BORDER SECURITY

Additional Actions 

Could Strengthen 

DHS Efforts to 

Address 

Subterranean, Aerial, 

and Maritime 

Smuggling

Report to Congressional Requesters

May 2017

GAO-17-474

United States Government Accountability Office
United States Government Accountability Office

Highlights of GAO-17-474, a report to 

congressional requesters

May 2017

BORDER SECURITY

Additional Actions Could Strengthen DHS Efforts to 

Address Subterranean, Aerial, and Maritime 

Smuggling

What GAO Found

GAO’s analysis of Department of Homeland Security (DHS) data showed that 

there were 67 discovered cross-border tunnels, 534 detected ultralight aircraft 

incursions, and 309 detected drug smuggling incidents involving panga boats (a 

fishing vessel) and recreational vessels along U.S. mainland borders from fiscal 

years 2011 through 2016. The number of known smuggling events involving 

these methods generally declined over this period, but they remain threats.

Examples of a Cross-Border Tunnel, Ultralight Aircraft, and Panga Boat

DHS has established various coordination mechanisms and invested in 

technology to address select smuggling methods in the subterranean, aerial, and 

maritime domains. For example, DHS established interagency task forces to 

investigate cross-border tunnels. However, DHS has not established 

comprehensive standard operating procedures for addressing cross-border 

tunnels, and we found that relevant officials were not aware of all DHS systems 

or offices with tunnel information. By establishing procedures for addressing 

cross-border tunnels, DHS could provide strategic guidance and facilitate 

information sharing departmentwide, consistent with standards for internal 

control. DHS has also invested or plans to invest in at least five technology 

projects to help detect and track ultralight aircraft. However, DHS has not 

assessed and documented how all of the alternative ultralight aircraft technical 

solutions it is considering will fully address operational requirements or the costs 

and benefits associated with these different solutions. This type of analysis could 

help better position DHS to use its resources effectively and ensure that 

operational needs are met, consistent with risk management best practices. 

DHS has established high-level smuggling performance measures and collects

data on smuggling by tunnels, ultralight aircraft, panga boats, and recreational 

vessels; however, DHS has not assessed its efforts specific to addressing these

smuggling methods to, for example, compare the percent of detected panga boat 

and recreational smuggling events that are interdicted against targeted 

performance levels. By establishing measures and regularly monitoring

performance against targets, managers could obtain valuable information on 

successful approaches and areas that could be improved to help ensure that 

technology investments and operational responses to address these smuggling 

methods are effective, consistent with standards for internal control. This is a 

public version of a For Official Use Only—Law Enforcement Sensitive report that 

GAO issued in February 2017. Information DHS deemed For Official Use Only—

Law Enforcement Sensitive has been redacted.

View GAO-17-474. For more information, 

contact Rebecca Gambler at (202) 512-8777 

or gamblerr@gao.gov.

Why GAO Did This Study

As DHS has increased the security of 

overland smuggling routes, 

transnational criminal organizations 

have adapted their techniques to 

smuggle drugs and humans through 

alternative methods. These methods 

include cross-border tunnels, ultralight 

aircraft, panga boats, and recreational 

maritime vessels. While these methods 

account for a small proportion of 

known smuggling, they can be used to 

transport significant quantities of drugs 

or for terrorist activity. GAO was asked 

to review DHS’s efforts to address 

subterranean, aerial, and maritime 

smuggling. This report addresses, 

among other things, (1) the known 

prevalence of the aforementioned 

smuggling methods, (2) efforts to 

address them, and (3) efforts to assess 

the results of activities to counter them.

GAO analyzed relevant procedures, 

reports, and data for fiscal years 2011 

through 2016. GAO also interviewed 

DHS officials and conducted site visits 

to locations in California, Arizona, and 

Florida, chosen based upon past 

detection of smuggling by the selected 

methods, among other things. The 

information from the site visits is not 

generalizable, but provided valuable 

insights.

What GAO Recommends

GAO is making six recommendations, 

including that DHS establish 

procedures for addressing tunnels, 

assess ultralight aircraft technology,

and establish performance measures 

and targets. DHS concurred with four 

recommendations and disagreed with 

those to establish tunnel procedures

and maritime performance measures, 

citing other efforts. GAO believes the 

recommendations remain valid, as 

discussed in the report.
Page i GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Letter 1

Background 5

Known Smuggling Events Persisted but Generally Declined from 

Fiscal Years 2011 through 2016, According to DHS Data 12

DHS Has Taken Steps to Assess Risks from the Selected 

Smuggling Methods but Could Enhance Assessment of 

Maritime Risk 20

DHS Coordinates Among Partners and Uses Technology to 

Address the Selected Smuggling Methods, but Could 

Strengthen its Efforts 29

Establishing and Monitoring Performance Measures Could Allow 

DHS to Better Assess Effectiveness of Efforts to Address the 

Selected Smuggling Methods 41

Conclusions 46

Recommendations for Executive Action 47

Agency Comments and Our Evaluation 47

Appendix I Objectives, Scope, and Methodology 52

Appendix II DHS S&T Projects Related to Selected Subterranean, Aerial, and 

Maritime Smuggling Methods 56

Appendix III Comments from Department of Homeland Security 58

Appendix IV GAO Contact and Staff Acknowledgments 63

Tables

Table 1: Maritime Vessel Definitions from Various Databases and 

Sources Used by Department of Homeland Security, 

Fiscal Years 2011-2016 26

Table 2: U.S. Customs and Border Protection (CBP) 

Technological Solutions to Address Low-Flying Aircraft 39

Table 3: Department of Homeland Security (DHS) Technology 

Research and Development Projects Related to Selected 

Subterranean, Aerial, and Maritime Smuggling Methods 56

Contents
Page ii GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Figures

Figure 1: Cross-Border Tunnels 7

Figure 2: Ultralight Aircraft 8

Figure 3: Maritime Smuggling Vessels 9

Figure 4: Cross-Border Tunnels Discovered by the Department of 

Homeland Security on U.S. Mainland Borders from Fiscal 

Years 2011 through 2016, by Border Patrol Sector 13

Figure 5: Ultralight Aircraft Incursions Detected by the Department 

of Homeland Security on U.S. Mainland Borders from 

Fiscal Years 2011 through 2016, by State 15

Figure 6: Known Panga Boat and Recreational Maritime Vessel 

Drug Smuggling Events along U.S. Mainland Borders, 

Fiscal Years 2011 through 2016 17

Figure 7: Migrants Interdicted by the Department of Homeland 

Security on U.S. Mainland Borders Aboard Panga Boats 

and Recreational Maritime Smuggling Vessels, Fiscal 

Years 2011 through 2016 19
Page iii GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Abbreviations

AMO Air and Marine Operations 

AMOC Air and Marine Operations Center

BEST Border Enforcement Security Task Force 

Border Patrol U.S. Border Patrol 

CBP U.S. Customs and Border Protection 

CCDB Consolidated Counterdrug Database 

Coast Guard U.S. Coast Guard 

CSS Coastal Surveillance System 

DHS Department of Homeland Security

DOD Department of Defense 

DVD Dark Vessel Detection 

HSI Homeland Security Investigations 

LFAD Low Flying Aircraft Detection 

LSTAR Lightweight Surveillance Target Acquisition Radar 

ICE U.S. Immigration and Customs Enforcement 

IMDE Integrated Maritime Domain Enterprise 

OIG Office of the Inspector General 

RECOM Regional Coordinating Mechanism 

SDA Small Dark Aircraft 

S&T Science and Technology Directorate

TARS Tethered Aerostat Radar System

TPMO Tunnel Program Management Office 

ULAD Ultralight Aircraft Detection

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.
Page 1 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

441 G St. N.W.

Washington, DC 20548

May 1, 2017

The Honorable Bennie G. Thompson

Ranking Member

Committee on Homeland Security

United States House of Representatives

The Honorable Martha McSally

Chairwoman

Subcommittee on Border and Maritime Security

Committee on Homeland Security

United States House of Representatives

The U.S. government has identified illicit drug and human smuggling, 

particularly along the U.S-Mexico border (the southwest border), as a 

threat to national security that poses risks to public safety and contributes 

to illicit drug use that harms families and communities across the country. 

To enhance security along the southwest border, the Department of 

Homeland Security (DHS)—the agency responsible for securing the 

nation’s borders—has made significant investments in personnel, 

technology, and tactical infrastructure, such as fencing. In recent years, 

DHS reports that it has interdicted millions of pounds of drugs and 

hundreds of thousands of individuals attempting to illegally enter the 

United States, mostly along the southwest border.1 In fiscal year 2015, 

DHS reported that it seized or prevented the delivery of more than 3.3 

million pounds of narcotics, of which about 2.1 million pounds were 

seized at the southwest border. In addition, DHS reported that it 

apprehended more than 337,000 illegal entrants between ports of entry, 

of which about 331,000 were apprehended along the southwest border.2

As DHS has increased the security of overland smuggling routes, 

transnational criminal organizations have adapted their techniques to 

 1

U.S. Customs and Border Protection, Fiscal Year 2015 CBP Border Security Report

(Dec. 22, 2015).

2

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

United States for persons or materials. 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, merchandise and other items, collect duties, 

and enforce customs laws; and where DHS officers inspect persons entering, applying for 

admission into, or departing the United States pursuant to U.S. immigration law. 

Letter
Page 2 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

smuggle drugs and humans through other methods to try to evade 

detection and interdiction. These adapted smuggling methods include but 

are not limited to illicit cross-border tunnels, ultralight aircraft, panga boats 

(a type of fishing vessel), recreational maritime vessels, and selfpropelled semi-submersible and fully submersible vessels. While the 

selected smuggling methods listed above generally account for a small 

proportion of drug seizures between ports of entry—DHS data indicate 

there were 49 seizures from tunnels, ultralight aircraft, and the selected 

maritime conveyances in fiscal year 2015 compared to almost 12,900 

total drug seizures—the actual number of smuggling events is unknown 

and thus seizure data may not reflect the true prevalence. Further, these 

selected smuggling methods can be used to transport significant 

quantities of drugs. For example, U.S. Customs and Border Protection’s 

(CBP) U.S. Border Patrol (Border Patrol) and U.S. Immigration and 

Customs Enforcement’s (ICE) Homeland Security Investigations (HSI)—

the components within DHS responsible for securing the border between 

land ports of entry and investigating cross-border and immigration-related 

crimes, respectively—and other federal and local law enforcement 

partners seized over 17,000 pounds of marijuana and 300 pounds of 

cocaine from a cross-border tunnel discovered in 2013. In addition, the 

U.S. Coast Guard (Coast Guard) and CBP Air and Marine Operations 

(AMO)—the DHS components that share maritime law enforcement 

responsibilities—seized 5,700 pounds of marijuana from one panga boat 

in March 2015. Human smugglers and migrants have also used panga 

boats and recreational maritime vessels on occasion. In addition to 

posing drug and human smuggling threats, transnational criminal 

organizations’ utilization of these methods also raises concerns that they 

could be used to smuggle terrorists and their weapons into the United 

States.

You asked us to review DHS’s efforts to address threats posed by 

smuggling in the subterranean, aerial, and maritime environments. This 

report addresses the following questions:

1. What do DHS data show about the prevalence of smuggling by crossborder tunnel, ultralight aircraft, and selected maritime methods from 

fiscal years 2011 through 2016?

2. To what extent has DHS assessed the risks from smuggling by these 

methods?

3. How has DHS addressed smuggling by these methods?
Page 3 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

4. To what extent has DHS assessed the results of its efforts to address 

smuggling by these methods?

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

provided to you in February 2017.3 DHS and the Department of Defense 

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 

intelligence assessments, law enforcement operations, and capabilities of 

technologies used to address subterranean, aerial, and maritime 

smuggling. 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.

To address these questions, we focused our review on smuggling across 

U.S. mainland borders, including coastal borders, and we selected the 

following smuggling methods: cross-border tunnels, ultralight aircraft, 

panga boats, recreational maritime vessels, and self-propelled semisubmersible and fully submersible vessels.4 We selected these smuggling 

methods to include only those that would occur between ports of entry 

through means other than overland (given our focus on subterranean, 

aerial, and maritime smuggling); have been identified in strategy 

documents or by senior DHS officials and DHS officials with whom we 

met as a challenge or risk; and were of a magnitude that DHS had taken 

steps to address them. We analyzed DHS policies, procedures, and 

reports. We also conducted site visits to San Diego, El Centro, and 

Riverside, California; Nogales and Yuma, Arizona; and Miami and Key 

West, Florida. During these visits, we observed DHS approaches to 

addressing the selected smuggling methods and interviewed cognizant 

officials from Coast Guard; ICE HSI; and CBP’s Border Patrol and AMO 

about their efforts. We selected these locations based upon a 

combination of factors, including the past detected use of the selected 

 3

GAO, Border Security: Additional Actions Could Strengthen DHS Efforts to Address 

Subterranean, Aerial, and Maritime Smuggling, GAO-17-205SU (Washington, D.C.: Feb. 

3, 2017).

4

Given its focus on smuggling across U.S. mainland borders (i.e., borders of the 

contiguous United States), our review does not address smuggling in the transit zone—a 6 

million square mile area that includes the eastern Pacific Ocean, the Gulf of Mexico, and 

the Caribbean Sea that is used to transport illicit drugs from South America to the United 

States. For additional information on DHS counterdrug efforts in the transit zone, see 

GAO, Coast Guard: Resources Provided for Drug Interdiction Operations in the Transit 

Zone, Puerto Rico, and the U.S. Virgin Islands, GAO-14-527 (Washington, D.C.: June 16, 

2014).
Page 4 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

smuggling methods and the presence of coordinated DHS efforts to 

counter them in these areas. The information gathered from our site visits 

is not generalizable to other locations but provides insights into DHS’s 

responses to these incursions and efforts to use risk and performance 

information to stop future smuggling incidents using these methods. 

Additionally, we interviewed headquarters officials from the Coast Guard; 

CBP’s Border Patrol, AMO, and Office of Acquisition, the office 

responsible for CBP’s acquisition of products and services; ICE HSI; and 

DHS’s Science and Technology Directorate (S&T), the office responsible 

for leading research and development efforts across the department, to 

obtain information and perspectives on their efforts to assess and 

address threats posed by the selected smuggling methods.

To address the first question, we obtained and analyzed DHS data from 

fiscal years 2011 through 2016.5 We assessed the reliability of these data 

by performing electronic testing, among other things, and found the data 

sufficiently reliable for the purposes of reporting trends in the selected 

smuggling methods from fiscal years 2011 through 2016. To address the 

second question, we analyzed DHS risk, threat, intelligence, and 

capability assessments against GAO’s risk management framework and 

leading practices for interagency collaboration.6 To address the third 

question, we analyzed DHS policies, procedures, and documentation on 

developing and acquiring new technology. We also interviewed officials 

from Border Patrol, AMO, ICE HSI, Coast Guard, and relevant 

Department of Defense (DOD) offices and organizations to determine the 

extent to which they have established mechanisms to coordinate assets, 

operations, and share technology to address the selected smuggling 

 5

We selected this time period to identify recent trends in known smuggling events.

6

GAO, Risk Management: Further Refinements Needed to Assess Risks and Prioritize 

Protective Measures at Ports and Other Critical Infrastructure, GAO-06-91 (Washington, 

D.C.: Dec. 15, 2005); and Managing for Results: Key Considerations for Implementing 

Interagency Collaborative Mechanisms, GAO-12-1022 (Washington, D.C.: Sept. 27, 

2010). As discussed in GAO-06-91, risk assessment addresses the process of evaluating 

threats—the probability that a specific type of incident will occur—and vulnerabilities—

weaknesses that can be exploited—so that countermeasures might be instituted. Risk 

assessment can also include an assessment of the consequence of an event to help 

prioritize which assets or areas require greater protection; however, as consequences of 

smuggling can reasonably be expected to be similar among different methods of 

smuggling, our analysis focused on the threat and vulnerability aspects of risk 

assessment. 
Page 5 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

methods.7 We assessed these efforts against GAO’s leading practices for 

interagency collaboration and risk management framework.8 To address 

the fourth question, we analyzed DHS and component performance 

reports, among other things, and interviewed DHS officials to determine 

how they use performance information. We assessed DHS’s performance 

monitoring efforts against Standards for Internal Control in the Federal 

Government and performance assessment best practices.9 Additional 

details on our scope and methodology are contained in appendix I.

We conducted this performance audit from November 2015 to May 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.

Transnational criminal organizations use subterranean, aerial, and 

maritime smuggling methods to try to avoid the security measures 

designed to address traditional overland smuggling routes. These 

smuggling methods—which are further described below—include but are 

not limited to, illicit cross-border tunnels, ultralight aircraft, panga boats, 

recreational maritime vessels, and self-propelled semi-submersible and 

fully submersible vessels. While the use of some of these conveyances is 

longstanding, DHS has identified changes in transnational criminal 

 7

These DOD offices and organizations included U.S. Northern Command, which oversees 

Joint Task Force North, the organization responsible for supporting federal counterdrug 

activities along the southwest border; and the U.S. Southern Command, which oversees 

the Joint Interagency Task Force South, the primary operations center and coordinator for 

detecting and monitoring suspected air and maritime drug trafficking in the Caribbean, 

Central America, and South America.

8

GAO-06-91 and GAO-12-1022.

9

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

(Washington, D.C.: September 2014); Results-Oriented Government: Practices That Can 

Help Enhance and Sustain Collaboration among Federal Agencies, GAO-06-15 

(Washington, D.C.: Oct. 21, 2005); Tax Administration: IRS Needs to Further Refine Its 

Tax Filing Season Performance Measures GAO-03-143 (Washington, D.C.: Nov. 22, 

2002); and Standards for Internal Control in the Federal Government, 

GAO/AIMD-00-21.3.1 (Washington, D.C.: November 1999).

Background

Selected Smuggling 

Methods
Page 6 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

organizations’ tactics, techniques, and procedures in using them that 

present new or different challenges to border security.

Cross-border tunnels. Cross-border tunnels are man-made sub-surface 

passageways that could be used to conceal the movement of humans or 

contraband and circumvent U.S. border defenses. Cross-border tunnels 

can be classified into one of four categories based on the predominant 

features of the tunnel, as described below and shown in figure 1:

• Sophisticated tunnels are elaborately constructed, may be of 

significant length and depth, and may have shoring, lighting, 

electricity, ventilation, and railways.

• Rudimentary tunnels are crudely constructed and shallow.

• Interconnecting tunnels exploit and connect to underground municipal 

infrastructure, such as storm water and sewage systems. 

Interconnecting tunnels typically connect to a rudimentary or 

sophisticated tunnel to operate; however, in these cases the entire 

tunnel would be classified into one category based on the 

predominant features of the tunnel. The exclusive unaltered use of 

underground municipal infrastructure to transport people or 

contraband is not considered a cross-border tunnel, but is another 

subterranean threat.

• Mechanically bored tunnels are those that are constructed primarily 

from mechanical means, instead of human diggers. Such mechanical 

means can include horizontal directional drilling devices and tunnel 

boring machines. These tunnels are generally lined by piping.
Page 7 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Figure 1: Cross-Border Tunnels

Note: Clockwise from top left, this figure depicts an interconnecting tunnel, a rudimentary tunnel, 

pipes for constructing a mechanically bored tunnel, and a sophisticated tunnel.

Ultralight aircraft. As shown in figure 2, ultralight aircraft are single-seat 

aircraft that have an empty weight of about 250 pounds or less. 

Smugglers modify ultralight aircraft to carry drug loads by, for example, 

attaching large metal baskets.
Page 8 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Figure 2: Ultralight Aircraft

Maritime vessels. Selected maritime smuggling methods include panga 

boats, recreational vessels, and self-propelled semi-submersible and fully 

submersible vessels, which are further described below and shown in 

figure 3.

• Panga boats are open-hulled, flat-bottomed fishing vessels designed 

to arrive and depart directly from a beach. These vessels are between 

20 and 60 feet long, and are fitted with one or more outboard motors.

• Recreational vessels are motorized vessels and sailboats used for 

leisure activities. Smugglers can exploit the ubiquity of legitimate 

recreational activity to blend in and avoid detection using these 

vessels.

• Self-propelled semi-submersible and fully submersible vessels have 

low profiles designed to have low radar reflectivity, making them 

difficult to detect. Semi-submersible vessels generally cut through the 
Page 9 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

water at wave height, while fully submersible vessels can be entirely 

submerged below the surface.10

Figure 3: Maritime Smuggling Vessels

Note: Clockwise from top left, this figure depicts a recreational vessel used to transport migrants, a 

panga boat used to transport drugs, another recreational vessel, and a self-propelled semisubmersible vessel.

 10DHS considers information on smuggling incidents involving self-propelled semisubmersible and fully submersible vessels law enforcement sensitive. Therefore, we do 

not discuss them in this report.
Page 10 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Multiple components within DHS have responsibilities for addressing 

subterranean, aerial, and maritime smuggling, including ICE HSI, Coast 

Guard, and CBP’s Border Patrol and AMO. Their specific roles and 

responsibilities with regard to the selected smuggling methods are 

discussed below.

Cross-border tunnels. CBP and ICE HSI share primary responsibility for 

countering cross-border tunnel threats. ICE HSI is responsible for crossborder tunnel investigations, Border Patrol is the primary component for 

interdiction, and CBP is responsible for the remediation of illicit tunnels. 

Both Border Patrol and ICE HSI efforts can lead to the identification of 

likely tunnel locations. In 2013, CBP established a Tunnel Program 

Management Office (TPMO) within Border Patrol to lead and coordinate 

CBP counter-tunnel efforts.

Ultralight aircraft. AMO, Border Patrol, and HSI have primary 

responsibility for countering ultralight aircraft smuggling. AMO’s Air and 

Marine Operations Center (AMOC) is to surveil the airspace above the 

nation’s border and identify the criminal use of noncommercial air 

conveyances, including ultralight aircraft. AMO and Border Patrol are 

responsible for responding to and interdicting ultralight aircraft used for 

smuggling, and ICE HSI is responsible for investigating ultralight aircraft 

incursions.

Maritime vessels. Coast Guard, AMO, and Border Patrol share 

responsibility for patrolling the U.S. maritime borders, and territorial sea 

(i.e., maritime approaches 12 nautical miles seaward of the U.S. coast) to 

interdict drugs and foreign nationals illegally entering the United States.11

Coast Guard is the lead federal maritime law enforcement agency on the 

 11The term “foreign national” refers to an “alien,” defined under U.S. immigration law as 

any person who is not a U.S. citizen or national. See 8 U.S.C. § 1101(a)(3). The term 

“U.S. territorial sea” generally refers to the waters, 12 nautical miles wide, adjacent to the 

U.S. coast and seaward of the territorial sea baseline—normally the mean low water line 

along the U.S. coast—consistent with the principles, as recognized by the United States, 

of the Convention on the Territorial Sea and the Contiguous Zone, 15 U.S.T. 1606, and 

the 1982 United Nations Convention on the Law of the Sea (UNCLOS), 21 I.L.M. 1261. 

See 33 C.F.R. §§ 2.20, 2.22(a); and Territorial Sea of the United States of America, Pres. 

Proc. No. 5928, 54 Fed. Reg. 777 (Dec. 27, 1988). In addition, CBP’s immigration-related 

enforcement authority over any U.S. external boundary encompasses U.S. land 

boundaries and territorial sea 12 nautical miles from U.S. baselines, consistent with 

international law. See 8 C.F.R. § 287.1(a)(1).

Roles and Responsibilities
Page 11 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

high seas (waters beyond 12 nautical miles seaward of the U.S. coast).12

ICE HSI and AMO may investigate cross-border maritime smuggling.

In addition, within DHS, DHS S&T and CBP’s Office of Acquisition 

(formerly the Office of Technology Innovation and Acquisition) are 

responsible for assisting DHS components in obtaining technology that 

can help them address the threats posed by the selected smuggling 

methods. DHS S&T is responsible for leading research and development, 

demonstration, testing, and evaluation to help bridge capability gaps. 

CBP’s Office of Acquisition is responsible for providing policy and 

acquisition oversight across CBP to help obtain products and services 

that enhance border security.

Outside of DHS, DOD is the lead federal agency for the detection and 

monitoring of aerial and maritime transit of illegal drugs into the United 

States and operates systems, such as radar systems, that can be used in 

support of DHS and other federal, state, and local law enforcement 

activities.

 12Under customary international law, and unless clearly indicated otherwise, “high seas”

means all waters that are not the exclusive economic zone, territorial sea, or internal 

waters of the United States or any other nation. See 33 C.F.R. §§ 2.22, 2.30, 2.32(d). 

Coast Guard’s, and AMO’s, law enforcement authorities on the high seas are generally 

defined in statute and regulation. See, e.g., 14 U.S.C. § 89 (states Coast Guard’s law 

enforcement authority on the high seas and U.S. waters, and provides that Coast Guard 

officers engaging in law enforcement pursuant to this section are deemed agents of the 

particular department or agency charged with the administration of the law being 

enforced); 19 U.S.C. § 1581 (CBP officers’ authority over vessels or vehicles in the United 

States or within U.S. customs waters or a customs-enforcement area, or any other 

authorized place); Pres. Proc. No. 4865, 46 Fed. Reg. 48,107 (Sept. 29, 1981); and 19 

C.F.R. § 162.3(a) (CBP officers may board any vessel in the United States or within U.S. 

customs waters; any American vessel on the high seas; and any vessel within a customsenforcement area, but a foreign vessel is not to be boarded in violation of any treaty with 

the foreign government, or in the absence of a special arrangement).
Page 12 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Our analysis of Border Patrol tunnel data showed that there were 67 

cross-border tunnels discovered along U.S. borders from fiscal years 

2011 through 2016, all located on the southwest border, as shown in 

figure 4.13 Nearly all cross-border tunnels—62 of 67—were discovered in 

Border Patrol’s Tucson, Arizona or San Diego, California sectors and the 

remaining 5 were discovered in the El Centro, California and Yuma, 

Arizona Border Patrol sectors.14 Additionally, the number of discovered 

cross-border tunnels generally declined during the period, with 18 tunnels 

discovered in fiscal year 2011 and 9 tunnels discovered in fiscal year 

2016. However, CBP’s 2015 tunnel report to Congress found that illicit 

cross-border tunnels are a persistent threat to national security and that 

increased border enforcement efforts would likely continue to push illicit 

cross-border smuggling underground.15

 13One cross-border tunnel was discovered on the northern border in the Blaine Border 

Patrol sector in fiscal year 2005, but this fiscal year falls outside the fiscal year range of 

focus—2011 through 2016—for this review. 

14CBP has divided geographic responsibility for border security operations into sectors, 

each of which has a headquarters with management personnel. There are nine sectors 

along the southwest border.

15Department of Homeland Security, Cross-Border Tunnels and Border Tunnel Prevention 

Fiscal Year 2015 Report to Congress (Washington, D.C.: March 2016).

Known Smuggling 

Events Persisted but 

Generally Declined 

from Fiscal Years 

2011 through 2016, 

According to DHS 

Data

Tunnel Discoveries Were 

Concentrated on the 

Southwest Border and 

Have Generally Declined 

since Fiscal Year 2011
Page 13 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Figure 4: Cross-Border Tunnels Discovered by the Department of Homeland 

Security on U.S. Mainland Borders from Fiscal Years 2011 through 2016, by Border 

Patrol Sector

Our analysis of Border Patrol tunnel data also showed that sophisticated 

and interconnecting were the most common tunnel types discovered from 

fiscal years 2011 through 2016. In particular, 54 of the 67 discovered 

cross-border tunnels from fiscal years 2011 through 2016 were 

sophisticated and interconnecting types while 13 were rudimentary or 

mechanically bored. Additionally, most drug seizures associated with 

cross-border tunnels involved marijuana. For example, 21 of the 23 

seizures involved marijuana, resulting in over 106,600 pounds of seized 

marijuana.16

 16DHS data do not indicate the extent to which cross-border tunnels have been used for 

human smuggling; however, DHS has assessed that tunnels are predominantly used for 

marijuana smuggling.
Page 14 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Our analysis of AMO data showed that there were 534 suspected 

ultralight aircraft incursions from fiscal years 2011 through 2016, all but 

one located on the southwest border in Arizona, California, New Mexico, 

and Texas.17 The number of suspected ultralight incursions declined each 

year from fiscal years 2011 through 2016. For example, according to 

AMO data, the overall number of suspected ultralight aircraft incursions 

declined from 199 in fiscal year 2011 to 28 in fiscal year 2016, as shown 

in figure 5. However, as discussed later in this report, AMO reports that 

ultralight aircraft are a flexible threat and a surge in activity could occur in 

any or all of the southwest border sectors. For example, while the overall 

number of ultralight aircraft incursions declined, an increase of ultralight 

activity occurred in Texas in fiscal year 2016. More specifically, 18 

suspected ultralight aircraft incursions were detected in Texas in fiscal 

year 2016, compared to 5 suspected ultralight aircraft incursions for all of 

fiscal years 2011 through 2015. Additionally, most drug seizures 

associated with ultralight aircraft incursions were of marijuana. For 

example, more than 98 percent (100 of 102) of the seizures involved 

marijuana, resulting in over 22,000 pounds of seized marijuana. Less 

than two percent (2 of 102) of these seizures involved methamphetamine, 

which resulted in nearly 8 kilograms of methamphetamine seized.18

 17One suspected ultralight aircraft incursion occurred in Washington state in fiscal year 

2015. This analysis includes data on suspected ultralight aircraft incursions to U.S. 

mainland borders, but does not include ultralight aircraft events which occurred outside 

the U.S. mainland, such as in Mexico, or for which geographical information was not 

recorded.

18DHS data do not indicate the extent to which ultralight aircraft have been used for 

human smuggling; however, DHS has assessed that ultralight aircraft are primarily used to 

transport marijuana and typically do not land in the United States. 

Detected Ultralight Aircraft 

Incursions Occurred 

Mostly on the Southwest 

Border and Have 

Generally Declined since 

Fiscal Year 2011
Page 15 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Figure 5: Ultralight Aircraft Incursions Detected by the Department of Homeland 

Security on U.S. Mainland Borders from Fiscal Years 2011 through 2016, by State

Note: One suspected ultralight aircraft incursion occurred in Washington in fiscal year 2015.
Page 16 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Our analysis of Consolidated Counterdrug Database (CCDB) data shows 

that the majority of known maritime drug smuggling events involving 

panga boats and recreational vessels along U.S. mainland borders—

nearly 76 percent (234 of 309)—took place on the west coast, specifically 

California, and over 24 percent (75 of 309) took place on the southeast 

coast, northeast coast, and the southwest border.19 As depicted in figure 

6, our analysis of CCDB data also showed that the number of known 

panga boat and recreational vessel drug smuggling events varied from 

fiscal years 2011 through 2016, with the highest number of events (82 of 

309) occurring in fiscal year 2013 and lowest number of events occurring 

in fiscal years 2015 and 2016, with 32 and 29 respectively. However, the 

actual number of maritime smuggling events and the amount of drugs 

smuggled by these methods is unknown. Additionally, a higher proportion 

of events—nearly 65 percent (200 of 309)—involved motorized, openhulled vessels, such as panga boats, and a lower proportion of events—

over 35 percent (109 of 309)—involved recreational vessels.20 Our 

analysis also showed that the majority of known panga boat and 

recreational vessel drug smuggling events—nearly 86 percent (265 of 

309)—involved marijuana, resulting in over 413,400 pounds of seized 

 19We used DOD’s Consolidated Counterdrug Database (CCDB), which consolidates 

existing drug-related data sets from U.S. federal government entities such as the Coast 

Guard, CBP, Defense Intelligence Agency, and Joint Interagency Task Force-South, to 

calculate the number of maritime drug smuggling events using panga boats and 

recreational vessels from fiscal years 2011 through 2016. Smuggling events in CCDB are 

categorized into four levels of certainty—confirmed, substantiated, suspect (1P), and 

suspect (2P)—all of which we included in our analysis. Confirmed means that law 

enforcement officials confiscated drugs associated with the event. Substantiated means 

that either visual identification of drugs aboard a conveyance occurred; or multiple, 

independent, corroborating intelligence reports with drug movement information such as 

departure, transfer, or delivery are either underway or complete. Suspect (1P) means that 

a single source of intelligence exists that documents, or has been assessed as 

documenting that illegal drugs departed, were transferred, were delivered, or were 

disrupted (e.g., by jettison) on a specific date or within a 3-day window. Suspect (2P) 

means that a single source of intelligence exists that documents (or has been assessed 

as documenting) that illegal drugs were scheduled to depart, be transferred, or be 

delivered on a specific date (generally, but not limited to, a 3-day window). 

20In addition to a general “panga” boat category, CCDB also includes three other 

categories of vessels that are motorized and open-hulled, consistent with a panga boat—

lanchas, pleasure “go-fast” vessels less than 40 feet in length, and pleasure “go-fast”

vessels greater than 40 feet. The panga boat data presented includes events involving all 

of these vessel categories. Additionally, the data presented on recreational boats includes 

all vessels categorized as motorized vessels and sailboats used for leisure activities, 

which include several types of pleasure craft—cabin cruiser, sailing vessel, yacht, sport 

fisher, and others. 

Known Maritime Drug 

Smuggling Events on 

Panga Boats and 

Recreational Vessels 

Mostly Occurred on the 

California Coast and 

Generally Declined since 

Fiscal Year 2011
Page 17 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

marijuana from fiscal years 2011 through 2016. Nearly 14 percent (42 of 

309) involved cocaine, resulting in over 3,200 kilograms of seized 

cocaine, and nearly 1 percent (2 of 309) involved methamphetamine, 

resulting in nearly 300 kilograms of seized methamphetamine from fiscal 

years 2011 through 2016.

Figure 6: Known Panga Boat and Recreational Maritime Vessel Drug Smuggling 

Events along U.S. Mainland Borders, Fiscal Years 2011 through 2016

Note: In addition to a general “panga” boat category, CCDB also includes three other categories of 

vessels that are motorized and open-hulled, consistent with a panga boat—lanchas, pleasure “gofast” vessels less than 40 feet in length, and pleasure “go-fast” vessels greater than 40 feet. The 

panga boat data presented in this figure include events involving all of these vessel categories. 

Additionally, the data presented on recreational boats include all vessels CCDB categorized as 

motorized vessels and sailboats used for leisure activities, which include several types of pleasure 

craft—cabin cruisers, sailing vessels, yachts, sport fisher, and “other.”
Page 18 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Our analysis of Coast Guard data from fiscal years 2011 through 2016 

showed that the majority of the known migrants being smuggled along 

U.S. mainland borders using panga boats and recreational vessels were 

interdicted off the Florida Coast.21 Specifically, Coast Guard interdicted 

nearly 92 percent (1,798 of 1,963) of these migrants off the Florida Coast 

(e.g., North and South Florida Straits), and over 8 percent (165 of 1,963) 

on the southwest border or southern California coastline. Our analysis of 

Coast Guard data also showed that the number of migrants Coast Guard 

interdicted in maritime smuggling-related events on panga boats and 

recreational vessels varied over time but generally increased from fiscal 

years 2011 through 2016. In particular, the lowest numbers were 

interdicted in fiscal year 2011 (211) and 2013 (239) and the highest 

number was interdicted in fiscal year 2016 (443), as shown in figure 7. 

Additionally, of the migrants interdicted from fiscal years 2011 through

2016, about 72 percent (1,374 of 1,899) were on recreational vessels and 

about 28 percent (525 of 1,899) were on panga boats. In fiscal year 2016, 

this trend changed and Coast Guard interdicted over half (233 of 443) of 

 21We analyzed Coast Guard data to determine the number of interdicted migrants, country 

of origin, and vessel type used from fiscal years 2011 through 2016 because Coast Guard 

is the DHS component tasked with reporting maritime migrant data. The interdiction of 

migrants in the maritime environment refers to the interdiction of aliens coming by sea to 

the United States without necessary documentation. See High Seas Interdiction of Illegal 

Aliens, Pres. Proc. No. 4865, 46 Fed. Reg. 48,107 (Sept. 29, 1981). In addition to a 

“panga” boat category, Coast Guard data includes other vessel types that are motorized, 

open-hulled vessels consistent with a panga boat—lanchas and go-fasts. The panga boat 

data presented includes events involving all of these vessel categories. Additionally, our 

data analysis of recreational boats includes all vessels Coast Guard categorized as 

motorized recreational vessels and sailboats which included sailing vessels, pleasure 

craft, fishing vessels, and yolas. Because Coast Guard data is limited to migrant 

interdictions in which Coast Guard participated, it excludes any interdictions of migrants in 

the selected maritime vessels in which solely CBP was involved. Coast Guard data 

include three categories—smuggling, suspected smuggling, and no evidence of 

smuggling—to document whether a maritime migrant event was smuggling related or not. 

For the purposes of this report, we are including smuggling and suspected smuggling 

data. Coast Guard defines “smuggling” as an interdiction where firm evidence existed that 

the migrants onboard the vessel were being smuggled by an organizer and “suspected 

smuggling” as an interdiction where indicators of smuggling, but not firm evidence, 

existed. We do not include data from the third category, no evidence of smuggling, as that 

falls outside the scope of this review. 

Known Maritime Migrant 

Smuggling on Panga 

Boats and Recreational 

Vessels Mostly Occurred 

off the Florida Coast and 

Has Generally Increased 

since Fiscal Year 2011
Page 19 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

these maritime migrants on panga boats and under half (210 of 443) on 

recreational vessels.22

Figure 7: Migrants Interdicted by the Department of Homeland Security on U.S. 

Mainland Borders Aboard Panga Boats and Recreational Maritime Smuggling 

Vessels, Fiscal Years 2011 through 2016

Note: In addition to a “panga” boat category, Coast Guard data includes other vessel types that are 

motorized, open-hulled vessels consistent with a panga boat—lanchas and go-fasts. The panga boat 

data presented in this figure include events involving all of these vessel categories. Additionally, our 

data analysis of recreational boats includes all vessels Coast Guard categorized as motorized 

recreational vessels and sailboats, which includes sailing vessels, pleasure craft, fishing vessels, and 

yolas.

 22Our review is focused on drug and migrant smuggling; however, many migrants using 

maritime routes do not hire smugglers and instead use homemade vessels known as 

rustics, chugs, and rafts. For example, Coast Guard data show that from fiscal years 2011 

through 2016, 11,254 migrants were interdicted aboard rustics, chugs, and rafts, and in 

over 99 percent of these cases there was no indication of these individuals being 

smuggled by an organizer, such as a transnational criminal organization. 
Page 20 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

DHS has taken steps to assess the risks from smuggling by cross-border 

tunnels, ultralight aircraft, panga boats, and recreational vessels.23

Specifically, DHS has assessed the threat of these selected smuggling 

methods by identifying geographic areas that have experienced greater 

incidence of smuggling and transnational criminal organization smuggling 

tactics. DHS has also assessed vulnerabilities by identifying capability 

gaps that affect the department’s ability to address the threats posed by 

the selected smuggling methods.

Cross-border tunnels. To assess the risk from cross-border tunnels, 

CBP commissioned a 2010 assessment that identified areas along the 

southern borders of California, Arizona, New Mexico, and western Texas 

as having a high risk from tunneling activity, based on factors such as soil 

composition, water table, and known tunneling activity.24 However, this 

assessment did not analyze the risk from rudimentary tunnels, 

interconnecting tunnels, or mechanically bored tunnels. CBP is currently 

in the process of obtaining a tunnel risk assessment tool that is to 

compute an estimated statistical likelihood for each of the four types of 

illicit tunnels along the southwest border. Further, unlike the 2010 

 23As discussed in GAO-06-91, risk assessment addresses the process of evaluating 

threats—the probability that a specific type of incident will occur—and vulnerabilities—

weaknesses that can be exploited—so that countermeasures might be instituted. Risk 

assessment can also include an assessment of the consequence of an event to help 

prioritize which assets or areas require greater protection; however, as consequences of 

smuggling can reasonably be expected to be similar among different methods of 

smuggling, our analysis focused on the threat and vulnerability aspects of risk 

assessment.

24Raytheon Company, Tunnel Threat Map – Phase 2 Task 2 Final Report (Springfield, VA: 

Mar. 26, 2010).

DHS Has Taken 

Steps to Assess 

Risks from the 

Selected Smuggling 

Methods but Could 

Enhance Assessment 

of Maritime Risk

DHS has Taken Steps to 

Assess the Smuggling 

Risk from Cross-Border 

Tunnels, Ultralight Aircraft, 

and Maritime Vessels
Page 21 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

assessment, this tool is to use a web-based platform that can be updated 

to allow risk to be re-assessed on an ongoing basis. CBP officials expect 

this tool to be completed in June 2017.

ICE HSI and Border Patrol have also conducted intelligence assessments 

to identify areas that are at a higher risk from tunneling based on factors 

such as transnational criminal organization smuggling tactics and past 

tunneling activity. For example, a 2014 ICE HSI intelligence report states 

that transnational criminal organizations primarily use tunnels to transport 

narcotics, particularly marijuana, which is an important source of profit. 

Marijuana is also relatively bulky, and tunnels have the advantage of 

being able to accommodate large drug loads, according to the 

assessment.

CBP has also identified capability gaps that affect its ability to address 

cross-border tunnels. As part of the process to acquire tunnel detection 

technology, CBP sought an independent examination of factors that affect 

counter tunnel capabilities using a framework that assesses the state of 

doctrine; organization; training; materiel; leadership; personnel; facilities; 

and regulations, grants, and standards.25 The analysis was issued in June 

2013 and identified some gaps in tunnel technology as well as nontechnological capability gaps in doctrine, among other things. CBP’s 

TPMO is responsible for addressing these capability gaps, and we 

discuss the status of key efforts later in this report.

Ultralight aircraft. To assess the risk from ultralight aircraft, AMO has 

analyzed ultralight aircraft data and, as previously discussed, found that 

the majority of ultralight incursions have occurred in Arizona and 

California, with a recent uptick in activity in Texas. AMO has reported in 

its General Aviation Threat Assessments that ultralight aircraft are a

flexible smuggling method and that a surge in activity could occur in any 

or all of the southwest border sectors, shifting when there is an increased 

law enforcement presence. To keep relevant Border Patrol agents 

informed of trends and recent ultralight aircraft activity, AMO and Border 

Patrol officials stationed at AMO’s AMOC, which monitors the airspace on 

the border, send each Border Patrol sector along the southwest border a 

monthly briefing as well as provide real-time coordination at the time of 

the incursions, as discussed later in this report.

 25Homeland Security Studies and Analysis Institute, CBP Counter-Tunnel Threat Analysis: 

DOTMLPF+RGS Capability Assessment (Falls Church, VA: June 25, 2013). 
Page 22 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

AMO has also analyzed ultralight aircraft smuggling tactics and found that 

ultralight aircraft smugglers generally will not land in the United States 

and instead will airdrop the narcotics load in order to quickly return to 

Mexico. AMO officials explained that pilots use this method hoping to 

avoid arrest. According to AMO analysis, the narcotics are generally 

dropped within a couple of miles of a main road so that the smugglers can 

quickly collect the narcotics and blend in with other vehicle traffic on the 

road. Additionally, AMO reports that ultralight aircraft smugglers operate 

like sub-contractors for transnational criminal organizations, and are 

financially responsible for the narcotics they transport. As a result, 

ultralight aircraft primarily transport low- to mid-grade marijuana, with an 

average load size around 200 pounds, because the cost of higher value 

narcotics is prohibitive and the risk from destroying a load during the air 

drop is too great.

CBP has identified gaps in its air domain awareness and made finding a 

technical solution a priority in 2009. CBP has efforts underway to address 

these capability gaps, which we discuss later in this report. According to 

CBP analysis, CBP has sufficient capabilities to respond to and resolve 

detected ultralight aircraft incursions and changes in non-technical 

capabilities, such as increased manpower, will not significantly enhance 

its ability to address the threat posed by ultralight aircraft.

Maritime vessels. To assess the risk from maritime smuggling through 

noncommercial vessels such as panga boats and recreational vessels, 

Coast Guard has produced annual cross-border drug smuggling 

intelligence assessments since 2014. These assessments have 

consistently identified Coast Guard Districts 11, 8, and 7, which cover the 

coastal borders of California and the Southeast United States from Texas 

through the east coasts of Florida, Georgia, and South Carolina, as well 

as Puerto Rico, as the primary threat area for cross-border drug 
Page 23 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

smuggling by noncommercial vessels.26 Further, the Coast Guard 

intelligence assessments identified marijuana smuggling from Mexico to 

California by panga boats as a primary threat to the U.S. mainland. In the 

fiscal year 2015 assessment, the most recent available, Coast Guard 

found that as with previous years, panga boat smuggling routes tended to 

be hundreds of miles off shore, with intended destinations north of Los 

Angeles—most often between Santa Barbara and San Luis Obispo, 

California—to avoid U.S. maritime law enforcement.27

Coast Guard has also assessed the risk from maritime migration through 

its biennial National Maritime Strategic Risk Assessment.28 Coast Guard’s 

2014 risk assessment, the most recent available, found that illegal 

maritime immigration was associated with societal costs and threats to 

the safety of the migrants at sea, and was ranked 16 among the 27 

incident types assessed in terms of the impact and severity of risks. 

Specifically, Coast Guard found that the risk from maritime migration was 

lower than the risks from drug smuggling, natural disasters, and overfishing, among others, and greater than the risks from events such as an 

 26Puerto Rico is outside of the scope of this review; however, it falls within the transit 

zone, which, as previously noted is a 6 million square mile area that includes the eastern 

Pacific Ocean, the Gulf of Mexico, and the Caribbean Sea that is used to transport illicit 

drugs—primarily cocaine—from South America to the United States. Disrupting the flow of 

illicit drugs through the transit zone is an important component of the Office of National 

Drug Control Policy and DHS’s counterdrug strategies. Both Coast Guard and CBP 

contribute assets and manpower to international efforts to interdict drugs in the transit 

zone. Coast Guard officials explained that interdicting drugs in the transit zone can have a 

greater impact on disrupting the flow of drugs to the United States than interdicting closer 

to U.S borders because they can interdict the large, multi-ton drug loads that transnational 

criminal organizations transport from the source countries in South America to countries in 

Central America. Once the drugs reach the secondary location, they are generally broken 

into smaller loads for further distribution, according to Coast Guard officials. For additional 

information on DHS counterdrug efforts in the transit zone, see GAO-14-527.

27U.S. Coast Guard, Fiscal Year 2015: United States Maritime Cross-Border Drug 

Smuggling, ICC-CRIM-001-16 (Washington, D.C.: June 7, 2016).

28Whereas the data on maritime migrant interdictions presented earlier in this report 

includes only incidents where panga boats and recreational vessels were used and there 

was evidence or indicators that an organizer was hired to smuggle the migrants, maritime 

migration includes all migrants attempting to enter the United States via maritime routes, 

regardless of vessel type. 
Page 24 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

accidental hazardous material release or a debris or sewage discharge, 

among others.29

The National Maritime Strategic Risk Assessment is designed to analyze 

risk at a national level to help inform resource allocation decisions and 

does not provide assessments at the local level or by vessel type; 

however, Coast Guard and its DHS partners have also conducted 

regional assessments. DHS’s Southern Border and Approaches 

Campaign Plan identified maritime migration from Cuba, Hispaniola, and 

the Bahamas as the primary illegal maritime migration threat, and Floridabased Coast Guard, AMO, ICE HSI, and Border Patrol have analyzed 

maritime migration from these areas.30 For example, intelligence 

assessments issued from 2015 through spring 2016 found that there has 

been an increase in Cuban maritime migration that will likely continue due 

to perceptions that U.S. immigration policies for Cubans will change.31

Coast Guard assessments show that most Cuban migrants use 

 29U.S. Coast Guard, National Maritime Strategic Risk Assessment 2014 Report (Sept. 31, 

2014). Coast Guard’s National Maritime Strategic Risk Assessment generates estimates 

of risk with a low level of fidelity and thus risk rankings do not have a high level of 

precision. With regard to drug smuggling, Coast Guard calculates risk based on cocaine 

movements in the transit zone, which is consistent with its management performance 

measure and national counterdrug strategies, but is outside of the scope of this review 

and does not account for risks posed by U.S. cross-border maritime smuggling. For

additional information on Coast Guard’s risk model, see GAO, Coast Guard: Security Risk 

Model Meets DHS Criteria, but More Training Could Enhance Its Use for Managing 

Programs and Operations, GAO-12-14 (Washington, D.C.: Nov. 17, 2011).

30In May, 2014, the Secretary of Homeland Security directed the creation of the Southern 

Border and Approaches Campaign, a unified approach to more effectively coordinate the 

assets of Coast Guard, CBP, ICE, U.S. Citizenship and Immigration Services, and other 

departmental resources. The campaign’s intent is for effective enforcement and 

interdiction across land, sea, and air; to degrade transnational criminal organizations; and 

to do these things while still facilitating flow of lawful trade, travel, and commerce across 

U.S. borders.

31On January 12, 2017, DHS rescinded certain policies unique to Cuban nationals. 

Specifically, DHS eliminated a special parole policy for arriving Cuban nationals commonly 

known as the “wet-foot/dry-foot” policy, as well as a policy for Cuban medical 

professionals known as the Cuban Medical Professional Parole Program. Currently, 

DHS’s policy is to consider any requests for such parole in the same manner as parole 

requests filed by nationals of other countries. See DHS, Press Office, Fact Sheet: 

Changes to Parole and Expedited Removal Policies Affecting Cuban Nationals 

(Washington, D.C.: Jan. 12, 2017). DHS also eliminated an exemption that previously 

prevented the use of expedited removal proceedings for Cuban nationals apprehended at 

ports of entry or near the border. See Eliminating Exception to Expedited Removal 

Authority for Cuban Nationals Arriving by Air, 82 Fed. Reg. 4769 (Jan. 17, 2017) (codified 

at 8 C.F.R. pts. 235, 1235).
Page 25 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

homemade vessels known as rustics, rafts, or chugs to travel to the 

Florida Keys; however, transnational criminal organizations commonly 

use stolen or personally owned recreational vessels to transport migrants, 

according to a fiscal year 2016 AMO assessment. Coast Guard, ICE HSI, 

AMO, and Border Patrol reported that another key maritime migrant 

smuggling route is from the Bahamas to Southeast Florida, a trip that can 

be as short as 45 nautical miles.

Coast Guard data show that maritime migrant smuggling occurs less 

frequently along the California coast, but California-based Coast Guard, 

AMO, ICE HSI, and Border Patrol officials we met with have also 

assessed this threat. Personal watercraft, such as jet skis, were the most 

commonly used vessel to smuggle migrants in the region, according to a 

joint fiscal year 2015 California Coastal Region assessment, though 

recreational vessels and panga boats were also used.32 In addition, the 

assessment reports that most migrant smuggling routes along the 

California coastal region are destined for locations south of Los Angeles, 

California.

Coast Guard and CBP have assessed maritime security capability gaps 

through DHS S&T’s Integrated Product Team process, which brings 

together component leaders to identify and prioritize technological 

capability gaps. As discussed later, DHS S&T has projects underway to 

enhance maritime domain awareness. Border Patrol and AMO have also 

initiated their own capability gap assessments to identify gaps and 

technical and nontechnical solutions to address gaps across the range of 

each component’s responsibilities, to include maritime security. Border 

Patrol is implementing its capability gap assessment and is expected to 

complete the documentation of requirements to address capability gaps in 

all Border Patrol sectors in 2019, according to officials. AMO expects to 

complete its capability gap assessment by the end of fiscal year 2017.

 32California Coastal Regional Coordinating Mechanisms, California Coastal Region 

Maritime Smuggling Intelligence Review FY 2015 (April 2016).
Page 26 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Coast Guard, AMO, Border Patrol, and ICE HSI all capture information on 

the types of maritime vessels used for smuggling drugs and migrants to 

inform their counter smuggling efforts; however, the use of different 

terminology for vessels in different regions and different data systems has 

impeded DHS’s ability to develop a full picture of the risks from panga 

boat and recreational vessel smuggling nationwide. For example, as 

shown in table 1, the definition of a panga is different in the interagency 

California coastal region intelligence assessment and data system than it 

is in Coast Guard’s intelligence assessments, with the former specifying

that a panga would have “multiple” outboard motors while the latter states 

that a panga would have “one or two” outboard motors. Furthermore, both 

definitions of pangas overlap with other categories of vessels, including 

“lanchas,” which Coast Guard has defined as open-hulled vessels with 

one outboard motor used in the Gulf Coast region, and “go-fasts,” which 

Coast Guard has defined as an open-hulled vessel with one or more 

outboard motors that can operate at 25 knots in shallow water. The panga 

boats that have been used to smuggle drugs in the California coastal 

region are classified as “lanchas” and “go-fast” vessels in the 

government-wide CCDB and “go-fasts” in a Coast Guard report and a 

national counternarcotic strategy.

Table 1: Maritime Vessel Definitions from Various Databases and Sources Used by Department of Homeland Security, Fiscal 

Years 2011-2016

Vessel Type Definition Source

Panga Open-hulled, flat bottomed fishing vessels designed to 

accommodate arrivals and departures directly from a beach. 

Pangas are typically between 25-35 feet long and have multiple 

outboard motors.

California Coastal Region Maritime 

Smuggling Intelligence Review and 

Maritime Tracking System

Typically originating in Mexico or Guatemala and have one or two 

outboard motors. Also called “shark boats.”

Coast Guard Maritime Cross-Border 

Drug Smuggling Intelligence 

Assessment

Ecuadorean Panga A small go-fast, typically traveling from Ecuador to Guatemala. Consolidated Counterdrug Database

Lancha Open-hulled fiberglass vessels that are 20-30 feet long and 

powered by one outboard motor. Vessels operate freely and in 

great numbers in the Gulf of Mexico.

Coast Guard Maritime Cross-Border 

Drug Smuggling Intelligence 

Assessment

Small passenger motorboat that in images resembles a go-fast. Consolidated Counterdrug Database

Small outboard powered fishing boat. Coast Guard Maritime Migrant Data

Pleasure Craft Motor and sailing vessels used for legitimate recreational 

purposes.

California Coastal Region Maritime 

Smuggling Intelligence Review and 

Maritime Tracking System

DHS Could Enhance 

Assessment of Maritime 

Smuggling Risk by 

Standardizing Definitions 

for Maritime Vessels 

Departmentwide
Page 27 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Vessel Type Definition Source

Go-fast A 28- to 45- foot open-hull boat with one or more high-powered 

outboard motors, capable of operating in excess of 25 knots in 

shallow waters.

Coast Guard Maritime Cross-Border 

Drug Smuggling Intelligence 

Assessment

Speed boat. Coast Guard Maritime Migrant Data

Pleasure Craft Go-Fast Vessel length is 40 feet or smaller. Consolidated Counterdrug Database

Pleasure Craft Sailing 

Vessel 

Sailing vessels including sailing yachts. Consolidated Counterdrug Database

Pleasure Craft Yacht Exclusively motor yachts. Consolidated Counterdrug Database

Source: GAO analysis of Consolidated Counterdrug Database and Department of Homeland Security information. | GAO-17-474

Additionally, the term “go-fast” is used by Coast Guard, AMO, Border 

Patrol, and ICE HSI in various assessments to describe maritime 

smuggling methods in Florida. However, the go-fast smuggling in Florida 

includes vessels that can blend in with the recreational boating traffic in 

the area—or what the California coastal region DHS partners would term 

a “pleasure craft.”

AMO officials stated that differences in terminology do not impact 

operations at the local level, as officials are familiar with smuggling 

methods in their area and local vernacular; however, these differences 

make it difficult to synthesize information across components and regions 

to get a full picture of the threats posed by panga boat and recreational 

vessel smuggling nationwide. Facilitating this type of comprehensive 

assessment could help better inform management resource allocation 

decisions. For example, Coast Guard and AMO officials we met with in 

California and Florida stated that vessel types are associated with 

different smuggling tactics that require different operational response; 

recreational vessels used for smuggling narcotics that blend into 

legitimate recreational maritime traffic may require additional tools, such 

as human intelligence and training, canines, and non-intrusive inspection 

equipment to identify suspect vessels and hidden compartments. In 

comparison, the officials told us that more “overt” forms of smuggling, 

such as panga boats with large unconcealed, or minimally concealed 

drug loads, and recreational vessels overcrowded with migrants, are 

relatively easier to address since they can be detected and identified as 

suspect by maritime patrol aircraft.

Differences in regional parlance and varying options in different 

databases have contributed to the lack of standardized definitions and 

categories of vessels, according to Coast Guard, AMO, and ICE HSI 

officials. Managers of the interagency CCDB recognized the issue of 

overlapping vessel definitions and are planning to revise the vessel 
Page 28 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

options to eliminate overlapping categories such as “lancha” and “panga”

under the category of “go-fast.” However, these changes will not affect 

the other databases or threat assessments used by DHS. Key 

considerations for implementing interagency collaborative mechanisms 

state that developing a common terminology can help bridge 

organizational cultures to enhance and sustain interagency efforts.33 DHS 

has also recognized the importance of common definitions and produces 

an annual DHS Lexicon to define terms and reduce the possibility of 

misunderstanding when communicating across the department and help 

DHS develop and manage knowledge, information, and data. Coast 

Guard, AMO, Border Patrol, and ICE HSI officials agreed that it would be 

beneficial to have standard vessel definitions DHS-wide to enhance the 

quality of data and intelligence assessments and facilitate information 

sharing across agencies.

However, Coast Guard and ICE HSI officials noted that it could be 

challenging to identify all relevant data systems that use vessel types and 

determine how to reconcile older data with new categories. While we 

recognize that this could be challenging, there are upcoming opportunities 

DHS could leverage to efficiently develop and promulgate common vessel 

definitions and categories. For example, once changes to CCDB vessel 

categories are finalized, relevant DHS components could consider 

whether these vessel categories will meet their needs. Additionally, in the 

next year DHS plans to draft a new Small Vessel Security Strategy to 

address the risks that terrorists will use small vessels for transportation or 

an attack, which could be used as a forum for developing standard 

definitions for the various types of small vessels for inclusion in the DHS 

Lexicon and use in future threat assessments.34 If updating all databases 

proves to be difficult or costly, components could, for example, create 

common terminology by documenting a crosswalk that demonstrates the 

relationship between their vessel categories and established DHS-wide 

vessel definitions. By standardizing definitions of panga boats and 

 33GAO-12-1022. 

34DHS defines a small vessel as any watercraft regardless of method of propulsion, less 

than 300 gross tons—a category which would generally include panga boats and 

recreational vessels. Although there is no exact correlation between a vessel’s length and 

its gross tonnage, a vessel of 300 gross tons is approximately 100 feet in length, 

according to DHS. For additional information about DHS’s implementation of the current 

Small Vessel Security Strategy, see GAO, Maritime Security: DHS Could Benefit from 

Tracking Progress in Implementing the Small Vessel Security Strategy, GAO-14-32 

(Washington, D.C.: Oct. 31, 2013). 
Page 29 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

recreational vessels in the DHS Lexicon for use in future threat 

assessments, DHS would be better able to leverage its threat 

assessments to develop a clearer and more comprehensive picture of the 

threats posed by these maritime smuggling methods across the nation. 

Having a complete picture of these maritime smuggling threats could, in 

turn, help better inform management decisions, including resource 

allocation decisions.

DHS components have established various coordination mechanisms to 

address smuggling by cross-border tunnels, ultralight aircraft, panga 

boats, and recreational maritime vessels, and to improve coordination 

among federal, state, and local partners. As previously discussed, in 2015 

DHS established a Border Security Integrated Product Team composed 

of representatives from DHS S&T, CBP, ICE, and Coast Guard to identify 

technology gaps and prioritize research and development efforts for 

enhancing border security. We discuss research and development 

projects that address the selected smuggling methods later in this report. 

In addition, DHS has established coordination mechanisms that 

specifically target the selected smuggling methods.

Cross-border tunnels. DHS has established two interagency Border 

Enforcement Security Task Force (BEST) Tunnel Task Forces to conduct 

investigations into cross-border tunnel incursions. These Tunnel Task 

Forces are located in San Ysidro, California, and Nogales, Arizona, within 

the two Border Patrol sectors with the highest number of illicit crossborder tunnels found.35 Participants in the task forces include Border 

 35The Tunnel Task Force in San Ysidro, California, was established in 2003 and the 

Tunnel Task Force in Nogales, Arizona, was established in 2012.

DHS Coordinates 

Among Partners and 

Uses Technology to 

Address the Selected 

Smuggling Methods, 

but Could Strengthen 

its Efforts

DHS Uses Various 

Coordination Mechanisms 

to Address Smuggling by 

Cross-Border Tunnels, 

Ultralight Aircraft, and the 

Selected Maritime 

Methods
Page 30 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Patrol, ICE HSI, and the Department of Justice’s Drug Enforcement 

Administration, among others. State and local law enforcement officials 

sometimes provide additional support during a tunnel investigation. For 

instance, state and local police will, at times, help provide personnel to 

surveil or search a warehouse suspected of housing a tunnel exit. In 

addition to participating in the interagency Tunnel Task Force, Border 

Patrol established a Western Corridor Tunnel Interdiction Group in 

California to patrol the subterranean drainage infrastructure to locate, 

map, and monitor interconnected tunnels. Also, Border Patrol and ICE 

officials in other sectors where tunnels pose threats have established 

informal task forces and partnerships to facilitate information sharing and 

leverage intelligence and resources on counter tunnel efforts. For 

instance, Border Patrol and ICE HSI officials in El Centro, California, 

stated they have monthly meetings to discuss trends and share 

information.

DHS further coordinates with other federal partners, such as DOD, to 

identify common tunnel requirements, test tunnel technologies, and 

exchange tunnel-related information. For instance, DHS officials 

participate in annual meetings led by the DOD Combating Terrorism 

Technical Support Office to discuss subterranean trends, developments, 

requirements, new and emerging technologies, and build relationships. 

Additionally, Border Patrol officials in Nogales, Arizona, coordinate with 

the DOD’s Combating Terrorism Technical Support Office and 

Asymmetric Warfare Group to test tunnel technology and operational 

scenarios in tunnels.

Ultralight aircraft. AMO’s AMOC surveils border airspace for ultralight 

aircraft incursions and works with AMO and Border Patrol agents in the 

field to interdict ultralight aircraft drug loads and crews. Currently, 

AMOC’s Air and Marine Operations Surveillance System can help detect 

ultralight aircraft. AMOC officials stated they can manually monitor 

movement patterns on border airspace radar feeds and look for indicators 

of ultralight activity. When AMOC officials detect a possible ultralight 

incursion, they then call the relevant Border Patrol and ICE HSI stations. 

Conversely, if Border Patrol agents or another federal law enforcement 

partner suspects a possible ultralight aircraft incursion, they call AMOC in 

order to confirm detection on radar. Border Patrol and ICE HSI 

representatives stationed at AMOC stated that their co-location further 

facilitates interagency coordination. AMO and Border Patrol officials noted 

transnational criminal organizations have employed counter-measures to 

thwart their efforts. For example, transnational criminal organizations use 

drones and scouts to conduct counter-surveillance. In order to help 
Page 31 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

mitigate the challenges, select Border Patrol sectors and ICE HSI field 

offices created ad hoc coordination mechanisms and operations to 

partner and better focus resources when the threat posed by ultralight 

aircraft is high in their areas of responsibility. These sectors and offices 

also established tip lines for the general public to report suspicious air 

activity and instruct their agents on ultralight detection methods.

DHS also coordinates with DOD to share information related to aerial 

incursions, identify technical solutions, and coordinate assets to support 

interdiction efforts. For example, DHS leverages DOD as well as Federal 

Aviation Administration radars to feed into Air and Marine Operations 

Surveillance System. Conversely, AMOC officials stated that AMOC has 

also provided a number of DOD entities access to the Air and Marine 

Operations Surveillance System, to help enhance their domain 

awareness and identify suspicious targets.

Maritime vessels. In 2011, DHS established Regional Coordinating 

Mechanisms (RECOM) to coordinate interagency operations and avoid 

duplicative efforts to address U.S. mainland threats in the maritime 

domain, including panga boats and recreational vessels.36 There are 

RECOMs in California, Florida, and Texas, addressing the primary threat 

areas of maritime smuggling. Participants include the Coast Guard, CBP 

AMO and Border Patrol, ICE HSI, the U.S. Attorney’s Offices, and may 

also include state and local law enforcement. To address maritime 

smuggling, RECOM partners host joint teleconferences to create 

interagency interdiction plans, coordinate asset deployment and 

schedules to de-conflict missions, and discuss post-interdiction 

prosecution of migrant cases. RECOMs also serve to share information 

and intelligence on the threats posed by maritime smuggling and trends 

among partners. While DHS component officials identified some 

challenges in addressing maritime smuggling, component officials also 

reported that the RECOMs help mitigate challenges. For example, DHS 

component officials noted the vastness of the maritime environment 

precludes DHS officials from having full awareness of the presence of 

maritime vessels, including panga boats and recreational vessels. 

 36RECOMs were officially established in 2011 through the Maritime Operations 

Coordination Plan, which was signed by the Director of ICE HSI, the Commissioner of 

CBP, and the Commandant of the Coast Guard. The Maritime Operations Coordination

Plan directs these agencies to utilize the fusion of intelligence, planning, and operations to 

target the threat of transnational terrorist and criminal acts along the coastal border. Coast 

Guard serves as the lead agency responsible for planning and coordinating among 

components.
Page 32 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

However, the RECOMs coordinate and leverage each partner’s resources 

in order to maximize assets and expand coverage. Additionally, Coast 

Guard and AMO perform routine patrols on aerial and marine assets to 

monitor potential smuggling routes, conduct public outreach at marinas 

regarding smuggling, surveil for transnational criminal organization 

scouts, and perform random searches of recreational vessels with 

canines. Coast Guard officials indicated the Federal Emergency 

Management Agency’s Operation Stonegarden grants have been 

instrumental in involving state and local law enforcement agencies in 

coastal border security operations.37 For example, Operation 

Stonegarden local law enforcement partners helped the San Francisco 

RECOM interdict 10 subjects involved in a panga boat landing in 2015.

RECOMs also conduct maritime smuggling investigations. For example, 

the San Diego BEST Marine Task Force is the investigative entity for the 

San Diego RECOM. Participants in the Marine Task Force include ICE 

HSI, Border Patrol, AMO, Coast Guard’s Investigative Service, San Diego 

Harbor Police, San Diego Sheriff’s Department, and the California Army 

National Guard.

As with cross-border tunnels and ultralight aircraft, DHS components also 

coordinate with DOD to share information and leverage technical 

solutions for addressing maritime smuggling. For example, DHS 

components and DOD share some cross-border drug removal data, in 

order to increase domain awareness. Additionally, DHS coordinates with 

DOD to address maritime smuggling in the transit zone through the Joint 

Interagency Task Force South—a national task force that facilitates 

international and interagency interdiction of illicit maritime trafficking. Joint 

Interagency Task Force South officials told us the task force primarily 

operates in the transit zone rather than along U.S. mainland borders due 

to the large quantities of narcotics being moved from source countries 

through the transit zone.

 37The Operation Stonegarden program supports enhanced cooperation and coordination 

among CBP, Border Patrol, and local, tribal, territorial, state, and federal law enforcement 

agencies. The program funds investments in joint efforts to secure U.S. borders along 

routes of ingress from international borders to include travel corridors in states bordering 

Mexico and Canada, as well as states and territories with international water borders.
Page 33 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

DHS’s approach to countering cross-border tunnels centers on 

collaboration to leverage the efforts of multiple agencies; however, no 

comprehensive department-level standard operating procedures have 

been established to provide strategic guidance and facilitate information 

sharing departmentwide. As previously discussed, ICE is the primary 

agency responsible for tunnel investigations, and CBP is responsible for 

tunnel interdiction and remediation. Both ICE and CBP have designated 

an authority within their agency for counter-tunnel responsibilities. 

Specifically, ICE HSI has designated a Unit Chief in its Contraband 

Smuggling Unit as responsible for oversight and coordination of ICE 

tunnel investigations at the headquarters-level, among other things. CBP 

designated Border Patrol as the primary point of contact for tunnels within 

CBP in 2010, and tasked it with establishing standardized detection and 

reporting procedures for CBP entities. CBP later formed the Tunnel 

Program Management Office (TPMO) in 2013 to serve as CBP’s 

centralized coordination point for addressing tunnels. However, as of 

November 2016, neither of these ICE or CBP authorities had established 

standard operating procedures guiding how agencies should individually 

or collectively address tunnels used for smuggling. A tunnel capability gap 

assessment commissioned by CBP in 2013 found that while standard 

operating procedures existed in some sectors, CBP did not have an 

accepted set of tactics, techniques, and procedures, such as best 

practices and tunnel activity indicators.38 The ICE-led BEST Tunnel Task 

Forces also do not have documented standard operating procedures for 

addressing tunnels.

In studies, CBP and ICE have identified the absence of standard 

operating procedures as a challenge. For example, the CBP capability 

gap assessment found that DHS personnel located in different areas had 

inconsistent knowledge of the primary methods for addressing tunnels 

and that selected Border Patrol personnel conducting tunnel prediction 

operations may not have access to all pertinent information.

During the course of our audit work, we further found that establishing 

standard operating procedures could strengthen DHS’s counter-tunnel 

efforts. Specifically, we found that not all officials addressing cross-border 

tunnels were aware of—and thus not accessing—all relevant DHS 

 38Homeland Security Studies and Analysis Institute, CBP Counter-Tunnel Threat Analysis: 

DOTMLPF+RGS Capability Assessment (Falls Church, VA: June 25, 2013). 

DHS Could Enhance its 

Collaboration Efforts to 

Address Cross-Border 

Tunnels with More 

Centralized Leadership 

and Guidance
Page 34 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

systems or offices with tunnel information. For example, ICE HSI officials 

we met with at one location were unaware of the existing TPMO or any 

national tunnel office. Further, TPMO, ICE HSI, and Border Patrol officials 

told us that standard operating procedures for tunnels could be beneficial. 

For example, ICE HSI and Border Patrol officials from three different 

sectors indicated a national-level office could help support counter-tunnel 

efforts by providing guidance, training, and strategic-level insight on 

tunnels. For instance, ICE HSI officials from one sector said it would be 

helpful to have guidance on detecting different types of tunnels and 

different investigative techniques for detecting tunnels used across 

sectors.

In recognition of these issues, both the CBP and ICE assessments 

recommended that DHS establish standard operating procedures for 

addressing tunnels in order to formalize methods and enhance 

information sharing for operational coordination. CBP accepted the CBP 

capability gap assessment’s recommendation and tasked the TPMO with 

leading the effort to provide strategic-level guidance and direction for CBP 

counter-tunnel efforts. However, according to the Assistant Chief who

leads the TPMO, it has not yet developed standard operating procedures 

due to lack of personnel and resources. According to the ICE HSI Unit 

Chief responsible for oversight and coordination of ICE tunnel 

investigations, no standard operating procedures could be drafted that 

would address the needs of specific locales due to the different 

operational areas. Additionally, both the TPMO and ICE HSI officials at 

the headquarters-level stated that establishing standard operating 

procedures is unnecessary because current coordination is effective and 

CBP and ICE have general memoranda of understanding from 2004 and 

2006 that govern their coordination. While we recognize there are 

different types of tunnel threats in varying geographic environments and 

that CBP and ICE coordinate to address tunnels, counter-tunnel standard 

operating procedures could include best practices and procedures 

applicable to all sectors—such as procedures for reporting and accessing 

information on tunnels—as well as key differentiated information to 

account for the distinct operational areas. Further, CBP and ICE 

assessments have recommended establishing standard operating 

procedures for counter-tunnel efforts and the general CBP-ICE 

memoranda of understanding do not speak specifically to counter-tunnel 

coordination procedures.

Additionally, the DHS Office of the Inspector General (OIG) 

recommended in a 2012 report that DHS designate an authority to 

provide leadership, strategy and coordination of DHS counter-tunnel 
Page 35 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

efforts across DHS components.39 The OIG identified the lack of a 

department-level focal point for tunnels as a concern and stated that it 

increased the risk of DHS not achieving its goal of disrupting criminal 

organizations that engage in cross-border smuggling. As an example, the 

DHS OIG reported that there were not sufficient policies or procedures in 

place to ensure that when acquiring tunnel detection technology, CBP 

would take into account ICE HSI investigative requirements, such as the 

need for covert use so as to not alert criminals to the presence of law 

enforcement. At the time, CBP and ICE stated they would designate a cochaired committee to satisfy the recommendation. DHS approved this 

decision in February 2013. However, according to the TPMO, the cochaired committee has never convened, nor has it had the need to take 

action. The ICE HSI Unit Chief responsible for tunnel coordination and 

oversight was unaware of the existence of the committee.

Convening this CBP-ICE committee to establish standard operating 

procedures could help provide strategic guidance that addresses the 

complexity of the threats posed by cross-border tunnels and ensure 

information is shared among the range of agencies involved. Once 

convened, this committee could also take the lead on other strategic 

counter-tunnel efforts, such as developing training. Standards for Internal 

Control in the Federal Government calls for agencies to implement control 

activities, such as policies, to help achieve objectives and ensure 

accountability for stewardship of government resources.40 Additionally, 

these standards state that control activities should be documented in, for 

example, management directives, administrative policies, or operating 

manuals. Leadership is a key feature for successful interagency 

collaboration, and we have previously reported that it is often beneficial to 

designate one lead in order to centralize accountability and expedite 

decision making.41 We have also previously reported that establishing a 

focal point with sufficient time, responsibility, authority, and resources can 

help ensure successful implementation of complex interagency and 

 39Department of Homeland Security, Office of Inspector General, CBP’s Strategy to 

Address Illicit Cross-Border Tunnels, DHS OIG-12-132 (Washington, D.C.: Sept. 26, 

2012).

40GAO/AIMD-00-21.3.1 and GAO-14-704G.

41GAO-12-1022. 
Page 36 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

intergovernmental undertakings.42 While developing standard operating 

procedures for detecting, identifying, and addressing cross-border tunnels 

may require some investment of resources, having such standardized 

procedures could reduce resource requirements over time by increasing 

the efficiency of counter-tunnel efforts by formalizing and enhancing 

information sharing and establishing protocols. Furthermore, according to 

the tunnel capability gap assessment, having standard operating 

procedures reduces the likelihood of gaps or conflict in roles and 

responsibilities among staff, and minimizes the likelihood that information 

and partnerships may be lost during personnel changes.

DHS currently uses multiple existing technological solutions and is 

researching additional technologies to address smuggling by cross-border 

tunnels, ultralight aircraft, and the selected maritime methods.

Cross-border tunnels. DHS initiated a Cross-Border Tunnel Threat 

program to acquire tunnel detection technology in 2012 and is currently 

completing an analysis of alternatives to evaluate different technology 

options. CBP’s preliminary concept of operations for tunnel detection 

technology states that detection capability is required in border 

environments that vary from urban, to coastal, to desert, to rugged, 

mountainous terrain. According to CBP officials, completion of the 

analysis of alternatives has been delayed as of November 2016 due to a 

number of reasons, including delays in obtaining security clearances for 

the contractor. CBP officials are currently determining new acquisition 

timeframes. In the meantime, DHS is leveraging multiple existing tunnel 

technologies.

DHS S&T is also in the process of developing additional technologies for 

predicting, detecting, tracking, and interdicting cross-border tunnels, but 

the projects are in the research and development phase. For example, 

DHS S&T is developing technology to determine how long ago a 

clandestine tunnel was built and infer the types of contraband and 

number of people that may have gone through the tunnel over that period 

 42GAO, Combating Terrorism: Selected Challenges and Related Recommendations, 

GAO-01-822 (Washington, D.C.: Sept. 20, 2001). See also GAO, Combating Terrorism: 

Evaluation of Selected Characteristics in National Strategies Related to Terrorism, 

GAO-04-408T (Washington, D.C.: Feb. 3, 2004); and GAO, Biosurveillance: Efforts to 

Develop a National Biosurveillance Capability Need a National Strategy and a Designated 

Leader, GAO-10-645 (Washington, D.C.: June 30, 2010).

DHS Employs Various 

Technologies to Address 

Smuggling by CrossBorder Tunnels, Ultralight 

Aircraft, and the Selected 

Maritime Methods
Page 37 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

of time. Appendix II provides more details on potential tunnel technology 

projects being researched and developed.

Ultralight aircraft. AMO and Border Patrol are using existing radar and 

surveillance camera technology, including DOD and Federal Aviation 

Administration radars, the Tethered Aerostat Radar System, Remote 

Video Surveillance Systems, Integrated Fixed Towers, and Mobile 

Surveillance Capabilities, to detect and track ultralight aircraft.43 The 

Tethered Aerostat Radar System has been helpful in detecting some 

ultralight incursions, according to AMO and Border Patrol officials we 

interviewed.

Maritime vessels. Coast Guard and AMO use both marine and aerial 

assets equipped with sensors, such as cameras and forward looking 

infrared radar, for surveillance and targeted interdictions of maritime 

vessels used for smuggling, including panga boats and recreational 

vessels. They also employ existing technologies, such as X-ray machines 

to identify hidden compartments of maritime vessels. Additionally, DHS 

leverages existing DOD maritime technology, such as a system called 

Minotaur, which integrates and processes sensor data from multiple 

sources for surveillance aircraft.

DHS S&T is in the process of developing additional technologies to be 

used for predicting, detecting, tracking, and interdicting illicit maritime 

vessels, but the technologies are not yet deployed. For example, DHS 

S&T is developing the Integrated Maritime Domain Enterprise and 

Coastal Surveillance System software to integrate multiple data systems 

and create new maritime security common operating data to share across 

DHS components. Appendix II provides more details on research and 

development technology projects.

 43The Tethered Aerostat Radar System is a helium-filled balloon moored to the ground, 

with elevated radar sensors to provide look-down capability. The Integrated Fixed Towers 

consists of, among other things, ground surveillance radars and surveillance cameras 

mounted on fixed (that is, stationary) towers. The Remote Video Surveillance System 

includes multiple color and infrared cameras mounted on monopoles, lattice towers, and 

buildings, but unlike the Integrated Fixed Towers, it does not include radars. The Mobile 

Surveillance Capabilities is a stand-alone, truck-mounted suite of radar and cameras that 

provides a display within the cab of the truck.
Page 38 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

CBP is considering various technological solutions to address ultralight 

aircraft, but does not have a plan to assess how the solutions will meet its 

operational needs. After Border Patrol identified ultralight aircraft 

incursions as a high priority threat, it requested assistance from CBP in 

September 2009 to identify a technology solution to aid in the detection 

and interdiction of ultralights. In response, CBP initiated the Ultralight 

Aircraft Detection acquisition program to acquire a technological solution. 

In 2011, CBP formalized the operational need for an Ultralight Aircraft 

Detection program in an Operational Needs Statement, in which it 

justified its need for the technology by referring the reader to capability 

gaps it had documented in a Mission Needs Statement for Small Dark 

Aircraft-Low Flying Aircraft Detection, an ongoing research and 

development project for technology to address the threats posed by 

ultralight aircraft and other low-flying aircraft.44 CBP deployed a limited 

number of Ultralight Aircraft Detection systems to detect ultralight aircraft 

along both the southern and northern borders. In June 2015, CBP, in 

accordance with recommendations from AMO and Border Patrol, ceased 

operational use of the Ultralight Aircraft Detection systems.45 CBP officials 

explained that a quick buy acquisition strategy and limited institutional 

technical knowledge contributed to poorly defined requirements and the 

acquisition of the Ultralight Aircraft Detection radar with limited capability.

In 2015, CBP began a technology demonstration to assess the ability of 

DOD’s Lightweight Surveillance Target Acquisition Radar systems to aid 

in the detection of low-flying aircraft along the southwest border. Once 

again, CBP used the Small Dark Aircraft-Low Flying Aircraft Detection 

Mission Needs Statement to describe the operational needs that 

Lightweight Surveillance Target Acquisition Radar was intended to 

address. The three ultralight aircraft technological solutions are further 

described in Table 2.

 44A mission needs statement provides a high-level description of the operational 

requirements to address a current or impending capability gap. It outlines the concept of 

the solution to fill the gap and does not provide information on specific types of 

acquisitions that could provide that capability.

45The contract for Ultralight Aircraft Detection remains active in order to identify potential 

ways to leverage the ten existing systems that have already been purchased in the 

maritime domain.

CBP Could Better Meet 

Operational Needs and 

Ensure Effective Use of 

Resources by 

Comprehensively 

Assessing Ultralight 

Technology Investments
Page 39 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Table 2: U.S. Customs and Border Protection (CBP) Technological Solutions to Address Low-Flying Aircraft

Technology Description Status

Small Dark Aircraft (SDA) -

Low Flying Aircraft Detection 

(LFAD)

In 2010, CBP and Department of Homeland 

Security (DHS) Science and Technology 

Directorate (S&T) sponsored the SDA project 

to serve as the research and development 

component of the LFAD acquisition program 

within CBP’s Office of Acquisition. 

DHS S&T completed its final system test in fall 2015. 

The SDA-LFAD demonstration is expected to be 

completed in March 2017, after additional CBP 

evaluation of operating and maintenance costs. LFAD 

could become a CBP acquisition program if Border 

Patrol and Air and Marine Operations determine the 

LFAD system meets its operational needs, according 

to CBP officials. Thus far, LFAD has received mixed 

customer reviews on its functionality.

Ultralight Aircraft Detection 

(ULAD)

In 2013, CBP awarded a $100 million 

contract to acquire ULAD systems, with 

approximately $8 million expended thus far.a

ULAD demonstrations have found that the technology 

provides limited capability to CBP components and 

falls short of meeting operational requirements. The 

system is not currently being pursued as a solution for 

detecting low flying aircraft.

Lightweight Surveillance 

Target Acquisition Radar 

(LSTAR)

In 2015, CBP modified excess Department of 

Defense ‘Lightweight Counter Mortar Radar’

systems into LSTARs and started testing the 

LSTARs to demonstrate the viability of the 

systems in tracking ultralight aircraft flying 

into the southwestern United States.

The LSTAR successfully detected and tracked aircraft 

in the first phase of the LSTAR demonstration and 

CBP is proceeding to the second demonstration 

phase, which consists of deploying 10-30 LSTAR 

systems along the Southwest border. 

Source: GAO analysis of CBP documentation. | GAO-17-474

a

CBP initially awarded a contract to acquire ULAD systems in August 2012. However, because the 

contractor was unable to deliver a key capability—a communications sub-system to transmit 

information—CBP subsequently re-awarded the contract to another vendor.

Although CBP used the same mission needs statement for the three 

projects, CBP officials stated that CBP is demonstrating separate 

ultralight aircraft technological solutions to address different geographic 

areas. For example, CBP officials told us the Small Dark Aircraft-Low 

Flying Aircraft Detection technology demonstration is geared towards 

identifying a technical solution for addressing aerial smuggling on the 

northern border, which is more mountainous and remote, and the 

Ultralight Aircraft Detection program was meant to detect and track 

ultralight aircraft along the southern border, which has a relatively flatter 

terrain. While we recognize that there may need to be multiple technical 

solutions to address the threats posed by ultralight aircraft and account 

for operational differences, such as terrain and manpower, CBP has not 

assessed and documented how the technological solutions will fully 

address Border Patrol and AMO’s operational needs to detect ultralight 

aircraft in all operational environments or how these solutions fit into the 

broader aerial domain awareness efforts. While the Ultralight Aircraft 

Detection program is no longer being pursued, there are a number of 

efforts that could be used to address ultralight aircraft smuggling. Both the 
Page 40 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Small Dark Aircraft-Low Flying Aircraft Detection and Lightweight 

Surveillance Target Acquisition Radar are still being demonstrated and 

considered as potential solutions to acquire to address ultralight aircraft. 

Furthermore, DHS S&T plans to extend the Small Dark Aircraft-Low 

Flying Aircraft Detection project to the southern border to help detect and 

track low-flying aircraft. Additionally, CBP intends to replace or modernize 

the Tethered Aerostat Radar System and states in its acquisition 

documentation that it is seeking alternative capabilities to improve target 

detection of low flying aircraft, among other things. DHS has also 

identified small unmanned aerial systems as an emerging smuggling 

method and CBP is starting to look for technological solutions to address 

this new threat that potentially could also detect ultralight aircraft.46

We have previously identified the need for agencies to evaluate 

alternatives by considering the costs and benefits of different measures

and to document management’s decisions and the rationale for the 

investment of resources.47 Additionally, Standards for Internal Control in 

the Federal Government states that significant events—including 

decisions—need to be clearly documented, and the documentation 

should be readily available for examination.48 There are multiple ongoing 

analytical efforts that CBP could leverage to analyze how the alternative 

technologies for detecting and tracking ultralight aircraft address 

operational needs in various environments and the associated costs and 

benefits. For example, AMO and John Hopkins University Applied 

Physics Laboratory are leading the development of a formal Capability 

Gap Assessment process to gather mission needs and elicit capability 

gaps in both the air and maritime domains from the field; AMO and CBP’s 

Office of Acquisition are jointly developing a comprehensive capabilities 

analysis report for aerial domain awareness; and AMO and DHS S&T 

have a Value Focused Modeling project to estimate return on investment 

of AMOC’s existing radars and sensor technologies. CBP officials 

acknowledged the benefit of analyzing alternatives and plan to analyze 

the costs and benefits of some alternatives (e.g., existing Tethered 

 46According to DHS S&T, to help address the threat of nefarious small unmanned aerial 

systems, the DHS Undersecretary of Science and Technology recently established a 

Program Executive Office for Unmanned Aerial Systems in DHS S&T. This Executive 

Office is responsible for guiding, assessing, advising, and enabling technical solutions for 

using small unmanned aerial systems and for leading national efforts to counter small 

unmanned aerial system misuse in the United States. 

47GAO-06-91.

48GAO/AIMD-00-21.3.1 and GAO-14-704G.
Page 41 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Aerostat Radar Systems) as part of the process to determine whether or 

not to acquire the Small Dark Aircraft-Low Flying Aircraft Detection 

system. However, they did not say that this analysis would include all 

alternative approaches for addressing ultralight aircraft—such as 

modernized Tethered Aerostat Radar Systems, the Lightweight 

Surveillance Target Acquisition Radar, or any solutions DHS S&T is 

developing.

CBP could be better positioned to use its resources more effectively and 

ensure the technological solutions selected will fully meet operational 

needs prior to making investment decisions by assessing and 

documenting how the ongoing technology demonstrations and any other 

potential technological solutions for detecting and tracking ultralight 

aircraft will fully address operational needs. Documenting such 

assessments, consistent with standards for internal control, prior to 

making investment decisions would also enhance transparency by 

providing stakeholders visibility into rationales for investment decisions 

over time.

DHS has established or is in the process of establishing high-level 

smuggling-related performance measures and DHS components collect 

data regarding the prevalence of cross-border tunnel, ultralight aircraft 

and selected maritime smuggling, but DHS has not assessed the 

effectiveness of its efforts specific to addressing these smuggling 

methods. With respect to high-level smuggling-related performance 

measures, DHS has, for example, established a performance measure 

through which it monitors and reports on the percentage of ICE’s drug 

investigations resulting in the disruption or dismantlement of high-threat 

transnational drug trafficking organizations or individuals in its Annual 

Performance Report.49 This performance measure includes data on any 

investigations in which smugglers leveraged cross-border tunnels, 

ultralight aircrafts, panga boats or recreational vessels, but does not 

separately assess investigative performance by these conveyances. 

Additionally, CBP AMO is in the process of developing high-level 

measures related to interdiction, investigation, and domain awareness. 

These high-level performance measures may include performance and 

capabilities relevant to ultralight aircraft incursions such as the amount of 

radar coverage for detecting a range of aerial threats within a given 

 49Department of Homeland Security, Annual Performance Report Fiscal Years 2014-2016 

(Washington, D.C.: February 2015), 34.

Establishing and 

Monitoring 

Performance 

Measures Could 

Allow DHS to Better 

Assess Effectiveness 

of Efforts to Address 

the Selected 

Smuggling Methods
Page 42 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

volume of airspace along the southwest border but will not be specific to 

ultralight aircraft, according to these officials. Furthermore, DHS 

established performance measures through which Coast Guard reports 

on maritime migrant interdiction effectiveness and cocaine removal rates 

in the transit zone, but there is not a unified effort among all DHS 

components responsible for maritime security to jointly assess their 

performance to address panga boat and recreational vessel maritime 

smuggling at U.S. mainland borders.50 Additionally, DHS components 

collect various data regarding the prevalence of cross-border tunnel, 

ultralight aircraft and selected maritime smuggling methods, but have not 

established performance measures and associated targets to assess the 

effectiveness of their efforts specific to addressing cross-border tunnels, 

ultralight aircraft, or non-traditional maritime threats, as described below.

• Cross-border tunnels. Border Patrol’s TPMO tracks and reports 

DHS’s official tunnel data such as the number, location, type, and 

dimensions of cross-border tunnels to Congress and plans to use this 

information in its new threat assessments tool discussed earlier in this 

report. Similarly, the ICE HSI Unit Chief responsible for tunnel 

coordination and oversight stated that ICE also collects data on crossborder tunnels. However, Border Patrol and ICE HSI have not used 

tunnel-related information to assess their collective performance to, 

for example, help identify effective approaches to discover tunnels, 

including technologies, investigative approaches, or patrols.

• Ultralight aircraft. CBP AMO collects various data regarding 

ultralight aircraft incursions, and has developed performance 

measures specific to its efforts to address ultralight aircraft, but these 

measures do not have targets that would allow it to gauge progress 

toward goals. Specifically, CBP AMO collects ultralight data regarding 

the number and location of suspected ultralight aircraft incursions, 

how the ultralight aircraft was detected (i.e., by technology such as 

ground or aerostat radars, or reported by an individual who heard or 

saw the ultralight aircraft activity), if a law enforcement response was 

coordinated, and if there was an arrest or seizure. AMOC uses these 

data to track certain performance measures specific to its efforts to 

address ultralight aircraft, such as the percent of detected ultralight 

aircraft incursions where AMOC coordinated a law enforcement 

 50Department of Homeland Security, Annual Performance Report Fiscal Years 2014-2016 

(Washington, D.C.: February 2015), 26; and Future Years Homeland Security Program 

Fiscal Years 2014- 2018, Appendix: Component Resources, Performance Plan, and 

Capital Investment (Washington, D.C.: May 2013), 32.
Page 43 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

response and the percent of ultralight incursions that resulted in a 

violation (e.g., an arrest or seizure). For example, in fiscal year 2015, 

AMOC reported that it coordinated a law enforcement response for 94 

percent of the suspect ultralight aircraft incursions and that 32 percent 

of the suspect ultralight aircraft incursions resulted in a violation. 

However, AMO and Border Patrol have not assessed their 

performance against targets in order to determine if these rates 

represent a satisfactory level of performance, given the level of risk 

and investment.

• Maritime vessels. Coast Guard and the RECOMs collect data on 

drug and migrant interdiction by fiscal year and vessel type as well as 

the number of arrests and the outcome of the cases prosecuted. 

However, data collection efforts are not consistent across RECOMs 

and there are no established performance measures and targets, to 

monitor, for example, how maritime smuggling events are identified 

and detected, the number or percent of detected smuggling events 

that resulted in interdictions, or the number of interdictions that 

resulted in prosecutions.

DHS component officials provided a variety of reasons why they have not 

established and monitored performance measures and targets to assess 

effectiveness of DHS efforts to address cross-border tunnel, ultralight 

aircraft and selected maritime smuggling, such as limited resources, 

difficulty measuring unknown information, limitations of measures focused 

on specific smuggling methods, and difficulty of jointly establishing and 

monitoring performance among DHS components. For example, 

according to the Border Patrol TPMO Assistant Chief, the office has not 

established performance measures due to its previously discussed limited 

resources and the difficulty of fully measuring the effectiveness of counter 

tunnel efforts. In particular, Border Patrol officials told us that measuring 

the performance of activities which detect and deter threats to the United 

States where the universe of the total prevalence of smuggling is 

unknown—as with the case of cross-border tunnels—is difficult.51

Furthermore, ICE HSI and CBP AMO officials reported that performance 

 51For cross-border tunnels, in addition to our analysis, in 2013, a capability gap 

assessment commissioned by CBP found there were not performance standards or 

oversight processes for CBP counter-tunnel operations, primarily due to limited resources. 

As a result, the assessment recommended that CBP fully establish and resource the CBP 

Tunnel Program Office to assess performance, among other things. CBP has not 

implemented this recommendation. Homeland Security Studies and Analysis Institute, 

CBP Counter-Tunnel Threat Analysis: DOTMLPF+RGS Capability Assessment (Falls 

Church, VA: June 25, 2013). 
Page 44 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

measures which focus on a particular smuggling method or conveyance 

would not be the best measure of their efforts to combat smuggling. For 

example, AMO officials reported that higher-level measures linked to 

AMO’s goals and objectives can better address the full range of 

smuggling methods. Additionally, CBP and ICE officials told us that jointly 

establishing and monitoring performance measures and targets is difficult 

due to the component’s different missions. For example, a performance 

measure relevant to CBP, such as the number of miles of border under 

surveillance for tunnels, would not be relevant to ICE.

We recognize the challenges associated with resource constraints and 

establishing performance measures, as well as the value of higher level 

performance measures; however, agency resources are being invested to 

address cross-border tunnel, ultralight aircraft, and selected maritime 

smuggling methods and without some type of performance measurement, 

DHS does not have reasonable assurance that efforts to address these 

selected smuggling methods are effective. DHS already collects data on 

these selected smuggling threats that could be leveraged to mitigate the 

resources needed to measure performance. Additionally, DHS could 

leverage other DHS efforts as avenues to establish performance 

measures. For example, DHS could utilize the planned Maritime Security 

Coordination Working Group to establish performance measures and 

targets related to assessing the effectiveness of efforts to address panga 

boats and recreational vessels.

52 Further, even if it is not possible to 

collect certain data, such as the full universe of cross-border tunnels, 

GAO, the Office of Management and Budget, and the Performance 

Improvement Council’s Law Enforcement Measures Working Group—an 

interagency effort to address issues related to law enforcement 

performance measures chaired by the Office of Management and 

Budget—have previously reported that agencies can use proxy measures 

 52According to an October 2016 DHS Office of Inspector General report, the DHS Under 

Secretary for Management will charter and lead a Maritime Security Coordination Working 

Group that includes key leaders from applicable DHS components. The working group will 

ensure DHS implements oversight mechanisms to coordinate AMO, Coast Guard, and 

ICE operations on a sustained basis. Additionally, the working group will review how the 

principles and goals outlined in the Maritime Operations Coordination Plan, together with 

suitable means of oversight, can be incorporated into recently established coordination 

forums at both the department and field levels. The estimated completion date for these 

efforts is December 2017. See Department of Homeland Security Office of Inspectors 

General, AMO and Coast Guard Maritime Missions Are Not Duplicative, But Could 

Improve with Better Coordination, OIG-17-03 (Washington, D.C.: October 2016).
Page 45 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

to determine how well a program is functioning.53 These proxy measures 

should be closely tied to the desired outcome—preventing smuggling 

through cross-border tunnels—and could include measures such as the 

percent of tunnels discovered prior to completion or the percent of tunnels 

discovered prior to being operational. In addition, by assessing the 

performance for each selected smuggling method, DHS could obtain 

valuable information on the relative risks posed by these smuggling 

methods as compared to other methods to capture the overall smuggling 

threat picture and better inform resource allocation decisions for 

addressing smuggling. Moreover, assessing performance information 

across components could help components determine cost-effective 

means for improving performance. For example, if CBP established and 

monitored performance measures related to subterranean domain 

awareness, both ICE HSI and Border Patrol could use this information to 

inform investigations and patrol operations.

Standards for Internal Control in the Federal Government states that 

regular monitoring is needed to assess the quality of performance over 

time, and information should be communicated to management to 

achieve its objectives and ensure any issues are resolved.54 We have 

previously reported that performance measures are important 

management tools that can be used by individual programs or initiatives 

and that performance measures should have quantifiable, numerical 

targets or other measurable values to allow for easier comparison with 

actual performance.55 Furthermore, interagency collaboration best 

practices call for federal agencies engaged in collaborative efforts to 

 53GAO, Overstay Enforcement: Additional Mechanisms for Collecting, Assessing, and 

Sharing Data Could Strengthen DHS’s Efforts but Would Have Costs,

GAO-11-411(Washington, D.C.: Apr. 15, 2011); Office of Management and Budget, 

Performance Measurement Challenges and Strategies (June 18, 2003); and Performance 

Improvement Council, Law Enforcement Measure Working Group (December 2015). The 

Performance Improvement Council, an inter-agency body that supports cross-agency 

collaboration and best practice sharing, was established under Executive Order 13450 in 

2007 and codified in law under the GPRA Modernization Act of 2010. See Improving 

Government Program Performance, Exec. Order No. 13450, 72 Fed. Reg. 64,519 (Nov. 

2007); Pub. L. No. 111-352, § 9, 124 Stat. 3866, 3878-80 (2011) (codified at 31 U.S.C. § 

1124). The Performance Improvement Council is chaired by the Deputy Director for 

Management of the Office of Management and Budget within the Executive Office of the 

President.

54GAO/AIMD-00-21.3.1 and GAO-14-704G.

55GAO-03-143, 52; and GAO, Veterans Justice Outreach Program: VA Could Improve 

Management by Establishing Performance Measures and Fully Assessing Risks,

GAO-16-393 (Washington, D.C.: Apr. 28, 2016).
Page 46 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

create the means to monitor and evaluate their efforts to enable them to 

identify areas for improvement.56 By working together to establish 

performance measures and regularly monitor performance against 

targets, managers could obtain valuable information on successful 

approaches and areas that could be improved to help ensure that both 

technology investments and operational responses to address crossborder tunnel, ultralight aircraft, and selected maritime smuggling are 

effective.

As transnational criminal organizations have adapted their techniques to 

smuggle drugs and humans through cross-border tunnels, ultralight 

aircraft, panga boats, and recreational vessels to evade detection, it is 

vital that DHS respond accordingly in its border security enforcement 

efforts. DHS has taken steps to assess and address the risk posed by 

these smuggling methods, but opportunities exist to ensure these efforts 

are effective and that managers and stakeholders have information 

needed to make decisions. In particular, DHS would be better able to 

develop a more comprehensive picture of the threats posed by panga 

boats and recreational vessels across the nation and leverage its 

maritime threat assessments to make decisions by standardizing vessel 

definitions departmentwide in the DHS Lexicon for use in future threat 

assessments. Additionally, convening the CBP-ICE committee to 

establish standard operating procedures for addressing cross-border 

tunnels could help provide strategic guidance that addresses the 

complexity of the threats posed by cross-border tunnels and ensure 

information is shared among the range of agencies involved.

DHS has also invested in technology to help detect and track 

subterranean, aerial, and maritime smuggling, including various 

technologies to help detect and track ultralight aircraft; however, CBP has 

not assessed and documented how all of the alternative ultralight aircraft 

technical solutions being considered will fully address operational 

requirements or the costs and benefits associated with different 

approaches. This type of analysis could help better position CBP to use 

its resources more effectively and ensure that technology solutions 

selected will fully meet operational needs prior to making investment 

decisions. Furthermore, DHS has not assessed its performance in 

addressing any of the selected smuggling methods. By establishing 

performance measures and regularly monitoring performance against 

 56GAO-06-15. 

Conclusions
Page 47 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

targets, managers could obtain valuable information on successful 

approaches and areas that could be improved to help ensure that both 

technology investments and operational responses to address smuggling 

through cross-border tunnels, ultralight aircraft, panga boats, and 

recreational vessels are effective.

To help ensure that efforts to address smuggling through cross-border 

tunnels, ultralight aircraft, panga boats, and recreational vessels are 

effective and that managers and stakeholders have the information 

needed to make decisions, we recommend the Secretary of Homeland 

Security take the following six actions:

1. develop standardized, departmentwide definitions for maritime 

vessels used for smuggling in the DHS Lexicon;

2. direct the CBP-ICE tunnel committee to convene and establish 

standard operating procedures for addressing cross-border tunnels, 

including procedures for sharing information;

3. direct the Commissioner of CBP to assess and document how the 

alternative technological solutions being considered will fully meet 

operational needs related to ultralight aircraft;

4. direct the Commissioner of CBP and the Director of ICE to jointly 

establish and monitor performance measures and targets related to 

cross-border tunnels;

5. direct the Commissioner of CBP to establish and monitor performance 

targets related to ultralight aircraft; and

6. direct the Commandant of the Coast Guard, Commissioner of CBP, 

and the Director of ICE to establish and monitor RECOM performance 

measures and targets related to panga boat and recreational vessel 

smuggling.

We provided a draft of this report to DHS and DOD for their review and 

comment. DHS provided written comments, which are summarized below 

and reproduced in full in appendix III, and DOD did not provide written 

comments. DHS concurred with four of the six recommendations in the 

report and described actions underway or planned to address them. DHS 

did not concur with two recommendations in the report. DHS also 

provided technical comments, which we incorporated as appropriate.

With regard to the first recommendation, that DHS develop definitions for 

maritime vessels used for smuggling in the DHS Lexicon, DHS concurred 

Recommendations for 

Executive Action

Agency Comments 

and Our Evaluation
Page 48 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

and described planned actions to address the recommendation. 

According to DHS, in March 2017, the DHS Lexicon Program created a 

terminology working group composed of Coast Guard, CBP, ICE, and 

other DHS maritime subject matter experts to address terminology and 

definition issues identified in our report. The terminology and definitions 

would then be published for use across the department. If implemented 

effectively, these actions should address the intent of the 

recommendation. 

With regard to the second recommendation, that the CBP-ICE tunnel 

committee convene and establish standard operating procedures for 

addressing cross-border tunnels, DHS did not concur. DHS noted that 

there are memoranda of understanding between CBP and ICE outlining

how they work together and share information as well as componentspecific procedures in place at the local sector level that DHS believes 

constitute the procedures we recommended. In addition, DHS cited the 

establishment of multi-agency BEST Tunnel Task Forces in the areas at 

the highest risk for cross-border tunnel activity as helping to ensure 

collaboration and information sharing. However, CBP and ICE agreed 

that there may be benefits from strengthening existing operating 

procedures and stated that they plan to review, revise, and potentially 

consolidate procedures as they deem appropriate. 

We continue to believe that establishing national-level, joint CBP-ICE 

standard operating procedures for addressing cross-border tunnels could 

help ensure that information is shared by CBP and ICE across all 

locations and minimize the likelihood that information and partnerships 

are lost during personnel changes. As discussed in this report, the 

memoranda of understanding between CBP and ICE do not speak 

specifically to counter-tunnel coordination procedures. Additionally, as we 

reported, both CBP and ICE have completed studies that identified the 

absence of standard operating procedures as a challenge and 

recommended the establishment of departmental standard operating 

procedures. During the course of our audit work, we further found that not 

all officials addressing cross-border tunnels were aware of relevant 

information systems or the TPMO, and ICE HSI and Border Patrol 

officials from three different sectors indicated additional guidance, 

training, and strategic-level insights would be helpful. While we agree that 

strengthening existing operating procedures could be helpful, not all 

sectors or relevant officials may benefit without the establishment of 

standard operating procedures that apply nationwide. For example, as 

noted in our report, the BEST Tunnel Task Forces do not currently have 

documented standard operating procedures for addressing tunnels.
Page 49 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Establishing departmental standard operating procedures for tunnels 

could help ensure that all relevant ICE and CBP officials have guidance 

on how to address tunnels.

With regard to the third recommendation, that CBP assess and document 

how alternative technological solutions being considered will fully meet 

operational needs related to ultralight aircraft, DHS concurred. DHS 

stated that AMO is developing a Capability Analysis Report, a Mission 

Need Statement, and a Concept of Operations for air domain awareness 

that will result in validated requirements for ultralight aircraft, among other 

threats. In addition, DHS stated that subsequent to these efforts, it will 

prepare operational requirements documents that will specify how 

technological solutions will meet the requirements. If implemented 

effectively, these actions should address the intent of the 

recommendation.

With regard to the fourth recommendation, that CBP and ICE jointly 

establish and monitor performance measures and targets related to 

cross-border tunnels, DHS concurred and stated that CBP and ICE will 

work together to harmonize performance data collection efforts and 

develop performance measures and targets. However, DHS stated that it 

would be premature to establish measures and targets prior to making 

tunnel detection technology acquisition and deployment decisions, and 

therefore will wait to develop them until it has addressed its technology 

challenges. We believe that DHS could benefit from establishing some 

performance measures and targets prior to making technology decisions. 

As discussed in this report, DHS initiated a program to acquire tunnel 

detection technology in 2012 and has an analysis of alternatives to 

evaluate different technology options underway, but this analysis has 

been delayed and CBP has not yet determined new time frames. Given 

that CBP has been working to acquire additional tunnel detection 

technology for several years and time frames for its acquisition have not 

been determined, we believe that establishing some measures and 

targets in the interim could help inform DHS’s current efforts to address 

cross-border tunnels and provide insights relevant to its tunnel detection 

technology acquisition decisions. Once fully implemented, DHS’s planned 

actions should address the intent of the recommendation.

With regard to the fifth recommendation, that CBP establish and monitor 

performance targets related to ultralight aircraft, DHS concurred and 

stated that CBP’s AMO and Border Patrol are developing a joint 

performance measure and targets for interdicting ultralight aircraft. 

According to DHS, AMO and Border Patrol plan to document how the 
Page 50 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

measure will be defined and validate the data reporting process. If 

implemented effectively, these actions should address the intent of the 

recommendation.

With regard to the sixth recommendation, that Coast Guard, CBP, and 

ICE establish and monitor RECOM performance measures and targets 

related to panga boat and recreational vessel smuggling, DHS did not 

concur. DHS stated that it believes that by establishing common 

terminology to address our first recommendation, the RECOMs will have 

more reliable, usable analyses to inform their maritime interdiction efforts. 

However, it did not believe that performance measures and targets 

related to smuggling by panga boats would provide the most useful 

strategic assessment of operations to prevent all illicit trafficking, 

regardless of area of operations or mode of transportation. DHS also 

cited the recent creation of the DHS Office of Policy, Strategy, and Plans 

that is to work with Coast Guard, CBP, ICE, and other components and 

offices to better evaluate the effectiveness of all operations that work to 

prevent the illegal entry of goods and people into the country, as 

appropriate. Additionally, DHS stated that it will continue to work with the 

Office of National Drug Control Policy to create a set of enterprise-wide, 

strategic-level measures of performance for drug supply reduction 

activities. DHS requested that we consider this recommendation resolved 

and closed. 

We continue to believe that by jointly establishing performance measures 

and targets related to panga boat and recreational vessel smuggling, 

Coast Guard, CBP, and ICE could track valuable performance 

information, such as how panga boat and recreational vessel smuggling 

events are identified and detected, or the percent of these detected 

smuggling events that result in interdictions, to help inform their 

collaborative efforts to address maritime smuggling. We agree that 

creating common terminology is a positive step; however, without 

performance measures or targets, DHS does not have reasonable 

assurance that its collaborative efforts and investments to counter crossborder smuggling by panga boats and recreational vessels are effective. 

Similarly, we recognize the value of high level strategic performance 

measures; however, these types of measures may not provide sufficiently 

detailed performance information to allow DHS to identify successful 

approaches to addressing smuggling by panga boats and recreational 

vessels and areas for improvement. Further, performance measures and 

targets related to panga boat and recreational vessel smuggling could, in 

turn, better position DHS to understand the overall smuggling threat 
Page 51 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

picture and better inform resource allocation decisions for addressing 

smuggling and drug supply reduction activities.

We are sending copies of this report to the appropriate congressional 

committees, the Secretary of Homeland Security, the Secretary of the 

Defense, 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 about this report, 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 key contributions to this 

report are listed in appendix IV.

Rebecca Gambler

Director, Homeland Security and Justice
Appendix I: Objectives, Scope, and 

Methodology

Page 52 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

This report addresses the following questions:

1. What do Department of Homeland Security (DHS) data show about 

the prevalence of smuggling by cross-border tunnel, ultralight aircraft, 

and selected maritime methods from fiscal years 2011 through 2016?

2. To what extent has DHS assessed the risks from smuggling by these 

methods?

3. How has DHS addressed smuggling by these methods?

4. To what extent has DHS assessed the results of its efforts to address 

smuggling by these methods?

To address these questions, we focused our review on smuggling across 

U.S. mainland borders, including coastal borders, and we selected the 

following smuggling methods: cross-border tunnels, ultralight aircraft, 

panga boats, recreational maritime vessels, and self-propelled semisubmersible and fully submersible vessels.1 We selected these smuggling 

methods to include only those that would occur between ports of entry 

through means other than overland (given our focus on subterranean, 

aerial, and maritime smuggling); have been identified in strategy 

documents or by senior DHS officials and DHS officials with whom we 

met as a challenge or risk; and were of a magnitude that DHS had taken 

steps to address them. We analyzed DHS policies, procedures, reports, 

and data regarding the selected smuggling methods from fiscal years 

2011 through 2016.2 We also conducted site visits to San Diego, El 

Centro, and Riverside, California; Nogales and Yuma, Arizona; and Miami 

and Key West, Florida. During these visits, we observed DHS approaches 

to addressing the selected smuggling methods and interviewed cognizant 

officials from U.S. Coast Guard (Coast Guard); U.S. Immigration and 

Customs Enforcement (ICE) Homeland Security Investigations (HSI); and 

U.S. Customs and Border Protection’s (CBP) U.S. Border Patrol (Border 

Patrol) and Air and Marine Operations (AMO) about their efforts. We 

 1

Given its focus on smuggling across U.S. mainland borders (i.e., borders of the 

contiguous United States), our review does not address smuggling in the transit zone—a 6 

million square mile area that includes the eastern Pacific Ocean, the Gulf of Mexico, and 

the Caribbean Sea that is used to transport illicit drugs from South America to the United 

States. For additional information on DHS counterdrug efforts in the transit zone, see 

GAO, Coast Guard: Resources Provided for Drug Interdiction Operations in the Transit 

Zone, Puerto Rico, and the U.S. Virgin Islands, GAO-14-527 (Washington, D.C.: June 16, 

2014).

2

We selected this time period to identify recent trends in known smuggling events by the 

selected methods.

Appendix I: Objectives, Scope, and 

Methodology
Appendix I: Objectives, Scope, and 

Methodology

Page 53 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

selected these locations based upon a combination of factors, including 

the past detected use of the selected smuggling methods and the 

presence of coordinated DHS efforts to counter them in these areas. The 

information gathered from our site visits is not generalizable to other 

locations but provides insights into DHS’s responses to these incursions 

and efforts to use risk and performance information to stop future 

smuggling incidents using these methods. Additionally, we interviewed 

headquarters officials from the Coast Guard; CBP’s Border Patrol, AMO, 

and Office of Acquisition, the office responsible for CBP’s acquisition of 

products and services; ICE HSI; and DHS’s Science and Technology 

Directorate (S&T), the office responsible for leading research and 

development efforts across the department, to obtain information and 

perspectives on their efforts to assess and address threats posed by the 

selected smuggling methods.

To determine what DHS data show about the prevalence of smuggling by 

cross-border tunnel, ultralight aircraft, and the selected maritime methods, 

we obtained and analyzed DHS data from fiscal years 2011 through 

2016. Due to the illicit nature of smuggling, there are limitations to 

identifying the total number of smuggling events. Therefore, in this report 

we discuss the number of known smuggling events such as the numbers 

of discovered cross-border tunnels and detected ultralight aircraft and 

maritime drug and migrant smuggling events. We assessed the reliability 

of these data by (1) performing electronic testing for obvious errors in 

accuracy and completeness, (2) reviewing existing information about the 

data and the systems that produced them, and (3) interviewing agency 

officials knowledgeable about the data. Additionally, where possible, we 

compared the data to similar data DHS previously reported in such 

products as a Congressional report on cross-border tunnels and an AMO 

management report that included data on aerial incursions.3 We found the 

data sufficiently reliable for the purposes of reporting trends in the 

selected smuggling methods from fiscal years 2011 through 2016.

To determine the extent to which DHS has assessed the risk from 

smuggling by cross-border tunnel, ultralight aircraft, and the selected 

maritime methods we analyzed Coast Guard, AMO, Border Patrol, and 

ICE HSI risk, threat, and intelligence assessments. We also reviewed 

CBP, DHS S&T, and Coast Guard documentation on capability gaps, 

 3

Department of Homeland Security, Cross-Border Tunnels and Border Tunnel Prevention 

Fiscal Year 2015 Report to Congress (March 29, 2016); and Air and Marine Operations, 

Assistance Commissioner’s Report (May 4, 2014).
Appendix I: Objectives, Scope, and 

Methodology

Page 54 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

such as capability assessments and requirements documents. We 

evaluated these efforts against GAO’s risk management framework and 

leading practices for interagency collaboration.

4

To determine how DHS has addressed smuggling by the selected 

methods, we analyzed DHS policies, procedures, training documents, 

and documentation on developing and acquiring new technology, such as 

project plans, mission needs statements, and concepts of operations. We 

also interviewed officials from Border Patrol, AMO, ICE HSI and Coast 

Guard to determine the extent to which they have established 

mechanisms to coordinate assets and operations related to smuggling by 

cross-border tunnels, ultralight aircraft, and the selected maritime 

conveyances, and associated challenges. Further, we met with 

Department of Defense (DOD) officials from the offices and organizations 

that have been involved in DHS efforts to address the selected smuggling 

methods to determine the extent to which DHS has coordinated with DOD 

to leverage any efforts or technologies.5 We assessed these efforts 

against GAO’s leading practices for interagency collaboration and risk 

management framework.6

To examine the extent to which DHS has assessed the results of its 

efforts to address the selected smuggling methods, we analyzed DHS 

and component performance reports, threat assessments, and strategic 

planning documents to determine what measures are in place to track the 

 4

GAO, Risk Management: Further Refinements Needed to Assess Risks and Prioritize 

Protective Measures at Ports and Other Critical Infrastructure, GAO-06-91 (Washington, 

D.C.: Dec. 15, 2005); and Managing for Results: Key Considerations for Implementing 

Interagency Collaborative Mechanisms, GAO-12-1022 (Washington, D.C.: Sept. 27, 

2010). As discussed in GAO-06-91, risk assessment addresses the process of evaluating 

threats—the probability that a specific type of incident will occur—and vulnerabilities—

weaknesses that can be exploited—so that countermeasures might be instituted. Risk 

assessment can also include an assessment of the consequence of an event to help 

prioritize which assets or areas require greater protection; however, as consequences of 

smuggling can reasonably be expected to be similar among different methods of 

smuggling, our analysis focused on the threat and vulnerability aspects of risk 

assessment. 

5

These DOD offices and organizations included U.S. Northern Command, which oversees 

Joint Task Force North, the organization responsible for supporting federal counterdrug 

activities along the southwest border; and the U.S. Southern Command, which oversees 

the Joint Interagency Task Force South, the primary operations center and coordinator for 

detecting and monitoring suspected air and maritime drug trafficking in the Caribbean, 

Central America, and South America.

6

GAO-06-91 and GAO-12-1022.
Appendix I: Objectives, Scope, and 

Methodology

Page 55 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

effectiveness of DHS’s counter cross-border tunnel, ultralight aircraft, and 

maritime smuggling efforts. We also interviewed DHS officials to 

determine how they use performance information to inform decision 

making. We assessed DHS’s performance monitoring efforts against 

Standards for Internal Control in the Federal Government and 

performance assessment best practices.7

We conducted this performance audit from November 2015 to May 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.

 7

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

(Washington, D.C.: September 2014); Results-Oriented Government: Practices That Can 

Help Enhance and Sustain Collaboration among Federal Agencies, GAO-06-15 

(Washington, D.C.: Oct. 21, 2005); Tax Administration: IRS Needs to Further Refine Its 

Tax Filing Season Performance Measures GAO-03-143 (Washington, D.C.: Nov. 22, 

2002); and Standards for Internal Control in the Federal Government, 

GAO/AIMD-00-21.3.1 (Washington, D.C.: November 1999).
Appendix II: DHS S&T Projects Related to 

Selected Subterranean, Aerial, and Maritime 

Smuggling Methods

Page 56 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

A number of technology systems are being researched and developed by 

the Department of Homeland Security (DHS) Science and Technology 

Directorate (S&T) to address selected subterranean, aerial, and maritime 

smuggling threats. Below is an overview of these ongoing DHS S&T 

projects.

Table 3: Department of Homeland Security (DHS) Technology Research and Development Projects Related to Selected 

Subterranean, Aerial, and Maritime Smuggling Methods

Technology Project Description Status

Integrated Maritime 

Domain Enterprise 

(IMDE) / Coastal 

Surveillance System 

(CSS) 

The IMDE/CSS project aims to identify and track small 

maritime vessels that may be engaged in illegal 

behavior. To better identify threats, IMDE/CSS 

integrates data feeds from existing sensors and 

multiple data systems to create new maritime security 

common operating data to share across DHS 

components. It then analyzes those data to provide 

law enforcement with real-time information, including 

vessel tracking. 

Technical demonstrations are ongoing. An initial 

version of the system was installed in December 

2012 for preliminary evaluation at the U.S. 

Customs and Border Protection (CBP) Air and 

Marine Operations Center (AMOC). Various 

technical demonstrations occurred between fiscal 

years 2015-2016, and more are planned for fiscal 

year 2017 including an operational demonstration.

Commercial SpaceBased Technologies Commercial space-based technologies would provide 

awareness of maritime threats and targets. 

Operational Utility Assessment is ongoing as of 

January 2017, as DHS determines best practices 

for this developing technology.

Dark Vessel Detection 

(DVD)

The DVD project aims to increase radar and optical 

sensor capabilities in order to detect vessels of all 

sizes which are not currently tracked through the 

Automatic Identification System.a

The DVD project is scheduled to commence in 

fiscal year 2017.

Small Dark Aircraft 

(SDA)

The SDA project aims to improve early detection and 

tracking of small aircraft, including ultralights, increase 

the opportunity for interdiction, and enable CBP to 

more efficiently deploy government assets. SDA is the 

research and development component of the Low 

Flying Aircraft Detection System (LFAD) acquisition 

program. This project involved the testing and 

installation of an integrated suite of multi-modal polemounted sensors to provide real-time information on 

air domain threats.

The SDA project has reached completion and U.S.

Border Patrol (Border Patrol) will determine if 

LFAD meets its operational needs, according to 

CBP officials. The DHS Science and Technology 

Directorate (S&T) began the SDA Project in fiscal 

year 2011 by identifying innovative technologies. 

Demonstrations and tests continued through fiscal 

year 2012 after which a long-duration test was 

done along the northern border. After the test the 

final developmental system was fully integrated 

with a high degree of autonomy, high 

performance, and reliability. The Phase II LFAD 

system test was conducted and completed in 

October 2015. 

Small Dark Aircraft 

Detection – Southern 

Border

The Small Dark Aircraft Detection – Southern Border 

project aims to provide a technical basis for the 

detection, tracking, and classification of small, low 

observable aircraft in areas of complex terrain on the 

southern border.

This effort is in the initial planning stage and an 

extension of the SDA work on the northern border. 

Appendix II: DHS S&T Projects Related to 

Selected Subterranean, Aerial, and Maritime 

Smuggling Methods
Appendix II: DHS S&T Projects Related to 

Selected Subterranean, Aerial, and Maritime 

Smuggling Methods

Page 57 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Tunnel Detection The Tunnel Detection project aims to evaluate the 

performance of existing tunnel detection technologies 

in a variety of geophysical conditions in order to 

determine optimal sensor placement. 

DHS S&T created and utilized a tunnel detection 

performance tool in order to optimize currently 

available equipment. Additional demonstrations 

were planned for the end of fiscal year 2016. A 

transition prototype and test report is scheduled for 

fiscal year 2018.

Tunnel Age The Tunnel Age project aims to develop a solution for 

determining how long ago a clandestine tunnel was 

built, and infer the types of contraband and number of 

people that may have gone through the tunnel over 

that period of time. 

DHS S&T has demonstrated the Tunnel Age Kit 

prototype for evaluation and plans to transition the 

kits to CBP and U.S. Immigration and Customs 

Enforcement (ICE). 

Robots for Tunnel 

Investigations

The Robots for Tunnel Investigations project aims to 

allow for safe investigation of discovered tunnels 

without having to put humans into the tunnels. This 

project will determine if existing tunnel robotic 

technologies meet Border Patrol and ICE’s needs or if 

improvements are needed. 

The project is scheduled to commence in fiscal 

year 2017. DHS S&T plans to first conduct a study 

on available technology for robotics for tunnels 

and on current communication techniques in 

confined locations. 

Source: GAO analysis of DHS S&T information | GAO-17-474

a

The Maritime Transportation Security Act of 2002 mandated that certain commercial vessels—

including self-propelled vessels 65 feet or more in length or that are certified to carry more than 150 

passengers—operate an automatic identification system while in U.S. navigable waters, which allows 

these vessels to be tracked. The automatic identification system transmits vessel information such as 

the identity of the vessel, its position, speed, course, navigational status, and other safety-related 

information automatically to appropriately equipped shore stations, other ships, and aircraft, and 

receives such information from similarly fitted vessels, and exchanges data with shore-based 

facilities. See Pub. L. No. 107-295, tit. I, § 102(a), 116 Stat. 2064, 2082-83 (codified at 46 U.S.C. § 

70114); see also 33 C.F.R. § 164.46.
Appendix III: Comments from Department of 

Homeland Security

Page 58 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Appendix III: Comments from Department of 

Homeland Security
Appendix III: Comments from Department of 

Homeland Security

Page 59 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling
Appendix III: Comments from Department of 

Homeland Security

Page 60 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling
Appendix III: Comments from Department of 

Homeland Security

Page 61 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling
Appendix III: Comments from Department of 

Homeland Security

Page 62 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling
Appendix IV: GAO Contact and Staff 

Acknowledgments

Page 63 GAO-17-474 Subterranean, Aerial, and Maritime Smuggling

Rebecca Gambler at (202) 512-8777 or gamblerr@gao.gov

In addition to the contact named above, Taylor Matheson (Assistant 

Director), David Alexander, Chuck Bausell, Jr., Dominick Dale, Wendy 

Dye, Megan Erwin, Eric Hauswirth, Kelsey Hawley, Susan Hsu, Richard 

Hung, Heather May, and Sasan J. “Jon” Najmi made key contributions to 

this report.

Appendix IV: GAO Contact and Staff 

Acknowledgments

GAO Contact

Staff 

Acknowledgments

(101696)
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