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1 SURVEY OBJECTIVES, KEY VARIABLES, AND OTHER 

PRELIMINARIES

1(a) Survey Objectives

For CWNS 2012, states will have the option to use the “Traditional” CWNS Method or a 

new “Gap Approach” option. The primary objective of the statistical methods applied in 

Section B of this information collection is for EPA to identify and select a sample of 

wastewater systems that is representative of systems within each state that chooses to 

participate in the GAP Approach to estimate the needs for the 2012 CWNS. For the 

selected sample of wastewater systems, states will collect information about asset 

inventory that will be used by EPA to estimate asset replacement cost. The 

representativeness of this sample of systems at the state level is critical to the CWNS 

because the estimated costs will be used to generate the CWNS Report to Congress, 

which presents costs data at the state level. 

1(b) Key Variables

The key variables associated with selecting a representative sample of wastewater 

systems at the state level are: system size (by population served), CWNS 2008 needs, and 

system type (i.e., combined sewer system or separate sewer system). 

1(c) Statistical Approach

In the previous data collection efforts for the CWNS a census approach (Traditional 

Approach) was used. For the CWNS 2012 EPA is providing states the option of using a 

more compressive infrastructure GAP Approach to estimate the needs for wastewater 

systems. This new approach will require participating states to submit significantly more 

information for each system, so selection of a sample of systems for participation allows 

for significant burden and costs savings as compared to a census approach. 

1(d) Feasibility

EPA anticipates that the survey (the statistical sample) objectives are achievable given 

the existing time and resource constraints. 

 State participation in the GAP Approach for CWNS is voluntary. 

 There will be an electronic version of the form (with picklists and calculations 

coded in). 

 The statistical approach to this data collection requires only a fraction of systems 

to complete the GAP form, resulting in equivalent or smaller cost and burden at 

the state level than would be incurred if all systems participate in CWNS 

 The survey results will be completed in time to inform the corresponding cycle of 

CWNS. 
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2 SURVEY DESIGN

2(a) Target Population and Coverage

Existing public wastewater systems are the target population for CWNS GAP Approach 

methodology. 

2(b) Sample Design

2(b)(i) Sampling Frame

For each participating state, EPA will develop the sample frame for the statistical 

selection of wastewater systems. Initial data will be pulled from the 2008 CWNS. Only

those systems in operation in 2008, expected to be in operation in the future, and 

reporting documented needs were used to estimate the sample characteristics, but the 

sample size calculations was applied to all wastewater systems, regardless of their 

reporting of needs. The initial universe will be adjusted to account for known anomalies 

inventory reporting (For example, states will be able to inform EPA about existing 

systems that were not entered in the 2008 CWNS or that were entered but not submitted 

for review).

2(b)(ii) Sample Size

Final sample sizes for participating states will be determine once the state makes a 

decision to be part of the GAP Approach methodology. Preliminary sample sizes were 

estimated by EPA and are presented in Appendix A. The sample design limits strata with 

less than 10,000 people to having a maximum error of 80% and strata of more than 

10,000 people to having a maximum error of 40%. All facilities in the state’s top 3% 

based on population will be included in the sample frame.

Typical sample rates are expected to be:

 10-25% for facilities serving less than 10,000 people

 30-60% for facilities serving between 10,000 and 100,000 people

 100% (census survey) for the largest 3% of facilities in each state

2(b)(iii) Stratification Variables

In developing the representative sample, EPA considers factors such as population served 

and geographic location. For each state the sample systems will be stratified by

population served (system size).

2(b)(iv) Sampling Method

The proposed sampling design is stratified random sampling. For each state the number 

of strata and stratification limits will be determined based on the population 

characteristics of the state and a representative sample of systems from each of the strata 

will account for different system sizes. EPA will include at least three systems from each 

stratum for each state. 
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2(b)(v) Multi-Stage Sampling

EPA does not anticipate the need for multi-stage sampling. Wastewater systems statuses 

often change little over short periods of time, so significant changes from the 2008 are 

not expected. 

2(c) Precision Requirements

2(c)(i) Precision Targets

For each state the sample design is selected based on two conditions:

 The total needs would be estimated within close to ± 10 percent of the amount of 

the true need within a 95% confidence interval, and

 Each stratum consisting of less than 10,000 people would have an error of ± 80 

percent, and each stratum consisting of more than 10,000 people would have an 

error of ± 40 percent. 

For most states one of the two conditions above drives the sample design. In cases where 

the individual stratum error drives the results, the total error will be less than 10 percent. 

Alternatively, where the total error drives the results, states will have stratum errors that 

are less than the 80 percent or 40 percent bounds.

2(c)(ii) Non-sampling error

Systems that do not complete the questionnaire will be considered as systems without 

justification for needs, and will be included as such in the analysis. This is consistent 

with how these facilities are handled in the CWNS Traditional Method. Given that many

less facilities are involved under the Gap Approach, states utilizing the gap approach will 

have a much greater ability to follow up with facilities on completing the form. Since 

non-completion of questionnaire will be assessed as a system not having justification for 

needs, and since CWNS 2012 results may be used to determine states’ Clean Water State 

Revolving Fund allocations, states will have a high incentive to obtain very close to 

100% form completion.

2(d) Questionnaire Design

The GAP Data Request form was design to minimize data entry by pre-populating it with 

data currently in the CWNS DEP. See Appendix B for the draft form.

Other features of the form are:

 The form will have optional extra pages for entering additional asset inventory

(section 5) information.

 The form will have a companion (~2 page) instructions document.

 There will be an electronic, editable version of the form (with picklists and 

calculations coded in). Like the hard copy form, this electronic Gap Approach

form will be pre-populated with the most current CWNS data. 
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 Asset replacement costs are not requested in any versions of the form. These 

costs will be calculated in the CWNS DEP based on other data entered in the form

 All data in the form is required, except where indicated by the italic text (several 

rows in page 4 tables, and far right 3 table columns on pages 5-7)

The form is divided into 6 sections, each with data item request that meet a clear and 

specific objective:

Sections 1 to 4: Basic system data. These four sections provide the information 

necessary to identify and characterize the system. Most of the information will be 

pre-populated but the respondents will have the ability to change any of the data 

items.

Section 5: Revenues and Expenses. Data items in this section are necessary to 

analyze the financial situation of the system. Most data item are voluntary with 

only the totals denoted as mandatory. 

Section 6: Asset Inventory. This is the most extensive section of the questionnaire 

and will allow EPA to estimate the type of asset, anticipated failure and 

replacement or rehabilitation costs. The data items required should be readily

available to most operators or managers.

Section 7: Certification. Signature requirements guarantee the validity of the data. 

EPA is implementing a tiered certification with smaller systems having less 

stringent requirements.

3 PRETESTS AND PILOT TESTS

The “Gap Approach” option is modeled after an asset management needs assessment 

approach used in Pennsylvania’s 2008 Governor’s Report on Sustainable Infrastructure.

For the 2008 CWNS, the state of Pennsylvania, in collaboration with EPA, conducted a 

sample of their wastewater systems and estimated their infrastructure needs using a GAP 

methodology approach. This study in Pennsylvania served as the pilot test for the nationwide CWNs GAP initiative to be included in the 2012 CWNS. The original Form used in 

Pennsylvania has been modified based on lessons learned and input from the other states 

that are interested in using the GAP methodology for 2012. 

4 COLLECTION METHODS AND FOLLOW-UP

4(a) Collection Methods

CWNS coordinators from states participating in the GAP approach methodology will 

have flexibility to choose the collection method that best fits the characteristics of their 

state. EPA is providing multiple options and flexibility to facilitate the data collection 

effort by states:

 Forms will being pre-populated with data currently in the 2008 CWNS.

 Forms will have a barcode CWNS ID #, so that forms faxed in can be connected 

for facilities within the CWNS DEP.
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 There will be either an electronic version of the form (with picklists and 

calculations coded in)

4(b) Survey Response and Follow-up

High compliance levels (97%) during Pennsylvania’s effort in 2008 have given EPA 

confidence that equivalent levels can be achieved during 2012 in other states. EPA plans 

to continue outreach and compliance assistance efforts, as needed. 

5 ANALYZING AND REPORTING SURVEY RESULTS

5(a) Data Preparation

States are ultimately responsible for collecting and entering the information into the 

CWNS DEP and for the quality of the data entered. The DEP is equipped with automatic 

error checks to identify systems that fall outside certain normal parameter and during the 

data entry period of the CWNS 2012 EPA and its contractors will perform reviews of the 

information and documentation submitted. 

5(b) Analysis

Data collected with the Gap Approach will be analyzed alongside other CWNS data to 

develop a much more complete picture of wastewater facility sustainability, with state 

level estimates on capital and O&M needs, revenues, and gaps projected over 20 years.

5(c) Reporting Results

Capital needs from the Gap Approach will be reported alongside Traditional Method 

capital needs in the CWNS 2012 Report to Congress. Additionally, a new section will be 

added to the Report that summarizes data from states participating in the Gap Approach 

to draw sustainable infrastructure conclusions (e.g. the gap between projected capital and 

O&M needs and expected revenues).
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Appendix A – Draft Sample Sizes by State

N 

(systems)

n 

(systems)

n/N, %

(systems)

N 

(Facilities)

n (facilities

estimated)

N 

(systems)

n 

(systems)

n/N, % 

(systems)

N 

(Facilities)

n (facilities

estimated)

N 

(systems)

n 

(systems)

n/N, %

(systems)

N 

(Facilities)

n (facilities 

estimated)

AL 218 26 11.9% 223 28 55 18 32.7% 62 20 273 44 16.1% 285 48

AR 336 279 83.0% 376 315 36 36 100.0% 62 62 372 315 84.7% 438 377

AZ 52 7 13.5% 61 9 48 21 43.8% 88 55 100 28 28.0% 149 64

CA 51 12 23.5% 54 13 110 28 25.5% 260 113 161 40 24.8% 314 126

CO 203 52 25.6% 212 56 26 26 100.0% 31 31 229 78 34.1% 243 87

CT 44 17 38.6% 55 23 35 28 80.0% 63 51 79 45 57.0% 118 74

DE 13 9 69.2% 23 17 3 3 100.0% 12 12 16 12 75.0% 35 29

FL 173 17 9.8% 177 20 178 43 24.2% 240 85 351 60 17.1% 417 105

GA 259 12 4.6% 275 15 41 14 34.1% 60 27 300 26 8.7% 335 42

ID 147 25 17.0% 164 30 16 12 75.0% 38 29 163 37 22.7% 202 59

IL 509 252 49.5% 535 262 76 64 84.2% 160 143 585 316 54.0% 695 405

IN 284 250 88.0% 303 269 19 19 100.0% 28 28 303 269 88.8% 331 297

IA 709 136 19.2% 722 142 19 19 100.0% 37 37 728 155 21.3% 759 179

KS 580 246 42.4% 598 252 35 22 62.9% 81 59 615 268 43.6% 679 311

KY 122 26 21.3% 143 35 30 26 86.7% 44 39 152 52 34.2% 187 74

LA 121 26 21.5% 141 31 33 15 45.5% 57 27 154 41 26.6% 198 58

MA 64 20 31.3% 69 22 34 15 44.1% 76 42 98 35 35.7% 145 64

MD 118 17 14.4% 140 24 27 15 55.6% 52 31 145 32 22.1% 192 55

ME 97 63 64.9% 110 74 4 4 100.0% 9 9 101 67 66.3% 119 83

MI 324 90 27.8% 371 114 65 52 80.0% 336 296 389 142 36.5% 707 410

MN 108 12 11.1% 124 16 27 21 77.8% 150 140 135 33 24.4% 274 156

MO 619 242 39.1% 689 269 44 42 95.5% 123 121 663 284 42.8% 812 390

MS 268 113 42.2% 316 136 35 32 91.4% 117 110 303 145 47.9% 433 246

MT 116 42 36.2% 121 46 8 8 100.0% 15 15 124 50 40.3% 136 61

NC 240 13 5.4% 338 21 73 27 37.0% 198 82 313 40 12.8% 536 103

NE 449 198 44.1% 451 200 12 12 100.0% 15 15 461 210 45.6% 466 215

NH 69 38 55.1% 77 42 12 12 100.0% 28 28 81 50 61.7% 105 70

NJ 67 7 10.4% 90 10 70 53 75.7% 284 245 137 60 43.8% 374 255

NV 31 12 38.7% 34 15 11 10 90.9% 37 36 42 22 52.4% 71 51

NY 433 32 7.4% 527 48 67 36 53.7% 194 113 500 68 13.6% 721 161

OH 503 256 50.9% 623 326 88 78 88.6% 178 161 591 334 56.5% 801 487

OK 446 266 59.6% 448 267 39 32 82.1% 46 39 485 298 61.4% 494 306

OR 86 39 45.3% 90 42 36 16 44.4% 75 42 122 55 45.1% 165 84

PA 589 262 44.5% 818 396 104 99 95.2% 337 324 693 361 52.1% 1,155 720

PR 18 6 33.3% 19 7 25 9 36.0% 25 9 43 15 34.9% 44 16

SC 136 103 75.7% 148 115 17 17 100.0% 45 45 153 120 78.4% 193 160

SD 20 12 60.0% 20 12 5 5 100.0% 5 5 25 17 68.0% 25 17

TN 182 128 70.3% 202 144 54 48 88.9% 85 76 236 176 74.6% 287 220

TX 291 15 5.2% 318 19 149 65 43.6% 382 227 440 80 18.2% 700 246

UT 80 14 17.5% 97 19 23 12 52.2% 94 63 103 26 25.2% 191 82

VA 176 11 6.3% 258 18 42 26 61.9% 103 68 218 37 17.0% 361 86

VT 62 43 69.4% 70 51 3 3 100.0% 5 5 65 46 70.8% 75 56

WA 59 10 16.9% 69 14 19 10 52.6% 43 27 78 20 25.6% 112 41

WI 531 77 14.5% 669 105 56 40 71.4% 263 225 587 117 19.9% 932 330

WV 176 54 30.7% 201 67 11 11 100.0% 27 27 187 65 34.8% 228 94

WY 84 75 89.3% 92 83 11 11 100.0% 25 25 95 86 90.5% 117 108

TOTAL 9,939 3,572 35.9% 11,290 4,125 1,866 1,163 62.3% 4,359 3,173 11,805 4,735 40.1% 15,649 7,708

< 10 K > 10 K Total