SOUTHWEST 

BORDER SECURITY

Additional Actions 

Needed to Better 

Assess Fencing's 

Contributions to 

Operations and 

Provide Guidance for 

Identifying Capability 

Gaps

Report to Congressional Requesters

February 2017

GAO-17-331

United States Government Accountability Office
United States Government Accountability Office

Highlights of GAO-17-331, a report to 

congressional requesters

February 2017

SOUTHWEST BORDER SECURITY

Additional Actions Needed to Better Assess 

Fencing's Contributions to Operations and Provide 

Guidance for Identifying Capability Gaps

What GAO Found

Border fencing is intended to benefit border security operations in various ways, 

according to officials from the U.S. Border Patrol (Border Patrol), which is within 

the Department of Homeland Security’s (DHS) U.S. Customs and Border 

Protection (CBP). For example, according to officials, border fencing supports 

Border Patrol agents’ ability to execute essential tasks, such as identifying illicitcross border activities. CBP collects data that could help provide insight into how 

border fencing contributes to border security operations, including the location of 

illegal entries. However, CBP has not developed metrics that systematically use 

these, among other data it collects, to assess the contributions of border fencing 

to its mission. For example, CBP could potentially use these data to determine 

the extent to which border fencing diverts illegal entrants into more rural and 

remote environments, and border fencing’s impact, if any, on apprehension rates 

over time. Developing metrics to assess the contributions of fencing to border 

security operations could better position CBP to make resource allocation 

decisions with the best information available to inform competing mission 

priorities and investments.

Pedestrian Fencing in San Diego, California, April 2016

CBP is taking a number of steps to sustain tactical infrastructure (TI) along the 

southwest border; however, it continues to face certain challenges in maintaining 

this infrastructure, such as addressing maintenance of roads owned or operated 

by other public and private entities. In 2014, according to Border Patrol officials, 

Border Patrol began implementing the Requirements Management Process that 

is designed to facilitate planning for funding and deploying TI and other 

requirements. Border Patrol headquarters and sector officials told GAO that 

Border Patrol lacks adequate guidance for identifying, funding, and deploying TI 

needs as part of this process. In addition, officials reported experiencing some 

confusion about their roles and responsibilities in this process. Developing 

guidance on this process would be consistent with federal internal control 

standards and would provide more reasonable assurance that the process is 

consistently followed across Border Patrol. This is a public version of a For 

Official Use Only—Law Enforcement Sensitive report that GAO issued in 

December 2016. Information DHS deemed For Official Use Only—Law 

Enforcement Sensitive has been redacted.

View GAO-17-331. For more information,

contact Rebecca Gambler at (202) 512-8777 

or gamblerr@gao.gov. 

Why GAO Did This Study

In fiscal years 2013 through 2015, 

Border Patrol recorded a total of 2.1 

million estimated known illegal entries 

between ports of entry along the 

southwest border. In an effort to secure 

the border between ports of entry, CBP 

spent approximately $2.4 billion 

between fiscal years 2007 and 2015 to 

deploy TI — fencing, gates, roads, 

bridges, lighting, and drainage 

infrastructure—along the nearly 2,000 

mile southwest border. 

GAO was asked to review the use of 

border fencing along the southwest 

border. In this report, GAO examines 

(1) border fencing’s intended 

contributions to border security 

operations and the extent to which 

CBP has assessed these contributions 

and (2) the extent that CBP has 

processes in place to ensure 

sustainment and deployment of TI 

along the southwest border and 

challenges in doing so. GAO reviewed 

CBP documentation and data and 

interviewed officials in headquarters 

and three southwest border locations. 

These locations were selected based 

on CBP’s extensive investments in TI 

in such areas.

What GAO Recommends

GAO recommends that Border Patrol 

develop metrics to assess the 

contributions of pedestrian and vehicle 

fencing to border security along the 

southwest border and develop 

guidance for its process for identifying, 

funding, and deploying TI assets for 

border security operations. DHS 

concurred with the recommendations.
Page i GAO-17-331 Tactical Infrastructure

Letter 1

Background 7

Fencing Is Intended to Assist Agents in Performing Their Duties, 

but Its Contributions to Border Security Operations Have Not 

Been Assessed 20

CBP Manages TI Sustainment but Border Patrol Has Not Provided 

Guidance on its Process for Identifying and Deploying TI 27

Conclusion 36

Recommendations for Executive Action 37

Agency Comments and Our Evaluation 37

Appendix I Descriptive Analysis of Selected Tactical Infrastructure (TI) and 

Estimated Known Illegal Entries in Southwest Border Zones from 

Fiscal Years 2013 Through 2015 40

Appendix II Objectives, Scope and Methodology 57

Appendix III Comments from the Department of Homeland Security 65

Appendix IV GAO Contact and Staff Acknowledgments 69

Tables

Table 1: Border Patrol Mission Essential Tasks 15

Table 2: Border Patrol Foundational Operational Capabilities 

(FOC) 15

Table 3: Average Cost per Mile of Completed Southwest Border 

Fence Replacement Projects, Fiscal Years 2011-2016 34

Figures

Figure 1: Total Miles of Primary Fencing on the Southwest Border, 

Fiscal Years 2005 to 2015 9

Figure 2: Selected Designs of Pedestrian Fencing on the 

Southwest Border 11

Contents 
Page ii GAO-17-331 Tactical Infrastructure

Figure 3: Selected Designs of Vehicle Fencing and Other Tactical 

Infrastructure on the Southwest Border 12

Figure 4: Border Patrol Sectors along the Southwest Border and 

Border Stations and Zones in the Tucson Sector 14

Figure 5: U.S. Border Patrol’s Requirements Management 

Process 17

Figure 6: U.S. Border Patrol’s Capability Gap Analysis Process 19

Figure 7: Select Methods used by Illegal Entrants to Defeat Border 

Fencing on the Southwest Border 24

Figure 8: Fence Breach Due To Drive-Through Entry and 

Subsequent Repair 30

Figure 9: Legacy Pedestrian Fencing in Sunland Park, New 

Mexico, March 2016 31

Figure 10: Legacy Pedestrian Fencing in Sunland Park, New 

Mexico, March 2016 32
Page iii GAO-17-331 Tactical Infrastructure

Abbreviations

BPETS Border Patrol Enforcement Tracking System

CBP U.S. Customs and Border Protection

CGAP Capability Gap Analysis Process

CTIMR Comprehensive Tactical Infrastructure Maintenance and 

 Repair

DHS Department of Homeland Security

EID Enforcement Integrated Database

FM&E Facilities Management and Engineering 

FOCs Foundational Operational Capabilities

GPRA Government Performance and Results Act of 1993

IIRIRA Illegal Immigration Reform and Immigrant Responsibility 

 Act of 1996

METs Mission Essential Tasks

ORMD Operational Requirements Management Division 

SPA Strategic Planning and Analysis Directorate

TI Tactical Infrastructure

WMS Work Management System

This is a work of the U.S. government and is not subject to copyright protection in the 

United States. The published product may be reproduced and distributed in its entirety 

without further permission from GAO. However, because this work may contain 

copyrighted images or other material, permission from the copyright holder may be 

necessary if you wish to reproduce this material separately.House of Representatives
Page 1 GAO-17-331 Tactical Infrastructure

441 G St. N.W.

Washington, DC 20548

February 16, 2017

Congressional Requesters

In fiscal years 2013 through 2015, U.S. Border Patrol (Border Patrol), 

within the Department of Homeland Security’s (DHS) U.S. Customs and 

Border Protection (CBP), recorded a total of 2.1 million estimated known 

illegal entries 1 between ports of entry along the southwest border.2 As the 

agency responsible for securing U.S. borders to prevent acts of terrorism 

and the unlawful movement of people, illegal drugs, and other contraband 

across U.S. borders, CBP spent approximately $2.4 billion between fiscal 

years 2007 and 2015 to deploy tactical infrastructure (TI)—fencing, gates, 

roads, bridges, lighting, and drainage infrastructure—along the nearly 

2,000 mile southwest border.3 CBP now has the responsibility of 

sustaining border TI over its lifetime—including 654 miles of primary 

pedestrian and vehicular fencing and approximately 5,000 miles of 

roads.4 In 2009, CBP estimated that it would need to spend more than 

$3.5 billion over the next 20 years on TI operations and maintenance to 

 

1Border Patrol defines estimated illegal entries as the total number of removable aliens 

who were apprehended, in addition to the number of entrants who illegally crossed the 

border but were not apprehended. We defined these illegal entries as estimated “known” 

illegal entries to clarify that the estimates do not include illegal entrants for which Border 

Patrol does not have reasonable indications of cross-border illegal activity. 

2Ports of entry are facilities that provide for the controlled entry into or departure from the 

United States. Specifically, a port of entry is any officially designated location (seaport, 

airport, or land border location) where DHS officers or employees are assigned to clear 

passengers and merchandise, collect duties, and enforce customs laws, and where DHS 

officers inspect persons entering or applying for admission into, or departing the United 

States pursuant to U.S. immigration law. 

3See 6 U.S.C. § 211(a) (establishing CBP within DHS), (c) (enumerating CBP’s duties).

4Pedestrian fencing is primarily intended to slow down and deter pedestrians from 

crossing the border. Vehicle fencing, which is intended to resist vehicles engaged in drug 

trafficking and alien smuggling operations, is typically used in rural or isolated locations 

that have a low occurrence of illegal pedestrian traffic. In March 2016 we reported that 652 

miles of fencing were deployed on the southwest border. See GAO, Southwest Border 

Security: Additional Actions Needed to Assess Resource Deployment and Progress, 

GAO-16-465T (Washington, D.C.: Mar. 1, 2016). CBP has conducted an in depth review 

of geospatial data on fencing and adjusted its estimate of deployed primary border fencing 

to 654 miles. 

Letter
Page 2 GAO-17-331 Tactical Infrastructure

sustain these investments and to ensure TI continues to support Border 

Patrol’s mission.5

Our prior work on TI highlighted DHS’s increased investment in TI and the 

challenges associated with increased construction and deployment of 

fencing on the southwest border. In September 2009, we found that CBP 

had not assessed TI’s impact on border security operations or mission 

goals and had not measured the effectiveness of TI.6 Specifically, we 

found that CBP had not accounted for the impact of its investment in 

border fencing and infrastructure on border security. We recommended 

that CBP conduct an evaluation of the impact of TI on effective control of 

the border.7

You requested that we review the use of border fencing along the 

southwest border. In this report, we examine (1) border fencing’s intended 

contributions to border security operations and the extent to which CBP 

has assessed these contributions and (2) the extent that CBP has 

processes in place to ensure sustainment8 and deployment of TI along 

the southwest border and challenges in doing so. In addition, in Appendix 

 

5Cost information is based on CBP’s 2009 Life Cycle Cost Estimate (LCCE) for all TI, 

which includes border fencing, roads, lighting, drainage, and vegetation control from 2009 

to 2026. CBP officials stated that CPB is currently updating the LCCE and expects to 

complete it by the end of fiscal year 2017.

6GAO, Secure Border Initiative: Technology Deployment Delays Persist and the Impact of 

Border Fencing Has Not Been Assessed, GAO-09-896 (Washington, D.C.: Sept. 9, 2009).

In response to our recommendation that CBP conduct an evaluation of the impact of TI, 

CBP developed interim metrics, and we closed the recommendation as implemented. 

However, in November 2015, CBP reported that it had not completed or implemented 

these interim metrics due to funding challenges.We discuss CBP’s efforts to develop 

performance measures later in this report.

7Prior to 2011, DHS used the number of border miles under “operational control”—also 

referred to as effective control—as its goal and outcome measure for border security and 

to assess resource needs to accomplish this goal. In 2012, Border Patrol transitioned to 

achieving a “low risk border” as its goal and uses a variety of data to assess risk, 

including: threats of cross-border terrorism, drug smuggling, illegal migration across 

locations; integrating border security operations with those of other law enforcement 

partners’ and developing rapid response capabilities to deploy the resources appropriate 

to changes in threat.

8For the purposes of this report, sustainment refers to the maintenance, repair, and new 

construction of TI.
Page 3 GAO-17-331 Tactical Infrastructure

I we provide analyses of border fencing and total estimated known illegal 

entries in each southwest border sector.9

This report is a public version of the prior sensitive report that we 

provided to you in December 2016.10 DHS deemed some of the 

information in the prior report as For Official Use Only—Law Enforcement 

Sensitive, which must be protected from public disclosure. Therefore, this 

report omits sensitive information on sustainment of TI and our analysis of 

Border Patrol data on fencing and enforcement activities. Although the 

information in this report is more limited in scope, it addresses the same 

questions as the sensitive report. Also, the overall methodology used for 

both reports is the same.11

To examine border fencing’s intended contributions to border security 

operations and the extent to which CBP has assessed these 

contributions, we analyzed relevant documentation, including Border 

Patrol’s State of the Border Risk Methodology, which Border Patrol uses 

to assess risk across the southwest border, and documents identifying 

CBP mission goals and objectives and related performance measures. 

We also reviewed relevant acquisition documents that CBP developed 

during the construction of TI across the southwest border. We interviewed 

officials from Border Patrol’s Strategic Planning and Analysis (SPA) 

Directorate, which is responsible for identifying risk along the southwest 

border and the Operational Requirements Management Division (ORMD) 

which is responsible for deploying operational requirements, including TI, 

to mitigate these risks. During these interviews we focused on the 

intended and actual contributions of border fencing in providing Border 

Patrol agents with Foundational Operational Capabilities (FOC) and 

assisting Border Patrol agents in executing their Mission Essential Tasks 

9Border Patrol divides responsibility for border security operations geographically among 

nine sectors, each with its own headquarters. Each sector is further divided into varying 

numbers of stations. 

10GAO, Southwest Border Security: Additional Actions Needed to Assess Fencing’s 

Contributions to Operations and Provide Guidance for Identifying Capability Gaps, 

GAO-17-167SU (Washington D.C.: Dec. 22, 2016). 

11 This work was conducted prior to the issuance of the Executive Order related to border

security and immigration enforcement, which the President signed on January 25, 2017. 

See Border Security and Immigration Enforcement Improvements, Exec. Order No. 

13767,82 Fed.Reg. 8793 (Jan. 30, 2017). 
Page 4 GAO-17-331 Tactical Infrastructure

(MET).12 For this objective, we also analyzed fence breaches by fence 

design. To do this analysis, we obtained pedestrian fence breach data 

from Border Patrol Facilities and Tactical Infrastructure (BPFTI) for fiscal 

years 2010 through 2015. To assess the reliability of these data, we 

reviewed how CBP collects and maintains breach data and found that the 

data were sufficiently reliable for the purposes of our report. We then 

analyzed the occurrences of breaches in modern compared to legacy 

pedestrian fence designs.13 We also discussed the limitations associated 

with border fencing, including the methods employed by illegal entrants in 

defeating border fencing, including breaches.

During our meetings with ORMD and SPA, we also focused on CBP’s 

efforts to assess border fencing’s contributions to border security 

operations, and the perceived challenges involved in conducting such an 

assessment. We compared these efforts against criteria established in 

our prior work on leading practices for performance management.14 To 

identify border fencing’s intended contributions to border security 

operations at the sector level, we visited the El Paso, San Diego, and 

Tucson Sectors. We selected these sectors for site visits due to CBP’s 

extensive investments in TI in each sector over the years. Combined, 

these sectors contain approximately 52 percent of all miles of primary 

pedestrian fencing and 80 percent of all miles of vehicle fencing along the 

southwest border. During these site visits, we interviewed Border Patrol 

sector officials, agents selected by sector officials, and agents assigned 

 

12Border Patrol defines FOCs as the essential combinations of resources (personnel, 

training, equipment, technology, and infrastructure) that provide Border Patrol agents with 

the fundamental operational means by which to conduct their Mission Essential Tasks 

(METs). Border Patrol defines the METs as a sequential set of discreet or unique tasks in 

which Border Patrol agents must be proficient to execute their duties in the furtherance of 

border security operations. 

13For the purposes of this report, we refer to any fencing designs used prior to CBP 

implementing requirements of the Secure Fence Act of 2006 (Pub. L. No. 109-367, 120 

Stat.2638) as “legacy” fencing and any fencing deployed subsequently as “modern” 

fencing designs. In addition, all “landing mat” fencing—constructed of army surplus carbon

steel landing mats which were used to create landing strips during the Vietnam War—is 

considered “legacy” fencing design, regardless of when it was constructed. 

14GAO, Managing for Results: Enhancing Agency Use of Performance Information for 

Management Decision Making, GAO-05-927 (Washington, D.C.: September 2009).
Page 5 GAO-17-331 Tactical Infrastructure

to various stations and zones within each sector.15 Our interviews in each 

sector focused on agents’ perspectives on border fencing’s specific 

contributions to border security within each sector as well as the extent to 

which border fencing has provided Border Patrol agents with the 

capabilities border fencing was intended to provide, and the extent to 

which border fencing assists Border Patrol agents in executing their 

METs. We also collected information on other perceived benefits of 

border fencing, including agent safety, as well as perceived limitations of 

border fencing. While the information we obtained from our site visits 

cannot be generalized to all Border Patrol sectors, it provided us with 

insights about border fencing’s contribution to border security operations.

To determine the extent that CBP has processes in place to ensure 

sustainment and deployment of TI along the southwest border and 

challenges in doing so, we reviewed relevant documentation and 

interviewed headquarters officials from CBP. Documents we reviewed 

included contracts, which CBP uses to maintain and repair all TI assets 

across the southwest border. To assess how CBP manages the 

deployment of TI across the southwest border, we reviewed relevant 

documentation from ORMD, which is responsible for executing Border 

Patrol’s requirements management process and deploying TI, among 

other assets, along the southwest border. These documents included 

Border Patrol’s Capability Gap Analysis Process (CGAP) and the various 

outputs of this process. We compared these documents against criteria 

outlined in Standards for Internal Control in the Federal Government.16

We also interviewed officials from BPFTI, which is responsible for 

sustaining TI along the southwest border, and ORMD. Our interviews with 

BPFTI officials focused on the program’s contracts and work plans, 

oversight of contractors, the system that BPFTI uses to track and oversee 

all TI related maintenance and repair work, and any challenges BPFTI or 

contractors may face in sustaining TI along the southwest border. Our 

interview with ORMD focused on Border Patrol’s process for identifying TI 

requirements in each sector, prioritizing TI requirements across all nine 

southwest border sectors, and allocating resources and deploying TI 

 

15Border Patrol has divided the southwest border into nine sectors. Each southwest 

border sector is divided into varying numbers of stations, with agents assigned to patrol 

defined geographic areas, or zones, within each station. Of these, zones that touch the 

international border are known as border zones, while zones that do not touch the 

international border are known as interior zones. 

16GAO, Standards for Internal Control in the Federal Government, GAO-14-704G

(Washington, D.C.: Sept. 2014). 
Page 6 GAO-17-331 Tactical Infrastructure

solutions. During our site visits, we interviewed relevant BPFTI and 

Border Patrol officials responsible for overseeing the sustainment of TI in 

the sector. In these meetings, we discussed past and ongoing TI 

projects–-including fence replacement projects and other major repairs-–

as well as any challenges the sectors face in sustaining the TI deployed 

there. We also toured each sector’s TI inventory, which include 

pedestrian and vehicle fencing, gates, roads, bridges, grates, and lighting.

In the El Paso and Tucson sectors, we visited segments of legacy 

pedestrian fencing slated for replacement with more modern pedestrian 

fencing.

To analyze the location of estimated illegal entries in conjunction with 

border fencing, we obtained Border Patrol data on estimated known 

illegal entries in border zones within each of the nine sectors along the 

southwest border for fiscal years 2013 through 2015.17 We also obtained 

data on the location of CBP’s 654 miles of primary border fencing, by 

fencing type, and design in each sector, and combined these two data 

sets. Through this analysis, we were able to identify the (1) total 

estimated known illegal entries, (2) estimated turn backs and got aways, 

(3) estimated drive throughs and (4) apprehension rates for estimated 

illegal entries in southwest border zones with border fencing, by fence

type, design, and zone coverage,18 and in southwest border zones 

without border fencing. We then used these data to create data tables for 

each sector that visually display the results of our analysis. We assessed 

the reliability of these data by interviewing knowledgeable CBP officials 

on the limitations of these data and digital testing of these data. To 

 

17We obtained apprehension data for fiscal years 2013 through 2015 from the 

Enforcement Integrated Database —a DHS-shared common database repository for 

several DHS law enforcement and homeland security applications. We obtained data on 

entrants who illegally crossed the border but were not apprehended either because they 

crossed back to Mexico—”turn backs”—or continued traveling to the U.S. interior and 

Border Patrol was no longer actively pursuing them—”got aways”—from the Border Patrol 

Enforcement Tracking System. We obtained data on border crossings by motor vehicles—

”drive throughs” —from the same database. (The individuals involved in a “drive through” 

are counted among apprehensions, turn backs, or got aways if agents are able to 

ascertain the number of individuals in the vehicle.) Apprehension, turn back, and got away 

data for fiscal years 2013 through 2015 were queried (i.e., obtained from relevant 

databases) as of February 2016. We selected these data for fiscal years 2013 through 

2015 because beginning fiscal year 2013, Border Patrol standardized how it collects and 

records got aways and turn backs, which improved the reliability of these data.

18For the purposes of this document, the term “zone coverage” refers to the extent to 

which the border miles of a border zone are fenced. In our analysis, we classified border 

zone coverage as follows: complete (100 percent) border fence coverage, partial border 

fence coverage, or no border fence coverage.
Page 7 GAO-17-331 Tactical Infrastructure

assess the reliability of the sector fence data we collected, we reviewed 

the data for any inconsistencies in fence mileage in each sector, by type 

and design. As a result of our data reliability assessment, we determined 

that both CBP’s estimated known illegal entry data and sector fence data 

were sufficiently reliable for our intended use. For more information on 

our scope and methodology for the sector data tables, see Appendix I. 

Appendix II provides further details on our scope and methodology.

We conducted this performance audit from October 2015 to February 

2017 in accordance with generally accepted government auditing 

standards. Those standards require that we plan and perform the audit to 

obtain sufficient, appropriate evidence to provide a reasonable basis for 

our findings and conclusions based on our audit objectives. We believe 

that the evidence obtained provides a reasonable basis for our findings 

and conclusions based on our audit objectives.

The Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA) 

of 1996, as amended, states that the Secretary of Homeland Security 

shall take actions, as necessary, to install physical barriers and roads in 

the vicinity of the border to deter illegal crossings in areas of high illegal 

entry.19 As originally enacted, IIRIRA also required the completion of a 

triple-layer fence and road improvements along 14 miles of border near 

San Diego, where Border Patrol had begun installing fence in the 

1990s.20 The Secure Fence Act of 2006 amended IIRIRA to require DHS 

to construct at least two layers of reinforced fencing as well as physical 

barriers, roads, lighting, cameras, and sensors on certain segments of the 

southwest border in California, Arizona, New Mexico, and Texas.21

Subsequently, the DHS Appropriations Act, 2008, rewrote the border 

 

19Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA) of 1996. Pub. L. 

No. 104-208, div. C, tit. I, subtit. A, § 102(a), 110 Stat. 3009, 3009-554 (classified, as 

amended at 8 U.S.C. § 1103 note).

20IIRIRA § 102(b), 110 Stat. at 3009-554 to -555.

21See Pub. L. No. 109-367, § 3, 120 Stat. 2638, 2638-2639. Under the Secure Fence Act 

of 2006, the Secretary of Homeland Security is to achieve and maintain operational 

control over the borders of the United States through surveillance activities and physical 

infrastructure enhancements to prevent unlawful entry by aliens and facilitate CBP’s 

access to the borders. See id. § 2, 120 Stat. at 2638 (classified at 8 U.S.C. § 1701 note).

Background

TI along the Southwest 

Border
Page 8 GAO-17-331 Tactical Infrastructure

fencing requirements section of IIRIRA to require that DHS construct not 

less than 700 miles of reinforced fencing along the southwest border 

where fencing would be most practical and effective, and to provide for 

the installation of additional physical barriers, roads, lighting, cameras, 

and sensors to gain operational control of the southwest border.22 GAO 

has ongoing work on roads used by Border Patrol and plans to complete 

this work in 2017.

From fiscal years 2005 through 2015, CBP increased the total miles of 

primary border fencing on the southwest border from 119 miles to 654

miles—including 354 miles of primary pedestrian fencing and 300 miles of 

primary vehicle fencing. With 654 miles of primary fencing currently 

deployed, CBP officials have stated that CBP is in compliance with its 

legal requirements for the construction of southwest border fencing based 

on the substantial discretion provided to the Secretary of Homeland 

Security to determine the appropriate placement of fencing.23 Figure 1 

shows the increase in the total miles of primary fencing on the southwest 

border from fiscal years 2005 to 2015.

 

22IIRIRA § 102(b), 110 Stat. at 3009-554 to -555, as amended by Pub. L. No. 110-161, 

div. E, tit. V, § 564(a)(2)(B)(ii), 121 Stat. 1844, 2090-91 (2007) (classified at 8 U.S.C. § 

1103 note). IIRIRA § 102(b), as amended, also gives the Secretary of Homeland Security 

discretion to install TI in particular locations along the border, as deemed appropriate. Id.

23See 8 U.S.C. § 1103 note (notwithstanding fencing requirements, DHS is not required to 

install fencing or other resources in a particular location along the border, if the Secretary 

of Homeland Security determines that the use or placement of such resources is not the 

most appropriate means to achieve and maintain operational control over the border at 

that location). See also United States v. Arizona, No. 2:10-cv-10-01413-SRB, Order 

Granting Government’s Motion to Dismiss Counterclaims (D. Ariz. Oct. 21, 2011).
Page 9 GAO-17-331 Tactical Infrastructure

Figure 1: Total Miles of Primary Fencing on the Southwest Border, Fiscal Years 

2005 to 2015

CBP used various fencing designs to construct the 654 miles of primary 

pedestrian and vehicle border fencing including, for example, bollard, wire 

mesh, and chain link style fencing designs. Border fencing designs have 

developed over time from legacy designs used prior to CBP implementing 

requirements of the Secure Fence Act of 2006, to subsequent modern 

designs. In addition to the 654 miles of primary fencing, CBP has also 

deployed additional layers of pedestrian fencing behind the primary 

border fencing, including 37 miles of secondary fencing and 14 miles of 

tertiary fencing.24 CBP has also deployed other types of TI along the 

southwest border with various purposes. For example, lighting along the 

border is designed to further deter illegal activities. Roads and bridges 

provide Border Patrol agents access to the border to interdict and 

 

24The first layer of fencing, the primary fence, may include both pedestrian and vehicle 

fencing and is the first fence encountered when moving north from the border; the 

secondary fence, located behind the primary fence, consists solely of pedestrian fencing; 

and the third layer, or tertiary fence, is primarily used to delineate property lines rather 

than deter illegal entries.
Page 10 GAO-17-331 Tactical Infrastructure

apprehend illegal entrants as well as supporting the maintenance and 

construction of TI. Drainage systems and grates facilitate the 

maintenance of roads and fences and can provide additional border 

security. See figures 2 and 3 for examples of selected fencing types and 

designs as well as other types of TI deployed at the border.
Page 11 GAO-17-331 Tactical Infrastructure

Figure 2: Selected Designs of Pedestrian Fencing on the Southwest Border

Note: For the purposes of this report, w e refer to any fencing constructed prior to Customs and 

Border Protection implementing requirements of the Secure Fence Act of 2006 as “legacy” fencing 

designs and any fencing deployed subsequently as having “modern” fencing designs. In addition, all 

“landing mat” fencing—constructed of army surplus carbon steel landing mats w hich were used to
Page 12 GAO-17-331 Tactical Infrastructure

create landing strips during the Vietnam War—is considered “legacy” fencing, regardless of when it 

w as constructed.

Figure 3: Selected Designs of Vehicle Fencing and Other Tactical Infrastructure on the Southwest Border
Page 13 GAO-17-331 Tactical Infrastructure

Note: For the purposes of this report, w e refer to any fencing constructed prior to Customs and 

Border Protection implementing requirements of the Secure Fence Act of 2006 as “legacy” fencing 

designs and any fencing deployed subsequently as having “modern” fencing designs.

Border Patrol, within CBP, is the federal agency with primary 

responsibility for securing the national borders by detecting, interdicting, 

and disrupting illegal cross-border activities between the designated U.S. 

land border ports of entry.25 To secure the nearly 2,000 mile southwest 

border, Border Patrol divides responsibility for border security operations 

geographically among nine sectors, as shown in figure 4. Each sector has 

its own headquarters and is further divided into varying numbers of 

stations, with agents assigned to patrol defined geographic areas, or 

zones, within each station. According to Border Patrol officials, zones 

allow sectors to more effectively analyze border conditions, including 

terrain, when planning how to deploy agents. Zone dimensions are largely 

determined by geography and topographical features, and zone size can 

vary significantly.

 

25See 6 U.S.C. § 211(e) (establishing and listing duties of U.S. Border Patrol within CBP).

Border Patrol Operations 

along the Southwest 

Border
Page 14 GAO-17-331 Tactical Infrastructure

Figure 4: Border Patrol Sectors along the Southwest Border and Border Stations and Zones in the Tucson Sector

Within each sector, station, and zone, Border Patrol agents’ primary 

mission is to prevent terrorists and terrorist weapons from entering the 

United States, and to detect, interdict, and apprehend those who attempt 

to enter illegally or smuggle any person or contraband across the nation’s 

borders. To accomplish this mission, Border Patrol agents must be 

proficient in a sequential set of “Mission Essential Tasks” (METs) in order 

to execute their duties in the furtherance of border security operations 

(see table 1).
Page 15 GAO-17-331 Tactical Infrastructure

Table 1: Border Patrol Mission Essential Tasks

Predict To anticipate and target illegal traffic actions prior to illegal entry

Detect To discover the presence of a possible item of interest or suspected contraband

Identify To determine whether an item of interest is human, animal, conveyance, or unknown

Classify To determine the level of threat, risk, and/or intent of item of interest

Track To follow the progress or movements of an item of interest

Respond To dispatch or employ law enforcement resources to address a potential incursion

Resolve To take final action, whether legal, administrative, or otherwise; capture data, and process information 

Source: U.S. Border Patrol. | GAO-17-331

To assist agents in executing their METs, Border Patrol deploys various 

resources, including surveillance technology and TI, to sectors, stations, 

and zones. Each of these resources provides agents with the essential 

operational capabilities necessary to execute each MET. Border Patrol 

defines these capabilities as “Foundational Operational Capabilities” 

(FOC) (see table 2).

Table 2: Border Patrol Foundational Operational Capabilities (FOC)

Impedance and Denial Capability to impede border incursions and deny the threat’s use of terrain to their advantage in 

conducting illegal activities or acts of terrorism. 

Operational Mobility Capability to gain and maintain access to Border Patrol areas of responsibility and rapidly move 

Border Patrol resources at any time.

Domain Awareness/ Persistent 

Surveillance

Ability to continuously detect, identify, classify, and track all border incursions in targeted areas 

at all times.

Logistics and Manpower/ Support 

and Sustainment

Ability to maintain, mature, refine, and integrate various capabilities to meet Border Patrol 

mission and statutory requirements.

Command, Control, 

Communications, and Coordination

Capability to effectively use and coordinate Border Patrol resources during operations.

Intelligence and CounterintelligenceCapability to produce and disseminate timely, well-formulated, and actionable intelligence 

concerning border security threats and prevent threat organizations from gathering intelligence 

against Border Patrol.

Security Partnerships Capabilityto harness the political, social, economic, information, infrastructure, and technology 

assets of the border area to enhance national security. 

Source: U.S. Border Patrol. | GAO-17-331

Note: FOCs are current as of May 2016. At the time of our review , Border Patrol officials told us they 

w ere in the process of updating the FOCs.

According to Border Patrol officials, TI facilitates the capabilities for 

“impedance and denial” and “operational mobility.” Border fencing, 

including pedestrian and vehicle fencing, is intended to facilitate the 

“impedance and denial” FOC by diverting and delaying illegal entries. 
Page 16 GAO-17-331 Tactical Infrastructure

Patrol roads and bridges are intended to facilitate the “operational 

mobility” FOC by enabling agents to efficiently traverse their areas of 

responsibility. Other resources that Border Patrol deploys, including 

surveillance technology, facilitate domain awareness, and do so by 

providing persistent surveillance capabilities along the border. According 

to Border Patrol officials, agents require the appropriate combination of 

resources in each sector, station, and zone to facilitate each FOC and 

ensure agents can successfully execute their METs. Due to variations in 

terrain and local population density, among other factors, the appropriate 

combination of these resources may vary across sectors, stations, and 

zones.

To assess cross-border threats, Border Patrol collects and analyzes data 

on the number and types of entrants who illegally cross the southwest 

border between the land border ports of entry. These data include 

estimates of the total number of directly or indirectly observed—or 

“known”—illegal entries by sector, station, and zone. Estimated known 

illegal entries consist of the total number of illegal entrants who were 

apprehended, in addition to the number of entrants who illegally crossed 

the border but were not apprehended—”turn backs” and “got aways.”26

Border Patrol also collects data on the number of vehicles that illegally 

cross the border, known as “drive throughs”. 

From fiscal year 2007 to 2015, CBP spent approximately $2.4 billion on TI 

on the southwestern border—about 95 percent, or $2.3 billion was spent 

on constructing pedestrian and vehicle fencing.27 In addition, CBP officials 

reported that TI operations and maintenance requirements totaled 

approximately $450 million during this same period. We reported in 2009 

that the average cost per mile for primary pedestrian fencing was $6.5 

million and $1.8 million per mile for vehicular fencing; according to CBP’s 

 

26Border Patrol began mandating the collection of longitude and latitude coordinates for all 

apprehensions in May 2009, and in September 2012, Border Patrol standardized the 

collection of turn back and got away data.

27CBP officials stated CBP did not track funding for acquisition and sustainment for border 

fencing prior to implementation of the Secure Fence Act of 2006.

Costs of Acquiring, 

Constructing, and 

Sustaining TI
Page 17 GAO-17-331 Tactical Infrastructure

2016 rough order of magnitude estimate, these averages remain the 

same.28

CBP estimates that the cost for secondary fencing is approximately $4.2 

million per mile but CBP officials identified several limitations of this 

estimate. First, due to their limited experience in constructing secondary 

fencing, CBP officials noted that they have not constructed sufficient 

secondary fencing to use historic costs to estimate an average cost per 

mile of the fencing. Currently, around 37 miles, or six percent of the total 

654 miles of primary fencing, are backed up by secondary pedestrian 

fencing. In addition, CBP officials stated that constructing secondary 

fencing in a location with existing primary fencing may result in additional 

costs not accounted for in their estimates, such as land acquisition, 

removing existing structures, and utility relocations.

According to Border Patrol officials, in 2014, Border Patrol began 

implementing the Requirements Management Process. This new process 

is designed to facilitate planning in order to fund and deploy TI and other 

operational requirements, such as surveillance technology for border 

security operations. The Requirements Management Process consists of 

six steps as shown in figure 5.

Figure 5: U.S. Border Patrol’s Requirements Management Process

• The initial step requires Border Patrol to identify mission priorities and 

goals by analyzing relevant strategic DHS, CBP, and Border Patrol 

goals, missions, and objectives from applicable guidance and policies.

In this initial step, the state of the threat is also assessed.

 

28GAO-09-896. Cost per mile estimates for primary and secondary fence construction 

includes labor, construction and supply chain, planning/oversight, environmental planning, 

design, and real estate planning, but does not include the cost of real estate acquisition 

including litigation costs, environmental mitigation costs, unforeseen site conditions, 

relocation of utilities, removal or retirement of existing structures, and market fluctuations 

(e.g. increased fuel costs, labor,raw materials) as well as any other costs not explicitly 

stated as included in the estimate. 

Border Patrol’s 

Requirements 

Management Process
Page 18 GAO-17-331 Tactical Infrastructure

• The second step is Mission Analysis. This step is designed to assess 

the delta between Border Patrol’s capabilities against currently known 

and anticipated threats in order to determine capability gaps in Border 

Patrol mission essential tasks. Border Patrol Agents are encouraged 

to participate in this step by recommending potential solutions—such 

as tactical infrastructure or technology—to mitigate capability gaps.

• The third step—Planning—involves, among other things, determining 

potential requirements that may address the identified capability gaps 

for funding consideration. To conduct this step, Border Patrol officials 

examine the identified capability gaps in detail and determine courses 

of action and initial capability requirements. These initial capability 

requirements are documented in a sector-specific Initial Requirements 

Document.

• The fourth step—Execution—involves Border Patrol executing 

courses of action. Border Patrol officials stated that courses of action 

are recommended options for Border Patrol commanders and 

executives to select and implement. Once implemented, these options 

are expected to resolve identified capability gaps in operations, 

according to Border Patrol officials.

• The fifth and sixth steps of the process—Assessment and Lifecycle 

Management—involve implementing and monitoring solutions to 

determine the ability of the requirement to resolve capability gaps and 

sectors providing feedback on how the solutions affect border security 

operations.

The initial activity to complete step two of the Requirements Management 

Process is the Capabilities Gap Analysis Process (CGAP). The CGAP is 

intended to identify each station’s capability gaps by determining the 

difference between a station’s baseline capabilities and a station’s 

required set of capabilities needed to perform mission essential tasks. 

The identified shortfall in required capability is a capability gap.

After identifying capability gaps, Border Patrol agents assigned to each 

sector are to identify potential solutions to solve or mitigate each gap. For 

example, in 2015, as part of the CGAP, agents identified additional 

maintenance and repair as a solution where patrol roads were in poor 

condition and negatively affected agents’ ability to respond and resolve 

illicit activity. Other solutions to capability gaps may include adjustments 

to the technologies or personnel deployed in a specific area. For fiscal 

year 2015, Border Patrol conducted the CGAP and identified potential 

solutions in all nine southwest sectors, according to Border Patrol 

officials. Identified solutions and their corresponding capability gaps are to 
Page 19 GAO-17-331 Tactical Infrastructure

be documented in Station Capability Gaps Analysis Reports. Figure 6 

outlines the steps of the CGAP, and describes an example using the 

steps of the CGAP to identify a capability gap and solution.

Figure 6: U.S. Border Patrol’s Capability Gap Analysis Process

Border Patrol officials stated that sectors may request additional TI and 

other requirements for border security operations to address capability 

gaps not included in the documented CGAP. Officials stated that 

additional capability gaps may be identified by sectors or stations during 

the course of border security operations that were not captured at the 

time a station conducted the process. Border Patrol officials stated that 

when stations identify these capability gaps and a need exists for a 

requirement to address the capability gap, the station is required to 

submit documentation to Border Patrol Headquarters in order for the 

requirement to be approved, funded, and subsequently deployed.

According to Border Patrol officials, this documentation should include (1) 

the identified capability gap and (2) the new or additional TI or other 

requirement and how it addresses the identified capability gap.
Page 20 GAO-17-331 Tactical Infrastructure

According to CBP officials, pedestrian and vehicle fencing have benefited 

border security operations in various ways as intended, by (1) supporting 

Border Patrol agents’ ability to execute essential tasks; (2) improving 

agent safety; and (3) reducing vehicle incursions.

Supporting Agents’ Ability to Execute Mission Essential Tasks.

According to Border Patrol officials, pedestrian fencing is intended to 

divert illegal entrants–which include migrants and criminal organizations 

that engage in illicit cross-border activities–to areas of the border where 

agents can execute their METs and interdict illicit-cross border activities 

more effectively.29 Border Patrol officials told us that populated urban 

environments offer an advantageous setting for illegal entrants because 

they require only seconds to minutes to blend in with the local U.S. 

community after crossing the border. By constructing pedestrian fencing 

in more populated urban environments, Border Patrol officials stated that 

DHS intended to divert illicit cross-border activities into more remote or 

rural environments, where illegal entrants may require hours or days to 

reach the nearest U.S. community. For example, Border Patrol officials in 

the San Diego sector told us that from 1994 to present, pedestrian 

fencing, along with investments in manpower and surveillance 

technology, assisted in diverting a large share of illicit cross-border 

activity away from the densely populated urban areas near San Diego 

and into more rural and remote environments east of the city. Officials 

told us that these rural and remote environments east of San Diego 

provide an advantage to agents assigned there since they have more 

29For the purposes of this report, illicit cross-border activity refers to any activity in which 

people or goods, such as narcotics, money, or weapons, illegally enter the United States.

Fencing Is Intended 

to Assist Agents in 

Performing Their 

Duties, but Its 

Contributions to 

Border Security 

Operations Have Not 

Been Assessed

CBP Has Identified the 

Intended Benefits of 

Pedestrian and Vehicle 

Fencing to Border Security 

Operations
Page 21 GAO-17-331 Tactical Infrastructure

time to detect, identify, classify, track, respond and resolve the illicit 

cross-border activities that occur there. Similarly, Border Patrol officials in 

the Tucson sector told us that bollard pedestrian fencing in urban areas 

has helped divert much of the illicit cross-border activities that occurred 

there into more rural and remote environments where agents are better 

able to interdict these activities.

Agents assigned to the Nogales station—within the Tucson sector—told 

us that bollard pedestrian fencing has helped divert illicit cross-border 

activities away from the City of Nogales and into more rural and remote 

areas.

In addition to diverting illicit cross-border activities into more rural and 

remote environments, pedestrian fencing is intended to serve as a 

physical barrier that impedes and slows the progress of illegal entrants 

who attempt to cross the border, and in doing so, provides Border Patrol 

agents assigned to these areas additional time and opportunities to 

execute their METs, which include detecting, responding, and resolving 

illicit cross-border activities. Border Patrol agents in the El Paso sector 

told us that pedestrian fencing deployed in the sector’s urban border 

environments has assisted in improving agents’ ability to execute their 

METs, resulting in higher apprehension rates in these areas. These 

agents told us that urban border environments, such as the border 

between downtown El Paso from Ciudad Juarez, offer an ideal crossing 

point for illegal entrants because they can quickly blend in with the local 

U.S population, reach a safe house, or obtain transportation after 

crossing the border. However, these agents told us that the primary, 

secondary, and tertiary pedestrian fencing that separate downtown El 

Paso and Ciudad Juarez have been effective in slowing the progress of 

illegal entrants who attempt to cross in this area and providing agents 

with additional time to detect, respond, and resolve the illicit cross-border 

activities that occur there.

Improving Agent Safety. Border Patrol officials we spoke with in the El 

Paso, Tucson, and San Diego sectors stated that modern pedestrian 

fencing, including bollard style fencing, improves agent safety during 

operations. Specifically, San Diego sector officials told us that modern 

style pedestrian fencing reduces illegal entrants’ ability to stage mass 

crossings, which can overwhelm agents and jeopardize agents’ safety. 

According to Border Patrol officials in the Tucson sector, bollard fencing 

has helped reduce agent assaults because this fencing provides agents 

with a clear line of sight into Mexico and makes it more difficult for illegal 

entrants to ambush agents. These officials told us that older fence 
Page 22 GAO-17-331 Tactical Infrastructure

designs, including landing mat fencing, obstruct agents’ line of sight into 

Mexico and provided illegal entrants and other individuals in Mexico with 

cover and the ability to conceal their location along the border. They 

explained that individuals on the Mexican side of the border would 

regularly use the landing mat fence to launch surprise assaults on agents 

by hurling projectiles, including rocks, from behind it. Border Patrol 

officials reported that after replacing legacy landing mat fencing with 

bollard pedestrian fencing in the Nogales station, ambushes and assaults 

declined. Specifically, Border Patrol officials told us they recorded 376 

assaults on agents in the Nogales station in 2010 and 2011, two years 

prior to constructing modern bollard pedestrian fencing. In 2012 and 

2013, two years following construction, assaults on agents in the Nogales 

station dropped to 71, a decline of 81 percent.

Reducing Illicit Vehicular Border Incursions. Vehicle fencing is 

intended to serve as a physical barrier that slows and prevents vehicles 

engaged in drug trafficking and human smuggling operations from 

crossing the border, also known as drive throughs. Vehicle fencing is 

typically deployed in more rural and remote environments where criminal 

organizations engaged in trafficking and smuggling are more likely to use 

vehicles to shorten the time they are at risk of being encountered by 

Border Patrol agents. Border Patrol officials in the El Paso and Tucson 

sectors told us that they experienced significant decreases in drive 

throughs following the deployment of vehicle fencing. Officials in the 

Tucson sector reported that vehicle fencing deployed improved Border 

Patrol agents’ ability to impede and deny the entry of large amounts of 

illegal narcotics transported by motorized vehicles. Officials reported that 

rural land tracts within the sector provided criminal organizations with 

large areas to traffic narcotics and engage in other illicit cross-border 

activities. Border Patrol officials reported that after deploying vehicle 

fencing in these areas, drive throughs dropped by an average of 73 

percent. Although Tucson sector officials stated vehicle fencing has been 

effective in slowing and prohibiting drive throughs, vehicle fencing is not 

designed to slow or deter illegal entrants from entering or smuggling 

contraband into the United States on foot.

In addition to citing the benefits of pedestrian and vehicle fencing, Border 

Patrol officials and agents also identified the various methods used by 

illegal entrants to exploit border fencing’s limitations in their attempts to 

defeat it. Agents we spoke with in the El Paso and Tucson sectors 

explained that one of the most common methods employed by illegal 

entrants involves cutting openings, or breaches, in pedestrian and vehicle 

Border Patrol Agents 

Identified Various 

Limitations with Border 

Fencing
Page 23 GAO-17-331 Tactical Infrastructure

fencing. Once breached, illegal entrants can cross through the fence or 

smuggle people and contraband into the United States. Between fiscal 

years 2010 and 2015, CBP recorded a total of 9,287 breaches in 

pedestrian fencing. According to our analysis of these data, illegal 

entrants breached legacy pedestrian fencing at an average rate of 82 

breaches per fence mile, compared to an average of 14 breaches per 

fence mile of modern pedestrian fencing.30

Agents we spoke with in the El Paso sector explained that creating 

breaches in legacy pedestrian fencing requires less effort compared to 

modern designs, and can be done using bolt or pipe cutters. In addition, 

these agents also described observing illegal entrants cutting and 

dragging sections of vehicle fencing off the border and illegally entering 

the United States in vehicles. Agents we spoke with in the Tucson sector 

also told us that while pedestrian fencing is generally easier to breach, 

they have also observed breaches in more modern fence designs, 

including bollard fence, which agents stated were cut using portable 

power tools.

Agents we spoke with in these sectors also described witnessing illegal 

entrants defeating border fencing through other methods. For example, 

agents we spoke with in the Tucson sector told us they have witnessed 

illegal entrants attempting to use ramps to drive vehicles up and over 

vehicle fencing in the sector as well as burrowing under legacy pedestrian 

fencing, as shown in figure 7. In addition, agents in the Tucson sector 

stated that illegal entrants scale the taller pedestrian fencing designs, 

such as bollard fencing. In contrast, agents we spoke with in the San 

Diego sector stated that some segments of legacy fencing are low and 

that they have witnessed illegal entrants jumping over the fence. Other 

methods used to defeat border fencing described to us by Border Patrol 

agents include using small aircraft to transport contraband over 

pedestrian fencing and into the United States and building subterranean 

tunnels from Mexico into the United States.31

 

30DHS deemed that specific details about the number of breaches for pedestrian fencing 

to be sensitive; therefore, we did not include this information in this report.

31We have ongoing work on selected smuggling threats along the southwest border, 

which include subterranean, aerial, and maritime methods used to smuggle contraband 

into the United States. We plan to report on the results of our work in 2017. 
Page 24 GAO-17-331 Tactical Infrastructure

Figure 7: Select Methods used by Illegal Entrants to Defeat Border Fencing on the Southwest Border
Page 25 GAO-17-331 Tactical Infrastructure

CBP takes steps to identify intentional destruction or exploitation of 

border fencing, including breaches, burrows, and tunnels, and addresses 

them when they occur. For example, Border Patrol officials we met with in 

the El Paso sector told us that agents regularly identify breaches in 

border fencing during patrols. Once identified, agents notify the 

appropriate Border Patrol officials at the station and sector level, who in 

turn schedule the necessary repair work through one of CBP’s 

maintenance and repair contracts, which we discuss later in this report.

CBP collects data that could be useful to assessing the contributions of 

border fencing to border security operations at the sector level, but has 

not conducted such an assessment. According to CBP, from fiscal year 

2007 through 2015, it spent approximately $2.3 billion to deploy border 

fencing along the southwest border, and CBP will need to spend a 

substantial amount to sustain these investments over their lifetimes. CBP 

did not provide a current life-cycle costs estimate to maintain pedestrian 

and vehicle fencing, however, in 2009 CBP estimated that maintaining 

fencing would cost more than $1 billion over 20 years.32 Despite these 

investments, CBP cannot measure the contribution of fencing to border 

security operations along the southwest border because it has not 

developed metrics for this assessment. According to CBP officials, CBP 

suspended its efforts to measure the contributions of border fencing to 

border security in 2013 due to sequestration related funding shortfalls. 

CBP officials also stated that border fencing is a part of a system of 

capabilities, including Border Patrol agents, surveillance technology, and 

other TI, and as a result, developing metrics for a single element of this 

system is challenging.

Although CBP does not have metrics to assess the contributions of 

border fencing, it does collect data on the location of illegal entries that 

can provide insight into where these illegal activities occurred in relation 

to the various designs of pedestrian and vehicle fencing at the zone level. 

For example, CBP collects data on apprehensions, turn backs, got 

aways, and drive throughs, and border fencing, by type and design. CBP 

could potentially use these data to develop metrics that compare 

estimated known illegal entries before and after fence construction. CBP 

could also use these data to help determine the extent to which border 

 

32CBP’s 2009 Life Cycle Cost Estimate (LCCE) estimated operations and maintenance 

costs for fencing would be approximately $1.4 billion from 2009 to 2029.

CBP Has Not Assessed 

Pedestrian or Vehicle 

Fencing’s Contributions to 

Border Security 

Operations Along the 

Southwest Border
Page 26 GAO-17-331 Tactical Infrastructure

fencing contributes to diverting illegal entrants into more rural and remote 

environments as well as border fencing’s impact on apprehension rates 

over time However, CBP has not developed metrics that systematically 

use these data, or other available information, to assess the contributions 

of border fencing to border security operations along the southwest 

border. We used these data to conduct a descriptive analysis on (1) the 

total estimated known illegal entries, (2) estimated drive throughs, (3) 

estimated turn backs and got aways, and (4) apprehension rates of 

estimated illegal entries in southwest border zones with border fencing, 

by fence type, design, and zone coverage, and in southwest border zones 

without border fencing. See Appendix I for more detailed information on 

our analysis.

These data, in combination with information on other factors that affect 

the location of illegal entries and agents’ ability to predict, detect, identify, 

classify, and resolve illicit cross-border activities, could help CBP gain 

insight into the contributions of pedestrian and vehicle fencing to border 

security operations. For example, the locations of apprehensions, turn 

backs, got aways, and drive throughs with the various types and designs 

of fencing at the sector and zone level in conjunction with information on 

geography, demographics, staffing, technology, and other TI, could help 

CBP assess the contributions of border fencing to border security 

operations as well as current and future fencing deployments and 

replacement projects in light of other resource allocation priorities.

Past GAO reports on leading practices for performance management 

have noted that agencies can use performance information to make 

decisions that affect future strategies, planning and budgeting, identifying 

priorities, and allocating resources.33 These leading practices also note 

that outcome-based performance information should be used for the 

allocation of resources and in deciding among competing priorities in a 

results oriented management system. We have also found that linking 

cost with performance information infuses performance concerns into 

planning and budgetary deliberations, prompting agencies to reassess 

their performance goals and strategies to more clearly understand the 

cost of performance. Performance information also allows program 

managers to compare results with goals and thus determine where to 

target resources to improve performance.

 

33GAO, Managing for Results: Enhancing Agency Use of Performance Information for 

Management Decision Making, GAO-05-927 (Washington, D.C.: September 2009). 
Page 27 GAO-17-331 Tactical Infrastructure

Developing metrics that can help CBP measure the contributions of 

fencing to border security operations along the southwest border, could 

better position CBP to make these and other resource allocation 

decisions without the best available information to inform competing 

mission priorities and investments, such as additional manpower and 

surveillance technologies. An assessment of border fencing’s 

contributions to border security operations could help position CBP to 

identify the cost effectiveness of border fencing compared to other assets 

the agency deploys, including Border Patrol agents and various 

surveillance technologies. This information would also help position CBP 

to justify continued investments in border fencing and, if needed, help 

CBP identify future investment priorities, and more effectively target 

public resources.

CBP contracts with private contractors who provide sustainment 

services— maintenance, repair, and new construction—for TI in the nine 

southwest border sectors, which are subdivided into four maintenance 

and repair work areas. In providing these sustainment services, 

contractors are tasked with identifying and performing routine TI 

maintenance and repair requirements, which are classified in five general 

categories – (1) fences and gates, (2) roads and bridges, (3) drainage 

and grates, (4) lighting and electrical, and (5) vegetation control and 

debris removal. Contractors record these requirements in work plans and 

submit them to Border Patrol for approval. Once Border Patrol approves 

the work plan, the contractors complete the approved TI maintenance and 

repair requirements, such as blading a degraded road or clearing and 

removing vegetation.

CBP and contractors are to classify maintenance and repair requirements 

in each category as urgent or routine. Routine maintenance and repair 

CBP Manages TI 

Sustainment but 

Border Patrol Has Not 

Provided Guidance 

on its Process for 

Identifying and 

Deploying TI

CBP Manages the 

Sustainment of TI and Has 

Taken Steps to Mitigate 

Challenges
Page 28 GAO-17-331 Tactical Infrastructure

includes work that is required due to normal wear and tear, deterioration 

due to age, and other damage to TI assets not caused by severe weather 

events or intentional sabotage. For example, TI contractors may 

reposition and upgrade lighting used to illuminate operational areas along 

the southwest border. In addition, contractors are to perform routine 

maintenance on patrol roads that erode and degrade over time due to 

weather and wear and tear caused by the Border Patrol agents who use 

them. However, Border Patrol agents from sectors we visited identified 

several challenges in sustaining TI, including:

Addressing Maintenance and Repair of Roads on Other Public or 

Private Lands. Border Patrol has authority to use public roads owned or 

operated by federal, state or local, and tribal entities, as well as certain 

privately owned roads, for border security operations.34 However, sector 

officials stated that they face challenges in addressing maintenance and 

repair of these roads. Specifically, sector officials in two sectors we visited 

told us that it may take time to secure an agreement providing for 

maintenance of some roads needed to conduct border security 

operations. In addition, sector officials stated that in instances where 

portions of a single road have different owners, CBP must enter into 

separate agreements with each owner. Officials in one sector stated that 

these challenges may hinder CBP’s ability to address maintenance of 

roads in a timely manner for use in border security operations.

Funding for TI Sustainment Requirements. CBP has funding allocated 

for addressing TI sustainment requirements; however, CBP must 

prioritize its requirements to make best use of available funding, and it 

can take time to address all requirements. For example, officials in one 

sector we visited stated that an increase in its inventory of surveillance 

technology has been accompanied by the construction of new roads, 

which adds to the sector’s TI inventory. In order to address this increase 

in TI inventory, CBP and sector officials stated that they prioritize 

maintenance and repair of roads and other requirements in each work 

plan based on funding availability and how these requirements affect 

border security operations. CBP officials told us that the contractor and 

 

34See 23 U.S.C. § 101(a)(22), which defines a “public road” as any road or street under 

the jurisdiction of and maintained by a public authority and open to public travel. In 

addition, Border Patrol is statutorily authorized to, without a warrant, access private lands 

(but not dwellings) within 25 miles of the border, for the purpose of patrolling the border to 

prevent illegal entry of aliens (see 8 U.S.C. § 1357(a)(3)); and CBP may seek to establish 

agreements with private landowners to use, and in certain instances address maintenance 

and repair of, their property in furtherance of border security operations.
Page 29 GAO-17-331 Tactical Infrastructure

CBP develop and communicate the work plan to sector officials. Sector 

officials then review the work plan and prioritize maintenance and repair 

that are critical to border security operations and communicate these 

updates to CBP officials for execution. Sector officials in one sector stated 

that in general, roads that are critical to border security operations are 

prioritized over roads that are less used by agents. Sector officials in this 

sector also stated that continually prioritizing the maintenance and repair 

of certain roads over others can result in degraded roads in the sector. 

Officials in this sector also stated that the use of degraded roads in border 

security operations increases the wear and tear on patrol vehicles and 

increases the cost of maintaining these vehicles.

While CBP and Border Patrol officials stated they prioritize routine 

maintenance requirements that are most critical to border security 

operations, contractors are also required to address urgent repair 

requirements. Urgent repair requirements are typically the result of severe 

weather events or intentional damage to TI assets. CBP requires 

contractors to address these requirements within a 24-hour period to 

mitigate any negative effects on border security operations. For example, 

CBP classifies breaches to fencing, grates, or gates as urgent and 

requires immediate repair because, according to Border Patrol officials, 

breaches increase illegal entrants’ ability to enter the country unimpeded. 

According to Border Patrol officials, the majority of urgent TI repairs on 

the southwest border are fence breaches. From fiscal year 2010 through 

fiscal year 2015 CBP recorded a total of 9,287 breaches in pedestrian 

fencing at an average cost of $784 per breach to repair. Figure 8 shows 

an example of a fence breach and subsequent repair.
Page 30 GAO-17-331 Tactical Infrastructure

Figure 8: Fence Breach Due To Drive-Through Entry and Subsequent Repair

While contractors provide routine maintenance and address urgent 

repairs on TI, certain TI assets used by Border Patrol become degraded 

beyond repair and must be replaced. For example, in the Yuma sector, 

Border Patrol officials identified portions of primary legacy pedestrian 

fencing that had become so degraded by illegal entrants digging 

underneath the fencing and land erosion in the area that it required 

additional support to remain erect. In addition, Border Patrol officials in 

the El Paso sector stated that while CBP provides routine maintenance 

and repair services to the primary legacy pedestrian fencing in Sunland 

Park, New Mexico, significant weather events have eroded the foundation 

of the fencing. In addition, the erosion in the area has caused damage to 

nearby roads used by agents to conduct border security operations. 

Sector officials identified, and we observed, primary legacy pedestrian 

fencing that leans toward Mexican territory and that required additional 

support to prevent the fencing from collapsing. Sector officials noted that 

that due to the erosion and terrain in the area, they have been limited in 

their repair efforts. See figure 9.
Page 31 GAO-17-331 Tactical Infrastructure

Figure 9: Legacy Pedestrian Fencing in Sunland Park, New Mexico, March 2016

In addition, sector officials identified, and we observed, other primary 

legacy pedestrian fencing in Sunland Park, New Mexico, where debris 

had accumulated on the Mexican side of the border, reducing the overall 

height of the fencing to approximately two feet in certain areas. Officials 

told us that the fencing is located three feet from the official U.S. border 

and that conducting maintenance on the fencing would require debris 

removal machinery that would encroach into Mexican territory. See 

figure 10.
Page 32 GAO-17-331 Tactical Infrastructure

Figure 10: Legacy Pedestrian Fencing in Sunland Park, New Mexico, March 2016

Sector officials stated that the condition of the fencing in Sunland Park, 

New Mexico, negatively affects border security operations due to its 

proximity to populated urban areas on both sides of the border, among 

other factors. Border Patrol officials in the El Paso sector stated that the 

degraded fencing is located approximately one quarter of a mile from an 

urban area on the U.S. side of the border where illegal entrants can 

quickly obtain transportation and blend in with the local U.S. population. 

While in general, agents stated they have seconds to minutes to interdict 

illegal entrants in urban areas, sector officials and agents stated that the 

condition of the fencing reduces the time agents have to interdict illicit 

cross-border activity because the degraded fencing does not slow down 

the progress of illegal entrants. As a result, sector officials stated the 

sector deploys additional manpower in the area in order to conduct 

effective border security operations.
Page 33 GAO-17-331 Tactical Infrastructure

In addition, sector officials stated that modern pedestrian fencing in 

downtown El Paso, Texas, had diverted illegal entrant activity to Sunland 

Park, New Mexico, where the primary legacy pedestrian fencing is 

compromised. El Paso sector officials stated that while the Sunland Park, 

New Mexico, area of operations has the greatest amount of illegal activity 

in the El Paso sector, the condition of the primary legacy pedestrian 

fencing does not achieve its intended purpose of slowing the progress of 

illegal entrants. In addition to the fencing in Sunland Park, Border Patrol 

has identified other degraded primary legacy fencing along the southwest 

border, such as the Yuma and Tucson sectors.

To address degraded legacy pedestrian fencing, CBP is replacing this 

fencing with more modern, bollard style fencing. For example, in fiscal 

year 2015, CBP began the process of replacing 1.4 miles of existing 

primary pedestrian fencing in Sunland Park, New Mexico—within the El 

Paso sector—with new bollard style pedestrian fencing. The fence 

replacement project also entails constructing a widened and elevated 

patrol road adjacent to the fence and the installation of culverts designed 

to mitigate the effects of severe weather events in the area. CBP 

estimates the fence replacement project will cost approximately $13.41 

million with a planned completion date in May 2017.35 In addition, in fiscal 

year 2016, CBP began removing and replacing an estimated 7.5 miles of 

legacy primary pedestrian fencing with modern bollard style fencing in 

Naco, Arizona, within the Tucson sector. CBP estimates this fence 

replacement project will cost $44.7 million, at an estimated cost of 

approximately $6 million per mile of replacement fencing.

In addition to the ongoing fence replacement projects, from fiscal years 

2011 through 2016, CBP completed four fence replacement projects that 

replaced 14.1 miles of primary pedestrian legacy fencing in the Tucson 

and Yuma sectors with modern bollard style pedestrian fencing, at a total 

cost of approximately $68.26 million and an average cost of $4.84 million 

per mile of replacement fencing. See table 4.

 

35CBP noted that the estimated completion date is tentative, due to a contract protest. 
Page 34 GAO-17-331 Tactical Infrastructure

Table 3: Average Cost per Mile of Completed Southwest Border Fence Replacement Projects, Fiscal Years 2011-2016 

Name of Fence 

Replacement Project Sectora Miles Replaced Total Cost (millions)

Average Cost

Per Mile (millions)

Nogales Tucson 2.8 $19.19 $6.85

Douglas I Tucson 6.1 $25.41 $4.16

Douglas II Tucson 3.4 $15.86 $4.61

San Luis Yuma 1.8 $7.80 $4.33

Total 14.1 $68.26 $4.84

Source: U.S. Customs and Border Protection. | GAO-17-331

a

Border Patrol divides responsibility for border security operations geographically among nine sectors, 

each w ith its ow n headquarters.

Prior to 2014, Border Patrol headquarters and sector officials stated that 

Border Patrol’s process for identifying, funding, and deploying TI 

requirements entailed Border Patrol stations and sectors identifying TI 

requirements and providing written justification to Border Patrol 

headquarters for review. Border Patrol Headquarters officials reviewed 

the justification. If approved, the TI requirement was funded and deployed 

by CBP. For example, El Paso sector officials stated that sector officials 

provided Border Patrol headquarters written justification documenting the 

need for a fence replacement project in the Sunland Park, New Mexico, 

for seven years. Border Patrol approved the identified need and in fiscal 

year 2015 CBP began implementing the Sunland Park fence replacement 

project.

In 2014, Border Patrol began implementing the Requirements 

Management Process that, among other things, is intended to identify 

capability gaps in border security operations and identify solutions to 

those capability gaps, including TI. In addition, the process also identifies 

maintenance and repair solutions such as road improvements that may 

improve Border Patrol’s operational mobility. Border Patrol has 

documented the process, including the steps involved in the process. 

However, Border Patrol has not developed written guidance on this 

process, including how officials are to use the information and analyses 

resulting from the process when requesting TI for deployment purposes. 

For example, following the implementation of the Process in fiscal year 

2015, Border Patrol provided the sectors with the Capability Gap Analysis 

Report that contained the identified capability gaps in the sector and the 

agent identified solutions for resource and planning purposes, according 

to Border Patrol Headquarter officials.

Border Patrol Lacks 

Documented Guidance on 

the Requirements 

Management Process
Page 35 GAO-17-331 Tactical Infrastructure

However, sector officials we visited varied in their understanding of the 

process documentation, including how to use the documentation to inform 

sector planning. For example, using the analyses recorded in the 

Capability Gap Analysis Report, the Tucson sector identified a capability 

gap in its operations—a seasonal river bed in the San Pedro River in 

Naco, Arizona—that impeded Border Patrol’s capability to gain access to 

the area after heavy rains. In addition, sector officials used the analyses 

to identify solutions to the capability gap and began researching options 

to improve agents’ access to the area. In contrast, Border Patrol officials 

at another sector we visited were unaware of the analysis included in the 

Capabilities Gap Analysis Report or how to use the analyses to inform 

sector planning. Officials in another sector we visited noted that while 

they received the Capabilities Gap Analysis Report and stated that 

capability gaps identified in the report would help stations better 

understand where limitations in border security operations exist, agents 

need more guidance about how to use the analyses in the report for 

resource allocation decisions. Further, officials in two sectors we visited 

noted that guidance on the process would be helpful in terms of how to 

use the capability gap documentation to identify TI requirements for 

deployment purposes.

In addition to the confusion with the process cited by sector officials, 

Border Patrol headquarters officials in the Law Enforcement Operations 

Directorate—the office within Border Patrol responsible for making TI 

resource decisions, according to Border Patrol officials—were not aware 

of their roles and responsibilities in the process. Officials within the 

Directorate told us that as of March 2016 they had not received 

documentation of the process and cited the Operational Requirements 

Based Budget Process, and not the Requirements Management Process, 

as the current process for Border Patrol sectors and stations to use when 

identifying TI and other requirements for funding and deployment 

purposes.36

According to the Standards for Internal Control in the Federal 

Government, program managers should document responsibilities 

 

36The Operational Requirements Based Budget Process is Border Patrol’s standardized 

national planning process that links sector- and station-level planning, operations, and 

budgets. This process documents how sectors identify and justify their requests to achieve 

effective control of the border in their area of responsibility, and enables Border Patrol to 

determine how the deployment of resources, such as technology, infrastructure, and 

personnel, can be used to secure the border. 
Page 36 GAO-17-331 Tactical Infrastructure

through policies and procedures and communicate these policies and 

procedures so that personnel can implement control activities for their 

assigned responsibilities.37 Border Patrol headquarters officials confirmed 

that in 2014, when Border Patrol transitioned to the new Requirements 

Management Process, they prioritized implementing the new process 

ahead of developing relevant guidance on roles and responsibilities for 

headquarters and sector staff responsible for executing each step in the 

process. While Border Patrol officials noted that the process is new and 

they plan to take steps to improve it, such as developing an online 

module that will host policy and guidance on the process, one sector we 

visited has already used the outputs of the process for decision making 

and planning purposes. In addition, two of the three sectors we visited 

noted that guidance would improve sector and station understanding of 

the process as well as how to use the outputs for planning purposes. As 

Border Patrol continues to take steps to implement its process for 

identifying TI and other assets for border security operations, providing 

guidance to the appropriate officials within Border Patrol would help 

provide reasonable assurance that steps within the process are followed. 

In addition, developing and implementing written guidance on the 

remaining steps of the process reduces the risk of relevant agency 

officials lacking the information to perform their appropriate role in the 

process.

According to CBP, from fiscal year 2007 to 2015, CBP spent 

approximately $2.3 billion to deploy border fencing along the southwest 

border, and CBP will need to spend a substantial amount to sustain these 

investments over their lifetimes. Given these costs, developing metrics 

that measure the contributions of pedestrian and vehicular fencing to 

border security operations as part of a system of capabilities along the 

southwest border would provide Border Patrol with the best information 

available to inform and justify future investments in these assets against 

competing priorities and other investment opportunities. Further, as 

Border Patrol continues to take steps to implement its requirements 

management process for identifying TI and other operational 

requirements for border security operations, providing guidance to the 

appropriate officials within Border Patrol would help ensure that steps 

within the requirements process are followed by Border Patrol officials, 

 

37GAO, Standards for Internal Control in the Federal Government, GAO-14-704G 

(Washington, D.C.: September 2014). 

Conclusion
Page 37 GAO-17-331 Tactical Infrastructure

and that they are clear about their roles and responsibilities in the 

process.

To ensure Border Patrol has the best available information to inform 

future investments in TI and resource allocation decisions among TI and 

other assets Border Patrol deploys in the furtherance of border security 

operations, and to ensure that key parties within Border Patrol’s 

Requirements Management Process are aware of their roles and 

responsibilities within the process, we recommend that the Chief of the 

Border Patrol:

• Develop metrics to assess the contributions of pedestrian and vehicle 

fencing to border security along the southwest border using the data 

Border Patrol already collects and apply this information, as 

appropriate, when making investment and resource allocation 

decisions; and

• Develop and implement written guidance to include roles and 

responsibilities for the steps within its requirements process for 

identifying, funding, and deploying tactical infrastructure assets for 

border security operations.

We provided a draft of this report to DHS for review and comment. In its 

written comments, which are reproduced in full in appendix III, DHS 

concurred with the two recommendations and described actions planned 

to address them. DHS also provided technical comments that we 

incorporated, as appropriate. 

With regard to the first recommendation to develop metrics to assess the 

contributions of pedestrian and vehicle fencing to border security along 

the southwest border using the data Border Patrol already collects, DHS 

concurred and stated that it planned to develop and incorporate metrics 

into Border Patrol’s Requirements Management Process. According to 

DHS, it plans to develop metrics by December 2017 and update the 

Requirements Management Process to include these metrics by March 

2018. With regard to the second recommendation to develop and 

implement written guidance to include roles and responsibilities within the 

Requirements Management Process, DHS concurred and stated that it 

plans to update the Requirements Management Process and, as part of 

that update, plans to add communication and training methods and tools 

to better implement the Process. DHS plans to complete these efforts by 

Recommendations for 

Executive Action

Agency Comments 

and Our Evaluation
Page 38 GAO-17-331 Tactical Infrastructure

September 2019. These actions, if implemented effectively, should 

address the intent of our recommendations.

We are sending copies of this report to the appropriate congressional 

committees, the Secretary of Homeland Security, and other interested 

parties. In addition, the report is available at no charge on the GAO 

website at http://www.gao.gov. 

If you or your staff have any questions, please contact me at (202) 512-

8777 or gamblerr@gao.gov. Contact points for our Offices of 

Congressional Relations and Public Affairs may be found on the last page 

of this report. GAO staff who made significant contributions to this report 

are listed in appendix IV.

Rebecca Gambler

Director, Homeland Security and Justice
Page 39 GAO-17-331 Tactical Infrastructure

List of Requesters

The Honorable Ron Johnson

Chairman

The Honorable Claire McCaskill

Ranking Member

Committee on Homeland Security and Governmental Affairs

United States Senate

The Honorable Thomas R. Carper

Ranking Member

Permanent Subcommittee on Investigations

Committee on Homeland Security and Governmental Affairs

United States Senate

The Honorable John Cornyn

United States Senate

The Honorable Michael T. McCaul

Chairman

The Honorable Bennie G. Thompson

Ranking Member

Committee on Homeland Security

House of Representatives

The Honorable Martha McSally

Chairwoman

Subcommittee on Border and Maritime Security 

Committee on Homeland Security 

House of Representatives
Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Page 40 GAO-17-331 Tactical Infrastructure

To provide a concise descriptive overview of border fencing and other 

tactical infrastructure (TI) in each border sector, we developed a profile 

for each sector along the southwest border and for the border as a whole. 

These profiles contain information about TI in each sector with a focus on 

border fencing as well as other data, such as geographic information and 

an analysis of estimated known illegal entries in the sector from fiscal 

years 2013 through 2015.

As part of its border security operations, U.S. Customs and Border 

Protection (CBP) deploys border fencing across nine sectors along the 

southwest border. Each border sector has its own headquarters and is 

further divided into varying numbers of stations, with agents assigned to 

patrol defined geographic areas, or zones, within each station. Of these, 

zones that touch the international border are known as border zones, 

while zones that do not touch the international border are known as 

interior zones. Zone dimensions are largely determined by geography and 

topographical features, and zone size can vary significantly.

Each border zone has a unique combination of border fencing types, 

designs, and coverage. Border fencing types include pedestrian fencing, 

which is primarily intended to slow down and deter pedestrians from 

crossing the border, and vehicle fencing, which is intended to resist 

vehicles engaged in drug trafficking and alien smuggling operations and 

is typically used in rural or isolated locations that have a low occurrence 

of illegal pedestrian traffic. For the purposes of this report, we refer to any 

fencing designs used prior to CBP implementing requirements of the 

Secure Fence Act of 2006 as “legacy” fencing designs and any fencing 

designs deployed subsequently as “modern” fencing designs.1 In addition, 

all “landing mat” fencing—constructed of army surplus carbon steel

landing mats which were used to create landing strips during the Vietnam 

War—is considered a “legacy” fencing design, regardless of when it was 

constructed. Zone “coverage” refers to the presence and extent of border 

fencing in a border zone. In our analysis, we classified border zone 

coverage as follows: complete (100 percent) border fence coverage, 

partial border fence coverage, or no border fence coverage.

Border Patrol collects data on the number of entrants who illegally cross 

the southwest border between the land border ports of entry. These data 

 

1 Pub. L. No. 109-367, 120 Stat. 2638.

Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Overview
Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Page 41 GAO-17-331 Tactical Infrastructure

include estimates on the total number of directly or indirectly observed—

or “known”—illegal entries by sector and zone.2 Estimated known illegal 

entries consist of the total number of illegal entrants who were 

apprehended, in addition to the number of entrants who illegally crossed 

the border but were not apprehended either because they crossed back 

to Mexico—”turn backs”—or continued traveling to the U.S. interior and 

Border Patrol was no longer actively pursuing them—”got aways.” Border 

Patrol also collects data on the number of vehicles that illegally cross the 

border, known as “drive throughs”.3 To show each border zone’s unique 

combination of border fencing in conjunction with estimated known illegal 

entries, we analyzed Border Patrol data to determine, for each border 

zone, the (1) total estimated known illegal entries, (2) total estimated drive 

throughs, (3) estimated turn backs and got aways, and (4) apprehension 

rates for estimated known illegal entries.

The following profiles of each southwest border sector and the southwest 

border as a whole are meant to provide a concise descriptive overview of 

border fencing and TI in each border sector. Each profile presents sectorspecific data on geography, border zones, miles of fencing and patrol 

roads, staffing levels, spending on fencing operations and maintenance, 

and relative number of estimated known illegal entries in border zones; a 

map highlighting sector boundaries and urban areas; and a chart 

illustrating fencing layers as of September 2016. Each profile includes a 

table, based on CBP data, showing estimated known illegal entries, drive 

throughs, turn backs and got aways, and apprehension rates for fiscal 

years 2013 through 2015 by the type of primary fencing (pedestrian or 

vehicle), design of primary fencing (legacy or modern), and coverage of 

primary fencing (complete, partial, or none) in the border zone where 

Border Patrol agents recorded the apprehension or observation. A brief 

narrative describing the data in the table is also included.

The descriptive information in the following sector profiles was compiled 

from a variety of CBP sources. We obtained information on the number of 

agents assigned to each sector from the U.S. Border Patrol (Border 

 

2We defined these illegal entries as estimated “known” illegal entries to clarify that the 

estimates do not include illegal entrants for which Border Patrol does not have reasonable 

indications of cross-border illegal activity.

3“Drive throughs” are border crossings by a motor vehicle, often carrying drugs. The 

individuals involved in a “drive through” are counted among apprehensions, turn backs, or 

got aways if agents are able to ascertain the number of individuals in the vehicle.

Methodology for 

Developing Sector Profiles
Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Page 42 GAO-17-331 Tactical Infrastructure

Patrol) as of September 25, 2015. We obtained information on patrol 

roads and on the extent of primary, secondary, and tertiary fencing in 

each sector as of fiscal year 2016 from CBP’s Facilities Maintenance and 

Engineering office (FM&E). To assess the reliability of CBP’s road and 

fencing data, we reviewed how CBP collects and maintains these data 

and found them sufficiently reliable for our intended use. Finally, we 

obtained information on the number of sector zones and geographic 

information included in sector maps from Border Patrol and located the 

data geographically using Mapinfo.

To analyze estimated known illegal entries in border zones in relation to 

border fencing, we obtained apprehension, turn back, got away, and drive 

through data by sector and zone for fiscal years 2013 through 2015 from 

DHS and Border Patrol databases—apprehension data came from the 

Enforcement Integrated Database (EID) and turn back, got away, and 

drive through data came from the Border Patrol Enforcement Tracking 

System (BPETS).4 In addition, we also obtained sector map data 

identifying the border zones in each sector from Border Patrol and data 

identifying the location of legacy and modern pedestrian and vehicle 

fencing along the border from the Border Patrol Facilities and Tactical 

Infrastructure (BPFTI) Office. Merging data on the location of border 

zones in each sector and the location of fencing allowed us to categorize 

each border zone according to the design, type, and coverage of fencing 

in the border zone, including “mixed” categories for border zones where 

CBP deployed a mixture of legacy and modern fencing or a mixture of 

pedestrian and vehicle fencing. We then combined this border zone 

fencing data with the estimated known illegal entry data for border zones 

to determine the (1) total estimated number of known illegal entries, (2) 

drive throughs, (3) turn-backs and got-aways in border zones, and (4) 

apprehension rates in border zones with border fencing, by fence design, 

type and zone coverage, and in border zones without border fencing. We 

focus our analysis on border zones rather than interior zones. (For a more 

detailed description of our scope and methodology, see Appendix II.)

 

4EID is a Department of Homeland Security-shared common database repository for 

several DHS law enforcement and homeland security applications. Data on 

apprehensions are held in the EID; data on turn backs, got aways, drive throughs are held 

in BPETS.
Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Page 43 GAO-17-331 Tactical Infrastructure

The data in the tables included in the following profiles is descriptive and 

do not establish or suggest causation between border fencing and the 

total estimated known illegal entries, estimated drive throughs, estimated 

turn backs and got aways, or apprehension rates of estimated illegal 

entries. Conclusions regarding the contributions of fencing to Border 

Patrol’s efforts to secure the border cannot be formed solely on the basis 

of the location of apprehensions, turn backs, got aways, and drive 

throughs relative to the location of various types and designs of fencing. 

For example, at the sector level, the data displayed in the following 

profiles show differences in estimated known illegal entries, turn backs 

and got aways, and estimated apprehension rates for border zones with 

the same types and design of fencing, indicating that other factors 

affected the number of known illegal entries and apprehension rates 

recorded in those zones. In fiscal years 2013 through 2015, for example, 

agents in the Yuma sector had an apprehension rate of 81 percent in 

border zones that were completely covered by modern pedestrian 

fencing, while agents in the El Paso sector had an apprehension rate of 

17 percent in border zones that were completely covered by modern 

pedestrian fencing. Within the Tucson sector, agents recorded 169 known 

drive throughs in border zones with vehicle fencing, whereas in the El 

Centro sector, agents recorded 25 drive throughs in border zones with 

vehicle fencing. Furthermore, despite no change in the miles of primary 

pedestrian fencing on the southwest border between fiscal years 2011-

2015, total southwest border apprehensions ranged from approximately 

328,000 to 479,000.

Other factors, including terrain, geography, demographics, Border Patrol 

agent manpower, and surveillance technology along the southwest 

border, may affect the location of illegal entries and agents’ ability to 

predict, detect, identify, classify, track, respond, and resolve illicit crossborder activities. For example, according to Border Patrol officials, 

entrants in some border zones may be apprehended before reaching any 

border fencing in zones where primary border fencing is not located on 

the border. In the Rio Grande sector, for example, about 30 percent of all 

primary border fencing miles in the sector are located more than half a 

mile from the border. In other cases, entrants may make no attempt to 

evade Border Patrol, choosing to turn themselves in to Border Patrol 

agents, according to officials. For example, according to CBP officials, 

while the Rio Grande Valley sector had an apprehension rate of 56 

percent in fiscal years 2013 through 2015, in fiscal year 2014 the sector 

experienced a spike in illegal entries consisting largely of unaccompanied 

children and adults with children, many of whom turned themselves in to 

Scope and Data 

Limitations of Sector 

Profiles
Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Page 44 GAO-17-331 Tactical Infrastructure

Border Patrol agents without attempting to evade security or defeat 

fencing.

We determined that there were no significant data reliability issues with 

CBP apprehension data that affect our use for the purposes of this report.

However, CBP has identified some potential limitations concerning drive 

through, turn back, and got away data. To identify and report estimated 

known illegal entries, Border Patrol agents use various sources of 

information, including direct agent observation, referrals from credible 

sources (such as local residents), camera monitoring, and detection of 

physical evidence left by migrants (such as footprints). Border Patrol’s 

estimate of illegal entries does not include estimates of illegal entries for 

which Border Patrol does not have reasonable support, such as the 

number of illegal entries conducted through illicit cross-border tunnels. As 

a result, the estimated illegal entry data reported by Border Patrol for 

fiscal years 2013 through 2015 may not represent all illegal entries across 

the southwest border during that period. Furthermore, according to 

Border Patrol officials, agents’ ability to obtain accurate or consistent data 

using these identification sources depends on various factors, such as 

terrain and weather. For example, data on turn backs and got aways may 

be understated in areas with rugged mountains and steep canyons that 

can hinder detection of illegal entries. In other cases, data may be over or 

understated—for example, in cases where the same turn-back identified 

by a camera is also identified by footprints.

We determined the data were sufficiently reliable for the purposes of our 

descriptive analysis. Border Patrol uses these data, among other data, to 

assign risk scores to each sector, which informs resource deployments. 

Border Patrol also uses these data to calculate the “Interdiction 

Effectiveness Rate,” which is a performance metric used by the agency to 

evaluate progress toward meeting its border security goal(s) consistent 

with the Government Performance and Results Act (GPRA) of 1993, as 

updated by the GPRA Modernization Act of 2010.5 Nonetheless, CBP 

officials said that they did not consider the data sufficiently reliable to 

 

5GPRA, Pub. L. No. 103-62, 107 Stat. 285 (1993), was updated by the GPRA 

Modernization Act of 2010, Pub. L. No. 111-352, 124 Stat. 3866 (2011). CBP reports the 

“Interdiction Effectiveness Rate” as a GPRA measure, and calculates this figure by 

dividing apprehensions + turn backs, by apprehensions + turn backs + got aways. While 

GPRA is applicable to the department or agency level, performance goals and measures 

are important management tools applicable to all levels of an agency, including the 

program, project, or activity level, consistent with leading practices and internal controls 

related to performance monitoring.
Appendix I: Descriptive Analysis of Selected 

Tactical Infrastructure (TI) and Estimated 

Known Illegal Entries in Southwest Border 

Zones from Fiscal Years 2013 Through 2015

Page 45 GAO-17-331 Tactical Infrastructure

compare results from one sector to another due to various challenges in 

estimating known entries such as differences in local demographics, 

geography, staffing, and technology in each sector. However, according 

to CPB, the data were sufficiently reliable to compare zones within each 

sector, and to compare sectors against a border-wide summation of these 

data.
Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

United States

Mexico

Brownsville

Matamoros

McAllen

Reynosa

Nuevo Laredo

Laredo

Piedras Negras

Ciudad

Acuña

El Paso Sunland Park

Ciudad

Juarez

Las Cruces

Nogales

Tucson

Nogales

Yuma

Mexicali

San Luis

Rio Colorado

San Diego

Tijuana

State line

Sector boundary

State name

Sector name

U.S.city

Mexican city

Border

California Nevada Arizona New Mexico

Texas

Oklahoma

San Diego

Yuma

Big Bend

El Paso Tucson

El Centro

Del Rio

Laredo

Rio Grande Valley

Legend

Southwest Border

Land border / river border

Land area 

Border zones / interior zones

Primary fencing 

Patrol roads 

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Total estimated known illegal entries in 

southwest border zones (FYs 2013-2015)

Border profile

696 / 1,295 miles

893,480 square miles

214 / 441

654 miles

4,904 miles

17,522

$43.4 million

1.3 million

Border overview

As of 2015, approximately one third (33 percent) of the 

nearly 2,000 mile southwest border is covered by primary 

pedestrian and vehicle fencing. Of the 354 miles of 

primary pedestrian fencing currently deployed, 82 percent 

(291 miles) have modern designs and 18 percent (63 

miles) have legacy designs. Of the 300 miles of vehicle 

fencing deployed, 75 percent (225 miles) have modern 

designs and 25 percent (75 miles) have legacy designs. 

About six percent of all primary fencing is backed up by 

secondary fencing and about four percent of primary and 

secondary fencing is backed up by tertiary fencing. The 

approximately 37 miles of secondary fencing and 14 

Tertiary layer

Secondary layer

Primary layer

Percentage covered

0 20 40 60 80 100

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by fencing, 

by layer, type, and design (September 2016)

Source: GAO. | GAO-17-331

Southwest border map

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and 

layers of fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, 

Sept. 2015 (includes sector and Special Operations Group staff).

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 46 GAO-17-331 Tactical Infrastructure
Funds obligated for tactical infrastructure operations 

and maintenance on the southwest border in fiscal 

year 2015 

Percent of total estimated known illegal entries 

recorded in southwest border zones in fiscal years 

2013-2015, by sector

Tucson

1% Big Bend

Rio Grande

Valley

40%

1% Yuma

29%

9%

4% Del Rio

4% El Centro

5% El Paso

7% San Diego

Laredo

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

San Diego

1% Big Bend

28% Tucson

3% Laredo

15%

14%

4% Del Rio

El Centro

Rio Grande

Valley

El Paso

17% Yuma

9%

9%

Source: U.S. Customs and Border Protection data. | GAO-17-331

miles of tertiary fencing currently deployed are located 

primarily in three border sectors: San Diego, El Paso, 

and Yuma. All secondary and tertiary fencing is legacy 

pedestrian fencing. Approximately 90 percent of primary 

border fencing on the southwest border is located in the 

five western-most sectors, with the remaining 10 percent 

of primary fencing located in the four eastern-most sectors 

where the majority of the border is delineated by the Rio 

Grande River.

Border Patrol uses approximately 4900 miles of 

operational patrol roads, 29 percent of which are roads 

owned by U.S. Customs and Border Protection (CBP) 

or on federal land where CBP has obtained the right to 

perform maintenance and repair work. The other two-thirds 

of operational patrol roads are on non-federal lands that 

CBP has the right to maintain or repair through a license or 

permit.

Our analysis was conducted at the zone level. Of the 214 

border zones across all nine sectors, about 73 percent 

have at least some fencing. Approximately seven percent 

of southwest border zones are completely covered by 

pedestrian fencing and one southwest border zone is 

completely covered by vehicle fencing. 

In fiscal year 2015, CBP obligated an estimated 

$43.3 million for tactical infrastructure operations and 

maintenance on the southwest border. CBP obligated an 

estimated 28 percent of these funds ($12.1 million) for 

the Tucson sector, where 25 percent of southwest border 

patrol roads and 30 percent of southwest border fencing 

are located.

In fiscal years 2013 through 2015, CBP recorded 

approximately 1.3 million estimated known illegal entries 

in southwest border zones, with the Rio Grande Valley 

(40 percent), Tucson (29 percent), and Laredo (9 percent) 

sectors recording the most entries. 

Page 47 GAO-17-331 Tactical Infrastructure
Fencing overview

San Diego, California

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (3, 8%) 7,905 8 0 1,792 6 77

Pedestrian fence (PF) total (32, 82%) 86,000 89 14 29,172 91 66

Modern PF complete coverage (1, 3%) 2,761 3 0 660 2 76

Modern PF partial coverage (4, 10%) 11,341 12 0 3,025 9 73

Legacy PF complete coverage (3, 8%) 6,669 7 0 4,793 15 28

Legacy PF partial coverage (15, 38%) 44,746 46 12 15,240 48 66

Mixed PF complete coverage (1, 3%) 1,561 2 0 598 2 62

Mixed PF partial coverage (8, 21%) 18,922 19 2 4,856 15 74

Mixed PF and vehicle fence (VF) total (4, 10%) 3,266 3 0 1,120 3 66

Mixed PF/VF complete coverage (2, 5%) 1,680 2 0 583 2 65

Mixed PF/VF partial coverage (2, 5%) 1,586 2 0 537 2 66

Total (39, 100%) 97,171 100 14 32,084 100 67

The San Diego sector is one of the most densely populated areas 

in the United States including the cities of San Diego (1.3 million) 

and Tijuana and Tecate, Mexico (combined population of 1.7 

million). Sector terrain includes beaches, coastal plains, steep 

canyons and ravines, high desert, mountains over 6,000 feet in 

elevation, and sparsely populated remote and rural wilderness 

areas. 

United States

Mexico

Sunland Park

Nogales

Tucson

Nogales

Yuma

Mexicali San Luis

Rio Colorado

San Diego

Tijuana

California

Nevada

Arizona

San Diego

Yuma Tucson

El Centro

San Luis

Rio Colorado

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

Land border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the San Diego sector (FYs 2013-2015)

60 miles

56,830 square miles

39 / 89

46 miles

309 miles 

2,430

$6.5 million

7 percent

Sector profile Sector map

Approximately seven percent of all miles of primary border fencing 

and 30 percent of the miles of all secondary and tertiary fencing 

along the southwest border are located in the San Diego sector. 

Approximately 14 percent of the sector’s 39 border zones are 

completely covered with modern or legacy pedestrian fencing. In 

fiscal years 2013-2015, Border Patrol agents in the sector recorded 

the majority of estimated known illegal entries (93 percent) and 

got aways and turn backs (95 percent) in border zones with at 

least some pedestrian fencing. Agents had the highest estimated 

apprehension rate in the sector (77 percent) in zones with no 

fencing. In the 15 border zones partially covered by legacy 

pedestrian fencing, agents had an apprehension rate of 66 percent.

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: Due to rounding, percentages may not total 100.

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Note: “Mixed” fencing coverage refers to border zones with a mixture of legacy and modern fencing designs. Due to rounding, percentages may not total 100.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 48 GAO-17-331 Tactical Infrastructure
Percentage of sector border miles covered by 

Fencing overview fencing, by layer, type, and design (September 2016)

El Centro, California

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (2, 10%) 6,147 12 9 1,814 11 70

Pedestrian fence (PF) total (11, 55%) 32,001 61 0 11,896 69 63

Modern PF complete coverage (2, 10%) 2,273 4 0 617 4 73

Modern PF partial coverage (5, 25%) 9,178 17 0 3,560 21 61

Legacy PF partial coverage (3, 15%) 15,426 29 0 6,177 36 60

Mixed PF complete coverage (1, 5%) 5,124 10 0 1,542 9 70

Mixed vehicle fence (VF) partial coverage 

(4, 20%)

5,947 11 19 1,505 9 75

Mixed PF/VF complete coverage (3, 15%) 8,508 16 6 1,980 12 77

Total (20, 100%) 52,603 100 34 17,195 100 67

The geography of El Centro is largely desert, but also includes 

rugged mountains, agricultural areas, a designated wilderness 

area, and several military reservations. Cities near the border 

include Mexicali, Mexico (population 900,000) and Calexico, CA 

(population 40,000).

United States

Mexico

Sunland Park

Nogales

Tucson

Nogales

Yuma

Mexicali San Luis

Rio Colorado

San Diego

Tijuana

California

Nevada

Arizona

San Diego

Yuma Tucson

El Centro

San Luis

Rio Colorado

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

Land border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the El Centro sector (FYs 2013-2015)

70 miles

107,750 square miles

20 / 30

59 miles

214 miles

1004

$3.7 million

4 percent

Sector profile Sector map

About nine percent of all miles of primary fencing along the 

southwest border are located in the El Centro sector, where three of 

the sector’s 20 border zones are completely covered by pedestrian 

fencing and an additional 11 border zones are partially covered by 

pedestrian fencing. Border Patrol agents recorded approximately 

30 percent of estimated known illegal entries in the sector in fiscal 

years 2013-2015 in the three border zones partially covered by 

legacy pedestrian fencing, where agents had apprehension rates of 

60 percent. Agents recorded 23 percent of estimated known illegal 

entries in the six border zones without any pedestrian fencing and 

apprehended 70 percent of illegal entrants in those zones. Border 

Patrol agents in the sector had an estimated overall apprehension 

rate of 67 percent, higher than the 56 percent apprehension rate for 

the southwest border as a whole.

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: Due to rounding, percentages may not total 100.

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Note: “Mixed” fencing coverage refers to border zones with a mixture of legacy and modern fencing designs. Due to rounding, percentages may not total 100.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 49 GAO-17-331 Tactical Infrastructure
Fencing overview

Yuma, California and Arizona

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

Pedestrian fence (PF) total (7, 47%) 12,337 67 0 4,117 62 67

Modern PF complete coverage (2, 13%) 433 2 0 83 1 81

Modern PF partial coverage (1, 7%) 1,104 6 0 619 9 44

Legacy PF partial coverage (1, 7%) 1,520 8 0 722 11 53

Mixed PF complete coverage (1, 7%) 2,394 13 0 411 6 83

Mixed PF partial coverage (2, 13%) 6,886 37 0 2,282 34 67

Modern vehicle fence (VF) partial coverage 

(5, 33%)

4,896 26 0 2,174 33 56

Mixed PF/VF partial coverage (3, 20%) 1,311 7 0 380 6 71

Total (15, 100%) 18,544 100 0 6,671 100 64

The Yuma sector contains desert terrain, mountain ranges (some 

with elevations over 4,000 feet), agricultural areas, and the 

Colorado River. Large portions of the sector fall within federal 

land and military reservations. Approximately two miles of primary 

fencing are located between a half mile and mile from the border. 

Urban areas include Yuma, AZ (population 93,000) and San Luis 

Rio Colorado, Mexico (population 180,000).

United States

Mexico

Sunland Park

Nogales

Tucson

Nogales

Yuma

Mexicali San Luis

Rio Colorado

San Diego

Tijuana

California

Nevada

Arizona

San Diego

Yuma Tucson

El Centro

San Luis

Rio Colorado

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

Land border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the Yuma sector (FYs 2013-2015)

126 miles

181,670 square miles

15 / 26

107 miles

209 miles 

804

$7.4 million

1 percent

Sector profile Sector map

Approximately 16 percent of all primary border fencing miles along 

the southwest border are located in the Yuma Sector, including a 

third of all secondary and tertiary fencing. While all 15 border zones 

in the sector have some border fencing, only three border zones 

are completely covered by pedestrian fencing. In zones with no 

pedestrian fencing, agents recorded 26 percent of total estimated 

known illegal entries and had an apprehension rate of 56 percent. 

Yuma Border Patrol agents had the highest apprehension rate (83 

percent) of all border zones on the southwest border in the one 

border zone in the sector with complete coverage by a mixture of 

legacy and modern pedestrian fencing. 

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: “Mixed” fencing coverage refers to border zones with a mixture of legacy and modern fencing designs. Due to rounding, percentages may not total 100.

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 50 GAO-17-331 Tactical Infrastructure
Fencing overview

Tucson, Arizona

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

Pedestrian fence (PF) total (7, 19%) 108,741 28 41 36,807 20 66

Modern PF complete coverage (1, 3%) 1,620 0 19 798 0 51

Modern PF partial coverage (1, 3%) 1,919 0 0 1,145 1 40

Mixed PF partial coverage (5, 14%) 105,202 27 22 34,864 19 67

Vehicle fence (VF) total (22, 59%) 192,391 49 104 107,927 60 44

Modern VF complete coverage (1, 3%) 13,342 3 1 6,241 3 53

Modern VF partial coverage (9, 24%) 54,199 14 37 26,400 15 51

Legacy VF partial coverage (7, 19%) 86,167 22 50 53,430 29 38

Mixed VF partial coverage (5, 14%) 38,683 10 16 21,856 12 43

Mixed PF/VF partial coverage (8, 22%) 92,149 23 65 36,655 20 60

Total (37, 100%) 393,281 100 210 181,389 100 54

The Tucson sector’s geography includes mountain ranges and 

valleys, as well as several areas of protected federal land and two 

American Indian reservations, one that includes 63 miles of border 

with Mexico. Urban areas include Nogales, AZ (population 21,000) 

and Nogales, Mexico (population 200,000).

Mexico

El Paso Sunland Park

Ciudad

Juarez

Las Cruces

Nogales

Tucson

Nogales

San Luis

Rio Colorado

Arizona New Mexico

Texas

Big Bend

El Paso Tucson

Del Rio

San Luis

Rio Colorado

United States

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

Land border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the Tucson sector (FYs 2013-2015)

262 miles

90,500 square miles

37 / 26

211 miles

1256 miles 

3,991

$12.1 million

29 percent

Sector profile Sector map

The Tucson sector has more primary fencing than any other sector 

on the southwest border (32 percent of all border fencing) and 

every border zone in the sector is either completely or partially 

covered by some type and design of border fencing. One of the 

sector’s 37 border zones is completely covered by pedestrian 

fencing. Tucson Border Patrol agents recorded approximately 

half (49 percent) of estimated known illegal entries in fiscal years 

2013-2015 in border zones in the sector with no pedestrian fencing, 

where agents had an estimated apprehension rate of 44 percent. 

The sector has more border zones with vehicle fencing than any 

other sector along the southwest border, with complete or partial 

vehicle fencing covering about 80 percent of the sector’s border 

zones. Tucson Border Patrol agents recorded about half (169) of all 

known drive throughs on the southwest border in fiscal years 2013-

2015 in border zones with at least some vehicle fencing. 

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: “Mixed” fencing coverage refers to border zones with a mixture of legacy and modern fencing designs. Due to rounding, percentages may not total 100.

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 51 GAO-17-331 Tactical Infrastructure
Fencing overview

El Paso, New Mexico and Texas

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (7, 18%) 8,021 13 15 3,848 11 52

Pedestrian fence (PF) total (21, 54%) 41,066 68 1 27,667 78 33

Modern PF complete coverage (3, 8%) 2,661 4 0 2,203 6 17

Modern PF partial coverage (13, 33%) 18,534 30 1 12,474 35 33

Legacy PF partial coverage (2, 5%) 7,072 12 0 5,391 15 24

Mixed PF complete coverage (1, 3%) 2,273 4 0 1,689 5 26

Mixed PF partial coverage (2, 5%) 10,526 17 0 5,910 17 44

Vehicle fence (VF) total (9, 23%) 7,004 12 14 2,919 8 58

Modern VF partial coverage (7, 18%) 5,454 9 7 2,334 7 57

Legacy VF partial coverage (1, 3%) 703 1 6 406 1 42

Mixed VF partial coverage (1, 3%) 847 1 1 179 1 79

Mixed PF/VF partial coverage (2, 5%) 4,737 8 2 1,188 3 75

Total (39, 100%) 60,828 100 32 35,622 100 41

The sector includes mountains, deserts, irrigation canals, and 

rivers and just over a half of the sector area consists of small 

towns and isolated rural areas. The international border 

separates the cities of Ciudad Juarez, Mexico (population 1.3 

million) and El Paso, TX (population 670,000).

Mexico

El Paso Sunland Park

Ciudad

Juarez

Las Cruces

Nogales

Tucson

Nogales

San Luis

Rio Colorado

Arizona New Mexico

Texas

Big Bend

El Paso Tucson

Del Rio

San Luis

Rio Colorado

United States

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

Land border / river border

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the El Paso sector (FYs 2013-2015)

180 miles / 88 miles 

125,000 square miles

39 / 41

166 miles

465 miles 

2,364

$5.9 million

5 percent

Sector profile Sector map

Approximately 25 percent of all primary border fencing miles 

along the southwest border are located in the El Paso sector, as 

well as about a third of all secondary and tertiary fencing. Agents 

recorded about 67 percent of estimated known illegal entries in 

border zones partially covered with pedestrian fencing and eight 

percent in zones with complete pedestrian fencing. Agents recorded 

the lowest estimated zone apprehension rate on the southwest 

border (17 percent) in the three border zones in the sector that are 

completely covered by modern pedestrian fencing; four percent of 

total estimated known illegal entries were recorded in these zones. 

Agents recorded 25 percent of estimated known illegal entries in 

the sector in border zones with no pedestrian fencing, where the 

estimated apprehension rate ranged from 52 to 58 percent.

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Note: “Mixed” fencing coverage refers to border zones with a mixture of legacy and modern fencing designs. Due to rounding, percentages may not total 100.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 52 GAO-17-331 Tactical Infrastructure
Fencing overview

Big Bend, Texas

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (19, 95%) 8,276 94 15 2,878 96 65

Mixed pedestrian and vehicle partial 

coverage (1, 5%)

505 6 0 122 4 76

Total (20, 100%) 8,781 100 15 3,000 100 66

The terrain of the Big Bend sector varies from dry sandy desert to 

tree-covered hills and also includes remote and rugged mountains 

reaching to elevations of 8,000 feet. The Rio Grande River is the 

international boundary and includes areas of thick vegetation. The 

sector contains the most border miles of all Border Patrol sectors 

on the southwest border.

United States

Mexico

Piedras Negras

Ciudad

Acuña

El Paso Sunland Park

Ciudad

Juarez

Las Cruces

Nogales

Tucson

Nogales

Arizona New Mexico

Texas

Oklahoma

Big Bend

El Paso Tucson

Del Rio

Laredo

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

River border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the Big Bend sector (FYs 2013-2015)

510 miles

165,150 square miles

20 / 62

5 miles

393 miles 

549

$.4 million

1 percent

Sector profile Sector map

One zone in the Big Bend sector has fencing and is partially 

covered with a mix of pedestrian and vehicle fencing. The 

apprehension rate in the 19 zones without fencing was 65 percent 

in fiscal years 2013-2015 while the estimated rate in the one zone 

with partial fencing was 76 percent, both higher than the borderwide average apprehension rate (56 percent). Border Patrol agents 

recorded most (94 percent) of estimated known illegal entries in the 

sector in the 19 zones with no fencing.

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: “Mixed” fencing coverage refers to border zones with a mixture of legacy and modern fencing designs.

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 53 GAO-17-331 Tactical Infrastructure
Fencing overview

Del Rio, Texas

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension 

rate of estimated 

known entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (4, 57%) 21,923 43 0 9,399 44 57

Modern pedestrian partial coverage (3, 43%) 29,549 57 1 11,909 56 60

Total (7, 100%) 51,472 100 1 21,308 100 59

The geography of the Del Rio sector varies from rugged canyons 

and steep hills to rolling hills and flatland. The Rio Grande 

River, which establishes the international boundary, is oriented 

predominately north to south and cuts through deep canyons. 

The river can be forded by individuals in many places, but not by 

vehicles. Approximately one mile of the primary border fencing 

deployed in the sector is located between half a mile and a mile 

from the border. While the United States side of the border is 

sparsely populated and consists mostly of farms and ranches, the 

Mexican towns of Piedras Negras (population 150,000) and Ciudad 

Acuña (population 140,000) are located just south of the border. 

United States

Mexico

Nuevo Laredo

Laredo

Piedras Negras

Ciudad

Acuña

El Paso Sunland Park

Ciudad

Juarez

Las Cruces

Nogales

Tucson

New Mexico Texas

Big Bend

El Paso

Del Rio

Laredo

Rio Grande Valley

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

River border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

theDel Rio sector (FYs 2013-2015)

210 miles

59,540 square miles

7 / 24

4 miles

1198 miles 

1,536

$1.9 million

4 percent

Sector profile Sector map

Approximately one percent of all miles of primary border fencing 

along the southwest border are located in the Del Rio sector. During 

fiscal years 2013-2015, Border Patrol agents had an estimated 

overall apprehension rate of 59 percent, higher than the 56 percent 

apprehension rate for the southwest border as a whole. Estimated 

apprehension rates were 60 percent in border zones that are 

partially covered by modern pedestrian fencing compared with 57 

percent in the four border zones without any fencing. 

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 54 GAO-17-331 Tactical Infrastructure
Fencing overview

Laredo, Texas

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (15, 94%) 93,794 76 20 47,559 75 49

Legacy pedestrian partial coverage (1, 6%) 30,117 24 6 15,469 25 49

Total (16, 100%) 123,911 100 26 63,028 100 49

The Laredo sector contains brush covered rolling and steep hills as 

well as several deep arroyos, washouts, and creeks that drain into

the Rio Grande River, which defines the entire international border. 

Border cities include Laredo, TX (population 245,000) and Nuevo 

Laredo, Mexico (population 380,000).

United States

Mexico

Brownsville

Matamoros

McAllen

Reynosa

Nuevo Laredo

Laredo

Piedras Negras

Ciudad

Acuña

El Paso Sunland Park

Ciudad

Juarez

Las Cruces Texas

Big Bend Del Rio

Laredo

Rio Grande Valley

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

River border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the Laredo sector (FYs 2013-2015)

171 miles

88,460 square miles

16 / 105

1 mile

144 miles

1,670

$1.4 million

9 percent

Sector profile Sector map

The one zone with border fencing in the Laredo sector is partially 

covered by legacy pedestrian fencing. Border Patrol agents 

recorded approximately 76 percent of illegal entries in the 

sector in fiscal years 2013-2015 in the 15 border zones with no 

fencing, where approximately half (49 percent) of entrants were 

apprehended. 

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 55 GAO-17-331 Tactical Infrastructure
Percentage of sector border miles covered by 

fencing, by layer, type, and design (September 2016)

Fencing overview

Rio Grande Valley, Texas

Total estimated known 

illegal entries 

Estimated known 

drive throughs

Estimated known turn 

backs and got aways

Apprehension rate 

of estimated known 

entrants

Primary fence type (2015)

(number and percent of border zones) Number Percentage Number Number Percentage Percentage

No fence (8, 38%) 259,308 49 0 151,244 65 42

Modern pedestrian partial coverage (13, 62%) 272,011 51 0 82,345 35 70

Total (21, 100%) 531,319 100 0 233,589 100 56

The Rio Grande Valley sector contains terrain that varies from 

rural farmland and ranchland to a large coastal shoreline and also

includes densely populated areas including Brownsville, Texas 

(population 180,000), McAllen, Texas (population 135,000), 

Matamoros, Mexico (population 490,000), and Reynosa, Mexico 

(population 600,000). The Rio Grande River defines the entire 

international border. Approximately 14 miles of the primary border 

fencing in the sector is located between half a mile and a mile from 

the border and an additional two miles of primary fencing is located 

between one and one and a half miles from the border.

United States

Mexico

Brownsville

Matamoros

McAllen

Reynosa

Nuevo Laredo

Laredo

Piedras Negras

Ciudad

Acuña

El Paso Sunland Park

Ciudad

Juarez

Las Cruces Texas

Big Bend Del Rio

Laredo

Rio Grande Valley

Legend

State line Sector boundary

State name Sector name U.S. city Mexican city

Border

Source: U.S. Customs and Border Protection; MapInfo (map). | GAO-17-331

River border 

Land area 

Border zones / interior zones

Primary fencing

Patrol roads

Agents assigned 

Funds obligated for tactical infrastructure 

operations and maintenance (FY 2015)

Percentage of total estimated known illegal 

entries in southwest border zones recorded in 

the Rio Grande Valley sector (FYs 2013-2015)

273 miles

18,580 square miles

21 / 38

55 miles

716 miles 

3,056

$3.9 million

40 percent

Sector profile Sector map

Approximately eight percent of all miles of border fencing along 

the southwest border are located in the Rio Grande Valley sector. 

In fiscal years 2013-2015, Border Patrol agents in the sector 

recorded 40 percent of all estimated known illegal entries on the 

southwest border and apprehended approximately half (56 percent) 

of those entrants. Estimated apprehension rates were higher in the 

13 border zones that are partially covered by modern pedestrian 

fencing (70 percent) than in zones without any fencing (42 percent). 

Estimated known illegal entries in border zones, by fencing type, design, and coverage, fiscal years 2013-2015

Percentage covered

0 20 40 60 80 100

Tertiary layer

Secondary layer

Primary layer

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Legacy pedestrian

Modern pedestrian

Legacy vehicle

Modern vehicle

No fence

Source: GAO analysis of U.S. Customs and Border Protection data. | GAO-17-331

Note: FY: Fiscal Year. Zone counts are as of Sept. 2015; miles and layers of 

fencing, Sept. 2016; patrol roads, Nov. 2015; agents assigned, Sept. 2015.

Source: U.S. Customs and Border Protection. | GAO-17-331

Page 56 GAO-17-331 Tactical Infrastructure
Appendix II: Objectives, Scope and 

Methodology

Page 57 GAO-17-331 Tactical Infrastructure

This report examines U.S. Customs and Border Protection’s (CBP) 

tactical infrastructure (TI) along the southwest border. Our objectives 

were to review (1) border fencing’s intended contributions to border 

security operations and the extent to which CBP has assessed these 

contributions and (2) the extent that CBP has processes in place to 

ensure sustainment1 and deployment of TI along the southwest border 

and challenges in doing so.

To examine border fencing’s intended contributions on border security 

operations, and the extent to which CBP has assessed these 

contributions, we analyzed relevant documentation, including Border 

Patrol’s State of the Border Risk Methodology, which Border Patrol uses 

to assess risk across the southwest border, and documents identifying 

CBP mission goals and objectives, and related performance measures. 

We also reviewed relevant acquisition documents that CBP developed for 

the construction of TI across the southwest border. We interviewed 

officials from Border Patrol’s Strategic Planning and Analysis (SPA) 

Directorate, which is responsible for assessing risk along the southwest 

border, and the Operational Requirements Management Division 

(ORMD), which is responsible for deploying operational requirements, 

including TI, to mitigate these risks. During these interviews we focused 

on the intended contributions of TI in providing Border Patrol agents with 

Foundational Operational Capabilities (FOC) and assisting Border Patrol 

agents in executing their Mission Essential Tasks (METs).2 We also 

discussed the limitations associated with border fencing, including the 

methods employed by illegal entrants in defeating border fencing, 

including breaches. To analyze breaches by fence design, we obtained 

pedestrian fence breach data from Border Patrol Facilities and Tactical 

Infrastructure (BPFTI) for fiscal years 2010 through 2015.3 To assess the 

 

1For the purposes of this report, sustainment refers to the maintenance, repair, and new 

construction of TI.

2Border Patrol defines FOCs as the essential combinations of resources (personnel, 

training, equipment, technology, and infrastructure) that provide Border Patrol agents with 

the fundamental operational means by which to conduct their Mission Essential Tasks 

(METS). Border Patrol defines the METs as a sequential set of discreet or unique tasks in 

which Border Patrol agents must be proficient to execute their duties in the furtherance of 

border security operations.

3For the purposes of this report, we refer to any fencing designs used prior to CBP 

implementing requirements of the Secure Fence Act of 2006 (Pub. L. No. 109-367, 120 

Stat. 2638) as “legacy” fencing and any fencing deployed subsequently as “modern” 

fencing designs. In addition, all “landing mat” fencing—constructed of army surplus carbon

steel landing mats which were used to create landing strips during the Vietnam War — is 

considered “legacy” fencing design, regardless of when it was constructed.

Appendix II: Objectives, Scope and 

Methodology
Appendix II: Objectives, Scope and 

Methodology

Page 58 GAO-17-331 Tactical Infrastructure

reliability of these data, we reviewed how CBP collects and maintains 

breach data, and found the data to be sufficiently reliable for the purposes 

of our report. We then analyzed the occurrences of breaches in modern 

compared to legacy pedestrian fence designs. During our meetings with 

ORMD and SPA, we also focused on CBP’s efforts to assess TI’s 

contributions to border security operations, and the perceived challenges 

involved in conducting such an assessment. We then compared these 

efforts against criteria established in GAO’s past reporting on leading 

practices for performance management.4

To identify border fencing’s intended contributions to border security 

operations at the sector level, we visited the El Paso, San Diego, and 

Tucson sectors. We selected these sectors for site visits due to CBP’s 

extensive investments in TI in each sector over the years. Combined, 

these sectors contain approximately 65 percent of all primary pedestrian 

and vehicle fencing along the southwest border. These three sectors also 

contain 66 percent of all secondary and tertiary fencing across the 

southwest border. During these site visits, we interviewed Border Patrol 

sector headquarters officials and agents, as well as agents assigned to 

various stations and zones within each sector.5 Our interviews in each 

sector focused on border fencing’s specific contributions within each 

sector as well as the extent to which border fencing has provided Border 

Patrol agents with the FOCs border fencing was intended to provide, and 

the extent to which border fencing assists Border Patrol agents in 

executing their METs. We also collected information on other perceived 

benefits of border fencing not associated with the FOC or METs, including 

agent safety, as well as perceived limitations of border fencing. While the 

information we obtained from our visits cannot be generalized to all 

Border Patrol sectors, it provided us with insights about border fencing’s 

contribution to border security operations.

To examine the extent that CBP has processes in place to ensure 

sustainment and deployment of TI along the southwest border and 

challenges in doing so, we reviewed relevant documentation and 

interviewed headquarters officials from BPFTI, which is responsible for 

 

4GAO, Managing for Results: Enhancing Agency Use of Performance Information for 

Decision Making, GAO-05-927 (Washington, D.C.: Sept. 2009).

5Each southwest border sector is divided into varying numbers of stations, with agents 

assigned to patrol defined geographic areas, or zones, within each station. Of these, 

zones that touch the international border are known as border zones, while zones that do 

not touch the international border are known as interior zones.
Appendix II: Objectives, Scope and 

Methodology

Page 59 GAO-17-331 Tactical Infrastructure

sustaining TI along the southwest border. These documents included 

CBP’s Comprehensive Tactical Infrastructure Maintenance and Repair 

(CTIMR) contracts, which CBP uses to maintain and repair TI assets 

across the southwest border. To assess how CBP manages the 

deployment of TI across the southwest border, we reviewed relevant 

documentation from Border Patrol’s ORMD, which is responsible for 

executing Border Patrol’s requirements management process and 

deploying TI, among other assets. These documents included Border 

Patrol’s Capability Gap Analysis Process (CGAP) and the various outputs 

of this process, including capability gaps and agent identified solutions. 

We compared these documents against criteria outlined in Standards for 

Internal Control in the Federal Government.6

We also interviewed officials from BPFTI and ORMD. Our interviews with 

BPFTI officials focused on the program’s CTIMR contracts and work 

plans, BPFTI’s oversight of CTIMR contractors, the Work Management 

System that BPFTI uses to track and oversee all TI related maintenance 

and repair work, and any challenges BPFTI or contractors may face in 

sustaining TI along the southwest border. Our interviews with ORMD 

focused on Border Patrol’s process for identifying TI requirements, 

prioritizing TI requirements, and ultimately allocating resources. During 

our site visits, we interviewed relevant BPFTI and Border Patrol officials 

responsible for overseeing the sustainment – maintenance and repair–of 

CBP’s TI in the sector. In these meetings, we discussed fence 

replacement projects and other TI repairs–as well as any challenges the 

sector faces in sustaining the TI deployed there. We also toured each 

sector’s TI inventory, which include pedestrian and vehicle fencing, gates, 

roads, bridges, grates, and lighting. In the El Paso and Tucson sectors, 

we also visited segments of legacy pedestrian fencing slated for 

replacement with more modern pedestrian fencing within the coming 

months.

The descriptive information in the sector profiles in Appendix I was 

compiled from a variety of CBP sources. We obtained information on the 

number of agents assigned to each sector from Border Patrol as of 

September 2015. We obtained information on roads in each sector as of 

November 2015 and on the extent of primary, secondary, and tertiary 

 

6 GAO-14-704G. 
Appendix II: Objectives, Scope and 

Methodology

Page 60 GAO-17-331 Tactical Infrastructure

fencing7 in each sector as of September 2016 from CBP’s Facilities 

Management and Engineering office (FM&E). Finally, we obtained the 

geographic information on the number of sector zones and geographic 

information included in sector maps from Border Patrol and located the 

data geographically using Mapinfo.

To analyze the location of illegal entries in conjunction with border 

fencing, we reviewed the types of data Border Patrol already collects, 

including apprehension data from the Enforcement Integrated Database 

(EID) and turn back, got away, and drive through data from the Border 

Patrol Enforcement Tracking System (BPETS).8 We assessed the 

reliability of these data through interviews with knowledgeable Border 

Patrol officials on the limitations of these data and digital testing of these 

data. As a result of our data reliability assessment, we determined that 

Border Patrol’s data were sufficiently reliable for our intended use. 

However, Border Patrol has identified some limitations concerning drive 

through, turn back, and got away data. To identify and report estimated 

known illegal entries, Border Patrol agents use various sources of 

information, including direct agent observation, referrals from credible 

sources (such as local residents), camera monitoring, and detection of 

physical evidence left by migrants (such as footprints).9 Border Patrol’s 

estimate of illegal entries does not include estimates of illegal entries for 

which Border Patrol does not have reasonable support. As a result, the 

estimated illegal entry data for a given period of time may not represent 

all illegal entries across the southwest border during that period. 

 

7Up to three layers of fencing may run parallel to the border to support border operations. 

The first layer, the primary fence, may include both pedestrian and vehicle fencing and is 

the first fence encountered when moving north from the border; the secondary fence, 

located behind the primary fence; and the third layer, or tertiary fence, is primarily used to 

delineate property lines rather than deter pedestrian traffic.

8EID is a DHS-shared common database repository for several DHS law enforcement and 

homeland security applications. Data on apprehensions are held in the EID; data on turn 

backs, got aways, drive throughs are held in BPETS.

9Border Patrol defines estimated illegal entries as the total number of aliens who were 

apprehended, in addition to the number of entrants who illegally crossed the border but 

were not apprehended either because they crossed back to Mexico—”turn backs”—or 

continued traveling to the U.S. interior and Border Patrol was no longer actively pursuing 

them—”got aways.” “Drive throughs” are border crossings by a motor vehicle, often 

carrying drugs. The individuals involved in a “drive through” are counted among 

apprehensions, turn backs, or got aways if agents are able to ascertain the number of 

individuals in the vehicle. We defined these illegal entries as estimated “known” illegal 

entries to clarify that the estimates do not include illegal entrants for which Border Patrol 

does not have reasonable indications of cross-border illegal activity. 
Appendix II: Objectives, Scope and 

Methodology

Page 61 GAO-17-331 Tactical Infrastructure

Furthermore, according to Border Patrol officials, agents’ ability to obtain 

accurate or consistent data using these identification sources depends on 

various factors, such as terrain and weather. For example, data on turn 

backs and got aways may be understated in areas with rugged mountains 

and steep canyons that can hinder detection of illegal entries. In other 

cases, data may be over or understated—for example, in cases where 

the same turn-back identified by a camera is also identified by footprints.

Nonetheless, Border Patrol uses these data, among other data, to assign 

risk scores to each sector, which informs resource deployments. Border 

Patrol also uses these data to calculate the “Interdiction Effectiveness 

Rate,” which is a performance metric used by the agency to evaluate 

progress toward meeting its border security goal(s) consistent with the 

Government Performance and Results Act (GPRA) of 1993, as updated 

by the GPRA Modernization Act of 2010.10 Border Patrol officials said that 

they did not consider the data sufficiently reliable to compare results 

across sectors due to various challenges in estimating known entries 

such as differences in local demographics, geography, staffing, and 

technology. However, according to Border Patrol, the data were 

sufficiently reliable to compare zones within each sector, and to compare 

sectors against a border-wide summation. Therefore, after interviewing 

Border Patrol officials about these data and their possible limitations, we 

determined the data were sufficiently reliable for the purposes of our 

descriptive analysis.

We obtained data for fiscal years 2013 through 2015 for all southwest 

border zones and developed four indicators.11 These indicators 

 

10GPRA, Pub. L. No. 103-62, 107 Stat. 285 (1993), was updated by the GPRA 

Modernization Act of 2010, Pub. L. No. 111-352, 124 Stat. 3866 (2011). CBP reports the 

“Interdiction Effectiveness Rate” as a GPRA measure, and calculates this figure by 

dividing apprehensions + turn backs, by apprehensions + turn backs + got aways. While 

GPRA is applicable to the department or agency level, performance goals and measures 

are important management tools applicable to all levels of an agency, including the 

program, project, or activity level, consistent with leading practices and internal controls 

related to performance monitoring.

11We obtained apprehension data for fiscal years 2013 through 2015 from the 

Enforcement Integrated Database - a DHS-shared common database repository for 

several DHS law enforcement and homeland security applications. We obtained data on 

turn backs, got aways, drive throughs from the Border Patrol Enforcement Tracking 

System. Apprehension, turn back, and got away data for fiscal years 2013 through 2015 

were queried (i.e. obtained from relevant databases) as of February 2016. We selected 

these data for fiscal years 2013 through 2015 because beginning fiscal year 2013, Border 

Patrol standardized how it collects and records got aways and turn backs, which improved 

the reliability of these data.
Appendix II: Objectives, Scope and 

Methodology

Page 62 GAO-17-331 Tactical Infrastructure

specifically focus on pedestrian and vehicle fencing, and do not analyze 

other types of TI, including: roads, lighting, boat launches, gates, grates, 

culverts and drainage ditches. These indicators also do not account for 

other assets that CBP deploys as part of its border security operations, 

including manpower and surveillance technology, including integrated 

fixed towers or remote video surveillance systems. The indicators are:

• Total estimated known illegal entries in southwest border zones with 

varying coverage, types, and designs of border fencing and border 

zones with no border fencing (apprehensions + turn backs + got 

aways)

• Total estimated turn backs and got aways in southwest border zones 

with varying coverage, types and designs of border fencing and 

border zones with no border fencing (turn backs + got aways)

• Total estimated drive throughs in southwest border zones with varying 

coverage, types, and designs of border fencing and border zones with 

non-border fencing (drive throughs)

• Apprehension rates of estimated known illegal entries in southwest 

border zones with varying coverage, types, and designs of border 

fencing and border zones with no border fencing (apprehensions / 

apprehensions + turn backs + got aways)

We then obtained sector data for the southwest border, current as of 

December 2015, identifying the border zones in each sector from the 

Office of Border Patrol and data identifying the location of legacy and 

modern pedestrian and vehicle fencing along the border from BPFTI. To 

assess the reliability of the sector fence data we obtained, we reviewed 

for any inconsistencies in fence mileage in each sector, by type and 

design. As a result of our data reliability assessment, we determined that 

CBP’s sector fence data were sufficiently reliable for our intended use. To 

identify the presence and extent of border fencing, by design and type, in 

each border zone within the nine Border Patrol sectors along the 

southwest border, we combined Border Patrol sector and border zone 

data with data provided by BPFTI identifying the location of fence, by 

design (pedestrian or vehicle) and type (legacy or modern), across the 
Appendix II: Objectives, Scope and 

Methodology

Page 63 GAO-17-331 Tactical Infrastructure

southern border.12 After combining these data, we created a single 

dataset identifying border zones by the presence of border fencing, by 

type, design, and coverage.13 To further classify each border zone based 

off of the presence and extent of border fencing, by design and type, we 

developed the following categories:

• Border zones with No Fence

• Border zones with Modern Pedestrian Fence Complete Coverage

• Border zones with Modern Pedestrian Fence Partial Coverage

• Border zones with Legacy Pedestrian Fence Complete Coverage

• Border zones with Legacy Pedestrian Fence Partial Coverage

• Border zones with Mixed Modern/ Legacy Pedestrian Fence Complete 

Coverage

• Border zones with Mixed Modern/ Legacy Pedestrian Fence Partial 

Coverage

• Border zones with Modern Vehicle Fence Complete Coverage

• Border zones with Modern Vehicle Fence Partial Coverage

• Border zones with Legacy Vehicle Fence Complete Coverage

• Border zones with Legacy Vehicle Fence Partial Coverage

• Border zones with Mixed Modern/ Legacy Pedestrian/ Vehicle Fence 

Complete Coverage

• Border zones with Mixed Modern/ Legacy Pedestrian/ Vehicle Fence 

Partial Coverage

 

12Pedestrian fencing is primarily intended to slow down and deter pedestrians from 

crossing the border, while vehicle fencing is intended to resist vehicles engaged in drug 

trafficking and alien smuggling operations. “Legacy” pedestrian fencing refers to fencing 

constructed prior to the implementation of the Secure Fence Act of 2006 as well as any

“landing mat” fencing—constructed of army surplus carbon steel landing mats which were 

used to create landing strips during the Vietnam War—deployed in any year; and 

“modern” fencing refers to fencing first deployed as part of implementation of the Secure 

Fence Act of 2006. For the purposes of this report, the term “zone coverage” refers to the 

extent to which the border miles of a border zone are fenced. In our analysis, we classified 

border zones as follows: Complete (100 percent) border fence coverage, partial border 

fence coverage (less than 100 percent), or no border fence coverage.

13For the purposes of this document, the term “zone coverage” refers to the extent to 

which the border miles of a border zone are fenced. In our analysis, we classified border 

zones as follows: Complete (100 percent) border fence coverage, partial border fence 

coverage (less than 100 percent), or no border fence coverage.
Appendix II: Objectives, Scope and 

Methodology

Page 64 GAO-17-331 Tactical Infrastructure

After grouping each border zone within each sector along the southwest 

border into the appropriate fence category listed above, we then 

combined these data with data we received from Border Patrol identifying 

total known illegal entries in southwest border zones for fiscal years 2013 

through 2015, by sector and calculated each indicator for each fence 

category grouping within each sector. The results of this analysis are 

available in Appendix I. Because Border Patrol occasionally adjusts the 

geometric shapes of zones, we requested map data as of January 2013, 

December 2013, December 2014, and December 2015. We then 

identified and measured the extent of each border zone modification over 

these years. In instances where Border Patrol had modified within this 

date range, we measured the percentage of each modification and redistributed border zone level apprehension, turn back, and got away data 

to the appropriate adjacent zone, in equal proportion.

We conducted this audit from October 2015 to February 2017 in 

accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives.
Appendix III: Comments from the Department 

of Homeland Security

Page 65 GAO-17-331 Tactical Infrastructure

Appendix III: Comments from the 

Department of Homeland Security
Appendix III: Comments from the Department 

of Homeland Security

Page 66 GAO-17-331 Tactical Infrastructure
Appendix III: Comments from the Department 

of Homeland Security

Page 67 GAO-17-331 Tactical Infrastructure
Appendix III: Comments from the Department 

of Homeland Security

Page 68 GAO-17-331 Tactical Infrastructure
Appendix IV: GAO Contact and Staff 

Acknowledgments

Page 69 GAO-17-331 Tactical Infrastructure

Rebecca Gambler, (202) 512-8777 or gamblerr@gao.gov

In addition to the contact named above, Jeanette Espinola (Assistant 

Director); Bruce Crise, Eric Hauswirth, Brandon Jones, Krista Mantsch, 

John Mingus, Sasan J. “Jon” Najmi, and Adam Vogt made contributions 

to this report.

Appendix IV: GAO Contact and Staff 

Acknowledgments

GAO Contact

Staff 

Acknowledgments

(101237)
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