Supporting Statement for:

Willingness To Pay Survey for Santa Cruz River Management Options in Southern Arizona

1. Identification of the Information Collection.

1(a) Title of the Information Collection

Willingness To Pay Survey for Santa Cruz River Management Options in Southern Arizona 

(New), EPA #2484.01, OMB #2080-NEW

1(b) Short Characterization/Abstract

The USEPA Office of Research and Development is investigating public values for scenarios of 

change for perennial reaches of the effluent-dominated Santa Cruz River, Arizona. These values 

will be estimated via a willingness to pay mail survey instrument. There are two effluentdominated perennial reaches considered in the survey. A “South” reach which starts at an outfall 

in Rio Rico, AZ, flowing northward through Tumacácori National Historical Park. A “North”

reach, fed by two outfalls in northwest Tucson, Arizona, flows northwest through Marana, AZ. 

In other locations north of where the channel crosses the border with Mexico about 5 miles east 

of Nogales the Santa Cruz River is ephemeral. For each of the South and North reaches, two 

different scenarios of change are considered. The first is a reduction in flow length, and 

associated decreases in cottonwood-willow riparian forest, a rare forest type in the region. The 

second is an increase in water quality to allow full contact recreation, such as submersion, at 

normal flow levels. The baseline flow length and forest acreages, as well as the acreages of forest 

that would be associated with reduced flow lengths, are derived from natural scientists. A choice 

experiment framework is used with statistically designed tradeoff questions, where options to 

maintain flow length and forest, or increase effluent water quality, are posed as increases in a 

yearly household tax. Each choice question allows a zero cost “opt out” option. The choice 

experiment is designed to allow isolation of the value of marginal change for each reach. A few 

additional questions to further understand the motivations for respondent choices, as well as their 

river-related recreation behavior, are also included. Several pages of background introduce the 

issue to respondents. Limited sociodemographic questions are included to gauge how well the 

sample respondents represent the target population. Samples of the two major metropolitan areas 

in southern Arizona, Phoenix and Tucson, will receive the survey. 

2. Need for and use of the Collection

2(a) Need/Authority for the Collection

Current ORD research revolves around the theme of sustainability (USEPA, 2013a). An 

overarching goal cited on the EPA website for sustainability research is:

“EPA Sustainable communities research is providing decision tools and data for 

communities to make strategic decisions for a prosperous and environmentally
sustainable future, and providing the foundation to better understand the balance between 

the three pillars of sustainability- environment, society and economy” (USEPA, 2013b).

As part of including public input for finding the “balance” of sustainability, this survey research 

will estimate public values for potential management changes to the Santa Cruz River in 

southern Arizona. The Santa Cruz watershed is a subject of continuing research collaboration 

between USGS, ORD, and other partners, with a peer-reviewed research plan published by

Norman et al. (2010). ORD is also collaborating with recipients of a recent National Science 

Foundation grant engaging in Santa Cruz River natural and social science research, led by the 

University of Arizona (NSF, 2010). The survey will gather public value information on Santa 

Cruz River management scenarios to complement partnering natural science research. 

2(b) Practical Utility/Users of the Data

The primary reason for the proposed survey is public value research. The Santa Cruz River is a

case study of a waterway highly impacted by human modifications. However it still represents 

potentially valuable ecological goods such as rare riparian habitat and recreational opportunities 

for the regional population. As a secondary purpose, the survey results may be informative to 

local decision-makers considering Santa Cruz River management options. Water scarcity in the 

region raises periodic debates on the best uses of effluent.

3. Non duplication, Consultations, and Other Collection Criteria

3(a) Non duplication

Willingness to pay survey research has occurred for changes to other US rivers, as well as other 

southwestern US rivers (e.g. Weber and Stewart, 2009; Berrens et al., 2000). While techniques of 

benefit transfer could be applied to the results of prior studies in an attempt to gain a limited 

sense of the public value for Santa Cruz River management options, there are a number of 

hurdles to value estimates derived by benefit transfer (e.g. Desvousges et al., 1992, Brouwer, 

2000). Differences in the ecological good being considered, local availability of substitute 

resources, and local tastes and preferences are some of the limitations in transferring estimates 

from one study or group of studies to a new valuation context. The proposed survey incorporates 

natural science modeling of the relationship between surface water and riparian forest. The 

ecological changes respondents would value are tailored to the Santa Cruz River, have been 

explicitly defined in the survey, and the survey has been extensively pretested on the regional 

population to minimize cognitive problems.

EPA has not identified any other studies that would consider public values for Santa Cruz River 

options considered in the proposed survey. The survey options were specifically designed to 

encompass changes to both the South and North effluent-dominated perennial reaches. The 

options were also carefully defined to specify miles of flow, acreage of riparian forest, and safety

of water contact for different types of recreation. The language, graphics, and question formats in 

the survey were carefully pretested. However, there is prior willingness to pay survey research 

pertaining to the South reach of the Santa Cruz River (Frisvold and Sprouse, 2006). Although 

full documentation and results of that survey are neither available nor published, further 
information on this survey was sought before initiating plans for this new collection (personal 

communication with G. Frisvold, August, 2009). It was determined that the prior survey, even if 

results become available, would not be sufficient for the Santa Cruz research goals of this study. 

This survey will ask respondents to choose between numerically defined levels of environmental 

attributes matching natural science quantitative modeling (alongside varying cost levels). In 

contrast, the prior survey asked a more general question of willingness to pay “to permanently

preserve the Santa Cruz River habitat as it is today”, using photos to describe a baseline 

perennial stream habitat, and a changed habitat without perennial flow. Unfortunately the 

specific marginal change to be valued was not defined, limiting the reliability of respondent data 

as well as clouding how the data could be applied to a specific management scenario. 

Furthermore, a major geographic difference is that the prior survey focused on the South Santa 

Cruz only, whereas this survey considers management changes to both the South and North

Santa Cruz River, and the reaches have significant differences in both vegetation and proximity

to the Tucson urban area. 

3(b) Public Notice Required Prior to ICR submission to OMB

This is the first of two federal register notices.

3(c) Consultations

The principal investigator for this effort is Matthew Weber, postdoctoral researcher at USEPA, 

ORD, Western Ecology Division, Corvallis, OR. The principal investigator has past direct

experience with willingness to pay survey research, with a study estimating public values for 

management changes for the river and riparian area of the Rio Grande in Albuquerque, New

Mexico (Weber and Stewart, 2009). Previously approved OMB surveys were consulted in 

designing this survey, in particular a NOAA coral reef valuation study (OMB # 0648-0585) and 

an EPA study on fish and aquatic habitat impacts from cooling water intake structures (OMB # 

2020-0283). The survey instrument booklet format and several questions were adapted from the 

EPA study. The principal investigator participated in a workshop amongst stated preference 

survey practitioners working on federal government projects, convened by NOAA and Stratus 

Consulting in June of 2012 (NOAA and Stratus Consulting, 2012). This workshop was a helpful 

forum for comparing notes in willingness to pay survey design, with an emphasis on strategies 

for presenting ecological goods in a way meaningful to the lay public. Several completed or 

working draft willingness to pay survey instruments were presented for group discussion. 

This survey uses an explicit approach to defining ecological commodities to be valued, following 

guidance in Boyd and Banzhaf (2007). Dr. Paul L. Ringold, research ecologist at at USEPA, 

ORD was consulted for his experience identifying publicly valued stream commodities and 

metrics (Ringold et al., 2009; Ringold et al., 2013). Although the need to clearly define the 

ecological good to be valued is established advice for stated preference research (Arrow et al., 

1993), Boyd and Krupnick (2009) found that practitioners sometimes use only vague language to 

define water-related ecological commodities.

This survey includes natural science modeling outcomes which quantify the relationship between 

riparian forest acreage and surface flow extent in both the South and North Santa Cruz River, 
two river areas with different hydrogeological conditions. The natural science modeling is based 

on dissertation research at Arizona State University (White, 2011) and further analysis by

Arizona State University Professor Dr. Juliet Stromberg (personal communication, May, 2013). 

Drs. White and Stromberg were consulted throughout development of the natural science 

background provided in the survey instrument as well as the ecological changes the survey

poses. 

Additional consultations were conducted to ensure changes associated with river flow and forest 

extent posed in the survey are realistically aligned with potential changes for Santa Cruz River 

management, to facilitate respondent acceptance of the scenarios. Dr. Thomas Meixner and 

Ph.D. student Rewati Niraula at the University of Arizona were consulted on potential surface 

streamflow extents under different effluent release scenarios for the North and South reaches of 

the Santa Cruz River. The most recent Arizona Department of Environmental Quality (2010) 

report summarizing water quality status for the South and North reaches of river were reviewed. 

Persons with either research or management interests in the Santa Cruz River (USGS, University 

of Arizona, Pima County, and Tumacácori National Historical Park) were consulted on the range 

of likely treated wastewater releases into the South and North reaches of the Santa Cruz River, 

and the current state of water quality. 

3(d) Effects of Less Frequent Collection

Without this collection the public values for Santa Cruz River management scenarios being 

modeled by collaborating natural scientists could not be estimated. There would then be a gap in 

understanding the public welfare relevance of the associated natural science studies. 

Furthermore, results from the case study would not be available to the willingness to pay

literature. Finally, there would also be less information on public values regarding Santa Cruz 

River management available to the local community for their planning purposes.

3(e) General Guidelines

The survey will not violate any of the general guidelines described in 5 CFR 1320.5 or in

EPA’s ICR handbook.

3(f) Confidentiality

All responses to the survey will be kept confidential. The surveys will be processed, including 

data entry, by the principal investigator; nobody else will have a record of who has responded or 

the answers of any given respondent. A list of the addresses of the members of the sample who 

have responded versus those who have not will be maintained in order to more efficiently mail 

reminders and replacement surveys. This will be a single file, accessible to and updated only by 

the principal investigator. To protect confidentiality in survey results, each respondent will be 

identified by a numeric code in that file rather than their name or address. The survey questions 

do not ask for any personally identifiable information and personally identifiable information 

will not be entered in the results even if volunteered by the respondent, for example in the 

comments section. In the cover letter, respondents will be informed that their responses will be 

kept confidential. After the data collection is complete, the respondent status file will be deleted, 
and only the numeric code assigned to each respondent will remain. After data entry is complete, 

the surveys themselves will be destroyed.

The USEPA office location (the Western Ecology Division of USEPA) and USEPA electronic 

file system used by the principal investigator are highly secure. A keycard possessed only by 

USEPA employees and contractors is necessary to enter the building. The principal investigator 

is then in a separate keyed office space within the secure building. The computer system where 

the personal names and addresses associated with respondent numeric codes will be stored 

during the process of data entry is a secure server requiring principal investigator personal login

username and password. At the conclusion of data entry, this file linking personal names and 

addresses to respondent codes will destroyed (along with hard copy survey responses 

themselves) at the conclusion of data entry and only respondent codes will remain. 

3(g) Sensitive Questions

In focus groups two questions were found to be sensitive by some of the participants; the 

question of racial category, and the question of income category. However it was found that 

describing the research need for these questions, of gauging how well different groups are 

represented in survey results, was accepted by these participants as a worthwhile reason for

asking these questions. The reason for these questions now prominently appears preceding those 

questions within the survey: "We need the following questions to ensure votes from all groups 

have been fairly represented in this survey". Confidentiality of responses is then reiterated.

4. The Respondents and the Information Requested

4(a) Respondents/SIC Codes

The target respondents for this survey are representatives 18 yrs or older of households in the 

two most populated urban areas of Arizona, the Phoenix metro area, and the Tucson metro area. 

A sample of household representatives 18 yrs or older in each metro area will be contacted by

mail following multiple contact protocol in Dillman (2009). A response rate of 30% will be 

targeted. To increase response rates from the sample, several contacts will be used, including a 

prenotice to all recipients, a reminder postcard, and followup mailing. The target responses from 

the Phoenix and Tucson metro areas is 250 households each, or 500 households total.

4(b) Information Requested

(i) Data items, including record keeping requirements

The current draft survey has also been uploaded to the federal register (note that the pages 

numbers are out of sequence on the electronic file, they are sequenced so that they will print 

correctly double-sided). The survey is divided into 4 main parts. The first part is background for 

the choice questions. The second part is the choice questions themselves. The third part is 

questions designed to understand the context for why respondents responded to the choice 

questions as they did. These questions include attitudinal questions as well as recreational 

preferences questions. The fourth part is designed to assess whether major sociodemographic 
categories of the received sample are representative of the population sampled. There are no 

record keeping requirements.

(ii) Respondent Activities

The following respondent activities are envisioned. Participants will read the cover letter and 

survey, respond to the survey questions, and return the survey using a provided postage paid 

envelope. Focus group and cognitive interview participants typically took no longer than 30 

minutes to complete the survey, so 30 minutes per response is the estimated burden for the 

average respondent. 

5. The Information Collected–Agency Activities, Collection Methodology, and Information 

Management

5(a) Agency Activities

Development of the survey questionnaire through focus group and cognitive interview pretesting 

is occurring under the separate ICR# 2090-0028. Pretest techniques follow standard approaches 

in the qualitative methods literature (Morgan and Krueger, 1998; Rubin and Rubin, 2005), as 

well as guidance in the economics literature for the specific purposes of pretesting a willingness 

to pay survey (Johnston et al., 1995; Kaplowitz et al. 2001, Hoehn et al. 2003).

Under this ICR, agency activities will include:

 Develop the choice experiment design

 Obtain a representative sample mailing list for each of the two target metro area 

populations, Phoenix and Tucson

 Printing of questionnaires

 Mailing of prenotices

 Mailing of cover letters and questionnaires

 Reminder mailings

 Follow-up mailings and replacement questionnaires to non-respondents as needed

 Data entry and quality assurance of data file

 Analysis of survey results, including characterization of nonresponse and potential 

degree of nonresponse bias

 Modeling choice experiment results with a standard multinomial logit approach

 Reporting survey results

5(b) Collection Methodology and Management

The proposed survey is a choice experiment questionnaire delivered and returned by mail. 

Standard multi-contact mail survey methods will be used to increasing response rate (Dillman, 

2009, pg. 242). The desired number of completed surveys is 250 in each of the Phoenix and 

Tucson metro areas with a target response rate of 30% in each area. Thus it will be necessary to 

contact approximately 834 households in each metro area.
Data quality will be monitored by checking returned survey responses for consistency, and by 

assessing any comments made on the survey or returned with the survey that signal strategic 

responses or respondent confusion. Coded survey data will not include any identifying 

information of the respondents. Returned survey data will be coded and used as the dataset for 

multinomial logit regression modelling.

5(c) Small Entity Flexibility

This survey will be administered to individuals, not businesses. Thus, no small entities

will be affected by this information collection.

5(d) Collection Schedule

A breakdown of the expected collection schedule is as follows:

 Week 1: Printing surveys

 Week 2: First contact mailing for pilot survey, notifying that a survey will be mailed in 1-

2 weeks

 Week 3 and 4: Pilot survey mailing

 Week 5 and 6: Pilot survey reminder postcards mailing

 Week 7 through 9: Data entry of pilot survey results. Revising estimation of the beta 

vector (coefficients on utility variables, see part B of the supporting statement). Adjusting 

the choice experiment and cost levels for the main survey mailing based on the beta 

vector estimated from the pilot survey

 Week 10: First contact mailing for main survey mailing, notifying that a survey will be 

mailed in 1-2 weeks

 Week 11 and 12: Main survey mailing

 Week 13 and 14: Main survey reminder postcards mailing

 Week 15 through 18: Main survey additional reminders and replacement surveys as 

necessary to reach target response rate

 Week 19 to 20: Data entry

The schedule above is staged such that if response rates are higher or lower than expected, the 

appropriate number of replacement surveys will be printed and mailed to most efficiently use

funds.

6. Estimating The Burden and Cost of the Collection

6(a) Estimating Respondent Burden

For a typical respondent, a conservative estimate of their time to review and respond to survey

questions is 30 minutes. Assuming the target of 500 people total respond to the survey, the 

burden is 250 hours. This would be a one-time expenditure of their time. 

6(b) Estimating Respondent Costs

(i) Estimating Labor Costs
The Bureau of Labor Statistics reports average wage rates for some metropolitan areas, with the 

most recent data being May 2011 (Bureau of Labor Statistics, 2011). The average hourly wage 

for all occupations in the Phoenix metro area was $21.61, or an average cost per participant of 

$10.81. The average hourly wage for all occupations in the Tucson metro area was $20.55, or an 

average cost per participant of $10.28. Assuming 250 participants in each metro area fill out the 

survey, the total estimated respondent labor cost is $5,270. 

(ii) Estimating Capital and Operations and Maintenance Costs

There are no anticipated capital, operations or maintenance costs associated with this collection.

(iii) Capital/Start-up Operating and Maintenance (O&M) Costs

There are no anticipated capital, operations or maintenance costs associated with this collection.

(iv) Annualizing Capital Costs

There are no anticipated capital, operations or maintenance costs associated with this collection.

6(c) Estimating Agency Burden and Cost

The various aspects of the survey mailing are assumed to be done by the principal investigator, 

with an associated hourly wage rate of $32.50. Preparing survey mailings, tracking 

nonrespondents, sending new mailings as needed, and data entry are anticipated to amount to 8 

weeks total or 320 hours of work. Agency labor cost would be 320 hours times $32.50 per hour 

or $10,400. 

6(d) Estimating the Respondent Universe and Total Burden and Costs

Assuming 250 participants in each of the Phoenix and Tucson metro areas fill out the survey, the 

total labor cost will be $5,270.

6(e) Bottom Line Burden Hours and Cost Tables

Item Quantity Cost

Public Burden

Time burden: 0.5 hours per 

respondent

500 persons 250 hours; $5,270 labor

Agency Burden

Time burden Entire project 320 hrs; $10,400 labor

Mailing list 1,000 names in Tucson area & 

1,000 names in Phoenix area 

(accounts for % of incorrect 

addresses)

$800

Prenotice letter paper and 1,700 pieces $100
printing

Prenotice envelopes 1,700 pieces $150

Prenotice postage (bulk mail) 1,700 pieces $700

Color surveys paper and printing 2,000 pieces

(includes estimated 

replacements)

$2,900

Printing return envelopes 10.5” x 

7.5”

2,000 pieces

(includes estimated 

replacements)

$450

Outgoing envelopes 11.5” x 

8.75”

2,000 pieces

(includes estimated 

replacements)

$300

Outgoing survey postage (bulk 

mail)

2,000 pieces

(includes estimated 

replacements)

$1,900

Return survey postage (bulk 

mail)

500 pieces $500

Reminder postcard paper & 

printing

1,700 pieces $100

Total $23,570

The estimated respondent burden for this study is 250 hours and $5,270. The estimated agency

cost for this study is 320 hours and $10,400. Agency costs besides labor hours total $7,900 for

the mailing list, paper, printing, and postage.

6(f) Reasons for Change in Burden

The survey is a one-time data collection activity.

6(g) Burden Statement

The annual public reporting and recordkeeping burden for this collection of information is 

estimated to average 0.5 hours per response. Burden means the total time, effort, or financial 

resources expended by persons to generate, maintain, retain, or disclose or provide information 

to or for a Federal agency. This includes the time needed to review instructions; develop, 

acquire, install, and utilize technology and systems for the purposes of collecting, validating, and 

verifying information, processing and maintaining information, and disclosing and providing 

information; adjust the existing ways to comply with any previously applicable instructions and 

requirements; train personnel to be able to respond to a collection of information; search data 

sources; complete and review the collection of information; and transmit or otherwise disclose 

the information. An agency may not conduct or sponsor, and a person is not required to respond 

to, a collection of information unless it displays a currently valid OMB control number. The 

OMB control numbers for EPA's regulations are listed in 40 CFR part 9 and 48 CFR chapter 15. 

To comment on the Agency's need for this information, the accuracy of the provided burden 

estimates, and any suggested methods for minimizing respondent burden, including the use of 
automated collection techniques, EPA has established a public docket for this ICR under Docket 

ID Number EPA-HQ-ORD-2013-0282, which is available for online viewing at 

www.regulations.gov, or in person viewing at the Office of Research & Development (ORD) 

Docket in the EPA Docket Center (EPA/DC), EPA West, Room 3334, 1301 Constitution 

Avenue, NW, Washington, D.C. The EPA Docket Center Public Reading Room is open from 

8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number 

for the Reading Room is (202) 566-1744, and the telephone number for the ORD Docket is (202) 

566-1752. An electronic version of the public docket is available at www.regulations.gov. This 

site can be used to submit or view public comments, access the index listing of the contents of 

the public docket, and to access those documents in the public docket that are available 

electronically. When in the system, select “search,” then key in the Docket ID Number 

identified above. Also, you can send comments to the Office of Information and Regulatory

Affairs, Office of Management and Budget, 725 17th Street, NW, Washington, D.C. 20503, 

Attention: Desk Officer for EPA. Please include the EPA Docket ID Number EPA-HQ-ORD2013-0282 and OMB Control Number 2080-NEW in any correspondence.

Part B of Supporting Statement

1. Survey Objectives, Key Variables, And Other Preliminaries

(a) Survey Objectives

The objectives of the survey are bulleted below:

 To estimate public values for changing the extent of the flow mileage and associated 

forest vegetation acreage along the effluent-dominated Santa Cruz River.

 To estimate public values for full contact recreation in the effluent-dominated Santa Cruz

such as submersion, as a change from partial body contact recreation such as wading.

 To provide a case study for estimating public values for modifying river attributes of a 

waterway highly impacted by urban processes.

 To compare estimated public values for changing attributes of two different reaches of 

the Santa Cruz River, the South and the North.

 To compare estimated public values between two population centers, the Phoenix metro 

area and the Tucson metro area. 

 

(b) Key Variables

The survey asks respondents whether they would choose a permanent tax increase for their 

household in exchange for changes in Santa Cruz River attributes. The key variables are:

North Santa Cruz Flow and Forest: This is a bundled variable with two numeric values for each 

level specific to the North Santa Cruz. One number shows miles of surface flow, and another 

number shows acres of cottonwood/willow forest associated with that flow. The survey considers

three possible levels of this variable. The future baseline level is termed the “expected future”. 

Two different increases from the expected future are posed, the largest of which is the same as 

the current condition. 
North Santa Cruz Full Body Contact: This is a binary “Yes” or “No” variable specific to the 

surface flows in the North Santa Cruz. A “Yes” means the surface flow would be considered safe 

for full body contact at normal flow levels, including submersion. A “No” means the surface 

flow would be considered safe only for partial body contact, i.e. wading, and normal flow levels. 

The Expected Future and Current Condition are both “No”, but the survey poses the possibility

of a “Yes”.

South Santa Cruz Flow and Forest: This is a bundled variable with two numeric values for each 

level specific to the South Santa Cruz. One number shows miles of surface flow, and another 

number shows acres of cottonwood/willow forest associated with that flow. The survey considers 

three possible levels of this variable. The future baseline level is termed the “expected future”. 

Two different increases from the expected future are posed, the largest of which is the same as 

the current condition. 

South Santa Cruz Full Body Contact: This is a binary “Yes” or “No” variable specific to the 

surface flows in the South Santa Cruz. A “Yes” means the surface flow would be considered safe 

for full body contact at normal flow levels, including submersion. A “No” means the surface 

flow would be considered safe only for partial body contact, i.e. wading, and normal flow levels. 

The Expected Future and Current Condition are both “No”, but the survey poses the possibility

of a “Yes”.

Tax increase per year: Each change varying from the expected future of reduced flows and 

cottonwood/willow acreages in the North and South has an associated cost. These cost levels 

currently vary from $0 for the Expected Future, to as high as $50 (subject to change based on 

pilot survey results). These cost levels are not tied to actual costs estimates for the changes, but 

rather are designed to bracket values. That is, the design goal is to set cost levels such that some 

people agree to them and some people don’t agree to them. A pilot survey will be used to test 

whether cost levels posed in the survey should be revised.

(c) Statistical Approach

The statistical approach to analyzing survey results will be a multinomial logit model (BenAkiva and Lerman, 1985).

(d) Feasibility

The survey has been extensively pretested, as described below, to reduce cognitive difficulties 

for respondents. The principal investigator has research funding to cover the costs of the survey. 

2. Survey Design

(a) Target Population And Coverage

The target population is households of the Phoenix and Tucson metropolitan areas in southern 

Arizona. Respondent coverage will be such that each household in each respective area has an 

equal probability of being selected to receive a survey, based on the mailing list.
(b) Sample Design

(i) Sampling Frame

The sample frame is households of the Phoenix and Tucson metropolitan areas in southern 

Arizona. A sample will be such that each household in each respective area has an equal 

probability of being selected to receive a survey, based on best available mailing lists, available 

from companies specializing in preparing mailing lists for surveys.

(ii) Sample Size

There is no single sample size choice since there will be uncertainty with estimates regardless of 

sample size. This survey design will utilize the rule of thumb of available from the developers of 

Sawtooth Software (Orme, 1998), a software popular for designing choice sets. This formula was 

also recently utilized by NOAA (OMB # 0648-0585). The rule of thumb formula for a minimum 

sample size is:

(n × t × a)/c > = 500

Where:

n = minimum number of respondents

t = number choice questions

a = number of alternatives per task (not including the “status quo” option)

c = number of “analysis cells.”

When considering main effects, c is equal to the largest number of levels for any single attribute. 

If considering all two-way interactions, c is equal to the largest product of levels of any two

attributes (Orme, 1998). The sample size will be based on a main effects model. A minimum of 3 

choice questions will be in each survey, with two options each (not counting “expected future”), 

and the maximum number of levels for any single attribute is 3. Thus the minimum sample size 

“n” is 250 for each population to be sampled, and this is our target number of respondents for 

both the Phoenix and Tucson metro areas. This value is larger than the 200 minimum suggested 

when the intent is to compare subgroups (Orme, pg 67). Bateman et al. (2002; pg. 110) 

recommend a sample size of 500 to 1,000 (for each subgroup) for close-ended contingent 

valuation questions, but also note a smaller sample size can be used if one collects more 

information per respondent (as with replications in choice experiments). With a target response 

rate of 30%, this means approximately 834 households in each metro area will receive a survey.

(iii) Stratification Variables

The Phoenix and Tucson metro areas will be treated as different populations.

(iv) Sampling Method

A sample mailing list for each of the two metro areas will be purchased from a mail survey

support company. The company will be given instructions to prepare the sample such that each 
household in each metro area has an equal chance of being chosen (a simple random sample

approach).

(v) Multi-Stage Sampling

Not applicable.

(c) Precision Requirements

(i) Precision Targets

Louviere et al. (2000) provide a formula, based on elementary statistical theory, for the minimum 

sample size “n” for target accuracy and confidence interval of predicting a proportion, assuming 

a large sample frame population, a simple random sample strategy is used, and choice occasions 

from each respondent can be assumed to be independent:

n > = (q/rpa2)Φ-1((1+α)/2)

where “p” is the population proportion, as predicted within “a” percent of the true value with 

probability “α” or greater, “q” = 1-p, “r” is replications (choice occasions per respondent) and 

“Φ

-1

(.)” is the inverse cumulative normal distribution function. This study will use a target of 

plus or minus 10% for predicting population proportions to be estimated, with a probability of 

0.95. Assuming a population proportion of 0.3, and a minimum r of 3, the minimum sample size 

is 174 respondents, less than the 250 sample size planned for each metro area.

(ii) Nonsampling error

With a target response rate of 30% there will be a large percentage of nonrespondents. If 

preferences of nonrespondents differ markedly from respondents, nonresponse bias will affect 

the results. A nonresponse analysis will be conducted by comparing the sociodemographics of 

the respondents with the sampling frame. A description of any sociodemographics that were less 

represented in the responses will be included in the results writeup. If respondents and 

nonrespondents have markedly different sociodemographics, the sociodemographic vector of the 

sampling frame (as opposed to the respondents) will be fed into the model to obtain valuation 

estimates for an “average” household (Morrison, 2000).

(d) Questionnaire Design

The current draft survey is also uploaded to the federal register (note that the pages numbers are 

out of sequence on the electronic file, they are sequenced so that they will print correctly doublesided). Below is a description of the sections and questions.

PART 1

Background. The cover photo shows the result of a reduction in perennial stream length that has 

been recently documented on the Santa Cruz River. This change has already occurred and is not 

a change considered in the survey, but does pictorially shows a “before” and “after” view at a 
single location. Page 2 shows the Santa Cruz River within the landscape of the broader river 

network in Arizona, for perspective. Page 3 shows where the treated wastewater flow in the 

South and North reaches are in southern Arizona, background on how they came to exist, and 

introduces why these resources might be relevant to the respondent. Page 4 describes the 

partitioning of treated wastewater releases and the relatively small fraction that is consumptively 

used by plants or that evaporates in the perennial river ecosystem. Page 5 describes the type of 

riparian forest that will be a topic in the survey, and some of the wildlife that are found in that 

type of habitat. Pages 6, 7, and 8 describe the different attributes that will be in the later choice 

questions. The “Expected Future” with no intervention is described as opposed to potential 

management changes. The first attribute of management changes are those that would retain 

more of the current condition flow miles and riparian forest acres in the North or South. 

Representative photos are shown of the riparian area with and without perennial water, along 

with specified numeric changes of flow mileage and forest acres that the survey will consider. 

Representative photos are shown for both South and North since the vegetation character is 

different; this difference is also described in the text and numerically in terms of acres of forest. 

Page 8 describes the second attribute of management changes, the safety of direct contact with 

the water in the South and North. The term Full Body Contact is equivalent to “swimmable” 

water quality but since the river reaches are typically not deep enough to swim in, we did not use 

the more familiar “swimmable” term since it could be misleading. Page 9 is an example vote 

showing the format of the choice question and page 10 describes how the attribute levels will be 

described.

PART 2

Question 1: This question begins the respondent’s thought process of weighing the relative 

importance of the different attributes within the choice experiment in questions 2 - 6.

Questions 2 through 6: These questions comprise the choice experiment portion of the survey, 

where respondents choose between different cost levels and different marginal changes in riverrelated attributes. There is always an opt-out zero cost option. Following standard techniques of 

choice experiments, the options (also known as profiles) participants choose between will be a 

fraction of the theoretically possible combinations of attributes, selected to yield the most 

informative preference information. There will be different survey versions, with five questions 

per survey (also known as “replications”), as an efficient method of allowing sufficient number 

of tradeoffs for model estimation. Different survey versions allow “blocking” the still large 

number of tradeoff questions posed into different groups. These practices save expense and also 

reduce the sample size and associated public burden.

Choice Experiment Design

All possible choice profile tradeoffs could be presented to respondents, but would be an 

inefficient way to gauge preferences. Instead, “fractional factorial” models are a standard 

approach (Louviere et al., 2000). A statistical software will be used to develop the most efficient 

choice experiment design, given a total number of design choice sets to manipulate, as well as a 

provisional beta vector (Kuhfeld, 2010). Essentially the software will search for the questions, 

given the constraint on choice sets, likely to yield the most preference information. The computer 

generated design will be manually checked for any potentially dominating choices, or scenarios 

that may seem unlikely to respondents. The total number of choice sets must be at least as large 
as the number of parameters to be estimated and is typically much more. A number of choice sets 

that allows each level to occur an equal number of times is also desirable, for balance (Kuhfeld, 

2010; pg. 78).

PART 3

Questions 7 through 14: These questions shed light on motivations for respondents’ answers, 

and also test for inconsistencies in their responses. Question 9 helps identify “protest bids”, that 

is, occasions when people choose not to pay for philosophical reasons rather than a price that is 

too high. Recreation behavior questions 12 and 13 allow insight into recreational preferences 

specific to the resources being considered. 

PART 4

Questions 15 through 22: These are sociodemographic questions that allow comparing the 

received sample with the sample population as a gauge of representativeness. 

3. PRETESTS AND PILOT TESTS

Pretests

The survey content and format has undergone extensive pretesting. Several phases of qualitative 

survey development have occurred and are ongoing under a different ICR (ICR # 2090-0028). 

The earliest phases of survey development did not present study participants with a survey, 

instead the intention of those research sessions was to identify the most relevant variables to 

include. The first phase of qualitative cognitive interviews occurred in October 2011. Interviews 

were held with a convenience sample of 12 neighborhood presidents in Tucson. In the spring of 

2012, there were 10 focus groups in southern Arizona, with 8 in Tucson, 1 in Rio Rico, and 1 in 

Tubac. Focus group participants were recruited from the general public by a market research 

contractor using standard market research methods, including paying participants an incentive 

fee as compensation for their opportunity cost of time. At this stage participants were still not 

asked to take or react to a survey, but instead were asked to help ORD identify attributes

important to them about southern Arizona rivers and streams, as well as for the Santa Cruz River 

in particular.

The information from the above qualitative research was used to develop a first draft of a survey

focusing on the North Santa Cruz, the reach nearest to southern Arizona population centers. This 

version was pretested in the fall of 2011. Cognitive interviews were conducted with 17 persons, 

all recruited from the general population of Tucson by a market research contractor, again paying 

incentive fees. The survey draft included key variables identified by earlier qualitative research, 

but the list of attributes seemed to be near the limit for respondents to effectively consider. In 

addition there were two attributes both dealing with forest acreage that were easily confused. At 

the conclusion of the pretest, participants were asked to comment on the relative appeal of 

preserving the North Santa Cruz River versus the South Santa Cruz River, based on a map of 

their respective locations and representative photos of the two areas. Many participants preferred 

maintaining the South Santa Cruz location despite it being further away from Tucson. Based on 

these pretests it was decided to narrow the scope of attribute types, and to feature both the North 

and South so as to include two different effluent-dominated sections of the same river.
For the revised survey, the principal investigator requested and received updated natural science 

modeling of the relationship between surface water and forest acreage for the North and South 

Santa Cruz River (personal communication, J. Stromberg, May 2013). In the spring of 2013, 

there were an additional 2 focus groups and 8 cognitive interviews, with one cognitive interview 

still pending. One of the focus groups and 2 of the interviews were with people living in the 

Phoenix area, the pending interview is also with someone living in the Phoenix area, with one 

focus group and the remaining interviews being with persons living in the Tucson area. The

survey booklet format and improved debriefing questions were adapted from a prior EPA survey

(OMB # 2020-0283). The current draft survey instrument has also been uploaded to the federal 

register (note that the pages numbers are out of sequence on the electronic file, they are 

sequenced so that they will print correctly double-sided).

The current draft reflects several edits that were made during the latest round of pretests (which 

is still ongoing). A primary change was revising the description of the full contact vs. partial 

contact recreation. It was originally posed as “Safe” for contact recreation or “Unsafe” for 

contact recreation. In the early sessions it was found that people frequently felt compelled to vote 

for “Safe”, presuming there to be a significant public health hazard if the water was left 

“Unsafe”. The labeling in the choice experiment matrix was thus changed to the current “Yes” 

vs. “No” language, along with a fuller description of the attribute, which helped participants have 

a more accurate grasp of the issue. Another change was inclusion of more background describing 

“expected future” and the competing options. In particular, the revisions emphasized the 

difference with North and South forest which was not well-conveyed for some respondents

despite photo visual aids. In addition, color coding for attributes that remain at “expected future”

levels was used to make differences between choice questions clear at a glance; previously, 

many participants described confusion that the series of choice questions appeared to be the 

same. 

Pilot Test

A pilot survey will be mailed to a subset of the Phoenix and Tucson samples. This will not 

represent an additional burden, but will be some designated fraction of the total mailing. This 

will allow for the possibility of adjusting the survey for any problems that may surface after this 

initial wave of survey returns before committing to the full mailing. The entire beta parameter 

vector (see econometric specification section below) may be revised based on analysis of the 

results, in particular the cost levels may need to be adjusted to efficiently bracket values. Costs 

will not vary between the Phoenix and Tucson samples to guard against “starting point bias” as 

being a potential reason for any statistically significant changes in values between Phoenix and 

Tucson respondents.

4. COLLECTION METHODS AND FOLLOW-UP.

(a) Collection Methods

A mail survey collection method is selected due to its frequent and successful use in the choice 

experiment literature and its relatively low cost.

(b) Survey Response And Follow-up
Multiple contact methods (Dillman, 2009; pg 242) will be used. Thus, those who have already 

responded will be tracked in a spreadsheet to ensure follow-up mailings are only sent to those 

who have not yet responded.

5. ANALYZING AND REPORTING SURVEY RESULTS

(a) Data Preparation

All data entry will be conducted by the Principal Investigator. Debriefing question responses that 

are at odds with voting question responses will be used to flag respondent confusion, and these 

data will not be used. Responses that indicate protest to the payment vehicle used in this survey, 

i.e. philosophical objection to increased taxes, will not be used. Responses from persons less than 

18 yrs of age as indicated from the ‘what year were you born’ question will not be used. 

(b) Analysis

A standard multinomial logit model, as described by Ben-Akiva and Lerman (1985), will be fit 

to the data. Let U = utility of household (well-being). Consider U to be a function of a vector zin

of attributes for alternative i, as perceived by household respondent n. The variation of 

preferences between individuals is partially explained by a vector Sn of sociodemographic 

characteristics for person n.

Uin = V(zin, Sn) + ε(zin, Sn) = Vin + εin

The “V” term is known as indirect utility and “ε” is an error term treated as a random variable 

(McFadden 1974), making utility itself a random variable. An individual is assumed to choose 

the option that maximizes their utility. The choice probability of any particular option (Expected 

Future, Option A, or Option B) is the probability that the utility of that option is greatest across

the choice set Cn:

P (i│Cn) = Pr[Vin + εin ≥ Vjn + εjn , for all j ∈ Cn, j not equal to i]

If error terms are assumed to be independently and identically distributed, and if this distribution 

can be assumed to be Gumbel, the above can be expressed in terms of the logistic distribution:

Pn(i) = eμVin / ∑ e

μVjn 

The summation occurs over all options Jn in a choice set. The assumption of independent and 

identically distributed error terms implies independence of irrelevant attributes, meaning the 

ratio of choice probabilities for any two alternatives is unchanged by addition or removal of 

other unchosen alternatives (Blamey et al. 2000). The “μ” term is a scale parameter, a convenient 

value for which may be chosen without affecting valuation results if the marginal utility of 

income is assumed to be linear. The analyst must specify the deterministic portion of the utility

equation ‘‘V,’’ with subvectors z and S. The vector z comes from choice experiment attributes, 

and the vector S comes from attitudinal, recreational, and sociodemographic questions in the 

survey. An econometrics software will be used to estimate the regression coefficients for z and S, 
with a linear-in-parameters model specification. These coefficients are used in estimating 

average household value for a change in one level to another level of a particular attribute for 

welfare estimation. Welfare of a change is given by (Holmes & Adamowicz 2003):

$ Welfare = (1/βc)[V0- V

1

] 

where βc is the coefficient on cost, V

0

is an initial scenario, and V1is a change scenario.

Econometric Specification

A main effects utility function is hypothesized for each of the Phoenix and Tucson metro areas. 

A generic format of the indirect utility function to be modeled is:

V = βo + β1(North Flow & Forest Change) + β2(North Full Contact Recreation Change) + 

β3(South Flow & Forest Change) + β4(South Full Contact Recreation Change) + β5(Cost)

(c) Reporting Results

The results will be written up and submitted to a peer-reviewed environmental journal.
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