Welcome to the U.S. Navy’s website for Surveillance Towed Array Sensor System (SURTASS) Low Frequency Active (LFA) Sonar

SURTASS LFA sonar is a long range surveillance sonar that is necessary for the U.S. Navy to meet its anti-submarine warfare and national security mission. SURTASS LFA sonar systems are operated onboard U.S. Navy surveillance ships to provide improved capability to detect quieter and harder-to-find foreign submarines at greater distances. These underwater sonar systems transmit low-frequency acoustic signals between 100 and 500 Hertz and include both active and passive components.

In 2019, the Department of the Navy, with the National Marine Fisheries Service (NMFS) as a cooperating agency, prepared a Supplemental Environmental Impact Statement/Supplemental Overseas Environmental Impact Statement (SEIS/SOEIS) for SURTASS LFA sonar in accordance with the National Environmental Policy Act and Executive Order 12114. The 2019 SEIS/SOEIS evaluated the potential environmental impacts associated with two training and testing action alternatives and a no-action alternative to the following resource areas: air quality, marine environment, biological, and economic resources. The 2019 Final SEIS/SOEIS is available for download here. After a 30-day public comment period, the Navy selected Alternative 2, the Preferred Action Alternative, which is documented in its Record of Decision.

In compliance with the Marine Mammal Protection Act (MMPA) and the Endangered Species Act (ESA), the Navy submitted applications to NMFS requesting authorizations to take marine mammals, sea turtles, and protected marine fishes incidental to the Navy’s training and testing activities using SURTASS LFA sonar. The Navy submitted an application for rulemaking and a letter of authorization (LOA) under the MMPA to take marine mammals incidental to the use of SURTASS LFA sonar for training and testing activities in the western and central North Pacific and eastern Indian oceans. The MMPA Final Rule and LOA were authorized and became effective on August 12, 2019. Additionally, the Navy submitted a Biological Evaluation to initiate Section 7 consultation under the ESA. In its ESA Biological Opinion on SURTASS LFA sonar, NMFS determined that the Navy’s planned use of SURTASS LFA sonar for training and testing activities is not likely to jeopardize the continued existence of threatened and endangered species under NMFS’s jurisdiction and is not likely to destroy or adversely modify designated critical habitat from August 2019 into the reasonably foreseeable future. The ESA 2019 Biological Opinion for SURTASS LFA sonar, which includes an Incidental Take Statement, was signed on July 30, 2019 and became effective on August 12, 2019.