

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3.2 Evaluation of Kuipers' RO Treatment Costs 

An evaluation of the economics of reverse osmosis treatment and brine disposal 

(Alternatives 5a and 5b in the technology limits report) was conducted to verify the 

projected treatment costs in the study document. Both options assume surface 

discharge. 

3.2.1 Assumptions 

Table 3-1 lists the process design assumptions for each RO treatment alternative. 

Based on these assumptions, the maximum produced water flow to the treatment 

system is 250-gpm with an average flow of 60-gpm. At a 95 percent RO recovery, the 

average brine flow rate is 3-gpm. 

While many of these assumptions appear to be consistent and/or acceptable for 

purposes of this evaluation, the following assumptions were found to be either 

inaccurate or unrealistic, resulting in an underestimate of the treatment economics: 

 Estimating 10,000 feet of pipe to connect the wells to a central treatment plant is 

too low given a well spacing of 80 acres/well. A more reasonable length of pipe 

needed to efficiently connect all of the wells together to a treatment plant is 16,700 

feet. 

 Assuming that all wells were brought into production at about the same time, the 

entire treatment capacity of 250-gpm would need to be provided. As the flows 

decline, the treatment capacity could be adjusted in increments, depending on the 

capacity of each RO treatment module. The assumed RO treatment capacity of 

120-gpm is therefore not accurate; however, its use for these purposes is 

understandable given the difficulty trying to relate cost to capacity when capacity 

changes with time. 

 An assumed RO recovery of 95 percent is more than likely the maximum possible 

using typical pretreatment methods and is therefore very aggressive. Also, this 

recovery is considered unconventional and will result in custom manufacturing, 

which adds both time and cost to the project. A recovery of 90 percent would be 

more appropriate. 

 The produced water volume to gas ratio of 1.0 bbl/MCF is inconsistent with all 

available data for the PRB. In fact, the table listed in Kuipers’ study shows an 

average ratio of 2.7, not 1.0. Using a lower ratio of 1.0 in economic calculations is 

significant since it underestimates the impact of treatment on overall gas 

production and return on investment (ROI) economics by a factor of 2.7. In other 

words, treatment results in much lower ROI’s than indicated in the technology 

limits report. 

A

 Based on input from operators, injection sites for RO concentrate are difficult to 

locate and require an exploratory program that is cost-prohibitive. Consequently, 

Alternative 5b may be technically and economically infeasible. 

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Table 3-1 

Kuipers’ Assumptions for RO Treatment of PRB Produced Water 

Description 5a – RO with Commercial 

Brine Disposal

5b – RO with Brine 

Injection/Reinjection 

No. of Wells 10 10 

Estimated Well Density 80 acres/well 80 acres/well 

Estimated Flow/Well (max) 25-gpm 25-gpm 

Estimated Flow/Well (avg) 6-gpm 6-gpm 

Estimated Life of Well 10 years 10 years 

Life of Well – Flow/Gas Ratio 1 bbl/MCF 1 bbl/MCF

Land Disturbance 1 acre 1 acre 

Piping from each well to pond to treatment 1,000 feet 1,000 feet 

Storage pond capacity 30 days storage 30 days storage

RO capacity 120-gpm at 100 HP 120-gpm at 100 HP 

RO recovery 95% 95% 

Brine Storage 15 days 15 days 

Membrane Replacement Freq Once/yr Once/yr 

RO Pump Replacement Once/yr Once/yr

Labor 0.35 FTE (90 days/yr) 0.35 FTE (90 days/yr) 

Injection well depth Not Applicable 1,500 feet 

Injection power demand 100 HP 100 HP 

Injection Pump Replacement Freq Once/yr Once/yr 

3.2.2 Recalculation of Costs Using Kuipers’ Model 

The technology limits report presents the input data and results of spreadsheet 

calculations used to estimate the capital and operating costs of RO treatment for 

Alternatives 5a and 5b. Using the input data and spreadsheet model, CDM 

completed an evaluation of calculations to verify treatment costs. Based on the results 

of this evaluation, it was determined that several calculation errors and cost omissions 

had occurred. To avoid confusion and to determine the magnitude of these errors 

and omissions, Kuipers’ same spreadsheet model was used to recalculate the costs. 

For comparison, an estimate of RO treatment costs using CDM’s model is presented in 

the next section. 

For Alternative 5a, the results of CDM’s findings and recalculation of costs using 

Kuipers’ model are as follows: 

 The quantity of pipe required to connect all the wells together was 

underestimated. Using the more accurate length of 16,700, the capital cost 

increased by $118,590. 

 The brine storage tanks appear to be undersized to collect 5 percent of the average 

feed flow for 15 days. Assuming a 5 percent brine rate, the total 15 day storage 

volume is 68,400 gallons. Assuming a unit purchase price of $0.75 per gallon, the 

cost of brine storage increases from $20,000 to $48,600. 

 Capital costs do not appear to include the cost of installing the RO system or brine 

tanks. This cost generally ranges between 100 and 300 percent of the purchased 

equipment price. For purposes of this study, an installation factor of 150 percent 

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of the purchase price of the RO system and brine storage tanks was used. This 

adds $297,900 to the capital cost. 

 The capital costs do not appear to include all of the indirect costs such as

engineering, construction oversight, contractor’s fee, etc. that are typically 

associated with a project of this type. The indirect costs were therefore increased 

from 10 to 20 percent. This increased the total capital cost by $129,980 (after 

adjusting the direct costs per the suggestions listed above). 

 The total capital cost, after making these changes, increased from $450,578 to 

$1,025,648. This represents a total increase of about $575,000. 

 Based on a review of the operating costs for Alternative 5a, it appears that the 

annual brine volume was miscalculated. At a 5 percent brine rate, the annual 

volume of brine requiring disposal is 37,543 not 6,257 as indicated. Using the unit 

disposal cost of $5/bbl, the annual disposal cost increases from $31,285 to

$187,714, representing an increase of about $156,429 in annual O&M costs. 

The same evaluation was completed for Alternative 5b. The results of these 

spreadsheet calculations are included in Appendix B. Table 3-2 shows a comparison 

between the reported costs (with errors and omissions) and recalculated costs after 

fixing the errors and adding omitted items. 

Table 3-2 

Revised Cost Estimates Using Correct Data 

5a – RO with Commercial 

Brine Disposal

5b – RO with Brine 

Description Injection/Reinjection 

Reported Recalculated Reported Recalculated

Capital Cost $450,578 $1,025,648 $744,278 $1,269,248

Annual O&M 

Cost $137,810 $309,882 $164,993 $164,993

NPV (1) $1,440,565 $3,418,476 $1,920,179 $2,543,280 

NPV cost per 

bbl $0.19 $ 0.46 $0.26 $0.34 

(1) Assuming 5 percent discount rate for 10 years. 

Based on a direct comparison of costs before and after recalculating the costs using 

Kuipers’ same spreadsheet model, the net present value per barrel of water treated 

increased from $0.19 to $0.46 for Alternative 5a and from $0.26 to $0.34 for Alternative 

5b. As shown in Figures 3-1 and 3-2, Kuipers’ cost estimates resulted in an omission

of approximately 59 percent and 23 percent of the costs for RO treatment for 

Alternatives 5a and 5b, respectively. 

In addition to the calculation errors and omissions for Alternative 5a, Kuipers’ cost 

estimate also does not include the cost of pretreatment. For example, cartridge 

filtration is required ahead of a first-pass RO treatment system to protect the 

membranes from colloidal fouling. This involves capital costs for dual cartridge filter

pressure vessels and monthly replacement of 5-micron filter cartridges. Also (as 

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Figure 3-2. Alternative 5b. RO Treatment with

Injection Brine Disposal

$0.26

77%

$0.08 

23%

Omitted Costs:

Additional Piping

Equip Installation

Engineering

Additional Brine Storage

Kuipers' Reported

Cost Estimate

Figure 3-1. Alternative 5a. RO Treatment with

Commercial Brine Disposal

0.19

41%

$0.27

59%

Omitted Costs:

Additional Piping

Equip Installation

Engineering

Additional Brine Storage

Full Brine Disposal

Kuipers' Reported

Cost Estimate

noted in Kuipers’ study) chemical treatment (acid or antiscalant addition) is usually 

incorporated as a pretreatment step to prevent mineral scale on the membrane 

surface. This is especially true for a system operating at 95 percent recovery. Major 

capital equipment for reagent addition involves a storage tank with secondary 

containment and a pair of chemical metering pumps. Annual operating costs must 

include the cost of the chemical. Hydrochloric acid generally costs around $0.15 per

pound (100 percent basis) while an antiscalant costs about $1.25 per pound. The 

amount and type of chemical is site-specific and depends on the water chemistry. In 

addition, Alternative 5b does not include the cost of exploration needed in the PRB to 

find a well that will accept the required amount of brine for disposal, as discussed in 

Section 2.5. 

In summary, Kuipers’ cost estimates do not represent a realistic estimate of capital or 

operating costs for treatment of produced water using RO in the PRB. The costs 

include several miscalculations and omit the most important requirement when 

considering RO, which is pretreatment. Selection of the appropriate pretreatment can 

not be assumed without site specific information, namely the feed water chemistry 

and potential foulants. Pretreatment is even more important when trying to attain 95

percent recovery since constituents in the feed water will be concentrated 20 times. 

3.3 CDM’s Cost Estimate for RO Treatment 

This section presents the results of a new cost estimate of RO treatment of produced 

water in the PRB using CDM’s internal spreadsheet model and RO membrane vendor 

software for comparison to Kuipers’ estimate. This model uses actual feed water 

quality as an input variable to produce a material and energy balance for the entire 

treatment process. The model includes performance and water chemistry calculations 

for all treatment steps, including pretreatment. For the feed water chemistry used in 

this study, pretreatment includes acid and antiscalant addition and cartridge 

filtration. 

The results of the material and energy balance are linked to a cost table that calculates 

operating and maintenance costs for the treatment system. Capital costs are estimated 

based on CDM’s experience. 

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3.3.1 Design and Cost Assumptions 

Table 3-3 shows the major design assumptions used for CDM’s cost estimate. 

Table 3-3 

Design Assumptions for CDM’s RO Treatment Cost Estimate 

Description 5a – RO with Commercial Brine Disposal 

No. of Wells 10 

Estimated Well Density 80 acres/well 

Estimated Flow/Well (max) 25-gpm 

Estimated Flow/Well (avg) 6-gpm 

Estimated Life of Well 10 years 

Land Disturbance 1 acre 

Piping from each well to pond to treatment 1,670 feet 

Storage pond capacity 10 days storage

RO capacity 120-gpm at 100 HP 

Average RO feed flow 60-gpm 

RO recovery 90% 

Brine Storage 15 days 

Membrane Replacement Freq Once/3-yrs 

Labor 1 FTE (2080 hours) 

A discussion of these assumptions and the assumptions used to develop the estimated 

capital and O&M costs is as follows:

 To be consistent with Kuipers’ cost estimate, the design feed flow was assumed to 

be 120-gpm with an average feed flow of 60-gpm. However, in order to handle 

the peak flow of 250-gpm for a 10-well gas system, additional treatment capacity 

or storage capacity would need to be temporarily installed. Since this requires 

additional, site-specific information this cost was not included in this evaluation. 

 For purposes of this study, the feed water chemistry was selected using “typical” 

PRB water quality data as presented in ALL Consultings’ “Handbook of Coal Bed 

Methane Produced Water: Management and Beneficial Use Alternatives” (ALL 

Consulting, 2004). 

 While this chemistry is relatively poor compared to most water in the basin, it is 

fairly representative of a quality that may require treatment as a water 

management practice in the PRB. 

 The total treatment system recovery was 90 percent and the design membrane flux 

was 13.9 gallons per square feet membrane per day (gfd). Based on the feed water 

chemistry, this recovery and flux is at or near the maximum limit without 

installation of more complex and costly pretreatment equipment. At 90 percent 

recovery and an average feed flow of 60-gpm, the brine rate is 6-gpm. For 

comparison, Kuipers’ report assumes 95 percent recovery and a 3-gpm brine rate 

at the average feed flow of 60-gpm.

 Membrane cleaning frequency was assumed to be once every four months. The 

frequency was assumed to be once per three years at a single element replacement 

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cost of $600. These are reasonable assumptions for treatment of industrial water 

sources. 

 Antiscalant is required to control fouling caused by barium sulfate and calcium 

fluoride. The amount of antiscalant needed for each option was based on 

discussions with chemical vendors. The cost of antiscalant was estimated to be 

$1.25 per pound of product. 

 Hydrochloric acid is also required to control membrane fouling from calcium 

carbonate. The cost of acid was assumed to be $0.15 per pound (100 percent 

basis). 

 Cartridge filter use was based on having a low amount of suspended solids in the 

feed water, and changing filters every month. Cartridges were assumed to be $25 

each. 

 Energy use was calculated based on flow and pressure for all pumps in the 

treatment process. Energy costs are based on a unit rate of $0.07 per Kw-hr. 

 Labor was assumed to be one full-time equivalent (FTE) employee. This assumes 

that the employee is drawn from a round-the-clock labor pool that provides 

support for other production activities, such as other RO systems, in the same 

vicinity. If this is not true, a higher labor rate would likely be necessary. 

 RO brine will be disposed of in a commercial facility at a cost of $6 per barrel. 

Injection of brine was not considered based on industry’s experience and 

difficulty finding suitable injection sites. 

 In CDM’s experience, RO treatment costs generally do not include the cost of 1) 

gathering and piping water to the treatment facility, 2) a storage pond, 3) 

discharge structures and 4) reclamation costs as presented in Kuipers’ study, since 

these components are generally provided by the operator. However, these items 

were added for comparison to Kuipers’ cost estimate. 

 Well water will be piped directly from the wells to the RO treatment system to 

eliminate aeration and minimize the potential for membrane fouling. 

Consequently, the storage pond was reduced from 30 days storage to 10 days 

storage since it will be used only for contingency purposes. 

 Total cost estimates for mechanical equipment were established based on the 

percentage cost basis method of cost estimation (1991, Peters, et. al.). This method 

uses purchased equipment costs to calculate total installed costs, based on

historical industry percentages for equipment installation. 

 The annual maintenance cost for all equipment was estimated to be 2 percent of 

the installed capital cost. 

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Feasibility of Treatment 

 Net present value calculations are based on a 5 percent discount rate over 10 

years. 

3.3.2 Cost Estimate Results 

Table 3-4 shows the results of CDM’s cost estimate and a comparison to Kuipers’ cost 

estimate for Alternative 5a. Appendix C includes a detailed summary of CDM’s 

capital and operating costs for treatment of the selected produced water quality from 

the PRB. 

Based on these results, CDM’s cost estimate resulted in a unit treatment cost of $0.73

per barrel of feed water. This compares with Kuipers’ original cost estimate of $0.19 

per bbl and the corrected cost estimate of $0.46. One of the major differences between 

the two cost estimates involves brine disposal. CDM’s costs are based on disposal of 

6-gpm brine (90 percent recovery) versus 3-gpm (95 percent recovery) assumed in 

Kuipers’ study. Based on vendor software, a 90 percent recovery is the maximum 

allowable without a significant increase in capital costs for additional pretreatment

and specialized equipment design. Therefore, a 6-gpm of brine disposal rate is 

reasonable and should be used for purposes of comparing to Kuipers’ study. 

Table 3-4 

Comparison of CDM and Kuipers’ Cost Estimates for RO Treatment

Kuipers' Estimate Description Initial Recalculated

CDM 

Estimate (1) 

Capital Cost $450,578 $1,025,648 $1,013,380

Annual O&M Cost $137,810 $309,882 $582,920 

NPV (1) $1,440,565 $3,418,476 $5,514,536

NPV cost per bbl $0.19 $0.46 $0.73 

(1) CDM determined that the maximum RO recovery is 90% (6-gpm brine) vs. a 95% 

recovery (3-gpm) assumed by Kuipers. 

Figure 3-3 illustrates the difference between CDM’s cost estimate and Kuipers’ 

original cost estimate for RO treatment and commercial brine disposal. In general, 

CDM’s experience indicates that Kuipers’ cost estimate captures only about 25 percent 

of the cost for RO treatment. As presented earlier, Kuipers’ low cost estimate was a 

result of calculation errors and omissions of important capital and operating cost 

items. 

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Feasibility of Treatment 

Figure 3-3. Comparison of CDM Cost Estimate to

Original Estimate for Alternative 5a

$0.19 

26%

$0.54

74%

Missing Costs Based on

CDM's Estimate of

Alternative 5A

Kuipers' Reported

Cost Estimate

3.4 Alternative Treatment Options 

As discussed in Kuipers’ study, there is wide range of treatment options besides 

conventional RO that have been developed, tested, and applied in the PRB for treating 

produced water. The treatment cost for the IX and RO options will be similar to 

CDM’s cost estimate presented above, but will vary based on the amount of brine 

requiring disposal. Each treatment option has advantages and disadvantages 

depending on various site specific considerations. Some of the specific treatment 

options CDM has experience with and/or is aware are included in this discussion. 

3.4.1 Conventional Ion Exchange (IX) 

Ion exchange technology is similar to RO in that it is capable of removing soluble, 

dissolved salts, such as sodium, from solution. Application of IX in the PRB is 

generally tailored to remove cations with a corresponding removal of bicarbonate. 

Acid is used to regenerate the resin once loaded with cation salts. Like RO, a waste 

stream is generated that requires disposal. The selection of IX over RO depends on 

site specific requirements, including feed water chemistry, treatment objectives, waste 

brine volume and disposal options and cost. Generally, if low-level anions (such as 

fluoride, arsenic, nitrate, etc.) require removal, RO is the preferred option since it is 

non-specific for cations or anions. However, anion specific treatment technologies, 

such as activated alumina for fluoride removal, can be used in combination with IX to

meet treatment objectives. 

3.4.2 Counter-Current IX 

A

This technology is similar to conventional IX, but regeneration of the resin is 

performed counter-currently resulting in a much lower volume of waste brine 

requiring disposal. Currently, there are several units operating in the PRB. Waste 

brine generated by the treatment process is acidic and may require neutralization 

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Feasibility of Treatment 

prior to disposal. Like most IX processes, the systems are generally designed to 

remove cations and bicarbonate alkalinity and will require additional treatment 

components if other anions require removal. Selection of this treatment technology 

depends on site-specific conditions, including feed water chemistry, treatment 

objectives, proximity to a disposal well and cost. 

3.4.3 Hydro Process 

The Hydro process, which is patented, consists of ion exchange, reverse osmosis and

degasification. The process was developed specifically for the PRB water chemistry 

and has a total system recovery as high as 95 percent depending on feed water 

chemistry and treatment objectives. The process is designed to cost-effectively 

remove cations and alkalinity. Although the process uses acid for regenerating the 

resin, the waste brine is less acidic than conventional IX and Higgins Loop treatment 

processes. Bench-testing has been completed, but no systems are currently operating 

in the basin. 

3.4.4 HERO Process 

The High Efficiency Reverse Osmosis (HERO) process is also patented. HERO is a 

specialized reverse osmosis system that combines IX, degasification and high 

recovery sea water RO technologies to allow very high system recoveries (above 95 

percent in many cases) with little or no membrane fouling. The waste brine is 

generally neutral and has TDS levels as high as 120,000 mg/L. The primary benefit of 

this technology is that it operates in a self-cleaning mode and can handle small 

amounts of oil and grease, organics, high silica concentrations, colloidal solids and 

other foulants that typically foul RO membranes. The disadvantage is that it is 

generally more complicated to operate than other systems and costs more. It has been 

pilot-tested in a number of different basins, but no full-scale systems are operating in 

the PRB. 

3.4.5 Zeolites 

Natural zeolites have properties very similar to IX and are capable of removing 

cations and bicarbonate alkalinity. Because the systems have much lower capacities 

than conventional IX resins, they tend to have limited application for high TDS feed 

water, but are suitable for some waters present in the basin. The cost is much lower 

than other technologies and its use is highly dependent on site-specific conditions. 

Currently, there are several zeolite treatment systems operating in the basin. 

3.4.6 Mechanical Evaporation/Crystallizer 

Mechanical evaporation systems and crystallizers are another proven technology 

capable of producing high quality water for discharge or beneficial use. The primary 

disadvantages include high energy costs; high capital costs; and limited flexibility to 

handle fluctuations in flow (the technology is not modular like IX and RO). Like IX 

and RO, feed chemistry and pretreatment are critical to prevent fouling of heat 

exchanger tubes. Currently, at least one system is being tested. 

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Feasibility of Treatment 

In summary, there are a wide range of treatment technologies and combinations of 

technologies that can be used to convert produced water into high quality water for 

beneficial use or discharge. Selecting the most cost-effective technology is based on 

the feed water chemistry, discharge limits and site specific conditions. Since each 

technology generates a waste stream, brine disposal is usually the primary issue (due 

to cost of disposal) that needs to be considered in the overall treatment selection 

process. 

3.4.7 Cost Comparison 

Table 3-5 presents a comparison of estimated costs for various treatment options 

discussed in this section. Treatment costs for each of these options were based on the

same feed water chemistry, flows and other relevant assumptions used to estimate the 

cost of RO treatment in Section 3.2.1. The results of this comparison illustrate the 

importance of system recovery to minimize the cost of brine disposal. 

Table 3-5. 

Comparison of Estimated Costs for Various Treatment Options

Ion Exchange

Reverse 

Osmosis 

Description 

Conv

Countercurrent Hydro Conv HERO

System Recovery 93.0% 98.6% 92.0% 90.0% 95.0%

NPV cost per bbl, breakdown by cost category (3) 

Primary Treatment (1) $0.22 $0.22 $0.20 $0.22 $0.24

Ancillary Facilities (2) $0.06 $0.06 $0.06 $0.04 $0.04

Commercial Brine Disposal $0.32 $0.06 $0.37 $0.46 $0.23

Total Cost $0.60 $0.35 $0.63 $0.73 $0.51 

(1) Includes all treatment capital and O&M costs except brine disposal 

(2) Ancillary facilities include piping, impoundment and reclamation related costs 

(3) Unit treatment costs are based on the Net Present Value (10 yrs at 5%) of the cash flow divided 

by the volume of water (barrels) treated over ten years 

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Beneficial Use 

In general, the two documents prepared by Kuipers and Associates provide an 

overview of produced water volumes and quality that typically occurs in each of the 

producing basins, including the PRB. The study documents also include a discussion 

of the produced water disposal practices, uses, and potential impacts to the 

environment. Some of the beneficial uses identified in these documents include: 

 Aquifer recharge 

 Improved surface flows 

 Increased water to downstream users 

 Constructed wetlands 

 Increased irrigation water and crop yields 

 Increased native plant pasture 

 Wildlife and livestock watering 

 Municipal 

 Recreation and 

 Industrial 

However, while the common uses of CBNG produced water are listed in the study 

documents, the primary focus of the discussion is on the potential negative effects to 

the environment rather than on the benefits that can be, and are being, provided in 

the PRB. 

To provide a more balanced perspective, this section presents data to show that, in 

general, CBNG produced water in the PRB has a much higher beneficial use than 

water from other areas of the country (where injection is the preferred option). This 

section also presents an example of how one important water management option, 

managed irrigation, is used convert relatively poor quality water into quality suitable 

for beneficial use. Of course, it is recognized by industry that in some cases the water 

quality is simply not amendable to beneficial use; in these cases, treatment and 

injection are the next best options for managing produced water. 

4.1 Water Quality Comparison 

The quality of the water generally dictates the preferred water management practice, 

including beneficial use. As presented in Kuipers’ study, Table 4-1 shows a general 

comparison of the quality of various CBNG produced water sources in the U.S. CDM 

calculated the bicarbonate and TDS values and added these to the table for purposes 

of comparison. Also, while there is potential disagreement with some of the data 

presented in this table, new information was not presented in an effort to simplify this 

analysis. 
Section 4 

Beneficial Use

As shown, the quality of produced water in the PRB varies widely throughout the 

country and even within the PRB. The data also shows that PRB basin water is much 

better than most parts of the country where injection is often the only disposal 

alternative. Additional data in the region shows that the SAR can be lower (near 7) 

and also higher than shown in Table 4-1, indicating the variability and need for sitespecific water management alternatives. 

Table 4-1 

Selected Water Quality Characterization Data for CBNG Well Fields in North America 

Water

Chem. 

Horseshoe

Canyon 

Formation 

Alberta, Canada

Power River 

Basin, WY

Piceance 

Basin, CO 

San Juan

Basin, CO, 

NM, AZ, UT 

Black Warrior 

Basin, AL

 Max Min Max Min Max Min Max Min Max Min 

Cations 

Na 861 112 800 110 2673 1976 5939 3674 3100 570

Ca 128 2.7 69 5.9 1839 13.2 118.7 6.5 100 2.5

Mg 23.5 0.2 46 1.6 7.77 0 39 2.88 34 1.1

K 8.9 2 18 3.8 NA NA NA NA 6 2

Anions 

As 0.0022 <0.0002 0.0026 <0.0002 NA NA NA NA 0.11 0

Fe 0.16 <0.01 4.9 0.2 NA NA NA NA 1.5 0.05

HCO3 1720 384 2466(2) 314 (2) 6612 5250 14701 6083 1120 670

Cl 229 0.5 64 5.2 600 4 2499 668 4200 450

SO4 1320 1 17 0.01 135 8.32 166.8 0 NA NA

TDS 4291 502 3485 441 11867 7252 23464 10434 8562 1696

SAR 18.36 17.72 18.3 10.37 17.11 149.77 120.9 301.66 68.33 75.57

Source: Taken from Kuipers’ managed irrigation report (Altera Geological Survey, 2003) 

NA = Not Available; All values in mg/L as ion 

(1) TDS was calculated based on the sum of ions 

(2) Bicarbonate alkalinity was calculated based on an ion balance at pH 7.0 and 15 C

Using the data presented by Kuipers, the following direct comparisons can be made:

 Some water produced in the PRB is very good, with TDS values lower than the 

secondary drinking water standard of 500 mg/L. 

 The poorest water quality in the PRB is better than the highest quality water in 

most CBNG producing regions in the United States. 

 Based on minimum water quality data, the TDS of produced water from the San 

Juan Basin is 24 times higher than in the PRB. 

 SAR values in PRB produced water are, in general, much better than the SAR 

values in other producing basins. 

Using this data, it can be concluded that the relatively high SAR and TDS values in 

produced water from other basins severely limits beneficial uses; consequently, in 

most instances, the petroleum industry selects injection as the preferred disposal 

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Beneficial Use

alternative. However, the same data also shows that water in the PRB is, in some 

cases, very good, making it ideal for beneficial use. 

Based on discussions with industry, it “does not make sense” to dispose of some PRB 

water into deep formations of potentially poorer water quality. Many CBNG 

producers believe the high quality water should be put to beneficial use. Operators’ 

experience is that many landowners who host CBNG development on their land want 

this water available for their livestock or for other surface uses. Many landowners 

would be opposed to injecting the water, and essentially wasting it, especially during 

the current drought conditions in the region. 

4.2 Managed Irrigation for Beneficial Use 

One effective method of managing produced water in the PRB is irrigation. Some 

Powder River Basin operators have applied CBNG-produced water as irrigation using 

circle pivots and atomizers. The complexity of the pivot system depends on the 

quantity of water, SAR, and the characteristics of the land being irrigated. CBNG 

operators are required to obtain a permit from the Wyoming State Engineer’s Office 

or the Montana Department of Environmental Quality prior to irrigation. The 

operators must manage the discharge to prevent impacts if the SAR is elevated and 

sodium-sensitive soils are present. This section presents an analysis by Kevin Harvey 

of managed irrigation, which has shown to be very effective at making beneficial use 

of a wide range of produced waters in the PRB. 

Kevin Harvey of KC Harvey, Inc. in Bozeman, Montana carried out this review. Mr. 

Harvey is a board certified professional soil scientist with 24 years experience, 

providing environmental consulting services to the private and public sectors 

throughout the U.S., Canada, Mexico, Asia, and Europe. Mr. Harvey earned a B.S. in 

Resource Conservation with an emphasis in soil science from the University of 

Montana School of Forestry and a M.S. in Land Rehabilitation with an emphasis in 

soil science from Montana State University. He is currently pursuing (part time) a 

Ph.D. in soil and water resources from Montana State University. He has held 

executive level positions in the consulting industry and has managed complex, multidisciplinary projects involving all environmental media. Mr. Harvey's technical 

strengths are in soil science, surface water resources, land reclamation, and general 

environmental problem solving. He has particular expertise in the management of 

water for the oil and gas, and mining industries, including the assessment of 

saline/sodic soil and water, development of innovative managed irrigation techniques, 

and NPDES permitting. Mr. Harvey’s experience includes over 100 CBNG produced 

water management projects throughout Wyoming, Montana, and Colorado. 

For the CBNG industry in Wyoming and Montana, “managed irrigation” with CBNG 

produced water has been defined as: the application of applied soil science, water 

chemistry, and agronomic principles to utilize CBNG produced water in a beneficial manner 

to produce forage for livestock and wildlife while protecting soil physical and chemical 

properties (Harvey et al., 2004a; Harvey et al., 2004b; Harvey, 2004). 

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Beneficial Use

Management practices include, among other things: 

 Selection of appropriate irrigation sites with suitable topography, soils, and 

hydrology. 

 Water balance modeling to support irrigation system design.

 Water treatment or soil amendments to mitigate the risks associated with the 

sodium bicarbonate water chemistry. 

 Irrigation scheduling and maintenance of a suitable leaching fraction to prevent 

the accumulation of salts in the root zone. 

 Selection and maintenance of a suitable crop that is tolerant of irrigated conditions 

and expected soil salt levels. 

 Prevention and control of irrigation water runoff. 

 Systematic monitoring of water, soil, and vegetation during the life of the project. 

 Implementing site closure actions in accordance with landowner objectives. 

 A close working relationship with the landowner to achieve the beneficial 

objectives of irrigation and the production of a crop. 

Managed irrigation is one alternative out of several available for managing CBNG 

produced water. Its suitability as a water management alternative depends on many 

factors, including produced water chemistry, site and soil characteristics, landowner 

objectives, and project economics. As such, its suitability can only be evaluated on a 

project- and site-specific basis. There is no technical, regulatory, or economical reason 

why this alternative should be eliminated for use by industry or throughout 

applicable regions of the U.S. 

Based on a review of the two study documents, Kuipers’ study does not address or 

analyze the process of managed irrigation as defined above. However, the 

management options report does make several positive statements regarding 

irrigation with CBNG water, including “[Irrigation] can be used to supplement 

precipitation in arid regions during the normal growing season...;” and “CBMproduced water of suitable quality can be beneficially used in agriculture for livestock 

watering or crop irrigation;” and “increased livestock and wildlife rangeland and 

enhanced crop growth [can be achieved] due to irrigation.” 

Regarding sustainability of the selected water management alternatives, the 

management options report concludes that “crop, livestock, municipal, or industrial 

use with water treatment and other mitigations, as required....” is among the “most 

sustainable practices.” These statements seem to be at odds with the rest of the two

reports since irrigation does not survive the “analysis” as an alternative water 

management tool for project- and site-specific consideration. 

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The analyses and conclusions regarding irrigation in the reports are largely based on

two inherent weaknesses: (1) the relevancy of the Clean Water Act and NPDES 

permitting to managed irrigation; and (2) the lack of a true technical and comparative 

analysis of water management alternatives. 

Section 1.1 of the effluent limitations report states that, “[this report]...evaluates water 

management practices to meet technology-based performance standards” and “this 

report is based on the requirements of [the] Clean Water Act (CWA), which 

authorizes the Environmental Protection Agency (EPA) and various state agencies to 

issue National Pollutant Discharge Elimination System (NPDES) permits or their 

equivalent.” It goes on to state that “the CWA requires technology-based 

performance standards for industrial water dischargers” and that “a BPJ (best 

professional judgment) analysis must be conducted before NPDES CBM permits are 

issued.” The management options report also reflects the influence of the CWA on 

evaluating water management alternatives. 

It is important to note that the Clean Water Act regulates the point-source discharge 

of wastewater to surface water in accordance with the NPDES permitting program. 

The term “discharge” is defined by the EPA in the Code of Federal Regulations 

(40CFR122.2) as the “discharge of a pollutant” or “discharge of a combination of 

pollutants” to “waters of the United States” from “surface runoff” which is “collected 

or channeled by man” or “through pipes, sewers, or other conveyances.” Irrigation 

used to grow forage is clearly not a “discharge” as defined by EPA. Therefore, it 

appears that the reviews described in the two reports are largely based on a 

regulatory program and a process that do not apply. Irrigation with CBNG is not 

regulated by the CWA, and an NPDES permit is not required if the water is applied in 

an agronomic manner and if there is no direct communication (i.e., saturated flow) 

between applied water, shallow groundwater and surface water (as may be the case 

in flood plain areas). This is not to say that irrigation of CBNG water is not regulated. 

For example, in Wyoming, irrigation projects are reviewed by the Wyoming State 

Engineers Office (water rights appropriations), the Wyoming Department of 

Environmental Quality (in the event pre-treatment is required), and the U.S. Bureau 

of Land Management (in the event water from federal coal leases are involved). 

It appears further that the study eliminates irrigation as an alternative water 

management tool based on convenience rather than technical evaluation. The 

introduction of the management options report promises an “analysis of available 

technologies.” While there is a comparative economic analysis presented in the 

effluent limitations report, there is no analysis of irrigation comparing it to other 

alternatives on a technical and regulatory basis. Instead, there are several 

unsupported statements describing potential negative impacts associated with the unmanaged application of CBNG produced water and an apparent lack of a thorough 

review of the scientific literature. In addition, no data is presented to substantiate 

generalizations that rule out irrigation as a potential water management option. 

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It is true that soil chemical and physical impacts may occur with the unmanaged

application of CBNG produced water, depending on the chemistry of the water and 

the characteristics of the soil receiving the water. However, managed irrigation (as 

defined above) systems that are designed, located, and managed in the proper 

manner will protect soil physical and chemical conditions. Anything else would be 

counter-productive to the CBNG producers and landowners who rely on the soil for 

application of water and production of forage.

As previously stated, managed irrigation of CBNG produced water involves 

techniques based on applied soil science, water chemistry, and agronomic principles 

to use CBNG produced water in a beneficial manner to produce forage while 

protecting soil physical and chemical properties. To successfully employ managed 

irrigation, knowledge of soil and water chemistry is a must. This reviewer feels that

the two NPRC reports provide an incomplete summary of soil and water chemistry 

associated with CBNG produced water irrigation, which is unfortunate because the 

primary reasons that this water must be managed are the soil and water chemical 

phenomena associated with salinity and sodicity. Appendix A provides additional 

information on managed irrigation practices to introduce relevant soil and water 

chemistry concepts while describing the process for evaluating and operating 

managed irrigation projects on a project- and site-specific basis. 

The conclusions listed in the management options report state that “industry should 

undertake significant investment into research and development of new technologies 

for CBM-produced water treatment and discharge practices.” With respect to 

managed irrigation, this has occurred. Beginning in 2001, Barrett Resources (now 

Williams) and Fidelity Exploration & Production Company funded unprecedented 

laboratory and field studies to support the development of irrigation using CBNG 

produced water. The studies and tests were extensive and included: 

 A review of the scientific literature. 

 Geochemical equilibrium modeling of various produced water chemistries and 

treatment scenarios. 

 Laboratory chemistry experiments. 

 Several statistically designed bench-scale column tests using produced water and 

soil from the Powder River Basin. 

 Full-scale field tests using center pivot irrigation equipment and various soil and 

water conditioning practices. 

 Continued experimental monitoring of full-scale operational irrigation systems. 

Scientists with KC Harvey, Inc. in Bozeman, Montana carried out the research and 

development programs with assistance from noted research scientists at Montana 

State University. Much of this information has already been presented at technical 

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Beneficial Use

conferences sponsored by academia, government and industry (Harvey et al., 2004a; 

Harvey et al., 2004b; Harvey, 2004; Brown and Harvey, 2004).

In addition to the general comments discussed above, the management options report 

identifies several potential concerns associated with land application/irrigation with 

CBNG produced water, including: 

 Soil sodicity and soil damage. 

 Impacts to drought tolerant native vegetation. 

 Plant toxicity of ions in produced water. 

 Increased erosion from runoff and wind. 

 Discharge to streams. 

 Landowner cooperation. 

 Suitability of produced water with or without treatment. 

 Groundwater contamination. 

These are reasonable concerns for an alternative that involves the application of 

sodium bicarbonate-based water to the soil. However, these are the issues that 

“managed” irrigation is designed to address. Comments regarding these issues are in 

Appendix A regarding the feasibility and operation of managed irrigation systems. 

In conclusion, the production of natural gas in the Powder River Basin of Wyoming 

and Montana and the concurrent production of unaltered groundwater are occurring

in a region that is naturally arid during a time of unprecedented drought. Research 

and development programs and full-scale irrigation projects have demonstrated that 

CBNG water can be beneficially used to grow forage where there was none, while 

protecting the soil resource. Upwards of four tons per acre of alfalfa from three 

cuttings per season are routinely produced with CBNG irrigation water. Managed 

irrigation has evolved into a practice that is based on established soil science, water 

chemistry, and agronomic principles. 

The Kuipers study did not appropriately consider managed irrigation in its analysis 

of the Clean Water Act policy. The Clean Water Act and the associated NPDES 

permitting program regulates point source and non-point source discharges of 

wastewater to surface waters of the U.S. The provisions of the Clean Water Act 

cannot be used to determine whether irrigation with CBNG water is a technically, 

legally or economically suitable water management alternative. Instead, managed

irrigation represents an important and beneficial use alternative that should be 

considered on a project- and site-specific basis. 

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Section 5 

CBNG Economics 

In the final section of the technology limits report, Kuipers presents a brief analysis of 

the economic basis used to conclude that injection and treatment is economical and 

affordable to industry. An example of this analysis for injection is as follows: 

If CBM producers in the Powder River Basin receive $2.50 per MCF of gas and are 

presently making a 40% return on investment (or $1.00 per MCF in profit), then if 

the cost of reinjection or injection is $0.15/MCF, their return would be reduced by the 

same amount resulting in a 34% return on investment, which would be unlikely to 

result in a significant reduction in CBM development in the Powder River Basin.

If future demand and supply causes an increase in the price of gas as most economists 

forecast is likely to happen, then the impact on the economics would be significantly 

less. At $5.00 per MCF, the return to CBM producers would be 233%, and the added 

cost of $0.15/MCF to achieve zero discharge would reduce the return to 223%. 

The result is that in the short-term, some gas may not be produced at lower prices as a 

result of implementation of zero discharge limitations, but eventually such limitations 

will have little or no effect on longer-term production and are therefore both sound and 

reasonable. 

Although the conclusions from this analysis may appear convincing, the accuracy and 

source of information of the cost and ROI values must be determined. Unfortunately, 

however, the document provides no information to complete this evaluation as stated

in the report: 

The information necessary to conduct an in-depth economic evaluation of how 

application of a zero discharge requirement will affect CBM production in the Powder 

River Basin would necessitate data that is not presently available. EPA has completed 

a draft economic analysis on the CBM industry if re-injection/injection were required. 

However, any analysis performed will reveal that the economic impacts on CBM 

production will be directly related to future prices as can be illustrated using 

information contained in this report 

It is presumed that the referenced EPA report is Guidance for Developing TechnologyBased Limits for Coal-Bed Methane Operations: Economic Analysis of the Powder River 

Basin. Although CDM was issued a copy of this report by the PAW, each page of the 

report is clearly marked Interagency Draft Report– DO NOT QUOTE OR CITE. 

Consequently, a detailed economic analysis cannot be completed to evaluate and 

verify Kuipers’ findings. 

Instead, based on CDM’s review of the treatment and injection economics in Kuipers’ 

study, available industry publications and input from industry on the economics of 

CBNG gas production, the following general comments need be considered when 

evaluating findings presented in Kuipers’ study: 

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CBNG Economics 

 All water management cost estimates erroneously assume that 1.0 barrels of 

water is equal to 1.0 units of gas production (1000 cubic feet or MCF). As shown

in Kuipers’ report, approximately 2.7 barrels of water were produced for every 

unit of gas production between the years 1996 and 2000. Using a one-to-one ratio, 

as Kuipers did, had a significant economic impact in their analysis, since the effect 

of treatment (and other water management practices) on overall gas production 

economics was underestimated by a factor of 2.7. 

 Site specific factors need to be considered for developing costs for injection and 

treatment to accurately assess overall gas production economics. For example, 

based on actual injection success data described in Section 2.5, the capital costs for 

injection must include the cost of installing four injection wells to find two wells 

capable of accepting the average volume of water from a 10-well producing 

system. With respect to treatment, costs must consider the cost of managing and 

disposing of waste brine. 

 A recent study (Sproule and Associates 2004) of current economics for CBNG 

production in the PRB indicates that initial development was marginal based 

on a gas price of $2.00/MCF. An extrapolation of this data may indicate that some 

areas within the PRB may experience less development than anticipated in the 

EIS's. 

 Most industry operators in the PRB believe that production of multiple coal 

seams at once versus back-to-back, single seam production is critical to the 

economic success of CBNG projects in the PRB since an economy of scale is 

achieved. However, multi-seam production involves larger up-front capital 

investments, which put companies at risk, given the nature of market fluctuations 

in the gas market. Consequently, a higher return on investment is necessary than 

conventional projects. This needs to be considered in any economic evaluation of 

the gas production industry. 

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Section 6 

Conclusions 

Kuipers’ study concludes that injection and treatment are technically feasible and 

affordable produced water management options in the PRB and should be required 

by operators as “best available treatment” technologies. To evaluate the basis for 

these recommendations, CDM completed a detailed technical review of the two study 

documents. This section presents the major findings from this evaluation. 

6.1 Injection of CBNG Produced Water 

Injection and reinjection is one of the primary methods used by industry throughout 

the U.S. for management of CBNG produced water. Injection is currently practiced in 

the PRB. However, based on the results of CDM’s study, several important factors 

unique to the PRB preclude its required use as a preferred water management option. 

The major factors include: 

 Injection/reinjection is not technically feasible in most Tertiary and Upper 

Cretaceous Formations within the PRB. Two CBNG operators have tested and 

are currently operating injection wells that are completed in sandstones within the 

coal bearing Fort Union Formation and in deeper sandstones in the Lance and Fox

Hills Formations. Data from these two operators indicate that the overall success 

ratio for shallow Fort Union injection wells was 48 percent and deeper Lance-Fox 

Hills injection wells was only 25 percent. This low success ratio combined with 

decreased injectivity over time reflects the discontinuous nature of the majority of 

the injection zones tested and indicates insufficient storage capacity to accept 

appreciable volumes of CBNG produced water. 

 Additional wells and infrastructure would be required for injection of CBNG 

produced water with a significant surface environmental impact not considered 

in the Kuipers study. Where injection was found to be successful in the Fort 

Union, the average injection rate averaged 36.7-gpm per well, indicating that more 

than one injection well would be required to handle the average flow of 60-gpm 

from a 10-well CBNG producing system. With this alternative, the Kuipers cost 

model for a 10-well, 800 acre development (Alternative 4a) is significantly 

underestimated in terms of surface disturbance and other capital costs. Actual 

development would require a surface disturbance of approximately 4.8 acres 

(versus 1 acre in the Kuipers model). The surface disturbance includes four 

injection well locations (two successful and two unsuccessful) ,well access roads, 

two permanent injection well pads, pump houses, pump electrical utilities, a 30-

day storage/settling pond, and water gathering pipelines. 

 CBNG production in the PRB will not cause subsidence and injection will not 

alleviate subsidence problems as indicated in the Kuipers study. The Wyoming 

Geological Survey has determined that no significant potential exists for 

subsidence associated with CBNG production in the PRB. This is supported by 

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Section 6 

Conclusions 

field observations and long term studies of groundwater induced subsidence in 

other areas of the United States by the U.S. Geological Survey. 

In summary, the Kuipers study does not adequately consider the technical feasibility 

and environmental impact of injection/injection as a preferred water management 

alternative in the PRB. 

6.2 Treatment 

Treatment of CBNG produced water is one of the water management methods 

currently being tested, and in some case, being used by industry in the PRB. Its 

primary use is reserved for situations where removal of TDS (namely sodium and 

bicarbonate) is required for discharge or beneficial use. Due to the high solubility of 

sodium in water, all treatment systems produce a waste brine stream requiring 

disposal. The logistics and costs related to brine management and disposal are the

greatest challenges faced by industry. Following is a summary of the specific findings 

from CDM’s evaluation of Kuipers’ study related to treatment: 

 Options and costs for RO waste disposal were not adequately addressed in 

Kuipers’ study. Brine disposal represents the single most difficult environmental, 

technical and economic issue related to the use of RO (and IX) treatment

technology in the PRB. This is evidenced by the fact that so many different 

configurations of RO (and IX) treatment have been, or are being, developed and 

tested. While meeting treatment objectives is relatively straight forward with 

these technologies, managing the disposal of brine in an environmentally, costeffective manner is not.

 The assumptions and costs for RO treatment in Kuipers’ study were found to be 

incomplete, unrealistic and containing significant calculation and omission 

errors. Some of major technical and economic conclusions included: a two-fold 

underestimate of capital costs; a six-fold underestimate of commercial brine 

disposal costs; omission of capital and O&M costs for RO pretreatment; and a 

significant underestimate of the complexity and cost of achieving 95 percent 

recovery in conventional RO systems. CDM’s independent cost estimate 

confirmed this finding. In fact, CDM’s cost estimate indicates that Kuipers’ 

estimate captured only about one-fourth of the estimated cost of RO treatment. 

 Only one known RO system is currently being operated in the PRB, despite the 

reference in Kuipers’ study that RO is the most common form of treatment 

being used. The most common form of treatment is managed irrigation followed 

by ion exchange-based treatment systems. The selection of the best technology is 

based largely on site-specific factors, including feed water quality, treatment 

objectives, location within the basin, brine rate and disposal method and cost, to 

name a few. As noted above, brine disposal is probably the most important overriding site-specific issue. 

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Section 6 

Conclusions 

6.3 Beneficial Use 

Kuipers’ study only briefly mentions beneficial use as a water management option, 

but does not address the major benefits currently being realized by landowners in the 

PRB. This section presents a summary of the primary issues that were not adequately 

addressed: 

 Produced water in the PRB has much better quality than other basins and, 

consequently, has a high potential for use as a beneficial water resource. In 

many of the other producing basins, where the water quality contains 10 to 30 

times the TDS levels found in the PRB, industry seeks injection as a primary water 

management alternative. 

 Injection of produced water represents a loss of a valuable resource to 

landowners in the semi-arid PRB, particularly during the current period of 

extended drought. Industry’s experience is that most landowners want the water 

and often negotiate for its use for livestock watering and other agricultural and 

industrial beneficial purposes. 

 Kuipers’ study did not address or analysis the process of managed irrigation for 

beneficial use. According to industry sources, more than 50 managed irrigation 

systems are currently in operation in the PRB. Managed irrigation involves the

application of soil amendments to allow beneficial use of CBNG produced water 

for production of forage for livestock and wildlife, while protecting the soils 

physical and chemical properties. Currently in the PRB, managed irrigation 

projects yield two and even three crop seasons, the products from which are 

highly desired by landowners. 

6.4 CBNG Economics 

In the final section of the technology limits report, Kuipers’ presents a brief analysis of 

the economic basis used to conclude that injection and treatment is economical and 

affordable to industry. However, the data used to develop their conclusions could 

not be evaluated because the information was obtained from a source that has not 

been published. The apparent source of information was from an unpublished EPA 

report marked InterAgency Draft Report– DO NOT QUOTE OR CITE. 

Nonetheless, the following general comments need be considered when evaluating 

findings presented in Kuipers’ study: 

 All water management cost estimates erroneously assume that 1.0 barrel of 

water is equal to 1.0 unit of gas production (1000 cubic feet or MCF). As shown 

in Kuipers’ report, approximately 2.7 barrels of water were produced for every 

unit of gas production between the years 1996 and 2000. This has a significant 

economic impact, even in Kuipers’ analysis, since the impact of treatment on 

overall gas production economics was underestimated by a factor of 2.7. 

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Section 6 

Conclusions 

 Site specific factors need to be considered for developing costs for injection and 

treatment to accurately assess overall gas production economics. For example, 

based on actual injection success data described in Section 2.5, the capital costs for 

injection need to include the cost of installing four injection wells to find two wells 

capable of accepting the average volume of water from a 10-well gas producing 

system. In addition, treatment costs need to consider the management and 

disposal of waste brine.

In summary, the results of this study show that the cost of water management 

options, including injection and treatment, and its effect on CBNG gas production 

economics is complex and difficult to predict. Any evaluation of these economics will 

require industry specific data for the results to be meaningful. 

6.5 Flexible Water Management

In summary, there were no data to support Kuipers’ key assertions that the current 

water management practices in the PRB are harmful to the environment and put 

agricultural water resources at risk. In addition, there were no data to support 

Kuipers’ findings that injection and treatment as exclusive water management 

practices is both practical and affordable to industry. In fact, the results of CDM’s 

evaluation indicate that many of the cost estimates and key assertions by Kuipers’ 

study were either inaccurate or without a basis for review. 

Data presented in this report supports the current need for industry regulators and 

operators to maintain flexibility to regulate and manage CBNG produced water for 

purposes of accommodating site specific factors, satisfying landowners, protecting the

environment, maintaining beneficial use of valuable water supplies, and ensuring 

long-term economic viability of operations. Where it makes sense and is technically 

feasible, CBNG operators have shown that injection and water treatment will be used 

as important water management practices. However, limiting water management 

practices to only injection and treatment severely limits operators’ and regulators’ 

ability to achieve maximum benefit of both water and natural gas resources in the 

PRB. 

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Section 7 

References 

Case, J.C.; Edgar, T.V.; De Bruin, R.H. 2000. “Subsidence potential related to water 

withdrawal in the Powder River Basin.” Wyoming State Geol. Survey., Laramie, WY. 

4 p. http://www.wsgs.uwyo.edu/oilandgas/Subsidence.aspx

U.S. Geological Survey. 1999. “Land Subsidence in the United States, U.S. Geological 

Survey Circular 1182, Devin Galloway, David R. Jones, and S.E. Ingebritsen, eds.

ALL Consulting, 2004, “Handbook of Coal Bed Methane Produced Water: 

Management and Beneficial Use Alternatives”, p. 5-3. http://www.allllc.com/CBM/BU/index.htm

Peters, Max S. and Klaus D. Timmerhaus, “Plant Design and Economics for Chemical 

Engineers”, Fourth Edition, McGraw hill, Inc., New York, 1991. 

Ayers, R.S. and D.W. Westcot. 1985. Water Quality for Agriculture. FAO Irrigation 

and Drainage Paper 29 (Rev. 1). Food and Agriculture Organization of the United 

Nations, Rome. 

Brown, D.E. and K.C. Harvey. 2004. Controlling sodicity during irrigation with 

CBNG produced water. Presentation from the First Annual Coalbed Natural Gas 

Research, Monitoring, and Applications Conference. University of Wyoming, 

Laramie, WY. August 17-19, 2004. 

Hanson, B., S.R. Grattan, and A. Fulton. 1999. Agricultural Salinity and Drainage. 

Division of Agriculture and Natural Resources Publication 3375, University of 

California, Davis. 

Harvey, K.C., D.E. Brown, and A.J. DeJoia. 2004a. Managed Irrigation Systems for the 

Beneficial Use of CBNG Produced Water. presentation from Living with Coal-Bed 

Methane, Soil and Water Conservation Society – Montana/Wyoming Chapter Annual 

Conference, Billings, MT. January 22-23, 2004. 

Harvey, K.C., D.E. Brown, and A.J. DeJoia. 2004b. Managed Irrigation Systems for the 

Beneficial Use of CBNG Produced Water. Presentation from the Rocky Mountain 

Coalbed Natural Gas Forum: Produced Water. Denver, CO. April 28-29, 2004. 

Harvey, K.C. 2004. Managed Irrigation Systems for the Beneficial Use of CBNG 

Produced Water. Presentation from the 2004 CBM Fair, Gillette, WY. June 3-4, 2004. 

Hill, R.W. and S. Olsen. 2001. Sprinklers, crop water use, and irrigation time, Davis 

County. Utah State University Extension. 

Majerus M. 1996. Threshold and maximum salt tolerance levels of various forage and 

crop species. http://www.animalrangeextension.montana.edu/Articles/Forage/ 

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Section 7 

References 

General/Salt-electrical-conductivity.htm. USDA-NRCS Bridger Plant Materials 

Center, Bridger, MT. (Verified on 12/1/04). 

Merrill, S.D., J.R. Deutsch, and M.W. Pole. 1987. Saturation percentage. p. 35-58. In

R.D.Williams and G.E. Schuman, (eds.) Reclaiming mine soils and overburden in the

western United States – Analytic parameters and procedures. Soil Conservation 

Society of America, Ankeny, IA. 

“National Engineering Handbook. Part 652 Irrigation Guide.” 2001. United States

Department of Agriculture Natural Resources Conservation Service. 

http://www.wcc.nrcs.usda.gov/nrcsirrig/Handbooks_Manuals/Part_652/part_652.

html (Accessed 20 January 2002). 

Rhoades, J.D. A Kandiah and A.M. Mashali. 1992. The use of saline waters for crop 

production – FAO Irrigation and Drainage Paper 48. Rome, Italy. 

Soil Science Society of America. 2001. Glossary of Soil Science Terms. Madison, WI. 

Soil Survey Division Staff. 1993. Soil Survey Manual. United States Department of 

Agriculture. Washington, DC. 

Sparks, D.L. 1995. Environmental Soil Chemistry. Academic Press, San Diego, CA. 

U.S. Salinity Laboratory Staff. 1954. Diagnosis and Improvement of Saline and Alkali 

Soils. U.S.D.A. Agriculture Handbook No. 60. U.S. Government Printing Office, 

Washington, DC. 

Leslie S. O’Connor, Seidle, J.P. 2004. “The Revenge of the Powder River Basin: 

Current Economics of Coal Gas Production”. Presentation at the AAPG Rocky 

Mountain Section Meeting -Rocky Mountain Natural Gas 2004, Denver Colorado, 

August 9-11. 

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Appendix A 

Feasibility, Design, Operation and 

Monitoring of CBNG Managed 

Irrigation System 

A
Feasibility, Design, Operation and Monitoring of CBNG Managed 

Irrigation Systems 

The research and development program discussed above, along with four years of full-scale operational 

experience has led to the development of a process for evaluating feasibility, designing, operating, and 

monitoring CBNG managed irrigation systems. This process has been presented to industry associations, 

the regional scientific community, the Wyoming DEQ, and the US BLM (Harvey et al., 2004a; Harvey et 

al., 2004b; Harvey, 2004; Brown and Harvey, 2004). This process has been employed on managed 

irrigation projects totaling over 2,000 acres in the Powder River Basin of Wyoming. This process has also 

been recently employed in the management of produced water from the conventional gas industry in 

western Wyoming and western Colorado. The primary components of this process are as follows: 

Irrigation Feasibility Evaluations: 

 Water Quality Suitability Assessments 

 Derivation of Soil and/or Water Conditioning Prescriptions 

 Project Water Balance Projections 

 Site Selection 

Irrigation Design, Operations, and Monitoring: 

 Site Characterization 

 Selection and Design of Irrigation Systems 

 Crop Selection 

 Soil Water Balance Modeling and Irrigation Scheduling 

 Development of Irrigation and Crop Management Plans 

 Water, Soil and Vegetation Monitoring 

 Site Closure Planning 

Each step in this process is discussed below in order to demonstrate the level of science employed in 

managed irrigation and to address the concerns identified in the Kuipers study. 

Irrigation Feasibility Evaluations 

To assess the feasibility of irrigating produced water for a particular production area several factors are 

evaluated, including (1) water quality, (2) the need for soil and/or water conditioning to mitigate the 

sodicity of the water, (3) the project water balance, and (4) the topography, hydrology, and soils of 

potential irrigation sites. 

Water Quality Suitability Assessments 

CBNG water is naturally occurring groundwater. Chemicals contained in the water result from natural 

processes that occur as rainfall and snowmelt recharge the groundwater system. These natural processes 

result in what is termed a “sodium-bicarbonate” type water chemistry. This means that the dominant 

dissolved minerals in the water are sodium and bicarbonate. No chemicals or salts are added to CBNG 

water by the drilling or production process. 

CBNG water is often of higher quality than other available water sources in the Powder River Basin. It is 

commonly used for domestic purposes. Because of its low to moderate level of salinity, it is a very good 

source of water for livestock and wildlife use. 

To assess the suitability of untreated produced water for irrigation, four specific areas are addressed: 

salinity, sodicity, alkalinity, and specific ion toxicity using the criteria specified in Ayers and Westcot 

(1985) and Hanson et al. (1999). Soil and/or water conditioning prescriptions are then developed (if 

necessary) based on the chemistry of the water to allow long-term irrigation with CBNG produced water. 
Salinity 

All irrigation waters contain a mixture of naturally occurring salts. Soils irrigated with water will contain a 

similar mix of salts but usually at a higher concentration than in the applied water. Salts can be defined as 

minerals that dissolve in water, e.g., table salt, which is sodium chloride. Typical salt components in water 

and soil include calcium, magnesium, sodium, potassium, sulfate, chloride, carbonate, and bicarbonate. 

The concentration of salts in water are measured two ways: total dissolved solids (TDS) or electrical 

conductivity (EC). The TDS, reported in milligrams per liter of water (mg/L), simply refers to the weight 

of dissolved minerals or ions (e.g., calcium, bicarbonate, etc.) that remain after the water in a sample is 

evaporated. The EC is the most commonly used measure of water and soil salinity because it is a rapid and 

inexpensive test. As the dissolved salt content of a water sample increases, its ability to conduct electricity 

also increases. Therefore, the EC, measured in deci-Siemens per meter (dS/m) provides a reliable and 

widely used index of salinity. 

The salinity of irrigation water does not directly impact soil physical properties. Instead, salts make it more 

difficult for plants to extract water from the soil and are a concern if the crop yield is affected. Plant 

species vary with respect to salt tolerance. For example, based on research conducted by the USDA 

National Resource Conservation Service (NRCS) at the Bridger Plant Materials Center in Bridger, 

Montana, the average root zone soil salinity threshold where alfalfa begins to exhibit yield declines is 5.0 

dS/m (Majerus, 1996). The concentration of salts in a soil due to the use of saline irrigation water can be 

managed by way of agronomic leaching (i.e., applying more water to the soil than is evaporated and 

transpired by the crop) to prevent the concentration of salts in the root zone. With careful management and 

suitable crops, water with EC ranging from 4.0 to 7.5 dS/m has been used successfully for irrigation 

(Rhoades et al., 1992). The “leaching requirement” is an important management tool and is discussed in 

more detail below under Soil Water Balance Modeling and Irrigation Scheduling.

The EC of CBNG produced water samples from the Powder River Basin typically range between 1.0 and 

3.0 dS/m. At these levels, guidelines developed by Ayers and Westcot (1985) indicate that there would be a 

slight to moderate restriction on the use of these waters for irrigation for moderately saline sensitive crops 

and no restriction for use on moderately saline tolerant and saline tolerant crops. It should be noted that 

soil amendments, such as gypsum, will likely be required to add calcium to the soil-water system to lower 

the SAR risk (see below). Soil amendments will result in an increase in the total salinity of the soil; i.e., 

they contribute additional salt upon dissolution. 

Sodicity 

The infiltration and permeability of clayey soils can decrease if an abundance of sodium ions are adsorbed 

by the clay minerals in soil. Excessive adsorbed or exchangeable sodium can result from sustained use of 

irrigation water that is high in sodium and low in calcium and magnesium. Consequently, the ratio of 

sodium to calcium and magnesium ions in water is an important property affecting the infiltration and 

permeability hazard. The index used to measure the hazard related to sodium abundance or sodicity is the 

sodium adsorption ratio or SAR. 

The SAR is the ratio of the dissolved sodium concentration in water divided by the square root of the 

average calcium plus magnesium concentration. The SAR can be calculated from the sodium, calcium and 

magnesium concentrations via the formula: 

 SAR = [sodium] / (([calcium] + [magnesium])/2)1/2 

where the concentrations are in milliequivelents per liter (meq/L). 

The SAR formula indicates that if calcium and magnesium concentrations are low and sodium is high, the 

SAR will be high (as is the case for CBNG produced water). Conversely, if calcium and/or magnesium 

concentrations increase relative to sodium, SAR will decrease. 

Clay minerals in soils are negatively charged and consequently attract ions with a positive charge such as 

sodium, calcium and magnesium. When sodium comprises more than about 15 percent of the 
exchangeable ions, the clays can begin to repel one another causing the soil structure to degrade. The 

continued swelling and dispersion of clay minerals and subsequent degradation of soil structure can reduce 

the rate of water infiltrating the soil and the permeability of water through the soil. In general, soils with 

moderately high to high clay contents are at higher risk. 

What is not apparent from the SAR formula is the fact that the higher the salinity of the water, the higher 

the SAR can be without impairing soil infiltration and permeability. Put another way, for a given SAR, 

infiltration rates generally increase as salinity (measured by the EC) increases. The changes in soil 

infiltration and permeability occur at varying SAR levels, higher if the salinity is high, and lower if the 

salinity is low. 

For irrigation water with a low EC of 0.7 dS/m, an SAR of 3 to 12 will pose a slight to moderate 

permeability hazard (Ayers and Westcot (1985) and Hanson et al. (1999), meaning clayey soils may be 

affected at the upper end of this range. When the EC is 2.0 dS/m, the upper SAR range that can be 

tolerated is 12 to 30. 

Most CBNG water produced in the Powder River Basin of Wyoming and Montana have SAR values above 

this range making them unsuitable for irrigation on most soils. Therefore, to be used beneficially to 

produce forage some type of water treatment (e.g., sodium removal) or soil conditioning (e.g., calcium 

addition) is required to mitigate the effects of the elevated SAR. This process is described below under 

Derivation of Soil and/or Water Conditioning Prescriptions. 

Alkalinity 

Alkalinity is a measure of the buffer capacity of water or the ability to neutralize an acid. The major form 

of alkalinity in produced water is bicarbonate. High bicarbonate levels in irrigation water will react with 

the available calcium and magnesium and form a calcium carbonate (lime) or magnesium carbonate 

precipitate. As can be seen by the SAR formula above, the reduction of available calcium and magnesium 

thus raises the effective SAR of the water. High levels of bicarbonate can also result in elevated pH values 

due to degassing of carbon dioxide (this is analogous to a can of cola which is “carbonated” under pressure 

during the manufacturing process – when it is depressurized, the carbonation degasses causing the cola to 

become “flat” and the pH to increase). The subsequent increase in soil-water pH hastens the transformation 

of bicarbonate to carbonate, which readily reacts with calcium and magnesium forming a relatively 

insoluble compound. The net result is less dissolved calcium and magnesium relative to sodium and higher 

effective SAR values. 

Bicarbonate concentrations in CBNG produced water from the Powder River Basin typically range from 

750 mg/L to 3,000 mg/L. These are relatively high values for irrigation water and can cause pH increases 

in water and soil, and subsequent increases in water and soil SAR. If calcium addition is used to reduce the 

SAR of the produced water, the bicarbonate may need to be removed through treatment, or an acidifying 

agent may need to be added to the soil (e.g., elemental sulfur) as an amendment to maintain the calcium in 

solution and prevent the formation of lime. This is discussed below under Derivation of Soil and/or Water 

Conditioning Prescriptions. 

Specific Ion Toxicity 

Sodium, chloride, and boron ions can be toxic to plants if their concentrations are too high in the irrigation 

water. Damage from sodium and chloride toxicity usually occurs only in woody plants such as tree and 

vine crops where soil salinity is extremely high or when saline water is used for sprinkler irrigation. 

Chloride concentrations in CBNG produced water from the Powder River Basin are typically very low. 

Since tree and vine crop types are not usually grown on managed irrigation sites, or by local farmers and 

ranchers in the Powder River Basin, sodium and chloride toxicity is not an issue. Boron concentrations in 

produced water are typically below detectable levels to very low levels. Based on the guidelines presented 

in Hanson et al. (1999), boron should not be a potential toxicity problem for any crops grown on managed 

irrigation sites. 
Derivation of Soil and/or Water Conditioning Prescriptions 

Based on the water quality suitability analysis presented above, it is apparent that the natural sodicity of 

CBNG produced water is the primary issue to be addressed before the water can be used for irrigation and 

forage production. The SAR formula presented above indicates that two general treatment methods would 

result in a reduction in SAR prior to irrigation: (1) removal of sodium, or (2) addition of calcium and/or 

magnesium (the scientific literature suggests that calcium is more effective than magnesium in lowering the 

effect of sodium in soils, therefore, magnesium addition will not be discussed further). Sodium removal 

systems (e.g., reverse osmosis, ion exchange, etc.) are technically feasible and have been described in detail 

in the two Kuipers reports. The process of calcium addition, however, is not described in any detail by the 

Kuipers reports and is a common practice in use today; therefore, calcium addition will be discussed further 

here. 

There are geochemical limitations to the maximum amount of calcium that can be dissolved in produced 

water. Depending mainly on bicarbonate alkalinity and its effect on pH, calcite (calcium carbonate or lime) 

precipitation will limit the maximum level of soluble calcium delivered to the soil. The chemical process 

responsible for this is discussed above under Alkalinity. As it happens, the bicarbonate alkalinity of 

produced water is relatively high. Minimum SAR will be achieved by maximizing dissolved calcium 

concentrations in the soil-water system. Because of the solubility limitations mentioned above, one cannot 

simply add amendments such as gypsum (calcium sulfate dihydrate) to the irrigation water or the irrigated 

soils and expect a marked decrease in water or soil SAR. It will require a combination of a calcium source 

(e.g., gypsum) and pH control (due to the bicarbonate alkalinity levels) to maintain the solubility of the 

added calcium. The approaches most commonly selected for managed irrigation in the Powder River Basin 

involve (1) the application of conventional agricultural amendments such as gypsum (calcium sulfate 

dihydrate) and elemental sulfur to the soil, or (2) injecting gypsum and an acid product (e.g., sulfuric acid) 

directly into the water before it is applied to the soil. Both processes have been proven to work equally 

well under laboratory controlled conditions (Brown and Harvey, 2004). 

Gypsum provides dissolved calcium to the soil or water as follows: 

 Dissolution of gypsum (CaSO4.2H2O): CaSO4.2H2O = Ca2+ + SO4

2- + 2H2O 

The added calcium will compete very effectively against sodium for the negatively charged exchange sites 

on soil clay particles. The positively charged calcium ions (two positive charges) are more strongly 

attracted to clay particles in soil than are sodium ions (one positive charge), resulting in a stronger bond 

between the particles. This prevents the clay particles from dispersing and causing a reduction in soil 

infiltration and permeability. 

The naturally elevated bicarbonate alkalinity of the produced water will result in an increase in water pH 

upon exposure to the atmosphere after the produced water is pumped to the surface. As discussed above, 

the rise in pH will result in the precipitation of residual and added calcium to form the insoluble mineral 

calcite (calcium carbonate). If left unchecked, this phenomenon will render the added calcium less 

effective in lowering the SAR. To prevent this, agricultural sulfur products can be applied to the soil. The 

elemental sulfur product will oxidize in the presence of air, water, and soil microbial activity to form 

sulfuric acid, which in turn dissociates to sulfate and hydrogen ions (protons) as follows: 

 Oxidation of sulfur (S): S + 1.5O2 + H2O = H2SO4

 

Dissociation of sulfuric acid (H2SO4): H2SO4 = 2H+

 + SO4

2-

Sulfuric acid neutralizes the bicarbonate alkalinity and controls soil pH as follows: 

 Neutralization of bicarbonate (HCO3

2-): H+

 + HCO3

2- = H2O + CO2

Another method employed by irrigators is to add sulfuric acid (or other form of acid) directly to the 

produced water before the water is applied to the soil. 
The rates of soil and water amendments are based on the chemistry and the volume of water applied to 

manage the SAR of the soil. Geochemical equilibrium models such as PHREEQC and MINTEQA are used 

to derive the application rate of soil or water amendments. The models are used to determine changes in 

chemistry when produced water is equilibrated with atmospheric pCO2 levels (-3.5 atm), gypsum and sulfur 

(or acid); to predict if the gypsum and sulfur at various rates of application would dissolve; and to 

determine if target pH and SAR goals could realistically be obtained. 

The general approach to geochemical equilibrium modeling is to mix the waters with amendments and 

determine if the resulting solutions are oversaturated with respect to calcite (CaCO3) and/or gypsum 

(CaSO4.2H2O). These minerals are then allowed to precipitate and the solution is equilibrated with 

atmospheric carbon dioxide (CO2 gas). This equilibration step is very important because the high 

bicarbonate (HCO3

-

) concentrations in the produced water indicate that this water is in equilibrium with 

considerably higher CO2 levels, which results in a lower solution pH value. As the carbon dioxide exsolves 

(degasses) and equilibrates with atmospheric carbon dioxide, the pH increases. 

Soil amendment rates derived by geochemical equilibrium modeling depend on the chemistry of the water 

and the expected volume of water to be applied to the soil. Gypsum and sulfur amendment rates for 

irrigation sites within the Powder River Basin typically range between 2 and 6 tons per acre per year, and 

0.5 and 1.5 tons per acre per year, respectively. Soil amendment scheduling is site-specific. Typically, soil 

amendments are applied proactively in the spring prior to the initiation of irrigation for the season. 

Calculated soil amendment rates are adjusted for product purity and a 1.25 to 1.5 multiplier is applied to 

account for imperfect field application and irrigation variability. If necessary, gypsum alone can be applied 

in the fall at calculated rates to lower the exchangeable sodium percentage (ESP) of the soil over the winter. 

This technique takes advantage of winter and early spring moisture to dissolve the gypsum and allow 

calcium to exchange with sodium on the clay minerals. Not only does this reduce the sodicity of the soil, it 

also increases the salinity of the soil to safer levels at a time when excess leaching may be occurring. 

The cost for purchasing, shipping and spreading agricultural gypsum and sulfur amendments in the Powder 

River Basin is approximately $65/ton (or $0.033/pound) and $125/ton (or $0.063/pound), respectively. The 

economic analysis presented in the Kuipers effluent limitations report utilizes a cost of $80/ton for gypsum 

and $2,000/ton for sulfur. With respect to sulfur, the cost input and the resulting economic analysis for 

managed irrigation is significantly overestimated. 

Project Water Balance Projections 

Development of water management plans for CBNG produced water requires a detailed understanding of 

water inventory at project startup and throughout the projected operational life. In other words, how much 

water will we have to manage and when will we have it? Spreadsheet-based water balance modeling or 

simulations provide a valuable tool to facilitate initial planning, feasibilty evaluations (alternative 

screening), design and permitting, and operations. During each phase of project planning and development 

the water balance may be considered one of the most important decision making tools. 

The baseline water balance for a new project provides the foundation for planning by estimating the 

magnitude of produced water that will need to be managed. The feasibility of water management 

alternatives such as storage and seasonal irrigation, injection, discharge to surface water, treatment, or any 

other alternatives may be evaluated using the water balance as a screening tool. Feasibility costs for these 

management alternatives may then be evaluated considering net present value for capital and operating 

costs. Once the operation/management strategy is defined, design optimization can be evaluated using the 

water balance. Design assumptions may be updated and verified as pumping rates and other information 

become available. The operational water balance is used to monitor and manage operations. 

The model should include deterministic functions to reflect project specific operations such as annual 

drawdown rates for wells and development schedules, and probabilistic functions to predict water balance 

uncertainty and variability associated with climate and pumping rates. 
Site Selection 

Screening the soils in the general area of the CBNG project using geographical information system (GIS) 

technology and published USDA-NRCS soil survey data is conducted to determine the possible extent and 

suitability of soils for managed irrigation. The GIS-based screening examines topography, soil texture, soil 

permeability, and soil depth to categorize the soils on maps as very likely suitable, possibly suitable, and 

not likely suitable for managed irrigation. Other site selection factors include vegetation presently growing 

on the site, hydrology and depth to groundwater, current land use, landowner preferences, and the overall 

beneficial use potential (e.g., can the site be improved as in the case of overgrazed upland areas). The soil 

screening is a preliminary evaluation tool used to identify candidate irrigation sites. If it demonstrates that 

there is a high likelihood of suitable soils in the area, a more thorough field site and soil investigation 

would be required (see below). 

Irrigation System Design, Operations and Monitoring 

Site Characterization 

Soil survey information is developed by the NRCS at fairly large scales, using aerial photographs and 

landscape relationships to delineate soil types. Because of the fairly large scales used to develop the soilmapping units, the accuracy of the GIS-based soil screening information described above must be verified 

in the field. An on-site evaluation of the soils is necessary to determine the exact soil types present and 

their current chemical and physical properties. This on-site evaluation will ultimately determine the 

suitability of a site for irrigation. The on-site evaluation is also necessary to collect soil data to assist in 

design of the irrigation system, establish baseline (pre-irrigation) soil conditions, and to meet Bureau of 

Land Management requirements for the Water Management Plan of the Plan of Development. 

It is strongly recommended that an Order 1 soil survey (as defined by the USDA-NRCS) be completed for 

all managed irrigation sites. This equates to approximately one test pit per five to ten acres of area 

investigated (more for highly variable soils, less for less variable soils). Test pits are excavated with a 

backhoe to a depth of 60 inches. At each soil test pit a soil profile description is performed in accordance 

with USDA-NRCS protocols (Soil Survey Division Staff, 1993). Bulk samples from each natural soil 

horizon are collected and submitted to a contract laboratory for analysis of pH, electrical conductivity (EC), 

sodium adsorption ratio (SAR), saturation percentage, exchangeable sodium percentage (ESP), percent 

lime, percent organic matter (surface horizon only), fertilizer requirements, bulk density, and soil texture 

(percent sand, silt and clay). In addition to the soil profile description and soil physicochemical analyses, 

baseline soil infiltration rates are measured near several of the test pit locations representing each soil 

mapping unit using state-of-the-art tension infiltrometer, and other scientifically defensible techniques. 

Two important soil parameters are introduced in the preceding paragraph, exchangeable sodium percentage 

or ESP, and saturation percentage. These parameters, in conjunction with soil pH and EC, are used to 

judge the level of soil sodicity and are therefore very useful measurements in managed irrigation. 

The ESP of a soil is the “percentage of the cation exchange capacity of a soil occupied by sodium ions (Soil 

Science Society of America, 2001).” Every soil has a definite capacity to adsorb the positively charged 

constituents of dissolved salts, such as calcium, magnesium, potassium, sodium, etc. This is termed the 

cation exchange capacity (CEC). The various adsorbed cations (such as calcium and sodium) can be 

exchanged one for another and the extent of exchange depends upon their relative concentrations in the soil 

solution (dissolved), the ionic charge (valence), the nature and amount of other cations, etc. ESP is, 

accordingly, the amount of adsorbed sodium on the soil exchange complex expressed in percent of the 

cation exchange capacity in milliequivalents per 100 grams of soil (meq/100 g). Thus, 

 

ESP = (exchangeable sodium / cation exchange capacity) x 100 

Sodic soils are “nonsaline soils containing sufficient exchangeable sodium to adversely affect crop 

production and soil structure (Soil Science Society of America, 2001).” High levels of sodium tend to 

disperse soil particles thereby sealing the soil. The result can produce hard surface crusts, reduced 

infiltration rates, and reduced oxygen diffusion rates, all of which interfere with or prevent plant growth. 
By definition, sodic soils are those that have an ESP of more than 15 percent, an EC less than 4 dS/m, and a 

pH between 8.5 and 10 (U.S. Salinity Laboratory Staff, 1954). 

Saturation percentage is the amount of water, by weight, necessary to form a minimally flowable mud from 

dry soil materials and is used as an index of the swelling capacity and dispersive condition of the soil 

(Merrill, et.al, 1987). Saturation percentage is affected by clay content, clay mineral type (i.e., swelling vs. 

non-swelling clay types), and sodium adsorption. In general, a saturation percentage of less than 80 percent 

indicates non-dispersed, non-sodic soil conditions. 

Selection and Design of Irrigation Systems 

Several mechanized and non-mechanized irrigation systems are available for applying CBNG water to 

managed irrigation sites, including center pivot sprinklers, side roll/wheel line sprinklers, hand move/solid 

set sprinklers, big gun sprinklers, surface drip, subsurface drip, gated pipe flood, and ditch flood. The 

preferred system is center pivot because of the significant advantages in automation, overall control, runoff 

control, distribution of water, operation costs, and reliability. The selection of a particular system is based 

on topography, soil conditions, landowner preferences, size of the site, crop type, post-irrigation land use, 

available labor, and project economics. Other components of the irrigation system include flow 

equilization ponds and delivery piping systems. 

Crop Selection 

Crops typically grown under managed irrigation systems in the Powder River Basin are alfalfa and native 

forage grass mixes. Crop selection is based primarily on landowner preference, soil type, available 

equipment for harvesting, and the projected root zone salinity level resulting from the produced water in 

equilibrium with the soil amendments. For alfalfa, the average root zone EC at which it is expected to 

begin to decline is 5.0 dS/m (Majerus, 1996). Alfalfa can tolerate much higher average root zone EC levels 

before significant yield reductions or mortality. Native forage grass species can typically tolerate much 

higher average root zone salinity levels than alfalfa. Regardless of the yield, most landowners believe that 

any reasonably good forage crop is better than no crop yield at all, which is usually the case prior to 

irrigation with CBNG water. 

With respect to potential impacts to native drought tolerant vegetation, most managed irrigation projects are 

constructed on private land for a landowner who wants and appreciates the extra high quality forage for 

livestock. The sites are usually overgrazed, upland range areas that support little in the way of native 

plants, except for sagebrush. Typically, these sites are vegetated with prickly pear cactus and weedy 

species such as cheat grass. Managed irrigation projects have been shown to rehabilitate these small areas 

into productive forage sources for both livestock and wildlife. 

Soil Water Balance Modeling and Irrigation Scheduling 

A spreadsheet-based soil-water balance assessment is used to determine the amount and timing of irrigation 

required to produce a healthy forage crop and to ensure that sound agronomic leaching practices are 

followed. With a soil-water balance assessment, all water inputs to and outputs from the soil are identified 

and balanced according to the following equation (“National Engineering Handbook. Part 652 Irrigation 

Guide,” 2001): 

 Fg = ET + LF + SDL – Ppt - ∆SW 

where: 

 Fg = gross irrigation water applied, 

ET = crop evapotranspiration, 

 LF = leaching fraction, 

 SDL = spray, drift losses, and canopy intercept evaporation from sprinkler systems, 

 Ppt = precipitation, 

∆SW = change in soil-water content within the crop rooting zone. 
For sprinkler irrigation systems, the following assumptions are used in developing the soil-water budget. 

To account for spray, drift losses, and canopy intercept evaporation, the gross amount of irrigation water is 

reduced by the efficiency of the irrigation system (i.e., the irrigation efficiency) to yield the net irrigation 

amount. Irrigation efficiency values for sprinklers range from 60 to 95% and a value of 80% is assumed for 

most center pivot sprinkler irrigation systems (Hill and Olsen, 2001). A leaching fraction of approximately 

20 to 30 percent is included in the water balance to prevent the soil salinity concentration from exceeding 

the salinity of the produced water in equilibrium with the soil amendments (Ayers and Westcot, 1985). In 

addition to these assumptions, regional climate and crop-specific evapotranspiration data are consulted to 

provide input into the model. 

As discussed in the water quality suitability assessment above, salt removal through leaching with excess 

water is required to minimize the concentration of salts in the root zone. With irrigation, the EC of the 

produced water by itself should not cause any serious increases in soil salinity. However, amendments 

applied to the soil to negate the possible impacts caused by the SAR of the produced water will cause an 

increase in soil EC, requiring leaching with excess water. In most cases, a leaching fraction of 20 to 30 

percent will result in a soil EC approximately equivalent to the EC resulting from the equilibration of the 

produced water with the soil amendments. At the end of each irrigation season, actual (as opposed to 

projected) soil-water balances are prepared for each irrigation site with site-specific climatic data and total 

irrigation amounts. This is necessary, among other things, to ensure that the required leaching fraction is 

achieved. 

Discussion of the soil water balance and the amount of water to be applied to support crop growth and a 

suitable leaching requirement brings up an important point regarding potential groundwater contamination. 

In order for groundwater to be significantly influenced by managed irrigation systems, or any source of 

water applied to the surface, there must be saturated flow through the soil/unsaturated zone and into the 

groundwater. As defined above, managed irrigation is not a process whereby water is applied to the ground 

on a continual basis throughout the year. It is applied in an agronomic manner in accordance with crop 

needs, soil water holding capacities, climatic characteristics, soil infiltration rates, and leaching 

requirements. It is not desirable or practical to irrigate crops in a way that results in saturating the soil to 

the point where water is moving in a continuous wetting front under gravity to the water table. Under these 

conditions water is moving in accordance with what is called “saturated flow.” When the soil water 

content is less than saturation, the water moves in accordance with what is called “unsaturated flow.” 

Simply put, water moving through the soil under unsaturated flow conditions moves from areas of higher 

water content to lower water content, which means it can move diffusely in almost any direction. 

Under managed irrigation conditions and in accordance with the soil water balance approach to irrigation 

scheduling, water is applied in amounts that will be evaporated from the soil and transpired through the 

roots and out the leaves during crop growth. Under these conditions, there is no net movement of water 

beneath the root zone. As discussed above, additional water is applied over the course of the irrigation 

season to ensure that salts do not accumulate within the root zone. This leaching requirement typically 

equates to approximately 10 to 14 inches of additional water spread out over the entire year as it includes 

natural precipitation. Therefore, a volume of water of this magnitude spread out over an entire year is not 

expected to induce saturated flow conditions beneath the root zone and communication with groundwater. 

This is especially true in project areas that are located on upland range sites that have relatively deep water 

tables. 

Irrigation scheduling also brings to mind the issues associated with runoff and erosion, and potential 

runoff/discharge into streams. This is certainly possible if irrigation systems were allowed to run 

continuously resulting in an exceedance of the soil infiltration rate. Managed irrigation systems are 

designed and operated in a way that supplies enough water to meet the demands of the crop, provides for an 

adequate leaching requirement, and applies water at or below the infiltration rate of the soil. 

Water, Soil and Vegetation Monitoring 

The purpose of the soil, water, crop, and climate monitoring plan is to help ensure that the specific 

managed irrigation site is operated and managed in a manner that (1) promotes the beneficial use of CBNG 

produced water to produce forage, (2) maintains soil productivity and sustainability, and (3) minimizes the 
possible impacts associated with saline and sodic water irrigation. The data collected from soil, water, crop 

and climate monitoring is used to determine the overall performance of the managed irrigation system as 

well as to make adjustments to irrigation scheduling, water treatment, and amendment application rates. 

Site monitoring is intended to help document how the managed irrigation system is performing and data 

collected during monitoring is utilized in the creation of annual operations and monitoring reports. 

Each component of the monitoring plan is discussed below. 

Water Monitoring 

Water quality monitoring is typically conducted prior to the beginning of the irrigation season and in July 

of each year. Water quality results are reviewed and modeled using a geochemical equilibrium model to 

assess if the amendment recommendations need to be modified. Produced water samples are analyzed at a 

minimum for pH, EC, major ions, and SAR. 

Water quantity delivered to each irrigation area is measured by flow meters. The flow meter readings are 

recorded on a weekly basis to calculate total volume of produced water delivered to each irrigation area. 

Monitoring the depth of water applied to each irrigation area is critical in order to monitor the irrigation 

schedule, leaching requirements, and soil amendment rates. 

Vegetation Monitoring 

Vegetation monitoring is typically conducted on an ongoing basis. Vegetation monitoring is intended to 

ensure that forage crop growth and development is not being negatively impacted by irrigation and is 

adequate to beneficially utilize the produced water. General visual observations regarding crop 

germination, emergence, establishment, vigor, and weed pressure are noted monthly. 

Soil Monitoring 

Soil monitoring programs can be based on several different sampling strategies, including discrete grab 

sampling or systematic composite sampling. All sampling programs include pre-irrigation baseline 

sampling and analysis conducted in the same manner as subsequent monitoring and closure events. 

Operational soil sampling and analysis events are usually scheduled in the spring (pre-irrigation), midseason, and in the fall (post-irrigation). One such sampling and analysis scheme is described below. 

Baseline and fall (post-irrigation) soil conditions are defined in the upper eight feet of the soil profile. 

Spring and mid-season conditions are limited to the upper two feet of the soil profile. For all sampling 

events, composite soil samples are collected from an established transect in each irrigation field. 

Composite soil samples consist of subsamples collected every five acres (if the field is less than 50 acres, a 

minimum of 10 samples are collected). Samples are typically collected using a truck-mounted Giddings 

push probe to a depth of two feet in the case of spring and mid-season sampling events, and eight feet in the 

case of baseline and fall sampling events. Samples are collected from the 0 to 6”, 6 to 12”, and 12 to 24” 

increments during the spring and mid-season events, and from 0 to 6”, 6 to 12”, 12 to 24”, 24 to 36”, 36 to 

60”, and 60 to 96” during the baseline and fall monitoring events. All subsamples are composited by depth 

for a total of six composite soil samples per irrigation field for analysis. The composite samples are 

analyzed for pH, electrical conductivity (EC), sodium adsorption ratio (SAR), saturation percentage, 

exchangeable sodium percentage (ESP), an percent lime. The 0 to 6” sampling increment is also analyzed 

for percent organic matter (OM). Baseline samples include textural analysis (percent sand, silt and clay). 

The physical structure of the soil is visually inspected by a qualified soil scientist at the beginning and end 

of each irrigation season. The soil scientist visually inspects the soil structure to at least 24 inches and 

records general soil structure observations including the presence or absence of soil swelling and/or 

dispersion. Soil water content is estimated by the feel method and any obvious soil sealing, salt 

precipitation, crusting, erosion, or other notable observations are recorded. 

The infiltration rate of the soil is tested prior to the start of irrigation at the site (baseline conditions) and 

then as required until the completion of the project. 
Development of Irrigation and Crop Management Plans 

The purpose of the irrigation and crop management plan is to address landowner and land use goals, crop 

selection, site preparation, seeding, irrigation system operations, harvesting/grazing plans, soil amendment 

application rates and scheduling, irrigation scheduling, leaching requirements, and soil/water/vegetation 

monitoring. This document serves as the overall planning, operations, and monitoring guide. The 

irrigation and crop management plan is revised each winter based on the monitoring results and other input 

from the previous irrigation season, and the operational requirements for the upcoming irrigation season. 

Site Closure Planning 

A critical component of the managed irrigation planning process is site closure. Issues to be addressed 

during site closure planning are: 

• What are the post-irrigation land use goals and landowner preferences? 

• Will the site continue to be cropped or will it be put back into native vegetation? 

• Will the irrigation equipment be removed or will it be left in place to be used by the landowner? 

• If the irrigation equipment is to be left, what are the water sources available for continued 

irrigation? 

• What do we expect in the way of post-irrigation soil physical and chemical conditions? 

• What level of post-irrigation monitoring will be required to meet post-irrigation land use and 

landowner goals? 

Some of the answers to these questions can be anticipated at project startup, while others can only be 

answered towards the end of the project. In any event, the primary goal of site closure is to leave a 

physically and chemically stable site capable of moving towards a sustainable vegetative community that 

meets or exceeds landowner goals. 
Appendix B 

Re-evaluation of Kuipers’ Reverse Osmosis 

Treatment Cost Estimates Figures 
Alternative 5a 

Reverse Osmosis with Commercial 

Disposal and Surface Discharge 
Alternative 5a. Original Reported Cost Estimate

Description Qty Unit Unit Cost Total Cost 

Operating Specifications and Assumptions

No. Wells 10

Estimated Well Density (acres/well) 80

Estimated PW Flow/Well (Maximum - gpm) 25

Estimated PW Flow/Well (Average - gpm) 6

Estimated Life of Well (years) 10

Life of Well PW/Gas Ratio (bbl/MCF) 1

Capital Costs

Site Preparation 1 acre 5000 $5,000 

Piping (from well to pond to treatment) 10,000 ft $17.70 $177,000 

Storage Pond Excavation 24,691 cu yd $2.05 $50,617 

Reverse Osmosis Plant (120 gpm nominal) 1 lot $150,000 $150,000 

Brine Storage Tanks (15 day at 5% flow) 1 lot $20,000 $20,000 

Discharge Equipment (header or outfall structure) 1 lot $2,000 $2,000 

Reclamation Costs 1 acre $5,000 $5,000 

Equipment Installation (Brine Tanks/RO)

Subtotal Direct Costs $409,617 

Indirect Costs 10% $40,962 

Total Capital Cost $450,578 

Annual Operating and Maintenance Costs

Electrical Costs (100 hp @ $0.06 kwh) 683,280 kwh $0.06 $40,997 

Supplies and Parts 1 lot $25,000 $25,000 

Replacement Equipment 1 lot $10,000 $10,000 

Labor 720 hrs $25 $18,000 

Commercial Disposal (5% of avg) 6,257 bbl $5 $31,285 

Subtotal Direct Costs $125,282 

Indirect Costs 10% $12,528 

Total Annual O&M Costs $137,810 

Total Costs

Total Cost $1,828,678 

NPV (5% DROR) Cost (1) $1,440,565 

NPV Cost per bbl or MCF $0.19 

(1) A re-calculation of the NPV using the same basis and cash flow scenario resulted in a NPV of $1,514,710

compared to $1,440,565 as shown. However, the original reported value was left unchanged to simplify 

comparisons made in the this report.
Alternative 5a. Recalculated Cost Estimate

Description Qty Unit Unit Cost Total Cost 

Operating Specifications and Assumptions

No. Wells 10

Estimated Well Density (acres/well) 80

Estimated PW Flow/Well (Maximum - gpm) 25

Estimated PW Flow/Well (Average - gpm) 6

Estimated Life of Well (years) 10

Life of Well PW/Gas Ratio (bbl/MCF) 1

Capital Costs

Site Preparation 1 acre 5000 $5,000 

Piping (from well to pond to treatment) 16,700 ft $17.70 $295,590 

Storage Pond Excavation 24,691 cu yd $2.05 $50,617 

Reverse Osmosis Plant (120 gpm nominal) 1 lot $150,000 $150,000 

Brine Storage Tanks (15 day at 5% flow) 1 lot $48,600 $48,600 

Discharge Equipment (header or outfall structure) 1 lot $2,000 $2,000 

Reclamation Costs 1 acre $5,000 $5,000 

Equipment Installation (Brine Tanks/RO) 150% Total $297,900 $297,900 

Subtotal Direct Costs $854,707 

Indirect Costs 20% $170,941 

Total Capital Cost $1,025,648 

Annual Operating and Maintenance Costs

Electrical Costs (100 hp @ $0.06 kwh) 683,280 kwh $0.06 $40,997 

Supplies and Parts 1 lot $25,000 $25,000 

Replacement Equipment 1 lot $10,000 $10,000 

Labor 720 hrs $25 $18,000 

Commercial Disposal (5% of avg) 37,543 bbl $5 $187,714 

Subtotal Direct Costs $281,711 

Indirect Costs 10% $28,171 

Total Annual O&M Costs $309,882 

Total Costs

Total Cost $4,124,470 

NPV (5% DROR) Cost $3,418,476 

NPV Cost perbbl or MCF $0.46 
Alternative 5a. Comparison between Reported and Recalculated Costs

Description Original Revised Difference

Operating Specifications and Assumptions

No. Wells

Estimated Well Density (acres/well)

Estimated PW Flow/Well (Maximum - gpm)

Estimated PW Flow/Well (Average - gpm)

Estimated Life of Well (years)

Life of Well PW/Gas Ratio (bbl/MCF) 

Capital Costs

Site Preparation $5,000 $5,000 $0 

Piping (from well to pond to treatment) $177,000 $295,590 $118,590 

Storage Pond Excavation $50,617 $50,617 $0 

Reverse Osmosis Plant (120 gpm nominal) $150,000 $150,000 $0 

Brine Storage Tanks (15 day at 5% flow) $20,000 $48,600 $28,600 

Discharge Equipment (header or outfall structure) $2,000 $2,000 $0 

Reclamation Costs $5,000 $5,000 $0 

Equipment Installation (Brine Tanks/RO) $0 $297,900 $297,900 

Subtotal Direct Costs $409,617 $854,707 $445,090 

Indirect Costs $40,962 $170,941 $129,980 

Total Capital Cost $450,578 $1,025,648 $575,070 

Annual Operating and Maintenance Costs $0 $0 

Electrical Costs (100 hp @ $0.06 kwh) $40,997 $40,997 $0 

Supplies and Parts $25,000 $25,000 $0 

Replacement Equipment $10,000 $10,000 $0 

Labor $18,000 $18,000 $0 

Commercial Disposal (5% of avg) $31,285 $187,714 $156,429 

Subtotal Direct Costs $125,282 $281,711 $156,429 

Indirect Costs $12,528 $28,171 $15,643 

Total Annual O&M Costs $137,810 $309,882 $172,072 

Total Costs

Total Cost $1,828,678 $4,124,470 $2,295,792 

NPV (5% DROR) Cost $1,440,565 $3,418,476 $1,977,911 

NPV Cost per bbl or MCF $0.19 $0.46 $0.27 
Alternative 5b 

Reverse Osmosis with Injection 

Reinjection and Surface Discharge 
Alternative 5b. Original Reported Cost Estimate

Description Qty Unit Unit Cost Total Cost 

Operating Specifications and Assumptions

No. Wells 10

Estimated Well Density (acres/well) 80

Estimated PW Flow/Well (Maximum - gpm) 25

Estimated PW Flow/Well (Average - gpm) 6

Estimated Life of Well (years) 10

Life of Well PW/Gas Ratio (bbl/MCF) 1

Capital Costs

Site Preparation 1 acre 5000 $5,000 

Piping (from well to pond to treatment) 10,000 ft $17.70 $177,000 

Storage Pond Excavation 24,691 cu yd $2.05 $50,617 

Reverse Osmosis Plant (120 gpm nominal) 1 lot $150,000.00 $150,000 

Reinjection Well (1500ft) 1 lot $262,000.00 $262,000 

Reinjection Pump (100 hp) 1 ea $25,000.00 $25,000 

Discharge Equipment (header or outfall structures) 1 lot $2,000.00 $2,000 

Reclamation Costs 1 acre $5,000.00 $5,000 

Subtotal Direct Costs $676,617 

Indirect Costs 10% $67,662 

Total Capital Cost $744,278 

Annual Operating and Maintenance Costs

Electrical Costs (200 hp @ $0.06 kwh) 1,366,560 kwh $0.06 $81,994 

Supplies and Parts 1 lot $25,000.00 $25,000 

Replacement Equipment 1 lot $25,000.00 $25,000 

Labor 720 hrs $25.00 $18,000 

Subtotal Direct Costs $149,994 

Indirect Costs 10% $14,999 

Total Annual O&M Costs $164,993 

Total Costs

Total Cost $2,394,208 

NPV (5% DROR) Cost (1) $1,920,179 

NPV Cost per bbl or MCF $0.26 

(1) A re-calculation of the NPV using the same basis and cash flow scenario resulted in a NPV of $2,018,310

compared to $1,920,179 as shown. However, the original reported value was left unchanged to simplify 

comparisons made in the this report.
Alternative 5b. Recalculated Cost Estimate

Description Qty Unit Unit Cost Total Cost 

Operating Specifications and Assumptions

No. Wells 10

Estimated Well Density (acres/well) 80

Estimated PW Flow/Well (Maximum - gpm) 25

Estimated PW Flow/Well (Average - gpm) 6

Estimated Life of Well (years) 10

Life of Well PW/Gas Ratio (bbl/MCF) 1

Capital Costs

Site Preparation 1 acre 5000 $5,000 

Piping (from well to pond to treatment) 16,700 ft $17.70 $295,590 

Storage Pond Excavation 24,691 cu yd $2.05 $50,617 

Reverse Osmosis Plant (120 gpm nominal) 1 lot $150,000.00 $150,000 

Reinjection Well (1500ft) 1 lot $262,000.00 $262,000 

Reinjection Pump (100 hp) 1 $25,000.00 $25,000 

Discharge Equipment (header or outfall structures) 1 lot $2,000.00 $2,000 

Reclamation Costs 1 acre $5,000.00 $5,000 

Installation Costs (RO and well pump) 1.5 Total $262,500 $262,500 

Subtotal Direct Costs $1,057,707 

Indirect Costs 20% $211,541 

Total Capital Cost $1,269,248 

Annual Operating and Maintenance Costs

Electrical Costs (200 hp @ $0.06 kwh) 1,366,560 kwh $0.06 $81,994 

Supplies and Parts 1 lot $25,000.00 $25,000 

Replacement Equipment 1 lot $25,000.00 $25,000 

Labor 720 hrs $25.00 $18,000 

Subtotal Direct Costs - bbl $149,994 

Indirect Costs 10% $14,999 

Total Annual O&M Costs $164,993 

Total Costs

Total Cost $2,919,177 

NPV (5% DROR) Cost $2,543,280 

NPV Cost perbbl or MCF $0.34 
Alternative 5b. Comparison between Reported and Recalculated Costs

Description Original Revised Difference

Operating Specifications and Assumptions

No. Wells

Estimated Well Density (acres/well)

Estimated PW Flow/Well (Maximum - gpm)

Estimated PW Flow/Well (Average - gpm)

Estimated Life of Well (years)

Life of Well PW/Gas Ratio (bbl/MCF) 

Capital Costs

Site Preparation $5,000 $5,000 $0 

Piping (from well to pond to treatment) $177,000 $295,590 $118,590 

Storage Pond Excavation $50,617 $50,617 $0 

Reverse Osmosis Plant (120 gpm nominal) $150,000 $150,000 $0 

Reinjection Well (1500ft) $262,000 $262,000 $0 

Reinjection Pump (100 hp) $25,000 $25,000 $0 

Discharge Equipment (header or outfall structures) $2,000 $2,000 $0 

Reclamation Costs $5,000 $5,000 $0 

Installation Costs (RO and well pump) $0 $262,500 $262,500 

Subtotal Direct Costs $676,617 $1,057,707 $381,090 

Indirect Costs $67,662 $211,541 $143,880 

Total Capital Cost $744,278 $1,269,248 $524,970 

Annual Operating and Maintenance Costs 0 0 $0 

Electrical Costs (200 hp @ $0.06 kwh) $81,994 $81,994 $0 

Supplies and Parts $25,000 $25,000 $0 

Replacement Equipment $25,000 $25,000 $0 

Labor $18,000 $18,000 $0 

Subtotal Direct Costs $149,994 $149,994 $0 

Indirect Costs $14,999 $14,999 $0 

Total Annual O&M Costs $164,993 $164,993 $0 

Total Costs

Total Cost $2,394,208 $2,919,177 $524,970 

NPV (5% DROR) Cost $1,920,179 $2,543,280 $623,101 

NPV Cost per bbl or MCF $0.26 $0.34 $0.08 
Appendix C 

CDM Cost Estimates for Reverse Osmosis 

Treatment 
RO Treatment Facility

Estimated Purchased Equipment Costs 

Equipment Description Est. Purchase Price

RO System 120 gpm feed, 90% recovery, skid-mounted $155,520

Hydrochloric Acid Storage Tank 6,000 gal plastic storage tank w/secondary containment $15,000

Hydrochloric Acid Metering Pumps Diaphragm metering pumps, duplex $5,000

Antiscalent Storage Tank 500gal plastic storage tank $1,000

Antiscalent Metering Pumps Diaphragm metering pumps, duplex $5,000

Cartridge Filters Two, 125 gpm, 5 micron, 42 10" equiv/filter housing $6,600

Brine Storage Tanks Four 30,000 gallon CS tanks $84,672

Brine Storage Transfer Pumps Two centrifugal, 316 SS, 100-gpm, 30 ft head pumps $7,000

Total $279,792

Estimated Installed Cost

Description Percentage (1) Est. Cost

Direct Costs

Equipment: Process, Fabricated 40% $279,792

Equipment Installation 11% $76,943

Instrumentation And Control 4% $27,979

Piping, Valves, And Fittings 5% $34,974

Electrical And Lighting 5% $32,176

Buildings And Services 5% $32,176

Land And Site Work 3% $19,585

Utilities And Service Facilities 7% $48,964

Total Direct Costs 79% $552,589

Indirect Costs

Engineering, Design, Management 8% $55,958

Construction Expenses And Fees 8% $55,958

Total Contingencies 5% $34,974

Total Indirect Costs 21% $146,891

Installed Cost for RO Treatment 100% $699,480

Ancillary Facilities

Estimated Capital Cost

Item Description Est. Construction 

Cost

Piping 16,700 feet HDPE Burried Piping $283,900

Storage Pond Excavation 10,000 cubic yards excavation $25,000

Reclamation Costs Estimated $5,000

Total $313,900

TOTAL CAPITAL $1,013,380

RO Treatment Facility

(1) Peters, Max S. and Klaus D. Timmerhaus, “Plant Design and Economics for Chemical Engineers”, Fourth Edition, McGraw hill, Inc., New 

York, 1991.
Description Units Qty Unit Cost Total Cost

Capital (1) $/yr, 5%,10 yr $ 1,013,380

O&M Costs (2)

Energy

Electricity kw-hr/K gal 3.62 $ 0.070 $7,991

Reagents (100% basis) - Chem Market Report Oct. 2003 $0

Anitscalent lb/K gal 0.02 $ 1.25 $657

Hydrochloric Acid lb/K gal 6.15 $ 0.150 $29,090

Membrane Replacement Mem/yr 9 $ 600 $5,600

Membrane Cleaning Mem/yr 84 $ 50 $4,200

Cartridge Filters cartrides/mo. 42 $ 25.00 $12,600

Labor FTE 1 $ 25.00 $52,000

Maintenance % of Total Capital/yr 2.0% 25,946 $ $20,268

Waste Disposal bbl/yr 75,086 6.000 $ $450,514

Total O&M $582,920

NPV (5%, 10 years) $5,514,536

NPV per bbl cost $0.73

(1) Capital costs are based on a design capacity of 120-gpm feed flow.

(2) O&M costs are based on an average feed flow of 60-gpm.

CDM RO Treatment Cost Summary

Based on Typical PRB Water Quality