9 Jan 2026

Review of Hydroacoustic Data Associated with Small-Diameter Vinyl and Timber Pile Driving Operations

This review investigates root-mean-square sound levels, peak sound levels, and single-strike sound exposure levels resulting from small-diameter vinyl and timber pile driving operations with sufficient supporting information to assess potential impact on endangered species identified in the NOAA acoustic impact calculator. We identify 49 relevant records associated with installing timber pilings 14 in. in diameter and smaller and one record associated with vinyl piling. While acceptable for use as proxy data within the NOAA tool, the records exhibit significant unexplainable scatter of as much as +20 dB. Example calculations show that well intentioned hypothetical proposals coordinated in the permit application process could project vastly different impacts to endangered species. We therefore conclude that, within the framework of current practices and tools, these data cannot support informed decision-making by US Army Corps of Engineers (USACE) regulators as to whether small-scale timber or vinyl pile driving operations will jeopardize the continued existence of protected species or result in the destruction or adverse modification of critical habitat to comply with the Endangered Species Act. We recommend supplementing existing data with targeted collections as well as developing pile-specific coordination and assessment guidance for use by USACE regulators during the permitting process.

9 Jan 2026

Design of River Training Structures Using Isogeomorphic Constraints

Abstract: Prepared for the Mississippi River Geomorphology and Potamology program of the United States Army Corps of Engineers (USACE), through the Coastal and Hydraulics Laboratory (CHL), this report introduces the concept of river control structure design using isogeomorphic constraints. The report defines isogeomorphic design methodology and demonstrates the application of the methodology using both analytic and numerical examples. The examples investigated herein are idealized, and application to real-world conditions (such as a dike-field) would be far more complex than what is demonstrated herein. This report merely serves as an introduction to a novel design paradigm that future studies can further investigate and refine with the ultimate objective of developing improved design guidance for USACE.

7 Jan 2026

Evaluation of Seven Bridges at Fort Hunter Liggett, California, for Eligibility to the National Register of Historic Places

Abstract: The US Congress codified the National Historic Preservation Act of 1966 (NHPA), the nation’s most effective cultural resources legislation to date, mostly through establishing the National Register of Historic Places (NRHP). The NHPA requires federal agencies to address their cultural re-sources, which are defined as any prehistoric or historic district, site, building, structure, or object. Section 110 of the NHPA requires federal agencies to inventory and evaluate their cultural resources, and Section 106 requires them to determine the effect of federal undertakings on those potentially eligible for the NRHP. Fort Hunter Liggett is in central California, within Monterey County. It was first established as the Hunter Liggett Military Reservation in 1941. The post was renamed Fort Hunter Liggett in 1975. This report provides a determination of eligibility for the NRHP for seven properties (Bridges 749, 750, 753, 760, 767, 779, and 781) constructed between 1965 and 2010 and recommends that none are eligible under the NRHP and the California Register of Historic Resources (CRHR) criteria.